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1

Absorption and emission spectroscopic characterization of 10-phenyl-isoalloxazine derivatives  

NASA Astrophysics Data System (ADS)

The flavoquinone dyes 10-phenyl-isoalloxazine-3-acetic acid ethyl ester ( 1) and 10-(4-bromo-phenyl)-3-methyl-isoalloxazine ( 2) in dichloromethane, acetonitrile, and methanol are characterized by absorption and emission spectroscopy. Absorption cross-section spectra, stimulated emission cross-section spectra, fluorescence quantum distributions, quantum yields, lifetimes, and degrees of fluorescence polarization are determined. The blue-light photo-degradation of the dyes is studied. Mass spectroscopic measurements reveal the formation of phenyl-benzo-pteridine (isoalloxazine) derivatives, tetraaza-benzo-aceanthrylene derivatives, dihydro-quinooxaline derivatives, and pyrazino-carbazole derivatives. An enhancement of photo-degradation is observed by the formed photo-fragments.

Shirdel, J.; Penzkofer, A.; Procházka, R.; Daub, J.; Hochmuth, E.; Deutzmann, R.

2006-08-01

2

X-Ray Absorption Spectroscopic Characterization of the Molybdenum Site of 'Escherichia Coli' Dimethyl Sulfoxide Reductase  

SciTech Connect

Structural studies of dimethyl sulfoxide (DMSO) reductases were hampered by modification of the active site during purification. We report an X-ray absorption spectroscopic analysis of the molybdenum active site of Escherichia coli DMSO reductase contained within its native membranes. The enzyme in these preparations is expected to be very close to the form found in vivo. The oxidized active site was found to have four Mo-S ligands at 2.43 angstroms, one Mo=O at 1.71 angstroms, and a longer Mo-O at 1.90 angstroms. We conclude that the oxidized enzyme is a monooxomolybdenum(VI) species coordinated by two molybdopterin dithiolenes and a serine. The bond lengths determined for E. coli DMSO reductase are very similar to those determined for the well-characterized Rhodobacter sphaeroides DMSO reductase, suggesting similar active site structures for the two enzymes. Furthermore, our results suggest that the form found in vivo is the monooxobis(molybdopterin) species.

George, G.N.; Doonan, C.J.; Rothery, R.A.; Boroumand, N.; Weiner, J.H.; /Saskatchewan U. /Alberta U.

2007-07-09

3

Absorption and emission spectroscopic characterization of BLUF protein Slr1694 from Synechocystis sp. PCC6803 with roseoflavin cofactor.  

PubMed

The wild-type BLUF protein Slr1694 from Synechocystis sp. PCC6803 (BLUF=blue-light sensor using FAD) has flavin adenosine dinucleotide (FAD) as natural cofactor. This light sensor causes positive phototaxis of the marine cyanobacterium. In this study the FAD cofactor of the wild-type Slr1694 was replaced by roseoflavin (RoF) and the roseoflavin derivatives RoFMN and RoFAD during heterologous expression in a riboflavin auxotrophic E. coli strain. An absorption and emission spectroscopic characterization of the cofactor-exchanged-Slr1694 (RoSlr) was carried out both under dark conditions and under illuminated conditions. The behaviour of RoF embedded in RoSlr in aqueous solution at pH 8 is compared with the behaviour of RoF in aqueous solution. The fluorescence of RoF and RoSlr is quenched by photo-induced twisted intra-molecular charge transfer at room temperature with stronger effect for RoF. The fluorescence quenching is diminished at liquid nitrogen temperature. Light exposure of RoSlr causes irreversible conversion of the protein embedded roseoflavins to 8-methylamino-flavins, 8-dimethylamino-lumichrome and 8-methylamino-lumichrome. PMID:19758819

Zirak, P; Penzkofer, A; Mathes, T; Hegemann, P

2009-08-08

4

Confocal light absorption and scattering spectroscopic microscopy  

NASA Astrophysics Data System (ADS)

We have developed a novel optical method for observing submicrometer intracellular structures in living cells, which is called confocal light absorption and scattering spectroscopic (CLASS) microscopy. It combines confocal microscopy, a well-established high-resolution microscopic technique, with light-scattering spectroscopy. CLASS microscopy requires no exogenous labels and is capable of imaging and continuously monitoring individual viable cells, enabling the observation of cell and organelle functioning at scales of the order of 100 nm.

Fang, Hui; Qiu, Le; Vitkin, Edward; Zaman, Munir M.; Andersson, Charlotte; Salahuddin, Saira; Kimerer, Lauren M.; Cipolloni, Patsy B.; Modell, Mark D.; Turner, Bradley S.; Keates, Sarah E.; Bigio, Irving; Itzkan, Irving; Freedman, Steven D.; Bansil, Rama; Hanlon, Eugene B.; Perelman, Lev T.

2007-04-01

5

Confocal light scattering and absorption spectroscopic microscopy  

NASA Astrophysics Data System (ADS)

We have developed a novel optical method for observing submicron intracellular structures in living cells which is called confocal light absorption and scattering spectroscopic (CLASS) microscopy. It combines confocal microscopy, a well-established high-resolution microscopic technique, with light scattering spectroscopy (LSS). CLASS microscopy requires no exogenous labels and is capable of imaging and continuously monitoring individual viable cells, enabling the observation of cell and organelle functioning at scales on the order of 100 nm. In addition, it provides not only size information but also information about the biochemical and physical properties of the cell.

Qiu, Le; Vitkin, Edward; Salahuddin, Saira; Zaman, Munir M.; Andersson, Charlotte; Freedman, Steven D.; Hanlon, Eugene B.; Itzkan, Irving; Perelman, Lev T.

2008-05-01

6

Spectroscopic characterization of Nd:Y2O3: application toward a differential absorption lidar system for remote sensing of ozone  

NASA Astrophysics Data System (ADS)

Neodymium-doped yttria (Nd:Y2O3) is investigated as a solid-state laser material for frequency-tripled generation of ultraviolet laser wavelengths for use in remote sensing of ozone. Emphasis is placed both on the spectroscopy of the fundamental wavelengths at ~0.914 ?m and ~0.946 ?m to assess their feasibility for laser oscillation and on the absorption spectroscopy in the 0.8-?m wavelength region for determination of suitable pump sources. The temperature dependence of the emission and absorption characteristics of Nd:Y2O3 are examined, since aggressive cooling may be required for efficient ~0.914-?m lasing due to its quasi four-level nature. Data for flash-lamp-pumped laser performance on the 4F3/2-->4I11/2 is presented for Nd:Y2O3 and compared with Nd:YAG. Diode-pumped threshold-fluence and threshold-pump energy estimates for Nd:Y2O3 lasing on the 4F3/2-->4I9/2 at 0.914 ?m and 0.946 ?m are calculated based on the data presented here. The measurements presented here for the Nd:Y2O3 indicate favorable absorption and emission properties. Favorable absorption properties in the ~0.8-?m pump wavelength are compatible with a variety of potential pump sources. Favorable emission properties at reduced temperatures near 150 K indicate that Nd:Y2O3 operating at 0.914 ?m and 0.946 ?m will have normal-mode laser thresholds similar to that of room-temperature Nd:YAG operating at 0.946 ?m. In Q-switched operation, however, Nd:Y2O3 is predicted to exceed the performance of Nd:YAG due to the lower 1.06/0.94 cross-section ratio, which helps to limit amplified spontaneous-emission effects. Although Nd:Y2O3 is not a new material, it has not been the topic of study due to growth problems associated with its high melting point. New advances in growth techniques and the favorable spectroscopic features of Nd:Y2O3 have inspired a new examination of this material.

Walsh, Brian M.; McMahon, John M.; Edwards, William C.; Barnes, Norman P.; Equall, Randy W.; Hutcheson, Ralph L.

2002-12-01

7

Synthesis, Spectroscopic and Thermal Characterization of Copper(II) and Iron(III) Complexes of Folic Acid and Their Absorption Efficiency in the Blood  

PubMed Central

The absorption efficiency of any drug in blood is of prime importance. Compounds having the general formula: Kn[M(FO)2(H2O)2] · xH2O, where (M = Cu(II) or Fe(III), n = 2 or 1, FO = folate anion, x = 2 or 3 with respect), were prepared, and their absorption efficiency in rodent's blood was determined. The obtained compounds were characterized by elemental analysis, infrared as well as thermogravimetric analysis and polarization of light. The results suggest that the two folate complexes were formed in 1 : 2 molar ratio (metal : folic acid) which acted as a bidentate ligand through both carboxylic groups. Polarization of light proved that the folate complexes have symmetric geometry. Biological application proved that Cu(II) and Fe(III) complexes were absorbed more efficiently in rodent blood than folic acid itself.

Hamed, E.; Attia, M. S.; Bassiouny, K.

2009-01-01

8

Spectroscopic study of small absorptions in optical coatings  

NASA Astrophysics Data System (ADS)

This report concerns research performed by the Utah University surface physics group for the Air Force Weapons Laboratory (AFWL), Kirtland Air Force Base, New Mexico. It is a supplement to AFWL-TR-79-197. It reports the continued study of thorium fluoride (ThF4) as an optical coating, showing that the moisture found in the ThF4 films probably originated from the preparation itself, and that ThF4 may not degrade by moisture absorption from the atmosphere as rapidly as previously thought. Further advances are reported in the characterization procedures themselves, including computer methods for data handling. New procedures were instituted for determining the optical constants of liquids. To test the procedures, the optical constants of liquid water were determined and compared with values found in literature. The procedures used are reported. A sample of Si3N4 film on germanium was analyzed spectroscopically. The dominant feature was a large infrared band revealing the presence of large amounts of silicon hydride. Finally, new procedures are reported for determining impurity concentrations in optical thin films which takes into account the local electromagnetic field strength seen by an impurity in a known optical material as matrix.

Hansen, W. N.

1982-07-01

9

Spectroscopic and Laser Characterization Emerald.  

National Technical Information Service (NTIS)

The spectroscopic characteristics and laser properties of emerald were investigated. The laser measurements showed that the emerald laser tuning range was 720-842 nm and exhibited a high gain and high efficiency in the 760-790 nm range. Under a crystal gr...

S. T. Lai B. H. Chai

1986-01-01

10

Characterization of Phyllanthus amarus herb by inductively coupled plasma mass spectrometric (ICP-MS) analysis, optical absorption and electron paramagnetic resonance (EPR) spectroscopic methods  

NASA Astrophysics Data System (ADS)

A powdered sample of Phyllanthus amarus herb of Kadapa district of Andhra Pradesh, India, is used in the present study. ICP-MS analysis indicates that copper is present in higher concentration when compared to other elements. Although the Pb is toxic, it is within the permissible limit. The evaluated soil and herb physico-chemical parameters indicate that the sample is acidic in nature in comparison with the soil. An EPR study on powdered sample confirms the presence of Fe(III), Mn(II) and Cu(II). Optical absorption spectrum indicates that Fe(III) impurity is present in octahedral structure whereas Cu(II) is present in rhombically distorted octahedral environment. MIR results are due to carbonate fundamentals.

Reddy, S. Lakshmi; Reddy, N. C. Gangi; Reddy, R. Rama Subba; Reddy, G. Siva; Rao, P. Sambasiva; Reddy, B. Jagannatha; Frost, R. L.

11

Absorption spectroscopic studies on gamma irradiated bismuth borosilicate glasses  

NASA Astrophysics Data System (ADS)

FT-IR spectroscopic measurements have been employed to investigate the structural changes in quaternary xBi2O3-15 Na2O-(70 - x) B2O3-15 SiO2 glass system with x = 5, 10, 15, 20 and 25 (mol%). The effect of gamma irradiation in the dose range of 0.1-60 kGy on the infrared absorption spectra of these glasses is also reported. The IR spectra of the prepared samples show characteristic bands related to the sharing of triangular and tetrahedral borate and silicate groups together with Bi-O groups. The effect of the heavy metal oxide Bi2O3 on the glass composition is also studied.

Kaur, Ravneet; Singh, Surinder; Pandey, O. P.

2013-10-01

12

Absorption and fluorescence spectroscopic characterisation of a phenothiazine flavin dyad  

NASA Astrophysics Data System (ADS)

The phenothiazine phenylene isoalloxazine dyad, 3-methyl-10-[4-(10-heptyl-10H-phenothiazin-3-yl)-phenyl]-10H-benzo[g]pteridine-2,4-dione, dissolved in either dichloromethane or acetonitrile is characterized by absorption and emission spectroscopy. Absorption cross-section spectra, stimulated emission cross-section spectra, fluorescence quantum distributions, fluorescence quantum yields, and degrees of fluorescence polarisation are determined. The fluorescence decay is determined by time-resolved measurements. The dye photo-stability is investigated by observation of absorption spectral changes due to prolonged blue-light excitation. The absorption spectrum of the dyad resembles the superposition of the absorption of the isoalloxazine (flavin) moiety and of the phenylphenothiazine moiety. Photo-excitation of the flavin moiety causes fluorescence quenching by ground-state reductive electron transfer from phenylphenothiazine to isoalloxazine followed by charge recombination. Photo-excitation of the phenothiazine moiety causes (i) efficient excited-state oxidative electron transfer from phenothiazine to isoalloxazine with successive recombination, and (ii) moderate energy transfer followed by ground-state phenothiazine electron transfer and recombination.

Shirdel, J.; Penzkofer, A.; Procházka, R.; Shen, Z.; Daub, J.

2007-07-01

13

A Far Ultraviolet Spectroscopic Explorer Survey of Interstellar O vi Absorption in the Small Magellanic Cloud  

Microsoft Academic Search

We present the results of a Far Ultraviolet Spectroscopic Explorer (FUSE) survey of O vi ? 1031.93 and ? 1037.62 absorption toward 18 OB stars in the Small Magellanic Cloud (SMC). The FUSE data are of very high quality, allowing a detailed study of the coronal temperature gas in the SMC. We find that Ovi is ubiqui- tous in the

2002-01-01

14

Chapter 15 Isolation of Saccharomyces Cerevisiae Mitochondria for Mössbauer, Epr, and Electronic Absorption Spectroscopic Analyses  

Microsoft Academic Search

Methods are presented to aid in the study of iron metabolism in isolated mitochondria. The “iron?ome” of mitochondria, including the type and concentration of all Fe?containing species in the organelle, is evaluated by integrating the results of four spectroscopic methods, including Mössbauer spectroscopy, electron paramagnetic resonance, electronic absorption spectroscopy, and inductively coupled plasma mass spectrometry. Although this systems biology approach

Paul A. Lindahl; Jessica Garber Morales; Ren Miao

2009-01-01

15

Spectroscopic characterization and laser performance of diode-laser-pumped Nd: GdVO 4  

Microsoft Academic Search

We have carried out a detailed spectroscopic characterization of Nd: GdVO4, a new laser crystal with high effective absorption and emission cross sections. The accidental degeneracy of the upper4F3\\/2 laser level decreases the number of emission lines and creates -together with the anisotropic crystal field - high emission cross sections (7.6 × 10-19 cm2 at 1.06 µm and 300 K).

T. Jensen; V. G. Ostroumov; J.-P. Meyn; G. Huber; A. I. Zagumennyi; I. A. Shcherbakov

1994-01-01

16

Spectroscopic absorption measurement of a low-Z plasma  

Microsoft Academic Search

Low-Z plasmas have been produced by x-ray radiative heating of a low-Z sample on the ``Xingguang II'' laser facility. High-resolution transmission spectra of the low-Z plasma (CHO) have been measured by using a flat field grating spectrometer. Absorption lines of oxygen and carbon ions in the region from 1.6 nm to 5.0 nm have been observed clearly and identified. The

Jiamin Yang; Yaonan Ding; Jun Yan; Zhijan Zheng; Jiaming Li; Baohan Zhang; Guohong Yang; Wenhai Zhang; Yaomei Wang

2002-01-01

17

The Far Ultraviolet Spectroscopic Explorer Survey of O VI Absorption in and near the Galaxy  

Microsoft Academic Search

We present Far Ultraviolet Spectroscopic Explorer (FUSE) observations of the O VI lambdalambda1031.926, 1037.617 absorption lines associated with gas in and near the Milky Way, as detected in the spectra of a sample of 100 extragalactic targets and two distant halo stars. We combine data from several FUSE Science Team programs with guest observer data that were public before 2002

B. P. Wakker; B. D. Savage; K. R. Sembach; P. Richter; M. Meade; E. B. Jenkins; J. M. Shull; T. B. Ake; W. P. Blair; W. V. Dixon; S. D. Friedman; J. C. Green; R. F. Green; J. W. Kruk; H. W. Moos; E. M. Murphy; W. R. Oegerle; D. J. Sahnow; G. Sonneborn; E. Wilkinson; D. G. York

2003-01-01

18

A Far Ultraviolet Spectroscopic Explorer Survey of Interstellar O VI Absorption in the Small Magellanic Cloud  

Microsoft Academic Search

We present the results of a Far Ultraviolet Spectroscopic Explorer (FUSE) survey of O VI lambda1031.93 and lambda1037.62 absorption toward 18 OB stars in the Small Magellanic Cloud (SMC). The FUSE data are of very high quality, allowing a detailed study of the coronal temperature gas in the SMC. We find that O VI is ubiquitous in the SMC, with

Charles G. Hoopes; Kenneth R. Sembach; J. Christopher Howk; Blair D. Savage; Alex W. Fullerton

2002-01-01

19

Extraction, Purification, and Spectroscopic Characterization of a Mixture of Capsaicinoids  

ERIC Educational Resources Information Center

|This laboratory experiment provides a safe and effective way to instruct undergraduate organic chemistry students about natural-product extraction, purification, and NMR spectroscopic characterization. On the first day, students extract dried habanero peppers with toluene, perform a pipet silica gel column to separate carotenoids from…

Wagner, Carl E.; Cahill, Thomas M.; Marshall, Pamela A.

2011-01-01

20

Spectroscopic characterization of natural humic substances  

NASA Astrophysics Data System (ADS)

The chemical composition and structure of humic substances were established based on spectroscopic studies (EDXS, SRATR FTIR, and 13C NMR). Humic acids were isolated from different matrices such as soils, compost, lignite, and commercial lignohumate. The btained results showed the highest content of aromatic groups in lignite and humic acids of Chernozem. The aromaticity degree (a) calculated from 13C NMR spectroscopy data decreased in the following order: lignite > Chernozems > lignohumate > Luvisols > compost > Cambisols. Infrared spectroscopy detected bands indicative of aliphatic groups (C-H at 2925 cm-1); aromatic groups (C=C at 1620 cm-1); phenolic groups (at 1404-1419 cm-1); and carboxyl and carbonyl groups (at 1225-1223 cm-1) in all studied humic acid samples. The main differences were found in the fingerprint region of 1700-1000 cm-1. The reactivity of humic acids given by the O/R ratio showed that the highest amount of n-alkyl groups were in the lignohumate samples. EDX spectroscopy indicated elements occurring in situ. Soil humic acids contained Fe, Cu, Zn, Ti, Ca, K, S, P, Si, and Br.

Hladký, J.; Pospíšilová, L.; Liptaj, T.

2013-03-01

21

Infrared spectroscopic characterization of aluminized diphenyl carbazide  

NASA Astrophysics Data System (ADS)

Infrared spectroscopy is used to determine the effect of a partial reaction of melted diphenyl carbazide (DPC) with pure aluminum cations during the formation of aluminized diphenyl carbazide (ADPC) complex by a new technique. For this purpose a detailed IR analysis is carried out for pure DPC, pure aluminum and ADPC in the range 400-4000 cm-1. The analysis includes all of the internal fundamental modes of vibrations of symmetric and asymmetric stretching of N-H, aromatic C-H stretching, bending N-H, C--O stretching absorption band, mono-substituted benzene and N-H oscillation using different mole aluminum concentration x. Changes in the spectral shape, mode frequency, mode shift, intensity are studied as a function of x and attributed to Al polarizability. The study revealed the presence of a critical value x=0.3 required for the formation of ideal ADPC complex which contains minimum traces of unreacted aluminum. The variations in transmittance, relaxation time, rotational energy barrier with mole concentration x are also studied and support the presence of critical mole concentration for ADPC complex formation. Detailed X-ray analysis is used to confirm and check the validity of the obtained results. Critical molar aluminum concentration value x=0.3 is determined. The absence of C--N stretching mode and the presence of symmetric stretching and bending modes of N-H prove that ADPC complex is ketonic in nature. This conclusion is supported by the very little change in the IR absorption spectra of the carbonyl group.

El-Kabbany, F.; Taha, S.; Shehap, A.; El-Naggar, M. M.

1999-08-01

22

Mass spectroscopic characterization of small nanoclusters  

NASA Astrophysics Data System (ADS)

Laser desorption/vaporization time-of-flight mass spectrometry (TOF-MS) has proven indispensable in the determination of the properties of small particles. Its usefulness has been realized both in conjunction with molecular beams to investigate the properties of atomic clusters (both homogeneous and heterogeneous) and as an analytical tool in the characterization of larger nanoparticles developed through synthetic methods. In the latter case, the limited amount of analyte has led to methods with great sensitivity at the expense of mass resolution. This thesis concentrates on the development of a new mass spectrometer with greatly enhanced resolution, yet capable of using samples marginally larger than those used in standard laser desorption techniques. In addition to a more accurate and unambiguous mass determination for the desorbed particles, the use of a carrier gas to transport the desorbed species from the source to the extraction region of the TOF-MS, allows molecular beam analytical techniques to be applied to these larger compounds. These techniques include photoionization/neutralization and photofragmentation. This instrument has been used to determine the true profile of laser desorption mass spectra commonly used to monitor the synthesis and purification/separation of gold nanocrystals with surfactant (alkylthiolate) groups. In addition, studies have been performed to analyze atomic clusters formed by laser vaporization techniques including wavelength-dependant photoionization and chemical reactions. In an analogous small size regime, the properties of atomic-sized electrical contacts are investigated. Experiments have been conducted on single contact- junctions using gold contacts in three configurations that give rise to distinct timescales of junction formation and evolution. Under low bias voltage, these structures show step-like changes in current, near the quantum limit, which vary with intercontact distance and/or time, and are often highly reversible.

Salisbury, Brian Eugene

23

Crystallographic and X-ray absorption spectroscopic characterization of Helicobacter pylori UreE bound to Ni2+ and Zn2+ reveal a role for the disordered C-terminal arm in metal trafficking  

PubMed Central

The survival and growth of the pathogen Helicobacter pylori in the gastric acidic environment is ensured by the activity of urease, an enzyme containing two essential Ni2+ ions in the active site. The metallo-chaperone UreE facilitates in vivo Ni2+ insertion into the apo-enzyme. Crystals of apo-HpUreE and its Ni2+ and Zn2+ bound forms were obtained from protein solutions in the absence and presence of the metal ions. The crystal structures of the homodimeric protein, determined at 2.00 Å (apo), 1.59 Å (Ni) and 2.52 Å (Zn) resolution, show the conserved proximal and solvent-exposed His102 residues from two adjacent monomers invariably involved in metal binding. The C-terminal regions of the apo-protein are disordered in the crystal, but acquire significant ordering in the presence of the metal ions due to the binding of His152. The analysis of X-ray absorption spectral data obtained on solutions of Ni2+- and Zn2+-HpUreE provided accurate information of the metal ion environment in the absence of solid-state effects. These results reveal the role of the histidine residues at the protein C-terminus in metal ion binding, and the mutual influence of protein framework and metal ion stereo-electronic properties in establishing coordination number and geometry leading to metal selectivity.

Banaszak, Katarzyna; Martin-Diaconescu, Vlad; Bellucci, Matteo; Zambelli, Barbara; Rypniewski, Wojciech; Maroney, Michael J.; Ciurli, Stefano

2012-01-01

24

Crystallographic and X-ray absorption spectroscopic characterization of Helicobacter pylori UreE bound to Ni²? and Zn²? reveals a role for the disordered C-terminal arm in metal trafficking.  

PubMed

The survival and growth of the pathogen Helicobacter pylori in the gastric acidic environment is ensured by the activity of urease, an enzyme containing two essential Ni²? ions in the active site. The metallo-chaperone UreE facilitates in vivo Ni²? insertion into the apoenzyme. Crystals of apo-HpUreE (H. pylori UreE) and its Ni?- and Zn?-bound forms were obtained from protein solutions in the absence and presence of the metal ions. The crystal structures of the homodimeric protein, determined at 2.00 Å (apo), 1.59 Å (Ni²?) and 2.52 Å (Zn²?) resolution, show the conserved proximal and solvent-exposed His¹?² residues from two adjacent monomers invariably involved in metal binding. The C-terminal regions of the apoprotein are disordered in the crystal, but acquire significant ordering in the presence of the metal ions due to the binding of His¹?². The analysis of X-ray absorption spectral data obtained using solutions of Ni²?- and Zn²?-bound HpUreE provided accurate information of the metal-ion environment in the absence of solid-state effects. These results reveal the role of the histidine residues at the protein C-terminus in metal-ion binding, and the mutual influence of protein framework and metal-ion stereo-electronic properties in establishing co-ordination number and geometry leading to metal selectivity. PMID:22010876

Banaszak, Katarzyna; Martin-Diaconescu, Vlad; Bellucci, Matteo; Zambelli, Barbara; Rypniewski, Wojciech; Maroney, Michael J; Ciurli, Stefano

2012-02-01

25

Thermaland spectroscopic characterization of polypropylene-carbon nanotube composites  

Microsoft Academic Search

Thermogravimetric\\u000a (TG) and varied temperature Raman spectroscopic measurements of melt-blended\\u000a polypropylene composites (PP) with double wall (DWNT) and multi-wall carbon\\u000a nanotubes (MWNT) revealed that the incorporation of carbon nanotubes into\\u000a polymer matrix increased the thermal stability comparing to the virgin polypropylene.\\u000a The characterization of reference nanotubes was also done by Raman microscopy\\u000a and TG measurements. Varied temperature rheological analysis provided

B. B. Marosf?i; A. Szabó; Gy. Marosi; D. Tabuani; G. Camino; S. Pagliari

2006-01-01

26

X-ray absorption spectroscopic investigation of the electronic structure differences in solution and crystalline oxyhemoglobin.  

PubMed

Hemoglobin (Hb) is the heme-containing O2 transport protein essential for life in all vertebrates. The resting high-spin (S = 2) ferrous form, deoxy-Hb, combines with triplet O2, forming diamagnetic (S = 0) oxy-Hb. Understanding this electronic structure is the key first step in understanding transition metal-O2 interaction. However, despite intense spectroscopic and theoretical studies, the electronic structure description of oxy-Hb remains elusive, with at least three different descriptions proposed by Pauling, Weiss, and McClure-Goddard, based on theory, spectroscopy, and crystallography. Here, a combination of X-ray absorption spectroscopy and extended X-ray absorption fine structure, supported by density functional theory calculations, help resolve this debate. X-ray absorption spectroscopy data on solution and crystalline oxy-Hb indicate both geometric and electronic structure differences suggesting that two of the previous descriptions are correct for the Fe-O2 center in oxy-Hb. These results support the multiconfigurational nature of the ground state developed by theoretical results. Additionally, it is shown here that small differences in hydrogen bonding and solvation effects can tune the ground state, tipping it into one of the two probable configurations. These data underscore the importance of solution spectroscopy and show that the electronic structure in the crystalline form may not always reflect the true ground-state description in solution. PMID:24062465

Wilson, Samuel A; Green, Evan; Mathews, Irimpan I; Benfatto, Maurizio; Hodgson, Keith O; Hedman, Britt; Sarangi, Ritimukta

2013-09-23

27

Characterization of semiconductor layered structures by spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

Spectroscopic ellipsometry (SE) is a non-destructive optical technique suitable for the characterization of materials. The measurement is based on the accurate determination of the change of polarization state of a polarized incident light beam after interaction with the specimen. In this work, a rotating analyzer type spectroscopic ellipsometer has been constructed and aligned for the non-destructive characterization of semiconductor materials in the wavelength range from UV to NIR. New results on the mathematical formulation for layers of gradually varying dielectric functions have been obtained and included in the software developed for the analysis of the experimental SE spectra. With these software programs, the interpretation of the measured SE spectra of complex structures becomes possible by using appropriate physical models and non-linear least-square fitting. The system is first tested by a few different types of material systems, such as thermally grown SiO2 on Si substrate and SIMOX structures. Then, it is applied to the study of a series of ion beam synthesized (IBS) material systems, such as SiC/Si heterostructures formed by carbon implantation into silicon, and CoSi2/Si layered structures formed by cobalt implantation into silicon. From the ellipsometric spectra of these samples, useful information on these material structures have been obtained and discussed.

Guo, Wensheng

1997-07-01

28

Absorption and emission spectroscopic characterisation of a pyrene-flavin dyad  

NASA Astrophysics Data System (ADS)

The pyrene-flavin (isoalloxazine) dyad, PFD {C44H31N5O5; CA Index name: 1-pyrenepropanoic acid, ?-[[4,10-dihydro-2,4-dioxo-10-phenylbenzo[g]pteridin-3(2H)-yl)acetyl]amino]-, phenylmethyl ester, (?R) (9Cl); CA Registry number: 618907-57-6}, dissolved in either dichloromethane or acetonitrile is characterized by absorption and emission spectroscopy. Absorption cross-section spectra, stimulated emission cross-section spectra, fluorescence quantum distributions, quantum yields, and degrees of fluorescence polarisation are determined. The fluorescence decay after femtosecond pulse excitation is determined by fluorescence up-conversion. The ground-state absorption recovery is determined by picosecond pump and probe transmission measurements. The dye photo-stability is investigated by observation of absorption spectral changes due to prolonged blue-light excitation. The absorption spectrum of PFD dyad resembles the superposition of the absorption of isoalloxazine (flavin) and 1-methylpyrene. Long-wavelength photo-excitation of the flavin moiety causes fluorescence quenching by ground-state electron transfer from pyrene to isoalloxazine. Short-wavelength photo-excitation of the pyrene moiety causes (i) excited-state electron transfer from pyrene to isoalloxazine, and (ii) Förster-type energy transfer from pyrene to flavin followed by ground-state electron transfer from pyrene to flavin.

Shirdel, J.; Penzkofer, A.; Procházka, R.; Shen, Z.; Strauss, J.; Daub, J.

2007-01-01

29

Spectroscopic characterization and photoinduced processes of 4-oxoquinoline derivatives  

Microsoft Academic Search

Derivatives of 1,4-dihydro-4-oxoquinoline substituted at 4-pyridone or\\/and benzene moieties were synthesized (Q1–Q17), and characterized by UV\\/vis and FT-IR spectroscopy. In dimethylsulfoxide and acetonitrile solvents a significant influence of the substituent's character and position on the quinolone skeleton was observed on the absorption bands in the UVA region (315–400nm). Electron-withdrawing substituents (nitro, cyano, acetyl or trifluoroacetyl) caused a red shift, resulting

Zuzana Barbieriková; Maroš Bella; Jozef Lietava; Dana Dvoranová; Andrej Staško; Tibor Füzik; Viktor Milata; So?a Jantová; Vlasta Brezová

2011-01-01

30

Characterization by spectroscopic Ellipsometry, the physical properties of silver nanoparticles.  

NASA Astrophysics Data System (ADS)

Physicists are able to change their minds through their experiments. I think it is time to go kick the curse and go further in research if we want a human future. I work in the Nano-Optics and Plasmonics research. I defined with ellipsomètrie the structure of new type of Nano particles of silver. It's same be act quickly to replace the old dirty leaded electronic-connexion chip and by the other hand to find a new way for the heath care of cancer disease by nanoparticles the next killers of bad cells. Silver nanoparticle layers are obtained by Spark Plasma Sintering are investigated as an alternative to lead alloy based material for solder joint in power mechatronics modules. These layers are characterized by mean of conventional techniques that is the dilatometry technique, the resistivity measurement through the van der Pauw method, and the flash laser technique. Furthermore, the nanoparticles of silver layer are deeply studied by UV-Visible spectroscopic ellipsometry. Spectroscopic angles parameters are determined in function of temperature and dielectric constants are deduced and analyzed through an optical model which takes into account a Drude and a Lorentz component within the Bruggeman effective medium approximation (EMA). The relaxation times and the electrical conductivity are plot in function of temperature. The obtained electrical conductivity give significant result in good agreement to those reported by four points electrical measurement method.

Coanga, Jean-Maurice

2013-04-01

31

Vibrational spectroscopic characterization of new calcium phosphate bioactive coatings.  

PubMed

In this work calcium phosphate (CaP) compounds with different PO(3-)(4)/HPO(2-)(4) R molar ratios in the 0.65-149 range were synthesized. In fact, all these CaPs contain different amounts of HPO(2-)(4) and PO(3-)(4) ions as well as the amorphous precursors (tricalcium phosphate and octacalcium phosphate) of hydroxyapatite deposition, which was shown by in vitro and in vivo measurements. Spectroscopical IR and Raman results showed the presence of bands whose intensity ratio can be related to the molar ratio R; in particular, the Raman I(962)/I(987) and the IR I(1035)/I(1125) intensity ratios were characterized as markers of the molar ratio. For these CaP compounds a nucleation model, which was based on the ability of HPO(2-)(4) ions to form strong H bonds with PO(3-)(4) ions, was proposed. PMID:10805911

Taddei, P; Tinti, A; Bottura, G; Bertoluzza, A

2000-01-01

32

Synthesis and spectroscopic characterization of nanostructured anatase titania: A photocatalyst  

SciTech Connect

Nanocrystalline TiO{sub 2} was synthesized by the sol-gel process by controlling the crystallite size through calcination. The resulting nanocrystals were characterized using XRD, FT-Raman, SEM/EDX, DSC/TGA and UV-Vis spectroscopic techniques. XRD patterns confirmed the presence of only pure 100% anatase phase TiO{sub 2}. The surface morphology of the nanotitania was evaluated with Scanning Electron Microscopy. The purity of the sol-gel-derived TiO{sub 2} was confirmed through EDX measurements. The band gap of the nanotitania was found to be 3.6 eV from UV-Vis measurements. The pHzpc of the titania sample was measured as 5.90.

Porkodi, K. [Department of Chemistry, PSG College of Technology, Coimbatore-641 004 (India)]. E-mail: porkodikathirvel@yahoo.com; Arokiamary, S. Daisy [Department of Physics, Sri Krishna College of Engineering and Technology, Coimbatore (India)

2007-06-15

33

Thermal and spectroscopic characterization of a proton pumping rhodopsin from an extreme thermophile.  

PubMed

So far retinylidene proteins (?rhodopsin) have not been discovered in thermophilic organisms. In this study we investigated and characterized a microbial rhodopsin derived from the extreme thermophilic bacterium Thermus thermophilus, which lives in a hot spring at around 75 °C. The gene for the retinylidene protein, named thermophilic rhodopsin (TR), was chemically synthesized with codon optimization. The codon optimized TR protein was functionally expressed in the cell membranes of Escherichia coli cells and showed active proton transport upon photoillumination. Spectroscopic measurements revealed that the purified TR bound only all-trans-retinal as a chromophore and showed an absorption maximum at 530 nm. In addition, TR exhibited both photocycle kinetics and pH-dependent absorption changes, which are characteristic of rhodopsins. Of note, time-dependent thermal denaturation experiments revealed that TR maintained its absorption even at 75 °C, and the denaturation rate constant of TR was much lower than those of other proton pumping rhodopsins such as archaerhodopsin-3 (200 ×), Haloquadratum walsbyi bacteriorhodopsin (by 10-times), and Gloeobacter rhodopsin (100 ×). Thus, these results suggest that microbial rhodopsins are also distributed among thermophilic organisms and have high stability. TR should allow the investigation of the molecular mechanisms of ion transport and protein folding. PMID:23740255

Tsukamoto, Takashi; Inoue, Keiichi; Kandori, Hideki; Sudo, Yuki

2013-06-05

34

Spectroscopic system for emission and absorption studies of laser produced plasmas in the extreme ultraviolet  

SciTech Connect

The experimental characterization of a stigmatic spectroscopic system for the diagnostics of laser-produced plasmas in the 50-450 A spectral region is presented. The instrument provides stigmatic spectra for on-axis sources and fully preserves spectral resolution also for off-axis sources. Expected theoretical performances have been compared with experimental results. Spectral and spatial resolution capabilities have been proved to match the nominal ones theoretically predicted. A laser-produced plasma experiment has been also carried out to demonstrate the instrument capabilities. The use of a stigmatic spectrometer and an image detector gives spectrally and spatially resolved images of the plasma source. The good instrumental sensitivity and high dynamic range allow to acquire complete spectra in almost single-shot experiments.

Nicolosi, P.; Pelizzo, M.-G.; Poletto, L.; Epulandi, L. [INFM Laboratory for Ultraviolet and X-Ray Optical Research, Department of Information Engineering, University of Padova, Padova (Italy)

2005-08-15

35

BASE: Bayesian Astrometric and Spectroscopic Exoplanet Detection and Characterization Tool  

NASA Astrophysics Data System (ADS)

BASE is a novel program for the combined or separate Bayesian analysis of astrometric and radial-velocity measurements of potential exoplanet hosts and binary stars. The tool fulfills two major tasks of exoplanet science, namely the detection of exoplanets and the characterization of their orbits. BASE was developed to provide the possibility of an integrated Bayesian analysis of stellar astrometric and Doppler-spectroscopic measurements with respect to their binary or planetary companions - signals, correctly treating the astrometric measurement uncertainties and allowing to explore the whole parameter space without the need for informative prior constraints. The tool automatically diagnoses convergence of its Markov chain Monte Carlo (MCMC[2]) sampler to the posterior and regularly outputs status information. For orbit characterization, BASE delivers important results such as the probability densities and correlations of model parameters and derived quantities. BASE is a highly configurable command-line tool developed in Fortran 2008 and compiled with GFortran. Options can be used to control the program - behaviour and supply information such as the stellar mass or prior information. Any option can be supplied in a configuration file and/or on the command line.

Schulze-Hartung, Tim

2012-08-01

36

Spectroscopic method for determination of the absorption coefficient in brain tissue.  

PubMed

I use Monte Carlo simulations and phantom measurements to characterize a probe with adjacent optical fibres for diffuse reflectance spectroscopy during stereotactic surgery in the brain. Simulations and measurements have been fitted to a modified Beer-Lambert model for light transport in order to be able to quantify chromophore content based on clinically measured spectra in brain tissue. It was found that it is important to take the impact of the light absorption into account when calculating the apparent optical path length, lp, for the photons in order to get good estimates of the absorption coefficient, ?a. The optical path length was found to be well fitted to the equation lp=a+b ln(Is)+c ln(?a)+d ln(Is)ln(?a), where Is is the reflected light intensity for scattering alone (i.e., zero absorption). Although coefficients a-d calculated in this study are specific to the probe used here, the general form of the equation should be applicable to similar probes. PMID:21054121

Johansson, Johannes D

37

Confocal Light Absorption and Scattering Spectroscopic (CLASS) imaging: From cancer detection to sub-cellular function  

NASA Astrophysics Data System (ADS)

Light scattering spectroscopy (LSS), an optical technique that relates the spectroscopic properties of light elastically scattered by small particles to their size, refractive index and shape, has been recently successfully employed for sensing morphological and biochemical properties of epithelial tissues and cells in vivo. LSS does not require exogenous markers, is non-invasive, and, due to its multispectral nature, can sense biological structures well beyond the diffraction limit. All that makes LSS be a very good candidate to be used both in clinical medicine for in vivo detection of disease and in cell biology to monitor cell function on the organelle scale. Recently we developed two LSS-based imaging modalities: clinical Polarized LSS (PLSS) Endoscopic Technique for locating early pre-cancerous changes in GI tract and Confocal Light Absorption and Scattering Spectroscopic (CLASS) Microscopy for studying cells in vivo without exogenous markers. One important application of the clinical PLSS endoscopic instrument, a noncontact scanning imaging device compatible with the standard clinical endoscopes and capable of detecting dysplastic changes, is to serve as a guide for biopsy in Barrett's esophagus (BE). The instrument detects parallel and perpendicular components of the polarized light, backscattered from epithelial tissues, and determines characteristics of epithelial nuclei from the residual spectra. It also can find tissue oxygenation, hemoglobin content and other properties from the diffuse light component. By rapidly scanning esophagus the PLSS endoscopic instrument makes sure the entire BE portion is scanned and examined for the presence of dysplasia. CLASS microscopy, on the other hand, combines principles of light scattering spectroscopy (LSS) with confocal microscopy. Its main purpose is to image cells on organelle scale in vivo without the use of exogenous labels which may affect the cell function. The confocal geometry selects specific region and images are obtained by scanning the confocal volume across the sample. The new beam scanning CLASS microscope is a significant improvement over the previous proof-of-principle device. With this new device we have already performed experiments to monitor morphological changes in cells during apoptosis, differentiated fetal from maternal nucleated red blood cells, and detected plasmon scattering spectra of single gold nanorod.

Qiu, Le

38

Validation of visible/near-IR atmospheric absorption and solar emission spectroscopic models at 1 cm-1 resolution  

NASA Astrophysics Data System (ADS)

A Fourier transform infrared (FTIR) spectrometer, operating at 1 cm-1 resolution between 9000 and 24,669 cm-1 (0.405-1.111 ?m) has been used to check the spectral composition of databases that form the basis for most atmospheric absorption parameterizations used in climate models, remote sensing, and other radiative transfer simulations. The spectrometer, operating near sea level under clear skies, obtained relative atmospheric transmission measurements of the direct solar beam by means of a heliostat. The spectroscopic data were compared with a line-by-line radiative transfer model (LBLRTM) calculation of direct solar beam flux, which used a input data a monochromatic model extraterrestrial solar flux spectrum currently in common use. This intercomparison revealed that the extraterrestrial solar flux spectrum contains 266 solar absorption features that do not appear in the data, resulting in an excess of approximately 1.92 W m-2 in the model's solar constant. The intercomparison also revealed 97 absorption features in the data that do not appear in the HITRAN-96 database as used by LBLRTM, resulting in a model underestimate of shortwave absorption of ˜0.23 W m-2 for a solar zenith angle of 42°. These small discrepancies revealed by the intercomparison indicate that current extraterrestrial solar irradiance models and spectroscopic databases used by shortwave atmospheric radiative transfer models are nearly entirely complete for purposes of atmospheric energy budget calculation. Thus clear or cloudy sky `excess absorption' is unlikely to be related to an incomplete identification of atmospheric absorbing gases and their spectroscopic features, at 1 cm-1 resolution, for a clean troposphere of normal composition.

Lubin, Dan; Vogelmann, Andrew; Lehr, Pamela J.; Kressin, Ann; Ehramjian, James; Ramanathan, V.

2000-09-01

39

Synthesis, spectroscopic characterization and comparative DNA binding studies of Schiff base complexes derived from L-leucine and glyoxal  

NASA Astrophysics Data System (ADS)

The mononuclear Schiff base complexes of the type, [ML(CH 3OH) 2] [M = Co(II), Ni(II), Cu(II) and Zn(II)] have been synthesized by template condensation of L-leucine and glyoxal. The complexes have been characterized on the basis of the results of the elemental analysis, molar conductance, magnetic susceptibility measurements and spectroscopic studies viz, FT-IR, Mass, 1H NMR and 13C NMR spectra. The UV-vis and magnetic moment data revealed an octahedral geometry around Co(II), Ni(II) ion with distortion around Cu(II) ion complex confirmed by EPR data. The conductivity data show a non-electrolytic nature of the complexes. Absorption and fluorescence spectroscopic studies support that all the complexes exhibit a significant binding to calf thymus DNA.

Shakir, Mohammad; Shahid, Nida; Sami, Naushaba; Azam, Mohammad; Khan, Asad U.

2011-11-01

40

Synthesis, characterization, and spectroscopic investigation of benzoxazole conjugated Schiff bases.  

PubMed

Two Schiff bases were synthesized by reaction of 2-(4'-aminophenyl)benzoxazole derivatives with 4-N,N-diethylaminobenzaldehyde. UV-visible (UV-vis) and steady-state fluorescence in solution were applied in order to characterize its photophysical behavior. The Schiff bases present absorption in the UV region with fluorescence emission in the blue-green region, with a large Stokes' shift. The UV-vis data indicates that each dye behaves as two different chromophores in solution in the ground state. The fluorescence emission spectra of the dye 5a show that an intramolecular proton transfer (ESIPT) mechanism takes place in the excited state, whereas a twisted internal charge transfer (TICT) state is observed for the dye 5b. Theoretical calculations were performed in order to study the conformation and polarity of the molecules at their ground and excited electronic states. Using density functional theory (DFT) methods at theoretical levels BLYP/Aug-SV(P) for geometry optimizations and B3LYP/6-311++G(2d,p) for single-point energy evaluations, the calculations indicate that the lowest energy conformations are in all cases nonplanar and that the dipole moments of the excited state relaxed structures are much larger than those of the ground state structures, which corroborates the experimental UV-vis absorption results. PMID:21988352

Santos, Fabiano S; Costa, Tania M H; Stefani, Valter; Gonçalves, Paulo F B; Descalzo, Rodrigo R; Benvenutti, Edilson V; Rodembusch, Fabiano S

2011-10-27

41

Spectroscopic and Computational Characterization of the Base-off Forms of Cob(II)alamin  

PubMed Central

The one-electron reduced form of vitamin B12, cob(II)alamin (Co2+Cbl), is found in several essential human enzymes, including the cobalamin-dependent methionine synthase (MetH). In this work, experimentally validated electronic structure descriptions for two “base-off” Co2+Cbl species have been generated by using a combined spectroscopic and computational approach, so as to obtain definitive clues as to how these and related enzymes catalyze the thermodynamically challenging reduction of Co2+Cbl to cob(I)alamin (Co1+Cbl). Specifically, electron paramagnetic resonance (EPR), electronic absorption (Abs), and magnetic circular dichroism (MCD) spectroscopic techniques have been employed as complementary tools to characterize the two distinct forms of base-off Co2+Cbl that can be trapped in the H759G variant of MetH, one possessing a five-coordinate and the other a four-coordinate, square-planar Co2+ center. Accurate spin Hamiltonian parameters for these low-spin Co2+ centers have been determined by collecting EPR data using both X- and Q-Band microwave frequencies, while Abs and MCD spectroscopic techniques have been employed to probe the corrin-centered ? ? ?* and Co-based d ? d excitations, respectively. By using these spectroscopic data for evaluating electronic structure calculations, it was found that density functional theory provides a reasonable electronic structure description for the five-coordinate form of base-off Co2+Cbl. However, it was necessary to resort to a multireference ab initio treatment to generate a more realistic description of the electronic structure of the four-coordinate form. Consistent with this finding, our computational data indicate that in the five-coordinate Co2+Cbl species, the unpaired spin density is primarily localized in the Co 3dz2-based molecular orbital, as expected, whereas in the four-coordinate form, extensive Co 3d orbital mixing, configuration-interaction, and spin-orbit coupling cause the unpaired electron to delocalize over several Co 3d orbitals. These results provide important clues with regards to the mechanism of enzymatic Co2+Cbl ? Co1+Cbl reduction.

Liptak, Matthew D.; Fleischhacker, Angela S.; Matthews, Rowena G.; Telser, Joshua; Brunold, Thomas C.

2011-01-01

42

High-resolution atmospheric absorption by water vapor in the 830-985 nm region: Evaluation of spectroscopic databases  

NASA Astrophysics Data System (ADS)

We present high spectral resolution (0.05 cm-1) ground-based measurements of direct solar absorption in the clear-sky atmosphere by water vapor over the 830 to 985 nm (10,150-12,050 cm-1) region. Observations were made from the Rutherford Appleton Laboratory on several days in different seasons during 1999. Using these observations water vapor line data in HITRAN and the ESA-WVR database, derived from new laboratory measurements and theoretical calculations, are evaluated. Examples of inter-comparisons between these databases and high-resolution atmospheric transmittance spectra are given. The ESA-WVR and HITRAN 2000 databases were found to give consistently better representations of clear-sky absorption by water vapor in our measurements than previous editions of HITRAN, confirming that spectroscopic errors in databases account in part for discrepancies between modeled and observed short-wave absorption.

Smith, K. M.; Newnham, D. A.

43

Spectroscopic characterization of III-V semiconductor nanomaterials  

NASA Astrophysics Data System (ADS)

III-V semiconductor materials form a broad basis for optoelectronic applications, including the broad basis of the telecom industry as well as smaller markets for high-mobility transistors. In a somewhat analogous manner as the traditional silicon logic industry has so heavily depended upon process manufacturing development, optoelectronics often relies instead on materials innovations. This thesis focuses particularly on III-V semiconductor nanomaterials, detailed characterization of which is invaluable for translating the exhibited behavior into useful applications. Specifically, the original research described in these thesis chapters is an investigation of semiconductors at a fundamental materials level, because the nanostructures in which they appear crystallize in quite atypical forms for the given semiconductors. Rather than restricting the experimental approaches to any one particular technique, many different types of optical spectroscopies are developed and applied where relevant to elucidate the connection between the crystalline structure and exhibited properties. In the first chapters, for example, a wurtzite crystalline form of the prototypical zincblende III-V binary semiconductor, GaAs, is explored through polarization-dependent Raman spectroscopy and temperature-dependent photoluminescence, as well as second-harmonic generation (SHG). The altered symmetry properties of the wurtzite crystalline structure are particularly evident in the Raman and SHG polarization dependences, all within a bulk material realm. A rather different but deeply elegant aspect of crystalline symmetry in GaAs is explored in a separate study on zincblende GaAs samples quantum-confined in one direction, i.e. quantum well structures, whose quantization direction corresponds to the (110) direction. The (110) orientation modifies the low-temperature electron spin relaxation mechanisms available compared to the usual (001) samples, leading to altered spin coherence times explored through a novel spectroscopic technique first formulated for the rather different purpose of dispersion engineering for slow-light schemes. The frequency-resolved technique combined with the unusual (110) quantum wells in a furthermore atypical waveguide experimental geometry has revealed fascinating behavior of electron spin splitting which points to the possibility of optically orienting electron spins with linearly polarized light---an experimental result supporting a theoretical description of the phenomenon itself only a few years old. Lastly, to explore a space of further-restricted dimensionality, the final chapters describe InP semiconductor nanowires with dimensions small enough to be considered truly one-dimensional. Like the bulk GaAs of the first few chapters, the InP nanowires here crystallize in a wurtzite structure. In the InP nanowire case, though, the experimental techniques explored for characterization are temperature-dependent time-integrated photoluminescence at the single-wire level (including samples with InAsP insertions) and time-resolved photoluminescence at the ensemble level. The carrier dynamics revealed through these time-resolved studies are the first of their kind for wurtzite InP nanowires. The chapters are thus ordered as a progression from three (bulk), to two (quantum well), to one (nanowire), to zero dimensions (axially-structured nanowire), with the uniting theme the emphasis on connecting the semiconductor nanomaterials' crystallinity to its exhibited properties by relevant experimental spectroscopic techniques, whether these are standard methods or effectively invented for the case at hand.

Crankshaw, Shanna Marie

44

Structural and spectroscopic characterization of mixed planetary ices.  

PubMed

Mixed ices play a central role in characterizing the origin, evolution, stability and chemistry of planetary ice surfaces. Examples include the polar areas of Mars, the crust of the Jupiter moon Europa, or atmospheres of planets and their satellites, particularly in the outer solar system. Atomistic simulations using accurate representations of the interaction potentials have recently shown to be suitable to quantitatively describe both, the mid- and the far-infrared spectrum of mixed H2O/CO amorphous ices. In this work, molecular dynamics simulations are used to investigate structural and spectroscopic properties of mixed and crystalline ices containing H2O, CO and CO2. Particular findings include: (a) the sensitivity of the water bending mode to the local environment of the water molecules which, together with structural insights from MD simulations, provides a detailed picture for the relationship between spectroscopy and structure; and (b) the sensitivity of the low-frequency spectrum to the structure of the mixed CO2/H2O ice. Specifically, for mixed H2O/CO2 ices with low water contents isolated water molecules are found which give rise to a band shifted by only 12 cm(-1) from the gas-phase value whereas for increasing water concentration (for a 1 : 1 mixture) the band progressively shifts to higher frequency because water clusters can form. More generally it is found that changes in the ice structure due to the presence of CO2 are larger compared to changes induced by the presence of CO and that this difference is reflected in the shape of the water bending vibration. Thus, the water bending vibration appears to be a suitable diagnostic for structural and chemical aspects of mixed ices. PMID:21302549

Plattner, Nuria; Lee, Myung Won; Meuwly, Markus

2010-01-01

45

X-ray absorption fine structure spectroscopic study of uranium nitrides  

SciTech Connect

Uranium mononitride (UN), sesquinitride (U2N3) and dinitride (UN2) were characterized by extended X-Ray absorption fine structure spectroscopy. Analysis on UN indicate the presence of three uranium shells at distances of 3.46(3), 4.89(5) and 6.01(6) A and a nitrogen shell at a distance of 2.46(2) A . For U2N3, two absorbing uranium atoms at different crystallographic positions are present in the structure. One of the uranium atoms is surrounded by nitrogen atoms at 2.28(2) A and by uranium atoms at 3.66(4) and 3.95(4) A . The second type of uranium atom is surrounded by nitrogen atoms at 2.33(2) and 2.64(3) A and by uranium atoms at 3.66(4), 3.95(4) and 5.31(5) A . Results on UN2 indicate two uranium shells at 3.71(4) and 5.32(5) A and two nitrogen shells at 2.28(2).

Poineau, Frederic [University of Nevada, Las Vegas; Yeamans, Charles B. [University of California, Berkeley; Cerefice, Gary S. [University of Nevada, Las Vegas; Sattelberger, Alfred P [Argonne National Laboratory (ANL); Czerwinski, Ken R. [University of Nevada, Las Vegas

2012-01-01

46

Characterization of Spectroscopic and Laser Properties of Pr3+ in S-FAP Crystal  

NASA Astrophysics Data System (ADS)

Spectroscopic and laser properties have been characterized for Pr3+ in Sr5(PO4)3F (S-FAP). The standard Judd-Ofelt analysis has been applied to the measured optical absorption intensities to determine the radiative decay rates, branching ratios, and emission cross sections of principal intermanifold transitions of Pr3+. The Judd-Ofelt parameters Omega(2), Omega(4), and Omega(6) are smaller than those reported for Pr3+ in other laser host crystals. The measured room temperature fluorescence lifetimes of the 1D2 -> 3H4 and 3P0 -> 3F2 transitions are 325 and 105 microseconds, while the Judd-Ofelt analysis predicts the radiative lifetimes for the 1D2 and 3P0 states to be 822 and 116 ms, resulting in the fluorescence quantum efficiencies of 40 and 91sections of the 1D2 -> 3H4 and 3P0 -> 3F2 intermanifold transitions have been also determined to be 0.54 x 10-20 and 4.15 x 10-20 cm2, respectively. *Supported by the NSF grant No. DMR-0099479

Castano, Francisco; Sardar, Dhiraj

2001-10-01

47

Spectroscopic characterization of alkali modified zinc-tellurite glasses doped with neodymium.  

PubMed

Neodymium doped zinc-tellurite glasses of composition TeO(2)-ZnO-Na(2)O-Li(2)O have been prepared and characterized for their thermal, structural and optical properties. Differential thermal analysis revealed reasonably good forming tendency of the glass composition. FTIR spectra were used to analyze the functional groups present in the glass. Judd-Ofelt intensity parameters were derived from the absorption spectrum and used to calculate the radiative lifetime, branching ratio and stimulated emission cross-section for (4)F(3/2)-->(4)I(9/2, 11/2, 13/2) transitions. The quantum efficiency of the (4)F(3/2) level is comparable to the typical values obtained for the Nd(2)O(3)-doped glasses. The decay properties for higher concentration of Nd(2)O(3) were analyzed using Inokuti-Hirayama model to investigate the non-radiative relaxation of the (4)F(3/2) emitting level. The experimental values of branching ratio and saturation intensity of (4)F(3/2)-->(4)I(11/2) transition and calculated spectroscopic quality factor indicate the favourable lasing action in these glasses. PMID:20570210

Rajeswari, R; Babu, S Surendra; Jayasankar, C K

2010-05-06

48

Photochemistry of furyl- and thienyldiazomethanes: spectroscopic characterization of triplet 3-thienylcarbene.  

PubMed

Photolysis (? > 543 nm) of 3-thienyldiazomethane (1), matrix isolated in Ar or N(2) at 10 K, yields triplet 3-thienylcarbene (13) and ?-thial-methylenecyclopropene (9). Carbene 13 was characterized by IR, UV/vis, and EPR spectroscopy. The conformational isomers of 3-thienylcarbene (s-E and s-Z) exhibit an unusually large difference in zero-field splitting parameters in the triplet EPR spectrum (|D/hc| = 0.508 cm(-1), |E/hc| = 0.0554 cm(-1); |D/hc| = 0.579 cm(-1), |E/hc| = 0.0315 cm(-1)). Natural Bond Orbital (NBO) calculations reveal substantially differing spin densities in the 3-thienyl ring at the positions adjacent to the carbene center, which is one factor contributing to the large difference in D values. NBO calculations also reveal a stabilizing interaction between the sp orbital of the carbene carbon in the s-Z rotamer of 13 and the antibonding ? orbital between sulfur and the neighboring carbon-an interaction that is not observed in the s-E rotamer of 13. In contrast to the EPR spectra, the electronic absorption spectra of the rotamers of triplet 3-thienylcarbene (13) are indistinguishable under our experimental conditions. The carbene exhibits a weak electronic absorption in the visible spectrum (?(max) = 467 nm) that is characteristic of triplet arylcarbenes. Although studies of 2-thienyldiazomethane (2), 3-furyldiazomethane (3), or 2-furyldiazomethane (4) provided further insight into the photochemical interconversions among C(5)H(4)S or C(5)H(4)O isomers, these studies did not lead to the spectroscopic detection of the corresponding triplet carbenes (2-thienylcarbene (11), 3-furylcarbene (23), or 2-furylcarbene (22), respectively). PMID:22463599

Pharr, Caroline R; Kopff, Laura A; Bennett, Brian; Reid, Scott A; McMahon, Robert J

2012-03-30

49

Raman spectroscopic characterization on cervical neoplasm in biopsy direction  

NASA Astrophysics Data System (ADS)

Raman spectroscopy was applied to distinguish the spectroscopic information between normal cervical tissues (14) and cervical neoplasia (17), including low grade squamous intraepithelial lesions (6) and high grade squamous intraepithelial lesions (11). Standard pathological sections of these cervical tissues were measured from superficial to stroma layers. We have normalized significant Raman peaks, 1250 and 1579-1656 cm-1 by taking a ratio over a stationary Raman at 1004 cm-1, and successfully discriminated between normal and neoplasm cervical tissues.

Shin, Hsiao Hsin; Tsai, Yan Sheng; Wang, Tao Yuan; Chu, Shou Chia; Chiang, Huihua Kenny

2007-03-01

50

Nanofluid optical property characterization: towards efficient direct absorption solar collectors  

PubMed Central

Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 ?m). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ?10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase.

2011-01-01

51

Nanofluid optical property characterization: towards efficient direct absorption solar collectors.  

PubMed

Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 ?m). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ?10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase. PMID:21711750

Taylor, Robert A; Phelan, Patrick E; Otanicar, Todd P; Adrian, Ronald; Prasher, Ravi

2011-03-15

52

Preliminary results of IR spectroscopic characterization of cholesterol  

Microsoft Academic Search

The authors propose the use of skin over the bony prominences of the hands as a site for infrared (IR) exposure to measure blood cholesterol. Cholesterol, when exposed to IR radiation, generates an absorption spectrum Characteristic of its molecular composition. Aqueous solution of bovine cholesterol, (Sigma Chemicals) with 100mg% and 200mg% of concentration was exposed to laser using attenuated total

Nadeem Haq; Martin D. Fox

1991-01-01

53

Characterization of potassium glycinate for carbon dioxide absorption purposes  

Microsoft Academic Search

Aqueous solutions of potassium glycinate were characterized for carbon dioxide absorption purposes. Density and viscosity of these solutions, with concentrations ranging from 0.1 to 3M, were determined at temperatures from 293 to 313K. Diffusivity of CO2 in solution was estimated applying the modified Stokes–Einstein relation. Solubilities of N2O at the same temperatures and concentrations were measured and the ion specific

A. F. Portugal; P. W. J. Derks; G. F. Versteeg; F. D. Magalhães; A. Mendes

2007-01-01

54

Absorption spectroscopic probe to investigate the interaction between Nd(III) and calf-thymus DNA  

NASA Astrophysics Data System (ADS)

The interaction between Nd(III) and Calf Thymus DNA (CT-DNA) in physiological buffer (pH 7.4) has been studied using absorption spectroscopy involving 4f-4f transition spectra in different aquated organic solvents. Complexation with CT-DNA is indicated by the changes in absorption intensity following the subsequent changes in the oscillator strengths of different 4f-4f bands and Judd-Ofelt intensity ( T?) parameters. The other spectral parameters namely Slator-Condon ( Fk's), nephelauxetic effect ( ?), bonding ( b1/2) and percent covalency ( ?) parameters are computed to correlate with the binding of Nd(III) with DNA. The absorption spectra of Nd(III) exhibited hyperchromism and red shift in the presence of DNA. The binding constant, Kb has been determined by absorption measurement. The relative viscosity of DNA decreased with the addition of Nd(III). Thermodynamic parameters have been calculated according to relevant absorption data and Van't Hoff equation. The characterisation of bonding mode has been studied in detail. The results suggested that the major interaction mode between Nd(III) and DNA was external electrostatic binding.

