Selective protein extraction from Chlorobium tepidum chlorosomes using detergents. Evidence that CsmA forms multimers and binds bacteriochlorophyll a.

PubMed

Bryant, Donald A; Vassilieva, Elena V; Frigaard, Niels-Ulrik; Li, Hui

2002-12-03

Chlorosomes of the photosynthetic green sulfur bacterium Chlorobium tepidum consist of bacteriochlorophyll (BChl) c aggregates that are surrounded by a lipid-protein monolayer envelope that contains ten different proteins. Chlorosomes also contain a small amount of BChl a, but the organization and location of this BChl a are not yet clearly understood. Chlorosomes were treated with sodium dodecyl sulfate (SDS), Lubrol PX, or Triton X-100, separately or in combination with 1-hexanol, and the extracted components were separated from the residual chlorosomes by ultrafiltration on centrifugal filters. When chlorosomes were treated with low concentrations of SDS, all proteins except CsmA were extracted. However, this treatment did not significantly alter the size and shape of the chlorosomes, did not extract the BChl a, and caused only minor changes in the absorption spectrum of the chlorosomes. Cross-linking studies with SDS-treated chlorosomes revealed the presence of multimers of the major chlorosome protein, CsmA, up to homooctamers. Extraction of chlorosomes with SDS and 1-hexanol solubilized all ten chlorosome envelope proteins as well as BChl a. Although the size and shape of these extracted chlorosomes did not initially differ significantly from untreated chlorosomes, the extracted chlorosomes gradually disintegrated, and rod-shaped BChl c aggregates were sometimes observed. These results strongly suggest that CsmA binds the BChl a in Chlorobium-type chlorosomes and further indicate that none of the nine other chlorosome envelope proteins are absolutely required for maintaining the shape and integrity of chlorosomes. Quantitative estimates suggest that chlorosomes contain approximately equimolar amounts of CsmA and BChl a and that roughly one-third of the surface of the chlorosome is covered by CsmA.

Magnetic Nanocomposites and Their Incorporation into Higher Order Biosynthetic Functional Architectures

DOE PAGES

Watt, John; Collins, Aaron M.; Vreeland, Erika C.; ...

2018-01-17

A magnetically active Fe 3O 4/poly(ethylene oxide)-block-poly(butadiene) (PEO-b-PBD) nanocomposite is formed by the encapsulation of magnetite nanoparticles with a short-chain amphiphilic block copolymer. This material is then incorporated into the self-assembly of higher order polymer architectures, along with an organic pigment, to yield biosynthetic, bifunctional optical and magnetically active Fe 3O 4/bacteriochlorophyll c/PEO-b-PBD polymeric chlorosomes.

Absorption spectral change of peripheral-light harvesting complexes 2 induced by magnesium protoporphyrin IX monomethyl ester association

NASA Astrophysics Data System (ADS)

Yue, Huiying; Zhao, Chungui; Li, Kai; Yang, Suping

2015-02-01

Several spectrally different types of peripheral light harvesting complexes (LH) have been reported in anoxygenic phototrophic bacteria in response to environmental changes. In this study, two spectral forms of LH2 (T-LH2 and U-LH2) were isolated from Rhodobacter azotoformans. The absorption of T-LH2 was extremely similar to the LH2 isolated from Rhodobacter sphaeroides. U-LH2 showed an extra peak at ∼423 nm in the carotenoid region. To explore the spectral origin of this absorption peak, the difference in pigment compositions of two LH2 was analyzed. Spheroidene and bacteriochlorophyll aP were both contained in the two LH2. And magnesium protoporphyrin IX monomethyl ester (MPE) was only contained in U-LH2. It is known that spheroidene and bacteriochlorophyll aP do not produce ∼423 nm absorption peak either in vivo or in vitro. Whether MPE accumulation was mainly responsible for the formation of the ∼423 nm peak? The interactions between MPE and different proteins were further studied. The results showed that the maximum absorption of MPE was red-shifted from ∼415 nm to ∼423 nm when it was mixed with T-LH2 and its apoproteins, nevertheless, the Qy transitions of the bound bacteriochlorophylls in LH2 were almost unaffected, which indicated that the formation of the ∼423 nm peak was related to MPE-LH2 protein interaction. MPE did not bind to sites involved in the spectral tuning of BChls, but the conformation of integral LH2 was affected by MPE association, the alkaline stability of U-LH2 was lower than T-LH2, and the fluorescence intensity at 860 nm was decreased after MPE combination.

Absorption spectral change of peripheral-light harvesting complexes 2 induced by magnesium protoporphyrin IX monomethyl ester association.

PubMed

Yue, Huiying; Zhao, Chungui; Li, Kai; Yang, Suping

2015-02-25

Several spectrally different types of peripheral light harvesting complexes (LH) have been reported in anoxygenic phototrophic bacteria in response to environmental changes. In this study, two spectral forms of LH2 (T-LH2 and U-LH2) were isolated from Rhodobacter azotoformans. The absorption of T-LH2 was extremely similar to the LH2 isolated from Rhodobacter sphaeroides. U-LH2 showed an extra peak at ∼423 nm in the carotenoid region. To explore the spectral origin of this absorption peak, the difference in pigment compositions of two LH2 was analyzed. Spheroidene and bacteriochlorophyll aP were both contained in the two LH2. And magnesium protoporphyrin IX monomethyl ester (MPE) was only contained in U-LH2. It is known that spheroidene and bacteriochlorophyll aP do not produce ∼423 nm absorption peak either in vivo or in vitro. Whether MPE accumulation was mainly responsible for the formation of the ∼423 nm peak? The interactions between MPE and different proteins were further studied. The results showed that the maximum absorption of MPE was red-shifted from ∼415 nm to ∼423 nm when it was mixed with T-LH2 and its apoproteins, nevertheless, the Qy transitions of the bound bacteriochlorophylls in LH2 were almost unaffected, which indicated that the formation of the ∼423 nm peak was related to MPE-LH2 protein interaction. MPE did not bind to sites involved in the spectral tuning of BChls, but the conformation of integral LH2 was affected by MPE association, the alkaline stability of U-LH2 was lower than T-LH2, and the fluorescence intensity at 860 nm was decreased after MPE combination. Copyright © 2014 Elsevier B.V. All rights reserved.

Spectroscopic studies of two spectral variants of light-harvesting complex 2 (LH2) from the photosynthetic purple sulfur bacterium Allochromatium vinosum.

PubMed

Niedzwiedzki, Dariusz M; Bina, David; Picken, Nichola; Honkanen, Suvi; Blankenship, Robert E; Holten, Dewey; Cogdell, Richard J

2012-09-01

Two spectral forms of the peripheral light-harvesting complex (LH2) from the purple sulfur photosynthetic bacterium Allochromatium vinosum were purified and their photophysical properties characterized. The complexes contain bacteriochlorophyll a (BChl a) and multiple species of carotenoids. The composition of carotenoids depends on the light conditions applied during growth of the cultures. In addition, LH2 grown under high light has a noticeable split of the B800 absorption band. The influence of the change of carotenoid distribution as well as the spectral change of the excitonic absorption of the bacteriochlorophylls on the light-harvesting ability was studied using steady-state absorption, fluorescence and femtosecond time-resolved absorption at 77K. The results demonstrate that the change of the distribution of the carotenoids when cells were grown at low light adapts the absorptive properties of the complex to the light conditions and maintains maximum photon-capture performance. In addition, an explanation for the origin of the enigmatic split of the B800 absorption band is provided. This spectral splitting is also observed in LH2 complexes from other photosynthetic sulfur purple bacterial species. According to results obtained from transient absorption spectroscopy, the B800 band split originates from two spectral forms of the associated BChl a monomeric molecules bound within the same complex. Copyright © 2012 Elsevier B.V. All rights reserved.

Carotenoid radical cation formation in LH2 of purple bacteria: a quantum chemical study.

PubMed

Wormit, Michael; Dreuw, Andreas

2006-11-30

In LH2 complexes of Rhodobacter sphaeroides the formation of a carotenoid radical cation has recently been observed upon photoexcitation of the carotenoid S2 state. To shed more light onto the yet unknown molecular mechanism leading to carotenoid radical formation in LH2, the interactions between carotenoid and bacteriochlorophyll in LH2 are investigated by means of quantum chemical calculations for three different carotenoids--neurosporene, spheroidene, and spheroidenone--using time-dependent density functional theory. Crossings of the calculated potential energy curve of the electron transfer state with the bacteriochlorophyll Qx state and the carotenoid S1 and S2 states occur along an intermolecular distance coordinate for neurosporene and spheroidene, but for spheroidenone no crossing of the electron transfer state with the carotenoid S1 state could be found. By comparison with recent experiments where no formation of a spheroidenone radical cation has been observed, a molecular mechanism for carotenoid radical cation formation is proposed in which it is formed via a vibrationally excited carotenoid S1 or S*state. Arguments are given why the formation of the carotenoid radical cation does not proceed via the Qx, S2, or higher excited electron transfer states.

Mg2+ improves biomass production from soybean wastewater using purple non-sulfur bacteria.

PubMed

Wu, Pan; Zhang, Guangming; Li, Jianzheng

2015-02-01

Soybean wastewater was used to generate biomass resource by use of purple non-sulfur bacteria (PNSB). This study investigated the enhancement of PNSB cell accumulation in wastewater by Mg2+ under the light-anaerobic condition. Results showed that with the optimal Mg2+ dosage of 10 mg/L, biomass production was improved by 70% to 3630 mg/L, and biomass yield also was improved by 60%. Chemical Oxygen Demand (COD) removal reached above 86% and hydraulic retention time was shortened from 96 to 72 hr. The mechanism analysis indicated that Mg2+ could promote the content of bacteriochlorophyll in photosynthesis because Mg2+ is the bacteriochlorophyll active center, and thus improved adenosine triphosphate (ATP) production. An increase of ATP production enhanced the conversion of organic matter in wastewater into PNSB cell materials (biomass yield) and COD removal, leading to more biomass production. With 10 mg/L Mg2+, bacteriochlorophyll content and ATP production were improved by 60% and 33% respectively. Copyright © 2014. Published by Elsevier B.V.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arlt, T.; Penzkofer H.; Zinth, W.

The energetics of the primary electron donor (the special pair P) in reaction centers from Rhodopseudomonas viridis were modified by site-directed mutagenesis of histidine L168 to phenylalanine. This leads to the loss of a hydrogen bond between the amino acid side chain and the ring I acetyl carbonyl oxygen of the bacteriochlorophyll molecule BChl{sub LP}. As a result of the mutation, a 35 nm blue shift of the Q{sub y} band of the special pair and a decrease of 80 mV in the P/P{sup +} oxidation-reduction potential occur. Femtosecond spectroscopy revealed an acceleration of the first electron transfer step frommore » 3.5 ps in wild type to 1.1 ps in mutant. Analysis of change in the bacteriochlorophyll monomer (B) band of the mutant reaction centers showed strong bleaching. This is direct evidence that bacteriochlorophyll b is real intermediate in electron transfer. The changes in redox potential and time constants allow one to estimate the energetics in the wild-type and mutated reaction centers according to the Marcus electron transfer theory. 32 refs., 6 figs.« less

Vibronic coupling explains the ultrafast carotenoid-to-bacteriochlorophyll energy transfer in natural and artificial light harvesters

NASA Astrophysics Data System (ADS)

Perlík, Václav; Seibt, Joachim; Cranston, Laura J.; Cogdell, Richard J.; Lincoln, Craig N.; Savolainen, Janne; Šanda, František; Mančal, Tomáš; Hauer, Jürgen

2015-06-01

The initial energy transfer steps in photosynthesis occur on ultrafast timescales. We analyze the carotenoid to bacteriochlorophyll energy transfer in LH2 Marichromatium purpuratum as well as in an artificial light-harvesting dyad system by using transient grating and two-dimensional electronic spectroscopy with 10 fs time resolution. We find that Förster-type models reproduce the experimentally observed 60 fs transfer times, but overestimate coupling constants, which lead to a disagreement with both linear absorption and electronic 2D-spectra. We show that a vibronic model, which treats carotenoid vibrations on both electronic ground and excited states as part of the system's Hamiltonian, reproduces all measured quantities. Importantly, the vibronic model presented here can explain the fast energy transfer rates with only moderate coupling constants, which are in agreement with structure based calculations. Counterintuitively, the vibrational levels on the carotenoid electronic ground state play the central role in the excited state population transfer to bacteriochlorophyll; resonance between the donor-acceptor energy gap and the vibrational ground state energies is the physical basis of the ultrafast energy transfer rates in these systems.

15N photo-CIDNP MAS NMR analysis of reaction centers of Chloracidobacterium thermophilum.

PubMed

Zill, Jeremias C; He, Zhihui; Tank, Marcus; Ferlez, Bryan H; Canniffe, Daniel P; Lahav, Yigal; Bellstedt, Peter; Alia, A; Schapiro, Igor; Golbeck, John H; Bryant, Donald A; Matysik, Jörg

2018-03-30

Photochemically induced dynamic nuclear polarization (photo-CIDNP) has been observed in the homodimeric, type-1 photochemical reaction centers (RCs) of the acidobacterium, Chloracidobacterium (Cab.) thermophilum, by 15 N magic-angle spinning (MAS) solid-state NMR under continuous white-light illumination. Three light-induced emissive (negative) signals are detected. In the RCs of Cab. thermophilum, three types of (bacterio)chlorophylls have previously been identified: bacteriochlorophyll a (BChl a), chlorophyll a (Chl a), and Zn-bacteriochlorophyll a' (Zn-BChl a') (Tsukatani et al. in J Biol Chem 287:5720-5732, 2012). Based upon experimental and quantum chemical 15 N NMR data, we assign the observed signals to a Chl a cofactor. We exclude Zn-BChl because of its measured spectroscopic properties. We conclude that Chl a is the primary electron acceptor, which implies that the primary donor is most likely Zn-BChl a'. Chl a and 8 1 -OH Chl a have been shown to be the primary electron acceptors in green sulfur bacteria and heliobacteria, respectively, and thus a Chl a molecule serves this role in all known homodimeric type-1 RCs.

Terminal steps of bacteriochlorophyll a phytol formation in purple photosynthetic bacteria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shioi, Y.; Sasa, T.

1984-04-01

Four chemically different bacteriochlorophylls (Bchls) a esterified with geranylgeraniol, dihydrogeranyl-geraniol, tetrahydrogeraniol, and phytol have been detected by high-pressure liquid chromatography in cell extracts from Rhodopseudomonas sphaeroides and Chromatium vinosum. Bchl a containing phytol is the principal component, and the other three Bchls a comprise about 4% of the total Bchls a in stationary-phase cells of R. sphaeroides and C. vinosum. The high levels of the minor pigments occur in the beginning of Bchl a phytol formation, indicating that they are not degradation products, but intermediates of Bchl a phytol formation.

Construction of hybrid photosynthetic units using peripheral and core antennae from two different species of photosynthetic bacteria: detection of the energy transfer from bacteriochlorophyll a in LH2 to bacteriochlorophyll b in LH1.

PubMed

Fujii, Ritsuko; Shimonaka, Shozo; Uchida, Naoko; Gardiner, Alastair T; Cogdell, Richard J; Sugisaki, Mitsuru; Hashimoto, Hideki

2008-01-01

Typical purple bacterial photosynthetic units consist of supra-molecular arrays of peripheral (LH2) and core (LH1-RC) antenna complexes. Recent atomic force microscopy pictures of photosynthetic units in intact membranes have revealed that the architecture of these units is variable (Scheuring et al. (2005) Biochim Bhiophys Acta 1712:109-127). In this study, we describe methods for the construction of heterologous photosynthetic units in lipid-bilayers from mixtures of purified LH2 (from Rhodopseudomonas acidophila) and LH1-RC (from Rhodopseudomonas viridis) core complexes. The architecture of these reconstituted photosynthetic units can be varied by controlling ratio of added LH2 to core complexes. The arrangement of the complexes was visualized by electron-microscopy in combination with Fourier analysis. The regular trigonal array of the core complexes seen in the native photosynthetic membrane could be regenerated in the reconstituted membranes by temperature cycling. In the presence of added LH2 complexes, this trigonal symmetry was replaced with orthorhombic symmetry. The small lattice lengths for the latter suggest that the constituent unit of the orthorhombic lattice is the LH2. Fluorescence and fluorescence-excitation spectroscopy was applied to the set of the reconstituted membranes prepared with various proportions of LH2 to core complexes. Remarkably, even though the LH2 complexes contain bacteriochlorophyll a, and the core complexes contain bacteriochlorophyll b, it was possible to demonstrate energy transfer from LH2 to the core complexes. These experiments provide a first step along the path toward investigating how changing the architecture of purple bacterial photosynthetic units affects the overall efficiency of light-harvesting.

Structural Variations in Chlorosomes from Wild-Type and a bchQR Mutant of Chlorobaculum tepidum Revealed by Single-Molecule Spectroscopy.

PubMed

Günther, Lisa M; Löhner, Alexander; Reiher, Carolin; Kunsel, Tenzin; Jansen, Thomas L C; Tank, Marcus; Bryant, Donald A; Knoester, Jasper; Köhler, Jürgen

2018-06-21

Green sulfur bacteria can grow photosynthetically by absorbing only a few photons per bacteriochlorophyll molecule per day. They contain chlorosomes, perhaps the most efficient light-harvesting antenna system found in photosynthetic organisms. Chlorosomes contain supramolecular structures comprising hundreds of thousands of bacteriochlorophyll molecules, which are properly positioned with respect to one another solely by self-assembly and not by using a protein scaffold as a template for directing the mutual arrangement of the monomers. These two features-high efficiency and self-assembly-have attracted considerable attention for developing light-harvesting systems for artificial photosynthesis. However, reflecting the heterogeneity of the natural system, detailed structural information at atomic resolution of the molecular aggregates is not yet available. Here, we compare the results for chlorosomes from the wild type and two mutants of Chlorobaculum tepidum obtained by polarization-resolved, single-particle fluorescence-excitation spectroscopy and theoretical modeling with results previously obtained from nuclear-magnetic resonance spectroscopy and cryo-electron microscopy. Only the combination of information obtained from all of these techniques allows for an unambiguous description of the molecular packing of bacteriochlorophylls within chlorosomes. In contrast to some suggestions in the literature, we find that, for the chlorosomes from the wild type as well as for those from mutants, the dominant secondary structural element features tubular symmetry following a very similar construction principle. Moreover, the results suggest that the various options for methylation of the bacteriochlorophyll molecules, which are a primary source of the structural (and spectral) heterogeneity of wild-type chlorosome samples, are exploited by nature to achieve improved spectral coverage at the level of individual chlorosomes.

Vibronic coupling explains the ultrafast carotenoid-to-bacteriochlorophyll energy transfer in natural and artificial light harvesters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perlík, Václav; Seibt, Joachim; Šanda, František

The initial energy transfer steps in photosynthesis occur on ultrafast timescales. We analyze the carotenoid to bacteriochlorophyll energy transfer in LH2 Marichromatium purpuratum as well as in an artificial light-harvesting dyad system by using transient grating and two-dimensional electronic spectroscopy with 10 fs time resolution. We find that Förster-type models reproduce the experimentally observed 60 fs transfer times, but overestimate coupling constants, which lead to a disagreement with both linear absorption and electronic 2D-spectra. We show that a vibronic model, which treats carotenoid vibrations on both electronic ground and excited states as part of the system’s Hamiltonian, reproduces all measuredmore » quantities. Importantly, the vibronic model presented here can explain the fast energy transfer rates with only moderate coupling constants, which are in agreement with structure based calculations. Counterintuitively, the vibrational levels on the carotenoid electronic ground state play the central role in the excited state population transfer to bacteriochlorophyll; resonance between the donor-acceptor energy gap and the vibrational ground state energies is the physical basis of the ultrafast energy transfer rates in these systems.« less

Cultivation of Aquincola tertiaricarbonis L108 on the fuel oxygenate intermediate tert-butyl alcohol induces aerobic anoxygenic photosynthesis at extremely low feeding rates.

PubMed

Rohwerder, Thore; Müller, Roland H; Weichler, M Teresa; Schuster, Judith; Hübschmann, Thomas; Müller, Susann; Harms, Hauke

2013-10-01

Aerobic anoxygenic photosynthesis (AAP) is found in an increasing number of proteobacterial strains thriving in ecosystems ranging from extremely oligotrophic to eutrophic. Here, we have investigated whether the fuel oxygenate-degrading betaproteobacterium Aquincola tertiaricarbonis L108 can use AAP to compensate kinetic limitations at low heterotrophic substrate fluxes. In a fermenter experiment with complete biomass retention and also during chemostat cultivation, strain L108 was challenged with extremely low substrate feeding rates of tert-butyl alcohol (TBA), an intermediate of methyl tert-butyl ether (MTBE). Interestingly, formation of photosynthetic pigments, identified as bacteriochlorophyll a and spirilloxanthin, was only induced in growing cells at TBA feeding rates less than or equal to maintenance requirements observed under energy excess conditions. Growth continued at rates between 0.001 and 0.002 h(-1) even when the TBA feed was decreased to values close to 30 % of this maintenance rate. Partial sequencing of genomic DNA of strain L108 revealed a bacteriochlorophyll synthesis gene cluster (bchFNBHL) and photosynthesis regulator genes (ppsR and ppaA) typically found in AAP and other photosynthetic proteobacteria. The usage of light as auxiliary energy source enabling evolution of efficient degradation pathways for kinetically limited heterotrophic substrates and for lowering the threshold substrate concentration Smin at which growth becomes zero is discussed.

Photodynamic inactivation of Staphylococcus aureus and Escherichia coli using a new bacteriochlorin as photosensitizer

NASA Astrophysics Data System (ADS)

Barboza, Diego D.; Martins, Laura C. A.; Corrêa, Thaila Quatrini; Geralde, Mariana Carreira; Pratavieira, Sebastião.; de Oliveira, Kleber Thiago; Uliana, Marciana P.; de Souza, Clovis W.

2018-02-01

In this study, we used bacteriochlorin as a photosensitizer, characterized by their low toxicity in the absence of light, presenting absorption around 780 nm, with the objective of evaluating their photodynamic inactivation potential on Staphylococcus aureus and Escherichia coli. Bacteriochlorins were synthesized from the extraction of bacteriochlorophylls from non-sulfurous purple bacteria and were then converted to bacteriochlorins. S. aureus and E. coli microorganisms were used in the planktonic and biofilm forms. For the formation of biofilms on glass coverslips, suspensions of the microorganisms at the concentration of 106 CFU/mL were inoculated into each well of a microplate. There was an exchange of culture medium (Tryptic Soy Broth - TSB) every 24 hours for 7 days, pre-washing the coverslips with a phosphate-buffered saline (PBS), to ensure that only adhered microorganisms were grown and then incubated at (36 +/- 1)°C between the middle exchanges. After 7 days of induction, the biofilm was mature, like those normally found in nature, and then it was applied different treatments (light doses associated with FS concentrations). At the end of the treatment, the coverslips underwent an ultrasonic disintegration, and the quantitative evaluation of viable cells was performed by plate counting using the plate method in Tryptic Soy Agar (TSA), incubating at (36 +/- 1)°C for 24 hours. The results showed that the PDI for E. coli was not successful even when it was more susceptible to the planktonic form, whereas for S. aureus the results showed a reduction in cell viability 6 logs for the planktonic forms, but lower to 1 log in biofilms. Therefore, novel studies using bacteriochlorins and surfactants will be performed to verify the potential of this alternative treatment method.

Raman spectrum of bacteriochlorophyll a in the S1 state

NASA Astrophysics Data System (ADS)

Nishizawa, Ei-ichi; Hashimoto, Hideki; Koyama, Yasushi

1991-07-01

The S 1 Raman spectrum of bacteriochlorophyll a is reported for the first time. A one-color experiment using the 351 nm picosecond pulses (duration 50 ps and repetition 1 kHz) for tetrahydrofuran solution detected a transient species, which showed distinct Raman lines at 1567, 1409 and 1320 cm -1 and weak profiles around 1169, 1092, 1051 and 794 cm -1. The other one-color experiment using the 355 nm nanosecond pulses (duration 12 ns and repetition 10 Hz) detected the T 1 species reported previously showing Raman lines at 1578 and 1330 cm -1. Thus, the newly identified transient species, which was pumped and probed within 50 ps, is assigned to S 1.

Excitation energy transfer from the bacteriochlorophyll Soret band to carotenoids in the LH2 light-harvesting complex from Ectothiorhodospira haloalkaliphila is negligible.

PubMed

Razjivin, A P; Lukashev, E P; Kompanets, V O; Kozlovsky, V S; Ashikhmin, A A; Chekalin, S V; Moskalenko, A A; Paschenko, V Z

2017-09-01

Pathways of intramolecular conversion and intermolecular electronic excitation energy transfer (EET) in the photosynthetic apparatus of purple bacteria remain subject to debate. Here we experimentally tested the possibility of EET from the bacteriochlorophyll (BChl) Soret band to the singlet S 2 level of carotenoids using femtosecond pump-probe measurements and steady-state fluorescence excitation and absorption measurements in the near-ultraviolet and visible spectral ranges. The efficiency of EET from the Soret band of BChl to S 2 of the carotenoids in light-harvesting complex LH2 from the purple bacterium Ectothiorhodospira haloalkaliphila appeared not to exceed a few percent.

Synthesis and properties of new chlorin and bacteriochlorin photosensitizers

NASA Astrophysics Data System (ADS)

Mironov, Andrei F.

1996-01-01

A series of novel sensitizers, which absorb in the range of 660 - 820 nm, derived from natural occurring chlorophyll and bacteriochlorophyll was synthesized. Biomass of blue-green algae Spirulina platensis was used to prepare chlorophyll a derivatives, and biomass of purple bacteria Rhodobacter capsulatus was applied for preparation of bacteriochlorophyll a. The influence of different substituents on spectral characteristics and the amphipility of the sensitizer was investigated. The route for the synthesis of porphyrin macrocycle with the spacer that bears the isothiocyanate group capable for binding with proteins was proposed. Photophysical properties of chlorin p6, purpurin 18 and their esters in different solvents are investigated. Accumulation of two chlorins in the model Erlich tumor was studied.

Carotenoid-bacteriochlorophyll energy transfer in LH2 complexes studied with 10-fs time resolution.

PubMed

Polli, Dario; Cerullo, Giulio; Lanzani, Guglielmo; De Silvestri, Sandro; Hashimoto, Hideki; Cogdell, Richard J

2006-04-01

In this report, we present a study of carotenoid-bacteriochlorophyll energy transfer processes in two peripheral light-harvesting complexes (known as LH2) from purple bacteria. We use transient absorption spectroscopy with approximately 10 fs temporal resolution, which is necessary to observe the very fast energy relaxation processes. By comparing excited-state dynamics of the carotenoids in organic solvents and inside the LH2 complexes, it has been possible to directly evaluate their energy transfer efficiency to the bacteriochlorophylls. In the case of okenone in the LH2 complex from Chromatium purpuratum, we obtained an energy transfer efficiency of etaET2=63+/-2.5% from the optically active excited state (S2) and etaET1=61+/-2% from the optically dark state (S1); for rhodopin glucoside contained in the LH2 complex from Rhodopseudomonas acidophila these values become etaET2=49.5+/-3.5% and etaET1=5.1+/-1%. The measurements also enabled us to observe vibrational energy relaxation in the carotenoids' S1 state and real-time collective vibrational coherence initiated by the ultrashort pump pulses. Our results are important for understanding the dynamics of early events of photosynthesis and relating it to the structural arrangement of the chromophores.

Localisation and origin of the bacteriochlorophyll-derived photosensitizer in the retina of the deep-sea dragon fish Malacosteus niger

PubMed Central

Douglas, Ronald H.; Genner, Martin J.; Hudson, Alan G.; Partridge, Julian C.; Wagner, Hans-Joachim

2016-01-01

Most deep-sea fish have a single visual pigment maximally sensitive at short wavelengths, approximately matching the spectrum of both downwelling sunlight and bioluminescence. However, Malcosteus niger produces far-red bioluminescence and its longwave retinal sensitivity is enhanced by red-shifted visual pigments, a longwave reflecting tapetum and, uniquely, a bacteriochlorophyll-derived photosensitizer. The origin of the photosensitizer, however, remains unclear. We investigated whether the bacteriochlorophyll was produced by endosymbiotic bacteria within unusual structures adjacent to the photoreceptors that had previously been described in this species. However, microscopy, elemental analysis and SYTOX green staining provided no evidence for such localised retinal bacteria, instead the photosensitizer was shown to be distributed throughout the retina. Furthermore, comparison of mRNA from the retina of Malacosteus to that of the closely related Pachystomias microdon (which does not contain a bacterichlorophyll-derived photosensitzer) revealed no genes of bacterial origin that were specifically up-regulated in Malacosteus. Instead up-regulated Malacosteus genes were associated with photosensitivity and may relate to its unique visual ecology and the chlorophyll-based visual system. We also suggest that the unusual longwave-reflecting, astaxanthin-based, tapetum of Malacosteus may protect the retina from the potential cytotoxicity of such a system. PMID:27996027

[Influence of LDAO on the conformation and release of bacteriochlorophyll of peripheral light-harvesting complex (LH2) from Rhodobacter azotoformans].

PubMed

Zhao, Gen-gui; Dong, Yan-min; Yang, Su-ping; Jiao, Nian-zhi; Qu, Yin-bo

2010-10-01

The aim of this study is to reveal the interaction relationships between lauryl dimethylamine N-oxide (LDAO) and peripheral light-harvesting complex (LH2) as well as the influence of LDAO on structure and function of LH2. In the present work, the effects of LDAO on the conformation and release processes of bacteriochlorophyll (BChl) of LH2 when incubated under different temperature and pH in the presence and absence of LDAO were investigated by spectroscopy. The results indicated that (1) the presence of LDAO resulted in alterations in the conformation, alpha-helix content, and spectra of Tyr and B850 band of LH2 at room temperature and pH 8.0. Moreover, energy transfer efficiency of LH2 was enhanced markedly in the presence of LDAO. (2) At 60 degrees C, both the B800 and B850 band of LH2 were released and transited into free BChl at pH 8.0. However, the release rates of bacteriochlorophylls of B800 and B850 band from LH2 were slowed down and the release processes were changed when incubated in the presence of LDAO. Hence, the stability of LH2 was improved in the presence of LDAO. (3) The accelerated release processes of bacteriochlorophylls of B800 and B850 band of LH2 were induced to transform into bacteriopheophytin (BPhe) and free BChl by LDAO in strong acid and strong alkalic solution at room temperature. However, the kinetic patterns of the B800 and B850 band were remarkably different. The release and self-assemble processes of B850 in LH2 were observed in strong acid solution without LDAO. Therefore, the different release behaviors of B800 and B850 of LH2 are induced by LDAO under different extreme environmental conditions.

Ultrafast time-resolved carotenoid to-bacteriochlorophyll energy transfer in LH2 complexes from photosynthetic bacteria.

PubMed

Cong, Hong; Niedzwiedzki, Dariusz M; Gibson, George N; LaFountain, Amy M; Kelsh, Rhiannon M; Gardiner, Alastair T; Cogdell, Richard J; Frank, Harry A

2008-08-28

Steady-state and ultrafast time-resolved optical spectroscopic investigations have been carried out at 293 and 10 K on LH2 pigment-protein complexes isolated from three different strains of photosynthetic bacteria: Rhodobacter (Rb.) sphaeroides G1C, Rb. sphaeroides 2.4.1 (anaerobically and aerobically grown), and Rps. acidophila 10050. The LH2 complexes obtained from these strains contain the carotenoids, neurosporene, spheroidene, spheroidenone, and rhodopin glucoside, respectively. These molecules have a systematically increasing number of pi-electron conjugated carbon-carbon double bonds. Steady-state absorption and fluorescence excitation experiments have revealed that the total efficiency of energy transfer from the carotenoids to bacteriochlorophyll is independent of temperature and nearly constant at approximately 90% for the LH2 complexes containing neurosporene, spheroidene, spheroidenone, but drops to approximately 53% for the complex containing rhodopin glucoside. Ultrafast transient absorption spectra in the near-infrared (NIR) region of the purified carotenoids in solution have revealed the energies of the S1 (2(1)Ag-)-->S2 (1(1)Bu+) excited-state transitions which, when subtracted from the energies of the S0 (1(1)Ag-)-->S2 (1(1)Bu+) transitions determined by steady-state absorption measurements, give precise values for the positions of the S1 (2(1)Ag-) states of the carotenoids. Global fitting of the ultrafast spectral and temporal data sets have revealed the dynamics of the pathways of de-excitation of the carotenoid excited states. The pathways include energy transfer to bacteriochlorophyll, population of the so-called S* state of the carotenoids, and formation of carotenoid radical cations (Car*+). The investigation has found that excitation energy transfer to bacteriochlorophyll is partitioned through the S1 (1(1)Ag-), S2 (1(1)Bu+), and S* states of the different carotenoids to varying degrees. This is understood through a consideration of the energies of the states and the spectral profiles of the molecules. A significant finding is that, due to the low S1 (2(1)Ag-) energy of rhodopin glucoside, energy transfer from this state to the bacteriochlorophylls is significantly less probable compared to the other complexes. This work resolves a long-standing question regarding the cause of the precipitous drop in energy transfer efficiency when the extent of pi-electron conjugation of the carotenoid is extended from ten to eleven conjugated carbon-carbon double bonds in LH2 complexes from purple photosynthetic bacteria.

Singlet-triplet fission of carotenoid excitation in light-harvesting LH2 complexes of purple phototrophic bacteria.

PubMed

Klenina, I B; Makhneva, Z K; Moskalenko, A A; Gudkov, N D; Bolshakov, M A; Pavlova, E A; Proskuryakov, I I

2014-03-01

The current generally accepted structure of light-harvesting LH2 complexes from purple phototrophic bacteria conflicts with the observation of singlet-triplet carotenoid excitation fission in these complexes. In LH2 complexes from the purple bacterium Allochromatium minutissimum, a drop in the efficiency of carotenoid triplet generation is demonstrated, which correlates with the extent of selective photooxidation of bacteriochlorophylls absorbing at ~850 nm. We conclude that singlet-triplet fission of carotenoid excitation proceeds with participation of these excitonically coupled bacteriochlorophylls. In the framework of the proposed mechanism, the contradiction between LH2 structure and photophysical properties of carotenoids is eliminated. The possibility of singlet-triplet excitation fission involving a third mediator molecule was not considered earlier.

Second-generation photosensitizers based on natural chlorines and bacteriochlorines

NASA Astrophysics Data System (ADS)

Mironov, Andrei F.

1996-01-01

New sensitizers for photodynamic therapy were synthesized on the base of biologically generated chlorins and bacteriochlorins. Derivatives of chlorophyll a and bacteriochlorophyll were prepared from the biomass of blue-green algae Spirulina Platensis and purple bacteria Rhodobacter Capsulatus, generated using specially designed photobioreactor. The strategy for chemical transformation of natural chlorophylls and bacteriochlorophyll has been discussed. Purpurin 18 and its dihydroanalogue bacteriopurpurin were chosen as the key intermediates. Modifications of peripheral substituents, such as introducing the new functional groups, hydrogenation of the B-pyrrolic ring, and insertion of amino acid residues gave the series of novel sensitizers, including water soluble chlorin p6 analogues, and derivatives with graded amphiphility for the studies of tumor accumulation in the malignant tissues.

Function of membrane protein in silica nanopores: incorporation of photosynthetic light-harvesting protein LH2 into FSM.

PubMed

Oda, Ippei; Hirata, Kotaro; Watanabe, Syoko; Shibata, Yutaka; Kajino, Tsutomu; Fukushima, Yoshiaki; Iwai, Satoshi; Itoh, Shigeru

2006-01-26

A high amount of functional membrane protein complex was introduced into a folded-sheet silica mesoporous material (FSM) that has nanometer-size pores of honeycomb-like hexagonal cylindrical structure inside. The photosynthetic light-harvesting complex LH2, which is a typical membrane protein, has a cylindrical structure of 7.3 nm diameter and contains 27 bacteriochlorophyll a and nine carotenoid molecules. The complex captures light energy in the anoxygenic thermophilic purple photosynthetic bacterium Thermochromatium tepidum. The amount of LH2 adsorbed to FSM was determined optically and by the adsorption isotherms of N2. The FSM compounds with internal pore diameters of 7.9 and 2.7 nm adsorbed LH2 at 1.11 and 0.24 mg/mg FSM, respectively, suggesting the high specific affinity of LH2 to the interior of the hydrophobic nanopores with a diameter of 7.9 nm. The LH2 adsorbed to FSM showed almost intact absorption bands of bacteriochlorophylls, and was fully active in the capture and transfer of excitation energy. The LH2 complex inside the FSM showed increased heat stability of the exciton-type absorption band of bacteriochlorophylls (B850), suggesting higher circular symmetry. The environment inside the hydrophobic silica nanopores can be a new matrix for the membrane proteins to reveal their functions. The silica-membrane protein adduct will be useful for the construction of new probes and reaction systems.

Nonpigmented and Bacteriochlorophyll-Containing Bradyrhizobia Isolated from Aeschynomene indica

PubMed Central

van Berkum, P.; Tully, R. E.; Keister, D. L.

1995-01-01

The legume genus Aeschynomene is unusual, since many species develop stem nodules and the bradyrhizobia isolated from these nodules produce bacteriochlorophyll (Bchl). Evidence is presented that the bradyrhizobia of Aeschynomene indica have wide distribution throughout the world, since A. indica was nodulated when grown in 58 soils collected in 14 different countries. Only 38 of 79 isolates tested synthesized Bchl and carotenoids during heterotrophic growth. Nine isolates produced Bchl constitutively, and cultures were pigmented after growth in the dark. The other isolates required light for Bchl production. The DNA from seven pigmented and three nonpigmented bradyrhizobia hybridized with a DNA probe containing the genes for the photosynthetic apparatus of Rhodobacter capsulatus, but DNA from two other nonpigmented isolates did not hybridize with this probe. A relationship between pigmentation in culture and symbiotic phenotype was not evident, since bradyrhizobia of both Bchl phenotypes nodulated stems of A. indica and formed nitrogen-fixing symbioses. Several isolates, which were ineffective on A. indica, probably do belong to the proposed cross-inoculation group 3 (D. Alazard, Appl. Environ. Microbiol. 50:732-734, 1985), since they did not nodulate Aeschynomene americana or Macroptilium atropurpureum. Since it has been suggested that extant rhizobia arose from photosynthetic ancestors (J. I. Sprent, p. 45-54, in P. M. Gresshoff, L. E. Roth, G. Stacey, and W. E. Newton, ed., Nitrogen Fixation: Achievements and Objectives, 1990), we propose that the nonpigmented isolates may represent an extant lineage of an intermediate evolutionary stage. PMID:16534933

Two-photon excitation spectroscopy of carotenoid-containing and carotenoid-depleted LH2 complexes from purple bacteria.

PubMed

Stepanenko, Ilya; Kompanetz, Viktor; Makhneva, Zoya; Chekalin, Sergey; Moskalenko, Andrei; Razjivin, Andrei

2009-08-27

We applied two-photon fluorescence excitation spectroscopy to LH2 complex from purple bacteria Allochromatium minutissimum and Rhodobacter sphaeroides . Bacteriochlorophyll fluorescence was measured under two-photon excitation of the samples within the 1200-1500 nm region. Spectra were obtained for both carotenoid-containing and -depleted complexes of each bacterium to allow their direct comparison. The depletion of carotenoids did not alter the two-photon excitation spectra of either bacteria. The spectra featured a wide excitation band around 1350 nm (2x675 nm, 14,800 cm(-1)) which strongly resembled two-photon fluorescence excitation spectra of similar complexes published by other authors. We consider obtained experimental data to be evidence of direct two-photon excitation of bacteriochlorophyll excitonic states in this spectral region.

Electron-Transfer Secondary Reaction Matrices for MALDI MS Analysis of Bacteriochlorophyll a in Rhodobacter sphaeroides and Its Zinc and Copper Analogue Pigments

NASA Astrophysics Data System (ADS)

Calvano, Cosima Damiana; Ventura, Giovanni; Trotta, Massimo; Bianco, Giuliana; Cataldi, Tommaso R. I.; Palmisano, Francesco

2017-01-01

Bacteriochlorophyll a ( BChl a), a photosynthetic pigment performing the same functions of chlorophylls in plants, features a bacteriochlorin macrocycle ring (18 π electrons) with two reduced pyrrole rings along with a hydrophobic terpenoid side chain (i.e., the phytol residue). Chlorophylls analysis by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) is not so straightforward since pheophytinization (i.e., release of the central metal ion) and cleavage of the phytol-ester linkage are invariably observed by employing protonating matrices such as 2,5-dihydroxybenzoic acid, sinapinic acid, and α-cyano-4-hydroxycinnamic acid. Using BChl a from Rhodobacter sphaeroides R26 strain as a model system, different electron-transfer (ET) secondary reaction matrices, leading to the formation of almost stable radical ions in both positive ([M]+•) and negative ([M]-•) ionization modes at m/z 910.55, were evaluated. Compared with ET matrices such as trans-2-[3-(4-t-butyl-phenyl)-2-methyl-2-propenylidene]malononitrile (DCTB), 2,2':5',2''-terthiophene (TER), anthracene (ANT), and 9,10-diphenylanthracene (DP-ANT), 1,5-diaminonaphthalene (DAN) was found to provide the highest ionization yield with a negligible fragmentation. DAN also displayed excellent ionization properties for two metal ion-substituted bacteriochlorophylls, (i.e., Zn- and Cu-BChl a at m/z 950.49 and 949.49), respectively. MALDI MS/MS of both radical charged molecular species provide complementary information, thus making analyte identification more straightforward.

Presence of exclusively bacteriochlorophyll-c containing substrain in the culture of green sulfur photosynthetic bacterium Chlorobium vibrioforme strain NCIB 8327 producing bacteriochlorophyll-d.

PubMed

Saga, Yoshitaka; Oh-oka, Hirozo; Hayashi, Takashi; Tamiaki, Hitoshi

2003-12-01

The light-dependent composition change of light harvesting bacteriochlorophyll(BChl)s in the present culture of a green sulfur photosynthetic bacterium Chlorobium (Chl.) vibrioforme f. sp. thiosulfatophilum strain NCIB 8327 was investigated by visible absorption spectroscopy and HPLC analyses. When the culture was repeatedly grown in liquid media under a low light condition, both the Soret and Qy absorption bands of the in vivo spectrum were shifted to longer wavelengths. Analysis of the extracted pigments by HPLC revealed that the ratio of the amount of BChl-c to that of BChl-d molecules gradually increased during repeated cultivation. In contrast, when the culture grown under a low light intensity was transferred to a high light condition and continued to be grown, the absorption bands were shifted to shorter wavelengths and the ratio of BChls-c/d decreased finally to the almost original value. Colonies were prepared on solid agar media from the liquid culture containing both BChls-c and d, which was grown under a low light intensity. Each colony obtained was found to contain either BChl-c or d, but not both of them. Two types of cells isolated in this study were derived from the same clone, judged from their genetic analyses. The variation of pigment composition in our liquid culture observed here could be ascribed to the difference of growth rates between two substrains containing BChl-c and BChl-d, respectively, depending on light conditions.

The structure and thermal motion of the B800-850 LH2 complex from Rps.acidophila at 2.0A resolution and 100K: new structural features and functionally relevant motions.

PubMed

Papiz, Miroslav Z; Prince, Steve M; Howard, Tina; Cogdell, Richard J; Isaacs, Neil W

2003-03-07

The structure at 100K of integral membrane light-harvesting complex II (LH2) from Rhodopseudomonas acidophila strain 10050 has been refined to 2.0A resolution. The electron density has been significantly improved, compared to the 2.5A resolution map, by high resolution data, cryo-cooling and translation, libration, screw (TLS) refinement. The electron density reveals a second carotenoid molecule, the last five C-terminal residues of the alpha-chain and a carboxy modified alpha-Met1 which forms the ligand of the B800 bacteriochlorophyll. TLS refinement has enabled the characterisation of displacements between molecules in the complex. B850 bacteriochlorophyll molecules are arranged in a ring of 18 pigments composed of nine approximate dimers. These pigments are strongly coupled and at their equilibrium positions the excited state dipole interaction energies, within and between dimers, are approximately 370cm(-1) and 280cm(-1), respectively. This difference in coupling energy is similar in magnitude to changes in interaction energies arising from the pigment displacements described by TLS tensors. The displacements appear to be non-random in nature and appear to be designed to optimise the modulation of pigment energy interactions. This is the first time that LH2 pigment displacements have been quantified experimentally. The calculated energy changes indicate that there may be significant contributions to inter-pigment energy interactions from molecular displacements and these may be of importance to photosynthetic energy transfer.

Discrepancy between experimental and theoretical excitation transfer rates in LH2 bacteriochlorophyll-protein complexes of purple bacteria.

PubMed

Borisov, A Y

2008-02-01

Discrepancy is revealed between the values of excitation transfer times measured experimentally, and those calculated, for the atomic structures of B800 --> B850 bacteriochlorophylls within the LH2 light-harvesting pigment-protein complex of the purple bacterium Rhodopseudomonas acidophila. The value 2.9-3.2 ps for the B800 --> B850 excitation transfer, calculated on the basis of atomic structure of LH2, is about 4-times longer than that measured for this bacterium (0.7 ps). This discrepancy appears common in at least two purple bacteria. Possible sources responsible for this discrepancy are discussed. It may either signify some drawback/s/ in our notions about the precise in vivo structure of LH2 complexes, for example, possible changes of LH2 structure during crystallization, or it may reflect our ignorance of some mechanisms involved in excitation migration.

Triplet excited state spectra and dynamics of carotenoids from the thermophilic purple photosynthetic bacterium Thermochromatium tepidum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niedzwiedzki, Dariusz; Kobayashi, Masayuki; Blankenship, R. E.

Light-harvesting complex 2 from the anoxygenic phototrophic purple bacterium Thermochromatium tepidum was purified and studied by steady-state absorption, fluorescence and flash photolysis spectroscopy. Steady-state absorption and fluorescence measurements show that carotenoids play a negligible role as supportive energy donors and transfer excitation to bacteriochlorophyll-a with low energy transfer efficiency of ~30%. HPLC analysis determined that the dominant carotenoids in the complex are rhodopin and spirilloxanthin. Carotenoid excited triplet state formation upon direct (carotenoid) or indirect (bacteriochlorophyll-a Q{sub x} band) excitation shows that carotenoid triplets are mostly localized on spirilloxanthin. In addition, no triplet excitation transfer between carotenoids was observed. Suchmore » specific carotenoid composition and spectroscopic results strongly suggest that this organism optimized carotenoid composition in the light-harvesting complex 2 in order to maximize photoprotective capabilities of carotenoids but subsequently drastically suppressed their supporting role in light-harvesting process.« less

Photosynthesis Is Widely Distributed among Proteobacteria as Demonstrated by the Phylogeny of PufLM Reaction Center Proteins

PubMed Central

Imhoff, Johannes F.; Rahn, Tanja; Künzel, Sven; Neulinger, Sven C.

2018-01-01

Two different photosystems for performing bacteriochlorophyll-mediated photosynthetic energy conversion are employed in different bacterial phyla. Those bacteria employing a photosystem II type of photosynthetic apparatus include the phototrophic purple bacteria (Proteobacteria), Gemmatimonas and Chloroflexus with their photosynthetic relatives. The proteins of the photosynthetic reaction center PufL and PufM are essential components and are common to all bacteria with a type-II photosynthetic apparatus, including the anaerobic as well as the aerobic phototrophic Proteobacteria. Therefore, PufL and PufM proteins and their genes are perfect tools to evaluate the phylogeny of the photosynthetic apparatus and to study the diversity of the bacteria employing this photosystem in nature. Almost complete pufLM gene sequences and the derived protein sequences from 152 type strains and 45 additional strains of phototrophic Proteobacteria employing photosystem II were compared. The results give interesting and comprehensive insights into the phylogeny of the photosynthetic apparatus and clearly define Chromatiales, Rhodobacterales, Sphingomonadales as major groups distinct from other Alphaproteobacteria, from Betaproteobacteria and from Caulobacterales (Brevundimonas subvibrioides). A special relationship exists between the PufLM sequences of those bacteria employing bacteriochlorophyll b instead of bacteriochlorophyll a. A clear phylogenetic association of aerobic phototrophic purple bacteria to anaerobic purple bacteria according to their PufLM sequences is demonstrated indicating multiple evolutionary lines from anaerobic to aerobic phototrophic purple bacteria. The impact of pufLM gene sequences for studies on the environmental diversity of phototrophic bacteria is discussed and the possibility of their identification on the species level in environmental samples is pointed out. PMID:29472894

Ultrafast Energy Flow and Equilibration Dynamics in Photosynthetic Light-Harvesting Complexes

NASA Astrophysics Data System (ADS)

Maiuri, Margherita; Lüer, Larry; Henry, Sarah; Carey, Anne-Marie; Cogdell, Richard J.; Cerullo, Giulio; Polli, Dario

We disentangle various energy transfer pathways in the bacterio-chlorophyll excitation cascade from LH2 to LH1 in Chromatium vinosum grown under high-light or low-light illumination using tunable narrowband selective excitation and broadband infrared probing.

Microbial Mat Communities along an Oxygen Gradient in a Perennially Ice-Covered Antarctic Lake

PubMed Central

Hawes, Ian; Mackey, Tyler J.; Krusor, Megan; Doran, Peter T.; Sumner, Dawn Y.; Eisen, Jonathan A.; Hillman, Colin; Goroncy, Alexander K.

2015-01-01

Lake Fryxell is a perennially ice-covered lake in the McMurdo Dry Valleys, Antarctica, with a sharp oxycline in a water column that is density stabilized by a gradient in salt concentration. Dissolved oxygen falls from 20 mg liter−1 to undetectable over one vertical meter from 8.9- to 9.9-m depth. We provide the first description of the benthic mat community that falls within this oxygen gradient on the sloping floor of the lake, using a combination of micro- and macroscopic morphological descriptions, pigment analysis, and 16S rRNA gene bacterial community analysis. Our work focused on three macroscopic mat morphologies that were associated with different parts of the oxygen gradient: (i) “cuspate pinnacles” in the upper hyperoxic zone, which displayed complex topography and were dominated by phycoerythrin-rich cyanobacteria attributable to the genus Leptolyngbya and a diverse but sparse assemblage of pennate diatoms; (ii) a less topographically complex “ridge-pit” mat located immediately above the oxic-anoxic transition containing Leptolyngbya and an increasing abundance of diatoms; and (iii) flat prostrate mats in the upper anoxic zone, dominated by a green cyanobacterium phylogenetically identified as Phormidium pseudopriestleyi and a single diatom, Diadesmis contenta. Zonation of bacteria was by lake depth and by depth into individual mats. Deeper mats had higher abundances of bacteriochlorophylls and anoxygenic phototrophs, including Chlorobi and Chloroflexi. This suggests that microbial communities form assemblages specific to niche-like locations. Mat morphologies, underpinned by cyanobacterial and diatom composition, are the result of local habitat conditions likely defined by irradiance and oxygen and sulfide concentrations. PMID:26567300

How nature designs light-harvesting antenna systems: design principles and functional realization in chlorophototrophic prokaryotes

NASA Astrophysics Data System (ADS)

Bryant, Donald A.; Canniffe, Daniel P.

2018-02-01

Chlorophyll-based phototrophs, or chlorophototrophs, convert light energy into stored chemical potential energy using two types of photochemical reaction center (RC), denoted type-1 and type-2. After excitation with light, a so-called special pair of chlorophylls in the RC is oxidized, and an acceptor is reduced. To ensure that RCs function at maximal rates in diffuse and variable light conditions, chlorophototrophs have independently evolved diverse light-harvesting antenna systems to rapidly and efficiently transfer that energy to the RCs. Energy transfer between weakly coupled chromophores is generally believed to proceed by resonance energy transfer, a dipole-induced-dipole process that was initially described theoretically by Förster. Nature principally optimizes three parameters in antenna systems: the distance separating the donor and acceptor chromophores, the relative orientations of those chromophores, and the spectral overlap between the donor and the acceptor chromophores. However, there are other important biological parameters that nature has optimized, and some common themes emerge from comparisons of different antenna systems. This tutorial considers structural and functional characteristics of three fundamentally different light-harvesting antenna systems of chlorophotrophic bacteria: phycobilisomes of cyanobacteria, the light-harvesting complexes (LH1 and LH2) of purple bacteria, and chlorosomes of green bacteria. Phycobilisomes are generally considered to represent an antenna system in which the chromophores are weakly coupled, while the strongly coupled bacteriochlorophyll molecules in LH1 and LH2 are strongly coupled and are better described by exciton theory. Chlorosomes can contain up to 250 000 bacteriochlorophyll molecules, which are very strongly coupled and form supramolecular, nanotubular arrays. The general and specific principles that have been optimized by natural selection during the evolution of these diverse light-harvesting antenna systems are discussed.

Optimizing multi-step B-side charge separation in photosynthetic reaction centers from Rhodobacter capsulatus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faries, Kaitlyn M.; Kressel, Lucas L.; Dylla, Nicholas P.

Using high-throughput methods for mutagenesis, protein isolation and charge-separation functionality, we have assayed 40 Rhodobacter capsulatus reaction center (RC) mutants for their P+ QB- yield (P is a dimer of bacteriochlorophylls and Q is a ubiquinone) as produced using the normally inactive B-side cofactors BB and HB (where B is a bacteriochlorophyll and H is a bacteriopheophytin). Two sets of mutants explore all possible residues at M131 (M polypeptide, native residue Val near HB) in tandem with either a fixed His or a fixed Asn at L181 (L polypeptide, native residue Phe near BB). A third set of mutants exploresmore » all possible residues at L181 with a fixed Glu at M131 that can form a hydrogen bond to HB. For each set of mutants, the results of a rapid millisecond screening assay that probes the yield of P+ QB- are compared among that set and to the other mutants reported here or previously. For a subset of eight mutants, the rate constants and yields of the individual B-side electron transfer processes are determined via transient absorption measurements spanning 100 fs to 50 μs. The resulting ranking of mutants for their yield of P+ QB- from ultrafast experiments is in good agreement with that obtained from the millisecond screening assay, further validating the efficient, high-throughput screen for B-side transmembrane charge separation. Results from mutants that individually show progress toward optimization of P+ HB- → P+ QB- electron transfer or initial P* → P+ HB- conversion highlight unmet challenges of optimizing both processes simultaneously.« less

Towards first-principles calculation of electronic excitations in the ring of the protein-bound bacteriochlorophylls

NASA Astrophysics Data System (ADS)

Polyakov, Igor V.; Khrenova, Maria G.; Moskovsky, Alexander A.; Shabanov, Boris M.; Nemukhin, Alexander V.

2018-04-01

Modeling electronic excitation of bacteriochlorophyll (BChl) molecules in light-harvesting (LH) antennae from photosynthetic centers presents a challenge for the quantum theory. We report on a quantum chemical study of the ring of 32 BChl molecules from the bacterial core complex LH1-RC. Diagonal and off-diagonal elements of the excitonic Hamiltonian matrices are estimated in quantum chemical calculations of relevant fragments using the TD-DFT and CIS approaches. The deviation of the computed excitation energy of this BChl system from the experimental data related to the Qy band maximum of this LH1-RC complex is about 0.2 eV. We demonstrate that corrections due to improvement in modeling of an individual BChl molecule and due to contributions from the protein environment are in the range of the obtained discrepancy between theory and experiment. Differences between results of the excitonic model and direct quantum chemical calculations of BChl aggregates fall in the same range.

Origin of the Two Bands in the B800 Ring and Their Involvement in the Energy Transfer Network of Allochromatium vinosum.

PubMed

Schröter, Marco; Alcocer, Marcelo J P; Cogdell, Richard J; Kühn, Oliver; Zigmantas, Donatas

2018-03-15

Bacterial photosynthesis features robust and adaptable energy-harvesting processes in which light-harvesting proteins play a crucial role. The peripheral light-harvesting complex of the purple bacterium Allochromatium vinosum is particularly distinct, featuring a double peak structure in its B800 absorption band. Two hypotheses-not necessarily mutually exclusive-concerning the origin of this splitting have been proposed; either two distinct B800 bacteriochlorophyll site energies are involved, or an excitonic dimerization of bacteriochlorophylls within the B800 ring takes place. Through the use of two-dimensional electronic spectroscopy, we present unambiguous evidence that excitonic interaction shapes the split band. We further identify and characterize all of the energy transfer pathways within this complex by using a global kinetic fitting procedure. Our approach demonstrates how the combination of two-dimensional spectral resolution and self-consistent fitting allows for extraction of information on light-harvesting processes, which would otherwise be inaccessible due to signal congestion.

Isolation of Optically Targeted Single Bacteria by Application of Fluidic Force Microscopy to Aerobic Anoxygenic Phototrophs from the Phyllosphere

PubMed Central

Stiefel, Philipp; Zambelli, Tomaso

2013-01-01

In their natural environment, bacteria often behave differently than they do under laboratory conditions. To gain insight into the physiology of bacteria in situ, dedicated approaches are required to monitor their adaptations and specific behaviors under environmental conditions. Optical microscopy is crucial for the observation of fundamental characteristics of bacteria, such as cell shape, size, and marker gene expression. Here, fluidic force microscopy (FluidFM) was exploited to isolate optically selected bacteria for subsequent identification and characterization. In this study, bacteriochlorophyll-producing bacteria, which can be visualized due to their characteristic fluorescence in the infrared range, were isolated from leaf washes. Bacterial communities from the phyllosphere were investigated because they harbor genes indicative of aerobic anoxygenic photosynthesis. Our data show that different species of Methylobacterium express their photosystem in planta, and they show a distinct pattern of bacteriochlorophyll production under laboratory conditions that is dependent on supplied carbon sources. PMID:23770907

Completion of biosynthetic pathways for bacteriochlorophyll g in Heliobacterium modesticaldum: The C8-ethylidene group formation.

PubMed

Tsukatani, Yusuke; Yamamoto, Haruki; Mizoguchi, Tadashi; Fujita, Yuichi; Tamiaki, Hitoshi

2013-10-01

Heliobacteria have the simplest photosynthetic apparatus, i.e., a type-I reaction center lacking a peripheral light-harvesting complex. Bacteriochlorophyll (BChl) g molecules are bound to the reaction center complex and work both as special-pair and antenna pigments. The C8-ethylidene group formation for BChl g is the last missing link in biosynthetic pathways for bacterial special-pair pigments, which include BChls a and b as well. Here, we report that chlorophyllide a oxidoreductase (COR) of Heliobacterium modesticaldum catalyzes the C8-ethylidene formation from 8-vinyl-chlorophyllide a, producing bacteriochlorophyllide g, the direct precursor for BChl g without the farnesyl tail. The finding led to plausible biosynthetic pathways for 8(1)-hydroxy-chlorophyll a, a primary electron acceptor from the special pair in heliobacterial reaction centers. Proposed catalytic mechanisms on hydrogenation reaction of the ethylidene synthase-type CORs are also discussed. Copyright © 2013 Elsevier B.V. All rights reserved.

Analysis of the Electronic Structure of the Special Pair of a Bacterial Photosynthetic Reaction Center by 13 C Photochemically Induced Dynamic Nuclear Polarization Magic-Angle Spinning NMR Using a Double-Quantum Axis.

PubMed

Najdanova, Marija; Gräsing, Daniel; Alia, A; Matysik, Jörg

2018-01-01

The origin of the functional symmetry break in bacterial photosynthesis challenges since several decades. Although structurally very similar, the two branches of cofactors in the reaction center (RC) protein complex act very differently. Upon photochemical excitation, an electron is transported along one branch, while the other remains inactive. Photochemically induced dynamic nuclear polarization (photo-CIDNP) magic-angle spinning (MAS) 13 C NMR revealed that the two bacteriochlorophyll cofactors forming the "Special Pair" donor dimer are already well distinguished in the electronic ground state. These previous studies are relying solely on 13 C- 13 C correlation experiments as radio-frequency-driven recoupling (RFDR) and dipolar-assisted rotational resonance (DARR). Obviously, the chemical-shift assignment is difficult in a dimer of tetrapyrrole macrocycles, having eight pyrrole rings of similar chemical shifts. To overcome this problem, an INADEQUATE type of experiment using a POST C7 symmetry-based approach is applied to selectively isotope-labeled bacterial RC of Rhodobacter (R.) sphaeroides wild type (WT). We, therefore, were able to distinguish unresolved sites of the macromolecular dimer. The obtained chemical-shift pattern is in-line with a concentric assembly of negative charge within the common center of the Special Pair supermolecule in the electronic ground state. © 2017 The American Society of Photobiology.

Role of B800 in carotenoid-bacteriochlorophyll energy and electron transfer in LH2 complexes from the purple bacterium Rhodobacter sphaeroides.

PubMed

Polívka, Tomas; Niedzwiedzki, Dariusz; Fuciman, Marcel; Sundström, Villy; Frank, Harry A

2007-06-28

The role of the B800 in energy and electron transfer in LH2 complexes has been studied using femtosecond time-resolved transient absorption spectroscopy. The B800 site was perturbed by application of lithium dodecyl sulfate (LDS), and comparison of treated and untreated LH2 complexes from Rhodobacter sphaeroides incorporating carotenoids neurosporene, spheroidene, and spheroidenone was used to explore the role of B800 in carotenoid to bacteriochlorophyll-a (BChla) energy transfer and carotenoid radical formation. Efficiencies of the S1-mediated energy transfer in the LDS-treated complexes were 86, 61, and 57% in the LH2 complexes containing neurosporene, spheroidene, and spheroidenone, respectively. Analysis of the carotenoid S1 lifetimes in solution, LDS-treated, and untreated LH2 complexes allowed determination of B800/B850 branching ratio in the S1-mediated energy transfer. It is shown that B800 is a major acceptor, as approximately 60% of the energy from the carotenoid S1 state is accepted by B800. This value is nearly independent of conjugation length of the carotenoid. In addition to its role in energy transfer, the B800 BChla is the only electron acceptor in the event of charge separation between carotenoid and BChla in LH2 complexes, which is demonstrated by prevention of carotenoid radical formation in the LDS-treated LH2 complexes. In the untreated complexes containing neurosporene and spheroidene, the carotenoid radical is formed with a time constant of 300-400 fs. Application of different excitation wavelengths and intensity dependence of the carotenoid radical formation showed that the carotenoid radical can be formed only after excitation of the S2 state of carotenoid, although the S2 state itself is not a precursor of the charge-separated state. Instead, either a hot S1 state or a charge-transfer state lying between S2 and S1 states of the carotenoid are discussed as potential precursors of the charge-separated state.

Microbial Mat Communities along an Oxygen Gradient in a Perennially Ice-Covered Antarctic Lake.

PubMed

Jungblut, Anne D; Hawes, Ian; Mackey, Tyler J; Krusor, Megan; Doran, Peter T; Sumner, Dawn Y; Eisen, Jonathan A; Hillman, Colin; Goroncy, Alexander K

2016-01-15

Lake Fryxell is a perennially ice-covered lake in the McMurdo Dry Valleys, Antarctica, with a sharp oxycline in a water column that is density stabilized by a gradient in salt concentration. Dissolved oxygen falls from 20 mg liter(-1) to undetectable over one vertical meter from 8.9- to 9.9-m depth. We provide the first description of the benthic mat community that falls within this oxygen gradient on the sloping floor of the lake, using a combination of micro- and macroscopic morphological descriptions, pigment analysis, and 16S rRNA gene bacterial community analysis. Our work focused on three macroscopic mat morphologies that were associated with different parts of the oxygen gradient: (i) "cuspate pinnacles" in the upper hyperoxic zone, which displayed complex topography and were dominated by phycoerythrin-rich cyanobacteria attributable to the genus Leptolyngbya and a diverse but sparse assemblage of pennate diatoms; (ii) a less topographically complex "ridge-pit" mat located immediately above the oxic-anoxic transition containing Leptolyngbya and an increasing abundance of diatoms; and (iii) flat prostrate mats in the upper anoxic zone, dominated by a green cyanobacterium phylogenetically identified as Phormidium pseudopriestleyi and a single diatom, Diadesmis contenta. Zonation of bacteria was by lake depth and by depth into individual mats. Deeper mats had higher abundances of bacteriochlorophylls and anoxygenic phototrophs, including Chlorobi and Chloroflexi. This suggests that microbial communities form assemblages specific to niche-like locations. Mat morphologies, underpinned by cyanobacterial and diatom composition, are the result of local habitat conditions likely defined by irradiance and oxygen and sulfide concentrations. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Hydrogen bonds in the vicinity of the special pair of the bacterial reaction center probed by hydrostatic high-pressure absorption spectroscopy.

PubMed

Kangur, Liina; Jones, Michael R; Freiberg, Arvi

2017-12-01

Using the native bacteriochlorophyll a pigment cofactors as local probes, we investigated the response to external hydrostatic high pressure of reaction center membrane protein complexes from the photosynthetic bacterium Rhodobacter sphaeroides. Wild-type and engineered complexes were used with a varied number (0, 1 or 2) of hydrogen bonds that bind the reaction center primary donor bacteriochlorophyll cofactors to the surrounding protein scaffold. A pressure-induced breakage of hydrogen bonds was established for both detergent-purified and membrane-embedded reaction centers, but at rather different pressures: between 0.2 and 0.3GPa and at about 0.55GPa, respectively. The free energy change associated with the rupture of the single hydrogen bond present in wild-type reaction centers was estimated to be equal to 13-14kJ/mol. In the mutant with two symmetrical hydrogen bonds (FM197H) a single cooperative rupture of the two bonds was observed corresponding to an about twice stronger bond, rather than a sequential rupture of two individual bonds. Copyright © 2017 Elsevier B.V. All rights reserved.

Complete genome sequence of the bacteriochlorophyll a-containing Roseibacterium elongatum type strain (DSM 19469T), a representative of the Roseobacter group isolated from Australian coast sand

PubMed Central

Riedel, Thomas; Fiebig, Anne; Göker, Markus; Klenk, Hans-Peter

2014-01-01

Roseibacterium elongatum Suzuki et al. 2006 is a pink-pigmented and bacteriochlorophyll a-producing representative of the Roseobacter group within the alphaproteobacterial family Rhodobacteraceae. Representatives of the marine ‘Roseobacter group’ were found to be abundant in the ocean and play an important role in global and biogeochemical processes. In the present study we describe the features of R. elongatum strain OCh 323T together with its genome sequence and annotation. The 3,555,102 bp long genome consists of one circular chromosome with no extrachromosomal elements and is one of the smallest known Roseobacter genomes. It contains 3,540 protein-coding genes and 59 RNA genes. Genome analysis revealed the presence of a photosynthetic gene cluster, which putatively enables a photoheterotrophic lifestyle. Gene sequences associated with quorum sensing, motility, surface attachment, and thiosulfate and carbon monoxide oxidation could be detected. The genome was sequenced as part of the activities of the Transregional Collaborative Research Centre 51 (TRR51) funded by the German Research Foundation (DFG). PMID:25197467

Complete genome sequence of the bacteriochlorophyll a-containing Roseibacterium elongatum type strain (DSM 19469(T)), a representative of the Roseobacter group isolated from Australian coast sand.

PubMed

Riedel, Thomas; Fiebig, Anne; Göker, Markus; Klenk, Hans-Peter

2014-06-15

Roseibacterium elongatum Suzuki et al. 2006 is a pink-pigmented and bacteriochlorophyll a-producing representative of the Roseobacter group within the alphaproteobacterial family Rhodobacteraceae. Representatives of the marine 'Roseobacter group' were found to be abundant in the ocean and play an important role in global and biogeochemical processes. In the present study we describe the features of R. elongatum strain OCh 323(T) together with its genome sequence and annotation. The 3,555,102 bp long genome consists of one circular chromosome with no extrachromosomal elements and is one of the smallest known Roseobacter genomes. It contains 3,540 protein-coding genes and 59 RNA genes. Genome analysis revealed the presence of a photosynthetic gene cluster, which putatively enables a photoheterotrophic lifestyle. Gene sequences associated with quorum sensing, motility, surface attachment, and thiosulfate and carbon monoxide oxidation could be detected. The genome was sequenced as part of the activities of the Transregional Collaborative Research Centre 51 (TRR51) funded by the German Research Foundation (DFG).

[Rhodobaculum claviforme gen. nov., sp. nov., a New Alkaliphilic Nonsulfur Purple Bacterium].

PubMed

Bryantseva, I A; Gaisin, V A; Gorlenko, V M

2015-01-01

Two alkaliphilic strains of nonsulfur purple bacteria (NPB), B7-4 and B8-2, were isolated from southeast Siberia moderately saline alkaline steppe lakes with pH values above 9.0. The isolates were motile, polymorphous cells (from short rods to long spindly cells) 2.0-3.2 x 9.6-20.0 μm. Intracellular membranes of vesicular type were mostly located at the cell periphery. The microorganisms contained bacteriochlorophyll a and carotenoids of the spheroidene and spirilloxanthin series. The photosynthetic apparatus was represented by LH2 and LH1 light-harvesting complexes. In the presence of organic compounds, the strains grew aerobically in the dark or anaerobically in the light. Capacity for photo- and chemoautotrophic growth was not detected. The cbbl gene encoding RuBisCO was not revealed. Optimal growth of both strains occurred at 2% NaCl (range from 0.5 to 4%), pH 8.0-8.8 (range from 7.5 to 9.7), and 25-35 degrees C. The DNA G+C content was 67.6-69.8 mol %. Pairwise comparison of the nucleotides of the 16S rRNA genes revealed that strains B7-4 and B8-2 belonged to the same species (99.9% homology) and were most closely related to the aerobic alkaliphilic bacteriochlorophyll a-containing anoxygenic phototrophic bacterium (APB) Roseibacula alcaliphilum De (95.2%) and to NPB strains Rhodobaca barguzinensis VKM B-2406(T) (94.2%) and Rbc. bogoriensis LBB1(T) (93.9%). The isolates were closely related to the NPB Rhodobacter veldkampii DSM 11550(T) (94.8%) and to aerobic bacteriochlorophyll a-containing bacteria Roseinatronobacter monicus ROS 35(T) and Roseicitreum antarcticul ZS2-28(T) (93.5 and 93.9%, respectively). New strains were described as a new NPB genus and species of the family Rhodobacteriaceae, Rhodobaculum claviforme gen. nov., sp. nov., with B7-4(T) (VKM B-2708, LMG 28126) as the type strain.

Genome Sequence of Gammaproteobacterial Pseudohaliea rubra Type Strain DSM 19751, Isolated from Coastal Seawater of the Mediterranean Sea

PubMed Central

Fiebig, Anne; Riedel, Thomas; Göker, Markus; Klenk, Hans-Peter

2014-01-01

Pseudohaliea rubra strain DSM 19751T is an aerobic marine gammaproteobacterium that was isolated from surface coastal seawater of the Mediterranean Sea. Here, we present its genome sequence and annotation. Genome analysis revealed the presence of genes involved in the synthesis of bacteriochlorophyll-a and the reserve compound glycogen. PMID:25414506

Solvation effect of bacteriochlorophyll excitons in light-harvesting complex LH2.

PubMed

Urboniene, V; Vrublevskaja, O; Trinkunas, G; Gall, A; Robert, B; Valkunas, L

2007-09-15

We have characterized the influence of the protein environment on the spectral properties of the bacteriochlorophyll (Bchl) molecules of the peripheral light-harvesting (or LH2) complex from Rhodobacter sphaeroides. The spectral density functions of the pigments responsible for the 800 and 850 nm electronic transitions were determined from the temperature dependence of the Bchl absorption spectra in different environments (detergent micelles and native membranes). The spectral density function is virtually independent of the hydrophobic support that the protein experiences. The reorganization energy for the B850 Bchls is 220 cm(-1), which is almost twice that of the B800 Bchls, and its Huang-Rhys factor reaches 8.4. Around the transition point temperature, and at higher temperatures, both the static spectral inhomogeneity and the resonance interactions become temperature-dependent. The inhomogeneous distribution function of the transitions exhibits less temperature dependence when LH2 is embedded in membranes, suggesting that the lipid phase protects the protein. However, the temperature dependence of the fluorescence spectra of LH2 cannot be fitted using the same parameters determined from the analysis of the absorption spectra. Correct fitting requires the lowest exciton states to be additionally shifted to the red, suggesting the reorganization of the exciton spectrum.

Intermolecular Modes between LH2 Bacteriochlorophylls and Protein Residues: The Effect on the Excitation Energies.

PubMed

Anda, André; De Vico, Luca; Hansen, Thorsten

2017-06-08

Light-harvesting system 2 (LH2) executes the primary processes of photosynthesis in purple bacteria; photon absorption, and energy transportation to the reaction center. A detailed mechanistic insight into these operations is obscured by the complexity of the light-harvesting systems, particularly by the chromophore-environment interaction. In this work, we focus on the effects of the protein residues that are ligated to the bacteriochlorophylls (BChls) and construct potential energy surfaces of the ground and first optically excited state for the various BChl-residue systems where we in each case consider two degrees of freedom in the intermolecular region. We find that the excitation energies are only slightly affected by the considered modes. In addition, we see that axial ligands and hydrogen-bonded residues have opposite effects on both excitation energies and oscillator strengths by comparing to the isolated BChls. Our results indicate that only a small part of the chromophore-environment interaction can be associated with the intermolecular region between a BChl and an adjacent residue, but that it may be possible to selectively raise or lower the excitation energy at the axial and planar residue positions, respectively.

Early bacteriopheophytin reduction in charge separation in reaction centers of Rhodobacter sphaeroides.

PubMed

Zhu, Jingyi; van Stokkum, Ivo H M; Paparelli, Laura; Jones, Michael R; Groot, Marie Louise

2013-06-04

A question at the forefront of biophysical sciences is, to what extent do quantum effects and protein conformational changes play a role in processes such as biological sensing and energy conversion? At the heart of photosynthetic energy transduction lie processes involving ultrafast energy and electron transfers among a small number of tetrapyrrole pigments embedded in the interior of a protein. In the purple bacterial reaction center (RC), a highly efficient ultrafast charge separation takes place between a pair of bacteriochlorophylls: an accessory bacteriochlorophyll (B) and bacteriopheophytin (H). In this work, we applied ultrafast spectroscopy in the visible and near-infrared spectral region to Rhodobacter sphaeroides RCs to accurately track the timing of the electron on BA and HA via the appearance of the BA and HA anion bands. We observed an unexpectedly early rise of the HA⁻ band that challenges the accepted simple picture of stepwise electron transfer with 3 ps and 1 ps time constants. The implications for the mechanism of initial charge separation in bacterial RCs are discussed in terms of a possible adiabatic electron transfer step between BA and HA, and the effect of protein conformation on the electron transfer rate. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Evaluating the Nature of So-Called S*-State Feature in Transient Absorption of Carotenoids in Light-Harvesting Complex 2 (LH2) from Purple Photosynthetic Bacteria.

PubMed

Niedzwiedzki, Dariusz M; Hunter, C Neil; Blankenship, Robert E

2016-11-03

Carotenoids are a class of natural pigments present in all phototrophic organisms, mainly in their light-harvesting proteins in which they play roles of accessory light absorbers and photoprotectors. Extensive time-resolved spectroscopic studies of these pigments have revealed unexpectedly complex photophysical properties, particularly for carotenoids in light-harvesting LH2 complexes from purple bacteria. An ambiguous, optically forbidden electronic excited state designated as S* has been postulated to be involved in carotenoid excitation relaxation and in an alternative carotenoid-to-bacteriochlorophyll energy transfer pathway, as well as being a precursor of the carotenoid triplet state. However, no definitive and satisfactory origin of the carotenoid S* state in these complexes has been established, despite a wide-ranging series of studies. Here, we resolve the ambiguous origin of the carotenoid S* state in LH2 complex from Rba. sphaeroides by showing that the S* feature can be seen as a combination of ground state absorption bleaching of the carotenoid pool converted to cations and the Stark spectrum of neighbor neutral carotenoids, induced by temporal electric field brought by the carotenoid cation-bacteriochlorophyll anion pair. These findings remove the need to assign an S* state, and thereby significantly simplify the photochemistry of carotenoids in these photosynthetic antenna complexes.

A rapid method for the extraction and analysis of carotenoids and other hydrophobic substances suitable for systems biology studies with photosynthetic bacteria.

PubMed

Bóna-Lovász, Judit; Bóna, Aron; Ederer, Michael; Sawodny, Oliver; Ghosh, Robin

2013-10-11

A simple, rapid, and inexpensive extraction method for carotenoids and other non-polar compounds present in phototrophic bacteria has been developed. The method, which has been extensively tested on the phototrophic purple non-sulphur bacterium Rhodospirillum rubrum, is suitable for extracting large numbers of samples, which is common in systems biology studies, and yields material suitable for subsequent analysis using HPLC and mass spectroscopy. The procedure is particularly suitable for carotenoids and other terpenoids, including quinones, bacteriochlorophyll a and bacteriopheophytin a, and is also useful for the analysis of polar phospholipids. The extraction procedure requires only a single step extraction with a hexane/methanol/water mixture, followed by HPLC using a Spherisorb C18 column, with a mobile phase consisting of acetone-water and a non-linear gradient of 50%-100% acetone. The method was employed for examining the carotenoid composition observed during microaerophilic growth of R. rubrum strains, and was able to determine 18 carotenoids, 4 isoprenoid-quinones, bacteriochlorophyll a and bacteriopheophytin a as well as four different phosphatidylglycerol species of different acyl chain compositions. The analytical procedure was used to examine the dynamics of carotenoid biosynthesis in the major and minor pathways operating simultaneously in a carotenoid biosynthesis mutant of R. rubrum.

An endolithic microbial community in dolomite rock in central Switzerland: characterization by reflection spectroscopy, pigment analyses, scanning electron microscopy, and laser scanning microscopy.

PubMed

Horath, T; Neu, T R; Bachofen, R

2006-04-01

A community of endolithic microorganisms dominated by phototrophs was found as a distinct band a few millimeters below the surface of bare exposed dolomite rocks in the Piora Valley in the Alps. Using in situ reflectance spectroscopy, we detected chlorophyll a (Chl a), phycobilins, carotenoids, and an unknown type of bacteriochlorophyll-like pigment absorbing in vivo at about 720 nm. In cross sections, the data indicated a defined distribution of different groups of organisms perpendicular to the rock surface. High-performance liquid chromatography analyses of pigments extracted with organic solvents confirmed the presence of two types of bacteriochlorophylls besides chlorophylls and various carotenoids. Spherical organisms of varying sizes and small filaments were observed in situ with scanning electron microscopy and confocal laser scanning microscopy (one- and two-photon technique). The latter allowed visualization of the distribution of phototrophic microorganisms by the autofluorescence of their pigments within the rock. Coccoid cyanobacteria of various sizes predominated over filamentous ones. Application of fluorescence-labeled lectins demonstrated that most cyanobacteria were embedded in an exopolymeric matrix. Nucleic acid stains revealed a wide distribution of small heterotrophs. Some biological structures emitting a green autofluorescence remain to be identified.

Light-Harvesting Antenna System from the Phototrophic Bacterium Roseiflexus castenholzii

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collins, Aaron M.; Qian, Pu; Tang, Qun

Photosynthetic organisms have evolved diverse light-harvesting complexes to harness light of various qualities and intensities. Photosynthetic bacteria can have (bacterio)chlorophyll Q y antenna absorption bands ranging from ~650 to ~1100 nm. This broad range of wavelengths has allowed many organisms to thrive in unique light environments. Roseiflexus castenholzii is a niche-adapted, filamentous anoxygenic phototroph (FAP) that lacks chlorosomes, the dominant antenna found in most green bacteria, and here we describe the purification of a full complement of photosynthetic complexes: the light-harvesting (LH) antenna, reaction center (RC), and core complex (RC-LH). By high-performance liquid chromatography separation of bacteriochlorophyll and bacteriopheophytin pigmentsmore » extracted from the core complex and the RC, the number of subunits that comprise the antenna was determined to be 15 ± 1. Resonance Raman spectroscopy of the carbonyl stretching region displayed modes indicating that 3C-acetyl groups of BChl a are all involved in molecular interactions probably similar to those found in LH1 complexes from purple photosynthetic bacteria. Finally, two-dimensional projections of negatively stained core complexes and the LH antenna revealed a closed, slightly elliptical LH ring with an average diameter of 130 ± 10 Å surrounding a single RC that lacks an H-subunit but is associated with a tetraheme c-type cytochrome.« less

Descriptions of Roseiarcus fermentans gen. nov., sp. nov., a bacteriochlorophyll a-containing fermentative bacterium related phylogenetically to alphaproteobacterial methanotrophs, and of the family Roseiarcaceae fam. nov.

