Functional assignment of solute-binding proteins of ABC transporters using a fluorescence-based thermal shift assay.

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

Giulliani, S. E.; Frank, A. E.; Collart, F. R.

2008-12-08

We have used a fluorescence-based thermal shift (FTS) assay to identify amino acids that bind to solute-binding proteins in the bacterial ABC transporter family. The assay was validated with a set of six proteins with known binding specificity and was consistently able to map proteins with their known binding ligands. The assay also identified additional candidate binding ligands for several of the amino acid-binding proteins in the validation set. We extended this approach to additional targets and demonstrated the ability of the FTS assay to unambiguously identify preferential binding for several homologues of amino acid-binding proteins with known specificity andmore » to functionally annotate proteins of unknown binding specificity. The assay is implemented in a microwell plate format and provides a rapid approach to validate an anticipated function or to screen proteins of unknown function. The ABC-type transporter family is ubiquitous and transports a variety of biological compounds, but the current annotation of the ligand-binding proteins is limited to mostly generic descriptions of function. The results illustrate the feasibility of the FTS assay to improve the functional annotation of binding proteins associated with ABC-type transporters and suggest this approach that can also be extended to other protein families.« less

Cu-rGO subsurface layer creation on copper substrate and its resistance to oxidation

NASA Astrophysics Data System (ADS)

Pietrzak, Katarzyna; Strojny-Nędza, Agata; Olesińska, Wiesława; Bańkowska, Anna; Gładki, Andrzej

2017-11-01

On the basis of a specially designed experiment, this paper presents a model, which is an attempt to explain the mechanism of formatting and creating oxidation resistance of Cu-rGO subsurface layers. Practically zero chemical affinity of copper to carbon is a fundamental difficulty in creating composite structures of Cu-C, properties which are theoretically possible to estimate. In order to bind the thermally reduced graphene oxide with copper surface, the effect of structural rebuilding of the copper oxide, in the process of annealing in a nitrogen atmosphere, have been used. On intentionally oxidized and anoxic copper substrates the dispersed graphene oxide (GO) and thermally reduced graphene oxide (rGO) were loaded. Annealing processes after the binding effects of both graphene oxide forms to Cu substrates were tested. The methods for high-resolution electron microscopy were found subsurface rGO-Cu layer having a substantially greater resistance to oxidation than pure copper. The mechanism for the effective resistance to oxidation of the Cu-rGO has been presented in a hypothetical form.

Increases thermal stability and cellulose-binding capacity of Cryptococcus sp. S-2 lipase by fusion of cellulose binding domain derived from Trichoderma reesei.

PubMed

Thongekkaew, Jantaporn; Ikeda, Hiroko; Iefuji, Haruyuki

2012-03-30

To improve the thermal stability and cellulose-binding capacity of Cryptococcus sp. S-2 lipase (CSLP), the cellulose-binding domain originates from Trichoderma reesei cellobiohydrolase I was engineered into C-terminal region of the CSLP (CSLP-CBD). The CSLP and CSLP-CBD were successfully expressed in the Pichia pastoris using the strong methanol inducible alcohol oxidase 1 (AOX1) promoter and the secretion signal sequence from Saccharomyces cerevisiae (α factor). The recombinant CSLP and CSLP-CBD were secreted into culture medium and estimated by SDS-PAGE to be 22 and 27 kDa, respectively. The fusion enzyme was stable at 80 °C and retained more than 80% of its activity after 120-min incubation at this temperature. Our results also found that the fusion of fungal exoglucanase cellulose-binding domain to CSLP is responsible for cellulose-binding capacity. This attribute should make it an attractive applicant for enzyme immobilization. Copyright © 2012 Elsevier Inc. All rights reserved.

The effect of feeding high corn oil on fatty-acid-binding-protein isolated from rat liver.

PubMed

Catalá, A

1987-12-01

Fatty-acid-binding-protein isolated from liver of rats receiving normal or high fat diet was studied by three different methods. The effect of high fat diet on the thermal stability of the protein was determined employing differential scanning calorimetry. Fatty acids have a stabilizing effect on the thermal stability of the protein. In order to determine the relative binding affinity of native and delipidated protein a Sephadex G-50 assay was employed using [1-14C] oleate as ligand. The delipidated protein exhibited greater binding of oleate than did the native material. Increases in the transfer of oleic acid from rat liver microsomes to egg lecithin liposomes in vitro were also observed when protein obtained from both sources were delipidated. The results suggest that high corn oil diet would modify the properties of fatty-acid-binding-protein in the uptake and cytosolic transport of long-chain fatty acids.

What Controls the Limit of Supercooling and Superheating of Pinned Ice Surfaces?

PubMed

Naullage, Pavithra M; Qiu, Yuqing; Molinero, Valeria

2018-04-05

Cold-adapted organisms produce antifreeze proteins and glycoproteins to control the growth, melting and recrystallization of ice. It has been proposed that these molecules pin the crystal surface, creating a curvature that arrests the growth and melting of the crystal. Here we use thermodynamic modeling and molecular simulations to demonstrate that the curvature of the superheated or supercooled surface depends on the temperature and distances between ice-binding molecules, but not the details of their interactions with ice. We perform simulations of ice pinned with the antifreeze protein TmAFP, polyvinyl alcohol with different degrees of polymerization, and model ice-binding molecules to determine the thermal hystereses on melting and freezing, i.e. the maximum curvature that can be attained before, respectively, ice melts or grows irreversibly over the ice-binding molecules. We find that the thermal hysteresis is controlled by the bulkiness of the ice-binding molecules and their footprint at the ice surface. We elucidate the origin of the asymmetry between freezing and melting hysteresis found in experiments and propose guidelines to design synthetic antifreeze molecules with potent thermal hysteresis activity.

Porphyrin-substrate binding to murine ferrochelatase: effect on the thermal stability of the enzyme

PubMed Central

2004-01-01

Ferrochelatase (EC 4.99.1.1), the terminal enzyme of the haem biosynthetic pathway, catalyses the chelation of Fe(II) into the protoporphyrin IX ring. The energetics of the binding between murine ferrochelatase and mesoporphyrin were determined using isothermal titration calorimetry, which revealed a stoichiometry of one molecule of mesoporphyrin bound per protein monomer. The binding is strongly exothermic, with a large intrinsic enthalpy (ΔH=−97.1 kJ · mol−1), and is associated with the uptake of two protons from the buffer. This proton transfer suggests that hydrogen bonding between ferrochelatase and mesoporphyrin is a key factor in the thermodynamics of the binding reaction. Differential scanning calorimetry thermograms indicated a co-operative two-state denaturation process with a single transition temperature of 56 °C for wild-type murine ferrochelatase. An increase in the thermal stability of ferrochelatase is dependent upon mesoporphyrin binding. Similarly, murine ferrochelatase variants, in which the active site Glu-289 was replaced by either glutamine or alanine and, when purified, contained specifically-bound protoporphyrin, exhibited enhanced protein stability when compared with wild-type ferrochelatase. However, in contrast with the wild-type enzyme, the thermal denaturation of ferrochelatase variants was best described as a non-co-operative denaturation process. PMID:15496139

The Design and Delivery of a Thermally Responsive Peptide to Inhibit S100B Mediated Neurodegeneration

PubMed Central

Hearst, Scoty M; Walker, Leslie R; Shao, Qingmei; Lopez, Mariper; Raucher, Drazen; Vig, Parminder J S

2011-01-01

S100B, a glial secreted protein is believed to play a major role in neurodegeneration in Alzheimer's disease, Down syndrome, traumatic brain injury and spinocerebellar ataxia type 1 (SCA1). SCA1 is a trinucleotide repeat disorder in which the expanded polyglutamine mutation in the protein ataxin-1 primarily targets Purkinje cells (PCs) of the cerebellum. Currently, the exact mechanism of S100B mediated PC damage in SCA1 is not clear. However, here we show that S100B may act via the activation of the RAGE signaling pathway resulting in oxidative stress mediated injury to mutant ataxin-1 expressing neurons. To combat S100B mediated neurodegeneration, we have designed a selective thermally responsive S100B inhibitory peptide, Synb1-ELP-TRTK. Our therapeutic polypeptide was developed using three key elements: (1) the elastin-like polypeptide (ELP), a thermally responsive polypeptide, (2) the TRTK12 peptide, a known S100B inhibitory peptide and (3) a cell penetrating peptide, Synb1, to enhance intracellular delivery. Binding studies revealed that our peptide, Synb1-ELP-TRTK, interacts with its molecular target S100B and maintains a high S100B binding affinity as comparable with the TRTK12 peptide alone. In addition, in vitro studies revealed that Synb1-ELP-TRTK treatment reduces S100B uptake in SHSY5Y cells. Furthermore, the Synb1-ELP-TRTK peptide decreased S100B induced oxidative damage to mutant ataxin-1 expressing neurons. To test the delivery capabilities of ELP based therapeutic peptides to the cerebellum; we treated mice with fluorescently labeled Synb1-ELP and observed that thermal targeting enhanced peptide delivery to the cerebellum. Here, we have laid the framework for thermal based therapeutic targeting to regions of the brain, particularly the cerebellum. Overall, our data suggests that thermal targeting of ELP based therapeutic peptides to the cerebellum is a novel treatment strategy for cerebellar neurodegenerative disorders. PMID:21958864

Interaction of sucralose with whey protein: Experimental and molecular modeling studies

NASA Astrophysics Data System (ADS)

Zhang, Hongmei; Sun, Shixin; Wang, Yanqing; Cao, Jian

2017-12-01

The objective of this research was to study the interactions of sucralose with whey protein isolate (WPI) by using the three-dimensional fluorescence spectroscopy, circular dichroism spectroscopy and molecular modeling. The results showed that the peptide strands structure of WPI had been changed by sucralose. Sucralose binding induced the secondary structural changes and increased content of aperiodic structure of WPI. Sucralose decreased the thermal stability of WPI and acted as a structure destabilizer during the thermal unfolding process of protein. In addition, the existence of sucralose decreased the reversibility of the unfolding of WPI. Nonetheless, sucralose-WPI complex was less stable than protein alone. The molecular modeling result showed that van der Waals and hydrogen bonding interactions contribute to the complexation free binding energy. There are more than one possible binding sites of WPI with sucralose by surface binding mode.

Synthesis, DNA binding ability and anticancer activity of 2-heteroaryl substituted benzimidazoles linked pyrrolo[2,1-c][1,4]benzodiazepine conjugates.

PubMed

Kamal, Ahmed; Pogula, Praveen Kumar; Khan, Mohammed Naseer Ahmed; Seshadri, Bobburi Naga; Sreekanth, Kokkonda

2013-08-01

As a continuation of our efforts to develop the benzimidazole-PBD conjugates as potential anticancer agents, a series of heteroaryl substituted benzimidazole linked PBD conjugates has been synthesized and evaluated for their anticancer potential in 60 human cancer cell lines. Most of the compounds exhibited promising anticancer activity and interestingly, compounds 4c and 4d displayed significant activity in most of the cell lines tested. Whereas, compound 4e showed selectivity in renal cancer cells with GI50 values of <10 and 70 nM against RXF 393 and UO-31 cell lines, respectively. Further, these compounds also showed significant DNA-binding affinity by thermal denaturation study using duplex form of calf thymus (CT) DNA.

RecA binding to a single double-stranded DNA molecule: A possible role of DNA conformational fluctuations

PubMed Central

Leger, J. F.; Robert, J.; Bourdieu, L.; Chatenay, D.; Marko, J. F.

1998-01-01

Most genetic regulatory mechanisms involve protein–DNA interactions. In these processes, the classical Watson–Crick DNA structure sometimes is distorted severely, which in turn enables the precise recognition of the specific sites by the protein. Despite its key importance, very little is known about such deformation processes. To address this general question, we have studied a model system, namely, RecA binding to double-stranded DNA. Results from micromanipulation experiments indicate that RecA binds strongly to stretched DNA; based on this observation, we propose that spontaneous thermal stretching fluctuations may play a role in the binding of RecA to DNA. This has fundamental implications for the protein–DNA binding mechanism, which must therefore rely in part on a combination of flexibility and thermal fluctuations of the DNA structure. We also show that this mechanism is sequence sensitive. Theoretical simulations support this interpretation of our experimental results, and it is argued that this is of broad relevance to DNA–protein interactions. PMID:9770480

Binding of (-)-epigallocatechin-3-gallate with thermally-induced bovine serum albumin/ι-carrageenan particles.

PubMed

Li, Jinbing; Wang, Xiaoyong

2015-02-01

Novel thermally-induced BSA/ι-carrageenan particles are used as a protective carrier for (-)-epigallocatechin-3-gallate (EGCG). The addition of EGCG to BSA/ι-carrageenan particles can highly quench the intrinsic fluorescence of BSA, which is explained in terms of the binding of EGCG to the hydrophobic pockets of BSA mainly through the hydrophobic force. According to the double logarithm equation, the binding constant is determined as 1.1×10(8)M(-1) for the binding of EGCG with BSA/ι-carrageenan particles. The high binding affinity is ascribed to both the molecular structure of EGCG and the partial unfolding state of BSA in BSA/ι-carrageenan particles. The circular dichroism spectra and calculated α-helix of BSA suggest that the bound EGCG leads to a more random secondary structure of BSA. Furthermore, BSA/ι-carrageenan particles are found to be superior to native BSA and pure BSA particles for improving the stability and radical scavenging activity of EGCG. Copyright © 2014 Elsevier Ltd. All rights reserved.

Evaluation of IgE reactivity of active and thermally inactivated actinidin, a biomarker of kiwifruit allergy.

PubMed

Grozdanovic, Milica; Popovic, Milica; Polovic, Natalija; Burazer, Lidija; Vuckovic, Olga; Atanaskovic-Markovic, Marina; Lindner, Buko; Petersen, Arnd; Gavrovic-Jankulovic, Marija

2012-03-01

Actinidin, an abundant cysteine protease from kiwifruit, is a specific biomarker of isolated allergy to kiwifruit. This study evaluates the IgE-binding properties of biologically active and thermally inactivated actinidin. Employing two different activity assays (caseinolytic assay and zymogram with gelatin) we showed that actinidin obtained from kiwifruit extract under native conditions represents a mixture of inactive and active enzyme. The structural integrity of actinidin was confirmed by SDS-PAGE, Edman degradation, mass fingerprint and Western blot with polyclonal antibodies. Although it was capable of inducing positive skin prick test reactions, we failed to detect IgE reactivity of active actinidin in Western blot with patient sera. Thermally inactivated actinidin exhibited IgE reactivity both in vivo and in vitro, indicating that heat processed kiwifruit products may induce clinical reactivity. These findings imply that apart from the allergenic epitopes on its surface, actinidin also contains hidden epitopes inside the protein which become accessible to IgE upon thermal treatment. Copyright © 2011 Elsevier Ltd. All rights reserved.

Arcjet exploratory tests of ARC optical window design for the AFE vehicle

NASA Technical Reports Server (NTRS)

Whiting, Ellis E.; Terrazas-Salinas, Imelda; Craig, Roger A.; Sobeck, Charles K.; Sarver, George L., III; Salerno, Louis J.; Love, Wendell; Maa, Scott; Covington, AL

1991-01-01

Tests were made in the 20 MW arc jet facility at the NASA ARC to determine the suitability of sapphire and fused silica as window materials for the Aeroassist Flight Experiment (AFE) entry vehicle. Twenty nine tests were made; 25 at a heating rate about 80 percent of that expected during the AFE entry and 4 at approximately the full, 100 percent AFE heating rate profile, that produces a temperature of about 2900 F on the surface of the tiles that protect the vehicle. These tests show that a conductively cooled window design using mechanical thermal contacts and sapphire is probably not practical. Cooling the window using mechanical thermal contacts produces thermal stresses in the sapphire that cause the window to crack. An insulated design using sapphire, that cools the window as little as possible, appears promising although some spectral data in the vacuum-ultra-violet (VUV) will be lost due to the high temperature reached by the sapphire. The surface of the insulated sapphire windows, tested at the 100 percent AFE heating rate, showed some slight ablation, and cracks appeared in two of three test windows. One small group of cracks were obviously caused by mechanical binding of the window in the assembly, which can be eliminated with improved design. Other cracks were long, straight, thin crystallographic cracks that have very little effect on the optical transmission of the window. Also, the windows did not fall apart along these crystallographic cracks when the windows were removed from their assemblies. Theoretical results from the thermal analysis computer program SINDA indicate that increasing the window thickness from 4 to 8 mm may enable surface ablation to be avoided. An insulated design using a fused silica window tested at the nominal AFE heating rate experienced severe ablation, thus fused silica is not considered to be an acceptable window material.

A robust methodology to subclassify pseudokinases based on their nucleotide-binding properties

PubMed Central

Murphy, James M.; Zhang, Qingwei; Young, Samuel N.; Reese, Michael L.; Bailey, Fiona P.; Eyers, Patrick A.; Ungureanu, Daniela; Hammaren, Henrik; Silvennoinen, Olli; Varghese, Leila N.; Chen, Kelan; Tripaydonis, Anne; Jura, Natalia; Fukuda, Koichi; Qin, Jun; Nimchuk, Zachary; Mudgett, Mary Beth; Elowe, Sabine; Gee, Christine L.; Liu, Ling; Daly, Roger J.; Manning, Gerard; Babon, Jeffrey J.; Lucet, Isabelle S.

2017-01-01

Protein kinase-like domains that lack conserved residues known to catalyse phosphoryl transfer, termed pseudokinases, have emerged as important signalling domains across all kingdoms of life. Although predicted to function principally as catalysis-independent protein-interaction modules, several pseudokinase domains have been attributed unexpected catalytic functions, often amid controversy. We established a thermal-shift assay as a benchmark technique to define the nucleotide-binding properties of kinase-like domains. Unlike in vitro kinase assays, this assay is insensitive to the presence of minor quantities of contaminating kinases that may otherwise lead to incorrect attribution of catalytic functions to pseudokinases. We demonstrated the utility of this method by classifying 31 diverse pseudokinase domains into four groups: devoid of detectable nucleotide or cation binding; cation-independent nucleotide binding; cation binding; and nucleotide binding enhanced by cations. Whereas nine pseudokinases bound ATP in a divalent cation-dependent manner, over half of those examined did not detectably bind nucleotides, illustrating that pseudokinase domains predominantly function as non-catalytic protein-interaction modules within signalling networks and that only a small subset is potentially catalytically active. We propose that henceforth the thermal-shift assay be adopted as the standard technique for establishing the nucleotide-binding and catalytic potential of kinase-like domains. PMID:24107129

Supramolecular approach to enantioselective DNA recognition using enantiomerically resolved cationic 4-amino-1,8-naphthalimide-based Tröger's bases.

PubMed

Banerjee, Swagata; Bright, Sandra A; Smith, Jayden A; Burgeat, Jeremy; Martinez-Calvo, Miguel; Williams, D Clive; Kelly, John M; Gunnlaugsson, Thorfinnur

2014-10-03

The synthesis and photophysical studies of two cationic Tröger's base (TB)-derived bis-naphthalimides 1 and 2 and the TB derivative 6, characterized by X-ray crystallography, are presented. The enantiomers of 1 and 2 are separated by cation-exchange chromatography on Sephadex C25 using sodium (-)-dibenzoyl-l-tartarate as the chiral mobile phase. The binding of enantiomers with salmon testes (st)-DNA and synthetic polynucleotides are studied by a variety of spectroscopic methods including UV/vis absorbance, circular dichroism, linear dichroism, and ethidium bromide displacement assays, which demonstrated binding of these compounds to the DNA grooves with very high affinity (K ∼ 10(6) M(-1)) and preferential binding of (-)-enantiomer. In all cases, binding to DNA resulted in a significant stabilization of the double-helical structure of DNA against thermal denaturation. Compound (±)-2 and its enantiomers possessed significantly higher binding affinity for double-stranded DNA compared to 1, possibly due to the presence of the methyl group, which allows favorable hydrophobic and van der Waals interactions with DNA. The TB derivatives exhibited marked preference for AT rich sequences, where the binding affinities follow the order (-)-enantiomer > (±) > (+)-enantiomer. The compounds exhibited significant photocleavage of plasmid DNA upon visible light irradiation and are rapidly internalized into malignant cell lines.

Improved thrombin binding aptamer by incorporation of a single unlocked nucleic acid monomer

PubMed Central

Pasternak, Anna; Hernandez, Frank J.; Rasmussen, Lars M.; Vester, Birte; Wengel, Jesper

2011-01-01

A 15-mer DNA aptamer (named TBA) adopts a G-quadruplex structure that strongly inhibits fibrin-clot formation by binding to thrombin. We have performed thermodynamic analysis, binding affinity and biological activity studies of TBA variants modified by unlocked nucleic acid (UNA) monomers. UNA-U placed in position U3, U7 or U12 increases the thermodynamic stability of TBA by 0.15–0.50 kcal/mol. In contrast, modification of any position within the two G-quartet structural elements is unfavorable for quadruplex formation. The intramolecular folding of the quadruplexes is confirmed by Tm versus ln c analysis. Moreover, circular dichroism and thermal difference spectra of the modified TBAs displaying high thermodynamic stability show bands that are characteristic for antiparallel quadruplex formation. Surface plasmon resonance studies of the binding of the UNA-modified TBAs to thrombin show that a UNA monomer is allowed in many positions of the aptamer without significantly changing the thrombin-binding properties. The biological effect of a selection of the modified aptamers was tested by a thrombin time assay and showed that most of the UNA-modified TBAs possess anticoagulant properties, and that the construct with a UNA-U monomer in position 7 is a highly potent inhibitor of fibrin-clot formation. PMID:20870750

Photophysicochemical, calf thymus DNA binding and in vitro photocytotoxicity properties of tetra-morpholinoethoxy-substituted phthalocyanines and their water-soluble quaternized derivatives.