Devi, Ch. Victory; Singh, N. Rajmuhon

2011-03-01

55

Combined interferometric and absorption-spectroscopic technique for determining molecular line strengths: Applications to CO{sub 2}  

SciTech Connect

A diode-laser-based technique has been developed for absolute line strength measurements with high precision and accuracy, combining a spectroscopic determination of the integrated absorbance with an optical measurement of the absorption path length by means of a Michelson interferometer. This method has been applied to several {sup 12}C{sup 16}O{sub 2} vibrorotational transitions belonging to the {nu}{sub 1}+2{nu}{sub 2}{sup 0}+{nu}{sub 3} combination band, in the spectral region around 2 {mu}m. The 1{sigma} overall accuracy in line strength determination ranges between 0.4% and 0.7%, while the experimental reproducibility is estimated to be around 0.1%. To our knowledge, these levels are the highest ever reached before. The pressure-broadening coefficients for the same transitions are also reported.

Castrillo, A.; Gagliardi, G.; Casa, G.; Gianfrani, L. [Dipartimento di Scienze Ambientali, Seconda Universita di Napoli, and INFM-Gruppo Coordinato Napoli 2, Via Vivaldi 43, I-81100 Caserta (Italy)

2003-06-01

56

Thermal, electrochemical, and spectroscopic characterizations of hyperbranched polymer electrolyte  

SciTech Connect

Novel polymer electrolytes have been prepared with hyperbranched polymers as the host and lithium trifluoromethanesulfonimide, LiN(CF{sub 3}SO{sub 2}){sub 2}, as the ion source. Analysis of the salt concentration dependence of the glass transition temperature indicates that intermolecular interactions occur in the polymer electrolytes and that these hyperbranched polymers can function as a solvent for the lithium salt. Two maxima were observed in the isotherm of conductivity vs. the lithium salt concentration in the polymer electrolyte by ac impedance measurements. Fourier transform infrared spectroscopic analysis of the polymer electrolytes over a large range of lithium salt concentration has been made. It is shown that these two conductivity maximas might be related to the Li{sup +}-polymer coordination at low lithium salt concentration and the formation of ion pairs and higher ion aggregates at high lithium salt concentration, respectively.

Wang, Z.; Ikeda, Motoka; Hirata, Nobuyuki; Kubo, Masataka; Itoh, Takahito; Yamamoto, Osamu [Mie Univ. (Japan). Dept. of Chemistry for Materials

1999-06-01

57

Spectroscopic characterization of biological agents using FTIR, normal Raman and surface-enhanced Raman spectroscopies  

Microsoft Academic Search

FTIR, Raman spectroscopy and Surface Enhanced Raman Scattering (SERS) requires a minimum of sample allows fast identification of microorganisms. The use of this technique for characterizing the spectroscopic signatures of these agents and their stimulants has recently gained considerable attention due to the fact that these techniques can be easily adapted for standoff detection from considerable distances. The techniques also

Tatiana Luna-Pineda; Kristina Soto-Feliciano; Edwin De La Cruz-Montoya; Leonardo C. Pacheco Londoño; Carlos Ríos-Velázquez; Samuel P. Hernández-Rivera

2007-01-01

58

Spectroscopic Characterization of Bendazac and Benzydamine: Possible Photochemical Modes of Action  

Microsoft Academic Search

The involvement of near-UV light in cataract development suggests that potential anti-cataract drugs may display unusual spectroscopic properties. As bendazac impedes certain effects associated with lens opacification, we have characterized the singlet and triplet states of bendazac and its analog, benzydamine, by fluorescence and phosphorescence methods. These compounds have much shorter triplet state lifetimes compared to the triplet state lifetimes

Joseph M. Jez; Jane M. Vanderkooi; Alan M. Laties

1996-01-01

59

Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of some fluoroquinolone antibacterials using ammonium reineckate  

Microsoft Academic Search

Three accurate, rapid and simple atomic absorption spectrometric (AAS), conductometric and colorimetric methods were developed for the determination of gatifloxacin (GTF), moxifloxacin (MXF) and sparfloxacin (SPF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by

Sheikha M. Al-Ghannam

2008-01-01

60

Infrared spectroscopic characterization of human white matter, grey matter, and multiple sclerosis lesions  

Microsoft Academic Search

FT-IR spectroscopy has been used to characterize white matter, grey matter, and multiple sclerosis (MS) plaques from human central nervous system (CNS) tissue. Discrimination among these three tissue types is possible due to variations in composition. Spectra of white matter exhibit strong lipid absorptions. In contrast, spectra of grey matter reveal a reduced lipid contribution and a significant absorption from

Lin-P'ing Choo; Michael Jackson; William C. Halliday; Henry H. Mantsch

1994-01-01

61

Spectroscopic characterization of fluorescein- and tetramethylrhodamine-labeled oligonucleotides and their complexes with a DNA template  

Microsoft Academic Search

We measured absorption and emission spectra, fluorescence quantum yield, anisotropy, fluorescence resonance energy transfer (FRET), and melting temperature to characterize fluorescein- and tetramethylrhodamine (TMR)-labeled oligonucleotides in solution and when hybridized to a common DNA template. Upon hybridization to the template, both the absorption and emission spectra of TMR-labeled duplexes exhibited a shift with respect to those of labeled oligonucleotides, depending

L. Wang; A. K. Gaigalas; J. Blasic; M. J. Holden

2004-01-01

62

Spectroscopic characterization of (57)Fe-enriched cytochrome c.  

PubMed

Investigation of the heme iron dynamics in cytochrome c with Mössbauer spectroscopy and especially nuclear resonance vibrational spectroscopy requires the replacement of the natural abundant heme iron with the (57)Fe isotope. For demetallization, we use a safer and milder ferrous sulfate-hydrochloric acid method in addition to the harsher commonly used hydrofluoric acid-based procedure. The structural integrity of the (57)Fe-reconstituted protein in both oxidation states is confirmed from absorption spectra and a detailed analysis of the rich resonance Raman spectra. These results reinforce the application of metal-substituted heme c proteins as reliable models for the native proteins. PMID:22310496

Leu, Bogdan M; Ching, Tom H; Tran, Cuong; Sage, J Timothy

2011-12-21

63

X-ray absorption spectroscopic studies of mononuclear non-heme iron enzymes  

SciTech Connect

Fe-K-edge X-ray absorption spectroscopy (XAS) has been used to investigate the electronic and geometric structure of the iron active site in non-heme iron enzymes. A new theoretical extended X-ray absorption fine structure (EXAFS) analysis approach, called GNXAS, has been tested on data for iron model complexes to evaluate the utility and reliability of this new technique, especially with respect to the effects of multiple-scattering. In addition, a detailed analysis of the 1s{yields}3d pre-edge feature has been developed as a tool for investigating the oxidation state, spin state, and geometry of iron sites. Edge and EXAFS analyses have then been applied to the study of non-heme iron enzyme active sites.

Westre, T.E.

1996-01-01

64

Atomic absorption spectroscopic determination of molybdenum in plant tissue and blood plasma  

Microsoft Academic Search

A method is presented for determining molybdenum in plant tissue and blood plasma by flame and flameless atomic absorption spectroscopy (AAS). The samples are digested with HNOâ-HClOâ, and the metal is separated by chelation, extracted into methyl isobutyl ketone, and analyzed by AAS. Recoveries of molybdenum from fortified samples ranged from 92.0 to 98.9%. The limits of detection on the

S. U. Khan; R. O. Cloutier; M. Hidiroglou

1979-01-01

65

UV\\/VIS absorption and fluorescence spectroscopic study of some 3-substituted derivatives of 4-hydroxycoumarin  

Microsoft Academic Search

Purpose – The purpose of this paper is to test absorption characteristics of some newly synthesised 4-hidroxycoumarins, containing phenyl-prop-2-enoyl group at the 3-position. Change in spectral characteristics in solvents of different polarity (chloroform and acetonitrile) was followed in regard to the influence of the substitution at the phenyl ring and influence of concentration H+ ions. Effectiveness of tested substances was

Ervina Be?i?; Miroslav Šober; Belma Imamovi?; Davorka Završnik; Selma Špirtovi?-Halilovi?

2011-01-01

66

Electron Spin Resonance and optical absorption spectroscopic studies of manganese centers in aluminium lead borate glasses.  

PubMed

Electron Spin Resonance (ESR) and optical absorption studies of 5Al(2)O(3)+75H(3)BO(3)+(20-x)PbO+xMnSO(4) (where x=0.5, 1,1.5 and 2 mol% of MnSO(4)) glasses at room temperature have been studied. The ESR spectrum of all the glasses exhibits resonance signals with effective isotropic g values at ?2.0, 3.3 and 4.3. The ESR resonance signal at isotropic g?2.0 has been attributed to Mn(2+) centers in an octahedral symmetry. The ESR resonance signals at isotropic g?3.3 and 4.3 have been attributed to the rhombic symmetry of the Mn(2+) ions. The zero-field splitting parameter (zfs) has been calculated from the intensities of the allowed hyperfine lines. The optical absorption spectrum exhibits an intense band in the visible region and it has been attributed to (5)E(g)?(5)T(2g) transition of Mn(3+)centers in an octahedral environment. The optical band gap and the Urbach energies have been calculated from the ultraviolet absorption edges. PMID:23000927

SivaRamaiah, G; LakshmanaRao, J

2012-08-19

67

Spectroscopic characterization and aggregation of azine compounds in different media  

NASA Astrophysics Data System (ADS)

In this study, we have reported for the first time a complete experimental investigation on the compound Neutral Red and the new monobrominated derivative in different media as a function of the concentration. These compounds belong to the quinone-imine class of dyes and have good potential to be applied as photosensitizers in Photodynamic Therapy.Although the aggregation of Neutral Red has been reported by several authors, this has not been thoroughly evaluated due to spectral changes occurring depending on the solvent and concentration of dye.We investigated and compared the effects of aggregation properties in water, ethanol, water-ethanol mixtures, water-polyethylene glycol 400 (75:25 v/v) and N,N-dimethylformamide.An analysis of the changes in the absorption spectra with respect to the solvent as a function of dye concentration together with theoretical calculations confirmed the monomeric species and the formation of different types of aggregates in this class of compounds.

Urrutia, María Noel; Ortiz, Cristina Susana

2013-02-01

68

Raman spectroscopic characterization of some commercially available carbon black materials  

Microsoft Academic Search

Some commercially available carbon black materials were characterized by Raman spectroscopy. The Raman spectra were recorded between 1000 and 1800 cm?1, which corresponds to the spectral region that provides the most valuable data on the microstructure of carbons. A comparative study of the intensity, bandwidth and frequency shifts of the D and G bands, as well as the broad amorphous

T. Jawhari; A. Roid; J. Casado

1995-01-01

69

Characterization of mesoporous materials via flourescent spectroscopic methods  

NASA Astrophysics Data System (ADS)

There are three components that need to be understood to create new porous membranes for industrial applications. 1) To understand appropriate synthesis conditions to create a successful membrane system. 2) To understand how the microstructures generated in synthesis affect the transport properties of that system. 3) To be able to characterize the heterogeneity of the fabricated membrane's transport and physical structure. Presented within this manuscript are new characterization methods to increase the understanding in membrane technology. It will be demonstrated that the novel application of standard fluorescent methods and the development of new fluorescent methods techniques allows for the measurement of molecular interactions and transport properties on length scales capable of providing valuable information in the field of membrane science, as well as expanding new applications in fluorescent techniques.

Kennard, Raymond Russell

70

Surface layer formation on Sn anode: ATR FTIR spectroscopic characterization  

Microsoft Academic Search

Surface layer formed on Sn thin film electrode in 1M LiPF6\\/EC:DMC electrolyte was characterized using ex situ FTIR spectroscopy with the attenuated total reflection technique. IR spectral analyses showed that the immersion of Sn film in the electrolyte resulted in a chemical interfacial reaction leading to the passivation of Sn surface with primarily PF-containing inorganic surface species and small amount

Seung-Wan Song; Seung-Won Baek

2009-01-01

71

Synthesis, characterization and spectroscopic studies of pyrazinamide metal complexes  

Microsoft Academic Search

The present paper deals with the synthesis and characterization of Schiff base complexes of pyrazinamide an antitubercular drug. Metals selected for complexation are copper, silver, gold, zinc, mercury, iron and cobalt. The complexes have been suitably synthesized and isolated in pure powdered form. Analytical data agrees with the compositions M(L), M?(L)2 and M?(L)2·2H2O, respectively where M=Ag, M?=Cu, Au, Zn and

Priya Budhani; Sayed Aftab Iqbal; Suman Malik Mamta Bhattacharya; Liviu Mitu

2010-01-01

72

X-ray absorption spectroscopic study on Ti/n-GaN  

NASA Astrophysics Data System (ADS)

Formation of low resistance and thermally stable ohmic contacts to GaN is of considerable importance for device applications. Several metallization schemes for ohmic contacts to n-GaN with low contact resistance have been proposed and investigated by different techniques. We investigate 500 Å Ti/n-GaN contacts of as-deposited and rapid furnace annealed at 900 °C for 30 s, using X-ray diffraction pattern, I-V measurements, and X-ray absorption near edge spectra at Ti K- and L3,2-edges and elucidate the mechanism responsible for the high ohmic behaviour. These measurements indicate the formation of an interfacial TixN layer and intermetallic alloys of Ti and Ga at the Ti/n-GaN interface upon high temperature annealing.

Senthil Kumar, M.; Kumar, V. Suresh; Asokan, K.; Chiou, J. W.; Jan, J. C.; Pong, W. F.; Kumar, J.

2005-11-01

73

In situ X-ray absorption spectroscopic study of electrodeposited nickel oxide films during redox reactions  

SciTech Connect

The quick-scanning extended X-ray absorption fine structure technique of X-ray absorption spectroscopy has been employed to monitor structural changes during the cyclic electrochemical oxidation and reduction of nickel oxide thin film electrodes. The films were prepared by anodic deposition onto a graphite substrate at 1.1 V vs. SCE from a solution of 0.05 M NiSO{sub 4} + 0.5 M CH{sub 3}COONa. The freshly as-deposited film contained mainly Ni{sup 2+} and Ni{sup 4+} with highly disordered structures. The phase containing Ni{sup 2+} can be charged in 1 M of KOH solution to a phase containing Ni{sup 4+}. Electrochemical reduction of a charged nickel oxide film at constant current leads to the formation of {alpha}-Ni(OH){sub 2} which transforms to {beta}-Ni(OH){sub 2} with time in the KOH solution. The discharged film can be recharged to form a phase which contains mostly Ni{sup 4+}. The fraction of Ni{sup 4+} in the film increased with charging time and reached a value of 0.8 (i.e., 80% of Ni is present as Ni{sup 4+}) after 38 min of charging at a constant current of 1.68 mA/cm{sup 2}. The Ni{sup 4+} phase is structurally similar to that of a NiO{sub 2} phase produced by electrochemical oxidation of LiNiO{sub 2} in a nonaqueous electrolyte as has been shown previously.

Mansour, A.N. [Naval Surface Warfare Center, West Bethesda, MD (United States). Carderock Div.; Melendres, C.A. [Argonne National Lab., IL (United States). Materials Science and Chemical Technology Div.; Wong, J. [Lawrence Livermore National Lab., CA (United States)

1998-04-01

74

Resonance Raman spectroscopic characterization of compound III of lignin peroxidase  

SciTech Connect

Resonance Raman (RR) spectra of several compounds III of lignin peroxidase (LiP) have been measured at 90 K with Soret and visible excitation wavelengths. The samples include LiPIIIa (or oxyLiP) prepared by oxygenation of the ferrous enzyme, LiPIIIb generated by reaction of the native ferric enzyme with superoxide, LiPIIIc prepared from native LiP plus H{sub 2}O{sub 2} followed by removal of excess peroxide with catalase, and LiPIII made by addition of excess H{sub 2}O{sub 2} to the native enzyme. The RR spectra of these four products appear to be similar and, thus, indicate that the environments of these hexacoordinate, low-spin ferriheme species must also be very similar. Nonetheless, the Soret absorption band of LiPIII is red-shifted by 5 nm from the 414-nm maximum common to LiPIIIa, -b, and -c. Analysis of the iron-porphyrin vibrational frequencies indicates that the electronic structures for the various compounds III are consistent with an Fe{sup III}O{sub 2}{sup {center dot}-}formulation. The spectral changes observed between the oxygenated complex and the ferrous heme of lignin peroxidase are similar to those between oxymyoglobin and deoxymyoglobin. The contraction in the core sizes in compound III relative to the native peroxidase is analyzed and compared with that of other heme systems. The Fe-O{sub 2} stretching vibration of the oxygenated peroxidase is observed at 563 cm{sup {minus}1} and shifts of 538 cm{sup {minus}1} with {sup 18}O isotope. The Fe-histidine stretching vibration is observed at 245 cm{sup {minus}1} in ferrous peroxidase and appears to shift to 276 cm{sup {minus}1} in the oxygenated complex.

Mylrajan, M.; Valli, K.; Wariishi, Gold, M.H.; Loehr, T.M. (Oregon Graduate Institute of Science and Technology, Beaverton (USA))

1990-10-01

75

FTIR spectroscopic characterization of differently cultivated food related yeasts.  

PubMed

The application of Fourier Transform Infrared Spectroscopy for characterization of yeasts is growing rapidly. Since it is known that the phenotypic expression of yeast cells depends sensitively on the nutrients that are available in the growth medium, one standardized growth medium is usually used for identification and characterization purposes in order to obtain reproducible FTIR signals. Since our recently developed high-throughput micro-cultivation protocol has the capacity to use more than one standardized growth medium, we wanted to investigate if the parallel use of multiple growth media can improve identification results. For this purpose, five different cultivation media (YP, YPD, YMB, SAB and SD) were used. In total 91 food spoilage yeast strains of 12 different genera were cultivated in different cultivation media and subsequently characterized by FTIR spectroscopy. For spectral identifications, Radial Basis Function-Partial Least Squares (RBF-PLS) was used in combination with cross-model validation where an inner cross-validation loop was used to optimize the model, while in an outer loop an independent test set was kept aside to test the optimized model. Sensitivity and specificity were evaluated for each studied genus class. The results show that the YMB selective medium gave the best discrimination results for 9 of the 12 genera with sensitivity above 90%. Only three genera showed better identification results on other media (Clavispora and Metschnikowia on medium SD, Debaryomyces on medium YPD). We therefore suggest to use the media SD, YPD in combination with the YMB medium for the identification of food spoilage yeasts. PMID:23741734

Shapaval, V; Walczak, B; Gognies, S; Møretrø, T; Suso, H P; Wold Åsli, A; Belarbi, A; Kohler, A

2013-06-05

76

NMR spectroscopic characterization of ?-cyclodextrin inclusion complex with vanillin  

NASA Astrophysics Data System (ADS)

The inclusion of vanillin by ?-cyclodextrin was investigated by 1H NMR. The continuous variation technique was used to evidence the formation of soluble 1:1 complex in aqueous solution. The association constant of vanillin with ?-cyclodextrin has been obtained at 298 K by fitting the experimental chemical shifts differences, ??obs = ?free - ?obs of the observed guest and host protons, with a non-linear regression method. Besides the effective association constant, the fitting procedure allows a precise determination of all chemical shift parameters characterizing the pure complex. They can by used for an analysis of the geometry of the molecular complex in solution.

Pîrnau, Adrian; Bogdan, Mircea; Floare, Calin G.

2009-08-01

77

Characterization of spectroscopic of Pr(DBM)3(TPPO)2 containing poly(methyl methacrylate).  

PubMed

The absorption and fluorescence spectra of Pr(DBM)3(TPPO)2 (DBM: dibenzoylmethane, TPPO: triphenylphosphine oxide) containing poly(methyl methacrylate) (PMMA) were measured. The energy levels are assigned and analyzed in terms of the free-ion Hamiltonian model. From the data available in the absorption spectrum, various spectroscopic parameters such as the spherically symmetric part of the free-ion Hamiltonian (E(AVG)), Slater-Condon (F2, F4, F6), spin-orbit interaction (zeta), Judd-Ofelt (omega2, omega4, omega6) parameters and the reduced matrix elements are derived. The radiative properties of Pr(DBM)3(TPPO)2 containing PMMA were also predicted according to the Judd-Ofelt theory. The values of the fluorescence branching ratio and the emission cross section of 3P0 --> 3F2 fluorescence transition revealed that Pr(DBM)3(TPPO)2 containing PMMA is an efficient luminescent material. PMID:15979398

Chen, Biao; Dong, Ning; Xu, Jie; Liang, Hao; Zhang, Qijin; Yin, Min; Zheng, Zhi

2005-06-23

78

Crystal structure characterization as well as theoretical study of spectroscopic properties of novel Schiff bases containing pyrazole group  

NASA Astrophysics Data System (ADS)

A series of novel Schiff bases containing pyrazole group were synthesized using 1-aryl-3-methyl-4-benzoyl-5-pyrazolone and phenylenediamine as the starting materials. All as-synthesized Schiff bases were characterized by means of NMR, FT-IR, and MS; and the molecular geometries of two Schiff bases as typical examples were determined by means of single crystal X-ray diffraction. In the meantime, the ultraviolet-visible light absorption spectra and fluorescent spectra of various as-synthesized products were also measured. Moreover, the B3LYP/6-1G(d,p) method was used for the optimization of the ground state geometry of the Schiff bases; and the spectroscopic properties of the products were computed and compared with corresponding experimental data based on cc-pVTZ basis set of TD-B3LYP method. It has been found that all as-synthesized Schiff bases show a remarkable absorption peak in a wavelength range of 270-370 nm; and their maximum emission peaks are around 344 nm and 332 nm, respectively.

Guo, Jia; Ren, Tiegang; Zhang, Jinglai; Li, Guihui; Li, Weijie; Yang, Lirong

2012-09-01

79

On-line atomization of selenium hydride in graphite furnaces: estimate of atomic absorption coefficient and spectroscopic temperature  

NASA Astrophysics Data System (ADS)

A transversely heated graphite tube atomizer (THGA) has been employed to ensure constant temperature within the observation volume. A method of sampling of gaseous selenium hydride from a container has been developed including a relation between observed peak area (integrated absorbance) and selenium mass injected into the furnace. This makes it possible to control fully the composition of the atomizer atmosphere. A boron nitride tube sealed to the injection hole of the graphite tube has been used as the interface. It performed well even at the highest tested atomization temperature (2400°C). Spectroscopic temperature measurements based on atomic absorption at the 196.1 nm and 204.0 nm Se lines have been used to determine the influence of carrier gas flow rates on the effective gas phase temperature in the atomizer at set furnace temperatures of 1800°C and 2200°C. Characteristic masses m0 at the 196.1 nm line, in pure argon atmosphere, have been determined at these set furnace temperatures for various argon gas flow rates. The data are employed to estimate an experimental value of the atomic absorption coefficient: (17.1 ± 0.8) × 10 -18 m 2. The value does not significantly differ from the theoretical value. m0 values found for the temperature range 1800-2400°C for the hydride injection into the furnace at the minimum feasible carrier gas flow rate are compared with characteristic masses for the traditional liquid sampling to the furnace in the same temperature range. This made it possible to estimate that the analyte losses through the injection port in the case of the traditional liquid sampling to the furnace are in the range 20-25%.

D?dina, Ji?í; Matoušek, Tomáš; Frech, Wolfgang

1996-07-01

80

Spectroscopic characterization of the structural and functional properties of natural organic matter fractions  

Microsoft Academic Search

Natural organic matter (NOM) is known to be complex in nature with varying structural and functional charac- teristics. In this study, an aquatic NOM was fractionated into the polyphenolic-rich (NOM-PP) and the carbohydrate- rich (NOM-CH) fractions in an attempt to better characterize their chemical and structural properties along with a reference soil humic acid (SHA). Various spectroscopic techniques were employed

Jie Chen; Eugene J. LeBoeuf; Hongjun Pan; Sheng Dai; Sheng Dai

2002-01-01

81

Optical characterization of SnO 2:F films by spectroscopic ellipsometry  

Microsoft Academic Search

Spectroscopic ellipsometry (SE), which is a non-destructive and a non-contact optical technique used in characterization of thin films, is widely used to determine thickness, microstructure and optical constants. In this work, the effect of F incorporation on optical properties of SnO2 films grown by ultrasonic spray pyrolysis technique (USP) is presented. The reflections, refractive indices and thicknesses of the films

F. Atay; V. Bilgin; I. Akyuz; E. Ketenci; S. Kose

2010-01-01

82

Atomic absorption spectroscopic analysis of some Pakistani herbal medicinal products used in respiratory tract infections.  

PubMed

Heavy metals are one of the major causes of widespread occurrence of respiratory tract infections (RTIs). Unani system of medicines utilizing plant extracts and herbal medicinal products (HMPs) are known to have remedial potential in different RTIs (flue, cough, bronchitis, allergy, asthma, nasal and chest congestion). Being natural in origin chances of metal contamination cannot be ignored in Phytopharmaceuticals, therefore toxic metal contents (Pb, Cd, As, and Hg) were determined in some Pakistani branded HMPs being used in various RTIs through atomic absorption spectrophotometer. Research findings showed detectable levels of metals in all these formulations. Daily metals intakes via these HMPs were calculated as: 0.86-277.44 (Pb), 1.442-10.986 (Cd), 0.16-5.83 (As), and 0.00-0.09 ?g/ day (Hg). Prevalence of toxic metals in HMPs especially elevated levels of Pb and Cd, pose severe health risks to the consumers. Statistical interpretation of data using ANOVA followed by LSD (p<0.05), revealed significantly different metal concentrations among HMPs. To identify the metal contaminant of HMPs and highlight their toxic manifestations is the basic aim of this research. The study is not a bias to the beneficial effects of the Phytopharmaceuticals, rather is done to improve their quality and safety parameter according to the international health standards. PMID:22186337

Hina, Bushra; Rizwani, Ghazala Hafeez; Shareef, Huma; Ahmed, Maryam

2012-01-01

83

Biotransformations of anticancer ruthenium(III) complexes: an X-ray absorption spectroscopic study.  

PubMed

An anti-metastatic drug, NAMI-A ((ImH)[Ru(III) Cl4 (Im)(dmso)]; Im=imidazole, dmso=S-bound dimethylsulfoxide), and a cytotoxic drug, KP1019 ((IndH)[Ru(III) Cl4 (Ind)2 ]; Ind=indazole), are two Ru-based anticancer drugs in human clinical trials. Their reactivities under biologically relevant conditions, including aqueous buffers, protein solutions or gels (e.g, albumin, transferrin and collagen), undiluted blood serum, cell-culture medium and human liver (HepG2) cancer cells, were studied by Ru K-edge X-ray absorption spectroscopy (XAS). These XAS data were fitted from linear combinations of spectra of well-characterised Ru compounds. The absence of XAS data from the parent drugs in these fits points to profound changes in the coordination environments of Ru(III) . The fits point to the presence of Ru(IV/III) clusters and binding of Ru(III) to S-donor groups, amine/imine and carboxylato groups of proteins. Cellular uptake of KP1019 is approximately 20-fold higher than that of NAMI-A under the same conditions, but it diminishes drastically after the decomposition of KP1019 in cell-culture media, which indicate that the parent complex is taken in by cells through passive diffusion. PMID:23361836

Levina, Aviva; Aitken, Jade B; Gwee, Yee Yen; Lim, Zhi Jun; Liu, Mimi; Singharay, Anannya Mitra; Wong, Pok Fai; Lay, Peter A

2013-01-30

84

Atomic absorption spectroscopic measurements of silicon atom concentrations in electron cyclotron resonance silicon oxide deposition plasmas  

NASA Astrophysics Data System (ADS)

The silicon atom densities in both silane/oxygen and tetraethoxysilane (TEOS)/oxygen electron cyclotron resonance (ECR) plasmas were measured as functions of microwave power, pressure, and gas flow rates. An atomic absorption spectrometer with a Si hollow-cathode lamp was constructed for these measurements. Silicon atom densities in silane/oxygen ECR discharges increase with rising plasma density, and a strong correlation was found between the Si atom gas-phase abundance and the silicon oxide film deposition rate. The measured Si concentrations [(1-7)×1010 cm-3] were high enough to account for a significant part of the film growth in the silane based chemistry. In TEOS/O2 discharges Si atom concentrations were lower by an order of magnitude, so Si is probably not a major contributor to the growth rate in that case. The internal temperature of Si atoms was found to vary from 380 to 720 K with increasing microwave power (200-650 W).

Augustyniak, Edward; Chew, Kok Heng; Shohet, J. Leon; Woods, R. Claude

1999-01-01

85

Sub-THz spectroscopic characterization of vibrational modes in artificially designed DNA monocrystal  

NASA Astrophysics Data System (ADS)

Sub-terahertz (sub-THz) vibrational spectroscopy is a new spectroscopic branch for characterizing biological macromolecules. In this work, highly resolved sub-THz resonance spectroscopy is used for characterizing engineered molecular structures, an artificially designed DNA monocrystal, built from a short DNA sequence. Using a recently developed frequency domain spectroscopic instrument operating at room temperature with high spectral and spatial resolution, we demonstrated very intense and specific spectral lines from a DNA crystal in general agreement with a computational molecular dynamics (MD) simulation of a short double stranded DNA fragment. The spectroscopic signature measured in the frequency range between 310 and 490 GHz is rich in well resolved and reproducible spectral features thus demonstrating the capability of THz resonance spectroscopy to be used for characterizing custom macromolecules and structures designed and implemented via nanotechnology for a wide variety of application domains. Analysis of MD simulation indicates that intense and narrow vibrational modes with atomic movements perpendicular (transverse) and parallel (longitudinal) to the long DNA axis coexist in dsDNA, with much higher contribution from longitudinal vibrations.

Sizov, Igor; Rahman, Masudur; Gelmont, Boris; Norton, Michael L.; Globus, Tatiana

2013-11-01

86

Spectroscopic characterization of silicalite-1 and titanium silicalite-1  

SciTech Connect

Titanium silicalite samples were prepared by two different procedures. A titanium-free sample (silicalite-1) was also prepared. The samples were characterized by XRD, SEM, skeletal FT-FIR and FT-Raman, UV-vis FT-IR of hydroxy-groups and of adsorbed ammonia. The skeletal spectra have been analyzed on the basis of a general interpretation of the vibrational structure of tetrahedra-based silica polymorphs. This leads to a partial modification of the traditional assignments of the skeletal vibrations of zeolites. Framework Ti is found to be responsible for a band near 960 cm{sup -1}, in both IR and Raman spectra, and for a shoulder near 510 cm{sup -1} in the IR spectra, as well as for other weak perturbations of the silicalite spectra. The two main features have been assigned to the asymmetric stretching and to the rocking modes of Si-O-Ti bridges. Framework Ti is found to act as a Lewis acid center, being able to coordinate ammonia from gas-phase. Extraframework Ti is observed in the form of anatase in samples prepared with the procedure 1 only with Ti content above 2%, while TiO{sub 2} is found in all samples prepared with the procedure 2. Both series of samples are active catalysts of phenol hydroxylation by H{sub 2}O{sub 2}. 57 refs., 13 figs., 2 tabs.

Astorino, E.; Peri, J.B.; Willey, R.J. [Northeastern Univ., Boston, MA (United States)] [and others

1995-12-01

87

Spectroscopic characterization of tetradentate macrocyclic ligand: it's transition metal complexes  

NASA Astrophysics Data System (ADS)

Manganese(II), cobalt(II), nickel(II) and copper(II) complexes are synthesized with a novel tetradentate ligand viz. 1,3,9,11-tetraaza-4,8,12,16-tetraoxo-2,6,10,14-tetrathiacyclohexadecane (L) and characterized by the elemental analysis, molar conductance measurements, magnetic susceptibility measurements, electron impact mass, 1H NMR, IR, electronic and EPR spectral studies. The molar conductance measurements of the complexes in DMSO correspond to be nonelectrolytic nature for Mn(II), Co(II) and Cu(II) while 1:2 electrolytes for Ni(II) complexes. Thus these complexes may be formulated as [M(L)X 2] and [Ni(L)]X 2 (where M: Mn(II), Co(II), and Cu(II) and X = Cl - and NO 3-). On the basis of IR, electronic and EPR spectral studies an octahedral geometry has been assigned for Mn(II) and Co(II) complexes, square-planar for Ni(II) whereas tetragonal for Cu(II) complexes. The ligand and its complexes were also evaluated against the growth of bacteria and pathogenic fungi in vitro.

Chandra, Sulekh; Gupta, Lokesh Kumar

2004-10-01

88

Spectroscopic and morphologic characterization of the dentin/adhesive interface  

NASA Astrophysics Data System (ADS)

The potential environmental risks associated with mercury release have forced many European countries to ban the use of dental amalgam. Alternative materials such as composite resins do not provide the clinical function for the length of time characteristically associated with dental amalgam. The weak link in the composite restoration is the dentin/adhesive bond. The purpose of this study was to correlate morphologic characterization of the dentin/adhesive bond with chemical analyses using micro- Fourier transform infrared and micro-Raman spectroscopy. A commercial dental adhesive was placed on dentin substrates cut from extracted, unerupted human third molars. Sections of the dentin/adhesive interface were investigated using infrared radiation produced at the Aladdin synchrotron source; visible radiation from a Kr+ laser was used for the micro-Raman spectroscopy. Sections of the dentin/adhesive interface, differentially stained to identify protein, mineral, and adhesive, were examined using light microscopy. Due to its limited spatial resolution and the unknown sample thickness the infrared results cannot be used quantitatively in determining the extent of diffusion. The results from the micro-Raman spectroscopy and light microscopy indicate exposed protein at the dentin/adhesive interface. Using a laser that reduces background fluorescence, the micro-Raman spectroscopy provides quantitative chemical and morphologic information on the dentin/adhesive interface. The staining procedure is sensitive to sites of pure protein and thus, complements the Raman results.

Lemor, R. M.; Kruger, Michael B.; Wieliczka, David M.; Swafford, Jim R.; Spencer, Paulette

1999-01-01

89

Spectroscopic characterization of the first ultrafast catalytic intermediate in protochlorophyllide oxidoreductase.  

PubMed

The enzyme NADPH:protochlorophyllide oxidoreductase (POR) catalyses the reduction of protochlorophyllide into chlorophyllide, a precursor of chlorophyll a in photosynthetic organisms. The enzyme binds the substrate and the cofactor in the dark and catalysis is initiated by the absorption of light by the substrate. We have carried out spectroscopic measurements with ultrafast time resolution under single pulse conditions, which reveal a biphasic formation of the first catalytic intermediate, I675* with average rates of (3.7 ± 0.7 ps)(-1) and (177 ± 78 ps)(-1), as obtained from a systematic analysis of 15 datasets. Measurements in the mid-IR absorption spectral region show that I675* is associated with a decrease of the PChlide C[double bond, length as m-dash]O keto oscillator strength. The spectroscopic changes in the visible and mid-IR regions are specific for the enzyme reaction as they do not occur in the photoexcited substrate alone. In deuterated samples, the rates of I675* formation are reduced by a factor of 1.5-2 compared to protonated samples, suggesting the involvement of a proton movement in this reaction step. The quantum yield of this step is determined to be 0.64 ± 0.11, and the quantum yield of the final reaction product formed on a later time scale, chlorophyllide, is 0.26 ± 0.06. Several possible interpretations of these data are discussed. PMID:22121506

Sytina, Olga A; van Stokkum, Ivo H M; Heyes, Derren J; Hunter, C Neil; Groot, Marie Louise

2011-11-28

90

Spectroscopic and Functional Characterization of Iron-Bound Forms of Azotobacter vinelandiiNifIscA†  

PubMed Central

The ability of Azotobacter vinelandii NifIscA to bind Fe has been investigated to assess the role of Fe-bound forms in NIF-specific Fe-S cluster biogenesis. NifIscA is shown to bind one Fe(III) or one Fe(II) per homodimer and the spectroscopic and redox properties of both the Fe(III)- and Fe(II)-bound forms have been characterized using the UV-visible absorption, CD and VTMCD, EPR, Mössbauer and resonance Raman spectroscopies. The results reveal a rhombic intermediate-spin (S = 3/2) Fe(III) center (E/D = 0.33, D = 3.5 ± 1.5cm?1) that is most likely 5-coordinate with two or three cysteinate ligands and a rhombic high spin (S = 2) Fe(II) center (E/D = 0.28, D = 7.6 cm?1) with properties similar to reduced rubredoxins or rubredoxin variants with three cysteinate and one or two oxygenic ligands. Iron-bound NifIscA undergoes reversible redox cycling between the Fe(III)/Fe(II) forms with a midpoint potential of +36 ±15 mV at pH 7.8 (versus NHE). L-cysteine is effective in mediating release of free Fe(II) from both the Fe(II)- and Fe(III)-bound forms of NifIscA. Fe(III)-bound NifIscA was also shown to a competent iron source for in vitro NifS-mediated [2Fe-2S] cluster assembly on the N-terminal domain of NifU, but the reaction occurs via cysteine-mediated release of free Fe(II) rather than direct iron transfer. The proposed roles of A-type proteins in storing Fe under aerobic growth conditions and serving as iron donors for cluster assembly on U-type scaffold proteins or maturation of biological [4Fe-4S] centers are discussed in light of these results.

Mapolelo, Daphne T.; Zhang, Bo; Naik, Sunil G.; Huynh, Boi Hanh; Johnson, Michael K.

2012-01-01

91

Absorption  

NSDL National Science Digital Library

The process of absorption is a cellular process (microscopic). Absorption cells line the stomach and intestine walls and allow small nutrients (broken down from the food we eat) to pass through and into our blood. The process of absorption is much like a leaking balloon filled with water. The balloon is the stomach or intestine, the tiny holes are the absorption cells, and the water is nutrients leaving.

Katie Hale (CSUF;)

2002-09-26

92

Spectroscopically labeled peptaibiotic analogs: the 4-nitrophenylalanine infrared absorption probe inserted at different positions into trichogin GA IV.  

PubMed

A set of three analogs of the 10-residue, membrane-active lipopeptaibiotic trichogin GA IV, labeled with the promising 4-nitrophenylalanine IR absorption probe for local polarity, was synthesized by the solid-phase methodology, chromatographically purified, and extensively characterized. A single residue modification was inserted near the N-terminus, in the central region, or at the C-terminus. A solution conformational analysis, carried out by FT-IR absorption, CD, and 2D-NMR combined with molecular dynamics calculations, indicates that the mono-labeled analogs maintain the overall helical properties of the parent compound. Membrane permeabilization measurements and antimicrobial tests revealed that they possess membrane-modifying properties and in vitro antibacterial activities analogous to those of the natural lipopeptaibiotic. Our IR absorption and attenuated total reflectance investigations in various environments, from which water was excluded for solubility reasons, showed that the 1350 cm(-1) 4-nitrobenzyl band is a reporter group of rather limited sensitivity. PMID:23280709

Peggion, Cristina; Biondi, Barbara; De Zotti, Marta; Oancea, Simona; Formaggio, Fernando; Toniolo, Claudio

2012-12-27

93

Reactivity of Chromium(III) Nutritional Supplements in Biological Media: An X-Ray Absorption Spectroscopic Study  

SciTech Connect

Chromium(III) nutritional supplements are widely used due to their purported ability to enhance glucose metabolism, despite growing evidence on low activity and the potential genotoxicity of these compounds. Reactivities of Cr(III) complexes used in nutritional formulations, including [Cr3O(OCOEt)6(OH2)3]+ (A), [Cr(pic)3] (pic) = 2-pyridinecarboxylato(-) (B), and trans-[CrCl2(OH2)4]+ (CrCl3 {center_dot} 6H2O; C), in a range of natural and simulated biological media (artificial digestion systems, blood and its components, cell culture media, and intact L6 rat skeletal muscle cells) were studied by X-ray absorption near-edge structure (XANES) spectroscopy. The XANES spectroscopic data were processed by multiple linear-regression analyses with the use of a library of model Cr(III) compounds, and the results were corroborated by the results of X-ray absorption fine structure spectroscopy and electrospray mass spectrometry. Complexes A and B underwent extensive ligand-exchange reactions under conditions of combined gastric and intestinal digestion (in the presence of a semisynthetic meal, 3 h at 310 K), as well as in blood serum and in a cell culture medium (1-24 h at 310 K), with the formation of Cr(III) complexes with hydroxo and amino acid/protein ligands. Reactions of compounds A-C with cultured muscle cells led to similar ligand-exchange products, with at least part of Cr(III) bound to the surface of the cells. The reactions of B with serum greatly enhanced its propensity to be converted to Cr(VI) by biological oxidants (H2O2 or glucose oxidase system), which is proposed to be a major cause of both the insulin-enhancing activity and toxicity of Cr(III) compounds (Mulyani, I.; Levina, A.; Lay, P. A. Angew. Chem. Int. Ed. 2004, 43, 4504-4507). This finding enhances the current concern over the safety of consumption of large doses of Cr(III) supplements, particularly [Cr(pic)3].

Nguyen, A.; Mulyani, I.; Levina, A.; Lay, P.A.

2009-05-22

94

Characterization of plasmonic effects in thin films and metamaterials using spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

In this article, spectroscopic ellipsometry studies of plasmon resonances at metal-dielectric interfaces of thin films are reviewed. We show how ellipsometry provides valuable non-invasive amplitude and phase information from which one can determine the effective dielectric functions, and how these relate to the material nanostructure and define exactly the plasmonic characteristics of the system. There are three related plasmons that are observable using spectroscopic ellipsometry; volume plasmon resonances, surface plasmon polaritons and particle plasmon resonances. We demonstrate that the established method of exploiting surface plasmon polaritons for chemical and biological sensing may be enhanced using the ellipsometric phase information and provide a comprehensive theoretical basis for the technique. We show how the particle and volume plasmon resonances in the ellipsometric spectra of nanoparticle films are directly related to size, surface coverage and constituent dielectric functions of the nanoparticles. The regularly observed splitting of the particle plasmon resonance is theoretically described using modified effective medium theories within the framework of ellipsometry. We demonstrate the wealth of information available from real-time in situ spectroscopic ellipsometry measurements of metal film deposition, including the evolution of the plasmon resonances and percolation events. Finally, we discuss how generalized and Mueller matrix ellipsometry hold great potential for characterizing plasmonic metamaterials and sub-wavelength hole arrays.

Oates, T. W. H.; Wormeester, H.; Arwin, H.

2011-12-01

95

Spectroscopic characterization of photoinduced Mn5+ ions in YAlO3  

NASA Astrophysics Data System (ADS)

We have spectroscopically studied the photoinduced color center in Mn:YAlO3, the promising material for holographic data storage. We have proved that grayish-bluish coloration in photoexposed Mn:YAlO3 is due to Mn5+ ions in octahedral sites. We assign the main features observed in the absorption and emission spectra of photodarkened Mn:YAlO3 to the 1T2(t22), 3T2(t2e), 3T1(t2e), 1A1(t22), and 3A2(e2) excited states of Mn5+. We show that Mn5+ ions can be stabilized in Mn:YAlO3 codoped with Ca ions and in the crystals grown in reducing atmosphere and subsequently annealed in air at 310-460 °C.

Noginov, M. A.; Loutts, G. B.; Noginova, N.; Hurling, S.; Kück, S.

2000-01-01

96

Fe-complex of a tetraamido macrocyclic ligand: Spectroscopic characterization and catalytic oxidation studies  

NASA Astrophysics Data System (ADS)

This work presents the spectroscopic characterization and reaction studies of a Fe III-complex (2) of a tetraamido macrocyclic ligand (1, 15,15-dimethyl-5,8,13,17-tetrahydro-5,8,13,17-tetraaza-dibenzo[a,g]cyclotridecene-6,7,14,16-tetraone). 2 was characterized primarily by means of EPR. In agreement with the magnetic moment ( ?eff = 3.87 BM), EPR spectroscopy of 2 shows signals consistent with S = 3/2 intermediate-spin ferric-iron. Besides EPR, mass spectrometry, UV/vis spectroscopy and cyclic voltammetry were used to further characterize 2. 2 is soluble in water and activates hydrogen peroxide under ambient conditions. 2 catalytically bleaches dyes, pulp and paper effluents and oxidizes several amines to their corresponding N-oxides with high turnover number and good yields.

Sullivan, Shane Z.; Ghosh, Anindya; Biris, Alexandru S.; Pulla, Sharon; Brezden, Anna M.; Collom, Samulel L.; Woods, Ross M.; Munshi, Pradip; Schnackenberg, Laura; Pierce, Brad S.; Kannarpady, Ganesh K.

2010-10-01

97

Spectroscopic characterization of biological agents using FTIR, normal Raman and surface-enhanced Raman spectroscopies  

NASA Astrophysics Data System (ADS)

FTIR, Raman spectroscopy and Surface Enhanced Raman Scattering (SERS) requires a minimum of sample allows fast identification of microorganisms. The use of this technique for characterizing the spectroscopic signatures of these agents and their stimulants has recently gained considerable attention due to the fact that these techniques can be easily adapted for standoff detection from considerable distances. The techniques also show high sensitivity and selectivity and offer near real time detection duty cycles. This research focuses in laying the grounds for the spectroscopic differentiation of Staphylococcus spp., Pseudomonas spp., Bacillus spp., Salmonella spp., Enterobacter aerogenes, Proteus mirabilis, Klebsiella pneumoniae, and E. coli, together with identification of their subspecies. In order to achieve the proponed objective, protocols to handle, cultivate and analyze the strains have been developed. Spectroscopic similarities and marked differences have been found for Spontaneous or Normal Raman spectra and for SERS using silver nanoparticles have been found. The use of principal component analysis (PCA), discriminate factor analysis (DFA) and a cluster analysis were used to evaluate the efficacy of identifying potential threat bacterial from their spectra collected on single bacteria. The DFA from the bacteria Raman spectra show a little discrimination between the diverse bacterial species however the results obtained from the SERS demonstrate to be high discrimination technique. The spectroscopic study will be extended to examine the spores produced by selected strains since these are more prone to be used as Biological Warfare Agents due to their increased mobility and possibility of airborne transport. Micro infrared spectroscopy as well as fiber coupled FTIR will also be used as possible sensors of target compounds.

Luna-Pineda, Tatiana; Soto-Feliciano, Kristina; De La Cruz-Montoya, Edwin; Pacheco Londoño, Leonardo C.; Ríos-Velázquez, Carlos; Hernández-Rivera, Samuel P.

2007-05-01

98

Mass spectroscopic characterization of yttrium-containing metallofullerene YC82 using resonant laser ablation  

Microsoft Academic Search

In this paper, resonant laser ablation time-of-flight mass spectroscopy (RLA-TOF-MS) has been used to mass spectroscopic characterization of yttrium-containing fullerenes. Solvent soluble, yttrium-containing fullerenes are extracted from yttrium\\/carbon soot produced by the carbon-arc fullerene generation method. The RLA-TOF mass spectra indicate the presence of YC82. The metallofullerences YC60, YC70, Y2C82 and a series of Y2C2n are not observed by RLA-TOF-MS.

Shiliang Wang; Jiahe Tian; Songtao Dai; Dieyan Chen; Chuping Luo; Haisong Tan; Liangbing Gan; Chunhui Huang

1995-01-01

99

Analytical and spectroscopic characterization of humic acids extracted from sewage sludge, manure, and worm compost  

SciTech Connect

Humic acids extracted from sewage sludges, manure, and worm compost have been characterized by chemical and spectroscopic methods. Meaningful differences in the composition were revealed by FTIR, {sup 1}H, {sup 13}C NMR, and visible spectroscopies. These differences allow a differentiation among the products depending on the source from which they were obtained. Humic acid extracted from sewage sludges contains the highest percentage of aliphatic carbon, associated with polysaccharides and proteinaceous structures, and has characteristics close to those of aquatic humic acids. On the other hand, humic acids from manure and worm compost are similar to the humic acids originating from soil.

Deiana, S.; Gessa, C.; Manunza, B.; Seeber, R. (Universita di Sassari (Italy)); Rausa, R. (Eniricerche S.p.A., Milanese (Italy))

1990-07-01

100

The first structural and spectroscopic characterization of a neptunyl polyoxometalate complex.  

PubMed

The reaction between PW9O349- and NpO2+ has yielded the first structurally characterized neptunyl(V) polyoxometalate complex, [Na2(NpO2)2(A-PW9O34)2]14-. This complex is isostructural with the uranyl(VI) analogue, and there is also spectroscopic evidence for its existence in solution. The complex is readily extracted into toluene, and this may have significance in the sequestering and/or separation of the neptunyl ion in terms of nuclear waste management. PMID:12418864

Gaunt, Andrew J; May, Iain; Helliwell, Madeleine; Richardson, Steve

2002-11-13

101

Processing of High Level Waste: Spectroscopic Characterization of Redox Reactions in Supercritical Water - Final Report  

SciTech Connect

Current efforts are focused on the oxidative dissolution of chromium compounds found in Hanford tank waste sludge. Samples of chromium oxides and hydroxides with varying degrees of hydration are being characterized using Raman, FTIR, and XPS spectroscopic techniques. Kinetics of oxidation reactions at subcritical and supercritical temperatures are being followed by Raman spectroscopy using a high temperature stainless steel cell with diamond windows. In these reactions both hydrogen peroxide and nitrate anions are used as the oxidizing species with Cr(III) compounds and organic compounds as reducing agents.

Arrington Jr., C. A.

2000-11-15

102

Mass spectroscopic characterization of yttrium-containing metallofullerene YC82 using resonant laser ablation  

SciTech Connect

In this paper, resonant laser ablation time-of-flight mass spectroscopy (RLA-TOF-MS) has been used to mass spectroscopic characterization of yttrium-containing fullerenes. Solvent soluble, yttrium-containing fullerenes are extracted from yttrium/carbon soot produced by the carbon-arc fullerene generation method. The RLA-TOF mass spectra indicate the presence of YC82. The metallofullerences YC60, YC70, Y2C82 and a series of Y2C2n are not observed by RLA-TOF-MS. This result is consistent with the ESR spectral result reported by Shinohara et al.

Wang Shiliang; Tian Jiahe; Dai Songtao; Chen Dieyan; Luo Chuping; Tan Haisong; Gan Liangbing; Huang Chunhui [Laser Single Atom Detection Laboratory, Department of Physics, Tsinghua University, Beijing 100084 (China); State Key Laboratory of Rare Earth Material Chemistry and Applications, Peking University, Beijing 100871 (China)

1995-04-01

103

Infrared spectroscopic characterization of human white matter, grey matter, and multiple sclerosis lesions  

NASA Astrophysics Data System (ADS)

FT-IR spectroscopy has been used to characterize white matter, grey matter, and multiple sclerosis (MS) plaques from human central nervous system (CNS) tissue. Discrimination among these three tissue types is possible due to variations in composition. Spectra of white matter exhibit strong lipid absorptions. In contrast, spectra of grey matter reveal a reduced lipid contribution and a significant absorption from water. MS plaques exhibit spectra indicative of lipid loss and, depending upon whether the plaques are chronic or acute, changes in the protein and/or water content.

Choo, Lin-P'ing; Jackson, Michael; Halliday, William C.; Mantsch, Henry H.

1994-01-01

104

Fluorescence and UV\\/Vis spectroscopic behaviour of novel biindolizines  

Microsoft Academic Search

Indolizines, known as a useful class of fluorophores, were bridged yielding biindolizines. We intended to obtain long wavelength absorbing and emitting fluorescent systems suitable for fluorescence labeling of biomolecules. The influence of the different kinds of coupling on the absorption and fluorescence behaviour of the resulting biidolizines was studied. The new fluorophore systems were characterized spectroscopically by their absorption and

Helmut Sonnenschein; Gunther Hennrich; Ute Resch-Genger; B. Schulz

2000-01-01

105

Label-Free Characterization of Cancer-Activated Fibroblasts Using Infrared Spectroscopic Imaging  

PubMed Central

Glandular tumors arising in epithelial cells comprise the majority of solid human cancers. Glands are supported by stroma, which is activated in the proximity of a tumor. Activated stroma is often characterized by the molecular expression of ?-smooth muscle actin (?-SMA) within fibroblasts. However, the precise spatial and temporal evolution of chemical changes in fibroblasts upon epithelial tumor signaling is poorly understood. Here we report a label-free method to characterize fibroblast changes by using Fourier transform infrared spectroscopic imaging and comparing spectra with ?-SMA expression in primary normal human fibroblasts. We recorded the fibroblast activation process by spectroscopic imaging using increasingly tissue-like conditions: 1), stimulation with the growth factor TGF?1; 2), coculture with MCF-7 human breast cancerous epithelial cells in Transwell coculture; and 3), coculture with MCF-7 in three-dimensional cell culture. Finally, we compared the spectral signatures of stromal transformation with normal and malignant human breast tissue biopsies. The results indicate that this approach reveals temporally complex spectral changes and thus provides a richer assessment than simple molecular imaging based on ?-SMA expression. Some changes are conserved across culture conditions and in human tissue, providing a label-free method to monitor stromal transformations.

Holton, S.E.; Walsh, M.J.; Kajdacsy-Balla, A.; Bhargava, R.

2011-01-01

106

The Reaction Coordinate of a Functional Model of Tyrosinase: Spectroscopic and Computational Characterization  

PubMed Central

The ?-?2:?2-peroxodicopper(II) complex synthesized by reacting the Cu(I) complex of the bis-diamine ligand N,N?-di-tert-butyl-ethylenediamine (DBED) with O2 is a functional and spectroscopic model of the coupled binuclear copper protein tyrosinase. This complex reacts with 2,4-di-tert-butylphenolate at low temperature to produce a mixture of the catechol and quinone products, which proceeds through three intermediates (A – C) that have been characterized. A, stabilized at 153K, is characterized as a phenolate-bonded bis-?-oxo dicopper(III) species, which proceeds at 193K to B, presumably a catecholate-bridged coupled bis-copper(II) species via an electrophilic aromatic substitution mechanism wherein aromatic ring distortion is the rate-limiting step. Isotopic labeling shows that the oxygen inserted into the aromatic substrate during hydroxylation derives from dioxygen, and a late-stage ortho-H+ transfer to an exogenous base is associated with C-O bond formation. Addition of a proton to B produces C, determined from resonance Raman spectra to be a Cu(II)-semiquinone complex. The formation of C (the oxidation of catecholate and reduction to Cu(I)) is governed by the protonation state of the distal bridging oxygen ligand of B. Parallels and contrasts are drawn between the spectroscopically and computationally supported mechanism of the DBED system, presented here, and the experimentally-derived mechanism of the coupled binuclear copper protein tyrosinase.

Op't Holt, Bryan T.; Vance, Michael A.; Mirica, Liviu M.; Stack, T. Daniel P.; Solomon, Edward I.

2009-01-01

107

Spectroscopic characterization of Ti3+:AgGaS2 and Fe2+:MgAl2O4 crystals for mid-IR laser applications  

NASA Astrophysics Data System (ADS)

Mid-IR lasers based on Cr2+ and Fe2+ ions in II-VI tetrahedral crystal hosts have been proven useful as tunable solid-state lasers operating over the 1.9-6 ?m spectral range. However, the development of new effective gain media promising for lasing over 3-4 ?m and with wavelengths longer than 6 ?m is still under progress. In this paper we report spectroscopic characterization of Titanium doped AgGaS2 and Iron doped MgAl2O4 crystals with coordination number four. Polarized absorption and luminescence spectra of titanium doped AgGaS2 crystals were measured at room and low temperatures. It was shown that Ti ions in the AgGaS2 crystal were in both 1+ and 3+ valence states substituting silver and gallium sites, correspondingly. Ti3+ ions in AgGaS2 and Fe2+ in MgAl2O4 crystals feature broad absorption bands with a maximums near 2?m. These ions have no second excited state absorption bands and could potentially be used as effective saturable absorbers for passive Q-switching of 2.1 ?m holmium laser cavities. Broad emission covering the 3-6 ?m spectral range was observed under 1.9 ?m excitation into Ti3+ absorption band. A luminescence signal between 3 and 6 ?m was also observed in the Fe:MgAl2O4 crystal.

Sackuvich, Rose K.; Peppers, Jeremy M.; Myoung, NoSoung; Badikov, Valery V.; Fedorov, Vladimir V.; Mirov, Sergey B.

2012-02-01

108

Isolation and spectroscopic characterization of two isomers of the metallofullerene NdatC82  

NASA Astrophysics Data System (ADS)

For the first time, two types of the metallofullerene NdatC82 have been isolated and characterized. HPLC was used to isolate NdatC82(I, II). The two isomers were characterized by mass spectrometry and UV-Vis-NIR absorption spectroscopy. NdatC82(I) was found to be similar in structure to the main isomer of other lanthanofullerenes such as LaatC82, as was previously reported. We assign NdatC82(I) to have a C2v cage symmetry. NdatC82(II) showed a markedly different UV-Vis-NIR absorption spectrum to NdatC82(I). Its spectrum is in good agreement with that of the minor isomer of metallofullerenes such as PratC82. We therefore assign NdatC82(II) to have a Cs cage symmetry. In contrast to other metallofullerenes, both isomers appear to be equally abundant.

Porfyrakis, Kyriakos; Kanai, Mito; Morley, Gavin W.; Ardavan, Arzhang; Dennis, T. John S.; Briggs, G. Andrew D.

2005-09-01

109

Attempted Isolation, Spectroscopic Characterization, and Computational Study of Diazirinone (N2CO), its Analogs, and their Precursors  

NASA Astrophysics Data System (ADS)

Intrigued by the 2005 reported synthesis of diazirinone, we carried out further experimental and theoretical studies aimed at the detailed matrix-isolation and millimeter-wave spectroscopic characterizations. Diazirinone is a peculiar isoconjugate of two very stable molecules, CO and N2, which may be of astrochemical interest. Unfortunately, the previous reported methods of diazirinone generation did not yield this species, but rather its decomposition products. Encouraged by the many computational studies of the N2CO potential energy surface that all found diazirinone to be the lowest energy isomer, save its decomposition products, we proposed a new method of preparation of diazirinone from the photolysis or thermolysis of carbonyl diazide by loss of two nitrogen molecules. We were able to generate the highly explosive carbonyl diazide in sufficient yield from the reaction of triphosgene and sodium azide. This has allowed us to obtain a matrix-isolation and gas phase IR spectrum of carbonyl diazide which has a gas-phase lifetime of several days. We are currently engaged in the safe purification and distillation of our sample and obtaining a millimeter-wave spectrum of carbonyl diazide. We will attempt to photolyze or thermolyze this molecule to release diazirinone and characterize it by millimeter-wave spectroscopy to pave the way for possible astrochemical detection. In order to provide better mechanistic insight into the decomposition of carbonyl diazide to diazirinone, we have engaged in a DFT and ab initio computational study of several possible pathways. Our preliminary results suggest that of the pathways studied, a step-wise process in which an acyclic CON4 species is generated by loss of nitrogen followed by possible rearrangement and further loss of N2 is most likely. These results will be compared to the analogous reactions for azirinone (HC2NO), our next likely synthetic and spectroscopic target. The millimeter-wave absorption spectrometer used in this research project has been used previously for the investigation of numerous small inorganic molecules and ions. The apparatus consists of a three-meter Pyrex discharge chamber with cylindrical electrodes at each end. The discharge operates at mTorr pressures and at temperatures as low as 77 K. The microwave signal is generated by a Gunn-diode microwave source, which is then further amplified and multiplied to reach the desired frequencies. The signal is focused onto a liquid-helium-cooled indium antimonide detector.

Esselman, Brian J.; Nolan, Alex M.; Amberger, Brent K.; Shaffer, Chris J.; Woods, R. Claude; Stanton, John F.; McMahon, Robert J.

2010-11-01

110

Absorption  

PubMed Central

Given that mind–body interventions constitute a major portion of complementary and alternative medicine used by the public, it seems important to explore those human characteristics that may contribute to the efficacy of mind–body interventions in those who are most likely to benefit. One such characteristic, absorption, reflects an individual’s cognitive capacity for involvement in sensory and imaginative experiences in ways that alter an individual’s perception, memory, and mood with behavioral and biological consequences. Thus, one’s level of absorption may potentially create differential treatment effects in mind–body intervention outcomes. Conducting practical clinical trials helps address the challenge of determining whether a specific mind–body modality intervention may be effective. Such trials may be strengthened by including measures of personality dimensions such as absorption.

Menzies, Victoria; Taylor, Ann Gill; Bourguignon, Cheryl

2009-01-01

111

The synthesis, structural, and spectroscopic characterization of uranium(IV) perrhenate complexes.  