PubMed

Kulichevskaya, Irina S; Danilova, Olga V; Tereshina, Vera M; Kevbrin, Vadim V; Dedysh, Svetlana N

2014-08-01

A light-pink-pigmented, microaerophilic bacterium was obtained from a methanotrophic consortium enriched from acidic Sphagnum peat and designated strain Pf56(T). Cells of this bacterium were Gram-negative, non-motile, thick curved rods that contained a vesicular intracytoplasmic membrane system characteristic of some purple non-sulfur alphaproteobacteria. The absorption spectrum of acetone/methanol extracts of cells grown in the light showed maxima at 363, 475, 505, 601 and 770 nm; the peaks at 363 and 770 nm are characteristic of bacteriochlorophyll a. However, in contrast to purple non-sulfur bacteria, strain Pf56(T) was unable to grow phototrophically under anoxic conditions in the light. Best growth occurred on some sugars and organic acids under micro-oxic conditions by means of fermentation. The fermentation products were propionate, acetate and hydrogen. Slow chemo-organotrophic growth was also observed under fully oxic conditions. Light stimulated growth. C1 substrates were not utilized. Strain Pf56(T) grew at pH 4.0-7.0 (optimum pH 5.5-6.5) and at 15-30 °C (optimum 22-28 °C). The major cellular fatty acids were 19 : 0 cyclo ω8c and 18 : 1ω7c; quinones were represented by ubiquinone Q-10. The G+C content of the DNA was 70.0 mol%. Strain Pf56 displays 93.6-94.7 and 92.7-93.7% 16S rRNA gene sequence similarity to members of the families Methylocystaceae and Beijerinckiaceae, respectively, and belongs to a large cluster of environmental sequences retrieved from various wetlands and forest soils in cultivation-independent studies. Phenotypic, genotypic and chemotaxonomic characteristics of strain Pf56(T) suggest that it represents a novel genus and species of bacteriochlorophyll a-containing fermentative bacteria, for which the name Roseiarcus fermentans gen. nov., sp. nov. is proposed. Strain Pf56(T) ( = DSM 24875(T) = VKM B-2876(T)) is the type strain of Roseiarcus fermentans, and is also the first characterized member of a novel family within the class Alphaproteobacteria, Roseiarcaceae fam. nov. © 2014 IUMS.

Purple non-sulfur photosynthetic bacteria monitor environmental stresses.

PubMed

Kis, Mariann; Sipka, Gábor; Asztalos, Emese; Rázga, Zsolt; Maróti, Péter

2015-10-01

Heavy metal ion pollution and oxygen deficiency are major environmental risks for microorganisms in aqueous habitat. The potential of purple non-sulfur photosynthetic bacteria for biomonitoring and bioremediation was assessed by investigating the photosynthetic capacity in heavy metal contaminated environments. Cultures of bacterial strains Rhodobacter sphaeroides, Rhodospirillum rubrum and Rubrivivax gelatinosus were treated with heavy metal ions in micromolar (Hg(2+)), submillimolar (Cr(6+)) and millimolar (Pb(2+)) concentration ranges. Functional assays (flash-induced absorption changes and bacteriochlorophyll fluorescence induction) and electron micrographs were taken to specify the harmful effects of pollution and to correlate to morphological changes of the membrane. The bacterial strains and functional tests showed differentiated responses to environmental stresses, revealing that diverse mechanisms of tolerance and/or resistance are involved. The microorganisms were vulnerable to the prompt effect of Pb(2+), showed weak tolerance to Hg(2+) and proved to be tolerant to Cr(6+). The reaction center controlled electron transfer in Rvx. gelatinosus demonstrated the highest degree of resistance against heavy metal exposure. Copyright © 2015 Elsevier B.V. All rights reserved.

Effects of dissolved oxygen concentration on photosynthetic bacteria wastewater treatment: Pollutants removal, cell growth and pigments production.

PubMed

Meng, Fan; Yang, Anqi; Zhang, Guangming; Wang, Hangyao

2017-10-01

Dissolved oxygen (DO) is an important parameter in photosynthetic bacteria (PSB) wastewater treatment. This study set different DO levels and detected the pollutants removal, PSB growth and pigments production. Results showed that DO significantly influenced the performances of PSB wastewater treatment process. The highest COD (93%) and NH 3 -N removal (83%) was achieved under DO of 4-8mg/L, but DO of 2-4mg/L was recommended considering the aeration cost. PSB biomass reached 1645mg/L under DO of 4-8mg/L with satisfying co-enzyme Q10 content. The biomass yield was relatively stable at all DO levels. For bacteriochlorophyll and carotenoids, DO>1mg/L could satisfy their production. On the other hand, DO<0.5mg/L led to the highest dehydrogenase activity. According to the different purposes, the optimal treatment time was different. The most pigments production occurred at 24h; biomass reached peak at 48h; and the optimal time for pollutants removal was 72h. Copyright © 2017 Elsevier Ltd. All rights reserved.

Carotenoid-to-bacteriochlorophyll energy transfer through vibronic coupling in LH2 from Phaeosprillum molischianum.

PubMed

Thyrhaug, Erling; Lincoln, Craig N; Branchi, Federico; Cerullo, Giulio; Perlík, Václav; Šanda, František; Lokstein, Heiko; Hauer, Jürgen

2018-03-01

The peripheral light-harvesting antenna complex (LH2) of purple photosynthetic bacteria is an ideal testing ground for models of structure-function relationships due to its well-determined molecular structure and ultrafast energy deactivation. It has been the target for numerous studies in both theory and ultrafast spectroscopy; nevertheless, certain aspects of the convoluted relaxation network of LH2 lack a satisfactory explanation by conventional theories. For example, the initial carotenoid-to-bacteriochlorophyll energy transfer step necessary on visible light excitation was long considered to follow the Förster mechanism, even though transfer times as short as 40 femtoseconds (fs) have been observed. Such transfer times are hard to accommodate by Förster theory, as the moderate coupling strengths found in LH2 suggest much slower transfer within this framework. In this study, we investigate LH2 from Phaeospirillum (Ph.) molischianum in two types of transient absorption experiments-with narrowband pump and white-light probe resulting in 100 fs time resolution, and with degenerate broadband 10 fs pump and probe pulses. With regard to the split Q x band in this system, we show that vibronically mediated transfer explains both the ultrafast carotenoid-to-B850 transfer, and the almost complete lack of transfer to B800. These results are beyond Förster theory, which predicts an almost equal partition between the two channels.

Evaluating the Nature of So-Called S*-State Feature in Transient Absorption of Carotenoids in Light-Harvesting Complex 2 (LH2) from Purple Photosynthetic Bacteria

PubMed Central

2016-01-01

Carotenoids are a class of natural pigments present in all phototrophic organisms, mainly in their light-harvesting proteins in which they play roles of accessory light absorbers and photoprotectors. Extensive time-resolved spectroscopic studies of these pigments have revealed unexpectedly complex photophysical properties, particularly for carotenoids in light-harvesting LH2 complexes from purple bacteria. An ambiguous, optically forbidden electronic excited state designated as S* has been postulated to be involved in carotenoid excitation relaxation and in an alternative carotenoid-to-bacteriochlorophyll energy transfer pathway, as well as being a precursor of the carotenoid triplet state. However, no definitive and satisfactory origin of the carotenoid S* state in these complexes has been established, despite a wide-ranging series of studies. Here, we resolve the ambiguous origin of the carotenoid S* state in LH2 complex from Rba. sphaeroides by showing that the S* feature can be seen as a combination of ground state absorption bleaching of the carotenoid pool converted to cations and the Stark spectrum of neighbor neutral carotenoids, induced by temporal electric field brought by the carotenoid cation–bacteriochlorophyll anion pair. These findings remove the need to assign an S* state, and thereby significantly simplify the photochemistry of carotenoids in these photosynthetic antenna complexes. PMID:27726397

Synthesis of covalently linked dimeric derivatives of chlorophyll a, pyrochlorophyll a, chlorophyll b, and bacteriochlorophyll a

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wasielewski, M.R.; Svec, W.A.

1980-05-09

Bis(chlorophyllide) ethylene glycol diesters were prepared for each of the title compounds. Pheophytins a and b isolated from alfalfa and bacteriochlorophyll a isolated from R. sphaeroides were treated with 80% aqueous trifluoroacetic acid to yield the corresponding pheophorbides. Pyropheophorbide was prepared by a literature procedure. Carbonic anhydride and benzotriazole-1-methanesulfonate activation methods were used in the esterification of the pheophorbides with ethylene glycol at ambient temperature. Each method yielded 75%+ of the pheophorbide ethylene glycol monoester. These monoesters were treated with equimolar amounts of the corresponding pheophorbide by using benzotriazol-1-methanesulfonate/4-(dimethylamino)pyridine in CH/sub 2/Cl/sub 2/ or dicyclohexylcarbodiimide/4-(dimethylamino)pyridine in CH/sub 2/Cl/sub 2/ atmore » ambient temperature. Yields of bis(phenophorbide) ethylene glycol diesters averaged about 50% for the former method and 70% for the latter method. Insertion of the magnesium atoms into the a series macrocycles was accomplished with iodomagnesium 2,6-di-tert-butyl-4-methylphenolate, IMgBHT, in CH/sub 2/Cl/sub 2/, while the metalation of the b and bacterial series macrocycles was carried out with a mixture of IMgBHT and lithium 2,2,6,6-tetramethylpiperidide in thiophen, all at ambient temperature. Both mono- and dimetalated derivatives were isolated and characterized in each case.« less

Evaluating the nature of so-called S*-State feature in transient absorption of carotenoids in light-harvesting complex 2 (LH2) from purple photosynthetic bacteria

DOE PAGES

Niedzwiedzki, Dariusz M.; Hunter, C. Neil; Blankenship, Robert E.

2016-10-11

Carotenoids are a class of natural pigments present in all phototrophic organisms, mainly in their light-harvesting proteins in which they play roles of accessory light absorbers and photoprotectors. Extensive time-resolved spectroscopic studies of these pigments have revealed unexpectedly complex photophysical properties, particularly for carotenoids in light-harvesting LH2 complexes from purple bacteria. An ambiguous, optically forbidden electronic excited state designated as S* has been postulated to be involved in carotenoid excitation relaxation and in an alternative carotenoid-to-bacteriochlorophyll energy transfer pathway, as well as being a precursor of the carotenoid triplet state. However, no definitive and satisfactory origin of the carotenoid S*more » state in these complexes has been established, despite a wide-ranging series of studies. Here, we resolve the ambiguous origin of the carotenoid S* state in LH2 complex from Rba. sphaeroides by showing that the S* feature can be seen as a combination of ground state absorption bleaching of the carotenoid pool converted to cations and the Stark spectrum of neighbor neutral carotenoids, induced by temporal electric field brought by the carotenoid cation- bacteriochlorophyll anion pair. Lastly, these findings remove the need to assign an S* state, and thereby significantly simplify the photochemistry of carotenoids in these photosynthetic antenna complexes.« less

Evaluating the nature of so-called S*-State feature in transient absorption of carotenoids in light-harvesting complex 2 (LH2) from purple photosynthetic bacteria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niedzwiedzki, Dariusz M.; Hunter, C. Neil; Blankenship, Robert E.

Carotenoids are a class of natural pigments present in all phototrophic organisms, mainly in their light-harvesting proteins in which they play roles of accessory light absorbers and photoprotectors. Extensive time-resolved spectroscopic studies of these pigments have revealed unexpectedly complex photophysical properties, particularly for carotenoids in light-harvesting LH2 complexes from purple bacteria. An ambiguous, optically forbidden electronic excited state designated as S* has been postulated to be involved in carotenoid excitation relaxation and in an alternative carotenoid-to-bacteriochlorophyll energy transfer pathway, as well as being a precursor of the carotenoid triplet state. However, no definitive and satisfactory origin of the carotenoid S*more » state in these complexes has been established, despite a wide-ranging series of studies. Here, we resolve the ambiguous origin of the carotenoid S* state in LH2 complex from Rba. sphaeroides by showing that the S* feature can be seen as a combination of ground state absorption bleaching of the carotenoid pool converted to cations and the Stark spectrum of neighbor neutral carotenoids, induced by temporal electric field brought by the carotenoid cation- bacteriochlorophyll anion pair. Lastly, these findings remove the need to assign an S* state, and thereby significantly simplify the photochemistry of carotenoids in these photosynthetic antenna complexes.« less

Evidence for a cysteine-mediated mechanism of excitation energy regulation in a photosynthetic antenna complex

PubMed Central

Orf, Gregory S.; Saer, Rafael G.; Niedzwiedzki, Dariusz M.; Zhang, Hao; McIntosh, Chelsea L.; Schultz, Jason W.; Mirica, Liviu M.; Blankenship, Robert E.

2016-01-01

Light-harvesting antenna complexes not only aid in the capture of solar energy for photosynthesis, but regulate the quantity of transferred energy as well. Light-harvesting regulation is important for protecting reaction center complexes from overexcitation, generation of reactive oxygen species, and metabolic overload. Usually, this regulation is controlled by the association of light-harvesting antennas with accessory quenchers such as carotenoids. One antenna complex, the Fenna–Matthews–Olson (FMO) antenna protein from green sulfur bacteria, completely lacks carotenoids and other known accessory quenchers. Nonetheless, the FMO protein is able to quench energy transfer in aerobic conditions effectively, indicating a previously unidentified type of regulatory mechanism. Through de novo sequencing MS, chemical modification, and mutagenesis, we have pinpointed the source of the quenching action to cysteine residues (Cys49 and Cys353) situated near two low-energy bacteriochlorophylls in the FMO protein from Chlorobaculum tepidum. Removal of these cysteines (particularly removal of the completely conserved Cys353) through N-ethylmaleimide modification or mutagenesis to alanine abolishes the aerobic quenching effect. Electrochemical analysis and electron paramagnetic resonance spectra suggest that in aerobic conditions the cysteine thiols are converted to thiyl radicals which then are capable of quenching bacteriochlorophyll excited states through electron transfer photochemistry. This simple mechanism has implications for the design of bio-inspired light-harvesting antennas and the redesign of natural photosynthetic systems. PMID:27335466

Ultra-broadband 2D electronic spectroscopy of carotenoid-bacteriochlorophyll interactions in the LH1 complex of a purple bacterium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maiuri, Margherita; Department of Chemistry, Princeton University, Washington Road, Princeton, New Jersey 08544; Réhault, Julien

We investigate the excitation energy transfer (EET) pathways in the photosynthetic light harvesting 1 (LH1) complex of purple bacterium Rhodospirillum rubrum with ultra-broadband two-dimensional electronic spectroscopy (2DES). We employ a 2DES apparatus in the partially collinear geometry, using a passive birefringent interferometer to generate the phase-locked pump pulse pair. This scheme easily lends itself to two-color operation, by coupling a sub-10 fs visible pulse with a sub-15-fs near-infrared pulse. This unique pulse combination allows us to simultaneously track with extremely high temporal resolution both the dynamics of the photoexcited carotenoid spirilloxanthin (Spx) in the visible range and the EET betweenmore » the Spx and the B890 bacterio-chlorophyll (BChl), whose Q{sub x} and Q{sub y} transitions peak at 585 and 881 nm, respectively, in the near-infrared. Global analysis of the one-color and two-color 2DES maps unravels different relaxation mechanisms in the LH1 complex: (i) the initial events of the internal conversion process within the Spx, (ii) the parallel EET from the first bright state S{sub 2} of the Spx towards the Q{sub x} state of the B890, and (iii) the internal conversion from Q{sub x} to Q{sub y} within the B890.« less

Resonance Raman and surface-enhanced resonance Raman spectra of LH2 antenna complex from Rhodobacter sphaeroides and Ectothiorhodospira sp. excited in the Qx and Qy transitions.

PubMed

Chumanov, G; Picorel, R; Ortiz de Zarate, I; Cotton, T M; Seibert, M

2000-05-01

Well-resolved vibrational spectra of LH2 complex isolated from two photosynthetic bacteria, Rhodobacter sphaeroides and Ectothiorhodospira sp., were obtained using surface-enhanced resonance Raman scattering (SERRS) exciting into the Qx and the Qy transitions of bacteriochlorophyll a. High-quality SERRS spectra in the Qy region were accessible because the strong fluorescence background was quenched near the roughened Ag surface. A comparison of the spectra obtained with 590 nm and 752 nm excitation in the mid- and low-frequency regions revealed spectral differences between the two LH2 complexes as well as between the LH2 complexes and isolated bacteriochlorophyll a. Because peripheral modes of pigments contribute mainly to the low-frequency spectral region, frequencies and intensities of many vibrational bands in this region are affected by interactions with the protein. The results demonstrate that the microenvironment surrounding the pigments within the two LH2 complexes is somewhat different, despite the fact that the complexes exhibit similar electronic absorption spectra. These differences are most probably due to specific pigment-pigment and pigment-protein interactions within the LH2 complexes, and the approach might be useful for addressing subtle static and dynamic structural variances between pigment-protein complexes from different sources or in complexes altered chemically or genetically.

Spectroscopic study of the microbial community in chemocline zones of relic meromictic lakes separating from the White Sea

NASA Astrophysics Data System (ADS)

Kharcheva, Anastasia V.; Krasnova, Elena D.; Voronov, Dmitry A.; Patsaeva, Svetlana V.

2015-03-01

As a result of a recent years study on the Karelia shore of the White Sea more than ten relict lakes in different stages of separation from the sea have been discovered. Five of them are located close to the Nikolai Pertsov White Sea Biological Station of Moscow State University. Such separated lakes are interesting to explore for their firm vertical stratification. Water layers differ not only by temperature, salinity and other physic and chemical characteristics and optical properties, but also by ibhabiting microorganisms and by the quality of dissolved organic matter. To study phototropic organisms in water sampled from different depths we used spectroscopic techniques. Identification of the main bands in the absorption and fluorescence spectra showed that there are two main groups of photosynthetic organisms in the redox zone (chemocline): unicellular algae containing chlorophyll a and green sulfur bacteria with bacteriochlorophylls c, d, e. Spectral data were compared with physical and chemical characteristics of the water layer (temperature, salinity, pH, dissolved oxygen and sunlight illumination at certain depth). It gave an opportunity to compare vertical profiles of oxygen and hydrogen sulphide concentration with the number and distribution of oxygenic and anoxygenic phototrophic microorganisms. Maximum abundance of both algae and green sulfur bacteria were achieved within the redox zone. Typical thickness of the layer with the highest concentration of microorganisms did not exceed 10-20 cm.

High abundances of aerobic anoxygenic photosynthetic bacteria in the South Pacific Ocean.

PubMed

Lami, Raphaël; Cottrell, Matthew T; Ras, Joséphine; Ulloa, Osvaldo; Obernosterer, Ingrid; Claustre, Hervé; Kirchman, David L; Lebaron, Philippe

2007-07-01

Little is known about the abundance, distribution, and ecology of aerobic anoxygenic phototrophic (AAP) bacteria, particularly in oligotrophic environments, which represent 60% of the ocean. We investigated the abundance of AAP bacteria across the South Pacific Ocean, including the center of the gyre, the most oligotrophic water body of the world ocean. AAP bacteria, Prochlorococcus, and total prokaryotic abundances, as well as bacteriochlorophyll a (BChl a) and divinyl-chlorophyll a concentrations, were measured at several depths in the photic zone along a gradient of oligotrophic conditions. The abundances of AAP bacteria and Prochlorococcus were high, together accounting for up to 58% of the total prokaryotic community. The abundance of AAP bacteria alone was up to 1.94 x 10(5) cells ml(-1) and as high as 24% of the overall community. These measurements were consistent with the high BChl a concentrations (up to 3.32 x 10(-3) microg liter(-1)) found at all stations. However, the BChl a content per AAP bacterial cell was low, suggesting that AAP bacteria are mostly heterotrophic organisms. Interestingly, the biovolume and therefore biomass of AAP bacteria was on average twofold higher than that of other prokaryotic cells. This study demonstrates that AAP bacteria can be abundant in various oligotrophic conditions, including the most oligotrophic regime of the world ocean, and can account for a large part of the bacterioplanktonic carbon stock.

Specific inhibition of antenna bacteriochlorophyll synthesis in Chlorobium vibrioforme by anesthetic gases.

PubMed Central

Ormerod, J G; Nesbakken, T; Beale, S I

1990-01-01

The green sulfur bacterium Chlorobium vibrioforme contains two types of bacteriochlorophyll (Bchl). The minor pigment, Bchl a, is associated primarily with the cell membrane and its reaction centers; and the major light-harvesting antenna pigment, Bchl d, is found primarily in the chlorosomes, which are attached to the inner surface of the cell membrane. Anesthetic gases, such as N2O, ethylene, and acetylene, were found to inhibit the synthesis of Bchl d, but not of Bchl a, thus allowing the cells to grow at high light intensities with a greatly diminished content of antenna pigment. Chlorosomes were absent or sparse in inhibited cells. Porphyrins accumulated in the inhibited cells. The major one was identified as the Bchl precursor magnesium-protoporphyrin IX monomethyl ester (Mg-PPME) by comparative absorption and fluorescence spectroscopy and thin-layer chromatography of the porphyrin and its derivatives with those of authentic protoporphyrin IX. Small amounts of Mg-PPME were present in control cells, but the addition of inhibitor caused a rapid increase in the Mg-PPME concentration, accompanying the inhibition of Bchl d synthesis. Cells grown in the presence of ethephon (as a source of ethylene) and allowed to stand in dim light for long periods accumulated large amounts of PPME and other porphyrins and excreted or released porphyrins, which accumulated as a brown precipitate in the culture. Inhibition of Bchl d synthesis was relieved upon removal of the inhibitor. These results suggest that the gases act at a step in pigment biosynthesis that affects the utilization of Mg-PPME for isocyclic ring formation. Synthesis of Bchl d and Bchl a may be differentially affected by the gases because of compartmentation of their biosynthetic apparatus or because competition for precursors favors Bchl a synthesis. An ethephon-resistant mutant strain was isolated by selection for growth in dim, long-wavelength light. The mutant cells were also resistant to acetylene, but not to N2O. The ability to reversibly generate viable Chlorobium cells that lack antenna pigments may be useful in photosynthesis research. The ethephon- and acetylene-resistant strain may be useful in the study of the enzymes and genes that are involved in the biosynthetic step that the gases affect. Images FIG. 2 PMID:2307651

[Roseibacula alcaliphilum gen. nov. sp. nov., a new alkaliphilic aerobic anoxygenic phototrophic bacterium from a meromictic soda Lake Doroninskoe (East Siberia, Russia)].

PubMed

Nuianzina-Boldareva, E N; Gorlenko, V M

2014-01-01

A bacterial strain De was isolated from the surface water layer of the meromictic soda lake Doroninskoe. When grown in the dark, it formed-pink colonies on agar media. The cells were nonmotile, contained bacteriochlorophyll a and carotenoids. Stationary-phase cells contained intracellular vesicular membranes similar to the membranes of the photosynthetic apparatus of some ndnsulfur purple bacteria. Aerobic growth did not occur. Sucrose, citrate, mannitol, sorbitol, case in hydrolysate,and yeast extract were the preferable substrates for aerobic growth, Xylose, lactose, aspartate, benzoate, malate, malonate, succinate, tartrate, formate, fumarate, glycerol, methanol, and ethanol were not utilized; Growth occurred at up to 50.g/L NaCl (optimum at 5 g/L) and pH 9.8. According to the 16S rRNA gene sequencing, similarity between the isolate and the known alkaliphilic genera of nonsulfur purple bacteria (Rhodobaca) and of aerobic anoxygenic phototrophic bacteria (Roseinatronobacter) was 96%, which was sufficient for description ofa new genus of aerobic anoxygenic phototrophic bacteria. The name Roseibacula alcaliphiluin gen. nov., sp. nov. was, proposed for the isolate.

Lifetimes of bacteriochlorophyll fluorescence in Rhodopseudomonas viridis and Heliobacterium chlorum at low temperatures

NASA Technical Reports Server (NTRS)

Kleinherenbrink, F. A.; Cheng, P.; Amesz, J.; Blankenship, R. E.

1993-01-01

Fluorescence lifetimes of isolated membranes of Rhodopseudomonas viridis were measured in the temperature range of 77 K to 25 K. At room temperature, the main component of the fluorescence decay of bacteriochlorophyll (BChl) b had a time constant of 50 ps. In contrast to other purple bacteria, the emission at low temperature was spectrally homogeneous and showed essentially single lifetimes of 140 ps at 77 K and 180 ps at 25 K, with the primary electron donor in the oxidized state. Taking into account the relative fluorescence yields with open and closed reaction centers, we arrive at numbers of 125 ps and 215 ps, respectively, for open reaction centers. These numbers are significantly smaller than expected on the basis of measurements of the efficiency of charge separation, perhaps suggesting that the excitation decay in the absence of reaction centers is considerably faster at low temperature than at room temperature. At least four different spectral components with different lifetimes were observed at 25 K in the emission of Heliobacterium chlorum, a short-wavelength component of about 30 ps and three longer-wavelength components of about 100 ps, 300 ps, and 900 ps. This indicates a strong heterogeneity in the emitting pigment, BChl g-808. The component with the shortest lifetime does not appear to be affected by the redox state of the reaction center and might reflect energy transfer to BChl g species which are connected to the reaction center.

The photophysics of monomeric bacteriochlorophylls c and d and their derivatives: properties of the triplet state and singlet oxygen photogeneration and quenching

NASA Technical Reports Server (NTRS)

Krasnovsky, A. A. Jr; Cheng, P.; Blankenship, R. E.; Moore, T. A.; Gust, D.

1993-01-01

Measurements of pigment triplet-triplet absorption, pigment phosphorescence and photosensitized singlet oxygen luminescence were carried out on solutions containing monomeric bacteriochlorophylls (Bchl) c and d, isolated from green photosynthetic bacteria, and their magnesium-free and farnesyl-free analogs. The energies of the pigment triplet states fell in the range 1.29-1.34 eV. The triplet lifetimes in aerobic solutions were 200-250 ns; they increased to 280 +/- 70 microseconds after nitrogen purging in liquid solutions and to 0.7-2.1 ms in a solid matrix at ambient or liquid nitrogen temperatures. Rate constants for quenching of the pigment triplet state by oxygen were (2.0-2.5) x 10(9) M-1 s-1, which is close to 1/9 of the rate constant for diffusion-controlled reactions. This quenching was accompanied by singlet oxygen formation. The quantum yields for the triplet state formation and singlet oxygen production were 55-75% in air-saturated solutions. Singlet oxygen quenching by ground-state pigment molecules was observed. Quenching was the most efficient for magnesium-containing pigments, kq = (0.31-1.2) x 10(9) M-1 s-1. It is caused mainly by a physical process of singlet oxygen (1O2) deactivation. Thus, Bchl c and d and their derivatives, as well as chlorophyll and Bchl a, combine a high efficiency of singlet oxygen production with the ability to protect photochemical and photobiological systems against damage by singlet oxygen.

Utilizing the dynamic stark shift as a probe for dielectric relaxation in photosynthetic reaction centers during charge separation.

PubMed

Guo, Zhi; Lin, Su; Woodbury, Neal W

2013-09-26

In photosynthetic reaction centers, the electric field generated by light-induced charge separation produces electrochromic shifts in the transitions of reaction center pigments. The extent of this Stark shift indirectly reflects the effective field strength at a particular cofactor in the complex. The dynamics of the effective field strength near the two monomeric bacteriochlorophylls (BA and BB) in purple photosynthetic bacterial reaction centers has been explored near physiological temperature by monitoring the time-dependent Stark shift during charge separation (dynamic Stark shift). This dynamic Stark shift was determined through analysis of femtosecond time-resolved absorbance change spectra recorded in wild type reaction centers and in four mutants at position M210. In both wild type and the mutants, the kinetics of the dynamic Stark shift differ from those of electron transfer, though not in the same way. In wild type, the initial electron transfer and the increase in the effective field strength near the active-side monomer bacteriochlorophyll (BA) occur in synchrony, but the two signals diverge on the time scale of electron transfer to the quinone. In contrast, when tyrosine is replaced by aspartic acid at M210, the kinetics of the BA Stark shift and the initial electron transfer differ, but transfer to the quinone coincides with the decay of the Stark shift. This is interpreted in terms of differences in the dynamics of the local dielectric environment between the mutants and the wild type. In wild type, comparison of the Stark shifts associated with BA and BB on the two quasi-symmetric halves of the reaction center structure confirm that the effective dielectric constants near these cofactors are quite different when the reaction center is in the state P(+)QA(-), as previously determined by Steffen et al. at 1.5 K (Steffen, M. A.; et al. Science 1994, 264, 810-816). However, it is not possible to determine from static, low-temperature measurments if the difference in the effective dielectric constant between the two sides of the reaction center is manifest on the time scale of initial electron transfer. By comparing directly the Stark shift dynamics of the ground-state spectra of the two monomer bacteriochlorophylls, it is evident that there is, in fact, a large dielectric difference between protein environments of the two quasi-symmetric electron-transfer branches on the time scale of initial electron transfer and that the effective dielectric constant in the region continues to evolve on a time scale of hundreds of picoseconds.

Mutual control of axial and equatorial ligands: model studies with [Ni]-bacteriochlorophyll-a.

PubMed

Yerushalmi, Roie; Noy, Dror; Baldridge, Kim K; Scherz, Avigdor

2002-07-17

Modification of the metal's electronic environment by ligand association and dissociation in metalloenzymes is considered cardinal to their catalytic activity. We have recently presented a novel system that utilizes the bacteriochlorophyll (BChl) macrocycle as a ligand and reporter. This system allows for charge mobilization in the equatorial plane and experimental estimate of changes in the electronic charge density around the metal with no modification of the metal's chemical environment. The unique spectroscopy, electrochemistry and coordination chemistry of [Ni]-bacteriochlorophyll ([Ni]-BChl) enable us to follow directly fine details and steps involved in the function of the metal redox center. This approach is utilized here whereby electro-chemical reduction of [Ni]-BChl to the monoanion [Ni]-BChl(-) results in reversible dissociation of biologically relevant axial ligands. Similar ligand dissociation was previously detected upon photoexcitation of [Ni]-BChl (Musewald, C.; Hartwich, G.; Lossau, H.; Gilch, P.; Pollinger-Dammer, F.; Scheer, H.; Michel-Beyerle, M. E. J. Phys. Chem. B 1999, 103, 7055-7060 and Noy, D.; Yerushalmi, R.; Brumfeld, V.; Ashur, I.; Baldridge, K. K.; Scheer, H.; Scherz, A. J. Am. Chem. Soc. 2000, 122, 3937-3944). The electrochemical measurements and quantum mechanical (QM) calculations performed here for the neutral, singly reduced, monoligated, and singly reduced, monoligated [Ni]-BChl suggest the following: (a) Electroreduction, although resulting in a pi anion [Ni]-BChl(-) radical, causes electron density migration to the [Ni]-BChl core. (b) Reduction of nonligated [Ni]-BChl does not change the macrocycle conformation, whereas axial ligation results in a dramatic expansion of the metal core and a flattening of the highly ruffled macrocycle conformation. (c) In both the monoanion and singly excited [Ni]-BChl ([Ni]-BChl*), the frontier singly occupied molecular orbital (SOMO) has a small but nonnegligible metal character. Finally, (d) computationally, we found that a reduction of [Ni]-BChl*imidazole results in a weaker metal-axial ligand bond. Yet, it remains weakly bound in the gas phase. The experimentally observed ligand dissociation is accounted for computationally when solvation is considered. On the basis of the experimental observations and QM calculations, we propose a mechanism whereby alterations in the equatorial pi system and modulation of sigma bonding between the axial ligands and the metal core are mutually correlated. Such a mechanism highlights the dynamic role of axial ligands in regulating the activity of metal centers such as factor F430 (F430), a nickel-based coenzyme that is essential in methanogenic archea.

Sequence of the bchG gene from Chloroflexus aurantiacus: relationship between chlorophyll synthase and other polyprenyltransferases

NASA Technical Reports Server (NTRS)

Lopez, J. C.; Ryan, S.; Blankenship, R. E.

1996-01-01

The sequence of the Chloroflexus aurantiacus open reading frame thought to be the C. aurantiacus homolog of the Rhodobacter capsulatus bchG gene is reported. The BchG gene product catalyzes esterification of bacteriochlorophyllide a by geranylgeraniol-PPi during bacteriochlorophyll a biosynthesis. Homologs from Arabidopsis thaliana, Synechocystis sp. strain PCC6803, and C. aurantiacus were identified in database searches. Profile analysis identified three related polyprenyltransferase enzymes which attach an aliphatic alcohol PPi to an aromatic substrate. This suggests a broader relationship between chlorophyll synthases and other polyprenyltransferases.

PucC and LhaA direct efficient assembly of the light‐harvesting complexes in Rhodobacter sphaeroides

PubMed Central

Mothersole, David J.; Jackson, Philip J.; Vasilev, Cvetelin; Tucker, Jaimey D.; Brindley, Amanda A.; Dickman, Mark J.

2015-01-01

Summary The mature architecture of the photosynthetic membrane of the purple phototroph R hodobacter sphaeroides has been characterised to a level where an atomic‐level membrane model is available, but the roles of the putative assembly proteins LhaA and PucC in establishing this architecture are unknown. Here we investigate the assembly of light‐harvesting LH2 and reaction centre‐light‐harvesting1‐PufX (RC‐LH1‐PufX) photosystem complexes using spectroscopy, pull‐downs, native gel electrophoresis, quantitative mass spectrometry and fluorescence lifetime microscopy to characterise a series of lha A and puc C mutants. LhaA and PucC are important for specific assembly of LH1 or LH2 complexes, respectively, but they are not essential; the few LH1 subunits found in Δlha A mutants assemble to form normal RC‐LH1‐PufX core complexes showing that, once initiated, LH1 assembly round the RC is cooperative and proceeds to completion. LhaA and PucC form oligomers at sites of initiation of membrane invagination; LhaA associates with RCs, bacteriochlorophyll synthase (BchG), the protein translocase subunit YajC and the YidC membrane protein insertase. These associations within membrane nanodomains likely maximise interactions between pigments newly arriving from BchG and nascent proteins within the SecYEG‐SecDF‐YajC‐YidC assembly machinery, thereby co‐ordinating pigment delivery, the co‐translational insertion of LH polypeptides and their folding and assembly to form photosynthetic complexes. PMID:26419219

Conformational Switching in a Light-Harvesting Protein as Followed by Single-Molecule Spectroscopy

PubMed Central

Gall, Andrew; Ilioaia, Cristian; Krüger, Tjaart P.J.; Novoderezhkin, Vladimir I.; Robert, Bruno; van Grondelle, Rienk

2015-01-01

Among the ultimate goals of protein physics, the complete, experimental description of the energy paths leading to protein conformational changes remains a challenge. Single protein fluorescence spectroscopy constitutes an approach of choice for addressing protein dynamics, and, among naturally fluorescing proteins, light-harvesting (LH) proteins from purple bacteria constitute an ideal object for such a study. LHs bind bacteriochlorophyll a molecules, which confer on them a high intrinsic fluorescence yield. Moreover, the electronic properties of these pigment-proteins result from the strong excitonic coupling between their bound bacteriochlorophyll a molecules in combination with the large energetic disorder due to slow fluctuations in their structure. As a result, the position and probability of their fluorescence transition delicately depends on the precise realization of the disorder of the set of bound pigments, which is governed by the LH protein dynamics. Analysis of these parameters using time-resolved single-molecule fluorescence spectroscopy thus yields direct access to the protein dynamics. Applying this technique to the LH2 protein from Rhodovulum (Rdv.) sulfidophilum, the structure—and consequently the fluorescence properties—of which depends on pH, allowed us to follow a single protein, pH-induced, reversible, conformational transition. Hence, for the first time, to our knowledge, a protein transition can be visualized through changes in the electronic structure of the intrinsic cofactors, at a level of a single LH protein, which opens a new, to our knowledge, route for understanding the changes in energy landscape that underlie protein function and adaptation to the needs of living organisms. PMID:26039172

Synthesis and Spectral Properties of meso-Arylbacteriochlorins, Including Insights into Essential Motifs of their Hydrodipyrrin Precursors

DOE PAGES

Reddy, Muthyala Nagarjuna; Zhang, Shaofei; Kim, Han-Je; ...

2017-04-14

Synthetic bacteriochlorins—analogues of bacteriochlorophylls, Nature’s near-infrared absorbers—are attractive for diverse photochemical studies. meso-Arylbacteriochlorins have been prepared by the self-condensation of a dihydrodipyrrin–carbinol or dihydrodipyrrin–acetal following an Eastern-Western (E-W) or Northern-Southern (N-S) joining process. The bacteriochlorins bear a gem-dimethyl group in each pyrroline ring to ensure stability toward oxidation. The two routes differ in the location of the gem-dimethyl group at the respective 3- or 2-position in the dihydrodipyrrin, and the method of synthesis of the dihydrodipyrrin. Treatment of a known 3,3-dimethyldihydrodipyrrin-1-carboxaldehyde with an aryl Grignard reagent afforded the dihydrodipyrrin-1-(aryl)carbinol, and upon subsequent acetylation, the corresponding dihydrodipyrrin-1-methyl acetate (dihydrodipyrrin– acetate). Self-condensationmore » of the dihydrodipyrrin–acetate gave a meso-diarylbacteriochlorin (E-W route). A 2,2-dimethyl-5-aryldihydrodipyrrin-1-(aryl)carbinol underwent self-condensation to give a trans-A 2B 2-type meso-tetraarylbacteriochlorin (N-S route). In each case, the aromatization process entails a 2e -/2H + (aerobic) dehydrogenative oxidation following the dihydrodipyrrin self-condensation. Comparison of a tetrahydrodipyrrin–acetal (0%) versus a dihydrodipyrrin–acetal (41%) in bacteriochlorin formation and results with various 1-substituted dihydrodipyrrins revealed the importance of resonance stabilization of the reactive hydrodipyrrin intermediate. Altogether 10 new dihydrodipyrrins and five new bacteriochlorins have been prepared. The bacteriochlorins exhibit characteristic bacteriochlorophyll-like absorption spectra, including a Q y band in the region 726–743 nm.« less

Synthesis and Spectral Properties of meso-Arylbacteriochlorins, Including Insights into Essential Motifs of their Hydrodipyrrin Precursors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, Muthyala Nagarjuna; Zhang, Shaofei; Kim, Han-Je

Synthetic bacteriochlorins—analogues of bacteriochlorophylls, Nature’s near-infrared absorbers—are attractive for diverse photochemical studies. meso-Arylbacteriochlorins have been prepared by the self-condensation of a dihydrodipyrrin–carbinol or dihydrodipyrrin–acetal following an Eastern-Western (E-W) or Northern-Southern (N-S) joining process. The bacteriochlorins bear a gem-dimethyl group in each pyrroline ring to ensure stability toward oxidation. The two routes differ in the location of the gem-dimethyl group at the respective 3- or 2-position in the dihydrodipyrrin, and the method of synthesis of the dihydrodipyrrin. Treatment of a known 3,3-dimethyldihydrodipyrrin-1-carboxaldehyde with an aryl Grignard reagent afforded the dihydrodipyrrin-1-(aryl)carbinol, and upon subsequent acetylation, the corresponding dihydrodipyrrin-1-methyl acetate (dihydrodipyrrin– acetate). Self-condensationmore » of the dihydrodipyrrin–acetate gave a meso-diarylbacteriochlorin (E-W route). A 2,2-dimethyl-5-aryldihydrodipyrrin-1-(aryl)carbinol underwent self-condensation to give a trans-A 2B 2-type meso-tetraarylbacteriochlorin (N-S route). In each case, the aromatization process entails a 2e -/2H + (aerobic) dehydrogenative oxidation following the dihydrodipyrrin self-condensation. Comparison of a tetrahydrodipyrrin–acetal (0%) versus a dihydrodipyrrin–acetal (41%) in bacteriochlorin formation and results with various 1-substituted dihydrodipyrrins revealed the importance of resonance stabilization of the reactive hydrodipyrrin intermediate. Altogether 10 new dihydrodipyrrins and five new bacteriochlorins have been prepared. The bacteriochlorins exhibit characteristic bacteriochlorophyll-like absorption spectra, including a Q y band in the region 726–743 nm.« less

Binding and Energetics of Electron Transfer between an Artificial Four-Helix Mn-Protein and Reaction Centers from Rhodobacter sphaeroides.

PubMed

Espiritu, Eduardo; Olson, Tien L; Williams, JoAnn C; Allen, James P

2017-12-12

The ability of an artificial four-helix bundle Mn-protein, P1, to bind and transfer an electron to photosynthetic reaction centers from the purple bacterium Rhodobacter sphaeroides was characterized using optical spectroscopy. Upon illumination of reaction centers, an electron is transferred from P, the bacteriochlorophyll dimer, to Q A , the primary electron acceptor. The P1 Mn-protein can bind to the reaction center and reduce the oxidized bacteriochlorophyll dimer, P + , with a dissociation constant of 1.2 μM at pH 9.4, comparable to the binding constant of c-type cytochromes. Amino acid substitutions of surface residues on the Mn-protein resulted in increases in the dissociation constant to 8.3 μM. The extent of reduction of P + by the P1 Mn-protein was dependent on the P/P + midpoint potential and the pH. Analysis of the free energy difference yielded a midpoint potential of approximately 635 mV at pH 9.4 for the Mn cofactor of the P1 Mn-protein, a value similar to those found for other Mn cofactors in proteins. The linear dependence of -56 mV/pH is consistent with one proton being released upon Mn oxidation, allowing the complex to maintain overall charge neutrality. These outcomes demonstrate the feasibility of designing four-helix bundles and other artificial metalloproteins to bind and transfer electrons to bacterial reaction centers and establish the usefulness of this system as a platform for designing sites to bind novel metal cofactors capable of performing complex oxidation-reduction reactions.

Biosynthesis and Isotopic Composition of Bacteriochlorophyll a and Okenone in Purple Sulfur Bacteria

NASA Astrophysics Data System (ADS)

Smith, D.; Scott, J. H.; Steele, A.; Cody, G. D.; Ohara, S.; Bowden, R.; Fogel, M. L.

2011-12-01

Phototrophic sulfur bacteria play an integral part in the anaerobic cycling of sulfur. Bacteriochloroyphll a (Bchl a) is a well-studied photosynthetic compound required for photosynthesis in the organisms that possess it. The only known fossil of purple sulfur bacteria (PSB) in the geologic record is okenane, believed to be of biologic origin originating from the carotenoid pigment okenone, which has only been documented in eleven species of Chromatiaceae. Organic geochemical studies have identified okenane in preserved organic matter in rocks and ancient sediments and further, okenone production has been observed in modern water columns and sediment surfaces. We have undertaken a comprehensive study on the biosynthesis of bacterial pigments including okenone and C, N, and S isotopic fractionation during various growth modes in controlled laboratory experiments of purple sulfur bacteria. Cultures of Marichromatium purpuratum 1591, M. purpuratum 1711, Thiocapsa marina 5653, and FGL21 (isolated from the chemocline of Fayetteville Green Lake, NY) were grown under autotrophic and photoheterotrophic (e.g. acetate or pyruvate) conditions in batch cultures. Concentrations of okenone and Bchl a were quantified as a function of time and growth by Ultra Performance-Liquid Chromatography-Mass Spectrometry (UP-LC-MS) and spectrophotometry. Overall okenone and Bchl a concentrations reached μM levels in the cultures. At stationary phase, all four strains achieved concentrations of okenone and Bchl a that were approximately 2.5 fM and 0.2 fM per cell, respectively, with okenone to Bchl a ratios of approximately 12 to 1. Isotope Ratio Mass Spectrometry (IRMS) was performed on bulk cells and compound specific analysis of Bchl a and okenone to better understand the fractionation associated with the production of the compounds.

Self-assembled chromophores within mesoporous nanocrystalline TiO2: towards biomimetic solar cells.

PubMed

Marek, Peter L; Sieger, Hermann; Scherer, Torsten; Hahn, Horst; Balaban, Teodor Silviu

2009-06-01

Artificial light-harvesting antennas consisting of self-assembled chromophores that mimic the natural pigments of photosynthetic bacteria have been inserted into voids induced in porous titania (TiO2, anatase) in order to investigate their suitability for hybrid solar cells. Mesoporous nanocrystalline TiO2 with additional uniform macropores was treated with precursor solutions of the pigment which was then induced to self-assemble within the voids. The chromophores were tailored to combine the self-assembly characteristics of the natural bacteriochlorophylls with the robustness of artificial Zn-porphyrins being stable for prolonged periods even upon heating to over 200 degrees C. They assemble on the TiO2 surface to form nano- to micro-crystalline structures with lengths from tens of nm up to several microm and show a photosensitization effect which is supposed to be dependent on the assembly size. The natural examples of these antennas are found in green sulfur bacteria which are able to use photosynthesis in deep water regions with minute light intensities. The implementation of biomimetic antennas for light harvesting and a better photon management may lead to a rise in efficiency of dye-sensitized solar cells also under low light illumination conditions.

High efficiency light harvesting by carotenoids in the LH2 complex from photosynthetic bacteria: unique adaptation to growth under low-light conditions.

PubMed

Magdaong, Nikki M; LaFountain, Amy M; Greco, Jordan A; Gardiner, Alastair T; Carey, Anne-Marie; Cogdell, Richard J; Gibson, George N; Birge, Robert R; Frank, Harry A

2014-09-25

Rhodopin, rhodopinal, and their glucoside derivatives are carotenoids that accumulate in different amounts in the photosynthetic bacterium, Rhodoblastus (Rbl.) acidophilus strain 7050, depending on the intensity of the light under which the organism is grown. The different growth conditions also have a profound effect on the spectra of the bacteriochlorophyll (BChl) pigments that assemble in the major LH2 light-harvesting pigment-protein complex. Under high-light conditions the well-characterized B800-850 LH2 complex is formed and accumulates rhodopin and rhodopin glucoside as the primary carotenoids. Under low-light conditions, a variant LH2, denoted B800-820, is formed, and rhodopinal and rhodopinal glucoside are the most abundant carotenoids. The present investigation compares and contrasts the spectral properties and dynamics of the excited states of rhodopin and rhodopinal in solution. In addition, the systematic differences in pigment composition and structure of the chromophores in the LH2 complexes provide an opportunity to explore the effect of these factors on the rate and efficiency of carotenoid-to-BChl energy transfer. It is found that the enzymatic conversion of rhodopin to rhodopinal by Rbl. acidophilus 7050 grown under low-light conditions results in nearly 100% carotenoid-to-BChl energy transfer efficiency in the LH2 complex. This comparative analysis provides insight into how photosynthetic systems are able to adapt and survive under challenging environmental conditions.

High Efficiency Light Harvesting by Carotenoids in the LH2 Complex from Photosynthetic Bacteria: Unique Adaptation to Growth under Low-Light Conditions

PubMed Central

2015-01-01

Rhodopin, rhodopinal, and their glucoside derivatives are carotenoids that accumulate in different amounts in the photosynthetic bacterium, Rhodoblastus (Rbl.) acidophilus strain 7050, depending on the intensity of the light under which the organism is grown. The different growth conditions also have a profound effect on the spectra of the bacteriochlorophyll (BChl) pigments that assemble in the major LH2 light-harvesting pigment–protein complex. Under high-light conditions the well-characterized B800-850 LH2 complex is formed and accumulates rhodopin and rhodopin glucoside as the primary carotenoids. Under low-light conditions, a variant LH2, denoted B800-820, is formed, and rhodopinal and rhodopinal glucoside are the most abundant carotenoids. The present investigation compares and contrasts the spectral properties and dynamics of the excited states of rhodopin and rhodopinal in solution. In addition, the systematic differences in pigment composition and structure of the chromophores in the LH2 complexes provide an opportunity to explore the effect of these factors on the rate and efficiency of carotenoid-to-BChl energy transfer. It is found that the enzymatic conversion of rhodopin to rhodopinal by Rbl. acidophilus 7050 grown under low-light conditions results in nearly 100% carotenoid-to-BChl energy transfer efficiency in the LH2 complex. This comparative analysis provides insight into how photosynthetic systems are able to adapt and survive under challenging environmental conditions. PMID:25171303

Linear-scaling time-dependent density-functional theory beyond the Tamm-Dancoff approximation: Obtaining efficiency and accuracy with in situ optimised local orbitals.

PubMed

Zuehlsdorff, T J; Hine, N D M; Payne, M C; Haynes, P D

2015-11-28

We present a solution of the full time-dependent density-functional theory (TDDFT) eigenvalue equation in the linear response formalism exhibiting a linear-scaling computational complexity with system size, without relying on the simplifying Tamm-Dancoff approximation (TDA). The implementation relies on representing the occupied and unoccupied subspaces with two different sets of in situ optimised localised functions, yielding a very compact and efficient representation of the transition density matrix of the excitation with the accuracy associated with a systematic basis set. The TDDFT eigenvalue equation is solved using a preconditioned conjugate gradient algorithm that is very memory-efficient. The algorithm is validated on a small test molecule and a good agreement with results obtained from standard quantum chemistry packages is found, with the preconditioner yielding a significant improvement in convergence rates. The method developed in this work is then used to reproduce experimental results of the absorption spectrum of bacteriochlorophyll in an organic solvent, where it is demonstrated that the TDA fails to reproduce the main features of the low energy spectrum, while the full TDDFT equation yields results in good qualitative agreement with experimental data. Furthermore, the need for explicitly including parts of the solvent into the TDDFT calculations is highlighted, making the treatment of large system sizes necessary that are well within reach of the capabilities of the algorithm introduced here. Finally, the linear-scaling properties of the algorithm are demonstrated by computing the lowest excitation energy of bacteriochlorophyll in solution. The largest systems considered in this work are of the same order of magnitude as a variety of widely studied pigment-protein complexes, opening up the possibility of studying their properties without having to resort to any semiclassical approximations to parts of the protein environment.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ponomarenko, Nina S.; Li, Liang; Marino, Antony R.

Heterodimer mutant reaction centers (RCs) of Blastochloris viridis were crystallized using microfluidic technology. In this mutant, a leucine residue replaced the histidine residue which had acted as a fifth ligand to the bacteriochlorophyll (BChl) of the primary electron donor dimer M site (HisM200). With the loss of the histidine-coordinated Mg, one bacteriochlorophyll of the special pair was converted into a bacteriopheophytin (BPhe), and the primary donor became a heterodimer supermolecule. The crystals had dimensions 400 x 100 x 100 {micro}m, belonged to space group P4{sub 3}2{sub 1}2, and were isomorphous to the ones reported earlier for the wild type (WT)more » strain. The structure was solved to a 2.5 {angstrom} resolution limit. Electron-density maps confirmed the replacement of the histidine residue and the absence of Mg. Structural changes in the heterodimer mutant RC relative to the WT included the absence of the water molecule that is typically positioned between the M side of the primary donor and the accessory BChl, a slight shift in the position of amino acids surrounding the site of the mutation, and the rotation of the M194 phenylalanine. The cytochrome subunit was anchored similarly as in the WT and had no detectable changes in its overall position. The highly conserved tyrosine L162, located between the primary donor and the highest potential heme C{sub 380}, revealed only a minor deviation of its hydroxyl group. Concomitantly to modification of the BChl molecule, the redox potential of the heterodimer primary donor increased relative to that of the WT organism (772 mV vs. 517 mV). The availability of this heterodimer mutant and its crystal structure provides opportunities for investigating changes in light-induced electron transfer that reflect differences in redox cascades.« less

Red and near-infrared fluorophores inspired by chlorophylls: consideration of practical brightness in multicolor flow cytometry and biomedical sciences

NASA Astrophysics Data System (ADS)

Taniguchi, Masahiko; Hu, Gongfang; Liu, Rui; Du, Hai; Lindsey, Jonathan S.

2018-02-01

Demands in flow cytometry for increased multiplexing (for detection of multiple antigens) and brightness (for detection of rare entities) require new fluorophores (i.e., "colors") with spectrally distinct fluorescence outside the relatively congested visible spectral region. Flow cytometry fluorophores typically must function in aqueous solution upon bioconjugation and ideally should exhibit a host of photophysical features: (i) strong absorption, (ii) sizable Stokes shift, (iii) modest if not strong fluorescence, and (iv) narrow fluorescence band. Tandem dyes have long been pursued to achieve a large effective Stokes shift, increased brightness, and better control over the excitation and emission wavelengths. Here, the attractive photophysical features of chlorophylls and bacteriochlorophylls - Nature's chosen photoactive pigments for photosynthesis - are described with regards to use in flow cytometry. A chlorophyll (or bacteriochlorophyll) constitutes an intrinsic tandem dye given the red (or near-infrared) fluorescence upon excitation in the higher energy ultraviolet (UV) or visible absorption bands (due to rapid internal conversion to the lowest energy state). Synthetic (bacterio)chlorins are available with strong absorption (near-UV molar absorption coefficient ɛ(λexc) 105 M-1cm-1), modest fluorescence quantum yield (Φf = 0.05-0.30), and narrow fluorescence band (10-25 nm) tunable from 600-900 nm depending on synthetic design. The "relative practical brightness" is given by intrinsic brightness [ɛ(λexc) x Φf] times ηf, the fraction of the fluorescence band that is captured by an emission filter in a multicolor experiment. The spectroscopic features of (bacterio)chlorins are evaluated quantitatively to illustrate practical brightness for this novel class of fluorophores in a prospective 8-color panel.

Redox regulation of energy transfer efficiency in antennas of green photosynthetic bacteria

NASA Technical Reports Server (NTRS)

Blankenship, R. E.; Cheng, P.; Causgrove, T. P.; Brune, D. C.; Wang, J.

1993-01-01

The efficiency of energy transfer from the peripheral chlorosome antenna structure to the membrane-bound antenna in green sulfur bacteria depends strongly on the redox potential of the medium. The fluorescence spectra and lifetimes indicate that efficient quenching pathways are induced in the chlorosome at high redox potential. The midpoint redox potential for the induction of this effect in isolated chlorosomes from Chlorobium vibrioforme is -146 mV at pH 7 (vs the normal hydrogen electrode), and the observed midpoint potential (n = 1) decreases by 60 mV per pH unit over the pH range 7-10. Extraction of isolated chlorosomes with hexane has little effect on the redox-induced quenching, indicating that the component(s) responsible for this effect are bound and not readily extractable. We have purified and partially characterized the trimeric water-soluble bacteriochlorophyll a-containing protein from the thermophilic green sulfur bacterium Chlorobium tepidum. This protein is located between the chlorosome and the membrane. Fluorescence spectra of the purified protein indicate that it also contains groups that quench excitations at high redox potential. The results indicate that the energy transfer pathway in green sulfur bacteria is regulated by redox potential. This regulation appears to operate in at least two distinct places in the energy transfer pathway, the oligomeric pigments in the interior of the chlorosome and in the bacteriochlorophyll a protein. The regulatory effect may serve to protect the cell against superoxide-induced damage when oxygen is present. By quenching excitations before they reach the reaction center, reduction and subsequent autooxidation of the low potential electron acceptors found in these organisms is avoided.

Aerobic Anoxygenic Phototrophic Bacteria in the Mid-Atlantic Bight and the North Pacific Gyre. Revised

NASA Technical Reports Server (NTRS)

Cottrell, Matthew T.; Mannino, Antonio; Kirchman, David L.

2005-01-01

The abundance of aerobic anoxygenic phototrophic (AM) bacteria, cyanobacteria and heterotrophs was examined in the Mid-Atlantic Bight and the central North Pacific gyre using infrared fluorescence microscopy coupled with image analysis and flow cytometry. AAP bacteria comprised 5% to 16% of total prokaryotes in the Atlantic but only 5% or less in the Pacific. In the Atlantic, AAP bacterial abundance was as much as 2-fold higher than Prochlorococcus and 10-folder higher than Synechococcus. In contrast, Prochlorococcus outnumbered AAP bacteria 5- to 50-fold in the Pacific. In both oceans, subsurface abundance maxima occurred within the photic zone, and AAP bacteria were least abundant below the 1% light depth. Concentrations of bacteriochlorophyll a (BChl a) were low (approx.1%) compared to chlorophyll a. Although the BChl a content of AAP bacteria per cell was typically 20- to 250-fold lower than the divinyl-chlorophyll a content of Prochlorococcus, in shelf break water the pigment content of AAP bacteria approached that of Prochlorococcus. The abundance of AAP bacteria rivaled some groups of strictly heterotrophic bacteria and was often higher than the abundance of known AAP genera (Erythrobacter and Roseobacter spp.). The distribution of AAP bacteria in the water column, which was similar in the Atlantic and the Pacific, was consistent with phototrophy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wasielewski, M.R.; Gast, P.; Norris, J.R.

Photoexcitation of the reaction center protein from purple photosynthetic bacteria results in rapid (< 5 ps) formation of a radical pair, P/sup F/ composed of an oxidized bacteriochlorophyll a dimer, P/sup +/ and a reduced bacteriopheophytin a, I/sup -/. The recent crystallization of the reaction center protein from R. viridis enables us to use magnetic resonance to obtain structural information about the reaction center relatively rapidly. We have grown large numbers of R. viridis reaction center crystals and have determined the orientation of the triplet axis system of the primary donor to within + 1 degree as well as amore » number of magnetically non-equivalent donor sites in the crystal.« less

Spectral diffusion and electron-phonon coupling of the B800 BChl a molecules in LH2 complexes from three different species of purple bacteria.

PubMed

Baier, J; Gabrielsen, M; Oellerich, S; Michel, H; van Heel, M; Cogdell, R J; Köhler, J

2009-11-04

We have investigated the spectral diffusion and the electron-phonon coupling of B800 bacteriochlorophyll a molecules in the peripheral light-harvesting complex LH2 for three different species of purple bacteria, Rhodobacter sphaeroides, Rhodospirillum molischianum, and Rhodopseudomonas acidophila. We come to the conclusion that B800 binding pockets for Rhodobacter sphaeroides and Rhodopseudomonas acidophila are rather similar with respect to the polarity of the protein environment but that the packaging of the alphabeta-polypeptides seems to be less tight in Rb. sphaeroides with respect to the other two species.

Path induced coherent energy transfer in light-harvesting complexes in purple bacteria

NASA Astrophysics Data System (ADS)

Sun, Kewei; Ye, Jun; Zhao, Yang

2014-09-01

Features of path dependent energy transfer in a dual-ring light-harvesting (LH2) complexes (B850) system have been examined in detail systematically. The Frenkel-Dirac time dependent variational method with the Davydov D1 Ansatz is employed with detailed evolution of polaron dynamics in real space readily obtained. It is found that the phase of the transmission amplitude through the LH2 complexes plays an important role in constructing the coherent excitonic energy transfer. It is also found that the symmetry breaking caused by the dimerization of bacteriochlorophylls and coherence or correlation between two rings will be conducive in enhancing the exciton transfer efficiency.

Stoichiometry of ATP hydrolysis and chlorophyllide formation of dark-operative protochlorophyllide oxidoreductase from Rhodobacter capsulatus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nomata, Jiro; Terauchi, Kazuki; Fujita, Yuichi, E-mail: fujita@agr.nagoya-u.ac.jp

Dark-operative protochlorophyllide (Pchlide) oxidoreductase (DPOR) is a nitrogenase-like enzyme catalyzing a reduction of the C17 = C18 double bond of Pchlide to form chlorophyllide a (Chlide) in bacteriochlorophyll biosynthesis. DPOR consists of an ATP-dependent reductase component, L-protein (a BchL dimer), and a catalytic component, NB-protein (a BchN–BchB heterotetramer). The L-protein transfers electrons to the NB-protein to reduce Pchlide, which is coupled with ATP hydrolysis. Here we determined the stoichiometry of ATP hydrolysis and the Chlide formation of DPOR. The minimal ratio of ATP to Chlide (ATP/2e{sup –}) was 4, which coincides with that of nitrogenase. The ratio increases with increasing molar ratiomore » of L-protein to NB-protein. This profile differs from that of nitrogenase. These results suggest that DPOR has a specific intrinsic property, while retaining the common features shared with nitrogenase. - Highlights: • The stoichiometry of nitrogenase-like protochlorophyllide reductase was determined. • The minimal ATP/2e{sup –} ratio was 4, which coincides with that of nitrogenase. • The ATP/2e{sup –} ratio increases with increasing L-protein/NB-protein molar ratio. • DPOR has an intrinsic property, but retains features shared with nitrogenase.« less

Apo-bacteriophytochromes modulate bacterial photosynthesis in response to low light.

PubMed

Fixen, Kathryn R; Baker, Anna W; Stojkovic, Emina A; Beatty, J Thomas; Harwood, Caroline S

2014-01-14

Bacteriophytochromes (BphPs) are light-sensing regulatory proteins encoded by photosynthetic and nonphotosynthetic bacteria. This protein class has been characterized structurally, but its biological activities remain relatively unexplored. Two BphPs in the anoxygenic photosynthetic bacterium Rhodopseudomonas palustris, designated regulatory proteins RpBphP2 and RpBphP3, are configured as light-regulated histidine kinases, which initiate a signal transduction system that controls expression of genes for the low light harvesting 4 (LH4) antenna complex. In vitro, RpBphP2 and RpBphP3 respond to light quality by reversible photoconversion, a property that requires the light-absorbing chromophore biliverdin. In vivo, RpBphP2 and RpBphP3 are both required for the expression of the LH4 antenna complex under anaerobic conditions, but biliverdin requires oxygen for its synthesis by heme oxygenase. On further investigation, we found that the apo-bacteriophytochrome forms of RpBphP2 and RpBphP3 are necessary and sufficient to control LH4 expression in response to light intensity in conjunction with other signal transduction proteins. One possibility is that the system senses a reduced quinone pool generated when light energy is absorbed by bacteriochlorophyll. The biliverdin-bound forms of the BphPs have the additional property of being able to fine-tune LH4 expression in response to light quality. These observations support the concept that some bacteriophytochromes can function with or without a chromophore and may be involved in regulating physiological processes not directly related to light sensing.

Effects of aggregation on the excitation dynamics of LH2 from Thermochromatium tepidum in aqueous phase and in chromatophores.

PubMed

Yang, Fan; Yu, Long-Jiang; Wang, Peng; Ai, Xi-Cheng; Wang, Zheng-Yu; Zhang, Jian-Ping

2011-06-23

We carried out femtosecond magic-angle and polarized pump-probe spectroscopies for the light-harvesting complex 2 (LH2) from Thermochromatium (Tch.) tepidum in aqueous phase and in chromatophores. To examine the effects of LH2 aggregation on the dynamics of excitation energy transfer, dominant monodispersed and aggregated LH2s were prepared by controlling the surfactant concentrations. The aqueous preparations solubilized with different concentrations of n-dodecyl-β-D-maltoside (DDM) show similar visible-to-near-infrared absorption spectra, but distinctively different aggregation states, as revealed by using dynamic light scattering. The B800 → B850 intra-LH2 energy transfer time was determined to be 1.3 ps for isolated LH2, which, upon aggregation in aqueous phase or clustering in chromatophores, shortened to 1.1 or 0.9 ps, respectively. The light-harvesting complex 1 (LH1) of this thermophilic purple sulfur bacterium contains bacteriochlorophyll a absorbing at 915 nm (B915), and the LH2(B850) → LH1(B915) intercomplex transfer time in chromatophores was found to be 6.6 ps. For chromatophores, a depolarization time of 21 ps was derived from the anisotropy kinetics of B850*, which is attributed to the migration of B850* excitation before being trapped by LH1. In addition, the B850* annihilation is accelerated upon LH2 aggregation in aqueous phase, but it is much less severe upon LH2 clustering in the intracytoplasmic membrane. These results are helpful in understanding the light-harvesting function of a bacterial photosynthetic membrane incorporating different types of antenna complexes.

Chlorophyll and carotenoid pigments in solar saltern microbial mats

NASA Astrophysics Data System (ADS)

Villanueva, Joan; Grimalt, Joan O.; de Wit, Rutger; Keely, Brendan J.; Maxwell, James R.

1994-11-01

The distributions of carotenoids, chlorophylls, and their degradation products have been studied in two microbial mat systems developed in the calcite and calcite/gypsum evaporite domains of a solar saltern system. Phormidium valderianum and Microcoleus chthonoplastes are the dominant cyanobacterial species, respectively, and large amounts of Chloroflexus-like bacteria occur in the carbonate/gypsum mat. In both systems, the major pigments are chlorophyll a, zeaxanthin, β-carotene and myxoxanthophyll, which originate from these mat-building cyanobacteria. This common feature contrasts with differences in other pigments that are specific for each mat community. Thus, chlorophyll c and fucoxanthin, reflecting diatom inputs, are only found in the calcite mat, whereas the calcite/gypsum mat contains high concentrations of bacteriochlorophylls c produced by the multicellular green filamentous bacteria. In both cases, the depth concentration profiles (0-30 and 0-40 mm) show a relatively good preservation of the cyanobacterial carotenoids, zeaxanthin, β-carotene, myxoxanthophyll, and echinenone. This contrasts with the extensive biodegradation of cyanobacterial remains observed microscopically. Fucoxanthin in the calcite mat is also transformed at a faster rate than the cyanobacterial carotenoids. Chlorophyll a, the major pigment in both mats, exhibits different transformation pathways. In the calcite/gypsum mat, it is transformed via C-13 2 carbomethoxy defunctionalization prior to loss of the phytyl chain, leading to the formation of pyrophaeophytin a and, subsequently, pyrophaeophorbide a. On the other hand, the occurrence of the enzyme chlorophyllase, attributed to diatoms in the calcite mat, gives rise to extensive phytyl hydrolysis, with the formation of chlorophyllide a, pyrophaeophorbide a and, in minor proportion, phaeophorbide a. Studies of the sources of the photosynthetic pigments and of their transformation pathways in such simplified ecosystems provide a basis for the understanding of the distribution patterns of these compounds in more complex aquatic environments.

Seasonal occurrence of anoxygenic photosynthesis in Tillari and Selaulim reservoirs, Western India

NASA Astrophysics Data System (ADS)

Kurian, S.; Roy, R.; Repeta, D. J.; Gauns, M.; Shenoy, D. M.; Suresh, T.; Sarkar, A.; Narvenkar, G.; Johnson, C. G.; Naqvi, S. W. A.

2012-07-01

Phytoplankton and bacterial pigment compositions were determined by high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) in two freshwater reservoirs (Tillari Dam and Selaulim Dam), which are located at the foothills of the Western Ghats in India. These reservoirs experience anoxia in the hypolimnion during summer. Water samples were collected from both reservoirs during anoxic periods while one of them (Tillari Reservoir) was also sampled in winter, when convective mixing results in well-oxygenated conditions throughout the water column. During the period of anoxia (summer), bacteriochlorophyll (BChl) e isomers and isorenieratene, characteristic of brown sulfur bacteria, were dominant in the anoxic (sulfidic) layer of the Tillari Reservoir under low light intensities. The winter observations showed the dominance of small cells of Chlorophyll b-containing green algae and cyanobacteria, with minor presence of fucoxanthin-containing diatoms and peridinin-containing dinoflagellates. Using total BChl e concentration observed in June, the standing stock of brown sulfur bacteria carbon in the anoxic compartment of Tillari Reservoir was estimated to be 2.27 gC m-2, which is much higher than the similar estimate for carbon derived from oxygenic photosynthesis (0.82 gC m-2. The Selaulim Reservoir also displayed similar characteristics with the presence of BChl e isomers and isorenieratene in the anoxic hypolimnion during summer. Although sulfidic conditions prevailed in the water column below the thermocline, the occurrence of photo-autotrophic bacteria was restricted only to mid-depths (maximal concentration of BChl e isomers was detected at 0.2% of the surface incident light). This shows that the vertical distribution of photo-autotrophic sulfur bacteria is primarily controlled by light penetration in the water column where the presence of H2S provides a suitable biogeochemical environment for them to flourish.

Investigation on chlorosomal antenna geometries: tube, lamella and spiral-type self-aggregates.

PubMed

Linnanto, Juha M; Korppi-Tommola, Jouko E I

2008-06-01

Molecular mechanics calculations and exciton theory have been used to study pigment organization in chlorosomes of green bacteria. Single and double rod, multiple concentric rod, lamella, and Archimedean spiral macrostructures of bacteriochlorophyll c molecules were created and their spectral properties evaluated. The effects of length, width, diameter, and curvature of the macrostructures as well as orientations of monomeric transition dipole moment vectors on the spectral properties of the aggregates were studied. Calculated absorption, linear dichroism, and polarization dependent fluorescence-excitation spectra of the studied long macrostructures were practically identical, but circular dichroism spectra turned out to be very sensitive to geometry and monomeric transition dipole moment orientations of the aggregates. The simulations for long multiple rod and spiral-type macrostructures, observed in recent high-resolution electron microscopy images (Oostergetel et al., FEBS Lett 581:5435-5439, 2007) gave shapes of circular dichroism spectra observed experimentally for chlorosomes. It was shown that the ratio of total circular dichroism intensity to integrated absorption of the Q(y) transition is a good measure of degree of tubular structures in the chlorosomes. Calculations suggest that the broad Q(y) line width of chlorosomes of sulfur bacteria could be due to (1) different orientations of the transition moment vectors in multi-walled rod structures or (2) a variety of Bchl-aggregate structures in the chlorosomes.

Linear-scaling time-dependent density-functional theory beyond the Tamm-Dancoff approximation: Obtaining efficiency and accuracy with in situ optimised local orbitals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zuehlsdorff, T. J., E-mail: tjz21@cam.ac.uk; Payne, M. C.; Hine, N. D. M.

2015-11-28

We present a solution of the full time-dependent density-functional theory (TDDFT) eigenvalue equation in the linear response formalism exhibiting a linear-scaling computational complexity with system size, without relying on the simplifying Tamm-Dancoff approximation (TDA). The implementation relies on representing the occupied and unoccupied subspaces with two different sets of in situ optimised localised functions, yielding a very compact and efficient representation of the transition density matrix of the excitation with the accuracy associated with a systematic basis set. The TDDFT eigenvalue equation is solved using a preconditioned conjugate gradient algorithm that is very memory-efficient. The algorithm is validated on amore » small test molecule and a good agreement with results obtained from standard quantum chemistry packages is found, with the preconditioner yielding a significant improvement in convergence rates. The method developed in this work is then used to reproduce experimental results of the absorption spectrum of bacteriochlorophyll in an organic solvent, where it is demonstrated that the TDA fails to reproduce the main features of the low energy spectrum, while the full TDDFT equation yields results in good qualitative agreement with experimental data. Furthermore, the need for explicitly including parts of the solvent into the TDDFT calculations is highlighted, making the treatment of large system sizes necessary that are well within reach of the capabilities of the algorithm introduced here. Finally, the linear-scaling properties of the algorithm are demonstrated by computing the lowest excitation energy of bacteriochlorophyll in solution. The largest systems considered in this work are of the same order of magnitude as a variety of widely studied pigment-protein complexes, opening up the possibility of studying their properties without having to resort to any semiclassical approximations to parts of the protein environment.« less

The effect of β-saturated pyrrolic rings on the electronic structures and aromaticity of magnesium porphyrin derivatives: a density functional study.

PubMed

Wan, Liang; Qi, Dongdong; Zhang, Yuexing

2011-09-01

Density functional theory (DFT) calculation on the molecular structures, molecular orbitals, electronic absorption spectra, and magnetic properties of magnesium porphyrin (MgPor) and a series of five hydrogenated magnesium porphyrin complexes with different number of β-saturated pyrrolic rings, namely MgPor-β-1Hy, MgPor-β-opp-2Hy, MgPor-β-adj-2Hy, MgPor-β-3Hy, and MgPor-β-4Hy, clarifies the red-shift of the lowest energy absorption band from chlorophyll a to bacteriochlorophyll and reveals the strong chemical stability for both of them. The energy levels of highest occupied molecular orbitals (HOMO) and HOMO-1 for MgPor are reversed upon hydrogenation at β-positions (2 and 3, 7 and 8, 12 and 13, and 17 and 18) of porphyrin ring. Along with the increase of β-saturated pyrrolic rings from 1, 2, 3, to 4, the HOMO energy increases from -4.78 eV to -3.10 eV in a regular manner. In contrast, the lowest unoccupied molecular orbitals (LUMO) energy levels of MgPor, MgPor-β-1Hy, and MgPor-β-opp-2Hy are very similar with each other. As a result, the lowest energy absorption band involving main transition from HOMO to LUMO is red-shifted from MgPor-β-1Hy to MgPor-β-opp-2Hy which is representative of chlorophyll a and bacteriochlorophyll, respectively. Natural hydroporphyrins represented by MgPor, MgPor-β-1Hy, and MgPor-β-opp-2Hy have turned out to be aromatic and stable enough, in good accordance with the ubiquity of their derivatives in the nature. In contrast, MgPor-β-adj-2Hy, MgPor-β-3Hy, and MgPor-β-4Hy with relatively weak aromaticity seem to be unstable and therefore were not found in nature. Copyright © 2011 Elsevier Inc. All rights reserved.

Proposal for probing energy transfer pathway by single-molecule pump-dump experiment.

PubMed

Tao, Ming-Jie; Ai, Qing; Deng, Fu-Guo; Cheng, Yuan-Chung

2016-06-09

The structure of Fenna-Matthews-Olson (FMO) light-harvesting complex had long been recognized as containing seven bacteriochlorophyll (BChl) molecules. Recently, an additional BChl molecule was discovered in the crystal structure of the FMO complex, which may serve as a link between baseplate and the remaining seven molecules. Here, we investigate excitation energy transfer (EET) process by simulating single-molecule pump-dump experiment in the eight-molecules complex. We adopt the coherent modified Redfield theory and non-Markovian quantum jump method to simulate EET dynamics. This scheme provides a practical approach of detecting the realistic EET pathway in BChl complexes with currently available experimental technology. And it may assist optimizing design of artificial light-harvesting devices.

Proposal for probing energy transfer pathway by single-molecule pump-dump experiment

NASA Astrophysics Data System (ADS)

Tao, Ming-Jie; Ai, Qing; Deng, Fu-Guo; Cheng, Yuan-Chung

2016-06-01

The structure of Fenna-Matthews-Olson (FMO) light-harvesting complex had long been recognized as containing seven bacteriochlorophyll (BChl) molecules. Recently, an additional BChl molecule was discovered in the crystal structure of the FMO complex, which may serve as a link between baseplate and the remaining seven molecules. Here, we investigate excitation energy transfer (EET) process by simulating single-molecule pump-dump experiment in the eight-molecules complex. We adopt the coherent modified Redfield theory and non-Markovian quantum jump method to simulate EET dynamics. This scheme provides a practical approach of detecting the realistic EET pathway in BChl complexes with currently available experimental technology. And it may assist optimizing design of artificial light-harvesting devices.

Proposal for probing energy transfer pathway by single-molecule pump-dump experiment

PubMed Central

Tao, Ming-Jie; Ai, Qing; Deng, Fu-Guo; Cheng, Yuan-Chung

2016-01-01

The structure of Fenna-Matthews-Olson (FMO) light-harvesting complex had long been recognized as containing seven bacteriochlorophyll (BChl) molecules. Recently, an additional BChl molecule was discovered in the crystal structure of the FMO complex, which may serve as a link between baseplate and the remaining seven molecules. Here, we investigate excitation energy transfer (EET) process by simulating single-molecule pump-dump experiment in the eight-molecules complex. We adopt the coherent modified Redfield theory and non-Markovian quantum jump method to simulate EET dynamics. This scheme provides a practical approach of detecting the realistic EET pathway in BChl complexes with currently available experimental technology. And it may assist optimizing design of artificial light-harvesting devices. PMID:27277702

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norris, J.R.; Budil, D.E.; Gast, P.

The orientation of the principal axes of the primary electron donor triplet state measured in single crystals of photosynthetic reaction centers is compared to the x-ray structures of the bacteria Rhodobacter (Rb.) sphaeroides R-26 and Rhodopseudomonas (Rps.) viridis. The primary donor of Rps. viridis is significantly different from that of Rb. sphaeroides. The measured directions of the axes indicate that triplet excitation is almost completely localized on the L-subunit half of the dimer in Rps. viridis but is more symmetrically distributed on the dimeric donor in Rb. sphaeroides R-26. The large reduction of the zero field splitting parameters relative tomore » monomeric bacteriochlorophyll triplet in vitro suggests significant participation of asymmetrical charge transfer electronic configurations in the special pair triplet state of both organisms.« less

[On the influence of local molecular environment on the redox potential of electron transfer cofactors in bacterial photosynthetic reaction centers].

PubMed

Krasil'nikov, P M; Noks, P P; Rubin, A B

2011-01-01

The addition of cryosolvents (glycerol, dimethylsulfoxide) to a water solution containing bacterial photosynthetic reaction centers changes the redox potential of the bacteriochlorophyll dimer, but does not affect the redox potential of the quinone primary acceptor. It has been shown that the change in redox potential can be produced by changes of the electrostatic interactions between cofactors and the local molecular environment modified by additives entered into the solution. The degree of influence of a solvent on the redox potential of various cofactors is determined by degree of availability of these cofactors for molecules of solvent, which depends on the arrangement of cofactors in the structure of reaction centers.

Novel substrate (algal protein) for cultivation of Rhodospirillum rubrum.

PubMed

Vatsala, T M; Rekha, R; Srividhya, R

2011-10-01

Rhodospirillum rubrum was grown under light anaerobic conditions with phycocyanin (C-pc) extracted from Spirulina platensis as the sole source of carbon and nitrogen. When grown under these conditions cellular components like lipids, carbohydrates, protein, carotenoids, bacteriochlorophyll were similar to the one grown with malic acid and ammonium chloride. Growth of R. rubrum increased with increase in concentration of C-pc (200 to 1000 mg/l). R. rubrum also utilized C-pc under dark anaerobic condition. With both malic acid and C-pc as carbon sources C-pc was consumed only after exhaustion of malic acid under light anaerobic condition. No aberration of cell morphology was seen under scanning electron microscope (SEM). R. rubrum utilized both phycocyanobilin and phycoprotein individually as well as in combination. When grown with 1000 mg/l of phycoprotein 450 mg/l of biomass was obtained, and with combination of phycocyanobilin (75 mg/l) and phycoprotein (925 mg/l) 610 mg/l of biomass was obtained. Phycocyanobilin alone did not inhibit the growth of R. rubrum. Utilization of C-pc with protease like activity was observed in plate assay. Protease like activity was also observed as zones around the colonies in plates containing sterilized casein, gelatin and filter sterilized bovine serum albumin. No amino acids were detected in the supernatant when analyzed with ninhydrin. Extracellular protease like activity was highest when C-pc was used as substrate (2.8 U/ml). Intracellular protease like activity was not detected in cell free extracts.

Multipulse spectroscopy on the wild-type and YM210W Bacterial Reaction Centre uncovers a new intermediate state in the special pair excited state

NASA Astrophysics Data System (ADS)

Cohen Stuart, T. A.; van Grondelle, R.

2009-06-01

The Bacterial Reaction Centre (BRC) has a complex electronic excited state, P ∗, that evolves into subsequent charge separated product states P +H - and P +B -. Pump-dump-probe spectroscopy on the wild-type BRC and on YM210W, a mutant with a stabilized, long-lived P ∗ excited state, has uncovered a new charge-separated state in both BRC's. When P ∗ is dumped, a fraction of its population is transferred to this state that has a strong Stark shift in the accessory bacteriochlorophyll (B M) region which serves as a signature for P + and a lifetime highly comparable to the slow phase of P ∗ decay. This lead us propose this intermediate to be P +/P -.

Polarized pump-probe spectroscopy of exciton transport in bacteriochlorophyll a- protein from Prosthecochloris aestuarii

DOE Office of Scientific and Technical Information (OSTI.GOV)

Causgrove, T.P.; Yang, S.; Struve, W.S.

1988-11-17

The polarization of the Q/sub x/ electronic transition in the BChl a-protein complex from the green sulfur bacterium Prosthecochloris aestuarii was monitored by pump-probe spectroscopy with approx. 1.5-ps resolution at 598, 603, and 609 nm. At 603 nm, the polarization decays with a mean lifetime of 4.78 ps. Substantial residual polarization appears at long times (the ratio A/sub parallel//A/sub perpendicular/ of optical densities for probe pulses polarized parallel and perpendicular to the excitation pulse is approx. 1.7) in consequence of the nonrandom chromophore orientations. The polarized pump-probe transients have been analyzed in terms of an exciton hopping model that incorporatesmore » the known geometry of the BChl a-protein.« less

Dependence of singlet-energy transfer on the conjugation length of carotenoids reconstituted into the LH1 complex from Rhodospirillum rubrum G9

NASA Astrophysics Data System (ADS)

Akahane, Junji; Rondonuwu, Ferdy S.; Fiedor, Leszek; Watanabe, Yasutaka; Koyama, Yasushi

2004-07-01

A set of carotenoids, i.e., neurosporene, spheroidene, lycopene, anhydrorhodovibrin and spirilloxanthin, having the number of conjugated double bonds n=9, 10, 11, 12 and 13, were incorporated into the LH1 antenna complex from Rhodospirillum rubrum G9, and the carotenoid-bacteriochlorophyll (Cars-BChl) singlet energy-transfer efficiencies were determined by subpicosecond time-resolved absorption spectroscopy to be 78%, 75%, 46%, 40% and 36%, respectively. In carotenoids with n=9 and 10, all the 1B u+, 1B u- and 2A g- channels were open, whereas in carotenoids with n=11-13 the 1B u- and 2A g- channels were closed, causing a sudden drop in the efficiency on going from n=10 to 11.