PubMed

Koçan, Halit; Kaya, Kerem; Özçeşmeci, İbrahim; Sesalan, B Şebnem; Göksel, Meltem; Durmuş, Mahmut; Burat, Ayfer Kalkan

2017-12-01

In this study, morpholinoethoxy-substituted metal-free (3), zinc(II) (4) and indium(III) (5) phthalocyanines were synthesized. These phthalocyanines were converted to their water-soluble quaternized derivatives (3Q-5Q) using excess methyl iodide as a quaternization agent. All these phthalocyanines (Pcs) were characterized by elemental analysis and different spectroscopic methods such as FT-IR, 1 H NMR, UV-Vis and mass spectrometry. The photophysical and photochemical properties such as fluorescence and generation of singlet oxygen were investigated for determination of these phthalocyanines as photosensitizers in photodynamic therapy (PDT) applications. The binding properties of quaternized phthalocyanines (3Q-5Q) to calf thymus DNA (CT-DNA) were investigated by UV-Vis and fluorescence spectrophotometric methods. The quenching effect of all quaternized phthalocyanines on the fluorescence intensity of SYBR Green-DNA complex was determined. The mixtures of 3Q, 4Q or 5Q and DNA solutions were used to determine the change in T m of double helix DNA with thermal denaturation profile. In addition, thermodynamic parameters considering their aggregation in buffer solution, which shows the spontaneity of the reactions between DNA and quaternized Pcs were investigated. On the other hand, in vitro phototoxicity and cytotoxicity behavior of the quaternized water-soluble phthalocyanine photosensitizers (3Q-5Q) were tested against the cervical cancer cell line named HeLa for evaluation of their suitability for treatment of cancer by PDT method. Peripherally tetra-substituted neutral and quaternized metal-free and metallophthalocyanines (MPcs) (Zn, In) bearing morpholinoethoxy groups were prepared. The binding of quaternized compounds (3Q-5Q) to CT-DNA were examined using UV-Vis, fluorescence spectra, thermal denaturation profiles and K SV values. Besides, thermodynamic studies indicated that binding of 3Q-5Q to DNA was spontaneous. On the other hand, in vitro phototoxicity and cytotoxicity behavior of the quaternized water-soluble phthalocyanine photosensitizers (3Q-5Q) were tested against the cervical cancer cell line named HeLa for evaluation of their suitability for treatment of cancer by PDT method.

Protein–ligand interactions investigated by thermal shift assays (TSA) and dual polarization interferometry (DPI)

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

Grøftehauge, Morten K., E-mail: m.k.groftehauge@durham.ac.uk; Hajizadeh, Nelly R.; Swann, Marcus J.

2015-01-01

The biophysical characterization of protein–ligand interactions in solution using techniques such as thermal shift assay, or on surfaces using, for example, dual polarization interferometry, plays an increasingly important role in complementing crystal structure determinations. Over the last decades, a wide range of biophysical techniques investigating protein–ligand interactions have become indispensable tools to complement high-resolution crystal structure determinations. Current approaches in solution range from high-throughput-capable methods such as thermal shift assays (TSA) to highly accurate techniques including microscale thermophoresis (MST) and isothermal titration calorimetry (ITC) that can provide a full thermodynamic description of binding events. Surface-based methods such as surface plasmonmore » resonance (SPR) and dual polarization interferometry (DPI) allow real-time measurements and can provide kinetic parameters as well as binding constants. DPI provides additional spatial information about the binding event. Here, an account is presented of new developments and recent applications of TSA and DPI connected to crystallography.« less

Life on the edge: O2 binding in Atlantic cod red blood cells near their southern distribution limit is not sensitive to temperature or haemoglobin genotype

PubMed Central

Barlow, Samantha L.; Metcalfe, Julian; Righton, David A.

2017-01-01

ABSTRACT Atlantic cod are a commercially important species believed to be threatened by warming seas near their southern, equatorward upper thermal edge of distribution. Limitations to circulatory O2 transport, in particular cardiac output, and the geographic distribution of functionally different haemoglobin (Hb) genotypes have separately been suggested to play a role in setting thermal tolerance in this species. The present study assessed the thermal sensitivity of O2 binding in Atlantic cod red blood cells with different Hb genotypes near their upper thermal distribution limit and modelled its consequences for the arterio-venous O2 saturation difference, Sa–vO2, another major determinant of circulatory O2 supply rate. The results showed statistically indistinguishable red blood cell O2 binding between the three HbI genotypes in wild-caught Atlantic cod from the Irish Sea (53° N). Red blood cells had an unusually low O2 affinity, with reduced or even reversed thermal sensitivity between pH 7.4 and 7.9, and 5.0 and 20.0°C. This was paired with strongly pH-dependent affinity and cooperativity of red blood cell O2 binding (Bohr and Root effects). Modelling of Sa–vO2 at physiological pH, temperature and O2 partial pressures revealed a substantial capacity for increases in Sa–vO2 to meet rising tissue O2 demands at 5.0 and 12.5°C, but not at 20°C. Furthermore, there was no evidence for an increase of maximal Sa–vO2 with temperature. It is suggested that Atlantic cod at such high temperatures may solely depend on increases in cardiac output and blood O2 capacity, or thermal acclimatisation of metabolic rate, for matching circulatory O2 supply to tissue demand. PMID:28148818

Life on the edge: O2 binding in Atlantic cod red blood cells near their southern distribution limit is not sensitive to temperature or haemoglobin genotype.

PubMed

Barlow, Samantha L; Metcalfe, Julian; Righton, David A; Berenbrink, Michael

2017-02-01

Atlantic cod are a commercially important species believed to be threatened by warming seas near their southern, equatorward upper thermal edge of distribution. Limitations to circulatory O 2 transport, in particular cardiac output, and the geographic distribution of functionally different haemoglobin (Hb) genotypes have separately been suggested to play a role in setting thermal tolerance in this species. The present study assessed the thermal sensitivity of O 2 binding in Atlantic cod red blood cells with different Hb genotypes near their upper thermal distribution limit and modelled its consequences for the arterio-venous O 2 saturation difference, Sa-v O 2 , another major determinant of circulatory O 2 supply rate. The results showed statistically indistinguishable red blood cell O 2 binding between the three HbI genotypes in wild-caught Atlantic cod from the Irish Sea (53° N). Red blood cells had an unusually low O 2 affinity, with reduced or even reversed thermal sensitivity between pH 7.4 and 7.9, and 5.0 and 20.0°C. This was paired with strongly pH-dependent affinity and cooperativity of red blood cell O 2 binding (Bohr and Root effects). Modelling of Sa-v O 2  at physiological pH, temperature and O 2 partial pressures revealed a substantial capacity for increases in Sa-v O 2  to meet rising tissue O 2 demands at 5.0 and 12.5°C, but not at 20°C. Furthermore, there was no evidence for an increase of maximal Sa-v O 2  with temperature. It is suggested that Atlantic cod at such high temperatures may solely depend on increases in cardiac output and blood O 2 capacity, or thermal acclimatisation of metabolic rate, for matching circulatory O 2 supply to tissue demand. © 2017. Published by The Company of Biologists Ltd.

Preparation and evaluation of molecularly imprinted polymer for selective recognition and adsorption of gossypol.

PubMed

Zhi, Keke; Wang, Lulu; Zhang, Yagang; Zhang, Xuemin; Zhang, Letao; Liu, Li; Yao, Jun; Xiang, Wei

2018-03-01

Molecularly imprinted polymers (MIPs) were designed and prepared via bulk thermal polymerization with gossypol as the template molecule and dimethylaminoethyl methacrylate as the functional monomer. The morphology and microstructures of MIPs were characterized by scanning electron microscope and Brunauer-Emmett-Teller surface areas. Static adsorption tests were performed to evaluate adsorption behavior of gossypol by the MIPs. It was found that adsorption kinetics and adsorption isotherms data of MIPs for gossypol were fit well with the pseudo-second-order model and Freundlich model, respectively. Scatchard analysis showed that heterogeneous binding sites were formed in the MIPs, including lower-affinity binding sites with the maximum adsorption of 252 mg/g and higher-affinity binding sites with the maximum adsorption of 632 mg/g. Binding studies also revealed that MIPs had favorable selectivity towards gossypol compared with non-imprinted polymers. Furthermore, adsorption capacity of MIPs maintained above 90% after 5 regeneration cycles, indicating MIPs were recyclable and could be used multiple times. These results demonstrated that prepared MIPs could be a promising functional material for selective adsorption of gossypol. Copyright © 2017 John Wiley & Sons, Ltd.

Protein-ligand interactions investigated by thermal shift assays (TSA) and dual polarization interferometry (DPI).

PubMed

Grøftehauge, Morten K; Hajizadeh, Nelly R; Swann, Marcus J; Pohl, Ehmke

2015-01-01

Over the last decades, a wide range of biophysical techniques investigating protein-ligand interactions have become indispensable tools to complement high-resolution crystal structure determinations. Current approaches in solution range from high-throughput-capable methods such as thermal shift assays (TSA) to highly accurate techniques including microscale thermophoresis (MST) and isothermal titration calorimetry (ITC) that can provide a full thermodynamic description of binding events. Surface-based methods such as surface plasmon resonance (SPR) and dual polarization interferometry (DPI) allow real-time measurements and can provide kinetic parameters as well as binding constants. DPI provides additional spatial information about the binding event. Here, an account is presented of new developments and recent applications of TSA and DPI connected to crystallography.

Protein–ligand interactions investigated by thermal shift assays (TSA) and dual polarization interferometry (DPI)

PubMed Central

Grøftehauge, Morten K.; Hajizadeh, Nelly R.; Swann, Marcus J.; Pohl, Ehmke

2015-01-01

Over the last decades, a wide range of biophysical techniques investigating protein–ligand interactions have become indispensable tools to complement high-resolution crystal structure determinations. Current approaches in solution range from high-throughput-capable methods such as thermal shift assays (TSA) to highly accurate techniques including microscale thermophoresis (MST) and isothermal titration calorimetry (ITC) that can provide a full thermodynamic description of binding events. Surface-based methods such as surface plasmon resonance (SPR) and dual polarization interferometry (DPI) allow real-time measurements and can provide kinetic parameters as well as binding constants. DPI provides additional spatial information about the binding event. Here, an account is presented of new developments and recent applications of TSA and DPI connected to crystallography. PMID:25615858

Isoquinoline alkaloids and their binding with DNA: calorimetry and thermal analysis applications.

PubMed

Bhadra, Kakali; Kumar, Gopinatha Suresh

2010-11-01

Alkaloids are a group of natural products with unmatched chemical diversity and biological relevance forming potential quality pools in drug screening. The molecular aspects of their interaction with many cellular macromolecules like DNA, RNA and proteins are being currently investigated in order to evolve the structure activity relationship. Isoquinolines constitute an important group of alkaloids. They have extensive utility in cancer therapy and a large volume of data is now emerging in the literature on their mode, mechanism and specificity of binding to DNA. Thermodynamic characterization of the binding of these alkaloids to DNA may offer key insights into the molecular aspects that drive complex formation and these data can provide valuable information about the balance of driving forces. Various thermal techniques have been conveniently used for this purpose and modern calorimetric instrumentation provides direct and quick estimation of thermodynamic parameters. Thermal melting studies and calorimetric techniques like isothermal titration calorimetry and differential scanning calorimetry have further advanced the field by providing authentic, reliable and sensitive data on various aspects of temperature dependent structural analysis of the interaction. In this review we present the application of various thermal techniques, viz. isothermal titration calorimetry, differential scanning calorimetry and optical melting studies in the characterization of drug-DNA interactions with particular emphasis on isoquinoline alkaloid-DNA interaction.

Validation of dye-binding/high-resolution thermal denaturation for the identification of mutations in the SLC22A5 gene.

PubMed

Dobrowolski, Steven F; McKinney, Jason T; Amat di San Filippo, Cristina; Giak Sim, Keow; Wilcken, Bridget; Longo, Nicola

2005-03-01

Primary carnitine deficiency is an autosomal recessive disorder of fatty acid oxidation resulting from defective carnitine transport. This disease is caused by mutations in the OCTN2 carnitine transporter encoded by the SLC22A5 gene. Here we validate dye-binding/high-resolution thermal denaturation as a screening procedure to identify novel mutations in this gene. This procedure is based on the amplification of DNA by PCR in capillaries with the dsDNA binding dye LCGreen I. The PCR reaction is then analyzed in the same capillary by high-resolution thermal denaturation. Samples with abnormal melting profiles are sequenced. This technique correctly identified all known patients who were compound heterozygotes for different mutations in the carnitine transporter gene and about 30% of homozygous patients. The remaining 70% of homozygous patients were identified by a second amplification, in which the patient's DNA was mixed with the DNA of a normal control. This screening system correctly identified eight novel mutations and both abnormal alleles in six new families with primary carnitine deficiency. The causative role of the missense mutations identified (c.3G>T/p.M1I, c.695C>T/p.T232M, and c.1403 C>G/p.T468R) was confirmed by expression in Chinese hamster ovary (CHO) cells. These results expand the mutational spectrum in primary carnitine deficiency and indicate dye-binding/high-resolution thermal denaturation as an ideal system to screen for mutations in diseases with no prevalent molecular alteration. (c) 2005 Wiley-Liss, Inc.

Supramolecular interaction of 6-shogaol, a therapeutic agent of Zingiber officinale with human serum albumin as elucidated by spectroscopic, calorimetric and molecular docking methods.

PubMed

Feroz, S R; Mohamad, S B; Lee, G S; Malek, S N A; Tayyab, S

2015-06-01

6-Shogaol, one of the main bioactive constituents of Zingiber officinale has been shown to possess various therapeutic properties. Interaction of a therapeutic compound with plasma proteins greatly affects its pharmacokinetic and pharmacodynamic properties. The present investigation was undertaken to characterize the interaction between 6-shogaol and the main in vivo transporter, human serum albumin (HSA). Various binding characteristics of 6-shogaol-HSA interaction were studied using fluorescence spectroscopy. Thermal stability of 6-shogaol-HSA system was determined by circular dichroism (CD) and differential scanning calorimetric (DSC) techniques. Identification of the 6-shogaol binding site on HSA was made by competitive drug displacement and molecular docking experiments. Fluorescence quench titration results revealed the association constant, Ka of 6-shogaol-HSA interaction as 6.29 ± 0.33 × 10(4) M(-1) at 25 ºC. Values of the enthalpy change (-11.76 kJ mol(-1)) and the entropy change (52.52 J mol(-1) K(-1)), obtained for the binding reaction suggested involvement of hydrophobic and van der Waals forces along with hydrogen bonds in the complex formation. Higher thermal stability of HSA was noticed in the presence of 6-shogaol, as revealed by DSC and thermal denaturation profiles. Competitive ligand displacement experiments along with molecular docking results suggested the binding preference of 6-shogaol for Sudlow's site I of HSA. All these results suggest that 6-shogaol binds to Sudlow's site I of HSA through moderate binding affinity and involves hydrophobic and van der Waals forces along with hydrogen bonds. Copyright © 2015 Elsevier GmbH. All rights reserved.

FecB, a periplasmic ferric-citrate transporter from E. coli, can bind different forms of ferric-citrate as well as a wide variety of metal-free and metal-loaded tricarboxylic acids.

PubMed

Banerjee, Sambuddha; Paul, Subrata; Nguyen, Leonard T; Chu, Byron C H; Vogel, Hans J

2016-01-01

The Escherichia coli Fec system, consisting of an outer membrane receptor (FecA), a periplasmic substrate binding protein (FecB) and an inner membrane permease-ATPase type transporter (FecC/D), plays an important role in the uptake and transport of Fe(3+)-citrate. Although several FecB sequences from various organisms have been reported, there are no biophysical or structural data available for this protein to date. In this work, using isothermal titration calorimetry (ITC), we report for the first time the ability of FecB to bind different species of Fe(3+)-citrate as well as other citrate complexes with trivalent (Ga(3+), Al(3+), Sc(3+) and In(3+)) and a representative divalent metal ion (Mg(2+)) with low μM affinity. Interestingly, ITC experiments with various iron-free di- and tricarboxylic acids show that FecB can bind tricarboxylates with μM affinity but not biologically relevant dicarboxylates. The ability of FecB to bind with metal-free citrate is also observed in (1)H,(15)N HSQC-NMR titration experiments reported here at two different pH values. Further, differential scanning calorimetry (DSC) experiments indicate that the ligand-bound form of FecB has greater thermal stability than ligand-free FecB under all pH and ligand conditions tested, which is consistent with the idea of domain closure subsequent to ligand binding for this type of periplasmic binding proteins.

Stabilization of coiled-coil peptide domains by introduction of trifluoroleucine.

PubMed

Tang, Y; Ghirlanda, G; Vaidehi, N; Kua, J; Mainz, D T; Goddard III, W A; DeGrado, W F; Tirrell, D A

2001-03-06

Substitution of leucine residues by 5,5,5-trifluoroleucine at the d-positions of the leucine zipper peptide GCN4-p1d increases the thermal stability of the coiled-coil structure. The midpoint thermal unfolding temperature of the fluorinated peptide is elevated by 13 degrees C at 30 microM peptide concentration. The modified peptide is more resistant to chaotropic denaturants, and the free energy of folding of the fluorinated peptide is 0.5-1.2 kcal/mol larger than that of the hydrogenated form. A similarly fluorinated form of the DNA-binding peptide GCN4-bZip binds to target DNA sequences with affinity and specificity identical to those of the hydrogenated form, while demonstrating enhanced thermal stability. Molecular dynamics simulation on the fluorinated GCN4-p1d peptide using the Surface Generalized Born implicit solvation model revealed that the coiled-coil binding energy is 55% more favorable upon fluorination. These results suggest that fluorination of hydrophobic substructures in peptides and proteins may provide new means of increasing protein stability, enhancing protein assembly, and strengthening receptor-ligand interactions.

Cofilin-Linked Changes in Actin Filament Flexibility Promote Severing

PubMed Central

McCullough, Brannon R.; Grintsevich, Elena E.; Chen, Christine K.; Kang, Hyeran; Hutchison, Alan L.; Henn, Arnon; Cao, Wenxiang; Suarez, Cristian; Martiel, Jean-Louis; Blanchoin, Laurent; Reisler, Emil; De La Cruz, Enrique M.

2011-01-01

The actin regulatory protein, cofilin, increases the bending and twisting elasticity of actin filaments and severs them. It has been proposed that filaments partially decorated with cofilin accumulate stress from thermally driven shape fluctuations at bare (stiff) and decorated (compliant) boundaries, thereby promoting severing. This mechanics-based severing model predicts that changes in actin filament compliance due to cofilin binding affect severing activity. Here, we test this prediction by evaluating how the severing activities of vertebrate and yeast cofilactin scale with the flexural rigidities determined from analysis of shape fluctuations. Yeast actin filaments are more compliant in bending than vertebrate actin filaments. Severing activities of cofilactin isoforms correlate with changes in filament flexibility. Vertebrate cofilin binds but does not increase the yeast actin filament flexibility, and does not sever them. Imaging of filament thermal fluctuations reveals that severing events are associated with local bending and fragmentation when deformations attain a critical angle. The critical severing angle at boundaries between bare and cofilin-decorated segments is smaller than in bare or fully decorated filaments. These measurements support a cofilin-severing mechanism in which mechanical asymmetry promotes local stress accumulation and fragmentation at boundaries of bare and cofilin-decorated segments, analogous to failure of some nonprotein materials. PMID:21723825

Impact of linker and conjugation chemistry on antigen binding, Fc receptor binding and thermal stability of model antibody-drug conjugates

PubMed Central

Acchione, Mauro; Kwon, Hyewon; Jochheim, Claudia M.; Atkins, William M.

2012-01-01

Antibody-drug conjugates (ADCs) with biotin as a model cargo tethered to IgG1 mAbs via different linkers and conjugation methods were prepared and tested for thermostability and ability to bind target antigen and Fc receptor. Most conjugates demonstrated decreased thermostability relative to unconjugated antibody, based on DSC, with carbohydrate and amine coupled ADCs showing the least effect compared with thiol coupled conjugates. A strong correlation between biotin-load and loss of stability is observed with thiol conjugation to one IgG scaffold, but the stability of a second IgG scaffold is relatively insensitive to biotin load. The same correlation for amine coupling was less significant. Binding of antibody to antigen and Fc receptor was investigated using surface plasmon resonance. None of the conjugates exhibited altered antigen affinity. Fc receptor FcγIIb (CD32b) interactions were investigated using captured antibody conjugate. Protein G and Protein A, known inhibitors of Fc receptor (FcR) binding to IgG, were also used to extend the analysis of the impact of conjugation on Fc receptor binding. H10NPEG4 was the only conjugate to show significant negative impact to FcR binding, which is likely due to higher biotin-load compared with the other ADCs. The ADC aHISNLC and aHISTPEG8 demonstrated some loss in affinity for FcR, but to much lower extent. The general insensitivity of target binding and effector function of the IgG1 platform to conjugation highlight their utility. The observed changes in thermostability require consideration for the choice of conjugation chemistry, depending on the system being pursued and particular application of the conjugate. PMID:22531451

Cannabinoid-mediated diversity of antinociceptive efficacy of parecoxib in Wistar and Sprague Dawley rats in the chronic constriction injury model of neuropathic pain.

PubMed

Becker, Axel; Geisslinger, Gerd; Murín, Radovan; Grecksch, Gisela; Höllt, Volker; Zimmer, Andreas; Schröder, Helmut

2013-05-01

We studied nociceptive behavior and the effects of analgesics in Wistar (Wist) and Sprague Dawley (SPD) rats and in CB1 receptor-deficient mice with neuropathic pain experimentally. Neuropathic pain was induced by loose ligation of the sciatic nerve (chronic constriction injury, CCI). In CCI rats from both strains, cold allodynia and a reduced thermal pain threshold were detected, whereas no effect was found in the hot plate test. Thermal pain threshold was used to study the antinociceptive effects of morphine, gabapentin, and parecoxib 5 days after surgery. Doses of gabapentin and morphine which had no effect on sham-operated animals provoked antinociceptive activity in CCI rats from both strains. An antinociceptive effect of parecoxib was only found in CCI Wist rats. No pharmacokinetic differences were detected between the two strains in parecoxib metabolism. Antinociceptive activity caused by parecoxib was attenuated by the CB1 antagonist rimonabant. To further clarify parecoxib-CB1 interaction, the effect of parecoxib was investigated in CB1-deficient mice and wild-type animals. CCI did not affect thermal pain threshold and mechanical pain threshold was decreased. Parecoxib normalized the altered mechanical pain threshold in CCI wild-type animals, whereas it had only a marginal effect in CB1 receptor deficient mice. Receptor binding experiments showed increased CB1 binding in parecoxib-treated CCI Wist rats. Levels of the CB1 receptor mRNA remained constant in both strains of rats 5 days after surgery. Differences in antinociceptive activity might be due to modification of the cannabinoid system.