PubMed

We report the synthesis, structural, and spectroscopic characterization of a series of uranium(IV)-perrhenato complexes. Three isostructural complexes with general formula [U(ReO4)4(L)4] (where L = tri-n-butylphosphine oxide/TBPO (2), triethyl phosphate/TEP (3), or tri-iso-butyl phosphate/TiBP (4)), have been synthesized, both through the photoreduction of ethanolic {UO2}2+ solutions and also via a novel U(IV) starting material, U(ReO4)4.5H2O (1). Compound 1 has also been used in the preparation of [U(ReO4)4(TPPO)3(CH3CN)].2CH3CN (5) and [U(ReO4)(DPPMO2)3(OH)][ReO4]2.2CH3CN (6), where TPPO represents triphenylphosphine oxide and DPPMO2 represents bis(diphenylphosphino)methane dioxide. All six complexes have been spectroscopically characterized using NMR, UV-vis-NIR, and IR techniques, with 2, 3, 5, and 6 also fully structurally characterized. The U atoms in compounds 2-6 all exhibit eight-coordinate geometry with up to four perrhenate groups in addition to three (DPPMO2 and TPPO) or four (TEP, TiBP, TBPO) coordinated organic ligands. In the case of compounds 5 and 6, the coordination of eight ligands to the U(IV) center is completed by the binding of a solvent molecule (CH3CN) and OH-, respectively. Solid-state physical analysis (elemental and thermogravimetric) and infrared spectroscopy are in agreement with the structural studies. The crystallographic data suggest that the strength of the U(IV)-O-donor ligand bonds decreases across the series R3PO > [ReO4]- > (RO)3PO. Solution-state IR and 31P NMR spectroscopy appear to be in agreement with these solid-state results. PMID:16212387

John, Gordon H; May, Iain; Sharrad, Clint A; Sutton, Andrew D; Collison, David; Helliwell, Madeleine; Sarsfield, Mark J

2005-10-17

112

Elemental and spectroscopic methods with chemometric analysis for characterizing composition and transformation of dissolved organic matter during chicken manure composting.  

PubMed

Dissolved organic matter was extracted from chicken manure after 1, 8, 16, 28 and 40 days of composting and characterized by combining elemental and spectroscopic methods with chemometric analysis to investigate the evolution of composting materials. The elemental and spectroscopic analysis results showed that the composting process was characterized by the biodegradation of aliphatics, polysaccharide and proteins, as well as by the synthesis of aromatic structures, humic-like substances and macromolecules. Principal component analysis and correlation analysis indicated that the data from elemental and spectroscopic analysis fell into three main groups, and corresponded to the biodegradation, aromatization, and humification and polymerization state of the composting materials. Hierarchical cluster analysis indicated rapid biodegradation of organic matter during the first eight days, and the formation of aromatic structures, humic-like materials and macromolecules in dissolved organic matter after eight days. PMID:23240197

He, Xiao-Song; Xi, Bei-Dou; Jiang, Yong-Hai; Li, Ming-Xiao; Yu, Hui-Bin; An, Da; Yang, Yu; Liu, Hong-Liang

2012-09-01

113

Chemical Vapor Deposition Synthesis and Raman Spectroscopic Characterization of Large-Area Graphene Sheets.  

PubMed

We present a chemical vapor deposition (CVD) method to catalytically synthesize large-area, transferless, single- to few-layer graphene sheets using hexamethyldisilazane (HMDS) on a SiO2/Si substrate as a carbon source and thermally evaporated alternating Ni/Cu/Ni layers as a catalyst. The as-synthesized graphene films were characterized by Raman spectroscopic imaging to identify single- to few-layer sheets. This HMDS-derived graphene layer is continuous over the entire growth substrate, and single- to trilayer mixed sheets can be up to 30 ?m in the lateral dimension. With the synthetic CVD method proposed here, graphene can be grown into tailored shapes directly on a SiO2/Si surface through vapor priming of HMDS onto predefined photolithographic patterns. The transparent and conductive HMDS-derived graphene exhibits its potential for widespread electronic and opto-electronic applications. PMID:23461419

Liao, Chun-Da; Lu, Yi-Ying; Tamalampudi, Srinivasa Reddy; Cheng, Hung-Chieh; Chen, Yit-Tsong

2013-03-19

114

Chemical Vapor Deposition Synthesis and Raman Spectroscopic Characterization of Large-Area Graphene Sheets  

NASA Astrophysics Data System (ADS)

We present a chemical vapor deposition (CVD) method to catalytically synthesize large-area, transferless, single- to few-layer graphene sheets using hexamethyldisilazane (HMDS) on a SiO2/Si substrate as a carbon source and thermally evaporated alternating Ni/Cu/Ni layers as a catalyst. The as-synthesized graphene films were characterized by Raman spectroscopic imaging to identify single- to few-layer sheets. This HMDS-derived graphene layer is continuous over the entire growth substrate, and single- to trilayer mixed sheets can be up to 30 -m in the lateral dimension. With the synthetic CVD method proposed here, graphene can be grown into tailored shapes directly on a SiO2/Si surface through vapor priming of HMDS onto predefined photolithographic patterns. The transparent and conductive HMDS-derived graphene exhibits its potential for widespread electronic and opto-electronic applications.

Liao, Chun-Da; Lu, Yi-Ying; Tamalampudi, Srinivasa Reddy; Cheng, Hung-Chieh; Chen, Yit-Tsong

2013-10-01

115

Synthesis, spectroscopic characterization, DNA interaction and antibacterial study of metal complexes of tetraazamacrocyclic Schiff base  

NASA Astrophysics Data System (ADS)

The template condensation reaction between benzil and 3,4-diaminotoulene resulted mononuclear 12-membered tetraimine macrocyclic complexes of the type, [MLCl2] [M = Co(II), Ni(II), Cu(II) and Zn(II)]. The synthesized complexes have been characterized on the basis of the results of elemental analysis, molar conductance, magnetic susceptibility measurements and spectroscopic studies viz. FT-IR, 1H and 13C NMR, FAB mass, UV-vis and EPR. An octahedral geometry has been envisaged for all these complexes, while a distorted octahedral geometry has been noticed for Cu(II) complex. Low conductivity data of all these complexes suggest their non-ionic nature. The interactive studies of these complexes with calf thymus DNA showed that the complexes are avid binders of calf thymus DNA. The in vitro antibacterial studies of these complexes screened against pathogenic bacteria proved them as growth inhibiting agents.

Shakir, Mohammad; Khanam, Sadiqa; Firdaus, Farha; Latif, Abdul; Aatif, Mohammad; Al-Resayes, Saud I.

116

Metal ion binding by a bicyclic diamide: Deep UV Raman spectroscopic characterization  

SciTech Connect

Deep UV resonance Raman spectroscopy was used for characterizing ligand-metal ion complexes. The obtained results demonstrated a strong intrinsic sensitivity and selectivity of a Raman spectroscopic signature of a bicyclic diamide, a novel chelating agent for lanthanides and actinides (Lumetta, G. J.; Rapko, B. M.; Garza, P. A.; Hay, B. P.; Gilbertson, R. D.; Weakley, T. J. R.; Hutchison, J. E. J. Am. Chem. Soc. 2002, 124, 5644). Molecular modeling, which included structure optimization and calculation of Raman frequencies and resonance intensities, allowed for assigning all strong Raman bands of the bicyclic diamide as well as predicting the band shifts observed because of complex formation with metal ions. A comparative analysis of Raman spectra and the results of the molecular modeling could be used for elucidating the structure of complexes in solution.

Shashilov, Victor A.; Ermolenkov, Vladimir V.; Levitskaia, Tatiana G.; Lednev, Igor K.

2005-08-18

117

The synthesis and spectroscopic characterization of nano calcium fluorapatite using tetra-butylammonium fluoride.  

PubMed

Pure homogeneous nano sized biocompatible fluorapatite (FAp) particles were synthesized by a wet chemical procedure using water soluble tetra-butylammonium fluoride (TBAF) without using high temperatures and any purification processes. Combination of the Bragg's law and the plane-spacing equation for the two high intensity lines, namely, (002) and (300), gives a=9.3531 ?, c=6.8841 ?, confirms the identity of the highly crystalline synthetic material as well as its purity. The effect of various pH's in crystal formation and on their size was also evaluated. The calculated crystallinities were excellent with a rate around 5.0. The synthesized nano FAp was fully characterized by spectroscopic techniques (XRD, SEM, EDS, BET, FT-IR and ICP-AES). The nitrogen adsorption-desorption isotherm showed a type IV diagram and calculation of the surface area was investigated as well. PMID:21930424

Sheykhan, Mehdi; Heydari, Akbar; Ma'mani, Leila; Badiei, Alireza

2011-08-31

118

Spectroscopic characterization of effective components anthraquinones in Chinese medicinal herbs binding with serum albumins  

NASA Astrophysics Data System (ADS)

The interactions of serum albumins such as human serum albumin (HSA) and bovine serum albumin (BSA) with emodin, rhein, aloe-emodin and aloin were assessed employing fluorescence quenching and absorption spectroscopic techniques. The results obtained revealed that there are relatively strong binding affinity for the four anthraquinones with HSA and BSA and the binding constants for the interactions of anthraquinones with HSA or BSA at 20 °C were obtained. Anthraquinone-albumin interactions were studied at different temperatures and in the presence of some metal ions. And the competition binding of anthraquinones with serum albumins was also discussed. The Stern-Volmer curves suggested that the quenching occurring in the reactions was the static quenching process. The binding distances and transfer efficiencies for each binding reactions were calculated according to the Föster theory of non-radiation energy transfer. Using thermodynamic equations, the main action forces of these reactions were also obtained. The reasons of the different binding affinities for different anthraquinone-albumin reactions were probed from the point of view of molecular structures.

Bi, Shuyun; Song, Daqian; Kan, Yuhe; Xu, Dong; Tian, Yuan; Zhou, Xin; Zhang, Hanqi

2005-11-01

119

EXAFS, EPR, and electronic absorption spectroscopic study of the {alpha} metallosubunit of CO dehydrogenase from Clostridium thermoaceticum  

SciTech Connect

The {alpha} metallosubunit of carbon monoxide dehydrogenase from Clostridium thermoaceticum was isolated by subjecting native enzyme to low concentrations of the detergent sodium dodecyl sulfate, followed by anaerobic preparative native polyacrylamide gel electrophoresis. The isolated {alpha} subunit absorbs in the 400 nm region and contains one Ni and four Fe ions. The irons are organized into an [Fe{sub 4}S{sub 4}]{sup 2+21} cluster, the reduced form of which exhibits EPR features between g = 6 and 3, and a weak (0.1 spin/{alpha}) g{sub av} = 1.94 signal. The reduced cluster appears to exist in an S = 3/2 : S = 1/2 spin-state mixture and to be predominantly S = 3/2 at 10 K. The Ni center is EPR silent and presumably Ni(II). X-ray absorption edge and EXAFS spectra reveal that the Ni center has a distorted square-planar geometry with two S donors at 2.19 A and two N/O donors at 1.89 A. Comparison of the Ni edge spectrum with those of structurally characterized Ni(II)N{sub 2}S{sub 2} model compounds suggests a D{sub 2d} distortion with a dihedral angle of about 20-30{degree}. The Ni center does not appear to be incorporated into the cluster, and it may or may not be bridged to the cluster. These centers may be decompositional relatives of the A-cluster, the active site for acetyl-coenzyme A synthesis. 47 refs., 5 figs., 2 tabs.

Xia, J.; Lindahl, P.A. [Texas A& M Univ., College Station, TX (United States); Dong, J.; Scott, R.A. [Univ. of Georgia, Atlanta, GA (United States); Wang, S. [Univ. of Georgia, Atlanta, GA (United States)]|[Brookhaven National Lab., Upton, NY (United States)

1995-07-12

120

Absorption  

NSDL National Science Digital Library

This activity can be used to allow students to explore the concept of absorption using a variety of materials. Extensions include exploring how Native Americans used absorbtion in a number of ways. This inquiry activity was developed by a K-12 science teacher in the American Physiological SocietyÃÂs 1998 Frontiers in Physiology Program. The NSES Standards addressed by this activity are current as of the year of development. For more information on the Frontiers in Physiology Program, please visit www.frontiersinphys.org.

Katherine M Knudson (Polson Middle School)

1998-04-01

121

A multi-epoch spectroscopic study of the BAL quasar APM 08279+5255. I. C IV absorption variability  

NASA Astrophysics Data System (ADS)

Context. Broad absorption lines indicate gas outflows with velocities from thousands of km s-1 to about 0.2 the speed of light, which may be present in all quasars and may play a major role in the evolution of the host galaxy. The variability of absorption patterns can provide information on changes in the density and velocity distributions of the absorbing gas and its ionisation status. Aims: We want to accurately follow the evolution in time of the luminosity and both the broad and narrow C IV absorption features of an individual object, the quasar APM 08279+5255, and analyse the correlations among these quantities. Methods: We have collected 23 photometrical and spectro-photometrical observations at the 1.82 m Telescope of the Asiago Observatory since 2003, plus 5 other spectra from the literature. We analysed the evolution in time of the equivalent width of the broad absorption feature and two narrow absorption systems, the correlation among them and with the R band magnitude. We performed a structure function analysis of the equivalent width variations. Results: We present an unprecedented monitoring of a broad absorption line quasar based on 28 epochs during 14 years. The shape of broad absorption feature shows relative stability, while its equivalent width slowly declines until it sharply increases during 2011. At the same time, the R magnitude stays almost constant until it sharply increases during 2011. The equivalent width of the narrow absorption redwards of the systemic redshift only shows a decline. Conclusions: The broad absorption behaviour suggests changes in the ionisation status as the main cause of variability. We show for the first time a correlation of this variability with the R band flux. The different behaviour of the narrow absorption system might be due to recombination time delay. The structure function of the absorption variability has a slope comparable with typical optical variability of quasars. This is consistent with variations of the 200 Å ionising flux originating in the inner part of the accretion disk.

Trevese, D.; Saturni, F. G.; Vagnetti, F.; Perna, M.; Paris, D.; Turriziani, S.

2013-09-01

122

IR spectroscopic characterization of oh defects in jadeite from a vein occurrence  

NASA Astrophysics Data System (ADS)

The role of OH defects in pyroxenes is of considerable geological interest in view of characterizing the chemistry of nominally anhydrous mineral phases likely to be present in the Earth's mantle. Pyroxene may indeed be the main storage site for hydrogen in the Earth's upper mantle, revealing concentrations ranging from about 100 to 1300 wt.ppm H2O (Ingrin and Skogby, 2000). The jadeite sample of the present study originates from the locality of the Clear Creek area, New Idria district, California (Coleman, 1961). Small colorless cleavage fragments of near end-member jadeite single-crystals found within veins of "white jadeite" were separated and oriented. Under the microscope the strongly elongated crystal fragment, 500 x 200 x 150 70?m in size, proved in parts to be free from impurities and inclusions. The OH defect incorporation mode in vein jadeite must also be considered for pyroxenes formed in mantle regions. IR spectroscopy provides an extremely sensitive method for detecting trace hydrogen bonded to oxygen, thus forming structural OH defects. In the present case it was necessary to use an FTIR microscope providing suitable measuring spot sizes for the absorption measurements. Using polarized IR radiation, the pleochroic scheme of the OH absorption bands allows to impose defined constraints on the OH orientation. Polarized single-crystal spectra of the oriented jadeite crystal fragment were recorded from 4000 to 2000 cm-1. Jadeite is characterized by two small but broad absorption bands centered at 3618 and 3556 cm-1. Both bands show a distinct pleochroism in the (010) plane. The maximum of absorption is observed when the angle between the E vector of the polarized radiation and the c-axis, measured within the positive a- and c-axis, amounts to 70o. In contrast, only a weak pleochroism was observed in (100) with a slightly stronger absorption parallel to the b-axis. Some similarities exist with the pleochroic behavior of group II bands in diopside, which occur around 3535, 3460, and 3355 cm-1 (Ingrin and Skogby, 2000), suggesting a partial replacement of the O2 oxygen atoms by OH groups with an OH dipole orientation pointing to the vicinity of vacant M2 sites also in jadeite. Literature Coleman RG (1961) J Petrol 2, 209 Ingrin J, Skogby H (2000) Eur J Mineral 12, 543 Acknowledgements: This work was partly supported by the EU through the Human Potential Program under Grant HPRN-CT-2000-0056.

Andrut, M.; Beran, A.; Wildner, M.

2003-04-01

123

Solution properties and spectroscopic characterization of polymeric precursors to SiNCB and BN ceramic materials  

SciTech Connect

Boron Nitride, BN, and composite SiNCB ceramic fibers are important structural materials because of their excellent thermal and oxidative stabilities. Consequently, polymeric materials as precursors to ceramic composites are receiving increasing attention. Characterization of these materials requires the ability to evaluate simultaneous molecular weight and compositional heterogeneity within the polymer. Size exclusion chromatography equipped with viscometric and refractive index detection as well as coupled to a LC-transform device for infrared absorption analysis has been employed to examine these heterogeneities. Using these combined approaches, the solution properties and the relative amounts of individual functional groups distributed through the molecular weight distribution of SiNCB and BN polymeric precursors were characterized. {copyright} {ital 1998 American Institute of Physics.}

Cortez, E.; Remsen, E; Chlanda, V. [Analytical Science Center, Monsanto Corporate Research, Monsanto Company, 800 North Lindbergh, St. Louis, Missouri 63167 (United States); Carrol, P. [Department of Chemistry and Laboratory for the Research on the Structure of Matter, University of Pennsylvania, Pennsylvania 19107-6323 (United States); Sneddon, L. [The Advanced Ceramics Program, Dow Corning Corporation, Midland, Michigan, 48686-0995 (United States)

1998-06-01

124

X-Ray Absorption Characterization of Diesel Exhaust Particulates  

SciTech Connect

We have characterized particulates from a 1993 11.1 Detroit Diesel Series 60 engine with electronic unit injectors operated using fuels with and without methylcyclopentadienyl manganese tricarbonyl (MMT) and overbased calcium sulfonate added. X-ray photoabsorption (XAS) spectroscopy was used to characterize the diesel particulates. Results reveal a mixture of primarily Mn-phosphate with some Mn-oxide, and Ca-sulfate on the surface of the filtered particulates from the diesel engine.

Nelson, A J; Ferreira, J L; Reynolds, J G; Roos, J W

1999-11-18

125

Fourier Transform Infrared Characterization of Moisture Absorption in SiOF Films  

Microsoft Academic Search

In this paper, the water absorption characteristics of as-deposited and annealed liquid-phase-deposited fluorinated silicon oxide (LPD-SiOF) films were investigated to clarify the film properties. The stability of moisture absorption was characterized under an air-exposure environment of 23°C and 65% humidity. The as-deposited LPD-SiOF film was found to easily absorb moisture from air and therefore to become unstable in terms of

Wai-Jyh Chang; Mau-Phon Houng; Yeong-Her Wang

1999-01-01

126

Characterization and kinetics of carbon dioxide absorption into aqueous tetramethylammonium glycinate solution  

Microsoft Academic Search

An advanced aqueous amine solvent of tetramethylammonium glycinate ([N1111][Gly]) was characterized for carbon dioxide (CO2) absorption purposes. Density, viscosity and pH of the [N1111][Gly] solution, with concentrations ranging from 5% to 30%, were determined at temperatures from 298 to 323K. Solubility and diffusivity of CO2 in [N1111][Gly] solution at the same temperatures and concentrations was estimated. Absorption of CO2 into

Jing Guo-Hua; Zhou Lan-Juan; Zhou Zuo-Ming

127

Smooth and conductive DNA-templated Cu2O nanowires: growth morphology, spectroscopic and electrical characterization  

NASA Astrophysics Data System (ADS)

DNA strands have been used as templates for the self-assembly of smooth and conductive cuprous oxide (Cu2O) nanowires of diameter 12-23 nm and whose length is determined by the template (16 ?m for ?-DNA). A combination of spectroscopic, diffraction and probe microscopy techniques showed that these nanowires comprise single crystallites of Cu2O bound to the DNA molecules which fused together over time in a process analogous to Ostwald ripening, but driven by the free energy of interaction with the template as well as the surface tension. Electrical characterization of the nanowires by a non-contact method, scanned conductance microscopy and by contact mode conductive AFM showed the wires are electrically conductive. The conductivity estimated from the AFM cross section and the zero-bias conductance in conductive AFM experiments was 2.2-3.3 S cm-1. These Cu2O nanowires are amongst the thinnest reported and show evidence of strong quantum confinement in electronic spectra.

Hassanien, Reda; Farha Al-Said, Said A.; Šiller, Lidija; Little, Ross; Wright, Nicholas G.; Houlton, Andrew; Horrocks, Benjamin R.

2012-02-01

128

Characterizing the Quality of DOM with Spectroscopic Approaches to Monitor Response to Climate and Landuse Change  

NASA Astrophysics Data System (ADS)

Dissolved organic material (DOM) is a major pool of organic carbon in aquatic ecosystems, representing a substrate for microbial growth and regulating light penetration in lakes and streams and the bioavailability of trace metals and organic contaminants. In lakes and streams, DOM can originate from the surrounding watershed (allochthonous sources) and from production and decomposition of DOM within the aquatic ecosystem (authochthonous sources). One important step towards understanding the biogeochemical processes controlling DOM reactivity is increasing the application of advanced analytical methods for chemical characterization of DOM. Towards this goal we compared the chemical properties of DOM samples collected by scientists from the LTER participating in a workshop based on spectroscopic and elemental analyses. The dataset includes results from 140 samples representing the full diversity of DOM sources and aquatic and soil environments. The results show that substantial variations on DOM properties occur across the terrestrial- aquatic continuum, and the extent of these variations can be quantified using methods that can be incorporated into monitoring studies. These methods have the potential to provide a greater understanding of changes in DOM associated with climate and land use change.

McKnight, D. M.; Cory, R.; Jaffe, R.; Maie, N.

2006-12-01

129

Germatranyl substituted organotin (IV) carboxylates: synthesis spectroscopic characterization and biological activities.  

PubMed

Eight new organotin (IV) derivatives of general formula [N(CH2CH2O)3GeCH(R1)CH2COO](4-n)SnR(2)n, where n= 2, R(2) = C2H5 (1-5); R(1) = CH3 (1); C6H5 (2); p-CH3C6H4 (3); p-FC6H4(4); p-CH3OC6H4 (5) and n = 3, R(2) = CH2C6H5 (6-8), R(1) = CH3 (6); C6H5 (7); p-CH3C6H4 (8) have been synthesized by the reaction of di- or tri-organotin chloride with the corresponding germatranyl (substituted) propionic acid in the appropriate mole ratios using triethylamine as a base. The synthesized compounds were characterized by various spectroscopic techniques such as IR, multi-nuclear (1H, 13C, 119Sn) NMR, 119mSn Mössbauer, along with elemental analyses. They were also screened for in vitro anti-leishmanial activity against promastigotes of leishmania donovani and found some encouraging results. PMID:20041833

Salma, U; Imtiaz-ud-Din; Mazhar, M; Khan, Khalid Mohammed

2009-11-01

130

Replacement of the axial histidine heme ligand with cysteine in nitrophorin I: Spectroscopic and crystallographic characterization  

PubMed Central

To evaluate the potential of using the heme containing lipocalin nitrophorin 1 as a template for protein engineering, we have replaced the native axial heme coordinating histidine residue with glycine, alanine and cysteine. We report here the characterization of the cysteine mutant H60C_NP1 by spectroscopic and crystallographic methods. The UV/Vis, resonance Raman, and magnetic circular dichroism spectra suggest weak thiolate coordination of the ferric heme in the H60C_NP1 mutant. Reduction to the ferrous state resulted in loss of cysteine coordination, while addition of exogenous imidazole ligands gave coordination changes that varied with the ligand. Depending on the substitution of the imidazole, three heme coordination states could be distinguished: 5-coordinate mono-imidazole, 6-coordinate bis-imidazole and 6-coordinate imidazole/thiolate. Ligand binding affinities were measured and found to be generally 2-3 orders of magnitude lower for the H60C mutant relative to NP1. Two crystal structures of the H60C_NP1 in complex with imidazole and histamine were solved to 1.7 Å and 1.96 Å resolution, respectively. Both structures show that the H60C mutation is well tolerated by the protein scaffold and suggest that heme-thiolate coordination in H60C_NP1 requires some movement of the heme within its binding cavity. This adjustment may be responsible for the ease with which the engineered heme-thiolate coordination can be displaced by exogenous ligands.

Vetter, Stefan W.; Terentis, Andrew C.; Osborne, Robert L.; Dawson, John H.

2008-01-01

131

Interaction of phenol with xenon and nitrogen: Spectroscopic and computational characterization  

NASA Astrophysics Data System (ADS)

Intermolecular complexes of phenol with xenon and nitrogen are studied by infrared absorption spectroscopy in a neon matrix and by quantum chemistry calculations. The ? complex is theoretically the most stable 1:1 phenol...Xe structure, but it has no characteristic shifts in the calculated vibrational spectrum, which complicates its experimental characterization. However, the formation of the ? complex finds indirect but significant support from the experimental results. The calculated spectrum of the less stable H-bonded complex shows a number of characteristic absorptions, but they are not observed in the experiment, indicating the lack of its formation. For the phenol...Xen (n = 2-4) complexes, the calculations predict substantial changes in the vibrational spectra, and the corresponding bands are observed in the matrices with large concentrations of xenon. Our experiments show the high efficiency of the formation of large xenon clusters in a neon matrix that can accommodate a major part of phenol molecules. In contrast to the case of xenon, the H-bonded 1:1 phenol...N2 complex is found in a neon matrix, and the formation of large N2 clusters embedding phenol molecules is relatively inefficient.

Cao, Qian; Andrijchenko, Natalya; Ahola, Anna-Elina; Domanskaya, Alexandra; Räsänen, Markku; Ermilov, Alexander; Nemukhin, Alexander; Khriachtchev, Leonid

2012-10-01

132

Time-resolved spectroscopic characterization of photo-induced valence tautomerism for a cobalt dioxolene complex  

NASA Astrophysics Data System (ADS)

The valence tautomerism of low-spin CoIII(Cat-N-BQ)(Cat-N-SQ) (where Cat-N-BQ is 2-(2-hydroxy-3,5-di-tert-butylphenylimino)-4,6-di-tert-butylcyclohexa-3,5-dienone and Cat-N-SQ is the dianionic radical analogue) was investigated by means of UV vis pump probe transient absorption spectroscopy and 1H NMR technique in chloroform and dichloromethane. By exciting the CT transition of the complex at 480 nm, an intramolecular electron transfer process is selectively triggered. The photo-induced charge transfer is pursued by a cascade of two main molecular events characterized by the ultrafast transient absorption spectroscopy: the first gives rise to the metastable high-spin CoII(Cat-N-BQ)2 that, secondly, reaches the chemical equilibrium with the reactant species. The rate constant of back valence tautomerization estimated by measuring the lifetime of high-spin CoII(Cat-N-BQ)2 species and the equilibrium constant for the CoIII(Cat-N-BQ)(Cat-N-SQ) ? CoII(Cat-N-BQ)2 interconversion, is significantly large (on the order of 109 s-1). It is interpreted under the point of view of the theory formulated by Jortner and Buhks et al. for non-adiabatic radiationless processes.

Gentili, Pier Luigi; Bussotti, Laura; Righini, Roberto; Beni, Alessandra; Bogani, Lapo; Dei, Andrea

2005-07-01

133

Interaction of phenol with xenon and nitrogen: spectroscopic and computational characterization.  

PubMed

Intermolecular complexes of phenol with xenon and nitrogen are studied by infrared absorption spectroscopy in a neon matrix and by quantum chemistry calculations. The ? complex is theoretically the most stable 1:1 phenol???Xe structure, but it has no characteristic shifts in the calculated vibrational spectrum, which complicates its experimental characterization. However, the formation of the ? complex finds indirect but significant support from the experimental results. The calculated spectrum of the less stable H-bonded complex shows a number of characteristic absorptions, but they are not observed in the experiment, indicating the lack of its formation. For the phenol???Xe(n) (n = 2-4) complexes, the calculations predict substantial changes in the vibrational spectra, and the corresponding bands are observed in the matrices with large concentrations of xenon. Our experiments show the high efficiency of the formation of large xenon clusters in a neon matrix that can accommodate a major part of phenol molecules. In contrast to the case of xenon, the H-bonded 1:1 phenol???N(2) complex is found in a neon matrix, and the formation of large N(2) clusters embedding phenol molecules is relatively inefficient. PMID:23039597

Cao, Qian; Andrijchenko, Natalya; Ahola, Anna-Elina; Domanskaya, Alexandra; Räsänen, Markku; Ermilov, Alexander; Nemukhin, Alexander; Khriachtchev, Leonid

2012-10-01

134

Synergic use of TOMS and AERONET observations for characterization of aerosol absorption  

NASA Astrophysics Data System (ADS)

The role of aerosol absorption on the radiative transfer balance of the earth-atmosphere system is one of the largest sources of uncertainty in the analysis of global climate change. Global measurements of aerosol single scattering albedo are, therefore, necessary to properly assess the radiative forcing effect of aerosols. Remote sensing of aerosol absorption is currently carried out using both ground (Aerosol Robotic Network) and space (Total Ozone Mapping Spectrometer) based observations. The satellite technique uses measurements of backscattered near ultraviolet radiation. Carbonaceous aerosols, resulting from the combustion of biomass, are one of the most predominant absorbing aerosol types in the atmosphere. In this presentation, TOMS and AERONET retrievals of single scattering albedo of carbonaceous aerosols, are compared for different environmental conditions: agriculture related biomass burning in South America and Africa and peat fires in Eastern Europe. The AERONET and TOMS derived aerosol absorption information are in good quantitative agreement. The most absorbing smoke is detected over the African Savanna. Aerosol absorption over the Brazilian rain forest is less absorbing. Absorption by aerosol particles resulting from peat fires in Eastern Europe is weaker than the absorption measured in Africa and South America. This analysis shows that the near UV satellite method of aerosol absorption characterization has the sensitivity to distinguish different levels of aerosol absorption. The analysis of the combined AERONET-TOMS observations shows a high degree of synergy between satellite and ground based observations.

Torres, O.; Sinyuk, A.; Bhartia, P. K.; Dubovik, O.; Holben, B.

2003-04-01

135

Characterization of fresh and aged natural ingredients used in historical ointments by molecular spectroscopic techniques: IR, Raman and fluorescence.  

PubMed

Natural organic materials used to prepare pharmaceutical mixtures including ointments and balsams have been characterized by a combined non-destructive spectroscopic analytical approach. Three classes of materials which include vegetable oils (olive, almond and palm tree), gums (Arabic and Tragacanth) and beeswax are considered in this study according to their widespread use reported in ancient recipes. Micro-FTIR, micro-Raman and fluorescence spectroscopies have been applied to fresh and mildly thermally aged samples. Vibrational characterization of these organic compounds is reported together with tabulated frequencies, highlighting all spectral features and changes in spectra which occur following artificial aging. Synchronous fluorescence spectroscopy has been shown to be particularly useful for the assessment of changes in oils after aging; spectral difference between Tragacanth and Arabic gum could be due to variations in origin and processing of raw materials. Analysis of these materials using non-destructive spectroscopic techniques provided important analytical information which could be used to guide further study. PMID:21725834

Brambilla, L; Riedo, C; Baraldi, C; Nevin, A; Gamberini, M C; D'Andrea, C; Chiantore, O; Goidanich, S; Toniolo, L

2011-07-03

136

Direct spectroscopic characterization of a transitory dirhodium donor-acceptor carbene complex.  

PubMed

A multitude of organic transformations catalyzed by dirhodium(II) (Rh2) complexes are thought to proceed via the intermediacy of highly reactive, electrophilic carbenoid intermediates that have eluded direct observation. Herein, we report the generation of a metastable Rh2-carbenoid intermediate supported by a donor-acceptor carbene fragment. This intermediate is stable for a period of ~20 hours in chloroform solution at 0°C, allowing for an exploration of its physical and chemical properties. The Rh=C bond, characterized by vibrational and nuclear magnetic resonance spectroscopy, extended x-ray absorption fine structure analysis, and quantum-chemical calculations, has weak ? and ? components. This intermediate performs stoichiometric cyclopropanation and C-H functionalization reactions to give products that are identical to those obtained from analogous Rh2 catalysis. PMID:24030489

Kornecki, Katherine P; Briones, John F; Boyarskikh, Vyacheslav; Fullilove, Felicia; Autschbach, Jochen; Schrote, Kaitlin E; Lancaster, Kyle M; Davies, Huw M L; Berry, John F

2013-09-12

137

An X-ray absorption spectroscopic structural investigation of the nickel site in Escherichia coli NikA protein  

SciTech Connect

Since the discovery of the involvement of Ni in the active site of the enzyme urease in 1975, the role of Ni in biology has been rapidly expanding. The list of nickel-dependent metalloenzymes now includes acetyl coenzyme A synthase/carbon monoxide dehydrogenase, methyl coenzyme M reductase, Ni/Fe hydrogenases, and superoxide dismutases from Streptomyces. Each of these enzymes appears to be dependent on several gene products that constitute a Ni-specific transport and metallocenter assembly system. The authors report here the results of an X-ray spectroscopic structural investigation of the Ni site in a Ni transport protein, the periplasmic Ni-binding protein, NikA, from Escherichia coli.

Allan, C.B.; Gu, Z.; Choudhury, S.B.; Al-Mjeni, F.; Sharma, M.L.; Maroney, M.J. [Univ. of Massachusetts, Amherst, MA (United States). Dept. of Chemistry; Wu, L.F.; Mandrand-Berthelot, M.A. [CNRS-URA, Villeurbanne (France). Lab. de Genetique Moleculaire des Microorganismes

1998-11-02

138

Emergence of charge-transfer-to-solvent band in the absorption spectra of hydrogen halides on ice nanoparticles: spectroscopic evidence for acidic dissociation.  

PubMed

Extensive ab initio calculations complemented by a photodissociation experiment at 193 nm elucidate the nature of hydrogen halide molecules bound on free ice nanoparticles. Electronic absorption spectra of small water clusters (up to 5 water molecules) and water clusters doped with hydrogen fluoride, hydrogen chloride and hydrogen bromide were calculated. The spectra were modeled at the time-dependent density functional (TDDFT) level of theory with the BHandHLYP functional using the reflection principle. We observe the emergence of a charge-transfer-to-solvent (CTTS) band in the absorption spectra upon the acidic dissociation of the hydrogen halides. The CTTS band provides a spectroscopically observable feature for the acidic dissociation. The calculated spectra were compared with our new experimental photodissociation data for larger water clusters doped with HCl and HBr. We conclude that HCl and HBr dissociate to a large extent on the surface of ice nanoparticles at temperatures near 120 K and photoactive products are formed. The acidic dissociation of HX leads to an enhancement by about 4 orders of magnitude of the HCl photolysis rate in the 200-300 nm region, which is potentially relevant for the halogen budget in the atmosphere. PMID:18507365

Oncák, Milan; Slavícek, Petr; Poterya, Viktoriya; Fárník, Michal; Buck, Udo

2008-05-29

139

Dichromated poly(vinyl alchohol)-xanthene dye systems: holographic characterization and electron spin resonance spectroscopic study  

Microsoft Academic Search

Dichromated poly(vinyl alcohol)-xanthene dye (DCPVA-XD) systems have been employed as real-time holographic recording materials. In this paper, holographic characterization of dichromated poly(vinyl alcohol) with fluorescein (Fl), eosin Y (EY) and Rose Bengal (RB) is presented. In addition, a systematic ESR spectroscopic investigation was also performed on these systems. The photochemical evolution of Cr(V), Cr(III), polymer radical and dye radical in

Gurusamy Manivannan; Rupak Changkakoti; Roger A. Lessard; Gilles Mailhot; Michele Bolte

1994-01-01

140

Electronic structure and anomalous band-edge absorption feature in multiferroic MnWO4 : An optical spectroscopic study  

NASA Astrophysics Data System (ADS)

We investigated the electronic structure and lattice dynamics of multiferroic MnWO4 by optical spectroscopy. With variation in polarization, temperature, and magnetic field, we obtained optical responses over a wide range of photon energies. The electronic structure of MnWO4 near to the Fermi level was examined with interband transitions identified in optical conductivity spectra above a band gap of 2.5 eV. As for the lattice dynamics, we identified all the infrared transverse optical-phonon modes available according to the group-theory analysis. Although we did not observe much change in global electronic structure across the phase-transition temperatures, an optical absorption at around 2.2 eV showed an evident change depending upon the spin configuration and magnetic field. The behavior of this band-edge absorption indicates that spin-orbit coupling plays an important role in multiferroic MnWO4 .

Choi, Woo Seok; Taniguchi, K.; Moon, S. J.; Seo, S. S. A.; Arima, T.; Hoang, H.; Yang, I.-S.; Noh, T. W.; Lee, Y. S.

2010-05-01

141

Nuclear Magnetic Resonance and X-Ray Absorption Spectroscopic Studies of Lithium Insertion in Silver Vanadium Oxide Cathodes  

Microsoft Academic Search

Structural studies have been carried out on AgVO (silver vanadium oxide, SVO) and LiAgVO, lithiated SVO with x=0.72, 2.13, and 5.59 using nuclear magnetic resonance (NMR) and X-ray absorption spectroscopy (XAS). Lithium-7 NMR indicates the formation of a solid electrolyte interphase layer on the x=0.72 sample and lithium intercalation into both octahedral and tetrahedral sites in the SVO lattice, and

N. D. Leifer; A. Colon; k. Martocci; S. G. Greenbaum; F. M. Alamgir; T. B. Reddy; N. R. Gleason; R. A. Leising; E. S. Takeuchi

2007-01-01

142

Induced absorption spectroscopic determination of exciton binding energies in type-II GaAs\\/AlAs superlattices  

Microsoft Academic Search

The binding energies of magnetoexcitons in a range of GaAs\\/AlAs type-II superlattices have been measured directly for the first time, using a novel induced far-infrared absorption technique. Zero-field binding energies in the range 13.2-17.4 meV are found, and these are in excellent agreement with recently published variational calculations. Good fits to the experimental data in the range B=0-8 T are

C. C. Hodge; C. C. Phillips; M. S. Skolnick; G. W. Smith; C. R. Whitehouse; P. Dawson; C. T. Foxon

1990-01-01

143

Gamma-irradiation and UV-C light-induced lipid peroxidation: a Fourier transform-infrared absorption spectroscopic study.  

PubMed

Fourier transform-infrared spectroscopy of dry, multibilayer films has been used to study gamma-radiation and UV-C light induced lipid peroxidation in 1,2-dilinoleoyl-sn-glycero-3-phosphocholine liposomes. The observed spectral changes were compared with the results obtained from measurement of hydroperoxides, conjugated dienes and to the formation of thiobarbituric acid reactive substances, such as malondialdehyde (MDA) or MDA-like substances. Upon irradiation a decrease in intensity of the asymmetric C - H stretching vibration (va(CH2)) of the isolated cis C = C - H groups (3010 cm-1) was observed. Directly correlated with the decrease of the va(CH2) absorption was a shift of the asymmetric phosphate ester stretching vibration (va(P = O)) towards smaller wavenumbers (1260-->1244 cm-1), indicating that the lipid peroxidation induced molecular alterations in the fatty acid chains influence the packing of the phospholipids in dry multibilayer films. In addition, the formation of a new absorption band at 1693 cm-1 could be detected, the intensity of which was comparable with the formation of thiobarbituric acid reactive substances and, therefore, attributed to the (C = O) stretching of alpha, beta unsaturated aldehydes. Dose-dependent studies using ionizing radiation showed that the decrease of va(CH2) was directly correlated with an increase in absorption of the conjugated dienes at 234 nm and with the formation of hydroperoxides suggesting that the absorption at 3010 cm-1 is solely due to isolated cis C = C - H groups and hence subject to the early stages of the radical chain reaction. UV-C light induced lipid peroxidation revealed a non-linear decrease of I3010, which was directly correlated with the formation of hydroperoxides. The observed early saturation of the conjugated dienes was attributed to an early photodecomposition of the conjugated double bonds. PMID:9191901

Kinder, R; Ziegler, C; Wessels, J M

1997-05-01

144

High-resolution atmospheric absorption by water vapor in the 830-985 nm region: Evaluation of spectroscopic databases  

Microsoft Academic Search

We present high spectral resolution (0.05 cm-1) ground-based measurements of direct solar absorption in the clear-sky atmosphere by water vapor over the 830 to 985 nm (10,150-12,050 cm-1) region. Observations were made from the Rutherford Appleton Laboratory on several days in different seasons during 1999. Using these observations water vapor line data in HITRAN and the ESA-WVR database, derived from

K. M. Smith; D. A. Newnham

2001-01-01

145

High-resolution atmospheric absorption by water vapor in the 830–985 nm region: Evaluation of spectroscopic databases  

Microsoft Academic Search

We present high spectral resolution (0.05 cm?1) ground-based measurements of direct solar absorption in the clear-sky atmosphere by water vapor over the 830 to 985 nm (10,150–12,050 cm?1) region. Observations were made from the Rutherford Appleton Laboratory on several days in different seasons during 1999. Using these observations water vapor line data in HITRAN and the ESA-WVR database, derived from

K. M. Smith; D. A. Newnham

2001-01-01

146

Spectroscopic Determination of Leaf Biochemistry Using Band-Depth Analysis of Absorption Features and Stepwise Multiple Linear Regression  

Microsoft Academic Search

We develop a new method for estimating the biochemistry of plant material using spectroscopy. Normalized band depths calculated from the continuum-removed reflectance spectra of dried and ground leaves were used to estimate their concentrations of nitrogen, lignin, and cellulose. Stepwise multiple linear regression was used to select wavelengths in the broad absorption features centered at 1.73 ?m, 2.10 ?m, and

Raymond F. Kokaly; Roger N. Clark

1999-01-01

147

Chemical Characterization of Riverine Dissolved Organic Matter Using a Combination of Spectroscopic and Pyrolytic Methods  

NASA Astrophysics Data System (ADS)

It is now well established that riverine dissolved organic matter (DOM) play a major role in environmental processes. However natural organic matter exhibit different properties depending on their sources and the fractions considered. As a result chemical characterization of DOM has appeared essential for a better understanding of their reactivity. The purpose of this work was to characterize all of the DOM at molecular level, including the non-hydrolysable fraction, which is a major part of this OM. To this aim a new analytical approach had to be considered. A combination of spectroscopic and pyrolytic methods has been applied to various fractions of DOM originating from different catchments (French and Amazonian rivers). The fractions were termed hydrophilic, transphilic and colloids according to the IHSS fractionation procedure, and account for at least 70% of the total dissolved organic carbon. Solid state 13C NMR and FTIR afford information on the nature and relative abundance of the chemical functions occurring in macromolecules. Differential thermogravimetric analysis allows to determine the thermal behaviour of the studied material and hence to optimize analytical pyrolysis conditions. Curie point pyrolysis combined to gas chromatography and mass spectrometry leads to identification of characteristic pyrolysis products, some of them being specific of a macromolecular source. Additional information can be provided by thermochemolysis with tetramethylammonium hydroxide (TMAH). TMAH was shown to allow an increase in the efficiency of the cracking of macromolecular structures and an enhancement of the detection of the polar pyrolysis products especially due to methylation of the alcohol, phenol and acid groups. The results obtained have established the importance of terrestrial contribution to DOM. Hydrophobic fractions mainly originate from lignin-derived units, whereas transphilic fractions mostly contain cellulose units together with lignin derived ones and substantial amount of nitrogen-containing moieties. Characterization of colloidal fraction has indicated the presence of compounds from bacterial origin, especially specific nitrogen-containing molecules that are characteristic pyrolysis products of peptidoglycans, along with lignin-derived units. However pyrolysis has revealed significant differences in the detection of nitrogen-containing molecules, which do not parallel nitrogen content of the fractions. Moreover in hydrophobic and transphilic fractions the molecular structure of these compounds, which are mainly nitrogen- and oxygen- containing molecules, has not allowed to ascertain their origin. As the major biological sources of organic nitrogen (proteins, amino sugars, or tetrapyrrole pigments) involve differences in the main nitrogen functionality, two additional spectroscopic methods, namely X-ray photoelectron spectroscopy (XPS) and solid state 15N NMR, have been used to determine the nitrogen functional groups (amide, amine, and N-heterocycle) present in the different fractions of DOM. The combination of these two methods has revealed the occurrence of different functionality of nitrogen, with relative contributions depending on the considered fraction. It has also appeared that Curie point pyrolysis does not account for the presence of nitrogen in macromolecules with the same efficiency depending on the functional group involved. This study has highlighted the importance of combining different analytical approaches to obtain a whole insight into chemical structure of OM and avoid biased information.

Templier, J.; Derenne, S.

2006-12-01

148

N-[4-(3-methyl-3-mesityl-cyclobutyl)-thiazol-2-yl]-succinamic acid: X-ray structure, spectroscopic characterization and quantum chemical computational studies  

NASA Astrophysics Data System (ADS)

N-[4-(3-methyl-3-mesityl-cyclobutyl)-thiazol-2-yl]-succinamic acid (CBTSA).Spectroscopic and structural characterization of CBTSA.HF and DFT electronic structure investigation of CBTSA.The conformational analysis of CBTSA.

?en, Fatih; Dinçer, Muharrem; Çukuroval?, Alaaddin; Y?lmaz, ?brahim

2013-08-01

149

X-ray absorption fine structure spectroscopic determination of plutonium speciation at the Rocky Flats environmental technology  

SciTech Connect

X-ray Absorption Fine Structure spectroscopy was used to probe the speciation of the ppm level Pu in thirteen soil and concrete samples from the Rocky Flats Environmental Technology Site in support of the site remediation effort that has been successfully completed since these measurements. In addition to X-ray Absorption Near Edge Spectra, two of the samples yielded Extended X-ray Absorption Fine Structure spectra that could be analyzed by curve-fits. Most of these spectra exhibited features consistent with PU(IV), and more specificaJly, PuO{sub 2+x}-type speciation. Two were ambiguous, possibly indicating that Pu that was originally present in a different form was transforming into PuO{sub 2+x}, and one was interpreted as demonstrating the presence of an unusual Pu(VI) compound, consistent with its source being spills from a PUREX purification line onto a concrete floor and the resultant extreme conditions. These experimental results therefore validated models that predicted that insoluble PuO{sub 2+x} would be the most stable form of Pu in equilibrium with air and water even when the source terms were most likely Pu metal with organic compounds or a Pu fire. A corollary of these models' predictions and other in situ observations is therefore that the minimal transport of Pu that occurred on the site was via the resuspension and mobilization of colloidal particles. Under these conditions, the small amounts of diffusely distributed Pu that were left on the site after its remediation pose only a negligible hazard.

Lezama-pacheco, Juan S [Los Alamos National Laboratory; Conradson, Steven D [Los Alamos National Laboratory; Clark, David L [Los Alamos National Laboratory

2008-01-01

150

Preparation and spectroscopic characterization of visible light sensitized N doped TiO{sub 2} (rutile)  

SciTech Connect

Nitrogen doped TiO{sub 2} represents one of the most promising material for photocatalitic degradation of environmental pollutants with visible light. However, at present, a great deal of activity is devoted to the anatase polymorph while few data about rutile are available. In the present paper we report an experimental characterization of N doped polycrystalline rutile TiO{sub 2} prepared via sol-gel synthesis. Nitrogen doping does not affect the valence band to conduction band separation but, generates intra band gap localized states which are responsible of the on set of visible light absorption. The intra band gap states correspond to a nitrogen containing defect similar but not coincident with that recently reported for N doped anatase. - Graphical abstract: Nitrogen doped TiO{sub 2} represents one of the most promising material for photocatalitic degradation of environmental pollutants with visible light. However, at present, a great deal of activity is devoted to the anatase polymorph while few data about rutile are available. In the present paper we report an experimental characterization of N doped polycrystalline rutile TiO{sub 2} prepared via sol-gel synthesis.

Livraghi, S.; Czoska, A.M. [Dipartimento di Chimica I.F.M. and NIS, Universita degli Studi di Torino, Via P. Giuria, 7, 10125 Torino (Italy); Paganini, M.C. [Dipartimento di Chimica I.F.M. and NIS, Universita degli Studi di Torino, Via P. Giuria, 7, 10125 Torino (Italy)], E-mail: mariacristina.paganini@unito.it; Giamello, E. [Dipartimento di Chimica I.F.M. and NIS, Universita degli Studi di Torino, Via P. Giuria, 7, 10125 Torino (Italy)

2009-01-15

151

Replacement of the axial histidine heme ligand with cysteine in nitrophorin 1: spectroscopic and crystallographic characterization.  

PubMed

To evaluate the potential of using heme-containing lipocalin nitrophorin 1 (NP1) as a template for protein engineering, we have replaced the native axial heme-coordinating histidine residue with glycine, alanine, and cysteine. We report here the characterization of the cysteine mutant H60C_NP1 by spectroscopic and crystallographic methods. The UV/vis, resonance Raman, and magnetic circular dichroism spectra suggest weak thiolate coordination of the ferric heme in the H60C_NP1 mutant. Reduction to the ferrous state resulted in loss of cysteine coordination, while addition of exogenous imidazole ligands gave coordination changes that varied with the ligand. Depending on the substitution of the imidazole, we could distinguish three heme coordination states: five-coordinate monoimidazole, six-coordinate bisimidazole, and six-coordinate imidazole/thiolate. Ligand binding affinities were measured and found to be generally 2-3 orders of magnitude lower for the H60C mutant relative to NP1. Two crystal structures of the H60C_NP1 in complex with imidazole and histamine were solved to 1.7- and 1.96-A resolution, respectively. Both structures show that the H60C mutation is well tolerated by the protein scaffold and suggest that heme-thiolate coordination in H60C_NP1 requires some movement of the heme within its binding cavity. This adjustment may be responsible for the ease with which the engineered heme-thiolate coordination can be displaced by exogenous ligands. PMID:18923851

Vetter, Stefan W; Terentis, Andrew C; Osborne, Robert L; Dawson, John H; Goodin, David B

2008-10-16

152

Absorption and fluorescence spectroscopic characterisation of the circadian blue-light photoreceptor cryptochrome from Drosophila melanogaster (dCry)  

NASA Astrophysics Data System (ADS)

The absorption and fluorescence behaviour of the circadian blue-light photoreceptor cryptochrome from Drosophila melanogaster (dCry) in a pH 8 aqueous buffer solution is studied. The flavin adenine dinucleotide (FAD) cofactor of dCry is identified to be present in its oxidized form (FAD ox), and the 5,10-methenyltetrahydrofolate (MTHF) cofactor is found to be hydrolyzed and oxidized to 10-formyldihydrofolate (10-FDHF). The absorption and the fluorescence behaviour of dCry is investigated in the dark-adapted (receptor) state, the light-adapted (signalling) state, and under long-time violet light exposure. Photo-excitation of FAD ox in dCry causes a reductive electron transfer to the formation of anionic FAD semiquinone (FAD rad - ), and photo-excitation of the generated FAD rad - causes an oxidative electron transfer to the back formation of FAD ox. In light adapted dCry a photo-induced equilibrium between FAD ox and FAD rad - exists. The photo-cycle dynamics of signalling state formation and recovery is discussed. Quantum yields of photo-induced signalling state formation of about 0.2 and of photo-induced back-conversion of about 0.2 are determined. A recovery of FAD rad - to FAD ox in the dark with a time constant of 1.6 min at room temperature is found.

Shirdel, J.; Zirak, P.; Penzkofer, A.; Breitkreuz, H.; Wolf, E.

2008-09-01

153

Quantitative spectroscopic determination of hemoglobin concentration and saturation in a turbid medium: analysis of the effect of water absorption  

NASA Astrophysics Data System (ADS)

The contribution of water to the quantitative determination of hemoglobin concentration and saturation by near-IR spectroscopy in turbid media was investigated. The study consisted of in vitro measurements of an aqueous suspension containing Liposyn, bovine blood, and yeast buffered at pH 7.2. The optical coefficients of the medium were similar to those of biological tissue n the near-infrared, and the hemoglobin concentration was about 23 (mu) M. It was possible to reversibly saturate and desaturate hemoglobin in the full range of 0 to 100 percent by flowing either oxygen or nitrogen through the suspension. In these experimental conditions, water absorption must be taken into account to obtain accurate oxyhemoglobin concentrations and low hemoglobin saturation values. By contrast, the water correction has a small effect on the determination of deoxyhemoglobin concentration and high hemoglobin saturation values. By extrapolating the result to physiological conditions, where water content is lower and hemoglobin content is higher than in the experimental conditions, it was concluded that water absorption should have a smaller effect on the determination of hemoglobin concentrations and saturation in tissues at the wavelengths used in this study. In particular, for hemoglobin concentrations larger than 100 (mu) M, the water correction is less than 5 percent at saturation values higher than 50 percent.

Franceschini, Maria A.; Fantini, Sergio; Cerussi, Albert E.; Barbieri, Beniamino F.; Chance, Britton; Gratton, Enrico

1997-04-01

154

Elemental and spectroscopic characterization of fractions of an acidic extract of oil sands process water.  

PubMed

'Naphthenic acids' (NAs) in petroleum produced water and oil sands process water (OSPW), have been implicated in toxicological effects. However, many are not well characterized. A method for fractionation of NAs of an OSPW was used herein and a multi-method characterization of the fractions conducted. The unfractionated OSPW acidic extract was characterized by elemental analysis, electrospray ionization-Orbitrap-mass spectrometry (ESI-MS), and an esterified extract by Fourier Transform infrared (FTIR) and ultraviolet-visible (UV) absorption spectroscopy and by comprehensive multidimensional gas chromatography-MS (GCxGC-MS). Methyl esters were fractionated by argentation solid phase extraction (Ag(+) SPE) and fractions eluting with: hexane; diethyl ether: hexane and diethyl ether, examined. Each was weighed, examined by elemental analysis, FTIR, UV, GC-MS and GCxGC-MS (both nominal and high resolution MS). The ether fraction, containing sulfur, was also examined by GCxGC-sulfur chemiluminescence detection (GCxGC-SCD). The major ions detected by ESI-MS in the OSPW extract were assigned to alicyclic and aromatic 'O2' acids; sulfur was also present. Components recovered by Ag(+) SPE were also methyl esters of alicyclic and aromatic acids; these contained little sulfur or nitrogen. FTIR spectra showed that hydroxy acids and sulfoxides were absent or minor. UV spectra, along with the C/H ratio, further confirmed the aromaticity of the hexane:ether eluate. The more minor ether eluate contained further aromatics and 1.5% sulfur. FTIR spectra indicated free carboxylic acids, in addition to esters. Four major sulfur compounds were detected by GCxGC-SCD. GCxGC-high resolution MS indicated these were methyl esters of C18 S-containing, diaromatics with ?C3 carboxylic acid side chains. PMID:23856466

Jones, D; Scarlett, A G; West, C E; Frank, R A; Gieleciak, R; Hager, D; Pureveen, J; Tegelaar, E; Rowland, S J

2013-07-12

155

Development of Cellular Absorptive Tracers (CATs) for a Quantitative Characterization of Microbial Mass in Flow Systems  

SciTech Connect

We report on a new Cellular Absorptive Tracers (CATs) method, for a simple, non-destructive characterization of bacterial mass in flow systems. Results show that adsorption of a CAT molecule into the cellular mass results in its retardation during flow, which is a good, quantitative measure of the biomass quantity and distribution. No such methods are currently available for a quantitative characterization of cell mass.

Saripalli, Prasad; Brown, Christopher F.; Lindberg, Michael J.

2005-03-16

156

Calibration method for spectroscopic systems  

DOEpatents

Calibration spots of optically-characterized material placed in the field of view of a spectroscopic system allow calibration of the spectroscopic system. Response from the calibration spots is measured and used to calibrate for varying spectroscopic system operating parameters. The accurate calibration achieved allows quantitative spectroscopic analysis of responses taken at different times, different excitation conditions, and of different targets.

Sandison, David R. (Edgewood, NM)

1998-01-01

157

Spectroscopic determination of leaf biochemistry using band-depth analysis of absorption features and stepwise multiple linear regression  

USGS Publications Warehouse

We develop a new method for estimating the biochemistry of plant material using spectroscopy. Normalized band depths calculated from the continuum-removed reflectance spectra of dried and ground leaves were used to estimate their concentrations of nitrogen, lignin, and cellulose. Stepwise multiple linear regression was used to select wavelengths in the broad absorption features centered at 1.73 ??m, 2.10 ??m, and 2.30 ??m that were highly correlated with the chemistry of samples from eastern U.S. forests. Band depths of absorption features at these wavelengths were found to also be highly correlated with the chemistry of four other sites. A subset of data from the eastern U.S. forest sites was used to derive linear equations that were applied to the remaining data to successfully estimate their nitrogen, lignin, and cellulose concentrations. Correlations were highest for nitrogen (R2 from 0.75 to 0.94). The consistent results indicate the possibility of establishing a single equation capable of estimating the chemical concentrations in a wide variety of species from the reflectance spectra of dried leaves. The extension of this method to remote sensing was investigated. The effects of leaf water content, sensor signal-to-noise and bandpass, atmospheric effects, and background soil exposure were examined. Leaf water was found to be the greatest challenge to extending this empirical method to the analysis of fresh whole leaves and complete vegetation canopies. The influence of leaf water on reflectance spectra must be removed to within 10%. Other effects were reduced by continuum removal and normalization of band depths. If the effects of leaf water can be compensated for, it might be possible to extend this method to remote sensing data acquired by imaging spectrometers to give estimates of nitrogen, lignin, and cellulose concentrations over large areas for use in ecosystem studies.We develop a new method for estimating the biochemistry of plant material using spectroscopy. Normalized band depths calculated from the continuum-removed reflectance spectra of dried and ground leaves were used to estimate their concentrations of nitrogen, lignin, and cellulose. Stepwise multiple linear regression was used to select wavelengths in the broad absorption features centered at 1.73 ??m, 2.10 ??m, and 2.301 ??m that were highly correlated with the chemistry of samples from eastern U.S. forests. Band depths of absorption features at these wavelengths were found to also be highly correlated with the chemistry of four other sites. A subset of data from the eastern U.S. forest sites was used to derive linear equations that were applied to the remaining data to successfully estimate their nitrogen, lignin, and cellulose concentrations. Correlations were highest for nitrogen (R2 from 0.75 to 0.94). The consistent results indicate the possibility of establishing a single equation capable of estimating the chemical concentrations in a wide variety of species from the reflectance spectra of dried leaves. The extension of this method to remote sensing was investigated. The effects of leaf water content, sensor signal-to-noise and bandpass, atmospheric effects, and background soil exposure were examined. Leaf water was found to be the greatest challenge to extending this empirical method to the analysis of fresh whole leaves and complete vegetation canopies. The influence of leaf water on reflectance spectra must be removed to within 10%. Other effects were reduced by continuum removal and normalization of band depths. If the effects of leaf water can be compensated for, it might be possible to extend this method to remote sensing data acquired by imaging spectrometers to give estimates of nitrogen, lignin, and cellulose concentrations over large areas for use in ecosystem studies.

Kokaly, R. F.; Clark, R. N.

1999-01-01

158

Infrared spectroscopic, x-ray, and nanoscale characterization of strontium titanate thin films  

SciTech Connect

Attenuated total reflectance (ATR) measurements were performed using Fourier transform infrared (FTIR) spectroscopy in the ATR mode with a thallium iodobromide (KRS-5) crystal to measure the frequencies of the v{sub 3} and v{sub 4} phonon absorption bands in thin Sr titanate films deposited on single-crystal Y-Ba Cu oxide (YBCO), La aluminate, Mg oxide, and Sr titanate substrates. The KRS-5 crystal enabled FTIR-ATR measurements at frequencies above 400 cm{sup -1}. Atomic force microscopy (AFM) and x-ray diffraction (XRD) measurements were also made to further characterize the films. The measurements were repeated on single-crystal specimens of Sr titanate and the substrates for comparison. Softening in the frequency of the v{sub 4} transverse optical phonon in the lattice-mismatched films below the established value of 544 cm{sup -1} is indicative of the highly textured, polycrystalline ceramic nature of the films and is consistent with the XRD and AFM results.

Webb, J.D.; Moutinho, H.R.; Kazmerski, L.L. [National Renewable Energy Lab., Golden, CO (United States); Mueller, C.H.; Rivkin, T.V.; Treece, R.E. [Superconducting Core Technologies, Inc., Golden, CO (United States); Dalberth, M.; Rogers, C.T. [Colorado Univ., Boulder, CO (United States). Dept. of Physics

1996-06-01

159

Infrared spectroscopic, x-ray, and nanoscale characterization of strontium titanate thin films  

SciTech Connect

Attenuated total reflectance (ATR) measurements were performed using Fourier transform infrared (FTIR) spectroscopy in the ATR mode with a thallium iodobromide (KRS-5) crystal to measure the frequencies of the {nu}{sub 3} and {nu}{sub 4} phonon absorption bands in thin strontium titanate films deposited on single-crystal yttrium-barium copper oxide (YBCO), lanthanum aluminate, magnesium oxide, and strontium titanate substrates. The KRS-5 crystal enabled FTIR-ATR measurements to be made at frequencies above 400 cm{sup {minus}1}. Atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements were also made to further characterize the films. The measurements were repeated on single-crystal specimens of strontium titanate and the substrates for comparison. Softening in the frequency of the {nu}{sub 4} transverse optical phonon in the lattice- mismatched films below the established value of 544 cm{sup {minus}1} is indicative of the highly textured, polycrystalline ceramic nature of the films and is consistent with the XRD and AFM results.

Webb, J.D.; Moutinho, H.R.; Kazmerski, L.L. [National Renewable Energy Lab., Golden, CO (United States); Mueller, C.H.; Rivkin, T.V.; Treece, R.E. [Superconducting Core Technologies, Inc., Golden, CO (United States); Dalberth, M.; Rogers, C.T. [Colorado Univ., Boulder, CO (United States). Dept. of Physics

1996-04-01

160

Spectroscopic characterization of the excitation energy transfer in the fucoxanthin-chlorophyll protein of diatoms.  