Spatial variability in photosynthetic and heterotrophic activity drives localized δ13C org fluctuations and carbonate precipitation in hypersaline microbial mats.

PubMed

Houghton, J; Fike, D; Druschel, G; Orphan, V; Hoehler, T M; Des Marais, D J

2014-11-01

Modern laminated photosynthetic microbial mats are ideal environments to study how microbial activity creates and modifies carbon and sulfur isotopic signatures prior to lithification. Laminated microbial mats from a hypersaline lagoon (Guerrero Negro, Baja California, Mexico) maintained in a flume in a greenhouse at NASA Ames Research Center were sampled for δ(13) C of organic material and carbonate to assess the impact of carbon fixation (e.g., photosynthesis) and decomposition (e.g., bacterial respiration) on δ(13) C signatures. In the photic zone, the δ(13) C org signature records a complex relationship between the activities of cyanobacteria under variable conditions of CO2 limitation with a significant contribution from green sulfur bacteria using the reductive TCA cycle for carbon fixation. Carbonate is present in some layers of the mat, associated with high concentrations of bacteriochlorophyll e (characteristic of green sulfur bacteria) and exhibits δ(13) C signatures similar to DIC in the overlying water column (-2.0‰), with small but variable decreases consistent with localized heterotrophic activity from sulfate-reducing bacteria (SRB). Model results indicate respiration rates in the upper 12 mm of the mat alter in situ pH and HCO3- concentrations to create both phototrophic CO2 limitation and carbonate supersaturation, leading to local precipitation of carbonate minerals. The measured activity of SRB with depth suggests they variably contribute to decomposition in the mat dependent on organic substrate concentrations. Millimeter-scale variability in the δ(13) C org signature beneath the photic zone in the mat is a result of shifting dominance between cyanobacteria and green sulfur bacteria with the aggregate signature overprinted by heterotrophic reworking by SRB and methanogens. These observations highlight the impact of sedimentary microbial processes on δ(13) C org signatures; these processes need to be considered when attempting to relate observed isotopic signatures in ancient sedimentary strata to conditions in the overlying water column at the time of deposition and associated inferences about carbon cycling. © 2014 John Wiley & Sons Ltd.

Manipulating the Energetics and Rates of Electron Transfer in Rhodobacter capsulatus Reaction Centers with Asymmetric Pigment Content

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faries, Kaitlyn M.; Dylla, Nicholas P.; Hanson, Deborah K.

2017-07-17

Seemingly redundant parallel pathways for electron transfer (ET), composed of identical sets of cofactors, are a cornerstone feature of photosynthetic reaction centers (RCs) involved in light-energy conversion. In native bacterial RCs, both A and B branches house one bacteriochlorophyll (BChl) and one bacteriopheophytin (BPh), but the A branch is used exclusively. Described herein are the results-obtained for two Rhodobacter capsulatus RCs with an unnaturally high degree of cofactor asymmetry, two BPh on the RC's B side and two BChl on the A side. These pigment changes derive, respectively, from the His(M180)Leu mutation [a BPh ((Phi(B)) replaces the B-side BChl (BB)],more » and the Leu(M212)His mutation [a BChl (beta(A))) replaces the A-side BPh (H-A)]. Additionally, Tyr(M208)Phe was employed to disfavor ET to the A branch; in one mutant, Val(M131)Glu creates a hydrogen bond to H-B to enhance ET to H-B. In both Phi(B) mutants, the decay kinetics of the excited primary ET donor (P*) resolve three populations with lifetimes of similar to 9 ps (50-60%), similar to 40 ps (10-20%), and similar to 200 ps (20-30%), with P+Phi(-)(B) formed predominantly from the 9 ps fraction. The 50-60% yield of P+Phi(B)- is the highest yet observed for a Phi(B)-containing RC. The results provide insight into factors needed for efficient multistep ET.« less

Dynamics of energy transfer from lycopene to bacteriochlorophyll in genetically-modified LH2 complexes of Rhodobacter sphaeroides.

PubMed

Hörvin Billsten, H; Herek, J L; Garcia-Asua, G; Hashøj, L; Polívka, T; Hunter, C N; Sundström, V

2002-03-26

LH2 complexes from Rb. sphaeroides were modified genetically so that lycopene, with 11 saturated double bonds, replaced the native carotenoids which contain 10 saturated double bonds. Tuning the S1 level of the carotenoid in LH2 in this way affected the dynamics of energy transfer within LH2, which were investigated using both steady-state and time-resolved techniques. The S1 energy of lycopene in n-hexane was determined to be approximately 12 500 +/- 150 cm(-1), by direct measurement of the S1-S2 transient absorption spectrum using a femtosecond IR-probing technique, thus placing an upper limit on the S1 energy of lycopene in the LH2 complex. Fluorescence emission and excitation spectra demonstrated that energy can be transferred from lycopene to the bacteriochlorophyll molecules within this LH2 complex. The energy-transfer dynamics within the mutant complex were compared to wild-type LH2 from Rb. sphaeroides containing the carotenoid spheroidene and from Rs. molischianum, in which lycopene is the native carotenoid. The results show that the overall efficiency for Crt --> B850 energy transfer is approximately 80% in lyco-LH2 and approximately 95% in WT-LH2 of Rb. sphaeroides. The difference in overall Crt --> BChl transfer efficiency of lyco-LH2 and WT-LH2 mainly relates to the low efficiency of the Crt S(1) --> BChl pathway for complexes containing lycopene, which was 20% in lyco-LH2. These results show that in an LH2 complex where the Crt S1 energy is sufficiently high to provide efficient spectral overlap with both B800 and B850 Q(y) states, energy transfer via the Crt S1 state occurs to both pigments. However, the introduction of lycopene into the Rb. sphaeroides LH2 complex lowers the S1 level of the carotenoid sufficiently to prevent efficient transfer of energy to the B800 Q(y) state, leaving only the Crt S1 --> B850 channel, strongly suggesting that Crt S1 --> BChl energy transfer is controlled by the relative Crt S1 and BChl Q(y) energies.

Mechanism of energy transfer from carotenoids to bacteriochlorophyll : light-harvesting by carotenoids having different extents of {pi}-electron conjugation incorporated into the B850 antenna complex from the carotenoidless bacterium Rhodobacter sphaeroides R-26.1.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Desamero, R. Z. B.; Chynwat, V.; van der Hoef, I.

1998-10-15

Spheroidene and a series of spheroidene analogues with extents of p-electron conjugation ranging from 7 to 13 carbon-carbon double bonds were incorporated into the B850 light-harvesting complex of Rhodobacter sphaeroides R-26.1. The structures and spectroscopic properties of the carotenoids and the dynamics of energy transfer from the carotenoid to bacteriochlorophyll (BChl) in the B850 complex were studied by using steady-state absorption, fluorescence, fluorescence excitation, resonance Raman, and time-resolved absorption spectroscopy. The spheroidene analogues used in this study were 5',6'-dihydro-7',8'-didehydrospheroidene, 7',8'-didehydrospheroidene, and 1',2'-dihydro-3',4',7',8'-tetradehydrospheroidene. These data, taken together with results from 3,4,7,8-tetrahydrospheroidene, 3,4,5,6-tetrahydrospheroidene, 3,4-dihydrospheroidene, and spheroidene already published (Frank, H. A.; Farhoosh,more » R.; Aldema, M. L.; DeCoster, B.; Christensen, R. L.; Gebhard, R.; Lugtenburg, J. Photochem. Photobiol. 1993, 57, 49. Farhoosh, R.; Chynwat, V.; Gebhard, R.; Lugtenburg, J.; Frank, H. A. Photosynth. Res. 1994, 42, 157), provide a systematic series of molecules for understanding the molecular features that determine the mechanism of energy transfer from carotenoids to BChl in photosynthetic bacterial light-harvesting complexes. The data support the hypothesis that only carotenoids having 10 or less carbon-carbon double bonds transfer energy via their 21Ag (S1) states to BChl to any significant degree. Energy transfer via the 11Bu (S2) state of the carotenoid becomes more important than the S1 route as the number of conjugated carbon-carbon double bonds increases. The results also suggest that the S2 state associated with the Qx transition of the B850 BChl is the most likely acceptor state for energy transfer originating from both the 2{sup 1}A{sub g} (S{sub 1}) and 1{sup 1}B{sub u} (S{sub 2}) states of all carotenoids.« less

The nature of the lower excited state of the special pair of bacterial photosynthetic reaction center of Rhodobacter Sphaeroides and the dynamics of primary charge separation

NASA Astrophysics Data System (ADS)

Ivashin, N. V.; Shchupak, E. E.

2016-08-01

Quantum-chemical calculations of the structure in the ground and lower singlet excited states and the vibrations (in the ground state) of special pair P of photosynthetic reaction center of purple bacteria (RCPb) Rhodobacter Sphaeroides, consisting of two bacteriochlorophyll molecules PA and PB, have been carried out. It is shown that excitation of the special pair is followed by fast relaxation dynamics, accompanied by the transformation of the initial P* state into the P A δ+ P B δ- state (δ ~ 0.5) with charge separation. This behavior is due to the presence of several nonplanar vibrations with participation of the acetyl group of macrocycle PB in the nuclear wave packet on the potential surface of the P* state; these vibrations facilitate destabilization of the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) of the macrocycle PA and formation of the P A δ+ P B δ- state. The structural transformations in the P* state are due to its linking character in the contact region of the acetyl group-containing pyrrole rings of PA and PB. The transition from the P* state to specifically the P A δ+ P B δ- state is related to the fact that the acetyl group PA is involved in the intermolecular hydrogen bond with amino acid residue HisL168; for this reason, this group and the pyrrole ring linked with it can hardly participate in structural transformations. The electronic matrix element H12 of the electron transfer from the special pair in the P A δ+ P B δ- state to a molecule of accessory bacteriochlorophyll BA greatly exceeds that for the transfer to BB. This circumstance and the fact that the P A δ+ P B δ- state is energetically more favorable than the P* state facilitate the preferred directionality of the electron transfer in RCPb Rhodobacter Sphaeroides with participation of the cofactors located in its subunit L.

Time-resolved tryptophan fluorescence in photosynthetic reaction centers from Rhodobacter sphaeroides

NASA Technical Reports Server (NTRS)

Godik, V. I.; Blankenship, R. E.; Causgrove, T. P.; Woodbury, N.

1993-01-01

Tryptophan fluorescence of reaction centers isolated from Rhodobacter sphaeroides, both stationary and time-resolved, was studied. Fluorescence kinetics were found to fit best a sum of four discrete exponential components. Half of the initial amplitude was due to a component with a lifetime of congruent to 60 ps, belonging to Trp residues, capable of efficient transfer of excitation energy to bacteriochlorophyll molecules of the reaction center. The three other components seem to be emitted by Trp ground-state conformers, unable to participate in such a transfer. Under the influence of intense actinic light, photooxidizing the reaction centers, the yield of stationary fluorescence diminished by congruent to 1.5 times, while the number of the kinetic components and their life times remained practically unchanged. Possible implications of the observed effects for the primary photosynthesis events are considered.

Multilayer-MCTDH approach to the energy transfer dynamics in the LH2 antenna complex

NASA Astrophysics Data System (ADS)

Shibl, Mohamed F.; Schulze, Jan; Al-Marri, Mohammed J.; Kühn, Oliver

2017-09-01

The multilayer multiconfiguration time-dependent Hartree method is used to study the coupled exciton-vibrational dynamics in a high-dimensional nonameric model of the LH2 antenna complex of purple bacteria. The exciton-vibrational coupling is parametrized within the Huang-Rhys model according to phonon and intramolecular vibrational modes derived from an experimental bacteriochlorophyll spectral density. In contrast to reduced density matrix approaches, the Schrödinger equation is solved explicitly, giving access to the full wave function. This facilitates an unbiased analysis in terms of the coupled dynamics of excitonic and vibrational degrees of freedom. For the present system, we identify spectator modes for the B800 to B800 transfer and we find a non-additive effect of phonon and intramolecular vibrational modes on the B800 to B850 exciton transfer.

Influence of intra-pigment vibrations on dynamics of photosynthetic exciton.

PubMed

Sato, Yoshihiro; Doolittle, Brian

2014-11-14

We have numerically investigated the effect of an underdamped intra-pigment vibrational mode on an exciton's quantum coherence and energy transfer efficiency. Our model describes a bacteriochlorophyll a pigment-protein dimer under the conditions at which photosynthetic energy transfer occurs. The dimer is modeled using a theoretical treatment of a vibronic exciton, and its dynamics are numerically analyzed using a non-Markovian and non-perturbative method. We examined the system's response to various values of the Huang-Rhys factor, site energy difference, reorganization energy, and reorganization energy difference. We found that the inclusion of the intra-pigment vibronic mode allows for long-lived oscillatory quantum coherences to occur. This excitonic coherence is robust against static site-energy disorder. The vibrational mode also promotes exciton transfer along the site-energy landscape thus improving the overall energy transfer efficiency.

Ab initio quantum chemical calculation of electron transfer matrix elements for large molecules

NASA Astrophysics Data System (ADS)

Zhang, Linda Yu; Friesner, Richard A.; Murphy, Robert B.

1997-07-01

Using a diabatic state formalism and pseudospectral numerical methods, we have developed an efficient ab initio quantum chemical approach to the calculation of electron transfer matrix elements for large molecules. The theory is developed at the Hartree-Fock level and validated by comparison with results in the literature for small systems. As an example of the power of the method, we calculate the electronic coupling between two bacteriochlorophyll molecules in various intermolecular geometries. Only a single self-consistent field (SCF) calculation on each of the monomers is needed to generate coupling matrix elements for all of the molecular pairs. The largest calculations performed, utilizing 1778 basis functions, required ˜14 h on an IBM 390 workstation. This is considerably less cpu time than would be necessitated with a supermolecule adiabatic state calculation and a conventional electronic structure code.

The energies and kinetics of triplet carotenoids in the LH2 antenna complexes as determined by phosphorescence spectroscopy

NASA Astrophysics Data System (ADS)

Rondonuwu, Ferdy S.; Taguchi, Tokio; Fujii, Ritsuko; Yokoyama, Kyosuke; Koyama, Yasushi; Watanabe, Yasutaka

2004-01-01

The triplet (T 1) states of carotenoids (Cars) and bacteriochlorophyll a (BChl) in the LH2 antenna complexes from Rhodobacter sphaeroides G1C, Rba. sphaeroides 2.4.1 and Rhodospirillum molischianum, containing neurosporene, spheroidene and lycopene, respectively, were examined by stationary-state and time-resolved phosphorescence spectroscopy. The T 1 energies of Cars were determined, irrespective of the Car or BChl excitation, to be 7030 cm -1 (neurosporene), 6920 cm -1 (spheroidene) and 6870 cm -1 (lycopene), respectively, whereas that of BChl to be 7590 cm -1. In the Rba. sphaeroides G1C, the Car and BChl triplet states decayed in similar time constant as the BChl Q y state, a fact which indicates that the pair of triplet states decays through the triplet-triplet annihilation mechanism.

Patterns in Abundance, Cell Size and Pigment Content of Aerobic Anoxygenic Phototrophic Bacteria along Environmental Gradients in Northern Lakes

PubMed Central

Fauteux, Lisa; Cottrell, Matthew T.; Kirchman, David L.; Borrego, Carles M.; Garcia-Chaves, Maria Carolina; del Giorgio, Paul A.

2015-01-01

There is now evidence that aerobic anoxygenic phototrophic (AAP) bacteria are widespread across aquatic systems, yet the factors that determine their abundance and activity are still not well understood, particularly in freshwaters. Here we describe the patterns in AAP abundance, cell size and pigment content across wide environmental gradients in 43 temperate and boreal lakes of Québec. AAP bacterial abundance varied from 1.51 to 5.49 x 105 cells mL-1, representing <1 to 37% of total bacterial abundance. AAP bacteria were present year-round, including the ice-cover period, but their abundance relative to total bacterial abundance was significantly lower in winter than in summer (2.6% and 7.7%, respectively). AAP bacterial cells were on average two-fold larger than the average bacterial cell size, thus AAP cells made a greater relative contribution to biomass than to abundance. Bacteriochlorophyll a (BChla) concentration varied widely across lakes, and was not related to AAP bacterial abundance, suggesting a large intrinsic variability in the cellular pigment content. Absolute and relative AAP bacterial abundance increased with dissolved organic carbon (DOC), whereas cell-specific BChla content was negatively related to chlorophyll a (Chla). As a result, both the contribution of AAP bacteria to total prokaryotic abundance, and the cell-specific BChla pigment content were positively correlated with the DOC:Chla ratio, both peaking in highly colored, low-chlorophyll lakes. Our results suggest that photoheterotrophy might represent a significant ecological advantage in highly colored, low-chlorophyll lakes, where DOC pool is chemically and structurally more complex. PMID:25927833

Patterns in Abundance, Cell Size and Pigment Content of Aerobic Anoxygenic Phototrophic Bacteria along Environmental Gradients in Northern Lakes.

PubMed

Fauteux, Lisa; Cottrell, Matthew T; Kirchman, David L; Borrego, Carles M; Garcia-Chaves, Maria Carolina; Del Giorgio, Paul A

2015-01-01

There is now evidence that aerobic anoxygenic phototrophic (AAP) bacteria are widespread across aquatic systems, yet the factors that determine their abundance and activity are still not well understood, particularly in freshwaters. Here we describe the patterns in AAP abundance, cell size and pigment content across wide environmental gradients in 43 temperate and boreal lakes of Québec. AAP bacterial abundance varied from 1.51 to 5.49 x 105 cells mL-1, representing <1 to 37% of total bacterial abundance. AAP bacteria were present year-round, including the ice-cover period, but their abundance relative to total bacterial abundance was significantly lower in winter than in summer (2.6% and 7.7%, respectively). AAP bacterial cells were on average two-fold larger than the average bacterial cell size, thus AAP cells made a greater relative contribution to biomass than to abundance. Bacteriochlorophyll a (BChla) concentration varied widely across lakes, and was not related to AAP bacterial abundance, suggesting a large intrinsic variability in the cellular pigment content. Absolute and relative AAP bacterial abundance increased with dissolved organic carbon (DOC), whereas cell-specific BChla content was negatively related to chlorophyll a (Chla). As a result, both the contribution of AAP bacteria to total prokaryotic abundance, and the cell-specific BChla pigment content were positively correlated with the DOC:Chla ratio, both peaking in highly colored, low-chlorophyll lakes. Our results suggest that photoheterotrophy might represent a significant ecological advantage in highly colored, low-chlorophyll lakes, where DOC pool is chemically and structurally more complex.

[Chlorobaculum macestae sp. nov., a new green sulfur bacterium].

PubMed

Koppen, O I; Berg, I A; Lebedeva, N V; Taisova, A S; Kolganova, T V; Slobodova, N V; Bulygina, E S; Turova, T P; Ivanovskiĭ, R N

2008-01-01

The investigated green sulfur bacterium, strain M, was isolated from a sulfidic spring on the Black Sea Coast of the Caucasus. The cells of strain M are straight or curved rods 0.6-0.9 x 1.8-4.2 microm in size. According to the cell wall structure, the bacteria are gram-negative. Chlorosomes are located along the cell periphery. Strain M is an obligate anaerobe capable of photoautotrophic growth on sulfide, thiosulfate, and H2. It utilizes ammonium, urea, casein hydrolysate, and N2 as nitrogen sources and sulfide, thiosulfate, and elemental sulfur as sulfur sources. Bacteriochlorophyll c and the carotenoid chlorobactene are the main pigments. The optimal growth temperature is 25-28 degrees C; the optimal pH is 6.8. The strain does not require NaCl. Vitamin B12 stimulates growth. The content of the G+C base pairs in the DNA of strain M is 58.3 mol %. In the phylogenetic tree constructed on the basis of analysis of nucleotide sequences of 16S rRNA genes, strain M forms a separate branch, which occupies an intermediate position between the phylogenetic cluster containing representatives of the genus Chlorobaculum (94.9-96.8%) and the cluster containing species of the genus Chlorobium (94.1-96.5%). According to the results of analysis of the amino acid sequence corresponding to the fmo gene, strain M represents a branch which, unlike that in the "ribosomal" tree, falls into the cluster of the genus Chlorobaculum (95.8-97.2%). Phylogenetic analysis of the amino acid sequence corresponding to the nifH gene placed species of the genera Chlorobaculum and Chlorobium into a single cluster, whereas strain M formed a separate branch. The results obtained allow us to describe strain M as a new species of the genus Chlorobaculum. Chlorobaculum macestae sp. nov.

Lipophilic pigments from cyanobacterial (blue-green algal) and diatom mats in Hamelin Pool, Shark Bay, Western Australia

NASA Technical Reports Server (NTRS)

Palmisano, A. C.; Summons, R. E.; Cronin, S. E.; Des Marais, D. J.

1989-01-01

Lipophilic pigments were examined in microbial mat communities dominated by cyanobacteria in the intertidal zone and by diatoms in the subtidal and sublittoral zones of Hamelin Pool, Shark Bay, Western Australia. These microbial mats have evolutionary significance because of their similarity to lithfied stromatolites from the Proterozoic and Early Paleozoic eras. Fucoxanthin, diatoxanthin, diadinoxanthin, beta-carotene, and chlorophylls a and c characterized the diatom mats, whereas cyanobacterial mats contained myxoxanthophyll, zeaxanthin, echinenone, beta-carotene, chlorophyll a and, in some cases, sheath pigment. The presence of bacteriochlorophyll a within the mats suggest a close association of photosynthetic bacteria with diatoms and cyanobacteria. The high carotenoids : chlorophyll a ratios (0.84-2.44 wt/wt) in the diatom mats suggest that carotenoids served a photoprotective function in this high light environment. By contrast, cyanobacterial sheath pigment may have largely supplanted the photoprotective role of carotenoids in the intertidal mats.

Syntheses and Functionalizations of Porphyrin Macrocycles

PubMed Central

Vicente, Maria da G.H.; Smith, Kevin M.

2014-01-01

Porphyrin macrocycles have been the subject of intense study in the last century because they are widely distributed in nature, usually as metal complexes of either iron or magnesium. As such, they serve as the prosthetic groups in a wide variety of primary metabolites, such as hemoglobins, myoglobins, cytochromes, catalases, peroxidases, chlorophylls, and bacteriochlorophylls; these compounds have multiple applications in materials science, biology and medicine. This article describes current methodology for preparation of simple, symmetrical model porphyrins, as well as more complex protocols for preparation of unsymmetrically substituted porphyrin macrocycles similar to those found in nature. The basic chemical reactivity of porphyrins and metalloporphyrin is also described, including electrophilic and nucleophilic reactions, oxidations, reductions, and metal-mediated cross-coupling reactions. Using the synthetic approaches and reactivity profiles presented, eventually almost any substituted porphyrin system can be prepared for applications in a variety of areas, including in catalysis, electron transport, model biological systems and therapeutics. PMID:25484638

Analysis of lipophilic pigments from a phototrophic microbial mat community by high performance liquid chromatography

NASA Technical Reports Server (NTRS)

Palmisano, A. C.; Cronin, S. E.; Des Marais, D. J.

1988-01-01

As assay for lipophilic pigments in phototrophic microbial mat communities using reverse phase-high performance liquid chromatography was developed which allows the separation of 15 carotenoids and chloropigments in a single 30 min program. Lipophilic pigments in a laminated mat from a commercial salina near Laguna Guerrero Negro, Baja California Sur, Mexico reflected their source organisms. Myxoxanthophyll, echinenone, canthaxanthin, and zeaxanthin were derived from cyanobacteria; chlorophyll c, and fucoxanthin from diatoms; chlorophyll a from cyanobacteria and diatoms; bacteriochlorophylls a and c, bacteriophaeophytin a, and gamma-carotene from Chloroflexus spp.; and beta-carotene from a variety of phototrophs. Sensitivity of detection was 0.6-6.1 ng for carotenoids and 1.7-12 ng for most chloropigments. This assay represents a significant improvement over previous analyses of lipophilic pigments in microbial mats and promises to have a wider application to other types of phototrophic communities.

Subtle spectral effects accompanying the assembly of bacteriochlorophylls into cyclic light harvesting complexes revealed by high-resolution fluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Rätsep, Margus; Pajusalu, Mihkel; Linnanto, Juha Matti; Freiberg, Arvi

2014-10-01

We have observed that an assembly of the bacteriochloropyll a molecules into B850 and B875 groups of cyclic bacterial light-harvesting complexes LH2 and LH1, respectively, results an almost total loss of the intra-molecular vibronic structure in the fluorescence spectrum, and simultaneously, an essential enhancement of its phonon sideband due to electron-phonon coupling. While the suppression of the vibronic coupling in delocalized (excitonic) molecular systems is predictable, as also confirmed by our model calculations, a boost of the electron-phonon coupling is rather unexpected. The latter phenomenon is explained by exciton self-trapping, promoted by mixing the molecular exciton states with charge transfer states between the adjacent chromophores in the tightly packed B850 and B875 arrangements. Similar, although less dramatic trends were noted for the light-harvesting complexes containing chlorophyll pigments.

Femtosecond dynamics of energy transfer in B800-850 light-harvesting complexes of Rhodobacter sphaeroides.

PubMed Central

Trautman, J K; Shreve, A P; Violette, C A; Frank, H A; Owens, T G; Albrecht, A C

1990-01-01

We report femtosecond transient absorption studies of energy transfer dynamics in the B800-850 light-harvesting complex (LHC) of Rhodobacter sphaeroides 2.4.1. For complexes solubilized in lauryldimethylamine-N-oxide (LDAO), the carotenoid to bacteriochlorophyll (Bchl) B800 and carotenoid to Bchl B850 energy transfer times are 0.34 and 0.20 ps, respectively. The B800 to B850 energy transfer time is 2.5 ps. For complexes treated with lithium dodecyl sulfate (LDS), a carotenoid to B850 energy transfer time of less than or equal to 0.2 ps is seen, and a portion of the total carotenoid population is decoupled from Bchl. In both LDAO-solubilized and LDS-treated complexes an intensity-dependent picosecond decay component of the excited B850 population is ascribed to excitation annihilation within minimal units of the LHC. PMID:2404276

Carotenoids and Photosynthesis.

PubMed

Hashimoto, Hideki; Uragami, Chiasa; Cogdell, Richard J

2016-01-01

Carotenoids are ubiquitous and essential pigments in photosynthesis. They absorb in the blue-green region of the solar spectrum and transfer the absorbed energy to (bacterio-)chlorophylls, and so expand the wavelength range of light that is able to drive photosynthesis. This is an example of singlet-singlet energy transfer, and so carotenoids serve to enhance the overall efficiency of photosynthetic light reactions. Carotenoids also act to protect photosynthetic organisms from the harmful effects of excess exposure to light. Triplet-triplet energy transfer from chlorophylls to carotenoids plays a key role in this photoprotective reaction. In the light-harvesting pigment-protein complexes from purple photosynthetic bacteria and chlorophytes, carotenoids have an additional role of structural stabilization of those complexes. In this article we review what is currently known about how carotenoids discharge these functions. The molecular architecture of photosynthetic systems will be outlined first to provide a basis from which to describe carotenoid photochemistry, which underlies most of their important functions in photosynthesis.

Strong Coupling of Localized Surface Plasmons to Excitons in Light-Harvesting Complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsargorodska, Anna; Cartron, Michaël L.; Vasilev, Cvetelin

Gold nanostructure arrays exhibit surface plasmon resonances that split after attaching light harvesting complexes 1 and 2 (LH1 and LH2) from purple bacteria. The splitting is attributed to strong coupling between the localized surface plasmon resonances and excitons in the light-harvesting complexes. Wild-type and mutant LH1 and LH2 from Rhodobacter sphaeroides containing different carotenoids yield different splitting energies, demonstrating that the coupling mechanism is sensitive to the electronic states in the light harvesting complexes. Plasmon–exciton coupling models reveal different coupling strengths depending on the molecular organization and the protein coverage, consistent with strong coupling. Strong coupling was also observed formore » self-assembling polypeptide maquettes that contain only chlorins. However, it is not observed for monolayers of bacteriochlorophyll, indicating that strong plasmon–exciton coupling is sensitive to the specific presentation of the pigment molecules.« less

Biotechnology of Anoxygenic Phototrophic Bacteria.

PubMed

Frigaard, Niels-Ulrik

Anoxygenic phototrophic bacteria are a diverse collection of organisms that are defined by their ability to grow using energy from light without evolving oxygen. The dominant groups are purple sulfur bacteria, purple nonsulfur bacteria, green sulfur bacteria, and green and red filamentous anoxygenic phototrophic bacteria. They represent several bacterial phyla but they all have bacteriochlorophylls and carotenoids and photochemical reaction centers which generate ATP and cellular reductants used for CO 2 fixation. They typically have an anaerobic lifestyle in the light, although some grow aerobically in the dark. Some of them oxidize inorganic sulfur compounds for light-dependent CO 2 fixation; this ability can be exploited for photobiological removal of hydrogen sulfide from wastewater and biogas. The anoxygenic phototrophic bacteria also perform bioremediation of recalcitrant dyes, pesticides, and heavy metals under anaerobic conditions. Finally, these organisms may be useful for overexpression of membrane proteins and photobiological production of H 2 and other valuable compounds.

Strong Coupling of Localized Surface Plasmons to Excitons in Light-Harvesting Complexes

DOE PAGES

Tsargorodska, Anna; Cartron, Michaël L.; Vasilev, Cvetelin; ...

2016-09-30

Gold nanostructure arrays exhibit surface plasmon resonances that split after attaching light harvesting complexes 1 and 2 (LH1 and LH2) from purple bacteria. The splitting is attributed to strong coupling between the localized surface plasmon resonances and excitons in the light-harvesting complexes. Wild-type and mutant LH1 and LH2 from Rhodobacter sphaeroides containing different carotenoids yield different splitting energies, demonstrating that the coupling mechanism is sensitive to the electronic states in the light harvesting complexes. Plasmon–exciton coupling models reveal different coupling strengths depending on the molecular organization and the protein coverage, consistent with strong coupling. Strong coupling was also observed formore » self-assembling polypeptide maquettes that contain only chlorins. However, it is not observed for monolayers of bacteriochlorophyll, indicating that strong plasmon–exciton coupling is sensitive to the specific presentation of the pigment molecules.« less

Modeling Electronic-Nuclear Interactions for Excitation Energy Transfer Processes in Light-Harvesting Complexes.

PubMed

Lee, Mi Kyung; Coker, David F

2016-08-18

An accurate approach for computing intermolecular and intrachromophore contributions to spectral densities to describe the electronic-nuclear interactions relevant for modeling excitation energy transfer processes in light harvesting systems is presented. The approach is based on molecular dynamics (MD) calculations of classical correlation functions of long-range contributions to excitation energy fluctuations and a separate harmonic analysis and single-point gradient quantum calculations for electron-intrachromophore vibrational couplings. A simple model is also presented that enables detailed analysis of the shortcomings of standard MD-based excitation energy fluctuation correlation function approaches. The method introduced here avoids these problems, and its reliability is demonstrated in accurate predictions for bacteriochlorophyll molecules in the Fenna-Matthews-Olson pigment-protein complex, where excellent agreement with experimental spectral densities is found. This efficient approach can provide instantaneous spectral densities for treating the influence of fluctuations in environmental dissipation on fast electronic relaxation.

Mimicking the photosynthetic triplet energy-transfer relay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gust, D.; Moore, T.A.; Moore, A.L.

1993-06-30

In the reaction centers of photosynthetic organisms, chlorophyll triplet states are sometimes formed by recombination of charge-separated intermediates. These triplets are excellent sensitizers for singlet oxygen formation. Carotenoid polyenes can provide photoprotection from singlet oxygen generation by rapidly quenching chlorophyll triplet states via triplet-triplet energy transfer. Because in bacteria the reaction center carotenoid is not located adjacent to the bacteriochlorophyll special pair, which is the origin of the charge separation, it has been postulated that quenching may occur via a triplet relay involving an intermediate chlorophyll monomer. We now report the synthesis and spectroscopic study of a covalently linked carotenoidmore » (C)-porphyrin (P)-pyropheophorbide (Ppd) triad molecule which mimics this triplet relay. The pyropheophorbide singlet-state C-P-[sup 1]Ppd (generated by direct excitation or energy transfer from the attached porphyrin) undergoes intersystem crossing to the triplet C-P-[sup 3]Ppd. In oxygen-free solutions, this triplet decays to [sup 3]C-p-Ppd through a triplet-transfer relay involving an intermediate C-[sup 3]P-Ppd species. In aerated solutions, quenching of C-P-[sup 3]Ppd by the attached carotenoid competes with singlet oxygen sensitization and thus provides a degree of photoprotection. In a similar traid containing a zinc porphyrin moiety, triplet transfer is slow due to the higher energy of the C-[sup 3]P[sub Zn]-Ppd intermediate, and photoprotection via the relay is nonexistent. The triplet relay ceases to function at low temperatures in both the natural and biomimetic cases due to the endergonicity of the first step. 37 refs., 6 figs., 1 tab.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ponomarenko, N. S.; Poluektov, O. G.; Bylina, E. J.

High-field electron paramagnetic resonance (HF EPR) has been employed to investigate the primary electron donor electronic structure of Blastochloris viridis heterodimer mutant reaction centers (RCs). In these mutants the amino acid substitution His(M200)Leu or His(L173)Leu eliminates a ligand to the primary electron donor, resulting in the loss of a magnesium in one of the constituent bacteriochlorophylls (BChl). Thus, the native BChl/BChl homodimer primary donor is converted into a BChl/bacteriopheophytin (BPhe) heterodimer. The heterodimer primary donor radical in chemically oxidized RCs exhibits a broadened EPR line indicating a highly asymmetric distribution of the unpaired electron over both dimer constituents. Observed tripletmore » state EPR signals confirm localization of the excitation on the BChl half of the heterodimer primary donor. Theoretical simulation of the triplet EPR lineshapes clearly shows that, in the case of mutants, triplet states are formed by an intersystem crossing mechanism in contrast to the radical pair mechanism in wild type RCs. Photooxidation of the mutant RCs results in formation of a BPhe anion radical within the heterodimer pair. The accumulation of an intradimer BPhe anion is caused by the substantial loss of interaction between constituents of the heterodimer primary donor along with an increase in the reduction potential of the heterodimer primary donor D/D{sup +} couple. This allows oxidation of the cytochrome even at cryogenic temperatures and reduction of each constituent of the heterodimer primary donor individually. Despite a low yield of primary donor radicals, the enhancement of the semiquinone-iron pair EPR signals in these mutants indicates the presence of kinetically viable electron donors.« less

On Light-Induced Photoconversion of B800 Bacteriochlorophylls in the LH2 Antenna of the Purple Sulfur Bacterium Allochromatium vinosum.

PubMed

Kell, Adam; Jassas, Mahboobe; Hacking, Kirsty; Cogdell, Richard J; Jankowiak, Ryszard

2017-11-02

The B800-850 LH2 antenna from the photosynthetic purple sulfur bacterium Allochromatium vinosum exhibits an unusual spectral splitting of the B800 absorption band; i.e., two bands are well-resolved at 5 K with maxima at 805 nm (B800 R ) and 792 nm (B800 B ). To provide more insight into the nature of the B800 bacteriochlorophyll (BChl) a molecules, high-resolution hole-burning (HB) spectroscopy is employed. Both white light illumination and selective laser excitations into B800 R or B800 B lead to B800 R → B800 B phototransformation. Selective excitation into B800 B leads to uncorrelated excitation energy transfer (EET) to B800 R and subsequent B800 R → B800 B phototransformation. The B800 B → B800 R EET time is 0.9 ± 0.1 ps. Excitation at 808.4 nm (into the low-energy side of B800 R ) shows that the lower limit of B800 R → B850 EET is about 2 ps, as the B800 R → B800 B phototransformation process could contribute to the corresponding zero-phonon hole width. The phototransformation of B800 R leads to a ∼ 200 cm -1 average blue-shift of transition energies, i.e., B800 R changes into B800 B . We argue that it is unlikely that B800-B850 excitonic interactions give rise to a splitting of the B800 band. We propose that the latter is caused by different protein conformations that can lead to both strong or weak hydrogen bond(s) between B800 pigments and the protein scaffolding. Temperature-dependent absorption spectra of B800, which revealed a well-defined isosbestic point, support a two-site model, likely with strongly and weakly hydrogen-bonded B800 BChls. Thus, BChls contributing to B800 R and B800 B could differ in the position of the proton in the BChl carbonyl-protein hydrogen bond, i.e., proton dynamics along the hydrogen bond may well be the major mechanism of this phototransformation. However, the effective tunneling mass is likely larger than the proton mass.

Origin and spread of photosynthesis based upon conserved sequence features in key bacteriochlorophyll biosynthesis proteins.

PubMed

Gupta, Radhey S

2012-11-01

The origin of photosynthesis and how this capability has spread to other bacterial phyla remain important unresolved questions. I describe here a number of conserved signature indels (CSIs) in key proteins involved in bacteriochlorophyll (Bchl) biosynthesis that provide important insights in these regards. The proteins BchL and BchX, which are essential for Bchl biosynthesis, are derived by gene duplication in a common ancestor of all phototrophs. More ancient gene duplication gave rise to the BchX-BchL proteins and the NifH protein of the nitrogenase complex. The sequence alignment of NifH-BchX-BchL proteins contain two CSIs that are uniquely shared by all NifH and BchX homologs, but not by any BchL homologs. These CSIs and phylogenetic analysis of NifH-BchX-BchL protein sequences strongly suggest that the BchX homologs are ancestral to BchL and that the Bchl-based anoxygenic photosynthesis originated prior to the chlorophyll (Chl)-based photosynthesis in cyanobacteria. Another CSI in the BchX-BchL sequence alignment that is uniquely shared by all BchX homologs and the BchL sequences from Heliobacteriaceae, but absent in all other BchL homologs, suggests that the BchL homologs from Heliobacteriaceae are primitive in comparison to all other photosynthetic lineages. Several other identified CSIs in the BchN homologs are commonly shared by all proteobacterial homologs and a clade consisting of the marine unicellular Cyanobacteria (Clade C). These CSIs in conjunction with the results of phylogenetic analyses and pair-wise sequence similarity on the BchL, BchN, and BchB proteins, where the homologs from Clade C Cyanobacteria and Proteobacteria exhibited close relationship, provide strong evidence that these two groups have incurred lateral gene transfers. Additionally, phylogenetic analyses and several CSIs in the BchL-N-B proteins that are uniquely shared by all Chlorobi and Chloroflexi homologs provide evidence that the genes for these proteins have also been laterally transferred between these groups. Other results and observations reported here indicate that the genes for the BchL-N-B proteins in Proteobacteria are derived from the Clade C Cyanobacteria, whereas those in Chlorobi were acquired from Chloroflexus or related bacteria by means of LGTs. Some implications of these observations regarding the origin and spread of photosynthesis are discussed.

Isotopic replacement of pigments and a lipid in chlorosomes from Chlorobium limicola: characterization of the resultant chlorosomes.

PubMed

Kakitani, Yoshinori; Harada, Ken-ichi; Mizoguchi, Tadashi; Koyama, Yasushi

2007-06-05

Pigments including bacteriochlorophyll (BChl) c, carotenoids, and a trace of BChl a together with a lipid, monogalactosyl diglyceride (MGDG), were extracted with chloroform/methanol (1:1 v/v) from an aqueous suspension (50 mM Tris-HCl, pH 8.0) of chlorosomes from Chlorobium limicola; other lipids and proteins were left behind in the aqueous layer by funnel separation. The chloroform layer was dried by purging N2 gas, dissolved in methanol, and rapidly injected into the aqueous layer to reassemble chlorosomes. This technique has been developed to replace one-half of the inherent 12C-BChl c by 13C-BChl c to identify the intermolecular 13C...13C magnetic dipole correlation peaks (that are supposed to reduce their intensities to one-fourth by reducing the 13C-BChl c concentration into one-half) and to determine the structure of BChl c aggregates in the rod elements by means of solid-state NMR spectroscopy. The isotopically replaced chlorosomes were characterized (1) by sucrose density gradient centrifugation, zeta potential measurement, electron microscopy, and dynamic light scattering measurement to determine the morphology of chlorosomes, (2) by 13C NMR spectroscopy, electronic absorption and circular dichroism spectroscopies, and low-angle X-ray diffraction to determine the pigment assembly in the rod elements, and (3) by subpicosecond time-resolved absorption spectroscopy to determine the excited-state dynamics in the pigment assembly. The results characterized the reassembled chlorosomes to have (1) similar but longer morphological structures, (2) almost the same pigment assembly in the rod elements, and (3) basically the same excited-state dynamics in the pigment assembly.

Roseomonas aerofrigidensis sp. nov., isolated from an air conditioner.

PubMed

Hyeon, Jong Woo; Jeon, Che Ok

2017-10-01

A Gram-stain-negative, strictly aerobic bacterium, designated HC1 T , was isolated from an air conditioner in South Korea. Cells were orange, non-motile cocci with oxidase- and catalase-positive activities and did not contain bacteriochlorophyll a. Growth of strain HC1 T was observed at 10-45 °C (optimum, 30 °C), pH 4.5-9.5 (optimum, pH 7.0) and 0-3 % (w/v) NaCl (optimum, 0 %). Strain HC1 T contained summed feature 8 (comprising C18 : 1ω7c/C18 : 1ω6c), C16 : 0 and cyclo-C19 : 0ω8c as the major fatty acids and ubiquinone-10 as the sole isoprenoid quinone. Phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and an unknown aminolipid were detected as the major polar lipids. The major carotenoid was hydroxyspirilloxanthin. The G+C content of the genomic DNA was 70.1 mol%. Phylogenetic analysis, based on 16S rRNA gene sequences, showed that strain HC1 T formed a phylogenetic lineage within the genus Roseomonas. Strain HC1 T was most closely related to the type strains of Roseomonas oryzae, Roseomonas rubra, Roseomonas aestuarii and Roseomonas rhizosphaerae with 98.1, 97.9, 97.6 and 96.8 % 16S rRNA gene sequence similarities, respectively, but the DNA-DNA relatedness values between strain HC1 T and closely related type strains were less than 70 %. Based on phenotypic, chemotaxonomic and molecular properties, strain HC1 T represents a novel species of the genus Roseomonas, for which the name Roseomonas aerofrigidensis sp. nov. is proposed. The type strain is HC1 T (=KACC 19097 T =JCM 31878 T ).

Antimicrobial Photodynamic Therapy to Kill Gram-negative Bacteria

PubMed Central

Sperandio, Felipe F; Huang, Ying-Ying; Hamblin, Michael R

2013-01-01

Antimicrobial photodynamic therapy (PDT) or photodynamic inactivation (PDI) is a new promising strategy to eradicate pathogenic microorganisms such as Gram-positive and Gram-negative bacteria, yeasts and fungi. The search for new approaches that can kill bacteria but do not induce the appearance of undesired drug-resistant strains suggests that PDT may have advantages over traditional antibiotic therapy. PDT is a non-thermal photochemical reaction that involves the simultaneous presence of visible light, oxygen and a dye or photosensitizer (PS). Several PS have been studied for their ability to bind to bacteria and efficiently generate reactive oxygen species (ROS) upon photostimulation. ROS are formed through type I or II mechanisms and may inactivate several classes of microbial cells including Gram-negative bacteria such as Pseudomonas aeruginosa, which are typically characterized by an impermeable outer cell membrane that contains endotoxins and blocks antibiotics, dyes, and detergents, protecting the sensitive inner membrane and cell wall. This review covers significant peer-reviewed articles together with US and World patents that were filed within the past few years and that relate to the eradication of Gram-negative bacteria via PDI or PDT. It is organized mainly according to the nature of the PS involved and includes natural or synthetic food dyes; cationic dyes such as methylene blue and toluidine blue; tetrapyrrole derivatives such as phthalocyanines, chlorins, porphyrins, chlorophyll and bacteriochlorophyll derivatives; functionalized fullerenes; nanoparticles combined with different PS; other formulations designed to target PS to bacteria; photoactive materials and surfaces; conjugates between PS and polycationic polymers or antibodies; and permeabilizing agents such as EDTA, PMNP and CaCl2. The present review also covers the different laboratory animal models normally used to treat Gram-negative bacterial infections with antimicrobial PDT. PMID:23550545

Temperature shift effect on the Chlorobaculum tepidum chlorosomes.

PubMed

Tang, Joseph Kuo-Hsiang; Xu, Ying; Muhlmann, Guillermo M; Zare, Farrokh; Khin, Yadana; Tam, Sun W

2013-05-01

Chlorobaculum [Cba.] tepidum is known to grow optimally at 48-52 °C and can also be cultured at ambient temperatures. In this paper, we prepared constant temperature, temperature shift, and temperature shift followed by backshift cultures and investigated the intrinsic properties and spectral features of chlorosomes from those cultures using various approaches, including temperature-dependent measurements on circular dichroism (CD), UV-visible, and dynamic light scattering. Our studies indicate that (1) chlorosomes from constant temperature cultures at 50 and 30 °C exhibited more resistance to heat relative to temperature shift cultures; (2) as temperature increases bacteriochlorophyll c (BChl c) in chlorosomes is prone to demetalation, which forms bacteriopheophytin c, and degradation under aerobic conditions. Some BChl c aggregates inside reduced chlorosomes prepared in low-oxygen environments can reform after heat treatments; (3) temperature shift cultures synthesize and incorporate more BChl c homologs with a smaller substituent at C-8 on the chlorin ring and less BChl c homologs with a larger long-chain alcohol at C-17(3) versus constant-temperature cultures. We hypothesize that the long-chain alcohol at C-17(3) (and perhaps together with the substituent at C-8) may account for thermal stability of chlorosomes and the substituent at C-8 may assist self-assembling BChls; and (4) while almost identical absorption spectra are detected, chlorosomes from different growth conditions exhibited differences in the rotational length of the CD signal, and aerobic and reduced chlorosomes also display different Qy CD intensities. Further, chlorosomes exhibited changes of CD features in response to temperature increases. Additionally, we compare temperature-dependent studies for the Cba. tepidum chlorosomes and previous studies for the Chloroflexus aurantiacus chlorosomes. Together, our work provides useful and novel insights on the properties and organization of chlorosomes.

Physical stage of photosynthesis charge separation

NASA Astrophysics Data System (ADS)

Yakovlev, A. G.; Shuvalov, V. A.

2016-06-01

An analytical review is given concerning the biophysical aspects of light-driven primary charge separation in photosynthesis reaction centers (RCs) which are special pigment-protein complexes residing in a cell membrane. The primary (physical) stage of charge separation occurs in the pico- and femtosecond ranges and consists of transferring an electron along the active A-branch of pigments. The review presents vast factual material on both the general issues of primary photosynthesis and some more specific topics, including (1) the role of the inactive B-branch of pigments, (2) the effect of the protein environment on the charge separation, and (3) the participation of monomeric bacteriochlorophyll BA in primary electron acceptance. It is shown that the electron transfer and stabilization are strongly influenced by crystallographic water and tyrosine M210 molecules from the nearest environment of BA. A linkage between collective nuclear motions and electron transfer upon charge separation is demonstrated. The nature of the high quantum efficiency of primary charge separation reactions is discussed.

Molecular Level Design Principle behind Optimal Sizes of Photosynthetic LH2 Complex: Taming Disorder through Cooperation of Hydrogen Bonding and Quantum Delocalization.

PubMed

Jang, Seogjoo; Rivera, Eva; Montemayor, Daniel

2015-03-19

The light harvesting 2 (LH2) antenna complex from purple photosynthetic bacteria is an efficient natural excitation energy carrier with well-known symmetric structure, but the molecular level design principle governing its structure-function relationship is unknown. Our all-atomistic simulations of nonnatural analogues of LH2 as well as those of a natural LH2 suggest that nonnatural sizes of LH2-like complexes could be built. However, stable and consistent hydrogen bonding (HB) between bacteriochlorophyll and the protein is shown to be possible only near naturally occurring sizes, leading to significantly smaller disorder than for nonnatural ones. Extensive quantum calculations of intercomplex exciton transfer dynamics, sampled for a large set of disorder, reveal that taming the negative effect of disorder through a reliable HB as well as quantum delocalization of the exciton is a critical mechanism that makes LH2 highly functional, which also explains why the natural sizes of LH2 are indeed optimal.

Ultrafast time-resolved spectroscopy of the light-harvesting complex 2 (LH2) from the photosynthetic bacterium Thermochromatium tepidum.

PubMed

Niedzwiedzki, Dariusz M; Fuciman, Marcel; Kobayashi, Masayuki; Frank, Harry A; Blankenship, Robert E

2011-10-01

The light-harvesting complex 2 from the thermophilic purple bacterium Thermochromatium tepidum was purified and studied by steady-state absorption and fluorescence, sub-nanosecond-time-resolved fluorescence and femtosecond time-resolved transient absorption spectroscopy. The measurements were performed at room temperature and at 10 K. The combination of both ultrafast and steady-state optical spectroscopy methods at ambient and cryogenic temperatures allowed the detailed study of carotenoid (Car)-to-bacteriochlorophyll (BChl) as well BChl-to-BChl excitation energy transfer in the complex. The studies show that the dominant Cars rhodopin (N=11) and spirilloxanthin (N=13) do not play a significant role as supportive energy donors for BChl a. This is related with their photophysical properties regulated by long π-electron conjugation. On the other hand, such properties favor some of the Cars, particularly spirilloxanthin (N=13) to play the role of the direct quencher of the excited singlet state of BChl. © Springer Science+Business Media B.V. 2011

Optical properties of benthic photosynthetic communities: fiber-optic studies of cyanobacterial mats

NASA Technical Reports Server (NTRS)

Jorgensen, B. B.; Des Marais, D. J.

1988-01-01

A fiber-optic microphobe was used to analyze the spectral light gradients in benthic cyanobacterial mats with 50-micrometer depth resolution and 10-nm spectral resolution. Microcoleus chthononplastes mats were collected from hypersaline, coastal ponds at Guerrero Negro, Baja California. Gradients of spectral radiance, L, were measured at different angles through the mats and the spherically integrated scalar irradiance, Eo, was calculated. Maximal spectral light attenuation was found at the absorption peaks for the dominant photosynthetic pigments: chlorophyll a at 430 and 670 nm, carotenoids at 450-500 nm, phycocyanin at 620 nm, and bacteriochlorophyll a at 800-900 nm. Scattered light had a marked spectral effect on the scalar irradiance which near the mat surface reached up to 190% of the incident irradiance. The spherically integrated irradiance thus differed strongly from the incident irradiance both in total intensity and in spectral composition. These basic optical properties are important for the understanding of photosynthesis and light harvesting in benthic and epiphytic communities.

Rhodoferax antarcticus sp. nov., a moderately psychrophilic purple nonsulfur bacterium isolated from an Antarctic microbial mat

NASA Technical Reports Server (NTRS)

Madigan, M. T.; Jung, D. O.; Woese, C. R.; Achenbach, L. A.

2000-01-01

A new species of purple nonsulfur bacteria isolated from an Antarctic microbial mat is described. The organism, designated strain ANT.BR, was mildly psychrophilic, growing optimally at 15-18 degrees C with a growth temperature range of 0-25 degrees C. Cells of strain ANT.BR were highly motile curved rods and spirals, contained bacteriochlorophyll a, and showed a multicomponent in vivo absorption spectrum. A specific phylogenetic relationship was observed between strain ANT.BR and the purple bacterium Rhodoferax fermentans FR2T, and the two organisms shared several physiological and other phenotypic properties, with the notable exception of growth temperature optimum. Tests of genomic DNA hybridization, however, showed Rfx. fermentans FR2T and strain ANT.BR to be genetically distinct bacteria. Because of its unique set of properties, especially its requirement for low growth temperatures, we propose to recognize strain ANT.BR as a new species of the genus Rhodoferax, Rhodoferax antarcticus, named for its known habitat, the Antarctic.

Temperature and Carbon Assimilation Regulate the Chlorosome Biogenesis in Green Sulfur Bacteria

PubMed Central

Tang, Joseph Kuo-Hsiang; Saikin, Semion K.; Pingali, Sai Venkatesh; Enriquez, Miriam M.; Huh, Joonsuk; Frank, Harry A.; Urban, Volker S.; Aspuru-Guzik, Alán

2013-01-01

Green photosynthetic bacteria adjust the structure and functionality of the chlorosome—the light-absorbing antenna complex—in response to environmental stress factors. The chlorosome is a natural self-assembled aggregate of bacteriochlorophyll (BChl) molecules. In this study, we report the regulation of the biogenesis of the Chlorobaculum tepidum chlorosome by carbon assimilation in conjunction with temperature changes. Our studies indicate that the carbon source and thermal stress culture of C. tepidum grows slower and incorporates fewer BChl c in the chlorosome. Compared with the chlorosome from other cultural conditions we investigated, the chlorosome from the carbon source and thermal stress culture displays (a) smaller cross-sectional radius and overall size, (b) simplified BChl c homologs with smaller side chains, (c) blue-shifted Qy absorption maxima, and (d) a sigmoid-shaped circular dichroism spectra. Using a theoretical model, we analyze how the observed spectral modifications can be associated with structural changes of BChl aggregates inside the chlorosome. Our report suggests a mechanism of metabolic regulation for chlorosome biogenesis. PMID:24047985

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saijo, Shinya; Sato, Takao; Kumasaka, Takashi

The reaction center–light-harvesting 1 core complex from R. viridis was crystallized and X-ray diffraction data were collected to 8.0 Å resolution. The reaction center–light-harvesting 1 (RC–LH1) core complex is the photosynthetic apparatus in the membrane of the purple photosynthetic bacterium Rhodopseudomonas viridis. The RC is surrounded by an LH1 complex that is constituted of oligomers of three types of apoproteins (α, β and γ chains) with associated bacteriochlorophyll bs and carotenoid. It has been crystallized by the sitting-drop vapour-diffusion method. A promising crystal diffracted to beyond 8.0 Å resolution. It belonged to space group P1, with unit-cell parameters a =more » 141.4, b = 136.9, c = 185.3 Å, α = 104.6, β = 94.0, γ = 110.7°. A Patterson function calculated using data between 15.0 and 8.0 Å resolution suggested that the LH1 complex is distributed with quasi-16-fold rotational symmetry around the RC.« less

A simple fiber-optic microprobe for high resolution light measurements: application in marine sediment

NASA Technical Reports Server (NTRS)

Jorgensen, B. B.; Des Marais, D. J.

1986-01-01

A fiber-optic microphobe is described which is inexpensive and simple to build and use. It consists of an 80-micrometers optical fiber which at the end is tapered down to a rounded sensing tip of 20-30-micrometers diameter. The detector is a hybrid photodiode/amplifier. The probe has a sensitivity of 0.01 microEinst m-2 s-1 and a spectral range of 300-1,100 nm. Spectral light gradients were measured in fine-grained San Francisco Bay sediment that had an undisturbed diatom coating on the surface. The photic zone of the mud was only 0.4 mm deep. Measured in situ spectra showed extinction maxima at 430-520, 620-630, 670, and 825-850 nm due to absorption by chlorophyll a, carotenoids, phycocyanin, and bacterio-chlorophyll a. Maximum light penetration in the visible range was found in both the violet and the red < or = 400 and > or = 700 nm.

Carbon isotope fractionation by thermophilic phototrophic sulfur bacteria: evidence for autotrophic growth in natural populations

NASA Technical Reports Server (NTRS)

Madigan, M. T.; Takigiku, R.; Lee, R. G.; Gest, H.; Hayes, J. M.

1989-01-01

Purple phototrophic bacteria of the genus Chromatium can grow as either photoautotrophs or photoheterotrophs. To determine the growth mode of the thermophilic Chromatium species, Chromatium tepidum, under in situ conditions, we have examined the carbon isotope fractionation patterns in laboratory cultures of this organism and in mats of C. tepidum which develop in sulfide thermal springs in Yellowstone National Park. Isotopic analysis (13C/12C) of total carbon, carotenoid pigments, and bacteriochlorophyll from photoautotrophically grown cultures of C. tepidum yielded 13C fractionation factors near -20%. Cells of C. tepidum grown on excess acetate, wherein synthesis of the Calvin cycle enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase ribulose bisphosphate carboxylase) was greatly repressed, were isotopically heavier, fractionation factors of ca. -7% being observed. Fractionation factors determined by isotopic analyses of cells and pigment fractions of natural populations of C. tepidum growing in three different sulfide thermal springs in Yellowstone National Park were approximately -20%, indicating that this purple sulfur bacterium grows as a photoautotroph in nature.

Subcellular storage compartments of bacteriopheophorbide sensitizers

NASA Astrophysics Data System (ADS)

Moser, Joerg G.; Dembeck, U.; Hubert, M.; Spengler, Bernhard; Bayer, Rainer; Wagner, Birgit

1994-03-01

Fluorescence colocalization with the Golgi specific stain, NBD-ceramide, and the mitochondrial localizing stain, Rhodamine 123, confirmed the earlier assumption that the Golgi apparatus is one of the prominent storage compartments for bacteriopheophorbide esters in OAT 75 SCLC cells and several amelanotic melanoma cell lines (A375, Melur SP18, SkAMel 25). Furthermore, a diffuse staining of mitochondria, of non-structured cytoplasm, and an additional storage in melanine vesicles of the amelanotic melanoma cells suggests further storage compartments with quantitatively different contributions to the phototoxicity of bacteriochlorophyll-derived photosensitizers. Independent observations of early phototoxic effects on microfilamentous networks, enzymatic activities (succinate dehydrogenase, lactate dehydrogenase), and redistribution phenomena following primary uptake of the sensitizers let us assume that only a part of the 108 molecules taken up by a cell contribute directly to phototoxicity. Thus it may be asked if a proper subcellular positioning of only a few sensitizer molecules may have similar phototoxic effects as the huge amounts stored at apparently ineffective sites.

Coherent wavepackets in the Fenna-Matthews-Olson complex are robust to excitonic-structure perturbations caused by mutagenesis

NASA Astrophysics Data System (ADS)

Maiuri, Margherita; Ostroumov, Evgeny E.; Saer, Rafael G.; Blankenship, Robert E.; Scholes, Gregory D.

2018-02-01

Femtosecond pulsed excitation of light-harvesting complexes creates oscillatory features in their response. This phenomenon has inspired a large body of work aimed at uncovering the origin of the coherent beatings and possible implications for function. Here we exploit site-directed mutagenesis to change the excitonic level structure in Fenna-Matthews-Olson (FMO) complexes and compare the coherences using broadband pump-probe spectroscopy. Our experiments detect two oscillation frequencies with dephasing on a picosecond timescale—both at 77 K and at room temperature. By studying these coherences with selective excitation pump-probe experiments, where pump excitation is in resonance only with the lowest excitonic state, we show that the key contributions to these oscillations stem from ground-state vibrational wavepackets. These experiments explicitly show that the coherences—although in the ground electronic state—can be probed at the absorption resonances of other bacteriochlorophyll molecules because of delocalization of the electronic excitation over several chromophores.

Biomass and pigments production in photosynthetic bacteria wastewater treatment: effects of light sources.

PubMed

Zhou, Qin; Zhang, Panyue; Zhang, Guangming

2015-03-01

This study is aimed at enhancing biomass and pigments production together with pollution removal in photosynthetic bacteria (PSB) wastewater treatment via different light sources. Red, yellow, blue, white LED and incandescent lamp were used. Results showed different light sources had great effects on the PSB. PSB had the highest biomass production, COD removal and biomass yield with red LED. The corresponding biomass, COD removal and biomass yield reached 2580 mg/L, 88.6% and 0.49 mg-biomass/mg-COD-removal, respectively. The hydraulic retention time of wastewater treatment could be shortened to 72 h with red LED. Mechanism analysis showed higher ATP was produced with red LED than others. Light sources could significantly affect the pigments production. The pigments productions were greatly higher with LED than incandescent lamp. Yellow LED had the highest pigments production while red LED produced the highest carotenoid/bacteriochlorophyll ratio. Considering both efficiency and energy cost, red LED was the optimal light source. Copyright © 2014 Elsevier Ltd. All rights reserved.

Evidence for the presence of key chlorophyll-biosynthesis-related proteins in the genus Rubrobacter (Phylum Actinobacteria) and its implications for the evolution and origin of photosynthesis.

PubMed

Gupta, Radhey S; Khadka, Bijendra

2016-02-01

Homologs showing high degree of sequence similarity to the three subunits of the protochlorophyllide oxidoreductase enzyme complex (viz. BchL, BchN, and BchB), which carries out a central role in chlorophyll-bacteriochlorophyll (Bchl) biosynthesis, are uniquely found in photosynthetic organisms. The results of BLAST searches and homology modeling presented here show that proteins exhibiting a high degree of sequence and structural similarity to the BchB and BchN proteins are also present in organisms from the high G+C Gram-positive phylum of Actinobacteria, specifically in members of the genus Rubrobacter (R. x ylanophilus and R. r adiotolerans). The results presented exclude the possibility that the observed BLAST hits are for subunits of the nitrogenase complex or the chlorin reductase complex. The branching in phylogenetic trees and the sequence characteristics of the Rubrobacter BchB/BchN homologs indicate that these homologs are distinct from those found in other photosynthetic bacteria and that they may represent ancestral forms of the BchB/BchN proteins. Although a homolog showing high degree of sequence similarity to the BchL protein was not detected in Rubrobacter, another protein, belonging to the ParA/Soj/MinD family, present in these bacteria, exhibits high degree of structural similarity to the BchL. In addition to the BchB/BchN homologs, Rubrobacter species also contain homologs showing high degree of sequence similarity to different subunits of magnesium chelatase (BchD, BchH, and BchI) as well as proteins showing significant similarity to the BchP and BchG proteins. Interestingly, no homologs corresponding to the BchX, BchY, and BchZ proteins were detected in the Rubrobacter species. These results provide the first suggestive evidence that some form of photosynthesis either exists or was anciently present within the phylum Actinobacteria (high G+C Gram-positive) in members of the genus Rubrobacter. The significance of these results concerning the origin of the Bchl-based photosynthesis is also discussed.

Fire Extinguishing Agents, Aqueous Film Forming Foam (AFFF) Liquid Concentration Partial Percentage

DTIC Science & Technology

1989-08-31

AFFF concentrations. aqueous film forming foam , AFFF , firefighting ...Extinguishing Agents, Aqueous Film Forming Foam ( AFFF ) Liquid Concentration Partial Percentage F08637-88-C-0067 06022104F 2104 30 21043034 Applied Research...objective of this test series was to qualify 3/4 and 1 percent Aqueous Film Forming Foam ( AFFF ) concentrate for use in Air Force fire fighting

1-Aminocyclopropane-1-carboxylic acid concentrations in shoot-forming and non-shoot-forming tobacco callus cultures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grady, K.L.; Bassham, J.A.

1982-09-01

Shoot-forming tobacco (Nicotiana tabacum var. Wisconsin 38) callus tissues contain significantly lower concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid compared to non-shoot-forming callus tissues. This difference is evident 1 day after subculture to shoot-forming or non-shoot-forming medium, and is maintained through the first week of growth. The lack of auxin in shoot-forming medium is the probable cause for this difference in ACC concentrations.

Cloning and heterologous expression of chlorophyll a synthase in Rhodobacter sphaeroides.

PubMed

Ipekoğlu, Emre M; Göçmen, Koray; Öz, Mehmet T; Gürgan, Muazzez; Yücel, Meral

2017-03-01

Rhodobacter sphaeroides is a purple non-sulfur bacterium which photoheterotrophically produces hydrogen from organic acids under anaerobic conditions. A gene coding for putative chlorophyll a synthase (chlG) from cyanobacterium Prochlorococcus marinus was amplified by nested polymerase chain reaction and cloned into an inducible-expression plasmid which was subsequently transferred to R. sphaeroides for heterologous expression. Induced expression of chlG in R. sphaeroides led to changes in light absorption spectrum within 400-700 nm. The hydrogen production capacity of the mutant strain was evaluated on hydrogen production medium with 15 mM malate and 2 mM glutamate. Hydrogen yield and productivity were increased by 13.6 and 22.6%, respectively, compared to the wild type strain. The results demonstrated the feasibility of genetic engineering to combine chlorophyll and bacteriochlorophyll biosynthetic pathways which utilize common intermediates. Heterologous expression of key enzymes from biosynthetic pathways of various pigments is proposed here as a general strategy to improve absorption spectra and yield of photosynthesis and hydrogen gas production in bacteria. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A quantum mechanical analysis of the light-harvesting complex 2 (LH2) from purple photosynthetic bacteria: insights into the electrostatic effects of transmembrane helices.

PubMed

Pichierri, Fabio

2011-02-01

We perform a quantum mechanical study of the peptides that are part of the LH2 complex from Rhodopseudomonas acidophila, a non-sulfur purple bacteria that has the ability of producing chemical energy from photosynthesis. The electronic structure calculations indicate that the transmembrane helices of these peptides are characterized by dipole moments with a magnitude of about 150D. When the full nonamer assembly made of 18 peptides is considered, then a macrodipole of magnitude 806D is built up from the vector sum of each monomer dipole. The macrodipole is oriented normal to the membrane plane and with the positive tip toward the cytoplasm thereby indicating that the electronic charge of the protein scaffold is polarized toward the periplasm. The results obtained here suggest that the asymmetric charge distribution of the protein scaffold contributes an anisotropic electrostatic environment which differentiates the absorption properties of the bacteriochlorophyll pigments, B800 and B850, embedded in the LH2 complex. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Spectroscopic Studies of Carotenoid-to-Bacteriochlorophyll Energy Transfer in LHRC Photosynthetic Complex from Roseiflexus castenholzii

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niedzwiedzki, Dariusz; Collins, Aaron M.; LaFountain, Amy M.

Carotenoids present in the photosynthetic light-harvesting reaction center (LHRC) complex from chlorosome lacking filamentous anoxygenic phototroph, Roseiflexus castenholzii were purified and characterized for their photochemical properties. The LHRC from anaerobically grown cells contains five different carotenoids, methoxy-keto-myxocoxanthin, γ-carotene, and its three derivatives, whereas the LHRC from aerobically grown cells contains only three carotenoid pigments with methoxy-keto-myxocoxanthin being the dominant one. The spectroscopic properties and dynamics of excited singlet states of the carotenoids were studied by steady-state absorption, fluorescence and ultrafast time-resolved optical spectroscopy in organic solvent and in the intact LHRC complex. Time-resolved transient absorption spectroscopy performed in the near-infraredmore » (NIR) on purified carotenoids combined with steady-state absorption spectroscopy led to the precise determination of values of the energies of the S 1(2 1A g -) excited state. Global and single wavelength fitting of the ultrafast spectral and temporal data sets of the carotenoids in solvents and in the LHRC revealed the pathways of de-excitation of the carotenoid excited states.« less

Strategies to enhance the excitation energy-transfer efficiency in a light-harvesting system using the intra-molecular charge transfer character of carotenoids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yukihira, Nao; Sugai, Yuko; Fujiwara, Masazumi

Fucoxanthin is a carotenoid that is mainly found in light-harvesting complexes from brown algae and diatoms. Due to the presence of a carbonyl group attached to polyene chains in polar environments, excitation produces an excited intra-molecular charge transfer. This intra-molecular charge transfer state plays a key role in the highly efficient (~95%) energy-transfer from fucoxanthin to chlorophyllain the light-harvesting complexes from brown algae. In purple bacterial light-harvesting systems the efficiency of excitation energy-transfer from carotenoids to bacteriochlorophylls depends on the extent of conjugation of the carotenoids. In this study we were successful, for the first time, in incorporating fucoxanthin intomore » a light-harvesting complex 1 from the purple photosynthetic bacterium,Rhodospirillum rubrumG9+ (a carotenoidless strain). Femtosecond pump-probe spectroscopy was applied to this reconstituted light-harvesting complex in order to determine the efficiency of excitation energy-transfer from fucoxanthin to bacteriochlorophyllawhen they are bound to the light-harvesting 1 apo-proteins.« less

Temperature and carbon assimilation regulate the chlorosome biogenesis in green sulfur bacteria.

PubMed

Tang, Joseph Kuo-Hsiang; Saikin, Semion K; Pingali, Sai Venkatesh; Enriquez, Miriam M; Huh, Joonsuk; Frank, Harry A; Urban, Volker S; Aspuru-Guzik, Alán

2013-09-17

Green photosynthetic bacteria adjust the structure and functionality of the chlorosome-the light-absorbing antenna complex-in response to environmental stress factors. The chlorosome is a natural self-assembled aggregate of bacteriochlorophyll (BChl) molecules. In this study, we report the regulation of the biogenesis of the Chlorobaculum tepidum chlorosome by carbon assimilation in conjunction with temperature changes. Our studies indicate that the carbon source and thermal stress culture of C. tepidum grows slower and incorporates fewer BChl c in the chlorosome. Compared with the chlorosome from other cultural conditions we investigated, the chlorosome from the carbon source and thermal stress culture displays (a) smaller cross-sectional radius and overall size, (b) simplified BChl c homologs with smaller side chains, (c) blue-shifted Qy absorption maxima, and (d) a sigmoid-shaped circular dichroism spectra. Using a theoretical model, we analyze how the observed spectral modifications can be associated with structural changes of BChl aggregates inside the chlorosome. Our report suggests a mechanism of metabolic regulation for chlorosome biogenesis. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Plasmonic bio-sensing for the Fenna-Matthews-Olson complex

NASA Astrophysics Data System (ADS)

Chen, Guang-Yin; Lambert, Neill; Shih, Yen-An; Liu, Meng-Han; Chen, Yueh-Nan; Nori, Franco

2017-01-01

We study theoretically the bio-sensing capabilities of metal nanowire surface plasmons. As a specific example, we couple the nanowire to specific sites (bacteriochlorophyll) of the Fenna-Matthews-Olson (FMO) photosynthetic pigment protein complex. In this hybrid system, we find that when certain sites of the FMO complex are subject to either the suppression of inter-site transitions or are entirely disconnected from the complex, the resulting variations in the excitation transfer rates through the complex can be monitored through the corresponding changes in the scattering spectra of the incident nanowire surface plasmons. We also find that these changes can be further enhanced by changing the ratio of plasmon-site couplings. The change of the Fano lineshape in the scattering spectra further reveals that “site 5” in the FMO complex plays a distinct role from other sites. Our results provide a feasible way, using single photons, to detect mutation-induced, or bleaching-induced, local defects or modifications of the FMO complex, and allows access to both the local and global properties of the excitation transfer in such systems.

Native Mass Spectrometry Characterizes the Photosynthetic Reaction Center Complex from the Purple Bacterium Rhodobacter sphaeroides

NASA Astrophysics Data System (ADS)

Zhang, Hao; Harrington, Lucas B.; Lu, Yue; Prado, Mindy; Saer, Rafael; Rempel, Don; Blankenship, Robert E.; Gross, Michael L.

2017-01-01

Native mass spectrometry (MS) is an emerging approach to study protein complexes in their near-native states and to elucidate their stoichiometry and topology. Here, we report a native MS study of the membrane-embedded reaction center (RC) protein complex from the purple photosynthetic bacterium Rhodobacter sphaeroides. The membrane-embedded RC protein complex is stabilized by detergent micelles in aqueous solution, directly introduced into a mass spectrometer by nano-electrospray (nESI), and freed of detergents and dissociated in the gas phase by collisional activation. As the collision energy is increased, the chlorophyll pigments are gradually released from the RC complex, suggesting that native MS introduces a near-native structure that continues to bind pigments. Two bacteriochlorophyll a pigments remain tightly bound to the RC protein at the highest collision energy. The order of pigment release and their resistance to release by gas-phase activation indicates the strength of pigment interaction in the RC complex. This investigation sets the stage for future native MS studies of membrane-embedded photosynthetic pigment-protein and related complexes.

BciD Is a Radical S-Adenosyl-l-methionine (SAM) Enzyme That Completes Bacteriochlorophyllide e Biosynthesis by Oxidizing a Methyl Group into a Formyl Group at C-7.

PubMed

Thweatt, Jennifer L; Ferlez, Bryan H; Golbeck, John H; Bryant, Donald A

2017-01-27

Green bacteria are chlorophotorophs that synthesize bacteriochlorophyll (BChl) c, d, or e, which assemble into supramolecular, nanotubular structures in large light-harvesting structures called chlorosomes. The biosynthetic pathways of these chlorophylls are known except for one reaction. Null mutants of bciD, which encodes a putative radical S-adenosyl-l-methionine (SAM) protein, are unable to synthesize BChl e but accumulate BChl c; however, it is unknown whether BciD is sufficient to convert BChl c (or its precursor, bacteriochlorophyllide (BChlide) c) into BChl e (or BChlide e). To determine the function of BciD, we expressed the bciD gene of Chlorobaculum limnaeum strain DSMZ 1677 T in Escherichia coli and purified the enzyme under anoxic conditions. Electron paramagnetic resonance spectroscopy of BciD indicated that it contains a single [4Fe-4S] cluster. In assays containing SAM, BChlide c or d, and sodium dithionite, BciD catalyzed the conversion of SAM into 5'-deoxyadenosine and BChlide c or d into BChlide e or f, respectively. Our analyses also identified intermediates that are proposed to be 7 1 -OH-BChlide c and d Thus, BciD is a radical SAM enzyme that converts the methyl group of BChlide c or d into the formyl group of BChlide e or f This probably occurs by a mechanism involving consecutive hydroxylation reactions of the C-7 methyl group to form a geminal diol intermediate, which spontaneously dehydrates to produce the final products, BChlide e or BChlide f The demonstration that BciD is sufficient to catalyze the conversion of BChlide c into BChlide e completes the biosynthetic pathways for all "Chlorobium chlorophylls." © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Roseovarius salinarum sp. nov., isolated from a marine solar saltern.

PubMed

Wang, Nan-Nan; Liu, Zuan-Yan; Jiang, Lai-Xiang; Li, Ying-Xiu; Du, Zong-Jun

2018-06-01

A Gram-stain-negative, rod-shaped, non-motile and halophilic bacterium, designated N53 T , was isolated from a marine solar saltern in Wendeng, China. Cells of strain N53 T were 0.3-0.4 µm wide and 2.0-5.5 µm long, catalase-positive and oxidase-positive. The bacterium grew optimally at 33 °C, at pH 7.0-8.0 and in the presence of 6.0 % (w/v) NaCl. Bacteriochlorophyll a was not found. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain N53 T formed a phylogenetic lineage with members of the genus Roseovarius. Strain N53 T exhibited the highest levels of similarity to Roseovarius pacificus (94.6 %) and Roseovarius confluentis (94.6 %), with a lower level to Roseovarius tolerans was 94.0 %. The percentage of conserved proteins and average nucleotide identity values between N53 T and the type strain of the type species, Roseovarius tolerans, were 66.1 and 76.4 %, respectively. The genomic DNA G+C content was 68.1 mol%. The sole respiratory quinone was ubiquinone-10. The predominant cellular fatty acids (>10 %) were C18 : 1ω7c (54.0 %) and C16 : 0 (17.9 %). The polar lipids of strain N53 T consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, an unidentified aminolipid, two unidentified phospholipids and two unidentified glycolipids. The differential phenotypic properties, together with the chemotaxonomic and genomic distinctiveness, revealed that strain N53 T was separate from other recognized species of the genus Roseovarius. On the basis of the data presented here, strain N53 T represents a novel species of the genus Roseovarius, for which the name Roseovariussalinarum sp. nov. is proposed. The type strain is N53 T (=MCCC 1H00200 T =KCTC 52886 T ).

Beam-Forming Concentrating Solar Thermal Array Power Systems

NASA Technical Reports Server (NTRS)

Hoppe, Daniel J. (Inventor); Cwik, Thomas A. (Inventor); Dimotakis, Paul E. (Inventor)

2016-01-01

The present invention relates to concentrating solar-power systems and, more particularly, beam-forming concentrating solar thermal array power systems. A solar thermal array power system is provided, including a plurality of solar concentrators arranged in pods. Each solar concentrator includes a solar collector, one or more beam-forming elements, and one or more beam-steering elements. The solar collector is dimensioned to collect and divert incoming rays of sunlight. The beam-forming elements intercept the diverted rays of sunlight, and are shaped to concentrate the rays of sunlight into a beam. The steering elements are shaped, dimensioned, positioned, and/or oriented to deflect the beam toward a beam output path. The beams from the concentrators are converted to heat at a receiver, and the heat may be temporarily stored or directly used to generate electricity.

Inhibition and Promotion of Heat-Induced Gelation of Whey Proteins in the Presence of Calcium by Addition of Sodium Caseinate.

PubMed

Nguyen, Bach T; Balakrishnan, Gireeshkumar; Jacquette, Boris; Nicolai, Taco; Chassenieux, Christophe; Schmitt, Christophe; Bovetto, Lionel

2016-11-14

Heat-induced aggregation and gelation of aqueous solutions of whey protein isolate (WPI) in the presence of sodium caseinate (SC) and CaCl 2 was studied at pH 6.6. The effect of adding SC (0-100 g/L) on the structure of the aggregates and the gels was investigated by light scattering and confocal laser scanning microscopy at different CaCl 2 concentration ([CaCl 2 ] = 0-30 mM). The gelation process was studied by oscillatory shear rheology. At the whey protein concentrations studied here (34 and 60 g/L), no gels were formed in the absence of CaCl 2 and SC. However, WPI solutions gelled above a critical CaCl 2 concentration that increased with increasing SC concentration. In the absence of CaCl 2 , WPI gels were formed only above a critical SC concentration. The critical SC concentration needed to induce WPI gelation decreased weakly when CaCl 2 was added. In an intermediate range of CaCl 2 concentrations, gels were formed both at low and high SC concentrations, but not at intermediate SC concentrations. Finally, at high CaCl 2 concentrations gels were formed at all SC concentrations. The gelation rate and the gel structure of the gels formed at low and high casein concentrations were very different. The effect of SC on the thermal gelation of WPI was interpreted by competition for Ca 2+ , a chaperon effect, and microphase separation.

Evaluation of Solidification/Stabilization for Treating Contaminates Soils from the Frontier Hard Chrome Site

DTIC Science & Technology

1992-05-01

replicates were ɘ.020 mg/L. The chromium present was in the trivalent form. 139. Vendor 2. The replicate total chromium TCLP concentrations in the...criterion. The chromium present in the leachates was in the trivalent form, shown by concentrations of Cr(VI) of ɘ.020, ɘ.020, and 0.042 mg/L. 142...concentrations of total chromium were 4.7, 3.7, and 4.1 mg/L. Chromium is present in the trivalent form. The total chromium concentrations were below

High-resolution AFM topographs of Rubrivivax gelatinosus light-harvesting complex LH2

PubMed Central

Scheuring, Simon; Reiss-Husson, Francoise; Engel, Andreas; Rigaud, Jean-Louis; Ranck, Jean-Luc

2001-01-01

Light-harvesting complexes 2 (LH2) are the accessory antenna proteins in the bacterial photosynthetic apparatus and are built up of αβ-heterodimers containing three bacteriochlorophylls and one carotenoid each. We have used atomic force microscopy (AFM) to investigate reconstituted LH2 from Rubrivivax gelatinosus, which has a C-terminal hydrophobic extension of 21 amino acids on the α-subunit. High-resolution topographs revealed a nonameric organization of the regularly packed cylindrical complexes incorporated into the membrane in both orientations. Native LH2 showed one surface which protruded by ∼6 Å and one that protruded by ∼14 Å from the membrane. Topographs of samples reconstituted with thermolysin-digested LH2 revealed a height reduction of the strongly protruding surface to ∼9 Å, and a change of its surface appearance. These results suggested that the α-subunit of R.gelatinosus comprises a single transmembrane helix and an extrinsic C-terminus, and allowed the periplasmic surface to be assigned. Occasionally, large rings (∼120 Å diameter) surrounded by LH2 rings were observed. Their diameter and appearance suggest the large rings to be LH1 complexes. PMID:11406579

Thalassospira lucentensis gen. nov., sp. nov., a new marine member of the alpha-Proteobacteria.

PubMed

López-López, Arantxa; Pujalte, María J; Benlloch, Susana; Mata-Roig, Manuel; Rosselló-Mora, Ramón; Garay, Esperanza; Rodríguez-Valera, Francisco

2002-07-01

A novel bacterium from the Mediterranean Sea was isolated under oligotrophic conditions at in situ temperature after prolonged continuous culture. The isolates were initially characterized by partial 16S rRNA gene sequencing. Similarity searches of one of the isolates, QMT2T, indicated high sequence identity to the well-characterized Rhodospirillum rubrum, [Aquaspirillum] itersonii and [Oceanospirillum] pusillum micro-organisms, which are representatives of the alpha-subclass of the Proteobacteria. The highest level of similarity of the complete 165 rRNA gene with respect to these microorganisms was 89%. Features such as the low similarities of 165 rRNA of QMT2T with its phylogenetically close neighbours, the distinct G+C content, and the differences in phenotypic features, including pigmentation, fatty acid composition, salt tolerance, the lack of bacteriochlorophyll a, and the capacity to use carbohydrates as carbon sources, are indicative of the novel nature of the isolate QMT2T among the alpha-Proteobacteria. This report describes the classification of strain QMT2T (= DSM 14000T = CECT 5390T) as a new genus and species, Thalassospira lucentensis gen. nov, sp. nov., in the family Rhodospirillaceae.