Increases thermal stability and cellulose-binding capacity of Cryptococcus sp. S-2 lipase by fusion of cellulose binding domain derived from Trichoderma reesei

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

Thongekkaew, Jantaporn, E-mail: jantaporn_25@yahoo.com; Ikeda, Hiroko; Iefuji, Haruyuki

Highlights: Black-Right-Pointing-Pointer The CSLP and fusion enzyme were successfully expressed in the Pichia pastoris. Black-Right-Pointing-Pointer The fusion enzyme was stable at 80 Degree-Sign C for 120-min. Black-Right-Pointing-Pointer The fusion enzyme was responsible for cellulose-binding capacity. Black-Right-Pointing-Pointer The fusion enzyme has an attractive applicant for enzyme immobilization. -- Abstract: To improve the thermal stability and cellulose-binding capacity of Cryptococcus sp. S-2 lipase (CSLP), the cellulose-binding domain originates from Trichoderma reesei cellobiohydrolase I was engineered into C-terminal region of the CSLP (CSLP-CBD). The CSLP and CSLP-CBD were successfully expressed in the Pichia pastoris using the strong methanol inducible alcohol oxidase 1 (AOX1)more » promoter and the secretion signal sequence from Saccharomyces cerevisiae ({alpha} factor). The recombinant CSLP and CSLP-CBD were secreted into culture medium and estimated by SDS-PAGE to be 22 and 27 kDa, respectively. The fusion enzyme was stable at 80 Degree-Sign C and retained more than 80% of its activity after 120-min incubation at this temperature. Our results also found that the fusion of fungal exoglucanase cellulose-binding domain to CSLP is responsible for cellulose-binding capacity. This attribute should make it an attractive applicant for enzyme immobilization.« less

Measurement of Nanomolar Dissociation Constants by Titration Calorimetry and Thermal Shift Assay – Radicicol Binding to Hsp90 and Ethoxzolamide Binding to CAII

PubMed Central

Zubrienė, Asta; Matulienė, Jurgita; Baranauskienė, Lina; Jachno, Jelena; Torresan, Jolanta; Michailovienė, Vilma; Cimmperman, Piotras; Matulis, Daumantas

2009-01-01

The analysis of tight protein-ligand binding reactions by isothermal titration calorimetry (ITC) and thermal shift assay (TSA) is presented. The binding of radicicol to the N-terminal domain of human heat shock protein 90 (Hsp90αN) and the binding of ethoxzolamide to human carbonic anhydrase (hCAII) were too strong to be measured accurately by direct ITC titration and therefore were measured by displacement ITC and by observing the temperature-denaturation transitions of ligand-free and ligand-bound protein. Stabilization of both proteins by their ligands was profound, increasing the melting temperature by more than 10 ºC, depending on ligand concentration. Analysis of the melting temperature dependence on the protein and ligand concentrations yielded dissociation constants equal to 1 nM and 2 nM for Hsp90αN-radicicol and hCAII-ethoxzolamide, respectively. The ligand-free and ligand-bound protein fractions melt separately, and two melting transitions are observed. This phenomenon is especially pronounced when the ligand concentration is equal to about half the protein concentration. The analysis compares ITC and TSA data, accounts for two transitions and yields the ligand binding constant and the parameters of protein stability, including the Gibbs free energy and the enthalpy of unfolding. PMID:19582223

Novel characteristics of a carbohydrate-binding module 20 from hyperthermophilic bacterium.

PubMed

Oh, Il-Nam; Jane, Jay-Lin; Wang, Kan; Park, Jong-Tae; Park, Kwan-Hwa

2015-03-01

In this study, a gene fragment coding carbohydrate-binding module 20 (CBM20) in the amylopullulanase (APU) gene was cloned from the hyperthermophilic bacteria Thermoanaerobacter pseudoethanolicus 39E and expressed in Escherichia coli. The protein, hereafter Tp39E, possesses very low sequence similarity with the CBM20s previously reported and has no starch binding site 2. Tp39E did not demonstrate thermal denaturation at 50 °C; however, thermal unfolding of the protein was observed at 59.5 °C. A binding assay with Tp39E was conducted using various soluble and insoluble substrates, and starch was the best binding polysaccharide. Intriguingly, Tp39E bound, to a lesser extent, to soluble and insoluble xylan as well. The dissociation constant (K d) and the maximum specific binding (B max) of Tp39E to corn starch granules were 0.537 μM and 5.79 μM/g, respectively, at pH 5.5 and 20 °C. 99APU1357 with a Tp39E domain exhibited 2.2-fold greater activity than a CBM20-truncation mutant when starch granules were the substrate. Tp39E was an independently thermostable CBM and had a considerable effect on APU activity in the hydrolysis of insoluble substrates.

Antibacterial action of a heat-stable form of L-amino acid oxidase isolated from king cobra (Ophiophagus hannah) venom.

PubMed

Lee, Mui Li; Tan, Nget Hong; Fung, Shin Yee; Sekaran, Shamala Devi

2011-03-01

The major l-amino acid oxidase (LAAO, EC 1.4.3.2) of king cobra (Ophiophagus hannah) venom is known to be an unusual form of snake venom LAAO as it possesses unique structural features and unusual thermal stability. The antibacterial effects of king cobra venom LAAO were tested against several strains of clinical isolates including Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli using broth microdilution assay. For comparison, the antibacterial effects of several antibiotics (cefotaxime, kanamycin, tetracycline, vancomycin and penicillin) were also examined using the same conditions. King cobra venom LAAO was very effective in inhibiting the two Gram-positive bacteria (S. aureus and S. epidermidis) tested, with minimum inhibitory concentration (MIC) of 0.78μg/mL (0.006μM) and 1.56μg/mL (0.012μM) against S. aureus and S. epidermidis, respectively. The MICs are comparable to the MICs of the antibiotics tested, on a weight basis. However, the LAAO was only moderately effective against three Gram-negative bacteria tested (P. aeruginosa, K. pneumoniae and E. coli), with MIC ranges from 25 to 50μg/mL (0.2-0.4μM). Catalase at the concentration of 1mg/mL abolished the antibacterial effect of LAAO, indicating that the antibacterial effect of the enzyme involves generation of hydrogen peroxide. Binding studies indicated that king cobra venom LAAO binds strongly to the Gram-positive S. aureus and S. epidermidis, but less strongly to the Gram-negative E. coli and P. aeruginosa, indicating that specific binding to bacteria is important for the potent antibacterial activity of the enzyme. Copyright © 2010 Elsevier Inc. All rights reserved.

Functional Analysis of a Bacterial Antifreeze Protein Indicates a Cooperative Effect between Its Two Ice-Binding Domains.

PubMed

Wang, Chen; Oliver, Erin E; Christner, Brent C; Luo, Bing-Hao

2016-07-19

Antifreeze proteins make up a class of ice-binding proteins (IBPs) that are possessed and expressed by certain cold-adapted organisms to enhance their freezing tolerance. Here we report the biophysical and functional characterization of an IBP discovered in a bacterium recovered from a deep glacial ice core drilled at Vostok Station, Antarctica (IBPv). Our study showed that the recombinant protein rIBPv exhibited a thermal hysteresis of 2 °C at concentrations of >50 μM, effectively inhibited ice recrystallization, and enhanced bacterial viability during freeze-thaw cycling. Circular dichroism scans indicated that rIBPv mainly consists of β strands, and its denaturing temperature was 53.5 °C. Multiple-sequence alignment of homologous IBPs predicted that IBPv contains two ice-binding domains, a feature unique among known IBPs. To examine functional differences between the IBPv domains, each domain was cloned, expressed, and purified. The second domain (domain B) expressed greater ice binding activity. Data from thermal hysteresis and gel filtration assays supported the idea that the two domains cooperate to achieve a higher ice binding effect by forming heterodimers. However, physical linkage of the domains was not required for this effect.

Spectroscopic detection of etoposide binding to chromatin components: The role of histone proteins

NASA Astrophysics Data System (ADS)

Chamani, Elham; Rabbani-Chadegani, Azra; Zahraei, Zohreh

2014-12-01

Chromatin has been introduced as a main target for most anticancer drugs. Etoposide is known as a topoisomerase II inhibitor, but its effect on chromatin components is unknown. This report, for the first time, describes the effect of etoposide on DNA, histones and DNA-histones complex in the structure of nucleosomes employing thermal denaturation, fluorescence, UV absorbance and circular dichroism spectroscopy techniques. The results showed that the binding of etoposide decreased UV absorbance and fluorescence emission intensity, altered secondary structure of chromatin and hypochromicity was occurred in thermal denaturation profiles. The drug exhibited higher affinity to chromatin compared to DNA. Quenching of drug chromophores with tyrosine residues of histones indicated that globular domain of histones is the site of etoposide binding. Moreover, the binding of etoposide to histones altered their secondary structure accompanied with hypochromicity revealing compaction of histones in the presence of the drug. From the results it is concludes that apart from topoisomerase II, chromatin components especially its protein moiety can be introduced as a new site of etoposide binding and histone proteins especially H1 play a fundamental role in this process and anticancer activity of etoposide.

The Thermal Stabilization of Vaccines Against Agents of Bioterrorism

DTIC Science & Technology

2005-09-01

to determine (1) whether rPA in the formulation buffer in the absence of excipients binds to Alhydrogel®and (2) the binding capacity . The aluminum...botulinum toxin (Allergan), A ricin vaccine (DOR Biopharma ) and a vaccine against Norwalk virus (Ligocyte) were also initiated and are in various

Lignin triggers irreversible cellulase loss during pretreated lignocellulosic biomass saccharification.

PubMed

Gao, Dahai; Haarmeyer, Carolyn; Balan, Venkatesh; Whitehead, Timothy A; Dale, Bruce E; Chundawat, Shishir Ps

2014-01-01

Non-productive binding of enzymes to lignin is thought to impede the saccharification efficiency of pretreated lignocellulosic biomass to fermentable sugars. Due to a lack of suitable analytical techniques that track binding of individual enzymes within complex protein mixtures and the difficulty in distinguishing the contribution of productive (binding to specific glycans) versus non-productive (binding to lignin) binding of cellulases to lignocellulose, there is currently a poor understanding of individual enzyme adsorption to lignin during the time course of pretreated biomass saccharification. In this study, we have utilized an FPLC (fast protein liquid chromatography)-based methodology to quantify free Trichoderma reesei cellulases (namely CBH I, CBH II, and EG I) concentration within a complex hydrolyzate mixture during the varying time course of biomass saccharification. Three pretreated corn stover (CS) samples were included in this study: Ammonia Fiber Expansion(a) (AFEX™-CS), dilute acid (DA-CS), and ionic liquid (IL-CS) pretreatments. The relative fraction of bound individual cellulases varied depending not only on the pretreated biomass type (and lignin abundance) but also on the type of cellulase. Acid pretreated biomass had the highest levels of non-recoverable cellulases, while ionic liquid pretreated biomass had the highest overall cellulase recovery. CBH II has the lowest thermal stability among the three T. reesei cellulases tested. By preparing recombinant family 1 carbohydrate binding module (CBM) fusion proteins, we have shown that family 1 CBMs are highly implicated in the non-productive binding of full-length T. reesei cellulases to lignin. Our findings aid in further understanding the complex mechanisms of non-productive binding of cellulases to pretreated lignocellulosic biomass. Developing optimized pretreatment processes with reduced or modified lignin content to minimize non-productive enzyme binding or engineering pretreatment-specific, low-lignin binding cellulases will improve enzyme specific activity, facilitate enzyme recycling, and thereby permit production of cheaper biofuels.

Chirality dependent interaction of ammonia with carbon nanotubes

NASA Astrophysics Data System (ADS)

Talukdar, Keka; Shantappa, Anil

2018-04-01

For the specific structure and extraordinary properties, carbon nanotubes (CNTs) have many applications in diversified fields. The interaction of CNTs with ammonia is a very interesting matter to study as it is related to the application of CNTs as ammonia sensor. Here the interaction of single walled zigzag, armchair and chiral carbon nanotubes is studied in respect of the change in energies before and after binding with ammonia by molecular dynamics simulation. Their deformation after simulation is modeled. The change of thermal conductivity of the CNTs is also found by simulation. The potential energy before and after absorption of ammonia gives useful information of the system. Thermal conductivities of the ammonia bound CNTs are changed considerably. It is observed that the potential energy and thermal conductivity both are changing for the interaction with ammonia and hence they are sensitive to ammonia binding.

Bench-Scale Testing and Process Performance Projections of CO2 Capture by CO2–Binding Organic Liquids (CO2BOLs) With and Without Polarity-Swing-Assisted Regeneration

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

Zheng, Feng; Heldebrant, David J.; Mathias, Paul M.

This manuscript provides a detailed analysis of a continuous flow, bench scale study of the CO2BOL solvent platform with and without its Polarity Swing Assisted Regeneration (PSAR). This study encompassed four months of continuous flow testing of a candidate CO2BOL with a thermal regeneration and PSAR regeneration using decane antisolvent. In both regeneration schemes, steady state capture of >90 %CO2 was achieved using simulated flue gas at acceptable L/G ratios. Aspen Plus™ modeling was performed to assess process performance compared to previous equilibrium performance projections. This paper also includes net power projections, and comparisons to DOE’s Case 10 amine baseline.

Heat and pressure treatments effects on peanut allergenicity

USDA-ARS?s Scientific Manuscript database

Peanut allergy is recognized as one of the most severe food allergies. The aim of this study was to investigate the changes in IgE binding capacity of peanut proteins produced by thermal-processing methods, including autoclaving. Immunoreactivity to raw and thermally processed peanut extracts was ev...

Design and fabrication of a differential scanning nanocalorimeter

NASA Astrophysics Data System (ADS)

Zuo, Lei; Chen, Xiaoming; Yu, Shifeng; Lu, Ming

2017-02-01

This paper describes the design, fabrication, and characterization of a differential scanning nanocalorimeter that significantly reduces the sample volume to microliters and can potentially improve the temperature sensitivity to 10 µK. The nanocalorimeter consists of a polymeric freestanding membrane, four high-sensitive low-noise thermistors based on silicon carbide (SiC), and a platinum heater and temperature sensor. With the integrated heater and sensors, temperature scanning and power compensation can be achieved for calorimetric measurement. Temperature sensing SiC film was prepared by using sintered SiC target and DC magnetron sputtering under different gas pressures and sputtering power. The SiC sensing material is characterized through the measurement of current-voltage curves and noise levels. The thermal performance of a fabricated nanocalorimeter is studied in simulation and experiment. The experiment results show the device has excellent thermal isolation to hold thermal energy. The noise test together with the simulation show the device is promising for micro 10 µK temperature sensitivity and nanowatt resolution which will lead to low-volume ultra-sensitive nanocalorimetry for biological processes, such as protein folding and ligand binding.

[Sauna effect on blood oxygen transport function and proxidant/antioxidant balance in youths].

PubMed

Zinchuk, V V; Zhad'ko, D D

2012-01-01

There was investigated sauna effect on blood oxygen transport function and proxidant/antioxidant balance in 18 to 22 years old males. Subjects being tested underwent thermal exposure once per week over a period of 5 months (20 procedures). There were two exposure over the course of sauna bathing (temperature 85-90 degrees C, humidity 10-15%): the first exposure lasted for 5 minutes and the second one for 10 minutes. Dry air sauna in youth's leads to respiratory alkalosis, increases pO2, decreases haemoglobin binding capacity to venous blood oxygen thus facilitating oxygen transport into body tissues. Single sauna visit results in oxidative stress (augmentation of free radical processes and deterioration of antioxidant defence mechanisms), while its manifestations being diminished after multiple thermal exposures. Increase in nitrogen monoxide formation being observed might matter for the modification of the oxygen dependent processes of the human body.

Thermal decay of rhodopsin: role of hydrogen bonds in thermal isomerization of 11-cis retinal in the binding site and hydrolysis of protonated Schiff base.

PubMed

Liu, Jian; Liu, Monica Yun; Nguyen, Jennifer B; Bhagat, Aditi; Mooney, Victoria; Yan, Elsa C Y

2009-07-01

Although thermal stability of the G protein-coupled receptor rhodopsin is directly related to its extremely low dark noise level and has recently generated considerable interest, the chemistry behind the thermal decay process of rhodopsin has remained unclear. Using UV-vis spectroscopy and HPLC analysis, we have demonstrated that the thermal decay of rhodopsin involves both hydrolysis of the protonated Schiff base and thermal isomerization of 11-cis to all-trans retinal. Examining the unfolding of rhodopsin by circular dichroism spectroscopy and measuring the rate of thermal isomerization of 11-cis retinal in solution, we conclude that the observed thermal isomerization of 11-cis to all-trans retinal happens when 11-cis retinal is in the binding pocket of rhodopsin. Furthermore, we demonstrate that solvent deuterium isotope effects are involved in the thermal decay process by decreasing the rates of thermal isomerization and hydrolysis, suggesting that the rate-determining step of these processes involves breaking hydrogen bonds. These results provide insight into understanding the critical role of an extensive hydrogen-bonding network on stabilizing the inactive state of rhodopsin and contribute to our current understanding of the low dark noise level of rhodopsin, which enables this specialized protein to function as an extremely sensitive biological light detector. Because similar hydrogen-bonding networks have also been suggested by structural analysis of two other GPCRs, beta1 and beta2 adrenergic receptors, our results could reveal a general role of hydrogen bonds in facilitating GPCR function.

The hydrophobic region of the DmsA twin-arginine leader peptide determines specificity with chaperone DmsD.

PubMed

Winstone, Tara M L; Tran, Vy A; Turner, Raymond J

2013-10-29

The system specific chaperone DmsD plays a role in the maturation of the catalytic subunit of dimethyl sulfoxide (DMSO) reductase, DmsA. Pre-DmsA contains a 45-amino acid twin-arginine leader peptide that is important for targeting and translocation of folded and cofactor-loaded DmsA by the twin-arginine translocase. DmsD has previously been shown to interact with the complete twin-arginine leader peptide of DmsA. In this study, isothermal titration calorimetry was used to investigate the thermodynamics of binding between synthetic peptides composed of different portions of the DmsA leader peptide and DmsD. Only those peptides that included the complete and contiguous hydrophobic region of the DmsA leader sequence were able to bind DmsD with a 1:1 stoichiometry. Each of the peptides that were able to bind DmsD also showed some α-helical structure as indicated by circular dichroism spectroscopy. Differential scanning calorimetry revealed that DmsD gained very little thermal stability upon binding any of the DmsA leader peptides tested. Together, these results suggest that a portion of the hydrophobic region of the DmsA leader peptide determines the specificity of binding and may produce helical properties upon binding to DmsD. Overall, this study demonstrates that the recognition of the DmsA twin-arginine leader sequence by the DmsD chaperone shows unexpected rules and confirms further that the biochemistry of the interaction of the chaperone with their leaders demonstrates differences in their molecular interactions.

Correlation between CD16a binding and immuno effector functionality of an antigen specific immunoglobulin Fc fragment (Fcab).

PubMed

Kainer, Manuela; Antes, Bernhard; Wiederkum, Susanne; Wozniak-Knopp, Gordana; Bauer, Anton; Rüker, Florian; Woisetschläger, Max

2012-10-15

Antigen binding immunoglobulin Fc fragments (Fcab) are generated by engineering loop regions in the CH3 domain of human IgG1 Fc. Variants of an Fcab specific for Her-2 were designed to display either enhanced (S239D:A330L:I332E) or diminished (L234A:L235A) binding affinities to the Fc receptor CD16a based on mutations described previously. The two mutant Fcab proteins demonstrated the expected modulation of CD16a binding. Interaction with recombinant or cell surface expressed Her-2 was unaffected in both mutants compared to the parental Fcab. Binding affinities for CD16a correlated with the ADCC-potencies of the Fcab variants. Additional studies indicated that the L234A:L235A variant Fcab had equivalent structural features as the unmodified Fcab since their DSC profiles were similar and antigen binding after re-folding upon partial heat denaturation had not changed. Introduction of the S239D:A330L:I332E mutations resulted in a significant reduction of the CH2 domain melting temperature, a moderate decrease of the thermal transition of the CH3 domain and lower antigen binding after thermal stress compared to the parental Fcab. We conclude that the known correlation between CD16a binding affinity and ADCC potency is also valid in Fcab proteins and that antigen specific Fcab molecules can be further engineered for fine tuning of immuno effector functions. Copyright © 2012 Elsevier Inc. All rights reserved.

Fastener load tests and retention systems tests for cryogenic wind-tunnel models

NASA Technical Reports Server (NTRS)

Wallace, J. W.

1984-01-01

A-286 stainless steel screws were tested to determine the tensile load capability and failure mode of various screw sizes and types at both cryogenic and room temperature. Additionally, five fastener retention systems were tested by using A-286 screws with specimens made from the primary metallic alloys that are currently used for cryogenic models. The locking system effectiveness was examined by simple no-load cycling to cryogenic temperatures (-275 F) as well as by dynamic and static loading at cryogenic temperatures. In general, most systems were found to be effective retention devices. There are some differences between the various devices with respect to ease of application, cleanup, and reuse. Results of tests at -275 F imply that the cold temperatures act to improve screw retention. The improved retention is probably the result of differential thermal contraction and/or increased friction (thread-binding effects). The data provided are useful in selecting screw sizes, types, and locking devices for model systems to be tested in cryogenic wind tunnels.

Thermal Inactivation of Enteric Viruses and Bioaccumulation of Enteric Foodborne Viruses in Live Oysters (Crassostrea virginica)

PubMed Central

Araud, Elbashir; DiCaprio, Erin; Ma, Yuanmei; Lou, Fangfei; Gao, Yu; Kingsley, David; Hughes, John H.

2016-01-01

Human enteric viruses are among the main causative agents of shellfish-associated outbreaks. In this study, the kinetics of viral bioaccumulation in live oysters and the heat stabilities of the predominant enteric viruses were determined both in tissue culture and in oyster tissues. A human norovirus (HuNoV) GII.4 strain, HuNoV surrogates (murine norovirus [MNV-1], Tulane virus [TV]), hepatitis A virus (HAV), and human rotavirus (RV) bioaccumulated to high titers within oyster tissues, with different patterns of bioaccumulation for the different viruses. We tested the thermal stability of each virus at 62, 72, and 80°C in culture medium. The viruses can be ranked from the most heat resistant to the least stable as follows: HAV, RV, TV, MNV-1. In addition, we found that oyster tissues provided protection to the viruses during heat treatment. To decipher the mechanism underlying viral inactivation by heat, purified TV was treated at 80°C for increasing time intervals. It was found that the integrity of the viral capsid was disrupted, whereas viral genomic RNA remained intact. Interestingly, heat treatment leading to complete loss of TV infectivity was not sufficient to completely disrupt the receptor binding activity of TV, as determined by the porcine gastric mucin–magnetic bead binding assay. Similarly, HuNoV virus-like particles (VLPs) and a HuNoV GII.4 strain retained some receptor binding ability following heat treatment. Although foodborne viruses have variable heat stability, 80°C for >6 min was sufficient to completely inactivate enteric viruses in oysters, with the exception of HAV. PMID:26826225

Identification of amino acids important for binding of Clostridium perfringens epsilon toxin to host cells and to HAVCR1.

PubMed

Ivie, Susan E; McClain, Mark S

2012-09-25

Clostridium perfringens epsilon toxin belongs to the aerolysin-like family of pore-forming toxins and is one of the most potent bacterial toxins known. The epsilon toxin causes fatal enterotoxemia in sheep, goats, and possibly humans. Evidence indicates that the toxin binds to protein receptors including hepatitis A virus cellular receptor 1 (HAVCR1), but the region of the toxin responsible for cell binding has not been identified. In the present study, we identify amino acids within the epsilon toxin important for this cell interaction. Site-specific mutagenesis was used to investigate the role of a surface-accessible cluster of aromatic amino acids, and purified mutant proteins were tested in a series of cell-culture assays to assess cytotoxic activity and cell binding. When added to cells, four mutant proteins (Etx-Y29E, Etx-Y30E, Etx-Y36E and Etx-Y196E) were severely impaired in their ability to not only kill host cells, but also in their ability to permeabilize the plasma membrane. Circular dichroism spectroscopy and thermal stability studies revealed that the wild-type and mutant proteins were similarly folded. Additional experiments revealed that these mutant proteins were defective in binding to host cells and to HAVCR1. These data indicate that an amino acid motif including Y29, Y30, Y36, and Y196 is important for the ability of epsilon toxin to interact with cells and HAVCR1.