PubMed

We characterized the energy transfer pathways in the fucoxanthin-chlorophyll protein (FCP) complex of the diatom Cyclotella meneghiniana by conducting ultrafast transient absorption measurements. This light harvesting antenna has a distinct pigment composition and binds chlorophyll a (Chl-a), fucoxanthin and chlorophyll c (Chl-c) molecules in a 4:4:1 ratio. We find that upon excitation of fucoxanthin to its S2 state, a significant amount of excitation energy is transferred rapidly to Chl-a. The ensuing dynamics illustrate the presence of a complex energy transfer network that also involves energy transfer from the unrelaxed or 'hot' intermediates. Chl-c to Chl-a energy transfer occurs on a timescale of a 100 fs. We observe no significant spectral evolution in the Chl-a region of the spectrum. We have applied global and target analysis to model the measured excited state dynamics and estimate the spectra of the states involved; the energy transfer network is discussed in relation to the pigment organization of the FCP complex. PMID:16172942

Papagiannakis, Emmanouil; H M van Stokkum, Ivo; Fey, Holger; Büchel, Claudia; van Grondelle, Rienk

2005-11-01

161

Spectroscopic characterization of TiO sub 2 /SiO sub 2 catalysts  

SciTech Connect

TiO{sub 2}/SiO{sub 2} (7 wt% TiO{sub 2}) has been prepared via modification of the SiO{sub 2} surface by reaction with Ti(OHC(CH{sub 3}){sub 2}){sub 4}. Physical characterization of the material was performed by means of XRD, diffuse reflectance spectroscopy (DRS), XPS, and low-temperature IR spectroscopy of adsorbed CO. TiO{sub 2} exists in highly dispersed form on the SiO{sub 2} surface. Interestingly, a quantum size effect leads to a shift of the absorption edge of TiO{sub 2} toward higher energy. XPS difference spectra indicate the formation of Ti{sup 3+} during reduction. This is confirmed by CO adsorption in the temperature range 80 < T {le} 300 K. IR spectroscopy of adsorbed CO provides advantages over XPS in that it responds exclusively to coordinatively unsatured Ti{sup 3+} sites which are located and exposed in the surface.

Fernandez, A.; Gonzalez-Elipe, A.R.; Munuera, G. (Universidad de Sevilla (Spain)); Leyrer, J.; Knoezinger, H. (Univ. Muenchen (West Germany))

1988-08-01

162

Spectroscopic characterization and photobleaching kinetics of hypericin-N-methyl pyrrolidone formulations.  

PubMed

Hypericin (HY) is a promising photosensitizer in photodynamic therapy (PDT). It was recently reported that appropriate use of N-methyl pyrrolidone (NMP) enhanced in vivo PDT efficacy of HY and enhanced in vivo delivery of HY. This present study further investigates the use of NMP and other known non-toxic pharmaceutical additives, polyvinylpyrrolidone (PVP, K29/32) and copolyvidonum (S630), for formulating HY to enhance its delivery with photodynamic activity as a goal in mind. Hence, the first objective of this study was to characterize the solubilization of HY by NMP, K29/32 and S630. Thermodynamic considerations were used to explain the solvation process. Photobleaching is another important property of photosensitizers. There is no report on the photostability of HY in pharmaceutical formulations used for PDT. Therefore, the second objective of this study was to investigate the photobleaching of HY in these formulations. The fluorescence of HY was found to increase significantly in higher concentrations of NMP or when 5% of polymer was co-mixed with 5% of NMP solution. The photobleaching of HY in these formulations followed first-order kinetics. The loss of fluorescence paralleled to the loss of absorption of HY. The formulation of HY with 40% NMP was found to be the most stable. PMID:17077897

Saw, Constance Lay Lay; Olivo, Malini; Soo, Khee Chee; Heng, Paul Wan Sia

2006-08-14

163

X-ray absorption spectroscopic evidence for the complexation of Hg(II) by reduced sulfur in soil humic substances  

SciTech Connect

Analysis of Hg(II) complexed by a soil humic acid (HA) using synchrotron-based X-ray absorption spectroscopy (XAS) revealed the importance of reduces sulfur functional groups (thiol (R-SH) and disulfide (R-SS-R)/disulfane (R-SSH)) in humic substances in the complexation of Hg(II). A two-coordinate binding environment with one oxygen atom and one sulfur atom at distances of 2.02 and 2.38 {angstrom}, respectively, was found in the first coordination shell of Hg(II) complexed by humic acid. Model calculations show that a second coordination sphere could contain one carbon atom and a second sulfur atom at 2.78 and 2.93 {angstrom}, respectively. This suggests that in addition to thiol S, disulfide/disulfane S may be involved with the complexation of Hg(II) in soil organic matter. The appearance of carbon atom in the second coordination shell suggests that one O-containing ligand such as carboxyl and phenol ligands rather than H{sub 2}O molecule is bound to the Hg(II). The involvement of oxygen ligand in addition to the reduced S ligands in the complexation of Hg(II) is due to the low density of reduced S ligands in humic substances. The XAS results from this experiment provided direct molecular level evidence for the preference of reduced S functional groups over oxygen ligands by Hg(II) in the complexation with humic substances.

Xia, K. [Kansas State Univ., Manhattan, KS (United States). Dept. of Agronomy; Skyllberg, U.L. [Swedish Univ. of Agricultural Sciences, Umeaa (Sweden). Dept. of Forest Ecology; Bleam, W.F.; Helmke, P.A. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Soil Science; Bloom, P.R.; Nater, E.A. [Univ. of Minnesota, St. Paul, MN (United States). Dept. of Soil, Water, and Climate

1999-01-15

164

Optical absorption of Zn(V,Al)O thin films studied by spectroscopic ellipsometry from 1 to 6 eV  

NASA Astrophysics Data System (ADS)

Aerogel nanoparticles prepared with various Al concentrations were used as a target for the deposition of (V,Al) co-doped ZnO films by rf-magnetron sputtering on glass substrates. The influence of Al content on the structural and the optical properties of the Zn(V,Al)O films was investigated by X-ray diffraction and spectroscopic ellipsometry (SE). It is found that all films exhibit one high intensity (0 0 2) peak, indicating that they have c-axis preferred orientation due to self-texturing mechanism. SE measurements, used to determine the complex pseudo dielectric functions, were carried out at room temperature in the 1-6 eV photon energy region. The excitonic edge of the fundamental band gap (E0) transition in the imaginary part of the dielectric function of the Zn(V,Al)O films is observed around 3.5 eV and shows a dependence on the Al content. The E0 absorption edge of the Zn0.9-x V0.1AlxO alloys shows a blueshift from that of pure ZnO, reaching 389 meV for x = 0.02. This blueshift is interpreted by the Burstein-Moss effect. By analyzing the dielectric function, reduced effective mass m* of the Zn0.9-x V0.1AlxO alloy is extracted and shows good agreement with literature values.

Sayari, Amor; El Mir, Lassaad; Al-Heniti, Saleh; Al-Harbi, Talal; Yaghmour, Saud Jamil; Abdullah Al-Ghamdi, Ahmad

2013-06-01

165

Spectroscopic characterization of van der Waals interactions in a metal organic framework with unsaturated metal centers: MOF-74-Mg.  

PubMed

The adsorption energies of small molecules in nanoporous materials are often determined by isotherm measurements. The nature of the interaction and the response of the host material, however, can best be studied by spectroscopic methods. We show here that infrared absorption and Raman spectroscopy measurements together with density functional theory calculations, utilizing the novel van der Waals density functional vdW-DF, constitute a powerful approach to studying the weak van der Waals interactions associated with the incorporation of small molecules in these materials. In particular, we show how vdW-DF assists the interpretation of the vibrational spectroscopy data to uncover the binding sites and energies of these molecules, including the subtle dependence on loading of the IR asymmetric stretch mode of CO(2) when adsorbed in MOF-74-Mg. To gain a better understanding of the adsorption mechanism of CO(2) in MOF-74-Mg, the results are compared with CO within MOF-74-Mg. PMID:23032253

Nijem, Nour; Canepa, Pieremanuele; Kong, Lingzhu; Wu, Haohan; Li, Jing; Thonhauser, Timo; Chabal, Yves J

2012-10-03

166

Synthesis, conformational and spectroscopic characterization of monomeric styrene derivatives having pendant p-substituted benzylic ether groups.  

PubMed

Three derivatives of styrene monomer, 4-chlorophenyl-4-vinylbenzyl ether (I), 4-methoxyphenyl-4-vinylbenzyl ether (II) and 4-ethylphenyl-4-vinylbenzyl ether (III) were synthesized. The synthesized two novel compounds (I and III) and one with undefined structural features were identified by experimental spectroscopic techniques and density functional approach. The optimized geometrical structure, vibrational and electronic transitions along with chemical shifts of those compounds were presented in this study. The vibrational spectra of investigated compounds were recorded in solid state with FT-IR spectrometry in the range of 4000-400 cm(-1). The computational vibrational wavenumbers and also ground state equilibrium conformations were carried out by using density functional method with 6-311++G(d,p) basis set. Assignments of the fundamental vibrational modes were examined on the basis of the measured data and total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanical (SQM) method. Isotropic chemical shift of hydrogen and carbon nuclei were investigated via observed (1)H and (13)C NMR spectra in deuterated DMSO solution and predicted data applied with gauge-invariant atomic orbitals (GIAOs) method. The UV absorption spectra of monomers were observed in the range of 200-800 nm in ethanol, and time dependent DFT method was used to obtain the electronic properties. A detailed description of spectroscopic behaviors of compound was given based on the comparison of experimental measurements and theoretical computations. PMID:23608133

Cinar, Mehmet; Ozcan, Levent; Karabacak, Mehmet; Erol, Ibrahim

2013-03-28

167

Synthesis, conformational and spectroscopic characterization of monomeric styrene derivatives having pendant p-substituted benzylic ether groups  

NASA Astrophysics Data System (ADS)

Three derivatives of styrene monomer, 4-chlorophenyl-4-vinylbenzyl ether (I), 4-methoxyphenyl-4-vinylbenzyl ether (II) and 4-ethylphenyl-4-vinylbenzyl ether (III) were synthesized. The synthesized two novel compounds (I and III) and one with undefined structural features were identified by experimental spectroscopic techniques and density functional approach. The optimized geometrical structure, vibrational and electronic transitions along with chemical shifts of those compounds were presented in this study. The vibrational spectra of investigated compounds were recorded in solid state with FT-IR spectrometry in the range of 4000-400 cm-1. The computational vibrational wavenumbers and also ground state equilibrium conformations were carried out by using density functional method with 6-311++G(d,p) basis set. Assignments of the fundamental vibrational modes were examined on the basis of the measured data and total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanical (SQM) method. Isotropic chemical shift of hydrogen and carbon nuclei were investigated via observed 1H and 13C NMR spectra in deuterated DMSO solution and predicted data applied with gauge-invariant atomic orbitals (GIAOs) method. The UV absorption spectra of monomers were observed in the range of 200-800 nm in ethanol, and time dependent DFT method was used to obtain the electronic properties. A detailed description of spectroscopic behaviors of compound was given based on the comparison of experimental measurements and theoretical computations.

Cinar, Mehmet; Ozcan, Levent; Karabacak, Mehmet; Erol, Ibrahim

2013-07-01

168

Mineralogical characterization of Los Escullos (Cabo de Gata) using spectroscopic techniques  

NASA Astrophysics Data System (ADS)

In this work a detailed mineral spectroscopic analysis has been performed in the area of Los Escullos, wich is of the great astrobiological interest. Spectra were taken in-situ using portable Raman, LIBS and Mössbauer instruments and complementary data were also obtained at the laboratory using XRD and IR.

Rull, F.; Klingelhöfer, G.; Venegas, G.; Medina, J.; Martínez-Frías, J.

2012-09-01

169

An integrated spectroscopic approach to the chemical characterization of pyrolysis oils  

Microsoft Academic Search

The hydrocarbon (''oil'') fraction of a coal pyrolysis tar prepared by open column liquid chromatography (LC) was separated into 16 subfractions by a second LC run. The first 13 of these fractions were chosen for integrated spectroscopic analysis. Low voltage mass spectrometry (MS), infrared spectroscopy (IR), and proton (PMR) as well as carbon -13 nuclear magnetic resonance spectrometry (CMR) were

B. L. Hoesterey; W. Windig; H. L. C. Meuzelaar; E. M. Eyring; D. M. Grant; R. J. Pugmire

1987-01-01

170

New 1,2,4-triazole-based azo-azomethine dyes. Part I: Synthesis, characterization and spectroscopic studies  

NASA Astrophysics Data System (ADS)

Four new 1,2,4-triazole-based azo-azomethine dyes were synthesized via condensation of 3,5-diamino-1,2,4-triazole with azo-coupled o-vanillin precursors. The prepared dyes were characterized by IR, UV-vis and 1H NMR spectroscopic methods as well as elemental analyses. Thermal properties of the prepared dyes were examined by thermogravimetric analysis. Results indicated that the framework of the dyes was stable up to 225 °C. Also, the influence of various factors including time and mixed DMSO/EtOH solution on UV-vis spectra of the dyes were investigated.

Khanmohammadi, Hamid; Erfantalab, Malihe

2012-02-01

171

Synthesis, spectroscopic characterizations and quantum chemical computational studies of (Z)-4-[(E)-p-tolyldiazenyl]-6-[(2-hydroxyphenylamino)methylene]-2-methoxycyclohexa-2,4-dienone  

NASA Astrophysics Data System (ADS)

In this study, the molecular structure and spectroscopic properties of title compound were characterized by X-ray diffraction, FT-IR and UV-vis spectroscopies. These properties of title compound were also investigated from calculative point of view. The X-ray diffraction and FT-IR analyses reveal the existence of keto form in the solid state. UV-vis spectra were recorded in different organic solvents. The results show that title compound exists in both keto and enol forms in DMSO, EtOH but it exists in enol form in benzene. In addition, the title compound in DMSO showed new absorption band at 436 nm due to the high ionizing effect of this solvent. The geometry optimization of title compound in gas phase was performed using DFT method with B3LYP applying 6-311G(d,p) basis set. TD-DFT calculations starting from optimized geometry were carried out in gas phase to calculate excitation energies of title compound. The non-linear optical properties were computed with the same level of theory and title compound showed a good second order nonlinear optical property. In addition, thermodynamic properties were obtained in the range of 100-500 K.

Odaba?o?lu, Mustafa; Albayrak, Çi?dem; Ko?ar, Ba?ak; Büyükgüngör, Orhan

172

Synthesis, spectroscopic characterization and quantum chemical computational studies of (S)-N-benzyl-1-phenyl-5-(pyridin-2-yl)-pent-4-yn-2-amine.  

PubMed

The synthesis and characterization of a novel compound (S)-N-benzyl-1-phenyl-5-(pyridin-2-yl)-pent-4-yn-2-amine (abbreviated as BPPPYA) was presented in this study. The spectroscopic properties of the compound were investigated by FT-IR, NMR and UV spectroscopy experimentally and theoretically. The molecular geometry and vibrational frequencies of the BPPPYA in the ground state were calculated by using density functional theory (DFT) B3LYP method invoking 6-311++G(d,p) basis set. The geometry of the BPPPYA was fully optimized, vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. The results of the energy and oscillator strength calculated by time-dependent density functional theory (TD-DFT) and CIS approach complement with the experimental findings. Total and partial density of state (TDOS and PDOS) and also overlap population density of state (COOP or OPDOS) diagrams analysis were presented. The theoretical NMR chemical shifts ((1)H and (13)C) complement with experimentally measured ones. The dipole moment, linear polarizability and first hyperpolarizability values were also computed. The linear polarizabilities and first hyper polarizabilities of the studied molecule indicate that the compound is a good candidate of nonlinear optical materials. The calculated vibrational wavenumbers, absorption wavelengths and chemical shifts showed the best agreement with the experimental results. PMID:22820047

Kose, Etem; Atac, Ahmet; Karabacak, Mehmet; Karaca, Caglar; Eskici, Mustafa; Karanfil, Abdullah

2012-07-03

173

Synthesis, spectroscopic characterization and DNA nuclease activity of Cu(II) complexes derived from pyrazolone based NSO-donor Schiff base ligands  

NASA Astrophysics Data System (ADS)

Two neutral mononuclear Cu(II) complexes have been prepared in EtOH using Schiff bases derived from 4-toluoyl pyrazolone and thiosemicarbazide. Both the ligands have been characterized on the basis of elemental analysis, IR, 1H NMR, 13C NMR and mass spectral data. The molecular geometry of one of these ligands has been determined by single crystal X-ray study. It reveals that these ligands exist in amine-one tautomeric form in the solid state. Microanalytical data, Cu-estimation, molar conductivity, magnetic measurements, IR, UV-Visible, FAB-Mass, TG-DTA data and ESR spectral studies were used to confirm the structures of the complexes. Electronic absorption and IR spectra of the complexes suggest a square-planar geometry around the central metal ion. The interaction of complexes with pET30a plasmid DNA was investigated by spectroscopic measurements. Results suggest that the copper complexes bind to DNA via an intercalative mode and can quench the fluorescence intensity of EB bound to DNA. The interaction between the complexes and DNA has also been investigated by agarose gel electrophoresis, interestingly, we found that the copper(II) complexes can cleave circular plasmid DNA to nicked and linear forms.

Vyas, Komal M.; Joshi, Rushikesh G.; Jadeja, R. N.; Ratna Prabha, C.; Gupta, Vivek K.

2011-12-01

174

Synthesis, spectroscopic characterizations and quantum chemical computational studies of (Z)-4-[(E)-p-tolyldiazenyl]-6-[(2-hydroxyphenylamino)methylene]-2-methoxycyclohexa-2,4-dienone.  

PubMed

In this study, the molecular structure and spectroscopic properties of title compound were characterized by X-ray diffraction, FT-IR and UV-vis spectroscopies. These properties of title compound were also investigated from calculative point of view. The X-ray diffraction and FT-IR analyses reveal the existence of keto form in the solid state. UV-vis spectra were recorded in different organic solvents. The results show that title compound exists in both keto and enol forms in DMSO, EtOH but it exists in enol form in benzene. In addition, the title compound in DMSO showed new absorption band at 436 nm due to the high ionizing effect of this solvent. The geometry optimization of title compound in gas phase was performed using DFT method with B3LYP applying 6-311G(d,p) basis set. TD-DFT calculations starting from optimized geometry were carried out in gas phase to calculate excitation energies of title compound. The non-linear optical properties were computed with the same level of theory and title compound showed a good second order nonlinear optical property. In addition, thermodynamic properties were obtained in the range of 100-500 K. PMID:22446785

Odaba?o?lu, Mustafa; Albayrak, Ci?dem; Ko?ar, Ba?ak; Büyükgüngör, Orhan

2012-03-03

175

X-ray absorption and magnetic circular dichroism characterizations of Mn doped ZnO  

Microsoft Academic Search

We report the near-edge x-ray absorption fine structure (NEXAFS) and x-ray magnetic circular dichroism (XMCD) experiments on well characterized Mn doped ZnO thin films that show ferromagnetism at room temperature. The NEXAFS measurements at O K edge clearly exhibit a preedge spectral feature which evolves with Mn doping, similar to one observed in hole-doped cuprates and manganites. The Mn L3,2

P. Thakur; K. H. Chae; J.-Y. Kim; M. Subramanian; R. Jayavel; K. Asokan

2007-01-01

176

Spectroscopic and Electrochemical Characterization of the [NiFeSe] Hydrogenase from Desulfovibrio vulgaris Miyazaki F: Reversible Redox Behavior and Interactions between Electron Transfer Centers.  

PubMed

Characterizing a new hydrogenase: The newly isolated [NiFeSe] hydrogenase from Desulfovibrio vulgaris Miyazaki F displays catalytic properties distinct from other hydrogenase proteins. Here we apply site-specific spectroscopic and electrochemical techniques to characterize these unique features at the molecular level. PMID:24038675

Riethausen, Jana; Rüdiger, Olaf; Gärtner, Wolfgang; Lubitz, Wolfgang; Shafaat, Hannah S

2013-09-03

177

Development of cellular absorptive tracers (CATs) for a quantitative characterization of microbial mass in flow systems.  

PubMed

A new method was developed for a simple non-destructive characterization of bacterial mass in flow systems. Results of partition and transport experiments showed that adsorption of a CAT molecule into the cellular mass resulted in its retardation during flow, which was a good measure of the biomass quantity and distribution. Three dyes, acridine orange (AO), toluidine blue (TB), and safranin O (SO), were chosen as CATs to demonstrate their utility to quantitatively characterize the biomass, its location and morphology in flow system. The results clearly demonstrated the applicability of AO, TB, and SO as cellular absorptive tracers in columnar flow experiments. PMID:17329099

Choi, Jaeyoung; Saripalli, Prasad; Meldrum, Deirdre; Lee, Ju Young

2007-02-27

178

Mass spectroscopic and ESR characterization of soluble yttrium-containing metallofullerenes YCââ and YâCââ  

Microsoft Academic Search

Solvent soluble, yttrium-containing fullerenes are extracted from yttrium\\/carbon soot produced by the carbon-arc fullerene generation method. An yttrium-graphite composite yields solvent extractable molecules such as YCââ and YâCââ as evidenced by a laser desorption time-of-flight (LD-TOF) mass spectroscopic analysis of the extracts. This is consistent with the very recent results by Smalley et al. where YCââ and YâCââ are prepared

Hisanori Shinohara; Hiroyasu Sato; Yahachi Saito; Masato Ohkohchi; Yoshinori Ando

1992-01-01

179

ESR spectroscopic characterization of V 2O 5\\/AlF 3 ammoxidation catalysts  

Microsoft Academic Search

Electron spin resonance (ESR) spectroscopic study has been made at 25 °C on a series of V2O5\\/AlF3 catalysts, prepared by wet impregnation method with different V2O5 loadings ranging from 2 to 15 wt%. V2O5\\/AlF3 solids have been used as catalysts in the ammoxidation of 3-picoline to nicotinonitrile. The ESR parameters like g?, g?, A?, A? were obtained from the spectra

K. V Narayana; B David Raju; S Khaja Masthan; V Venkat Rao; P Kanta Rao; R Subrahmanian; A Martin

2004-01-01

180

Synthesis and spectroscopic characterization of solution processable highly ordered polythiophene–carbon nanotube nanohybrid structures  

Microsoft Academic Search

We report on the synthesis and spectroscopic study of a novel highly ordered nanohybrid structure consisting of a single-walled carbon nanotube (SWNT) coated with highly crystalline regio-regular poly(3-hexylthiophene) (rrP3HT) and discuss the applicability of the nanohybrids in organic photovoltaics. The use of a solvent extraction technique allows the nanohybrids to be produced with a high yield and high purity. We

T Schuettfort; H J Snaith; A Nish; R J Nicholas

2010-01-01

181

Synthesis and spectroscopic characterization of solution processable highly ordered polythiophene-carbon nanotube nanohybrid structures  

Microsoft Academic Search

We report on the synthesis and spectroscopic study of a novel highly ordered nanohybrid structure consisting of a single-walled carbon nanotube (SWNT) coated with highly crystalline regio-regular poly(3-hexylthiophene) (rrP3HT) and discuss the applicability of the nanohybrids in organic photovoltaics. The use of a solvent extraction technique allows the nanohybrids to be produced with a high yield and high purity. We

T. Schuettfort; H. J. Snaith; A. Nish; R. J. Nicholas

2010-01-01

182

Calorimetric and spectroscopic studies characterization of newborn rat’ blood serum after maternal administration of cyclophosphamide  

Microsoft Academic Search

Differential scanning microcalorimetry (DSC) and UV–VIS absorption spectroscopy were used to obtain the characteristics of\\u000a blood serum from newborn rat’ after maternal treatment with cyclophosphamide in comparison with control. The obtained DSC\\u000a curves reveal a complex endothermic peak due to the unfolding process of various serum proteins. Thermal profiles and absorption\\u000a spectra of blood serum are sensitive to the age

Zofia Drzazga; Katarzyna Michalik; Tomasz Halat; Anna Michnik; Henryk I. Trzeciak

2010-01-01

183

Spectroscopic characterization of the stabilising activity of migrating HALS in a pigmented PP\\/EPR blend  

Microsoft Academic Search

In previous work, the FT-IR maximum of absorption of a low molecular weight HALS containing a sebacate structure was reported to shift from 1738 to 1732cm?1 during the photo-aging of polypropylene. Previous studies have shown that the reduced mobility of the molecule caused the absorption to shift towards lower frequencies while decreasing its stabilizing activity. This paper presents further results

Olivier Haillant

2008-01-01

184

Attenuation of Photosynthetically Active Radiation by Aerosols and Characterization of Aerosol Absorption from AERONET  

NASA Astrophysics Data System (ADS)

Accurate knowledge of the intensity of incident photosynthetically active radiation (PAR; 400-700 nm) at the surface is important for understanding possible effects on crop productivity and on the net primary productivity of natural ecosystems. Not only the magnitude of the PAR irradiance but also the distribution of that irradiance into direct and diffuse components can have an effect on photosynthesis. In many regions clouds are the primary attenuator of PAR flux, however in some regions there are significant reductions in PAR irradiance at the surface due to aerosol attenuation. The two primary aerosol optical parameters affecting PAR attenuation are the aerosol optical depth which is related to particulate concentration in the total column, and aerosol absorption which is related to the black carbon concentration for pollution and biomass burning aerosols. Model computations show the magnitude of reduction in PAR irradiance as optical depth increases and as aerosol absorption increases, and the increases in diffuse fraction as aerosol optical depth increases and decreases in diffuse fraction as absorption increases. Examples are shown of the retrieval of aerosol absorption (parameterized by the single scattering albedo) from measurements of irradiance and diffuse fraction in conjunction with spectral aerosol optical depth in the PAR wavelength interval. Since PAR flux reduction by aerosols increases as optical path length increases, there is also the effect of greater attenuation in early morning and late afternoon, possibly reducing the effective photoperiod. We also show aerosol absorption retrievals from the new Version 2.0 AERONET retrievals that are more accurate than Version 1.0 due to better characterization of surface reflectance, providing the basic aerosol characterization needed to estimate cloudless sky PAR fluxes.

Eck, T. F.; Holben, B. N.; Schafer, J. S.; Sinyuk, A.; Smirnov, A.; Slutsker, I.

2007-05-01

185

Electrochemical Kinetics and X-ray Absorption Spectroscopic Investigations of Oxygen Reduction on Chalcogen-Modified Ruthenium Catalysts in Alkaline Media  

SciTech Connect

The oxygen reduction reaction (ORR) in alkaline media has been investigated on chalcogen-modified ruthenium nanoparticles (Ru/C, Se/Ru/C, Se/RuMo/C, S/Ru/C, S/RuMo/C) synthesized in-house via aqueous routes. In acidic medium, it is well known that modification by a chalcogen prevents the oxidation of the underlying transition-metal (Ru) surface, thereby promoting direct molecular O{sub 2} adsorption on the Ru metal. On an unmodified Ru catalyst in alkaline media, the surface oxides on Ru mediate the 2e{sup -} reduction of molecular O{sub 2} to a stable peroxide anion (HO{sub 2}{sup -}) intermediate via an outer-sphere electron-transfer mechanism. This increases the activity of HO{sub 2}{sup -} near the electrode surface and decreases the overpotential for ORR by effectively carrying out the reduction of HO{sub 2}{sup -} to OH{sup -} at the oxide-free ruthenium metal site. An increase in ORR activity of Ru is observed by modification with a chalcogen; however, the increase is not as significant as observed in acidic media. Ternary additives, such as Mo, were found to significantly improve the stability of the chalcogen-modified catalysts. Detailed investigations of the ORR activity of this class of catalyst have been carried out in alkaline media along with comparisons to acidic media wherever necessary. A combination of electrochemical and X-ray absorption spectroscopic (EXAFS, XANES, {Delta}{mu}) studies has been performed in order to understand the structure/property relationships of these catalysts within the context of ORR in alkaline electrolytes.

N Ramaswamy; R Allen; S Mukerjee; Y

2011-12-31

186

X-Ray Absorption Spectroscopic And Theoretical Studies on (L)(2)[Cu-2(S-2)N](2+) Complexes: Disulfide Versus Disulfide(Center Dot 1-) Bonding  

SciTech Connect

Cu K-, Cu L-, and S K-edge X-ray absorption spectroscopic (XAS) data have been combined with density functional theory (DFT) calculations on [{l_brace}(TMPA)Cu{r_brace}{sub 2}S{sub 2}](ClO{sub 4}){sub 2} (1), [{l_brace}Cu[HB(3,5-Pr{sub 2}{sup i}pz){sub 3}]{r_brace}{sub 2}(S{sub 2})] (2), and [{l_brace}(TMEDA)Cu{r_brace}{sub 2}(S{sub 2}){sub 2}](OTf){sub 2} (3) to obtain a quantitative description of their ground state wavefunctions. The Cu L-edge intensities give 63 and 37% Cu d-character in the ground state of 1 and 2, respectively, whereas the S K-pre-edge intensities reflect 20 and 48% S character in their ground states, respetively. These data indicate a more than 2-fold increase in the total disulfide bonding character in 2 relative to 1. The increase in the number of Cu?S bonds in 2 ({mu}-{eta}{sup 2}:{eta}{sup 2} S{sub 2}{sup 2-} bridge) compared to 1 ({mu}-{eta}{sup 1}:{eta}{sup 1} S{sub 2}{sup 2-} bridge) dominantly determines the large increase in covalency and Cu-disulfide bond strength in 2. Cu K- and L- and S K-pre-edge energy positions directly demonstrate the Cu{sup II}/(S{sub 2}{sup -}){sub 2} nature of 3. The two disulfide({center_dot}1?)'s in 3 undergo strong bonding interactions that destabilize the resultant filled antibonding {pi}* orbitals of the (S{sub 2}{sup -}){sub 2} fragment relative to the Cu 3d levels. This leads to an inverted bonding scheme in 3 with dominantly ligand-based holes in its ground state, consistent with its description as a dicopper(II)-bis-disulfide({center_dot}1?) complex.

Sarangi, R.; York, J.T.; Helton, M.E.; Fujisawa, K.; Karlin, K.D.; Tolman, W.B.; Hodgson, K.O.; Hedman, B.; Solomon, E.I.; /Stanford U., Chem. Dept. /SLAC, SSRL /Minnesota U. /Johns Hopkins U. /Tsukuba U.

2009-04-30

187

Time-resolved contrast function and optical characterization of spatially varying absorptive inclusions at different depths in diffusing media  

Microsoft Academic Search

The role of a spatially varying absorptive inhomogeneity located at different depths within a turbid material has been investigated. This inhomogeneity has been characterized by a spatially dependent Gaussian distribution of its absorption coefficient. The present study has been performed calculating the time-resolved contrast function in the framework of the first-order perturbative approach to the diffusion equation for a slab

S. de Nicola; R. Esposito; M. Lepore; P. L. Indovina

2004-01-01

188

Remarkable effect of iridium cyclometalation on the nonlinear absorption properties of a quadrupolar imine ligand.  

PubMed

A new type of dinuclear iridium complex, based on a quadrupolar Schiff base ligand, is synthesized and its structure fully characterized. Its linear and nonlinear spectroscopic properties are investigated, evidencing a strong contribution of the metal-to-ligand transitions not only to the linear absorption but also to the two- and three-photon absorption properties. PMID:24020389

Massue, Julien; Olesiak-Banska, Joanna; Jeanneau, Erwann; Aronica, Christophe; Matczyszyn, Katarzyna; Samoc, Marek; Monnereau, Cyrille; Andraud, Chantal

2013-09-10

189

Study of Characterization of Pure and Malachite Green Doped Samples Using Spectroscopic Studies  

NASA Astrophysics Data System (ADS)

This paper describes the results of SEM, EDX, UV-vis and TSDC study of malachite green doped PVK thermelectrets. TSDC study has been carried out in the temperature range 300 °C to 1500 °C with four different polarizing fields. One peak was observed at 110+/-10 °C which shifts toward high temperature with the increase in polarizing field. The activation energy found by initial rise method are 0.27+/-0.02 eV for pure and 0.40+/-0.03 eV for malachite green doped PVK thermoelectrets. Spectroscopic study concluded that impregnation of malachite green in polymer matrix forms charge transfer complexes.

Mishra, Jyoti; Mishra, Pankaj K.; Khare, P. K.

2011-07-01

190

Spectroscopic characterization of Yb3+-doped laser materials at cryogenic temperatures  

NASA Astrophysics Data System (ADS)

We present measurements of the absorption and emission cross-sections for Yb:YAG, Yb:LuAG and Yb:CaF 2 as a function of temperature between 80 and 340 K. The cross-sections are determined by the combination of the McCumber relation and the Fuchtbauer-Ladenburg (FL) equation to achieve reliable results in spectral regions of high and low absorption. The experimental setup used for the fluorescence measurements minimizes re-absorption effects due to the measurement from small sample volume, providing nearly undisturbed raw data for the FL approach. The retrieved cross-sections together with the spectral characteristics of the tested materials provide important information for the design of energy efficient, high-power laser amplifiers.

Körner, J.; Jambunathan, V.; Hein, J.; Seifert, R.; Loeser, M.; Siebold, M.; Schramm, U.; Sikocinski, P.; Lucianetti, A.; Mocek, T.; Kaluza, M. C.

2013-09-01

191

Characterization of the influence of nitric oxide donors on intestinal absorption of macromolecules.  

PubMed

To characterize the influence of nitric oxide (NO) donors on the intestinal absorption of macromolecules, the relationship between the release rate of NO from NO donors and their absorption-enhancing effects and the effects of several scavengers and generators on the absorption-enhancing effects of NO donor were investigated. The t1/2 values of the NO release rate from 3-(2-hydroxy-1-methylethyl-2-nitrosohydrazino)-1-propanamine (NOC5), 3-(2-hydroxy-1-methylethyl-2-nitrosohydrazino)-N-methyl-1-propanamine (NOC7) and N-ethyl-2-(1-ethyl-hydroxy-2-nitrosohydrazino)-ethanamine (NOC12) are 25, 5 and 100min, respectively. The absorption-enhancing effects of NO donors on the absorption of fluorescein isothiocyanate dextrans with an average molecular weight of 4400 (FD-4) are NOC5 > NOC7 > NOC12 in the colon. The lowest enhancing effect of NOC12 may be due to the slow rate of NO release. The enhancing effect of NOC7 rapidly disappeared compared with the effect of NOC5. The results raise the possibility that the difference between NOC5 and NOC7 on enhancing effect is related to the t1/2 of the NO release. The NOC7-induced enhancing effect was prevented by the co-administration of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazole-1-oxyl-3-oxide sodium salt (C-PTIO), an NO scavenger; tiron, an O2(-) scavenger; mannitol, an OH* scavenger, and deferoxamine, peroxynitrate scavenger. Pyrogallol, an O2(-) generator, potentiated the NOC7-induced enhancing effect. These results support a role for peroxynitrate, and possibly OH*, in the NO donor-induced intestinal enhancing effect. PMID:15501005

Takahashi, Koichi; Numata, Nanako; Kinoshita, Natsumi; Utoguchi, Naoki; Mayumi, Tadanori; Mizuno, Nobuyasu

2004-11-22

192

Toward an alternative intrinsic probe for spectroscopic characterization of a protein.  

PubMed

The intrinsic fluorescent amino acid tryptophan is the unanimous choice for the spectroscopic investigation of proteins. However, several complicacies in the interpretation of tryptophan fluorescence in a protein are inevitable and an alternative intrinsic protein probe is a longstanding demand. In this contribution, we report an electron-transfer reaction in a human transporter protein (HSA) cavity which causes the tryptophan residue (Trp214) to undergo chemical modification to form one of its metabolites kynurenine (Kyn214). Structural integrity upon modification of the native protein is confirmed by dynamic light scattering (DLS) as well as near and far circular dichroism (CD) spectroscopy. Femtosecond-resolved fluorescence transients of the modified protein describe the dynamics of solvent molecules in the protein cavity in both the native and denatured states. In order to establish general use of the probe, we have studied the dipolar interaction of Kyn214 with a surface-bound ligand (crystal violet, CV) of the protein. By using the sensitivity of FRET, we have determined the distance between Kyn214 (donor) and CV (acceptor). Our study is an attempt to explore an alternative intrinsic fluorescence probe for the spectroscopic investigation of a protein. In order to establish the efficacy of the modification technique we have converted the tryptophan residues of other proteins (bovine serum albumin, chymotrypsin and subtilisin Carlsberg) to kynurenine and confirmed their structural integrity. We have also shown that catalytic activity of the enzymes remains intact upon the modification. PMID:21028859

Goswami, Nirmal; Makhal, Abhinandan; Pal, Samir Kumar

2010-10-28

193

Biochemical and spectroscopic characterization of the blue-green photoreceptor in Halobacterium halobium  

SciTech Connect

Spectroscopic evidence indicates the presence of a second sensory receptor sR-II in Halobacterium halobium, which causes a repellent response to blue-green light. Reactions with hydroxylamine and NaCNBH/sub 3/ and reconstitution of the bleached pigment with retinal show that it is very similar to the other retinylidene pigments bacteriorhodopsin, halorhodopsin, and especially the earlier-discovered phototaxis receptor, sensory rhodopsin, renamed sR-I587. The second sensory receptor, sR-II480, has an absorbance maximum at 480 nm and undergoes a cyclic photoreaction with a half-time of approximately 200 msec. Its predominant photocycle intermediate absorbs maximally near 360 nm. The receptor can be detected spectroscopically in the presence of sR-I587 and quantitated through its transient response to 450-nm excitation. It is selectively bleached by low hydroxylamine concentrations that are insufficient to bleach sR-I587 significantly. Its photochemical and phototactic activities can be restored by addition of retinal. The mobility of the receptor, on NaDodSO4/polyacrylamide gels, was similar or identical to that of sR-I587 and slightly faster than bacteriorhodopsin, yielding an apparent molecular mass of 23-24 kDa.

Scherrer, P.; McGinnis, K.; Bogomolni, R.A.

1987-01-01

194

Cyanide/isocyanide abundances in the interstellar medium - I. Theoretical spectroscopic characterization  

NASA Astrophysics Data System (ADS)

Modelling molecular abundances in the interstellar medium requires accurate molecular data. In this work, structural and spectroscopic properties of a series of metal cyanides/isocyanide species containing Na, Mg, Al and Si are calculated and compared using highly correlated ab initio calculations. The metal substitution effect on molecular properties is discussed. Isomerization pathways and transitions states are detailed. NaCN shows three isomeric structures, one T shaped and two linear forms, whereas the remaining compounds display two linear minimum energy geometries. For the first time, NaCN secondary minima are described. Second-order perturbation theory spectroscopic parameters are determined from an anharmonic RCCSD(T)/aug-cc-pV5Z force field. Very accurate rotational constants are calculated using a complete basis set and taking into account vibrational effects and the structure variation with core electron correlation. For l-SiCN and l-SiNC, spin-orbit parameters are also provided. Present theoretical results are compared with available experimental data attaining a good agreement.

Senent, M. L.; Dumouchel, F.; Lique, F.

2012-02-01

195

Raman spectroscopic characterization of isomers of metal N-phenyl protoporphyrin IX dimethylesters  

SciTech Connect

The reaction of heme proteins with phenylhydrazine results in N-phenylprotoporphyrin formation. The authors are using resonance Raman and UV-visible adsorption spectroscopies to investigate the structure of N-phenylprotoporphyrin dimethylesters (N[Phi]PPDME) metal derivatives. Distortion from planarity of the protoporphyrin macrocycle results from addition of the phenyl group. Porphyrin planarity is thought to influence chemical and electron-transfer properties of tetrapyrroles contained in proteins such as methylreductase and the photosynthetic reaction center. Specifically, the authors investigated the conformation of regioisomers obtained by substitution at the A, B, C, and D pyrrole rings on the distal side. Isomers A and B of Cu- and ZnN[Phi]PPDME show spectroscopic similarities and isomers C and D are similar; A and B are different from isomers C and D. This difference is due mainly to the location of the vinyl substituents at the periphery of the porphyrin. In the Raman spectra, the differences show up primarily in the vinyl vibrational modes and vinyl-sensitive porphyrin modes. Molecular mechanics calculations also are used to interpret the spectroscopic results. The calculations were carried out for various isomers and conformers of Fe(III) N-phenylprotoporphyrin chloride and Cu(II) N-phenylprotoporphyrin. Predicted structures are similar to reported N-substituted tetraphenylporphyrins, with the major distortion from planarity occurring for the N-substituted pyrrole ring. The energies are found to be affected by orientations of the vinyl substituent groups.

Shelnutt, J.A.; Sparks, L.D.; Chamberlain, J.R.; Hsu, P.; Ondrias, M.R. (Sandia National Lab., Albuquerque, NM (United States) Univ. of New Mexico, Albuquerque (United States)); Swanson, B.; Montellano, P.O. de (Univ. of California, San Francisco (United States))

1992-01-01

196

Synthesis, characterization and interaction studies of copper based drug with Human Serum Albumin (HSA): spectroscopic and molecular docking investigations.  

PubMed

A new water soluble copper(II) complex, [Cu(glygly)(ssz)(H(2)O)]?6H(2)O, 1 derived from dipeptide (glycyl glycine anion) and sulfasalazine was synthesized and characterized by elemental analysis (CHN), molar conductance measurements and spectroscopic methods (IR, UV-vis, ESI-MS). The complex 1 is non-ionic in nature and possess octahedral geometry around Cu(II) metal ion. The interaction of complex 1 with Human Serum Albumin (HSA) was investigated under physiological condition in Tris-HCl buffer solution at pH 7.4 by means of various spectroscopic methods (fluorescence, CD and FTIR) and molecular docking technique. The results of fluorescence titration revealed that the complex 1 strongly quench the intrinsic fluorescence of HSA through a static quenching procedure. Binding constants (K(b)) and the number of binding sites (n?1) were calculated using modified Stern-Volmer equations. The thermodynamic parameters ?G at different temperatures were calculated subsequently the value of ?H and ?S was also calculated which revealed that the hydrophobic and hydrogen bonding interactions play a major role in HSA-complex 1 association. The distance r between donor (HSA) and acceptor (complex 1) was obtained according to fluorescence resonance energy transfer and the alterations of HSA secondary structure induced by complex 1 were confirmed by FT-IR and CD measurements. PMID:22750083

Tabassum, Sartaj; Al-Asbahy, Waddhaah M; Afzal, Mohd; Arjmand, Farukh

2012-06-15

197

Characterization of organic and inorganic optoelectronic semiconductor devices using advanced spectroscopic methods  

Microsoft Academic Search

In this thesis, advanced spectroscopy methods are discussed and applied to gain understanding of the physical properties of organic conjugated molecules, II-VI thin film semiconductors, and vertical cavity surface emitting lasers (VCSEL). Experiments include single photon and two-photon excitation with lasers, with subsequent measurements of the absorption and photoluminescence, as well as photocurrent measurements using tungsten and xenon lamps, measuring

Raoul Schroeder

2001-01-01

198

Spectroscopic and structural characterization of electrochemically grown ZnO quantum dots  

Microsoft Academic Search

We report a novel method for the synthesis of stable, OH free zinc oxide quantum dots, using an electrochemical route. The optical properties of these quantum dots were studied at room temperature, by taking the optical absorption and luminescence spectra. The band gap luminescence is predominant in ZnO quantum dots synthesized by the present technique, while the green defect induced

Shailaja Mahamuni; Kavita Borgohain; B. S. Bendre; Valerie J. Leppert; Subhash H. Risbud

1999-01-01

199

Intestinal absorption of dideoxynucleosides: characterization using a multiloop in situ technique.  

PubMed

The intestinal absorption of dideoxynucleosides was studied in rabbits, using a closed-loop mesenteric-sampling in situ technique developed in this laboratory, and the kinetic profiles were characterized. Each of the dideoxynucleosides exhibited different dependence on the intestinal regions studied: 3'-azido-2',3'-dideoxythymidine was best absorbed from the ileum, while 2',3'-dideoxyinosine and 2',3'-dideoxycytidine were preferentially absorbed from the jejunum. The results were validated by the mass-balance approach; the percent of drug retained in the intestinal lumen and that degraded at the intestinal pH, by colonic flora, in the intestinal tissue, and in plasma were assessed. PMID:7714742

Mirchandani, H L; Chien, Y W

1995-01-01

200

Studies related to Norway spruce galactoglucomannans: chemical synthesis, conformation analysis, NMR spectroscopic characterization, and molecular recognition of model compounds.  

PubMed

Galactoglucomannan (GGM) is a polysaccharide mainly consisting of mannose, glucose, and galactose. GGM is the most abundant hemicellulose in the Norway spruce (Picea abies), but is also found in the cell wall of flax seeds, tobacco plants, and kiwifruit. Although several applications for GGM polysaccharides have been developed in pulp and paper manufacturing and the food and medical industries, attempts to synthesize and study distinct fragments of this polysaccharide have not been reported previously. Herein, the synthesis of one of the core trisaccharide units of GGM together with a less-abundant tetrasaccharide fragment is described. In addition, detailed NMR spectroscopic characterization of the model compounds, comparison of the spectral data with natural GGM, investigation of the acetyl-group migration phenomena that takes place in the polysaccharide by using small model compounds, and a binding study between the tetrasaccharide model fragment and a galactose-binding protein (the toxin viscumin) are reported. PMID:23008171

Ekholm, Filip S; Ardá, Ana; Eklund, Patrik; André, Sabine; Gabius, Hans-Joachim; Jiménez-Barbero, Jesús; Leino, Reko

2012-09-24

201

Synthesis, spectroscopic characterization and crystal structure of novel NNNN-donor ?-bis(bidentate) tetraaza acyclic Schiff base ligands  

NASA Astrophysics Data System (ADS)

Novel NNNN-donor ?-bis(bidentate) tetraaza acyclic Schiff base ligands with different substituents (CF3, N(CH3)2 or OH groups) were synthesized by the condensation reaction of triethylenetetramine with 4-substituted benzaldehydes. Triethylenetetramine tris(4-trifluoromethylbenzylidene) (TTFMB), triethylenetetramine tris(4-dimethylaminobenzylidene) (TTDMB) and triethylenetetramine tris(2,4-dihydroxybenzylidene) (TTDHB) were formed as N4 donor ligands. The formation of a five-membered imidazolidine ring from the ethylenediamine backbone as a spacer-cumbridging unit gives rise to a new type of imidazolidine ligand. The structure of the TTFMB and TTDMB were determined by single crystal X-ray crystallography. The synthesized ligands have been characterized on the basis of the results of cyclic voltammetry (CV) and spectroscopic studies viz. FT-IR spectroscopy (FT-IR), mass spectroscopy (MS) and UV-Vis spectroscopy (UV-Vis).

Habibi, Mohammad Hossein; Shojaee, Elahe; Nichol, Gary S.

2012-12-01

202

Synthesis, spectroscopic characterization and crystal structure of novel NNNN-donor ?-bis(bidentate) tetraaza acyclic Schiff base ligands.  

PubMed

Novel NNNN-donor ?-bis(bidentate) tetraaza acyclic Schiff base ligands with different substituents (CF(3), N(CH(3))(2) or OH groups) were synthesized by the condensation reaction of triethylenetetramine with 4-substituted benzaldehydes. Triethylenetetramine tris(4-trifluoromethylbenzylidene) (TTFMB), triethylenetetramine tris(4-dimethylaminobenzylidene) (TTDMB) and triethylenetetramine tris(2,4-dihydroxybenzylidene) (TTDHB) were formed as N(4) donor ligands. The formation of a five-membered imidazolidine ring from the ethylenediamine backbone as a spacer-cumbridging unit gives rise to a new type of imidazolidine ligand. The structure of the TTFMB and TTDMB were determined by single crystal X-ray crystallography. The synthesized ligands have been characterized on the basis of the results of cyclic voltammetry (CV) and spectroscopic studies viz. FT-IR spectroscopy (FT-IR), mass spectroscopy (MS) and UV-Vis spectroscopy (UV-Vis). PMID:23010628

Habibi, Mohammad Hossein; Shojaee, Elahe; Nichol, Gary S

2012-09-01

203

Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa phototropin 1  

NASA Astrophysics Data System (ADS)

The phototropins are plant blue-light receptors that base their light-dependent action on the reversible formation of a covalent bond between a flavin mononucleotide (FMN) cofactor and a conserved cysteine residue in light, oxygen or voltage (LOV) domains. The spectroscopic properties of the LOV2 domain of phototropin 1 of Avena sativa (oat) have been investigated by means of low-temperature absorption and fluorescence spectroscopy and by time-resolved fluorescence spectroscopy. The low-temperature absorption spectrum of the LOV2 domain showed a fine structure around 473 nm, indicating heterogeneity in the flavin binding pocket. The fluorescence quantum yield of the flavin cofactor increased from 0.13 to 0.41 upon cooling the sample from room temperature to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K, allowing for an accurate positioning of the flavin triplet state in the LOV2 domain at 16900 cm-1. Fluorescence from the cryotrapped covalent adduct state was extremely weak, with a fluorescence spectrum showing a maximum at 440 nm. Time-resolved fluorescence experiments utilizing a synchroscan streak camera revealed a singlet-excited state lifetime of the LOV2 domain of 2.4 ns. FMN dissolved in aqueous solution showed a pH-dependent lifetime ranging between 2.9 ns at pH 2.0 to 4.7 ns at pH 8.0. No spectral shifting of the flavin emission was observed in the LOV2 domain nor in FMN in aqueous solution.

Gauden, Magdalena; Crosson, Sean; van Stokkum, I. H. M.; van Grondelle, Rienk; Moffat, Keith; Kennis, John T. M.

2004-09-01

204

Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa phototropin  

SciTech Connect

The phototropins are plant blue-light receptors that base their light-dependent action on the reversible formation of a covalent bond between a flavin mononucleotide (FMN) cofactor and a conserved cysteine residue in light, oxygen or voltage (LOV) domains. The spectroscopic properties of the LOV2 domain of phototropin 1 of Avena sativa (oat) have been investigated by means of low-temperature absorption and fluorescence spectroscopy and by time-resolved fluorescence spectroscopy. The low-temperature absorption spectrum of the LOV2 domain showed a fine structure around 473 nm, indicating heterogeneity in the flavin binding pocket. The fluorescence quantum yield of the flavin cofactor increased from 0.13 to 0.41 upon cooling the sample from room temperature to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K, allowing for an accurate positioning of the flavin triplet state in the LOV2 domain at 16900 cm{sup -1}. Fluorescence from the cryotrapped covalent adduct state was extremely weak, with a fluorescence spectrum showing a maximum at 440 nm. Time-resolved fluorescence experiments utilizing a synchroscan streak camera revealed a singlet-excited state lifetime of the LOV2 domain of 2.4 ns. FMN dissolved in aqueous solution showed a pH-dependent lifetime ranging between 2.9 ns at pH 2.0 to 4.7 ns at pH 8.0. No spectral shifting of the flavin emission was observed in the LOV2 domain nor in FMN in aqueous solution.

Gauden, Magdalena; Crosson, Sean; van Stokkum, I.H.; Grondelle, Rienkvan; Moffat, Keith; Kennis, John T. (UC)

2004-12-13

205

Spectroscopic characterization of the oxo-transfer reaction from a bis(mu-oxo)dicopper(III) complex to triphenylphosphine.  

PubMed

The oxygen-atom transfer reaction from the bis(mu-oxo)dicopper(III) complex [Cu(III)(2)(mu-O)(2)(L)(2)](2+), where L =N,N,N',N' -tetraethylethylenediamine, to PPh(3) has been studied by UV-vis, EPR, (1)H NMR and Cu K-edge X-ray absorption spectroscopy in parallel at low temperatures (193 K) and above. Under aerobic conditions (excess dioxygen), 1 reacted with PPh(3), giving O=Ph(3) and a diamagnetic species that has been assigned to an oxo-bridged dicopper(II) complex on the basis of EPR and Cu K-edge X-ray absorption spectroscopic data. Isotope-labeling experiments ((18)O(2)) established that the oxygen atom incorporated into the triphenylphosphine oxide came from both complex 1 and exogenous dioxygen. Detailed kinetic studies revealed that the process is a third-order reaction; the rate law is first order in both complex 1 and triphenylphosphine, as well as in dioxygen. At temperatures above 233 K, reaction of 1 with PPh(3) was accompanied by ligand degradation, leading to oxidative N-dealkylation of one of the ethyl groups. By contrast, when the reaction was performed in the absence of excess dioxygen, negligible substrate (PPh(3)) oxidation was observed. Instead, highly symmetrical copper complexes with a characteristic isotropic EPR signal at g= 2.11 were formed. These results are discussed in terms of parallel reaction channels that are activated under various conditions of temperature and dioxygen. PMID:15483710

Pavlova, Svetlana V; Chen, Kelvin H-C; Chan, Sunney I

2004-08-31

206

Characterization of novel lithium battery cathode materials by spectroscopic methods: the Li5+xFeO? system.  

PubMed

The novel, lithium-rich oxide-phase Li?FeO? (LFO) could, in theory, deliver a specific capacity >900 mAh/g when deployed as a cathode or cathode precursor in a battery with a lithium-based anode. However, research results to date on LFO indicate that less than one of the five Li? cations can be reversibly de-intercalated/re-intercalated during repetitive charging and discharging cycles. In the present research, the system Li5+xFeO? with x values in the range of 0.0-2.0 was investigated by a combination of Raman and X-ray absorption spectroscopic methods supported by X-ray diffraction (XRD) analysis in order to determine if the Li?FeO? lattice would accommodate additional Li? ions, with concomitant lowering of the valence on the FeIII cations. Both the Raman phonon spectra and the XRD patterns were invariant for all values of x, strongly indicating that additional Li? did not enter the Li?FeO? lattice. Also, Raman spectral results and high-resolution synchrotron XRD data revealed the presence of second-phase Li?O in all samples with x greater than 0.0. Synchrotron X-ray absorption spectroscopy at the Fe k? edge performed on the sample with a Li-Fe ratio of 7.0 (i.e., x = 2.0) showed no evidence for the presence of FeII. This resistance to accepting more lithium into the Li?FeO? structure is attributed to the exceedingly stable nature of high-spin FeIII in tetrahedral "FeIIIO?" structural units of Li?FeO?. Partial substitution of the FeIII with other cations could provide a path toward increasing the reversible Li? content of Li5xFeO?-type phases. PMID:23876729

Maroni, Victor A; Johnson, Christopher S; Rood, Shawn C M; Kropf, A Jeremy; Bass, Dean A

2013-08-01

207

Effect of steric hindrance on carbon dioxide absorption into new amine solutions: thermodynamic and spectroscopic verification through solubility and NMR analysis.  

PubMed

Acid gas absorption technology is of great importance in these days for the prevention of global warming and the resulting worldwide climate change. More efficient process design and development for the removal of acid gases has become important, together with the development of new absorbents as one of urgent areas of research in addressing global-warming problems. In the present work, aqueous solutions of 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD), a sterically hindered amine, has been examined as a potential CO2 absorbent and compared with the most commonly used absorbent, monoethanolamine (MEA) solution, through equilibrium solubility measurements and 13C NMR spectroscopic analyses. The solubilities of CO2 in aqueous 10 mass % AHPD solutions were higher than those in aqueous 10 mass % MEA solutions above 4 kPa at 298.15 K, but below 4 kPa, the solubility behavior appeared to be the opposite. The solubility difference between these two solutions increased with the CO2 partial pressures above the crossover pressure. Equilibrated CO2-MEA-H2O and CO2-AHPD-H2O solutions at various CO2 partal pressures ranging from 0.01 to 3000 kPa were analyzed by 13C NMR spectroscopy to provide a more microscopic understanding of the reaction mechanisms in the two solutions. In the CO2-amine-H2O solutions, amine reacted with CO2 to form mainly the protonated amine (AMH+), bicarbonate ion (HCO3-), and carbamate anion (AMCO2-), where the quantitative ratio of bicarbonate ion to carbamate anion strongly influenced the CO2 loading in the amine solutions. A profusion of bicarbonate ions, but a very small amount of carbamate anions, was identified in the CO2-AHPD-H2O solution, whereas a considerable amount of carbamate anions was formed in the CO2-MEA-H2O solution. AHPD contains more hydroxyl groups than nonhindered MEA, and hence, the chemical shifts in its 13C NMR spectra were strongly influenced by the solution pH values. In contrast, MEA appeared to be insensitive to pH. The strong interrelations among CO2 solubility, CO2 partial pressure, bulkiness of the amine structure, and pH identified through the present experimental investigations can provide basic guidelines for finding new potential organic absorbents, including specifically designed amine chemicals. PMID:12731852

Park, Jung-Yeon; Yoon, Sang Jun; Lee, Huen

2003-04-15

208

Surface Effects of the HgI(2) Crystal Characterized by Spectroscopic Ellipsometry.  

PubMed

We report on determination of the surface effects of mercuric iodide (HgI(2)) uniaxial HgI(2) optical parameters with a fixed-polarizer, rotating-polarizer, and fixed-analyzer spectroscopic ellipsometer (PRPSE) after chemical polishing. The characteristics of the chemical complex [KHgI(3), H(2)O] that forms on the HgI(2) surface during KI etching have been investigated over the spectral range from 400 to 800 nm. Surface roughness and effects of the ellipsometric parameters of HgI(2) were treated, and the thickness of the layer formed on the surface was determined and analyzed by PRPSE. The surface roughness was modeled with the Bruggeman effective medium approximation. PMID:18360492

En Naciri, A; Johann, L; Kleim, R; Sieskind, M; Amann, M

2001-09-01

209

Chemical and spectroscopic characterization of water extractable organic matter during vermicomposting of cattle dung.  

PubMed

This work illustrated the characteristics and transformation of water extractable organic matter (WEOM) during vermistabilization (Eisenia fetida) of cattle dung by means of chemical and spectroscopic methods. The independent experiment conducted in triplicate was sampled at the 0, 7, 14, 21, 35, 60 and 90days. Results showed that the DOC kept steady around 2.7gkg(-1) after day 60 and the DOC/DON ratio decreased from 19.77 to 5.26 till the end of vermicomposting. On the other hand, vermicomposting decreased the aliphatic, proteinaceous, carbohydrates components and increased the aromaticity and oxygen-containing functional groups in the WEOM. Moreover, fluorescence spectra and fluorescence regional integration (FRI) results indicated that protein-like groups were degraded and fulvic and humic acid-like compounds were evolved during the vermicomposting process. In all, this study suggested the suitability of WEOM for monitoring the organics transformation and assessing the maturity in the vermicomposting. PMID:23416619

Lv, Baoyi; Xing, Meiyan; Yang, Jian; Qi, Wensheng; Lu, Yongsen

2013-01-16

210

IR-LD spectroscopic characterization of L-Tryptophan containing dipeptides.  

PubMed

IR-spectroscopic and stereo-structural analysis of aromatic l-Tryptophan containing dipeptides l-Tryptophan-l-Tryptophan (Trp-Trp), l-Tyrosine-l-Tryptophan (Tyr-Trp) and cyclo(Trp-Trp) have been carried out by means of solid-state linear-dichroic infrared (IR-LD) spectroscopy of oriented as suspension in nematic liquid crystal solids. The experimental data have been compared with analogous ones of the simple amino acids l-Tyrosnine (l-Tyr) and l-Tryptophan (l-Trp). In cyclo(Trp-Trp), the IR-spectral changes towards the IR-ones of acyclic Trp-Trp have been determined. A theoretical analysis of Tyr-Trp at Hartree-Fock level of theory and 6-31G** basis set is also applied. PMID:16488186

Ivanova, Bojidarka B

2006-02-20

211

Spectroscopic characterization and quantitative determination of atorvastatin calcium impurities by novel HPLC method  

NASA Astrophysics Data System (ADS)

Seven process related impurities were identified by LC-MS in the atorvastatin calcium drug substance. These impurities were identified by LC-MS. The structure of impurities was confirmed by modern spectroscopic techniques like 1H NMR and IR and physicochemical studies conducted by using synthesized authentic reference compounds. The synthesized reference samples of the impurity compounds were used for the quantitative HPLC determination. These impurities were detected by newly developed gradient, reverse phase high performance liquid chromatographic (HPLC) method. The system suitability of HPLC analysis established the validity of the separation. The analytical method was validated according to International Conference of Harmonization (ICH) with respect to specificity, precision, accuracy, linearity, robustness and stability of analytical solutions to demonstrate the power of newly developed HPLC method.

Gupta, Lokesh Kumar

2012-11-01

212

The experimental characterization of the absorption and scatter properties of photopolymers  

NASA Astrophysics Data System (ADS)

In this paper we studied the photosensitivity and scatter properties of several types of photopolymers that are used in the printing industry. We applied different measurement methodologies to experimentally characterize both the absorption and scatter properties of the photopolymers. In a first part we measured the absorption spectra of different unexposed photopolymers in the range between 350 and 1600 nm. From these spectra we calculated the absorbance coefficients. After this, we repeated this procedure for the cured material which we obtained by illuminating the photopolymers with a laser source. We investigated the absorption properties for different illumination times in the range between 0 and 2000 ms. From these measurements we could calculate for the different materials the difference in absorbance between the cured and the non-cured material. Depending on the material the absorbance of the non-cured material was a factor 20 to 60 higher compared to the absorbance of the cured material. These results were used as input for the optical model. In a next step we measured the BTDF for the different materials and calculated the scatter angle at 1/e2. As a result we obtained scatter angles between 2° and 6°. In a last step we verified and confirmed these differences in scatter behavior by measuring the MTF of a real imaging system that included the photopolymer.