Submolecular Gates Self-Assemble for Hot-Electron Transfer in Proteins.

PubMed

Filip-Granit, Neta; Goldberg, Eran; Samish, Ilan; Ashur, Idan; van der Boom, Milko E; Cohen, Hagai; Scherz, Avigdor

2017-07-27

Redox reactions play key roles in fundamental biological processes. The related spatial organization of donors and acceptors is assumed to undergo evolutionary optimization facilitating charge mobilization within the relevant biological context. Experimental information from submolecular functional sites is needed to understand the organization strategies and driving forces involved in the self-development of structure-function relationships. Here we exploit chemically resolved electrical measurements (CREM) to probe the atom-specific electrostatic potentials (ESPs) in artificial arrays of bacteriochlorophyll (BChl) derivatives that provide model systems for photoexcited (hot) electron donation and withdrawal. On the basis of computations we show that native BChl's in the photosynthetic reaction center (RC) self-assemble at their ground-state as aligned gates for functional charge transfer. The combined computational and experimental results further reveal how site-specific polarizability perpendicular to the molecular plane enhances the hot-electron transport. Maximal transport efficiency is predicted for a specific, ∼5 Å, distance above the center of the metalized BChl, which is in remarkably close agreement with the distance and mutual orientation of corresponding native cofactors. These findings provide new metrics and guidelines for analysis of biological redox centers and for designing charge mobilizing machines such as artificial photosynthesis.

Isolation and characterization of aerobic anoxygenic phototrophs from exposed soils from the Sør Rondane Mountains, East Antarctica.

PubMed

Tahon, Guillaume; Willems, Anne

2017-09-01

This study investigated the culturable aerobic phototrophic bacteria present in soil samples collected in the proximity of the Belgian Princess Elisabeth Station in the Sør Rondane Mountains, East Antarctica. Until recently, only oxygenic phototrophic bacteria (Cyanobacteria) were well known from Antarctic soils. However, more recent non-cultivation-based studies have demonstrated the presence of anoxygenic phototrophs and, particularly, aerobic anoxygenic phototrophic bacteria in these areas. Approximately 1000 isolates obtained after prolonged incubation under different growth conditions were studied and characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Representative strains were identified by sequence analysis of 16S rRNA genes. More than half of the isolates grouped among known aerobic anoxygenic phototrophic taxa, particularly with Sphingomonadaceae, Methylobacterium and Brevundimonas. In addition, a total of 330 isolates were tested for the presence of key phototrophy genes. While rhodopsin genes were not detected, multiple isolates possessed key genes of the bacteriochlorophyll synthesis pathway. The majority of these potential aerobic anoxygenic phototrophic strains grouped with Alphaproteobacteria (Sphingomonas, Methylobacterium, Brevundimonas and Polymorphobacter). Copyright © 2017 The Authors. Published by Elsevier GmbH.. All rights reserved.

Developing Tools for Ecological Forestry and Carbon Management in Longleaf Pine

DTIC Science & Technology

2016-08-01

22 Table 5.2. Carbon concentrations of plants in the ground cover layer by growth form and carbon concentrations in longleaf...harvest. The stand is connected at the edges to form periodic boundary conditions (toroidal) ...............................................241...coarse root mass. Table 5.2. Carbon concentrations (%) of plants in the ground cover layer (< 1 m in height) by growth form and C

Concentrations of Water-Soluble Forms of Choline in Human Milk from Lactating Women in Canada and Cambodia

PubMed Central

Wiedeman, Alejandra M.; March, Kaitlin M.; Chen, Nancy N.; Kroeun, Hou; Sokhoing, Ly; Sophonneary, Prak; Dyer, Roger A.; Xu, Zhaoming; Kitts, David D.; Innis, Sheila M.

2018-01-01

Choline has critical roles during periods of rapid growth and development, such as infancy. In human milk, choline is mostly present in water-soluble forms (free choline, phosphocholine, and glycerophosphocholine). It is thought that milk choline concentration is influenced by maternal choline intake, and the richest food sources for choline are of animal origin. Scarce information exists on milk choline from countries differing in animal-source food availability. In this secondary analysis of samples from previous trials, the concentrations of the water-soluble forms of choline were quantified by liquid chromatography-tandem mass spectrometry in mature milk samples collected from lactating women in Canada (n = 301) and in Cambodia (n = 67). None of the water-soluble forms of choline concentrations in milk differed between Canada and Cambodia. For all milk samples (n = 368), free choline, phosphocholine, glycerophosphocholine, and the sum of water-soluble forms of choline concentrations in milk were (mean (95%CI)) 151 (141, 160, 540 (519, 562), 411 (396, 427), and 1102 (1072, 1133) µmol/L, respectively. Theoretically, only 19% of infants would meet the current Adequate Intake (AI) for choline. Our findings suggest that the concentrations in milk of water-soluble forms of choline are similar in Canada and Cambodia, and that the concentration used to set the infant AI might be inaccurate. PMID:29558412

Concentrations of Water-Soluble Forms of Choline in Human Milk from Lactating Women in Canada and Cambodia.

PubMed

Wiedeman, Alejandra M; Whitfield, Kyly C; March, Kaitlin M; Chen, Nancy N; Kroeun, Hou; Sokhoing, Ly; Sophonneary, Prak; Dyer, Roger A; Xu, Zhaoming; Kitts, David D; Green, Timothy J; Innis, Sheila M; Barr, Susan I

2018-03-20

Choline has critical roles during periods of rapid growth and development, such as infancy. In human milk, choline is mostly present in water-soluble forms (free choline, phosphocholine, and glycerophosphocholine). It is thought that milk choline concentration is influenced by maternal choline intake, and the richest food sources for choline are of animal origin. Scarce information exists on milk choline from countries differing in animal-source food availability. In this secondary analysis of samples from previous trials, the concentrations of the water-soluble forms of choline were quantified by liquid chromatography-tandem mass spectrometry in mature milk samples collected from lactating women in Canada ( n = 301) and in Cambodia ( n = 67). None of the water-soluble forms of choline concentrations in milk differed between Canada and Cambodia. For all milk samples ( n = 368), free choline, phosphocholine, glycerophosphocholine, and the sum of water-soluble forms of choline concentrations in milk were (mean (95%CI)) 151 (141, 160, 540 (519, 562), 411 (396, 427), and 1102 (1072, 1133) µmol/L, respectively. Theoretically, only 19% of infants would meet the current Adequate Intake (AI) for choline. Our findings suggest that the concentrations in milk of water-soluble forms of choline are similar in Canada and Cambodia, and that the concentration used to set the infant AI might be inaccurate.

Faro Lake, a big picture from a small ecosystem

NASA Astrophysics Data System (ADS)

Saccà, Alessandro

2017-04-01

Faro Lake is a small coastal basin located by the Straits of Messina (Central Mediterranean Sea) and is the deepest basin in Sicily and one of the deepest coastal lakes in Italy. Considering the correspondence of the shorelines of the lake with half-graben faults, a tectonic event is the most likely explanation for its remarkable depth (30 m in the central region). Due to its funnel-shape bathymetry and its limited water exchanges with the nearby sea, Faro Lake shows the typical trait of a meromictic basin, that is a persistent physical and chemical stratification of the water column. While the upper water layer is well oxygenated, chiefly due to advection processes, the bottom layer is anoxic and characterized by a vertical gradient of hydrogen sulfide concentration, reaching a maximum at the water/sediment interface. A transition zone also exists between these two layers where oxygen concentration sharply decreases with depth. As a result of this environmental heterogeneity, a variety of ecological niches arise along the water column of Faro Lake, which are exploited by a host of prokaryote groups showing a multiplicity of metabolic pathways. These microbes, in turn, affect the chemical gradients of the water column in a complex interplay and also serve as a food source for microbial eukaryotes in the so-called microbial food web. In summer, thanks to enhanced light availability and higher water temperature, a bloom of brown-colored photosynthetic sulfur bacteria develops in the upper part of the anoxic zone, resulting in a distinct "red water layer", coupled with significantly high biomasses of ciliated protozoa. During my researches, I have documented and quantified the trophic interactions between phagotrophic protozoa and the prokaryotes thriving in the "red water layer". I have also found a peculiar photosynthetic sulfur bacterium and a unique bacteriochlorophyll homologue that have been retrieved, to date, only from Faro Lake and from the Black Sea. I have, finally, reconstructed the biogeography of a "flagship" protozoan species, which I have redescribed from specimens collected in the lake, and I have hypothesized its introduction as an "alien" species via aquaculture activities. In conclusion, Faro Lake is a very interesting environment and an object of research and it also represents a valuable educational model for discussing of various scientific subjects, such as geology, land/sea transition zones, biogeochemistry, metabolism, ecology, microbiology, alien species introduction, biogeography, taxonomy and a variety of related topics.

Simple Köhler homogenizers for image-forming solar concentrators

NASA Astrophysics Data System (ADS)

Zhang, Weiya; Winston, Roland

2010-08-01

By adding simple Köhler homogenizers in the form of aspheric lenses generated with an optimization approach, we solve the problems of non-uniform irradiance distribution and non-square irradiance pattern existing in some image-forming solar concentrators. The homogenizers do not require optical bonding to the solar cells or total internal reflection surface. Two examples are shown including a Fresnel lens based concentrator and a two-mirror aplanatic system.

Chlorophyll J-aggregates: from bioinspired dye stacks to nanotubes, liquid crystals, and biosupramolecular electronics.

PubMed

Sengupta, Sanchita; Würthner, Frank

2013-11-19

Among the natural light-harvesting (LH) systems, those of green sulfur and nonsulfur photosynthetic bacteria are exceptional because they lack the support of a protein matrix. Instead, these so-called chlorosomes are based solely on "pigments". These are self-assembled bacteriochlorophyll c, d, and e derivatives, which consist of a chlorophyll skeleton bearing a 3(1)-hydroxy functional group. Chemists consider the latter as an essential structural unit to direct the formation of light-harvesting self-assembled dye aggregates with J-type excitonic coupling. The intriguing properties of chlorosomal J-type aggregates, particularly narrow red-shifted absorption bands, compared with monomers and their ability to delocalize and migrate excitons, have inspired intense research activities toward synthetic analogues in this field. The ultimate goal of this research field is the development of (opto-)electronic devices based on the architectural principle of chlorosomal LH systems. In this regard, the challenge is to develop small, functional building blocks with appropriate substituents that are preprogrammed to self-assemble across different length scales and to emulate functions of natural LH systems or to realize entirely new functions beyond those found in nature. In this Account, we highlight our achievements in the past decade with semisynthetic zinc chlorins (ZnChls) as model compounds of bacteriochlorophylls obtained from the naturally most abundant chlorin precursor: chlorophyll a. To begin, we explore how supramolecular strategies involving π-stacking, hydrogen bonding, and metal-oxygen coordination can be used to design ZnChl-based molecular stack, tube, and liquid crystalline assemblies conducive to charge and energy transport. Our design principle is based on the bioinspired functionalization of the 3(1)-position of ZnChl with a hydroxy or methoxy group; the former gives rise to tubular assemblies, whereas the latter induces stack assemblies. Functionalization of the 17(2)-position with esterified hydrophilic or hydrophobic chains, dendron-wedge substituents, and chromophores having complementary optical properties such as naphthalene bisimides (NBIs) is used to modulate the self-assembly of ZnChl dyes. The resulting assemblies exhibit enhanced charge transport and energy transfer abilities. We have used UV/vis, circular dichroism (CD), fluorescence spectroscopy, and dynamic light scattering (DLS) for the characterization of these assemblies in solution. In addition, we have studied assembly morphologies by atomic force microscopy (AFM), scanning tunneling microscopy (STM), transmission electron microscopy (TEM), and cryogenic-TEM. Crystallographic techniques such as powder X-ray and solid-state NMR have been used to explain the precise long- and short-range packing of dyes in these assemblies. Finally, functional properties such as charge and energy transport have been explored by pulse radiolysis time-resolved microwave conductivity (PR-TRMC), conductive AFM, and time-resolved fluorescence spectroscopy. The design principles discussed in this Account are important steps toward the utilization of these materials in biosupramolecular electronics and photonics in the future.

Evidence for the complex relationship between free amino acid and sugar concentrations and acrylamide-forming potential in potato

PubMed Central

Muttucumaru, N; Powers, SJ; Elmore, JS; Briddon, A; Mottram, DS; Halford, NG

2014-01-01

Free amino acids and reducing sugars participate in the Maillard reaction during high-temperature cooking and processing. This results not only in the formation of colour, aroma and flavour compounds, but also undesirable contaminants, including acrylamide, which forms when the amino acid that participates in the reaction is asparagine. In this study, tubers of 13 varieties of potato (Solanum tuberosum), which had been produced in a field trial in 2010 and sampled immediately after harvest or after storage for 6 months, were analysed to show the relationship between the concentrations of free asparagine, other free amino acids, sugars and acrylamide-forming potential. The varieties comprised five that are normally used for crisping, seven that are used for French fry production and one that is used for boiling. Acrylamide formation was measured in heated flour, and correlated with glucose and fructose concentration. In French fry varieties, which contain higher concentrations of sugars, acrylamide formation also correlated with free asparagine concentration, demonstrating the complex relationship between precursor concentration and acrylamide-forming potential in potato. Storage of the potatoes for 6 months at 9°C had a significant, variety-dependent impact on sugar and amino acid concentrations and acrylamide-forming potential. PMID:25540460

Impact of biomass burning emission on total peroxy nitrates: fire plume identification during the BORTAS campaign

NASA Astrophysics Data System (ADS)

Aruffo, Eleonora; Biancofiore, Fabio; Di Carlo, Piero; Busilacchio, Marcella; Verdecchia, Marco; Tomassetti, Barbara; Dari-Salisburgo, Cesare; Giammaria, Franco; Bauguitte, Stephane; Lee, James; Moller, Sarah; Hopkins, James; Punjabi, Shalini; Andrews, Stephen J.; Lewis, Alistair C.; Palmer, Paul I.; Hyer, Edward; Le Breton, Michael; Percival, Carl

2016-11-01

Total peroxy nitrate ( ∑ PN) concentrations have been measured using a thermal dissociation laser-induced fluorescence (TD-LIF) instrument during the BORTAS campaign, which focused on the impact of boreal biomass burning (BB) emissions on air quality in the Northern Hemisphere. The strong correlation observed between the ∑ PN concentrations and those of carbon monoxide (CO), a well-known pyrogenic tracer, suggests the possible use of the ∑ PN concentrations as marker of the BB plumes. Two methods for the identification of BB plumes have been applied: (1) ∑ PN concentrations higher than 6 times the standard deviation above the background and (2) ∑ PN concentrations higher than the 99th percentile of the ∑ PNs measured during a background flight (B625); then we compared the percentage of BB plume selected using these methods with the percentage evaluated, applying the approaches usually used in literature. Moreover, adding the pressure threshold ( ˜ 750 hPa) as ancillary parameter to ∑ PNs, hydrogen cyanide (HCN) and CO, the BB plume identification is improved. A recurrent artificial neural network (ANN) model was adapted to simulate the concentrations of ∑ PNs and HCN, including nitrogen oxide (NO), acetonitrile (CH3CN), CO, ozone (O3) and atmospheric pressure as input parameters, to verify the specific role of these input data to better identify BB plumes.

Reversible Activation of Halophilic β-lactamase from Methanol-Induced Inactive Form: Contrast to Irreversible Inactivation of Non-Halophilic Counterpart.

PubMed

Tokunaga, Hiroko; Maeda, Junpei; Arakawa, Tsutomu; Tokunaga, Masao

2017-06-01

Effects of a water-miscible organic solvent, methanol, on the structure and activity of halophilic β-lactamase derived from Chromohalobacter sp.560 (HaBla), were investigated by means of circular dichroism (CD) measurement and enzymatic activity determination. Beta-lactamase activity was enhanced about 1.2-fold in the presence of 10-20% methanol. CD measurement of HaBla revealed different structures depending on the methanol concentration: native-like active form (Form I) in 10-20% methanol and methanol-induced inactive form at higher concentration (Form II in 40-60% and Form III in 75-80% methanol). Incubation of HaBla with 40% methanol led to the complete loss of activity within ~80 min accompanied by the formation of Form II, whose activity was recovered promptly up to ~80% of full activity upon dilution of the methanol concentration to 10%. In addition, when the protein concentration was sufficiently high (e.g., 0.7 mg/ml), HaBla activity of Form III in 75% methanol could be recovered in the same way (with slightly slower recovery rate), upon dilution of the methanol concentration. In contrast, non-halophilic β-lactamase from Escherichia coli K12 strain MG1655 (EcBla) was irreversibly denatured in the presence of 40% methanol. HaBla showed remarkable ability to renature from the methanol-induced inactive states.

Selective concentration of aromatic bases from water with a resin adsorbent

USGS Publications Warehouse

Stuber, H.A.; Leenheer, J.A.

1983-01-01

Aromatic bases are concentrated from water on columns of a resin adsorbent and recovered by aqueous-acid elution. The degree of concentration attainable depends on the ratio of the capacity factor (k) of the neutral form of the amine to that of the ionized form. Capacity factors of ionic forms of amines on XAD-8 resin (a methylacrylic ester polymer) are greater than zero, ranging from 20 to 250 times lower than those of their neutral forms; they increase with increasing hydrophobicity of the amine. Thus, desorption by acid is an edition (k during desorption >0) rather than a displacement (k during desorption = 0) process. The degree of concentration attainable on XAD-8 resin varies with the hydrophobicity of the amine, being limited for hydrophilic solutes (for example, pyridine) by small neutral-form k's, reaching a maximum for amines of intermediate hydrophobicity (for example, quinoline), and decreasing for more hydrophobc solutes (for example, acridine) because of their large ionic-form k's.

Designs for thermal harvesting with nonlinear coordinate transformation

NASA Astrophysics Data System (ADS)

Ji, Qingxiang; Fang, Guodong; Liang, Jun

2018-04-01

In this paper a thermal concentrating design method was proposed based on the concept of generating function without knowing the needed coordinate transformation beforehand. The thermal harvesting performance was quantitatively characterized by heat concentrating efficiency and external temperature perturbation. Nonlinear transformations of different forms were employed to design high order thermal concentrators, and corresponding harvesting performances were investigated by numerical simulations. The numerical results shows that the form of coordinate transformation directly influences the distributions of heat flows inside the concentrator, consequently, influences the thermal harvesting behaviors significantly. The concentrating performance can be actively controlled and optimized by changing the form of coordinate transformations. The analysis in this paper offers a beneficial method to flexibly tune the harvesting performance of the thermal concentrator according to the requirements of practical applications.

Concentric ring flywheel without expansion separators

DOEpatents

Kuklo, Thomas C.

1999-01-01

A concentric ring flywheel wherein the adjacent rings are configured to eliminate the need for differential expansion separators between the adjacent rings. This is accomplished by forming a circumferential step on an outer surface of an inner concentric ring and forming a matching circumferential step on the inner surface of an adjacent outer concentric ring. During operation the circumferential steps allow the rings to differentially expand due to the difference in the radius of the rings without the formation of gaps therebetween, thereby eliminating the need for expansion separators to take up the gaps formed by differential expansion.

Characterization and In Situ Carbon Metabolism of Phototrophic Consortia

PubMed Central

Glaeser, Jens; Overmann, Jörg

2003-01-01

A dense population of the phototrophic consortium “Pelochromatium roseum” was investigated in the chemocline of a temperate holomictic lake (Lake Dagow, Brandenburg, Germany). Fluorescence in situ hybridization revealed that the brown epibionts of “P. roseum” constituted up to 37% of the total bacterial cell number and up to 88% of all green sulfur bacteria present in the chemocline. Specific amplification of 16S rRNA gene fragments of green sulfur bacteria and denaturing gradient gel electrophoresis fingerprinting yielded a maximum of four different DNA bands depending on the year of study, indicating that the diversity of green sulfur bacteria was low. The 465-bp 16S rRNA gene sequence of the epibiont of “P. roseum” was obtained after sorting of individual consortia by micromanipulation, followed by a highly sensitive PCR. The sequence obtained represents a new phylotype within the radiation of green sulfur bacteria. Maximum light-dependent H14CO3− fixation in the chemocline in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea suggested that there was anaerobic autotrophic growth of the green sulfur bacteria. The metabolism of the epibionts was further studied by determining stable carbon isotope ratios (δ13C) of their specific biomarkers. Analysis of photosynthetic pigments by high-performance liquid chromatography revealed the presence of high concentrations of bacteriochlorophyll (BChl) e and smaller amounts of BChl a and d and chlorophyll a in the chemocline. Unexpectedly, isorenieratene and β-isorenieratene, carotenoids typical of other brown members of the green sulfur bacteria, were absent. Instead, four different esterifying alcohols of BChl e were isolated as biomarkers of green sulfur bacterial epibionts, and their δ13C values were determined. Farnesol, tetradecanol, hexadecanol, and hexadecenol all were significantly enriched in 13C compared to bulk dissolved and particulate organic carbon and compared to the biomarkers of purple sulfur bacteria. The difference between the δ13C values of farnesol, the major esterifying alcohol of BChl e, and CO2 was −7.1%, which provides clear evidence that the mode of growth of the green sulfur bacterial epibionts of “P. roseum” in situ is photoautotrophic. PMID:12839739

Low-Light Anoxygenic Photosynthesis and Fe-S-Biogeochemistry in a Microbial Mat

PubMed Central

Haas, Sebastian; de Beer, Dirk; Klatt, Judith M.; Fink, Artur; Rench, Rebecca McCauley; Hamilton, Trinity L.; Meyer, Volker; Kakuk, Brian; Macalady, Jennifer L.

2018-01-01

We report extremely low-light-adapted anoxygenic photosynthesis in a thick microbial mat in Magical Blue Hole, Abaco Island, The Bahamas. Sulfur cycling was reduced by iron oxides and organic carbon limitation. The mat grows below the halocline/oxycline at 30 m depth on the walls of the flooded sinkhole. In situ irradiance at the mat surface on a sunny December day was between 0.021 and 0.084 μmol photons m-2 s-1, and UV light (<400 nm) was the most abundant part of the spectrum followed by green wavelengths (475–530 nm). We measured a light-dependent carbon uptake rate of 14.5 nmol C cm-2 d-1. A 16S rRNA clone library of the green surface mat layer was dominated (74%) by a cluster (>97% sequence identity) of clones affiliated with Prosthecochloris, a genus within the green sulfur bacteria (GSB), which are obligate anoxygenic phototrophs. Typical photopigments of brown-colored GSB, bacteriochlorophyll e and (β-)isorenieratene, were abundant in mat samples and their absorption properties are well-adapted to harvest light in the available green and possibly even UV-A spectra. Sulfide from the water column (3–6 μmol L-1) was the main source of sulfide to the mat as sulfate reduction rates in the mats were very low (undetectable-99.2 nmol cm-3 d-1). The anoxic water column was oligotrophic and low in dissolved organic carbon (175–228 μmol L-1). High concentrations of pyrite (FeS2; 1–47 μmol cm-3) together with low microbial process rates (sulfate reduction, CO2 fixation) indicate that the mats function as net sulfide sinks mainly by abiotic processes. We suggest that abundant Fe(III) (4.3–22.2 μmol cm-3) is the major source of oxidizing power in the mat, and that abiotic Fe-S-reactions play the main role in pyrite formation. Limitation of sulfate reduction by low organic carbon availability along with the presence of abundant sulfide-scavenging iron oxides considerably slowed down sulfur cycling in these mats. PMID:29755448

Low-Light Anoxygenic Photosynthesis and Fe-S-Biogeochemistry in a Microbial Mat.

PubMed

Haas, Sebastian; de Beer, Dirk; Klatt, Judith M; Fink, Artur; Rench, Rebecca McCauley; Hamilton, Trinity L; Meyer, Volker; Kakuk, Brian; Macalady, Jennifer L

2018-01-01

We report extremely low-light-adapted anoxygenic photosynthesis in a thick microbial mat in Magical Blue Hole, Abaco Island, The Bahamas. Sulfur cycling was reduced by iron oxides and organic carbon limitation. The mat grows below the halocline/oxycline at 30 m depth on the walls of the flooded sinkhole. In situ irradiance at the mat surface on a sunny December day was between 0.021 and 0.084 μmol photons m -2 s -1 , and UV light (<400 nm) was the most abundant part of the spectrum followed by green wavelengths (475-530 nm). We measured a light-dependent carbon uptake rate of 14.5 nmol C cm -2 d -1 . A 16S rRNA clone library of the green surface mat layer was dominated (74%) by a cluster (>97% sequence identity) of clones affiliated with Prosthecochloris , a genus within the green sulfur bacteria (GSB), which are obligate anoxygenic phototrophs. Typical photopigments of brown-colored GSB, bacteriochlorophyll e and (β-)isorenieratene, were abundant in mat samples and their absorption properties are well-adapted to harvest light in the available green and possibly even UV-A spectra. Sulfide from the water column (3-6 μmol L -1 ) was the main source of sulfide to the mat as sulfate reduction rates in the mats were very low (undetectable-99.2 nmol cm -3 d -1 ). The anoxic water column was oligotrophic and low in dissolved organic carbon (175-228 μmol L -1 ). High concentrations of pyrite (FeS 2 ; 1-47 μmol cm -3 ) together with low microbial process rates (sulfate reduction, CO 2 fixation) indicate that the mats function as net sulfide sinks mainly by abiotic processes. We suggest that abundant Fe(III) (4.3-22.2 μmol cm -3 ) is the major source of oxidizing power in the mat, and that abiotic Fe-S-reactions play the main role in pyrite formation. Limitation of sulfate reduction by low organic carbon availability along with the presence of abundant sulfide-scavenging iron oxides considerably slowed down sulfur cycling in these mats.

Design of nonimaging concentrators as second stages in tandem with image-forming first-stage concentrators

NASA Technical Reports Server (NTRS)

Winston, R.; Welford, W. T.

1980-01-01

The paper discusses the paraboloidal mirror as a tracking solar concentrator, fitting a nonimaging second stage to the paraboloidal mirror, other image-forming systems as first stages, and tracking systems in two-dimensional geometry. Because of inherent aberrations, the paraboloidal mirror cannot achieve the thermodynamic limit. It is shown how paraboloidal mirrors of short focal ratio and similar systems can have their flux concentration enhanced to near the thermodynamic limit by the addition of nonimaging compound elliptical concentrators.

Design of nonimaging concentrators as second stages in tandem with image-forming first-stage concentrators

NASA Astrophysics Data System (ADS)

Winston, R.; Welford, W. T.

1980-02-01

The paper discusses the paraboloidal mirror as a tracking solar concentrator, fitting a nonimaging second stage to the paraboloidal mirror, other image-forming systems as first stages, and tracking systems in two-dimensional geometry. Because of inherent aberrations, the paraboloidal mirror cannot achieve the thermodynamic limit. It is shown how paraboloidal mirrors of short focal ratio and similar systems can have their flux concentration enhanced to near the thermodynamic limit by the addition of nonimaging compound elliptical concentrators.

Concentrations and chemical forms of trace metals in coastal seawater on coral reef and their seasonal variation

NASA Astrophysics Data System (ADS)

Ganaha, S.; ITOH, A.

2011-12-01

Coastal seawater on coral reef near Okinawa island in Japan, which is in oligotrophic condition, has a diverse and unique ecosystem. It is possible that nutritive sals and trace metals, classified into nutrient type, are effectively supplied to marine phytoplankton and zooxanthellae from seawater. However, the concentrations and chemical forms of trace metals in coastal seawater on coral reef have been scarcely reported so far. In the present study, the characteristics of the concentrations and chemical forms of trace metals in such a seawater were investigated with seasonal variation by analyzing the coastal seawater at every month, after an analytical method for a simple chemical speciation including on-site treatment was established. The analytical method using a chelating resin and a disposable syringe was employed for de-salt and preconcentration of trace metals in costal seawater. After that, trace metals in the concentrated solution were measured by ICP-MS. Three types of chemical forms of an ionic, a dissolved, and an acid-soluble were separated without any treatment, by filtering with membrane filter of 0.45 μm, and by filtering after adding nitric acid, respectively. Then, a monitoring investigation of the coastal seawater on coral reef, located at Sesoko island near the northern part of Okinawa island, was carried out once at every month from Sep. 2010 to Aug. 2011. As a result, 10 elements in the dissolved form in each sample could be determined. The average concentrations for all samples from Sep. 2010 to Apr. 2011 were as follows: Mo:10.7 ppb, U:3.2 ppb, V:1.5 ppb, Mn:0.17 ppb, Ni:0.16 ppb, Zn:0.13 ppb, Cu:0.070 ppb, Pb:0.024 ppb, Co:0.0022 ppb, Cd:0.0016ppb. The concentrations for most trace metals were almost close to ones in open surface seawater of the Pacific ocean. For the acid-soluble form, the concentrations of V, Mo, and U were almost same with those of the dissolved form, and ones of Mn, Co, Ni, Cu, and Cd were slightly larger than ones in the dissolved form, while ones in Zn and Pb were 3.1- and 2.5-fold larger. These results suggest that a part of trace metals in the nutrient type exists as biogenic particulate matters. For the ionic form, the concentration of Cu was 3-fold smaller than one in the dissolved form. It is considered from the result that a part of Cu in the dissolved form exists not only as the ionic form but also as the colloids and organic complexes. The seasonal variation for each chemical form is now being investigated.

Upper bound on the efficiency of certain nonimaging concentrators in the physical-optics model

NASA Astrophysics Data System (ADS)

Welford, W. T.; Winston, R.

1982-09-01

Upper bounds on the performance of nonimaging concentrators are obtained within the framework of scalar-wave theory by using a simple approach to avoid complex calculations on multiple phase fronts. The approach consists in treating a theoretically perfect image-forming device and postulating that no non-image-forming concentrator can have a better performance than such an ideal image-forming system. The performance of such a system can be calculated according to wave theory, and this will provide, in accordance with the postulate, upper bounds on the performance of nonimaging systems. The method is demonstrated for a two-dimensional compound parabolic concentrator.

Obtention of injectable platelets rich-fibrin (i-PRF) and its polymerization with bone graft: technical note.

PubMed

Mourão, Carlos Fernando de Almeida Barros; Valiense, Helder; Melo, Elias Rodrigues; Mourão, Natália Belmock Mascarenhas Freitas; Maia, Mônica Diuana-Calasans

2015-01-01

The use of autologous platelet concentrates, represent a promising and innovator tools in the medicine and dentistry today. The goal is to accelerate hard and soft tissue healing. Among them, the platelet-rich plasma (PRP) is the main alternative for use in liquid form (injectable). These injectable form of platelet concentrates are often used in regenerative procedures and demonstrate good results. The aim of this study is to present an alternative to these platelet concentrates using the platelet-rich fibrin in liquid form (injectable) and its use with particulated bone graft materials in the polymerized form.

Air quality and urban form in U.S. urban areas: evidence from regulatory monitors.

PubMed

Clark, Lara P; Millet, Dylan B; Marshall, Julian D

2011-08-15

The layout of an urban area can impact air pollution via changes in emissions and their spatial distribution. Here, we explore relationships between air quality and urban form based on cross-sectional observations for 111 U.S. urban areas. We employ stepwise linear regression to quantify how long-term population-weighted outdoor concentrations of ozone, fine particulate matter (PM(2.5)), and other criteria pollutants measured by the U.S. Environmental Protection Agency depend on urban form, climate, transportation, city size, income, and region. Aspects of urban form evaluated here include city shape, road density, jobs-housing imbalance, population density, and population centrality. We find that population density is associated with higher population-weighted PM(2.5) concentrations (p < 0.01); population centrality is associated with lower population-weighted ozone and PM(2.5) concentrations (p < 0.01); and transit supply is associated with lower population-weighted PM(2.5) concentrations (p < 0.1). Among pollutants, interquartile range changes in urban form variables are associated with 4%-12% changes in population-weighted concentrations-amounts comparable, for example, to changes in climatic factors. Our empirical findings are consistent with prior modeling research and suggest that urban form could potentially play a modest but important role in achieving (or not achieving) long-term air quality goals.

Tinea Capitis in the form of Concentric Rings in an HIV Positive Adult on Antiretroviral Treatment

PubMed Central

Narang, Kirti; Pahwa, Manish; Ramesh, V

2012-01-01

Dermatophyte infection may present in the form of concentric rings caused by Trichophyton concentricum, known as Tinea Imbricata. In immunosuppressed patients, there are reports of lesions in the form of concentric rings caused by dermatophytes other than Trichophyton concentricum too, mostly by Trichophyton tonsurans, known as Tinea indesiciva or Tinea pseudoimbricata. We report a case of tinea capitis in a HIV-positive adult woman on antiretroviral therapy, who presented with concentric rings of papules and pustules with slight scaling on the scalp along with diffuse thinning of hair. Both Potassium hydroxide mount and culture showed the presence of Dermatophytes. Tinea capitis is considered rare in adults, but new cases are being reported in immunocompromised as well as in immunocompetent patients. The pertinent features of this case are: HIV-positive adult female on antiretroviral therapy, presenting with tinea capitis in the form of concentric rings; culture from the lesion grew Microsporum audouinii; responding to oral Terbinafine. PMID:22837564

[Influence of decomposition of Cladophora sp. on phosphorus concentrations and forms in the overlying water].

PubMed

Hou, Jin-Zhi; Wei, Quan; Gao, Li; Sun, Wei-Ming

2013-06-01

Sediments were sampled in the dominated zone of Cladophora sp. in Rongcheng Swan Lake, and cultivated with algae in the laboratory to reveal the influence of Cladophora decomposition on concentrations and forms of phosphorus in the overlying water. Concentrations of total phosphorus (TP), dissolved total phosphorus (DTP), soluble reactive phosphorus (SRP), particulate phosphorus (PP) and dissolved organic phosphorus (DOP) in overlying water were investigated, and some physicochemical parameters, such as dissolved oxygen (DO), pH and conductivity were monitored during the experiment. In addition, the influence of algae decomposition on P release from sediments was analyzed. Due to the decomposition of Cladophora, DO concentration in the overlying water declined remarkably and reached the anoxic condition (0-0.17 mg x L(-1)). The pH value of different treatments also decreased, and treatments with algae reduced by about 1 unit. Concentrations of TP and different P forms all increased obviously, and the increasing extent was larger with the adding algae amount. TP concentrations of different treatments varied from 0.04 mg x L(-1) to 1.34 mg x L(-1). DOP and PP were the main P forms in the overlying water in algae without sediments treatments, but SRP concentrations became much higher in algae with sediments treatments. The result showed that P forms released from decomposing Cladophora were mainly DOP and PP, and the Cladophora decomposition could also promote the sediments to release P into the overlying water.

Combined processing of lead concentrates

NASA Astrophysics Data System (ADS)

Kubasov, V. L.; Paretskii, V. M.; Sidorin, G. N.; Travkin, V. F.

2013-06-01

A combined scheme of processing of lead concentrates with the production of pure metallic lead and the important components containing in these concentrates is considered. This scheme includes sulfating roasting of the lead concentrates and two-stage leaching of the formed cinder with the formation of a sulfate solution and lead sulfate. When transformed into a carbonate form, lead sulfate is used for the production of pure metallic lead. Silver, indium, copper, cadmium, nickel, cobalt, and other important components are separately extracted from a solution. At the last stage, zinc is extracted by either extraction followed by electrolytic extraction of a metal or the return of the forming solution of sulfuric acid to cinder leaching.

Concentration and mindfulness meditations: unique forms of consciousness?

PubMed

Dunn, B R; Hartigan, J A; Mikulas, W L

1999-09-01

Electroencephalographic (EEG) recordings from 19 scalp recording sites were used to differentiate among two posited unique forms of mediation, concentration and mindfulness, and a normal relaxation control condition. Analyzes of all traditional frequency bandwidth data (i.e., delta 1-3 Hz; theta, 4-7 Hz; alpha, 8-12 Hz; beta 1, 13-25 Hz; beta 2, 26-32 Hz) showed strong mean amplitude frequency differences between the two meditation conditions and relaxation over numerous cortical sites. Furthermore, significant differences were obtained between concentration and mindfulness states at all bandwidths. Taken together, our results suggest that concentration and mindfulness "meditations" may be unique forms of consciousness and are not merely degrees of a state of relaxation.

A Comparative Study of Children's Concentration Performance on Picture Books: Age, Gender, and Media Forms

ERIC Educational Resources Information Center

Ma, Min-Yuan; Wei, Chun-Chun

2016-01-01

The reading development of children depends on various sensory stimuli, which help them construct reading contexts and facilitate active learning and exploration. This study uses sensory stimuli provided by picture books using various forms of media to improve children's concentration performance. We employ picture books using four forms of media:…

Rhodoblastus sphagnicola sp. nov., a novel acidophilic purple non-sulfur bacterium from Sphagnum peat bog.

PubMed

Kulichevskaya, Irina S; Guzev, Vladimir S; Gorlenko, Vladimir M; Liesack, Werner; Dedysh, Svetlana N

2006-06-01

An isolate of purple non-sulfur bacteria was obtained from an acidic Sphagnum peat bog and designated strain RS(T). The colour of cell suspensions of this bacterium growing in the light under anaerobic conditions is purplish red. Cells of strain RS(T) are rod-shaped, 0.8-1.0 microm wide and 2.0-6.0 microm long, motile by means of polar flagella, reproduce by budding and have a tendency to form rosette-like clusters in older cultures. The cells contain lamellar intracytoplasmic membranes underlying, and parallel to, the cytoplasmic membrane. The photosynthetic pigments are bacteriochlorophyll a and carotenoids; the absorption spectrum of living cells shows maxima at 377, 463, 492, 527, 592, 806 and 867 nm. The cells grow photoheterotrophically under anaerobic or microaerobic conditions with various organic carbon sources or grow photolithoautotrophically with H(2) and CO(2). Strain RS(T) is a moderately acidophilic organism exhibiting growth at pH values between 4.8 and 7.0 (with an optimum at pH 5.2-5.5). The major fatty acids are 16 : 1omega7c and 18 : 1omega7c; the major quinones are Q-10 and Q-9. The DNA G + C content of strain RS(T) is 62.6 mol%. Analysis of the 16S rRNA gene sequence revealed that the novel isolate is most closely related (97.3 % sequence similarity) to the type strain ATCC 25092(T) of the moderately acidophilic purple non-sulfur bacterium Rhodoblastus acidophilus, formerly named Rhodopseudomonas acidophila. However, in contrast to Rbl. acidophilus, strain RS(T) is not capable of aerobic growth in the dark, has no spirilloxanthin among the carotenoids and differs in the pattern of substrate utilization. The value for DNA-DNA hybridization between strain RS(T) and Rbl. acidophilus ATCC 25092(T) is only 22 %. Thus, strain RS(T) represents a novel species of the genus Rhodoblastus, for which the name Rhodoblastus sphagnicola sp. nov. is proposed. Strain RS(T) (=DSM 16996(T) = VKM B-2361(T)) is the type strain.

Phaeobacterium nitratireducens gen. nov., sp. nov., a phototrophic gammaproteobacterium isolated from a mangrove forest sediment sample.

PubMed

Nupur; Tanuku, Naga Radha Srinivas; Shinichi, Takaichi; Pinnaka, Anil Kumar

2015-08-01

A novel brown-coloured, Gram-negative-staining, rod-shaped, motile, phototrophic, purple sulfur bacterium, designated strain AK40T, was isolated in pure culture from a sediment sample collected from Coringa mangrove forest, India. Strain AK40T contained bacteriochlorophyll a and carotenoids of the rhodopin series as major photosynthetic pigments. Strain AK40T was able to grow photoheterotrophically and could utilize a number of organic substrates. It was unable to grow photoautotrophically and did not utilize sulfide or thiosulfate as electron donors. Thiamine and riboflavin were required for growth. The dominant fatty acids were C12 : 0, C16 : 0, C18 : 1ω7c and summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH). The polar lipid profile of strain AK40T was found to contain diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and eight unidentified lipids. Q-10 was the predominant respiratory quinone. The DNA G+C content of strain AK40T was 65.5 mol%. 16S rRNA gene sequence comparisons indicated that the isolate represented a member of the family Chromatiaceae within the class Gammaproteobacteria. 16S rRNA gene sequence analysis indicated that strain AK40T was closely related to Phaeochromatium fluminis, with 95.2% pairwise sequence similarity to the type strain; sequence similarity to strains of other species of the family was 90.8-94.8%. Based on the sequence comparison data, strain AK40T was positioned distinctly outside the group formed by the genera Phaeochromatium, Marichromatium, Halochromatium, Thiohalocapsa, Rhabdochromatium and Thiorhodovibrio. Distinct morphological, physiological and genotypic differences from previously described taxa supported the classification of this isolate as a representative of a novel species in a new genus, for which the name Phaeobacterium nitratireducens gen. nov., sp. nov. is proposed. The type strain of Phaeobacterium nitratireducens is AK40T ( = JCM 19219T = MTCC 11824T).

Analysis of the kinetics of P+ HA- recombination in membrane-embedded wild-type and mutant Rhodobacter sphaeroides reaction centers between 298 and 77 K indicates that the adjacent negatively charged QA ubiquinone modulates the free energy of P+ HA- and may influence the rate of the protein dielectric response.

PubMed

Gibasiewicz, Krzysztof; Pajzderska, Maria; Dobek, Andrzej; Brettel, Klaus; Jones, Michael R

2013-09-26

Time-resolved spectroscopic studies of recombination of the P(+)HA(-) radical pair in photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides give an opportunity to study protein dynamics triggered by light and occurring over the lifetime of P(+)HA(-). The state P(+)HA(-) is formed after the ultrafast light-induced electron transfer from the primary donor pair of bacteriochlorophylls (P) to the acceptor bacteriopheophytin (HA). In order to increase the lifetime of this state, and thus increase the temporal window for the examination of protein dynamics, it is possible to block forward electron transfer from HA(-) to the secondary electron acceptor QA. In this contribution, the dynamics of P(+)HA(-) recombination were compared at a range of temperatures from 77 K to room temperature, electron transfer from HA(-) to QA being blocked either by prereduction of QA or by genetic removal of QA. The observed P(+)HA(-) charge recombination was significantly slower in the QA-deficient RCs, and in both types of complexes, lowering the temperature from RT to 77 K led to a slowing of charge recombination. The effects are explained in the frame of a model in which charge recombination occurs via competing pathways, one of which is thermally activated and includes transient formation of a higher-energy state, P(+)BA(-). An internal electrostatic field supplied by the negative charge on QA increases the free energy levels of the state P(+)HA(-), thus decreasing its energetic distance to the state P(+)BA(-). In addition, the dielectric response of the protein environment to the appearance of the state P(+)HA(-) is accelerated from ∼50-100 ns in the QA-deficient mutant RCs to ∼1-16 ns in WT RCs with a negatively charged QA(-). In both cases, the temperature dependence of the protein dynamics is weak.

Low potential manganese ions as efficient electron donors in native anoxygenic bacteria.

PubMed

Deshmukh, Sasmit S; Protheroe, Charles; Ivanescu, Matei-Alexandru; Lag, Sarah; Kálmán, László

2018-04-01

Systematic control over molecular driving forces is essential for understanding the natural electron transfer processes as well as for improving the efficiency of the artificial mimics of energy converting enzymes. Oxygen producing photosynthesis uniquely employs manganese ions as rapid electron donors. Introducing this attribute to anoxygenic photosynthesis may identify evolutionary intermediates and provide insights to the energetics of biological water oxidation. This work presents effective environmental methods that substantially and simultaneously tune the redox potentials of manganese ions and the cofactors of a photosynthetic enzyme from native anoxygenic bacteria without the necessity of genetic modification or synthesis. A spontaneous coordination with bis-tris propane lowered the redox potential of the manganese (II) to manganese (III) transition to an unusually low value (~400 mV) at pH 9.4 and allowed its binding to the bacterial reaction center. Binding to a novel buried binding site elevated the redox potential of the primary electron donor, a dimer of bacteriochlorophylls, by up to 92 mV also at pH 9.4 and facilitated the electron transfer that is able to compete with the wasteful charge recombination. These events impaired the function of the natural electron donor and made BTP-coordinated manganese a viable model for an evolutionary alternative. Copyright © 2018 Elsevier B.V. All rights reserved.

Excited state conformational dynamics in carotenoids: dark intermediates and excitation energy transfer.

PubMed

Beck, Warren F; Bishop, Michael M; Roscioli, Jerome D; Ghosh, Soumen; Frank, Harry A

2015-04-15

A consideration of the excited state potential energy surfaces of carotenoids develops a new hypothesis for the nature of the conformational motions that follow optical preparation of the S2 (1(1)Bu(+)) state. After an initial displacement from the Franck-Condon geometry along bond length alternation coordinates, it is suggested that carotenoids pass over a transition-state barrier leading to twisted conformations. This hypothesis leads to assignments for several dark intermediate states encountered in femtosecond spectroscopic studies. The Sx state is assigned to the structure reached upon the onset of torsional motions near the transition state barrier that divides planar and twisted structures on the S2 state potential energy surface. The X state, detected recently in two-dimensional electronic spectra, corresponds to a twisted structure well past the barrier and approaching the S2 state torsional minimum. Lastly, the S(∗) state is assigned to a low lying S1 state structure with intramolecular charge transfer character (ICT) and a pyramidal conformation. It follows that the bent and twisted structures of carotenoids that are found in photosynthetic light-harvesting proteins yield excited-state structures that favor the development of an ICT character and optimized energy transfer yields to (bacterio)chlorophyll acceptors. Copyright © 2015 Elsevier Inc. All rights reserved.

Accurate Differentiation of Carotenoid Pigments Using Flight Representative Raman Spectrometers

NASA Astrophysics Data System (ADS)

Malherbe, Cedric; Hutchinson, Ian B.; McHugh, Melissa; Ingley, Richard; Jehlička, Jan; Edwards, Howell G. M.

2017-04-01

Raman spectrometers will be utilized on two Mars rover missions, ExoMars and Mars 2020, in the near future, to search for evidence of life and habitable geological niches on Mars. Carotenoid pigments are recognized target biomarkers, and as they are highly active in Raman spectroscopy, they can be readily used to characterize the capabilities of space representative instrumentation. As part of the preparatory work being performed for the ExoMars mission, a gypsum crust colonized by microorganisms was interrogated with commercial portable Raman instruments and a flight representative Raman laser spectrometer. Four separate layers, each exhibiting different coloration resulting from specific halophilic microorganism activities within the gypsum crust, were studied by using two excitation wavelengths: 532 and 785 nm. Raman or fluorescence data were readily obtained during the present study. Gypsum, the main constituent of the crust, was detected with both excitation wavelengths, while the resonance Raman signal associated with carotenoid pigments was only detected with a 532 nm excitation wavelength. The fluorescence originating from bacteriochlorophyll a was found to overwhelm the Raman signal for the layer colonized by sulfur bacteria when interrogated with a 785 nm excitation wavelength. Finally, it was demonstrated that portable instruments and the prototype were capable of detecting a statistically significant difference in band positions of carotenoid signals between the sample layers.

Development of massive multilevel molecular dynamics simulation program, Platypus (PLATform for dYnamic Protein Unified Simulation), for the elucidation of protein functions.

PubMed

Takano, Yu; Nakata, Kazuto; Yonezawa, Yasushige; Nakamura, Haruki

2016-05-05

A massively parallel program for quantum mechanical-molecular mechanical (QM/MM) molecular dynamics simulation, called Platypus (PLATform for dYnamic Protein Unified Simulation), was developed to elucidate protein functions. The speedup and the parallelization ratio of Platypus in the QM and QM/MM calculations were assessed for a bacteriochlorophyll dimer in the photosynthetic reaction center (DIMER) on the K computer, a massively parallel computer achieving 10 PetaFLOPs with 705,024 cores. Platypus exhibited the increase in speedup up to 20,000 core processors at the HF/cc-pVDZ and B3LYP/cc-pVDZ, and up to 10,000 core processors by the CASCI(16,16)/6-31G** calculations. We also performed excited QM/MM-MD simulations on the chromophore of Sirius (SIRIUS) in water. Sirius is a pH-insensitive and photo-stable ultramarine fluorescent protein. Platypus accelerated on-the-fly excited-state QM/MM-MD simulations for SIRIUS in water, using over 4000 core processors. In addition, it also succeeded in 50-ps (200,000-step) on-the-fly excited-state QM/MM-MD simulations for the SIRIUS in water. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.

Chlorophyll Biosynthesis Gene Evolution Indicates Photosystem Gene Duplication, Not Photosystem Merger, at the Origin of Oxygenic Photosynthesis

PubMed Central

Sousa, Filipa L.; Shavit-Grievink, Liat; Allen, John F.; Martin, William F.

2013-01-01

An open question regarding the evolution of photosynthesis is how cyanobacteria came to possess the two reaction center (RC) types, Type I reaction center (RCI) and Type II reaction center (RCII). The two main competing theories in the foreground of current thinking on this issue are that either 1) RCI and RCII are related via lineage divergence among anoxygenic photosynthetic bacteria and became merged in cyanobacteria via an event of large-scale lateral gene transfer (also called "fusion" theories) or 2) the two RC types are related via gene duplication in an ancestral, anoxygenic but protocyanobacterial phototroph that possessed both RC types before making the transition to using water as an electron donor. To distinguish between these possibilities, we studied the evolution of the core (bacterio)chlorophyll biosynthetic pathway from protoporphyrin IX (Proto IX) up to (bacterio)chlorophyllide a. The results show no dichotomy of chlorophyll biosynthesis genes into RCI- and RCII-specific chlorophyll biosynthetic clades, thereby excluding models of fusion at the origin of cyanobacteria and supporting the selective-loss hypothesis. By considering the cofactor demands of the pathway and the source genes from which several steps in chlorophyll biosynthesis are derived, we infer that the cell that first synthesized chlorophyll was a cobalamin-dependent, heme-synthesizing, diazotrophic anaerobe. PMID:23258841

A monogalactosyldiacylglycerol synthase found in the green sulfur bacterium Chlorobaculum tepidum reveals important roles for galactolipids in photosynthesis.

PubMed

Masuda, Shinji; Harada, Jiro; Yokono, Makio; Yuzawa, Yuichi; Shimojima, Mie; Murofushi, Kazuhiro; Tanaka, Hironori; Masuda, Hanako; Murakawa, Masato; Haraguchi, Tsuyoshi; Kondo, Maki; Nishimura, Mikio; Yuasa, Hideya; Noguchi, Masato; Oh-Oka, Hirozo; Tanaka, Ayumi; Tamiaki, Hitoshi; Ohta, Hiroyuki

2011-07-01

Monogalactosyldiacylglycerol (MGDG), which is conserved in almost all photosynthetic organisms, is the most abundant natural polar lipid on Earth. In plants, MGDG is highly accumulated in the chloroplast membranes and is an important bulk constituent of thylakoid membranes. However, precise functions of MGDG in photosynthesis have not been well understood. Here, we report a novel MGDG synthase from the green sulfur bacterium Chlorobaculum tepidum. This enzyme, MgdA, catalyzes MGDG synthesis using UDP-Gal as a substrate. The gene encoding MgdA was essential for this bacterium; only heterozygous mgdA mutants could be isolated. An mgdA knockdown mutation affected in vivo assembly of bacteriochlorophyll c aggregates, suggesting the involvement of MGDG in the construction of the light-harvesting complex called chlorosome. These results indicate that MGDG biosynthesis has been independently established in each photosynthetic organism to perform photosynthesis under different environmental conditions. We complemented an Arabidopsis thaliana MGDG synthase mutant by heterologous expression of MgdA. The complemented plants showed almost normal levels of MGDG, although they also had abnormal morphological phenotypes, including reduced chlorophyll content, no apical dominance in shoot growth, atypical flower development, and infertility. These observations provide new insights regarding the importance of regulated MGDG synthesis in the physiology of higher plants.

Chlorophyll biosynthesis gene evolution indicates photosystem gene duplication, not photosystem merger, at the origin of oxygenic photosynthesis.

PubMed

Sousa, Filipa L; Shavit-Grievink, Liat; Allen, John F; Martin, William F

2013-01-01

An open question regarding the evolution of photosynthesis is how cyanobacteria came to possess the two reaction center (RC) types, Type I reaction center (RCI) and Type II reaction center (RCII). The two main competing theories in the foreground of current thinking on this issue are that either 1) RCI and RCII are related via lineage divergence among anoxygenic photosynthetic bacteria and became merged in cyanobacteria via an event of large-scale lateral gene transfer (also called "fusion" theories) or 2) the two RC types are related via gene duplication in an ancestral, anoxygenic but protocyanobacterial phototroph that possessed both RC types before making the transition to using water as an electron donor. To distinguish between these possibilities, we studied the evolution of the core (bacterio)chlorophyll biosynthetic pathway from protoporphyrin IX (Proto IX) up to (bacterio)chlorophyllide a. The results show no dichotomy of chlorophyll biosynthesis genes into RCI- and RCII-specific chlorophyll biosynthetic clades, thereby excluding models of fusion at the origin of cyanobacteria and supporting the selective-loss hypothesis. By considering the cofactor demands of the pathway and the source genes from which several steps in chlorophyll biosynthesis are derived, we infer that the cell that first synthesized chlorophyll was a cobalamin-dependent, heme-synthesizing, diazotrophic anaerobe.

Serum free 1,25-dihydroxy-vitamin D is more closely associated with fibroblast growth factor 23 than other vitamin D forms in chronic dialysis patients.

PubMed

Chao, Chia-Ter; Lee, Szu-Ying; Yen, Chung-Jen; Chiang, Chih-Kang; Huang, Jenq-Wen; Hung, Kuan-Yu

2015-01-15

Mineral bone disorder (MBD) is prevalent among chronic dialysis patients. However, relationship between different forms of vitamin D and fibroblast growth factor 23 (FGF-23) remains unclear in this population. A multicenter hemodialysis cohort was assembled. We evaluated 25-OH-D and 1,25-(OH)2-D, vitamin D-binding protein, and FGF-23, in this cohort. Multiple regression analyses were performed to investigate the relationship and stewardship between different vitamin D forms and FGF-23 concentrations. Chronic dialysis patients presented significantly higher FGF-23 concentrations. 25-OH-D concentrations of <20 ng/ml (deficiency), 20-30 ng/ml (insufficiency), and ≥30 ng/ml (sufficiency) were associated with progressively lower FGF-23 concentrations (p<0.01). Serum FGF-23 concentrations were significantly correlated with total (p=0.02), free (p<0.01) and bioavailable (p<0.01) 25-OH-D and total (p=0.04), free (p=0.02), and bioavailable (p=0.03) 1,25-(OH)2-D concentrations. With all 25-OH-D and 1,25-(OH)2-D forms in the regression model, we found that free 1,25-(OH)2-D outweighed all other vitamin D forms regarding its association with FGF-23 (p=0.03). The relationship between FGF-23 and vitamin D is stronger using free forms of 25-OH-D and 1,25-(OH)2-D. Subsequent studies aiming at MBD should consider including free 25-OH-D and 1,25-(OH)2-D in the analysis. Copyright © 2014 Elsevier B.V. All rights reserved.

Hydraulic effects in a radiative atmosphere with ionization

NASA Astrophysics Data System (ADS)

Bhat, P.; Brandenburg, A.

2016-03-01

Context. In his 1978 paper, Eugene Parker postulated the need for hydraulic downward motion to explain magnetic flux concentrations at the solar surface. A similar process has also recently been seen in simplified (e.g., isothermal) models of flux concentrations from the negative effective magnetic pressure instability (NEMPI). Aims: We study the effects of partial ionization near the radiative surface on the formation of these magnetic flux concentrations. Methods: We first obtain one-dimensional (1D) equilibrium solutions using either a Kramers-like opacity or the H- opacity. The resulting atmospheres are then used as initial conditions in two-dimensional (2D) models where flows are driven by an imposed gradient force that resembles a localized negative pressure in the form of a blob. To isolate the effects of partial ionization and radiation, we ignore turbulence and convection. Results: Because of partial ionization, an unstable stratification always forms near the surface. We show that the extrema in the specific entropy profiles correspond to the extrema in the degree of ionization. In the 2D models without partial ionization, strong flux concentrations form just above the height where the blob is placed. Interestingly, in models with partial ionization, such flux concentrations always form at the surface well above the blob. This is due to the corresponding negative gradient in specific entropy. Owing to the absence of turbulence, the downflows reach transonic speeds. Conclusions: We demonstrate that, together with density stratification, the imposed source of negative pressure drives the formation of flux concentrations. We find that the inclusion of partial ionization affects the entropy profile dramatically, causing strong flux concentrations to form closer to the surface. We speculate that turbulence effects are needed to limit the strength of flux concentrations and homogenize the specific entropy to a stratification that is close to marginal.

Aquatic Toxicity Screening of Fire Fighting Agents; 2003 Report

DTIC Science & Technology

2003-06-02

Aqueous Film Forming Foam ( AFFF ), the reference toxicant. The aquatic toxicity screening consisted of an acute, static, range-finding...five concentrations of 3M Light Water Brand Aqueous Film Forming Foam ( AFFF ), the reference toxicant. The aquatic toxicity screening consisted of an...experimental foam concentrates against current Military Specification MIL-F-24385F Fire Extinguishing Agent, Aqueous Film Forming Foam

NoFoam Unit Installation, Evaluation and Operations Manual

DTIC Science & Technology

2003-03-10

Aqueous Film Forming Foam ( AFFF ) liquid concentrate in their fleet do not have the facilities...NoFoam Unit using AFRL vehicles and facilities. Currently, the majority of Fire Departments that use 3% Aqueous Film Forming Foam ( AFFF ) liquid...Departments that have ARFF vehicles that use 3% Aqueous Film Forming Foam ( AFFF ) liquid concentrate in their fleet do not have the facilities

Significance of the concentration of chelating ligands on Fe3+-solubility, bioavailability, and uptake in rice plant.

PubMed

Hasegawa, Hiroshi; Rahman, M Mamunur; Kadohashi, Kouta; Takasugi, Yui; Tate, Yousuke; Maki, Teruya; Rahman, M Azizur

2012-09-01

Present study investigated the significance of the concentration of chelating ligand on Fe(3+)-solubility in growth medium and its influence on Fe bioavailability and uptake in rice plant. Rice seedlings were grown in modified Murashige and Skoog (MS) hydroponic growth medium with moderate (250 μM) and high (500 μM) concentrations of ethylenediaminetetraacetate (EDTA) and hydroxyiminodisuccinate (HIDS) under sterile and non-sterile conditions. Concentrations of soluble Fe in the growth medium increased with increasing ligand concentrations, and the growth of rice seedlings was higher at moderate ligand concentration than at control (without chelant) and high ligand concentration. This explains the relationship between Fe solubility and bioavailability in the growth medium, and its effect on Fe uptake in rice plant. Fe exists in the growth medium predominantly as particulate (insoluble) forms at low ligand concentration, and as soluble [Fe(OH)(2+), Fe(OH)(2)(+), Fe-L complex] and apparently soluble (colloidal) forms at moderate ligand concentration. At high ligand concentration, most of the Fe(3+) in the growth medium forms soluble Fe-L complex, however, the bioavailability of Fe from Fe-L complex decreased due to lopsided complex formation equilibrium reaction (CFER) between Fe and the ligands. Also, Fe is solubilized forming stable and soluble Fe-L complex, which is then detached as less stable, but soluble and bioavailable substance(s) after (time-dependent) biodegradation. Therefore- i) ligand concentration and stability constant of Fe-L complex (K(Fe-L)) influence Fe bioavailability and uptake in rice plant, and ii) the biodegradable ligands (e.g., HIDS) would be more effective Fe fertilizer than the environmentally persistent and less biodegradable ligands (e.g., EDTA). Copyright © 2012 Elsevier Masson SAS. All rights reserved.

Simple Köhler Homogenizers for Image-forming Solar Concentrators

NASA Astrophysics Data System (ADS)

Winston, Roland; Zhang, Weiya

2011-12-01

We demonstrate that the Köhler illumination technique can be applied to the image-forming solar concentrators to solve the problem of "hot" spot and to generate the square irradiance pattern. The Köhler homogenizer can be simply a single aspheric lens optimized following a few guidelines. Two examples are given including a Fresnel lens based concentrator and a two-mirror aplanatic system.

Iron concentration, bioavailability, and nutritional quality of polished rice affected by different forms of foliar iron fertilizer.

PubMed

He, Wanling; Shohag, M J I; Wei, Yanyan; Feng, Ying; Yang, Xiaoe

2013-12-15

The present study compared the effects of four different forms of foliar iron (Fe) fertilizers on Fe concentration, bioavailability and nutritional quality of polished rice. The results showed that foliar fertilisation at the anthesis stage was an effective way to promote Fe concentration and bioavailability of polished rice, especially in case of DTPA-Fe. Compared to the control, foliar application of DTPA-Fe increased sulphur concentration and the nutrition promoter cysteine content, whereas decreased phosphorus concentration and the antinutrient phytic acid content of polished rice, as a result increased 67.2% ferrtin formation in Caco-2 cell. Moreover, foliar DTPA-Fe application could maintain amylase, protein and minerals quality of polished rice. According to the current study, DTPA-Fe is recommended as an excellent foliar Fe form for Fe biofortification program. Copyright © 2013 Elsevier Ltd. All rights reserved.

Phase control during the synthesis of nickel sulfide nanoparticles from dithiocarbamate precursors

NASA Astrophysics Data System (ADS)

Roffey, Anna; Hollingsworth, Nathan; Islam, Husn-Ubayda; Mercy, Maxime; Sankar, Gopinathan; Catlow, C. Richard A.; Hogarth, Graeme; de Leeuw, Nora H.

2016-05-01

Square-planar nickel bis(dithiocarbamate) complexes, [Ni(S2CNR2)2], have been prepared and utilised as single source precursors to nanoparticulate nickel sulfides. While they are stable in the solid-state to around 300 °C, heating in oleylamine at 230 °C, 5 mM solutions afford pure α-NiS, where the outcome is independent of the substituents. DFT calculations show an electronic effect rather than steric hindrance influences the resulting particle size. Decomposition of the iso-butyl derivative, [Ni(S2CNiBu2)2], has been studied in detail. There is a temperature-dependence of the phase of the nickel sulfide formed. At low temperatures (150 °C), pure α-NiS is formed. Upon raising the temperature, increasing amounts of β-NiS are produced and at 280 °C this is formed in pure form. A range of concentrations (from 5-50 mM) was also investigated at 180 °C and while in all cases pure α-NiS was formed, particle sizes varied significantly. Thus at low concentrations average particle sizes were ca. 100 nm, but at higher concentrations they increased to ca. 150 nm. The addition of two equivalents of tetra-iso-butyl thiuram disulfide, (iBu2NCS2)2, to the decomposition mixture was found to influence the material formed. At 230 °C and above, α-NiS was generated, in contrast to the results found without added thiuram disulfide, suggesting that addition of (iBu2NCS2)2 stabilises the metastable α-NiS phase. At low temperatures (150-180 °C) and concentrations (5 mM), mixtures of α-NiS and Ni3S4, result. A growing proportion of Ni3S4 is noted upon increasing precursor concentration to 10 mM. At 20 mM a metastable phase of nickel sulfide, NiS2 is formed and as the concentration is increased, α-NiS appears alongside NiS2. Reasons for these variations are discussed.Square-planar nickel bis(dithiocarbamate) complexes, [Ni(S2CNR2)2], have been prepared and utilised as single source precursors to nanoparticulate nickel sulfides. While they are stable in the solid-state to around 300 °C, heating in oleylamine at 230 °C, 5 mM solutions afford pure α-NiS, where the outcome is independent of the substituents. DFT calculations show an electronic effect rather than steric hindrance influences the resulting particle size. Decomposition of the iso-butyl derivative, [Ni(S2CNiBu2)2], has been studied in detail. There is a temperature-dependence of the phase of the nickel sulfide formed. At low temperatures (150 °C), pure α-NiS is formed. Upon raising the temperature, increasing amounts of β-NiS are produced and at 280 °C this is formed in pure form. A range of concentrations (from 5-50 mM) was also investigated at 180 °C and while in all cases pure α-NiS was formed, particle sizes varied significantly. Thus at low concentrations average particle sizes were ca. 100 nm, but at higher concentrations they increased to ca. 150 nm. The addition of two equivalents of tetra-iso-butyl thiuram disulfide, (iBu2NCS2)2, to the decomposition mixture was found to influence the material formed. At 230 °C and above, α-NiS was generated, in contrast to the results found without added thiuram disulfide, suggesting that addition of (iBu2NCS2)2 stabilises the metastable α-NiS phase. At low temperatures (150-180 °C) and concentrations (5 mM), mixtures of α-NiS and Ni3S4, result. A growing proportion of Ni3S4 is noted upon increasing precursor concentration to 10 mM. At 20 mM a metastable phase of nickel sulfide, NiS2 is formed and as the concentration is increased, α-NiS appears alongside NiS2. Reasons for these variations are discussed. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00053c

Interactions between concentric form-from-structure and face perception revealed by visual masking but not adaptation

PubMed Central

Feczko, Eric; Shulman, Gordon L.; Petersen, Steven E.; Pruett, John R.

2014-01-01

Findings from diverse subfields of vision research suggest a potential link between high-level aspects of face perception and concentric form-from-structure perception. To explore this relationship, typical adults performed two adaptation experiments and two masking experiments to test whether concentric, but not nonconcentric, Glass patterns (a type of form-from-structure stimulus) utilize a processing mechanism shared by face perception. For the adaptation experiments, subjects were presented with an adaptor for 5 or 20 s, prior to discriminating a target. In the masking experiments, subjects saw a mask, then a target, and then a second mask. Measures of discriminability and bias were derived and repeated measures analysis of variance tested for pattern-specific masking and adaptation effects. Results from Experiment 1 show no Glass pattern-specific effect of adaptation to faces; results from Experiment 2 show concentric Glass pattern masking, but not adaptation, may impair upright/inverted face discrimination; results from Experiment 3 show concentric and radial Glass pattern masking impaired subsequent upright/inverted face discrimination more than translational Glass pattern masking; and results from Experiment 4 show concentric and radial Glass pattern masking impaired subsequent face gender discrimination more than translational Glass pattern masking. Taken together, these findings demonstrate interactions between concentric form-from-structure and face processing, suggesting a possible common processing pathway. PMID:24563526

Methylmercury is the predominant form of mercury in bird eggs: a synthesis

USGS Publications Warehouse

Ackerman, Joshua T.; Herzog, Mark P.; Schwarzbach, Steven E.

2013-01-01

Bird eggs are commonly used in mercury monitoring programs to assess methylmercury contamination and toxicity to birds. However, only 6% of >200 studies investigating mercury in bird eggs have actually measured methylmercury concentrations in eggs. Instead, studies typically measure total mercury in eggs (both organic and inorganic forms of mercury), with the explicit assumption that total mercury concentrations in eggs are a reliable proxy for methylmercury concentrations in eggs. This assumption is rarely tested, but has important implications for assessing risk of mercury to birds. We conducted a detailed assessment of this assumption by (1) collecting original data to examine the relationship between total and methylmercury in eggs of two species, and (2) reviewing the published literature on mercury concentrations in bird eggs to examine whether the percentage of total mercury in the methylmercury form differed among species. Within American avocets (Recurvirostra americana) and Forster’s terns (Sterna forsteri), methylmercury concentrations were highly correlated (R2 = 0.99) with total mercury concentrations in individual eggs (range: 0.03–7.33 μg/g fww), and the regression slope (log scale) was not different from one (m = 0.992). The mean percentage of total mercury in the methylmercury form in eggs was 97% for American avocets (n = 30 eggs), 96% for Forster’s terns (n = 30 eggs), and 96% among all 22 species of birds (n = 30 estimates of species means). The percentage of total mercury in the methylmercury form ranged from 63% to 116% among individual eggs and 82% to 111% among species means, but this variation was not related to total mercury concentrations in eggs, foraging guild, nor to a species life history strategy as characterized along the precocial to altricial spectrum. Our results support the use of total mercury concentrations to estimate methylmercury concentrations in bird eggs.

Impact of model perfume molecules on the self-assembly of anionic surfactant sodium dodecyl 6-benzene sulfonate.

PubMed

Bradbury, Robert; Penfold, Jeffrey; Thomas, Robert K; Tucker, Ian M; Petkov, Jordan T; Jones, Craig; Grillo, Isabelle

2013-03-12

The impact of two model perfumes with differing degrees of hydrophobicity/hydrophilicity, linalool (LL) and phenylethanol (PE), on the solution structure of anionic surfactant sodium dodecyl 6-benzene sulfonate, LAS-6, has been studied by small angle neutron scattering, SANS. For both types of perfume molecules, complex phase behavior is observed. The phase behavior depends upon the concentration, surfactant/perfume composition, and type of perfume. The more hydrophilic perfume PE promotes the formation of more highly curved structures. At relatively low surfactant concentrations, small globular micelles, L1, are formed. These become perfume droplets, L(sm), stabilized by the surfactant at much higher perfume solution compositions. At higher surfactant concentrations, the tendency of LAS-6 to form more planar structures is evident. The more hydrophobic linalool promotes the formation of more planar structures. Combined with the greater tendency of LAS-6 to form planar structures, this results in the planar structures dominating the phase behavior for the LAS-6/linalool mixtures. For the LAS-6/linalool mixture, the self-assembly is in the form of micelles only at the lowest surfactant and perfume concentrations. Over most of the concentration-composition space explored, the structures are predominantly lamellar, L(α), or vesicle, L(v), or in the form of a lamellar/micellar coexistence. At low and intermediate amounts of LL, a significantly different structure is observed, and the aggregates are in the form of small, relatively monodisperse vesicles (i.e., nanovesicles), L(sv).

Distribution and heterogeneity of immunoreactive cholecystokinin (CCK) in the mucosa of the porcine gastrointestinal tract.

PubMed

Bacarese-Hamilton, A J; Adrian, T E; Bloom, S R

1984-11-01

The concentration and molecular nature of cholecystokinin-like immunoreactivity (CCK-LI) in extracts of porcine intestinal mucosa were determined using sequence-specific radioimmunoassays. Highest CCK concentrations were measured in duodenal mucosa (258 +/- 60 pmol/g in the distal duodenum) followed by jejunal mucosa (204 +/- 36 pmol/g in the proximal jejunum) and pylorus (51 +/- 9 pmol/g). All other gastrointestinal regions proximal to the pylorus and distal to the jejunum contained less than 20 pmol/g. Pancreas contained less than 1 pmol/g. Gel chromatography in 6 M urea revealed four immunoreactive forms and this was confirmed by reverse-phase high-pressure liquid chromatography (HPLC). The predominant molecular form in acid extracts of duodenal mucosa resembled CCK-33 although high concentrations of the larger CCK form ('CCK-58') and of the form intermediate in size between CCK-33 and CCK-8 were measured. A molecular form resembling CCK-8 was the principal form in neutral extracts of the duodenum.

Neuroleptic bioequivalency: tablet versus concentrate.

PubMed

Fann, W E; Moreira, A F

1985-01-01

Two forms of the antipsychotic neuroleptic molindone were administered to newly admitted psychotic patients. A coated tablet was administered for ten days, followed by administration of liquid concentrate in equivalent doses for four days. Plasma was analyzed by gas chromatography with electron capture for the parent compound following each dosing phase. Our data suggest that oral doses of the tablet and concentrate forms of this neuroleptic are equivalent in clinical bioavailability.

Effect of mineral viscosity-enhancing admixtures on the solidification of evaporator concentrates.

PubMed

Lin, Chung-Yung; Huang, Wan-Ting

2015-11-15

It is known that partial replacement of cement by viscosity-enhancing admixtures, also known as anti-washout admixtures, affects the quality of the waste form or concrete. To reduce the bleeding rate of the paste, the characteristics of various mineral viscosity-enhancing admixtures dispersed in saline solutions were investigated, including sedimentation and viscosity. The admixture candidates included fly ash, silica fume, bentonite, and palygorskite. The effect of these admixtures blended with a cement-based matrix on the bleeding rate of the solidification of evaporator concentrates was also examined in this paper. The experimental results show the palygorskite Type 400 is the best choice to improve the quality of waste form, due to its excellent suspension property in the saline solution. The bleeding rate of paste decreased as the dispersion volume of the admixture suspension increased. For consideration of the quality of waste forms and the concentrate loading, the optimization of the palygorskite/concentrate ratio of 15-17 wt% and solidification agent/concentrate ratio of 1.0-1.2 were adopted. With this recipe, the quality of waste forms resulting from the solidification of simulated and actual evaporator concentrates mainly containing chloride met the regulations' requirements. Copyright © 2015 Elsevier B.V. All rights reserved.

27 CFR 25.296 - Record of beer concentrate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... process; (2) Concentrate produced; (3) Concentrate transferred to other breweries; (4) Concentrate... report by specific entries on Form 5130.9, the quantity of beer entered into the concentration process... 5130.9, a summary accounting of all concentrate operations at the brewery for the reporting period...

A numerical analysis on forming limits during spiral and concentric single point incremental forming

NASA Astrophysics Data System (ADS)

Gipiela, M. L.; Amauri, V.; Nikhare, C.; Marcondes, P. V. P.

2017-01-01

Sheet metal forming is one of the major manufacturing industries, which are building numerous parts for aerospace, automotive and medical industry. Due to the high demand in vehicle industry and environmental regulations on less fuel consumption on other hand, researchers are innovating new methods to build these parts with energy efficient sheet metal forming process instead of conventionally used punch and die to form the parts to achieve the lightweight parts. One of the most recognized manufacturing process in this category is Single Point Incremental Forming (SPIF). SPIF is the die-less sheet metal forming process in which the single point tool incrementally forces any single point of sheet metal at any process time to plastic deformation zone. In the present work, finite element method (FEM) is applied to analyze the forming limits of high strength low alloy steel formed by single point incremental forming (SPIF) by spiral and concentric tool path. SPIF numerical simulations were model with 24 and 29 mm cup depth, and the results were compare with Nakajima results obtained by experiments and FEM. It was found that the cup formed with Nakajima tool failed at 24 mm while cups formed by SPIF surpassed the limit for both depths with both profiles. It was also notice that the strain achieved in concentric profile are lower than that in spiral profile.

Effect of reaction time on the formation of disinfection byproducts

USGS Publications Warehouse

Rathbun, R.E.

1997-01-01

The effect of reaction time on the trihalomethane and nonpurgeable total organic-halide formation potentials was determined by chlorinating water samples from the Mississippi, Missouri, and Ohio Rivers. Samples were collected for three seasons at 12 locations on the Mississippi from Minneapolis, Minnesota, to New Orleans, Louisiana, and on the Missouri and Ohio 1.6 kilometers above their confluences with the Mississippi. Both types of compounds formed rapidly during the initial stages of the reaction-time period, with formation rates decreasing with time. The ratio of the nonpurgeable total organic-halide and trihalomethane concentrations decreased with time, with the nonpurgeable total organic-halide compounds forming faster during the first stages of the time period and the trihalomethane compounds forming faster during the latter stages of the time period. Variation with distance along the Mississippi River of the formation rates approximately paralleled the variation of the dissolved organic carbon concentration, indicating that the rates of formation, as well as the concentrations of the compounds formed, depended on the dissolved organic carbon concentration.

Pharmacokinetic Comparison of a Single Oral Dose of Polymorph Form I versus Form V Capsules of the Antiorthopoxvirus Compound ST-246 in Human Volunteers

PubMed Central

Chinsangaram, Jarasvech; Honeychurch, Kady M.; Tyavanagimatt, Shanthakumar R.; Bolken, Tove' C.; Jordan, Robert; Jones, Kevin F.; Marbury, Thomas; Lichtenstein, Israel; Pickens, Margaret; Corrado, Michael; Landis, Patrick; Clarke, Jean M.; Frimm, Annie M.

2012-01-01

ST-246, a novel compound that inhibits egress of orthopoxvirus from mammalian cells, is being tested as a treatment for pathogenic orthopoxvirus infections in humans. This phase I, double-blind, randomized, crossover, exploratory study was conducted to compare the pharmacokinetics (PK) of a single daily 400-mg oral dose of ST-246 polymorph form I versus polymorph form V administered to fed, healthy human volunteers. Both forms appeared to be well tolerated, with no serious adverse events. The order of administration of the two forms had no effect on the results of the PK analyses. Form I and form V both exhibited comparable plasma concentration versus time profiles, but complete bioequivalence between the two forms was not found. Maximum drug concentration (Cmax) met the bioequivalence criteria, as the 90% confidence interval (CI) was 80.6 to 96.9%. However, the area under the concentration-time curve from time zero to time t (AUC0-t) and AUC0-∞ did not meet the bioequivalence criteria (CIs of 67.8 to 91.0% and 73.9 to 104.7%, respectively). The extent of absorption of form I, as defined by AUC0-∞, was 11.7% lower than that of form V. Since ST-246 form I is more thermostable than form V, form I was selected for further development and use in all future studies. PMID:22526314

Fluorometric determination of the DNA concentration in municipal drinking water.

PubMed Central

McCoy, W F; Olson, B H

1985-01-01

DNA concentrations in municipal drinking water samples were measured by fluorometry, using Hoechst 33258 fluorochrome. The concentration, extraction, and detection methods used were adapted from existing techniques. The method is reproducible, fast, accurate, and simple. The amounts of DNA per cell for five different bacterial isolates obtained from drinking water samples were determined by measuring DNA concentration and total cell concentration (acridine orange epifluorescence direct cell counting) in stationary pure cultures. The relationship between DNA concentration and epifluorescence total direct cell concentration in 11 different drinking water samples was linear and positive; the amounts of DNA per cell in these samples did not differ significantly from the amounts in pure culture isolates. We found significant linear correlations between DNA concentration and colony-forming unit concentration, as well as between epifluorescence direct cell counts and colony-forming unit concentration. DNA concentration measurements of municipal drinking water samples appear to monitor changes in bacteriological quality at least as well as total heterotrophic plate counting and epifluorescence direct cell counting. PMID:3890737

Enzymatic, urease-mediated mineralization of gellan gum hydrogel with calcium carbonate, magnesium-enriched calcium carbonate and magnesium carbonate for bone regeneration applications.

PubMed

Douglas, Timothy E L; Łapa, Agata; Samal, Sangram Keshari; Declercq, Heidi A; Schaubroeck, David; Mendes, Ana C; der Voort, Pascal Van; Dokupil, Agnieszka; Plis, Agnieszka; De Schamphelaere, Karel; Chronakis, Ioannis S; Pamuła, Elżbieta; Skirtach, Andre G

2017-12-01

Mineralization of hydrogel biomaterials is considered desirable to improve their suitability as materials for bone regeneration. Calcium carbonate (CaCO 3 ) has been successfully applied as a bone regeneration material, but hydrogel-CaCO 3 composites have received less attention. Magnesium (Mg) has been used as a component of calcium phosphate biomaterials to stimulate bone-forming cell adhesion and proliferation and bone regeneration in vivo, but its effect as a component of carbonate-based biomaterials remains uninvestigated. In the present study, gellan gum (GG) hydrogels were mineralized enzymatically with CaCO 3 , Mg-enriched CaCO 3 and magnesium carbonate to generate composite biomaterials for bone regeneration. Hydrogels loaded with the enzyme urease were mineralized by incubation in mineralization media containing urea and different ratios of calcium and magnesium ions. Increasing the magnesium concentration decreased mineral crystallinity. At low magnesium concentrations calcite was formed, while at higher concentrations magnesian calcite was formed. Hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 .4H 2 O) formed at high magnesium concentration in the absence of calcium. The amount of mineral formed and compressive strength decreased with increasing magnesium concentration in the mineralization medium. The calcium:magnesium elemental ratio in the mineral formed was higher than in the respective mineralization media. Mineralization of hydrogels with calcite or magnesian calcite promoted adhesion and growth of osteoblast-like cells. Hydrogels mineralized with hydromagnesite displayed higher cytotoxicity. In conclusion, enzymatic mineralization of GG hydrogels with CaCO 3 in the form of calcite successfully reinforced hydrogels and promoted osteoblast-like cell adhesion and growth, but magnesium enrichment had no definitive positive effect. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Historical changes in lead concentrations in tree-rings of sycamore, oak and Scots pine in north-west England.