Identification of amino acids important for binding of Clostridium perfringens epsilon toxin to host cells and to HAVCR1

PubMed Central

Ivie, Susan E.; McClain, Mark S.

2012-01-01

Clostridium perfringens epsilon toxin belongs to the aerolysin-like family of pore-forming toxins and is one of the most potent bacterial toxins known. The epsilon toxin causes fatal enterotoxemia in sheep, goats, and possibly humans. Evidence indicates that the toxin binds to protein receptors including hepatitis A virus cellular receptor 1 (HAVCR1), but the region of the toxin responsible for cell binding has not been identified. In the present study, we identify amino acids within the epsilon toxin important for this cell interaction. Site-specific mutagenesis was used to investigate the role of a surface-accessible cluster of aromatic amino acids, and purified mutant proteins were tested in a series of cell-culture assays to assess cytotoxic activity and cell binding. When added to cells, four mutant proteins (Etx-Y29E, Etx-Y30E, Etx-Y36E and Etx-Y196E) were severely impaired in their ability to not only kill host cells, but also in their ability to permeabilize the plasma membrane. Circular dichroism spectroscopy and thermal stability studies revealed that the wild-type and mutant proteins were similarly folded. Additional experiments revealed that these mutant proteins were defective in binding to host cells and to HAVCR1. These data indicate that an amino acid motif including Y29, Y30, Y36, and Y196 is important for the ability of epsilon toxin to interact with cells and HAVCR1. PMID:22938730

Application of polyhydroxyalkanoate binding protein PhaP as a bio-surfactant.

PubMed

Wei, Dai-Xu; Chen, Chong-Bo; Fang, Guo; Li, Shi-Yan; Chen, Guo-Qiang

2011-08-01

PhaP or phasin is an amphiphilic protein located on surfaces of microbial storage polyhydroxyalkanoates granules. This study aimed to explore amphiphilic properties of PhaP for possible application as a protein surfactant. Following agents were used to conduct this study as controls including bovine serum albumin, sodium dodecyl sulfate (SDS), Tween 20, sodium oleate, a commercial liquefied detergent together with the same amount of PhaP. Among all these tested control surfactants, PhaP showed the strongest effect to form emulsions with lubricating oil, diesel, and soybean oil, respectively. PhaP emulsion stability study compared with SDS revealed that PhaP had a stronger capability to maintain a very stable emulsion layer after 30 days while SDS lost half and two-thirds of its capacity after 2 and 30 days, respectively. When PhaP was more than 200 μg/ml in the water, all liquids started to exhibit stable emulsion layers. Similar to SDS, PhaP significantly reduced the water contact angles of water on a hydrophobic film of biaxially oriented polypropylene. PhaP was thermally very stable, it showed ability to form emulsion and to bind to the surface of polyhydroxybutyrate nanoparticles after a 60- min heating process at 95 °C. It is therefore concluded that PhaP is a protein with thermally stable property for application as natural and environmentally friendly surfactant for food, cosmetic, and pharmaceutical usages.

Pharmacology of Intracisternal or Intrathecal Glycine, Muscimol, and Baclofen in Strychnine-induced Thermal Hyperalgesia of Mice

PubMed Central

Son, Jin Kook; Lim, Eui-Sung; Kim, Yeon-Soo

2011-01-01

Glycine and γ-aminobutyric acid (GABA) are localized and released by the same interneurons in the spinal cord. Although the effects of glycine and GABA on analgesia are well known, little is known about the effect of GABA in strychnine-induced hyperalgesia. To investigate the effect of GABA and the role of the glycine receptor in thermal hyperalgesia, we designed an experiment involving the injection of muscimol (a GABAA receptor agonist), baclofen (a GABAB receptor agonist) or glycine with strychnine (strychnine sensitive glycine receptor antagonist). Glycine, muscimol, or baclofen with strychnine was injected into the cisterna magna or lumbar subarachnoidal spaces of mice. The effects of treatment on strychnine-induced heat hyperalgesia were observed using the pain threshold index via the hot plate test. The dosages of experimental drugs and strychnine we chose had no effects on motor behavior in conscious mice. Intracisternal or intrathecal administration of strychnine produced thermal hyperalgesia in mice. Glycine antagonize the effects of strychnine, whereas, muscimol or baclofen does not. Our results indicate that glycine has anti-thermal hyperalgesic properties in vivo; and GABA receptor agonists may lack the binding abilities of glycine receptor antagonists with their sites in the central nervous system. PMID:22022192

Pharmacology of intracisternal or intrathecal glycine, muscimol, and baclofen in strychnine-induced thermal hyperalgesia of mice.

PubMed

Lee, Il Ok; Son, Jin Kook; Lim, Eui-Sung; Kim, Yeon-Soo

2011-10-01

Glycine and γ-aminobutyric acid (GABA) are localized and released by the same interneurons in the spinal cord. Although the effects of glycine and GABA on analgesia are well known, little is known about the effect of GABA in strychnine-induced hyperalgesia. To investigate the effect of GABA and the role of the glycine receptor in thermal hyperalgesia, we designed an experiment involving the injection of muscimol (a GABA(A) receptor agonist), baclofen (a GABA(B) receptor agonist) or glycine with strychnine (strychnine sensitive glycine receptor antagonist). Glycine, muscimol, or baclofen with strychnine was injected into the cisterna magna or lumbar subarachnoidal spaces of mice. The effects of treatment on strychnine-induced heat hyperalgesia were observed using the pain threshold index via the hot plate test. The dosages of experimental drugs and strychnine we chose had no effects on motor behavior in conscious mice. Intracisternal or intrathecal administration of strychnine produced thermal hyperalgesia in mice. Glycine antagonize the effects of strychnine, whereas, muscimol or baclofen does not. Our results indicate that glycine has anti-thermal hyperalgesic properties in vivo; and GABA receptor agonists may lack the binding abilities of glycine receptor antagonists with their sites in the central nervous system.

Regular square planer bis-(4,4,4-trifluoro-1-(thiophen-2-yl)butane-1,3-dione)/copper(II) complex: Trans/cis-DFT isomerization, crystal structure, thermal, solvatochromism, hirshfeld surface and DNA-binding analysis

NASA Astrophysics Data System (ADS)

Hema, M. K.; Karthik, C. S.; Warad, Ismail; Lokanath, N. K.; Zarrouk, Abdelkader; Kumara, Karthik; Pampa, K. J.; Mallu, P.

2018-04-01

Trans-[Cu(O∩O)2] complex, O∩O = 4,4,4-trifluoro-1-(thiophen-2-yl)butane-1,3-dione was reported with high potential toward CT-DNA binder. The solved XRD-structure of complex indicated a perfect regular square-planer geometry around the Cu(II) center. The trans/cis-DFT-isomerization calculation supported the XRD seen in reflecting the trans-isomer as the kinetic-favor isomer. The desired complex structure was also characterized by conductivity measurement, CHN-elemental analyses, MS, EDX, SEM, UV-Vis., FT-IR, HAS and TG/DTG. The Solvatochromism behavior of the complex was evaluated using four different polar solvents. MPE and Hirshfeld surface analysis (HSA) come to an agreement that fluoride and thiophene protons atoms are with suitable electro-potential environment to form non-classical H-bonds of type CThsbnd H⋯F. The DNA-binding properties were investigated by viscosity tests and spectrometric titrations, the results revealed the complex as strong calf-thymus DNA binder. High intrinsic-binding constants value ∼1.8 × 105 was collected.

Multispectroscopic and Theoretical Exploration of the Comparative Binding Aspects of Bioflavonoid Fisetin with Triple- and Double-Helical Forms of RNA.

PubMed

Bhuiya, Sutanwi; Haque, Lucy; Goswami, Rapti; Das, Suman

2017-12-14

The interactions of RNA triplex (U.A*U) and duplex (A.U) with naturally occurring flavonoid fisetin (FTN) have been examined at pH 7.0 using various spectroscopic, viscometric, and theoretical studies. Experimental observations showed that the ligand binds with both double- and triple-helical forms of RNA, although the binding affinity is greater for the triplex structure (5.94 × 10 6 M -1 ) compared to that for the duplex counterpart (1.0 × 10 5 M -1 ). Thermal melting experiments revealed that the Hoogsteen base-paired third strand of triplex was stabilized to a greater extent (∼14 °C) compared with the Watson-Crick base-paired second strand (∼4 °C) in the presence of FTN. From fluorimetric study, we observed that U.A*U and A.U primarily bind to the photoproduced tautomer of FTN in the excited state. Steady-state and time-resolved anisotropy measurements illustrate considerable modulations of the spectroscopic properties of the tautomeric FTN within the RNA environment. Viscometric, fluorescence quenching, and thermal melting studies all together support the mode of binding to be intercalation. Theoretical study explains the experimental absorption and emission (dual fluorescence) behavior of FTN along with the excited-state intramolecular proton transfer process.

21 CFR 866.5765 - Retinol-binding protein immunological test system.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Retinol-binding protein immunological test system....5765 Retinol-binding protein immunological test system. (a) Identification. A retinol-binding protein... the retinol-binding protein that binds and transports vitamin A in serum and urine. Measurement of...

21 CFR 866.5765 - Retinol-binding protein immunological test system.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Retinol-binding protein immunological test system....5765 Retinol-binding protein immunological test system. (a) Identification. A retinol-binding protein... the retinol-binding protein that binds and transports vitamin A in serum and urine. Measurement of...

21 CFR 866.5765 - Retinol-binding protein immunological test system.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Retinol-binding protein immunological test system....5765 Retinol-binding protein immunological test system. (a) Identification. A retinol-binding protein... the retinol-binding protein that binds and transports vitamin A in serum and urine. Measurement of...

21 CFR 866.5765 - Retinol-binding protein immunological test system.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Retinol-binding protein immunological test system....5765 Retinol-binding protein immunological test system. (a) Identification. A retinol-binding protein... the retinol-binding protein that binds and transports vitamin A in serum and urine. Measurement of...

Strong Enrichment of Aromatic Residues in Binding Sites from a Charge-neutralized Hyperthermostable Sso7d Scaffold Library*

PubMed Central

Kiefer, Jonathan D.; Srinivas, Raja R.; Lobner, Elisabeth; Tisdale, Alison W.; Mehta, Naveen K.; Yang, Nicole J.; Tidor, Bruce; Wittrup, K. Dane

2016-01-01

The Sso7d protein from the hyperthermophilic archaeon Sulfolobus solfataricus is an attractive binding scaffold because of its small size (7 kDa), high thermal stability (Tm of 98 °C), and absence of cysteines and glycosylation sites. However, as a DNA-binding protein, Sso7d is highly positively charged, introducing a strong specificity constraint for binding epitopes and leading to nonspecific interaction with mammalian cell membranes. In the present study, we report charge-neutralized variants of Sso7d that maintain high thermal stability. Yeast-displayed libraries that were based on this reduced charge Sso7d (rcSso7d) scaffold yielded binders with low nanomolar affinities against mouse serum albumin and several epitopes on human epidermal growth factor receptor. Importantly, starting from a charge-neutralized scaffold facilitated evolutionary adaptation of binders to differentially charged epitopes on mouse serum albumin and human epidermal growth factor receptor, respectively. Interestingly, the distribution of amino acids in the small and rigid binding surface of enriched rcSso7d-based binders is very different from that generally found in more flexible antibody complementarity-determining region loops but resembles the composition of antibody-binding energetic hot spots. Particularly striking was a strong enrichment of the aromatic residues Trp, Tyr, and Phe in rcSso7d-based binders. This suggests that the rigidity and small size of this scaffold determines the unusual amino acid composition of its binding sites, mimicking the energetic core of antibody paratopes. Despite the high frequency of aromatic residues, these rcSso7d-based binders are highly expressed, thermostable, and monomeric, suggesting that the hyperstability of the starting scaffold and the rigidness of the binding surface confer a high tolerance to mutation. PMID:27582495

In vitro binding affinities of a series of flavonoids for μ-opioid receptors. Antinociceptive effect of the synthetic flavonoid 3,3-dibromoflavanone in mice.

PubMed

Higgs, Josefina; Wasowski, Cristina; Loscalzo, Leonardo M; Marder, Mariel

2013-09-01

The pharmacotherapy for the treatment of pain is an active area of investigation. There are effective drugs to treat this problem, but there is also a need to find alternative treatments free of undesirable side effects. In the present work the capacity of a series of flavonoids to bind to the μ opioid receptor was evaluated. The most active compound, 3,3-dibromoflavanone (31), a synthetic flavonoid, presented a significant inhibition of the binding of the selective μ opioid ligand [(3)H]DAMGO, with a Ki of 0.846 ± 0.263 μM. Flavanone 31 was further synthesized using a simple and cheap procedure with good yield. Its in vivo effects in mice, after acute treatments, were studied using antinociceptive and behavioral assays. It showed no sedative, anxiolytic, motor incoordination effects or inhibition of the gastrointestinal transit in mice at the doses tested. It evidenced antinociceptive activity on the acetic acid-induced nociception, hot plate and formalin tests (at 10 mg/kg and 30 mg/kg). The results showed that the 5-HT2 receptor and the adrenoceptors seem unlikely to be involved in its antinociceptive effects. Naltrexone, a nonselective opioid receptors antagonist, totally blocked compound 31 antinociceptive effects on the hot plate test, but naltrindole (δ opioid antagonist) and nor-binaltorphimine (κ opioid antagonist) did not. These findings demonstrated that 3,3-dibromoflavanone (31), at doses that did not interfere with the motor performance, exerted clear dose dependent antinociception when assessed in the chemical and thermal models of nociception in mice and it seems that its action is related to the activation of the μ opioid receptor. Copyright © 2013 Elsevier Ltd. All rights reserved.

Binding screen for cystic fibrosis transmembrane conductance regulator correctors finds new chemical matter and yields insights into cystic fibrosis therapeutic strategy.

PubMed

Hall, Justin D; Wang, Hong; Byrnes, Laura J; Shanker, Suman; Wang, Kelong; Efremov, Ivan V; Chong, P Andrew; Forman-Kay, Julie D; Aulabaugh, Ann E

2016-02-01

The most common mutation in cystic fibrosis (CF) patients is deletion of F508 (ΔF508) in the first nucleotide binding domain (NBD1) of the CF transmembrane conductance regulator (CFTR). ΔF508 causes a decrease in the trafficking of CFTR to the cell surface and reduces the thermal stability of isolated NBD1; it is well established that both of these effects can be rescued by additional revertant mutations in NBD1. The current paradigm in CF small molecule drug discovery is that, like revertant mutations, a path may exist to ΔF508 CFTR correction through a small molecule chaperone binding to NBD1. We, therefore, set out to find small molecule binders of NBD1 and test whether it is possible to develop these molecules into potent binders that increase CFTR trafficking in CF-patient-derived human bronchial epithelial cells. Several fragments were identified that bind NBD1 at either the CFFT-001 site or the BIA site. However, repeated attempts to improve the affinity of these fragments resulted in only modest gains. Although these results cannot prove that there is no possibility of finding a high-affinity small molecule binder of NBD1, they are discouraging and lead us to hypothesize that the nature of these two binding sites, and isolated NBD1 itself, may not contain the features needed to build high-affinity interactions. Future work in this area may, therefore, require constructs including other domains of CFTR in addition to NBD1, if high-affinity small molecule binding is to be achieved. © 2016 The Protein Society.

Increased responsiveness to MDMA in adult rats treated neonatally with MDMA.

PubMed

Piper, Brian J; Meyer, Jerrold S

2006-01-01

MDMA [(+/-)3,4-methylenedioxymethamphetamine, also known as ecstasy] is a popular recreational drug among women of reproductive age. The objective of this study was to investigate the long-term neurobehavioral consequences of early developmental MDMA exposure. On postnatal days (PD) 1-4, Sprague-Dawley rats received two 10 mg/kg injections of MDMA with an inter-dose interval of 4 h. Male subjects were tested in adulthood for their performance in an object-recognition memory task and for their thermal and behavioral responses to an acute MDMA challenge (10 mg/kg i.p.). Neonatal MDMA administration did not alter working memory in the object-recognition test in young adulthood (PD 68-73) and there were no differences in radiolabeled citalopram binding to the serotonin transporter at this age. However, the pretreated animals showed increased thermal dysregulation and serotonin syndrome responses (particularly headweaving stereotypy) following the MDMA challenge. These results add to the growing literature demonstrating that developmental MDMA administration can lead to long-lasting functional abnormalities, and they further suggest that the offspring of ecstasy-using women may be at risk for enhanced sensitivity to this drug due to their earlier exposure.

UV Thermal Melting Curves of tRNA[superscript Phe] in the Presence of Ligands

ERIC Educational Resources Information Center

Kirk, Sarah R.; Silverstein, Todd P.; McFarlane Holman, Karen L.

2008-01-01

This laboratory project is one component of a semester-long advanced biochemistry laboratory course that uses several complementary techniques to study tRNA[superscript Phe] conformational changes induced by ligand binding. In this article we describe a set of experiments in which the thermal unfolding of tRNA[superscript Phe] is studied with…

Instrumentation | Center for Cancer Research

Cancer.gov

Instrumentation [accordion collapsed] Circular Dichroism (CD) Spectroscopy Instrument: J-1500 CD Spectrophotometer (Jasco) Applications: Conformational analysis of biomolecules Protein thermal stability Binding studies Major Specifications:

Synthesis, characterization and biological evaluation of novel α, β unsaturated amides.

PubMed

Esmailzadeh, K; Housaindokht, M R; Moradi, A; Esmaeili, A A; Sharifi, Z

2016-05-15

Three derivatives of α,β unsaturated amides have been successfully synthesized via Ugi-four component (U-4CR) reaction. The interactions of the amides with calf thymus deoxyribonucleic acid (ct-DNA) have been investigated in the Tris-HCl buffer (pH=7.4) using viscometric, spectroscopic, thermal denaturation studies, and also molecular docking. By UV-Vis absorption spectroscopy studies, adding CT-DNA to the compound solution caused the hypochromism indicates that there are interactions between the compounds and DNA base pairs. In competitive fluorescence with methylene blue as an intercalator probe, adding compounds to DNA-MB solution caused an increase in emission spectra of the complex. This could be because of compound replacing, with similar binding mode of MB, between the DNA base pairs due to release of bonded MB molecules from DNA-MB complex. Thermal denaturation studies and viscometric experiments also indicated that all three investigated compounds bind to CT-DNA by non-classical intercalation mode. Additionally, molecular docking technique predicted partial intercalation binding mode for the compounds. Also, the highest binding energy was obtained for compound 5a. These results are in agreement with results obtained by empirical methods. Copyright © 2016 Elsevier B.V. All rights reserved.

Photoregulating RNA digestion using azobenzene linked dumbbell antisense oligodeoxynucleotides.

PubMed

Wu, Li; He, Yujian; Tang, Xinjing

2015-06-17

Introduction of 4,4'-bis(hydroxymethyl)-azobenzene (azo) to dumbbell hairpin oligonucleotides at the loop position was able to reversibly control the stability of the whole hairpin structure via UV or visible light irradiation. Here, we designed and synthesized a series of azobenzene linked dumbbell antisense oligodeoxynucleotides (asODNs) containing two terminal hairpins that are composed of an asODN and a short inhibitory sense strand. Thermal melting studies of these azobenzene linked dumbbell asODNs indicated that efficient trans to cis photoisomerization of azobenzene moieties induced large difference in thermal stability (ΔTm = 12.1-21.3 °C). In addition, photomodulation of their RNA binding abilities and RNA digestion by RNase H was investigated. The trans-azobenzene linked asODNs with the optimized base pairs between asODN strands and inhibitory sense strands could only bind few percentage of the target RNA, while it was able to recover their binding to the target RNA and degrade it by RNase H after light irradiation. Upon optimization, it is promising to use these azobenzene linked asODNs for reversible spatial and temporal regulation of antisense activities based on both steric binding and RNA digestion by RNase H.

21 CFR 866.5765 - Retinol-binding protein immunological test system.

Code of Federal Regulations, 2010 CFR

2010-04-01

... SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunological Test Systems § 866.5765 Retinol-binding protein immunological test system. (a) Identification. A retinol-binding protein... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Retinol-binding protein immunological test system...

Design and fabrication of a differential scanning nanocalorimeter

DOE PAGES

Zuo, Lei; Chen, Xiaoming; Yu, Shifeng; ...

2016-12-19

This paper describes the design, fabrication, and characterization of a differential scanning nanocalorimeter that significantly reduces the sample volume to microliters and can potentially improve the temperature sensitivity to 10 µK. The nanocalorimeter consists of a polymeric freestanding membrane, four high-sensitive low-noise thermistors based on silicon carbide (SiC), and a platinum heater and temperature sensor. With the integrated heater and sensors, temperature scanning and power compensation can be achieved for calorimetric measurement. Temperature sensing SiC film was prepared by using sintered SiC target and DC magnetron sputtering under different gas pressures and sputtering power. The SiC sensing material is characterizedmore » through the measurement of current–voltage curves and noise levels. The thermal performance of a fabricated nanocalorimeter is studied in simulation and experiment. The experiment results show the device has excellent thermal isolation to hold thermal energy. As a result, the noise test together with the simulation show the device is promising for micro 10 µK temperature sensitivity and nanowatt resolution which will lead to low-volume ultra-sensitive nanocalorimetry for biological processes, such as protein folding and ligand binding.« less

Unexpected Effects of K+ and Adenosine Triphosphate on the Thermal Stability of Na+,K+-ATPase.

PubMed

Placenti, M Agueda; Kaufman, Sergio B; González Flecha, F Luis; González Lebrero, Rodolfo M

2017-05-18

Na + ,K + -ATPase is an integral membrane protein which couples ATP hydrolysis to the transport of three Na + out and two K + into the cell. The aim of this work is to characterize the effect of K + , ATP, and Mg 2+ (essential activator) on the Na + ,K + -ATPase thermal stability. Under all conditions tested, thermal inactivation of the enzyme is concomitant with a structural change involving the ATP binding site and membrane-associated regions. Both ligands exert a clear stabilizing effect due to both enthalpic and entropic contributions. Competition experiments between ATP and K + showed that, when ATP is present, the inactivation rate coefficient exhibits a biphasic dependence on K + concentration. At low [K + ], destabilization of the enzyme is observed, while stabilization occurred at larger cation concentrations. This is not expected for a simple competition between the enzyme and two ligands that individually protect the enzyme. A model that includes enzyme species with none, one, or two K + and/or one molecule of ATP bound explains the experimental data. We concluded that, despite both ligands stabilizing the enzyme, the species with one K + and one ATP simultaneously bound is unstable.