Meulebroeck, Wendy; Meuret, Youri; Heyvaert, Stefaan; Thienpont, Hugo

2012-05-01

213

Fourier Transform Infrared Characterization of Moisture Absorption in SiOF Films  

NASA Astrophysics Data System (ADS)

In this paper, the water absorption characteristics of as-deposited and annealed liquid-phase-deposited fluorinated silicon oxide (LPD-SiOF) films were investigated to clarify the film properties. The stability of moisture absorption was characterized under an air-exposure environment of 23°C and 65% humidity. The as-deposited LPD-SiOF film was found to easily absorb moisture from air and therefore to become unstable in terms of the dielectric property. To obtain a highly stable dielectric film, a hydrofluosilicic acid concentration of 2.2 M (with the corresponding fluorine content of 4.9 at.%) is suggested because it has a minimum water absorption change (<3%). The related OH concentration was comparable (or even smaller) to those of other SiOF films grown by chemical vapor deposition. Moreover, high-temperature annealing in nitrogen ambient was utilized to drive out the moisture absorbed in an LPD-SiOF film. The annealing process after deposition tends to render the film surface hydrophobic. The resulting OH bonds were found to disappear after annealing and did not reappear even after long time of air exposure.

Chang, Wai-Jyh; Houng, Mau-Phon; Wang, Yeong-Her

1999-08-01

214

Spectroscopic Characterization of Thin Anodic Silicon Layers Grown by Short Monopulses of Current  

NASA Astrophysics Data System (ADS)

The optical properties of ultra thin anodic silicon layers containing silicon nanocrystals were investigated by photoluminescence spectroscopy and Fourier transform infrared absorption spectroscopy. The films were grown by electrochemical dissolution of bulk crystalline silicon at the early stages of anodization using short monopulses of anodic currents ranging from the regime of porous silicon formation to the transition regime between porosification and electropolishing. The conditions for obtaining light emitting films and the origin of light emission will be discussed.

Gardelis, Spiros; Jaziri, Sihem; Nassiopoulou, Androula G.

2007-09-01

215

Spectroscopic characterization of mechanisms of oxidation of Phe by SO 4 - radical: A pulse radiolysis study  

Microsoft Academic Search

By using time-resolved kinetic spectrophotometry and pulse radiolysis technique, the oxidation of Phe by SO4\\u000a - radical has been investigated both in aqueous and water\\/acetonitrile mixed solutions. The results reveal that attack of the\\u000a oxidizing SO4\\u000a - radical on Phe leads directly to the formation of Phe cation radical 3 with a strong absorption peak at 310 nm, then it

Gaosheng Chu; Shujuan Zhang; Side Yao; Zhenhui Han; Zhiwen Du; Zhicheng Zhang

2002-01-01

216

FTIR spectroscopic, thermal and XRD characterization of hydroxyapatite from new natural sources  

NASA Astrophysics Data System (ADS)

The inorganic constituents of 5 different plants (leaves and stalks) were investigated by using Fourier transformer infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermal analysis including thermal gravimetric analysis (TGA), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). These plants are Catha edulis (Khat), basil, mint, green tea and trifolium. The absorption bands of carbonate ions CO 32- was exhibited at 1446 cm -1, and the phosphate ions PO 43- was assigned at 1105 and 1035 cm -1. At high temperatures (600, 700 and 600 °C) further absorption bands of the phosphate ions PO 43- was assigned at the frequencies 572, 617, 962, 1043 and 1110 cm -1 and the vibrational absorption band of the carbonate ions CO 32- was assigned at 871, 1416 and 1461 cm -1. X-ray diffraction and thermal analysis confirm the obtained results of FITR. Results showed that the main inorganic constituents of C. edulis and basil leaves are hydroxyapatite whereas the hydroxyapatite content in the other plant samples is less than that in case of C. edulis and basil plant leaves.

Shaltout, Abdallah A.; Allam, Moussa A.; Moharram, Mohamed A.

2011-12-01

217

Spectroscopic characterization of polyethyleneglycol modified superoxide dismutase: 1H NMR studies on its Cu2Co2 derivative.  

PubMed

Spectroscopic methods have been employed in order to understand the molecular basis of the decrease in enzymatic activity of the antiinflammatory enzyme copper-zinc superoxide dismutase (SOD) following the covalent binding of polyethyleneglycol (PEG) chains to the protein amino-groups. The PEG modification is a general method recently proposed to improve the therapeutic index of enzymes. 1H NMR spectra on the cobalt substituted PEG-modified SOD, Cu2Co2-PEG-SOD, have been recorded. The signals are quite broad with respect to the unmodified enzyme. This has been interpreted on the basis of the effect of molecular weight on the linewidth. The analysis has shown that the histidine hydrogens involved in metal binding at the enzyme active site are the same in both native and PEG-modified SOD. Similarly, circular dichroism and absorption spectra indicate that the overall conformation of the metal clusters is not perturbed upon modification. On the other hand, azide titration shows that the affinity constant of N-3 for SOD is largely reduced upon PEG modification (K = 154 M-1 and 75 M-1 for the native and modified SOD, respectively). These results indicate that the decrease in enzymatic activity upon surface modification with PEG is not caused by a perturbation of the active site geometry, but to a decrease in the channeling of the O2- ion towards the enzyme active site. PMID:2166134

Banci, L; Bertini, I; Caliceti, P; Monsù Scolaro, L; Schiavon, O; Veronese, F M

1990-06-01

218

High-precision characterization of textured a-Si:H/SnO2:F structures by spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

Spectroscopic ellipsometry (SE) has been applied for the characterization of hydrogenated amorphous silicon (a-Si:H) layers formed on SnO2:F textured structures in an attempt to establish the structural characterization method for a-Si:H solar cells. In particular, an optical model that allows the complete evaluation of microscopically non-uniform a-Si:H/SnO2:F textured structures has been developed for the SE analysis. In order to express the complicated optical response in the textured structures, the optical model incorporates (i) the surface roughness and interface layers calculated using an effective-medium-approximation multilayer model and (ii) the a-Si:H/SnO2:F structure divided into two regions with different thicknesses. Using this optical model, SE spectra obtained experimentally from the a-Si:H/SnO2:F textured structure can be reproduced almost perfectly. The a-Si:H/SnO2:F structure deduced from the SE analysis shows remarkable agreement with that observed from transmission electron microscopy. Moreover, a variety of a-Si:H layers with different thicknesses are expressed from the identical optical model. The SE analysis method developed in this study can be utilized further to perform high-precision and non-destructive characterization of various a-Si:H layers incorporated in large-area a-Si:H modules.

Akagawa, Masataka; Fujiwara, Hiroyuki

2011-10-01

219

Complementary characterization of Ti–Si–C films by x-ray diffraction and absorption  

NASA Astrophysics Data System (ADS)

Advanced electronic devices based on III-N semiconductors, particularly these operated at the high power and high frequency or corrosive atmosphere, need elaboration of new technology for contacts metallization which are thermally and chemically stable. Performed studies aimed at the development of materials for applications in the improved metallization. Due to the unique combination of the metallic electro-thermal conductivity and ceramic resistance to oxidation and thermal stability, the MAX phases were chosen as the materials potentially applicable to this task. Particular interest lies in the MAX phases based on the Ti, Si and C or N atoms, especially on the Ti3SiC2 phase. The paper focuses on a comprehensive characterization of films grown by means of high-temperature magnetron Ti, Si and C co-sputtering. The complementary characterization by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) is presented.

Lawniczak-Jablonska, K.; Klepka, M. T.; Dynowska, E.; Wolska, A.; Borysiewicz, M. A.; Piotrowska, A.

2013-12-01

220

Biological activity studies on metal complexes of novel tridentate Schiff base ligand. Spectroscopic and thermal characterization  

Microsoft Academic Search

Metal complexes of novel Schiff base (HL) ligand, prepared via condensation of 4-aminoantipyrine and 2-aminophenol, are prepared. The ligand is characterized based on elemental analysis, mass, IR and 1H NMR spectra. Metal complexes are reported and characterized based on elemental analyses, IR, 1H NMR, solid reflectance, magnetic moment, molar conductance, ESR spectra and thermal analyses (TG, DTG and DTA). From

Gehad G. Mohamed; M. M. Omar; Amr A. Ibrahim

2009-01-01

221

Synthesis and spectroscopic characterization of fluorescent boron dipyrromethene-derived hydrazones.  

PubMed

Derivatives of 4,4-difluoro-4-bora-3a,4a,diaza-s-indacene (BODIPY® or BDP) that possess a hydrazine substituent on position 5 are potential "turn-on" fluorophores for labeling aldehydes The unnatural amino acid L-3-formyltyrosine can be incorporated into a protein or peptide; thus, these hydrazines are potentially site specific labels for such polymers. In this work, model compounds were synthesized to assess whether the photochemical properties of the BDP-hydrazone would be suitable for protein labeling. Hydrazones were synthesized from the fluorophore 3-chloro-5-hydrazino-BDP and different aldehydes, and the absorption and emission spectra of the products were compared. The hydrazone of an unsubstituted aromatic aldehyde displays absorption and emission maxima (531 nm and 559 nm, respectively in dioxane) that are red shifted relative to those of a hydrazone from an aliphatic aldehyde (513 nm and 543 nm, respectively, in dioxane) and an increased quantum yield (0.21 vs. 0.11, respectively, in dioxane). The presence of a hydroxyl group ortho- to the aldehyde produces a hydrazone in which the absorption and emission maxima are slightly red shifted (528 nm and 564 nm, respectively in dioxane) from the unsubstituted aromatic hydrazone, but the quantum yields of the two hydrazones are equivalent. Thus, an ortho-hydroxy substituted aromatic aldehyde is a suitable electrophile for "turn on" protein labeling using the hydrazino-BDP. The specificity of this labeling reaction for the unnatural amino acid was demonstrated through fluorescent labeling of just the 3-formyltyrosine-containing ?-subunit of ?,?-tubulin. PMID:20886269

Dilek, Ozlem; Bane, Susan L

2010-10-01

222

Synthesis and Spectroscopic Characterization of Fluorescent Boron Dipyrromethene-Derived Hydrazones  

PubMed Central

Derivatives of 4,4-difluoro-4-bora-3a,4a, diaza-s-indacene (BODIPY® or BDP) that possess a hydrazine substituent on position 5 are potential “turn-on” fluorophores for labeling aldehydes The unnatural amino acid L-3-formyltyrosine can be incorporated into a protein or peptide; thus, these hydrazines are potentially site specific labels for such polymers. In this work, model compounds were synthesized to assess whether the photochemical properties of the BDP-hydrazone would be suitable for protein labeling. Hydrazones were synthesized from the fluorophore 3-chloro-5-hydrazino-BDP and different aldehydes, and the absorption and emission spectra of the products were compared. The hydrazone of an unsubstituted aromatic aldehyde displays absorption and emission maxima (531 nm and 559 nm, respectively in dioxane) that are red shifted relative to those of a hydrazone from an aliphatic aldehyde (513 nm and 543 nm, respectively, in dioxane) and an increased quantum yield (0.21 vs. 0.11, respectively, in dioxane). The presence of a hydroxyl group ortho- to the aldehyde produces a hydrazone in which the absorption and emission maxima are slightly red shifted (528 nm and 564 nm, respectively in dioxane) from the unsubstituted aromatic hydrazone, but the quantum yields of the two hydrazones are equivalent. Thus, an ortho-hydroxy substituted aromatic aldehyde is a suitable electrophile for “turn on” protein labeling using the hydrazino-BDP. The specificity of this labeling reaction for the unnatural amino acid was demonstrated through fluorescent labeling of just the 3-formyltyrosine-containing ?-subunit of ?,?-tubulin.

Dilek, Ozlem

2011-01-01

223

Synthesis and spectroscopic characterization of water-soluble Mn-doped ZnO x S 1? x quantum dots  

Microsoft Academic Search

A non-cadmium and water-soluble Mn-doped ZnOxS1?x QDs was synthesized with denatured bovine serum albumin (dBSA) as stabilizer under nitrogen atmosphere, and the as-prepared products were characterized by X-ray powder diffraction (XRD), UV–vis absorption spectroscopy, fluorescence (FL) emission spectroscopy, high resolution transmission electronmicroscopy (HRTEM) and Raman spectrum. XRD patterns indicate that the Mn-doped ZnOxS1?x QDs have a zinc-blende structure, and that

Fangfang Xue; Jiangong Liang; Heyou Han

2011-01-01

224

Some polyhydroxy azo azomethine derivatives of salicylaldehyde: Synthesis, characterization, spectroscopic, molecular structure and antimicrobial activity studies  

NASA Astrophysics Data System (ADS)

Some new substituted polyhydroxy azo azomethine compounds were prepared by reaction of tris(hydroxymethyl)aminomethane with (E)-2-hydroxy-5-(phenyldiazenyl) benzaldehyde and its substituted derivatives. The structures of azo and azo azomethine compounds were determined by IR, UV vis, 1H NMR and 13C NMR spectroscopic techniques, and/or X-ray diffraction studies. According to IR spectra, all azo azomethine compounds adopt keto form in solid state. UV vis analysis has shown the presence of keto enol tautomerism in solution for all azo azomethine compounds, except that for nitro substituted derivative, enol form is dominantly favored in solution. At the same time, above mentioned derivative compounds were studied in vitro for their antimicrobial properties. Among the phenylazosalicylaldehyde series compound tested, 4-phenylazosalicylaldehyde, 4-(3-chlorophenylazo)salicylaldehyde, 4-(2-chlorophenylazo)salicylaldehyde, 4-(4-fluorophenylazo)salicylaldehyde, 4-(3-chlorophenylazo)salicylaldehyde and 4-(4-ethylphenylazo)salicylaldehyde showed a weak antimicrobial activity only against gram positive bacteria. On the contrary, phenylazosalicylaldehyde series compounds were reacted tris(hydroxmethyl)aminomethane, that exhibited a strong antimicrobial activity against gram positive bacteria, yeast and mould. Moreover, while the 2-{[1,3-dihydroxy-2-(hydroxymethyl)propan-2-ylimino]methyl}phenol did not show an inhibition on tested microorganism, the addition of phenyldiazine groups to 2-{[1,3-dihydroxy-2-(hydroxymethyl)propan-2-ylimino]methyl}phenol resulted in a strong increases in antimicrobial activity.

Odaba?o?lu, Mustafa; Albayrak, Çi?dem; Özkanca, Re?it; Aykan, Fatma Zehra; Lonecke, Peter

2007-09-01

225

Minerals from Macedonia XXIII. Spectroscopic and structural characterization of schorl and beryl cyclosilicates.  

PubMed

IR and Raman spectroscopy study on two collected cyclosilicate species: schorl (from tourmaline group), Na(Fe,Mg)(3)Al(6)(BO(3))(3)Si(6)O(18)(OH,F)(4) and beryl (Be,Mg,Fe)(3)Al(2)Si(6)O(18) were carried out. Although beryl is nominally anhydrous mineral, vibrational results strongly indicate that H(2)O molecules exist in the structural channels. The number of vibrational bands and their frequencies revealed the presence of H(2)O type II, in which C(2) symmetry axis of the water molecule is parallel to the structural channel (and to the c-axis of beryl). On the other hand, it was found that observed bands in the IR and Raman OH stretching region of the other tourmaline varieties appear as a result of the cation combinations involving dominant presence of Mg and Fe cations in the Y structural sites. The strong indication derived from the vibrational spectroscopic results that the studied mineral represents a schorl variety, coincide very well with the results obtained by powder X-ray diffraction and X-ray microprobe analysis. Both minerals show IR spectral similarities in the region below 1500 cm(-1), whereas the resemblance between the Raman spectra (1500-100 cm(-1)) is less expressed confirming that these spectra are more sensitive to compositional changes and to structural disorder. The identification of both minerals was additionally supported by studying the powder X-ray diffraction diagrams. PMID:18722809

Makreski, Petre; Jovanovski, Gligor

2008-07-17

226

Cloning, overexpression, purification, and spectroscopic characterization of human S100P.  

PubMed Central

The calcium-binding protein S100P has been found to be associated with human prostate cancer. We have overexpressed S100P in Escherichia coli using a T7 expression system. A rapid two-step procedure for the isolation of overexpressed S100P leads to a preparation of >95% pure protein with a yield of approximately 150 mg per liter of culture. The structural integrity of recombinant S100P was analyzed using CD and fluorescence spectroscopic techniques. The far-UV CD shows that secondary structure of recombinant S100P consists predominantly of a-helical structure. Both near-UV CD and tyrosine fluorescence spectra show that aromatic residues are involved in the formation of a specific, well packed structure, indicating that the recombinant S100P protein adopts a compact folded conformation. Ca2+ has a profound effect on S100P structure. Near-UV CD and fluorescence intensity of both internal (tyrosine) and external (ANS) probes suggest significant structural rearrangements in the tertiary structure of the molecule. The similarity of far-UV CD spectrum of S100P in the presence and in the absence of Ca2+ suggests that Ca2+ binding has only minor effects on secondary structure.

Gribenko, A.; Lopez, M. M.; Richardson, J. M.; Makhatadze, G. I.

1998-01-01

227

Spectroscopic and Chromatographic Characterization of Wastewater Organic Matter from a Biological Treatment Plant  

PubMed Central

Spectroscopic and chromatographic changes in dissolved organic matter (DOM) characteristics of influent and treated sewage were investigated for a wastewater treatment plant (WWTP) with a biological advanced process. Refractory DOM (R-DOM) was defined as the dissolved organic carbon concentrations of the samples after 28-day incubation for this study. Specific UV absorbance (SUVA), hydrophobicity, synchronous fluorescence spectra and molecular weight (MW) distributions were selected as DOM characteristics. The percent distribution of R-DOM for the effluent was much higher than that of the influent, indicating that biodegradable DOM was selectively removed during the process. Comparison of the influent versus the effluent sewage revealed that SUVA, fulvic-like fluorescence (FLF), humic-like fluorescence (HLF), the apparent MW values were enhanced during the treatment. This suggests that more aromatic and humic-like compounds were enriched during the biological process. No significant difference in the DOM characteristics was observed between the original effluent (i.e., prior to the incubation) and the influent sewage after the incubation. This result suggests that the major changes in wastewater DOM characteristics occurring during the biological advanced process were similar to those for simple microbial incubation.

Park, Min-Hye; Lee, Tae-Hwan; Lee, Bo-Mi; Hur, Jin; Park, Dae-Hee

2010-01-01

228

Evaluation of optical parameters and characterization of ultrasonically sprayed MgO films by spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

MgO is a chemically stable buffer layer and a good candidate with its unique optical and structural characteristics such as low refractive index and good lattice matching for the deposition of technologically important materials. In this work, we have produced MgO films by a low cost ultrasonic spray pyrolysis technique and tried to improve their characteristics by thermal annealing. MgO films have been obtained on glass substrates at 325 ± 5 °C and annealed at two different temperatures as 500 °C and 600 °C for 2 h. Elemental analyses have been made by energy-dispersive X-ray spectroscopy. Thicknesses, refractive indices and extinction coefficient values have been determined by spectroscopic ellipsometry technique using Cauchy-Urbach model. Band gap values of the films have been calculated using the absorbance spectra and optical method. X-ray diffraction patterns have been used to investigate the structural properties and to calculate lattice parameters. Atomic force microscope images have been taken to see the effect of thermal annealing on surface morphology. Electrical resistivity values of the films have been determined using a four-point probe set-up. As a result, annealing temperature has a strong effect on the mentioned properties and a low cost ultrasonic spray pyrolysis technique allows the production of new and alternative MgO buffer layers for technological applications.

Kurtaran, S.; Akyuz, I.; Atay, F.

2013-01-01

229

Spectroscopic characterization of Coomassie blue and its binding to amyloid fibrils.  

PubMed

Coomassie brilliant blue G-250 (CB) is the dye used frequently in the Bradford assay for protein concentration determination. In this study, we investigated how the solvent polarity and viscosity affect the CB absorption and fluorescence spectra and apply this understanding to investigate the binding of CB to lysozyme and insulin in the native and amyloid fibril states. Coomassie blue binds both to the native protein and to amyloid fibrils but gives distinctly different spectral responses. The absorption and fluorescence spectra of CB indicate that binding sites in the fibrils are less polar and hold the CB dye more rigidly than in the native forms. The spectral comparison of CB bound to the two different fibrils showed that the binding sites are different, and this was most likely due to differences in secondary structure as monitored by circular dichroism. Finally, linear dichroism was used to show that the fibril-bound CB is oriented preferentially parallel to the insulin amyloid fibril axis. PMID:21945461

Carlsson, Nils; Kitts, Catherine C; Åkerman, Björn

2011-08-31

230

Characterizing Widespread Oxidation Processes on Mars: Alteration Rind Development and Effects on Spectroscopic Investigations  

NASA Astrophysics Data System (ADS)

The chemical, mineralogical, and spectral products of oxidation are characterized using a variety of laboratory techniques. Orbital and in situ observations of the martian surface suggest that this process is widespread and spectrally significant.

Salvatore, M. R.; Mustard, J. F.; Head, J. W.; Cooper, R. F.; Marchant, D. R.; Wyatt, M. B.

2012-03-01

231

Arsenate uptake by calcite: Macroscopic and spectroscopic characterization of adsorption and incorporation mechanisms  

NASA Astrophysics Data System (ADS)

Batch uptake experiments and X-ray element mapping and spectroscopic techniques were used to investigate As(V) (arsenate) uptake mechanisms by calcite, including adsorption and coprecipitation. Batch sorption experiments in calcite-equilibrated suspensions (pH 8.3; PCO 2 = 10 -3.5 atm) reveal rapid initial sorption to calcite, with sorption rate gradually decreasing with time as available sorption sites decrease. An As(V)-calcite sorption isotherm determined after 24 h equilibration exhibits Langmuir-like behavior up to As concentrations of 300 ?M. Maximum distribution coefficient values ( Kd), derived from a best fit to a Langmuir model, are ˜190 L kg -1. Calcite single crystals grown in the presence of As(V) show well-developed rhombohedral morphology with characteristic growth hillocks on (101¯4) surfaces at low As(V) concentrations (?5 ?M), but habit modification is evident at As(V) concentrations ?30 ?M in the form of macrostep development preferentially on the - vicinal surfaces of growth hillocks. Micro-X-ray fluorescence element mapping of (101¯4) surfaces shows preferential incorporation of As in the - vicinal faces relative to + vicinals. EXAFS fit results for both adsorption and coprecipitation samples confirm that As occurs in the 5+ oxidation state in tetrahedral coordination with oxygen, i.e., as arsenate. For adsorption samples, As(V) forms inner-sphere surface complexes via corner-sharing with Ca octahedra. As(V) coprecipitated with calcite substitutes in carbonate sites but with As off-centered, as indicated by two Ca shells, and with likely disruption of local structure. The results indicate that As(V) interacts strongly with the calcite surface, similar to often-cited analog phosphate, and uptake can occur via both adsorption and coprecipitation reactions. Therefore, calcite may be effective for partial removal of dissolved arsenate from aquatic and soil systems.

Alexandratos, Vasso G.; Elzinga, Evert J.; Reeder, Richard J.

2007-09-01

232

Optical spectroscopic characterization of single tryptophan mutants of chicken skeletal troponin C: evidence for interdomain interaction.  

PubMed

The effects of metal ion binding on the optical spectroscopic properties and temperature stability of two single tryptophan mutants of chicken skeletal TnC, F78W and F154W, have been examined. The absence of tyrosine and other tryptophan residues allowed the unambiguous assignment of the spectral signal from the introduced Trp residue. Changes in the molar ellipticity values in the far-UV CD spectra of the mutant proteins on metal ion binding were similar to those of wild-type TnC suggesting that the introduction of the Trp residue had no effect on the total secondary structure content. The fluorescence and near-UV absorbance data reveal that, in the apo state, Trp-78 is buried while Trp-154 is exposed to solvent. Additionally, the highly resolved (1)L(b) band of Trp-78 seen in the near-UV absorbance and CD spectra of the apo state of F78W suggest that this residue is likely in a rigid molecular environment. In the calcium-saturated state, Trp-154 becomes buried while the solvent accessibility of Trp-78 increases. The fluorescence emission and near-UV CD of Trp-78 in the N-terminal domain were sensitive to calcium binding at the C-terminal domain sites. Measurements of the temperature stability reveal that events occurring in the N-terminal domain affect the stability of the C-terminal domain and vice versa. This, coupled with the titration data, strongly suggests that there are interactions between the N- and C-terminal domains of TnC. PMID:10508400

Moncrieffe, M C; Venyaminov, S Y; Miller, T E; Guzman, G; Potter, J D; Prendergast, F G

1999-09-14

233

First-principles spectroscopic characterization of PbSe nanoparticles passivated with Fe complexes  

NASA Astrophysics Data System (ADS)

Given that defining characteristics of nanoparticles -- morphology, catalytic reactivity, optical and electronic properties -- are often dictated by their surfaces, it is informative to investigate how surface chemistry and structure change as different ligands are introduced to the surface. Starting with oleate-passivated PbSe nanoparticles, we remove the oleate ligands and replace them with an organometallic complex: cyclopentadienyl iron dicarbonyl. Measured and calculated x-ray photoemission core-level shifts indicate a charge transfer between surface Pb atoms and Fe atoms. We investigate the nature of this charge transfer in more detail through analysis of x-ray absorption spectra (XAS) at the Fe L-edge. Fe XAS are calculated from first-principles using a GW-based Bethe-Salpeter approach. The spectra reveal that the extent to which pi-backbonding is possible between the Fe and associated carbonyls varies with the charge density on the Fe atom.

Gilmore, Keith; Hammack, Aaron; Sawvel, April; Rosen, Evelyn; Ogletree, D. Frank; Urban, Jeffrey; Milliron, Delia; Helms, Brett; Cohen, Bruce; Prendergast, David

2012-02-01

234

Synthesis, isolation and spectroscopic characterization of Yb-containing high metallofullerenes  

NASA Astrophysics Data System (ADS)

Here we report the first isolation of a series of Yb-containing high metallofullerene based on C 88/C 90/C 92/C 94, along with C 88, C 90 (I, II), C 92, C 94 (I, II) and C 96. Furthermore, the electronic structures of these high fullerenes and metallofullerenes are discussed according to their absorption spectra. It is concluded that for high metallofullerenes, there are usually different isomers with different molecular symmetries while the encaged metal is different, which differs from the case of other small metallofullerenes. In addition, from the discussion of the electronic structural features of the isolated high fullerenes, one can see the special electronic structures of C 94s.

Xu, Jianxun; Wang, Zhiyong; Shi, Zujin; Gu, Zhennan

2005-06-01

235

UV–vis absorption spectroscopic study for on-line monitoring of uranium concentration in LiCl–KCl eutectic salt  

Microsoft Academic Search

UV–vis absorption spectroscopy of uranium in LiCl–KCl eutectic salt at 773K was studied for the on-site use in pyrochemical process. Uranium(III) chloride was electrochemically prepared from uranium metal in LiCl–KCl eutectic salt at 773K by using chronopotentiometry. Three absorption peak positions were selected and calibrated for the quantitative analysis of uranium in the molten salt medium. The molar absorptivity and

Y. J. Park; S. E. Bae; Y. H. Cho; J. Y. Kim; K. Song

2011-01-01

236

Preparation and Spectroscopic Characterization of MoS2 and MoSe2 Nanoparticles  

Microsoft Academic Search

In this manuscript, we report an experiment for the upper division chemistry laboratory involving the synthesis and characterization of molybdenum (IV) chalcogenide nanoparticles. The reaction is a straightforward synthesis between molybdenum hexacarbonyl and sulfur or selenium. Students follow the progress of the reaction via monitoring the carbonyl stretch using Fourier transform infrared (FTIR) spectroscopy. The nanoparticles are found to absorb

Brian C. Helmly; Will E. Lynch; Delana A. Nivens

2007-01-01

237

Structural characterization of Ni-Al (111) interface by surface x-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

The evolution of the Ni/Al(111) interface has been studied in situ by x-ray absorption spectroscopy at the Ni-K edge. Ni films were deposited on bulk Al(111) with thickness ranging from 2 monolayers (ML) up to 30 ML. The aim was to determine the diffusion length of Ni and the phases that have formed. Ni diffused spontaneously at room temperature to a depth that we estimated to be of the order of 11 ML. The structure of Ni/Al(111) mixed interface has been characterized by x-ray absorption spectroscopy. With respect to previous studies on Al(110) the first phase formed on Al(111) is Al3Ni2-like instead of AlNi-like. Accordingly to previous observations, an AlNi3 phase forms on top of Al3Ni2 after the deposition of the first few monolayers. We propose that the pure Ni growth observed after deposition of 11 ML is due to the presence of the AlNi3 aluminide that acts as a diffusion barrier preventing deeper Ni penetration into Al at room temperature.

Damoc, L.; Fonda, E.; Le Fevre, P.; Traverse, A.

2002-08-01

238

Characterization of vibrational wave packets by core-level high-harmonic transient absorption spectroscopy  

NASA Astrophysics Data System (ADS)

The ground-state vibrational wave packet produced by strong-field ionization of Br2 is characterized by femtosecond high-harmonic transient absorption spectroscopy. Vibrational motion is observed in time by a change in the 3d core-level transition energy with bond length 0.14 eV/pm to higher energies at shorter bond lengths. The wave packet has the expected period of 104 fs for the predominant v0v1 vibrational quantum beat, which is prepared near the outer turning point with a phase of 0.21?±0.05? due to the preferential ionization at short bond lengths. Simultaneous observation of a wave packet on the Br2+2?g,3/2 ground state, prepared at the equilibrium bond distance of the ion, confirms preferential ionization near the inner turning point of the neutral. The Br2 ground-state wave packet has a degree of coherence ranging between 0.19 and 0.24, where unity is perfect coherence. The results utilize the sensitivity of core-level transient absorption spectroscopy to bond length and charge state, providing a means to analyze the formation and evolution of vibrational wave packets.

Hosler, Erik R.; Leone, Stephen R.

2013-08-01

239

Purification and initial kinetic and spectroscopic characterization of NO reductase from Paracoccus denitrificans.  

PubMed

A new and relatively simple procedure to purify NO reductase from Paracoccus denitrificans by using the detergent lauryl maltoside has been developed. The purified enzyme consists of two subunits according to SDS polyacrylamide gel electrophoresis. Analysis of the content of prosthetic groups indicates the presence of non-haem iron in addition to the presence b and c cytochromes yielding a stoichiometry of haem b/haem c/non-haem iron = 2:1:1. The optical spectrum of reduced NO reductase shows bands of low-spin haem c and haem b with alpha-band absorbance maxima at 551 nm and 558 nm, respectively. The optical spectrum of oxidized NO reductase shows a broad absorbance hand around 590 nm which disappears upon reduction. This latter absorbance is ascribed to a high-spin haem b (charge-transfer) transition. The presence of high-spin haem b is also indicated by the shifts observed in the optical spectrum of oxidized NO reductase in the presence of NO or in the spectrum of reduced enzyme after addition of CO. The main features of the EPR spectrum of the oxidized enzyme are resonances from a highly anisotropic low-spin haem b (gz = 3.53) and from an anisotropic low-spin haem c with gz, y, x = 2.99, 2.28, 1.46, the two haems being present in an approximate 1:1 stoichiometry. Minor signals representing about 1% of the enzyme concentration due to high-spin haem b (g = 5.8-6.2) and a novel type of signal with g = 2.009 ascribed to high-spin non-haem ferric iron were also observed. The analysis of steady-state kinetic measurements of the NO reductase activity shows a sigmoidal relation between rate of NO reduction and NO concentration, consistent with a model describing sequential binding of two molecules of NO to the reduced enzyme. At high NO concentrations substrate inhibition occurs (Ki(apparent) = 13.5 microM) suggested to be due to binding of NO to oxidized enzyme. The absence from the EPR spectrum of signals originating from ferric non-haem iron and ferric high-spin haem b in stoichiometric amounts with respect to the enzyme concentration is suggested to be due to an antiferromagnetic coupling between these two centers. The steady-state kinetic behaviour and the optical and EPR spectroscopic properties of the NO reductase are incorporated into a tentative structural and mechanistic model. PMID:9030265

Girsch, P; de Vries, S

1997-01-16

240

Arsenate Uptake by Calcite: Macroscopic and Spectroscopic Characterization of Adsorption and Incorporation Mechanisms  

SciTech Connect

Batch uptake experiments and X-ray element mapping and spectroscopic techniques were used to investigate As(V) (arsenate) uptake mechanisms by calcite, including adsorption and coprecipitation. Batch sorption experiments in calcite-equilibrated suspensions (pH 8.3; PCO{sub 2} = 10{sup -3.5} atm) reveal rapid initial sorption to calcite, with sorption rate gradually decreasing with time as available sorption sites decrease. An As(V)-calcite sorption isotherm determined after 24 h equilibration exhibits Langmuir-like behavior up to As concentrations of 300 {mu}M. Maximum distribution coefficient values (K{sub d}), derived from a best fit to a Langmuir model, are {approx}190 L kg{sup -1}. Calcite single crystals grown in the presence of As(V) show well-developed rhombohedral morphology with characteristic growth hillocks on (10{bar 1}4) surfaces at low As(V) concentrations ({<=}5 {mu}M), but habit modification is evident at As(V) concentrations {>=}30 {mu}M in the form of macrostep development preferentially on the - vicinal surfaces of growth hillocks. Micro-X-ray fluorescence element mapping of (10{bar 1}4) surfaces shows preferential incorporation of As in the - vicinal faces relative to + vicinals. EXAFS fit results for both adsorption and coprecipitation samples confirm that As occurs in the 5+ oxidation state in tetrahedral coordination with oxygen, i.e., as arsenate. For adsorption samples, As(V) forms inner-sphere surface complexes via corner-sharing with Ca octahedra. As(V) coprecipitated with calcite substitutes in carbonate sites but with As off-centered, as indicated by two Ca shells, and with likely disruption of local structure. The results indicate that As(V) interacts strongly with the calcite surface, similar to often-cited analog phosphate, and uptake can occur via both adsorption and coprecipitation reactions. Therefore, calcite may be effective for partial removal of dissolved arsenate from aquatic and soil systems.

Alexandratos,V.; Elzinga, E.; Reeder, R.

2007-01-01

241

Spectroscopic Characterization of Intermediates in the Iron Catalyzed Activation of Alkanes  

SciTech Connect

The present report begins with a brief survey of recent hypervalent iron chemistry and mentions two previously reported ferrate papers funded by the DOE/BES grant. The focus is then shifted to the seven publications acknowledging support of the grant that have not been reported since the last Progress Report, DOE/ER/14340-9, was prepared. These papers deal with: (a) the successful use of an ATR element in a stopped-flow infrared spectrometer, (b) the rationalization of a depolarization of a LiClO4 solution in polyethylene oxide high polymer, (c) an analysis of several coupled ultrasonic relaxations observed in solutions of pentoses undergoing isomerization, (d) the combination of ultrasonic absorption and Raman scattering measurements to elucidate zinc thiocyanate solutions in water, (e) the use of NMR to determine stability constants when LiClO4:12-crown-4 is dissolved in acetonitrile and in methanol, (f) the possible existence of triple ions in low permittivity solutions, and (g) the properties of a high surface area ceria aerogel. Collectively, these papers illustrate advantages of bringing several modern experimental techniques to bear on complex chemical systems.

Edward M. Eyring

2007-05-28

242

Steady state and time-resolved fluorescence spectroscopic characterization of normal and cancerous urine  

NASA Astrophysics Data System (ADS)

Urine is one of the diagnostically important bio fluids, as it has many metabolites and some of them are native fluorophores. There may be a variation in the distribution and the physiochemical properties of the fluorophores during any metabolic change and pathologic conditions. Native fluorescence spectroscopy has been considered as a promising tool to characterize the fluorophores present in the urine. In this study, we aimed at characterizing the urine of both normal and patients with confirmed cancer using steady state and time-resolved fluorescence spectroscopy at 280 nm and 350 nm excitation. It is observed that the metabolites indoxyl sulphate and neopterin and its derivatives are responsible for altered spectral signatures at 280 nm, and 350 nm excitation. The overall spectral data were subjected to Principal Component Analysis and the resultant components were used as input in the linear discriminant analysis. As a total, 84% and 81.8% of samples were correctly classified at 280 nm and 350 nm respectively.

Rajasekaran, Ramu; Aruna, Prakasa Rao; Balu David, Munusamy; Koteeswaran, Dornadula; Muthuvelu, Kulandaivel; Rai, R.; Ganesan, Singaravelu

243

Structural implications of spectroscopic characterization of a putative zinc finger peptide from HIV-1 integrase.  

PubMed

The N-terminal domain of human immunodeficiency virus (HIV-1) integrase (IN) contains the sequence motif His-Xaa3-His-Xaa23-Cys-Xaa2-Cys, which is strongly conserved in all retroviral and retrotransposon IN proteins. This structural motif constitutes a putative zinc finger in which a metal ion may be coordinately bound by the His and Cys residues. A recombinant peptide, IN(1-55), composed of the N-terminal 55 amino acids of HIV-1 IN was expressed in Escherichia coli and purified. Utilizing a combination of techniques including UV-visible absorption, circular dichroism, Fourier transform infrared, and fluorescence spectroscopies, we have demonstrated that metal ions (Zn2+, Co2+, and Cd2+) are bound with equimolar stoichiometry by IN(1-55). The liganded peptide assumes a highly ordered structure with increased alpha-helical content and exhibits remarkable thermal stability. UV-visible difference spectra of the peptide-Co2+ complexes directly implicate thiols in metal coordination, and Co2+ d-d transitions in the visible range indicate that Co2+ is tetrahedrally coordinated. Mutant peptides containing conservative substitutions of one of the conserved His or either of the Cys residues displayed no significant Zn(2+)-induced conformational changes as monitored by CD and fluorescence spectra. We conclude that the N terminus of HIV-1 IN contains a metal-binding domain whose structure is stabilized by tetrahedral coordination of metal by histidines 12 and 16 and cysteines 40 and 43. A preliminary structural model for this zinc finger is presented. PMID:1577801

Burke, C J; Sanyal, G; Bruner, M W; Ryan, J A; LaFemina, R L; Robbins, H L; Zeft, A S; Middaugh, C R; Cordingley, M G

1992-05-15

244

UV spectroscopic characterization of an alkyl substituted Criegee intermediate CH3CHOO  

NASA Astrophysics Data System (ADS)

Ozonolysis of alkenes in the troposphere proceeds through a Criegee intermediate, or carbonyl oxide, which has only recently been detected in the gas phase. The present study focuses on the production of an alkyl-substituted Criegee intermediate, CH3CHOO, in a pulsed supersonic expansion, and then utilizes VUV photoionization at 118 nm and UV-induced depletion of the m/z = 60 signal to probe the B 1A' <-- X 1A' transition. The UV-induced depletion approaches 100% near the peak of the profile at 320 nm, indicating rapid dynamics in the B state, and corresponds to a peak absorption cross section of ~5 × 10-17 cm2 molecule-1. The electronic spectrum for CH3CHOO is similar to that reported recently for CH2OO, but shifted 15 nm to shorter wavelength, which will result in a longer tropospheric lifetime for CH3CHOO with respect to solar photolysis. Complementary electronic structure calculations (EOM-CCSD) are carried out for the B and X potentials of these Criegee intermediates along the O-O coordinate. An intramolecular interaction stabilizes the ground state of the syn-conformer of CH3CHOO relative to anti-CH3CHOO, and indicates that the syn-conformer will be the more abundant species in the expansion. The excited B electronic state of syn-CH3CHOO is also predicted to be destabilized relative to that for anti-CH3CHOO and CH2OO, in accord with the shift in the B-X transition observed experimentally. Hydroxyl radicals produced concurrently with the generation of the Criegee intermediates are detected by 1+1' resonance enhanced multiphoton ionization. The OH yield observed with CH3CHOO is 4-fold larger than that from CH2OO, consistent with prior studies of OH generation from alkene ozonolysis.

Beames, Joseph M.; Liu, Fang; Lu, Lu; Lester, Marsha I.

2013-06-01

245

Infrared spectroscopic characterization of the low-albedo materials on Iapetus  

NASA Astrophysics Data System (ADS)

Iapetus, one of the large satellites of Saturn, has been studied over the centuries for its signature brightness contrast, light on one side and dark on the opposite. It has recently been suggested that the dark material is a combination of native and exogenous materials with distinct histories. We present an analysis of parts of the Cassini Regio, the darkest region on the leading hemisphere of Iapetus, focusing on the hydrocarbon signature with a view to detect and investigate differences in the material(s). We find variations in the hydrocarbon bands with geographic location, one type predominantly located on the leading hemisphere. A comparison with the equivalent spectral features on Phoebe and Hyperion reveals a predictable resemblance between the leading hemisphere material and Phoebe and an unexpected likeness between Hyperion's darkest material and Iapetus' trailing hemisphere surface. An analysis of the slope in the visible part of the spectrum is strongly affected by a rise in the continuum (˜0.35-0.65 ?m) attributed to Rayleigh scattering from nano-size particles on the surface. The continuum rise varies in strength with the albedo and H2O ice content, and when it is properly accounted for, the overall slope in all the identified spectral units is the same over the interval 0.35-2.3 ?m, independent of albedo or ice abundance. The interpretation of current and previous results offers two different scenarios illustrated by the presence of one vs. two dark materials distributed over the Iapetus surface. We describe the scenarios and their implications. The appearance of the aromatic and aliphatic absorption bands together in their measured relative strengths makes this spectral signature unique, and thus enables the comparison among the three satellites.

Dalle Ore, Cristina Morea; Cruikshank, Dale P.; Clark, Roger N.

2012-11-01

246

Infrared Spectroscopic Characterization of the Low-Albedo Materials on Iapetus  

NASA Astrophysics Data System (ADS)

Iapetus, one of the large satellites of Saturn, has been studied over the centuries for its trademark brightness contrast, light on one side and dark on the opposite. On the basis of multicolor images from the Cassini imaging system, Denk et al. (2010, Science 327, 435) have suggested that the dark material is a combination of native and exogenous materials with distinct histories. We present a Cassini VIMS analysis of parts of the Cassini Regio, the darkest region on the leading hemisphere of Iapetus, focusing on the hydrocarbon signature with a view to detect and investigate differences in the material(s). We find variations in the hydrocarbon bands with geographic location, one type predominantly located on the leading hemisphere. A comparison with the equivalent spectral features on Phoebe and Hyperion reveals a predictable resemblance between the leading hemisphere material and Phoebe and an unexpected likeness between Hyperion’s darkest material and Iapetus’ trailing hemisphere surface. The slope in the visible part of the spectrum, from which Denk's analysis is derived, is strongly affected by a rise in the continuum ( 0.35 - 0.65 µm) attributed to Rayleigh scattering from nano-size particles (Clark et al. 2012, Icarus 218, 831). The continuum rise varies in strength with albedo and H2O ice content, and when it is properly accounted for, the overall slope in all the identified spectral units is the same over the interval 0.35 - 2.3 µm, independent of albedo or ice abundance. The interpretation of current and previous results offers two different scenarios illustrated by the presence of one vs. two dark materials distributed over Iapetus' surface. The appearance and relative strengths of the aromatic and aliphatic absorption bands make this spectral signature unique, enabling the comparison among the satellites. The authors acknowledge support from Cassini Science Team funding and NASA grant NNX11AN90G.

Dalle Ore, Cristina M.; Cruikshank, D. P.; Clark, R. N.

2012-10-01

247

[UV-Vis spectroscopic characterization of active components from Scutellaria baicalensis georgi].  

PubMed

The molecular structures of three active components from scutellaria baicalensis have been studied by ultraviolet-visible spectra. The index flavonoid structures and substituted positions were deduced by analyzing the UV-Vis spectra in the methanol solution of three active components and the methanol solution with 5 diagnostic reagents, NaOMe, NaOAc, NaOAc/H3BO3, AlCl3, AlCl3/HCl respectively, which provided strong evidences for the structural characterization of the active components from natural products. PMID:17390668

Li, Yun-xia; Suo, Quan-ling; He, Wen-zhi; Li, Chun-ping; Huang, Yan-chun

2007-01-01

248

Optical spectroscopic approach as a rapid tool to characterize the interactions of retinoids with human nuclear receptors  

NASA Astrophysics Data System (ADS)

Retinoids are potent molecules that can affect a variety of fundamental biological processes including cell differentiation and proliferation and apoptosis. These molecules elicit their biological effects by activating a family of nuclear receptors which act as ligand-inducible transcription factors belonging to the steroid/thyroid receptor superfamily. Retinoic acid receptors form heterodimers in which response to ligand binding, both partners contribute to transactivation and/or DNA binding in vivo. Surface-enhanced Raman scattering (SERS), Fourier transform-SERS (FT-SERS), fluorescence and circular dichroism are proposed to rapidly give information on the interaction of the different RARs and RXRs with their specific ligands at physiological concentrations. FT-SERS data reveal a significant attenuation in intensity of the bands originating from the retinoic polyenic chain upon complexation. The spectrum is dominantly of the (Beta) - ionone ring. Fluorescence measurements supported the hydrophobic character of the ligand binding pocket and the circular dichroic data indicate that the protein helices extend upon ligand binding. These novel spectroscopic information are fully consistent with published x-ray crystallographic results and suggest that these techniques may be valuable additional tools to characterize the interactions of agonists and antagonists with residues of the ligand binding pocket retinoid receptor homo- and hetero-dimers.

Morjani, Hamid; Sockalingum, Ganesh D.; Beljebbar, Abdelilah; Manfait, Michel

1998-04-01

249

Spectroscopic and kinetic characterization of the light-dependent enzyme protochlorophyllide oxidoreductase (POR) using monovinyl and divinyl substrates  

PubMed Central

The enzyme POR [Pchlide (protochlorophyllide) oxidoreductase] catalyses the reduction of Pchlide to chlorophyllide, which is a key step in the chlorophyll biosynthesis pathway. This light-dependent reaction has previously been studied in great detail but recent reports suggest that a mixture of MV (monovinyl) and DV (divinyl) Pchlides may have influenced some of these properties of the reaction. Low-temperature absorbance and fluorescence spectroscopy have revealed several spectral differences between MV and DV Pchlides, which were purified from a Rhodobacter capsulatus strain that was shown to contain a mixture of the two pigments. A thorough steady-state kinetic characterization using both Pchlide forms demonstrates that neither pigment appears to affect the kinetic properties of the enzyme. The reaction has also been monitored following illumination at low temperatures and was shown to consist of an initial photochemical step followed by four ‘dark’ steps for both pigments. However, minor differences were observed in the spectral properties of some of the intermediates, although the temperature dependency of each step was nearly identical for the two pigments. This work provides the first detailed kinetic and spectroscopic study of this unique enzyme using biologically important MV and DV substrate analogues. It also has significant implications for the DV reductase enzyme, which is responsible for converting DV pigments into their MV counterparts, and its position in the sequence of reactions that comprise the chlorophyll biosynthesis pathway.

Heyes, Derren J.; Kruk, Jerzy; Hunter, C. Neil

2005-01-01

250

Synthesis, spectroscopic, structural characterization, electrochemical and antimicrobial activity studies of the Schiff base ligand and its transition metal complexes.  

PubMed

In this study, the Schiff base ligand trans-N,N'-bis[(2,4-dichlorophenyl) methylidene] cyclohexane-1,2-diamine (L) and its copper(II), nickel(II) and palladium(II) transition metal complexes were prepared and characterized by the analytical and spectroscopic methods. The (1)H((13)C) NMR spectra of the ligand and its diamagnetic complexes were recorded in DMSO-d(6) solvent and obtained data confirm that the nitrogen atoms of the imine groups coordinated to the metal ions. Electrochemical properties of the ligand and its metal complexes were investigated in the DMF solvent at the 100 and 250 mVs(-1) scan rates. The ligand and metal complexes showed both reversible and irreversible processes at these scan rates. The single crystal of the ligand (L) was obtained from MeOH solution, and its crystal structure was determined by X-ray diffraction. The C-Hcdots, three dots, centeredCl hydrogen bonding interactions in the molecule were seen which increase the stability of the crystal structure. The antimicrobial activity studies of the ligand and its metal complexes were carried out by using the various bacteria and fungi. PMID:19646919

Aslanta?, Mehmet; Kendi, Engin; Demir, Necmettin; Sabik, Ali E; Tümer, Mehmet; Kertmen, Metin

2009-07-15

251

Synthesis, spectroscopic characterization and biological activity of cis-[Ru(hesperidin)(1,10?-phenanthroline)2](PF6) complex  

NASA Astrophysics Data System (ADS)

The new complex cis-[Ru(phen)2(hesperidin)](PF6), complex 1, was synthesized and characterized by analytical (ESI-MS+, EA (C, H, N)) and spectroscopic (FTIR, UV-vis, 1H and 13C NMR) techniques and cyclic voltammetry. Complex 1 is chemically stable in the solid state and in organic solvents such as ethanol, methanol, acetone, and acetonitrile, as shown by spectrophotometric analysis. 1 is also photochemically and chemically stable (pH effects) and more hydrosoluble (518.83 ± 0.91 g mL-1) than free hesperidin (5.92 g mL-1). In accordance with this, the lipophilicity value in aqueous-octanol solution for 1 was -1.28, indicating its high hydrophilic characteristic. Although complex 1 showed to be essentially noncytotoxic, IC50 > 1.0 mmol L-1 as evaluated in the human cervical cancer cells line HeLa, it exhibited a moderate capacity of inhibiting the catalytic activity of the acetylcholinaesterase enzyme, IC50 = 63.6 mol L-1. The Lineweaver-Burk plot and the respective secondary replot indicated that the AChE inhibition was noncompetitive and reversible.These findings shows that complexation of the hesperidin improves physicochemical characteristics and increases the perspectives for development and medical applications of new bioactive-metal complexes.

Oliveira, Regina M. M.; de Souza Daniel, Juliana F.; Carlos, Rose M.

2013-01-01

252

Overexpression, Isolation, and Spectroscopic Characterization of the Bidirectional [NiFe] Hydrogenase from Synechocystis sp. PCC 6803*  

PubMed Central

The bidirectional [NiFe] hydrogenase of the cyanobacterium Synechocystis sp. PCC 6803 was purified to apparent homogeneity by a single affinity chromatography step using a Synechocystis mutant with a Strep-tag II fused to the C terminus of HoxF. To increase the yield of purified enzyme and to test its overexpression capacity in Synechocystis the psbAII promoter was inserted upstream of the hoxE gene. In addition, the accessory genes (hypF, C, D, E, A, and B) from Nostoc sp. PCC 7120 were expressed under control of the psbAII promoter. The respective strains show higher hydrogenase activities compared with the wild type. For the first time a Fourier transform infrared (FTIR) spectroscopic characterization of a [NiFe] hydrogenase from an oxygenic phototroph is presented, revealing that two cyanides and one carbon monoxide coordinate the iron of the active site. At least four different redox states of the active site were detected during the reversible activation/inactivation. Although these states appear similar to those observed in standard [NiFe] hydrogenases, no paramagnetic nickel state could be detected in the fully oxidized and reduced forms. Electron paramagnetic resonance spectroscopy confirms the presence of several iron-sulfur clusters after reductive activation. One [4Fe4S]+ and at least one [2Fe2S]+ cluster could be identified. Catalytic amounts of NADH or NADPH are sufficient to activate the reaction of this enzyme with hydrogen.

Germer, Frauke; Zebger, Ingo; Saggu, Miguel; Lendzian, Friedhelm; Schulz, Rudiger; Appel, Jens

2009-01-01

253

Structural and spectroscopic characterization of Mo1-xWxO3-? mixed oxides  

NASA Astrophysics Data System (ADS)

Mo1-xWxO3 oxides with different cationic fraction (x=0.2, 0.5 and 0.8) and, for comparison purposes, pure MoO3 and WO3 were prepared. Along with textural and structural characterizations, absorbance FT-IR, diffuse reflectance UV-vis-NIR and EPR spectroscopies were employed to study the changes in the electronic properties of these materials passing from Mo1-xWxO3 in oxidizing atmosphere to Mo1-xWxO3-? in reducing conditions. XRD analysis showed that the Mo-W mixed oxides are constituted by two or three crystalline phases, whose abundance and composition are well characterized by structural refinement with the Rietveld method. Only the sample with the highest Mo content (x=0.2) shows a predominant mixed phase and also a superior ability to lose oxygen with respect to the other mixed oxides. The oxygen loss in the reduced oxides induces the formation of defects with electronic levels in the band gap of the material, in particular, electrons trapped in oxygen vacancies and/or at cationic sites (polarons). While the nature of defect sites induced in the mixed and in the pure oxides is similar, the photo-ionization energies, the ratio between surface and bulk defects and the stability of the defects in oxygen at increasing temperature are peculiar of each mixed oxide.

Morandi, S.; Paganini, M. C.; Giamello, E.; Bini, M.; Capsoni, D.; Massarotti, V.; Ghiotti, G.

2009-12-01

254

IR spectroscopic characterization of intermediates in a gas-phase ionic reaction  

NASA Astrophysics Data System (ADS)

Decarbonylation of acetophenone is a facile process mediated by Co+ complexation. Structures of two species on the gas-phase reaction path have been characterized by their infrared photodissociation spectroscopy, namely the Co+(acetophenone) complex itself, and the decarbonylated but still complexed product ion Co+(C7H8). Infrared spectra over the 500-1800 cm-1 frequency range were obtained by wavelength-dependent multiple-photon dissociation using the FELIX free electron laser and a Fourier-transform ion cyclotron resonance mass spectrometer. Structural characterizations were made by comparison with predicted spectra calculated by density functional theory (DFT) using the B3LYP functional. The initial complex Co+(acetophenone) was found to be intact, with little or no presence of rearrangement or bond-inserted structures. The spectrum indicates a mixture of O-bound and ring-bound isomers of this complex. The decarbonylated product ion was assigned to have the most stable structure, namely Co+(toluene), with no indication of the presence of possible bond-inserted isomers having a two-coordinate metal ion. A decarbonylation path involving metal ion insertion adjacent to the carbonyl group was suggested, and the corresponding bond-inserted complexes were computed to be energetically reasonable intermediate structures on the reaction path.

Dunbar, Robert C.; Moore, David T.; Oomens, Jos

2007-09-01

255

Spectroscopic characterization of a newly isolated cytochrome P450 from Rhodococcus rhodochrous.  

PubMed Central

Cytochrome P450 (P450) from Rhodococcus rhodochrous have been characterized through circular dichroism and nuclear magnetic resonance (NMR) spectroscopy, both in the substrate-free and substrate-bound forms. The data are compared with those of P450cam and indicate a close similarity of the structure of the active site in the two proteins. The substrate-free species contains low-spin iron(III), while the 2-ethoxyphenol bound species contains high-spin iron(III). The substrate is in slow exchange on the NMR time scale. The binding of CN- has been investigated and the final adduct characterized through NMR spectra. Nuclear relaxation times of the isotropically shifted signals turn out to be shorter than in other heme proteins, both in the high- and in the low-spin species. This is the result of longer electron relaxation times in P450s than in peroxidases and metmyoglobin. This property, as well as the electron paramagnetic resonance (EPR) spectrum of the substrate-free form, are discussed in terms of the presence of the cysteine as the fifth ligand of the iron ion instead of a histidine as it occurs in peroxidases and myoglobin.

Banci, L; Bertini, I; Eltis, L D; Pierattelli, R

1993-01-01

256

Characterizing Protein Complexes with UV absorption, Light Scattering, and Refractive Index Detection.  

NASA Astrophysics Data System (ADS)

Many modern pharmaceuticals and naturally occurring biomolecules consist of complexes of proteins and polyethylene glycol or carbohydrates. In the case of vaccine development, these complexes are often used to induce or amplify immune responses. For protein therapeutics they are used to modify solubility and function, or to control the rate of degradation and elimination of a drug from the body. Characterizing the stoichiometry of these complexes is an important industrial problem that presents a formidable challenge to analytical instrument designers. Traditional analytical methods, such as using florescent tagging, chemical assays, and mass spectrometry perturb the system so dramatically that the complexes are often destroyed or uncontrollably modified by the measurement. A solution to this problem consists of fractionating the samples and then measuring the fractions using sequential non-invasive detectors that are sensitive to different components of the complex. We present results using UV absorption, which is primarily sensitive to the protein fraction, Light Scattering, which measures the total weight average molar mass, and Refractive Index detection, which measures the net concentration. We also present a solution of the problem inter-detector band-broadening problem that has heretofore made this approach impractical. Presented will be instrumentation and an analysis method that overcome these obstacles and make this technique a reliable and robust way of non-invasively characterizing these industrially important compounds.

Trainoff, Steven

2009-03-01

257

Spectroscopic characterization of a masterpiece: the Manueline foral charter of Sintra.  

PubMed

The foral charter attributed by D. Manuel I of Portugal, in 1514, to the village of Sintra was studied using Energy Dispersive X-ray Fluorescence spectrometry, Raman and Infrared micro-spectroscopies. A complete characterization of the pictorial materials used in the production of this masterpiece allowed the identification of iron gall inks used in the written text; pigments such as malachite, azurite, lead white, cinnabar, yellow ochre, gold, silver and carbon black in the illuminations and letterings; filler and binder used in the production of coloring materials and inks. Gum and calcium carbonate were the most recurrent binder and filler identified in this study. Silvering and gilding were mostly obtained by applying ground silver and gold on parchment. PMID:23318772

Manso, Marta; Le Gac, Agnès; Longelin, Stéphane; Pessanha, Sofia; Frade, José Carlos; Guerra, Mauro; Candeias, António José; Carvalho, Maria Luísa

2012-12-20

258

Solution NMR spectroscopic characterization of human VDAC-2 in detergent micelles and lipid bilayer nanodiscs.  

PubMed

Three isoforms of the human voltage-dependent anion channel (VDAC), located in the outer mitochondrial membrane, are crucial regulators of mitochondrial function. Numerous studies have been carried out to elucidate biochemical properties, as well as the three-dimensional structure of VDAC-1. However, functional and structural studies of VDAC-2 and VDAC-3 at atomic resolution are still scarce. VDAC-2 is highly similar to VDAC-1 in amino acid sequence, but has substantially different biochemical functions and expression profiles. Here, we report the reconstitution of functional VDAC-2 in lauryldimethylamine-oxide (LDAO) detergent micelles and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid bilayer nanodiscs. We find that VDAC-2 is properly folded in both membrane-mimicking systems and that structural and functional characterization by solution NMR spectroscopy is feasible. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism. PMID:22119777

Yu, Tsyr-Yan; Raschle, Thomas; Hiller, Sebastian; Wagner, Gerhard

2011-11-15

259

Synthesis, spectroscopic characterization and antibacterial activity of antimony(III) bis(dialkyldithiocarbamato)alkyldithiocarbonates  

NASA Astrophysics Data System (ADS)

Some mixed sulfur donor ligand complexes of antimony(III) of the general formula [(R 2NCS 2)] 2SbS 2COR' where R = CH 3, C 2H 5 and R' = Me, Et, Pr n, Pr i, Bu n and Bu i have been synthesized by the reaction of antimony(III) bis(dialkyldithiocarbamate) chloride with potassium organodithiocarbonate in an equimolar ratio by stirring at room temperature in benzene/CS 2 mixture. These complexes have been characterized by physicochemical [elemental analysis, melting points and molecular weight determinations] and spectral [UV, IR, Far-IR, NMR ( 1H and 13C), FAB + mass and powder X-ray diffraction] studies. Free ligands and synthesized complexes have also been screened against different bacterial strains and results obtained made it desirable to delineate a comparison between free ligands, standard drug used and synthesized complexes.

Chauhan, H. P. S.; Bakshi, Abhilasha; Bhatiya, Sumit

2011-10-01

260

Synthesis and spectroscopic characterization of gallic acid and some of its azo complexes  

NASA Astrophysics Data System (ADS)

A series of gallic acid and azo gallic acid complexes were prepared and characterized by elemental analysis, IR, electronic spectra and magnetic susceptibility. The complexes were of different geometries: Octahedral, Tetrahedral and Square Planar. ESR was studied for copper complexes. All of the prepared complexes were of isotropic nature. The thermal analyses of the complexes were studied by DTA and DSC techniques. The thermodynamic parameters and the thermal transitions, such as glass transitions, crystallization and melting temperatures for some ligands and their complexes were evaluated and discussed. The entropy change values, ?S#, showed that the transition states are more ordered than the reacting complexes. The biological activities of some ligands and their complexes are tested against Gram positive and Gram negative bacteria. The results showed that some complexes have a well considerable activity against different organisms.

Masoud, Mamdouh S.; Hagagg, Sawsan S.; Ali, Alaa E.; Nasr, Nessma M.

2012-04-01

261

Spectroscopic characterization of discharge products in Li-Air cells with aprotic carbonate electrolytes  

SciTech Connect

Raman, infrared and X-ray photoelectron spectroscopies were used to characterize the thick coating of reaction products on carbon and MnO2 coated carbon cathodes produced during discharge of Li-air cells. The results show that neither Li2O2 or Li2O are major components of the insoluble discharge products; instead the products are largely composed of fluorine, lithium, and carbon, with surprisingly little oxygen. The complex reaction chemistry also appears to involve the formation of ethers or alkoxide products at the expense of the carbonate solvent molecules (ethylene carbonate and dimethylcarbonate). The irreversible discharge reaction is likely electrochemically promoted with Li-anion species and dissolved oxygen. Exactly how the molecular O2 participates in the reaction is unclear and requires further study. The addition of a conformal coating of MnO2 on the carbon lowers the cell s operating voltage, but does not alter the overall discharge chemistry.