PubMed

Watmough, Shaun A; Hutchinson, Thomas C

2002-07-03

Lead concentrations in tree rings of sycamore (Acer pseudoplatanus L.), oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.) sampled at a parkland in north-west England were measured in wood formed since the mid-1800s. Concentrations of Pb in Scots pine and oak peaked in wood formed between 1900 and 1940, most likely because of Pb accumulation in heartwood, indicating that oak and Scots pine are unsuitable for monitoring temporal changes in Pb deposition at the study site. In contrast, Pb concentrations in sycamore, a species that has similar heartwood and sapwood chemistry, were relatively constant in wood formed between the mid-1800s and 1950. Lead concentrations decreased steadily in sycamore tree rings formed after the 1950s, and decreased more abruptly in wood formed after 1985. This sharp decrease in wood Pb cannot be due to decreases in soil Pb concentration. Stable Pb isotope analysis was used to further investigate Pb patterns in sycamore wood. Excess 206Pb/207Pb ratios in tree-rings of sycamore were relatively constant, approximately 1.17, in wood formed prior to the 1930s, but decreased steadily thereafter reaching a minimum value of approximately 1.16 in wood formed between 1975 and 1985 after which time 206Pb/207Pb ratios increased. This pattern is consistent with changes in Pb isotope ratios measured in peat, sediment and aerosol samples in the UK. However, the magnitude of the decrease in 206Pb/207Pb (largely due to gasoline Pb) is considerably lower than in other studies and our estimates indicate that less than 20% of the total Pb in sycamore wood measured since the mid-1800s is derived from gasoline emissions. A more likely explanation for the pattern of Pb observed in sycamore tree rings is that soil Pb accumulates within rings of the diffuse porous wood over a number of years. Such uptake patterns would result in lower Pb concentrations in the outer (more recently formed) tree rings, which coincide with recent reductions in Pb deposition in the UK. Overall, this study indicates that tree ring chemistry is unsuitable for monitoring historical changes in Pb deposition at the study site.

Spatiotemporal change of phosphorous speciation and concentration in stormwater in the St. Lucie Estuary watershed, South Florida.

PubMed

Li, Liguang; He, Zhenli; Li, Zhigang; Li, Suli; Wan, Yongshan; Stoffella, Peter J

2017-04-01

Phosphorous (P) concentration in stormwater runoff varies at different spatial and temporal scales. Excessive P loading from agriculture system into the St. Lucie Estuary (SLE) contributed to water quality deterioration in southern Indian River Lagoon. This study examines the spatial and temporal shifts of different P forms in runoff and storm water under different land use, water management, and rainfall conditions. Storm water samplings were conducted monthly between April 2013 and December 2014 in typical farmland and along the waterway (Canal C-24) that connects lands to the SLE. Concentrations of different P forms and related water quality variables were measured. Approximately 89% of the collected water samples contained total P (TP) concentrations exceeding the total maximum daily load (TMDL) level (0.081 mg L -1 ). Concentrations of different P forms declined from agricultural field furrows to the canal and then increased from the upstream to the downstream in the canal where urban activities dominated land use. Total dissolved P (TDP) was the predominant form of TP, followed by PO 4 -P. Speciation and concentrations of P varied with sites and sampling times, but were significantly higher in the summer months (from June to September) than in the winter. Water pH explained ∼20% of TP variation. Spatiotemporal variations of P concentrations and compositions provide a data-based guide for development of best management practices (BMPs) to minimize P export from the SLE watershed. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Effects of Inorganic Nitrogen form and CO2 Concentration on Wheat Yield and Nutrient Accumulation and Distribution

PubMed Central

Carlisle, Eli; Myers, Samuel; Raboy, Victor; Bloom, Arnold

2012-01-01

Inorganic N is available to plants from the soil as ammonium (NH4+) and nitrate (NO3-). We studied how wheat grown hydroponically to senescence in controlled environmental chambers is affected by N form (NH4+ vs. NO3−) and CO2 concentration (“subambient,” “ambient,” and “elevated”) in terms of biomass, yield, and nutrient accumulation and partitioning. Wheat supplied with NH4+ as a sole N source had the strongest response to CO2 concentration. Plants exposed to subambient and ambient CO2 concentrations typically had the greatest biomass and nutrient accumulation under both N forms. In general NH4+-supplied plants had higher concentrations of total N, P, K, S, Ca, Zn, Fe, and Cu, while NO3--supplied plants had higher concentrations of Mg, B, Mn, and NO3- - N. NH4+-supplied plants contained amounts of phytate similar to NO3−-supplied plants but had higher bioavailable Zn, which could have consequences for human health. NH4+-supplied plants allocated more nutrients and biomass to aboveground tissues whereas NO3+-supplied plants allocated more nutrients to the roots. The two inorganic nitrogen forms influenced plant growth and nutrient status so distinctly that they should be treated as separate nutrients. Moreover, plant growth and nutrient status varied in a non-linear manner with atmospheric CO2 concentration. PMID:22969784

21 CFR 355.3 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-04-01

... where the water supply contains 0 to 0.7 parts per million (ppm) fluoride ion. (i) Preventive treatment... rinse in a concentrated form to be mixed with water before using to result in the appropriate fluoride.... A fluoride treatment rinse prepared by adding the powder (a concentrated solid dosage form) to water...

21 CFR 355.3 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-04-01

... where the water supply contains 0 to 0.7 parts per million (ppm) fluoride ion. (i) Preventive treatment... rinse in a concentrated form to be mixed with water before using to result in the appropriate fluoride.... A fluoride treatment rinse prepared by adding the powder (a concentrated solid dosage form) to water...

21 CFR 355.3 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-04-01

... where the water supply contains 0 to 0.7 parts per million (ppm) fluoride ion. (i) Preventive treatment... rinse in a concentrated form to be mixed with water before using to result in the appropriate fluoride.... A fluoride treatment rinse prepared by adding the powder (a concentrated solid dosage form) to water...

Separation of arsenic(III) and arsenic(V) in ground waters by ion-exchange

USGS Publications Warehouse

Ficklin, W.H.

1983-01-01

The predominant species of arsenic in ground water are probably arsenite and arsenate. These can be separated with a strong anion-exchange resin (Dowex 1 ?? 8; 100-200 mesh, acetate form) in a 10 cm ?? 7 mm column. Samples are filtered and acidified with concentrated hydrochloric acid (1 ml per 100 ml of sample) at the sample site. Five ml of the acidified sample are used for the separation. At this acidity, As(III) passes through the acetate-form resin, and As(V) is retained. As(V) is eluted by passage of 0.12M hydrochloric acid through the column (resulting in conversion of the resin back into the chloride form). Samples are collected in 5-ml portions up to a total of 20 ml. The arsenic concentration in each portion is determined by graphite-furnace atomic-absorption spectrophotometry. The first two fractions give the As(III) concentration and the last two the As(V) concentration. The detection limit for the concentration of each species is 1 ??g l. ?? 1983.

Titanium, vanadium, and niobium mineralization and alkali metasomatism from the Magnet Cove complex, Arkansas

USGS Publications Warehouse

Flohr, M.J.K.

1994-01-01

The Christy deposit formed through a series of complex processes. The initial phase of mineralization is directly related to the infiltration of novaculite by alkali-rich fluids that were probably derived from carbonatite magma. Titanium, V, Nb, and Li were introduced by the alkali-rich fluids at temperatures that were as high as 600??C. During the initial stage of mineralization, V was concentrated in aegirine and sodic amphibole, Li was concentrated in taeniolite, minor amounts of Ti were concentrated in aegirine, and pyrite formed. The replacement of novaculite by the aforementioned minerals yielded excess silica, which precipitated as quartz. Niobium- and V-bearing brookite precipitated with the quartz. Minerals formed during the first stage reacted with a second fluid at temperatures of 100?? to 300??C and V was then concentrated in smectite and goethite. The second fluid was a mixture of low-temperature metasomatic fluid and groundwater. Vanadium was further concentrated in clay minerals in goethite, and in vug minerals as low-temperature alteration proceeded. -from Author

Photoluminescence Spectroscopy of Rhodamine 800 Aqueous Solution and Dye-Doped Polymer Thin-Film: Concentration and Solvent Effects

NASA Astrophysics Data System (ADS)

Le, Khai Q.; Dang, Ngo Hai

2018-05-01

This paper investigates solvent and concentration effects on photoluminescence (PL) or fluorescence properties of Rhodamine 800 (Rho800) dyes formed in aqueous solution and polymer thin-film. Various commonly used organic solvents including ethanol, methanol and cyclopentanol were studied at a constant dye concentration. There were small changes in the PL spectra for the different solvents in terms of PL intensity and peak wavelength. The highest PL intensity was observed for cyclopentanol and the lowest for ethanol. The longest peak wavelength was found in cyclopentanol (716 nm) and the shortest in methanol (708 nm). Dissolving the dye powder in the methanol solvent and varying the dye concentration in aqueous solution from the high concentrated solution to highly dilute states, the wavelength tunability was observed between about 700 nm in the dilute state and 730 nm at high concentration. Such a large shift may be attributed to the formation of dye aggregates. Rho800 dye-doped polyvinyl alcohol (PVA) polymer thin-film was further investigated. The PL intensity of the dye in the form of thin-film is lower than that of the aqueous solution form whereas the peak wavelength is redshifted due to the presence of PVA. This paper, to our best knowledge, reports the first study of spectroscopic properties of Rho800 dyes in various forms and provides useful guidelines for production of controllable organic luminescence sources.

Free and total urinary phthalate metabolite concentrations among pregnant women from the Healthy Baby Cohort (HBC), China.

PubMed

Zhu, Yingshuang; Wan, Yanjian; Li, Yuanyuan; Zhang, Bin; Zhou, Aifen; Cai, Zongwei; Qian, Zhengmin; Zhang, Chuncao; Huo, Wenqian; Huang, Kai; Hu, Jie; Cheng, Lu; Chang, Huailong; Huang, Zheng; Xu, Bing; Xia, Wei; Xu, Shunqing

2016-03-01

Total urinary phthalate metabolites (the free plus glucuronidated forms) have been frequently measured in the general population. However, data are limited on the free forms which may be more bioactive, especially for sensitive population such as pregnant women. Here the data gap was addressed by measuring concentrations of free and total forms of six phthalate metabolites in 293 urine samples from pregnant women at delivery, who were randomly selected from the prospective Healthy Baby Cohort (HBC), China. We observed detectable concentrations of the total amount of phthalate metabolites in all urine samples. The geometric mean (GM) urinary concentrations of free and total mono-butyl phthalate (MBP) (5.20, 54.49ng/mL) were the highest, followed by mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP) (4.52, 7.27ng/mL). For most of phthalate metabolites, urinary concentrations were significantly higher in women who were nulliparous. Significantly higher concentrations of mono-ethyl phthalate (MEP) and mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) were found in women who had higher educational level. To our knowledge, this is the first study to report the free and total forms of phthalate metabolites among pregnant women in China. The results suggest that exposure characteristics may be related to parity and education. Copyright © 2015 Elsevier Ltd. All rights reserved.

Dynamic light-scattering study of gelatin and aggregation of gastric mucin

NASA Astrophysics Data System (ADS)

Bansil, Rama; Cao, Xingxiang; Bhaskar, K. Ramakrishnan; LaMont, Jeffrey T.

1997-05-01

Dynamic light scattering studies show that concentration and pH play important roles in determining pig gastric mucin's (PGM) ability to aggregate and gel. At low concentrations, PGM macromolecules exist in solution predominantly in the form of monomers. At high concentrations, PGM macromolecules aggregate to form supra-macromolecular clusters. When the pH of the high concentration PGM solution is changed from 7.0 to 2.0, the system undergoes a sol-gel transition: from a solution of polydisperse aggregates to a gel. This pH and concentration dependent sol-gel transition of PGM solution may provide a mechanism for the mammalian stomach to protect itself against being digested by the gastric juice.

The RAPID method for blood processing yields new insight in plasma concentrations and molecular forms of circulating gut peptides.

PubMed

Stengel, Andreas; Keire, David; Goebel, Miriam; Evilevitch, Lena; Wiggins, Brian; Taché, Yvette; Reeve, Joseph R

2009-11-01

The correct identification of circulating molecular forms and measurement of peptide levels in blood entails that the endocrine peptide being studied is stable and recovered in good yields during blood processing. However, it is not clear whether this is achieved in studies using standard blood processing. Therefore, we compared peptide concentration and form of 12 (125)I-labeled peptides using the standard procedure (EDTA-blood on ice) and a new method employing Reduced temperatures, Acidification, Protease inhibition, Isotopic exogenous controls, and Dilution (RAPID). During standard processing there was at least 80% loss for calcitonin-gene-related peptide and cholecystokinin-58 (CCK-58) and more than 35% loss for amylin, insulin, peptide YY forms (PYY((1-36)) and PYY((3-36))), and somatostatin-28. In contrast, the RAPID method significantly improved the recovery for 11 of 12 peptides (P < 0.05) and eliminated the breakdown of endocrine peptides occurring after standard processing as reflected in radically changed molecular forms for CCK-58, gastrin-releasing peptide, somatostatin-28, and ghrelin. For endogenous ghrelin, this led to an acyl/total ghrelin ratio of 1:5 instead of 1:19 by the standard method. These results show that the RAPID method enables accurate assessment of circulating gut peptide concentrations and forms such as CCK-58, acylated ghrelin, and somatostatin-28. Therefore, the RAPID method represents an efficacious means to detect circulating variations in peptide concentrations and form relevant to the understanding of physiological function of endocrine peptides.

Influence of additive L-phenylalanine on stabilization of metastable α-form of L-glutamic acid in cooling crystallization

NASA Astrophysics Data System (ADS)

Quang, Khuu Chau; Nhan, Le Thi Hong; Huyen, Trinh Thi Thanh; Tuan, Nguyen Anh

2017-09-01

The influence of additive amino acid L-phenylalanine on stabilization of metastable α-form of L-glutamic acid was investigated in cooling crystallization. The present study found that the additive L-phenylalanine could be used to stabilize the pure metastable α-form in L-glutamic acid crystallization, where the additive concentration of 0.05-0.1 (g/L) was sufficient to stabilize the 100% wt metastable α-form in solid product at L-glutamic acid concentration of 30-45 (g/L). Additionally, the present results indicated that the adsorption of additive L-phenylalanine on the (001) surface of α-form was more favorable than that of the β-form molecular, so the nucleation sites of stable β-form was occupied by additive molecular, which resulted in inhibition of nucleation and growth of β-form, allowing stabilization of metastable α-form.

Design Of nonimaging concentrators as second stages in tandem with image-forming first-Stage concentrators.

PubMed

Winston, R; Welford, W T

1980-02-01

We show how paraboloidal mirrors of short focal ratio and similar systems can have their flux concentration enhanced to near the thermodynamic limit by the addition of nonimaging compound elliptical concentrators.

Abscisic acid form, concentration, and application timing influence phenology and bud cold hardiness in Merlot grapevines

USDA-ARS?s Scientific Manuscript database

The effects of abscisic acid (ABA) form, concentration and application timing on bud cold hardiness, phenology and fruiting performance on ‘Merlot’ grapevines (Vitis vinifera) were evaluated in a three year field trial with site locations in British Columbia Canada, Ontario Canada, Washington U.S. ...

76 FR 59184 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-23

... Personal Oxygen Concentrator (POC) Devices on Board Aircraft AGENCY: Federal Aviation Administration (FAA... Certain Personal Oxygen Concentrator (POC) Devices on Board Aircraft. Form Numbers: There are no FAA forms... prescribes extensive use of oxygen, brings a POC on board the aircraft. Also, we require passengers who have...

Phase transition of Fe oxides under reducing condition and its relation with the As behavior

NASA Astrophysics Data System (ADS)

Choi, S. H.; Kim, S. H.; Jeong, G. Y.; Kim, K.

2014-12-01

Fe oxides are very common in the earth's crust and easily transform into other minerals such as magnetite and siderite under reducing conditions by microbial reactions. It is well known that As concentrations in groundwater is strongly regulated by adsorption onto Fe oxides. Even though some studies have suggested that the formation of siderite can also control the As concentration, direct evidences are not sufficient. In this study, we performed microbial incubation experiments to see the phase transition of As-rich Fe oxides under anoxic condition and to see how the water As concentrations are controlled accordingly. Three experiments were performed by changing organic carbon concentrations. Natural groundwaters and yeast extracts were used for the sources of microorganisms and organic carbon. Seven reactors were prepared for each experiment and opened one by one to observe the changes of the water chemistry and solid phases for 60 days. The formation of magnetite was observed at the early stage of each experiment. Siderite was formed at the later stage only when the dissolved organic carbon concentrations were high (donor/accepter molar ratio = 1.5). Goethite and hematite, instead of siderite, were formed from the experiment using low organic carbon concentration (donor/accepter molar ratio = 0.75). It is likely that dissolved ferrous ion adsorbs onto the Fe oxides and recrystallizes into hematite and goethite when the DOC concentration was low. As concentrations were generally very low in the water (normally 10 ug/L) and we could not find any relations with the Fe minerals formed by anoxic microbial reactions, maybe due to high Fe oxide/water ratio of our experiments. The sequential extraction analysis indicated that most of the As in solids are mostly associated with Fe-oxides and organic matters. The As bound to carbonates were very low even in the precipitates containing siderite due to low As concentrations in the water where the siderite formed. Further experiments precipitating siderite in the water with high As concentrations are required.

Investigation of transient forms of sulfur during biological treatment of spent caustic.

PubMed

Kalantari, Hamed; Nosrati, Mohsen; Shojaosadati, Seyed Abbas; Shavandi, Mahmoud

2018-06-01

In the present study, the production of various transient forms of sulfur during biological oxidation of sulfidic spent caustics under haloalkaline conditions in a stirred tank bioreactor is investigated. Also, the effects of abiotic aeration (chemical oxidation), dissolved oxygen (DO) concentration and sodium concentration on forms of sulfur during biological treatment are demonstrated. Thioalkalivibrio versutus strain was used for sulfide oxidation in spent caustic (SC). The aeration had an important effect on sulfide oxidation and its final products. At DO concentrations above 2 mg l -1 , majority of sulfide was oxidized to sulfate. Maximum sulfide removal efficiency (%R) and yield of sulfate production [Formula: see text] was obtained in Na + concentration ranging from 0.6 to 2 M. Abiotic aeration, which is the most important factor of production of thiosulfate, resulted in the formation of an undesired product-polysulfide. However, abiotic aeration can be used as a pretreatment to biological treatment. In the bioreactor the removal efficiency was obtained as 82.7% and various forms of sulfur such as polysulfide, biosulfur, thiosulfate and sulfate was observed during biological treatment of SC.

Highly viscous antibody solutions are a consequence of network formation caused by domain-domain electrostatic complementarities: insights from coarse-grained simulations.

PubMed

Buck, Patrick M; Chaudhri, Anuj; Kumar, Sandeep; Singh, Satish K

2015-01-05

Therapeutic monoclonal antibody (mAb) candidates that form highly viscous solutions at concentrations above 100 mg/mL can lead to challenges in bioprocessing, formulation development, and subcutaneous drug delivery. Earlier studies of mAbs with concentration-dependent high viscosity have indicated that mAbs with negatively charged Fv regions have a dipole-like quality that increases the likelihood of reversible self-association. This suggests that weak electrostatic intermolecular interactions can form transient antibody networks that participate in resistance to solution deformation under shear stress. Here this hypothesis is explored by parametrizing a coarse-grained (CG) model of an antibody using the domain charges from four different mAbs that have had their concentration-dependent viscosity behaviors previously determined. Multicopy molecular dynamics simulations were performed for these four CG mAbs at several concentrations to understand the effect of surface charge on mass diffusivity, pairwise interactions, and electrostatic network formation. Diffusion coefficients computed from simulations were in qualitative agreement with experimentally determined viscosities for all four mAbs. Contact analysis revealed an overall greater number of pairwise interactions for the two mAbs in this study with high concentration viscosity issues. Further, using equilibrated solution trajectories, the two mAbs with high concentration viscosity issues quantitatively formed more features of an electrostatic network than the other mAbs. The change in the number of these network features as a function of concentration is related to the number of pairwise interactions formed by electrostatic complementarities between antibody domains. Thus, transient antibody network formation caused by domain-domain electrostatic complementarities is the most probable origin of high concentration viscosity for mAbs in this study.

Reevaluating the mechanism of excitation energy regulation in iron-starved cyanobacteria.

PubMed

Chen, Hui-Yuan S; Liberton, Michelle; Pakrasi, Himadri B; Niedzwiedzki, Dariusz M

2017-03-01

This paper presents spectroscopic investigations of IsiA, a chlorophyll a-binding membrane protein produced by cyanobacteria grown in iron-deficient environments. IsiA, if associated with photosystem I, supports photosystem I in light harvesting by efficiently transferring excitation energy. However, if separated from photosystem I, IsiA exhibits considerable excitation quenching observed as a substantial reduction of protein-bound chlorophyll a fluorescence lifetime. Previous spectroscopic studies suggested that carotenoids are involved in excitation energy dissipation and in addition play a second role in this antenna complex by supporting chlorophyll a in light harvesting by absorbing in the spectral range inaccessible for chlorophyll a and transferring excitation to chlorophylls. However, this investigation does not support these proposed roles of carotenoids in this light harvesting protein. This study shows that carotenoids do not transfer excitation energy to chlorophyll a. In addition, our investigations do not support the hypothesis that carotenoids are quenchers of the excited state of chlorophyll a in this protein complex. We propose that quenching of chlorophyll a fluorescence in IsiA is maintained by pigment-protein interaction via electron transfer from an excited chlorophyll a to a cysteine residue, an excitation quenching mechanism that was recently proposed to regulate the light harvesting capabilities of the bacteriochlorophyll a-containing Fenna-Mathews-Olson protein from green sulfur bacteria. Copyright © 2017 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, N.R.S.; Kolaczkowski, S.V.; Small, G.J.

Reddy et al. (Science, accepted) have reported persistent, nonphotochemical hole-burned (NPHB) spectra for the Q[sub y] states of the reaction center of Rhodopseudomonas viridis. The photoinduced structural transformation was shown to be highly localized on the special pair. This transformation leads to a red shift of the special pair's lowest-energy absorption band, P960, of 150 cm[sup [minus]1] and a comparable blue shift for a state at 850 nm, which, as a consequence, could be assigned as being most closely associated with the upper dimer component. Additional experimental results are presented here together with a theoretical analysis of the extent tomore » which the NPHB spectra provide information on the contribution from the bacteriochlorophyll monomers of the special pair to the Q[sub y] states that absorb higher in energy than P960. Structured photochemical hole-burned (PHB) spectra of P960 are also presented that underscore the importance of strong electron-phonon coupling from a broad distribution of modes with a mean frequency of 30 cm[sup [minus]1] for an understanding of the P960 absorption profile. These spectra also identify the zero-phonon hole of the strongly damped special pair marker mode (145 cm[sup [minus]1]) and its associated phonon sideband structure. Calculated spectra are presented which are in good agreement with the experimental PHB spectra. 30 refs., 6 figs., 4 tabs.« less

Synchronous Measurement of Ultrafast Anisotropy Decay of the B850 in Bacterial LH2 Complex

NASA Astrophysics Data System (ADS)

Wang, Yun-Peng; Du, Lu-Chao; Zhu, Gang-Bei; Wang, Zhuan; Weng, Yu-Xiang

2015-02-01

Ultrafast anisotropic decay is a prominent parameter revealing ultrafast energy and electron transfer; however, it is difficult to be determined reliably owing to the requirement of a simultaneous availability of the parallel and perpendicular polarized decay kinetics. Nowadays, any measurement of anisotropic decay is a kind of approach to the exact simultaneity. Here we report a novel method for a synchronous ultrafast anisotropy decay measurement, which can well determine the anisotropy, even at a very early time, as the rising phase of the excitation laser pulse. The anisotropic decay of the B850 in bacterial light harvesting antenna complex LH2 of Rhodobacter sphaeroides in solution at room temperature with coherent excitation is detected by this method, which shows a polarization response time of 30 fs, and the energy transfer from the initial excitation to the bacteriochlorophylls in B850 ring takes about 70 fs. The anisotropic decay that is probed at the red side of the absorption spectrum, such as 880 nm, has an initial value of 0.4, corresponding to simulated emission, while the blue side with an anisotropy of 0.1 contributes to the ground-state bleaching. Our results show that the coherent excitation covering the whole ring might not be realized owing to the symmetry breaking of LH2: from C9 symmetry in membrane to C2 symmetry in solution.

In vitro Cellular Uptake and Dimerization of Signal Transducer and Activator of Transcription-3 (STAT3) Identify the Photosensitizing and Imaging-Potential of Isomeric Photosensitizers Derived from Chlorophyll-a and Bacteriochlorophyll-a

PubMed Central

Srivatsan, Avinash; Wang, Yanfang; Joshi, Penny; Sajjad, Munawwar; Chen, Yihui; Liu, Chao; Thankppan, Krishnakumar; Missert, Joseph R.; Tracy, Erin; Morgan, Janet; Rigual, Nestor; Baumann, Heinz; Pandey, Ravindra K.

2011-01-01

Among the photosensitizers investigated, both ring-D and ring-B reduced chlorins containing the m-iodobenzyloxyethyl group at position-3 and a carboxylic acid functionality at position-172 showed highest uptake by tumor cells and light-dependent photo reaction that correlated with maximal tumor-imaging [positron emission tomography (PET) and fluorescence] and long-term photodynamic therapy (PDT) efficacy in BALB/c mice bearing Colon26 tumors. However, among the ring-D reduced compounds, the isomer containing 1′-m-iobenzyloxyethyl group at position-3 was more effective than the corresponding 8-(1′-m-iodobenzyloxyethyl) derivative. All photosensitizers showed maximum uptake by tumor tissue 24h after injection and the tumors exposed with light at low fluence and fluence rates (128 J/cm2, 14 mW/cm2) produced significantly enhanced tumor eradication than those exposed at higher fluence and fluence rate (135 J/cm,2 75mW/cm2). Interestingly, dose-dependent cellular uptake of the compounds and light-dependent STAT3 dimerization have emerged as sensitive rapid indicators for PDT efficacy in vitro and in vivo and could be used as in vitro/in vivo biomarkers for evaluating and optimizing the in vivo treatment parameters of the existing and new PDT candidates. PMID:21842893

Ecotype diversification of an abundant Roseobacter lineage.

PubMed

Sun, Ying; Zhang, Yao; Hollibaugh, James T; Luo, Haiwei

2017-04-01

The Roseobacter DC5-80-3 cluster (also known as the RCA clade) is among the most abundant bacterial lineages in temperate and polar oceans. Previous studies revealed two phylotypes within this cluster that are distinctly distributed in the Antarctic and other ocean provinces. Here, we report a nearly complete genome co-assembly of three closely related single cells co-occurring in the Antarctic, and compare it to the available genomes of the other phylotype from ocean regions where iron is more accessible but phosphorus and nitrogen are less. The Antarctic phylotype exclusively contains an operon structure consisting of a dicitrate transporter fecBCDE and an upstream regulator likely for iron uptake, whereas the other phylotype consistently carry a high-affinity phosphate pst transporter and the phoB-phoR regulatory system, a high-affinity ammonium amtB transporter, urea and taurine utilization systems. Moreover, the Antarctic phylotype uses proteorhodopsin to acquire light, whereas the other uses bacteriochlorophyll-a and the sulfur-oxidizing sox cluster for energy acquisition. This is potentially an iron-saving strategy for the Antarctic phylotype because only the latter two pathways have iron-requiring cytochromes. Therefore, the two DC5-80-3 phylotypes, while diverging by only 1.1% in their 16S rRNA genes, have evolved systematic differences in metabolism to support their distinct ecologies. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, M.S.; Forman, A.; Hanson, L.K.

Optical, ESR, ENDOR, and redox characteristics of anion and cation radicals of bacteriochlorophyll b (BChl) and bacteriopheophytin b (BPh) have been obtained in nonaqueous solvents. The radicals exhibit properties similar to those of BChl a derivatives, as expected from extended Huckel and Pariser-Parr-Pople MO calculations. The electronic configurations of the radicals have been assigned on the basis of the MO calculations and by analogy with BChl a and BPh a results. Oxidized reaction centers of Rhodopseudomonas viridis do not display the ..sqrt..2 narrowing of the ESR line width nor the 50% decrease in ENDOR splittings expected for a symmetric cationmore » dimer, when compared to BChl b/sup +/. Nonetheless, computer simulations indicate that a dimeric model for P960, the primary donor of R. viridis, can be rationalized by imposing a torsional angle on ring IV different from that found in crystals of Chl a, i.e., P960 may be a dimer with a twist. Comparison of the resolved ESR spectra and ENDOR splittings of the primary acceptor (I/sup -/) of R. viridis with in-vitro results indicates that I/sup -/ is a monomeric anion. Optical and redox data favor BPh over BChl as the primary acceptor. These results allow a description of the electronic profile of the species which evolve within a picosecond time domain in the primary conversion of light into chemical energy at approx. 1000 nm.« less

Sensitive, Selective Test For Hydrazines

NASA Technical Reports Server (NTRS)

Roundbehler, David; Macdonald, Stephen

1993-01-01

Derivatives of hydrazines formed, then subjected to gas chromatography and detected via chemiluminescence. In method of detecting and quantifying hydrazine vapors, vapors reacted with dinitro compound to enhance sensitivity and selectivity. Hydrazine (HZ), monomethyl hydrazine, (MMH), and unsymmetrical dimethylhydrazine (UDMH) analyzed quantitatively and qualitatively, either alone or in mixtures. Vapors collected and reacted with 2,4-dinitrobenzaldehyde, (DNB), making it possible to concentrate hydrazine in derivative form, thereby increasing sensitivity to low initial concentrations. Increases selectivity because only those constituents of sample reacting with DNB concentrated for analysis.

Engineering and Design. Containment and Disposal of Aqueous Film-Forming Foam Solution

DTIC Science & Technology

1997-05-23

Aqueous Film-Forming Foam (AFFF) concentrate used in DoD facilities must be "MIL-SPEC" foam conforming to MIL - F - 24385 . MIL-SPEC foam is recognized...requirements, the MIL - F - 24385 provides for important chemical and physical properties not specified by other standards. "MIL-SPEC" AFFF concentrate...is the standard by which others are measured. Other commercially available AFFF concentrates are simply not comparable to those conforming to MIL - F - 24385 . 3.2

Plants as sources of airborne bacteria, including ice nucleation-active bacteria.

PubMed

Lindemann, J; Constantinidou, H A; Barchet, W R; Upper, C D

1982-11-01

Vertical wind shear and concentration gradients of viable, airborne bacteria were used to calculate the upward flux of viable cells above bare soil and canopies of several crops. Concentrations at soil or canopy height varied from 46 colony-forming units per m over young corn and wet soil to 663 colony-forming units per m over dry soil and 6,500 colony-forming units per m over a closed wheat canopy. In simultaneous samples, concentrations of viable bacteria in the air 10 m inside an alfalfa field were fourfold higher than those over a field with dry, bare soil immediately upwind. The upward flux of viable bacteria over alfalfa was three- to fourfold greater than over dry soil. Concentrations of ice nucleation-active bacteria were higher over plants than over soil. Thus, plant canopies may constitute a major source of bacteria, including ice nucleation-active bacteria, in the air.

Effects of pelleted or powdered diets containing soy protein or sodium caseinate on lipid concentrations and bile acid excretion in golden Syrian hamsters.

PubMed

Butteiger, Dustie N; Krul, Elaine S

2015-08-01

Custom diets are a convenient vector for oral administration of test articles, but the processing and physical form of a diet can affect its nutritional properties and how it is consumed. Here, the authors evaluated the feeding behavior and physiology of golden Syrian hamsters fed diets of either soy or caseinate protein in pelleted or powdered forms for 28 d to determine whether dietary processing and form mediates the physiological effects of dietary proteins. The authors compared body weight, food consumption, serum cholesterol concentration, serum triglyceride concentration, fecal weight and fecal excretion of bile acids between treatment groups. Hamsters fed powdered diets showed higher food consumption than hamsters fed pelleted diets, regardless of protein source. Hamsters fed soy pelleted diets showed lower serum cholesterol concentration and higher fecal excretion of bile acid than hamsters fed caseinate pelleted diets, and serum cholesterol concentration correlated strongly with fecal excretion of bile acid. This correlation suggests that the physiological effects of soy protein on cholesterol and excretion of bile acid might be related or similarly mediated through diet. The differences observed between hamsters on different diets indicate that dietary form can influence both feeding behavior and the physiological effects of a diet in hamsters.

Setting and Stiffening of Cementitious Components in Cast Stone Waste Form for Disposal of Secondary Wastes from the Hanford waste treatment and immobilization plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, Chul-Woo; Chun, Jaehun; Um, Wooyong

2013-04-01

Cast stone is a cementitious waste form, a viable option to immobilize secondary nuclear liquid wastes generated from Hanford vitrification plant. While the strength and radioactive technetium leaching of different waste form candidates have been reported, no study has been performed to understand the flow and stiffening behavior of Cast Stone, which is essential to ensure the proper workability, especially considering necessary safety as a nuclear waste form in a field scale application. The rheological and ultrasonic wave reflection (UWR) measurements were used to understand the setting and stiffening Cast Stone batches. X-ray diffraction (XRD) was used to find themore » correlation between specific phase formation and the stiffening of the paste. Our results showed good correlation between rheological properties of the fresh Cast Stone mixture and phase formation during hydration of Cast Stone. Secondary gypsum formation originating from blast furnace slag was observed in Cast Stone made with low concentration simulants. The formation of gypsum was suppressed in high concentration simulants. It was found that the stiffening of Cast Stone was strongly dependent on the concentration of simulant. A threshold concentration for the drastic change in stiffening was found at 1.56 M Na concentration.« less

Influence of Calcium Carbonate on Cobalt Phytoavailability in Fluvo-aquic Soil

NASA Astrophysics Data System (ADS)

Wang, Mengyuan; Liu, Borui; Ma, Yufei; Xue, Qianhui; Huang, Qing

2017-12-01

In order to study the efficacy of calcium carbonate for cobalt (Co) fixation, as well as its influence on chemical speciation of Co in fluvo-aquic soil, pakchoies were planted in the soil with different quantities of exogenous Co and calcium carbonate. Co concentrations in the mature plant shoots were analyzed, and the chemical speciation of Co were detected with the Tessier five-step sequential extraction. The results showed that the Co concentration in plants tended to decrease first and then get higher with the concentration of calcium carbonate increasing (0-12g/kg) in soil (P < 0.05). The proportion of Co in the exchangeable form in the soil followed the similar tendency (P < 0.05), which might transform from the exchangeable form into the carbonate-associated and organic-associated forms. A regression analysis showed that when the concentrations of calcium carbonate were in the range of 5.0 to 7.5 g/kg, Co concentration in the plant reached to the lowest point, while the proportion of Co in the exchangeable form reached the minimum. In conclusion, to get the optimum effect, the dosage of calcium carbonate should be kept in the range of 5.0 to 7.5 g/kg when it is applied to Co fixation.

Aggregation behavior and complex structure between triblock copolymer and anionic surfactants

NASA Astrophysics Data System (ADS)

Li, Yiming; Bao, Mutai; Wang, Zhining; Zhang, Haixia; Xu, Guiying

2011-01-01

The aggregation behavior and complex structure of ABA triblock copolymer EO 76PO 30EO 76 (F68) with sodium dodecyl sulfate (SDS) and sodium bis(2-ethylhexyl)sulfonate (AOT) in aqueous solution were investigated by surface tension, fluorescence techniques and dynamic light-scattering (DLS) measurements. It is revealed that in certain regions of binding, surfactant/F68 complexes are formed. Structural informations and size of complexes are evaluated. When F68 is present in its nonassociated state, F68/micellar SDS complexes are formed at SDS concentrations above its critical aggregation concentration (cac). The cac is well below the critical micellar concentration (cmc) of pure SDS, and a model suggesting how complexes are formed at the cac in the presence of F68 is described. Experimental results show that SDS interacts with F68 mainly through hydrophobic forces, polypropylene oxide (PPO) groups of F68 are solubilized into SDS micellar cores and poly(ethylene oxide) (PEO) groups interact with SDS micelles. This interaction mechanism results in a "pearl-necklace" complex structure. However, a different structure occurs for F68/AOT complex at lower F68 concentrations, as nonassociated F68 interacts with AOT mainly through ion-dipole interactions. Complexes with a "wrapping" structure at lower F68 concentrations are formed.

Improvement of Leaching Resistance of Low-level Waste Form in Korea

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, J.Y.; Lee, B.C.; Kim, C.L.

2006-07-01

Low-level liquid concentrate wastes including boric acid have been immobilized with paraffin wax using concentrate waste drying system in Korean nuclear power plants since 1995. Small amount of low density polyethylene (LDPE) was added to increase the leaching resistance of the existing paraffin waste form and the influence of LDPE on the leaching behavior of waste form was investigated. It was observed that the leaching of nuclides immobilized within paraffin waste form remarkably reduced as the content of LDPE increased. The acceptance criteria of paraffin waste form associated with leachability index and compressive strength after the leaching test were successfullymore » satisfied with the help of LDPE. (authors)« less

Crystallization of Chicken Egg White Lysozyme from Sulfate Salts

NASA Technical Reports Server (NTRS)

Forsythe, Elizabeth; Pusey, Marc

1998-01-01

It has been "known" that chicken egg white lysozyme does not crystallize from sulfate, particularly ammonium sulfate, salts, but instead gives amorphous precipitates. This has been the basis of several studies using lysozyme comparing macromolecule crystal nucleation and amorphous precipitation. Recently Ries-Kautt et al (Acta Cryst D50, (1994) 366) have shown that purified isoionic CEWL could be crystallized from low concentrations of sulfate at basic pH, and we subsequently showed that in fact CEWL could be purified in both the tetragonal and orthorhombic forms using ammonium sulfate over the pH range 4.0 to 7.8 (Acta Cryst D53, (1997) 795). We have now extended these observations to include a range of common sulfate salts, specifically sodium, potassium, rubidium, magnesium, and manganese sulfates. In all cases but the manganese sulfates both the familiar tetragonal and orthorhombic forms were obtained, with unit cell dimensions close to those known for the "classic" sodium chloride crystallized forms. Manganese sulfate has only yielded orthorhombic crystals to date. All crystallizations were carried out using low (typically less than or equal to 6 M) salt and high (greater than approximately 90 mg/ml) protein concentrations. As with ammonium sulfate, the tetragonal - orthorhombic phase shift appears to be a function of both the temperature and the protein concentration, with higher temperatures and concentrations favoring the orthorhombic and lower the tetragonal form. The phase change range is somewhat reduced for the sulfate salts, depending upon conditions being typically between approximately 15 - 20 C. Both the magnesium and manganese sulfates gave crystals at salt concentrations over 0.6 M as well, with magnesium sulfate giving a very slowly nucleating and growing hexagonal form. A triclinic crystal form, characterized by aggressively small crystals (typically 0.1 mm in size) has been occasionally obtained from ammonium sulfate. Finally, preliminary spot solubility determinations have suggested that in some cases the solubility increases with increasing salt concentrations.

Fecal concentrations of bacterially derived vitamin K forms are associated with gut microbiota composition but not plasma or fecal cytokine concentrations in healthy adults.

PubMed

Karl, J Philip; Meydani, Mohsen; Barnett, Junaidah B; Vanegas, Sally M; Barger, Kathryn; Fu, Xueyan; Goldin, Barry; Kane, Anne; Rasmussen, Helen; Vangay, Pajau; Knights, Dan; Jonnalagadda, Satya S; Saltzman, Edward; Roberts, Susan B; Meydani, Simin N; Booth, Sarah L

2017-10-01

Background: Emerging evidence suggests novel roles for bacterially derived vitamin K forms known as menaquinones in health and disease, which may be attributable in part to anti-inflammatory effects. However, the relevance of menaquinones produced by gut bacteria to vitamin K requirements and inflammation is undetermined. Objective: This study aimed to quantify fecal menaquinone concentrations and identify associations between fecal menaquinone concentrations and serum vitamin K concentrations, gut microbiota composition, and inflammation. Design: Fecal and serum menaquinone concentrations, fecal microbiota composition, and plasma and fecal cytokine concentrations were measured in 80 men and postmenopausal women (48 men, 32 women, age 40-65 y) enrolled in a randomized, parallel-arm, provided-food trial. After consuming a run-in diet for 2 wk, participants were randomly assigned to consume a whole grain-rich (WG) or a refined grain-based (RG) diet for 6 wk. Outcomes were measured at weeks 2 and 8. Results: The median total daily excretion of menaquinones in feces was 850 nmol/d but was highly variable (range: 64-5358 nmol/d). The total median (IQR) fecal concentrations of menaquinones decreased in the WG diet compared with the RG diet [-6.8 nmol/g (13.0 nmol/g) dry weight for WG compared with 1.8 nmol/g (12.3 nmol/g) dry weight for RG; P < 0.01)]. However, interindividual variability in fecal menaquinone concentrations partitioned individuals into 2 distinct groups based on interindividual differences in concentrations of different menaquinone forms rather than the diet group or the time point. The relative abundances of several gut bacteria taxa, Bacteroides and Prevotella in particular, differed between these groups, and 42% of identified genera were associated with ≥1 menaquinone form. Menaquinones were not detected in serum, and neither fecal concentrations of individual menaquinones nor the menaquinone group was associated with any marker of inflammation. Conclusion: Menaquinone concentrations in the human gut appear highly variable and are associated with gut microbiota composition. However, the health implications remain unclear. This trial was registered at clinicaltrials.gov as NCT01902394. © 2017 American Society for Nutrition.

Localized redox relays as a privileged mode of cytoplasmic hydrogen peroxide signaling.

PubMed

Travasso, Rui D M; Sampaio Dos Aidos, Fernando; Bayani, Anahita; Abranches, Pedro; Salvador, Armindo

2017-08-01

Hydrogen peroxide (H 2 O 2 ) is a key signaling agent. Its best characterized signaling actions in mammalian cells involve the early oxidation of thiols in cytoplasmic phosphatases, kinases and transcription factors. However, these redox targets are orders of magnitude less H 2 O 2 -reactive and abundant than cytoplasmic peroxiredoxins. How can they be oxidized in a signaling time frame? Here we investigate this question using computational reaction-diffusion models of H 2 O 2 signaling. The results show that at H 2 O 2 supply rates commensurate with mitogenic signaling a H 2 O 2 concentration gradient with a length scale of a few tenths of μm is established. Even near the supply sites H 2 O 2 concentrations are far too low to oxidize typical targets in an early mitogenic signaling time frame. Furthermore, any inhibition of the peroxiredoxin or increase in H 2 O 2 supply able to drastically increase the local H 2 O 2 concentration would collapse the concentration gradient and/or cause an extensive oxidation of the peroxiredoxins I and II, inconsistent with experimental observations. In turn, the local concentrations of peroxiredoxin sulfenate and disulfide forms exceed those of H 2 O 2 by several orders of magnitude. Redox targets reacting with these forms at rate constants much lower than that for, say, thioredoxin could be oxidized within seconds. Moreover, the spatial distribution of the concentrations of these peroxiredoxin forms allows them to reach targets within 1 μm from the H 2 O 2 sites while maintaining signaling localized. The recruitment of peroxiredoxins to specific sites such as caveolae can dramatically increase the local concentrations of the sulfenic and disulfide forms, thus further helping these species to outcompete H 2 O 2 for the oxidation of redox targets. Altogether, these results suggest that H 2 O 2 signaling is mediated by localized redox relays whereby peroxiredoxins are oxidized to sulfenate and disulfide forms at H 2 O 2 supply sites and these forms in turn oxidize the redox targets near these sites. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Ink composition for making a conductive silver structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, Steven B.; Lewis, Jennifer A.

An ink composition for making a conductive silver structure comprises a silver salt and a complex of (a) a complexing agent and a short chain carboxylic acid or (b) a complexing agent and a salt of a short chain carboxylic acid, according to one embodiment. A method for making a silver structure entails combining a silver salt and a complexing agent, and then adding a short chain carboxylic acid or a salt of the short chain carboxylic acid to the combined silver salt and a complexing agent to form an ink composition. A concentration of the complexing agent in themore » ink composition is reduced to form a concentrated formulation, and the silver salt is reduced to form a conductive silver structure, where the concentrated formulation and the conductive silver structure are formed at a temperature of about 120.degree. C. or less.« less

Cysteine reacts to form blue-green pigments with thiosulfinates obtained from garlic (Allium sativum L.).

PubMed

Shin, Young Keum; Kyung, Kyu Hang

2014-01-01

Cysteine was found to form pigments with garlic thiosulfinates in this investigation, in contrast to previous reports. Pigments were formed only when the molar concentration ratios of cysteine to total thiosulfinates were smaller than 2:1. Cysteine does not form pigments with thiosulfinates in the same manner as other pigment-forming amino compounds because it has a sulfhydryl (SH) group. A colour reaction of cysteine with thiosulfinates is proposed where colourless disulphide-type S-alk(en)yl mercaptocysteines (SAMCs) are formed first by the SH-involved reaction between cysteine and thiosulfinates, and then SAMCs react with residual thiosulfinates to form pigments. When the cysteine to total thiosulfinate molar concentration ratio was 2:1 or greater, total thiosulfinates were consumed to form SAMCs without leaving any thiosulfinates remaining available for the following colour reactions. Copyright © 2013 Elsevier Ltd. All rights reserved.

A PARADOXICAL RELATION BETWEEN ZETA POTENTIAL AND SUSPENSION STABILITY IN S AND R VARIANTS OF INTESTINAL BACTERIA

PubMed Central

Joffe, Eleanore W.; Mudd, Stuart

1935-01-01

The relation between electrokinetic potential and suspension stability of four strains of non-flagellate intestinal bacteria has been studied. The smooth forms have ζ-potentials which approximate zero over a wide range of pH and salt concentration, yet nevertheless form stable suspensions. The rough variants have ζ-potentials which vary with pH and electrolyte concentration in the familiar way. The rough forms have values of ζ-potential critical for their suspension stability. PMID:19872869

Performance evaluation soil samples utilizing encapsulation technology

DOEpatents

Dahlgran, J.R.

1999-08-17

Performance evaluation soil samples and method of their preparation uses encapsulation technology to encapsulate analytes which are introduced into a soil matrix for analysis and evaluation by analytical laboratories. Target analytes are mixed in an appropriate solvent at predetermined concentrations. The mixture is emulsified in a solution of polymeric film forming material. The emulsified solution is polymerized to form microcapsules. The microcapsules are recovered, quantitated and introduced into a soil matrix in a predetermined ratio to form soil samples with the desired analyte concentration. 1 fig.

Performance evaluation soil samples utilizing encapsulation technology

DOEpatents

Dahlgran, James R.

1999-01-01

Performance evaluation soil samples and method of their preparation using encapsulation technology to encapsulate analytes which are introduced into a soil matrix for analysis and evaluation by analytical laboratories. Target analytes are mixed in an appropriate solvent at predetermined concentrations. The mixture is emulsified in a solution of polymeric film forming material. The emulsified solution is polymerized to form microcapsules. The microcapsules are recovered, quantitated and introduced into a soil matrix in a predetermined ratio to form soil samples with the desired analyte concentration.

Biochemical indicators of nephrotoxicity in blood serum of rats treated with novel 4-thiazolidinone derivatives or their complexes with polyethylene glycol-containing nanoscale polymeric carrier

PubMed

Kоbyli nska, L I; Havrylyuk, D Ya; Mitina, N E; Zaichenko, A S; Lesyk, R B; Zіme nkovsky, B S; Stoika, R S

2016-01-01

The aim of this study was to compare the effect of new synthetic 4-thiazolidinone derivatives (potential anticancer compounds denoted as 3882, 3288 and 3833) and doxorubicin (positive control) in free form and in their complexes with synthetic polyethylene glycol-containing nanoscale polymeric carrier on the biochemical indicators of nephrotoxicity in blood serum of rats. The concentration of total protein, urea, creatinine, glucose, ions of sodium, potassium, calcium, iron and chloride was measured. It was found that after injection of the investigated compounds, the concentration of sodium cations and chloride anions in blood serum was increased compared with control (untreated animals). Doxorubicin’s injection was accompanied by a decrease in the concentration of iron cations. The concentration of total protein, urea and creatinine decreased under the influence of the studied compounds. Complexation of these аntineoplastic substances with a synthetic polymeric nanocarrier lowered the concentration of the investigated metabolites substantially compared to the effect of these compounds in free form. The normalization of concentration of total protein, urea and creatinine in blood serum of rats treated with complexes of the studied compounds with the polymeric carrier comparing with increased concentration of these indicators at the introduction of such compounds in free form was found.

A functional form for injected MRI Gd-chelate contrast agent concentration incorporating recirculation, extravasation and excretion

NASA Astrophysics Data System (ADS)

Horsfield, Mark A.; Thornton, John S.; Gill, Andrew; Jager, H. Rolf; Priest, Andrew N.; Morgan, Bruno

2009-05-01

A functional form for the vascular concentration of MRI contrast agent after intravenous bolus injection was developed that can be used to model the concentration at any vascular site at which contrast concentration can be measured. The form is based on previous models of blood circulation, and is consistent with previously measured data at long post-injection times, when the contrast agent is fully and evenly dispersed in the blood. It allows the first-pass and recirculation peaks of contrast agent to be modelled, and measurement of the absolute concentration of contrast agent at a single time point allows the whole time course to be rescaled to give absolute contrast agent concentration values. This measure of absolute concentration could be performed at a long post-injection time using either MRI or blood-sampling methods. In order to provide a model that is consistent with measured data, it was necessary to include both rapid and slow extravasation, together with excretion via the kidneys. The model was tested on T1-weighted data from the descending aorta and hepatic portal vein, and on T*2-weighted data from the cerebral arteries. Fitting of the model was successful for all datasets, but there was a considerable variation in fit parameters between subjects, which suggests that the formation of a meaningful population-averaged vascular concentration function is precluded.

The solubility of the tetragonal form of hen egg white lysozyme from pH 4.0 to 5.4

NASA Technical Reports Server (NTRS)

Cacioppo, Elizabeth; Pusey, Marc L.

1991-01-01

Hen egg white lysozyme solubilities in the presence of the tetragonal crystal form have been determined. Conditions investigated cover the pH range 4.0 to 5.4, varying from 2.0 to 7.0 percent NaCl concentrations and from 4 to 25 C. In all instances, the solubilities were found to increase with temperature and decrease with increasing salt concentration. The effects of pH were more complex, showing a decreasing solubility with increasing pH at low salt concentration and an increasing solubility with increasing pH at high salt concentration.

Highly defective oxides as sinter resistant thermal barrier coating

DOEpatents

Subramanian, Ramesh

2005-08-16

A thermal barrier coating material formed of a highly defective cubic matrix structure having a concentration of a stabilizer sufficiently high that the oxygen vacancies created by the stabilizer interact within the matrix to form multi-vacancies, thereby improving the sintering resistance of the material. The concentration of stabilizer within the cubic matrix structure is greater than that concentration of stabilizer necessary to give the matrix a peak ionic conductivity value. The concentration of stabilizer may be at least 30 wt. %. Embodiments include a cubic matrix of zirconia stabilized by at least 30-50 wt. % yttria, and a cubic matrix of hafnia stabilized by at least 30-50 wt. % gadolinia.

Interfacial activity in alkaline flooding enhanced oil recovery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chan, M.K.

1981-01-01

The ionization of long-chained organic acids in the crude oil to form soaps was shown to be primarily responsible for the lowering of oil-water interfacial tension at alkaline pH. These active acids can be concentrated by silica gel chromatography into a minor polar fraction. An equilibrium chemical model was proposed based on 2 competing reactions: the ionization of acids to form active anions, and the formation of undissociated soap between acid anions and sodium ions. It correlates the interfacial activity with the interfacial concentration of active acid anions which is expressed in terms of the concentrations of the chemical speciesmore » in the system. The model successfully predicts the observed oil-alkaline solution interfacial phenomenon, including its dependence on pH, alkali and salt concentrations, type of acid present and type of soap formed. Flooding at different alkali concentrations to activate different acid species present in the crude was shown to give better recovery than flooding at a single high alkali concentration. Treating the crude oil with a dilute solution of mineral acids liberates additional free active acids and yields better interfacial activity during subsequent alkali contact.« less

Maternal and Cord Blood Adiponectin Multimeric Forms in Gestational Diabetes Mellitus

PubMed Central

Ballesteros, Mónica; Simón, Inmaculada; Vendrell, Joan; Ceperuelo-Mallafré, Victoria; Miralles, Ramon M.; Albaiges, Gerard; Tinahones, Francisco; Megia, Ana

2011-01-01

OBJECTIVE To analyze the relationship between maternal adiponectin (mAdiponectin) and cord blood adiponectin (cbAdiponectin) multimeric forms (high molecular weight [HMW], medium molecular weight [MMW], and low molecular weight [LMW]) in a cohort of gestational diabetes mellitus (GDM) and normal glucose–tolerant (NGT) pregnant women. RESEARCH DESIGN AND METHODS A total of 212 women with a singleton pregnancy, 132 with NGT and 80 with GDM, and their offspring were studied. Maternal blood was obtained in the early third trimester and cord blood was obtained at delivery. Total adiponectin and the multimeric forms of adiponectin were determined in cord blood and maternal serum. Spearman rank correlation and stepwise linear correlation analysis were used to assess the relationship between cbAdiponectin levels and clinical and analytical parameters. RESULTS No differences in cbAdiponectin concentration or its multimeric forms were observed in the offspring of diabetic mothers compared with NGT mothers. The HMW-to-total adiponectin ratio was higher in cord blood than in maternal serum, whereas the MMW- and LMW-to-total adiponectin ratio was lower. Cord blood total and HMW adiponectin levels were positively correlated with birth weight and the ponderal index (PI), whereas cord blood MMW adiponectin was negatively correlated with the PI. In addition, cbAdiponectin and its multimeric forms were correlated with mAdiponectin concentrations. In the multivariate analysis, maternal multimeric forms of adiponectin emerged as independent predictors of cbAdiponectin, its multimers, and their distribution. CONCLUSIONS cbAdiponectin concentrations are independently related to mAdiponectin levels and unrelated to the diagnosis of GDM. Maternal multimeric forms of adiponectin are independent predictors of the concentrations of cbAdiponectin and its multimeric forms at delivery. PMID:21911780

Response of potatoes to nitrogen concentrations differ with nitrogen forms

NASA Technical Reports Server (NTRS)

Cao, W.; Tibbitts, T. W.

1998-01-01

Two separate experiments were conducted to investigate plant growth and mineral composition of potatoes (Solanum tuberosum L.) at varied solution concentrations of nitrate (NO3-) and ammonium (NH4+). Each experiment evaluated five nitrogen (N) concentrations of 0.5, 2, 4, 8, and 12 mM, which were maintained with a non-recirculating nutrient film system in controlled environment. Plants were harvested on day 42 with NO3-; and day 35 with NH4+ after transplanting of tissue culture plantlets, and growth measurements were taken as leaf area, tuber number, and dry weights of different parts. With NO3-, plant growth was greatest and similar at 2, 4, and 8 mM of N whereas with NH4+, plant growth was best only at 2 and 4 mM of N. At 12 mM of N, plants exhibited interveinal ammonium toxicity with NH4+ nutrition, but healthy growth appearance with NO3- nutrition. With either N form, total N concentrations in tissues tended to increase with increased N concentrations, and tissue phosphorus (P) concentrations were reduced at 0.5 and 2 mM of N. Tissue concentrations of calcium (Ca), magnesium (Mg), and sulfur (S) changed only slightly at particular N concentrations, yet changed substantially with different N forms. The data indicate that the optimal ranges of N concentrations in both solution and tissues are wider and higher with NO3- than with NH4+ nutrition, and thus a careful control of NH4+ concentrations is necessary to minimize possible ammonium toxicity to potato plants.

Rotary Apparatus Concentrates And Separates Micro-Organisms

NASA Technical Reports Server (NTRS)

Noever, David A.

1992-01-01

Apparatus concentrates and separates swimming micro-organisms of different species into concentric rings in fluid. Fluid containing high concentration of desired species removed by use of small scoop placed into fluid at radius of one of rings formed by that species. Micro-organisms concentrated into concentric rings by combined dynamic effects of upward and horizontal components of swimming, rotation of dish, gravitation, and viscosity.

Mercury in wetlands at the Glacial Ridge National Wildlife Refuge, northwestern Minnesota, 2007-9

USGS Publications Warehouse

Cowdery, Timothy K.; Brigham, Mark E.

2013-01-01

The Glacial Ridge National Wildlife Refuge was established in 2004 on land in northwestern Minnesota that had previously undergone extensive wetland and prairie restorations. About 7,000 acres of drained wetlands were restored to their original hydrologic function and aquatic ecosystem. During 2007–9, the U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service and the Red Lake Watershed District, analyzed mercury concentrations in wetland water and sediment to evaluate the effect of wetland restoration on mercury methylation. The wetland waters sampled generally were of the calcium/magnesium bicarbonate type. Nitrogen in water was mostly in the form of dissolved-organic nitrogen, with very low dissolved-nitrate and dissolved-ammonia concentrations. About 71 percent of all phosphorus in water was dissolved, with one-half of that in the form of orthophosphorus. Wetland water had total-mercury and methylmercury concentrations ranging from 1.5 to 20 nanograms per liter (ng/L) and 0.2 to 16 ng/L, respectively. Median concentrations were 7.1 and 2.9 ng/L, respectively. About one-half of the mercury in wetland water samples was in the form of methylmercury, but this form ranged from 7 to 81 percent of each sample. Compared to concentrations in stream sediment samples collected throughout the United States, Glacial Ridge National Wildlife Refuge wetland sediment samples contained typical total-mercury concentrations, but methylmercury concentrations were nearly twice as high. The maximum concentration measured in Glacial Ridge National Wildlife Refuge wetland water approached the highest published water methylmercury concentration in uncontaminated waters of which we are aware. However, the upper quartile of water methylmercury concentrations is similar to concentrations reported for some impoundments and wetlands in northwestern Minnesota and North Dakota. Methylmercury concentrations in sampled wetlands were much higher than those from typical lakes or flowing streams throughout the United States. The high concentrations of methylmercury measured in sampled wetlands indicate the potential for substantial methylmercury concentrations in aquatic biota and wildlife that consume those biota. These wetlands also are a methylmercury source for downstream lakes and rivers. The high concentrations of methylmercury in water, its bioaccumulation potential, and its known toxicity in aquatic birds and food webs highlight a need to assess methylmercury in the biota within these ecosystems. Better understanding of factors that control methylmercury production concentrations within aquatic food webs in ecosystems of the Glacial Ridge National Wildlife Refuge would enable resource managers to better understand and manage risk to wildlife.

NHEXAS PHASE I ARIZONA STUDY--STANDARD OPERATING PROCEDURE FOR CODING: FIELD FORMS (UA-D-37.0)

EPA Science Inventory

The purpose of this SOP is to define the coding strategy for selected field forms. Forms addressed here will be scanned into databases; databases are created because the forms contain critical values needed to calculate pollutant concentrations. Other forms not addressed by thi...

Fluoride concentration in dentine as a biomarker of fluoride intake in European roe deer (Capreolus capreolus) - an electron-microprobe study.

PubMed

Richter, Heiko; Kierdorf, Uwe; Richards, Alan; Melcher, Frank; Kierdorf, Horst

2011-08-01

Fluoride concentration in dentine has been recommended as the best marker for the level of chronic fluoride intake and the most suitable indicator of an individual's total body burden of fluoride. We analysed fluoride concentrations in the dentine of cheek teeth of European roe deer from fluoride-polluted habitats to retrospectively assess the level of fluoride uptake into the tissue. Thereby, we tested the hypothesis of the existence of mechanisms that limit fluoride intake of individuals and fluoride exposure of forming dental hard tissues during the late foetal and early postnatal periods in the species. Using electron-microprobe analysis, fluoride profiles were obtained on sectioned P(4)s, M(1)s, and M(3)s from individuals exhibiting pronounced dental fluorosis. Fluoride concentrations were compared between early formed (peripheral) and late-formed (juxtapulpal) dentine both within single teeth and amongst the three different teeth studied. Peripheral dentine of the M(1), which is formed during the late foetal and early postnatal periods, exhibited markedly lower fluoride concentrations than juxtapulpal dentine of the same tooth and both, peripheral and juxtapulpal dentine of P(4) and M(3) that are formed post-weaning. Our study provides strong support for the hypothesis that in the European roe deer the prenatal and early postnatal (pre-weaning) stages of dental development are (largely) protected against exposure to excess fluoride. This is attributed to the operation of certain protective mechanisms during these periods. Copyright © 2011 Elsevier Ltd. All rights reserved.

Temperature-responsive and biodegradable PVA:PVP k30:poloxamer 407 hydrogel for controlled delivery of human growth hormone (hGH).

PubMed

Taheri, Azade; Atyabi, Fatemeh; Dinarvnd, Rassoul

2011-01-01

Recombinant human growth hormone (rhGH) is used for replacement therapy of pediatric hypopituitary dwarfism. Growth rate in children was observed to be better on the daily injection schedule compared with the currently used therapeutic regimen of thrice a week injection. Thus, a controlled release formulation would overcome the drawback of traditional rhGH therapy such as the need for multiple injections. Poloxamers are a family of triblock copolymers consisting of two hydrophilic blocks of polyoxyethylene separated by a hydrophobic block of polyoxypropylene, which form micelles at low concentrations and form clear thermally reversible gels at high concentrations. We used poloxamer gels to develop a controlled release formulation of hGH. The objective of this study was to develop an in situ gel forming drug delivery system for hGH using the minimum possible ratio of poloxamer 407 (P407). Decreasing the concentration of poloxamer could reduce the risk of hypertriglyceridemia induction. Different additives were added to the poloxamer formulations. It was observed that among different additives polyvinylpyrrolidone k30 (PVP k30) and polyvinyl alcohol (PVA) decrease poloxamer concentration required to form in situ gelation from 18% to 10%. The dynamic viscoelastic properties of the samples were determined. Both the storage modulus and the loss modulus of the samples increased abruptly as the temperature passed a certain point. It can be concluded that combining P407 and PVP and PVA could be a promising strategy for preparation of thermally reversible in situ gel forming delivery systems of hGH with low poloxamer concentration.

Ultraviolet-B radiation mobilizes uranium from uranium-dissolved organic carbon complexes in aquatic systems, demonstrated by asymmetrical flow field-flow fractionation.

PubMed

Nehete, Sachin Vilas; Christensen, Terje; Salbu, Brit; Teien, Hans-Christian

2017-05-05

Humic substances have a tendency to form complexes with metal ions in aquatic medium, impacting the metal mobility, decreasing bioavailability and toxicity. Ultraviolet-B (UV-B) radiation exposure degrades the humic substance, changes their molecular weight distribution and their metal binding capacity in aquatic medium. In this study, we experimented the effect of UV-B radiation on the uranium complexed with fulvic acids and humic acids in a soft water system at different pH, uranium concentrations and radiant exposure. The concentration and distribution of uranium in a complexed form were investigated by asymmetrical flow field-flow fractionation coupled to multi detection technique (AsFlFFF-UV-ICP-MS). The major concentration of uranium present in complexes was primarily associated with average and higher molecular weight fulvic and humic acids components. The concentration of uranium in a complexed form increased with increasing fulvic and humic acid concentrations as well as pH of the solution. The higher molecular weight fraction of uranium was degraded due to the UV-B exposure, transforming about 50% of the uranium-dissolved organic carbon complexes into low molecular weight uranium species in complex form with organic ligands and/or free form. The result also suggests AsFlFFF-UV-ICP-MS to be an important separation and detection technique for understanding the interaction of radionuclides with dissolved organic matter, tracking size distribution changes during degradation of organic complexes for understanding mobility, bioavailability and ecosystem transfer of radionuclides as well as metals. Copyright © 2017 Elsevier B.V. All rights reserved.

A study of flow in alluvial channels: the effect of large concentrations of fine sediment on the mechanics of flow in a small flume

USGS Publications Warehouse

Haushild, William Leland; Simons, Daryl Baldwin; Richadrson, Everett V.

1961-01-01

concentration with the dune bed form and was increased by as much as 550 percent for the transition, standing wave, and antidune forms of bed roughness. Resistance to flow was less (C/√ g increased by 45 percent) with fine sediment-laden flow than with clear-water flow for the dune, and transition bed forms; and was greater (C/√ g   reduced by 25 percent) for the standing waves and the antidunes. A narrow range of bentonite concentration for each form of bed roughness was established as a limit below which only minor changes in bed form, bed material transport, and resistance to flow occurred. The variation of the liquid properties, specific weight and viscosity, for water-bentonite dispersions were studied and their effect on the properties of the bed material particles measured. The fall velocity of the particles in a dispersion of 100, 000 parts per million fine sediment in water was reduced to about one-half their fall velocity in clear water.

Viral-templated nanocrystalline Pd nanowires for chemiresistive hydrogen (H2) sensors

NASA Astrophysics Data System (ADS)

Moon, Chung Hee; Yan, Yiran; Zhang, Miluo; Myung, Nosang V.; Haberer, Elaine D.

2014-08-01

A palladium (Pd) nanowire-based hydrogen (H2) sensor has been fabricated with a novel viral-templated assembly route. A filamentous M13 bacteriophage was used as the viral-template for assembly of Pd nanowires at ambient conditions. Scanning electron microscopy determined Pd nanowire distribution and morphology with the devices. The phage template concentration controlled the number of physical and electrical nanowire connections across the device. A greater phage concentration resulted in a higher connection density and thicker Pd deposition. A lower phage concentration generated devices which formed chain-like nanowires of Pd nanocrystals, whereas a higher phage concentration formed devices with a continuous mesh-like structure. The lower concentration devices showed 51-78% instantaneous response to 2000 ppm H2 and response time less than 30 s.

Fecal concentrations of bacterially-derived vitamin K forms are associated with gut microbiota composition but not plasma or fecal cytokine concentrations in healthy adults

USDA-ARS?s Scientific Manuscript database

Background: Emerging evidence suggests novel roles for bacterially-derived vitamin K forms known as menaquinones (MKn) in health and disease which may be attributable in part to anti-inflammatory effects. However, the relevance of MKn produced by gut bacteria to vitamin K requirements and inflammati...

Destabilization of Oil-in-Water Emulsions Formed Using Highly Hydrolyzed Whey Proteins.

PubMed

Agboola; Singh; Munro; Dalgleish; Singh

1998-01-19

Oil-in-water emulsions (4 wt % soy oil) were prepared with 0.5-5 wt % whey protein hydrolysate (WPH) (27% degree of hydrolysis), in a two-stage homogenizer using various first-stage pressures of 10.3, 20.6, and 34.3 MPa and a constant second-stage pressure of 3.4 MPa. Destabilization studies on the emulsions were carried out for up to 24 h, using both laser light scattering and confocal laser microscopy. It was found that emulsions formed with <2% WPH showed oiling off and coalescence at all homogenization pressures. Emulsions formed with 2, 3, and 4% WPH showed coalescence and creaming only, while slight flocculation but no creaming occurred in emulsions formed with 5% WPH. Furthermore, the apparent rate of coalescence increased with homogenization pressure but decreased with WPH concentration. In contrast, the surface concentration of WPH increased with the WPH concentration in the emulsions but decreased with homogenization pressure. Analysis of WPH by high-performance liquid chromatography showed an increase in the concentration of high molecular weight peptides at the droplet surface compared to the WPH solution. This was considered very important for the stability of these oil-in-water emulsions.

Relative Bioavailability of Niacin Supplements for Dairy Cows: Effects of Rumen Protection and of Feed Processing.

PubMed

Tienken, Reka; Kersten, Susanne; Hüther, Liane; Frahm, Jana; Meyer, Ulrich; Dänicke, Sven

2015-12-16

The present study aimed to examine the effective systemic bioavailability of niacin- with particular focus on its galenic form-and feed processing. Experiment 1 was conducted with 35 dairy cows to investigate the effects of various doses of oral supplemented nicotinic acid (NA) either in differing galenic forms (non-rumen protected (nRP) vs. rumen protected form (RP)) on serum niacin concentrations. Experiment 2 was designed as a pharmacokinetic study examining the serum niacin kinetics over 24 h after giving a single oral bolus of 24 g nRP or RP NA admixed in either pelleted or ground concentrate. In both experiments, only the niacin vitamer nicotinamide (NAM) was detected. Results of experiment 1 showed that both galenic forms at a dose of 24 g/cow daily elevated NAM concentrations at the beginning of the experiment. Despite a daily supplementation, NAM concentrations decreased continuously towards the end of the experiment which was more steeply in nRP NA ( p = 0.03). On experimental day 21, NAM concentrations were higher when feeding RP NA ( p = 0.03) and the highest dose (24 g/day and cow) ( p < 0.01). Results of experiment 2 indicated that nRP and RP were characterized by similar pharmacokinetic profiles resulting in similar areas under the curves as a net result of the kinetic counterbalancing alterations. Pelleting seemed not to influence the relative bioavailability.

Stable, concentrated solutions of polyaniline using amines as gel inhibitors

DOEpatents

Wang, Hsing-Lin; Mattes, Benjamin R.

2002-01-01

Stable, concentrated solutions of high-molecular weight polyaniline using amines as gel inhibitors. Certain amine compounds (gel inhibitors) are used to form highly concentrated, stable solutions of the emeraldine base form of polyaniline in numerous organic solvents from which coatings, films and fibers are readily prepared without problems associated with rapid gelation which occurs when concentrated solutions are attempted without the use of the gel inhibitors of the present invention. Tertiary amines are used to solubilize low-molecular weight fractions (M.sub.w <120,000, M.sub.n <30,000) of the pernigraniline, emeraldine, and leucoemeraldine oxidation states of polyaniline as concentrated (>20 wt. %) polyaniline solutions, while primary and secondary amines are used to produce solutions having 15-40 wt % of high-molecular weight polyaniline [M.sub.w.gtoreq.120,000, M.sub.n.gtoreq.30,000]. Concentrated solutions of polyaniline co-polymers or ring and/or nitrogen-substituted polyanilines may also be prepared.

Hydrothermal Synthesis of PbTiO3 Nanocrystals with a pH-Adjusting Agent of Ammonia Solution

NASA Astrophysics Data System (ADS)

Li, Xinyi; Huang, Zhixiong; Zhang, Lianmeng; Guo, Dongyun

2018-05-01

The PbTiO3 nanocrystals were synthesized by a hydrothermal method, and ammonia solution was firstly used as a pH-adjusting agent. The effect of ammonia concentration on formation and morphologies of PbTiO3 nanocrystals was investigated. At low ammonia concentration (0-2.2 mol/L), no perovskite PbTiO3 phase was formed. When the ammonia concentration was 4.4 mol/L, the rod-like PbTiO3 nanocrystals with highly crystalline were successfully synthesized. As the ammonia concentration further increased to 13.2 mol/L, the flake-like PbTiO3 nanocrystals were formed.

Concentric ring flywheel with hooked ring carbon fiber separator/torque coupler

DOEpatents

Kuklo, Thomas C.

1999-01-01

A concentric ring flywheel with expandable separators, which function as torque couplers, between the rings to take up the gap formed between adjacent rings due to differential expansion between different radius rings during rotation of the flywheel. The expandable separators or torque couplers include a hook-like section at an upper end which is positioned over an inner ring and a shelf-like or flange section at a lower end onto which the next adjacent outer ring is positioned. As the concentric rings are rotated the gap formed by the differential expansion there between is partially taken up by the expandable separators or torque couplers to maintain torque and centering attachment of the concentric rings.

Structure of the starch granule--a curved crystal.

PubMed

Larsson, K

1991-09-01

A structure model of the molecular arrangement in native starch proposed earlier is further considered, with special regard to the lateral packing of cluster units. The amylopectin molecules are radially distributed, with branches concentrated in clusters. Within each cluster the polyglucan chains form double helices which are hexagonally packed. The clusters form spherically concentric crystalline layers with amylose in an amorphous form acting as a space-filler. A translational mechanism for the change of helical direction at boundaries between clusters is proposed which can account for variations in the curvature of the concentric layers. The model is related to X-ray diffraction data and optical birefringence, considering dissembly at gelatinization. The structure is also discussed in relation to biosynthesis. Some aspects of gelatinization, such as the recent glass-transition approach, are then considered.

The free form XR photovoltaic concentrator: a high performance SMS3D design

NASA Astrophysics Data System (ADS)

Cvetkovic, Aleksandra; Hernandez, Maikel; Benítez, Pablo; Miñano, Juan C.; Schwartz, Joel; Plesniak, Adam; Jones, Russ; Whelan, David

2008-08-01

A novel photovoltaic concentrator is presented. The goal is to achieve high concentration design with high efficiency and high acceptance angle that in the same time is compact and convenient for thermal and mechanical management. This photovoltaic system is based on 1 cm2 multi-junction tandem solar cells and an XR concentrator. The XR concentrator in this system is an SMS 3D design formed by one reflective (X) and one refractive (R) free-form surfaces (i.e., without rotational or linear symmetry) and has been chosen for its excellent aspect ratio and for its ability to perform near the thermodynamic limit. It is a mirror-lens device that has no shadowing elements and has square entry aperture (the whole system aperture area is used for collecting light). This large acceptance angle relaxes the manufacturing tolerances of all the optical and mechanical components of the system included the concentrator itself and is one of the keys to get a cost competitive photovoltaic generator. For the geometrical concentration of 1000x the simulation results show the acceptance angle of +/-1.8 deg. The irradiance distribution on the cell is achieved with ultra-short homogenizing prism, whose size is optimised to keep the maximum values under the ones that the cell can accept. The application of the XR optics to high-concentration is being developed in a consortium leaded by The Boeing Company, which has been awarded a project by US DOE in the framework of the Solar America Initiative.

Hydrogel-forming microneedle arrays: Potential for use in minimally-invasive lithium monitoring.

PubMed

Eltayib, Eyman; Brady, Aaron J; Caffarel-Salvador, Ester; Gonzalez-Vazquez, Patricia; Zaid Alkilani, Ahlam; McCarthy, Helen O; McElnay, James C; Donnelly, Ryan F

2016-05-01

We describe, for the first time, hydrogel-forming microneedle (s) (MN) arrays for minimally-invasive extraction and quantification of lithium in vitro and in vivo. MN arrays, prepared from aqueous blends of hydrolysed poly(methyl-vinylether-co-maleic anhydride) and crosslinked by poly(ethyleneglycol), imbibed interstitial fluid (ISF) upon skin insertion. Such MN were always removed intact. In vitro, mean detected lithium concentrations showed no significant difference following 30min MN application to excised neonatal porcine skin for lithium citrate concentrations of 0.9 and 2mmol/l. However, after 1h application, the mean lithium concentrations extracted were significantly different, being appropriately concentration-dependent. In vivo, rats were orally dosed with lithium citrate equivalent to 15mg/kg and 30mg/kg lithium carbonate, respectively. MN arrays were applied 1h after dosing and removed 1h later. The two groups, having received different doses, showed no significant difference between lithium concentrations in serum or MN. However, the higher dosed rats demonstrated a lithium concentration extracted from MN arrays equivalent to a mean increase of 22.5% compared to rats which received the lower dose. Hydrogel-forming MN clearly have potential as a minimally-invasive tool for lithium monitoring in outpatient settings. We will now focus on correlation between serum and MN lithium concentrations. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Concentrate minimization and water recovery enhancement using pellet precipitator in a reverse osmosis process treating textile wastewater.

PubMed

Sahinkaya, Erkan; Sahin, Ahmet; Yurtsever, Adem; Kitis, Mehmet

2018-06-09

Industrial wastewater reuse together with zero or near zero liquid discharges have been a growing trend due to the requirement of sustainable water management mandated by water scarcity and tightening discharge regulations. Studies have been conducted on the reclamation of textile industry wastewater using RO processes. However a lot of scientific attention has been drawn upon limiting the amount of concentrate generated from RO processes, which depends on the concentrations of scale forming ions in the concentrate stream. Hence, this study aims at investigating the applicability of an ultra-filtration (UF) membrane integrated pellet reactor to remove scale forming ions, i.e. Ca 2+ , Mg 2+ and Si from the concentrate of a pilot-scale textile industry RO process, for the first time in the literature. The resulting effluent was further tested in a secondary RO process to decrease concentrate volume and increase total water recovery. The pellet reactor operated at an extremely low hydraulic retention time of 0.1 h removed scale forming ions, i.e. Ca 2+ , Mg 2+ , with 90-95% efficiency, which improved the secondary RO process performance up to 92-94% overall water recovery, i.e. near zero liquid discharge was reached. Ozonation of the concentrate partially removed COD and color, which further improved the secondary RO filtration performance. Copyright © 2018 Elsevier Ltd. All rights reserved.

Waste Form and Indrift Colloids-Associated Radionuclide Concentrations: Abstraction and Summary

DOE Office of Scientific and Technical Information (OSTI.GOV)

R. Aguilar

This Model Report describes the analysis and abstractions of the colloids process model for the waste form and engineered barrier system components of the total system performance assessment calculations to be performed with the Total System Performance Assessment-License Application model. Included in this report is a description of (1) the types and concentrations of colloids that could be generated in the waste package from degradation of waste forms and the corrosion of the waste package materials, (2) types and concentrations of colloids produced from the steel components of the repository and their potential role in radionuclide transport, and (3) typesmore » and concentrations of colloids present in natural waters in the vicinity of Yucca Mountain. Additionally, attachment/detachment characteristics and mechanisms of colloids anticipated in the repository are addressed and discussed. The abstraction of the process model is intended to capture the most important characteristics of radionuclide-colloid behavior for use in predicting the potential impact of colloid-facilitated radionuclide transport on repository performance.« less

Atomic force microscopy studies of native photosynthetic membranes.

PubMed

Sturgis, James N; Tucker, Jaimey D; Olsen, John D; Hunter, C Neil; Niederman, Robert A

2009-05-05

In addition to providing the earliest surface images of a native photosynthetic membrane at submolecular resolution, examination of the intracytoplasmic membrane (ICM) of purple bacteria by atomic force microscopy (AFM) has revealed a wide diversity of species-dependent arrangements of closely packed light-harvesting (LH) antennae, capable of fulfilling the basic requirements for efficient collection, transmission, and trapping of radiant energy. A highly organized architecture was observed with fused preparations of the pseudocrystalline ICM of Blastochloris viridis, consiting of hexagonally packed monomeric reaction center light-harvesting 1 (RC-LH1) core complexes. Among strains which also form a peripheral LH2 antenna, images of ICM patches from Rhodobacter sphaeroides exhibited well-ordered, interconnected networks of dimeric RC-LH1 core complexes intercalated by rows of LH2, coexisting with LH2-only domains. Other peripheral antenna-containing species, notably Rhodospirillum photometricum and Rhodopseudomonas palustris, showed a less regular organization, with mixed regions of LH2 and RC-LH1 cores, intermingled with large, paracrystalline domains. The ATP synthase and cytochrome bc(1) complex were not observed in any of these topographs and are thought to be localized in the adjacent cytoplasmic membrane or in inaccessible ICM regions separated from the flat regions imaged by AFM. The AFM images have served as a basis for atomic-resolution modeling of the ICM vesicle surface, as well as forces driving segregation of photosynthetic complexes into distinct domains. Docking of atomic-resolution molecular structures into AFM topographs of Rsp. photometricum membranes generated precise in situ structural models of the core complex surrounded by LH2 rings and a region of tightly packed LH2 complexes. A similar approach has generated a model of the highly curved LH2-only membranes of Rba. sphaeroides which predicts that sufficient space exists between LH2 complexes for quinones to diffuse freely. Measurement of the intercomplex distances between adjacent LH2 rings of Phaeospirillum molischianum has permitted the first calculation of the separation of bacteriochlorophyll a molecules in the native ICM. A recent AFM analysis of the organization of green plant photosystem II (PSII) in grana thylakoids revealed the protruding oxygen-evolving complex, crowded together in parallel alignment at three distinct levels of stacked membranes over the lumenal surface. The results also confirmed that PSII-LHCII supercomplexes are displaced relative to one another in opposing grana membranes.

Maternal influences on thiamine status of walleye Sander vitreus ova.

PubMed

Wiegand, M D; Johnston, T A; Brown, L R; Brown, S B; Casselman, J M; Leggett, W C

2011-03-01

Concentrations of the various forms of thiamine (vitamin B(1) ) were determined in walleye Sander vitreus ova from three central North American lakes. Total thiamine concentrations in ova from Lake Winnipeg S. vitreus were approximately three times greater (mean 12 nmol g(-1) ) than in those from Lakes Erie or Ontario. The percentage of thiamine in the active form (thiamine pyrophosphate, TPP) was highest in Lake Ontario ova (mean 88%) and lowest in those from Lake Winnipeg (mean 70%). Neither ova total thiamine concentration nor per cent ova thiamine as TPP showed any consistent relationships with maternal age, size, morphometric condition, somatic lipid concentrations or liver lipid concentrations. Ova total thiamine concentration, however, was negatively related to ovum size in some populations, as well as among populations, and was positively related to liver total thiamine concentration. Maternal transfer of thiamine to ova appears to be independent of female ontogenetic or conditional state in S. vitreus. © 2011 The Authors. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles.

Production and functional evaluation of a protein concentrate from giant squid (Dosidicus gigas) by acid dissolution and isoelectric precipitation.