Apollo telescope mount thermal systems unit thermal vacuum test

NASA Technical Reports Server (NTRS)

Trucks, H. F.; Hueter, U.; Wise, J. H.; Bachtel, F. D.

1971-01-01

The Apollo Telescope Mount's thermal systems unit was utilized to conduct a full-scale thermal vacuum test to verify the thermal design and the analytical techniques used to develop the thermal mathematical models. Thermal vacuum test philosophy, test objectives configuration, test monitoring, environment simulation, vehicle test performance, and data correlation are discussed. Emphasis is placed on planning and execution of the thermal vacuum test with particular attention on problems encountered in conducting a test of this maguitude.

An integrated, self-contained microfluidic cassette for isolation, amplification, and detection of nucleic acids

PubMed Central

Chen, Dafeng; Mauk, Michael; Qiu, Xianbo; Liu, Changchun; Kim, Jitae; Ramprasad, Sudhir; Ongagna, Serge; Abrams, William R.; Malamud, Daniel; Corstjens, Paul L. A. M.

2010-01-01

A self-contained, integrated, disposable, sample-to-answer, polycarbonate microfluidic cassette for nucleic acid—based detection of pathogens at the point of care was designed, constructed, and tested. The cassette comprises on-chip sample lysis, nucleic acid isolation, enzymatic amplification (polymerase chain reaction and, when needed, reverse transcription), amplicon labeling, and detection. On-chip pouches and valves facilitate fluid flow control. All the liquids and dry reagents needed for the various reactions are pre-stored in the cassette. The liquid reagents are stored in flexible pouches formed on the chip surface. Dry (RT-)PCR reagents are pre-stored in the thermal cycling, reaction chamber. The process operations include sample introduction; lysis of cells and viruses; solid-phase extraction, concentration, and purification of nucleic acids from the lysate; elution of the nucleic acids into a thermal cycling chamber and mixing with pre-stored (RT-)PCR dry reagents; thermal cycling; and detection. The PCR amplicons are labeled with digoxigenin and biotin and transmitted onto a lateral flow strip, where the target analytes bind to a test line consisting of immobilized avidin-D. The immobilized nucleic acids are labeled with up-converting phosphor (UCP) reporter particles. The operation of the cassette is automatically controlled by an analyzer that provides pouch and valve actuation with electrical motors and heating for the thermal cycling. The functionality of the device is demonstrated by detecting the presence of bacterial B.Cereus, viral armored RNA HIV, and HIV I virus in saliva samples. The cassette and actuator described here can be used to detect other diseases as well as the presence of bacterial and viral pathogens in the water supply and other fluids. PMID:20401537

An integrated, self-contained microfluidic cassette for isolation, amplification, and detection of nucleic acids.

PubMed

Chen, Dafeng; Mauk, Michael; Qiu, Xianbo; Liu, Changchun; Kim, Jitae; Ramprasad, Sudhir; Ongagna, Serge; Abrams, William R; Malamud, Daniel; Corstjens, Paul L A M; Bau, Haim H

2010-08-01

A self-contained, integrated, disposable, sample-to-answer, polycarbonate microfluidic cassette for nucleic acid-based detection of pathogens at the point of care was designed, constructed, and tested. The cassette comprises on-chip sample lysis, nucleic acid isolation, enzymatic amplification (polymerase chain reaction and, when needed, reverse transcription), amplicon labeling, and detection. On-chip pouches and valves facilitate fluid flow control. All the liquids and dry reagents needed for the various reactions are pre-stored in the cassette. The liquid reagents are stored in flexible pouches formed on the chip surface. Dry (RT-)PCR reagents are pre-stored in the thermal cycling, reaction chamber. The process operations include sample introduction; lysis of cells and viruses; solid-phase extraction, concentration, and purification of nucleic acids from the lysate; elution of the nucleic acids into a thermal cycling chamber and mixing with pre-stored (RT-)PCR dry reagents; thermal cycling; and detection. The PCR amplicons are labeled with digoxigenin and biotin and transmitted onto a lateral flow strip, where the target analytes bind to a test line consisting of immobilized avidin-D. The immobilized nucleic acids are labeled with up-converting phosphor (UCP) reporter particles. The operation of the cassette is automatically controlled by an analyzer that provides pouch and valve actuation with electrical motors and heating for the thermal cycling. The functionality of the device is demonstrated by detecting the presence of bacterial B.Cereus, viral armored RNA HIV, and HIV I virus in saliva samples. The cassette and actuator described here can be used to detect other diseases as well as the presence of bacterial and viral pathogens in the water supply and other fluids.

Charge-transfer interaction of drug quinidine with quinol, picric acid and DDQ: Spectroscopic characterization and biological activity studies towards understanding the drug-receptor mechanism.

PubMed

Eldaroti, Hala H; Gadir, Suad A; Refat, Moamen S; Adam, Abdel Majid A

2014-04-01

Investigation of charge-transfer (CT) complexes of drugs has been recognized as an important phenomenon in understanding of the drug-receptor binding mechanism. Structural, thermal, morphological and biological behavior of CT complexes formed between drug quinidine (Qui) as a donor and quinol (QL), picric acid (PA) or dichlorodicyanobenzoquinone (DDQ) as acceptors were reported. The newly synthesized CT complexes have been spectroscopically characterized via elemental analysis; infrared (IR), Raman, 1 H NMR and electronic absorption spectroscopy; powder X-ray diffraction (PXRD); thermogravimetric (TG) analysis and scanning electron microscopy (SEM). It was found that the obtained complexes are nanoscale, semi-crystalline particles, thermally stable and spontaneous. The molecular composition of the obtained complexes was determined using spectrophotometric titration method and was found to be 1:1 ratios (donor:acceptor). Finally, the biological activities of the obtained CT complexes were tested for their antibacterial activities. The results obtained herein are satisfactory for estimation of drug Qui in the pharmaceutical form.

Synthesis, characterization, thermal and biological evaluation of Cu (II), Co (II) and Ni (II) complexes of azo dye ligand containing sulfamethaxazole moiety

NASA Astrophysics Data System (ADS)

Mallikarjuna, N. M.; Keshavayya, J.; Maliyappa, M. R.; Shoukat Ali, R. A.; Venkatesh, Talavara

2018-08-01

A novel bioactive Cu (II), Co (II) and Ni (II) complexes of the azo dye ligand (L) derived from sulfamethoxazole were synthesized. The structures of the newly synthesized compounds were characterized by elemental analysis, molar conductance, magnetic susceptibility, FTIR, UV-visible, 1H NMR, mass, thermal and powder XRD spectral techniques. Molar conductivity measurements in DMSO solution confirmed the non-electrolytic nature of the complexes. All the synthesized metal complexes were found to be monomeric and showed square planar geometry except the Co (II) complex which has six coordinate, octahedral environment. The metal complexes have exhibited potential growth inhibitory effect against tested bacterial strains as compared to the free ligand. The ligand and complexes have also shown significant antioxidant and Calf Thymus DNA cleavage activities. Further, the in silico molecular docking studies were performed to predict the possible binding sites of the ligand (L) and its metal complexes with target receptor Glu-6P.

Protein dynamics and motions in relation to their functions: several case studies and the underlying mechanisms

PubMed Central

Yang, Li-Quan; Sang, Peng; Tao, Yan; Fu, Yun-Xin; Zhang, Ke-Qin; Xie, Yue-Hui; Liu, Shu-Qun

2013-01-01

Proteins are dynamic entities in cellular solution with functions governed essentially by their dynamic personalities. We review several dynamics studies on serine protease proteinase K and HIV-1 gp120 envelope glycoprotein to demonstrate the importance of investigating the dynamic behaviors and molecular motions for a complete understanding of their structure–function relationships. Using computer simulations and essential dynamic (ED) analysis approaches, the dynamics data obtained revealed that: (i) proteinase K has highly flexible substrate-binding site, thus supporting the induced-fit or conformational selection mechanism of substrate binding; (ii) Ca2+ removal from proteinase K increases the global conformational flexibility, decreases the local flexibility of substrate-binding region, and does not influence the thermal motion of catalytic triad, thus explaining the experimentally determined decreased thermal stability, reduced substrate affinity, and almost unchanged catalytic activity upon Ca2+ removal; (iii) substrate binding affects the large concerted motions of proteinase K, and the resulting dynamic pocket can be connected to substrate binding, orientation, and product release; (iv) amino acid mutations 375 S/W and 423 I/P of HIV-1 gp120 have distinct effects on molecular motions of gp120, facilitating 375 S/W mutant to assume the CD4-bound conformation, while 423 I/P mutant to prefer for CD4-unliganded state. The mechanisms underlying protein dynamics and protein–ligand binding, including the concept of the free energy landscape (FEL) of the protein–solvent system, how the ruggedness and variability of FEL determine protein's dynamics, and how the three ligand-binding models, the lock-and-key, induced-fit, and conformational selection are rationalized based on the FEL theory are discussed in depth. PMID:23527883

Protein dynamics and motions in relation to their functions: several case studies and the underlying mechanisms.

PubMed

Yang, Li-Quan; Sang, Peng; Tao, Yan; Fu, Yun-Xin; Zhang, Ke-Qin; Xie, Yue-Hui; Liu, Shu-Qun

2014-01-01

Proteins are dynamic entities in cellular solution with functions governed essentially by their dynamic personalities. We review several dynamics studies on serine protease proteinase K and HIV-1 gp120 envelope glycoprotein to demonstrate the importance of investigating the dynamic behaviors and molecular motions for a complete understanding of their structure-function relationships. Using computer simulations and essential dynamic (ED) analysis approaches, the dynamics data obtained revealed that: (i) proteinase K has highly flexible substrate-binding site, thus supporting the induced-fit or conformational selection mechanism of substrate binding; (ii) Ca(2+) removal from proteinase K increases the global conformational flexibility, decreases the local flexibility of substrate-binding region, and does not influence the thermal motion of catalytic triad, thus explaining the experimentally determined decreased thermal stability, reduced substrate affinity, and almost unchanged catalytic activity upon Ca(2+) removal; (iii) substrate binding affects the large concerted motions of proteinase K, and the resulting dynamic pocket can be connected to substrate binding, orientation, and product release; (iv) amino acid mutations 375 S/W and 423 I/P of HIV-1 gp120 have distinct effects on molecular motions of gp120, facilitating 375 S/W mutant to assume the CD4-bound conformation, while 423 I/P mutant to prefer for CD4-unliganded state. The mechanisms underlying protein dynamics and protein-ligand binding, including the concept of the free energy landscape (FEL) of the protein-solvent system, how the ruggedness and variability of FEL determine protein's dynamics, and how the three ligand-binding models, the lock-and-key, induced-fit, and conformational selection are rationalized based on the FEL theory are discussed in depth.

A Lorentz model for weak magnetic field bioeffects: part I--thermal noise is an essential component of AC/DC effects on bound ion trajectory.

PubMed

Muehsam, David J; Pilla, Arthur A

2009-09-01

We have previously employed the Lorentz-Langevin model to describe the effects of weak exogenous magnetic fields via the classical Lorentz force on a charged ion bound in a harmonic oscillator potential, in the presence of thermal noise forces. Previous analyses predicted that microT-range fields give rise to a rotation of the oscillator orientation at the Larmor frequency and bioeffects were based upon the assumption that the classical trajectory of the bound charge itself could modulate a biochemical process. Here, it is shown that the thermal component of the motion follows the Larmor trajectory. The results show that the Larmor frequency is independent of the thermal noise strength, and the motion retains the form of a coherent oscillator throughout the binding lifetime, rather than devolving into a random walk. Thermal equilibration results in a continual increase in the vibrational amplitude of the rotating oscillator towards the steady-state amplitude, but does not affect the Larmor orbit. Thus, thermal noise contributes to, rather than inhibits, the effect of the magnetic field upon reactivity. Expressions are derived for the ensemble average of position and the velocity of the thermal component of the oscillator motion. The projection of position and velocity onto a Cartesian axis measures the nonuniformity of the Larmor trajectory and is illustrated for AC and combined AC/DC magnetic fields, suggesting a means of interpreting resonance phenomena. It is noted that the specific location and height of resonances are dependent upon binding lifetime and initial AC phase.

Animal ice-binding (antifreeze) proteins and glycolipids: an overview with emphasis on physiological function.

PubMed

Duman, John G

2015-06-01

Ice-binding proteins (IBPs) assist in subzero tolerance of multiple cold-tolerant organisms: animals, plants, fungi, bacteria etc. IBPs include: (1) antifreeze proteins (AFPs) with high thermal hysteresis antifreeze activity; (2) low thermal hysteresis IBPs; and (3) ice-nucleating proteins (INPs). Several structurally different IBPs have evolved, even within related taxa. Proteins that produce thermal hysteresis inhibit freezing by a non-colligative mechanism, whereby they adsorb onto ice crystals or ice-nucleating surfaces and prevent further growth. This lowers the so-called hysteretic freezing point below the normal equilibrium freezing/melting point, producing a difference between the two, termed thermal hysteresis. True AFPs with high thermal hysteresis are found in freeze-avoiding animals (those that must prevent freezing, as they die if frozen) especially marine fish, insects and other terrestrial arthropods where they function to prevent freezing at temperatures below those commonly experienced by the organism. Low thermal hysteresis IBPs are found in freeze-tolerant organisms (those able to survive extracellular freezing), and function to inhibit recrystallization - a potentially damaging process whereby larger ice crystals grow at the expense of smaller ones - and in some cases, prevent lethal propagation of extracellular ice into the cytoplasm. Ice-nucleator proteins inhibit supercooling and induce freezing in the extracellular fluid at high subzero temperatures in many freeze-tolerant species, thereby allowing them to control the location and temperature of ice nucleation, and the rate of ice growth. Numerous nuances to these functions have evolved. Antifreeze glycolipids with significant thermal hysteresis activity were recently identified in insects, frogs and plants. © 2015. Published by The Company of Biologists Ltd.

Increased Hyperalgesia and Proinflammatory Cytokines in the Spinal Cord and Dorsal Root Ganglion After Surgery and/or Fentanyl Administration in Rats

PubMed Central

Chang, Lu; Ye, Fang; Luo, Quehua; Tao, Yuanxiang

2018-01-01

BACKGROUND: Perioperative fentanyl has been reported to induce hyperalgesia and increase postoperative pain. In this study, we tried to investigate behavioral hyperalgesia, the expression of proinflammatory cytokines, such as interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), and the activation of microglia in the spinal cord and dorsal root ganglion (DRG) in a rat model of surgical plantar incision with or without perioperative fentanyl. METHODS: Four groups of rats (n = 32 for each group) were subcutaneously injected with fentanyl at 60 μg/kg or normal saline for 4 times with 15-minute intervals. Plantar incisions were made to rats in 2 groups after the second drug injection. Mechanical and thermal nociceptive thresholds were assessed by the tail pressure test and paw withdrawal test on the day before, at 1, 2, 3, 4 hours, and on the days 1–7 after drug injection. The lumbar spinal cord, bilateral DRG, and cerebrospinal fluid of 4 rats in each group were collected to measure IL-1β, IL-6, and TNF-α on the day before, at the fourth hour, and on the days 1, 3, 5, and 7 after drug injection. The lumbar spinal cord and bilateral DRG were removed to detect the ionized calcium-binding adapter molecule 1 on the day before and on the days 1 and 7 after drug injection. RESULTS: Rats injected with normal saline only demonstrated no significant mechanical or thermal hyperalgesia or any increases of IL-1β, IL-6, and TNF-α in the spinal cord or DRG. However, injection of fentanyl induced analgesia within as early as 4 hours and a significant delayed tail mechanical and bilateral plantar thermal hyperalgesia after injections lasting for 2 days, while surgical plantar incision induced a significant mechanical and thermal hyperalgesia lasting for 1–4 days. The combination of fentanyl and incision further aggravated the hyperalgesia and prolonged the duration of hyperalgesia. The fentanyl or surgical incision upregulated the expression of IL-1β, IL-6, and TNF-α in the spinal cord and bilateral DRG for more than 7 days and increase of ionized calcium-binding adapter molecule 1 in the spinal cord. The combination of fentanyl and incision resulted in higher increase of IL-1β, IL-6, and TNF-α in the spinal cord and bilateral DRG. CONCLUSIONS: The surgical plantar incision with or without perioperative fentanyl induced significant mechanical and thermal hyperalgesia, an increased expression of IL-1β, IL-6, TNF-α in the spinal cord and DRG, and activation of microglia in the spinal cord. PMID:29135586

Increased Hyperalgesia and Proinflammatory Cytokines in the Spinal Cord and Dorsal Root Ganglion After Surgery and/or Fentanyl Administration in Rats.

PubMed

Chang, Lu; Ye, Fang; Luo, Quehua; Tao, Yuanxiang; Shu, Haihua

2018-01-01

Perioperative fentanyl has been reported to induce hyperalgesia and increase postoperative pain. In this study, we tried to investigate behavioral hyperalgesia, the expression of proinflammatory cytokines, such as interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), and the activation of microglia in the spinal cord and dorsal root ganglion (DRG) in a rat model of surgical plantar incision with or without perioperative fentanyl. Four groups of rats (n = 32 for each group) were subcutaneously injected with fentanyl at 60 μg/kg or normal saline for 4 times with 15-minute intervals. Plantar incisions were made to rats in 2 groups after the second drug injection. Mechanical and thermal nociceptive thresholds were assessed by the tail pressure test and paw withdrawal test on the day before, at 1, 2, 3, 4 hours, and on the days 1-7 after drug injection. The lumbar spinal cord, bilateral DRG, and cerebrospinal fluid of 4 rats in each group were collected to measure IL-1β, IL-6, and TNF-α on the day before, at the fourth hour, and on the days 1, 3, 5, and 7 after drug injection. The lumbar spinal cord and bilateral DRG were removed to detect the ionized calcium-binding adapter molecule 1 on the day before and on the days 1 and 7 after drug injection. Rats injected with normal saline only demonstrated no significant mechanical or thermal hyperalgesia or any increases of IL-1β, IL-6, and TNF-α in the spinal cord or DRG. However, injection of fentanyl induced analgesia within as early as 4 hours and a significant delayed tail mechanical and bilateral plantar thermal hyperalgesia after injections lasting for 2 days, while surgical plantar incision induced a significant mechanical and thermal hyperalgesia lasting for 1-4 days. The combination of fentanyl and incision further aggravated the hyperalgesia and prolonged the duration of hyperalgesia. The fentanyl or surgical incision upregulated the expression of IL-1β, IL-6, and TNF-α in the spinal cord and bilateral DRG for more than 7 days and increase of ionized calcium-binding adapter molecule 1 in the spinal cord. The combination of fentanyl and incision resulted in higher increase of IL-1β, IL-6, and TNF-α in the spinal cord and bilateral DRG. The surgical plantar incision with or without perioperative fentanyl induced significant mechanical and thermal hyperalgesia, an increased expression of IL-1β, IL-6, TNF-α in the spinal cord and DRG, and activation of microglia in the spinal cord.

Characterization of nicotine binding in mouse brain and comparison with the binding of alpha-bungarotoxin and quinuclidinyl benzilate

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

Marks, M.J.; Collins, A.C.

1982-11-01

The binding of (/sup 3/H)nicotine to mouse brain has been measured and subsequently compared with the binding of (/sup 125/I)alpha-bungarotoxin (alpha-BTX) and L-(/sup 3/H)quinuclidinyl benzilate (QNB). The binding of nicotine was saturable, reversible, and stereospecific. Although the rates of association and dissociation of nicotine were temperature-dependent, the incubation temperature had no effect on either KD or Bmax. Nicotine binding was unaffected by the addition of NaCl, KCl, CaCl/sub 2/, or MgSO/sub 4/ to the incubation medium. Nicotinic cholinergic agonists were potent inhibitors of nicotine binding; however, nicotinic antagonists were poor inhibitors. The regional distribution of binding was not uniform: midbrainmore » and striatum contained the highest number of receptors, whereas cerebellum had the fewest. Differences in site densities, regional distribution, inhibitor potencies, and thermal denaturation indicated that nicotine binding was not the same as either QNB or alpha-BTX binding, and therefore that receptors for nicotine may represent a unique population of cholinergic receptors.« less

Binding constants of membrane-anchored receptors and ligands depend strongly on the nanoscale roughness of membranes.

PubMed

Hu, Jinglei; Lipowsky, Reinhard; Weikl, Thomas R

2013-09-17

Cell adhesion and the adhesion of vesicles to the membranes of cells or organelles are pivotal for immune responses, tissue formation, and cell signaling. The adhesion processes depend sensitively on the binding constant of the membrane-anchored receptor and ligand proteins that mediate adhesion, but this constant is difficult to measure in experiments. We have investigated the binding of membrane-anchored receptor and ligand proteins with molecular dynamics simulations. We find that the binding constant of the anchored proteins strongly decreases with the membrane roughness caused by thermally excited membrane shape fluctuations on nanoscales. We present a theory that explains the roughness dependence of the binding constant for the anchored proteins from membrane confinement and that relates this constant to the binding constant of soluble proteins without membrane anchors. Because the binding constant of soluble proteins is readily accessible in experiments, our results provide a useful route to compute the binding constant of membrane-anchored receptor and ligand proteins.

Regolith-Derived Heat Shield for Planetary Body Entry and Descent System with In Situ Fabrication

NASA Technical Reports Server (NTRS)

Hogue, Michael D.; Mueller, Robert P.; Rasky, Daniel; Hintze, Paul; Sibille, Laurent

2012-01-01

In this paper we will discuss a new mass-efficient and innovative way of protecting high-mass spacecraft during planetary Entry, Descent & Landing (EDL). Heat shields fabricated in situ can provide a thermal-protection system (TPS) for spacecraft that routinely enter a planetary atmosphere. By fabricating the heat shield with space resources from regolith materials available on moons and asteroids, it is possible to avoid launching the heat-shield mass from Earth. Two regolith processing and manufacturing methods will be discussed: 1) Compression and sintering of the regolith to yield low density materials; 2) Formulations of a High-temperature silicone RTV (Room Temperature Vulcanizing) compound are used to bind regolith particles together. The overall positive results of torch flame impingement tests and plasma arc jet testing on the resulting samples will also be discussed.

Cryo-protective effect of an ice-binding protein derived from Antarctic bacteria.