Veith, Gabriel M [ORNL; Nanda, Jagjit [ORNL; Howe, Jane Y [ORNL; Dudney, Nancy J [ORNL

2011-01-01

262

Identification of pharmacophore in bioactive metal complexes: Synthesis, spectroscopic characterization and application.  

PubMed

Bacteria are amongst the most adaptable organisms on the Earth. The year 2010 was always remarkable for the article published in Lancet Infection Disease by Kumarasamy et al. and the enzyme NDM-1 which makes bacteria resist designed to kill them. Four rhodium(III) chloride complexes with Gatifloxacin have been prepared and characterized by elemental analyses, molar conductance measurements, FTIR, FAB-MS, TGA, (1)H NMR and electronic spectral studies. The general formula for complexes are [X](+)fac-[RhCl(3)(L)(GT)](-); where L = H(2)O, Dimethylsulfoxide (DMSO), Tetramethylenesulfoxide (TMSO); GT = Gatifloxacin and X = Na or [H(DMSO)(2)]. All complexes are found to possess prominent antibacterial activity against pathogenic Escherichia coli and Mycobacterium tuberculosis in comparison to Gatifloxacin. PMID:22330206

Mehrotra, Ripul; Shukla, Satyendra N; Gaur, Pratiksha; Dubey, Archana

2012-02-01

263

Synthesis, spectroscopic characterization and DFT calculations of ?-O-4 type lignin model compounds  

NASA Astrophysics Data System (ADS)

?-O-4 type lignin model compounds with the title of Erythro-2-(2-methoxyphenoxy)-1-(3,4,5-trimethoxyphenyl)-1,3-propanediol and Erythro-2-(2-methoxyphenoxy)-1-(4-Hydroxy-3,5-dimethoxyphenyl)-1,3-propanediol were synthesised and some modifications and improvements on them were introduced. These compounds were characterized by IR, Mass and NMR spectroscopy. Density functional theory (DFT) calculations were performed for the title compounds using the standard 6-31G* basis set. IR, 13C and 1H NMR of the title compounds were calculated at the DFT-B3LYP level of theory using the 6-31G* basis set. In this work comparison between the experimental and the theoretical results indicates that the DFT-B3LYP method is able to provide satisfactory results for predicting the properties of the considered compounds.

Mostaghni, Fatemeh; Teimouri, Abbas; Mirshokraei, Seyed Ahmad

2013-06-01

264

Laboratory studies of spectroscopic markers for the characterization of surface erosion by plasmas  

SciTech Connect

The erosion rates in portions of fusion plasma devices like the ITER tokamak are sufficiently high that nearly real-time information on cumulative removal is needed for control and machine safety. We are developing a digitally--encoded scheme to indicate the depth of erosion at numerous poloidal and toroidal locations around ITER. The scheme uses materials embedded in the walls and divertors, which, when uncovered, present remotely detectable signals. This paper reports laboratory experiments on prototype markers consisting of combinations of up to 5 elements (Au,Pd,Ag,In,Ga) along with Au,Pt, and Ta pure metals. The markers were bonded to 4-D carbon-carbon composite of the type proposed for use in the ITER first wall, and placed in the lower-hybrid-driven plasma of the atomic beam facility at PPL. The paper describes this device Light emission was characterized using a 1 meter Czerny-Turner vacuum ultraviolet monochromator. The samples were characterized both before and after plasma exposure by Auger spectroscopy. We report the time-dependent behavior of the spectra of the visible and ultraviolet light emitted by the plasma when the markers are uncovered by the erosion showing emission lines of the marker elements which are easily distinguished from the background plasma lines. The dependence of the light intensity on bias voltage is compared to the known sputtering yields of the elements. The optical detection method allows exploration of the threshold dependence of these multi-element targets. An exponential dependence of yield above threshold was observed for all of the elements studied.

Manos, D.M.; Bennett, T.; Herzer, M.; Schwarzmann, J.

1992-01-01

265

Laboratory studies of spectroscopic markers for the characterization of surface erosion by plasmas  

SciTech Connect

The erosion rates in portions of fusion plasma devices like the ITER tokamak are sufficiently high that nearly real-time information on cumulative removal is needed for control and machine safety. We are developing a digitally--encoded scheme to indicate the depth of erosion at numerous poloidal and toroidal locations around ITER. The scheme uses materials embedded in the walls and divertors, which, when uncovered, present remotely detectable signals. This paper reports laboratory experiments on prototype markers consisting of combinations of up to 5 elements (Au,Pd,Ag,In,Ga) along with Au,Pt, and Ta pure metals. The markers were bonded to 4-D carbon-carbon composite of the type proposed for use in the ITER first wall, and placed in the lower-hybrid-driven plasma of the atomic beam facility at PPL. The paper describes this device Light emission was characterized using a 1 meter Czerny-Turner vacuum ultraviolet monochromator. The samples were characterized both before and after plasma exposure by Auger spectroscopy. We report the time-dependent behavior of the spectra of the visible and ultraviolet light emitted by the plasma when the markers are uncovered by the erosion showing emission lines of the marker elements which are easily distinguished from the background plasma lines. The dependence of the light intensity on bias voltage is compared to the known sputtering yields of the elements. The optical detection method allows exploration of the threshold dependence of these multi-element targets. An exponential dependence of yield above threshold was observed for all of the elements studied.

Manos, D.M.; Bennett, T.; Herzer, M.; Schwarzmann, J.

1992-06-01

266

Biological activity studies on metal complexes of novel tridentate Schiff base ligand. Spectroscopic and thermal characterization.  

PubMed

Metal complexes of novel Schiff base (HL) ligand, prepared via condensation of 4-aminoantipyrine and 2-aminophenol, are prepared. The ligand is characterized based on elemental analysis, mass, IR and (1)H NMR spectra. Metal complexes are reported and characterized based on elemental analyses, IR, (1)H NMR, solid reflectance, magnetic moment, molar conductance, ESR spectra and thermal analyses (TG, DTG and DTA). From the elemental analyses, 1:1 [M]:[ligand] complexes are prepared with the general formulae [M(L)Cl(H(2)O)(2)] x yH(2)O (M = Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), y = 3-4), [Fe(L)Cl(2)(H(2)O)] x 3 H(2)O and [Th(L)Cl(H(2)O)(2)]Cl(2) x 3 H(2)O. The molar conductance data reveal that all the metal chelates are non-electrolytes (except Th(IV) complex, it is 2:1 electrolyte). IR spectra show that HL is coordinated to the metal ions in a uninegatively tridentate manner with NNO donor sites of the azomethine-N, amino N and deprotonated phenolic-O. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral. The thermal behaviour of these chelates shows that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The activation thermodynamic parameters are calculated from the DTG curves using Coats-Redfern method. The synthesized ligand, in comparison to its metal complexes is screened for its antibacterial activity against bacterial species, Escherichia coli, Pseudomonas putida, Exiguobacterium acetylicum and Bacillus simplex. The activity data show that the metal complexes to be more potent/antibacterial than the parent Schiff base ligand against one or more bacterial species. PMID:19758728

Mohamed, Gehad G; Omar, M M; Ibrahim, Amr A

2009-08-06

267

Spectroscopic characterization and the coordination behavior of isonicotinamide with lanthanide ions  

NASA Astrophysics Data System (ADS)

The coordination of amide groups to metal ions is important because it may be involved in the interactions between metal ions and proteins. The synthesis and characterization of nine novel lanthanide–isonicotinamide (ina) complexes, including LaCl3, PrCl3, NdCl3, SmCl3, EuCl3, GdCl3, TbCl3, ErCl3 and PrBr3 complexes are reported. The structures of these complexes in the solid state have been characterized by X-ray single crystal diffraction, FTIR, FIR, THz and Luminescence spectroscopy. Isonicotinamide has only one coordination mode in four structures as O-monodentate ligand to coordinate to metal ions, but four kinds of topological structures are observed for lanthanide–isonicotinamide complexes, including LnCl3?(C6H6N2O)2?4H2O (La, Pr, Nd and Sm), EuCl3?(C6H6N2O)2?7H2O, LnCl3?(C6H6N2O)2?6H2O (Gd, Tb and Er) and PrBr3?(C6H6N2O)2?7H2O. Chloride ions can coordinate to metal ions or hydrogen-bonded. FTIR spectra indicate the formation of four kinds of lanthanide–ina complexes, the extensive hydrogen bond networks after complexation and the coordinations and the changes of the conformation of the ligand. FIR and THz spectra also confirm the formation of lanthanide ion–ina complexes. Luminescence spectra of Eu and Tb-ina complexes have the characteristics of Eu and Tb ions.

Xue, Junhui; Hua, Xiaohui; Yang, Limin; Xu, Yizhuang; Li, Weihong; Zhao, Guozhong; Zhang, Gaohui; Wu, Jinguang

2013-11-01

268

Doppler-shifted optical absorption characterization of plume-lateral expansion in laser ablation of a cerium target  

NASA Astrophysics Data System (ADS)

The temporal evolution of the ablation plume of cerium was investigated by absorption spectroscopy. Cerium oxide pellets were ablated in a helium atmosphere by second-harmonic radiation (532 nm) from a Nd:YAG laser at a fluence of 0.5 J/cm2. The lateral velocity (expansion velocity horizontal to the sample surface) of the plume was determined from the magnitude of the Doppler splitting of the absorption spectra measured close to the sample surface. The lateral velocities of neutral and singly ionized atoms were systematically investigated by varying several parameters, such as ambient gas pressure, ablation laser fluence, observation timing, and observation height. In addition, temporal profiles of the absorption signal were measured by detuning the probe laser frequency from the atomic resonant frequency in order to obtain the temporal variation of the velocity. On the basis of the drag force model, the slowing coefficients for atomic and ionic species in a helium atmosphere were evaluated along with lateral velocity in a vacuum. This study may help in understanding the plume dynamics effect on deposited film properties as well as optimizing experimental conditions for ablation-based spectroscopic analysis.

Miyabe, M.; Oba, M.; Iimura, H.; Akaoka, K.; Maruyama, Y.; Ohba, H.; Tampo, M.; Wakaida, I.

2012-12-01

269

Spectroscopic and functional characterization of T state hemoglobin conformations encapsulated in silica gels.  

PubMed

Oxygen binding curves of sol-gel-encapsulated deoxy human adult hemoglobin (HbA) have previously revealed two distinct noncooperative populations with oxygen binding affinities approximately 1000 and 100 times lower than that of the high-affinity R state. The two populations which have been termed the low-affinity (LA) and high-affinity (HA) T states can be selectively stabilized using two different encapsulation protocols for deoxy-HbA. The present study seeks to understand the factors giving rise to these different affinity states. Visible and UV resonance Raman spectroscopies are used to characterize the conformational properties of both the deoxy and deoxy-turned-carbonmonoxy (CO) derivatives of HbA derived from the two encapsulation protocols. The geminate and bimolecular recombination of CO to the photodissociated CO derivatives is used to characterize the functional properties of the slowly evolving encapsulated populations. The results show that the initial deoxy-HbA populations are conformationally indistinguishable with respect to encapsulation protocol. The addition of CO to sol-gel-encapsulated deoxy-HbA triggers a detectable progression of conformational and functional changes. Visible resonance Raman spectra of the CO photoproduct reveal a progression of changes of the iron-proximal histidine stretching frequencies: 215, 222, 227, and 230 cm(-1). The low and high values correspond to the initial deoxy T state and liganded R (R(2)) state species, respectively. The 222 and 227 cm(-1) species are generated using encapsulation protocols that give rise to what are termed the LA and HA T states, respectively. The UV resonance Raman spectra of these and related species indicate that the progression from deoxy T to LA to HA is associated with a progressive loosening of T state constraints within the hinge and switch regions of the alpha(1)beta(2) interface. The time scale for the progression is determined by a balance between the ligation-initiated evolution toward high-affinity conformations and factors such as allosteric effectors, gel matrix, and added glycerol that slow ligand-binding-induced relaxation. Thus, it appears that the encapsulation protocol-dependent rate of ligand-binding-induced relaxation determines the functional properties of the initially encapsulated deoxy-HbA population. PMID:15504030

Samuni, Uri; Dantsker, David; Juszczak, Laura J; Bettati, Stefano; Ronda, Luca; Mozzarelli, Andrea; Friedman, Joel M

2004-11-01

270

Synthesis, characterization and spectroscopic studies of some boron-containing hydrogen storage materials  

NASA Astrophysics Data System (ADS)

In this dissertation the synthesis and characterization of boron-related nanostructures and dehydrogenation studies of metal borohydrides using FTIR are reported. Boron-related nanostructures are of interest because of their potential applications in nanoelectronics and in hydrogen storage. A low pressure chemical vapor deposition (LPCVD) apparatus was built in order to grow boron nanostructures. Various techniques, namely, Auger electron spectroscopy (AES), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy were used to characterize the synthesized boron and boride nanostructures, and boron coated carbon nanotubes (CNTs). By the uncatalyzed pyrolysis of diborane, at relatively low temperature, crystalline boron nanoribbons were synthesized. Nickel-catalyzed growth also produced Ca, Sr and Y boride nanowires that were found to be crystalline. Amorphous boron coated CNTs were synthesized by LPCVD. Two growth mechanisms, vapor-liquid-solid (VLS) and vapor-solid (VS) were invoked to explain the observed nanostructures. A high vacuum apparatus for FTIR studies was built. The capabilities of the apparatus were first tested by acquiring low temperature and room temperature spectra of sodium and lithium borohydrides. The metal borohydrides are of high hydrogen content and dehydrogenation studies using FTIR were done. NaBH 4 and the K2B12H12 salt were studied. It was found that above its melting point (673 K), NaBH4 is probably converted to its B12H12-2 salt, which then loses all hydrogen to produce amorphous boron. This conversion of B 12H12-2 to boron clusters was confirmed through dehydrogenation studies of K2B12H12. Both SIMS and AES are surface sensitive techniques to study thin film surfaces and interfaces at nano-dimentions. Thin (9-10 mum) cadmium telluride films have application as the buffer layer on silicon substrates to form high quality mercury cadmium telluride (MCT) films. MCT films find applications in IR detectors and in photovoltaic cells. Due to the lattice mismatch it is necessary to grow CdTe films on a monolayer of arsenic and 20 nm thick ZnTe on silicon. The purpose of this study was to show the capabilities of the Scanning Auger Multiprobe PHI 600 in the qualitative analysis of CdTe, ZnTe and As films on Si and of an MCT film surface, which was grown on CdZnTe.

Jash, Panchatapa

271

Synthesis, spectroscopic and thermal characterization of some transition metal complexes of folic acid  

NASA Astrophysics Data System (ADS)

Compounds having general formula: [M(FO)(Cl) x(H 2O) y]· zH 2O, where (M = Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II), FO = folate anion, x = 2 or 4, y = 2 or 4 and z = 0, 1, 2, 3, 5 or 15) were prepared. The obtained compounds were characterized by elemental analysis, infrared as well as electronic spectra, thermogravimetric analysis and the conductivity measurements. The results suggested that all folate complexes were formed by 2:1 molar ratio (metal:folic acid) as a bidentate through both of the two carboxylic groups. The molar conductance measurements proved that the folate complexes are electrolytes. The kinetic thermodynamic parameters such as: E*, ? H*, ? S* and ? G* were estimated from the DTG curves. The antibacterial evaluation of the folic acid and their complexes was also done against some Gram positive/negative bacteria as well as fungi.

El-Wahed, M. G. Abd; Refat, M. S.; El-Megharbel, S. M.

2008-09-01

272

Spectroscopic Characterization of B/KNO3 Diode-Laser Induced Combustion.  

PubMed

The combustion of a B/KNO3 pyrotechnic mixture was characterized by its chemiluminescence for the first time. The reaction was initiated by a continuous wave (cw) diode laser inside a novel multipurpose reaction cell, whose design and construction are described. As in the case of the extensively studied oxidation of boron by O2, the most intense luminescence, recorded in the 400-600 nm range, is assigned to BO2. Its appearance delay time (10(-2) to 10(-1) s) equals that measured for the pressure increase and is shortened as the laser power is increased. A band observed at 355 nm appears at longer delay times than the BO2 bands. The band, and some weaker ones, may be assigned to BO, although some bands expected for BO (based on reaction between B atoms and O2) are absent from the spectra. This observation is discussed in the text, and possible emission from BN is discussed. If the band is assigned to BO, the absence of known bands may be due to specific E-V resonance energy transfer. Possible oxidation mechanisms consistent with the different delay ignition times are discussed. PMID:23679891

Sivan, J; Haas, Y

2013-05-16

273

Raman imaging spectroscopic characterization of modified poly(dimethylsiloxane) for micro total analysis systems applications.  

PubMed

Methacryloxypropyl-modified poly(dimethylsiloxane) rubbers were obtained from poly(dimethylsiloxane), PDMS, and methacryloxypropyltrimethoxysilane, MPTMS, by polycondensation reactions. The modified rubbers, prepared with 20 and 30% (v/v) of MPTMS, were used as substrates for microchannel fabrication by the CO(2) laser ablation technique. Raman imaging spectroscopy was used for the surface characterization, showing the homogeneity of the rubbery material, with uniform distribution of the crosslinking centers. Under the experimental conditions used, damage to the rubber from the CO(2) laser radiation used for the channel engraving was not observed. Correlation maps of the surface were obtained in order to spatially evaluate the modification inside and outside the channels. The correlations between the methacryloxypropyl-modified poly(dimethylsiloxane) rubbers and MPTMS (spectral range of 1800-1550 cm(-1)) and PDMS (spectral range of 820-670 cm(-1)) precursors were higher than 0.95 and 0.99, respectively. In addition, Raman imaging spectroscopy allows monitoring the topography of the fabricated microchannel. PMID:22542689

de Campos, Richard Piffer Soares; Yoshida, Inez Valeria Pagotto; Breitkreitz, Márcia Cristina; Poppi, Ronei Jesus; Fracassi da Silva, José Alberto

2012-04-10

274

Chlorodifluoroacetyl cyanide, ClF2CC(O)CN: synthesis, structure, and spectroscopic characterization.  

PubMed

The novel molecule difluorochloroacetyl cyanide, ClF(2)CC(O)CN, has been characterized by IR (gas phase, Ar matrix), Raman (liquid), (19)F and (13)C NMR, and photoelectron (PES) spectroscopies; photoionization mass spectrometry (PIMS); and gas electron diffraction (GED). The conformational properties of ClF(2)CC(O)CN have been studied by joint application of vibrational spectroscopy, GED, and quantum chemical calculations. The existence of two conformers is detected in the gas and liquid phases, in which the C-Cl bond adopts gauche and syn orientations with respect to the C?O group. The computed enthalpy difference is in harmony with the experimental results of the gauche being more stable than the syn conformer by ?H° = 1.3 kcal mol(-1) (MP2/cc-pVTZ). The valence electronic properties and the possible ionization and dissociation processes of the title compound are studied using the PES and PIMS. The experimental first vertical ionization energy of 12.0 eV corresponds to the ejection of an electron of the oxygen lone pairs. Taking into account the properties and broad applications of acyl cyanides, ClF(2)CC(O)CN is a promising new precursor in preparative chemistry. PMID:21870792

Ramos, Luis A; Ulic, Sonia E; Romano, Rosana M; Tong, Shengrui; Ge, Maofa; Vishnevskiy, Yuri V; Berger, Raphael J; Mitzel, Norbert W; Beckers, Helmut; Willner, Helge; Della Védova, Carlos O

2011-08-26

275

Raman imaging spectroscopic characterization of modified poly(dimethylsiloxane) for micro total analysis systems applications  

NASA Astrophysics Data System (ADS)

Methacryloxypropyl-modified poly(dimethylsiloxane) rubbers were obtained from poly(dimethylsiloxane), PDMS, and methacryloxypropyltrimethoxysilane, MPTMS, by polycondensation reactions. The modified rubbers, prepared with 20 and 30% (v/v) of MPTMS, were used as substrates for microchannel fabrication by the CO2 laser ablation technique. Raman imaging spectroscopy was used for the surface characterization, showing the homogeneity of the rubbery material, with uniform distribution of the crosslinking centers. Under the experimental conditions used, damage to the rubber from the CO2 laser radiation used for the channel engraving was not observed. Correlation maps of the surface were obtained in order to spatially evaluate the modification inside and outside the channels. The correlations between the methacryloxypropyl-modified poly(dimethylsiloxane) rubbers and MPTMS (spectral range of 1800-1550 cm-1) and PDMS (spectral range of 820-670 cm-1) precursors were higher than 0.95 and 0.99, respectively. In addition, Raman imaging spectroscopy allows monitoring the topography of the fabricated microchannel.

de Campos, Richard Piffer Soares; Yoshida, Inez Valeria Pagotto; Breitkreitz, Márcia Cristina; Poppi, Ronei Jesus; Fracassi da Silva, José Alberto

276

Synchronous fluorescence spectroscopic characterization of DMBA-TPA-induced squamous cell carcinoma in mice  

NASA Astrophysics Data System (ADS)

While initially confined to the epidermis, squamous cell carcinoma can eventually penetrate into the underlying tissue if not diagnosed early and treated. The noninvasive early detection of the carcinoma is important to achieve a complete treatment of the disease. Of the various non-invasive optical techniques, the synchronous fluorescence (SF) technique is considered to provide a simplified spectral profile with more sharp spectral signatures of the endogenous fluorophores in complex systems. The potential use of the SF technique in the characterization of the sequential tissue transformation in 7,12-dimethylbenz(a)anthracene-12-O-tetradecanoylphorbol-13-acetate (DMBA-TPA)-induced mouse skin tumor model in conjunction with simple statistical analysis is explored. The SF spectra show distinct differences during the earlier weeks of the tumor-induction period. Intensity ratio variables are calculated and used in three discriminant analyses. All the discriminant analyses show better classification results with accuracy greater than 80%. From the observed differences in the spectral characteristics and the ratio variables that resulted in better classification between groups, it is concluded that tryptophan, collagen, and NADH are the key fluorophores that undergo changes during tissue transformation process and hence they can be targeted as tumor markers to diagnose normal from abnormal tissues using the SF technique.

Diagaradjane, Parmeswaran; Yaseen, Mohammad A.; Yu, Jie; Wong, Michael S.; Anvari, Bahman

2006-01-01

277

New copper(II) complexes with dopamine hydrochloride and vanillymandelic acid: Spectroscopic and thermal characterization  

NASA Astrophysics Data System (ADS)

The dopamine derivatives participate in the regulation of wide variety of physiological functions in the human body and in medication life. Increase and/or decrease in the concentration of dopamine in human body reflect an indication for diseases such as Schizophrenia and/or Parkinson diseases. The Cu(II) chelates with coupled products of dopamine hydrochloride (DO.HCl) and vanillymandelic acid (VMA) with 4-aminoantipyrine (4-AAP) are prepared and characterized. Different physico-chemical techniques namely IR, magnetic and UV-vis spectra are used to investigate the structure of these chelates. Cu(II) forms 1:1 (Cu:DO) and 1:2 (Cu:VMA) chelates. DO behave as a uninegative tridentate ligand in binding to the Cu(II) ion while VMA behaves as a uninegative bidentate ligand. IR spectra show that the DO is coordinated to the Cu(II) ion in a tridentate manner with ONO donor sites of the phenolic- OH, -NH and carbonyl- O, while VMA is coordinated with OO donor sites of the phenolic- OH and -NH. Magnetic moment measurements reveal the presence of Cu(II) chelates in octahedral and square planar geometries with DO and VMA, respectively. The thermal decomposition of Cu(II) complexes is studied using thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The activation thermodynamic parameters, such as, energy of activation, enthalpy, entropy and free energy change of the complexes are evaluated and the relative thermal stability of the complexes are discussed.

Mohamed, Gehad G.; Nour El-Dien, F. A.; El-Nahas, R. G.

2011-10-01

278

Preparation and spectroscopic characterization of methoxy poly(ethylene glycol)-grafted water-soluble chitosan.  

PubMed

The object of this study was to test the solubility of a methoxy poly(ethylene glycol) (MPEG)-grafted chitosan copolymer in organic solvents and aqueous solution. Water-soluble chitosan with low molecular weight (LMWSC) was used in a PEG-graft copolymerization. The MPEG was conjugated to chitosan using 4-dicyclohexylcarbodimide (DCC), and N-hydroxysuccimide (NHS). Introduction of PEG was confirmed by (1)H and (13)C NMR spectroscopy and FT-IR spectroscopy. The degree of substitution (DS) of MPEG into chitosan was calculated from (1)H NMR data and also by estimating the molecular weight (MW) using gel permeation chromatography (GPC). The DS values obtained from (1)H NMR spectroscopy and GPC were similar, indicating that MPEG-grafted LMWSC was synthesized and properly characterized. Furthermore, the introduction of PEG into chitosan increases the solubility in aqueous solutions over a range of pH values (4.0-11.0) and organic solvents such as DMF, DMSO, ethanol, and acetone. PMID:18035341

Jeong, Young-Il; Kim, Don-Gon; Jang, Mi-Kyeong; Nah, Jaw-Woon

2007-11-01

279

Spectroscopic characterization of zinc oxide nanorods synthesized by solid-state reaction  

NASA Astrophysics Data System (ADS)

Well-crystallized zinc oxide nanorods have been fabricated by single step solid-state reaction using zinc acetate and sodium hydroxide, at room temperature. The sodium lauryl sulfate (SLS) stabilized zinc oxide nanorods were characterized by using X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and photoluminescence spectroscopy. The X-ray diffraction revealed the wurtzite structure of zinc oxide. The size estimation by XRD and TEM confirmed that the ZnO nanorods are made of single crystals. The growth of zinc oxide crystals into rod shape was found to be closely related to its hexagonal nature. The mass ratio of SLS:ZnO in the nanorods was found to be 1:10 based on the thermogravimetric analysis. Blue shift of photoluminescence emission was noticed in the ZnO nanorods when compared to that of ZnO bulk. FT-IR analysis confirmed the binding of SLS with ZnO nanorods. Apart from ease of preparation, this method has the advantage of eco-friendliness since the solvent and other harmful chemicals were eliminated in the synthesis protocol.

Prasad, Virendra; D'Souza, Charlene; Yadav, Deepti; Shaikh, A. J.; Vigneshwaran, Nadanathangam

2006-09-01

280

A thermodynamic, spectroscopic, and mechanical characterization of the wood-polypropylene interphase  

NASA Astrophysics Data System (ADS)

Extruded composites composed of wood and semicrystalline polyolefin thermoplastics are gaining acceptance for use in structural, exterior applications. Wood and polyolefins are inherently incompatible making the use of a coupling agent necessary for improved stiffness and strength. However, the improvements to properties are negated by the addition of processing lubricants used in extrusion. The mechanisms for degrading the properties of the composite are largely unknown. The goal of this research is characterize the mechanisms that lead to improvements in properties in wood-polypropylene (PP) composites with the use of a coupling agent, maleic anhydride polypropylene (MAPP), and the degradation of properties with the incorporation of lubricants, a polyester (OP), zinc stearate (ZnSt), and ethylene bisstearamide (EBS). A combination of experimental techniques was used to probe the impact crystal and amorphous polymer morphology has on the mechanical response of the system. The use of dynamic mechanical spectroscopy allowed for the determination molecular, interaction at the wood-PP interface and between polymer molecules in the bulk. The analysis revealed that MAPP improved the stiffness of the composite by several different mechanisms. MAPP improves crystal nucleation off the wood surface and created a large interphase that likely increases bending stiffness. In addition, there is improved interaction between matrix and filler leading to decreased mechanical damping. These effects are negated with the incorporation of ZnSt because of a reaction with the MAPP's polar groups. This leads to poor packing and nucleation of PP molecules at the wood surface leading to a decrease in strength and stiffness.

Harper, David Paul

281

Comprehensive characterization of oil refinery effluent-derived humic substances using various spectroscopic approaches.  

PubMed

Refinery effluent-derived humic substances (HS) are important for developing refinery effluent reclamation techniques and studying the environmental chemistry of wastewater effluents. In this study, dissolved organic matter (DOM) from refinery effluent was concentrated using a portable reverse osmosis (RO) system. HS were isolated from RO retentates with XAD-8 resin. A variety of approaches such as specific UV absorbance at 254nm (SUV(254)), elemental analysis, size exclusion chromatography (SEC), solid-state cross polarization magic angle spinning (13)C nuclear magnetic resonance spectrometry ((13)C CPMAS NMR), Fourier transform infrared spectrometry (FTIR), and electrospray ionization/ion trap/mass spectrometry (ESI/ion trap/MS) were employed for characterization of HS. The portable RO system exhibited high yield and recovery of DOM for concentrating refinery effluent. The concentration of dissolved organic carbon (DOC) in the refinery effluent was 9.9mg/l, in which humic acids (HA) and fulvic acids (FA) accounted for 2.3% and 34.6%, respectively. Elemental and SUV(254) analyses indicated relative high amounts of aliphatic structures and low amounts of aromatic structures in refinery effluent-derived HS. Refinery effluent-derived HS displayed lower molecular weight than natural HS. The number-average molecular weight (M(n)) and the weight-average molecular weight (M(w)) of HA were 1069 and 2934, and those of FA were 679 and 1212 by SEC, respectively. By ESI/ion trap/MS, the M(n) and the M(w) of FA were 330 and 383. Four kinds of carbon structures (aliphatic, aromatic, heteroaliphatic, and carboxylic carbons) were found in refinery effluent-derived HS by (13)C NMR analysis. The quantitative results support the interpretation that these HS are rich in aliphatic carbons and poor in aromatic carbons. Proteinaceous materials were identified by FTIR analysis in refinery effluent-derived HS. PMID:15950039

Lingbo, Li; Song, Yan; Congbi, Han; Guangbo, Shan

2005-07-01

282

New copper(II) complexes with dopamine hydrochloride and vanillymandelic acid: spectroscopic and thermal characterization.  

PubMed

The dopamine derivatives participate in the regulation of wide variety of physiological functions in the human body and in medication life. Increase and/or decrease in the concentration of dopamine in human body reflect an indication for diseases such as Schizophrenia and/or Parkinson diseases. The Cu(II) chelates with coupled products of dopamine hydrochloride (DO.HCl) and vanillymandelic acid (VMA) with 4-aminoantipyrine (4-AAP) are prepared and characterized. Different physico-chemical techniques namely IR, magnetic and UV-vis spectra are used to investigate the structure of these chelates. Cu(II) forms 1:1 (Cu:DO) and 1:2 (Cu:VMA) chelates. DO behave as a uninegative tridentate ligand in binding to the Cu(II) ion while VMA behaves as a uninegative bidentate ligand. IR spectra show that the DO is coordinated to the Cu(II) ion in a tridentate manner with ONO donor sites of the phenolic-OH, -NH and carbonyl-O, while VMA is coordinated with OO donor sites of the phenolic-OH and -NH. Magnetic moment measurements reveal the presence of Cu(II) chelates in octahedral and square planar geometries with DO and VMA, respectively. The thermal decomposition of Cu(II) complexes is studied using thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The activation thermodynamic parameters, such as, energy of activation, enthalpy, entropy and free energy change of the complexes are evaluated and the relative thermal stability of the complexes are discussed. PMID:21795104

Mohamed, Gehad G; Nour el-Dien, F A; el-Nahas, R G

2011-06-23

283

Raman spectroscopic characterization of a synthetic, non-stoichiometric Cu-Ba uranyl phosphate  

NASA Astrophysics Data System (ADS)

Crystals of phases belonging to the autunite group (general formula X2+(UO2)2(X5+O4)2?nH2O), specifically the uranyl phosphates (X5+ = P) metauranocircite (X2+ = Ba2+), metatorbernite (X2+ = Cu2+) and a barian metatorbenite phase (X2+ = Cu2+/Ba2+), have been synthesized in a silica gel medium and characterized by Raman spectroscopy. The Raman spectra showed bands in the range 750-1100 cm-1, which were attributed to the ?1 and ?3( and ( stretching vibrations. By using the wavenumbers of the most intense and well defined ?1( vibration, the U-O bonds lengths were calculated for the three uranyl phosphate minerals. The results are in good agreement with previous single crystal structure analysis data. Bands in the spectra from 350 to 700 cm-1 were attributed to the ( bending modes. Moreover, in the range 70-350 cm-1, two groups of bands could be defined. The first group, with vibrations at lower wavenumbers, was attributed to the lattice modes and the second group, from 150 to 350 cm-1, was assigned to the ?2( bending mode. Finally, in the case of the barian metatorbernite, bands in the range 1500-3800 cm-1 were assigned to the OH stretching and the ?2 bending vibrations of water molecules. In this phase, all the vibrations show bandshifts when compared to the vibrations in metatorbernite. These bandshifts can be related to transitional Cu-O and Ba-O bond lengths.

Sánchez-Pastor, Nuria; Pinto, André J.; Astilleros, José Manuel; Fernández-Díaz, Lurdes; Gonçalves, Mário A.

2013-09-01

284

Osmium NAMI-A analogues: synthesis, structural and spectroscopic characterization, and antiproliferative properties.  

PubMed

The osmium(III) complex [(DMSO)2H][trans-OsIIICl4(DMSO)2] (1) has been prepared via stepwise reduction of OsO4 in concentrated HCl using N2H(4).2HCl and SnCl(2).2H2O in DMSO. 1 reacts with a number of azole ligands, namely, indazole (Hind), pyrazole (Hpz), benzimidazole (Hbzim), imidazole (Him), and 1H-1,2,4-triazole (Htrz), in organic solvents, affording novel complexes (H2ind)[OsIIICl4(Hind)(DMSO)] (2), (H2pz)[OsIIICl4(Hpz)(DMSO)] (3), (H2bzim)[OsIIICl4(Hbzim)(DMSO)] (4), (H2im)[OsIIICl4(Him)(DMSO)] (6), and (H2trz)[OsIIICl4(Htrz)(DMSO)] (7), which are close analogues of the antimetastatic complex NAMI-A. Metathesis reaction of 4 with benzyltriphenylphosphonium chloride in methanol led to the formation of (Ph3PCH2Ph)[OsIIICl4(Hbzim)(DMSO)] (5). The complexes were characterized by IR, UV-vis, ESI mass spectrometry, 1H NMR spectroscopy, cyclic voltammetry, and X-ray crystallography. In contrast to NAMI-A, 2-4, 6, and 7 are kinetically stable in aqueous solution and resistant to hydrolysis. Surprisingly, they show reasonable antiproliferative activity in vitro in two human cell lines, HT-29 (colon carcinoma) and SK-BR-3 (mammary carcinoma), when compared with analogous ruthenium compounds. Structure-activity relationships and the potential of the prepared complexes for further development are discussed. PMID:17497853

Cebrián-Losantos, Berta; Krokhin, Artem A; Stepanenko, Iryna N; Eichinger, Rene; Jakupec, Michael A; Arion, Vladimir B; Keppler, Bernhard K

2007-05-12

285

(TAML)Fe**IV=O Complex in Aqueous Solution: Synthesis And Spectroscopic And Computational Characterization  

SciTech Connect

Recently, we reported the characterization of the S = 1/2 complex [Fe{sup V}(O)B*]{sup -}, where B* belongs to a family of tetraamido macrocyclic ligands (TAMLs) whose iron complexes activate peroxides for environmentally useful applications. The corresponding one-electron reduced species, [Fe{sup IV}(O)B*]{sup 2-} (2), has now been prepared in >95% yield in aqueous solution at pH > 12 by oxidation of [Fe{sup III}(H{sub 2}O)B*]{sup -} (1), with tert-butyl hydroperoxide. At room temperature, the monomeric species 2 is in a reversible, pH-dependent equilibrium with dimeric species [B*Fe{sup IV}?O?Fe{sup IV}B*]{sup 2-} (3), with a pK{sub a} near 10. In zero field, the Moessbauer spectrum of 2 exhibits a quadrupole doublet with {Delta}E{sub Q} = 3.95(3) mm/s and {delta} = ?0.19(2) mm/s, parameters consistent with a S = 1 Fe{sup IV} state. Studies in applied magnetic fields yielded the zero-field splitting parameter D = 24(3) cm{sup -1} together with the magnetic hyperfine tensor A/g{sub n}{beta}{sub n} = (?27, ?27, +2) T. Fe K-edge EXAFS analysis of 2 shows a scatterer at 1.69 (2) {angstrom}, a distance consistent with a Fe{sup IV} = O bond. DFT calculations for [Fe{sup IV}(O)B*]{sup 2-} reproduce the experimental data quite well. Further significant improvement was achieved by introducing hydrogen bonding of the axial oxygen with two solvent-water molecules. It is shown, using DFT, that the {sup 57}Fe hyperfine parameters of complex 2 give evidence for strong electron donation from B* to iron.

Chanda, A.; Shan, X.; Chakrabarti, M.; Ellis, W.C.; Popescu, D.L.; Oliveira, F.Tiago de; Wang, D.; Que, L.; Jr.; Collins, T.J.; Munck, E.; Bominaar, E.L.

2009-05-12

286

Spectroscopic and Functional Characterization of Iron-Sulfur Cluster-Bound Forms of Azotobacter vinelandii NifIscA†  

PubMed Central

The mechanism of [4Fe-4S] cluster assembly on A-type Fe-S cluster assembly proteins, in general, and the specific role of NifIscA in the maturation of nitrogen fixation proteins are currently unknown. To address these questions, in vitro spectroscopic studies (UV–visible absorption/CD, resonance Raman and Mössbauer) have been used to investigate the mechanism of [4Fe-4S] cluster assembly on Azotobacter vinelandii NifIscA, and the ability of NifIscA to accept clusters from NifU and to donate clusters to the apo form of the nitrogenase Fe-protein. The results show that NifIscA can rapidly and reversibly cycle between forms containing one [2Fe-2S]2+ and one [4Fe-4S]2+ cluster per homodimer via DTT-induced two-electron reductive coupling of two [2Fe-2S]2+ clusters and O2-induced [4Fe-4S]2+ oxidative cleavage. This unique type of cluster interconversion in response to cellular redox status and oxygen levels is likely to be important for the specific role of A-type proteins in the maturation of [4Fe-4S] cluster-containing proteins under aerobic growth or oxidative stress conditions. Only the [4Fe-4S]2+-NifIscA was competent for rapid activation of apo-nitrogenase Fe protein under anaerobic conditions. Apo-NifIscA was shown to accept clusters from [4Fe-4S] cluster-bound NifU via rapid intact cluster transfer, indicating a potential role as a cluster carrier for delivery of clusters assembled on NifU. Overall the results support the proposal that A-type proteins can function as carrier proteins for clusters assembled on U-type proteins and suggest that they are likely to supply [2Fe-2S] clusters rather than [4Fe-4S] for the maturation of [4Fe-4S] cluster-containing proteins under aerobic or oxidative stress growth conditions.

Mapolelo, Daphne T.; Zhang, Bo; Naik, Sunil G.; Huynh, Boi Hanh; Johnson, Michael K.

2012-01-01

287

Spectroscopic characterizations of a mixed surfactant mesophase and its application in materials synthesis  

NASA Astrophysics Data System (ADS)

A viscous lyotropic crystalline mesophase containing bis (2-ethylhexyl) sodium sulfosuccinate (AOT), alpha-phosphatidylcholine (lecithin), with comparable volume fractions of isooctane and water was characterized by Fourier-transform 31P and 1H nuclear magnetic resonance (NMR) spectroscopy. Shear alignment on the reverse hexagonal mesophase was reflected through both 31P NMR and 1H NMR spectra. A complicated 31P spectrum was observed as a result of superposition of chemical shifts according to the distribution of crystalline domains prior to shear. The initially disordered samples with polydomain structures became macroscopically aligned after Couette shear and the alignment retained for a long period of time. 31P NMR chemical shift anisotropy characteristics were used to elucidate orientation of the hexagonal phase. Interestingly, 1H NMR of the water, methyl and methylene groups exhibited spectral changes upon shear alignment closely corresponding with that of 31P NMR spectra. A reverse hexagonal to lamellar phase transition was manifested as an expanding of the expressed 31P NMR chemical shift anisotropy and an apparent reversal of the powder pattern with increasing water content and/or temperature. Correspondingly, 1H NMR spectra also experienced a spectral pattern transition as the water content or temperature was increased. These observations complement the findings of mesophase alignment obtained using small angle neutron scattering (SANS) and imply that 31P and 1H NMR spectroscopy can be used as probes to define microstructure and monitor orientation changes in this binary surfactant system. This is especially beneficial if these mesophases are used as templates for materials synthesis. The mesophase retains its alignment for extended periods allowing materials synthesis to be decoupled from the application of shear. Highly aligned string-like silica nanostructures were obtained through templated synthesis in the columnar hexagonal structure of the viscous lyotropic crystalline mesophase. A two-step procedure was used to first shear-align the surfactant mesophase, and then conduct synthesis under quiescent conditions in the mesophase. Polystyrene was post-grafted to the silica surface without disturbing its nanostring morphology. The coupling of materials synthesis in surfactant mesophases with processing techniques (e.g. extrusion) may result in functional materials, such as new catalyst support and membrane nanoarchitectures.

Liu, Limin

288

Structural, spectroscopic, and computational characterization of the azide adduct of Fe(III)(2,6-diacetylpyridinebis(semioxamazide)), a functional analogue of iron superoxide dismutase.  

PubMed

We have prepared and thoroughly characterized, using X-ray crystallographic, spectroscopic, and computational methods, the diazide adduct of [Fe(III)(dapsox)(H2O)2](+) [dapsox = 2,6-diacetylpyridinebis(semioxamazide)], (1), a low-molecular weight, functional analogue of iron superoxide dismutase (FeSOD). The X-ray crystal structure of the dimeric form of 1, (Na[Fe(III)(dapsox)(N3)2]·DMF)2 (2) shows two axially coordinated, symmetry inequivalent azides with differing Fe-N3 bond lengths and Fe-N-N2 bond angles. This inequivalence of the azide ligands likely reflects the presence of an interdimer hydrogen bonding interaction between a dapsox NH group and the coordinated nitrogen of one of the two azide ligands. Resonance Raman (rR) data obtained for frozen aqueous solution and solid-state samples of 2 indicate that the azides remain inequivalent in solution, suggesting that one of the azide ligands of 1 engages in an intermolecular hydrogen bonding interaction with a water molecule. Density functional theory (DFT) and time-dependent DFT calculations have been used to study two different computational models of 1, one using coordinates taken from the X-ray crystal structure of 2, and the other generated via DFT geometry optimization. An evaluation of these models on the basis of electronic absorption, magnetic circular dichroism, and rR data indicates that the crystal structure based model yields a more accurate electronic structure description of 1, providing further support for the proposed intermolecular hydrogen bonding of 1 in the solid state and in solution. An analysis of the experimentally validated DFT results for this model reveals that the azides have both ?- and ?-bonding interactions with the Fe(III) center and that more negative charge is located on the Fe-bound, rather than on the terminal, nitrogen atom of each azide. These observations are reminiscent of the results previously reported for the azide adduct of FeSOD and provide clues regarding the origin of the high catalytic activity of Fe-dapsox for superoxide disproportionation. PMID:23875582

Gutman, Craig T; Guzei, Ilia A; Brunold, Thomas C

2013-07-22

289

In vivo bone marrow lipid characterization with line scan Carr-Purcell-Meiboom-Gill proton spectroscopic imaging  

Microsoft Academic Search

Line scan Carr-Purcell-Meiboom-Gill spectroscopic imaging sequences have been used to extract lipid chemical composition indices in healthy adult bone marrow in the knee at 1.5 T. Since several spectroscopic echo readouts follow each excitation, the information acquired reflects a balance between spectral T2 decay processes and spectral resolution. To examine this balance in detail, data sets with two different echo

Robert V Mulkern; Jiqun Meng; John L Bowers; Koichi Oshio; Chun Zuo; Haicheng Li; Robert A Krafi; Daniel S Williamson; Diego Jaramillo

1997-01-01

290

Errors in spectroscopic measurements of SO/sub 2/ due to nonexponential absorption of laser radiation, with application to the remote monitoring of atmospheric pollutants  

SciTech Connect

Methods of measuring the concentration of atmospheric pollutants by laser absorption spectroscopy, such as differential absorption lidar (DIAL) and integrated long-path techniques, all rely on the validity of Beer's exponential absorption law. It is shown here that departures from this law occur if the probing laser has a bandwidth larger than the wavelength scale of structure in the absorption spectrum of the pollutant. A comprehensive experimental and theoretical treatment of the errors resulting from these departures is presented for the particular case of SO/sub 2/ monitoring at approx.300 nm. It is shown that the largest error occurs where the initial calibration measurement of absorption cross section is made at low pressure, in which case errors in excess of 5% in the cross section could occur for laser bandwidths >0.01 nm. Atmospheric measurements by DIAL or long-path methods are in most cases affected less, because pressure broadening smears the spectral structure, but when measuring high concentrations errors can exceed 5%.

Brassington, D.J.; Moncrieff, T.M.; Felton, R.C.; Jolliffe, B.W.; Marx, B.R.; Rowley, W.R.C.; Woods, P.T.

1984-02-01

291

Generation, characterization and spectroscopic use of ultrashort pulses fully tunable from the deep UV to the MIR  

NASA Astrophysics Data System (ADS)

The impressive work of Ian Walmsley has brought us invaluable new possibilities for the full characterization of ultrashort pulses. Spectroscopy of physical, chemical and biological relevance does, however, need pulses far from the 800 nm Ti:sapphire wavelength used for testing SPIDER and its advanced versions. Fortunately, optical parametric amplification (OPA) allows for easy generation of fully tunable pulses. I will review our efforts, highlighting noncollinear OPA, i.e. NOPA, for visible pulses shorter than 10 fs, mixing into the UV down to below 200 nm at 20 fs duration and novel hybrid schemes to efficiently reach the middle IR. I will show that these schemes can be used equally well from kHz to MHz repetition rates. The tunable ultrafast pulses in turn also demand improvements in characterization. The UV range led us to use difference frequency generation instead of the sum frequency mixing employed in the original SPIDER. The lack of proper beam splitters and auto-referencing led us to the use of two auxiliary pulses and the avoidance of any additional chirp added to the test pulse. We termed this zero-additional-phase SPIDER, i.e. ZAP-SPIDER. Lately, with increased use of UV pulses, we came to the conclusion, that the ubiquitous two-photon-absorption can well serve as nonlinearity, at least in UV autocorrelation measurement. How do we use this for full characterization? Hopefully, Ian will tell us! Since the proof is known to be in the eating, I will demonstrate the success of our technical efforts with examples taken from ultrafast molecular dynamics. Highly pronounced vibronic wavepackets in the product of ultrafast excited state proton transfer and the very primary processes leading to homolytic and heterolytic bond cleavage will serve as easy to comprehend illustrations.

Riedle, Eberhard

2011-03-01

292

A perturbation approach to characterize absorptive inclusions in diffusing media by time-resolved contrast measurements  

Microsoft Academic Search

Time-resolved measurements of ultrashort light pulses transmitted through turbid scattering media have been performed to determine the possibilities and the limitations of a first-order perturbation approach to recover the absorption coefficient of different tissue-like cylindrical absorptive phantoms. The model accounts for the effect of a spatially varying absorption coefficient of an inclusion on the time-resolved transmittance. We have determined the

R. Esposito; S. DeNicola; M. Lepore; I. Delfino; P. L. Indovina

2004-01-01

293

Characterization of a bulk semiconductor's band gap via a near-absorption edge optical transmission experiment  

Microsoft Academic Search

An experimental setup that employs lock-in detection to measure the optical transmission data on a bulk semiconductor sample is described. A straightforward manipulation of these data yields the semiconductor's absorption coefficient alpha in the energy range near its absorption edge (0absorption spectra is presented. It is

John M. Essick; Richard T. Mather

1993-01-01

294

Synthesis, characterization and microwave absorption of carbon-coated Sn nanorods  

NASA Astrophysics Data System (ADS)

Carbon-coated Sn nanorods have been synthesized by an arc-discharge method. The Sn/C-paraffin composite shows excellent electromagnetic (EM) absorption properties. Reflection losses exceeding -20 dB can be realized in any interval within the 2-18 GHz range by choosing an appropriate thickness of the absorbent layer between 1.5 and 9 mm. The EM-wave absorption properties of nanocomposite materials are illustrated in detail by means of an absorption-tube-map. The carbon-coated Sn nanorods are attractive candidates for EM-wave absorption, which significantly enriches the family of EM-wave nano-absorbents.

Wang, Z. H.; Han, Z.; Geng, D. Y.; Zhang, Z. D.

2010-04-01

295

Powder synthesis and electrical, dielectric spectroscopic characterization of rare earth disilicates (D-Er2Si2O7): Transistor scaling-22 nm or beyond  

NASA Astrophysics Data System (ADS)

Rare earth disilicates are now a day's being analyzed as a dielectric layer for transistor scaling for the advanced 22 nm regime or beyond. So to explore these materials, the polymorphic powdered Er2Si2O7 (D phase) is synthesized by solid state double sintering method to study its characteristics. Structural characterization has been performed by X-ray diffraction. SEM and EDX results shows the rods like morphology of particles and composition. The dc electrical properties are evaluated by two probe method as a function of temperature. The dielectric spectroscopic measurements of D-Er2Si2O7 are performed in the temperature range 300-420 K and frequency range 1 kHz to 1 MHz. The dc electrical transport phenomenon is analyzed using Mott’s variable-range hopping approach. The ac conductivity ?ac(?) is obtained through the dielectric spectroscopic measurements.

Ameer, Shahid; Maqsood, Asghari

2012-10-01

296

Characterization of functionalized self-assembled monolayers and surface-attached interlocking molecules using near-edge X-ray absorption fine structure spectroscopy  

NASA Astrophysics Data System (ADS)

Quantitative knowledge of the fundamental structure and substrate binding, as well as the direct measurement of conformational changes, are essential to the development of self-assembled monolayers (SAMs) and surface-attached interlocking molecules, catenanes and rotaxanes. These monolayers are vital to development of nano-mechanical, molecular electronic, and biological/chemical sensor applications. This dissertation investigates properties of functionalized SAMs in sulfur-gold based adsorbed molecular monolayers using quantitative spectroscopic techniques including near-edge x-ray absorption fine structure spectroscopy (NEXAFS) and x-ray photoelectron spectroscopy (XPS). The stability of the gold-thiolate interface is addressed. A simple model SAM consisting of dodecanethiol adsorbed on Au(111) degrades significantly in less than 24 hours under ambient laboratory air. S 2p and O 1s XPS show the gold-bound thiolates oxidize to sulfinates and sulfonates. A reduction of organic material on the surface and a decrease in order are observed as the layer degrades. The effect of the carboxyl vs. carboxylate functionalization on SAM structure is investigated. Carboxyl-terminated layers consisting of long alkyl-chain thiols vs. thioctic acid with short, sterically separated, alkyl groups are compared and contrasted. NEXAFS shows a conformational change, or chemical switchability, with carboxyl groups tilted over and carboxylate endgroups more upright. Surface-attached loops and simple surface-attached rotaxanes are quantitatively characterized, and preparation conditions that lead to desired films are outlined. A dithiol is often insufficient to form a molecular species bound at each end to the substrate, while a structurally related disulfide-containing polymer yields surface-attached loops. Similarly, spectroscopic techniques show the successful production of a simple, surface-attached rotaxane that requires a "molecular riveting" step to hold the mechanically attached crown ether rings in place until disulfides in the molecules adsorb onto the gold. Finally, by introducing an aldehyde into the crown ether portion of this well-characterized surface-attached rotaxane, conformational changes are directly measured when the aldehyde is reacted with aniline. These fundamental results have implications for the creation of nanoscale functional surfaces using molecular monolayers.

Willey, Trevor Michael

297

Spectroscopic Character and Spatial Distribution of Hydroxyl and Water Absorption Features Measured on the Lunar Surface by the Moon Mineralogy Mapper Imaging Spectrometer on Chandrayaan-1  

Microsoft Academic Search

The Moon Mineralogy Mapper imaging spectrometer on Chandrayaan-1 has a broad spectral range from 430 to 3000 nm. By design, the range was specified to extend to 3000 nm to allow for possible detection of trace volatile compounds that possess absorption bands near 3000 nm. Soon after acquisition and calibration of a large fraction of the lunar surface in early

R. O. Green; C. M. Pieters; J. Goswami; R. N. Clark; M. Annadurai; J. W. Boardman; B. J. Buratti; J. Combe; M. D. Dyar; J. W. Head; C. Hibbitts; M. Hicks; P. Isaacson; R. L. Klima; G. Y. Kramer; S. Kumar; K. E. Livo; S. Lundeen; E. Malaret; T. B. McCord; J. F. Mustard; J. W. Nettles; N. E. Petro; C. J. Runyon; M. Staid; J. M. Sunshine; L. A. Taylor; S. Tompkins; P. Varanasi

2009-01-01

298

Infrared reflection absorption spectroscopic study of the adsorption structures of dimethyl ether and methyl ethyl ether on Cu(1 1 1) and Ag(1 1 1)  

NASA Astrophysics Data System (ADS)

Infrared reflection absorption (IRA) spectra measured for dimethyl ether (DME) adsorbed at 80 K on Cu(1 1 1) and Ag(1 1 1) give IR bands belonging only to the A1 and B2 species, indicating that the adsorbate takes on an orientation in which the C2 axis bisecting the COC bond angle tilts away from the surface normal within the plane perpendicular to the substrates. The DFT method was applied to simulate the IRA spectra, indicating that the tilt angles of DME on Cu(1 1 1) and Ag(1 1 1) are about 50° and 55°, respectively, at submonolayer coverages. The results are in contrast to the case of DME on Cu(1 1 0) and Ag(1 1 0), where the C2 axis is perpendicular to the substrates [T. Kiyohara et al., J. Phys. Chem. A 106 (2002) 3469]. Methyl ethyl ether (MEE) adsorbed at 80 K on Cu(1 1 1) gives IRA bands mainly ascribable to the gauche (G) form, whereas the IRA spectra measured for MEE on Ag(1 1 1) are characterized by the trans (T) form. The rotational isomers are identical with those on Cu(1 1 0) and Ag(1 1 0); i.e., MEE on Cu(1 1 0) takes the G form and the adsorbate on Ag(1 1 0) the T form [T. Kiyohara et al., J. Phys. Chem. B 107 (2003) 5008]. The simulation of the IRA spectra indicated that (i) the G form adsorbate on Cu(1 1 1) takes an orientation, in which the axis bisecting the COC bond angle tilts away from the surface normal by ca. 30° within the plane perpendicular to the surface to make the CH3 CH2 bond almost parallel to the surface, and (ii) the T form adsorbate on Ag(1 1 1) takes an orientation, in which the bisecting axis tilts away by ca. 60° from the surface normal within the perpendicular plane. Comparison of these adsorption structures of MEE on the (1 1 1) substrates with those of MEE on Cu(1 1 0) and Ag(1 1 0) indicates that the structures are mainly determined by a coordination interaction of the oxygen atom to the surface metals and an attractive van der Waals interaction between the ethyl group of MEE and the substrate surfaces. The coordination interaction plays an important role on Cu(1 1 1) and Cu(1 1 0), which makes the adsorbate on the Cu substrates to take the orientations with the bisecting axis near parallel to the surface normal and to assume the G form in order to make the ethyl group parallel to the surface, which is favorable for the van der Waals interaction. In the case of MEE on the Ag substrates the attractive van der Waals interaction plays a dominant role, resulting in the T form which is more favorable for the interaction than the G form.

Kasahara, Takahiro; Itoh, Koichi

2007-02-01

299

X-Ray Absorption And EPR Spectroscopic Studies of the Biotransformations of Chromium(Vi) in Mammalian Cells. Is Chromodulin An Artifact of Isolation Methods?  

SciTech Connect

Very different biological activities are usually ascribed to Cr(VI) (a toxin and carcinogen) and Cr(III) (an antidiabetic agent), although recent evidence suggests that both these types of actions are likely to arise from cellular uptake of varying concentrations of Cr(VI). The first systematic study of XANES spectra of Cr(III) complexes formed in Cr(VI)-treated mammalian cells (A549, HepG2, V79, and C2C12 cell lines), and in subcellular fractions of A549 cells, has been performed using a library of XANES spectra of model Cr(III) complexes. The results of multiple linear regression analyses of XANES spectra, in combination with multiple-scattering fits of XAFS spectra, indicate that Cr(III) formed in Cr(VI)-treated cells is most likely to bind to carboxylato, amine, and imidazole residues of amino acids, and to a lesser extent to hydroxo or aqua ligands. A combination of XANES and EPR spectroscopic data for Cr(VI)-treated cells indicates that the main component of Cr(III) formed in such cells is bound to high-molecular-mass ligands (>30 kDa, probably proteins), but significant redistribution of Cr(III) occurs during the cell lysis, which leads to the formation of a low-molecular-mass (<30 kDa) Cr(III)-containing fraction. The spectroscopic (XANES, XAFS, and EPR) properties of this fraction were strikingly similar to those of the purported natural Cr(III)-containing factor, chromodulin, that was reported to be isolated from the reaction of Cr(VI) with liver. These data support the hypothesis that a chromodulin-like species, which is formed from such a reaction, is an artifact of the reported isolation procedure.

Levina, A.; Harris, H.H.; Lay, P.A.; /Sydney U.

2007-07-10

300

Ground-based infrared spectroscopic measurements of carbonyl sulfide: Free tropospheric trends from a 24-year time series of solar absorption measurements  

Microsoft Academic Search

Solar absorption spectra recorded over a 24-year time span have been analyzed to retrieve average free tropospheric mixing ratios of carbonyl sulfide (OCS). The measurements were recorded with the Fourier transform spectrometer located in the U.S. National Solar Observatory McMath solar telescope facility on Kitt Peak (altitude 2.09 km, lat. 31.9°N, long. 111.6°W), southwest of Tucson, Arizona, and were obtained

C. P. Rinsland; A. Goldman; E. Mahieu; R. Zander; J. Notholt; N. B. Jones; D. W. T. Griffith; T. M. Stephen; L. S. Chiou

2002-01-01

301

Observations, compositional, and physical characterization of near-Earth and Mars-crosser asteroids from a spectroscopic survey  

NASA Astrophysics Data System (ADS)

Aims: We analyse a significantly large sample of spectroscopic data to provide a compositional characterization of the near-Earth asteroid population. We present visible and near-infrared spectra of a total of 74 near-Earth asteroids (NEAs) and Mars-crossers (MCs), covering the wavelength region from 0.5 to 2.5 ?m. Using spectra of NEAs from other databases to enlarge our sample, and compiling two comparison samples of main belt asteroids (MBs) and ordinary chondrites (OCs), we analyse a total of 79 NEAs, 91 MBs, and 103 OCs. Methods: We obtained our visible and near-infrared spectra using the instruments and the telescopes located at “El Roque de los Muchachos” Observatory, in the island of La Palma (Spain). We compute several diagnostic spectral parameters from the reflectance spectra of NEAs, MBs, and OCs, that are used to infer the mineralogical composition. The distribution of the obtained values are analysed in 2 different parameter spaces. We also apply a robust statistical method based on neuronal networks to those spectral parameters, to compare the NEAs with OCs. Space weathering effects and dynamical and physical properties of NEAs and MBs are also studied. Results: Compositional differences between MBs and NEAs are inferred from the mineralogical analysis. The most remarkable results are: (1) the high olivine content of the NEAs; (2) the compositional similarity between NEAs and a small group of meteorites, the LL ordinary chondrites; and (3) that NEAs are not compositionally similar to OCs, implying that they are not the most likely parent bodies of those meteorites, as has been widely believed. To explain their apparently fresh surfaces (NEAs are on average less red than MBs), a combination of composition and size distribution (NEAs have diameters of some kilometres) should be invoked. Dynamical models applied to our sample of NEAs indicate that most of them originate in the inner part of the main belt, as expected. Appendices are only available in electronic form at http://www.aanda.org

de León, J.; Licandro, J.; Serra-Ricart, M.; Pinilla-Alonso, N.; Campins, H.

2010-07-01

302

FT-IR spectroscopic assessment of gas-phase absorption of atmospheric molecular species at low concentrations and their associated adsorption effects on various material surfaces  

NASA Astrophysics Data System (ADS)

Changes in the infrared absorbance observed at levels of concentration in the subparts per million (sub-ppm) of atmospherically significant molecular species, such as HCl, SO2, NO2 and NH3, has been quantified as a function of pressure and temperature for the surface reactions of these gases with various materials (e.g. copper, aluminum, stainless steel and teflon). A Nicolet Magna-IR 550 Fourier transform infrared (FT-IR) spectrometer operating in the 400-4000 cm-1 region and fitted with a 10-meter multipass absorption cell and a deuterated triglycine sulfate (DTGS) detector has been used for recording the spectra. Tubing materials chosen are typically associated with the hardware of measuring instruments used to collect atmospheric trace gas samples. The FT-IR spectrometer has been used to determine the concentration levels at the inlet and outlet tubing of the absorption cell. Small changes in the species concentration down to sub-ppm levels have also been recorded in the 650-4000 cm-1 region using a liquid nitrogen-cooled Mercury Cadmium Telluride (MCT-A) detector interfaced with the FT-IR spectrometer. The associated adsorption effects at the various gas-solid interfaces in the measuring apparatus, including the `sticking' effects on the walls of the absorption cell, have been quantified. Carefully monitored pressure and temperature conditions were utilized to provide a controlled environment, so as to quantify minute changes in the absorption of infrared radiation due to variations in the concentration of the gas samples brought about by different adsorption effects. Values for the absorption coefficients of the different gas phase molecular species in the infrared region of interest were derived from the absorbance measurements. The degree of adsorption for specific gassolid interfaces and the kinetic theory of the adsorption process (assuming a mono-layer) enabled the determination of the corresponding rate constants. It is envisioned that the accurate determination of the adsorption coverage parameters and the Langmuir rate constants for the various gas-material combinations will aid in the refinement of precise values for the associated residence time and activation energies and thereby lead to the development of a comprehensive adsorption isotherm model for gas-surface interactions.