PubMed

Cortés-Ruiz, Juan A; Pacheco-Aguilar, Ramón; Elena Lugo-Sánchez, M; Gisela Carvallo-Ruiz, M; García-Sánchez, Guillermina

2008-09-15

A protein concentrate from giant squid (Dosidicus gigas) was produced under acidic conditions and its functional-technological capability evaluated in terms of its gel-forming ability, water holding capacity and colour attributes. Technological functionality of the concentrate was compared with that of squid muscle and a neutral concentrate. Protein-protein aggregates insoluble at high ionic strength (I=0.5M), were detected in the acidic concentrate as result of processing with no preclusion of its gel-forming ability during the sol-to-gel thermal transition. Even though washing under acidic condition promoted autolysis of the myosin heavy chain, the acidic concentrate displayed an outstanding ability to gel giving samples with a gel strength of 455 and 1160gcm at 75% and 90% compression respectively, and an AA folding test grade indicative of high gel strength, elasticity, and cohesiveness. The process proved to be a good alternative for obtaining a functional protein concentrate from giant squid muscle. Copyright © 2008. Published by Elsevier Ltd.

Photovoltaic generator with a spherical imaging lens for use with a paraboloidal solar reflector

DOEpatents

Angel, Roger P

2013-01-08

The invention is a generator for photovoltaic conversion of concentrated sunlight into electricity. A generator according to the invention incorporates a plurality of photovoltaic cells and is intended for operation near the focus of a large paraboloidal reflector pointed at the sun. Within the generator, the entering concentrated light is relayed by secondary optics to the cells arranged in a compact, concave array. The light is delivered to the cells at high concentration, consistent with high photovoltaic conversion efficiency and low cell cost per unit power output. Light enters the generator, preferably first through a sealing window, and passes through a field lens, preferably in the form of a full sphere or ball lens centered on the paraboloid focus. This lens forms a concentric, concave and wide-angle image of the primary reflector, where the intensity of the concentrated light is stabilized against changes in the position of concentrated light entering the generator. Receiving the stabilized light are flat photovoltaic cells made in different shapes and sizes and configured in a concave array corresponding to the concave image of a given primary reflector. Photovoltaic cells in a generator are also sized and interconnected so as to provide a single electrical output that remains high and stable, despite aberrations in the light delivered to the generator caused by, for example, mispointing or bending of the primary reflector. In some embodiments, the cells are set back from the image formed by the ball lens, and part of the light is reflected onto each cell small secondary reflectors in the form of mirrors set around its perimeter.

Hierarchical Cluster Formation in Concentrated Monoclonal Antibody Formulations

NASA Astrophysics Data System (ADS)

Godfrin, P. Douglas; Zarzar, Jonathan; Zarraga, Isidro Dan; Porcar, Lionel; Falus, Peter; Wagner, Norman; Liu, Yun

Reversible cluster formation has been identified as an underlying cause of large solution viscosities observed in some concentrated monoclonal antibody (mAb) formulations. As high solution viscosity prevents the use of subcutaneous injection as a delivery method for some mAbs, a fundamental understanding of the interactions responsible for high viscosities in concentrated mAb solutions is of significant relevance to mAb applications in human health care as well as of intellectual interest. Here, we present a detailed investigation of a well-studied IgG1 based mAb to relate the short time dynamics and microstructure to significant viscosity changes over a range of pharmaceutically relevant physiochemical conditions. Using a combination of experimental techniques, it is found that upon adding Na2SO4, these antibodies dimerize in solution. Proteins form strongly bounded reversible dimers at dilute concentrations that, when concentrated, interact with each other to form loosely bounded, large, transient clusters. The combined effect of forming strongly bounded dimers and a large transient network is a significant increase in the solution viscosity. Strongly bounded, reversible dimers may exist in many IgG1 based mAb systems such that these results contribute to a more comprehensive understanding of the physical mechanisms producing high viscosities in concentrated protein solutions.

U.S.-MEXICO BORDER PROGRAM ARIZONA BORDER STUDY--STANDARD OPERATING PROCEDURE FOR CODING: FIELD FORMS (UA-D-37.0)

EPA Science Inventory

The purpose of this SOP is to define the coding strategy for selected field forms. Forms addressed here will be scanned into databases. Databases are created because the forms contain critical values needed to calculate pollutant concentrations. Other forms not addressed by th...

Changes in polyamines, inorganic ions and glutamine synthetase activity in response to nitrogen availability and form in red spruce (Picea rubens)

Treesearch

Michelle J. Serapiglia; Rakesh Minocha; Subhash C. Minocha

2008-01-01

We analyzed effects of nitrogen availability and form on growth rates, concentrations of polyamines and inorganic ions and glutamine synthetase activity in in-vitro-cultured red spruce (Picea rubens Sarg.) cells. Growth rates, concentrations of polyamines and glutamine synthetase activity declined when either the amount of nitrate or the total amount...

Concentrating Solar Power Projects - Dish/Engine Projects | Concentrating

Science.gov Websites

together to form a dish-shaped structure. The receiver is supported above the panels by an arm-like structure and glows as it is heated by concentrated sunlight. A technician sits below the dish, in the shade

Performance Test on Polymer Waste Form - 12137

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Se Yup

Polymer solidification was attempted to produce stable waste form for the boric acid concentrates and the dewatered spent resins. The polymer mixture was directly injected into the mold or drum which was packed with the boric acid concentrates and the dewatered spent resins, respectively. The waste form was produced by entirely curing the polymer mixture. A series of performance tests was conducted including compressive strength test, water immersion test, leach test, thermal stability test, irradiation stability test and biodegradation stability test for the polymer waste forms. From the results of the performance tests for the polymer waste forms, it ismore » believed that the polymer waste form is very stable and can satisfy the acceptance criteria for permanent disposal. At present, performance tests with full scale polymer waste forms are being carried out in order to obtain qualification certificate by the regulatory institute in Korea. Polymer waste forms were prepared with the surrogate of boric acid concentrates and the surrogate of spent ion exchange resins respectively. Waste forms were also made in lab scale and in full scale. Lab. scale waste forms were directly subjected to a series of the performance tests. In the case of full scale waste form, the test specimens for the performance test were taken from a part of waste form by coring. A series of performance tests was conducted including compressive strength test, thermal stability test, irradiation stability test and biodegradation stability test, water immersion test, leach test, and free standing water for the polymer waste forms. In addition, a fire resistance test was performed on the waste forms by the requirement of the regulatory institute in Korea. Every polymer waste forms containing the boric acid concentrates and the spent ion exchange resins had exhibited excellent structural integrity of more than 27.58 MPa (4,000 psi) of compressive strength. On thermal stability testing, biodegradation testing and water immersion testing, no degradation was observed in the waste forms. Also, by measuring the compressive strength after these tests, it was confirmed that the structural integrity was still retained. A leach test was performed by using non radioactive cobalt, cesium and strontium. The leaching of cobalt, cesium and strontium from the polymer waste forms was very low. Also, the polymer waste forms were found to possess adequate fire resistance. From the results of the performance tests, it is believed that the polymer waste form is very stable and can satisfy the acceptance criteria for permanent disposal. At present, Performance tests with full scale polymer waste forms are on-going in order to obtain qualification certificate by the regulatory institute in Korea. (authors)« less

Germanium geochemistry and mineralogy

USGS Publications Warehouse

Bernstein, L.R.

1985-01-01

Germanium is enriched in the following geologic environments: 1. (1) iron meteorites and terrestrial iron-nickel; 2. (2) sulfide ore deposits, particularly those hosted by sedimentary rocks; 3. (3) iron oxide deposits; 4. (4) oxidized zones of Ge-bearing sulfide deposits; 5. (5) pegmatites, greisens, and skarns; and 6. (6) coal and lignitized wood. In silicate melts, Ge is highly siderophile in the presence of native iron-nickel; otherwise, it is highly lithophile. Among silicate minerals, Ge is concentrated in those having less polymerized silicate tetrahedra such as olivine and topaz. In deposits formed from hydrothermal solutions, Ge tends to be enriched mostly in either sulfides or in fluorine-bearing phases; it is thus concentrated both in some hydrothermal sulfide deposits and in pegmatites, greisens, and skarns. In sulfide deposits that formed from solutions having low to moderate sulfur activity, Ge is concentrated in sphalerite in amounts up to 3000 ppm. Sulfide deposits that formed from solutions having higher sulfur activity allowed Ge to either form its own sulfides, particularly with Cu, or to substitute for As, Sn, or other metals in sulfosalts. The Ge in hydrothermal fluids probably derives from enrichment during the fractional crystallization of igneous fluids, or is due to the incorporation of Ge from the country rocks, particularly from those containing organic material. Germanium bonds to lignin-derivative organic compounds that are found in peat and lignite, accounting for its common concentration in coals and related organic material. Germanium is precipitated from water together with iron hydroxide, accounting for its concentration in some sedimentary and supergene iron oxide deposits. It also is able to substitute for Fe in magnetite in a variety of geologic environments. In the oxidized zone of Ge-bearing sulfide deposits, Ge is concentrated in oxides, hydroxides, and hydroxy-sulfates, sometimes forming its own minerals. It is particularly enriched in some iron- and manganese-bearing oxides and hydroxides, including goethite (up to 5300 ppm) and hematite (up to 7000 ppm). ?? 1985.

Unveiling One-Dimensional Supramolecular Structures Formed through π-π Stacking of Phenothiazines by Differential Pulse Voltammetry.

PubMed

Carvalho, Fernando R; Zampieri, Eduardo H; Caetano, Wilker; Silva, Rafael

2017-05-19

Organic-based nanomaterials can be self-assembled by strong and directional intermolecular forces such as π-π interactions. Experimental information about the stability, size, and geometry of the formed structures is very limited for species that easily aggregate, even at very low concentrations. Differential pulse voltammetry (DPV) can unveil the formation, growth, and also the stability window of ordered, one-dimensional, lamellar self-aggregates formed by supramolecular π stacking of phenothiazines at micromolar (10 -6  mol L -1 ) concentrations. The self-diffusion features of the species at different concentrations are determined by DPV and used to probe the π staking process through the concept of the frictional resistance. It is observed that toluidine blue and methylene blue start to self-aggregate around 9 μmol L -1 , and that the self-aggregation process occurs by one-dimensional growth as the concentration of the phenothiazines is increased up to around 170 μmol L -1 for toluidine blue and 200 μmol L -1 for methylene blue. At higher concentrations, the aggregation process leads to structures with lower anisometry. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Streptomycin interference in Jaffe reaction - possible false positive creatinine estimation in excessive dose exposure.

PubMed

Syal, Kirtimaan; Srinivasan, Anand; Banerjee, Dibyajyoti

2013-01-01

To study the potential of commonly used aminoglycoside antibiotics to form non-creatinine chromogen with alkaline picrate reagent. We studied the non-creatinine chromogen formation of various concentrations of streptomycin, amikacin, kanamycin, netilmicin, gentamicin and tobramycin added to known creatinine concentrations by the Jaffe reaction based creatinine estimation. Only streptomycin above therapeutic concentrations of 10mg/mL interfered in the Jaffe reaction and acted as non-creatinine chromogen. Therapeutic doses of the aminoglycosides do not form non-creatinine chromogens. Copyright © 2012 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.

Antileishmanial Activity of Liposomal Clarithromycin against Leishmania Major Promastigotes.

PubMed

Sazgarnia, Ameneh; Zabolinejad, Naghmeh; Layegh, Pouran; Rajabi, Omid; Berenji, Fariba; Javidi, Zari; Salari, Roshanak

2012-11-01

Cutaneous leishmaniasis is a common parasitic disease which is endemic in some parts of the world. In vitro and in vivo studies have shown azithromycin efficacy on some Leishmania species. Because of structural similarity between clarithromycin and azithromycin and efficacy of clarithromycin against intracellular organisms and due to the absence of previous studies in this respect, we decided to evaluate the efficacy of clarithromycin against promastigotes of L. major in vitro. First, liposomal and non- liposomal clarithromycin were prepared, then both forms of the drug were incubated with promastigotes for 24 hr in NNN culture media without red phenol in the presence of 5% FCS with different concentrations as follows: 20, 40, 80, 100, 200 and 500 µg/ml. According to the results, clarithromycin in both liposomal and non- liposomal forms has in vitro activity against the promastigotes of L. major. The concentration of drug that killed 50% of parasites (ED 50) was 169 and 253.6 µg/ml for liposomal and non- liposomal forms, respectively which shows that lower concentrations of liposomal drug are required to have the same effect as non- liposomal drug and the liposomal form of the drug is more effective than non- liposomal form. Clarithromycin in both liposomal and non- liposomal forms has in vitro activity against the promastigotes of L. major.

Concentric ring flywheel with hooked ring carbon fiber separator/torque coupler

DOEpatents

Kuklo, T.C.

1999-07-20

A concentric ring flywheel with expandable separators, which function as torque couplers, between the rings to take up the gap formed between adjacent rings due to differential expansion between different radius rings during rotation of the flywheel. The expandable separators or torque couplers include a hook-like section at an upper end which is positioned over an inner ring and a shelf-like or flange section at a lower end onto which the next adjacent outer ring is positioned. As the concentric rings are rotated the gap formed by the differential expansion there between is partially taken up by the expandable separators or torque couplers to maintain torque and centering attachment of the concentric rings. 2 figs.

Pharmacokinetics and Bioavailability of the GnRH Analogs in the Form of Solution and Zn2+-Suspension After Single Subcutaneous Injection in Female Rats.

PubMed

Suszka-Świtek, Aleksandra; Ryszka, Florian; Dolińska, Barbara; Dec, Renata; Danch, Alojzy; Filipczyk, Łukasz; Wiaderkiewicz, Ryszard

2017-04-01

Although many synthetic gonadoliberin analogs have been developed, only a few of them, including buserelin, were introduced into clinical practice. Dalarelin, which differs from buserelin by just one aminoacid in the position 6 (D-Ala), is not widely used so far. Gonadotropin-releasing hormone (GnRH) analogs are used to treat many different illnesses and are available in different forms like solution for injection, nasal spray, microspheres, etc. Unfortunately, none of the above drug formulations can release the hormones for 24 h. We assumed that classical suspension could solve this problem. Two sets of experiments were performed. In the first one, buserelin and dalarelin were injected into mature female rats in two forms: suspension, in which the analogs are bounded by Zn 2+ ions and solution. The pharmacokinetic parameters and bioavailability of the analogs were calculated, based on their concentration in the plasma measured by high-performance liquid chromatography method (HPLC). In the second experiment, the hormones in two different forms were injected into superovulated immature female rats and then the concentration of Luteinizing hormone (LH), Follicle-stimulating hormone (FSH) and 17β-estradiol in the serum was measured by radioimmunological method. The Extent of Biological Availability (EBA), calculated on the base of AUC 0-∞ , showed that in the form of solution buserelin and dalarelin display, respectively, only 13 and 8 % of biological availability of their suspension counterparts. Comparing both analogs, the EBA of dalarelin was half (53 %) that of buserelin delivered in the form of solution and 83 % when they were delivered in the form of suspension. The injection of buserelin or dalarelin, in the form of solution or suspension, into superovulated female rats increased LH, FSH and estradiol concentration in the serum. However, after injection of the analogs in the form of suspension, the high concentration of LH and FSH in the serum persisted longer. Performed studies indicate that GnRH analogs in the form of suspension have higher bioavailability than their solution counterparts. It influences the effects of their action, especially in relation to LH and FSH.

[Effect of Radix scutellariae on the growth and form of Porphyromanus endodontics in vitro].

PubMed

Tan, Hong; Tang, Yaling; Zhou, Xuedong; Xiao, Xiaorong; Li, Jiyao

2003-07-01

To provide scientific evidence for underpinning the use of Radix Scutellariae in the treatment of pulp and periapical diseases. Using minute amount serial dilution test, this study assessed the minimal inhibitory concentration of Radix Scutellariae extreact against Porphyromanus Endodontics. The forms of Porphyromanus endodontics treated with Radix Scutellariae extract at different concentrations were observed by use of SEM. The MIC of Radix Scutellariae extract was determined to be 1 mg/ml. Radix Scutellariae changed the forms of Porphyromanus endodontics, making them become bigger, longer and crumbled. Radix Scutellariae could inhibit the growth of Porphyromanus Endodontics.

Molecular Form Differences Between Prostate-Specific Antigen (PSA) Standards Create Quantitative Discordances in PSA ELISA Measurements.

PubMed

McJimpsey, Erica L

2016-02-25

The prostate-specific antigen (PSA) assays currently employed for the detection of prostate cancer (PCa) lack the specificity needed to differentiate PCa from benign prostatic hyperplasia and have high false positive rates. The PSA calibrants used to create calibration curves in these assays are typically purified from seminal plasma and contain many molecular forms (intact PSA and cleaved subforms). The purpose of this study was to determine if the composition of the PSA molecular forms found in these PSA standards contribute to the lack of PSA test reliability. To this end, seminal plasma purified PSA standards from different commercial sources were investigated by western blot (WB) and in multiple research grade PSA ELISAs. The WB results revealed that all of the PSA standards contained different mass concentrations of intact and cleaved molecular forms. Increased mass concentrations of intact PSA yielded higher immunoassay absorbance values, even between lots from the same manufacturer. Standardization of seminal plasma derived PSA calibrant molecular form mass concentrations and purification methods will assist in closing the gaps in PCa testing measurements that require the use of PSA values, such as the % free PSA and Prostate Health Index by increasing the accuracy of the calibration curves.

Molecular Form Differences Between Prostate-Specific Antigen (PSA) Standards Create Quantitative Discordances in PSA ELISA Measurements

NASA Astrophysics Data System (ADS)

McJimpsey, Erica L.

2016-02-01

The prostate-specific antigen (PSA) assays currently employed for the detection of prostate cancer (PCa) lack the specificity needed to differentiate PCa from benign prostatic hyperplasia and have high false positive rates. The PSA calibrants used to create calibration curves in these assays are typically purified from seminal plasma and contain many molecular forms (intact PSA and cleaved subforms). The purpose of this study was to determine if the composition of the PSA molecular forms found in these PSA standards contribute to the lack of PSA test reliability. To this end, seminal plasma purified PSA standards from different commercial sources were investigated by western blot (WB) and in multiple research grade PSA ELISAs. The WB results revealed that all of the PSA standards contained different mass concentrations of intact and cleaved molecular forms. Increased mass concentrations of intact PSA yielded higher immunoassay absorbance values, even between lots from the same manufacturer. Standardization of seminal plasma derived PSA calibrant molecular form mass concentrations and purification methods will assist in closing the gaps in PCa testing measurements that require the use of PSA values, such as the % free PSA and Prostate Health Index by increasing the accuracy of the calibration curves.

Effect of surfactant concentration to aggregations of nanogold particles

NASA Astrophysics Data System (ADS)

Duangthanu, Methawee; Pattanaporkratana, Apichart

2017-09-01

This research presents a study of aggregation of colloidal gold nanoparticles using 400 nm diameter gold nanoparticles mixed with a surfactant (Plantacare 2000) at various concentrations. When observed under a microscope, we found that the nanoparticles aggregated to form nearly spherical clusters at the beginning of the formation, and then sedimented to the bottom of the container. These clusters moved with Brownian’s motion and collided with each other in the horizontal plane, forming branch-like clusters in 2D. The appearance and size of the clusters were different depending on the concentration of surfactant. The clusters’ size and appearance were rarely changed after mixing with surfactant for 90 minutes, and we found that the cluster’s shapes were nearly spherical at low surfactant concentration (c = 0.25%). At surfactant concentration between 0.50% - 5.00%, the aggregates formed branch-like clusters with skinnier branches and smaller sizes at higher surfactant concentration. Moreover, we also found that, at surfactant concentrations between 2.50% - 5.00%, nanoparticles and aggregates stuck to the bottom of the glass container quickly and rarely moved after 10 minutes. At c = 0.25%, the 2D fractal dimension of the aggregates was measured to be D = 1.88 ± 0.04, since the aggregates were nearly spherical. The fractal dimension decreased to the minimum of D = 1.50 ± 0.12 at c = 1.50%, similar to D ∼ 1.45 found in diffusion-limited cluster aggregation (DLCA). At surfactant concentration above 1.50%, the fractal dimension increased until it reached the value of D ∼ 1.66 at c = 5.00%.

A Simplified Undergraduate Laboratory Experiment to Evaluate the Effect of the Ionic Strength on the Equilibrium Concentration Quotient of the Bromcresol Green Dye

ERIC Educational Resources Information Center

Rodriguez, Hernan B.; Mirenda, Martin

2012-01-01

A modified laboratory experiment for undergraduate students is presented to evaluate the effects of the ionic strength, "I", on the equilibrium concentration quotient, K[subscript c], of the acid-base indicator bromcresol green (BCG). The two-step deprotonation of the acidic form of the dye (sultone form), as it is dissolved in water, yields…

Trypanocidal activity of the essential oils in their conventional and nanoemulsion forms: in vitro tests.

PubMed

Baldissera, Matheus D; Da Silva, Aleksandro S; Oliveira, Camila B; Zimmermann, Carine E P; Vaucher, Rodrigo A; Santos, Roberto C V; Rech, Virginia C; Tonin, Alexandre A; Giongo, Janice L; Mattos, Cristiane B; Koester, Letícia; Santurio, Janio M; Monteiro, Silvia G

2013-07-01

The aim of this study was to investigate the susceptibility in vitro of Trypanosoma evansi to the essential oils of andiroba (Carapa guaianensis) and aroeira (Schinus molle), in their conventional and nanostructured forms. For that, pure oils at concentrations of 0.5%, 1.0% and 2.0% were used. A negative control (untreated) and a positive control (diminazene aceturate 0.5%) were used as comparative parameters. Later, the same tests were performed, using nanoemulsions oils at concentrations of 0.5% and 1.0%. The tests were carried out in triplicates and the numbers of parasites were quantified on 1, 3 and 6 h from onset of the study. A dose-dependent reduction in the number of parasites to the forms of two oils tested was observed after 1 h. The concentration of parasites was significantly reduced at low concentrations after 3 h, as well as at 6 h no alive parasites were observed for the essential oils tested. Ours findings indicate, for the first time, that oils of andiroba and aroeira (in their conventional and nanoemulsion forms) have high activity against T. evansi in vitro, leading to the suggestion that these oils may be applied as an alternative treatment for this disease. Copyright © 2013 Elsevier Inc. All rights reserved.

Recommended oral sodium bicarbonate administration for urine alkalinization did not affect the concentration of mitomycin-C in non-muscle invasive bladder cancer patients.

PubMed

Seo, Ho Kyung; Kim, Sung Han; Ahn, Kyung-Ohk; Lee, Sang-Jin; Park, Weon Seo; Kim, Sohee; Hwang, Sang-Hyun; Lee, Do Hoon; Joung, Jae Young; Chung, Jinsoo; Joo, Jungnam; Jeong, Kyung-Chae

2017-11-10

Sodium bicarbonate has been reported to maximize the efficacy of intravesical instillation of mitomycin-C (IVI-MMC) therapy by urine alkalinization in non-muscle-invasive bladder cancer (NMIBC). This study aimed to analyze the changes in MMC concentration according to urinary pH and evaluate the efficacy of sodium bicarbonate to maintain the concentration of active form of MMC during IVI-MMC. We prospectively enrolled 26 patients with NMIBC after transurethral resection of bladder tumor. Patients with very high-risk and low-risk NMIBC were excluded. Urinary creatinine, volume, pH, and concentrations of MMC and its degraded form were measured immediately before and after IVI-MMC. The patients were administered 1.5 g of oral sodium bicarbonate during the preceding evening, in the morning, and immediately before the fourth cycle of the six-cycle IVI-MMC. The correlation between MMC concentration and urinary pH changes was explored with or without oral bicarbonate therapy. Recurrence without progression to muscle-invasive disease was noted in 4 of 26 patients in a 23.7-month follow-up. The mean urinary pH before and after the therapy increased from 6.03 to 6.50, and 6.46 to 7.24, without or with oral SB therapy, respectively. Despite this increase, the concentration of active form of MMC did not change significantly. No correlation was found between urinary pH and MMC concentration. Urine alkalinization by SB administration did not maintain the high concentration of urinary MMC. Urine alkalinization by sodium bicarbonate administration for IVI-MMC did not maintain the high concentration of active urinary MMC in NMIBC.

Nitrogen Forms Influence Microcystin Concentration and Composition via Changes in Cyanobacterial Community Structure

PubMed Central

Monchamp, Marie-Eve; Pick, Frances R.; Beisner, Beatrix E.; Maranger, Roxane

2014-01-01

The eutrophication of freshwaters is a global health concern as lakes with excess nutrients are often subject to toxic cyanobacterial blooms. Although phosphorus is considered the main element regulating cyanobacterial biomass, nitrogen (N) concentration and more specifically the availability of different N forms may influence the overall toxicity of blooms. In this study of three eutrophic lakes prone to cyanobacterial blooms, we examined the effects of nitrogen species and concentrations and other environmental factors in influencing cyanobacterial community structure, microcystin (MC) concentrations and MC congener composition. The identification of specific MC congeners was of particular interest as they vary widely in toxicity. Different nitrogen forms appeared to influence cyanobacterial community structure leading to corresponding effects on MC concentrations and composition. Total MC concentrations across the lakes were largely explained by a combination of abiotic factors: dissolved organic nitrogen, water temperature and ammonium, but Microcystis spp. biomass was overall the best predictor of MC concentrations. Environmental factors did not appear to affect MC congener composition directly but there were significant associations between specific MC congeners and particular species. Based on redundancy analyses (RDA), the relative biomass of Microcystis aeruginosa was associated with MC-RR, M. wesenbergii with MC-LA and Aphanizomenon flos-aquae with MC-YR. The latter two species are not generally considered capable of MC production. Total nitrogen, water temperature, ammonium and dissolved organic nitrogen influenced the cyanobacterial community structure, which in turn resulted in differences in the dominant MC congener and the overall toxicity. PMID:24427318

Selenoamino Acid-Enriched Green Pea as a Value-Added Plant Protein Source for Humans and Livestock.

PubMed

Garousi, Farzaneh; Domokos-Szabolcsy, Éva; Jánószky, Mihály; Kovács, Andrea Balláné; Veres, Szilvia; Soós, Áron; Kovács, Béla

2017-06-01

Selenium deficiency in various degrees affects around 15% of the world's population, contributing to a variety of health problems. In this study, we examined the accumulation and biotransformation of soil applied Se-supplementation (sodium selenite and sodium selenate forms) at different concentrations, along with growth and yield formation of green pea, in a greenhouse experiment. Biotransformation of inorganic Se was evaluated using HPLC-ICP-MS for Se-species separation in the above ground parts of green pea. Results showed 3 mg kg -1 Se IV increased green pea growth biomarkers and also caused an increase in protein content in leaves by 17%. Selenomethionine represented 65% of the total selenium content in shoots, but was lower in pods and seeds (54 and 38%, respectively). Selenomethionine was the major species in all plant parts and the only organic selenium form in the lower Se IV concentration range. Elevating the dose of Se IV (≥30 mg kg -1 ) triggered detrimental effects on growth and protein content and caused higher accumulation of inorganic Se in forms of Se VI and Se IV . Selenocysteine, another organic form of proteinogenic amino acid, was determined when Se IV (≥10 mg kg -1 ) was applied in higher concentrations. Thus, agronomic biofortification using the appropriate chemical form and concentration of Se will have positive effects on green pea growth and its enriched shoots and seeds provide a value-added protein source for livestock and humans with significant increased selenomethionine.

Stabilization of distearoylphosphatidylcholine lamellar phases in propylene glycol using cholesterol.

PubMed

Harvey, Richard D; Ara, Nargis; Heenan, Richard K; Barlow, David J; Quinn, Peter J; Lawrence, M Jayne

2013-12-02

Phospholipid vesicles (liposomes) formed in pharmaceutically acceptable nonaqueous polar solvents such as propylene glycol are of interest in drug delivery because of their ability to improve the bioavailability of drugs with poor aqueous solubility. We have demonstrated a stabilizing effect of cholesterol on lamellar phases formed by dispersion of distearoylphosphatidylcholine (DSPC) in water/propylene glycol (PG) solutions with glycol concentrations ranging from 0 to 100%. The stability of the dispersions was assessed by determining the effect of propylene glycol concentration on structural parameters of the lamellar phases using a complementary combination of X-ray and neutron scattering techniques at 25 °C and in the case of X-ray scattering at 65 °C. Significantly, although stable lamellar phases (and liposomes) were formed in all PG solutions at 25 °C, the association of the glycol with the liposomes' lamellar structures led to the formation of interdigitated phases, which were not thermostable at 65 °C. With the addition of equimolar quantities of cholesterol to the dispersions of DSPC, stable lamellar dispersions (and indeed liposomes) were formed in all propylene glycol solutions at 25 °C, with the significant lateral phase separation of the bilayer components only detectable in propylene glycol concentrations above 60% (w/w). We propose that the stability of lamellar phases of the cholesterol-containing liposomes formed in propylene glycol concentrations of up to 60% (w/w) represent potentially very valuable drug delivery vehicles for a variety of routes of administration.

Increasing extracellular matrix collagen level and MMP activity induces cyst development in polycystic kidney disease.

PubMed

Liu, Bin; Li, Chenghai; Liu, Zijuan; Dai, Zonghan; Tao, Yunxia

2012-09-11

Polycystic Kidney Disease (PKD) kidneys exhibit increased extracellular matrix (ECM) collagen expression and metalloproteinases (MMPs) activity. We investigated the role of these increases on cystic disease progression in PKD kidneys. We examined the role of type I collagen (collagen I) and membrane bound type 1 MMP (MT1-MMP) on cyst development using both in vitro 3 dimensional (3D) collagen gel culture and in vivo PCK rat model of PKD. We found that collagen concentration is critical in controlling the morphogenesis of MDCK cells cultured in 3D gels. MDCK cells did not form 3D structures at collagen I concentrations lower than 1 mg/ml but began forming tubules when the concentration reaches 1 mg/ml. Significantly, these cells began to form cyst when collagen I concentration reached to 1.2 mg/ml, and the ratios of cyst to tubule structures increased as the collagen I concentration increased. These cells exclusively formed cyst structures at a collagen I concentration of 1.8 mg/ml or higher. Overexpression of MT1-MMP in MDCK cells significantly induced cyst growth in 3D collagen gel culture. Conversely, inhibition of MMPs activity with doxycycline, a FDA approved pan-MMPs inhibitor, dramatically slowed cyst growth. More importantly, the treatment of PCK rats with doxycycline significantly decreased renal tubule cell proliferation and markedly inhibited the cystic disease progression. Our data suggest that increased collagen expression and MMP activity in PKD kidneys may induce cyst formation and expansion. Our findings also suggest that MMPs may serve as a therapeutic target for the treatment of human PKD.

Characterization of Mixed Polypeptide Colloidal Particles by Light Scattering

NASA Astrophysics Data System (ADS)

Shuman, Hannah E.; Gaeckle, Grace K.; Gavin, John; Holland, Nolan B.; Streletzky, Kiril A.

2014-03-01

Temperature-dependent polymer surfactants have been developed by connecting three elastin-like polypeptide (ELP) chains to a charged protein domain (foldon), forming a three-armed star polymer. At low temperatures the polymer is soluble, while at higher temperatures it forms micelles. The behavior of mixtures of the three-armed star ELP (E20-Foldon) and H40-Linear ELP chains was analyzed under different salt and protein concentrations and various foldon to linear ELP ratio using Depolarized Dynamic Light Scattering. It was expected that under certain conditions the pure E20-Foldon would form spherical micelles, which upon adding the linear ELP would change in size and possibly shape. The pure E20-Foldon indeed formed largely spherical micelles with Rh of 10-20nm in solutions with 15-100mM salt and protein concentration between 10 μM and 100 μM. For the mixtures of 50 μM E20-Foldon and varying concentrations of H40-Linear in 25mM of salt, it was discovered that low and high H40-Linear concentration (4 μM and 50 μM) had only one transition. For the mixtures with of 10 and 25 μM of H40-Linear the two distinct transition temperatures were observed by spectrophotometry. The first transition corresponded to significantly elongated diffusive particles of apparent Rh of 30-50nm, while the second transition corresponded to slightly anisotropic diffusive particles with apparent Rh of about 20nm. At all H40-Linear concentrations studied, diffusive particles were seen above the second transition. Their radius and ability to depolarize light increased with the increase of H40-Linear concentration.

The osteopontin-controlled switching of calcium oxalate monohydrate morphologies in artificial urine provides insights into the formation of papillary kidney stones.

PubMed

Langdon, Aaron; Grohe, Bernd

2016-10-01

The protein osteopontin (OPN) plays an important role in preventing the formation of calcium oxalate monohydrate (COM) kidney stones. To gain insight into these mechanisms, crystallization was induced by addition of human kidney OPN to artificial urine (ionic strength comparable to urine; without citrate), and the OPN-COM interaction studied using a combination of scanning electron (SEM) and confocal microscopy. By SEM, we found that increasing OPN concentrations formed large monoclinic penetration twins (no protein added) and, at higher concentrations (1-, 2μg/ml OPN), super and hyper twins with crystal habits not found in previous studies. For instance, the hyper twins indicate well-facetted gearwheel-like habits with "teeth" developed in all crystallographic directions. At OPN concentrations ≥2μg/ml, a switching to small dumbbell-shaped COM habits with fine-textured surfaces occurred. Confocal microscopy of these dumbbells indicates protein incorporation in almost the entire crystal structure (in contrast to facetted COM), proposing a threshold concentration of ∼2μg/ml OPN for the facetted to the non-facetted habit transformation. Both the gearwheel-like and the dumbbell-shaped habit are again found side-by-side (presumably triggered by OPN concentration gradients within the sample) in in-vitro formed conglomerates, which resemble cross-sections of papillary kidney stones. The abrupt transformation from facetted to non-facetted habits and the unique compliance of the two in-vitro formed habits with the two main morphologies found in papillary kidney stones propose that OPN is a main effector in direct stone-forming processes. Moreover, stone structures which exhibit these two morphologies side-by-side might serve as a novel indicator for OPN concentrations surrounding those structures. Copyright © 2016 Elsevier B.V. All rights reserved.

Serum Vitamin E Concentrations and Recovery of Physical Function During the Year After Hip Fracture

PubMed Central

Miller, Ram R.; Hicks, Gregory E.; Orwig, Denise L.; Hochberg, Marc C.; Semba, Richard D.; Yu-Yahiro, Janet A.; Ferrucci, Luigi; Magaziner, Jay; Shardell, Michelle D.

2011-01-01

Background. Poor nutritional status after hip fracture is common and may contribute to physical function decline. Low serum concentrations of vitamin E have been associated with decline in physical function among older adults, but the role of vitamin E in physical recovery from hip fracture has never been explored. Methods. Serum concentrations of α- and γ-tocopherol, the two major forms of vitamin E, were measured in female hip fracture patients from the Baltimore Hip Studies cohort 4 at baseline and at 2-, 6-, and 12-month postfracture follow-up visits. Four physical function measures—Six-Minute Walk Distance, Lower Extremity Gain Scale, Short Form-36 Physical Functioning Domain, and Yale Physical Activity Survey—were assessed at 2, 6, and 12 months postfracture. Generalized estimating equations modeled the relationship between baseline and time-varying serum tocopherol concentrations and physical function after hip fracture. Results. A total of 148 women aged 65 years and older were studied. After adjusting for covariates, baseline vitamin E concentrations were positively associated with Six-Minute Walk Distance, Lower Extremity Gain Scale, and Yale Physical Activity Survey scores (p < .1) and faster improvement in Lower Extremity Gain Scale and Yale Physical Activity Survey scores (p < .008). Time-varying vitamin E was also positively associated with Six-Minute Walk Distance, Lower Extremity Gain Scale, Yale Physical Activity Survey, and Short Form-36 Physical Functioning Domain (p < .03) and faster improvement in Six-Minute Walk Distance and Short Form-36 Physical Functioning Domain (p < .07). Conclusions. Serum concentrations of both α- and γ-tocopherol were associated with better physical function after hip fracture. Vitamin E may represent a potentially modifiable factor related to recovery of postfracture physical function. PMID:21486921

Myelin structures formed by thermotropic smectic liquid crystals

NASA Astrophysics Data System (ADS)

Peddireddy, Karthik Reddy; Kumar, Pramoda; Thutupalli, Shashi; Herminghaus, Stephan; Bahr, Christian

2014-03-01

We report on transient structures, formed by thermotropic smectic-A liquid crystals, resembling the myelin figures of lyotropic lamellar liquid crystals. The thermotropic myelin structures form during the solubilization of a smectic-A droplet in an aqueous phase containing a cationic surfactant at concentrations above the critical micelle concentration. Similar to the lyotropic myelin figures, the thermotropic myelins appear in an optical microscope as flexible tube-like structures growing at the smectic/aqueous interface. Polarizing microscopy and confocal fluorescence microscopy show that the smectic layers are parallel to the tube surface and form a cylindrically bent arrangement around a central line defect in the tube. We study the growth behavior of this new type of myelins and discuss similarities and differences to the classical lyotropic myelin figures.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thompson, M.A.; Schenter, G.K.

We present a hybrid quantum mechanical/molecular mechanical (QM/MM) model for microscopic solvation effects that includes polarizability in the MM region (QM/MMpol). QM/MMpol treatment of both ground and excited states is presented in the formalism. We present QM/MMpol analysis of the ground and electronic excited states of the bacteriochlorophyll b dimer (P) of the photosynthetic reaction center (RC) of Rhodopseudomonas viridis using the INDO/S method. The static-charge potential from the MM model of the RC alone causes Q{sub y1} to have significantly better agreement with the Stark effect results than isolated P. However, consideration of the protein polarization potential is furthermore » required to obtain more complete agreement with Stark effect experiments. Thus, we calculate a Q{sub y1} transition energy at 10826 cm{sup -1} with a ground to excited state change in dipole moment of 4.8 D; an absorption Stark effect angle of 43{degree}; a net shift of 0.15 electrons from the L subunit to the M subunit of P; and a linear dichroism angle (between the transition moment of Q{sub y1} and the pseudo-C{sub 2} axis of the RC) of 81{degree}. These results are in good agreement with experiment. Interestingly, we find that net CT increase is greater for Q{sub y1} than for the second excited state of P (Q{sub y2}), a result that we anticipated in an early model dimer study. 77 refs., 3 figs., 2 tabs.« less

Spin densities from subsystem density-functional theory: Assessment and application to a photosynthetic reaction center complex model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solovyeva, Alisa; Technical University Braunschweig, Institute for Physical and Theoretical Chemistry, Hans-Sommer-Str. 10, 38106 Braunschweig; Pavanello, Michele

2012-05-21

Subsystem density-functional theory (DFT) is a powerful and efficient alternative to Kohn-Sham DFT for large systems composed of several weakly interacting subunits. Here, we provide a systematic investigation of the spin-density distributions obtained in subsystem DFT calculations for radicals in explicit environments. This includes a small radical in a solvent shell, a {pi}-stacked guanine-thymine radical cation, and a benchmark application to a model for the special pair radical cation, which is a dimer of bacteriochlorophyll pigments, from the photosynthetic reaction center of purple bacteria. We investigate the differences in the spin densities resulting from subsystem DFT and Kohn-Sham DFT calculations.more » In these comparisons, we focus on the problem of overdelocalization of spin densities due to the self-interaction error in DFT. It is demonstrated that subsystem DFT can reduce this problem, while it still allows to describe spin-polarization effects crossing the boundaries of the subsystems. In practical calculations of spin densities for radicals in a given environment, it may thus be a pragmatic alternative to Kohn-Sham DFT calculations. In our calculation on the special pair radical cation, we show that the coordinating histidine residues reduce the spin-density asymmetry between the two halves of this system, while inclusion of a larger binding pocket model increases this asymmetry. The unidirectional energy transfer in photosynthetic reaction centers is related to the asymmetry introduced by the protein environment.« less

Structural and Epimeric Isomers of HPPH [3-Devinyl 3-{1-(1-hexyloxy) ethyl}pyropheophorbide-a]: Effects on Uptake and Photodynamic Therapy of Cancer.

PubMed

Saenz, Courtney; Cheruku, Ravindra R; Ohulchanskyy, Tymish Y; Joshi, Penny; Tabaczynski, Walter A; Missert, Joseph R; Chen, Yihui; Pera, Paula; Tracy, Erin; Marko, Aimee; Rohrbach, Daniel; Sunar, Ulas; Baumann, Heinz; Pandey, Ravindra K

2017-04-21

The tetrapyrrole structure of porphyrins used as photosentizing agents is thought to determine uptake and retention by malignant epithelial cancer cells. To assess the contribution of the oxidized state of individual rings to these cellular processes, bacteriochlorophyll a was converted into the ring "D" reduced 3-devinyl-3-[1-(1-hexyloxy)ethyl]pyropheophorbide-a (HPPH) and the corresponding ring "B" reduced isomer (iso-HPPH). The carboxylic acid analogs of both ring "B" and ring "D" reduced isomers showed several-fold higher accumulation into the mitochondria and endoplasmic reticulum by primary culture of human lung and head and neck cancer cells than the corresponding methyl ester analogs that localize primarily to granular vesicles and to a lesser extent to mitochondria. However, long-term cellular retention of these compounds exhibited an inverse relationship with tumor cells generally retaining better the methyl-ester derivatives. In vivo distribution and tumor uptake was evaluated in the isogenic model of BALB/c mice bearing Colon26 tumors using the respective 14 C-labeled analogs. Both carboxylic acid derivatives demonstrated similar intracellular localization and long-term tumor cure with no significant skin phototoxicity. PDT-mediated tumor action involved vascular damage, which was confirmed by a reduction in blood flow and immunohistochemical assessment of damage to the vascular endothelium. The HPPH stereoisomers (epimers) showed identical uptake (in vitro & in vivo), intracellular retention and photoreaction.

Influence of Force Fields and Quantum Chemistry Approach on Spectral Densities of BChl a in Solution and in FMO Proteins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandrasekaran, Suryanarayanan; Aghtar, Mortaza; Valleau, Stéphanie

2015-08-06

Studies on light-harvesting (LH) systems have attracted much attention after the finding of long-lived quantum coherences in the exciton dynamics of the Fenna–Matthews–Olson (FMO) complex. In this complex, excitation energy transfer occurs between the bacteriochlorophyll a (BChl a) pigments. Two quantum mechanics/molecular mechanics (QM/MM) studies, each with a different force-field and quantum chemistry approach, reported different excitation energy distributions for the FMO complex. To understand the reasons for these differences in the predicted excitation energies, we have carried out a comparative study between the simulations using the CHARMM and AMBER force field and the Zerner intermediate neglect of differential orbitalmore » (ZINDO)/S and time-dependent density functional theory (TDDFT) quantum chemistry methods. The calculations using the CHARMM force field together with ZINDO/S or TDDFT always show a wider spread in the energy distribution compared to those using the AMBER force field. High- or low-energy tails in these energy distributions result in larger values for the spectral density at low frequencies. A detailed study on individual BChl a molecules in solution shows that without the environment, the density of states is the same for both force field sets. Including the environmental point charges, however, the excitation energy distribution gets broader and, depending on the applied methods, also asymmetric. The excitation energy distribution predicted using TDDFT together with the AMBER force field shows a symmetric, Gaussian-like distribution.« less

Quenching Capabilities of Long-Chain Carotenoids in Light-Harvesting-2 Complexes from Rhodobacter sphaeroides with an Engineered Carotenoid Synthesis Pathway.

PubMed

Dilbeck, Preston L; Tang, Qun; Mothersole, David J; Martin, Elizabeth C; Hunter, C Neil; Bocian, David F; Holten, Dewey; Niedzwiedzki, Dariusz M

2016-06-23

Six light-harvesting-2 complexes (LH2) from genetically modified strains of the purple photosynthetic bacterium Rhodobacter (Rb.) sphaeroides were studied using static and ultrafast optical methods and resonance Raman spectroscopy. These strains were engineered to incorporate carotenoids for which the number of conjugated groups (N = NC═C + NC═O) varies from 9 to 15. The Rb. sphaeroides strains incorporate their native carotenoids spheroidene (N = 10) and spheroidenone (N = 11), as well as longer-chain analogues including spirilloxanthin (N = 13) and diketospirilloxantion (N = 15) normally found in Rhodospirillum rubrum. Measurements of the properties of the carotenoid first singlet excited state (S1) in antennas from the Rb. sphaeroides set show that carotenoid-bacteriochlorophyll a (BChl a) interactions are similar to those in LH2 complexes from various other bacterial species and thus are not significantly impacted by differences in polypeptide composition. Instead, variations in carotenoid-to-BChl a energy transfer are primarily regulated by the N-determined energy of the carotenoid S1 excited state, which for long-chain (N ≥ 13) carotenoids is not involved in energy transfer. Furthermore, the role of the long-chain carotenoids switches from a light-harvesting supporter (via energy transfer to BChl a) to a quencher of the BChl a S1 excited state B850*. This quenching is manifested as a substantial (∼2-fold) reduction of the B850* lifetime and the B850* fluorescence quantum yield for LH2 housing the longest carotenoids.

Effects of Calcium Ions on the Thermostability and Spectroscopic Properties of the LH1-RC Complex from a New Thermophilic Purple Bacterium Allochromatium tepidum.

PubMed

Kimura, Yukihiro; Lyu, Shuwen; Okoshi, Akira; Okazaki, Koudai; Nakamura, Natsuki; Ohashi, Akira; Ohno, Takashi; Kobayashi, Manami; Imanishi, Michie; Takaichi, Shinichi; Madigan, Michael T; Wang-Otomo, Zheng-Yu

2017-05-18

The light harvesting-reaction center (LH1-RC) complex from a new thermophilic purple sulfur bacterium Allochromatium (Alc.) tepidum was isolated and characterized by spectroscopic and thermodynamic analyses. The purified Alc. tepidum LH1-RC complex showed a high thermostability comparable to that of another thermophilic purple sulfur bacterium Thermochromatium tepidum, and spectroscopic characteristics similar to those of a mesophilic bacterium Alc. vinosum. Approximately 4-5 Ca 2+ per LH1-RC were detected by inductively coupled plasma atomic emission spectroscopy and isothermal titration calorimetry. Upon removal of Ca 2+ , the denaturing temperature of the Alc. tepidum LH1-RC complex dropped accompanied by a blue-shift of the LH1 Q y absorption band. The effect of Ca 2+ was also observed in the resonance Raman shift of the C3-acetyl νC═O band of bacteriochlorophyll-a, indicating changes in the hydrogen-bonding interactions between the pigment and LH1 polypeptides. Thermodynamic parameters for the Ca 2+ -binding to the Alc. tepidum LH1-RC complex indicated that this reaction is predominantly driven by the largely favorable electrostatic interactions that counteract the unfavorable negative entropy change. Our data support a hypothesis that Alc. tepidum may be a transitional organism between mesophilic and thermophilic purple bacteria and that Ca 2+ is one of the major keys to the thermostability of LH1-RC complexes in purple bacteria.

Accurate Differentiation of Carotenoid Pigments Using Flight Representative Raman Spectrometers.

PubMed

Malherbe, Cedric; Hutchinson, Ian B; McHugh, Melissa; Ingley, Richard; Jehlička, Jan; Edwards, Howell G M

2017-04-01

Raman spectrometers will be utilized on two Mars rover missions, ExoMars and Mars 2020, in the near future, to search for evidence of life and habitable geological niches on Mars. Carotenoid pigments are recognized target biomarkers, and as they are highly active in Raman spectroscopy, they can be readily used to characterize the capabilities of space representative instrumentation. As part of the preparatory work being performed for the ExoMars mission, a gypsum crust colonized by microorganisms was interrogated with commercial portable Raman instruments and a flight representative Raman laser spectrometer. Four separate layers, each exhibiting different coloration resulting from specific halophilic microorganism activities within the gypsum crust, were studied by using two excitation wavelengths: 532 and 785 nm. Raman or fluorescence data were readily obtained during the present study. Gypsum, the main constituent of the crust, was detected with both excitation wavelengths, while the resonance Raman signal associated with carotenoid pigments was only detected with a 532 nm excitation wavelength. The fluorescence originating from bacteriochlorophyll a was found to overwhelm the Raman signal for the layer colonized by sulfur bacteria when interrogated with a 785 nm excitation wavelength. Finally, it was demonstrated that portable instruments and the prototype were capable of detecting a statistically significant difference in band positions of carotenoid signals between the sample layers. Key Words: Gypsum-Raman spectrometers-Carotenoids-ExoMars-Mars exploration-Band position shift. Astrobiology 17, 351-362.

High-pressure and stark hole-burning studies of chlorosome antennas from Chlorobium tepidum.

PubMed

Wu, H M; Rätsep, M; Young, C S; Jankowiak, R; Blankenship, R E; Small, G J

2000-09-01

Results from high-pressure and Stark hole-burning experiments on isolated chlorosomes from the green sulfur bacterium Chlorobium tepidum are presented, as well as Stark hole-burning data for bacteriochlorophyll c (BChl c) monomers in a poly(vinyl butyral) copolymer film. Large linear pressure shift rates of -0.44 and -0.54 cm(-1)/MPa were observed for the chlorosome BChl c Q(y)-band at 100 K and the lowest Q(y)-exciton level at 12 K, respectively. It is argued that approximately half of the latter shift rate is due to electron exchange coupling between BChl c molecules. The similarity between the above shift rates and those observed for the B875 and B850 BChl a rings of the light-harvesting complexes of purple bacteria is emphasized. For BChl c monomer, fDeltamu++ = 0.35 D, where Deltamu+ is the dipole moment change for the Q(y) transition and f is the local field correction factor. The data establish that Deltamu+ is dominated by the matrix-induced contribution. The change in polarizability (Deltaalpha) for the Q(y) transition of the BChl c monomer is estimated at 19 A(3), which is essentially identical to that of the Chl a monomer. Interestingly, no Stark effects were observed for the lowest exciton level of the chlorosomes (maximum Stark field of 10(5) V/cm). Possible explanations for this are given, and these include consideration of structural models for the chlorosome BChl c aggregates.

Increasing the open-circuit voltage of photoprotein-based photoelectrochemical cells by manipulation of the vacuum potential of the electrolytes.

PubMed

Tan, Swee Ching; Crouch, Lucy I; Mahajan, Sumeet; Jones, Michael R; Welland, Mark E

2012-10-23

The innately highly efficient light-powered separation of charge that underpins natural photosynthesis can be exploited for applications in photoelectrochemistry by coupling nanoscale protein photoreaction centers to man-made electrodes. Planar photoelectrochemical cells employing purple bacterial reaction centers have been constructed that produce a direct current under continuous illumination and an alternating current in response to discontinuous illumination. The present work explored the basis of the open-circuit voltage (V(OC)) produced by such cells with reaction center/antenna (RC-LH1) proteins as the photovoltaic component. It was established that an up to ~30-fold increase in V(OC) could be achieved by simple manipulation of the electrolyte connecting the protein to the counter electrode, with an approximately linear relationship being observed between the vacuum potential of the electrolyte and the resulting V(OC). We conclude that the V(OC) of such a cell is dependent on the potential difference between the electrolyte and the photo-oxidized bacteriochlorophylls in the reaction center. The steady-state short-circuit current (J(SC)) obtained under continuous illumination also varied with different electrolytes by a factor of ~6-fold. The findings demonstrate a simple way to boost the voltage output of such protein-based cells into the hundreds of millivolts range typical of dye-sensitized and polymer-blend solar cells, while maintaining or improving the J(SC). Possible strategies for further increasing the V(OC) of such protein-based photoelectrochemical cells through protein engineering are discussed.

Effects of oxidants and reductants on the efficiency of excitation transfer in green photosynthetic bacteria

NASA Technical Reports Server (NTRS)

Wang, J.; Brune, D. C.; Blankenship, R. E.

1990-01-01

The efficiency of energy transfer in chlorosome antennas in the green sulfur bacteria Chlorobium vibrioforme and Chlorobium limicola was found to be highly sensitive to the redox potential of the suspension. Energy transfer efficiencies were measured by comparing the absorption spectrum of the bacteriochlorophyll c or d pigments in the chlorosome to the excitation spectrum for fluorescence arising from the chlorosome baseplate and membrane-bound antenna complexes. The efficiency of energy transfer approaches 100% at low redox potentials induced by addition of sodium dithionite or other strong reductants, and is lowered to 10-20% under aerobic conditions or after addition of a variety of membrane-permeable oxidizing agents. The redox effect on energy transfer is observed in whole cells, isolated membranes and purified chlorosomes, indicating that the modulation of energy transfer efficiency arises within the antenna complexes and is not directly mediated by the redox state of the reaction center. It is proposed that chlorosomes contain a component that acts as a highly quenching center in its oxidized state, but is an inefficient quencher when reduced by endogenous or exogenous reductants. This effect may be a control mechanism that prevents cellular damage resulting from reaction of oxygen with reduced low-potential electron acceptors found in the green sulfur bacteria. The redox modulation effect is not observed in the green gliding bacterium Chloroflexus aurantiacus, which contains chlorosomes but does not contain low-potential electron acceptors.

Gel phase formation in dilute triblock copolyelectrolyte complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Srivastava, Samanvaya; Andreev, Marat; Levi, Adam E.

Assembly of oppositely charged triblock copolyelectrolytes into phase-separated gels at low polymer concentrations (<1% by mass) has been observed in scattering experiments and molecular dynamics simulations. Here we show that in contrast to uncharged, amphiphilic block copolymers that form discrete micelles at low concentrations and enter a phase of strongly interacting micelles in a gradual manner with increasing concentration, the formation of a dilute phase of individual micelles is prevented in polyelectrolyte complexation-driven assembly of triblock copolyelectrolytes. Gel phases form and phase separate almost instantaneously on solvation of the copolymers. Furthermore, molecular models of self-assembly demonstrate the presence of oligo-chainmore » aggregates in early stages of copolyelectrolyte assembly, at experimentally unobservable polymer concentrations. Our discoveries contribute to the fundamental understanding of the structure and pathways of complexation-driven assemblies, and raise intriguing prospects for gel formation at extraordinarily low concentrations, with applications in tissue engineering, agriculture, water purification and theranostics.« less

Gel phase formation in dilute triblock copolyelectrolyte complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Srivastava, Samanvaya; Andreev, Marat; Levi, Adam E.

Assembly of oppositely charged triblock copolyelectrolytes into phase-separated gels at low polymer concentrations (<1% by mass) has been observed in scattering experiments and molecular dynamics simulations. Here we show that in contrast to uncharged, amphiphilic block copolymers that form discrete micelles at low concentrations and enter a phase of strongly interacting micelles in a gradual manner with increasing concentration, the formation of a dilute phase of individual micelles is prevented in polyelectrolyte complexation-driven assembly of triblock copolyelectrolytes. Gel phases form and phase separate almost instantaneously on solvation of the copolymers. Furthermore, molecular models of self-assembly demonstrate the presence of oligo-chainmore » aggregates in early stages of copolyelectrolyte assembly, at experimentally unobservable polymer concentrations. Finally, our discoveries contribute to the fundamental understanding of the structure and pathways of complexation-driven assemblies, and raise intriguing prospects for gel formation at extraordinarily low concentrations, with applications in tissue engineering, agriculture, water purification and theranostics.« less

Gel phase formation in dilute triblock copolyelectrolyte complexes

DOE PAGES

Srivastava, Samanvaya; Andreev, Marat; Levi, Adam E.; ...

2017-02-23

Assembly of oppositely charged triblock copolyelectrolytes into phase-separated gels at low polymer concentrations (<1% by mass) has been observed in scattering experiments and molecular dynamics simulations. Here we show that in contrast to uncharged, amphiphilic block copolymers that form discrete micelles at low concentrations and enter a phase of strongly interacting micelles in a gradual manner with increasing concentration, the formation of a dilute phase of individual micelles is prevented in polyelectrolyte complexation-driven assembly of triblock copolyelectrolytes. Gel phases form and phase separate almost instantaneously on solvation of the copolymers. Furthermore, molecular models of self-assembly demonstrate the presence of oligo-chainmore » aggregates in early stages of copolyelectrolyte assembly, at experimentally unobservable polymer concentrations. Finally, our discoveries contribute to the fundamental understanding of the structure and pathways of complexation-driven assemblies, and raise intriguing prospects for gel formation at extraordinarily low concentrations, with applications in tissue engineering, agriculture, water purification and theranostics.« less

Thin film concentrator panel development

NASA Technical Reports Server (NTRS)

Zimmerman, D. K.

1982-01-01

The development and testing of a rigid panel concept that utilizes a thin film reflective surface for application to a low-cost point-focusing solar concentrator is discussed. It is shown that a thin film reflective surface is acceptable for use on solar concentrators, including 1500 F applications. Additionally, it is shown that a formed steel sheet substrate is a good choice for concentrator panels. The panel has good optical properties, acceptable forming tolerances, environmentally resistant substrate and stiffeners, and adaptability to low to mass production rates. Computer simulations of the concentrator optics were run using the selected reflector panel design. Experimentally determined values for reflector surface specularity and reflectivity along with dimensional data were used in the analysis. The simulations provided intercept factor and net energy into the aperture as a function of aperture size for different surface errors and pointing errors. Point source and Sun source optical tests were also performed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eckstein, Sebastian; Hintermeier, Peter H.; Olarte, Mariefel V.

The hydronium ion normalized reaction rate in aqueous phase alkylation of phenol with ethanol on H-MFI zeolites increases with decreasing concentration of acid sites. Higher rates are caused by higher concentrations of phenol in the zeolite pores, as the concentration of hydronium ions generated by zeolite Brønsted acid sites decreases. Considering the different concentrations of reacting species it is shown that the intrinsic rate constant for alkylation is independent of the concentration of hydronium ions in the zeolite pores. Alkylation at the aromatic ring of phenol and of toluene as well as O-alkylation of phenol have the same activation energy,more » 104 ± 5 kJ/mol. This is energetic barrier to form the ethyl carbenium ion from ethanol associated to the hydronium ion. Thus, in both the reaction pathways the catalyst involves a carbenium ion, which forms a bond to a nucleophilic oxygen (ether formation) or carbon (alkylation).« less

Gel Phase Formation in Dilute Triblock Copolyelectrolyte Complexes

NASA Astrophysics Data System (ADS)

Srivastava, Samanvaya; Andreev, Marat; Prabhu, Vivek; de Pablo, Juan; Tirrell, Matthew

Assembly of oppositely charged triblock copolyelectrolytes into phase-separated gels at extremely low polymer concentrations (<1 % by mass) has been observed in scattering experiments and molecular dynamics simulations. In contrast to uncharged, amphiphilic block copolymers that form discrete micelles at low concentrations and enter a phase of strongly interacting micelles in a gradual manner with increasing polymer concentrations, the formation of a dilute phase of individual micelles is prevented in polyelectrolyte complexation-driven assemblies of triblock copolyelectrolytes. Gel phases form and phase separate almost instantaneously upon solvation of the copolymers. Furthermore, molecular models of self-assembly demonstrate the presence of oligo-chain aggregates in early stages of triblock copolyelectrolyte assembly, at experimentally unobservable polymer concentrations. Our discoveries not only contribute to our fundamental understanding of the structure and pathways of complexation driven assemblies, but also raise intriguing prospects for formation of gel structures at extraordinarily low concentrations, with applications in tissue engineering, agriculture, water purification and theranostics.

Gel phase formation in dilute triblock copolyelectrolyte complexes

NASA Astrophysics Data System (ADS)

Srivastava, Samanvaya; Andreev, Marat; Levi, Adam E.; Goldfeld, David J.; Mao, Jun; Heller, William T.; Prabhu, Vivek M.; de Pablo, Juan J.; Tirrell, Matthew V.

2017-02-01

Assembly of oppositely charged triblock copolyelectrolytes into phase-separated gels at low polymer concentrations (<1% by mass) has been observed in scattering experiments and molecular dynamics simulations. Here we show that in contrast to uncharged, amphiphilic block copolymers that form discrete micelles at low concentrations and enter a phase of strongly interacting micelles in a gradual manner with increasing concentration, the formation of a dilute phase of individual micelles is prevented in polyelectrolyte complexation-driven assembly of triblock copolyelectrolytes. Gel phases form and phase separate almost instantaneously on solvation of the copolymers. Furthermore, molecular models of self-assembly demonstrate the presence of oligo-chain aggregates in early stages of copolyelectrolyte assembly, at experimentally unobservable polymer concentrations. Our discoveries contribute to the fundamental understanding of the structure and pathways of complexation-driven assemblies, and raise intriguing prospects for gel formation at extraordinarily low concentrations, with applications in tissue engineering, agriculture, water purification and theranostics.

The dynamic quiet solar corona: 4 days of joint observing with MDI and EIT

NASA Technical Reports Server (NTRS)

Schrijver, C. J.; Shine, R. A.; Hurlburt, N. E.; Tarbell, T. D.; Lemen, J. R.

1997-01-01

The analysis of a sequence of joint extreme ultraviolet imaging telescope (EIT) Fe XII and Michelson Doppler imager (MDI) magnetogram observations of the quiet sun near disk center is presented. It was found that: all the emerging flux above the threshold of approximately 10(sup 17) Mx is associated with enhanced coronal emissions; loop systems between the polarities in ephemeral regions remain visible up to separations of 10000 up to 30000 km; brightenings between approaching opposite polarity network concentrations form when the concentrations are between 5000 and 25000 km apart, and that faint connections up to 40000 km in length form as sets of concentrations of the same polarity coagulate. The coronal emission over patches of the quiet sun depends on the total flux in connected concentrations, on their distance and on the positions and strengths of neighboring concentrations.

Mercury in soils of the agro-industrial zone of Zima city (Irkutsk oblast)

NASA Astrophysics Data System (ADS)

Butakov, E. V.; Kuznetsov, P. V.; Kholodova, M. S.; Grebenshchikova, V. I.

2017-11-01

Data on mercury concentrations in soils of the agro-industrial zone of Zima city in Irkutsk oblast are discussed. It is shown that mercury concentrations in the plow horizon of studied soils exceed background values. The distribution pattern of mercury in soils of the investigated area is characterized. The revealed mercury anomalies are allocated to the industrial zone of the Sayanskkhimprom plant. The combined analysis of data on mercury concentrations in the plow and subplow horizons and on the chemical composition of snow indicates that mercury enters the soil mainly with atmospheric precipitation and is present there in the adsorbed form. The correlation analysis indicates that the local thermal power station plays a significant role as the source of mercury emission to the atmosphere. Close relationships between mercury concentrations and concentrations of mobile forms of elements attest to the presence of mobile organomineral mercury compounds in the studied soils.

Phytoremediation of Mercury and Organomercurials in Chloroplast Transgenic Plants: Enhanced Root Uptake, Translocation to Shoots, and Volatilization

PubMed Central

Hussein, Hussein S.; Ruiz, Oscar N.; Terry, Norman; Daniell, Henry

2008-01-01

Transgenic tobacco plants engineered with bacterial merA and merB genes via the chloroplast genome were investigated to study the uptake, translocation of different forms of mercury (Hg) from roots to shoots, and their volatilization. Untransformed plants, regardless of the form of Hg supplied, reached a saturation point at 200 µM of phenylmercuric acetate (PMA) or HgCl2, accumulating Hg concentrations up to 500 µg g−1 with significant reduction in growth. In contrast, chloroplast transgenic lines continued to grow well with Hg concentrations in root tissues up to 2000 µg g−1. Chloroplast transgenic lines accumulated both the organic and inorganic Hg forms to levels surpassing the concentrations found in the soil. The organic-Hg form was absorbed and translocated more efficiently than the inorganic-Hg form in transgenic lines, whereas no such difference was observed in untransformed plants. Chloroplast-transgenic lines showed about 100-fold increase in the efficiency of Hg accumulation in shoots compared to untransformed plants. This is the first report of such high levels of Hg accumulation in green leaves or tissues. Transgenic plants attained a maximum rate of elemental-Hg volatilization in two days when supplied with PMA and in three days when supplied with inorganic-Hg, attaining complete volatilization within a week. The combined expression of merAB via the chloroplast genome enhanced conversion of Hg2+ into Hg,0 conferred tolerance by rapid volatilization and increased uptake of different forms of mercury, surpassing the concentrations found in the soil. These investigations provide novel insights for improvement of plant tolerance and detoxification of mercury. PMID:18200876

Characterization of Nanoparticles and Colloids in Aquatic Systems 1. Small Angle Neutron Scattering Investigations of Suwannee River Fulvic Acid Aggregates in Aqueous Solutions

NASA Astrophysics Data System (ADS)

Diallo, Mamadou S.; Glinka, Charles J.; Goddard, William A.; Johnson, James H.

2005-10-01

Fulvic acids (FA) and humic acids (HA) constitute 30-50% of dissolved organic matter in natural aquatic systems. In aqueous solutions, a commonly accepted view is that FA and HA exist as soluble macroligands at low concentration and as supramolecular aggregates at higher concentration. The size, shape and structure of these aggregates are still the subject of ongoing debate in the environmental chemistry literature. In this article, we use small angle neutron scattering (SANS) to assess the effects of solute concentration, solution pH and background electrolyte (NaCl) concentration on the structures of Suwannee River FA (SRFA) aggregates in D2O. The qualitative features of the SANS curves and data analysis are not consistent with the view point that SRFA forms micelle-like aggregates as its concentration in aqueous solution increases. We find that SRFA forms fractal aggregates in D20 with size greater than 242 nm. The SRFA aggregates undergo a significant degree of restructuring in compactness as solution pH, solute concentration and NaCl concentration increase.

Evaluation of Aqueous Film Forming Foams (AFFF) on Deck Fires.

DTIC Science & Technology

1983-10-01

effectiveness. The AFFF’s tested were 3% and 6% AFFF concentrates meeting Military Specification MIL - F - 24385 , two commercial 37 AFFF concentrates, two polar...percent AFFF meeting the requirements of MIL - F - 24385 Type 6 is the only firefighting foam concentrate authorized for use on Coast Guard cutters and boats...Specification MIL - F - 24385 , two commercial 3% AFFF concentrates, two polar solvent resistant 3% AFFF concentrates, and a 1% commercial AFFF concentrate. All the

76 FR 9810 - Agency Information Collection Activities: Comment Request for the Ferrous Metals Surveys (17 Forms)

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-22

... Activities: Comment Request for the Ferrous Metals Surveys (17 Forms) AGENCY: U.S. Geological Survey (USGS... with domestic consumption data of 13 ores, concentrates, metals, and ferroalloys, some of which are...-0068. Form Number: Various (17 forms). Title: Ferrous Metals Surveys. Type of Request: Extension of a...

The Effect of Lysozyme on Reducing Biofilms by Staphylococcus aureus, Pseudomonas aeruginosa, and Gardnerella vaginalis: An In Vitro Examination.

PubMed

Hukić, Mirsada; Seljmo, Dzenita; Ramovic, Amra; Ibrišimović, Monia Avdić; Dogan, Serkan; Hukic, Jasna; Bojic, Elma Feric

2018-05-01

Two basic questions about lysozyme activities on the selected microorganisms were investigated, namely whether lysozyme inhibits biofilm production and which concentrations of the enzyme have the ability to change the natural biofilm producing capacity of different strains of Staphylococcus aureus (methicillin sensitive and resistant), Streptococcus pyogenes, Pseudomonas aeruginosa, and Gardnerella vaginalis. The effect of lysozyme on biofilm formation capacities of 16 strains of selected microorganisms was investigated, whereby four testing replicates have been performed in vitro using the Test Tube method, and the potential of lysozyme to change biofilm forming capacities depending on its concentration, species, and strains of microorganisms is demonstrated. A lysozyme concentration of 30 μg/ml indicated to have the highest inhibiting effect on all tested microorganisms. Furthermore, G. vaginalis was the most sensitive of them all, as its biofilm formation was inhibited in the presence of as low as 2.5 μg/ml of lysozyme. At enzyme concentrations of 7.5-50 μg/ml (with the exception of 30 μg/ml) the biofilm forming capacities of P. aeruginosa were enhanced. Depending on the strain of P. aeruginosa, the total biofilm quantity was either reduced or unaffected at lysozyme concentrations of 2.5, 5, 7.5, and 30 μg/ml. In contrast, lysozyme concentrations below 15 or 20 μg/ml did not affect or increase the volume of biofilm formation, while higher concentrations (15, 20, 25 μg/ml) reduced biofilm formation by 50% (3/6) and 30 μg/ml of biofilm reduced biofilm forming capacity of S. aureus by 100% (6/6). The results of this study are a strong foundation for further research on lysozyme as a modulator of the biofilm forming capacity of different species with the potential to aid in the development of new drugs for the treatment of oral and vaginal infections.

Electrospun cross linked rosin fibers

NASA Astrophysics Data System (ADS)

Baek, Woo-il; Nirmala, R.; Barakat, Nasser A. M.; El-Newehy, Mohamed H.; Al-Deyab, Salem S.; Kim, Hak Yong

2011-12-01

In this study, we describe the first reported preparation of rosin in fiber form through use of an electrospinning technique utilizing various solvent systems. The polymer concentration of the formed fiber was studied by using various solvents such as chloroform, ethanol, N-N dimethylformamide (DMF), tetrahydrofuran (THF), acetone, and methylene chloride (MC). An electrospray of the solution resulted in the beaded form of the rosin. By varying the polymer concentration with MC, we were then able to obtain uniform fibers. However, the fibers exhibited large diameter. We believe that it is possible to reduce the diameter of the rosin fibers through appropriate selection of electrospinning parameters. In addition, the morphological transitions from beads, to beaded fiber, to fiber were studied at different polymer concentrations. We propose a possible physical cross linking mechanism for the formation of rosin fibers during the electrospinning process. Our results demonstrate the feasibility of producing fiber nanostructures of rosin by using an electrospinning technique.

Dependence of Morphology of SiOx Nanowires on the Supersaturation of Au-Si Alloy Liquid Droplets Formed on the Au-Coated Si Substrate

NASA Astrophysics Data System (ADS)

Zhang, Han; Li, Ji-Xue; Jin, Ai-Zi; Zhang, Ze

2001-11-01

A thermodynamic theory about the dependence of morphology of SiOx nanowires on the super-saturation of alloy liquid droplets has been proposed on the basis of the vapour-liquid-solid growth mechanism and has been supported experimentally. By changing the Si concentration in the Au-Si liquid droplets formed on the Au-coated Si substrate, firework-, tulip- and bud-shaped SiOx nanowires were synthesized by a thermal evaporation method and distributed concentrically around some void defects in the Si substrate. Voids were formed underneath the surface of the Si substrate during the thermal evaporation at 850°C and resulted in the Si-concentration deficient thus different saturation of Au-Si droplets. Electron microscopy analysis showed that the nanowires had an amorphous structure and were terminated by Au-Si particles.

Reinforcement for Stretch Formed Sheet Metal

NASA Technical Reports Server (NTRS)

Lea, J. B.; Baxter, C. R.

1983-01-01

Tearing of aluminum sheet metal durinng stretch forming prevented by flame spraying layer of aluminum on edges held in stretch-forming machine. Technique improves grip of machine on metal and reinforced sheet better able to with stand concentration of force in vicinity of grips.

Pharmacokinetics of the prototype and hydrolyzed carboxylic forms of ginkgolides A, B, and K administered as a ginkgo diterpene lactones meglumine injection in beagle dogs.

PubMed

Wang, Shu-Yao; A, Ji-Ye; Fei, Fei; Geng, Jian-Liang; Peng, Ying; Ouyang, Bing-Chen; Wang, Pei; Jin, Xiao-Liang; Zhao, Yu-Qing; Wang, Jian-Kun; Geng, Ting; Li, Yan-Jing; Huang, Wen-Zhe; Wang, Zhen-Zhong; Xiao, Wei; Wang, Guang-Ji

2017-10-01

Ginkgo diterpene lactones meglumine injection (GDLI) is a commercially available product used for neuroprotection. However, the pharmacokinetic properties of the prototypes and hydrolyzed carboxylic forms of the primary components in GDLI, i.e., ginkgolide A (GA), ginkgolide B (GB), and ginkgolide K (GK), have never been fully evaluated in beagle dogs. In this work, a simple, sensitive, and reliable method based on ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) was developed, and the prototypes and total amounts of GA, GB, and GK were determined in beagle dog plasma. The plasma concentrations of the hydrolyzed carboxylic forms were calculated by subtracting the prototype concentrations from the total lactone concentrations. For the first time, the pharmacokinetics of GA, GB, and GK were fully assessed in three forms, i.e., the prototypes, the hydrolyzed carboxylic forms, and the total amounts, after intravenous administration of GDLI in beagle dogs. It was shown that ginkgolides primarily existed in the hydrolyzed form in plasma, and the ratio of hydrolysates to prototype forms of GA and GB decreased gradually to a homeostatic ratio. All of the three forms of the three ginkgolides showed linear exposure of AUC to the dosages. GA, GB, and GK showed a constant half-life approximately 2.7, 3.4, and 1.2 h, respectively, which were consistent for the forms at three dose levels (0.3, 1.0, and 3.0 mg·kg -1 ) and after a consecutive injection of GDLI for 7 days (1.0 mg·kg -1 ). Copyright © 2017 China Pharmaceutical University. Published by Elsevier B.V. All rights reserved.

Compatible validated spectrofluorimetric and spectrophotometric methods for determination of vildagliptin and saxagliptin by factorial design experiments.

PubMed

Abdel-Aziz, Omar; Ayad, Miriam F; Tadros, Mariam M

2015-04-05

Simple, selective and reproducible spectrofluorimetric and spectrophotometric methods have been developed for the determination of vildagliptin and saxagliptin in bulk and their pharmaceutical dosage forms. The first proposed spectrofluorimetric method is based on the dansylation reaction of the amino group of vildagliptin with dansyl chloride to form a highly fluorescent product. The formed product was measured spectrofluorimetrically at 455 nm after excitation at 345 nm. Beer's law was obeyed in a concentration range of 100-600 μg ml(-1). The second proposed spectrophotometric method is based on the charge transfer complex of saxagliptin with tetrachloro-1,4-benzoquinone (p-chloranil). The formed charge transfer complex was measured spectrophotometrically at 530 nm. Beer's law was obeyed in a concentration range of 100-850 μg ml(-1). The third proposed spectrophotometric method is based on the condensation reaction of the primary amino group of saxagliptin with formaldehyde and acetyl acetone to form a yellow colored product known as Hantzsch reaction, measured at 342.5 nm. Beer's law was obeyed in a concentration range of 50-300 μg ml(-1). All the variables were studied to optimize the reactions' conditions using factorial design. The developed methods were validated and proved to be specific and accurate for quality control of vildagliptin and saxagliptin in their pharmaceutical dosage forms. Copyright © 2015. Published by Elsevier B.V.

Compatible validated spectrofluorimetric and spectrophotometric methods for determination of vildagliptin and saxagliptin by factorial design experiments

NASA Astrophysics Data System (ADS)

Abdel-Aziz, Omar; Ayad, Miriam F.; Tadros, Mariam M.

2015-04-01

Simple, selective and reproducible spectrofluorimetric and spectrophotometric methods have been developed for the determination of vildagliptin and saxagliptin in bulk and their pharmaceutical dosage forms. The first proposed spectrofluorimetric method is based on the dansylation reaction of the amino group of vildagliptin with dansyl chloride to form a highly fluorescent product. The formed product was measured spectrofluorimetrically at 455 nm after excitation at 345 nm. Beer's law was obeyed in a concentration range of 100-600 μg ml-1. The second proposed spectrophotometric method is based on the charge transfer complex of saxagliptin with tetrachloro-1,4-benzoquinone (p-chloranil). The formed charge transfer complex was measured spectrophotometrically at 530 nm. Beer's law was obeyed in a concentration range of 100-850 μg ml-1. The third proposed spectrophotometric method is based on the condensation reaction of the primary amino group of saxagliptin with formaldehyde and acetyl acetone to form a yellow colored product known as Hantzsch reaction, measured at 342.5 nm. Beer's law was obeyed in a concentration range of 50-300 μg ml-1. All the variables were studied to optimize the reactions' conditions using factorial design. The developed methods were validated and proved to be specific and accurate for quality control of vildagliptin and saxagliptin in their pharmaceutical dosage forms.

Distribution of selenium in zebrafish larvae after exposure to organic and inorganic selenium forms.

PubMed

Dolgova, N V; Hackett, M J; MacDonald, T C; Nehzati, S; James, A K; Krone, P H; George, G N; Pickering, I J

2016-03-01

Selenium is an essential micronutrient for many organisms, and in vertebrates has a variety of roles associated with protection from reactive oxygen species. Over the past two decades there have been conflicting reports upon human health benefits and detriments arising from consumption of selenium dietary supplements. Thus, early studies report a decrease in the incidence of certain types of cancer, whereas subsequent studies did not observe any anti-cancer effect, and adverse effects such as increased risks for type 2 diabetes have been reported. A possible contributing factor may be that different chemical forms of selenium were used in different studies. Using larval stage zebrafish (Danio rerio) as a model organism, we report a comparison of the toxicities and tissue selenium distributions of four different chemical forms of selenium. We find that the organic forms of selenium tested (Se-methyl-l-selenocysteine and l-selenomethionine) show considerably more toxicity than inorganic forms (selenite and selenate), and that this appears to be correlated with the level of bioaccumulation. Despite differences in concentrations, the tissue specific pattern of selenium accumulation was similar for the chemical forms tested; selenium was found to be highly concentrated in pigment (melanin) containing tissues especially for the organic selenium treatments, with lower concentrations in eye lens, yolk sac and heart. These results suggest that pigmented tissues might serve as a storage reservoir for selenium.

Antileishmanial Activity of Liposomal Clarithromycin against Leishmania Major Promastigotes

PubMed Central

Sazgarnia, Ameneh; Zabolinejad, Naghmeh; Layegh, Pouran; Rajabi, Omid; Berenji, Fariba; Javidi, Zari; Salari, Roshanak

2012-01-01

Objective(s) Cutaneous leishmaniasis is a common parasitic disease which is endemic in some parts of the world. In vitro and in vivo studies have shown azithromycin efficacy on some Leishmania species. Because of structural similarity between clarithromycin and azithromycin and efficacy of clarithromycin against intracellular organisms and due to the absence of previous studies in this respect, we decided to evaluate the efficacy of clarithromycin against promastigotes of L. major in vitro. Materials and Method First, liposomal and non- liposomal clarithromycin were prepared, then both forms of the drug were incubated with promastigotes for 24 hr in NNN culture media without red phenol in the presence of 5% FCS with different concentrations as follows: 20, 40, 80, 100, 200 and 500 µg/ml. Results According to the results, clarithromycin in both liposomal and non- liposomal forms has in vitro activity against the promastigotes of L. major. The concentration of drug that killed 50% of parasites (ED 50) was 169 and 253.6 µg/ml for liposomal and non- liposomal forms, respectively which shows that lower concentrations of liposomal drug are required to have the same effect as non- liposomal drug and the liposomal form of the drug is more effective than non- liposomal form. Conclusion Clarithromycin in both liposomal and non- liposomal forms has in vitro activity against the promastigotes of L. major. PMID:23658854

Cleaved Form of Osteopontin in Urine as a Clinical Marker of Lupus Nephritis

PubMed Central

Kitagori, Koji; Yoshifuji, Hajime; Oku, Takuma; Sasaki, Chiyomi; Miyata, Hitomi; Mori, Keita P.; Nakajima, Toshiki; Ohmura, Koichiro; Kawabata, Daisuke; Yukawa, Naoichiro; Imura, Yoshitaka; Murakami, Kosaku; Nakashima, Ran; Usui, Takashi; Fujii, Takao; Sakai, Kaoru; Yanagita, Motoko; Hirayama, Yoshitaka; Mimori, Tsuneyo

2016-01-01

We assessed the utility of two forms of osteopontin (OPN), OPN full and its cleaved form (OPN N-half), in plasma and urine as markers of disease activity in lupus nephritis (LN). Samples were collected from patients with systemic lupus erythematosus (SLE) (LN: N = 29, non-LN: N = 27), IgA nephropathy (IgAN) (N = 14), minimal change nephrotic syndrome (MCNS) (N = 5), diabetic nephropathy (DN) (N = 14) and healthy volunteers (HC) (N = 17). While there was no significant difference in urine OPN full concentration between groups, urine OPN N-half concentration was significantly higher in patients with LN than HC (p < 0.05). Moreover, urine OPN N-half was higher in LN patients with overt proteinuria (urine protein/creatinine ratio: P/C > 0.5) than LN patients with minimal proteinuria (P/C < 0.5, p < 0.0001), and also higher than in DN patients with overt proteinuria (P/C > 0.5, p < 0.01). Urine thrombin activity correlated with urine OPN N-half concentration (p < 0.0001), but not with urine OPN full concentration. These results suggest that urine OPN N-half concentration reflects renal inflammation. Thus, urine OPN N-half may be a novel disease activity marker for LN. PMID:27992535

Method for processing silicon solar cells

DOEpatents

Tsuo, Y.S.; Landry, M.D.; Pitts, J.R.