PubMed

Mangiagalli, Marco; Bar-Dolev, Maya; Tedesco, Pietro; Natalello, Antonino; Kaleda, Aleksei; Brocca, Stefania; de Pascale, Donatella; Pucciarelli, Sandra; Miceli, Cristina; Braslavsky, Ido; Lotti, Marina

2017-01-01

Cold environments are populated by organisms able to contravene deleterious effects of low temperature by diverse adaptive strategies, including the production of ice binding proteins (IBPs) that inhibit the growth of ice crystals inside and outside cells. We describe the properties of such a protein (EfcIBP) identified in the metagenome of an Antarctic biological consortium composed of the ciliate Euplotes focardii and psychrophilic non-cultured bacteria. Recombinant EfcIBP can resist freezing without any conformational damage and is moderately heat stable, with a midpoint temperature of 66.4 °C. Tested for its effects on ice, EfcIBP shows an unusual combination of properties not reported in other bacterial IBPs. First, it is one of the best-performing IBPs described to date in the inhibition of ice recrystallization, with effective concentrations in the nanomolar range. Moreover, EfcIBP has thermal hysteresis activity (0.53 °C at 50 μm) and it can stop a crystal from growing when held at a constant temperature within the thermal hysteresis gap. EfcIBP protects purified proteins and bacterial cells from freezing damage when exposed to challenging temperatures. EfcIBP also possesses a potential N-terminal signal sequence for protein transport and a DUF3494 domain that is common to secreted IBPs. These features lead us to hypothesize that the protein is either anchored at the outer cell surface or concentrated around cells to provide survival advantage to the whole cell consortium. © 2016 Federation of European Biochemical Societies.

Utilization of Yatagan Power Plant Fly Ash in Production of Building Bricks

NASA Astrophysics Data System (ADS)

Önel, Öznur; Tanriverdi, Mehmet; Cicek, Tayfun

2017-12-01

Fly ash is a by-product of coal combustion, which accumulates in large quantities near the coal-fired power plants as waste material. Fly ash causes serious operational and environmental problems. In this study, fly ash from Yatağgan thermal power plant was used to produce light-weight building bricks. The study aimed to reduce the problems related to fly ash by creating a new area for their use. The optimum process parameters were determined for the production of real size bricks to be used in construction industry. The commercial size bricks (200 × 200 × 90-110 mm) were manufactured using pilot size equipment. Mechanical properties, thermal conductivity coefficients, freezing and thawing strengths, water absorption rates, and unit volume weights of the bricks were determined. Etringite (Ca6Al2 (SO4)3 (OH)12 25(H2O)) and Calcium Silicate Hydrate (2CaO.SiO2.4H2O) were identified as the binding phases in the real size brick samples after 2 days of pre-curing and 28 days curing at 50° C and 95% relative moisture. The water absorption rate was found to be 27.7 % in terms of mass. The mechanical and bending strength of the brick samples with unit volume weight of 1.29 g.cm-3 were determined as 6.75 MPa and 1,56 MPa respectively. The thermal conductivity of the fly ash bricks was measured in average as 0,340 W m-1 K-1. The fly ash sample produced was subjected to toxic leaching tests (Toxic Property Leaching Procedure (EPA-TCLP 1311), Single-step BATCH Test and Method-A Disintegration Procedure (ASTM)). The results of these tests suggested that the materials could be classified as non-hazardous wastes / materials.

Ultrasonic Nondestructive Characterization of Adhesive Bonds

NASA Technical Reports Server (NTRS)

Qu, Jianmin

1997-01-01

Qualitative measurements of adhesion or binding forces can be accomplished, for example, by using the reflection coefficient of an ultrasound or by using thermal waves (Light and Kwun, 1989, Achenbach and Parikh, 1991, and Bostrom and wickham, 1991). However, a quantitative determination of binding forces is rather difficult. It has been observed that higher harmonics of the fundamental frequency are generated when an ultrasound passes through a nonlinear material. It seems that such non-linearity can be effectively used to characterize the bond strength. Several theories have been developed to model this nonlinear effect (Adler and Nagy, 1991; Achenbach and Parikh, 1991; Parikh and Achenbach, 1992; and Hirose and Kitahara, 1992; Anastasi and Roberts, 1992). Based on a microscopic description of the nonlinear interface binding force, a quantitative method was presented by Pangraz and Arnold (1994). Recently, Tang, Cheng and Achenbach (1997) made a comparison between the experimental and simulated results based on this theoretical model. A water immersion mode-converted shear wave through-transmission setup was used by Berndt and Green (1997) to analyze the nonlinear acoustic behavior of the adhesive bond. In this project, the nonlinear responses of an adhesive joint was investigated through transmission tests of ultrasonic wave and analyzed by the finite element simulations. The higher order harmonics were obtained in the tests. It is found that the amplitude of higher harmonics increases as the aging increases, especially the 3dorder harmonics. Results from the numerical simulation show that the material nonlinearity does indeed generate higher order harmonics. In particular, the elastic-perfect plastic behavior generates significant 3rd and 5th order harmonics.

Proportional and Integral Thermal Control System for Large Scale Heating Tests

NASA Technical Reports Server (NTRS)

Fleischer, Van Tran

2015-01-01

The National Aeronautics and Space Administration Armstrong Flight Research Center (Edwards, California) Flight Loads Laboratory is a unique national laboratory that supports thermal, mechanical, thermal/mechanical, and structural dynamics research and testing. A Proportional Integral thermal control system was designed and implemented to support thermal tests. A thermal control algorithm supporting a quartz lamp heater was developed based on the Proportional Integral control concept and a linearized heating process. The thermal control equations were derived and expressed in terms of power levels, integral gain, proportional gain, and differences between thermal setpoints and skin temperatures. Besides the derived equations, user's predefined thermal test information generated in the form of thermal maps was used to implement the thermal control system capabilities. Graphite heater closed-loop thermal control and graphite heater open-loop power level were added later to fulfill the demand for higher temperature tests. Verification and validation tests were performed to ensure that the thermal control system requirements were achieved. This thermal control system has successfully supported many milestone thermal and thermal/mechanical tests for almost a decade with temperatures ranging from 50 F to 3000 F and temperature rise rates from -10 F/s to 70 F/s for a variety of test articles having unique thermal profiles and test setups.

Study on immobilization of yeast alcohol dehydrogenase on nanocrystalline Ni-Co ferrites as magnetic support.

PubMed

Shakir, Mohammad; Nasir, Zeba; Khan, Mohd Shoeb; Lutfullah; Alam, Md Fazle; Younus, Hina; Al-Resayes, Saud Ibrahim

2015-01-01

The covalent binding of yeast alcohol dehydrogenase (YADH) enzyme complex in a series of magnetic crystalline Ni-Co nanoferrites, synthesized via sol-gel auto combustion technique was investigated. The structural analysis, morphology and magnetic properties of Ni-Co nanoferrites were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), vibrating-sample magnetometer (VSM), high resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectroscopy (FTIR). The comparative analysis of the HRTEM micrographs of bare magnetic nanoferrite particles and particles immobilized with enzyme revealed an uniform distribution of the particles in both the cases without undergoing change in the size which was found to be in the range 20-30 nm. The binding of YADH to Ni-Co nanoferrites and the possible binding mechanism have been suggested by comparing the FTIR results. The binding properties of the immobilized YADH enzyme were also studied by kinetic parameters, optimum operational pH, temperature, thermal stability and reusability. The immobilized YADH exhibits enhanced thermal stability as compared to the free enzyme over a wide range of temperature and pH, and showed good durability after recovery by magnetic separation for repeated use. Copyright © 2014 Elsevier B.V. All rights reserved.

Structural and Biochemical Consequences of Disease-Causing Mutations in the Ankyrin Repeat Domain of the Human TRPV4 Channel

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

Inada, Hitoshi; Procko, Erik; Sotomayor, Marcos

2012-10-23

The TRPV4 calcium-permeable cation channel plays important physiological roles in osmosensation, mechanosensation, cell barrier formation, and bone homeostasis. Recent studies reported that mutations in TRPV4, including some in its ankyrin repeat domain (ARD), are associated with human inherited diseases, including neuropathies and skeletal dysplasias, probably because of the increased constitutive activity of the channel. TRPV4 activity is regulated by the binding of calmodulin and small molecules such as ATP to the ARD at its cytoplasmic N-terminus. We determined structures of ATP-free and -bound forms of human TRPV4-ARD and compared them with available TRPV-ARD structures. The third inter-repeat loop region (Fingermore » 3 loop) is flexible and may act as a switch to regulate channel activity. Comparisons of TRPV-ARD structures also suggest an evolutionary link between ARD structure and ATP binding ability. Thermal stability analyses and molecular dynamics simulations suggest that ATP increases stability in TRPV-ARDs that can bind ATP. Biochemical analyses of a large panel of TRPV4-ARD mutations associated with human inherited diseases showed that some impaired thermal stability while others weakened ATP binding ability, suggesting molecular mechanisms for the diseases.« less

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

Miles, Andrew J.; Fedosova, Natalya U.; Hoffmann, Søren V.

Highlights: •Ouabain binding to pig and shark Na,K-ATPase enhances thermal stability. •Ouabain stabilises both membrane-bound and solubilised Na,K-ATPase. •Synchrotron radiation circular dichroism is used for structure determination. •Secondary structure in general is not affected by ouabain binding. •Stabilisation is due to re-arrangement of tertiary structure. -- Abstract: Cardiotonic steroids such as ouabain bind with high affinity to the membrane-bound cation-transporting P-type Na,K-ATPase, leading to complete inhibition of the enzyme. Using synchrotron radiation circular dichroism spectroscopy we show that the enzyme-ouabain complex is less susceptible to thermal denaturation (unfolding) than the ouabain-free enzyme, and this protection is observed with Na,K-ATPase purifiedmore » from pig kidney as well as from shark rectal glands. It is also shown that detergent-solubilised preparations of Na,K-ATPase are stabilised by ouabain, which could account for the successful crystallisation of Na,K-ATPase in the ouabain-bound form. The secondary structure is not significantly affected by the binding of ouabain. Ouabain appears however, to induce a reorganization of the tertiary structure towards a more compact protein structure which is less prone to unfolding; recent crystal structures of the two enzymes are consistent with this interpretation. These circular dichroism spectroscopic studies in solution therefore provide complementary information to that provided by crystallography.« less

Strong Enrichment of Aromatic Residues in Binding Sites from a Charge-neutralized Hyperthermostable Sso7d Scaffold Library.

PubMed

Traxlmayr, Michael W; Kiefer, Jonathan D; Srinivas, Raja R; Lobner, Elisabeth; Tisdale, Alison W; Mehta, Naveen K; Yang, Nicole J; Tidor, Bruce; Wittrup, K Dane

2016-10-21

The Sso7d protein from the hyperthermophilic archaeon Sulfolobus solfataricus is an attractive binding scaffold because of its small size (7 kDa), high thermal stability (T m of 98 °C), and absence of cysteines and glycosylation sites. However, as a DNA-binding protein, Sso7d is highly positively charged, introducing a strong specificity constraint for binding epitopes and leading to nonspecific interaction with mammalian cell membranes. In the present study, we report charge-neutralized variants of Sso7d that maintain high thermal stability. Yeast-displayed libraries that were based on this reduced charge Sso7d (rcSso7d) scaffold yielded binders with low nanomolar affinities against mouse serum albumin and several epitopes on human epidermal growth factor receptor. Importantly, starting from a charge-neutralized scaffold facilitated evolutionary adaptation of binders to differentially charged epitopes on mouse serum albumin and human epidermal growth factor receptor, respectively. Interestingly, the distribution of amino acids in the small and rigid binding surface of enriched rcSso7d-based binders is very different from that generally found in more flexible antibody complementarity-determining region loops but resembles the composition of antibody-binding energetic hot spots. Particularly striking was a strong enrichment of the aromatic residues Trp, Tyr, and Phe in rcSso7d-based binders. This suggests that the rigidity and small size of this scaffold determines the unusual amino acid composition of its binding sites, mimicking the energetic core of antibody paratopes. Despite the high frequency of aromatic residues, these rcSso7d-based binders are highly expressed, thermostable, and monomeric, suggesting that the hyperstability of the starting scaffold and the rigidness of the binding surface confer a high tolerance to mutation. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Method of Suppressing Sublimation in Advanced Thermoelectric Devices

NASA Technical Reports Server (NTRS)

Sakamoto, Jeffrey S. (Inventor); Caillat, Thierry (Inventor); Fleurial, Jean-Pierre (Inventor); Snyder, G. Jeffrey (Inventor)

2009-01-01

A method of applying a physical barrier to suppress thermal decomposition near a surface of a thermoelectric material including applying a continuous metal foil to a predetermined portion of the surface of the thermoelectric material, physically binding the continuous metal foil to the surface of the thermoelectric material using a binding member, and heating in a predetermined atmosphere the applied and physically bound continuous metal foil and the thermoelectric material to a sufficient temperature in order to promote bonding between the continuous metal foil and the surface of the thermoelectric material. The continuous metal foil forms a physical barrier to enclose a predetermined portion of the surface. Thermal decomposition is suppressed at the surface of the thermoelectric material enclosed by the physical barrier when the thermoelectric element is in operation.

The sorption properties of polymers with molecular imprints of 2,4-dichlorophenoxyacetic acid synthesized by various methods

NASA Astrophysics Data System (ADS)

Dmitrienko, S. G.; Popov, S. A.; Chumichkina, Yu. A.; Zolotov, Yu. A.

2011-03-01

New sorbents, polymers with molecular imprints of 2,4-dichlorophenoxyacetic acid (2,4-D), were prepared on the basis of acrylamide. The sorbents were synthesized by thermal polymerization methods with and without the use of ultrasound, photopolymerization, and suspension polymerization. The specific surface area of the products was estimated and their sorption properties were studied. Polymers with molecular imprints prepared by thermal polymerization with the use of ultrasound and by suspension polymerization showed the best ability to repeatedly bind 2,4-D. The selectivity of polymers was estimated for the example of structurally related compounds. It was shown that the method of synthesis decisively influenced not only the ability of sorbents to repeatedly bind 2,4-D but also their selectivity.

Structure of the Biliverdin Cofactor in the Pfr State of Bathy and Prototypical Phytochromes*

PubMed Central

Salewski, Johannes; Escobar, Francisco Velazquez; Kaminski, Steve; von Stetten, David; Keidel, Anke; Rippers, Yvonne; Michael, Norbert; Scheerer, Patrick; Piwowarski, Patrick; Bartl, Franz; Frankenberg-Dinkel, Nicole; Ringsdorf, Simone; Gärtner, Wolfgang; Lamparter, Tilman; Mroginski, Maria Andrea; Hildebrandt, Peter

2013-01-01

Phytochromes act as photoswitches between the red- and far-red absorbing parent states of phytochromes (Pr and Pfr). Plant phytochromes display an additional thermal conversion route from the physiologically active Pfr to Pr. The same reaction pattern is found in prototypical biliverdin-binding bacteriophytochromes in contrast to the reverse thermal transformation in bathy bacteriophytochromes. However, the molecular origin of the different thermal stabilities of the Pfr states in prototypical and bathy bacteriophytochromes is not known. We analyzed the structures of the chromophore binding pockets in the Pfr states of various bathy and prototypical biliverdin-binding phytochromes using a combined spectroscopic-theoretical approach. For the Pfr state of the bathy phytochrome from Pseudomonas aeruginosa, the very good agreement between calculated and experimental Raman spectra of the biliverdin cofactor is in line with important conclusions of previous crystallographic analyses, particularly the ZZEssa configuration of the chromophore and its mode of covalent attachment to the protein. The highly homogeneous chromophore conformation seems to be a unique property of the Pfr states of bathy phytochromes. This is in sharp contrast to the Pfr states of prototypical phytochromes that display conformational equilibria between two sub-states exhibiting small structural differences at the terminal methine bridges A-B and C-D. These differences may mainly root in the interactions of the cofactor with the highly conserved Asp-194 that occur via its carboxylate function in bathy phytochromes. The weaker interactions via the carbonyl function in prototypical phytochromes may lead to a higher structural flexibility of the chromophore pocket opening a reaction channel for the thermal (ZZE → ZZZ) Pfr to Pr back-conversion. PMID:23603902

Binding of vitamin A by casein micelles in commercial skim milk

PubMed Central

Mohan, M. S.; Jurat-Fuentes, J. L.; Harte, F.

2015-01-01

Recent studies have shown that reassembled micelles formed by caseinates and purified casein fractions (αs- and β-casein) bind to hydrophobic compounds, including curcumin, docosahexaenoic acid, and vitamin D. However, limited research has been done on the binding of hydrophobic compounds by unmodified casein micelles in skim milk. In the present study, we investigated the ability of casein micelles in commercial skim milk to associate with vitamin A (retinyl palmitate), a fat-soluble vitamin commonly used to fortify milk. Milk protein fractions from different commercially available skim milk samples subjected to different processing treatments, including pasteurized, ultrapasteurized, organic pasteurized, and organic ultrapasteurized milks, were separated by fast protein liquid chromatography. The fractions within each peak were combined and freeze-dried. Sodium dodecyl sulfate-PAGE with silver staining was used to identify the proteins present in each of the fractions. The skim milk samples and fractions were extracted for retinyl palmitate and quantified against a standard using normal phase-HPLC. Retinyl palmitate was found to associate with the fraction of skim milk containing caseins, whereas the other proteins (BSA, β-lactoglobulin, α-lactalbumin) did not show any binding. The retinyl palmitate content in the various samples ranged from 1.59 to 2.48 μg of retinyl palmitate per mL of milk. The casein fractions contained between 14 and 40% of total retinyl palmitate in the various milks tested. The variation in the retention of vitamin A by caseins was probably explained by differences in the processing of different milk samples, including thermal treatment, the form of vitamin A emulsion used for fortification, and the point of fortification during processing. Unmodified casein micelles have a strong intrinsic affinity toward the binding of vitamin A used to fortify commercially available skim milks. PMID:23261375

Investigation of the interaction between berberine and nucleosomes in solution: Spectroscopic and equilibrium dialysis approach

NASA Astrophysics Data System (ADS)

Rabbani-Chadegani, Azra; Mollaei, Hossein; Sargolzaei, Javad

2017-02-01

Berberine is a natural plant alkaloid with high pharmacological potential. Although its interaction with free DNA has been the subject of several reports, to date there is no work concerning the effect of berberine on nucleoprotein structure of DNA, the nucleosomes. The present study focuses on the binding affinity of berberine to nucleosomes and histone H1 employing various spectroscopic techniques, fluorescence, circular dichroism, thermal denaturation as well as equilibrium dialysis. The results showed that the binding of berberine to nucleosomes is positive cooperative with Ka = 5.57 × 103 M- 1. Berberine quenched with the chromophores of protein moiety of nucleosomes and reduced fluorescence emission intensity at 335 nm with Ksv value of 0.135. Binding of berberine to nucleosomes decreased the absorbance at 210 and 260 nm, produced hypochromicity in thermal denaturation profiles and its affinity to nucleoprotein structure of nucleosomes was much higher than to free DNA. Berberine also exhibited high affinity to histone H1 in solution and the binding was positive cooperative with. Ka = 3.61 × 103 M- 1. Moreover berberine decreased fluorescence emission intensity of H1 by quenching with tyrosine residue in its globular core domain. The circular dichroism profiles demonstrated that the binding of drug induced secondary structural changes in both DNA stacking and histone H1. It is concluded that berberine is genotoxic drug, interacts with nucleosomes and in this process histone H1 is involved to exert its anticancer activity.

Dynamics and unfolding pathway of chimeric azurin variants: insights from molecular dynamics simulation.

PubMed

Evoli, Stefania; Guzzi, Rita; Rizzuti, Bruno

2013-10-01

The spectroscopic, thermal, and functional properties of blue copper proteins can be modulated by mutations in the metal binding loop. Molecular dynamics simulation was used to compare the conformational properties of azurin and two chimeric variants, which were obtained by inserting into the azurin scaffold the copper binding loop of amicyanin and plastocyanin, respectively. Simulations at room temperature show that the proteins retain their overall structure and exhibit concerted motions among specific inner regions, as revealed by principal component analysis. Molecular dynamics at high temperature indicates that the first events in the unfolding pathway are structurally similar in the three proteins and unfolding starts from the region of the α-helix that is far from the metal binding loop. The results provide details of the denaturation process that are consistent with experimental data and in close agreement with other computational approaches, suggesting a distinct mechanism of unfolding of azurin and its chimeric variants. Moreover, differences observed in the dynamics of specific regions in the three proteins correlate with their thermal behavior, contributing to the determination of the basic factors that influence the stability.

Thermal stability and unfolding pathways of hyperthermophilic and mesophilic periplasmic binding proteins studied by molecular dynamics simulation.

PubMed

Chen, Lin; Li, Xue; Wang, Ruige; Fang, Fengqin; Yang, Wanli; Kan, Wei

2016-07-01

The ribose binding protein (RBP), a sugar-binding periplasmic protein, is involved in the transport and signaling processes in both prokaryotes and eukaryotes. Although several cellular and structural studies have been reported, a description of the thermostability of RBP at the molecular level remains elusive. Focused on the hyperthermophilic Thermoytoga maritima RBP (tmRBP) and mesophilic Escherichia coli homolog (ecRBP), we applied molecular dynamics simulations at four different temperatures (300, 380, 450, and 500 K) to obtain a deeper insight into the structural features responsible for the reduced thermostability of the ecRBP. The simulations results indicate that there are distinct structural differences in the unfolding pathway between the two homologs and the ecRBP unfolds faster than the hyperthermophilic homologs at certain temperatures in accordance with the lower thermal stability found experimentally. Essential dynamics analysis uncovers that the essential subspaces of ecRBP and tmRBP are non-overlapping and these two proteins show different directions of motion within the simulations trajectories. Such an understanding is required for designing efficient proteins with characteristics for a particular application.

Development of bisphenol A-removing recombinant Escherichia coli by monomeric and dimeric surface display of bisphenol A-binding peptide.

PubMed

Maruthamuthu, Murali Kannan; Hong, Jiyeon; Arulsamy, Kulandaisamy; Somasundaram, Sivachandiran; Hong, SoonHo; Choe, Woo-Seok; Yoo, Ik-Keun

2018-04-01

Peptide-displaying Escherichia coli cells were investigated for use in adsorptive removal of bisphenol A (BPA) both in Luria-Bertani medium including BPA or ATM thermal paper eluted wastewater. Two recombinant strains were constructed with monomeric and dimeric repeats of the 7-mer BPA-binding peptide (KSLENSY), respectively. Greater than threefold increased adsorption of BPA [230.4 µmol BPA per g dry cell weight (DCW)] was found in dimeric peptide-displaying cells compared to monomeric strains (63.4 µmol per g DCW) in 15 ppm BPA solution. The selective removal of BPA from a mixture of BPA analogs (bisphenol F and bisphenol S) was verified in both monomeric and dimeric peptide-displaying cells. The binding chemistry of BPA with the peptide was assumed, based on molecular docking analysis, to be the interaction of BPA with serine and asparagine residues within the 7-mer peptide sequence. The peptide-displaying cells also functioned efficiently in thermal paper eluted wastewater containing 14.5 ppm BPA.

Mutual positional preference of IPMDH proteins for binding studied by coarse-grained molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Ishioka, T.; Yamada, H.; Miyakawa, T.; Morikawa, R.; Akanuma, S.; Yamagishi, A.; Takasu, M.