Dowdye, Edward Henry, Jr.

2000-11-01

303

Characterization and intercomparison of aerosol absorption photometers: result of two intercomparison workshops  

NASA Astrophysics Data System (ADS)

Absorption photometers for real time application have been available since the 1980s, but the use of filter-based instruments to derive information on aerosol properties (absorption coefficient and black carbon, BC) is still a matter of debate. Several workshops have been conducted to investigate the performance of individual instruments over the intervening years. Two workshops with large sets of aerosol absorption photometers were conducted in 2005 and 2007. The data from these instruments were corrected using existing methods before further analysis. The inter-comparison shows a large variation between the responses to absorbing aerosol particles for different types of instruments. The unit to unit variability between instruments can be up to 30% for Particle Soot Absorption Photometers (PSAPs) and Aethalometers. Multi Angle Absorption Photometers (MAAPs) showed a variability of less than 5%. Reasons for the high variability were identified to be variations in sample flow and spot size. It was observed that different flow rates influence system performance with respect to response to absorption and instrumental noise. Measurements with non absorbing particles showed that the current corrections of a cross sensitivity to particle scattering are not sufficient. Remaining cross sensitivities were found to be a function of the total particle load on the filter. The large variation between the response to absorbing aerosol particles for different types of instruments indicates that current correction functions for absorption photometers are not adequate.

Müller, T.; Henzing, J. S.; de Leeuw, G.; Wiedensohler, A.; Alastuey, A.; Angelov, H.; Bizjak, M.; Collaud Coen, M.; Engström, J. E.; Gruening, C.; Hillamo, R.; Hoffer, A.; Imre, K.; Ivanow, P.; Jennings, G.; Sun, J. Y.; Kalivitis, N.; Karlsson, H.; Komppula, M.; Laj, P.; Li, S.-M.; Lunder, C.; Marinoni, A.; Martins Dos Santos, S.; Moerman, M.; Nowak, A.; Ogren, J. A.; Petzold, A.; Pichon, J. M.; Rodriquez, S.; Sharma, S.; Sheridan, P. J.; Teinilä, K.; Tuch, T.; Viana, M.; Virkkula, A.; Weingartner, E.; Wilhelm, R.; Wang, Y. Q.

2011-02-01

304

Characterization and intercomparison of aerosol absorption photometers: result of two intercomparison workshops  

NASA Astrophysics Data System (ADS)

Absorption photometers for real time application have been available since the 1980s, but the use of filter-based instruments to derive information on aerosol properties (absorption coefficient and black carbon, BC) is still a matter of debate. Several workshops have been conducted to investigate the performance of individual instruments over the intervening years. Two workshops with large sets of aerosol absorption photometers were conducted in 2005 and 2007. The data from these instruments were corrected using existing methods before further analysis. The inter-comparison shows a large variation between the responses to absorbing aerosol particles for different types of instruments. The unit to unit variability between instruments can be up to 30% for Particle Soot Absorption Photometers (PSAPs) and Aethalometers. Multi Angle Absorption Photometers (MAAPs) showed a variability of less than 5%. Reasons for the high variability were identified to be variations in sample flow and spot size. It was observed that different flow rates influence system performance with respect to response to absorption and instrumental noise. Measurements with non absorbing particles showed that the current corrections of a cross sensitivity to particle scattering are not sufficient. Remaining cross sensitivities were found to be a function of the total particle load on the filter. The large variation between the response to absorbing aerosol particles for different types of instruments indicates that current correction functions for absorption photometers are not adequate.

Müller, T.; Henzing, J. S.; de Leeuw, G.; Wiedensohler, A.; Alastuey, A.; Angelov, H.; Bizjak, M.; Collaud Coen, M.; Engström, J. E.; Gruening, C.; Hillamo, R.; Hoffer, A.; Imre, K.; Ivanow, P.; Jennings, G.; Sun, J. Y.; Kalivitis, N.; Karlsson, H.; Komppula, M.; Laj, P.; Li, S.-M.; Lunder, C.; Marinoni, A.; Martins Dos Santos, S.; Moerman, M.; Nowak, A.; Ogren, J. A.; Petzold, A.; Pichon, J. M.; Rodriquez, S.; Sharma, S.; Sheridan, P. J.; Teinilä, K.; Tuch, T.; Viana, M.; Virkkula, A.; Weingartner, E.; Wilhelm, R.; Wang, Y. Q.

2010-04-01

305

Structural characterization of the mononuclear iron site in Pseudomonas cepacia phthalate DB01 dioxygenase using X-ray absorption spectroscopy  

Microsoft Academic Search

Phthalate dioxygenase (PDO) from Pseudomonas cepacia contains a Rieske-like [2Fe-2S] cluster and a mononuclear non-heme Fe(II) site. The mononuclear iron can be replaced by a\\u000a variety of divalent metal ions, although only Fe(II) permits catalytic activity. We used X-ray absorption spectroscopy to\\u000a characterize the structural properties of the mononuclear iron site and to follow the structural changes in this site

Him-Tai Tsang; Christopher J. Batie; David P. Ballou; James E. Penner-Hahn

1996-01-01

306

Characterization of Pt-Ru\\/C catalysts by X-ray absorption spectroscopy and temperature-programmed surface reaction  

Microsoft Academic Search

X-ray absorption spectroscopy (XAS) was employed to characterize carbon black supported Pt-Ru catalysts, which are commercially available to be utilized as the anode of polymeric-electrolyte-membrane fuel cells. Both Pt and Ru were found partially oxidized in the as-received form. Upon exposure to hydrogen at room temperature, the catalysts were completely reduced to the metallic state. The bimetallic nanoparticles on the

Din-Goa Liu; Jyh-Fu Lee; Mau-Tsu Tang

2005-01-01

307

An X-ray absorption spectroscopic study on mixed conductive La0.6Sr0.4Co0.8Fe0.2O(3-?) cathodes. I. Electrical conductivity and electronic structure.  

PubMed

The electrical conduction mechanism of mixed conductive perovskite oxides, La(0.6)Sr(0.4)Co(0.8)Fe(0.2)O(3-?), for cathode materials of solid oxide fuel cells has been investigated from electronic structural changes during oxygen vacancy formation. La(0.6)Sr(0.4)Co(0.8)Fe(0.2)O(3-?) was annealed under various oxygen partial pressures p(O(2))s at 1073 K and quenched. Iodometric titration indicated that the oxygen nonstoichiometry of La(0.6)Sr(0.4)Co(0.8)Fe(0.2)O(3-?) depended on the annealing p(O(2)), with more oxygen vacancies introduced at lower than at higher p(O(2))s. X-Ray absorption spectroscopic measurements were performed at the O K-, Co L-, Fe L-, Co K-, and Fe K-edges. The valence states of the Co and Fe ions were investigated by the X-ray absorption near edge structure (XANES) at the Co and Fe L(III)-edges. While the Fe average valence was almost constant, the valence of the Co ions decreased with oxygen vacancy introduction. The O K-edge XANES spectra indicated that electrons were injected into the Co 3d/O 2p hybridization state with oxygen vacancy introduction. Both absorption edges at the Co and Fe K-edge XANES shifted towards lower energies with oxygen vacancy introduction. The shift at the Co K-edge resulted from the decrease in the Co average valence and that at the Fe K-edge appeared to be caused by changes in the coordination environment around the Fe ions. The total conductivity of La(0.6)Sr(0.4)Co(0.8)Fe(0.2)O(3-?) decreased with decreasing p(O(2)), due to a decreasing hole concentration. PMID:21850304

Orikasa, Yuki; Ina, Toshiaki; Nakao, Takayuki; Mineshige, Atsushi; Amezawa, Koji; Oishi, Masatsugu; Arai, Hajime; Ogumi, Zempachi; Uchimoto, Yoshiharu

2011-08-17

308

Isolation and characterization of two new alkaloids, norpandamarilactonine-A and -B, from Pandanus amaryllifolius by spectroscopic and synthetic methods.  

PubMed

Two new alkaloids, norpandamarilactonine-A (1) and -B (2), which have a pyrrolidinyl-alpha,beta-unsaturated gamma-lactone moiety as in the known pandamarilactonine alkaloids, were isolated from the leaves of Pandanus amaryllifolius. Their structures were determined by spectroscopic analysis and total synthesis. PMID:11575961

Takayama, H; Ichikawa, T; Kitajima, M; Nonato, M G; Aimi, N

2001-09-01

309

Vibrational, 1H-NMR spectroscopic, and thermal characterization of gladiolus root exudates in relation to Fusarium oxysporum f. sp. gladioli resistance.  

PubMed

Fourier transform Raman (FT Raman) and IR (FTIR) and (1)H-NMR spectroscopies coupled with differential scanning calorimetry (DSC) were applied to the characterization of root exudates from two cultivars of gladiolus (Spic Span and White Prosperity) with different degrees of resistance and susceptibility to Fusarium oxysporum gladioli, the main pathogen of gladiolus. This work was aimed at correlating the composition of root exudates with the varietal resistance to the pathogen. Spectroscopic analysis showed that White Prosperity root exudate differs from Spic Span root exudate by a higher relative amount of the aromatic-phenolic and sugarlike components and a lower relative amount of carbonylic and aliphatic compounds. DSC analysis confirmed the spectroscopic results and showed that White Prosperity root exudate is characterized by an aromatic component that is present in a higher amount than in the Spic Span root exudate. The results are discussed in relation to the spore germination tests showing that White Prosperity, which is characterized by a remarkable resistance toward F. oxysporum gladioli, exudes substances having a negative influence on microconidial germination of the pathogen; root exudates from Spic Span, one of the most susceptible cultivars to F. oxysporum gladioli, proved to have no effect. White Prosperity's ability to inhibit conidial germination of F. oxysporum gladioli can be mainly related to the presence of a higher relative amount of aromatic-phenolic compounds. PMID:12209451

Taddei, P; Tugnoli, V; Bottura, G; Dallavalle, E; Zechini D'Aulerio, A

2002-01-01

310

Cobalt(II) complexes of 5,7-dimethyl[1,2,4]-triazolo-[1,5-a]-pyrimidine. Spectroscopic characterization, XRD study and antimicrobial activity  

Microsoft Academic Search

Several cobalt(II) complexes of 5,7-dimethyl-[1,2,4]-tria-zolo-[1,5-a]-pyrimidine (DMTP) have been prepared and characterized by thermal and spectroscopic techniques. The crystal structure of [Co(DMTP)2(H2O)4]Br2·2H2O has been determined by XRD; the metal ion is octahedrally coordinated by two DMTP ligands through the usual N(3) site and four water molecules. Metal binding to N(3) for DMTP is consistent with the electronic properties calculated with the

María A. Romero; Juan M. Salas; Miguel Quirós; David J. Williams; José Molina

1993-01-01

311

Chemical, spectroscopic characterization, DFT studies and initial pharmacological assays of a silver(I) complex with N-acetyl- l-cysteine  

Microsoft Academic Search

A new silver(I) complex with N-acetyl-l-cysteine (NAC) of composition AgC5H8NO3S·H2O was synthesized and characterized by a set of chemical and spectroscopic measurements. Solid-state 13C nuclear magnetic resonance (SSNMR) and infrared (IR) analyses indicate the coordination of the ligand to Ag(I) through the sulfur atom. The Ag–NAC complex is slightly soluble in dimethyl sulfoxide. It is insoluble in water, methanol, ethanol,

Camilla Abbehausen; Tassiele A. Heinrich; Emiliana P. Abrão; Claudio M. Costa-Neto; Wilton R. Lustri; André L. B. Formiga; Pedro P. Corbi

2011-01-01

312

Mono and polynuclear silver(I) complexes with thiosaccharine and triphenylphosphine or 2,2?-bipyridine. Synthesis, spectroscopic and structural characterization  

NASA Astrophysics Data System (ADS)

Reaction of Ag6(tsac)6 (tsac- = thiosaccharinate anion) with PPh3 and 2,2?-bipyridine (bipy) ligands give rise to three new silver-thiosaccharinate complexes, [Ag(tsac)(PPh3)3], [Ag4(tsac)4(PPh3)3] , and [Ag2(tsac)2(bipy)2]. Their crystal structures established by single-crystal X-ray diffraction and IR spectroscopic characterizations are reported here. In each complex a singular coordination mode for the thiosaccharinate ligands is observed. The most important features of the different coordination modes of the thionates are discussed.

Dennehy, Mariana; Quinzani, Oscar V.; Jennings, Michael

2007-09-01

313

Synthesis, structural, spectroscopic and thermal characterization of cobalt complexes with 3- and 6-methylpicolinic acid. Voltammetric and spectrophotometric study in solution  

Microsoft Academic Search

Cobalt complexes of 3- and 6-methylpicolinic acid, namely [Co(3-Mepic)3] (1) and [Co(6-Mepic)2(H2O)2]·2H2O (2) were prepared and characterized by spectroscopic methods (IR, UV–Vis, NMR), their molecular and crystal structures were determined by X-ray crystal structure analysis and their thermal stability by TGA\\/DTA methods. Square-wave voltammetry showed that on mercury electrode the oxidation of 2 requires higher potential than the oxidation of

Boris-Marko Kukovec; Zora Popovi?; Šebojka Komorsky-Lovri?; Vlasta Vojkovi?; Marijana Vinkovi?

2009-01-01

314

Spectroscopic characterization of II-VI compounds and application to copper indium selenide-based solar cells  

NASA Astrophysics Data System (ADS)

Structures consisting of CuInSe2 films, deposited on molybdenum-coated glass substrates and covered by CdS or ZnO thin films, for application in solar cells, have been characterized by spectroscopic ellipsometry, atomic force microscopy, photoluminescence and photovoltaic response. Computer aided simulations of the photovoltaic operation of these structures have been made to reinforce and complement the results of the characterization studies. The optical properties of CuInSe2, CdS and ZnO films over ranges of photon energies from 1.0 through 4.0 eV were determined. The measured optical bandgaps, 0.96 eV for CuInSe2, 2.35 eV for CdS and 3.33 eV for ZnO, are in good agreement with the values reported in the literature for bulk samples of those materials. In the case of CuInSe2, a second transition photon energy was detected at 1.02 eV. This transition was assumed to be due to gallium content in the CuInSe 2 film near the Mo interface. Depth structure profiles of the films were generated. The one for as-deposited CuInSe2 was found to include a surface layer (ODC layer) about 230 nm thick which exhibited optical properties considerably different from those of the bulk of the film. In the case of US (as might be expected for films grown by the chemical bath deposition technique) it was found that the films consist of two layers: a very compact one, about 29 nm thick, at the bottom of the film; and a much thicker and porous one, about 127 nm thick, on top. CdS/CuInSe2 and ZnO/CuInSe2 test cells were fabricated from substrates with as-deposited CuInSe2 and CuInSe2 from which a layer had been removed by etching. Test cells with CdS buffer layers on etched CuInSe2 exhibited degraded performance compared to cells fabricated on as-deposited CuInSe2. These results suggest that some interaction between US and the absorber material occurs in the case of etched absorbers. Thus, CdS may play a greater role than simply providing protection for the absorber layer during deposition of the TCO (top contact) layer. Photoluminescence measurements from plain CuInSe2 films, compared with similar measurements taken for CdS- or ZnO-coated films, showed an increase in the photoluminescence emission in the later cases, indicative of a reduction of nonradiative recombination caused by a passivating effect of the buffer layers on the interface. Numerical simulations of the operation of CuInSe2-based solar cells disclosed a mechanism by which the resistivity of the buffer layer may enhance the performance of the cells, and one that would promote inflected current-voltage characteristics. A comparison between the simulated performance of devices with experimentally determined results revealed the effects of a process-related connection between the resistivity of buffer layers and the electronic properties of the absorber, which have an impact on the conversion efficiencies of solar cells.

Aguilar Juarez, Heriberto De Jesus

315

Absorption and emission spectroscopic characterisation of the LOV2-domain of phot from Chlamydomonas reinhardtii fused to a maltose binding protein  

NASA Astrophysics Data System (ADS)

The absorption and emission behaviour of flavin mononucleotide (FMN) in the wild-type light, oxygen and voltage-sensitive (LOV) domain LOV2 of the photoreceptor phot from the green alga Chlamydomonas reinhardtii is studied at pH 8. Actually a LOV2-MBP-fusion protein (MBP=maltose binding protein) expressed in an Escherichia coli strain is investigated. For fresh samples stored in the dark an initial fluorescence quantum yield of ?F=0.08±0.01 is determined. Blue-light photo-excitation generates a non-fluorescent intermediate photoproduct (flavin-C(4a)-cysteinyl adduct with absorption peak at 390 nm). In the aqueous solutions studied approximately seven percent of the FMN molecules are not bound to the protein (free FMN in oxidized form) and about seven percent of the non-covalently bound FMN are not convertible to an adduct. Approximately two thirds of the intermediate photoproduct recovers with a time constant of 41 ± 1 s, while approximately one third recovers with a time constant of about 7 min. The photo-adduct formation is thought to proceed via singlet excited-state electron transfer and triplet formation.

Holzer, W.; Penzkofer, A.; Susdorf, T.; Álvarez, M.; Islam, Sh. D. M.; Hegemann, P.

2004-07-01

316

Structure of the dinuclear active site of urease. X-ray absorption spectroscopic study of native and 2-mercaptoethanol-inhibited bacterial and plant enzymes  

SciTech Connect

The structures of the dinuclear Ni(II) active sites of urease from jack bean and Klebsiella aerogenes are compared with and without the addition of the inhibitor 2-mercaptoethanol (2-ME). No significant differences are observed by nickel K-edge X-ray absorption spectroscopy between the plant and bacterial enzymes. The Ni X-ray absorption edge spectra display an 8332-eV 1s[yields]3d peak intensity similar to that observed for five-coordinate Ni(II) compounds[sup 1] for both native and 2-ME-bound derivatives. Curve-fitting of Ni EXAFS data indicates that the average Ni(II) coordination environment in native urease can be described as Ni(imidazole)[sub x](N,O)[sub 5[minus]x], with x = 2 or 3. Addition of 2-ME results in replacement of one of the non-imidazole (N,O) ligands with (S,Cl) (most likely the thiolate sulfur of 2-ME) and results in the appearance of a new peak in the Fourier transforms that can only be fit with a Ni[center dot][center dot][center dot]Ni scattering component at a Ni-Ni distance of [approximately]3.26 [angstrom]. A structure for this 2-ME-bound dinuclear site is proposed to contain the two Ni(II) ions bridged by the thiolate sulfur of 2-ME.

Wang, Shengke; Scott, R.A. (Univ. of Georgia, Athens (United States)); Lee, M.H.; Hausinger, R.P. (Michigan State Univ., East Lansing (United States)); Clark, P.A.; Wilcox, D.E. (Dartmouth College, Hanover, NH (United States))

1994-04-13

317

Ultra-violet and visible absorption characterization of explosives by differential reflectometry  

NASA Astrophysics Data System (ADS)

This study presents some optical properties of TNT (2,4,6-trinitrotoluene), RDX, HMX and tetryl, specifically their absorption spectra as a function of concentration in various solvents in the ultraviolet and visible portion of the electromagnetic spectrum. We utilize a standoff explosives detection method, called differential reflectometry (DR). TNT was diluted in six different solvents (acetone, acetonitrile, ethanol, ethyl acetate, methanol, and toluene), which allowed for a direct comparison of absorption features over a wide range of concentrations. A line-shape analysis was adopted with great accuracy (R2 > 0.99) to model the absorption features of TNT in differential reflectivity spectra. We observed a blue shift in the pertinent absorption band with decreasing TNT concentration for all solvents. Moreover, using this technique, it was found that for all utilized solvents the concentration of TNT as well as of RDX, HMX, and tetryl, measured as a function of the transition wavelength of the ultra-violet absorption edge in differential reflectivity spectra shows three distinct regions. A model is presented to explain this behavior which is based on intermolecular hydrogen bonding of explosives molecules with themselves (or lack thereof) at different concentrations. Other intermolecular forces such as dipole-dipole interactions, London dispersion forces and ?-stacking contribute to slight variations in the resulting spectra, which were determined to be rather insignificant in comparison to hydrogen bonding. The results are aimed towards a better understanding of the DR spectra of explosives energetic materials.

Dubroca, Thierry; Moyant, Kyle; Hummel, Rolf E.

2013-03-01

318

In situ X-ray Absorption Spectroscopic Investigation of the Electrochemical Conversion Reactions of CuF2-MoO3 Nanocomposite  

SciTech Connect

We have used X-ray absorption spectroscopy at the Cu K-edge to investigate the electrochemical conversion reaction of 20 nm size 85 wt% CuF{sub 2}-15 wt% MoO{sub 3} nanocomposite under in situ conditions. The nanocomposite was prepared by high energy milling. Upon discharge, the lithiation reaction with the nanocomposite resulted in the formation of nanophase metallic Cu, which is consistent with the conversion of CuF{sub 2} into Cu and LiF. Based on XANES and Fourier transforms of EXAFS spectra, we show that the discharge process proceeded via the formation of highly dispersed Cu particles. Based on the coordination number of the first shell of Cu, the average size of the Cu particles was estimated to be in the 1-3 nm range in the fully discharged state.

A Mansour; F Badway; W Yoon; K Chung; G Amatucci

2011-12-31

319

Mass, NMR and IR spectroscopic characterization of pentedrone and pentylone and identification of their isocathinone by-products.  

PubMed

This study presents and discusses the mass spectrometric, nuclear magnetic resonance spectroscopic and infrared spectroscopic data of the designer drugs pentedrone (2-methylamino-1-phenylpentan-1-one) and its methylenedioxy analog pentylone (2-methylamino-1-(3,4-methylenedioxyphenyl)pentan-1-one). The structure elucidation of the aliphatic parts was carried out by product ion spectroscopy of the immonium ion with m/z=86 formed after electron ionization, and by one- and two-dimensional (1)H- and (13)C-NMR spectroscopy on the hydrochloride salts to verify the structure of the alkyl side chain and to determine the methylenedioxy position in the aromatic ring of pentylone. Furthermore, two typical cathinone synthesis by-products were detected besides the main compounds. Their mass spectra are discussed and for one of them (1-methylamino-1-phenylpentan-2-one (isopentedrone)) a NMR assignment was possible in the existing mixture. PMID:22115724

Westphal, Folker; Junge, Thomas; Girreser, Ulrich; Greibl, Wolfgang; Doering, Carmen

2011-11-23

320

Cyclodextrins as carriers for kavalactones in aqueous media: Spectroscopic characterization of ( S)-7,8-dihydrokavain and ?-cyclodextrin inclusion complex  

Microsoft Academic Search

Kavalactones represent the active constituents of kava–kava (Piper methysticum G. Forster), endowed with sedative and anaesthetic properties. Kavalactones are polar constituents, but poorly soluble in water with a low bioavailability. In this study, the formation of inclusion complexes of one of the most representative kavalactone isolated from kava–kava extract, (S)-7,8-dihydrokavain (DHK), with ?-cyclodextrin (?-CyD) was investigated mainly by spectroscopic methods.

G. Pescitelli; A. R. Bilia; M. C. Bergonzi; F. F. Vincieri; L. Di Bari

2010-01-01

321

Spectroscopic characterization of soft x-ray multilayer optics using a broadband laser-plasma radiation source  

Microsoft Academic Search

We present the spectroscopic techniques for studying imaging, spectral, and polarizing properties of multilayer optics intended for solar astronomy and laboratory applications. The measurements were performed using line or quasicontinuous radiation (15 - 400 angstrom) of a point-like source driven by 0.15-J, 5-ns laser pulses at 0.54 micrometer. The imaging quality of focusing normal-incidence multilayer mirrors (MMs) in the subarcsecond

Eugene N. Ragozin; Nikolai N. Kolachevsky; Mikhail M. Mitropolsky; Yurii Y. Pokrovsky

1997-01-01

322

Some polyhydroxy azo–azomethine derivatives of salicylaldehyde: Synthesis, characterization, spectroscopic, molecular structure and antimicrobial activity studies  

Microsoft Academic Search

Some new substituted polyhydroxy azo–azomethine compounds were prepared by reaction of tris(hydroxymethyl)aminomethane with (E)-2-hydroxy-5-(phenyldiazenyl) benzaldehyde and its substituted derivatives. The structures of azo and azo–azomethine compounds were determined by IR, UV–vis, 1H NMR and 13C NMR spectroscopic techniques, and\\/or X-ray diffraction studies. According to IR spectra, all azo–azomethine compounds adopt keto form in solid state. UV–vis analysis has shown the

Mustafa Odabasoglu; Çigdem Albayrak; Resit Özkanca; Fatma Zehra Aykan; Peter Lonecke

2007-01-01

323

Feasibility of Spectroscopic Characterization of Algal Lipids: Chemometric Correlation of NIR and FTIR Spectra with Exogenous Lipids in Algal Biomass  

Microsoft Academic Search

A large number of algal biofuels projects rely on a lipid screening technique for selecting a particular algal strain with\\u000a which to work. We have developed a multivariate calibration model for predicting the levels of spiked neutral and polar lipids\\u000a in microalgae, based on infrared (both near-infrared (NIR) and Fourier transform infrared (FTIR)) spectroscopy. The advantage\\u000a of an infrared spectroscopic

Lieve M. L. Laurens; Edward J. Wolfrum

2011-01-01

324

Mineralogical Characterization Studies on Unburnt Ceramic Product Made from Rock Residue Additives by Ft-Ir Spectroscopic Technique  

NASA Astrophysics Data System (ADS)

The usability of waste rock (rock residue) powder as an additive material in ceramic samples was investigated. Qualitative analysis was carried out to determine the major and minor constituent minerals present in ceramic bodies made from rock residue powder by using FT-IR spectroscopic technique. Further, the representative ceramic bodies are analyzed by FT-IR technique to yield more information about the functional groups and also to estimate the order or disorder of kaolinite structure.

Vijayaragavan, R.; Mullainathan, S.; Balachandramohan, M.; Krishnamoorthy, N.; Nithiyanantham, S.; Murugesan, S.; Vanathi, V.

2013-10-01

325

Optical absorption in twisted bilayer graphene  

NASA Astrophysics Data System (ADS)

We theoretically study the optical absorption property of twisted bilayer graphenes with various stacking geometries and demonstrate that the spectroscopic characteristics serve as a fingerprint to identify the rotation angle between two layers. We find that the absorption spectrum almost continuously evolves in changing the rotation angle, regardless of the lattice commensurability. The spectrum is characterized by series of peaks associated with the van Hove singularity, and the peak energies systematically shift with the rotation angle. We calculate the optical absorption in two frameworks: the tight-binding model and the effective continuum model based on the Dirac equation. For small rotation angles, less than 10?, the effective model well reproduces the low-energy band structure and the optical conductivity of the tight-binding model and, also, explains the optical selection rule analytically in terms of the symmetry of the effective Hamiltonian.

Moon, Pilkyung; Koshino, Mikito

2013-05-01

326

Infrared reflection absorption spectroscopic study of adsorption structure of self-assembled monolayer film of trithiocyanuric acid on evaporated silver film  

Microsoft Academic Search

The self-assembled monolayer film of trithiocyanuric acid (TCA) on evaporated silver films was characterized by using FT-IRAS and ab initio DFT calculation. Three hydrogen atoms in the most stable geometry of TCA tautomers were bonded to nitrogen atoms in the cyanuric ring. Observed IR bands for TCA in KBr disc at room temperature suggested that the TCA has a trithione

Naoki Osaka; Megumi Ishitsuka; Toshihiko Hiaki

2009-01-01

327

Characterization and DNA binding studies of unexplored imidazolidines by electronic absorption spectroscopy and cyclic voltammetry.  

PubMed

UV-Vis spectroscopic behavior of four imidazolidine derivatives i.e., [5-benzylideneimidazolidine-2,4-dione (NBI), 5-(2-hydroxybenzylidene)imidazolidine-2,4-dione (HBI), 5-(4-methoxybenzylidene)imidazolidine-2,4-dione (MBI) and 5-(3,4-di-methoxybenzylidene)imidazolidine-2,4-dione (DBI)] was studied in a wide pH range. Spectroscopic response of the studied compounds was found sensitive to pH and the attached substituents. Incited by anti-tumor activity, structural miscellany and biological applications of imidazolidines, the DNA binding affinity of some novel derivatives of this class of compounds was examined by cyclic voltammetry (CV) and UV-Vis spectroscopy at pH values of blood (7.4) and lysosomes (4.5). The CV results showed the following order of binding strength: KNBI (6.40×10(6)M(-1))>KHBI (1.77×10(5)M(-1))>KMBI (2.06×10(4)M(-1))>KDBI (1.01×10(4)M(-1)) at pH 7.4. The same order was also obtained from UV-Vis spectroscopy. The greater affinity of NBI justified its preferred candidature as an effective anti-cancer drug. The DNA binding propensity of these compounds was found comparable or greater than most of the clinically used anticancer drugs. PMID:23474470

Shah, Afzal; Nosheen, Erum; Munir, Shamsa; Badshah, Amin; Qureshi, Rumana; Rehman, Zia-Ur-; Muhammad, Niaz; Hussain, Hidayat

2013-02-06

328

X-Ray Absorption Fine Structure Spectroscopic Studies of Octakis(DMSO)Lanthanoid(III) Complexes in Solution And in the Solid Iodides  

SciTech Connect

Octakis(DMSO)lanthanoid(III) iodides (DMSO = dimethylsulfoxide), [Ln(OS(CH{sub 3}){sub 2}){sub 8}]I{sub 3}, of most lanthanoid(III) ions in the series from La to Lu have been studied in the solid state and in DMSO solution by extended X-ray absorption fine structure (EXAFS) spectroscopy. L{sub 3}-edge and also some K-edge spectra were recorded, which provided mean Ln-O bond distances for the octakis(DMSO)lanthanoid(III) complexes. The agreement with the average of the Ln-O bond distances obtained in a separate study by X-ray crystallography was quite satisfactory. The crystalline octakis(DMSO)lanthanoid(III) iodide salts have a fairly broad distribution of Ln-O bond distances, ca. 0.1 {angstrom}, with a few disordered DMSO ligands. Their EXAFS spectra are in excellent agreement with those obtained for the solvated lanthanoid(III) ions in DMSO solution, both of which show slightly asymmetric distributions of the Ln-O bond distances. Hence, all lanthanoid(III) ions are present as octakis(DMSO)lanthanoid(III) complexes in DMSO solution, with the mean Ln-O distances centered at 2.50 (La), 2.45 (Pr), 2.43 (Nd), 2.41 (Sm), 2.40 (Eu), 2.39 (Gd), 2.37 (Tb), 2.36 (Dy), 2.34 (Ho), 2.33 (Er), 2.31 (Tm), and 2.29 {angstrom} (Lu). This decrease in the Ln-O bond distances is larger than expected from the previously established ionic radii for octa-coordination. This indicates increasing polarization of the Ln{sup III}-O(DMSO) bonds with increasing atomic number. However, the S(1s) electron transition energies in the sulfur K-edge X-ray absorption near-edge structure (XANES) spectra, probing the unoccupied molecular orbitals of lowest energy of the DMSO ligands for the [Ln(OS(CH{sub 3}){sub 2}){sub 8}]{sup 3+} complexes, change only insignificantly from Ln = La to Lu. This indicates that there is no appreciable change in the ?-contribution to the S-O bond, probably due to a corresponding increase in the contribution from the sulfur lone pair to the bonding.

Persson, I.; Risberg, E.Damian; D'Angelo, P.; Panfilis, S.De; Sandstrom, M.; Abbasi, A.

2009-06-04

329

A spectroscopic proton-exchange membrane fuel cell test setup allowing fluorescence x-ray absorption spectroscopy measurements during state-of-the-art cell tests  

NASA Astrophysics Data System (ADS)

A test setup for membrane-electrode-assemblies (MEAs) of proton exchange membrane fuel cells which allows in situ fluorescence x-ray absorption spectroscopy studies of one electrode with safe exclusion of contributions from the counter electrode is described. Interference by the counter electrode is excluded by a geometry including a small angle of incidence (< 6°) between primary beam and electrode layer. The cell has been constructed by introducing just minor modifications to an electrochemical state-of-the-art MEA test setup, which ensures realistic electrochemical test conditions. This is at the expense of significant intensity losses in the path of the incident beam, which calls for the brilliance of third-generation synchrotrons to provide meaningful data. In measurements on Pt/C and Pt-Co/C cathodes combined with Pt-C anodes (H2/O2 feed), good data quality was demonstrated both for the majority element Pt as well as for Co despite of a low areal Co density in the order of 0.02 mg/cm2.

Petrova, Olga; Kulp, Christian; van den Berg, Maurits W. E.; Klementiev, Konstantin V.; Otto, Bruno; Otto, Horst; Lopez, Marco; Bron, Michael; Grünert, Wolfgang

2011-04-01

330

X-ray absorption spectroscopic evidence on the partial formation of copper(III) in the superconducting La{sub 2}CuO{sub 4.08}  

SciTech Connect

In the present work, we suggest for the first time the contribution of the unoccupied Cu 3d states to the newly formed holes using the bulk sensitive X-ray absorption spectroscopy at the Cu K edge for nonsuperconducting La{sub 2}CuO{sub 4} and two superconducting La{sub 2}CuO{sub 4-{delta}} phases prepared electrochemically and chemically, respectively, on the basis of the previous XAS study for the Cu{sup III} compounds. In summary, it has been clearly confirmed by XAS that the same doping effect on the stoichiometric La{sub 2}CuO{sub 4} could be induced by chemical and electrochemical methods. Comparing the Cu K edge XANES spectra between the present compounds and the chemically well defined Cu{sup III} references, it is concluded that a Cu{sup III} contribution is present in the ground state of the oxidized phase, La{sub 2}CuO{sub 4.08}. 19 refs., 2 figs., 1 tab.

Choy, J.H.; Kim, D.K.; Hwang, S.H. [Seoul National Univ. (Korea, Republic of); Park, J.C. [Pusan Women`s Univ. (Korea, Republic of)

1995-07-19

331

Combination of chiroptical, absorption and fluorescence spectroscopic methods reveals multiple, hydrophobicity-driven human serum albumin binding of the antimalarial atovaquone and related hydroxynaphthoquinone compounds.  

PubMed

High-affinity human serum albumin (HSA) binding of the C3-substituted antimalarial 2-hydroxy-1,4-naphthoquinone derivative atovaquone (ATQ) has been demonstrated and studied by circular dichroism (CD), UV/VIS absorption, fluorescence spectroscopy and affinity chromatography methods. The analysis of induced CD data generated upon HSA binding of ATQ revealed two high-affinity binding sites (K(a) ? 2 × 10(6) M(-1)). CD interaction studies and displacement of specific fluorescent and radioactive marker ligands indicated the contribution of both principal drug binding sites of HSA to complexation of ATQ, and also suggested the possibility of simultaneous binding of ATQ and some other drugs (e.g. warfarin, phenylbutazone, diazepam). Comparison of UV/VIS spectra of ATQ measured in aqueous solutions indicated the prevalence of the anionic species formed by dissociation of the 2-hydroxyl group. HSA binding of related natural hydroxynaphthoquinones, lapachol and lawsone also induces similar CD spectra. The much weaker binding affinity of lawsone (K(a) ? 10(4) M(-1)) bearing no C3 substituent highlights the importance of hydrophobic interactions in the strong HSA binding of ATQ and lapachol. Since neither drug exhibited significant binding to serum ?(1)-acid glycoprotein, HSA must be the principal plasma protein for the binding and transportation of 2-hydroxy-1,4-naphthoquinone-type compounds which are ionized at physiological pH values. PMID:20737064

Zsila, Ferenc; Fitos, Ilona

2010-08-24

332

X-ray Absorption Spectroscopic Investigatin of Partially Reduced Cobalt Species in Co-MCM-41 Catalysts During Synthesis of Single-Wall Carbon Nanotubes  

SciTech Connect

Chemometric tools were employed to analyze the in-situ dynamic X-ray absorption spectroscopy data to probe the state of Co-MCM-41 catalysts during reduction in pure hydrogen and under single-wall carbon nanotube synthesis reaction conditions. The use of the progressive correlation analysis established the sequence in which changes in the spectral features near the Co K edge occurred, and the evolving factor analysis provided evidence for the formation of an intermediate Co{sup 1+} ionic species during reduction of the Co-MCM-41 catalyst in pure hydrogen up to 720 C. This intermediate species preserves the tetrahedral environment in the silica framework and is resistant to complete reduction to the metal in H{sub 2}. While the Co{sup 2+} species is resistant to reduction in pure CO, the intermediate Co{sup 1+} species is more reactive in CO most likely forming cobalt carbonyl-like compounds with high mobility in the MCM-41. These mobile species are the precursors of the metallic clusters growing carbon nanotubes. Controlling the rates of each step of this two-stage reduction process is key to controlling the size of the metallic Co clusters formed in Co-MCM-41 catalysts.

Ciuparu,D.; Haider, P.; Fernandez-Garcia, M.; Chen, Y.; Lim, S.; Haller, G.; Pfefferle, L.

2005-01-01

333

Spectroscopic verification of zinc absorption and distribution in the desert plant Prosopis juliflora-velutina (velvet mesquite) treated with ZnO nanoparticles.  

PubMed

The impact of metal nanoparticles (NPs) on biological systems, especially plants, is still not well understood. The aim of this research was to determine the effects of zinc oxide (ZnO) NPs in velvet mesquite (Prosopis juliflora-velutina). Mesquite seedlings were grown for 15 days in hydroponics with ZnO NPs (10 nm) at concentrations varying from 500 to 4000 mg L(-1). Zinc concentrations in roots, stems and leaves were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). Plant stress was examined by the specific activity of catalase (CAT) and ascorbate peroxidase (APOX); while the biotransformation of ZnO NPs and Zn distribution in tissues was determined by X-ray absorption spectroscopy (XAS) and micro X-ray fluorescence (?XRF), respectively. ICP-OES results showed that Zn concentrations in tissues (2102 ± 87, 1135 ± 56, and 628 ± 130 mg kg(-1) d wt in roots, stems, and leaves, respectively) were found at 2000 mg ZnO NPs L(-1). Stress tests showed that ZnO NPs increased CAT in roots, stems, and leaves, while APOX increased only in stems and leaves. XANES spectra demonstrated that ZnO NPs were not present in mesquite tissues, while Zn was found as Zn(II), resembling the spectra of Zn(NO(3))(2). The ?XRF analysis confirmed the presence of Zn in the vascular system of roots and leaves in ZnO NP treated plants. PMID:22820414

Hernandez-Viezcas, J A; Castillo-Michel, H; Servin, A D; Peralta-Videa, J R; Gardea-Torresdey, J L

2010-12-15

334

Synthesis, spectroscopic characterization, thermal, and photostability studies of 2-(2?-hydroxy-5?-phenyl)-5-aminobenzotriazole complexes  

Microsoft Academic Search

Three Mn(II), Co(II), and Cu(II) new transition metal complexes of the fluorescence dye: 2-(2?-hydroxy-5?-phenyl)-5-aminobenzotriazole\\/PBT\\u000a derived from o-aminophenol and m-phenylenediamine have been synthesized. The structural interpretations were confirmed from elemental analyses, magnetic susceptibility\\u000a and molar conductivity, as well as from mass, IR, UV–Vis spectral studies. From the analytical, spectroscopic, and thermal\\u000a data, the stoichiometry of the mentioned complexes was found to

Moamen S. Refat

2010-01-01

335

Spectroscopic characterization of SC-NTR: a subsidiary dye of allura red AC dye (FD&C red no. 40).  

PubMed

A major subsidiary dye in US certified Allura Red AC dye (FD&C Red No. 40) has been isolated by preparative high performance liquid chromatography. The paper chromatographic properties of the isolated dye indicate that it is the dye designated as SC-NTR in a previous paper (Marmion 1971). Spectroscopic analysis of the isolated dye is consistent with the disodium salt of 6-hydroxy-5-(2-methoxy-5-methyl-3-sulphophenylazo)-2-naphthalen esulphonic acid, which is an azo-coupling product between the meta-isomer of cresidine-p-sulphonic acid (CSA) and Schaeffer's salt (SS). PMID:8181638

Takeda, Y; Goda, Y; Noguchi, H; Yamada, T; Yoshihira, K; Takeda, M

336

Acetylene-Substituted Two-Photon Absorbing Molecules With Rigid Elongated Pi-Conjugation: Synthesis, Spectroscopic Properties and Two-Photon Fluorescence Cell Imaging Applications  

Microsoft Academic Search

Two asymmetrical molecules with substituted acetylene as central rigid elongated conjugation are reported as potential chromophores\\u000a for two-photon microscopic imaging. These molecules consist of a typical D–?–A structure, have different donors (D), the same\\u000a ?-conjugated center (?) and the same acceptor (A). Structural characterization and spectroscopic properties, including single-photon\\u000a (linear) absorption, quantum yields, single-photon fluorescence, and two-photon absorption spectra, were

Bo Liu; Hai-Li Zhang; Jun Liu; Zhen-Li Huang; Yuan-Di Zhao; Qing-Ming Luo

2007-01-01

337

Laser induced fluorescence and absorption measurements for DUV optical thin film characterization  

NASA Astrophysics Data System (ADS)

Residual absorption in optical thin films due to impurities or defects causes thermal lens formation upon high power DUV laser irradiation. Furthermore, it may be one reason for functional degradation during prolonged laser irradiation. Pulsed ArF laser induced fluorescence (LIF) and direct absorption measurements (LID technique) are applied to investigate high reflecting coatings made from LaF3, MgF2 and AlF3 with respect to the influence of different raw materials and deposition temperatures. LIF measurements reveal emission bands that are partially attributed to certain impurities or defects which either origin from the raw material or the coating process. In addition, LIF measurements of single MgF2 and LaF3 layers are performed to investigate different raw material qualities and coating processes. The experimental results show the potential of both techniques for sensitive accompanying of coating process development.

Mühlig, Ch.; Triebel, W.; Kufert, S.; Bublitz, S.

2008-09-01

338

Characterization and optimization of AMG 517 supersaturatable self-emulsifying drug delivery system (S-SEDDS) for improved oral absorption.  

PubMed

Supersaturatable self-emulsifying drug delivery systems (S-SEDDS) were explored to improve the oral absorption of AMG 517, a poorly water-soluble drug candidate. In vitro characterizations indicate the level of Tween 80 in the formulation dictates the initial degree of supersaturation of AMG 517, and, therefore, its precipitation kinetics. The presence of a small amount of cellulosic polymer (e.g., HPMC) effectively sustained a metastable supersaturated state by retarding precipitation kinetics. Precipitates from the S-SEDDS formulations (with HPMC) from in vitro test media were identified as amorphous AMG 517 while crystalline AMG 517 precipitates were found when either HPMC was absent or PVP was present in the formulation. In vivo pharmacokinetic study in Cynomolgus monkeys reveals that the S-SEDDS formulation showed approximately 30% higher mean C(max) and comparable exposure (AUC) of AMG 517 as compared to an aqueous suspension at a dose of 12.5 mg. The rapid absorption characteristics of AMG 517 from the S-SEDDS formulation as evidenced by high C(max) and short T(max) are attributed to a high free drug concentration in vivo, implying a supersaturated state. This case demonstrates that S-SEDDS technology is an effective approach for improving the rate and extent of absorption of poorly soluble drugs. PMID:18543293

Gao, Ping; Akrami, Anna; Alvarez, Francisco; Hu, Jack; Li, Lan; Ma, Chandra; Surapaneni, Sekhar

2009-02-01

339

Spectroscopic properties of PSI–IsiA supercomplexes from the cyanobacterium Synechococcus PCC 7942  

Microsoft Academic Search

The cyanobacterium Synechococcus PCC 7942 grown under iron starvation assembles a supercomplex consisting of a trimeric Photosystem I (PSI) complex encircled by a ring of 18 CP43? or IsiA light-harvesting complexes [Nature 412 (2001) 745]. Here we present a spectroscopic characterization by temperature-dependent absorption and fluorescence spectroscopy, site-selective fluorescence spectroscopy at 5 K, and circular dichroism of isolated PSI–IsiA, PSI

Elena G. Andrizhiyevskaya; Tatjana M. E. Schwabe; Marta Germano; Sandrine D'Haene; Jochen Kruip; Rienk van Grondelle; Jan P. Dekker

2002-01-01

340

CD Spectroscope  

NSDL National Science Digital Library

In this activity, learners use an old CD to construct a spectroscope, a device that separates light into its component colors. Learners will hold it up to various light sources to examine how different light has different color strengths. Use this activity to introduce learners to the color spectrum and the tools scientists use to study it.

University, Colorado S.

2009-01-01

341

Synthesis and characterizations of ultra-small ZnS and Zn(1-x)Fe(x)S quantum dots in aqueous media and spectroscopic study of their interactions with bovine serum albumin.  

PubMed

This work reports a new experimental methodology for the synthesis of ultra small zinc sulfide and iron doped zinc sulfide quantum dots in aqueous media. The nanoparticles were obtained using a simple procedure based on the precipitation of ZnS in aqueous solution in the presence of 2-mercaptoethanol as a capping agent, at room temperature. The effect of Fe(3+) ion concentration as dopant on the optical properties of ZnS was studied. The size of quantum dots was determined to be about 1nm, using scanning tunneling microscopy. The synthesized nanoparticles were characterized by X-ray diffraction, UV-Vis absorption and photoluminescence emission spectroscopies. The presence and amount of iron impurity in the structure of Zn((1-x))Fe(x)S nanocrystals were confirmed by atomic absorption spectrometry. A blue shift in band-gap of ZnS was observed upon increasing incorporation of Fe(3+) ion in the iron doped zinc sulfide quantum dots. The photoluminescence investigations showed that, in the case of iron doped ZnS nanoparticles, the emission band of pure ZnS nanoparticles at 427nm shifts to 442nm with appearance of a new sharp emission band around 532nm. The X-ray diffraction analysis indicated that the iron doped nanoparticles are crystalline, with cubic zinc blend structure, having particle diameters of 1.7±022nm. Finally, the interaction of the synthesized nanoparticles with bovine serum albumin was investigated at pH 7.2. The UV-Vis absorption and fluorescence spectroscopic methods were applied to compare the optical properties of pure and iron doped ZnS quantum dots upon interaction with BSA. It was proved that, in both cases, the fluorescence quenching of BSA by the quantum dots is mainly a result of the formation of QDs-BSA complex in solution. In the steady-state fluorescence studies, the interaction parameters including binding constants (K(a)), number of binding sites (n), quenching constants ( [Formula: see text] ), and bimolecular quenching rate constants (k(q)) were determined at three different temperatures and the results were then used to evaluate the corresponding thermodynamic parameters ?H, ?S and ?G. PMID:21482179

Khani, Omid; Rajabi, Hamid Reza; Yousefi, Mohammad Hasan; Khosravi, Ali Azam; Jannesari, Mohammad; Shamsipur, Mojtaba

2011-03-21

342

Synthesis and characterizations of ultra-small ZnS and Zn (1- x) Fe xS quantum dots in aqueous media and spectroscopic study of their interactions with bovine serum albumin  

NASA Astrophysics Data System (ADS)

This work reports a new experimental methodology for the synthesis of ultra small zinc sulfide and iron doped zinc sulfide quantum dots in aqueous media. The nanoparticles were obtained using a simple procedure based on the precipitation of ZnS in aqueous solution in the presence of 2-mercaptoethanol as a capping agent, at room temperature. The effect of Fe 3+ ion concentration as dopant on the optical properties of ZnS was studied. The size of quantum dots was determined to be about 1 nm, using scanning tunneling microscopy. The synthesized nanoparticles were characterized by X-ray diffraction, UV-Vis absorption and photoluminescence emission spectroscopies. The presence and amount of iron impurity in the structure of Zn (1- x) Fe xS nanocrystals were confirmed by atomic absorption spectrometry. A blue shift in band-gap of ZnS was observed upon increasing incorporation of Fe 3+ ion in the iron doped zinc sulfide quantum dots. The photoluminescence investigations showed that, in the case of iron doped ZnS nanoparticles, the emission band of pure ZnS nanoparticles at 427 nm shifts to 442 nm with appearance of a new sharp emission band around 532 nm. The X-ray diffraction analysis indicated that the iron doped nanoparticles are crystalline, with cubic zinc blend structure, having particle diameters of 1.7 ± 022 nm. Finally, the interaction of the synthesized nanoparticles with bovine serum albumin was investigated at pH 7.2. The UV-Vis absorption and fluorescence spectroscopic methods were applied to compare the optical properties of pure and iron doped ZnS quantum dots upon interaction with BSA. It was proved that, in both cases, the fluorescence quenching of BSA by the quantum dots is mainly a result of the formation of QDs-BSA complex in solution. In the steady-state fluorescence studies, the interaction parameters including binding constants ( Ka), number of binding sites ( n), quenching constants ( KSV), and bimolecular quenching rate constants ( kq) were determined at three different temperatures and the results were then used to evaluate the corresponding thermodynamic parameters ? H, ? S and ? G.

Khani, Omid; Rajabi, Hamid Reza; Yousefi, Mohammad Hasan; Khosravi, Ali Azam; Jannesari, Mohammad; Shamsipur, Mojtaba

2011-07-01

343

Five monomeric hemocyanin subunits from Portunus trituberculatus: purification, spectroscopic characterization, and quantitative evaluation of phenol monooxygenase activity.  

PubMed

Five kinds of monomeric subunits of arthropod hemocyanin have been isolated from swimming crab Portunus trituberculatus hemolymph. The copper centers holding a peroxo species, [(?-?2:?2-peroxo)dicopper(II)], of these subunits exhibited almost the same UV-vis and visible region CD spectroscopic properties, indicating that they have a similar copper coordination geometry and an electronic structure. Under anaerobic conditions, the oxy-forms of the monomeric subunits were stable in 0.5 M borate buffer (pH 9.0) and reacted with 4-methylphenol (p-cresol) to show the phenolases (cresolase/phenol monooxygenase) activity in the presence of urea. To compare the phenolase (monooxygenase) reactivity, the reactivity of the isolated subunits has been examined quantitatively by using a simplified catalytic system, where the initial product catechol is trapped with borate anion of the buffer solution to prevent following catecholase reaction (Yamazaki and Itoh, 2003). The far-UV region CD spectra were measured in order to clarify the relationship between the content of the secondary structure and the phenolase reactivity. Even though the monomeric subunits exhibit a weak catalytic phenol monooxygenase activity, addition of urea (3 M) significantly enhances their catalytic activity. The differences of the phenolase activity among the monomeric subunits has been discussed on the basis of the spectroscopic analysis and reactivity studies in order to shed light on the enzymatic function of the arthropod hemocyanin in vivo. PMID:20727990

Fujieda, Nobutaka; Yakiyama, Aki; Itoh, Shinobu

2010-08-18

344

Synthesis, spectroscopic characterization, DFT studies, and antibacterial and antitumor activities of a novel water soluble Pd(II) complex with L-alliin  

NASA Astrophysics Data System (ADS)

A new water soluble Pd(II) complex with L-alliin (S-allyl-L-cysteine sulfoxide) was obtained and characterized by a set of chemical and spectroscopic measurements. Elemental and mass spectrometric data are consistent with the formula [Pd(C6H10NO3S)2]. The 1H and 13C nuclear magnetic resonance (NMR) data, [1H-15N] two dimensional (2D) NMR and infrared spectroscopic measurements indicate coordination of the ligand to Pd(II) through N and O atoms. DFT studies showed that the trans isomer is the most stable and preferred geometry for the complex. The complex is soluble in water and dimethylsulfoxide. An antibiogram assay revealed that the complex possess antibacterial activity against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus bacterial strains in the range 125-500 ?g mL-1. Antitumor assays revealed that the complex presents cytotoxic activity over HeLa cells with an estimated IC50 of 20 ?mol L-1.

Abbehausen, Camilla; Sucena, Suelen F.; Lancellotti, Marcelo; Heinrich, Tassiele A.; Abrão, Emiliana P.; Costa-Neto, Claudio M.; Formiga, André L. B.; Corbi, Pedro P.

2013-03-01

345

Spectroscopic ellipsometry applications in photomask technology  

Microsoft Academic Search

Development and manufacture of advanced photomasks requires understanding the optical properties of mask materials and the ability to carefully monitor and control the film thickness, refractive index, and absorption of each film layer. Spectroscopic Ellipsometry (SE), a nondestructive optical analysis technique for determination of film thickness, refractive index, absorption, and film microstructure has been applied to many applications in current

Ron A. Synowicki; James N. Hilfiker

2008-01-01

346

Spectroscopic applications of the plasma dispersion function  

Microsoft Academic Search

Using as a starting point a previously published approximate expression for the spectroscopic absorption Voigt profile, an absorption-dispersion pair for mildly Gaussian lines is constructed. With this information, the full asymptotic expansion of the plasma dispersion function (PDF) is obtained for the case of Im z > 0. As shapes and widths of spectral lines contain much information about the

H. Jimenezdominguez; S. Cruz-Jiménez; A. Cabral-Prieto

1996-01-01

347

Synthesis and investigations of the absorption spectra of hetarylazo disperse dyes derived from 2,4-quinolinediol  

Microsoft Academic Search

Synthesis of some novel hetarylazoquinoline dyes was achieved by diazotisation of nine heterocyclic amines using nitrosyl sulphuric acid, coupling with 2,4-quinolinediol. These dyes were characterized by UV–vis, FT-IR and 1H NMR spectroscopic techniques and elemental analysis. Visible absorption spectra of the dyes are discussed, both the effects of varying pH and solvent upon the absorption ability of azoquinolines. The colour

?zzet ?ener; Fikret Karc?; Nermin Ertan; Emine K?l?ç

2006-01-01

348

Characterization of magnetic CoFe cyanides by x-ray-absorption fine-structure spectroscopy  

NASA Astrophysics Data System (ADS)

X-ray-absorption fine-structure spectra were measured and analyzed for several FeCo cyanides MxCoyFe(CN)6.zH2O (M=Na, K, Rb) which are known to exhibit interesting magnetic properties depending on temperature. X-ray-absorption near-edge structure spectra allow us to confirm very clearly the spin transitions in Na0.4Co1.3Fe(CN)6.5H2O and K0.4Co1.3Fe(CN)6.5H2O and to evaluate the composition ratios of CoII and CoIII species quantitatively. The CoII:CoIII ratios are essentially important physical quantities with which to understand magnetic properties. The local structures around Fe and Co atoms were determined by the Fe and Co K-edge extended x-ray-absorption fine-structure spectra. It is confirmed that the local structures around Fe are Fe(CN)6Co6 (the subscripts denote the coordination numbers) while those around Co are Co(NC)6-1/y(H2O)1/yFe6-1/y. The first-nearest-neighbor Fe-C distances do not significantly change between FeII and FeIII species, while the first-nearest-neighbor Co-NO distances are noticeably different between CoII and CoIII ones. The difference of as much as 0.16-0.20 Å between CoII and CoIII, which corresponds well to that for typical Co tautomeric complexes, causes noticeable change of the lattice constant.

Yokoyama, Toshihiko; Ohta, Toshiaki; Sato, Osamu; Hashimoto, Kazuhito

1998-10-01

349

Synthesis, Characterization, and Microwave Absorption Property of the SnO2Nanowire/Paraffin Composites  

PubMed Central

In this article, SnO2nanowires (NWs) have been prepared and their microwave absorption properties have been investigated in detail. Complex permittivity and permeability of the SnO2NWs/paraffin composites have been measured in a frequency range of 0.1–18 GHz, and the measured results are compared with that calculated from effective medium theory. The value of maximum reflection loss for the composites with 20 vol.% SnO2NWs is approximately ?32.5 dB at 14 GHz with a thickness of 5.0 mm.

2009-01-01

350

Recent advances in characterization of CaCu3Ti4O12 thin films by spectroscopic ellipsometric metrology.  

PubMed

CaCu3Ti4O12 (CCTO) thin films were successfully grown on LaAlO3(100) and Pt/TiO2/SiO2/Si(100) substrates by a novel MOCVD approach. Epitaxial CCTO(001) thin films have been obtained on LaAlO3(100) substrates, while polycrystalline CCTO films have been grown on Pt/TiO2/SiO2/Si(100) substrates. Surface morphology and grain size of the different nanostructured deposited films were examined by AFM, and spectroscopic ellipsometry has been used to investigate the electronic part of the dielectric constant (epsilon2). Looking at the epsilon2 curves, it can be seen that by increasing the film structural order, a greater dielectric response has been obtained. The measured dielectric properties accounted for the ratio between grain volumes and grain boundary areas, which is very different in the different structured films. PMID:16201781

Lo Nigro, Raffaella; Malandrino, Graziella; Toro, Roberta G; Losurdo, Maria; Bruno, Giovanni; Fragalà, Ignazio L

2005-10-12

351

Large-scale synthesis, characterization and microwave absorption properties of carbon nanotubes of different helicities  

SciTech Connect

Carbon nanotubes of high helicity (H-HCNTs, Sample A) have been synthesized in large-scale by pyrolysis of acetylene at 450 deg. C over Fe nanoparticles derived from coprecipitation/hydrogen reduction method. With controlled introduction of hydrogen during acetylene pyrolysis, CNTs of low helicity (L-HCNTs, Sample B) and worm-like CNTs (Sample C) were obtained in large quantities. The yields of the CNTs products are high, especially that of H-HCNTs (ca. 7474%). The complex permittivity and permeability of Composites A, B, and C that contain Samples A, B and C (30 wt%) were measured in the 2-18 GHz frequency range. Good absorption of electromagnetic wave (reflection loss<-20 dB) was observed in the 7.18-10.68 and 7.5-10.7 GHz range over Composites B and C (2.0-3.0 mm thickness), respectively. Thus, through the suggested route, CNTs can be produced easily and selectively in large quantities. The lightweight materials can be utilized for microwave absorption. - Graphical abstract: FESEM image of Sample B and reflection loss versus frequency of Composite B (containing 30 wt% of Sample B) in the range of 2-18 GHz.

Qi Xiaosi; Yang Yi [Nanjing National Laboratory of Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); Zhong Wei, E-mail: wzhong@nju.edu.c [Nanjing National Laboratory of Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); Deng Yu [Nanjing National Laboratory of Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); Au Chaktong [Chemistry Department, Hong Kong Baptist University (Hong Kong); Du Youwei [Nanjing National Laboratory of Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China)

2009-10-15

352

The synthesis and spectroscopic characterization of poly( p-phenylene ethynylene) with 3-connected BODIPY end groups  

Microsoft Academic Search

A novel 3-connected BODIPY end-capped poly(p-phenylene ethynylene) and a matching model compound were synthesized by palladium-catalyzed cross-coupling reaction. The structures were confirmed using 1H NMR, UV–vis spectrophotometry and fluorescence spectroscopy. Both the polymer and the model compound showed absorption and emission bands characteristic for the BODIPY chromophore and the p-phenylene ethynylene linker. However, while upon excitation of the p-phenylene ethynylene

Shouchun Yin; Volker Leen; Carine Jackers; Mark Van der Auweraer; Mario Smet; Noël Boens; Wim Dehaen

2011-01-01

353

Crystal growth, spectroscopic characterization and laser performance of Nd:Lu0.33Y0.36Gd0.3VO4 crystal  

NASA Astrophysics Data System (ADS)

A new three-matrix mixed vanadate crystal Nd:Lu0.33Y0.36Gd0.3VO4 (Nd:LuYGdVO4) crystal was grown by the Czochralski method. Room temperature absorption and fluorescence spectra of the Nd:LuYGdVO4 crystals were measured and the spectroscopic parameters were calculated by the Judd-Ofelt theory. The intensity parameters of the Nd:LuYGdVO4 crystal were ?2 = 9.736 × 10-20 cm2, ?4 = 4.179 × 10-20 cm2, ?6 = 8.020 × 10-20 cm2 and the stimulate emission cross section was 5.3 × 10-19 cm2. Diodepumped actively Q-switched and passively Q-switched Nd:LuYGdVO4 and Nd:Lu0.14Y0.86VO4 lasers at 1.06 ?m were demonstrated. The results indicate that, for both actively and passively Q-switched lasers, the Nd:LuYGdVO4 lasers can generate shorter pulse width with higher peak power than the Nd:Lu0.14Y0.86VO4 lasers at the same cavity conditions.

Zhao, B.; Guo, F. Y.; Zhuang, N. F.; Cheng, K.; Chen, J. Z.