1997-05-06

The instant invention teaches a novel method for fabricating silicon solar cells utilizing concentrated solar radiation. The solar radiation is concentrated by use of a solar furnace which is used to form a front surface junction and back-surface field in one processing step. The present invention also provides a method of making multicrystalline silicon from amorphous silicon. The invention also teaches a method of texturing the surface of a wafer by forming a porous silicon layer on the surface of a silicon substrate and a method of gettering impurities. Also contemplated by the invention are methods of surface passivation, forming novel solar cell structures, and hydrogen passivation. 2 figs.

Method for processing silicon solar cells

DOEpatents

Tsuo, Y. Simon; Landry, Marc D.; Pitts, John R.

1997-01-01

The instant invention teaches a novel method for fabricating silicon solar cells utilizing concentrated solar radiation. The solar radiation is concentrated by use of a solar furnace which is used to form a front surface junction and back-surface field in one processing step. The present invention also provides a method of making multicrystallline silicon from amorphous silicon. The invention also teaches a method of texturing the surface of a wafer by forming a porous silicon layer on the surface of a silicon substrate and a method of gettering impurities. Also contemplated by the invention are methods of surface passivation, forming novel solar cell structures, and hydrogen passivation.

Cast Stone Formulation for Nuclear Waste Immobilization at Higher Sodium Concentrations

DOE PAGES

Fox, Kevin; Cozzi, Alex; Roberts, Kimberly; ...

2014-11-01

Low activity radioactive waste at U.S. Department of Energy sites can be immobilized for permanent disposal using cementitious waste forms. This study evaluated waste forms produced with simulated wastes at concentrations up to twice that of currently operating processes. The simulated materials were evaluated for their fresh properties, which determine processability, and cured properties, which determine waste form performance. The results show potential for greatly reducing the volume of material. Fresh properties were sufficient to allow for processing via current practices. Cured properties such as compressive strength meet disposal requirements. Leachability indices provide an indication of expected long-term performance.

Interconversion of large packets and small groups of cells of Micrococcus rubens: dependence upon magnesium and phosphate.

PubMed Central

Yamada, M; Koyama, T; Matsuhashi, M

1977-01-01

Micrococcus rubens, a gram-positive occus, usually forms large, cubic packets of more than 500 cells that are regularly arranged in three-dimensional cell groups. In medium with extremely low concentration of Mg2+ and phosphate, in which the cells can only grow on a agar surface, it formed small groups of 2 to 20 cells. Irregularly arraged cell groups of intermediated size were obtained in culture media containing intermediated concentrations of Mg2+ and phosphate. Mutants that formed irregular cell groups of intermediate size under normal culture conditions were also obtained. Images PMID:845123

21 CFR 172.385 - Whole fish protein concentrate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... CONSUMPTION Special Dietary and Nutritional Additives § 172.385 Whole fish protein concentrate. The food additive whole fish protein concentrate may be safely used as a food supplement in accordance with the... fish that are used in other forms for human food. (b) The additive consists essentially of a dried fish...

Interdependence of free zinc changes and protein complex assembly - insights into zinc signal regulation.

PubMed

Kocyła, Anna; Adamczyk, Justyna; Krężel, Artur

2018-01-24

Cellular zinc (Zn(ii)) is bound with proteins that are part of the proteomes of all domains of life. It is mostly utilized as a catalytic or structural protein cofactor, which results in a vast number of binding architectures. The Zn(ii) ion is also important for the formation of transient protein complexes with a Zn(ii)-dependent quaternary structure that is formed upon cellular zinc signals. The mechanisms by which proteins associate with and dissociate from Zn(ii) and the connection with cellular Zn(ii) changes remain incompletely understood. In this study, we aimed to examine how zinc protein domains with various Zn(ii)-binding architectures are formed under free Zn(ii) concentration changes and how formation of the Zn(ii)-dependent assemblies is related to the protein concentration and reactivity. To accomplish these goals we chose four zinc domains with different Zn(ii)-to-protein binding stoichiometries: classical zinc finger (ZnP), LIM domain (Zn 2 P), zinc hook (ZnP 2 ) and zinc clasp (ZnP 1 P 2 ) folds. Our research demonstrated a lack of changes in the saturation level of intraprotein zinc binding sites, despite various peptide concentrations, while homo- and heterodimers indicated a concentration-dependent tendency. In other words, at a certain free Zn(ii) concentration, the fraction of a formed dimeric complex increases or decreases with subunit concentration changes. Secondly, even small or local changes in free Zn(ii) may significantly affect protein saturation depending on its architecture, function and subcellular concentration. In our paper, we indicate the importance of interdependence of free Zn(ii) availability and protein subunit concentrations for cellular zinc signal regulation.

Mixotrophy in Heterocapsa rotundata: A Mechanism for Dominating the Winter Phytoplankton Community

NASA Astrophysics Data System (ADS)

Millette, N.; Pierson, J. J.; Aceves, A.; Stoecker, D.

2016-02-01

Heterocapsa rotundata is a dinoflagellate that forms large winter blooms in estuaries and coastal ecosystems. Past research has focused on the mechanisms necessary for these winter blooms to form but it is unknown why H. rotundata consistently forms these blooms. H. rotundata is a known mixotroph, and we conducted grazing experiments with a non-axenic culture of H. rotundata containing bacteria to test what environmental conditions increase H. rotundata's community grazing rate. We used microspheres to confirm that H. rotundata was grazing. We measured the change of bacterial abundance in control (without grazers) and experimental groups over 24 hours to estimate H. rotundata's community grazing rate on bacteria at different irradiance levels and ammonium concentrations. There was a significant interaction between the effect of ammonium concentration and irradiance levels. As irradiance levels decreased, the effect of ammonium concentrations on H. rotundata grazing rates became less pronounced. At lower irradiance levels H. rotundata grazing rates remained high, regardless of the ammonium concentration. Overall, changes in irradiance levels had a larger impact on H. rotundata grazing rates than changes in ammonium concentration. The findings will be discussed in light of ongoing lab and field research. The winter season is known for limiting light levels that most likely have a negative impact on phytoplankton growth rates. Heterocapsa rotundata has adapted to low light levels by increasing grazing on bacteria to consume enough carbon to maintain growth. Heterocapsa rotundata's response to low light levels is likely the mechanism that provides the competitive advantage to form winter blooms under the right conditions over other phytoplankton species.

Hygroscopicity of a sugarless coating layer formed by the interaction between mannitol and poly(vinyl alcohol) (PVA).

PubMed

Higuchi, Masaharu; Tanaka, Shouko; Tamura, Koichi; Sakata, Yukoh

2014-11-01

A sugarless layer that provides protection against moisture is formed on tablets when a coating solution comprising mannitol and poly(vinyl alcohol) (PVA) is applied. The objective of this study is to investigate the relationship between the formation of such a sugarless layer and the resulting hygroscopic properties in order to derive an appropriate sugarless coating. The hygroscopicity of the sugarless layer is shown to be strongly affected by the addition of PVA, and has the lowest at concentration ratios between 15:2.5 and 15:4 (w/w) of mannitol and PVA. The polymorphic form of mannitol is different in formulations with different mannitol:PVA concentration ratios. Mannitol occurs in the α-form at mannitol:PVA concentration ratios between 15:1 and 15:4 (w/w). Moreover, PVA affects the molecular motions in the region associated with the OH stretch, OH deformation, and CH2 wag of mannitol. In particular, the molecular motions change considerably at mannitol:PVA concentration ratio of 15:2.5 and 15:4 (w/w). In addition, the surface state of the sugarless layer depends on the amount of PVA added, and exhibits the smoothest surface at a mannitol:PVA concentration ratio between 15:2.5 and 15:4 (w/w). Thus, the hygroscopicity is related to the surface states of the sugarless layer, which, in turn, is affected by the change in the molecular motions of mannitol due to the interactions between mannitol and PVA. Copyright © 2014 Elsevier B.V. All rights reserved.

Concentration-dependent rheological properties of ECM hydrogel for intracerebral delivery to a stroke cavity

PubMed Central

Massensini, Andre R.; Ghuman, Harmanvir; Saldin, Lindsey T.; Medberry, Christopher J.; Keane, Timothy J.; Nicholls, Francesca J.; Velankar, Sachin S.; Badylak, Stephen F.; Modo, Michel

2015-01-01

Biomaterials composed of mammalian extracellular matrix (ECM) promote constructive tissue remodeling with minimal scar tissue formation in many anatomical sites. However, the optimal shape and form of ECM scaffold for each clinical application can vary markedly. ECM hydrogels have been shown to promote chemotaxis and differentiation of neuronal stem cells, but minimally invasive delivery of such scaffold materials to the central nervous system (CNS) would require an injectable form. These ECM materials can be manufactured to exist in fluid phase at room temperature, while forming hydrogels at body temperature in a concentration-dependent fashion. Implantation into the lesion cavity after a stroke could hence provide a means to support endogenous repair mechanisms. Herein, we characterize the rheological properties of an ECM hydrogel composed of urinary bladder matrix (UBM) that influence its delivery and in vivo interaction with host tissue. There was a notable concentration-dependence in viscosity, stiffness, and elasticity; all characteristics important for minimally invasive intracerebral delivery. An efficient MRI-guided injection with drainage of fluid from the cavity is described to assess in situ hydrogel formation and ECM retention at different concentrations (0, 1, 2, 3, 4, and 8 mg/mL). Only ECM concentrations >3 mg/mL gelled within the stroke cavity. Lower concentrations were not retained within the cavity, but extensive permeation of the liquid phase ECM into the peri-infarct area was evident. The concentration of ECM hydrogel is hence an important factor affecting gelation, host-biomaterial interface, as well intra-lesion distribution. PMID:26318805

Effect of phage and host concentration on the inactivation of Escherichia coli O157:H7 on cooked and raw beef.

PubMed

Hudson, J A; Billington, C; Wilson, T; On, S L W

2015-03-01

A previously described phage infecting Escherichia coli O157:H7 was added to raw and cooked beef pieces at concentrations ranging from 10(1)-10(8) plaque forming units/cm(2) to either low (<100 CFU/cm(2)) or high (10(4) CFU/cm(2)) concentrations of host bacterial cells. Incubation for up to 24 h was performed at 5 ℃ and 24 ℃ to simulate refrigerated and room temperature storage/temperature abuse. Surviving bacteria were enumerated during the incubation period, with phages being counted at the first and last sampling times. Significant reductions of E. coli O157:H7 of the order of >4 log10 CFU/cm(2) at both temperatures could be achieved compared to phage-free controls. There was a trend for greater inactivation to occur with increasing phage concentration. While re-growth of surviving cells occurred in nearly all samples incubated for 24 h at 24 ℃, these conditions are not typical of those experienced by perishable foods. It was concluded that phages can be used to reduce the concentration of a bacterial pathogen on meat, but the concentration of phages needs to be high (>4-5 log10 plaque forming units/cm(2)) for reductions to occur. A concentration of the order 8 log10 plaque forming units/cm(2) was needed to achieve a 4 log10 CFU/cm(2) reduction. © The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Ion mobility and clustering of sodium hydroxybenzoates in aqueous solutions: a molecular dynamics simulation study.

PubMed

Gujt, Jure; Podlipnik, Črtomir; Bešter-Rogač, Marija; Spohr, Eckhard

2014-09-28

The relative position of the hydroxylic and the carboxylic group in the isomeric hydroxybenzoate (HB) anions is known to have a large impact on transport properties of this species. It also influences crucially the self-organisation of cationic surfactants. In this article a systematic investigation of aqueous solutions of the ortho, meta, and para isomers of the HB anion is presented. Molecular dynamics simulations of all three HB isomers were conducted for two different concentrations at 298.15 K and using two separate water models. From the resulting trajectories we calculated the self-diffusion coefficient of each isomer. According to the calculated self-diffusion coefficients, isomers were ranked in the order o-HB > m-HB > p-HB at both concentrations for both the used SPC and SPC/E water models, which agrees very well with the experiment. The structural analysis revealed that at lower concentration, where the tendency for dimerisation or cluster formation is low, hydrogen bonding with water determines the mobility of the HB anion. o-HB forms the least hydrogen bonds and is therefore the most mobile, and p-HB, which forms the most hydrogen bonds with water, is the least mobile isomer. At higher concentration the formation of clusters also needs to be considered. The ortho isomer predominantly forms dimers with 2 hydrogen bonds per dimer between one OH and one carboxylate group of each anion. m-HB mostly forms clusters of sizes around 5 and p-HB forms clusters of sizes even larger than 10, which can be either rings or chains.

Optimum Concentration Ratio Analysis Using Dynamic Thermal Model for Concentrated Photovoltaic System

DTIC Science & Technology

2012-03-22

covalent bond with four adjacent atoms. Compound semiconductors such as GaAs have a crystal lattice similar to the diamond lattice, but since the...are found in both elemental (e.g. Si) and compound form (e.g. GaAs), but every semiconductor material is characterized by the properties of its crystal...lattice. The covalent bonds formed within a semiconducting material determine the shape of the crystal lattice [8]. For an in depth explanation

Uptake and partitioning of zinc in Lemnaceae.

PubMed

Lahive, Elma; O'Callaghan, Michael J A; Jansen, Marcel A K; O'Halloran, John

2011-11-01

Macrophytes provide food and shelter for aquatic invertebrates and fish, while also acting as reservoirs for nutrients and trace elements. Zinc accumulation has been reported for various Lemnaceae species. However, comparative accumulation across species and the link between zinc accumulation and toxicity are poorly understood. Morphological distribution and cellular storage, in either bound or soluble form, are important for zinc tolerance. This study shows differences in the uptake and accumulation of zinc by three duckweed species. Landoltia punctata and Lemna minor generally accumulated more zinc than Lemna gibba. L. minor, but not L. gibba or L. punctata, accumulated greater concentrations of zinc in roots compared to fronds when exposed to high levels of zinc. The proportion of zinc stored in the bound form relative to the soluble-form was higher in L. minor. L. punctata accumulated greater concentrations of zinc in fronds compared to roots and increased the proportion of zinc it stored in the soluble form, when exposed to high zinc levels. L. gibba is the only species that significantly accumulated zinc at low concentrations, and was zinc-sensitive. Overall, internal zinc concentrations showed no consistent correlation with toxic effect. We conclude that relationships between zinc toxicity and uptake and accumulation are species specific reflecting, among others, zinc distribution and storage. Differences in zinc distribution and storage are also likely to have implications for zinc bioavailability and trophic mobility.

Rare earth element concentrations in dissolved and acid available particulate forms for eastern UK rivers

NASA Astrophysics Data System (ADS)

Neal, C.

2007-01-01

Variations in concentration of yttrium (Y), lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm) and gadolinium (Gd) among rivers of eastern England and the border with Scotland are described in relation to the dissolved (<0.45 µM) fraction and acid-available particulate (AAP) fractions. The rivers cover a range of rural, agricultural and urban/industrial environments. Yttrium and the lanthanides show significant levels of both dissolved and acid-available particulate forms (typically about 40% in the dissolved form). For the dissolved phase, Y and the lanthanides are linearly correlated with each other and with iron: most of this dissolved component may be in a micro-particulate/colloidal form. The Y and lanthanide relationships show marked scatter and there are anomalously high La concentrations at times for the rivers Great Ouse, Thames and Wear that are probably linked to pollutant sources. For the Ouse, and especially for one of its tributaries, the Swale, relatively high Sm concentrations are probably associated with mineralisation within the catchment and contamination of the associated flood plain. For the AAP components, there are strong linear relationships with Y and the lanthanides across all the rivers. There is also a strong link between these AAP associated REE and AAP iron, although the scatter is greater and the industrial rivers have a lower lanthanide to iron ratio, probably due to iron-rich contaminants.

Toxicity of organic and inorganic selenium to mallard ducklings

USGS Publications Warehouse

Heinz, G.H.; Hoffman, D.J.; Gold, L.G.

1988-01-01

The toxicity of selenomethionine and sodium selenite to mallard ducklings (Anas platyrhynchos) was measured by feeding each form from hatching to six weeks of age at dietary concentrations of 0, 10, 20, 40, and 80 ppm selenium. At 80 ppm selenium, sodium selenite caused 97.5% mortality by six weeks and selenomethionine caused 100% mortality. At 40 ppm, these two forms of selenium caused 25 and 12.5% mortality. No mortality occurred at 10 or 20 ppm. Diets containing 20, 40, or 80 ppm selenium in both forms caused decreases in food consumption and growth. The only statistically significant effect of 10 ppm selenium was with sodium selenite, which resulted in larger livers than controls. Selenomethionine was more readily stored in the liver than sodium selenite at levels above 10 ppm selenium in the diet. Based on comparisons of residues of selenium in livers of surviving and dead ducklings, concentrations in the liver were not diagnostic of death due to selenium poisoning. Because both forms of selenium resulted in severe reductions in food consumption, selenium-induced starvation may have been related to duckling mortality. It was not clear whether either form of selenium at 10 ppm in the diet resulted in a leveling off of selenium concentrations in the liver within six weeks.

Integrated bicarbonate-form ion exchange treatment and regeneration for DOC removal: Model development and pilot plant study.

PubMed

Hu, Yue; Boyer, Treavor H

2017-05-15

The application of bicarbonate-form anion exchange resin and sodium bicarbonate salt for resin regeneration was investigated in this research is to reduce chloride ion release during treatment and the disposal burden of sodium chloride regeneration solution when using traditional chloride-form ion exchange (IX). The target contaminant in this research was dissolved organic carbon (DOC). The performance evaluation was conducted in a completely mixed flow reactor (CMFR) IX configuration. A process model that integrated treatment and regeneration was investigated based on the characteristics of configuration. The kinetic and equilibrium experiments were performed to obtain required parameters for the process model. The pilot plant tests were conducted to validate the model as well as provide practical understanding on operation. The DOC concentration predicted by the process model responded to the change of salt concentration in the solution, and showed a good agreement with pilot plant data with less than 10% difference in terms of percentage removal. Both model predictions and pilot plant tests showed over 60% DOC removal by bicarbonate-form resin for treatment and sodium bicarbonate for regeneration, which was comparable to chloride-form resin for treatment and sodium chloride for regeneration. Lastly, the DOC removal was improved by using higher salt concentration for regeneration. Copyright © 2017 Elsevier Ltd. All rights reserved.

Molecular Form Differences Between Prostate-Specific Antigen (PSA) Standards Create Quantitative Discordances in PSA ELISA Measurements

PubMed Central

McJimpsey, Erica L.

2016-01-01

The prostate-specific antigen (PSA) assays currently employed for the detection of prostate cancer (PCa) lack the specificity needed to differentiate PCa from benign prostatic hyperplasia and have high false positive rates. The PSA calibrants used to create calibration curves in these assays are typically purified from seminal plasma and contain many molecular forms (intact PSA and cleaved subforms). The purpose of this study was to determine if the composition of the PSA molecular forms found in these PSA standards contribute to the lack of PSA test reliability. To this end, seminal plasma purified PSA standards from different commercial sources were investigated by western blot (WB) and in multiple research grade PSA ELISAs. The WB results revealed that all of the PSA standards contained different mass concentrations of intact and cleaved molecular forms. Increased mass concentrations of intact PSA yielded higher immunoassay absorbance values, even between lots from the same manufacturer. Standardization of seminal plasma derived PSA calibrant molecular form mass concentrations and purification methods will assist in closing the gaps in PCa testing measurements that require the use of PSA values, such as the % free PSA and Prostate Health Index by increasing the accuracy of the calibration curves. PMID:26911983

Thermal and Denaturation Studies of the Time-Resolved Fluorescence Decay of Human Superoxide Dismutase

NASA Astrophysics Data System (ADS)

Silva, Norberto De Jesus

Previous studies have shown that time-resolved fluorescence decay of various single tryptophan proteins is best described by a distribution of fluorescence lifetimes rather than one or two lifetimes. The thermal dependence of the lifetime distributions is consistent with the hypothesis that proteins fluctuate between a hierarchy of many conformational substates. With this scenario as a theoretical framework, the correlations between protein dynamic and structure are investigated by studying the time-resolved fluorescence and anisotropy decay of the single tryptophan (Trp) residue of human superoxide dismutase (HSOD) over a wide range of temperatures and at different denaturant concentrations. First, it is demonstrated that the center of the lifetime distribution can characterize the average deactivation environment of the excited Trp-protein system. A qualitative model is introduced to explain the time-resolved fluorescence decay of HSOD in 80% glycerol over a wide range of temperatures. The dynamical model features isoenergetic conformational substates separated by a hierarchy of energy barriers. The HSOD system is also investigated as a function of denaturant concentration in aqueous solution. As a function of guanidine hydrochloride (GdHCl), the width of the fluorescence lifetime distribution of HSOD displays a maximum which is not coincident with the fully denatured form of HSOD at 6.5M GdHCl. Furthermore, the width for the fully denatured form of HSOD is greater than that of the native form. This is consistent with the scenario that more conformational substates are being created upon denaturation of HSOD. HSOD is a dimeric protein and it was observed that the width of the lifetime distribution of HSOD at intermediate GdHCl concentrations increased with decreasing protein concentration. In addition, the secondary structure of HSOD at intermediate GdHCl concentration does not change with protein concentration. These results suggest that HSOD display structural microheterogeneity which is consistent with the hypothesis of conformational substates. Further analysis show that, during denaturation, the monomeric form of HSOD is an intermediate which displays native-like secondary structure and fluctuating tertiary structure; i.e., the monomeric form of HSOD is a molten globule.

Rain water chemistry in Ankara, Turkey

NASA Astrophysics Data System (ADS)

Tuncel, Semra G.; Ungör, Sevgi

Samples of rain water were collected in Ankara for the period between September 1989 and May 1990, by using wet-only sampler. Concentrations of major cations (H +, Na + K + Ca 2+ and NH 4+) and major anions (Cl -, NO 3- and SO 42-) were determined for the first time in Turkey. The rain water was not acidic owing to high concentrations of alkaline soil particles in the atmosphere. However, the concentrations of acid forming ions, such as SO 4- and N03, were higher than the concentrations expected in a typical urban atmosphere. Most of the SO 4- in rain water was in the form of CaSO 4. Rain-aerosol coupling were examined by simultaneous sampling of aerosols with rain. The ions most efficiently scavenged from the atmosphere were found to be SO 42- and Ca 2+.

Concentration and purification of plutonium or thorium

DOEpatents

Hayden, John A.; Plock, Carl E.

1976-01-01

In this invention a first solution obtained from such as a plutonium/thorium purification process or the like, containing plutonium (Pu) and/or thorium (Th) in such as a low nitric acid (HNO.sub.3) concentration may have the Pu and/or Th separated and concentrated by passing an electrical current from a first solution having disposed therein an anode to a second solution having disposed therein a cathode and separated from the first solution by a cation permeable membrane, the Pu or Th cation permeating the cation membrane and forming an anionic complex within the second solution, and electrical current passage affecting the complex formed to permeate an anion membrane separating the second solution from an adjoining third solution containing disposed therein an anode, thereby effecting separation and concentration of the Pu and/or Th in the third solution.

Low-molecular-weight model study of peroxide cross-linking of ethylene-propylene-diene rubber using gas chromatography and mass spectrometry II. Addition and combination reactions.

PubMed

Peters, R; van Duin, M; Tonoli, D; Kwakkenbos, G; Mengerink, Y; van Benthem, R A T M; de Koster, C G; Schoenmakers, P J; van der Wal, Sj

2008-08-08

The dicumyl-peroxide-initiated addition and combination reactions of mixtures of alkanes (n-octane, n-decane) and alkenes [5,6-dihydrodicyclopentadiene (DCPDH), 5-ethylidene-2-norbornane (ENBH) and 5-vinylidene-2-norbornane (VNBH)] were studied to mimic the peroxide cross-linking reactions of terpolymerised ethylene, propylene and a diene monomer (EPDM). The reaction products of the mixtures were separated by both gas chromatography (GC) and comprehensive two-dimensional gas chromatography (GCxGC). The separated compounds were identified from their mass spectra and their GC and GCxGC elution pattern. Quantification of the various alkyl/alkyl, alkyl/allyl and allyl/allyl combination products shows that allylic-radicals comprise approximately 60% of the substrate radicals formed. The total concentration of the products formed by combination is found to be independent of the concentration and the type of alkene. The total concentration of the products formed by addition to the alkene increases with increasing concentration of alkene. In addition, the total concentration of the formed addition products depends strongly on the type of the alkene used, viz. VNBH>ENBH approximately DCPDH, which is a consequence of differences in steric hindrance of the unsaturation. The peroxide curing efficiency, defined as the number of moles of cross-linked products formed per mol of peroxide, is 173% using 9% (w/w) 5-vinylidene-2-norbornane (VNBH). This indicates that the addition reaction is recurrent. All these findings are consistent with experimental studies on peroxide curing of EPDM rubber. In addition, the present results provide more-detailed structural information, increasing the understanding of the mechanism of peroxide curing of EPDM. The described approach to use low-molecular-weight model compounds followed by GC-mass spectrometry (MS) and GCxGC-MS analysis is proven to be a very powerful tool to study the cross-linking of EPDM.

Continuous air agglomeration method for high carbon fly ash beneficiation

DOEpatents

Gray, McMahon L.; Champagne, Kenneth J.; Finseth, Dennis H.

2000-01-01

The carbon and mineral components of fly ash are effectively separated by a continuous air agglomeration method, resulting in a substantially carboree mineral stream and a highly concentrated carbon product. The method involves mixing the fly ash comprised of carbon and inorganic mineral matter with a liquid hydrocarbon to form a slurry, contacting the slurry with an aqueous solution, dispersing the hydrocarbon slurry into small droplets within the aqueous solution by mechanical mixing and/or aeration, concentrating the inorganic mineral matter in the aqueous solution, agglomerating the carbon and hydrocarbon in the form of droplets, collecting the droplets, separating the hydrocarbon from the concentrated carbon product, and recycling the hydrocarbon.

Effect of Filler Concentration on Thermal Stability of Vinyl Copolymer Elastomer (VCE) Composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Dali; Hubbard, Kevin Mark; Devlin, David James

To study the thermal stability of vinyl copolymer elastomer (VCE) in its composite form, systematic TGA characterizations were conducted in both nonisothermal and isothermal modes. The effects of filler concentration on the aging behaviors of the VCE/filler composites were investigated under nitroplasticizer (NP) environment. FTIR characterization was used to probe the structural changes in the VCE polymer before and after the thermal treatments. This study suggests that the filler concentration significantly deteriorates the thermal stability of NP at a moderate temperature (< 70 °C). The degradation of NP, in turn, accelerates the aging process of the VCE polymer in itsmore » composite form.« less

Apparatus for sensing volatile organic chemicals in fluids

DOEpatents

Hughes, Robert C.; Manginell, Ronald P.; Jenkins, Mark W.; Kottenstette, Richard; Patel, Sanjay V.

2005-06-07

A chemical-sensing apparatus is formed from the combination of a chemical preconcentrator which sorbs and concentrates particular volatile organic chemicals (VOCs) and one or more chemiresistors that sense the VOCs after the preconcentrator has been triggered to release them in concentrated form. Use of the preconcentrator and chemiresistor(s) in combination allows the VOCs to be detected at lower concentration than would be possible using the chemiresistor(s) alone and further allows measurements to be made in a variety of fluids, including liquids (e.g. groundwater). Additionally, the apparatus provides a new mode of operation for sensing VOCs based on the measurement of decay time constants, and a method for background correction to improve measurement precision.

Analysis of EPA and DHA in the viscera of marine fish using gas chromatography.

PubMed

Zhang, De-Yong; Xu, Xiao-Lu; Shen, Xiu-Ying; Mei, Yu; Xu, Hui-Ying

2016-03-01

The viscera of 10 kinds of marine fishes were collected for fish oil extraction and detection of DHA and EPA, two most important polyunsaturated fatty acids. The fish oil extraction ratio for the evaluated fishes varied from 0.95% to 10.18% (wt%). Pseudosciaena crocea presented the highest fish oil yield, followed by Mustelus manazo, Hippoglossus and Sciaenopsocellatus. A gas chromatography method was then established for analysis of EPA/DHA. The EPA concentration (in methyl ester form) in the fish oil varied from 1.39 to 10.65(mg/g). Epinephelus awoara presented the highest EPA concentration (p<0.05), followed by Epinephelussp, Sciaenopsocellatus and Hippoglossus. The DHA concentration (in methyl ester form) in the fish oil varied from 0.58 to 37.02 (mg/g). Epinephelus awoara presented the highest DHA concentration (p<0.05), followed by Sciaenopsocellatus, Pseudosciaena crocea and Hippoglossus. No strict positive correlation between the EPA/DHA concentration and the sea depth where the fish live was observed. The fishes living in middle depth presented highest EPA/DHA concentration.

Free-form Fresnel RXI Köhler design with spectrum-splitting for photovoltaics

NASA Astrophysics Data System (ADS)

Buljan, M.; Benítez, P.; Mohedano, R.; Miñano, J. C.; Sun, Y.; Falicoff, W.; Vilaplana, J.; Chaves, J.; Biot, G.; López, J.

2011-10-01

Here we present a novel optical design of the high concentration photovoltaics (HPCV) nonimaging concentrator (>500x) with built-in spectrum splitting concept. The primary optical element (POE) is a flat Fresnel lens and the secondary optical element (SOE) is a free-form RXI-type concentrator with a band-pass filter embedded in it, both POE and SOE performing Köhler integration to produce light homogenization on the target. It uses the combination of a commercial concentration GaInP/GaInAs/Ge 3J cell and a concentration Back-Point-Contact (BPC) silicon cell for efficient spectral utilization, and external confinement techniques for recovering the 3J cell's reflection. Design targets equivalent cell efficiency ~46% using commercial 39% 3J and 26% Si cells, and CPV module efficiency greater than 38%, achieved at a concentration level larger than 500X and wide acceptance angle (+/-1°). A first proof-of concept receiver prototype has been manufactured using a simpler optical architecture (with a lower concentration, ~100x and lower simulated added efficiency), and experimental measurements have shown up to 39.8% 4J receiver efficiency using a 3J with peak efficiency of 36.9%.

Mercury species, selenium, metallothioneins and glutathione in two dolphins from the southeastern Brazilian coast: Mercury detoxification and physiological differences in diving capacity.

PubMed

Kehrig, Helena A; Hauser-Davis, Rachel A; Seixas, Tercia G; Pinheiro, Ana Beatriz; Di Beneditto, Ana Paula M

2016-06-01

In the present study, the concentration of trace elements, total mercury (Hg) and selenium (Se) and mercury forms (MeHg, Hginorg and HgSe) in the vulnerable coastal dolphins Pontoporia blainvillei and Sotalia guianensis were appraised and compared, using metallothioneins (MT) and glutathione (GSH) as biomarkers for trace element exposure. The trace element concentrations varied between muscle and liver tissues, with liver of all dolphin specimens showing higher Hg and Se concentrations than those found in muscle. Hg, MeHg and Hginorg molar concentrations showed a clear increase with Se molar concentrations in the liver of both dolphins, and Se concentrations were higher than those of Hg on a molar basis. Se plays a relevant role in the detoxification of MeHg in the hepatic tissue of both dolphins, forming Hg-Se amorphous crystals in liver. In contrast, MT were involved in the detoxification process of Hginorg in liver. GSH levels in P. blainvillei and S. guianensis muscle tissue suggest that these dolphins have different diving capacities. Muscle Hg concentrations were associated to this tripeptide, which protects dolphin cells against Hg stress. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of thread shape on screw stress concentration by photoelastic measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dragoni, E.

1994-11-01

The screw stress concentration for six nut-bolt connections embodying three different thread profiles and two nut shapes is measured photoelastically. Buttress (nearly zero flank angle), trapezoidal (15-deg flank angle), and triangular (30-deg flank angle) thread forms are examined in combination with standard and lip-type nuts. The effect of the thread profile on the screw stress concentration appears to be dependent upon the kind of nut considered. If the fastening incorporates a standard nut, the buttress thread is stronger than the triangular one, which, in turn, behaves better than the trapezoidal contour. The improvement is roughly a 20% reduction in themore » stress concentration factor from the trapezoidal to the buttress thread. In the case of lip nut, conversely, this tendency is somewhat reversed, with the trapezoidal thread performing slightly (but not decidedly) better than the other two shapes. Finally, averaged over all three thread forms, the lip nut exhibits a stress concentration factor which is about 50% lower than that of the standard nut.« less

Preparation of Microcapsules Containing β-Carotene with Thermo Sensitive Curdlan by Utilizing Reverse Dispersion

PubMed Central

Taguchi, Yoshinari; Ono, Fumiyasu; Tanaka, Masato

2013-01-01

We have tried to microencapsulate β-carotene with curdlan of a thermogelation type polysaccharide. Microcapsules were prepared by utilizing reverse dispersion, in which salada oil was the continuous phase (O’) and the curdlan water slurry (W) was the dispersed phase. β-carotene (O) as a core material was broken into fine oil droplets in the dispersed phase to form the (O/W) dispersion. The (O/W) dispersion was poured in the continuous phase (O’) and stirred to form the (O/W)/O’ dispersion at room temperature and then, temperature of the dispersion was raised to 80 °C to prepare curdlan-microcapusles containing β-carotene. In this microencapsulation process, the concentrations of curdlan and oil soluble surfactant and the impeller speed to form the (O/W)/O’ dispersion were mainly changed stepwise. We were able to prepare microcapsules by the microencapsulation method adopted here. The content of core material was increased with the curdlan concentration and decreased with the impeller speed and the oil soluble surfactant concentration. With the curdlan concentration, the drying rate of microcapsules was decreased and the retention ability for water was increased due to the stable preservation of β-carotene. PMID:24300565

Searching the Sinus Amoris: Using profiles of geological units, impact and volcanic features to characterize a major terrane interface on the Moon

NASA Technical Reports Server (NTRS)

Clark, P.; Joerg, S.; Dehon, R.

1994-01-01

Geochemical profiles of surface units, impact, and volcanic features are studied in detail to determine the underlying structure in an area of extensive mare/highland interface, Sinus Amoris. This study region includes and surrounds the northeastern embayment of Mare Tranquillitatis. The concentrations of two major rock-forming elements (Mg and Al), which were derived from the Apollo 15 orbital geochemical measurements, were used in this study. Mapped units and deposits associated with craters in the northwestern part of the region tend to have correlated low Mg and Al concentrations, indicating the presence of Potassium (K)-Rare Earth Elements (REE)-Phosphorus (P) (KREEP)-enriched basalt. Found along the northeastern rim of Tranquillitatis were areas with correlated high Mg and Al concentration, indicating the presence of troctolite. Distinctive west/east and north/south trends were observed in the concentrations of Mg and Al, and, by implication, in the distribution of major rock components on the surface. Evidence for a systematic geochemical transition in highland or basin-forming units may be observed here in the form of distinctive differences in chemistry in otherwise similar units in the western and eastern portions of the study region.

Differences in Purinergic Amplification of Osmotic Cell Lysis by the Pore-Forming RTX Toxins Bordetella pertussis CyaA and Actinobacillus pleuropneumoniae ApxIA: the Role of Pore Size

PubMed Central

Fiser, Radovan; Linhartova, Irena; Osicka, Radim; Bumba, Ladislav; Hewlett, Erik L.; Benz, Roland; Sebo, Peter

2013-01-01

A large subgroup of the repeat in toxin (RTX) family of leukotoxins of Gram-negative pathogens consists of pore-forming hemolysins. These can permeabilize mammalian erythrocytes (RBCs) and provoke their colloid osmotic lysis (hemolytic activity). Recently, ATP leakage through pannexin channels and P2X receptor-mediated opening of cellular calcium and potassium channels were implicated in cell permeabilization by pore-forming toxins. In the study described here, we examined the role played by purinergic signaling in the cytolytic action of two RTX toxins that form pores of different sizes. The cytolytic potency of ApxIA hemolysin of Actinobacillus pleuropneumoniae, which forms pores about 2.4 nm wide, was clearly reduced in the presence of P2X7 receptor antagonists or an ATP scavenger, such as pyridoxalphosphate-6-azophenyl-2′,4′-disulfonic acid (PPADS), Brilliant Blue G, ATP oxidized sodium salt, or hexokinase. In contrast, antagonists of purinergic signaling had no impact on the hemolytic potency of the adenylate cyclase toxin-hemolysin (CyaA) of Bordetella pertussis, which forms pores of 0.6 to 0.8 nm in diameter. Moreover, the conductance of pores formed by ApxIA increased with the toxin concentration, while the conductance of the CyaA single pore units was constant at various toxin concentrations. However, the P2X7 receptor antagonist PPADS inhibited in a concentration-dependent manner the exacerbated hemolytic activity of a CyaA-ΔN489 construct (lacking 489 N-terminal residues of CyaA), which exhibited a strongly enhanced pore-forming propensity (>20-fold) and also formed severalfold larger conductance units in planar lipid bilayers than intact CyaA. These results point to a pore size threshold of purinergic amplification involvement in cell permeabilization by pore-forming RTX toxins. PMID:24082076

Elliptical concentrators.

PubMed

Garcia-Botella, Angel; Fernandez-Balbuena, Antonio Alvarez; Bernabeu, Eusebio

2006-10-10

Nonimaging optics is a field devoted to the design of optical components for applications such as solar concentration or illumination. In this field, many different techniques have been used to produce optical devices, including the use of reflective and refractive components or inverse engineering techniques. However, many of these optical components are based on translational symmetries, rotational symmetries, or free-form surfaces. We study a new family of nonimaging concentrators called elliptical concentrators. This new family of concentrators provides new capabilities and can have different configurations, either homofocal or nonhomofocal. Translational and rotational concentrators can be considered as particular cases of elliptical concentrators.

Impact of crystal polymorphism on the systemic bioavailability of rifaximin, an antibiotic acting locally in the gastrointestinal tract, in healthy volunteers

PubMed Central

Blandizzi, Corrado; Viscomi, Giuseppe Claudio; Scarpignato, Carmelo

2015-01-01

Background Rifaximin is an antibiotic, acting locally in the gastrointestinal tract, which may exist in different crystal as well as amorphous forms. The current marketed rifaximin formulation contains polymorph alpha, the systemic bioavailability of which is very limited. This study compared the pharmacokinetics of this formulation with those of the amorphous form. Methods Amorphous rifaximin was specifically prepared for the study and formulated as the marketed product. Two doses (200 mg and 400 mg) of both formulations were given to two groups of 12 healthy volunteers of either sex according to a single-blind, randomized, two-treatment, single-dose, two-period, cross-over design. Plasma and urine samples were collected at preset times (for 24 hours or 48 hours, respectively) after dosing, and assayed for rifaximin concentrations by high-performance liquid chromatography-mass spectrometry. Results For both dose levels, peak plasma concentration, area under the concentration-time curve, and cumulative urinary excretion were significantly higher after administration of amorphous rifaximin than rifaximin-α. Ninety percent confidence intervals for peak plasma concentration, area under the concentration-time curve, and urinary excretion ratios were largely outside the upper limit of the accepted (0.80–1.25) range, indicating higher systemic bioavailability of the amorphous rifaximin. The few adverse events recorded were not serious and not related to the study medications. Conclusion Rifaximin-α, a crystal polymorph, does differ from the amorphous form, the latter being systemically more bioavailable. In this regard, care must be taken when using – as a medicinal product – a formulation containing even small amounts of amorphous form, which may alter the peculiar pharmacologic properties of this poorly absorbed antibiotic. PMID:25565769

Impact of crystal polymorphism on the systemic bioavailability of rifaximin, an antibiotic acting locally in the gastrointestinal tract, in healthy volunteers.

PubMed

Blandizzi, Corrado; Viscomi, Giuseppe Claudio; Scarpignato, Carmelo

2015-01-01

Rifaximin is an antibiotic, acting locally in the gastrointestinal tract, which may exist in different crystal as well as amorphous forms. The current marketed rifaximin formulation contains polymorph alpha, the systemic bioavailability of which is very limited. This study compared the pharmacokinetics of this formulation with those of the amorphous form. Amorphous rifaximin was specifically prepared for the study and formulated as the marketed product. Two doses (200 mg and 400 mg) of both formulations were given to two groups of 12 healthy volunteers of either sex according to a single-blind, randomized, two-treatment, single-dose, two-period, cross-over design. Plasma and urine samples were collected at preset times (for 24 hours or 48 hours, respectively) after dosing, and assayed for rifaximin concentrations by high-performance liquid chromatography-mass spectrometry. For both dose levels, peak plasma concentration, area under the concentration-time curve, and cumulative urinary excretion were significantly higher after administration of amorphous rifaximin than rifaximin-α. Ninety percent confidence intervals for peak plasma concentration, area under the concentration-time curve, and urinary excretion ratios were largely outside the upper limit of the accepted (0.80-1.25) range, indicating higher systemic bioavailability of the amorphous rifaximin. The few adverse events recorded were not serious and not related to the study medications. Rifaximin-α, a crystal polymorph, does differ from the amorphous form, the latter being systemically more bioavailable. In this regard, care must be taken when using - as a medicinal product - a formulation containing even small amounts of amorphous form, which may alter the peculiar pharmacologic properties of this poorly absorbed antibiotic.

Four groups of new aromatic halogenated disinfection byproducts: effect of bromide concentration on their formation and speciation in chlorinated drinking water.

PubMed

Pan, Yang; Zhang, Xiangru

2013-02-05

Bromide is naturally present in source waters worldwide. Chlorination of drinking water can generate a variety of chlorinated and brominated disinfection byproducts (DBPs). Although substantial efforts have been made to examine the effect of bromide concentration on the formation and speciation of halogenated DBPs, almost all previous studies have focused on trihalomethanes and haloacetic acids. Given that about 50% of total organic halogen formed in chlorination remains unknown, it is still unclear how bromide concentration affects the formation and speciation of the new/unknown halogenated DBPs. In this study, chlorinated drinking water samples with different bromide concentrations were prepared, and a novel approach-precursor ion scan using ultra performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry-was adopted for the detection and identification of polar halogenated DBPs in these water samples. With this approach, 11 new putative aromatic halogenated DBPs were identified, and they were classified into four groups: dihalo-4-hydroxybenzaldehydes, dihalo-4-hydroxybenzoic acids, dihalo-salicylic acids, and trihalo-phenols. A mechanism for the formation of the four groups of new aromatic halogenated DBPs was proposed. It was found that increasing the bromide concentration shifted the entire polar halogenated DBPs as well as the four groups of new DBPs from being less brominated to being more brominated; these new aromatic halogenated DBPs might be important intermediate DBPs formed in drinking water chlorination. Moreover, the speciation of the four groups of new DBPs was modeled: the speciation patterns of the four groups of new DBPs well matched those determined from the model equations, and the reactivity differences between HOBr and HOCl in reactions forming the four groups of new DBPs were larger than those in reactions forming trihalomethanes and haloacetic acids.

Growth Behavior, Geometrical Shape, and Second CMC of Micelles Formed by Cationic Gemini Esterquat Surfactants.

PubMed

Bergström, L Magnus; Tehrani-Bagha, Alireza; Nagy, Gergely

2015-04-28

Micelles formed by novel gemini esterquat surfactants have been investigated with small-angle neutron scattering (SANS). The growth behavior of the micelles is found to differ conspicuously depending on the length of the gemini surfactant spacer group. The gemini surfactant with a long spacer form rather small triaxial ellipsoidal tablet-shaped micelles that grow weakly with surfactant concentration in the entire range of measured concentrations. Geminis with a short spacer, on the other hand, form weakly growing oblates or tablets at low concentrations that start to grow much more strongly into polydisperse rodlike or wormlike micelles at higher concentrations. The latter behavior is consistent with the presence of a second CMC that marks the transition from the weakly to the strongly growing regime. It is found that the growth behavior in terms of aggregation number as a function of surfactant concentration always appear concave in weakly growing regimes, while switching to convex behavior in strongly growing regimes. As a result, we are able to determine the second CMC of the geminis with short spacer by means of suggesting a rather precise definition of it, located at the point of inflection of the growth curve that corresponds to the transition from concave to convex growth behavior. Our SANS results are rationalized by comparison with the recently developed general micelle model. In particular, this theory is able to explain and reproduce the characteristic appearances of the experimental growth curves, including the presence of a second CMC and the convex strongly growing regime beyond. By means of optimizing the agreement between predictions from the general micelle model and results from SANS experiments, we are able to determine the three bending elasticity constants spontaneous curvature, bending rigidity, and saddle-splay constant for each surfactant.

Breakthrough curves for toluene adsorption on different types of activated carbon fibers: application in respiratory protection.

PubMed

Balanay, Jo Anne G; Floyd, Evan L; Lungu, Claudiu T

2015-05-01

Activated carbon fibers (ACF) are considered viable alternative adsorbent materials in respirators because of their larger surface area, lighter weight, and fabric form. The purpose of this study was to characterize the breakthrough curves of toluene for different types of commercially available ACFs to understand their potential service lives in respirators. Two forms of ACF, cloth (AC) and felt (AF), with three surface areas each were tested. ACFs were challenged with six toluene concentrations (50-500 p.p.m.) at constant air temperature (23°C), relative humidity (50%), and air flow (16 l min-1) at different bed depths. Breakthrough data were obtained using continuous monitoring by gas chromatography using a gas sampling valve. The ACF specific surface areas were measured by an automatic physisorption analyzer. Results showed unique shapes of breakthrough curves for each ACF form: AC demonstrated a gradual increase in breakthrough concentration, whereas AF showed abrupt increase in concentration from the breakpoint, which was attributed to the difference in fiber density between the forms. AF has steeper breakthrough curves compared with AC with similar specific surface area. AC exhibits higher 10% breakthrough times for a given bed depth due to higher mass per bed depth compared with AF, indicating more adsorption per bed depth with AC. ACF in respirators may be appropriate for use as protection in environments with toluene concentration at the Occupational Safety and Health Administration Permissible Exposure Limit, or during emergency escape for higher toluene concentrations. ACF has shown great potential for application in respiratory protection against toluene and in the development of thinner, lighter, and more efficient respirators. © The Author 2014. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

Sulfur redox chemistry governs diurnal antimony and arsenic cycles at Champagne Pool, Waiotapu, New Zealand

NASA Astrophysics Data System (ADS)

Ullrich, Maria K.; Pope, James G.; Seward, Terry M.; Wilson, Nathaniel; Planer-Friedrich, Britta

2013-07-01

Champagne Pool, a sulfidic hot spring in New Zealand, exhibits distinct diurnal variations in antimony (Sb) and arsenic (As) concentrations, with daytime high and night-time low concentrations. To identify the underlying mobilization mechanisms, five sites along the drainage channel of Champagne Pool were sampled every 2 h during a 24 h period. Temporal variations in elemental concentrations and Sb, As, and sulfur (S) speciation were monitored in the discharging fluid. Total trace element concentrations in filtered and unfiltered samples were analyzed using ICP-MS, and Sb, As and S species were determined by IC-ICP-MS. Sulfur speciation in the drainage channel was dominated by thiosulfate and sulfide at night, while sulfate dominated during the day. The distinct diurnal changes suggest that the transformations are caused by phototrophic sulfur-oxidizing bacteria. These bacteria metabolize thiosulfate and sulfide in daylight to form sulfate and, as suggested by modeling with PhreeqC, elemental sulfur. Sulfide consumption during the day results in undersaturation of antimony sulfides, which triggers the additional release of dissolved Sb. For As, diurnal cycles were much more pronounced in speciation than in total concentrations, with di- and trithioarsenate forming at night due to excess sulfide, and monothioarsenate forming from arsenite and elemental sulfur during the day. Sulfur speciation was thus found to control Sb and As in terms of both solubility and speciation.

[Coenzyme-induced slow transitions of NADP-sorbitol dehydrogenase from Gluconobacter oxydans].

PubMed

Liber, E E; Dorozhko, A I; Pomortseva, N V

1978-06-01

The kinetic properties of NADP-dependent sorbitol dehydrogenase from G. oxydans cell extract were studied at pH 8.8 and 9.3 in the direction of D-sorbitol oxydation. It was shown that the shape of the kinetic curves of NADPH accumulation in time is characterised by initial burst whose magnitude depends on the concentration of the enzyme extract used. Preincubation of the enzyme with NADP or D-sorbitol eliminated the initial burst on these curves and transformed them into straight lines coming from the start of co-ordinates. The dependence of the stationary reaction rate on the enzyme extract concentration is not a linear one. The kinetic dependences of stationary rate of the reaction catalysed by the enzyme on the concentration of D-sorbitol and NADP at pH 8.8 and 9.3 were examined under all conditions studied; the shape of these kinetic curves altered to considerable extent with the alteration of the enzyme extract concentration in the reaction mixture and pH. At pH 9.3 several intermiediate plateaux were found on the curves of the D-sorbitol concentration dependent stationary rate of the reaction. The preincubation of the enzyme extract with NADP during 1.5 h removed the intermediate plateau on these curves and made them hyperbolic. Disk-electrophoresis of the enzyme extract in PAAG concentration gradient showed that at pH 8.8 the enzyme exists in one active form, while at pH 9.3 it exists in three major and three minor active forms of the enzyme differing in their molecular weights are found. It is assumed that the enzyme from G. oxydans cell extract can exist in a great number of molecular equilibrium forms, the rate of quilibrium being comparable or significantly less than that of the enzymatic reaction. NADP significantly influences on the equilibrium of the molecular forms of the enzyme.

Effect of grinding intensity and pelleting of the diet on indoor particulate matter concentrations and growth performance of weanling pigs.

PubMed

Ulens, T; Demeyer, P; Ampe, B; Van Langenhove, H; Millet, S

2015-02-01

This study evaluated the effect of feed form and grinding intensity of the pig diet and the interaction between both on the particulate matter (PM) concentrations inside a pig nursery and the growth performances of weanling pigs. Four diets were compared: finely ground meal, coarsely ground meal, finely ground pellets, and coarsely ground pellets. Four weaning rounds with 144 pigs per weaning round, divided over 4 identical compartments, were monitored. Within each weaning round, each compartment was randomly assigned to 1 of 4 treatments. A hammer mill with a screen of 1.5 or 6 mm was used to grind the ingredients of the finely ground and coarsely ground feeds, respectively. Indoor concentrations of the following PM fractions were measured: PM that passes through a size-selective inlet with a 50 % efficiency cutoff at 10 (PM10) , 2.5 (PM2.5), or 1 (PM1) μm aerodynamic diameter, respectively (USEPA, 2004). Feeding pelleted diets instead of meal diets gave rise to higher PM10 (P < 0.001), PM2.5 (P < 0.001), and PM1 (P < 0.001) concentrations. Grinding intensity had an effect only on PM10 (P < 0.05) concentrations. No interaction between feed form and grinding intensity was found for any of the PM fractions. Interactions (P < 0.05) between feed form and grinding intensity on ADFI and ADG were found. Grinding intensity had an effect only on the meal diets with higher ADFI for the coarsely ground meal. Pigs fed the finely ground meal had a lower (P < 0.001) ADG than the other 3 diets. Feed efficiency was influenced only by the feed form (P < 0.001) and not by the grinding intensity. Pelleting the feed gave rise to a higher G:F. In conclusion, a contradiction between environmental concerns and performance results was found. Feeding pelleted diets to the piglets improved growth performance but also increased indoor PM concentrations.

Trace metals in estuaries in the Russian Far East and China: case studies from the Amur River and the Changjiang.

PubMed

Shulkin, Vladimir; Zhang, Jing

2014-11-15

This paper compares the distributions of dissolved and particulate forms of Mn, Fe, Ni, Cu, Zn, Cd, and Pb in the estuaries of the largest rivers in East Asia: the Amur River and the Changjiang (Yangtze River). High suspended solid concentrations, elevated pH, and relatively low dissolved trace metal concentrations are characteristics of the Changjiang. Elevated dissolved Fe and Mn concentrations, neutral pH, and relatively low suspended solid concentrations are characteristics of the Amur River. The transfer of dissolved Fe to suspended forms is typical in the Amur River estuary, though Cd and Mn tend to mobilize to solution, and Cu and Ni are diluted in the estuarine system. Metal concentrations in suspended matter in the Amur River estuary are controlled by the ratio of terrigenous riverine material, enriched in Al and Fe, and marine biogenic particles, enriched in Cu, Mn, Cd, and in some cases Ni. The increase in dissolved forms of Mn, Fe, Ni, Cu, Cd, and Pb compared with river end-member is unique to the Changjiang estuary. Particle-solution interactions are not reflected in bulk suspended-solid metal concentrations in the Changjiang estuary due to the dominance of particulate forms of these metals. Cd is an exception in the Changjiang estuary, where the increase in dissolved Cd is of comparable magnitude to the decrease in particulate Cd. Despite runoff in the Amur River being lower than that in the Changjiang, the fluxes of dissolved Mn, Zn and Fe in the Amur River exceed those in the Changjiang. Dissolved Ni, and Cd fluxes are near equal in both estuaries, but dissolved Cu is lower in the Amur River estuary. The hydrological and physico-chemical river characteristics are dominated at the assessment of river influence on the adjoining coastal sea areas despite differences in estuarine processes. Copyright © 2014 Elsevier B.V. All rights reserved.

pH effects on the hyaluronan hydrolysis catalysed by hyaluronidase in the presence of proteins: Part I. Dual aspect of the pH-dependence.

PubMed

Lenormand, Hélène; Deschrevel, Brigitte; Vincent, Jean-Claude

2010-05-01

Hyaluronan (HA) hydrolysis catalysed by hyaluronidase (HAase) is strongly inhibited when performed at a low ratio of HAase to HA concentrations and at low ionic strength. This is because long HA chains can form non-active complexes with HAase. Bovine serum albumin (BSA) is able to compete with HAase to form electrostatic complexes with HA so freeing HAase which then recovers its catalytic activity. This BSA-dependence is characterised by two main domains separated by the optimal BSA concentration: below this concentration the HAase activity increases when the BSA concentration is increased, above this concentration the HAase activity decreases. This occurs provided that HA is negatively charged and BSA is positively charged, i.e. in a pH range from 3 to 5.25. The higher the pH value the higher the optimal BSA concentration. Other proteins can also modulate HAase activity. Lysozyme, which has a pI higher than that of BSA, is also able to compete with HAase to form electrostatic complexes with HA and liberate HAase. This occurs over a wider pH range that extends from 3 to 9. These results mean that HAase can form complexes with HA and recover its enzymatic activity at pH as high as 9, consistent with HAase having either a high pI value or positively charged patches on its surface at high pH. Finally, the pH-dependence of HAase activity, which results from the influence of pH on both the intrinsic HAase activity and the formation of complexes between HAase and HA, shows a maximum at pH 4 and a significant activity up to pH 9. Copyright 2009 International Society of Matrix Biology. Published by Elsevier B.V. All rights reserved.

Primary centers and secondary concentrations of tectonic activity through time in the western hemisphere of Mars

USGS Publications Warehouse

Anderson, R.C.; Dohm, J.M.; Golombek, M.P.; Haldemann, A.F.C.; Franklin, B.J.; Tanaka, K.L.; Lias, J.; Peer, B.

2001-01-01

Five main stages of radial and concentric structures formed around Tharsis from the Noachian through the Amazonian as determined by geologic mapping of 24,452 structures within the stratigraphic framework of Mars and by testing their radial and concentric orientations. Tectonic activity peaked in the Noachian (stage 1) around the largest center, Claritas, an elongate center extending more than 20?? in latitude and defined by about half of the total grabens which are concentrated in the Syria Planum, Thaumasia, and Tempe Terra regions. During the Late Noachian and Early Hesperian (stage 2), extensional structures formed along the length of present-day Valles Marineris and in Thaumasia (with a secondary concentration near Warrego Vallis) radial to a region just to the south of the central margin of Valles Marineris. Early Hesperian (stage 3) radial grabens in Pavonis, Syria, Ulysses, and Tempe Terra and somewhat concentric wrinkle ridges in Lunae and Solis Plana and in Thaumasia, Sirenum, Memnonia, and Amazonis are centered northwest of Syria with secondary centers at Thaumasia, Tempe Terra, Ulysses Fossae, and western Valles Marineris. Late Hesperian/Early Amazonian (stage 4) structures around Alba Patera, the northeast trending alignment of Tharsis Montes, and Olympus Mons appears centered on Alba Patera. Stage 5 structures (Middle-Late Amazonian) represent the last pulse of Tharsis-related activity and are found around the large shield volcanoes and are centered near Pavonis Mons. Tectonic activity around Tharsis began in the Noachian and generally decreased through geologic time to the Amazonian. Statistically significant radial distributions of structures formed during each stage, centered at different locations within the higher elevations of Tharsis. Secondary centers of radial structures during many of the stages appear related to previously identified local magmatic centers that formed at different times and locations throughout Tharsis. Copyright 2001 by the American Geophysical Union.

Accumulation and depletion of liver copper stores in dairy cows challenged with a Cu-deficient diet and oral and injectable forms of Cu supplementation.

PubMed

Balemi, S C; Grace, N D; West, D M; Smith, S L; Knowles, S O

2010-06-01

To quantify the capacity of the liver to respond to a Cu-deficient diet and various forms of Cu supplementation in dairy cows with high Cu status. Sixty non-pregnant, non lactating mixed-age Friesian dairy cows were fed baled silage for 116 days, containing 5.8 mg Cu/kg dry matter (DM), that provided an inadequate Cu intake. They were either unsupplemented (Control); or treated thrice weekly orally with solutions containing the equivalent of 150 mg Cu/day as copper sulphate pentahydrate (CS), copper amino chelate (CAC), or copper glycinate (CG); 16 g Cu as CuO wire particles, administered in an intra-ruminal bolus on Day 0; or 100 mg Cu as calcium copper edetate, administered by S/C injection on Days 0 and 58. On Days -5, 14, 28, 58, 86 and 116, liver biopsies and blood samples were obtained for determination of Cu. Mean initial concentrations of Cu in liver for all groups was 827 (SE 42) micromol/kg fresh tissue. In control cows, this decreased to 552 micromol/kg on Day 116, and averaged 670 micromol/kg over the length of the trial. Oral forms of Cu supplementation increased overall mean concentrations in liver to 960 (SE 79), 1,050 (SE 81) and 1,100 (SE 84) micromol/kg for CS, CAC and CG, respectively, but there was no difference between form of supplement. Mean concentrations were significantly increased by bolus treatment, but not by injection. Concentrations of Cu in serum in all groups decreased from 12.1 (SE 0.3) to 10.4 (SE 0.6) micromol/L by Day 116, with no differences due to treatments. The initial concentration of Cu in liver significantly affected the rate of accumulation of Cu among cows supplemented orally. In cows with an initial concentration <1,100 micromol/kg, the average increase was 4.1 micromol/kg fresh tissue/day, whereas rates were variable, even negative, when initial concentrations were >1,100 micromol/kg. Release of Cu over 116 days in cows given the bolus was calculated to be equivalent to an oral intake of CS of 106 mg Cu/day. In dairy cows with a high Cu status fed a Cu-deficient diet, responses to supplementation with two chelated forms of Cu administrated orally were similar to those due to CS. Copper as CuO was about 77% as effective as oral supplementation with chemically similar inorganic Cu. Initial concentrations of Cu in liver influenced the rate of accumulation following oral supplementation. Changes in concentrations of Cu in liver were readily observed following oral supplementation over a wide range of initial concentrations, whereas these changes could not be detected in serum. The liver is thus a good index of the Cu status of dairy cows.

Formation of regulated and unregulated disinfection byproducts during chlorination of algal organic matter extracted from freshwater and marine algae.

PubMed

Liu, Chao; Ersan, Mahmut S; Plewa, Michael J; Amy, Gary; Karanfil, Tanju

2018-05-29

Seasonal algal blooms in freshwater and marine water can increase the input of algal organic matter (AOM) to the pool of dissolved organic matter. The impact of bromide (Br - ) and iodide (I - ) on the formation of regulated and unregulated disinfection byproducts (DBPs) was studied from chlorination of AOM solutions extracted from three species of cultured isolates of freshwater and marine algae (Microcystis aeruginosa (MA), Synechococcus (SYN), and Alexandrium tamarense (AT)). Comparable concentrations of DBPs were formed from three types of AOM. In the absence of Br - , trihalomethanes (THMs), haloacetic acids (HAAs), and haloacetaldehydes (HALs) were the main groups of DBP formed, and haloacetonitriles (HANs) were formed at lower concentrations. In contrast, the formation of iodinated THMs was <8 nM (1.7 μg/L) since most of initial I - was oxidized to iodate. Increasing initial Br - concentrations increased the formation of THMs and HANs, while concentrations of total organic halogen and HAA remained stable. On the contrary, total HAL concentrations decreased due to the instability of bromated HALs. Decreasing the specific UV absorbance (SUVA) value of AOM favours bromine substitution since bromine more preferentially reacts with low reactivity organic matter than chlorine. Increasing the pH enhanced the formation of THMs but decreased the formation of HANs. Concentrations of HANs and HALs decreased at high pH (e.g., 9.0), high initial chlorine concentration and long reaction time due to the decomposition. Based on the cytotoxicity calculations, unregulated HANs and HALs were the main contributors for the total toxicity of DBPs measured, even though based on the weight regulated THMs and HAAs predominated. Copyright © 2018 Elsevier Ltd. All rights reserved.

Interleukin-6 and neopterin levels in the serum and saliva of patients with Lichen planus and oral Lichen planus.

PubMed

Abdel-Haq, Ayman; Kusnierz-Cabala, Beata; Darczuk, Dagmara; Sobuta, Eliza; Dumnicka, Paulina; Wojas-Pelc, Anna; Chomyszyn-Gajewska, Maria

2014-11-01

Lichen planus together with its oral variant is a chronic, inflammatory disease of the skin and the mucosa of unclear aetiology and with an unpredictable course that still poses a major problem in terms of diagnosis and treatment. The objective of this study was to assess the concentrations of interleukin-6 (IL-6) and neopterin in saliva and serum of patients with lichen planus (including reticular and erosive form of oral lichen planus) and to compare them with the concentrations observed in healthy controls. The study material comprised serum and saliva samples from 56 patients diagnosed with lichen planus and 56 healthy volunteers. The ELISA test was used to measure concentrations of IL-6 and neopterin in the serum and saliva of the study participants. The concentrations of IL-6 in saliva and serum of patients with lichen planus were significantly higher than in controls (P = 0.0002; P < 0.0001). The difference remains significant after adjustment for gingivitis and age. Patients with atrophic-erosive oral lichen planus had significantly higher IL-6 concentrations in their saliva compared to patients with reticular form of disease (P = 0.01). The concentrations of neopterin were significantly higher in the serum but not in saliva of lichen planus patients vs. controls (P <0.0001). Serum levels of proinflammatory cytokines IL-6 and neopterin are increased in lichen planus as well as the salivary concentrations of IL-6. The differences observed in IL-6 levels in patients with erosive-atrophic forms of oral lichen planus may indicate a substantial role played by the cytokine in the disease. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Dynamically formed admicelle layer to control the amplitude of cathodic electroosmotic flow.

PubMed

Erny, Guillaume L; Gonçalves, Bruna M; Esteves, Valdemar I

2012-09-21

In this manuscript, a method to precisely adjust the amplitude of a cathodic electroosmotic flow is described. The method uses a capillary pre-coated with a cationic polymer (polybrene), in presence of an anionic surfactant such as sodium dodecyl sulfate. At low concentration of surfactant, molecules will self-assemble to form an immobilized hemimicelle layer with the anionic "head" in contact with the cationic coating and the hydrophobic tail reaching into the background electrolyte. At higher concentration, surfactant molecules in solution will then interact, via hydrophobic interactions, to form an admicelle layer. It has been demonstrated that the admicelle layer can be constructed with either pure anionic surfactant (SDS), or a mixture of anionic and neutral surfactants. Admicelle coatings can be used to control the electroosmotic flow (EOF). While at low surfactant concentration the amplitude of the EOF depends on the concentration of the surfactants concentration, when this concentration reaches the critical admicelle concentration the EOF becomes near constant. The amplitude of the EOF can also be adjusted via the relative proportion of neutral and ionic surfactant in solution. Using this approach, the EOF was varied from 0.450 to 3.848 × 10(-8)m(2)V(-1)s(-1) with a precision below 0.050 × 10(-8)m(2)V(-1)s(-1) (standard deviation measured with three replicates). The coating has been tested using a mix of triazines (atrazine, simazine and terbuthylazine) and a beer sample. With the beer sample an average relative standard deviation of 1.5% for the migration time and of 2.2% for the corrected peak area was obtained. Copyright © 2012 Elsevier B.V. All rights reserved.

[Determination of sensitivity of biofilm-positive forms of microorganisms to antibiotics].

PubMed

Holá, Veronika; Růzicka, Filip; Tejkalová, Renata; Votava, Miroslav

2004-10-01

Nosocomial infections caused by biofilm-positive microorganisms are a serious therapeutic problem. In the biofilm, microorganisms are protected against adverse effects of the external environment, including the action of antibiotics. It is well known that the values of minimum inhibitory concentrations (MIC) determined for planktonic forms do not correspond to the actual concentrations of antibiotics necessary for the eradication of bacteria in a biofilm. The purpose of the study was to propose a method of determining minimum biofilm inhibitory concentrations (MBIC) and minimum biofilm eradication concentrations (MBEC) and to compare these values with MIC values. Biofilm-positive strains of Staphylococcus epidermidis were cultured so as to form a biofilm layer on polystyrene pegs. The biofilm on the pegs was then exposed to the action of antibiotics and after 18 hours we determined the minimum biofilm inhibitory concentration (MBIC). The evaluation of minimum biofilm eradication concentrations was done colorimetrically from the metabolic activity of surviving cells. MBIC and MBEC values were many times higher than MIC values. We selected such a duration of the biofilms cultivation on the pegs of the plate, which ensured that the number of bacterial cells corresponded to standard MIC assessment. The MBEC values established in our study indicate that the currently used concentrations of tested antibiotics cannot be used in monotherapy for an efficacious eradication of a biofilm. The MBEC determination is a far more laborious and time-consuming method than the determination of MIC, but the use of plates with pegs facilitates the handling of biofilms. The advantage of our method is the possibility of standardization of the size of the inoculum and thus of the whole MBEC assessment.

Variation of rock-forming metals in sub-annual increments of modern Greenland snow

USGS Publications Warehouse

Hinkley, T.K.

1992-01-01

Modern snowpack from central south Greenland was sampled in sub-seasonal increments and analysed for a suite of major, minor and trace rock-forming metals (K, Rb, Cs, Ca, Sr, Ba). There is a sharp seasonal concentration maximum for all six metals that comes in summer, later than mid-June. Metal concentrations in all other parts of the year's snowpack are up to 10 or more times smaller. The concentration maximum is preceded by low values in autumn-winter, very low values in early-mid-spring, and moderate-to-high values in late spring early summer; this pattern is seen consistently in three separate time stratigraphic intervals representing the same seasonal periods, spanning the time interval 1981-1984. The absolute concentration values of the snow strata representing the low-concentration portion of the year, autumn-winter-spring, may vary substantially from year to year, by a factor of two, or more. The finding that all rock-forming metals are at a sharp concentration maximum in late summer contrasts with the interpretations of several other studies in high-latitude northern regions. Those studies have reported a broad maximum of continental dust-associated metals in late winter and spring. However samples of the other studies have mostly come from regions farther to the north, and the analyses have emphasized industrial pollutant metals rather than the matched rock-forming suite of the present study. The metals measured were chosen to give information about the origin and identity of the rock and soil dusts, and sea salts, present as impurities in the snow. Metal ratios indicate that the dusts in the snowpacks are of continental origin and from ferromagnesian rocks. Source rock types for dusts in central south Greenland snow contrast with the felsic rock dusts of the Sierra Nevada, CA, annual snowpacks, and with the very felsic rock dusts in large south central Alaskan mountain glaciers. Samples in which masses of sea salt are much larger than those of rock dusts may be identified by small changes in metal ratios caused by moderate increases of K and Ca from marine sources, nearly unaccompanied by the minor and trace metals Rb, Cs and Ba, that are very rare in the oceans. A sampling frequency, such as that of the present study, that divides a year's accumulation into 8-10 subsamples is sufficient to reveal details of the time pattern of variation in proportions and concentrations of metals that give information about atmospheric deposition of important types of earth materials.Modern snowpack from central south Greenland was sampled in sub-seasonal increments and analyzed for a suite of major, minor and trace rock-forming metals (K, Rb, Cs, Ca, Sr, Ba). There is a sharp seasonal concentration maximum for all six metals that comes in summer, later than mid-June. Metal concentrations in all other parts of the year's snowpack are up to 10 or more times smaller. The concentration maximum is preceded by low values in autumn-winter, very low values in early-mid-spring, and moderate-to-high values in late spring-early summer; this pattern is seen consistently in three separate time stratigraphic intervals representing the same seasonal periods, spanning the time interval 1981-1984. The absolute concentration values of the snow strata representing the low-concentration portion of the year, autumn-winter-spring, may vary substantially from year to year, by a factor of two, or more. The finding that all rock-forming metals are at a sharp concentration maximum in late summer contrasts with the interpretations of several other studies in high-latitude northern regions. Those studies have reported a broad maximum of continental dust-associated metals in late winter and spring. However, samples of the other studies have mostly come from regions farther to the north, and the analyses have emphasized industrial pollutant metals rather than the matched rock-forming suite of the present study. The metals measured were chosen to give informati

Viscoelastic and Functional Properties of Cod-Bone Gelatin in the Presence of Xylitol and Stevioside

NASA Astrophysics Data System (ADS)

Nian, Linyu; Cao, Ailing; Wang, Jing; Tian, Hongyu; Liu, Yongguo; Gong, Lingxiao; Cai, Luyun; Wang, Yuhao

2018-05-01

The physical, rheological, structural and functional properties of cod bone gelatin (CBG) with various concentrations (0, 2, 4, 6, 10 and 15%) of low-calorie sweeteners (xylitol (X) and stevioside (S)) to form gels were investigated. The gel strength of CBGX increased with increased xylitol due presumably to hydrogen bonds between xylitol and gelatin, but with CBGS the highest gel strength occurred when S concentration was 4%. Viscosity of CBGS samples were higher than CBGX due to S’s high molecular mass. The viscoelasticity (G' and G″), foaming capacity and fat binding capacity of CBGX were higher while foam stability was lower. The emulsion activity and emulsion stability of CBGX were a little lower than CBGS at the same concentration. The structure of X is linear making it easier to form a dense three-dimensional network structure, while the complex cyclic structure of S had more difficulty forming a network structure with cod bone gelatin. Therefore, X may be a better choice for sweetening gelatin gels.

Characterization of iron-phosphate-silicate chemical garden structures.

PubMed

Barge, Laura M; Doloboff, Ivria J; White, Lauren M; Stucky, Galen D; Russell, Michael J; Kanik, Isik

2012-02-28

Chemical gardens form when ferrous chloride hydrate seed crystals are added or concentrated solutions are injected into solutions of sodium silicate and potassium phosphate. Various precipitation morphologies are observed depending on silicate and phosphate concentrations, including hollow plumes, bulbs, and tubes. The growth of precipitates is controlled by the internal osmotic pressure, fluid buoyancy, and membrane strength. Additionally, rapid bubble-led growth is observed when silicate concentrations are high. ESEM/EDX analysis confirms compositional gradients within the membranes, and voltage measurements across the membranes during growth show a final potential of around 150-200 mV, indicating that electrochemical gradients are maintained across the membranes as growth proceeds. The characterization of chemical gardens formed with iron, silicate, and phosphate, three important components of an early earth prebiotic hydrothermal system, can help us understand the properties of analogous structures that likely formed at submarine alkaline hydrothermal vents in the Hadean-structures offering themselves as the hatchery of life. © 2011 American Chemical Society

Supra-physiological folic acid concentrations induce aberrant DNA methylation in normal human cells in vitro.

PubMed

Charles, Michelle A; Johnson, Ian T; Belshaw, Nigel J

2012-07-01

The micronutrients folate and selenium may modulate DNA methylation patterns by affecting intracellular levels of the methyl donor S-adenosylmethionine (SAM) and/or the product of methylation reactions S-adenosylhomocysteine (SAH). WI-38 fibroblasts and FHC colon epithelial cells were cultured in the presence of two forms of folate or four forms of selenium at physiologically-relevant doses, and their effects on LINE-1 methylation, gene-specific CpG island (CGI) methylation and intracellular SAM:SAH were determined. At physiologically-relevant doses the forms of folate or selenium had no effect on LINE-1 or CGI methylation, nor on intracellular SAM:SAH. However the commercial cell culture media used for the selenium studies, containing supra-physiological concentrations of folic acid, induced LINE-1 hypomethylation, CGI hypermethylation and decreased intracellular SAM:SAH in both cell lines. We conclude that the exposure of normal human cells to supra-physiological folic acid concentrations present in commercial cell culture media perturbs the intracellular SAM:SAH ratio and induces aberrant DNA methylation.

Chemical form analysis of reaction products in Cs-adsorption on stainless steel by means of HAXPES and SEM/EDX

NASA Astrophysics Data System (ADS)

Kobata, M.; Okane, T.; Nakajima, K.; Suzuki, E.; Ohwada, K.; Kobayashi, K.; Yamagami, H.; Osaka, M.

2018-01-01

In this study, for the understandings of Cesium (Cs) adsorption behavior on structure materials in severe accidents in a light water nuclear reactor, the chemical state of Cs and its distribution on the surface of SUS304 stainless steel (SS) with different Si concentrations was investigated by hard X-ray photoelectron spectroscopy (HAXPES) and scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDX). As a result, it was found that Cs is selectively adsorbed at the site where Si distributes with a high concentration. CsFeSiO4 is the dominant Cs products in case of low Si content, while Cs2Si2O5 and Cs2Si4O9 are formed in addition to CsFeSiO4 in case of high Si content. The chemical forms of the Cs compounds produced in the adsorption process on the SS surface have a close correlation with the concentration and chemical states of Si originally included in SS.

Viscoelastic and Functional Properties of Cod-Bone Gelatin in the Presence of Xylitol and Stevioside.

PubMed

Nian, Linyu; Cao, Ailing; Wang, Jing; Tian, Hongyu; Liu, Yongguo; Gong, Lingxiao; Cai, Luyun; Wang, Yuhao

2018-01-01

The physical, rheological, structural and functional properties of cod bone gelatin (CBG) with various concentrations (0, 2, 4, 6, 10, and 15%) of low-calorie sweeteners [xylitol (X) and stevioside (S)] to form gels were investigated. The gel strength of CBGX increased with increased xylitol due presumably to hydrogen bonds between xylitol and gelatin, but with CBGS the highest gel strength occurred when S concentration was 4%. Viscosity of CBGS samples were higher than CBGX due to S's high molecular mass. The viscoelasticity (G' and G''), foaming capacity and fat binding capacity of CBGX were higher while foam stability was lower. The emulsion activity and emulsion stability of CBGX were a little lower than CBGS at the same concentration. The structure of X is linear making it easier to form a dense three-dimensional network structure, while the complex cyclic structure of S had more difficulty forming a network structure with cod bone gelatin. Therefore, X may be a better choice for sweetening gelatin gels.

Subcellular distribution and chemical forms of cadmium in the edible seaweed, Porphyra yezoensis.

PubMed

Zhao, Yanfang; Wu, Jifa; Shang, Derong; Ning, Jinsong; Zhai, Yuxiu; Sheng, Xiaofeng; Ding, Haiyan

2015-02-01

The subcellular distribution and chemical forms of Cd were investigated in the edible seaweed, Porphyra yezoensis. The seaweed was exposed to different Cd concentrations (0.01, 0.05, 0.1, 0.5, 1.0 and 5.0mgl(-1)) for up to 96h. In both the controls (no Cd added) and treatment groups, 41.2-79.2% of Cd was localised in the cell wall, and the proportion of Cd in the cell wall increased with increasing concentrations of Cd and exposure time. In the control groups, 74.8% of Cd was extracted by 1M NaCl, followed by 2% acetic acid, HAC (18.9%). In the treatment groups, most Cd was extracted by 2% HAC. The proportion of Cd extracted by 2% HAC increased with exposure to increasing concentrations of Cd and over time. Cell wall deposition and forming of precipitates with phosphate may be a key strategy to reduce Cd toxicity in P. yezoensis. Copyright © 2014 Elsevier Ltd. All rights reserved.

Evaluation of thirteen haloacetic acids and ten trihalomethanes formation by peracetic acid and chlorine drinking water disinfection.

PubMed

Xue, Runmiao; Shi, Honglan; Ma, Yinfa; Yang, John; Hua, Bin; Inniss, Enos C; Adams, Craig D; Eichholz, Todd

2017-12-01

Free chlorine is a commonly used disinfectant in drinking water treatment. However, disinfection by-products (DBPs) are formed during water disinfection. Haloacetic acids (HAAs) and trihalomethanes (THMs) are two major groups of DBPs. Iodo-HAAs and iodo-THMs (I-HAAs and I-THMs) are formed during the disinfection of the water containing high levels of iodide and are much more toxic than their chlorinated and brominated analogs. Peracetic acid (PAA) is a strong antimicrobial disinfectant that is expected to reduce the formation of HAAs and THMs during disinfection. In this study, the formations of thirteen HAAs and ten THMs, including the iodinated forms, have been investigated during PAA disinfection and chlorination as the comparison. The DBP formations under different iodide concentrations, pHs, and contact times were systematically investigated. Two types of commercial PAAs containing different concentrations of PAA and hydrogen peroxide (H 2 O 2 ) were studied. A solid-phase microextraction gas chromatography-mass spectrometry method was upgraded for THM analysis including I-THMs. HAAs were analyzed by following a recently developed high performance ion chromatography-tandem mass spectrometry method. Results show that the ratio of PAA and H 2 O 2 concentration significantly affect the formation of I-THMs and I-HAAs. During PAA disinfection with lower PAA than H 2 O 2 , no detectable levels of THMs and HAAs were observed. During PAA disinfection with higher PAA than H 2 O 2 , low levels of monoiodoacetic acid, diiodoacetic acid, and iodoform were formed, and these levels were enhanced with the increase of iodide concentration. No significant quantities of chloro- or bromo-THMs and HAAs were formed during PAA disinfection treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Detergent effects on enzyme activity and solubilization of lipid bilayer membranes.

PubMed

Womack, M D; Kendall, D A; MacDonald, R C

1983-09-07

Over 50 detergents were tested to establish which would be most effective in releasing proteins from membrane-bounded compartments without denaturing them. Various concentrations each of detergent were tested for two activities: (1) solubilization of egg phospholipid liposomes as measured by reduction of turbidity and (2) effect of detergent concentration on the activities of soluble, hydrolytic enzymes. Those detergents most effective in solubilizing 0.2% lipid and least detrimental to enzymes were five pure, synthetic compounds recently introduced: CHAPS, CHAPSO, Zwittergents 310 and 312, and octylglucoside. Industrial detergents were generally much inferior, insofar as they solubilized membranes inefficiently and/or inactivated certain hydrolytic enzymes readily. The five detergents were characterized by (a) an unusually high critical micelle concentration and (b) a preference for forming mixed micelles with lipids instead of forming pure micelles, as indicated by an ability to solubilize lipid at concentrations of detergent significantly below the critical micelle concentration. This characteristic permits solubilization of high concentrations of membrane below the critical micelle concentration of the detergent so that protein denaturation is minimized. A generally applicable guideline that emerged from this study is that detergents should be used at approximately their critical micelle concentration which should not be exceeded by the concentration of membrane. Similar considerations should apply to the use of detergents in purifying and reconstituting intrinsic membrane proteins.

Carbon nanotube composite materials

DOEpatents

O'Bryan, Gregory; Skinner, Jack L; Vance, Andrew; Yang, Elaine Lai; Zifer, Thomas

2015-03-24

A material consisting essentially of a vinyl thermoplastic polymer, un-functionalized carbon nanotubes and hydroxylated carbon nanotubes dissolved in a solvent. Un-functionalized carbon nanotube concentrations up to 30 wt % and hydroxylated carbon nanotube concentrations up to 40 wt % can be used with even small concentrations of each (less than 2 wt %) useful in producing enhanced conductivity properties of formed thin films.

40 CFR 92.121 - Oxides of nitrogen analyzer calibration and check.

Code of Federal Regulations, 2010 CFR

2010-07-01

... of full-scale concentration. It is permitted to use additional concentrations. (v) Perform a linear least-square regression on the data generated. Use an equation of the form y=mx where x is the actual chart deflection and y is the concentration. (vi) Use the equation z=y/m to find the linear chart...

Compact Infrared Spectrometers

NASA Technical Reports Server (NTRS)

Mouroulis, Pantazis

2009-01-01

Concentric spectrometer forms are advantageous for constructing a variety of systems spanning the entire visible to infrared range. Spectrometer examples are given, including broadband or high resolution forms. Some issues associated with the Dyson catadioptric type are also discussed.

Triggered pore-forming agents

DOEpatents

Bayley, Hagan; Walker, Barbara J.; Chang, Chung-yu; Niblack, Brett; Panchal, Rekha

1998-01-01

An inactive pore-forming agent which is activated to lytic function by a condition such as pH, light, heat, reducing potential, or metal ion concentration, or substance such as a protease, at the surface of a cell.