2016-12-01

Proteins, which incorporate charged and hydrophobic amino acid residues, are useful as a material of nanotechnology. Among these proteins, IPMDH (3-isopropylmalate dehydrogenase), which has thermal stability, has potential as a material of nanofiber. In this study, we performed coarse-grained molecular dynamics simulation of IPMDH using MARTINI force fields, and we investigated the orientation for the binding of IPMDH. In simulation, we analyzed wild type of IPMDH and the mutated IPMDH proteins, where 13, 20, 27, 332, 335 and 338th amino acid residues are replaced by lysine residues which have positive charge and by glutamic acid residues which have negative charge. Since the binding of mutated IPMDH is advantageous compared with the binding of wild type for one orientation, we suggest that the Coulomb interaction for the binding of IPMDH is important.

Anderson localized state as a predissipative state: irreversible emission of thermalized quanta from a dynamically delocalized state.

PubMed

Yamada, Hiroaki; Ikeda, Kensuke S

2002-04-01

It was shown that localization in one-dimensional disordered (quantum) electronic system is destroyed against coherent harmonic perturbations and the delocalized electron exhibits an unlimited diffusive motion [Yamada and Ikeda, Phys. Rev. E 59, 5214 (1999)]. The appearance of diffusion implies that the system has potential for irreversibility and dissipation. In the present paper, we investigate dissipative property of the dynamically delocalized state, and we show that an irreversible quasistationary energy flow indeed appears in the form of a "heat" flow when we couple the system with another dynamical degree of freedom. In the concrete we numerically investigate dissipative properties of a one-dimensional tight-binding electronic system perturbed by time-dependent harmonic forces, by coupling it with a quantum harmonic oscillator or a quantum anharmonic oscillator. It is demonstrated that if the on-site potential is spatially irregular an irreversible energy transfer from the scattered electron to the test oscillator occurs. Moreover, the test oscillator promptly approaches a thermalized state characterized by a well-defined time-dependent temperature. On the contrary, such a relaxation process cannot be observed at all for periodic potential systems. Our system is one of the minimal quantum systems in which a distinct nonequilibrium statistical behavior is self-induced.

Donor states in inverse opals

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

Mahan, G. D.

We calculate the binding energy of an electron bound to a donor in a semiconductor inverse opal. Inverse opals have two kinds of cavities, which we call octahedral and tetrahedral, according to their group symmetry. We put the donor in the center of each of these two cavities and obtain the binding energy. The binding energies become very large when the inverse opal is made from templates with small spheres. For spheres less than 50 nm in diameter, the donor binding can increase to several times its unconfined value. Then electrons become tightly bound to the donor and are unlikelymore » to be thermally activated to the semiconductor conduction band. This conclusion suggests that inverse opals will be poor conductors.« less

Chitovibrin: a chitin-binding lectin from Vibrio parahemolyticus.

PubMed

Gildemeister, O S; Zhu, B C; Laine, R A

1994-12-01

A novel 134 kDa, calcium-independent chitin-binding lectin, 'chitovibrin', is secreted by the marine bacterium Vibrio parahemolyticus, inducible with chitin or chitin-oligomers. Chitovibrin shows no apparent enzymatic activity but exhibits a strong affinity for chitin and chito-oligomers > dp9. The protein has an isoelectric pH of 3.6, shows thermal tolerance, binds chitin with an optimum at pH 6 and is active in 0-4 M NaCl. Chitovibrin appears to be completely different from other reported Vibrio lectins and may function to bind V. parahemolyticus to chitin substrates, or to capture or sequester chito-oligomers. It may be a member of a large group of recently described proteins in Vibrios related to a complex chitinoclastic (chitinivorous) system.

Analysis of Paracoccidioides secreted proteins reveals fructose 1,6-bisphosphate aldolase as a plasminogen-binding protein.

PubMed

Chaves, Edilânia Gomes Araújo; Weber, Simone Schneider; Báo, Sonia Nair; Pereira, Luiz Augusto; Bailão, Alexandre Melo; Borges, Clayton Luiz; Soares, Célia Maria de Almeida

2015-02-27

Despite being important thermal dimorphic fungi causing Paracoccidioidomycosis, the pathogenic mechanisms that underlie the genus Paracoccidioides remain largely unknown. Microbial pathogens express molecules that can interact with human plasminogen, a protein from blood plasma, which presents fibrinolytic activity when activated into plasmin. Additionally, plasmin exhibits the ability of degrading extracellular matrix components, favoring the pathogen spread to deeper tissues. Previous work from our group demonstrated that Paracoccidioides presents enolase, as a protein able to bind and activate plasminogen, increasing the fibrinolytic activity of the pathogen, and the potential for adhesion and invasion of the fungus to host cells. By using proteomic analysis, we aimed to identify other proteins of Paracoccidioides with the ability of binding to plasminogen. In the present study, we employed proteomic analysis of the secretome, in order to identify plasminogen-binding proteins of Paracoccidioides, Pb01. Fifteen proteins were present in the fungal secretome, presenting the ability to bind to plasminogen. Those proteins are probable targets of the fungus interaction with the host; thus, they could contribute to the invasiveness of the fungus. For validation tests, we selected the protein fructose 1,6-bisphosphate aldolase (FBA), described in other pathogens as a plasminogen-binding protein. The protein FBA at the fungus surface and the recombinant FBA (rFBA) bound human plasminogen and promoted its conversion to plasmin, potentially increasing the fibrinolytic capacity of the fungus, as demonstrated in fibrin degradation assays. The addition of rFBA or anti-rFBA antibodies was capable of reducing the interaction between macrophages and Paracoccidioides, possibly by blocking the binding sites for FBA. These data reveal the possible participation of the FBA in the processes of cell adhesion and tissue invasion/dissemination of Paracoccidioides. These data indicate that Paracoccidioides is a pathogen that has several plasminogen-binding proteins that likely play important roles in pathogen-host interaction. In this context, FBA is a protein that might be involved somehow in the processes of invasion and spread of the fungus during infection.

Thermal-stability studies of electrode materials for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Jiang, Junwei

2005-07-01

The thermal stability of lithium-ion batteries has recently attracted attention for two major reasons. (1) Attempts to make large-size cells used in power tools, E-bikes and EVs. Large cells have lower surface area to volume ratios and hence heat dissipation is more problematic than 18650-size cells. Safety problems, therefore, for large cells are more serious. (2) Next generation high-capacity electrodes will increase the energy density of lithium-ion cells meaning even an 18650-size cell may face safety concerns. This thesis presents studies of the thermal stability of electrode materials in electrolytes to understand their reactivity. A search for new positive electrode materials with high thermal stability was made. The thermal stability of two common electrode materials (Li0.81 C6 and Li0.5CoO2) in lithium-ion cells was studied by Accelerating Rate Calorimeter (ARC). Li0.81C 6 has much lower reactivity with lithium bis(oxalato)borate (LiBOB) electrolyte compared to LiPF6 electrolyte. It is not the case, however, for Li0.5CoO2. Oven tests of full LiCoO 2/C 18650-size cells with LiBOB or LiPF6 electrolytes, confirmed the ARC results. ARC was then used to study the reactivity of existing electrode materials. The thermal stability of a negative electrode material was found to increase with the binding energy of Li atoms hosted in the material. Li0.5VO 2 (B) has a higher lithium binding energy (2.45 eV vs. Li) than Li 0.81C6 (0.1 eV vs. Li) and Li7Ti5O 12 (1.55 eV) and it shows the highest thermal stability in EC/DEC among the three materials. The reactivity of two existing positive electrode materials, LiMn2O4 and LiFePO4, was studied. Cell systems expected to be highly tolerant to thermal abuse were suggested: LiFePO 4/C or Li4Ti5O12 in LiBOB electrolytes. The system, x Li[Ni1/2Mn1/2]O2 • y LiCoO2 • z Li[Li1/3Mn2/3]O2 (x + y + z = 1), was explored for new positive electrode materials with large capacity and high thermal stability. Li[(Ni0.5Mn0.5) xCo1-x]O2 (0.4 ≤ x ≤ 0.7) samples have excellent electrochemical properties and thermal stability and are being commercialized by industry. Li[(Ni0.5Mn0.5)xCo y(Li1/3Mn2/3)z]O2 (1/12 ≤ y ≤ 1/4, 1/6 ≤ z ≤ 1/3) samples have high specific capacity (200 mA h g-1), excellent cycling performance, and are safer than LiCoO2. The materials are suggested for energy cells used in cell phones, laptops, and so on.

Synthesis of trimethoprim metal complexes: Spectral, electrochemical, thermal, DNA-binding and surface morphology studies.

PubMed

Demirezen, Nihat; Tarınç, Derya; Polat, Duygu; Ceşme, Mustafa; Gölcü, Ayşegül; Tümer, Mehmet

2012-08-01

Complexes of trimethoprim (TMP), with Cu(II), Zn(II), Pt(II), Ru(III) and Fe(III) have been synthesized. Then, these complexes have been characterized by spectroscopic techniques involving UV-vis, IR, mass and (1)H NMR. CHN elemental analysis, electrochemical and thermal behavior of complexes have also been investigated. The electrochemical properties of all complexes have been investigated by cyclic voltammetry (CV) using glassy carbon electrode. The biological activity of the complexes has been evaluated by examining their ability to bind to calf-thymus DNA (CT DNA) with UV spectroscopy and cyclic voltammetry. UV studies of the interaction of the complexes with DNA have shown that these compounds can bind to CT DNA. The binding constants of the complexes with CT DNA have also been calculated. The cyclic voltammograms of the complexes in the presence of CT DNA have shown that the complexes can bind to CT DNA by both the intercalative and the electrostatic binding mode. The antimicrobial activity of these complexes has been evaluated against three Gram-positive and four Gram-negative bacteria. Antifungal activity against two different fungi has been evaluated and compared with the reference drug TMP. Almost all types of complexes show excellent activity against all type of bacteria and fungi. The morphology of the CT DNA, TMP, metal ions and metal complexes has been investigated by scanning electron microscopy (SEM). To get the SEM images, the interaction of compounds with CT DNA has been studied by means of differential pulse voltammetry (DPV) at CT DNA modified pencil graphite electrode (PGE). The decrease in intensity of the guanine oxidation signals has been used as an indicator for the interaction mechanism. Copyright © 2012 Elsevier B.V. All rights reserved.

Effect of thermal treatment on the corrosion resistance of Type 316L stainless steel exposed in supercritical water

NASA Astrophysics Data System (ADS)

Jiao, Y.; Zheng, W.; Guzonas, D. A.; Cook, W. G.; Kish, J. R.

2015-09-01

There are still unknown aspects about the growth mechanism of oxide scales formed on candidate stainless steel fuel cladding materials during exposure in supercritical water (SCW) under the conditions relevant to the Canadian supercritical water-cooled reactor (SCWR). The tendency for intermetallic precipitates to form within the grains and on grain boundaries during prolonged exposure at high temperatures represents an unknown factor to corrosion resistance, since they tend to bind alloyed Cr. The objective of this study was to better understand the extent to which intermetallic precipitates affects the mode and extent of corrosion in SCW. Type 316L stainless steel, used as a model Fe-Cr-Ni-Mo alloy, was exposed to 25 MPa SCW at 550 °C for 500 h in a static autoclave for this purpose. Mechanically-abraded samples were tested in the mill-annealed (MA) and a thermally-treated (TT) condition. The thermal treatment was conducted at 815 °C for 1000 h to precipitate the carbide (M23C6), chi (χ), laves (η) and sigma (σ) phases. It was found that although relatively large intermetallic precipitates formed at the scale/alloy interface locally affected the oxide scale formation, their discontinuous formation did not affect the short-term overall apparent corrosion resistance.

Thermo-Mechanical Behavior of Textile Heating Fabric Based on Silver Coated Polymeric Yarn

PubMed Central

Hamdani, Syed Talha Ali; Potluri, Prasad; Fernando, Anura

2013-01-01

This paper presents a study conducted on the thermo-mechanical properties of knitted structures, the methods of manufacture, effect of contact pressure at the structural binding points, on the degree of heating. The test results also present the level of heating produced as a function of the separation between the supply terminals. The study further investigates the rate of heating and cooling of the knitted structures. The work also presents the decay of heating properties of the yarn due to overheating. Thermal images were taken to study the heat distribution over the surface of the knitted fabric. A tensile tester having constant rate of extension was used to stretch the fabric. The behavior of temperature profile of stretched fabric was observed. A comparison of heat generation by plain, rib and interlock structures was studied. It was observed from the series of experiments that there is a minimum threshold force of contact at binding points of a knitted structure is required to pass the electricity. Once this force is achieved, stretching the fabric does not affect the amount of heat produced. PMID:28809358

Free energy of a heavy quark-antiquark pair in a thermal medium from AdS/CFT

NASA Astrophysics Data System (ADS)

Ewerz, Carlo; Kaczmarek, Olaf; Samberg, Andreas

2018-03-01

We study the free energy of a heavy quark-antiquark pair in a thermal medium using the AdS/CFT correspondence. We point out that a commonly used prescription for calculating this quantity leads to a temperature dependence in conflict with general properties of the free energy. The problem originates from a particular way of subtracting divergences. We argue that the commonly used prescription gives rise to the binding energy rather than the free energy. We consider a different subtraction procedure and show that the resulting free energy is well-behaved and in qualitative agreement with results from lattice QCD. The free energy and the binding energy of the quark pair are computed for N=4 supersymmetric Yang-Mills theory and several non-conformal theories. We also calculate the entropy and the internal energy of the pair in these theories. Using the consistent subtraction, we further study the free energy, entropy, and internal energy of a single heavy quark in the thermal medium for various theories. Also here the results are found to be in qualitative agreement with lattice QCD results.

Minimized virus binding for tests of barrier materials.

PubMed Central

Lytle, C D; Routson, L B

1995-01-01

Viruses are used to test the barrier properties of materials. Binding of virus particles during passage through holes in the material may yield misleading test results. The choices of challenge virus and suspending medium may be important for minimizing confounding effects that might arise from such binding. In this study, different surrogate viruses, as well as different support media, were evaluated to determine optimal test parameters. Two membranes with high-binding properties (nitrocellulose and cationic polysulfone) were used as filters to compare binding activities of different surrogate challenge viruses (MS2, phi X174, T7, PRD1, and phi 6) in different media. The media consisted of buffered saline with surfactants, serum, or culture broth as additives. In addition, elution rates of viruses that bound to the membranes were determined. The results suggest that viruses can bind by hydrophobic and electrostatic interactions, with phi X174 displaying the lowest level of binding by either process. The nonionic detergents Triton X-100 and Tween 80 (0.1%) equally minimized hydrophobic interactions. Neither anionic nor cationic surfactants were as effective at nontoxic levels. Serum was effective at reducing both hydrophobic and electrostatic binding, with 2% being sufficient for eliminating binding under our test conditions. Thus, phi X174 remains the best choice as a surrogate virus to test barrier materials, and Triton X-100 (0.1%) remains a good choice for reducing hydrophobic binding. In addition, binding of viruses by barrier materials is unlikely to prevent passage of blood-borne pathogens. PMID:7574603

Lattice vibrational contribution to equation of state for tetrahedral compounds

NASA Astrophysics Data System (ADS)

Kagaya, H.-Matsuo; Kotoku, H.; Soma, T.

1989-02-01

The lattice vibrational contributions to the Helmholtz free energy and the thermal pressure of tetrahedral compounds such as GaP, InP, ZnS, ZnSe, ZnTe and CdTe are investigated from the electronic theory of solids in the dynamical treatment based on our presented binding force. The temperature dependence of Helmholtz free energy and thermal pressure from lattice vibrational term are quantitatively obtained, and vibrational contributions to free energy are small compared with the static crystal energy. The influence of the thermal pressure is important to the equation of state in high temperatures, and the reformulation of the volume scale for the pressure-volume relation is given by considering the thermal pressure.

Development of the GPM Observatory Thermal Vacuum Test Model

NASA Technical Reports Server (NTRS)

Yang, Kan; Peabody, Hume

2012-01-01

A software-based thermal modeling process was documented for generating the thermal panel settings necessary to simulate worst-case on-orbit flight environments in an observatory-level thermal vacuum test setup. The method for creating such a thermal model involved four major steps: (1) determining the major thermal zones for test as indicated by the major dissipating components on the spacecraft, then mapping the major heat flows between these components; (2) finding the flight equivalent sink temperatures for these test thermal zones; (3) determining the thermal test ground support equipment (GSE) design and initial thermal panel settings based on the equivalent sink temperatures; and (4) adjusting the panel settings in the test model to match heat flows and temperatures with the flight model. The observatory test thermal model developed from this process allows quick predictions of the performance of the thermal vacuum test design. In this work, the method described above was applied to the Global Precipitation Measurement (GPM) core observatory spacecraft, a joint project between NASA and the Japanese Aerospace Exploration Agency (JAXA) which is currently being integrated at NASA Goddard Space Flight Center for launch in Early 2014. From preliminary results, the thermal test model generated from this process shows that the heat flows and temperatures match fairly well with the flight thermal model, indicating that the test model can simulate fairly accurately the conditions on-orbit. However, further analysis is needed to determine the best test configuration possible to validate the GPM thermal design before the start of environmental testing later this year. Also, while this analysis method has been applied solely to GPM, it should be emphasized that the same process can be applied to any mission to develop an effective test setup and panel settings which accurately simulate on-orbit thermal environments.

Thermal/vacuum vs. thermal atmospheric testing of space flight electronic assemblies

NASA Technical Reports Server (NTRS)

Gibbel, Mark

1990-01-01

For space flight hardware, the thermal vacuum environmental test is the best test of a system's flight worthiness. Substituting an atmospheric pressure thermal test for a thermal/vacuum test can effectively reduce piece part temperatures by 20 C or more, even for low power density designs. Similar reductions in test effectiveness can also result from improper assembly level T/V test boundary conditions. The net result of these changes may reduce the effective test temperatures to the point where there is zero or negative margin over the flight thermal environment.

Thermal Management Coating As Thermal Protection System for Space Transportation System

NASA Technical Reports Server (NTRS)

Kaul, Raj; Stuckey, C. Irvin

2003-01-01

This paper presents viewgraphs on the development of a non-ablative thermal management coating used as the thermal protection system material for space shuttle rocket boosters and other launch vehicles. The topics include: 1) Coating Study; 2) Aerothermal Testing; 3) Preconditioning Environments; 4) Test Observations; 5) Lightning Strike Test Panel; 6) Test Panel After Impact Testing; 7) Thermal Testing; and 8) Mechanical Testing.

Crystal structures of the transpeptidase domain of the Mycobacterium tuberculosis penicillin-binding protein PonA1 reveal potential mechanisms of antibiotic resistance.

PubMed

Filippova, Ekaterina V; Kieser, Karen J; Luan, Chi-Hao; Wawrzak, Zdzislaw; Kiryukhina, Olga; Rubin, Eric J; Anderson, Wayne F

2016-06-01

Mycobacterium tuberculosis is a human respiratory pathogen that causes the deadly disease tuberculosis. The rapid global spread of antibiotic-resistant M. tuberculosis makes tuberculosis infections difficult to treat. To overcome this problem new effective antimicrobial strategies are urgently needed. One promising target for new therapeutic approaches is PonA1, a class A penicillin-binding protein, which is required for maintaining physiological cell wall synthesis and cell shape during growth in mycobacteria. Here, crystal structures of the transpeptidase domain, the enzymatic domain responsible for penicillin binding, of PonA1 from M. tuberculosis in the inhibitor-free form and in complex with penicillin V are reported. We used site-directed mutagenesis, antibiotic profiling experiments, and fluorescence thermal shift assays to measure PonA1's sensitivity to different classes of β-lactams. Structural comparison of the PonA1 apo-form and the antibiotic-bound form shows that binding of penicillin V induces conformational changes in the position of the loop β4'-α3 surrounding the penicillin-binding site. We have also found that binding of different antibiotics including penicillin V positively impacts protein stability, while other tested β-lactams such as clavulanate or meropenem resulted in destabilization of PonA1. Our antibiotic profiling experiments indicate that the transpeptidase activity of PonA1 in both M. tuberculosis and M. smegmatis mediates tolerance to specific cell wall-targeting antibiotics, particularly to penicillin V and meropenem. Because M. tuberculosis is an important human pathogen, these structural data provide a template to design novel transpeptidase inhibitors to treat tuberculosis infections. Structural data are available in the PDB database under the accession numbers 5CRF and 5CXW. © 2016 The Authors. The FEBS Journal published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.

A novel carbohydrate-binding surface layer protein from the hyperthermophilic archaeon Pyrococcus horikoshii.

PubMed

Goda, Shuichiro; Koga, Tomoyuki; Yamashita, Kenichiro; Kuriura, Ryo; Ueda, Toshifumi

2018-04-08

In Archaea and Bacteria, surface layer (S-layer) proteins form the cell envelope and are involved in cell protection. In the present study, a putative S-layer protein was purified from the crude extract of Pyrococcus horikoshii using affinity chromatography. The S-layer gene was cloned and expressed in Escherichia coli. Isothermal titration calorimetry analyses showed that the S-layer protein bound N-acetylglucosamine and induced agglutination of the gram-positive bacterium Micrococcus lysodeikticus. The protein comprised a 21-mer structure, with a molecular mass of 1,340 kDa, as determined using small-angle X-ray scattering. This protein showed high thermal stability, with a midpoint of thermal denaturation of 79 °C in dynamic light scattering experiments. This is the first description of the carbohydrate-binding archaeal S-layer protein and its characteristics.

A Proposed Mechanism for the Thermal Denaturation of a Recombinant Bacillus Halmapalus Alpha-amylase - the Effect of Calcium Ions

NASA Technical Reports Server (NTRS)

Nielsen, Anders D.; Pusey, Marc L.; Fuglsang, Claus C.; Westh, Peter

2003-01-01

The thermal stability of a recombinant alpha-amylase from Bacillus halmapalus alpha-amylase (BHA) has been investigated using circular dichroism spectroscopy (CD) and differential scanning calorimetry (DSC). This alpha-amylase is homologous to other Bacillus alpha-amylases where previous crystallographic studies have identified the existence of 3 calcium binding sites in the structure. Denaturation of BHA is irreversible with a Tm of approximately 89 C, and DSC thermograms can be described using a one-step irreversible model. A 5 C increase in T(sub m) in the presence of 10 fold excess CaCl2 was observed. However, a concomitant increase in the tendency to aggregate was also observed. The presence of 30-40 fold excess calcium chelator (EDTA or EGTA) results in a large destabilization of BHA corresponding to about 40 C lower T(sub m), as determined by both CD and DSC. Ten fold excess EGTA reveals complex DSC thermograms corresponding to both reversible and irreversible transitions, which possibly originate from different populations of BHA:calcium complexes. The observations in the present study have, in combination with structural information of homologous alpha-amylases, provided the basis for the proposal of a simple denaturation mechanism of BHA. The proposed mechanism describes the irreversible thermal denaturation of different BHA:calcium complexes and the calcium binding equilibrium involved. Furthermore, the model accounts for a temperature induced reversible structural change associated with calcium binding.