2012-05-01

354

Development of Cellular Absorptive Tracers (CATs) for a Quantitative Characterization of the Complexity of Nanoscale Biological Systems  

NASA Astrophysics Data System (ADS)

A new method is proposed in this study, which is entitled Cellular Absorptive Tracers (CATs; PNNL Invention Disclosure; Saripalli, P. 2001), to characterize the extent, location, and morphology of cell mass in microelectromechanical systems (MEMS), by preferentially absorbing into the living or lysed cells or adsorbing at the cell surfaces. The CATs were used to demonstrate their utility to quantitatively characterize the biomass, its location, and morphology in MEMS. A series of experiments had conducted, using different number/types of cells and morphologic distributions (e.g., concentrated vs. disperse) within the microenvironmental chamber. The experiments were conducted such that, simultaneously with CATs characterization, a number of metabolic parameters (such as oxygen, CO2, glucose, pH, methanol, formate and small molecule metabolites, etc.) also were measured by fluorescence microscopy (Lidstrom and Meldrum, Nature, 2003). Results of partition and transport experiments show that adsorption of a CAT molecule into the cellular mass results in its retardation during flow, which is a good measure of the biomass quantity and distribution. The molecules chosen were used to demonstrate their utility to quantitatively characterize the biomass, its location and morphology in MEMS. The results yield first-of-their-kind data sets relating metabolic parameters to location, heterogeneity, and morphology of cells. The data were used to obtain quantitative information needed for the characterization of biomass in MEMS, and to develop the theory relating the cellular phenomena of interest to cellular heterogeneity and morphology. The proposed research contributes a new set of tools for a rapid, noninvasive characterization of nano-scale biological systems.

Choi, J.; Saripalli, P.; Meldrum, D.; Lee, S.

2005-12-01

355

Subzero-temperature stabilization and spectroscopic characterization of homogeneous oxyferrous complexes of the cytochrome P450 BM3 (CYP102) oxygenase domain and holoenzyme  

SciTech Connect

We describe herein for the first time the formation and spectroscopic characterization of homogeneous oxyferrous complexes of the cytochrome P450 BM3 (CYP102) holoenzyme and heme domain (BMP) at -55 {sup o}C using a 70/30 (v/v) glycerol/buffer cryosolvent. The choice of buffer is a crucial factor with Tris [tris(hydroxymethyl)aminomethane] buffer being significantly more effective than phosphate. The oxyferrous complexes have been characterized with magnetic circular dichroism spectroscopy and the resulting spectra compared to those of the more well-characterized oxyferrous cytochrome P450-CAM. The formation of a stable substrate-bound oxyferrous CYP BM3 holoenzyme, despite the fact that it has the necessary reducing equivalents for turnover, indicates that electron transfer from the flavin domain to the oxyferrous center is very slow at this temperature. The ability to prepare stable homogeneous oxyferrous derivatives of both BMP and the CYP BM3 holoenzyme will enable these species to be used as starting materials for mechanistic investigation of dioxygen activation.

Perera, Roshan [Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208 (United States); Sono, Masanori [Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208 (United States); Raner, Gregory M. [Department of Chemistry and Biochemistry, University of North Carolina, Greensboro, NC 27402 (United States); Dawson, John H. [Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208 (United States) and School of Medicine, University of South Carolina, Columbia, SC 29208 (United States)]. E-mail: dawson@sc.edu

2005-12-09

356

Electronic transport characterization of silicon wafers by laterally resolved free-carrier absorption and multiparameter fitting  

NASA Astrophysics Data System (ADS)

Laterally resolved modulated free-carrier absorption (MFCA) is applied to the simultaneous determination of the electronic transport properties of semiconductor wafers. A rigorous three-dimensional carrier diffusion model is used to fit the observed dependences of the MFCA signal amplitude and phase on the separation between the pump and probe laser spots, measured at several modulation frequencies covering an appropriate range. This leads to a simultaneous and unambiguous determination of the values of three transport parameters, namely, the minority-carrier lifetime ?, the carrier diffusivity D, and the front surface recombination velocity s1. The extracted values for a n-type Si wafer with a resistivity of 7-10 ? cm are 53 ?s (?), 16.6 cm2/s (D), and <200 cm/s (s1), respectively.

Zhang, Xiren; Li, Bincheng; Gao, Chunming

2006-09-01

357

Self-eliminating instrumental frequency response from free carrier absorption signals for silicon wafer characterization  

NASA Astrophysics Data System (ADS)

Accurate determination of electronic transport properties of semiconductor wafers with modulated free carrier absorption (MFCA) and multiparameter fitting requires the total elimination of instrumental response from the MFCA signals. In this paper, an approach to eliminate the effect of instrumental response on the frequency dependence of MFCA amplitude and phase is developed both theoretically and experimentally to simultaneously determine the transport properties (minority-carrier lifetime, carrier diffusion coefficient, and front surface recombination velocity) of silicon wafers. Experimental results showed that with the proposed method the instrumental frequency response was fully eliminated from the experimental MFCA data and had no impact on the multiparameter fitting, while with conventional methods the accuracy of the fitted transport parameters was influenced detrimentally by the errors of the measured instrumental frequency responses, in particular for the minority-carrier lifetime and the front surface recombination velocity.

Huang, Qiuping; Li, Bincheng

2011-04-01

358

Loss of anion transport without increased sodium absorption characterizes newborn porcine cystic fibrosis airway epithelia  

PubMed Central

SUMMARY Defective transepithelial electrolyte transport is thought to initiate cystic fibrosis (CF) lung disease. Yet, how loss of CFTR affects electrolyte transport remains uncertain. CFTR?/? pigs spontaneously develop lung disease resembling human CF. At birth, their airways exhibit a bacterial host defense defect, but are not inflamed. Therefore, we studied ion transport in newborn nasal and tracheal/bronchial epithelia in tissue, cultures, and in vivo. CFTR?/? epithelia showed markedly reduced Cl? and HCO3? transport. However, in contrast to a widely held view, lack of CFTR did not increase transepithelial Na+ or liquid absorption or reduce periciliary liquid depth. Like human CF, CFTR?/? pigs showed increased amiloride-sensitive voltage and current, but lack of apical Cl? conductance caused the change, not increased Na+ transport. These results indicate that CFTR provides the predominant transcellular pathway for Cl? and HCO3? in porcine airway epithelia, and reduced anion permeability may initiate CF airway disease.

Chen, Jeng-Haur; Stoltz, David A.; Karp, Philip H.; Ernst, Sarah E.; Pezzulo, Alejandro A.; Moninger, Thomas O.; Rector, Michael V.; Reznikov, Leah R.; Launspach, Janice L.; Chaloner, Kathryn; Zabner, Joseph; Welsh, Michael J.

2011-01-01

359

Characterization and speciation of mercury-bearing mine wastes using X-ray absorption spectroscopy  

USGS Publications Warehouse

Mining of mercury deposits located in the California Coast Range has resulted in the release of mercury to the local environment and water supplies. The solubility, transport, and potential bioavailability of mercury are controlled by its chemical speciation, which can be directly determined for samples with total mercury concentrations greater than 100 mg kg-1 (ppm) using X-ray absorption spectroscopy (XAS). This technique has the additional benefits of being non-destructive to the sample, element-specific, relatively sensitive at low concentrations, and requiring minimal sample preparation. In this study, Hg L(III)-edge extended X-ray absorption fine structure (EXAFS) spectra were collected for several mercury mine tailings (calcines) in the California Coast Range. Total mercury concentrations of samples analyzed ranged from 230 to 1060 ppm. Speciation data (mercury phases present and relative abundances) were obtained by comparing the spectra from heterogeneous, roasted (calcined) mine tailings samples with a spectral database of mercury minerals and sorbed mercury complexes. Speciation analyses were also conducted on known mixtures of pure mercury minerals in order to assess the quantitative accuracy of the technique. While some calcine samples were found to consist exclusively of mercuric sulfide, others contain additional, more soluble mercury phases, indicating a greater potential for the release of mercury into solution. Also, a correlation was observed between samples from hot-spring mercury deposits, in which chloride levels are elevated, and the presence of mercury-chloride species as detected by the speciation analysis. The speciation results demonstrate the ability of XAS to identify multiple mercury phases in a heterogeneous sample, with a quantitative accuracy of ??25% for the mercury-containing phases considered. Use of this technique, in conjunction with standard microanalytical techniques such as X-ray diffraction and electron probe microanalysis, is beneficial in the prioritization and remediation of mercury-contaminated mine sites. (C) 2000 Elsevier Science B.V.

Kim, C. S.; Brown, Jr. , G. E.; Rytuba, J. J.

2000-01-01

360

Characterization and speciation of mercury-bearing mine wastes using X-ray absorption spectroscopy.  

PubMed

Mining of mercury deposits located in the California Coast Range has resulted in the release of mercury to the local environment and water supplies. The solubility, transport, and potential bioavailability of mercury are controlled by its chemical speciation, which can be directly determined for samples with total mercury concentrations greater than 100 mg kg(-1) (ppm) using X-ray absorption spectroscopy (XAS). This technique has the additional benefits of being non-destructive to the sample, element-specific, relatively sensitive at low concentrations, and requiring minimal sample preparation. In this study, Hg L(III)-edge extended X-ray absorption fine structure (EXAFS) spectra were collected for several mercury mine tailings (calcines) in the California Coast Range. Total mercury concentrations of samples analyzed ranged from 230 to 1060 ppm. Speciation data (mercury phases present and relative abundances) were obtained by comparing the spectra from heterogeneous, roasted (calcined) mine tailings samples with a spectral database of mercury minerals and sorbed mercury complexes. Speciation analyses were also conducted on known mixtures of pure mercury minerals in order to assess the quantitative accuracy of the technique. While some calcine samples were found to consist exclusively of mercuric sulfide, others contain additional, more soluble mercury phases, indicating a greater potential for the release of mercury into solution. Also, a correlation was observed between samples from hot-spring mercury deposits, in which chloride levels are elevated, and the presence of mercury-chloride species as detected by the speciation analysis. The speciation results demonstrate the ability of XAS to identify multiple mercury phases in a heterogeneous sample, with a quantitative accuracy of +/-25% for the mercury-containing phases considered. Use of this technique, in conjunction with standard microanalytical techniques such as X-ray diffraction and electron probe microanalysis, is beneficial in the prioritization and remediation of mercury-contaminated mine sites. PMID:11036987

Kim, C S; Brown, G E; Rytuba, J J

2000-10-16

361

Single molecule spectroscopic characterization of a far-red fluorescent protein (HcRed) from the Anthozoa coral Heteractis crispa  

NASA Astrophysics Data System (ADS)

We report on the photophysical properties of a far-red intrinsic fluorescent protein by means of single molecule and ensemble spectroscopic methods. The green fluorescent protein (GFP) from Aequorea victoria is a popular fluorescent marker with genetically encoded fluorescence and which can be fused to any biological structure without affecting its function. GFP and its variants provide emission colors from blue to yellowish green. Red intrinsic fluorescent proteins from Anthozoa species represent a recent addition to the emission color palette provided by GFPs. Red intrinsic fluorescent markers are on high demand in protein-protein interaction studies based on fluorescence-resonance energy transfer or in multicolor tracking studies or in cellular investigations where autofluorescence possesses a problem. Here we address the photophysical properties of a far-red fluorescent protein (HcRed), a mutant engineered from a chromoprotein cloned from the sea anemone Heteractis crispa, by using a combination of ensemble and single molecule spectroscopic methods. We show evidence for the presence of HcRed protein as an oligomer and for incomplete maturation of its chromophore. Incomplete maturation results in the presence of an immature (yellow) species absorbing/fluorescing at 490/530-nm. This yellow chromophore is involved in a fast resonance-energy transfer with the mature (purple) chromophore. The mature chromophore of HcRed is found to adopt two conformations, a Transoriented form absorbing and 565-nm and non-fluorescent in solution and a Cis-oriented form absorbing at 590-nm and emitting at 645-nm. These two forms co-exist in solution in thermal equilibrium. Excitation-power dependence fluorescence correlation spectroscopy of HcRed shows evidence for singlet-triplet transitions in the microseconds time scale and for cis-trans isomerization occurring in a time scale of tens of microseconds. Single molecule fluorescence data recorded from immobilized HcRed proteins, all point to the presence of two classes of molecules: proteins with Cis and Trans-oriented chromophores. Immobilization of HcRed in water-filled pores of polyvinyl alcohol leads to a polymer matrix - protein barrel interaction which results in a 'freezing' of the chromophore in a stable conformation for which non-radiative deactivation pathways are either suppressed or reduced. As a result, proteins with both Cis- and Trans-oriented chromophores can be detected at the single molecule level. Polymer chain motion is suggested as a mediator for an eventual cis-trans isomerization of the chromophore in the case of single immobilized proteins.

Cotlet, Mircea; Habuchi, Satoshi; Whitier, Jennifer E.; Werner, James H.; De Schryver, Frans C.; Hofkens, Johan; Goodwin, Peter M.

2006-03-01

362

One-dimensional WO{sub 3} and its hydrate: One-step synthesis, structural and spectroscopic characterization  

SciTech Connect

We report on a one-step hydrothermal growth of one-dimensional (1D) WO{sub 3} nanostructures, using urea as 1D growth-directing agent and a precursor free of metals other than tungsten. By decreasing the pH of the starting solution, the size of the nanostructures was reduced significantly, this development being accompanied by the realization of phase pure hexagonal WO{sub 3} nanorods (elimination of monoclinic impurity phase) and a red shift in optical absorption edge. Surface analyses indicated the presence of reduced tungsten species in the WO{sub 3} nanostructures, which increased two-fold in a hydrated WO{sub 3} phase obtained with further decrease in pH. We suggest that oxygen vacancies are responsible for this defect state in WO{sub 3}, while protons are responsible or contribute significantly to the same in the hydrated phase. - Graphical abstract: The figure illustrates the role of pH in morphological and absorption edge evolution of WO{sub 3} (hydrate) as well as the variation in the concentration of defect electrons between anhydrous and hydrated WO{sub 3}. Highlights: Black-Right-Pointing-Pointer WO{sub 3} nanorods prepared in a one step procedure. Black-Right-Pointing-Pointer HCl (aq) enables phase pure WO{sub 3} nanorods. Black-Right-Pointing-Pointer HCl (aq) induces significant reduction in dimension of and red shift in absorption edge of nanorods. Black-Right-Pointing-Pointer W{sup 5+} detected in hydrothermal WO{sub 3} phase, the concentration of which increases in the hydrated phase. Black-Right-Pointing-Pointer W{sup 5+} from the two phases due to different positive defects.

Iwu, Kingsley O., E-mail: k.o.iwu@smn.uio.no [Department of Chemistry, University of Oslo, Centre for Materials Science and Nanotechnology, FERMiO, Gaustadalleen 21, NO-0349 Oslo (Norway); Galeckas, Augustinas, E-mail: augustinas.galeckas@fys.uio.no [Department of Physics, University of Oslo, Centre for Materials Science and Nanotechnology, P.O. Box 1048 Blindern, NO-0316 Oslo (Norway); Rauwel, Protima, E-mail: protima.singh@fys.uio.no [Centre for Materials Science and Nanotechnology, University of Oslo, P.O. Box 1126 Blindern, NO-0318 Oslo (Norway); Kuznetsov, Andrej Y., E-mail: andrej.kuznetsov@fys.uio.no [Department of Physics, University of Oslo, Centre for Materials Science and Nanotechnology, P.O. Box 1048 Blindern, NO-0316 Oslo (Norway); Norby, Truls, E-mail: truls.norby@kjemi.uio.no [Department of Chemistry, University of Oslo, Centre for Materials Science and Nanotechnology, FERMiO, Gaustadalleen 21, NO-0349 Oslo (Norway)

2012-01-15

363

Spectral characterization of a tunable alexandrite laser by rubidium absorption at 780 nm  

Microsoft Academic Search

Rubidium vapor was used to characterize the output of a tunable, pulsed alexandrite laser operating at 780 nm. Rubidium spectra were obtained at temperatures of 23, 50, 110, and 140 C. Excellent agreement was obtained with computer-synthesized spectra which yielded values for the effective laser bandwidth at different operating conditions. The model assumed a Voigt profile for the rubidium 5

A. V. Nowak; B. J. Krohn

1985-01-01

364

Characterization of the structures of size-selected TiO2 nanoparticles using X-ray absorption spectroscopy.  

PubMed

To investigate the relationship between the size and structure of TiO(2) nanoparticles, three size-selected samples of TiO(2) nanoparticles were prepared via a hydrolysis method that uses Ti[OCH(CH(3))(2)](4) as the starting material. The structures of the nanoparticles were characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS). Analysis of the XRD patterns and of the TEM images showed that the samples were dispersed, with an average particle size of approximately 30 nm (sample A), approximately 12 nm (sample B), and approximately 7 nm (sample C). Their X-ray absorption spectra indicate that samples A and B have an anatase structure, whereas sample C has a structure very similar to that of the TiO( 2) II phase, which generally arises only under high-pressure conditions. This difference can be attributed to size-induced radial pressure within the smaller nanoparticles, which plays an important role in the phase of TiO(2) nanoparticles in sample C. PMID:15165337

Choi, Hyun Chul; Ahn, Hyo-Jin; Jung, Young Mee; Lee, Min Kyu; Shin, Hyun Joon; Kim, Seung Bin; Sung, Yung-Eun

2004-05-01

365

Time- and space-resolved spectroscopic characterization of a laser carbon plasma plume in an argon background  

NASA Astrophysics Data System (ADS)

We present time- and space-resolved spectroscopic observations of a laser-produced carbon plasma, in an argon background. An Nd?:?YAG laser pulse, 370 mJ, 3.5 ns, at 1.06 µm, with a fluence of 6.9 J cm-2, is used to produce a plasma from a solid graphite target in a 0.5 to 415 mTorr argon background. The spectral emission in the visible is recorded with 15 ns time resolution. We use 20 ns time resolution plasma imaging, filtered at characteristic carbon species emission wavelengths, to study the dynamics of the expanding plasma. The carbon plasma emission is found to evolve from the characteristic of single ionized carbon, to a more complex one, where C2 and C3 molecular bands dominate. Several plasma fronts, with either ionic or molecular composition, are seen to detach from the laser target plasma. The temporal and spatial features of the molecular carbon species evolution are found to be dependent on the actual argon background pressure.

Ruiz, H. M.; Guzmán, F.; Favre, M.; Bhuyan, H.; Chuaqui, H.; Wyndham, E. S.

2012-06-01

366

Spectroscopic characterization of the oxyferrous complex of prostacyclin synthase in solution and in trapped sol-gel matrix  

PubMed Central

Prostacyclin synthase (PGIS) is a member of the cytochrome P450 family in which the oxyferrous complexes are generally labile in the absence of substrate. At 4 °C, the on-rate constants and off-rate constants of oxygen binding to PGIS in solution are 5.9 × 105 m?1 ·s?1 and 29 s?1, respectively. The oxyferrous complex decays to a ferric form at a rate of 12 s?1. We report, for the first time, a stable oxyferrous complex of PGIS in a transparent sol–gel monolith. The encapsulated ferric PGIS retained the same spectroscopic features as in solution. The binding capabilities of the encapsulated PGIS were demonstrated by spectral changes upon the addition of O-based, N-based and C-based ligands. The peroxidase activity of PGIS in sol–gel was three orders of magnitude slower than that in solution owing to the restricted diffusion of the substrate in sol–gel. The oxyferrous complex in sol–gel was observable for 24 h at room temperature and displayed a much red-shifted Soret peak. Stabilization of the ferrous–carbon monoxide complex in sol–gel was observed as an enrichment of the 450-nm species over the 420-nm species. This result suggests that the sol–gel method may be applied to other P450s to generate a stable intermediate in the di-oxygen activation.

Yeh, Hui-Chun; Hsu, Pei-Yung; Tsai, Ah-Lim; Wang, Lee-Ho

2010-01-01

367

Spectroscopic characterization of molecular interactions between DNQ-PACs and phenolic resins using selectively nitrogen-15 labeled DNQs  

NASA Astrophysics Data System (ADS)

Interactions between diazonaphthoquinone (DNQ)-photoactive compounds (PACs) and phenolic resins with different degrees of ortho, ortho-bonding have been investigated using solid state nitrogen-15 nuclear magnetic resonance (NMR) and vibrational (infrared and Raman) spectroscopic techniques. A specifically nitrogen-15 labeled PAC was synthesized to facilitate solid state nitrogen-15 NMR experimentation, and to resolve ambiguities in vibrational spectra. Comparison of vibrational spectra of the 15N-labeled PAC and its natural abundance 14N analog showed conclusively that Fermi resonance as well as hydrogen-boding resin-PAC interactions influence changes in the out-of-phase diazo stretching region near 2100 cm-1. Solid state nitrogen-15 NMR of the 15N-labeled PAC in poly(p-hydroxystyrene), in a m-cresol 3,5-xylenol novolak, and in a mainly m,p- cresol novolak showed the binding situation in the resins to be diffuse, but quite similar. Although the three resins examined are lithographically very different, the observed nitrogen- 15 shifts were small compared to the broadening of the resonances, and did not show major differences due to ortho, ortho-bonding effects.

Borzo, Marie; Rafalko, Joseph J.; Joe, Monica; Dammel, Ralph R.; Rahman, M. Dalil; Ziliox, Martine A.

1995-06-01

368

Some new [(thione)2Au(diamine)]Cl3 complexes: Synthesis, spectroscopic characterization, computational and in vitro cytotoxic studies  

NASA Astrophysics Data System (ADS)

Recent advances in oncology are focused on developing new complexes of gold(III) with various ligands that show augmented anti-proliferative potential and reduced toxicity as compared to cis-platin. In this study, new Au(III) complexes of the type [(thione)2Au(diamine)]Cl3 are reported, where thione = 1,3-imidazolidine-2-thione (Imt), 1,3-Diazinane-2-thione (Diaz) and diamine = 1,2-diaminoethane (en), 1,3-diaminopropane (pn) or 1,4-diaminobutane (bn). The solid state IR as well as 13C and 15N NMR data indicate that Au(III) center is bonded via sulfur of thiocarbonyl Sdbnd Crbond2 site of the thiones and also chelated by the diamines from the trans side of coordinated thiones. Spectroscopic data are evaluated by comparisons with calculated data from the built and optimized structure by GAUSSIAN 09 at the RB3LYP level with LanL2DZ bases set. These new Au(III) complexes based on mixed thione and diamine ligands are very similar to the square planar structure of tetracoordinate [Au(en)2]Cl3complex. In this study, cytotoxicity data for these gold(III) complexes against C6 glioma cell lines are also reported, and the results indicate some complexes have cytotoxicity comparable to cis-platin.

Al-Maythalony, Bassem A.; Monim-ul-Mehboob, M.; Altaf, Muhammad; Wazeer, Mohammed I. M.; Isab, Anvarhusein A.; Altuwaijri, Saleh; Ahmed, Ayesha; Dhuna, Vikram; Bhatia, Gaurav; Dhuna, Kshitija; Kamboj, Sukhdev Singh

2013-11-01

369

Some new [(thione)2Au(diamine)]Cl3 complexes: Synthesis, spectroscopic characterization, computational and in vitro cytotoxic studies.  

PubMed

Recent advances in oncology are focused on developing new complexes of gold(III) with various ligands that show augmented anti-proliferative potential and reduced toxicity as compared to cis-platin. In this study, new Au(III) complexes of the type [(thione)2Au(diamine)]Cl3 are reported, where thione=1,3-imidazolidine-2-thione (Imt), 1,3-Diazinane-2-thione (Diaz) and diamine=1,2-diaminoethane (en), 1,3-diaminopropane (pn) or 1,4-diaminobutane (bn). The solid state IR as well as (13)C and (15)N NMR data indicate that Au(III) center is bonded via sulfur of thiocarbonyl SC site of the thiones and also chelated by the diamines from the trans side of coordinated thiones. Spectroscopic data are evaluated by comparisons with calculated data from the built and optimized structure by GAUSSIAN 09 at the RB3LYP level with LanL2DZ bases set. These new Au(III) complexes based on mixed thione and diamine ligands are very similar to the square planar structure of tetracoordinate [Au(en)2]Cl3complex. In this study, cytotoxicity data for these gold(III) complexes against C6 glioma cell lines are also reported, and the results indicate some complexes have cytotoxicity comparable to cis-platin. PMID:23876928

Al-Maythalony, Bassem A; Monim-Ul-Mehboob, M; Altaf, Muhammad; Wazeer, Mohammed I M; Isab, Anvarhusein A; Altuwaijri, Saleh; Ahmed, Ayesha; Dhuna, Vikram; Bhatia, Gaurav; Dhuna, Kshitija; Kamboj, Sukhdev Singh

2013-07-03

370

Characterization of Pt particle interaction with L-zeolite by x-ray absorption spectroscopy: Binding energy shifts, x-ray absorption near-edge structure, and extended x-ray absorption fine structure  

Microsoft Academic Search

The authors have used x-ray absorption to measure the binding energy, x-ray absorption near-edge structure (XANES), and extended x-ray absorption fine structure (EXAFS) of Pt particles in L-zeolite saturated with Hâ at room temperature and after desorption of Hâ in He. The desorption of Hâ causes the particles to disorder or perhaps breakup such that the coherence required for EXAFS

Brian J. McHugh; Gustavo. Larsen; Gary L. Haller

1990-01-01

371

Characterization of selective binding of alkali cations with carboxylate by x-ray absorption spectroscopy of liquid microjets  

SciTech Connect

We describe an approach for characterizing selective binding between oppositely charged ionic functional groups under biologically relevant conditions. Relative shifts in K-shell x-ray absorption spectra of aqueous cations and carboxylate anions indicate the corresponding binding strengths via perturbations of carbonyl antibonding orbitals. XAS spectra measured for aqueous formate and acetate solutions containing lithium, sodium, and potassium cations reveal monotonically stronger binding of the lighter metals, supporting recent results from simulations and other experiments. The carbon K-edge spectra of the acetate carbonyl feature centered near 290 eV clearly indicate a preferential interaction of sodium versus potassium, which was less apparent with formate. These results are in accord with the Law of Matching Water Affinities, relating relative hydration strengths of ions to their respective tendencies to form contact ion pairs. Density functional theory calculations of K-shell spectra support the experimental findings.

Saykally, Richard J; Uejio, Janel S.; Schwartz, Craig P.; Duffin, Andrew M.; Drisdell, Walter S.; Cohen, Ronald C.; Saykally, Richard J.

2008-01-08

372

Observation of x-ray absorption magnetic circular dichroism in well-characterized iron-cobalt-platinum multilayers  

SciTech Connect

Magnetic circular dichroism in the Fe 2p x-ray absorption is observed in multilayers of(Fe9.5{Angstrom}/Pt9.5{Angstrom}){sub 92}. The magnetization and helicity are both in the plane of this multilayer which is prepared by magnetron sputter deposition. This sample is part of a study to examine magnetization in the ternary multilayer system of FeCo/Pt. Lattice and layer pair spacings are measured using x-ray scattering. The atomic concentration profiles of the multilayer films are characterized using Auger electron spectroscopy coupled with depth profiling. Conventional and high resolution transmission electron microscopy are used to examine the thin film, growth morphology and atomic structure.

Jankowski, A.F.; Waddill, G.D.; Tobin, J.G.

1993-04-01

373

Temporally resolved characterization of shock-heated foam target with Al absorption spectroscopy for fast electron transport study  

SciTech Connect

The CH foam plasma produced by a laser-driven shock wave has been characterized by a temporally resolved Al 1s-2p absorption spectroscopy technique. A 200 mg/cm{sup 3} foam target with Al dopant was developed for this experiment, which used an OMEGA EP [D. D. Meyerhofer et al., J. Phys.: Conf. Ser. 244, 032010 (2010)] long pulse beam with an energy of 1.2 kJ and 3.5 ns pulselength. The plasma temperatures were inferred with the accuracy of 5 eV from the fits to the measurements using an atomic physics code. The results show that the inferred temperature is sustained at 40-45 eV between 6 and 7 ns and decreases to 25 eV at 8 ns. 2-D radiation hydrodynamic simulations show a good agreement with the measurements. Application of the shock-heated foam plasma platform toward fast electron transport experiments is discussed.

Yabuuchi, T.; Sawada, H.; Wei, M. S.; Beg, F. N. [Center for Energy Research, University of California, San Diego, La Jolla, California 92093 (United States); Regan, S. P.; Anderson, K.; Betti, R. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Hund, J.; Paguio, R. R.; Saito, K. M.; Stephens, R. B. [General Atomics, San Diego, California 92186 (United States); Key, M. H.; Mackinnon, A. J.; McLean, H. S.; Patel, P. K.; Wilks, S. C. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2012-09-15

374

Temporally resolved characterization of shock-heated foam target with Al absorption spectroscopy for fast electron transport study  

NASA Astrophysics Data System (ADS)

The CH foam plasma produced by a laser-driven shock wave has been characterized by a temporally resolved Al 1s-2p absorption spectroscopy technique. A 200 mg/cm3 foam target with Al dopant was developed for this experiment, which used an OMEGA EP [D. D. Meyerhofer et al., J. Phys.: Conf. Ser. 244, 032010 (2010)] long pulse beam with an energy of 1.2 kJ and 3.5 ns pulselength. The plasma temperatures were inferred with the accuracy of 5 eV from the fits to the measurements using an atomic physics code. The results show that the inferred temperature is sustained at 40-45 eV between 6 and 7 ns and decreases to 25 eV at 8 ns. 2-D radiation hydrodynamic simulations show a good agreement with the measurements. Application of the shock-heated foam plasma platform toward fast electron transport experiments is discussed.

Yabuuchi, T.; Sawada, H.; Regan, S. P.; Anderson, K.; Wei, M. S.; Betti, R.; Hund, J.; Key, M. H.; Mackinnon, A. J.; McLean, H. S.; Paguio, R. R.; Patel, P. K.; Saito, K. M.; Stephens, R. B.; Wilks, S. C.; Beg, F. N.

2012-09-01

375

Structural characterization of C-S-H and C-A-S-H samples-Part II: Local environment investigated by spectroscopic analyses  

SciTech Connect

Spectroscopic studies ({sup 1}H, {sup 23}Na and {sup 27}Al MAS NMR and Raman spectroscopy) have been used to characterize three series of C-S-H samples (0.8Spectroscopic investigations indicate that the main part of the Al atoms is readily incorporated into the interlayer region of the C-S-H structure. Al atoms are mainly inserted as four-fold coordinated aluminates in the dreierketten silicate chain (either in bridging or paired tetrahedra) at low Ca/Si ratio. Four-fold aluminates are progressively replaced by six-fold coordinated aluminates located into the interlayer region of the C-S-H structure and bonded to silicate chains. Investigation of the hydrogen bonding in C-S-H indicates that the main part of the hydrogen bonds is intra-main layer, and thus explains the low stacking cohesion of the C-S-H structure leading to its nanometric crystal size and the OD character of the tobermorite like structures. - Graphical abstract: The insertion of aluminum atoms into the C-S-H structure has been investigated by spectroscopic analyses ({sup 27}Al and {sup 1}H MAS NMR and Raman). The previously determined structural continuity, when increasing the C/S ratio from the C-S-H(I) type to the C-S-H(II) type, has been confirmed even in the presence of aluminum.

Renaudin, Guillaume, E-mail: guillaume.renaudin@ensccf.f [Clermont-Universite, Ecole Nationale Superieure de Chimie de Clermont-Ferrand, LMI, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6002, F-63177 Aubiere Cedex (France); Russias, Julie [Commissariat a l'Energie Atomique, DEN, Marcoule, Waste Treatment and Conditioning Research Department, F-30207 Bagnols sur Ceze (France); Leroux, Fabrice [Clermont Universite, UBP, Laboratoire des Materiaux Inorganiques, F-63000 Clermont-Ferrand (France); CNRS, UMR 6002, F-63177 Aubiere Cedex (France); Cau-dit-Coumes, Celine; Frizon, Fabien [Commissariat a l'Energie Atomique, DEN, Marcoule, Waste Treatment and Conditioning Research Department, F-30207 Bagnols sur Ceze (France)

2009-12-15

376

Carbonmonoxy dopamine beta-hydroxylase. Structural characterization by Fourier transform infrared, fluorescence, and x-ray absorption spectroscopy.  

PubMed

The carbon monoxide complex of ascorbate-reduced dopamine beta-hydroxylase has been prepared and characterized by Fourier transform infrared, fluorescence, and x-ray absorption spectroscopies. CO has previously been shown to be a competitive inhibitor with respect to O2, and binds to only one of the two copper atoms/active site (Blackburn, N. J., Pettingill, T. M., Seagraves, K. S., and Shigeta, R. T. (1990) J. Biol. Chem. 265, 15383-15386). Thus, it acts as an excellent probe of the O2-binding site. A single C-O infrared absorption band is observed at 2089 cm-1, shifting by 46 cm-1 to lower energy on substitution with either 13C16O or 12C18O. The 13C isotope shift is reversed to the position expected for 12CO upon vacuum flushing with 12CO gas, indicating that formation of the CO adduct is a fully reversible process. Binding of the substrate tyramine does not eliminate the infrared peak but causes a 3-cm-1 shift to lower energy. On the other hand, binding of a bifunctional inhibitor which cross-links the substrate and O2-binding site does eliminate the CO peak. These data, in conjunction with the competitive nature of CO binding with respect to O2, identify the CO-binding site as the O2-binding site, and place it in close proximity to the substrate-binding site. CO-dopamine beta-hydroxylase exhibits no luminescence in the visible region, suggesting a structure different from carbonmonoxy hemocyanin, and in all probability mononuclear. Analysis of extended x-ray absorption spectroscopy data is most consistent with an average coordination per Cu of 2-3 histidines, 0.5 CO, and 0.5 S atoms as ligands, and absorption edge comparisons indicates pseudo-4 coordination as the most likely geometry at each Cu(I) center. The results can be interpreted by a model involving inequivalent 4-coordination at each Cu(I) center in the CO adduct with CuAHis3S...CuBHis2CO-X as the coordination most consistent with all of the data. PMID:1894598

Pettingill, T M; Strange, R W; Blackburn, N J

1991-09-15

377

Spectroscopic features of cytochrome P450 reaction intermediates  

PubMed Central

Preface Cytochromes P450 constitute a broad class of heme monooxygenase enzymes with more than 11,500 isozymes which have been identified in organisms from all biological kingdoms [1]. These enzymes are responsible for catalyzing dozens chemical oxidative transformations such as hydroxylation, epoxidation, N-demethylation, etc., with very broad range of substrates [2-3]. Historically these enzymes received their name from ‘pigment 450’ due to the unusual position of the Soret band in UV-Vis absorption spectra of the reduced CO-saturated state [4-5]. Despite detailed biochemical characterization of many isozymes, as well as later discoveries of other ‘P450-like heme enzymes’ such as nitric oxide synthase and chloroperoxidase, the phenomenological term ‘cytochrome P450’ is still commonly used as indicating an essential spectroscopic feature of the functionally active protein which is now known to be due to the presence of a thiolate ligand to the heme iron [6]. Heme proteins with an imidazole ligand such as myoglobin and hemoglobin as well as an inactive form of P450 are characterized by Soret maxima at 420 nm [7]. This historical perspective highlights the importance of spectroscopic methods for biochemical studies in general, and especially for heme enzymes, where the presence of the heme iron and porphyrin macrocycle provides rich variety of specific spectroscopic markers available for monitoring chemical transformations and transitions between active intermediates of catalytic cycle.

Luthra, Abhinav; Denisov, Ilia G.; Sligar, Stephen G.

2010-01-01

378

Fourier transform infrared absorption spectroscopy characterization of gaseous atmospheric pressure plasmas with 2 mm spatial resolution  

NASA Astrophysics Data System (ADS)

This paper describes an optical setup built to record Fourier transform infrared (FTIR) absorption spectra in an atmospheric pressure plasma with a spatial resolution of 2 mm. The overall system consisted of three basic parts: (1) optical components located within the FTIR sample compartment, making it possible to define the size of the infrared beam (2 mm × 2 mm over a path length of 50 mm) imaged at the site of the plasma by (2) an optical interface positioned between the spectrometer and the plasma reactor. Once through the plasma region, (3) a retro-reflector module, located behind the plasma reactor, redirected the infrared beam coincident to the incident path up to a 45° beamsplitter to reflect the beam toward a narrow-band mercury-cadmium-telluride detector. The antireflective plasma-coating experiments performed with ammonia and silane demonstrated that it was possible to quantify 42 and 2 ppm of these species in argon, respectively. In the case of ammonia, this was approximately three times less than this gas concentration typically used in plasma coating experiments while the silane limit of quantification was 35 times lower. Moreover, 70% of the incoming infrared radiation was focused within a 2 mm width at the site of the plasma, in reasonable agreement with the expected spatial resolution. The possibility of reaching this spatial resolution thus enabled us to measure the gaseous precursor consumption as a function of their residence time in the plasma.

Laroche, G.; Vallade, J.; Bazinette, R.; van Nijnatten, P.; Hernandez, E.; Hernandez, G.; Massines, F.

2012-10-01

379

Electronic transport characterization of silicon wafers by combination of modulated free carrier absorption and photocarrier radiometry  

NASA Astrophysics Data System (ADS)

A combined modulated free carrier absorption (MFCA) and photocarrier radiometry (PCR) technique is developed to determine simultaneously the electronic transport properties (carrier diffusion coefficient, carrier lifetime, and front surface recombination velocity) of silicon wafers. Comparative computer simulations are carried out to investigate how the experimental measurement errors affect the simultaneous determination of the electronic transport parameters by introducing random or systematic errors into the simulated MFCA and PCR data and statistically analyzing the fitted results, by means of separate MFCA and PCR, as well as the combined MFCA and PCR through fitting the experimental dependences of signal amplitudes and phases to the corresponding theoretical models via a multiparameter fitting procedure, respectively. The simulation results show that with the combined MFCA and PCR the effect of experimental errors on the simultaneous determination of the transport parameters is significantly reduced and therefore the accuracy of the fitted results is greatly improved. Experiments with two c-Si wafers with the three methods were performed and the results were compared. The experimental results showed that the combined MFCA and PCR provided the most accurate fitted transport parameters, in agreement with the simulation results.

Huang, Qiuping; Li, Bincheng

2011-01-01

380

Americium characterization by X-ray fluorescence and absorption spectroscopy in plutonium uranium mixed oxide  

NASA Astrophysics Data System (ADS)

Plutonium uranium mixed oxide (MOX) fuels are currently used in nuclear reactors. The actinides in these fuels need to be analyzed after irradiation for assessing their behaviour with regard to their environment and the coolant. In this work the study of the atomic structure and next-neighbour environment of Am in the (Pu,U)O2 lattice in an irradiated (60 MW d kg?1) MOX sample was performed employing micro-X-ray fluorescence (µ-XRF) and micro-X-ray absorption fine structure (µ-XAFS) spectroscopy. The chemical bonds, valences and stoichiometry of Am (˜0.66 wt%) are determined from the experimental data gained for the irradiated fuel material examined in its peripheral zone (rim) of the fuel. In the irradiated sample Am builds up as Am3+ species within an [AmO8]13? coordination environment (e.g. >90%) and no (<10%) Am(IV) or (V) can be detected in the rim zone. The occurrence of americium dioxide is avoided by the redox buffering activity of the uranium dioxide matrix.

Degueldre, Claude; Cozzo, Cedric; Martin, Matthias; Grolimund, Daniel; Mieszczynski, Cyprian

2013-06-01

381

Characterization of the Electronic Structure of Silicon Nanoparticles Using X-ray Absorption and Emission  

SciTech Connect

Resolving open questions regarding transport in nanostructures can have a huge impact on a broad range of future technologies such as light harvesting for energy. Silicon has potential to be used in many of these applications. Understanding how the band edges of nanostructures move as a function of size, surface termination and assembly is of fundamental importance in understanding the transport properties of these materials. In this thesis work I have investigated the change in the electronic structure of silicon nanoparticle assemblies as the surface termination is changed. Nanoparticles are synthesized using a thermal evaporation technique and sizes are determined using atomic force microscopy (AFM). By passivating the particles with molecules containing alcohol groups we are able to modify the size dependent band edge shifts. Both the valence and conduction bands are measured using synchrotron based x-ray absorption spectroscopy (XAS) and soft x-ray fluorescence (SXF) techniques. Particles synthesized via recrystallization of amorphous silicon/SiO{sub 2} multilayers of thicknesses below 10 nm are also investigated using the synchrotron techniques. These samples also show quantum confinement effects but the electronic structure is different from those synthesized via evaporation methods. The total bandgap is determined for all samples measured. The origins of these differences in the electronic structures are discussed.

Vaverka, A M

2008-07-15

382

Spatiotemporal characterization of interfacial Faraday waves by means of a light absorption technique.  

PubMed

We present measurements of the complete spatiotemporal Fourier spectrum of Faraday waves. The Faraday waves are generated at the interface of two immiscible index matched liquids of different density. By use of a light absorption technique we are able to determine the bifurcation scenario from the flat surface to the patterned state for each complex spatial and temporal Fourier component separately. The surface spectra at onset are found to be in good agreement with the predictions from the linear stability analysis. For the nonlinear state our measurements show in a direct manner how energy is transferred from lower to higher harmonics and we quantify the nonlinear coupling coefficients. Furthermore we find that the nonlinear coupling generates static components in the temporal Fourier spectrum leading thus to a contribution of a nonoscillating permanent sinusoidal deformed surface state. A comparison of hexagonal and rectangular patterns reveals that spatial resonance can give rise to a spectrum that violates the temporal resonance conditions given by the weakly nonlinear theory. PMID:16241550

Kityk, A V; Embs, J; Mekhonoshin, V V; Wagner, C

2005-09-13

383

Spatiotemporal characterization of interfacial Faraday waves by means of a light absorption technique  

NASA Astrophysics Data System (ADS)

We present measurements of the complete spatiotemporal Fourier spectrum of Faraday waves. The Faraday waves are generated at the interface of two immiscible index matched liquids of different density. By use of a light absorption technique we are able to determine the bifurcation scenario from the flat surface to the patterned state for each complex spatial and temporal Fourier component separately. The surface spectra at onset are found to be in good agreement with the predictions from the linear stability analysis. For the nonlinear state our measurements show in a direct manner how energy is transferred from lower to higher harmonics and we quantify the nonlinear coupling coefficients. Furthermore we find that the nonlinear coupling generates static components in the temporal Fourier spectrum leading thus to a contribution of a nonoscillating permanent sinusoidal deformed surface state. A comparison of hexagonal and rectangular patterns reveals that spatial resonance can give rise to a spectrum that violates the temporal resonance conditions given by the weakly nonlinear theory.

Kityk, A. V.; Embs, J.; Mekhonoshin, V. V.; Wagner, C.

2005-09-01

384

Characterization of Silicon Wafers with Combined Photocarrier Radiometry and Free Carrier Absorption  

NASA Astrophysics Data System (ADS)

A combined photocarrier radiometry (PCR) and free carrier absorption (FCA) technique was employed to evaluate the electronic transport properties (carrier lifetime ?, diffusion coefficient D, and the front surface recombination velocity S1) of silicon wafers and to monitor the ion implantation and thermal annealing processes in the semiconductor manufacturing. For non-implanted silicon wafers, the experimental results showed that the accuracy of the simultaneous determination of the transport properties was greatly improved by fitting simultaneously the measured PCR and FCA signals to the theoretical models via a multi-parameter fitting procedure. For As^+ ion implanted and thermal annealed silicon wafers, the results showed that both PCR and FCA amplitudes increased monotonically with the increasing implantation dose (5× 10^{11} cm^{-2 } to 1× 10^{16 } cm^{-2}), the decreasing implantation energy (20 keV to 140 keV), and the increasing annealing temperature (500° C to 1000° C), respectively. To explain the dependences of the PCR signals on the implantation and annealing parameters, a multi-wavelength PCR technique was proposed to extract the electronic transport properties of the implanted and annealed wafers. The results showed that ion implantation and thermal annealing caused significant decreases of the minority carrier lifetime and diffusion coefficient of the implantation layer, as well as the recombination velocity at the front surface. All three parameters decreased with the increasing implantation dose.

Li, Bincheng; Huang, Qiuping; Ren, Shengdong

2013-09-01

385

Synthesis, isolation, and spectroscopic characterization of holmium-based mixed-metal nitride clusterfullerenes: HoxSc3-xN@C80 (x=1, 2).  

PubMed

The synthesis, isolation and spectroscopic characterization of holmium-based mixed metal nitride clusterfullerenes Ho(x) Sc(3-x) N@C(80) (x=1, 2) are reported. Two isomers of Ho(x) Sc(3-x) N@C(80) (x=1, 2) were synthesized by the reactive gas atmosphere method and isolated by multistep recycling HPLC. The isomeric structures of Ho(x) Sc(3-x) N@C(80) (x=1, 2) were characterized by laser-desorption time-of-flight (LD-TOF) mass spectrometry and UV/Vis/NIR, FTIR and Raman spectroscopy. A comparative study of M(x) Sc(3-x) N@C(80) (M=Gd, Dy, Lu, Ho) demonstrates the dependence of their electronic and vibrational properties on the encaged metal. Despite the distinct perturbation induced by 4f(10) electrons, we report the first paramagnetic (13) C?NMR study on Ho(x) Sc(3-x) N@C(80) (I; x=1, 2) and confirm I(h) -symmetric cage structure. A (45) Sc NMR study on HoSc(2) N@C(80) (I, II) revealed a temperature-dependent chemical shift in the temperature range of 268-308?K. PMID:22745152

Zhang, Yang; Popov, Alexey A; Schiemenz, Sandra; Dunsch, Lothar

2012-06-28

386

Spectroscopic and wet chemical characterization of solid waste organic matter of different age in landfill sites, southern Germany.  

PubMed

Landfill sites are potential sources of hazardous emissions by degradation and transformation processes of waste organic matter. Its chemical composition and microbial degradability are key factors for risk management, after-care, and estimation of potential emissions. The aim of the study is to provide information about composition and extent of transformation of waste organic matter in four landfill sites in Bavaria, Southern Germany by means of (13)C NMR spectroscopy, acid-hydrolyzable carbohydrates, chloroform-methanol extractable lipids, acid-hydrolyzable proteins, and lignin compounds after CuO oxidation. Ten samples of about 20 to 25 yr, 15 to 20 yr, and 5 to 10 yr of deposition each were taken at 2 m depth intervals by grab drilling till 10-m depth. Increasing temperatures from about 15 degrees C at 2-m depth to >40 degrees C at 10-m depth are found at some of the sites, representing optimum conditions for mesophile methane bacteria. Moisture contents of 160 to 310 g kg(-1) (oven dry), however, provide limiting conditions for anaerobic biodecay. Spectroscopic and chemical variables generally indicate a low extent of biodegradation and transformation at all sites despite a considerable heterogeneity of the samples. Independent of the time and depth of deposition more than 50% of the carbohydrate fraction of the waste organic matter provide a high potential for methane emissions and on-site energy production. There was no significant accumulation of long-chain organic and aromatic compounds, and of lignin degradation products even after more than 25 yr of rotting indicating higher extent of decomposition or stabilization of the waste organic matter. Installation of seepage water cleaning and recirculation systems are recommended to increase suboptimal moisture contents with respect to microbial methanogenesis, energy production, and long-term stabilization of municipal solid waste. PMID:18178887

Bäumler, Rupert; Kögel-Knabner, Ingrid

2008-01-04

387

Spectroscopic characterization of the atmospheres of potentially habitable planets: GL 581 d as a model case study  

Microsoft Academic Search

Context. Were a potentially habitable planet to be discovered, the next step would be the search for an atmosphere and its characterization. Eventually, surface conditions, hence habitability, and biomarkers as indicators for life would be assessed. Aims: The super-Earth candidate Gliese (GL) 581 d is the first potentially habitable extrasolar planet so far discovered. Therefore, GL 581 d is used

P. von Paris; J. Cabrera; M. Godolt; J. L. Grenfell; P. Hedelt; H. Rauer; F. Schreier; B. Stracke

2011-01-01

388

Spectroscopic characterization of heme iron-nitrosyl species and their role in NO reductase mechanisms in diiron proteins†  

PubMed Central

Nitric oxide (NO) plays an important role in cell signalling and in the mammalian immune response to infection. On its own, NO is a relatively inert radical, and when it is used as a signalling molecule, its concentration remains within the picomolar range. However, at infection sites, the NO concentration can reach the micromolar range, and reactions with other radical species and transition metals lead to a broad toxicity. Under aerobic conditions, microorganisms cope with this nitrosative stress by oxidizing NO to nitrate (NO3?). Microbial hemoglobins play an essential role in this NO-detoxifying process. Under anaerobic conditions, detoxification occurs via a 2-electron reduction of two NO molecules to N2O. In many bacteria and archaea, this NO-reductase reaction is catalyzed by diiron proteins. Despite the importance of this reaction in providing microorganisms with a resistance to the mammalian immune response, its mechanism remains ill-defined. Because NO is an obligatory intermediate of the denitrification pathway, respiratory NO reductases also provide resistance to toxic concentrations of NO. This family of enzymes is the focus of this review. Respiratory NO reductases are integral membrane protein complexes that contain a norB subunit evolutionarily related to subunit I of cytochrome c oxidase (CcO). NorB anchors one high-spin heme b3 and one non-heme iron known as FeB, i.e., analogous to CuB in CcO. A second group of diiron proteins with NO-reductase activity is comprised of the large family of soluble flavoprotein A found in strict and facultative anaerobic bacteria and archaea. These soluble detoxifying NO reductases contain a non-heme diiron cluster with a Fe–Fe distance of 3.4 Å and are only briefly mentioned here as a promising field of research. This article describes possible mechanisms of NO reduction to N2O in denitrifying NO-reductase (NOR) proteins and critically reviews recent experimental results. Relevant theoretical model calculations and spectroscopic studies of the NO-reductase reaction in heme/copper terminal oxidases are also overviewed.

Moenne-Loccoz, Pierre

2010-01-01

389

2-thiobarbituric acid test for lipid oxidation in food: Synthesis and spectroscopic study of 2-thiobarbituric acid-malonaldehyde adduct  

Microsoft Academic Search

Synthesis, purification, elemental analysis, and spectroscopic studies were undertaken to characterize the structure of the\\u000a red adduct 2:1 thiobarbituric acid (TBA)-malonaldehyde involved in the evaluation of oxidative rancidity in fats and oils.\\u000a Thin-layer chromatography, infrared and ultravioletvisible absorption, 1H (1H NMR) and 13C nuclear magnetic resonance (NMR) spectra were used. A yield of 93% was obtained in the synthesis. The

Matías Guzmán-Chozas; Isabel M. Vicario-Romero; Remedios Guillén-Sans

1998-01-01

390

Spectroscopic characterization of a multiband complex oxide: Insulating and conducting cement 12CaO·7Al2O3  

NASA Astrophysics Data System (ADS)

Natural 12CaO·7Al2O3 (C12A7) is a wide band gap insulator, but conductivity can be realized by introducing oxygen deficiency. Currently, there are two competing models explaining conductivity in oxygen-deficient C12A7, one involving the electron transfer via a “cage conduction band” inside the nominal band gap, the other involving electron hopping along framework lattice sites. To help resolve this debate, we probe insulating and conducting C12A7 with x-ray emission, x-ray absorption, and x-ray photoemission spectroscopy, which provide a full picture of both the valence and conduction band edges in these materials. These measurements suggest the existence of a narrow conduction band between the main conduction and valence bands common in both conducting and insulating C12A7 and support the theory that free electrons in oxygen-deficient C12A7 occupy the low-energy states of this narrow band. Our measurements are corroborated with density functional theory calculations.

McLeod, J. A.; Buling, A.; Kurmaev, E. Z.; Sushko, P. V.; Neumann, M.; Finkelstein, L. D.; Kim, S.-W.; Hosono, H.; Moewes, A.

2012-01-01

391

Spectroscopic Characterization of a Multiband Complex Oxide: Insulating and Conducting Cement 12CaO·7Al?O?  

SciTech Connect

Natural 12CaO·7Al?O? (C12A7) is a wide band gap insulator, but conductivity can be realized by introducing oxygen deficiency. Currently, there are two competing models explaining conductivity in oxygen-deficient C12A7, one involving the electron transfer via a “cage conduction band” inside the nominal band gap, the other involving electron hopping along framework lattice sites. To help resolve this debate, we probe insulating and conducting C12A7 with x-ray emission, x-ray absorption, and x-ray photoemission spectroscopy, which provide a full picture of both the valence and conduction band edges in these materials. Thesemeasurements suggest the existence of a narrow conduction band between themain conduction and valence bands common in both conducting and insulating C12A7 and support the theory that free electrons in oxygen-deficient C12A7 occupy the low-energy states of this narrow band. Our measurements are corroborated with density functional theory calculations.

McLeod, John A.; Buling, A.; Kurmaev, Ernst Z.; Sushko, Petr V.; Neumann, N.; Finkelstein, L. D.; Kim, S. W.; Hosono, H.; Moewes, Alexander

2012-01-13

392

Combined spectroscopic characterization of electron transfer at hybrid CuPcF(16)/GaAs semiconductor interfaces.  

PubMed

We characterize photoinduced charge injection at the interface between a fluorinated copper phthalocyanine (CuPcF(16)) film deposited over a GaAs(100) wafer by means of pump-probe spectroscopy combined with ultraviolet photoemission spectroscopy (UPS) and electromodulated transmission spectroscopy. UPS characterization of the hybrid interface demonstrates that the CuPcF(16) 's lowest unoccupied molecular level (LUMO) is almost aligned with the GaAs conduction band. Upon photoexcitation of the hybrid interface with 150 fs pulses we observe an efficient photoinduced electron transfer from CuPcF(16) to GaAs. The evolution of interfacial CuPcF(16) charges appear to be strongly influenced by energy level alignment at the GaAs/CuPcF(16) heterojunction. PMID:21832670

Cabanillas-Gonzalez, Juan; Egelhaaf, Hans-Joachim; Brambilla, Alberto; Sessi, Paolo; Duò, Lamberto; Finazzi, Marco; Ciccacci, Franco; Lanzani, Guglielmo

2008-09-25

393

Transition metal quinone–thiosemicarbazone complexes 3: Spectroscopic characterizations of spin-mixed iron (III) of naphthoquinone–thiosemicarbazones  

Microsoft Academic Search

An interesting series of iron (III) complexes with naphthoquinone–thiosemicarbazones are synthesized and physico-chemically characterized by elemental analysis, UV–vis, IR, EPR and magnetic susceptibility measurements. They possess a cationic octahedral [FeL2]+ species and a tetrahedral [FeCl4]? anion and exhibit unusual spin-mixed states involving high-spin and low-spin ferric centers as revealed from magnetic behavior with significant amount of exchange interactions mediated by

Rajeev C. Chikate; Subhash B. Padhye

2007-01-01

394

X-ray absorption fine structure and magnetization characterization of the metallic Co component in Co-doped ZnO thin films  

Microsoft Academic Search

X-ray absorption fine-structure (XAFS) measurements have been used to characterize a series of Co-doped ZnO films grown on sapphire substrates by pulsed laser deposition. The emphasis is on characterization of the fate of the Co dopant: metallic particles or substitutional Co2+ . It is shown that analysis of both the near edge and extended fine structure can provide a measurement

Steve M. Heald; Tiffany C. Kaspar; Timothy Droubay; V. Shutthanandan; Scott A. Chambers; Abbas Mokhtari; Anthony J. Behan; Harry J. Blythe; James R. Neal; A. Mark Fox; Gillian A. Gehring

2009-01-01

395

Microscopic and Spectroscopic Characterization of Calcified Microorganisms at the Nanometer-Scale in Experimental and Field Samples.  

NASA Astrophysics Data System (ADS)

Calcium phosphates and calcium carbonates are the most prevalent minerals involved in microbial fossilization. Structural characterization of both the organic and mineral components in such samples is, however, usually difficult at the appropriate spatial resolution, i.e., at the submicrometer scale. We have used a combination of Scanning Transmission X-ray microscopy (STXM), a synchrotron-based technique, and High-Resolution Transmission Electron Microscopy (HRTEM) to characterize both the Ca-containing biominerals and the functional groups present in the organic components associated with them (STXM). These data, in turn, provide a better understanding of the mechanisms, products, and biomolecules involved in microbial calcification. We have studied the experimental biomineralization of the model strain Caulobacter crescentus by calcium phosphates, and the calcification of natural biofilms by aragonite in an alkaline lake in Turkey. The precipitation of calcium phosphate and calcium carbonate by microorganisms likely involves different mechanisms. The resulting biominerals were found to have unique features with dimensions in the nanometer-range, preferential crystallographic orientations or unusual morphologies, which provide potential biosignatures. By using C K-edge NEXAFS spectroscopy at a submicrometer scale, we were also able to document the evolution of the organic molecules during the fossilization process and to characterize those involved as templates in the formation of calcium phosphate and carbonate minerals.

Benzerara, K.; Yoon, T.; Menguy, N.; Tyliszczak, T.; Brown, G. E.

2004-12-01

396

Absorption lines in quasar pairs  

NASA Astrophysics Data System (ADS)

The comparison of the absorption spectra of close pairs of QSOs makes it possible to study directly the sizes and clustering of absorbing regions. Phenomena of interest are related to Common Absorption (absorption in both spectra at the same redshift), and Associated Absorption (absorption at the redshift of the foreground QSO in the spectrum of the other member of the pair). The present study is concerned with a recent observation of the pair Q1548 + 114A,B. This pair was studied spectroscopically by Wampler et al. (1973) and by Burbidge et al. (1977). Spectra obtained of these two QSOs show that the absorption lines in B can be accounted for by five absorption systems. It was found that Q1548 + 114A,B exhibits neither associated nor common absorption. The implications of this result are discussed, taking into account the cosmological interpretation of QSO redshifts and the nature of the absorbing matter.

Shaver, P. A.; Robertson, J. G.

1983-06-01

397

Novel dithranol phospholipid microemulsion for topical application: development, characterization and percutaneous absorption studies.  

PubMed

The objective of this study was to develop and characterize a novel dithranol-containing phospholipid microemulsion systems for enhanced skin permeation and retention. Based on the solubility of dithranol, the selected oils were isopropyl myristate (IPM) and tocopherol acetate (TA), and the surfactants were Tween 80 (T80) and Tween 20 (T20). The ratios of cosurfactants comprising of phospholipids and ethanol (1?:?10) and surfactant to co-surfactant (1?:?1 and 2.75?:?1) were fixed for the phase diagram construction. Selected microemulsions were evaluated for globule size, zeta potential, viscosity, refractive index, per cent transmittance, stability (freeze thaw and centrifugation), ex vivo skin permeation and retention. The microemulsion systems composed of IPM and T80 with mean particle diameter of 72.8?nm showed maximum skin permeation (82.23%), skin permeation flux (0.281?mg/cm²/h) along with skin retention (8.31%) vis-à-vis systems containing TA and T20. The results suggest that the developed novel lecithinized microemulsion systems have a promising potential for the improved topical delivery of dithranol. PMID:21395406

Raza, Kaisar; Negi, Poonam; Takyar, Shweta; Shukla, Anshuman; Amarji, Basant; Katare, O P

2011-03-11

398

Investigation of Thiosemicarbazones as Chelating Agents. Synthesis and Spectroscopic Characterization of Some New Ruthenium(III) Complexes  

Microsoft Academic Search

New octahedral complexes of Ru(III) with salicylaldehyde, 5?chlorosalicylaldehyde, 5?methoxysalicylaldeyhyde, 2?hydroxynaphth?aldehyde and dehydroacetic acid thiosemicarbazones have been synthesized and characterized by elemental analyses, IR, UV?Vis. spectra, magnetic moments, conductivity, ESR spectra and thermal analysis. The molar conductance measurements indicate that, the complexes are non?electrolytes except for complex (LH)2Ru]Cl·2H2O (10). The ESR spectra of the complexes (LH)Ru(Cl)2(H2O)·2H2O (9) and (LH)2Ru]Cl·2H2O (10), (LH2 = dehydroacetic

Mohamed Ibrahim Ayad

2003-01-01

399

Characterization of interfacial water in MOF-5 (Zn4(O)(BDC)3)--a combined spectroscopic and theoretical study.  

PubMed

In this article we report the detection and characterization of adsorbed interfacial water within the cages of the metal-organic framework MOF-5 (Zn(4)O(BDC)(3)) by terahertz time-domain spectroscopy (THz TDS) in the frequency range from 5 to 46 cm(-1). The experimental spectra suggest a coupling of the intermolecular motions of the water molecules adsorbed to the collective vibrations of the network at 4 wt% hydration. This finding is supported by the results of MD simulations. When increasing the water content to 8 wt% we observed a non reversible decomposition of MOF-5. PMID:18688515

Schröck, K; Schröder, F; Heyden, M; Fischer, R A; Havenith, M

2008-07-15

400

Spectroscopic characterization of atmospheric pressure argon plasmas sustained with the Torche à Injection Axiale sur Guide d'Ondes  

NASA Astrophysics Data System (ADS)

An argon microwave (2.45 GHz) plasma produced by a microwave plasma torch known as "Torche à Injection Axiale sur Guide d'Ondes" (TIAGO) in air ambience at atmospheric pressure was experimentally characterized. The conditions for appropriate TIAGO torch operation in argon and flame morphology were researched under several experimental conditions of gas flow (0.15-5.00 L · min-1) rates and microwave input powers (100-1000 W). Gas temperature and electron density values were studied by means of optical emission spectroscopy. Besides, the processes inside the discharge and their interaction with the surrounding atmosphere were described according to the recorded spectra.

Rincón, R.; Muñoz, J.; Sáez, M.; Calzada, M. D.

2013-03-01