M-DNA is stabilised in G•C tracts or by incorporation of 5-fluorouracil

PubMed Central

Wood, David O.; Dinsmore, Michael J.; Bare, Grant A.; Lee, Jeremy S.

2002-01-01

M-DNA is a complex between the divalent metal ions Zn2+, Ni2+ and Co2+ and duplex DNA which forms at a pH of ∼8.5. The stability and formation of M-DNA was monitored with an ethidium fluorescence assay in order to assess the relationship between pH, metal ion concentration, DNA concentration and the base composition. The dismutation of calf thymus DNA exhibits hysteresis with the formation of M-DNA occurring at a higher pH than the reconversion of M-DNA back to B-DNA. Hysteresis is most prominent with the Ni form of M-DNA where complete reconversion to B-DNA takes several hours even in the presence of EDTA. Increasing the DNA concentration leads to an increase in the metal ion concentration required for M-DNA formation. Both poly(dG)•poly(dC) and poly(dA)•poly(dT) formed M-DNA more readily than the corresponding mixed sequence DNAs. For poly(dG)•(poly(dC) M-DNA formation was observed at pH 7.4 with 0.5 mM ZnCl2. Modified bases were incorporated into a 500 bp fragment of phage λ DNA by polymerase chain reaction. DNAs in which guanine was replaced with hypoxanthine or thymine with 5-fluorouracil formed M-DNA at pHs below 8 whereas substitutions such as 2-aminoadenine and 5-methylcytosine had little effect. Poly[d(A5FU)] also formed a very stable M-DNA duplex as judged from Tm measurements. It is evident that the lower the pKa of the imino proton of the base, the lower the pH at which M-DNA will form; a finding that is consistent with the replacement of the imino proton with the metal ion. PMID:12000844

Effects on soil phosphorus dynamics of municipal solid waste compost addition to a burnt and unburnt forest soil.

PubMed

Turrión, María-Belén; Bueis, Teresa; Lafuente, Francisco; López, Olga; San José, Esther; Eleftheriadis, Alexandros; Mulas, Rafael

2018-06-12

The main aim of this research was to assess the effects of municipal solid waste compost (MSWC) addition to a burnt and unburnt calcareous soil, on the distribution of soil P forms in particle-size and extractable fractions. Three MSWC doses (1, 2 and 4% w/w) were added to burnt and unburnt soil samples and were incubated for 92 days at 29 °C and 75% of field capacity moisture. A particle-size fractionation followed by a sequential P extraction procedure was carried out. The burnt soil showed significantly lower concentrations of organic P forms (P org ) and significantly higher concentrations of stable P forms than the unburnt soil. Besides, in both burnt and unburnt soils, most P-forms presented higher concentrations in the clay fractions than in the sand and silt fractions, possibly due to the different proportions of microbial synthesized and plant-derived substances in the different particle-size fractions. Finer fractions of MSWC showed higher total P and P org concentrations than coarser fractions. Our results showed that the highest dose of MSWC was the most effective one for the rehabilitation of the burnt soil. MSWC amendment also caused an increase in soil P availability in the unburnt soil which initially contained relatively low levels of P. During the incubation process, a high proportion of organic P contained in the MSWC was mineralized into inorganic P forms. These forms were precipitated with Ca cations which are very abundant in these calcareous soils, significantly increasing the P fraction extracted by HCl in both amended soils. Hence, adding compost to the soil involved an increase in the available P reservoir in the long term. The combination of particle-size fractionation, chemical sequential extraction and incubation experiments can be a valuable tool for splitting soil phosphorus into different fractions regarding their availability in relation to short and long-term transformations in soil. Copyright © 2017 Elsevier B.V. All rights reserved.

Simple, Flexible, Trigonometric Taper Equations

Treesearch

Charles E. Thomas; Bernard R. Parresol

1991-01-01

There have been numerous approaches to modeling stem form in recent decades. The majority have concentrated on the simpler coniferous bole form and have become increasingly complex mathematical expressions. Use of trigonometric equations provides a simple expression of taper that is flexible enough to fit both coniferous and hard-wood bole forms. As an illustration, we...

The impact of ethanol extract of propolis on biofilm forming by Proteus Mirabilis strains isolated from chronic wounds infections.

PubMed

Kwiecińska-Piróg, Joanna; Skowron, Krzysztof; Śniegowska, Agata; Przekwas, Jana; Balcerek, Maciej; Załuski, Daniel; Gospodarek-Komkowska, Eugenia

2018-05-04

Alcoholic propolis extracts may be used to eliminate microbes in mucous membranes and skin inflammations and in wound infections. The aim of this study was an assessment of the ethanol extract of propolis (EEP) activity against biofilm formation by P. mirabilis. Six clinical strains of P. mirabilis isolated from patients with chronic wound infection, and one reference strain of P. mirabilis ATCC 29906 were used. Biofilm was formed in 96-well plate. In order to evaluate the effect of EEP at a concentration range of 1.56-100 mg/mL on the forming and mature biofilm, P. mirabilis cells were released by sonication. In this study the effectiveness of 25-100 mg/mL of EEP on the forming P. mirabilis biofilm and concentrations of 25-50 mg/mL of EEP on formed biofilm has been demonstrated. Our results suggest the possibility of using the EEP in treatment of chronic wound infection caused by P. mirabilis.

Purification of trona ores by conditioning with an oil-in-water emulsion

DOEpatents

Miller, J. D.; Wang, Xuming; Li, Minhua

2009-04-14

The present invention is a trona concentrate and a process for floating gangue material from trona ore that comprises forming an emulsion, conditioning the trona ore at a high solids content in a saturated trona suspension, and then floating and removing the gangue material. The process for separating trona from gangue materials in trona ore can include emulsifying an oil in an aqueous solution to form an oil-in-water emulsion. A saturated trona suspension having a high solids content can also be formed having trona of a desired particle size. The undissolved trona in the saturated suspension can be conditioned by mixing the saturated suspension and the oil-in-water emulsion to form a conditioning solid suspension of trona and gangue material. A gas can be injected through the conditioning solid suspension to float the gangue material. Thus, the floated gangue material can be readily separated from the trona to form a purified trona concentrate without requirements of additional heat or other expensive processing steps.

Nanocrystal growth and morphology of PbTeSe-ZnSe composite thin films prepared by one-step synthesis method

NASA Astrophysics Data System (ADS)

Sato, Kazuhisa; Abe, Seishi

2016-10-01

The microstructure of polycrystalline PbTe1-xSex-ZnSe composite thin films has been studied by scanning transmission electron microscopy and electron diffraction. The films were prepared by the one-step synthesis method using simultaneous evaporation of PbTe and ZnSe. The nanocrystals of PbTe1-xSex are formed in a ZnSe matrix. Tellurium concentration can be tuned by controlling the PbTe evaporation source temperatures between 753 K and 793 K. Binary PbSe nanocrystals were formed at 753 K, while ternary PbTe1-xSex nanocrystals were formed at 793 K. The nanocrystals grow in a granular shape at the initial stage of film growth, and the morphology changes to nanowire-shape as the film grows, irrespective of the Te concentration. The ternary PbTe1-xSex nanocrystals were composed of two phases with different Te concentration; Te-rich (Se-poor) granular crystals were formed near the bottom half parts of the film and Te-poor (Se-rich) nanowires were formed at the upper half parts of the film. Columnar ZnSe crystals contain high-density {111} stacking faults due to the low stacking fault energy of ZnSe. A balance of deposition and re-evaporation on the substrate during the film growth will be responsible for the resultant nanocrystal morphology.

Use of an exchange method to estimate the association and dissociation rate constants of cadmium complexes formed with low-molecular-weight organic acids commonly exuded by plant roots.

PubMed

Schneider, André; Nguyen, Christophe

2011-01-01

Organic acids released from plant roots can form complexes with cadmium (Cd) in the soil solution and influence metal bioavailability not only due to the nature and concentration of the complexes but also due to their lability. The lability of a complex influences its ability to buffer changes in the concentration of free ions (Cd); it depends on the association (, m mol s) and dissociation (, s) rate constants. A resin exchange method was used to estimate and (m mol s), which is the conditional estimate of depending on the calcium (Ca) concentration in solution. The constants were estimated for oxalate, citrate, and malate, three low-molecular-weight organic acids commonly exuded by plant roots and expected to strongly influence Cd uptake by plants. For all three organic acids, the and estimates were around 2.5 10 m mol s and 1.3 × 10 s, respectively. Based on the literature, these values indicate that the Cd- low-molecular-weight organic acids complexes formed between Cd and low-molecular-weight organic acids may be less labile than complexes formed with soil soluble organic matter but more labile than those formed with aminopolycarboxylic chelates. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

The functional interaction between abaecin and pore-forming peptides indicates a general mechanism of antibacterial potentiation.

PubMed

Rahnamaeian, Mohammad; Cytryńska, Małgorzata; Zdybicka-Barabas, Agnieszka; Vilcinskas, Andreas

2016-04-01

Long-chain proline-rich antimicrobial peptides such as bumblebee abaecin show minimal activity against Gram-negative bacteria despite binding efficiently to specific intracellular targets. We recently reported that bumblebee abaecin interacts with Escherichia coli DnaK but shows negligible antibacterial activity unless it is combined with sublethal doses of the pore-forming peptide hymenoptaecin. These two bumblebee peptides are co-expressed in vivo in response to a bacterial challenge. Here we investigated whether abaecin interacts similarly with pore-forming peptides from other organisms by replacing hymenoptaecin with sublethal concentrations of cecropin A (0.3 μM) or stomoxyn (0.05 μM). We found that abaecin increased the membrane permeabilization effects of both peptides, confirming that it can reduce the minimal inhibitory concentrations of pore-forming peptides from other species. We also used atomic force microscopy to show that 20 μM abaecin combined with sublethal concentrations of cecropin A or stomoxyn causes profound structural changes to the bacterial cell surface. Our data indicate that the potentiating functional interaction between abaecin and pore-forming peptides is not restricted to specific co-expressed peptides from the same species but is likely to be a general mechanism. Combination therapies based on diverse insect-derived peptides could therefore be used to tackle bacteria that are recalcitrant to current antibiotics. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Radiation-induced polymerization of glass-forming systems. IV. Effect of the homogeneity of polymerization phase and polymer concentration on temperature dependence of initial polymerization rate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaetsu, I.; Ito, A.; Hayashi, K.

1973-06-01

The effect of homogeneity of polymerization phase and monomer concentration on the temperature dependence of initial polymerization rate was studied in the radiation-induced radical polymerization of binary systems consisting of glass-forming monomer and solvent. In the polymerization of a completely homogeneous system such as HEMA-propylene glycol, a maximum and a minimum in polymerization rates as a function of temperature, characteristic of the polymerization in glass-forming systems, were observed for all monomer concentrations. However, in the heterogeneous polymerization systems such as HEMA-triacetin and HEMAisoamyl acetate, maximum and minimum rates were observed in monomer-rich compositions but not at low monomer concentrations. Furthermore,more » in the HEMA-dioctyl phthalate polymerization system, which is extremely heterogeneous, no maximum and minimum rates were observed at any monomer concentration. The effect of conversion on the temperature dependence of polymerization rate in homogeneous bulk polymerization of HEMA and GMA was investigated. Maximum and minimum rates were observed clearly in conversions less than 10% in the case of HEMA and less than 50% in the case of GMA, but the maximum and minimum changed to a mere inflection in the curve at higher conversions. A similar effect of polymer concentration on the temperature dependence of polymerization rate in the GMA-poly(methyl methacrylate) system was also observed. It is deduced that the change in temperature dependence of polymerization rate is attributed to the decrease in contribution of mutual termination reaction of growing chain radicals to the polymerization rate. (auth)« less

The structure evolution mechanism of electrodeposited porous Ni films on NH4Cl concentration

NASA Astrophysics Data System (ADS)

Yu, Xiangtao; Wang, Mingyong; Wang, Zhi; Gong, Xuzhong; Guo, Zhancheng

2016-01-01

NH4Cl was an important component for the electrodeposition of porous metal films through hydrogen bubble template approach. The effects of NH4Cl concentrations on pore formation and structure evolution of the electrodeposited porous Ni films were studied. It was found that Ni films electrodeposited from solutions with 0.25⿿0.35 M NH4Cl were compact. When NH4Cl concentrations were 0.4⿿0.75 M and 0.85⿿3 M, porous Ni films with dish-like and honeycomb-like pores were electrodeposited, respectively. To form porous structure, the critical amounts of Ni in mass deposited onto the electrode must be achieved. However, at lower NH4Cl concentration, Ni electrodeposition was interrupted after about 15 s due to Ni2+ hydrolysis. The critical amounts of Ni in mass were not reached, and compact Ni films were obtained. When NH4Cl concentrations exceeded 0.4 M, Ni2+ hydrolysis was inhibited due to the enhanced buffer ability of solution and Ni(NH3)n2+ (2 ⿤ n ⿤ 6) complexes became the discharged ions. Ni electrodeposition proceeded continuously and reached the critical amounts of Ni in mass, and porous Ni films were formed. At higher NH4Cl concentration, hydrogen was produced mainly by the electrochemical reduction of NH4+. pH near cathode was hardly changed, and Ni2+ ions with low overpotential were reduced. The rough Ni films were formed, which led to smaller break-off diameter of bubbles. Therefore, the pore sizes of Ni films were decreased.

Characteristics of radionuclide contamination of different zones of Semipalatinsk Nuclear Test Site ``Opytnoe pole''

NASA Astrophysics Data System (ADS)

Kadyrzhanov, K. K.; Khazhekber, S.; Lukashenko, S. N.; Solodukhin, V. P.; Kazachevskiy, I. V.; Poznyak, V. L.; Knyazev, B. B.; Rofer, Ch.

2003-01-01

Data on the spatial distribution of radionuclides (241Am, 239Pu, 137Cs and 152Eu) formed during nuclear explosions of different types near P2 SNTS test site are presented. Radionuclide contamination induced by the explosions varies in the concentrations of individual radionuclides, their proportions and species. Examination of the variations is a crucial task to plan remediation activities as well as those aimed at decrease of radiation risk for population and prevention of repeated contamination. Concentrations of 241Am and 239+240Pu that are the most toxic radionuclides in the area lie in hundred thousands of Bqkg-1. The most contaminated areas are classified by the radionuclide concentration, ratio and form present in soil.

Effect of molecular structure on the hydration of structurally related antidepressant drugs

NASA Astrophysics Data System (ADS)

Cheema, M. A.; Taboada, P.; Barbosa, S.; Siddiq, M.; Mosquera, V.

Apparent molal volumes and adiabatic compressibilities of aqueous solutions of the amphiphilic cationic antidepressant drugs butriptyline and doxepin hydrochlorides have been determined from density and ultrasound velocity measurements in the temperature range 20-50°C. Critical concentrations for aggregation of these drugs were obtained from ultrasound velocity measurements. Negative deviations from the Debye-Hückel limiting law of the apparent molal volume were obtained from both drugs in all temperature ranges, except for doxepin at 50°C, which provides evidence of no pre-association at concentrations below the critical concentration. Apparent molal adiabatic compressibilities of the aggregates formed by these drugs were typical of those corresponding for an aggregate formed by a stacking process.

Membrane loop process for separating carbon dioxide for use in gaseous form from flue gas

DOEpatents

Wijmans, Johannes G; Baker, Richard W; Merkel, Timothy C

2014-10-07

The invention is a process involving membrane-based gas separation for separating and recovering carbon dioxide emissions from combustion processes in partially concentrated form, and then transporting the carbon dioxide and using or storing it in a confined manner without concentrating it to high purity. The process of the invention involves building up the concentration of carbon dioxide in a gas flow loop between the combustion step and a membrane separation step. A portion of the carbon dioxide-enriched gas can then be withdrawn from this loop and transported, without the need to liquefy the gas or otherwise create a high-purity stream, to a destination where it is used or confined, preferably in an environmentally benign manner.

Advection fog formation and aerosols produced by combustion-originated air pollution

NASA Technical Reports Server (NTRS)

Hung, R. J.; Liaw, G. S.; Vaughan, O. H., Jr.

1980-01-01

The way in which pollutants produced by the photochemical reaction of NO(X) and SO(X) affect the quality of the human environment through such phenomena as the formation of advection fog is considered. These pollutants provide the major source of condensation nuclei for the formation of fog in highways, airports and seaports. Results based on the monodisperse, multicomponent aerosol model show that: (1) condensation nuclei can grow and form a dense fog without the air having attained supersaturation; (2) the mass concentration range for NO(X) is one-third that of SO(X); and (3) the greater the mass concentration, the particle concentration, and the radius of condensation nuclei, the denser the fog that is formed.

Ice nucleation and dehydration in the Tropical Tropopause Layer.

PubMed

Jensen, Eric J; Diskin, Glenn; Lawson, R Paul; Lance, Sara; Bui, T Paul; Hlavka, Dennis; McGill, Matthew; Pfister, Leonhard; Toon, Owen B; Gao, Rushan

2013-02-05

Optically thin cirrus near the tropical tropopause regulate the humidity of air entering the stratosphere, which in turn has a strong influence on the Earth's radiation budget and climate. Recent high-altitude, unmanned aircraft measurements provide evidence for two distinct classes of cirrus formed in the tropical tropopause region: (i) vertically extensive cirrus with low ice number concentrations, low extinctions, and large supersaturations (up to ∼70%) with respect to ice; and (ii) vertically thin cirrus layers with much higher ice concentrations that effectively deplete the vapor in excess of saturation. The persistent supersaturation in the former class of cirrus is consistent with the long time-scales (several hours or longer) for quenching of vapor in excess of saturation given the low ice concentrations and cold tropical tropopause temperatures. The low-concentration clouds are likely formed on a background population of insoluble particles with concentrations less than 100 L(-1) (often less than 20 L(-1)), whereas the high ice concentration layers (with concentrations up to 10,000 L(-1)) can only be produced by homogeneous freezing of an abundant population of aqueous aerosols. These measurements, along with past high-altitude aircraft measurements, indicate that the low-concentration cirrus occur frequently in the tropical tropopause region, whereas the high-concentration cirrus occur infrequently. The predominance of the low-concentration clouds means cirrus near the tropical tropopause may typically allow entry of air into the stratosphere with as much as ∼1.7 times the ice saturation mixing ratio.

Ice Nucleation and Dehydration in the Tropical Tropopause Layer

NASA Technical Reports Server (NTRS)

Jensen, Eric J.; Diskin, Glenn S.; Lawson, R Paul; Lance, Sara; Bui, Thaopaul Van; Hlavka, Dennis L.; Mcgill, Matthew J.; Pfister, Leonhard; Toon, Owen B.; Gao, Rushan

2013-01-01

Optically thin cirrus near the tropical tropopause regulate the humidity of air entering the stratosphere, which in turn has a strong influence on the Earth's radiation budget and climate. Recent highaltitude, unmanned aircraft measurements provide evidence for two distinct classes of cirrus formed in the tropical tropopause region: (i) vertically extensive cirrus with low ice number concentrations, low extinctions, and large supersaturations (up to approx. 70%) with respect to ice; and (ii) vertically thin cirrus layers with much higher ice concentrations that effectively deplete the vapor in excess of saturation. The persistent supersaturation in the former class of cirrus is consistent with the long time-scales (several hours or longer) for quenching of vapor in excess of saturation given the low ice concentrations and cold tropical tropopause temperatures. The low-concentration clouds are likely formed on a background population of insoluble particles with concentrations less than 100 L-1 (often less than 20 L-1), whereas the high ice concentration layers (with concentrations up to 10,000 L-1) can only be produced by homogeneous freezing of an abundant population of aqueous aerosols. These measurements, along with past high-altitude aircraft measurements, indicate that the low-concentration cirrus occur frequently in the tropical tropopause region, whereas the high-concentration cirrus occur infrequently. The predominance of the low-concentration clouds means cirrus near the tropical tropopause may typically allow entry of air into the stratosphere with as much as approx. 1.7 times the ice saturation mixing ratio.

Irradiation effect on leaching behavior and form of heavy metals in fly ash of municipal solid waste incinerator.

PubMed

Nam, Sangchul; Namkoong, Wan

2012-01-15

Fly ash from a municipal solid waste incinerator (MSWI) is commonly classified as hazardous waste. High-energy electron beam irradiation systems have gained popularity recently as a clean and promising technology to remove environmental pollutants. Irradiation effects on leaching behavior and form of heavy metals in MSWI fly ash have not been investigated in any significant detail. An electron beam accelerator was used in this research. Electron beam irradiation on fly ash significantly increased the leaching potential of heavy metals from fly ash. The amount of absorbed dose and the metal species affected leaching behavior. When electron beam irradiation intensity increased gradually up to 210 kGy, concentration of Pb and Zn in the leachate increased linearly as absorbed dose increased, while that of Cu underwent no significant change. Concentration of Pb and Zn in the leachate increased up to 15.5% (10.7 mg/kg), and 35.6% (9.6 mg/kg) respectively. However, only 4.8% (0.3mg/kg) increase was observed in the case of Cu. The results imply that irradiation has significant effect on the leaching behavior of heavy metals in fly ash, and the effect is quite different among the metal species tested in this study. A commonly used sequential extraction analysis which can classify a metal species into five forms was conducted to examine any change in metal form in the irradiated fly ash. Notable change in metal form in fly ash was observed when fly ash was irradiated. Change in Pb form was much greater than that of Cu form. Change in metal form was related to leaching potential of the metals. Concentration of heavy metal in leachate was positively related to the exchangeable form which is the most mobile. It may be feasible to treat fly ash by electron beam irradiation for selective recovery of valuable metals or for pretreatment prior to conventional processes. Copyright © 2011 Elsevier B.V. All rights reserved.

Hydrogel-Forming Microneedle Arrays Allow Detection of Drugs and Glucose In Vivo: Potential for Use in Diagnosis and Therapeutic Drug Monitoring

PubMed Central

Caffarel-Salvador, Ester; Brady, Aaron J.; Eltayib, Eyman; Meng, Teng; Alonso-Vicente, Ana; Gonzalez-Vazquez, Patricia; Torrisi, Barbara M.; Vicente-Perez, Eva Maria; Mooney, Karen; Jones, David S.; Bell, Steven E. J.; McCoy, Colin P.; McCarthy, Helen O.; McElnay, James C.; Donnelly, Ryan F.

2015-01-01

We describe, for the first time the use of hydrogel-forming microneedle (MN) arrays for minimally-invasive extraction and quantification of drug substances and glucose from skin in vitro and in vivo. MN prepared from aqueous blends of hydrolysed poly(methyl-vinylether-co-maleic anhydride) (11.1% w/w) and poly(ethyleneglycol) 10,000 daltons (5.6% w/w) and crosslinked by esterification swelled upon skin insertion by uptake of fluid. Post-removal, theophylline and caffeine were extracted from MN and determined using HPLC, with glucose quantified using a proprietary kit. In vitro studies using excised neonatal porcine skin bathed on the underside by physiologically-relevant analyte concentrations showed rapid (5 min) analyte uptake. For example, mean concentrations of 0.16 μg/mL and 0.85 μg/mL, respectively, were detected for the lowest (5 μg/mL) and highest (35 μg/mL) Franz cell concentrations of theophylline after 5 min insertion. A mean concentration of 0.10 μg/mL was obtained by extraction of MN inserted for 5 min into skin bathed with 5 μg/mL caffeine, while the mean concentration obtained by extraction of MN inserted into skin bathed with 15 μg/mL caffeine was 0.33 μg/mL. The mean detected glucose concentration after 5 min insertion into skin bathed with 4 mmol/L was 19.46 nmol/L. The highest theophylline concentration detected following extraction from a hydrogel-forming MN inserted for 1 h into the skin of a rat dosed orally with 10 mg/kg was of 0.363 μg/mL, whilst a maximum concentration of 0.063 μg/mL was detected following extraction from a MN inserted for 1 h into the skin of a rat dosed with 5 mg/kg theophylline. In human volunteers, the highest mean concentration of caffeine detected using MN was 91.31 μg/mL over the period from 1 to 2 h post-consumption of 100 mg Proplus® tablets. The highest mean blood glucose level was 7.89 nmol/L detected 1 h following ingestion of 75 g of glucose, while the highest mean glucose concentration extracted from MN was 4.29 nmol/L, detected after 3 hours skin insertion in human volunteers. Whilst not directly correlated, concentrations extracted from MN were clearly indicative of trends in blood in both rats and human volunteers. This work strongly illustrates the potential of hydrogel-forming MN in minimally-invasive patient monitoring and diagnosis. Further studies are now ongoing to reduce clinical insertion times and develop mathematical algorithms enabling determination of blood levels directly from MN measurements. PMID:26717198

Concentric Crater Fill

NASA Image and Video Library

2003-01-24

The bizarre patterns on the floor of this crater in Nilosyrtis Mensae imaged by NASA Mars Odyssey defy an easy explanation. It is possible that some form of periglacial process combined with the vaporization of ground ice to form these patterns.

Meaningful traits for grouping plant species across arid ecosystems.

PubMed

Bär Lamas, Marlene Ivonne; Carrera, A L; Bertiller, M B

2016-05-01

Grouping species may provide some degree of simplification to understand the ecological function of plants on key ecosystem processes. We asked whether groups of plant species based on morpho-chemical traits associated with plant persistence and stress/disturbance resistance reflect dominant plant growth forms in arid ecosystems. We selected twelve sites across an aridity gradient in northern Patagonia. At each site, we identified modal size plants of each dominant species and assessed specific leaf area (SLA), plant height, seed mass, N and soluble phenol concentration in green and senesced leaves at each plant. Plant species were grouped according with plant growth forms (perennial grasses, evergreen shrubs and deciduous shrubs) and plant morphological and/or chemical traits using cluster analysis. We calculated mean values of each plant trait for each species group and plant growth form. Plant growth forms significantly differed among them in most of the morpho-chemical traits. Evergreen shrubs were tall plants with the highest seed mass and soluble phenols in leaves, deciduous shrubs were also tall plants with high SLA and the highest N in leaves, and perennial grasses were short plants with high SLA and low concentration of N and soluble phenols in leaves. Grouping species by the combination of morpho-chemical traits yielded 4 groups in which species from one growth form prevailed. These species groups differed in soluble phenol concentration in senesced leaves and plant height. These traits were highly correlated. We concluded that (1) plant height is a relevant synthetic variable, (2) growth forms adequately summarize ecological strategies of species in arid ecosystems, and (3) the inclusion of plant morphological and chemical traits related to defenses against environmental stresses and herbivory enhanced the potential of species grouping, particularly within shrubby growth forms.

Concentric tube support assembly

DOEpatents

Rubio, Mark F.; Glessner, John C.

2012-09-04

An assembly (45) includes a plurality of separate pie-shaped segments (72) forming a disk (70) around a central region (48) for retaining a plurality of tubes (46) in a concentrically spaced apart configuration. Each segment includes a support member (94) radially extending along an upstream face (96) of the segment and a plurality of annularly curved support arms (98) transversely attached to the support member and radially spaced apart from one another away from the central region for receiving respective upstream end portions of the tubes in arc-shaped spaces (100) between the arms. Each segment also includes a radial passageway (102) formed in the support member for receiving a fluid segment portion (106) and a plurality of annular passageways (104) formed in the support arms for receiving respective arm portions (108) of the fluid segment portion from the radial passageway and for conducting the respective arm portions into corresponding annular spaces (47) formed between the tubes retained by the disk.

Microfluidic quadrupole and floating concentration gradient.

PubMed

Qasaimeh, Mohammad A; Gervais, Thomas; Juncker, David

2011-09-06

The concept of fluidic multipoles, in analogy to electrostatics, has long been known as a particular class of solutions of the Navier-Stokes equation in potential flows; however, experimental observations of fluidic multipoles and of their characteristics have not been reported yet. Here we present a two-dimensional microfluidic quadrupole and a theoretical analysis consistent with the experimental observations. The microfluidic quadrupole was formed by simultaneously injecting and aspirating fluids from two pairs of opposing apertures in a narrow gap formed between a microfluidic probe and a substrate. A stagnation point was formed at the centre of the microfluidic quadrupole, and its position could be rapidly adjusted hydrodynamically. Following the injection of a solute through one of the poles, a stationary, tunable, and movable-that is, 'floating'-concentration gradient was formed at the stagnation point. Our results lay the foundation for future combined experimental and theoretical exploration of microfluidic planar multipoles including convective-diffusive phenomena.

Temporal metatranscriptomic patterning in phototrophic Chloroflexi inhabiting a microbial mat in a geothermal spring

PubMed Central

Klatt, Christian G; Liu, Zhenfeng; Ludwig, Marcus; Kühl, Michael; Jensen, Sheila I; Bryant, Donald A; Ward, David M

2013-01-01

Filamentous anoxygenic phototrophs (FAPs) are abundant members of microbial mat communities inhabiting neutral and alkaline geothermal springs. Natural populations of FAPs related to Chloroflexus spp. and Roseiflexus spp. have been well characterized in Mushroom Spring, where they occur with unicellular cyanobacteria related to Synechococcus spp. strains A and B′. Metatranscriptomic sequencing was applied to the microbial community to determine how FAPs regulate their gene expression in response to fluctuating environmental conditions and resource availability over a diel period. Transcripts for genes involved in the biosynthesis of bacteriochlorophylls (BChls) and photosynthetic reaction centers were much more abundant at night. Both Roseiflexus spp. and Chloroflexus spp. expressed key genes involved in the 3-hydroxypropionate (3-OHP) carbon dioxide fixation bi-cycle during the day, when these FAPs have been thought to perform primarily photoheterotrophic and/or aerobic chemoorganotrophic metabolism. The expression of genes for the synthesis and degradation of storage polymers, including glycogen, polyhydroxyalkanoates and wax esters, suggests that FAPs produce and utilize these compounds at different times during the diel cycle. We summarize these results in a proposed conceptual model for temporal changes in central carbon metabolism and energy production of FAPs living in a natural environment. The model proposes that, at night, Chloroflexus spp. and Roseiflexus spp. synthesize BChl, components of the photosynthetic apparatus, polyhydroxyalkanoates and wax esters in concert with fermentation of glycogen. It further proposes that, in daytime, polyhydroxyalkanoates and wax esters are degraded and used as carbon and electron reserves to support photomixotrophy via the 3-OHP bi-cycle. PMID:23575369

Quenching Capabilities of Long-Chain Carotenoids in Light-Harvesting-2 Complexes from Rhodobacter sphaeroides with an Engineered Carotenoid Synthesis Pathway

PubMed Central

2016-01-01

Six light-harvesting-2 complexes (LH2) from genetically modified strains of the purple photosynthetic bacterium Rhodobacter (Rb.) sphaeroides were studied using static and ultrafast optical methods and resonance Raman spectroscopy. These strains were engineered to incorporate carotenoids for which the number of conjugated groups (N = NC=C + NC=O) varies from 9 to 15. The Rb. sphaeroides strains incorporate their native carotenoids spheroidene (N = 10) and spheroidenone (N = 11), as well as longer-chain analogues including spirilloxanthin (N = 13) and diketospirilloxantion (N = 15) normally found in Rhodospirillum rubrum. Measurements of the properties of the carotenoid first singlet excited state (S1) in antennas from the Rb. sphaeroides set show that carotenoid-bacteriochlorophyll a (BChl a) interactions are similar to those in LH2 complexes from various other bacterial species and thus are not significantly impacted by differences in polypeptide composition. Instead, variations in carotenoid-to-BChl a energy transfer are primarily regulated by the N-determined energy of the carotenoid S1 excited state, which for long-chain (N ≥ 13) carotenoids is not involved in energy transfer. Furthermore, the role of the long-chain carotenoids switches from a light-harvesting supporter (via energy transfer to BChl a) to a quencher of the BChl a S1 excited state B850*. This quenching is manifested as a substantial (∼2-fold) reduction of the B850* lifetime and the B850* fluorescence quantum yield for LH2 housing the longest carotenoids. PMID:27285777

Nonphotochemical Hole-Burning Studies of Energy Transfer Dynamics in Antenna Complexes of Photosynthetic Bacteria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsuzaki, Satoshi

2001-01-01

This thesis contains the candidate's original work on excitonic structure and energy transfer dynamics of two bacterial antenna complexes as studied using spectral hole-burning spectroscopy. The general introduction is divided into two chapters (1 and 2). Chapter 1 provides background material on photosynthesis and bacterial antenna complexes with emphasis on the two bacterial antenna systems related to the thesis research. Chapter 2 reviews the underlying principles and mechanism of persistent nonphotochemical hole-burning (NPHB) spectroscopy. Relevant energy transfer theories are also discussed. Chapters 3 and 4 are papers by the candidate that have been published. Chapter 3 describes the application ofmore » NPHB spectroscopy to the Fenna-Matthews-Olson (FMO) complex from the green sulfur bacterium Prosthecochloris aestuarii; emphasis is on determination of the low energy vibrational structure that is important for understanding the energy transfer process associated within three lowest energy Q y-states of the complex. The results are compared with those obtained earlier on the FMO complex from Chlorobium tepidum. In Chapter 4, the energy transfer dynamics of the B800 molecules of intact LH2 and B800-deficient LH2 complexes of the purple bacterium Rhodopseudomonas acidophila are compared. New insights on the additional decay channel of the B800 ring of bacteriochlorophyll a (BChl a) molecules are provided. General conclusions are given in Chapter 5. A version of the hole spectrum simulation program written by the candidate for the FMO complex study (Chapter 3) is included as an appendix. The references for each chapter are given at the end of each chapter.« less

Nature does not rely on long-lived electronic quantum coherence for photosynthetic energy transfer.

PubMed

Duan, Hong-Guang; Prokhorenko, Valentyn I; Cogdell, Richard J; Ashraf, Khuram; Stevens, Amy L; Thorwart, Michael; Miller, R J Dwayne

2017-08-08

During the first steps of photosynthesis, the energy of impinging solar photons is transformed into electronic excitation energy of the light-harvesting biomolecular complexes. The subsequent energy transfer to the reaction center is commonly rationalized in terms of excitons moving on a grid of biomolecular chromophores on typical timescales [Formula: see text]100 fs. Today's understanding of the energy transfer includes the fact that the excitons are delocalized over a few neighboring sites, but the role of quantum coherence is considered as irrelevant for the transfer dynamics because it typically decays within a few tens of femtoseconds. This orthodox picture of incoherent energy transfer between clusters of a few pigments sharing delocalized excitons has been challenged by ultrafast optical spectroscopy experiments with the Fenna-Matthews-Olson protein, in which interference oscillatory signals up to 1.5 ps were reported and interpreted as direct evidence of exceptionally long-lived electronic quantum coherence. Here, we show that the optical 2D photon echo spectra of this complex at ambient temperature in aqueous solution do not provide evidence of any long-lived electronic quantum coherence, but confirm the orthodox view of rapidly decaying electronic quantum coherence on a timescale of 60 fs. Our results can be considered as generic and give no hint that electronic quantum coherence plays any biofunctional role in real photoactive biomolecular complexes. Because in this structurally well-defined protein the distances between bacteriochlorophylls are comparable to those of other light-harvesting complexes, we anticipate that this finding is general and directly applies to even larger photoactive biomolecular complexes.

Roseicyclus marinus sp. nov., isolated from a Synechococcus culture, and emended description of the genus Roseicyclus.

PubMed

Tang, Lili; Zhang, Zenghu; Zhou, Chao; Cui, Rong; Tian, Yu; Zhang, Yongyu

2018-05-01

A novel Gram-stain-negative, aerobic, non-flagellated, pink-pigmented and rod-shaped strain with gliding motility, designated strain CCMM001 T , was isolated from a mixed culture of Synechococcus species PCC7002 and a natural bacterial community from a sample of offshore seawater from Qingdao, China, during September 2014. The strain contained bacteriochlorophyll a with a small peak at 802 nm and a large in vivo absorption band at 870 nm. Strain CCMM001 T grew optimally at pH 7.0 and 30 °C in the presence of 3 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain CCMM001 T is most closely related to the genus Roseicyclus and its type and only species Roseicyclus mahoneyensis ML6 T with 96.9 % sequence similarity. The polar lipids of strain CCMM001 T consisted of phosphatidylethanolamine, phosphatidylcholine, one unidentified aminolipid, and five unidentified lipids. The predominant isoprenoid quinone was Q-10. The major fatty acids included C18 : 1ω7c and C19 : 0cyclo ω8c. The DNA G+C content of strain CCMM001 T was 63.5 mol%. These phylogenetic, physiological and chemotaxonomic data indicated that strain CCMM001 T represents a novel species of the genus Roseicyclus, for which the name Roseicyclus marinus sp. nov. is proposed. The type strain is CCMM001 T (=MCCC 1K03242 T =KCTC 52641 T ).

Quenching capabilities of long-chain carotenoids in light-harvesting-2 complexes from Rhodobacter sphaeroides with an engineered carotenoid synthesis pathway

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dilbeck, Preston L.; Tang, Qun; Mothersole, David J.

Here, six light-harvesting-2 complexes (LH2) from genetically modified strains of the purple photosynthetic bacterium Rhodobacter (Rb.) sphaeroides were studied using static and ultrafast optical methods and resonance Raman spectroscopy. These strains were engineered to incorporate carotenoids for which the number of conjugated groups (N = N C=C + N C=O) varies from 9 to 15. The Rb. sphaeroides strains incorporate their native carotenoids spheroidene (N = 10) and spheroidenone (N = 11), as well as longer-chain analogues including spirilloxanthin (N = 13) and diketospirilloxantion (N = 15) normally found in Rhodospirillum rubrum. Measurements of the properties of the carotenoid firstmore » singlet excited state (S1) in antennas from the Rb. sphaeroides set show that carotenoid-bacteriochlorophyll a (BChl a) interactions are similar to those in LH2 complexes from various other bacterial species and thus are not significantly impacted by differences in polypeptide composition. Instead, variations in carotenoid-to-BChl a energy transfer are primarily regulated by the N-determined energy of the carotenoid S 1 excited state, which for long-chain (N ≥ 13) carotenoids is not involved in energy transfer. Furthermore, the role of the long-chain carotenoids switches from a lightharvesting supporter (via energy transfer to BChl a) to a quencher of the BChl a S 1 excited state B850*. This quenching is manifested as a substantial (~2-fold) reduction of the B850* lifetime and the B850* fluorescence quantum yield for LH2 housing the longest carotenoids« less

B-side charge separation in bacterial photosynthetic reaction centers: nanosecond time scale electron transfer from HB- to QB.

PubMed

Kirmaier, Christine; Laible, Philip D; Hanson, Deborah K; Holten, Dewey

2003-02-25

We report time-resolved optical measurements of the primary electron transfer reactions in Rhodobacter capsulatus reaction centers (RCs) having four mutations: Phe(L181) --> Tyr, Tyr(M208) --> Phe, Leu(M212) --> His, and Trp(M250) --> Val (denoted YFHV). Following direct excitation of the bacteriochlorophyll dimer (P) to its lowest excited singlet state P, electron transfer to the B-side bacteriopheophytin (H(B)) gives P(+)H(B)(-) in approximately 30% yield. When the secondary quinone (Q(B)) site is fully occupied, P(+)H(B)(-) decays with a time constant estimated to be in the range of 1.5-3 ns. In the presence of excess terbutryn, a competitive inhibitor of Q(B) binding, the observed lifetime of P(+)H(B)(-) is noticeably longer and is estimated to be in the range of 4-8 ns. On the basis of these values, the rate constant for P(+)H(B)(-) --> P(+)Q(B)(-) electron transfer is calculated to be between approximately (2 ns)(-)(1) and approximately (12 ns)(-)(1), making it at least an order of magnitude smaller than the rate constant of approximately (200 ps)(-)(1) for electron transfer between the corresponding A-side cofactors (P(+)H(A)(-) --> P(+)Q(A)(-)). Structural and energetic factors associated with electron transfer to Q(B) compared to Q(A) are discussed. Comparison of the P(+)H(B)(-) lifetimes in the presence and absence of terbutryn indicates that the ultimate (i.e., quantum) yield of P(+)Q(B)(-) formation relative to P is 10-25% in the YFHV RC.

Thiorhodococcus fuscus sp. nov., isolated from a lagoon.

PubMed

Lakshmi, K V N S; Divyasree, B; Sucharita, K; Sasikala, Ch; Ramana, Ch V

2015-11-01

A brown, moderately halophilic, photoautotrophic bacterium designated strain JA363T was purified from a photoheterotrophic enrichment obtained from sediment from Chilika lagoon, Odisha, India. Cells of the isolate were coccoid, motile by means of single polar flagellum and Gram-stain-negative. Strain JA363T had an obligate requirement for NaCl and could tolerate up to 7 % (w/v) NaCl. Strain JA363T had complex growth factor requirements. Internal photosynthetic membranes were present as vesicles. Strain JA363T contained bacteriochlorophyll a and spirilloxanthin series carotenoids with rhodopin as a major (>85 %) component. C16 : 1ω7c/C16 : 1ω6c, C18 : 1ω7c and C16 : 0 were the major fatty acids and phosphatidylglycerol and phosphatidylethanolamine were the major polar lipids. Q8 was the predominant quinone system of strain JA363T. The DNA G+C content was 64 mol%. The highest 16S rRNA gene sequence similarity of strain JA363T was found with the type strains of Thiorhodococcus kakinadensis (98.7 %), Thiohalobacter thiocyanaticus (98.2 %), Thiophaeococcus fuscus (97.4 %) and Thiorhodococcus bheemlicus (96.3 %). However, the phylogenetic trees generated firmly placed strain JA363T in the genus Thiorhodococcus, which was further supported by phenotypic and chemotaxonomic evidence. Consequently, strain JA363T is described as representing a novel species of the genus Thiorhodococcus as Thiorhodococcus fuscus sp. nov. The type strain is JA363T ( = KCTC 5701T = NBRC 104959T).

Specific inhibition of antenna bacteriochlorophyll synthesis in Chlorobium vibrioforme by anesthetic gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ormerod, J.G.; Nesbakken, T.; Beale, S.I.

1990-03-01

The green sulfur bacterium Chlorobium vibrioforme contains two types of bacteriochlorophll (Bchl). The minor pigment, Bchl a, is associated primarily with the cell membrane and its reaction centers; and the major light-harvesting antenna pigment, Bchl d, is found primarily in the chlorosomes, which are attached to the inner surface of the cell membrane. Anesthetic gases, such as N{sub 2}O, ethylene, and acetylene, were found to inhibit the synthesis of Bchl d, but not of Bchl a, thus allowing the cells to grow at high light intensities with a greatly diminished content of antenna pgiment. Chlorosomes were absent or sparse inmore » inhibited cells. Porphyrins accumulated in the inhibited cells. Result suggest that the gases act at a step in pigment biosynthesis that affect the utilization of the major one was identified as the Bchl precursor magnesium-protoporphyrin IX monomethyl ester (Mg-PPME) for isocyclic ring formation. Synthesis of Bchl d and Bchl a may be differentially affected by the gases because of compartmentation of their biosynthetic apparatus or because competition for precursors favors Bchl a synthesis. An ethephon-resistant mutant strain was isolated by selection for growth in dim, long-wavelength light. The mutant cells were also resistant to acetylene, but not to N{sub 2}O. The ability to reversibly generate viable Chlorobium cells that lack antenna pigments may be useful in photosynthesis research. The ethephon-and acetylene-resistant strain may be useful in the study of the enzymes and genes that are involved in the biosynthetic step that the gases affect.« less

Nature does not rely on long-lived electronic quantum coherence for photosynthetic energy transfer

NASA Astrophysics Data System (ADS)

Duan, Hong-Guang; Prokhorenko, Valentyn I.; Cogdell, Richard J.; Ashraf, Khuram; Stevens, Amy L.; Thorwart, Michael; Miller, R. J. Dwayne

2017-08-01

During the first steps of photosynthesis, the energy of impinging solar photons is transformed into electronic excitation energy of the light-harvesting biomolecular complexes. The subsequent energy transfer to the reaction center is commonly rationalized in terms of excitons moving on a grid of biomolecular chromophores on typical timescales <<100 fs. Today’s understanding of the energy transfer includes the fact that the excitons are delocalized over a few neighboring sites, but the role of quantum coherence is considered as irrelevant for the transfer dynamics because it typically decays within a few tens of femtoseconds. This orthodox picture of incoherent energy transfer between clusters of a few pigments sharing delocalized excitons has been challenged by ultrafast optical spectroscopy experiments with the Fenna-Matthews-Olson protein, in which interference oscillatory signals up to 1.5 ps were reported and interpreted as direct evidence of exceptionally long-lived electronic quantum coherence. Here, we show that the optical 2D photon echo spectra of this complex at ambient temperature in aqueous solution do not provide evidence of any long-lived electronic quantum coherence, but confirm the orthodox view of rapidly decaying electronic quantum coherence on a timescale of 60 fs. Our results can be considered as generic and give no hint that electronic quantum coherence plays any biofunctional role in real photoactive biomolecular complexes. Because in this structurally well-defined protein the distances between bacteriochlorophylls are comparable to those of other light-harvesting complexes, we anticipate that this finding is general and directly applies to even larger photoactive biomolecular complexes.

Quenching capabilities of long-chain carotenoids in light-harvesting-2 complexes from Rhodobacter sphaeroides with an engineered carotenoid synthesis pathway

DOE PAGES

Dilbeck, Preston L.; Tang, Qun; Mothersole, David J.; ...

2016-06-10

Here, six light-harvesting-2 complexes (LH2) from genetically modified strains of the purple photosynthetic bacterium Rhodobacter (Rb.) sphaeroides were studied using static and ultrafast optical methods and resonance Raman spectroscopy. These strains were engineered to incorporate carotenoids for which the number of conjugated groups (N = N C=C + N C=O) varies from 9 to 15. The Rb. sphaeroides strains incorporate their native carotenoids spheroidene (N = 10) and spheroidenone (N = 11), as well as longer-chain analogues including spirilloxanthin (N = 13) and diketospirilloxantion (N = 15) normally found in Rhodospirillum rubrum. Measurements of the properties of the carotenoid firstmore » singlet excited state (S1) in antennas from the Rb. sphaeroides set show that carotenoid-bacteriochlorophyll a (BChl a) interactions are similar to those in LH2 complexes from various other bacterial species and thus are not significantly impacted by differences in polypeptide composition. Instead, variations in carotenoid-to-BChl a energy transfer are primarily regulated by the N-determined energy of the carotenoid S 1 excited state, which for long-chain (N ≥ 13) carotenoids is not involved in energy transfer. Furthermore, the role of the long-chain carotenoids switches from a lightharvesting supporter (via energy transfer to BChl a) to a quencher of the BChl a S 1 excited state B850*. This quenching is manifested as a substantial (~2-fold) reduction of the B850* lifetime and the B850* fluorescence quantum yield for LH2 housing the longest carotenoids« less

Isotropic-nematic phase transition in aqueous sepiolite suspensions.

PubMed

Woolston, Phillip; van Duijneveldt, Jeroen S

2015-01-01

Aqueous suspensions of sepiolite clay rods in water tend to form gels on increase of concentration. Here it is shown how addition of a small amount (0.1% of the clay mass) of a common stabiliser for clay suspensions, sodium polyacrylate, can allow the observation of an isotropic-nematic liquid crystal phase transition. This transition was found to move to higher clay concentrations upon adding NaCl, with samples containing 10(-3) M salt or above only displaying a gel phase. Even samples that initially formed liquid crystals had a tendency to form gels after several weeks, possibly due to Mg(2+) ions leaching from the clay mineral. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Self-assembly of nanocomposite materials

DOEpatents

Brinker, C. Jeffrey; Sellinger, Alan; Lu, Yunfeng

2001-01-01

A method of making a nanocomposite self-assembly is provided where at least one hydrophilic compound, at least one hydrophobic compound, and at least one amphiphilic surfactant are mixed in an aqueous solvent with the solvent subsequently evaporated to form a self-assembled liquid crystalline mesophase material. Upon polymerization of the hydrophilic and hydrophobic compounds, a robust nanocomposite self-assembled material is formed. Importantly, in the reaction mixture, the amphiphilic surfactant has an initial concentration below the critical micelle concentration to allow formation of the liquid-phase micellar mesophase material. A variety of nanocomposite structures can be formed, depending upon the solvent evaporazation process, including layered mesophases, tubular mesophases, and a hierarchical composite coating composed of an isotropic worm-like micellar overlayer bonded to an oriented, nanolaminated underlayer.

[Transfer characteristics of cadmium in soil-vegetable-insect food chain].

PubMed

Ding, Ping; Zhuang, Ping; Li, Zhi-An; Xia, Han-Ping; Tai, Yi-Ping; Lu, Huan-Ping

2012-11-01

Taking two kinds of vegetables (Brassica rapa and Amaranthus mangostanus) and one insect species (Prodenia litura) as test materials, a greenhouse pot experiment was conducted to study the transfer characteristics of cadmium (Cd) in soil-vegetable-insect food chain and the distribution patters of different Cd chemical forms in the organs of the two vegetables. With the increasing concentration of applied Cd in soil, the biomass of the two vegetables decreased significantly, while the Cd concentration in the vegetables had a significant increase. The Cd concentration in the vegetable organs decreased in the order of stem > root > leaf for A. mangostanus, and of stem > leaf > root for B. rapa. The Cd concentration in P. litura larvae also increased with the increasing concentration of Cd in soil, and the maximum Cd concentration in the P. litura larvae on B. rapa and A. mangostanus was 36.7 and 46.3 mg x kg(-1), respectively. In the feces of the larvae on B. rapa and A. mangostanus, the Cd concentration was up to 190 and 229.8 mg x kg(-1), respectively, suggesting that the most part of Cd absorbed by P. litura larvae was excreted out of their bodies via feces. In the organs of the two vegetables, NaCl-extractable Cd was the dominant Cd form (> 70%), followed by d-H2O- and ethanol-extractable Cd, while the HAc-extractable Cd (insoluble cadmium phosphate), HCl-extractable Cd (insoluble cadmium oxalate), and residual Cd only had a very low concentration. Such a present pattern of different Cd forms in vegetable organs could be conducive to the Cd transfer in the food chain. P. litura could ease Cd poison by excreting large amount of absorbed Cd via feces, and effectively restrict the transfer of Cd to next trophic level. Since B. rapa and A. mangostanus could accumulate large amount of Cd in their biomass, the two vegetables were suggested not to be planted in highly Cd-contaminated soil.

Radon as a natural tracer for underwater cave exploration and hypogenic cave formation

NASA Astrophysics Data System (ADS)

Csondor, Katalin; Erőss, Anita; Horváth, Ákos; Szieberth, Dénes

2017-04-01

Using 222Rn as a natural tracer is a novel approach in underwater cave exploration and in the research of active hypogenic caves. The research area, the Molnár János cave is one of the largest caves of an unique hypogenic karst system, the Buda Thermal Karst (Budapest, Hungary). The cave system is mainly characterized by water-filled passages. The cave is located at one of the main discharge areas of the Buda Thermal Karst and the major outflow point of the waters of the cave system is the Boltív spring, which feeds the artificial Malom Lake. Previous complex hydrogeological studies and radon measurements in the cave system and in the spring established the highest radon concentration (71 Bq/L, where the average is 44 Bq/L) in the springwater. The origin of radon was identified in the form of iron-hydroxide containing biofilms, which form by mixing of waters and efficiently adsorb radium from the thermal water component and cause local radon anomalies. Since mixing of waters is responsible for the formation of the cave as well, these iron-hydroxide containing biofilms and consequently high radon concentrations mark the active cave forming zones. The aim of the study was to use the radon as a natural tracer to locate active mixing and cave forming zones. Based on previous radon measurements it is supposed that the active mixing and cave forming zone has to be close to the spring, since the highest radon concentration was measured there. Therefore, the radon activity concentration mapping was carried out with the help of divers and involving that part of the cave which closest to the spring. Based on our measurements the highest radon concentration (84 Bq/L) ever was achieved in the springwater. Based on the radon concentration distribution direct connection and active karst conduit was established between the spring and the deepest room of the researched part of the cave, which was verified by artificial tracer as well. However, the distribution of radon in the cave passages shows lower concentrations (18-46 Bq/L) compared to the spring, therefore an addition deep inflow from a hitherto unknown cave passages is assumed, from which waters with high radon content arrive to the spring. These passages are supposed to be in the active cave formation (mixing) zone. The Buda Thermal Karst research was funded by the Hungarian Scientific Research Fund under the grant agreement no. NK 101356.

Acid and bile tolerance of spore-forming lactic acid bacteria.

PubMed

Hyronimus, B; Le Marrec, C; Sassi, A H; Deschamps, A

2000-11-01

Criteria for screening probiotics such as bile tolerance and resistance to acids were studied with 13 spore-forming lactic acid producing bacteria. Different strains of Sporolactobacillus, Bacillus laevolacticus, Bacillus racemilacticus and Bacillus coagulans grown in MRS broth were subjected to low pH conditions (2, 2.5 and 3) and increasing bile concentrations. Among these microorganisms, Bacillus laevolacticus DSM 6475 and all Sporolactobacillus strains tested except Sporolactobacillus racemicus IAM 12395, were resistant to pH 3. Only Bacillus racemilacticus and Bacillus coagulans strains were tolerant to bile concentrations over 0.3% (w/v).

NEUTRONIC REACTOR FUEL ELEMENT

DOEpatents

Shackleford, M.H.

1958-12-16

A fuel element possessing good stability and heat conducting properties is described. The fuel element comprises an outer tube formed of material selected from the group consisting of stainhess steel, V, Ti. Mo. or Zr, a fuel tube concentrically fitting within the outer tube and containing an oxide of an isotope selected from the group consisting of U/sup 235/, U/sup 233/, and Pu/sup 239/, and a hollow, porous core concentrically fitting within the fuel tube and formed of an oxide of an element selected from the group consisting of Mg, Be, and Zr.

Setting and stiffening of cementitious components in Cast Stone waste form for disposal of secondary wastes from the Hanford waste treatment and immobilization plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, Chul-Woo; Chun, Jaehun, E-mail: jaehun.chun@pnnl.gov; Um, Wooyong

2013-04-01

Cast Stone is a cementitious waste form, a viable option to immobilize secondary nuclear liquid wastes generated from the Hanford Waste Treatment and Immobilization Plant. However, no study has been performed to understand the flow and stiffening behavior, which is essential to ensure proper workability and is important to safety in a nuclear waste field-scale application. X-ray diffraction, rheology, and ultrasonic wave reflection methods were used to understand the specific phase formation and stiffening of Cast Stone. Our results showed a good correlation between rheological properties of the fresh mixture and phase formation in Cast Stone. Secondary gypsum formation wasmore » observed with low concentration simulants, and the formation of gypsum was suppressed in high concentration simulants. A threshold concentration for the drastic change in stiffening was found at 1.56 M Na concentration. It was found that the stiffening of Cast Stone was strongly dependent on the concentration of simulant. Highlights: • A combination of XRD, UWR, and rheology gives a better understanding of Cast Stone. • Stiffening of Cast Stone was strongly dependent on the concentration of simulant. • A drastic change in stiffening of Cast Stone was found at 1.56 M Na concentration.« less

Molecular Simulations of the Synthesis of Periodic Mesoporous Silica Phases at High Surfactant Concentrations

DOE PAGES

Chien, Szu-Chia; Pérez-Sánchez, Germán; Gomes, José R. B.; ...

2017-02-17

Molecular dynamics simulations of a coarse-grained model are used to study the formation mechanism of periodic mesoporous silica over a wide range of cationic surfactant concentrations. This follows up on an earlier study of systems with low surfactant concentrations. We started by studying the phase diagram of the surfactant–water system and found that our model shows good qualitative agreement with experiments with respect to the surfactant concentrations where various phases appear. We then considered the impact of silicate species upon the morphologies formed. We have found that even in concentrated surfactant systems—in the concentration range where pure surfactant solutions yieldmore » a liquid crystal phase—the liquid-crystal templating mechanism is not viable because the preformed liquid crystal collapses as silica monomers are added into the solution. Upon the addition of silica dimers, a new phase-separated hexagonal array is formed. The preformed liquid crystals were found to be unstable in the presence of monomeric silicates. In addition, the silica dimer is found to be essential for mesoscale ordering at both low and high surfactant concentrations. Our results support the view that a cooperative interaction of anionic silica oligomers and cationic surfactants determines the mesostructure formation in the M41S family of materials.« less

Concentrations and speciation of arsenic in New England seaweed species harvested for food and agriculture.

PubMed

Taylor, Vivien F; Jackson, Brian P

2016-11-01

A survey of arsenic (As) concentrations and speciation was conducted on 10 species of seaweed from commercial harvesters and from collection at two sites in New England. Concentrations of As ranged from 4 to 106 mg/kg, mostly in the form of arsenosugars, with the distribution of arsenosugar analogs varying between taxa. In brown algae, As levels were correlated with phosphate concentrations, and arsenosugar speciation reflected differences in sulfur and phosphate concentrations between taxa. Several samples of the brown algae species Laminaria digitata contained significant levels of inorganic As (2.8-20 mg/kg), the most toxic form of As. A weak acid extraction with microwave heating was compared with a weaker methanol: water extraction method, and found to give slightly higher extraction efficiency with comparable relative concentrations of inorganic As, supporting the use of this faster and simpler extraction method for monitoring. Seaweed is a niche dietary item in the U.S. but its popularity is increasing; it is also used in agriculture and livestock farming which provide potential indirect routes for human exposure. The presence of occasional high concentrations of iAs, as well as the lack of toxicity studies on organic As species, suggest that monitoring of these high As foods is warranted. Copyright © 2016 Elsevier Ltd. All rights reserved.

Tuning the optical properties of ZnO nanorods by variation of precursor concentration through hydrothermal method

NASA Astrophysics Data System (ADS)

Kumari, Lakshmi; Kar, Asit Kumar

2018-05-01

ZnO nanorods with varying precursor concentration have been successfully synthesized by the hydrothermal method. The effect of the precursor concentration on the structural, morphological and optical properties of the resulting nanorods was investigated by means of X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), UV-Vis spectroscopy and photoluminescence (PL) spectroscopy. The crystalline structural characterization demonstrated that the synthesized materials crystallize in pure ZnO wurtzite structure without any other secondary phase. SEM micrographs demonstrate nanorod type features in all the samples. In addition, they show that increase of precursor concentration changes the length and diameter of nanorods. The UV-Vis studies show a strong absorption band in UV region at 373 nm attributed to the band-edge absorption of wurtzite hexagonal ZnO, blue shifted relative to its bulk form (380 nm). The PL spectra of obtained nanorods excited at 360 nm present broad visible emission. Moreover, as the visible region (from 510 to 550 nm) is concerned, it is speculated that the increase of the precursor concentration affects strongly the kind of interstitial defects (Oi, Zni and Vo) formed in ZnO nanorods. The luminescence intensity decreases with the increase of precursor concentration.

The arsenic removal from arsenopyrite in sulfide mineral by physicochemical extraction

NASA Astrophysics Data System (ADS)

Jo, Jiyu; Cho, Kanghee; Choi, Nagchoul; Park*, Cheonyoung

2015-04-01

The most abundant As ore mineral is arsenopyrite (FeAsS). Arsenopyrite is present in sulfide ores associated with sediment-hosted Au deposits, it tends to be the earliest-formed mineral, derived from hydrothermal solutions and formed at temperatures typically of 100(degree Celsius) or more. The aim of this study was to investigate the mineralogical phase change and arsenic removal from arsenopyrite as a penalty element in sulfide mineral contained Au by physical extraction (high frequency) and chemical leaching (thiocyanate). Arsenic removal experiments for were performed under various conditions of high frequency exposure(1~35 min), thiocyanate concentration (0.1~1.0M), HCl concentration (0.1~2.0M), copper(2) sulfate concentration (0.1~1.0M), temperature (30~60 degree Celsius). Increasing the high frequency exposure produced a positive effect on arsenic removal in arsenopyrite. The highest percentage arsenic removal of 96.67% was obtained under the following conditions by thiocyanate leaching: thiocyanate concentration = 1.0M ; HCl concentration = 2.0M ; copper(2) sulfate concentration = 1.0M ; temperature = 60(degree Celsius) This study demonstrates the adequate performance of physical extraction (high frequency) and chemical leaching (thiocyanate) for the arsenic removal from arsenopyrite as a penalty element.

Impact of cationic surfactant on the self-assembly of sodium caseinate.

PubMed

Vinceković, Marko; Curlin, Marija; Jurašin, Darija

2014-08-27

The impact of a cationic surfactant, dodecylammonium chloride (DDACl), on the self-assembly of sodium caseinate (SC) has been investigated by light scattering, zeta potential, and rheological measurements as well as by microscopy (transmission electron and confocal laser scanning microscopy). In SC dilute solutions concentration-dependent self-assembly proceeds through the formation of spherical associates and their aggregation into elongated structures composed of connected spheres. DDACl interacts with SC via its hydrophilic and hydrophobic groups, inducing changes in SC self-assembled structures. These changes strongly depend on the surfactant aggregation states (monomeric or micellar) as well as concentration ratio of both components, leading to the formation of soluble and insoluble complexes of nano- to microdimensions. DDACl monomers interact with SC self-assembled entities in a different way compared to their micelles. Surfactant monomers form soluble complexes (similar to surfactant mixed micelles) at lower SC concentration but insoluble gelatinous complexes at higher SC concentration. At surfactant micellar concentration soluble complexes with casein chains wrapped around surfactant micelles are formed. This study suggests that the use of proper cationic surfactant concentration will allow modification and control of structural changes of SC self-assembled entities.

Fire Performance Evaluation of Solid Aqueous Film-Forming Foam (AFFF).

DTIC Science & Technology

1986-05-01

Aqueous Film - Forming Foam ( AFFF ) Concentrates as Firefighting Agents, USAF Report ESL-TR-81-18, Tyndall Air Force Base, Florida...Evaluation of Solid Aqueous Film - Forming Foam ( AFFF ) JOSEPH L. SCHEFFEY HUGHES ASSOCIATES, INC. , EDWIN J. JABLONSKI 2730 UNIVERSITY BLVD. W. JOSEPH T...performance evaluation of the solid agent is the 28-square-foot fire test described in ’L F-24385C, Military Specification for Aqueous Film - Forming

Comparative Toxicity of Nanoparticulate CuO and ZnO to Soil Bacterial Communities

PubMed Central

Rousk, Johannes; Ackermann, Kathrin; Curling, Simon F.; Jones, Davey L.

2012-01-01

The increasing industrial application of metal oxide Engineered Nano-Particles (ENPs) is likely to increase their environmental release to soils. While the potential of metal oxide ENPs as environmental toxicants has been shown, lack of suitable control treatments have compromised the power of many previous assessments. We evaluated the ecotoxicity of ENP (nano) forms of Zn and Cu oxides in two different soils by measuring their ability to inhibit bacterial growth. We could show a direct acute toxicity of nano-CuO acting on soil bacteria while the macroparticulate (bulk) form of CuO was not toxic. In comparison, CuSO4 was more toxic than either oxide form. Unlike Cu, all forms of Zn were toxic to soil bacteria, and the bulk-ZnO was more toxic than the nano-ZnO. The ZnSO4 addition was not consistently more toxic than the oxide forms. Consistently, we found a tight link between the dissolved concentration of metal in solution and the inhibition of bacterial growth. The inconsistent toxicological response between soils could be explained by different resulting concentrations of metals in soil solution. Our findings suggested that the principal mechanism of toxicity was dissolution of metal oxides and sulphates into a metal ion form known to be highly toxic to bacteria, and not a direct effect of nano-sized particles acting on bacteria. We propose that integrated efforts toward directly assessing bioavailable metal concentrations are more valuable than spending resources to reassess ecotoxicology of ENPs separately from general metal toxicity. PMID:22479561

Light Scattering Characterization of Elastin-Like Polypeptide Trimer Micelles

NASA Astrophysics Data System (ADS)

Tsuper, Ilona; Terrano, Daniel; Maraschky, Adam; Holland, Nolan; Streletzky, Kiril

The elastin-like polypeptides (ELP) nanoparticles are composed of three-armed star polypeptides connected by a negatively charged foldon. Each of the three arms extending from the foldon domain includes 20 repeats of the (GVGVP) amino acid sequence. The ELP polymer chains are soluble at room temperature and become insoluble at the transition temperature (close to 50 ° C), forming micelles. The size and shape of the micelle are dependent on the temperature and the pH of the solution, and on the concentration of the phosphate buffered saline (PBS). The depolarized dynamic light scattering (DDLS) was employed to study the structure and dynamics of micelles at 62 ° C. The solution was maintained at an approximate pH level of 7.3 - 7.5, while varying PBS concentration. At low salt concentrations (<15 mM), the micelle radius was about 10nm but not very reproducible on account of unstable pH levels arising from low buffer concentrations. At intermediate salt concentrations (15 - 60 mM), the system formed spherically-shaped micelles, exhibiting a steady growth in the hydrodynamic radius (Rh) from 10 to 21 nm, with increasing PBS concentration. Interestingly, higher salt concentrations (>60 mM) displayed an apparent elongation of the micelles evident by a significant VH signal, along with a surge in the apparent Rh. A model of micelle growth (and potential elongation) with increase in salt concentration is considered.

Oxygen concentration inside a functioning photosynthetic cell.

PubMed

Kihara, Shigeharu; Hartzler, Daniel A; Savikhin, Sergei

2014-05-06

The excess oxygen concentration in the photosynthetic membranes of functioning oxygenic photosynthetic cells was estimated using classical diffusion theory combined with experimental data on oxygen production rates of cyanobacterial cells. The excess oxygen concentration within the plesiomorphic cyanobacterium Gloeobactor violaceus is only 0.025 μM, or four orders of magnitude lower than the oxygen concentration in air-saturated water. Such a low concentration suggests that the first oxygenic photosynthetic bacteria in solitary form could have evolved ∼2.8 billion years ago without special mechanisms to protect them against reactive oxygen species. These mechanisms instead could have been developed during the following ∼500 million years while the oxygen level in the Earth's atmosphere was slowly rising. Excess oxygen concentrations within individual cells of the apomorphic cyanobacteria Synechocystis and Synechococcus are 0.064 and 0.25 μM, respectively. These numbers suggest that intramembrane and intracellular proteins in isolated oxygenic photosynthetic cells are not subjected to excessively high oxygen levels. The situation is different for closely packed colonies of photosynthetic cells. Calculations show that the excess concentration within colonies that are ∼40 μm or larger in diameter can be comparable to the oxygen concentration in air-saturated water, suggesting that species forming colonies require protection against reactive oxygen species even in the absence of oxygen in the surrounding atmosphere. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Oxygen Concentration Inside a Functioning Photosynthetic Cell

PubMed Central

Kihara, Shigeharu; Hartzler, Daniel A.; Savikhin, Sergei

2014-01-01

The excess oxygen concentration in the photosynthetic membranes of functioning oxygenic photosynthetic cells was estimated using classical diffusion theory combined with experimental data on oxygen production rates of cyanobacterial cells. The excess oxygen concentration within the plesiomorphic cyanobacterium Gloeobactor violaceus is only 0.025 μM, or four orders of magnitude lower than the oxygen concentration in air-saturated water. Such a low concentration suggests that the first oxygenic photosynthetic bacteria in solitary form could have evolved ∼2.8 billion years ago without special mechanisms to protect them against reactive oxygen species. These mechanisms instead could have been developed during the following ∼500 million years while the oxygen level in the Earth’s atmosphere was slowly rising. Excess oxygen concentrations within individual cells of the apomorphic cyanobacteria Synechocystis and Synechococcus are 0.064 and 0.25 μM, respectively. These numbers suggest that intramembrane and intracellular proteins in isolated oxygenic photosynthetic cells are not subjected to excessively high oxygen levels. The situation is different for closely packed colonies of photosynthetic cells. Calculations show that the excess concentration within colonies that are ∼40 μm or larger in diameter can be comparable to the oxygen concentration in air-saturated water, suggesting that species forming colonies require protection against reactive oxygen species even in the absence of oxygen in the surrounding atmosphere. PMID:24806920

Free-form Fresnel RXI-RR Köhler design for high-concentration photovoltaics with spectrum-splitting

NASA Astrophysics Data System (ADS)

Buljan, M.; Benítez, P.; Mohedano, R.; Miñano, J. C.; Sun, Y.; Falicoff, W.; Vilaplana, J.; Chaves, J.; Biot, G.; López, J.

2011-10-01

Development of a novel HCPV nonimaging concentrator with high concentration (>500x) and built-in spectrum splitting concept is presented. It uses the combination of a commercial concentration GaInP/GaInAs/Ge 3J cell and a concentration Back-Point-Contact (BPC) silicon cell for efficient spectral utilization, and external confinement techniques for recovering the 3J cell's reflection. The primary optical element (POE) is a flat Fresnel lens and the secondary optical element (SOE) is a free-form RXI-type concentrator with a band-pass filter embedded in it - Both the POE and SOE performing Köhler integration to produce light homogenization on the receiver. The band-pass filter transmits the IR photons in the 900-1200 nm band to the silicon cell. A design target of an "equivalent" cell efficiency ~46% is predicted using commercial 39% 3J and 26% Si cells. A projected CPV module efficiency of greater than 38% is achievable at a concentration level larger than 500X with a wide acceptance angle of +/-1°. A first proof-of concept receiver prototype has been manufactured using a simpler optical architecture (with a lower concentration, ~100x and lower simulated added efficiency), and experimental measurements have shown up to 39.8% 4J receiver efficiency using a 3J cell with a peak efficiency of 36.9%.

Nucleation of actin polymerization by gelsolin.

PubMed

Ditsch, A; Wegner, A

1994-08-15

The time-course of assembly of actin with gelsolin was measured by the fluorescence increase of a fluorescent label covalently linked to actin. The actin concentrations ranged from values far below the critical concentration to values above the critical concentration of the pointed ends of actin filaments. If the concentration of actin was in the range of the critical monomer concentration (0.64 microM), the time-course of the concentration of actin assembled with gelsolin revealed a sigmoidal shape. At higher actin concentrations the time-course of association of actin with gelsolin approximated an exponential curve. The measured time-courses of assembly were quantitatively interpreted by kinetic rate equations. A poor fit was obtained if two actin molecules were assumed to bind to gelsolin to form a 1:2 gelsolin-actin complex and subsequently further actin molecules were assumed to polymerize onto the 1:2 gelsolin-actin complex toward the pointed end. A considerably better agreement between calculated and measured time-courses was achieved if additional creation of actin filaments by fast fragmentation of newly formed actin filaments by not yet consumed gelsolin was assumed to occur. This suggests that both polymerization of actin onto gelsolin and fragmentation of actin filaments contribute to formation of new actin filaments by gelsolin. Furthermore it could be demonstrated that below the critical monomer concentration appreciable amounts of actin are incorporated into gelsolin-actin oligomers.

Susceptibility of Haemophilus influenzae to chloramphenicol and eight beta-lactam antibiotics.

PubMed Central

Thirumoorthi, M C; Kobos, D M; Dajani, A S

1981-01-01

We examined the minimal inhibitory concentrations and minimal bactericidal concentrations of chloramphenicol, ampicillin, ticarcillin, cefamandole, cefazolin, cefoxitin, cefotaxime, ceforanide, and moxalactam for 100 isolates of Haemophilus influenzae, 25 of which produced beta-lactamase. Susceptibility was not influenced by the capsular characteristic of the organism. The mean minimal inhibitory concentrations of cefamandole, ticarcillin, and ampicillin for beta-lactamase-producing strains were 3-, 120-, and 400-fold higher than their respective mean minimal inhibitory concentrations for beta-lactamase-negative strains. No such difference was noted for the other antibiotics. We performed time-kill curve studies, using chloramphenicol, ampicillin, cefamandole, cefotaxime, and moxalactam with two concentrations of the antimicrobial agents (4 or 20 times the minimal inhibitory concentrations) and two inoculum sizes (10(4) or 10(6) colony-forming units per ml). The inoculum size had no appreciable effect on the rate of killing of beta-lactamase-negative strains. The rates at which beta-lactamase-producing strains were killed by chloramphenicol, cefotaxime, and moxalactam was not influenced by the inoculum size. Whereas cefamandole in high concentrations was able to kill at 10(6) colony-forming units/ml of inoculum, it had only a temporary inhibiting effect at low drug concentrations. Methicillin and the beta-lactamase inhibitor CP-45,899 were able to neutralize the inactivation of cefamandole by a large inoculum of beta-lactamase-producing H. influenzae. PMID:6974541

Extinguishment and Burnback Testing of Fire Fighting Agents

DTIC Science & Technology

2005-09-26

resisting burnback for hydrocarbon fuel fires. Potential Aqueous Film Forming Foam ( AFFF ) replacements are required to exhibit an...simple, reliable test to evaluate the effectiveness of new foams being introduced into the market as potential Aqueous Film Forming Foam ( AFFF ...normal concentrations. Reference: Military Specification MIL-F-24385F, Fire Extinguishing Agent, Aqueous Film - Forming Foam

Micromachined spinneret

DOEpatents

Okandan, Murat; Galambos, Paul

2007-11-06

A micromachined spinneret is disclosed which has one or more orifices through which a fiber-forming material can be extruded to form a fiber. Each orifice is surrounded by a concentric annular orifice which allows the fiber to be temporarily or permanently coated with a co-extrudable material. The micromachined spinneret can be formed by a combination of surface and bulk micromachining.

Survival and reversion of a stable L form in soil

NASA Technical Reports Server (NTRS)

Horwitz, A. H.; Casida, L. E., Jr.

1978-01-01

The stable L form of Agromyces ramosus reverted to a bacterial form when incubated in sterilized soil. The cellular and colonial morphology of this bacterial form resembled that of the original parent bacterial form. The two forms differed, however, in that the revertant maintained its bacterial form when transferred onto a low-salt (NaCl) medium but was virtually completely induced into the L-form state on a high-salt medium. The original parent bacterial form was not sensitive to salt. The possibility is discussed that an L-form - bacterial-form cycle for this bacterium might occur naturally in soil. This cycle would be mediated by fluctuations in local salt concentrations in the soil.

Methanol induction optimization for scFv antibody fragment production in Pichia pastoris.

PubMed

Cunha, A E; Clemente, J J; Gomes, R; Pinto, F; Thomaz, M; Miranda, S; Pinto, R; Moosmayer, D; Donner, P; Carrondo, M J T

2004-05-20

Fibronectin splice variant ED B (extracellular domain B) is a promising marker for angiogenesis in growing solid tumors. Currently, recombinant antibodies against ED B are being investigated concerning their potential use, for either therapeutic or diagnostic purposes. Single-chain antibody fragments directed against the ED B can be efficiently expressed in Pichia pastoris; thus, a recombinant strain of the methylotropic yeast P. pastoris was used for this work. Three different forms of scFv antibody fragment are found in the supernatant from this fermentation: covalent homodimer, associative homodimer, and monomer. Both homodimeric forms can be converted to the monomeric form (under reducing conditions) and be efficiently radiolabeled, whereas the monomeric form of scFv already present in the supernatant cannot. It was also found that the fraction of protein in the monomeric form is highly dependent on the mode of induction rather than scFv concentration. This suggests that the monomeric form of the scFv present in the supernatant might be a result of events occurring at the expression, secretion, or folding level. A high cell density fermentation protocol was developed by optimizing methanol induction, yielding the highest scFv antibody fragment production rate and product quality; cell concentration at the induction point and specific methanol uptake rate were found to be the most important control variables. A decrease in specific methanol uptake rate led to a higher specific production rate for the scFv antibody fragment (5.4 microg g(cell) h(-1)). Product quality, i.e., percentage of product in a homodimeric form, also increased with the decrease in methanol uptake rate. Furthermore, the volumetric productivity depended on cell concentration at the induction point, increasing with the increase of cell concentration up to 320 g L(-1) wet cell weight (WCW). The reduction of the methanol feeding rate for induction, and consequently of the oxygen uptake rate, have important consequences for optimizing product titers and quality and thus on the scale-up of this production process; hence one of the major limitations upon high cell density cultivation in bioreactors is keeping the high oxygen transfer rate required. From the results obtained, a scale-up strategy was developed based on the available oxygen transfer rates at larger scales, allowing the definition of the optimum biomass concentration for induction and methanol feeding strategy for maximization of product titer and quality. Copyright 2004 Wiley Periodicals, Inc.

Antiparasitic effect of the Psidium guajava L. (guava) and Psidium brownianum MART. EX DC. (araçá-de-veado) extracts.

PubMed

Machado, Antonio J T; Santos, Antonia T L; Martins, Gioconda M A B; Cruz, Rafael P; Costa, Maria do S; Campina, Fábia F; Freitas, Maria A; Bezerra, Camila F; Leal, Antonio L A B; Carneiro, Joara N P; Coronel, Cathia; Rolón, Miriam; Gómez, Celeste V; Coutinho, Henrique D M; Morais-Braga, Maria F B

2018-03-13

In the search for new therapeutic agents against neglected diseases, both aqueous and hydroethanolic extracts from Psidium guajava L. and P. brownianum Mart ex DC leaves were investigated regarding their antiparasitic effect and cytotoxic potential. The extracts were tested at three concentrations (250, 500 and 1000 μg/mL) against Trypanosoma cruzi epimastigote forms (Chagas, 1909), Leishmania braziliensis (Vianna, 1911) and L. infantum promastigotes forms (Nicolle, 1908), as well as against fibroblasts. P. guajava showed no activity against T. cruzi forms, while the hydroethanolic (PBHE), aqueous by decoction (PBAED) and aqueous by infusion (PBAEI) P. browninaum extracts were responsible, respectively, for inhibiting 100, 100 and 92.68% of T. cruzi epimastigote growth at the 1000 μg/mL concentration. The P. brownianum hydroethanolic extract (PBHE) at the highest concentration caused 58.46% death in L. braziliensis, thus demonstrating moderate activity, however when tested against L. infantum, the PBHE inhibited their growth by 37.16%, revealing its low activity. As for the cytotoxicity assays, the P. brownianum aqueous extract by decoction (PBAED) obtained the highest death percentage when compared to the others, causing 90.85% fibroblast mortality at the 1000 μg/mL concentration. Copyright © 2018 Elsevier Ltd. All rights reserved.

Measuring kinetic drivers of pneumolysin pore structure.

PubMed

Gilbert, Robert J C; Sonnen, Andreas F-P

2016-05-01

Most membrane attack complex-perforin/cholesterol-dependent cytolysin (MACPF/CDC) proteins are thought to form pores in target membranes by assembling into pre-pore oligomers before undergoing a pre-pore to pore transition. Assembly during pore formation is into both full rings of subunits and incomplete rings (arcs). The balance between arcs and full rings is determined by a mechanism dependent on protein concentration in which arc pores arise due to kinetic trapping of the pre-pore forms by the depletion of free protein subunits during oligomerization. Here we describe the use of a kinetic assay to study pore formation in red blood cells by the MACPF/CDC pneumolysin from Streptococcus pneumoniae. We show that cell lysis displays two kinds of dependence on protein concentration. At lower concentrations, it is dependent on the pre-pore to pore transition of arc oligomers, which we show to be a cooperative process. At higher concentrations, it is dependent on the amount of pneumolysin bound to the membrane and reflects the affinity of the protein for its receptor, cholesterol. A lag occurs before cell lysis begins; this is dependent on oligomerization of pneumolysin. Kinetic dissection of cell lysis by pneumolysin demonstrates the capacity of MACPF/CDCs to generate pore-forming oligomeric structures of variable size with, most likely, different functional roles in biology.

Mechanical characteristics of beta sheet-forming peptide hydrogels are dependent on peptide sequence, concentration and buffer composition

PubMed Central

Müller, Michael; König, Finja; Meyer, Nina; Gattlen, Jasmin; Pieles, Uwe; Peters, Kirsten; Kreikemeyer, Bernd; Mathes, Stephanie; Saxer, Sina

2018-01-01

Self-assembling peptide hydrogels can be modified regarding their biodegradability, their chemical and mechanical properties and their nanofibrillar structure. Thus, self-assembling peptide hydrogels might be suitable scaffolds for regenerative therapies and tissue engineering. Owing to the use of various peptide concentrations and buffer compositions, the self-assembling peptide hydrogels might be influenced regarding their mechanical characteristics. Therefore, the mechanical properties and stability of a set of self-assembling peptide hydrogels, consisting of 11 amino acids, made from four beta sheet self-assembling peptides in various peptide concentrations and buffer compositions were studied. The formed self-assembling peptide hydrogels exhibited stiffnesses ranging from 0.6 to 205 kPa. The hydrogel stiffness was mostly affected by peptide sequence followed by peptide concentration and buffer composition. All self-assembling peptide hydrogels examined provided a nanofibrillar network formation. A maximum self-assembling peptide hydrogel dissolution of 20% was observed for different buffer solutions after 7 days. The stability regarding enzymatic and bacterial digestion showed less degradation in comparison to the self-assembling peptide hydrogel dissolution rate in buffer. The tested set of self-assembling peptide hydrogels were able to form stable scaffolds and provided a broad spectrum of tissue-specific stiffnesses that are suitable for a regenerative therapy. PMID:29657766