Interaction of ions, atoms, and small molecules with quantized vortex lines in superfluid (4)He.

PubMed

Mateo, David; Eloranta, Jussi; Williams, Gary A

2015-02-14

The interaction of a number of impurities (H2, Ag, Cu, Ag2, Cu2, Li, He3 (+), He(*) ((3)S), He2 (∗) ((3)Σu), and e(-)) with quantized rectilinear vortex lines in superfluid (4)He is calculated by using the Orsay-Trento density functional theory (DFT) method at 0 K. The Donnelly-Parks (DP) potential function binding ions to the vortex is combined with DFT data, yielding the impurity radius as well as the vortex line core parameter. The vortex core parameter at 0 K (0.74 Å) obtained either directly from the vortex line geometry or through the DP potential fitting is smaller than previously suggested but is compatible with the value obtained from re-analysis of the Rayfield-Reif experiment. All of the impurities have significantly higher binding energies to vortex lines below 1 K than the available thermal energy, where the thermally assisted escape process becomes exponentially negligible. Even at higher temperatures 1.5-2.0 K, the trapping times for larger metal clusters are sufficiently long that the previously observed metal nanowire assembly in superfluid helium can take place at vortex lines. The binding energy of the electron bubble is predicted to decrease as a function of both temperature and pressure, which allows adjusting the trap depth for either permanent trapping or to allow thermally assisted escape. Finally, a new scheme for determining the trapping of impurities on vortex lines by optical absorption spectroscopy is outlined and demonstrated for He(*).

Interaction of ions, atoms, and small molecules with quantized vortex lines in superfluid 4He

NASA Astrophysics Data System (ADS)

Mateo, David; Eloranta, Jussi; Williams, Gary A.

2015-02-01

The interaction of a number of impurities (H2, Ag, Cu, Ag2, Cu2, Li, He3 + , He* (3S), He2∗ (3Σu), and e-) with quantized rectilinear vortex lines in superfluid 4He is calculated by using the Orsay-Trento density functional theory (DFT) method at 0 K. The Donnelly-Parks (DP) potential function binding ions to the vortex is combined with DFT data, yielding the impurity radius as well as the vortex line core parameter. The vortex core parameter at 0 K (0.74 Å) obtained either directly from the vortex line geometry or through the DP potential fitting is smaller than previously suggested but is compatible with the value obtained from re-analysis of the Rayfield-Reif experiment. All of the impurities have significantly higher binding energies to vortex lines below 1 K than the available thermal energy, where the thermally assisted escape process becomes exponentially negligible. Even at higher temperatures 1.5-2.0 K, the trapping times for larger metal clusters are sufficiently long that the previously observed metal nanowire assembly in superfluid helium can take place at vortex lines. The binding energy of the electron bubble is predicted to decrease as a function of both temperature and pressure, which allows adjusting the trap depth for either permanent trapping or to allow thermally assisted escape. Finally, a new scheme for determining the trapping of impurities on vortex lines by optical absorption spectroscopy is outlined and demonstrated for He*.

Comprehensive insight into the binding of sunitinib, a multi-targeted anticancer drug to human serum albumin

NASA Astrophysics Data System (ADS)

Kabir, Md. Zahirul; Tee, Wei-Ven; Mohamad, Saharuddin B.; Alias, Zazali; Tayyab, Saad

2017-06-01

Binding studies between a multi-targeted anticancer drug, sunitinib (SU) and human serum albumin (HSA) were made using fluorescence, UV-vis absorption, circular dichroism (CD) and molecular docking analysis. Both fluorescence quenching data and UV-vis absorption results suggested formation of SU-HSA complex. Moderate binding affinity between SU and HSA was evident from the value of the binding constant (3.04 × 104 M-1), obtained at 298 K. Involvement of hydrophobic interactions and hydrogen bonds as the leading intermolecular forces in the formation of SU-HSA complex was predicted from the thermodynamic data of the binding reaction. These results were in good agreement with the molecular docking analysis. Microenvironmental perturbations around Tyr and Trp residues as well as secondary and tertiary structural changes in HSA upon SU binding were evident from the three-dimensional fluorescence and circular dichroism results. SU binding to HSA also improved the thermal stability of the protein. Competitive displacement results and molecular docking analysis revealed the binding locus of SU to HSA in subdomain IIA (Sudlow's site I). The influence of a few common ions on the binding constant of SU-HSA complex was also noticed.

Synthesis, spectroscopic, thermal and molecular modeling studies of Zn2+, Cd2+ and UO22+ complexes of Schiff bases containing triazole moiety. Antimicrobial, anticancer, antioxidant and DNA binding studies.

PubMed

Gaber, Mohamed; El-Ghamry, Hoda A; Fathalla, Shaimaa K; Mansour, Mohammed A

2018-02-01

A novel series of Zn 2+ , Cd 2+ and UO 2 2+ complexes of ligands namely 1-[(5-mercapto-1H-1,2,4-triazole-3-ylimino) methyl]naphthalene-2-ol (HL 1 ) and [(1H-1,2,4-triazole-3-ylimino) methyl] naphthalene-2-ol (HL 2 ) have been prepared and characterized by different analytical and spectral techniques. The stoichiometry, stereochemistry, conductivity measurements and mode of bonding of the complexes have been elucidated. Accurate comparison of the IR spectra of the ligands with their metal chelates proved the involvement of nitrogen atoms of the azomethine group and/or triazole ring in chelation in addition to the deprotonated hydroxyl oxygen. The UV-Vis and molar conductance data supported the octahedral geometry for the metal complexes. TGA technique has been used to study the thermal decomposition way of the metal complexes and the thermo kinetic parameters were estimated. Valuable information is obtained from calculations of molecular parameters using the molecular modeling techniques. The interaction between the metal complexes and CT-DNA has been studied from which the binding constants (k b ) were calculated. The Schiff bases and their metal chelates have shown potent antimicrobial, antioxidant and antitumor activities. The antitumor activities of the compounds have been tested in vitro against HEPG2 cell line and in silico by the molecular docking analysis with the VEGFR-2 receptor responsible for angiogenesis. Copyright © 2017 Elsevier B.V. All rights reserved.

Anisotropic energy flow and allosteric ligand binding in albumin

NASA Astrophysics Data System (ADS)

Li, Guifeng; Magana, Donny; Dyer, R. Brian

2014-01-01

Allosteric interactions in proteins generally involve propagation of local structural changes through the protein to a remote site. Anisotropic energy transport is thought to couple the remote sites, but the nature of this process is poorly understood. Here, we report the relationship between energy flow through the structure of bovine serum albumin and allosteric interactions between remote ligand binding sites of the protein. Ultrafast infrared spectroscopy is used to probe the flow of energy through the protein backbone following excitation of a heater dye, a metalloporphyrin or malachite green, bound to different binding sites in the protein. We observe ballistic and anisotropic energy flow through the protein structure following input of thermal energy into the flexible ligand binding sites, without local heating of the rigid helix bundles that connect these sites. This efficient energy transport mechanism enables the allosteric propagation of binding energy through the connecting helix structures.

Anisotropic energy flow and allosteric ligand binding in albumin.

PubMed

Li, Guifeng; Magana, Donny; Dyer, R Brian

2014-01-01

Allosteric interactions in proteins generally involve propagation of local structural changes through the protein to a remote site. Anisotropic energy transport is thought to couple the remote sites, but the nature of this process is poorly understood. Here, we report the relationship between energy flow through the structure of bovine serum albumin and allosteric interactions between remote ligand binding sites of the protein. Ultrafast infrared spectroscopy is used to probe the flow of energy through the protein backbone following excitation of a heater dye, a metalloporphyrin or malachite green, bound to different binding sites in the protein. We observe ballistic and anisotropic energy flow through the protein structure following input of thermal energy into the flexible ligand binding sites, without local heating of the rigid helix bundles that connect these sites. This efficient energy transport mechanism enables the allosteric propagation of binding energy through the connecting helix structures.

Anisotropic energy flow and allosteric ligand binding in albumin

PubMed Central

Li, Guifeng; Magana, Donny; Dyer, R. Brian

2014-01-01

Allosteric interactions in proteins generally involve propagation of local structural changes through the protein to a remote site. Anisotropic energy transport is thought to couple the remote sites, but the nature of this process is poorly understood. Here, we report the relationship between energy flow through the structure of bovine serum albumin and allosteric interactions between remote ligand binding sites of the protein. Ultrafast infrared spectroscopy is used to probe the flow of energy through the protein backbone following excitation of a heater dye, a metalloporphyrin or malachite green, bound to different binding sites in the protein. We observe ballistic and anisotropic energy flow through the protein structure following input of thermal energy into the flexible ligand binding sites, without local heating of the rigid helix bundles that connect these sites. This efficient energy transport mechanism enables the allosteric propagation of binding energy through the connecting helix structures. PMID:24445265

Characterization of nicotine binding in mouse brain and comparison with the binding of alpha-bungarotoxin and quinuclidinyl benzilate

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

Marks, M.J.; Collins, A.C.

1982-11-01

The binding of (/sup 3/H)nicotine to mouse brain has been measured and subsequently compared with the binding of (/sup 125/I)alpha-bungarotoxin (alpha-BTX) and L-(/sup 3/H)quinuclidinyl benzilate (QNB). The binding of nicotine was saturable, reversible, and stereospecific. The average KD and Bmax were 59 nM and 88 fmoles/mg of protein, respectively. Although the rates of association and dissociation of nicotine were temperature-dependent, the incubation temperature had no effect on either KD or Bmax. When measured at 20 degrees or 37 degrees, nicotine appeared to bind to a single class of binding sites, but a second, very low-affinity, binding site was observed atmore » 4 degrees. Nicotine binding was unaffected by the addition of NaCl, KCl, CaCl/sub 2/, or MgSO/sub 4/ to the incubation medium. Nicotinic cholinergic agonists were potent inhibitors of nicotine binding; however, nicotinic antagonists were poor inhibitors. The regional distribution of binding was not uniform: midbrain and striatum contained the highest number of receptors, whereas cerebellum had the fewest. Differences in site densities, regional distribution, inhibitor potencies, and thermal denaturation indicated that nicotine binding was not the same as either QNB or alpha-BTX binding, and therefore that receptors for nicotine may represent a unique population of cholinergic receptors.« less

A Direct Comparison of the MM-GB/SA Scoring Procedure and Free-Energy Perturbation Calculations Using Carbonic Anhydrase as a Test Case: Strengths and Pitfalls of Each Approach.

PubMed

Guimarães, Cristiano R W

2011-07-12

MM-GB/SA scoring and free energy perturbation (FEP) calculations have emerged as reliable methodologies to understand structural and energetic relationships to binding. In spite of successful applications to elucidate the structure-activity relationships for few pairs of ligands, the reality is that the performance of FEP calculations has rarely been tested for more than a handful of compounds. In this work, a series of 13 benzene sulfonamide inhibitors of carbonic anhydrase with binding free energies determined by isothermal titration calorimetry was selected as a test case. R(2) values of 0.70, 0.71, and 0.49 with the experiment were obtained with MM-GB/SA and FEP simulations run with MCPRO+ and Desmond, respectively. All methods work well, but the results obtained with Desmond are inferior to MM-GB/SA and MCPRO+. The main contrast between the methods is the level of sampling, ranging from full to restricted flexibility to single conformation for the complexes in Desmond, MCPRO+, and MM-GB/SA, respectively. The current and historical results obtained with MM-GB/SA qualify this approach as a more attractive alternative for rank-ordering; it can achieve equivalent or superior predictive accuracy and handle more structurally dissimilar ligands at a fraction of the computational cost of the rigorous free-energy methods. As for the large theoretical dynamic range for the binding energies, that seems to be a direct result of the degree of sampling in the simulations since MCPRO+ as well as MM-GB/SA are plagued by this. Van't Hoff analysis for selected pairs of ligands suggests that the wider scoring spread is not only affected by missing entropic contributions due to restricted sampling but also exaggerated enthalpic separation between the weak and potent compounds caused by diminished shielding of electrostatic interactions, thermal effects, and protein relaxation/strain.

Substituent Effects on Thermal Decolorization Rates of Bisbenzospiropyrans

PubMed Central

Lu, Nina T.; Nguyen, Vi N.; Kumar, Satish; McCurdy, Alison

2009-01-01

A novel application of photochromic molecules is to mimic physiological oscillatory calcium signals by reversibly binding and releasing calcium ions in response to light. Substituent changes on the largely unexplored photochromic bisbenzospiropyran scaffold led to significant changes in thermal fading rates in several organic solvents. Excellent correlations have been found between fading rates and empirical Hammett constants as well as calculated ground-state energies. These correlations can be used to improve scaffold design. PMID:16238356

Thermally activated persistent photoconductivity & donor binding energy in high mobility AlAs QWs

NASA Astrophysics Data System (ADS)

Dasgupta, S.; Knaak, C.; Fontcuberta, A.; Bichler, M.; Abstreiter, G.; Grayson, M.

2008-03-01

In AlAs, valley index is important quantum number which can help understand interactions. However, important parameters for growth such as donor binding energy and Si δ-doping efficiency were unknown and AlAs quantum wells (QWs) typically did not conduct in dark. We grew series of (001) and (110) oriented double-sided doped n-type AlAs QWs and deduced Si donor binding energy δ in Al0.45Ga0.55 As and doping efficiency η. They work in dark possibly because dilute charge traps in substrate are screened by backside doping. From dark saturation density for doping series we deduced δdk=65.2 meV [1]. Our studies show thermally activated PPC where sample is illuminated at 4 K and returned to dark without appreciable density increase. As temperature is increased to 30 K, density doubles, indicating shallow binding energy δPIA=0 meV post-illumination anneal (PIA). Doping efficiency after illumination for (001) facet was found to be η=n2D/nSi=35% and for (110) η=17%. With this understanding, we designed (001) AlAs QW with PIA density n=2.4 x 10^11 cm-2 and mobility μ=4.3 x 10^5 cm^2/Vs(330 mK), improvement of almost an order of magnitude over published results. [1] Dasgupta, et al. APL (2007)

Nano lead oxide and epdm composite for development of polymer based radiation shielding material: Gamma irradiation and attenuation tests

NASA Astrophysics Data System (ADS)

Özdemir, T.; Güngör, A.; Akbay, I. K.; Uzun, H.; Babucçuoglu, Y.

2018-03-01

It is important to have a shielding material that is not easily breaking in order to have a robust product that guarantee the radiation protection of the patients and radiation workers especially during the medical exposure. In this study, nano sized lead oxide (PbO) particles were used, for the first time, to obtain an elastomeric composite material in which lead oxide nanoparticles, after the surface modification with silane binding agent, was used as functional material for radiation shielding. In addition, the composite material including 1%, 5%, 10%, 15% and 20% weight percent nano sized lead oxide was irradiated with doses of 81, 100 and 120 kGy up to an irradiation period of 248 days in a gamma ray source with an initial dose rate of 21.1 Gy/h. Mechanical, thermal properties of the irradiated materials were investigated using DSC, DMA, TGA and tensile testing and modifications in thermal and mechanical properties of the nano lead oxide containing composite material via gamma irradiation were reported. Moreover, effect of bismuth-III oxide addition on radiation attenuation of the composite material was investigated. Nano lead oxide and bismuth-III oxide particles were mixed with different weight ratios. Attenuation tests have been conducted to determine lead equivalent values for the developed composite material. Lead equivalent thickness values from 0.07 to 0.65 (2-6 mm sample thickness) were obtained.

Characterization of textural, rheological, thermal, microstructural, and water mobility in wheat flour dough and bread affected by trehalose.

PubMed

Peng, Bo; Li, Youqian; Ding, Shiyong; Yang, Jun

2017-10-15

The study aims to elucidate the effects of trehalose on the mechanical, thermal, and rheological properties of wheat flour dough and water distribution in bread. Texture profile analysis, DSC, farinograph, extensograph, and frequency sweep were applied in dough. The results from SEM revealed that the gluten film became less notable with the presence of trehalose. The kinetics of staling process, low-field 1 H NMR, and water-binding capacity were employed to characterize physicochemical properties of bread. Trehalose decreased the staling rate constant k, indicating an inhibitory effect on firming process in bread. Trehalose had the ability to retain water by hindering the interaction among water molecules, gluten and starch, thus relatively increasing the immobility of the part of water represented by T 22 in low-field 1 H NMR tests. Trehalose restricted water mobilization during storage, resulting in a better water-holding capacity. Our findings reveal that trehalose could be an improver in dough and bread-making performance, as well as an antistaling agent in bread. Copyright © 2017 Elsevier Ltd. All rights reserved.

Size-dependent protein segregation at membrane interfaces

PubMed Central

Schmid, Eva M; Bakalar, Matthew H; Choudhuri, Kaushik; Weichsel, Julian; Ann, HyoungSook; Geissler, Phillip L; Dustin, Michael L; Fletcher, Daniel A

2016-01-01

Membrane interfaces formed at cell-cell junctions are associated with characteristic patterns of membrane protein organization, such as E-cadherin enrichment in epithelial junctional complexes and CD45 exclusion from the signaling foci of immunological synapses. To isolate the role of protein size in these processes, we reconstituted membrane interfaces in vitro using giant unilamellar vesicles decorated with synthetic binding and non-binding proteins. We show that size differences between binding and non-binding proteins can dramatically alter their organization at membrane interfaces in the absence of active contributions from the cytoskeleton, with as little as a ~5 nm increase in non-binding protein size driving its exclusion from the interface. Combining in vitro measurements with Monte Carlo simulations, we find that non-binding protein exclusion is also influenced by lateral crowding, binding protein affinity, and thermally-driven membrane height fluctuations that transiently limit access to the interface. This simple, sensitive, and highly effective means of passively segregating proteins has implications for signaling at cell-cell junctions and protein sorting at intracellular contact points between membrane-bound organelles. PMID:27980602

Thermodynamics of Aryl-Dihydroxyphenyl-Thiadiazole Binding to Human Hsp90

PubMed Central

Kazlauskas, Egidijus; Petrikaitė, Vilma; Michailovienė, Vilma; Revuckienė, Jurgita; Matulienė, Jurgita; Grinius, Leonas; Matulis, Daumantas

2012-01-01

The design of specific inhibitors against the Hsp90 chaperone and other enzyme relies on the detailed and correct understanding of both the thermodynamics of inhibitor binding and the structural features of the protein-inhibitor complex. Here we present a detailed thermodynamic study of binding of aryl-dihydroxyphenyl-thiadiazole inhibitor series to recombinant human Hsp90 alpha isozyme. The inhibitors are highly potent, with the intrinsic Kd approximately equal to 1 nM as determined by isothermal titration calorimetry (ITC) and thermal shift assay (TSA). Dissection of protonation contributions yielded the intrinsic thermodynamic parameters of binding, such as enthalpy, entropy, Gibbs free energy, and the heat capacity. The differences in binding thermodynamic parameters between the series of inhibitors revealed contributions of the functional groups, thus providing insight into molecular reasons for improved or diminished binding efficiency. The inhibitor binding to Hsp90 alpha primarily depended on a large favorable enthalpic contribution combined with the smaller favorable entropic contribution, thus suggesting that their binding was both enthalpically and entropically optimized. The enthalpy-entropy compensation phenomenon was highly evident when comparing the inhibitor binding enthalpies and entropies. This study illustrates how detailed thermodynamic analysis helps to understand energetic reasons for the binding efficiency and develop more potent inhibitors that could be applied for therapeutic use as Hsp90 inhibitors. PMID:22655030

Synthesis, DNA/RNA affinity and antitumour activity of new aromatic diamidines linked by 3,4-ethylenedioxythiophene.

PubMed

Stolić, Ivana; Mišković, Katarina; Piantanida, Ivo; Lončar, Mirela Baus; Glavaš-Obrovac, Ljubica; Bajić, Miroslav

2011-02-01

A series of novel 2,5-bis(amidinophenyl)-3,4-ethylenedioxythiophenes (5-10 and 15) has been synthesized. Compounds 5-10 bind to the DNA minor groove as the dominant binding site and strongly stabilize the double helix of ct-DNA. Surprisingly, the same compounds also thermally stabilize ds-RNA, whereby most of them form stacked dimers along the RNA double helix. The only exception is compound 15 which, due to its structural features, showed no interaction with DNA or RNA. Compounds 5-10 have shown a moderate to strong cytotoxic effect (GI50=1.5-9.0 μM) on a panel of seven tumour cell lines. The diimidazoline derivative 9, due to its highest inhibitory potential on the growth of all tested tumour cell lines, was investigated in more detail by testing its ability to enter into cells and influence the cell cycle. Compound 9 (5 μM) was internalized successfully in cell cytoplasm during a 30-min incubation period, followed by nuclear localization upon 90-min incubation. Significant arrest in HeLa cells in the G2/M phase, shown by cell cycle analysis at an equitoxic (50 μM) concentration, suggests interaction of a studied compound with cellular DNA as the main mode of biological action. Copyright © 2010 Elsevier Masson SAS. All rights reserved.

Ares I-X Thermal Model Correlation and Lessons Learned

NASA Technical Reports Server (NTRS)

Amundsen, Ruth M.

2010-01-01

The Ares I-X vehicle launched and flew successfully on October 28, 2009. This paper will describe the correlation of the vehicle thermal model to both ground testing and flight data. A main purpose of the vehicle model and ground testing was to ensure that the avionics within the vehicle were held within their thermal limits prior to launch and during flight. The correlation of the avionics box temperatures will be shown. Also, the lessons learned in the thermal discipline during the modeling, test, correlation to test, and flight of the Ares I-X flight test vehicle will be described. Lessons learned will cover thermal modeling, as well as management of the thermal discipline, thermal team, and thermal-related actions in design, testing, and flight.

Micro-Structured Two-Component 3D Metamaterials with Negative Thermal-Expansion Coefficient from Positive Constituents

PubMed Central

Qu, Jingyuan; Kadic, Muamer; Naber, Andreas; Wegener, Martin

2017-01-01

Controlling the thermal expansion of materials is of great technological importance. Uncontrolled thermal expansion can lead to failure or irreversible destruction of structures and devices. In ordinary crystals, thermal expansion is governed by the asymmetry of the microscopic binding potential, which cannot be adjusted easily. In artificial crystals called metamaterials, thermal expansion can be controlled by structure. Here, following previous theoretical work, we fabricate three-dimensional (3D) two-component polymer micro-lattices by using gray-tone laser lithography. We perform cross-correlation analysis of optical microscopy images taken at different sample temperatures. The derived displacement-vector field reveals that the thermal expansion and resulting bending of the bi-material beams leads to a rotation of the 3D chiral crosses arranged onto a 3D checkerboard pattern within one metamaterial unit cell. These rotations can compensate the expansion of the all positive constituents, leading to an effectively near-zero thermal length-expansion coefficient, or over-compensate the expansion, leading to an effectively negative thermal length-expansion coefficient. This evidences a striking level of thermal-expansion control. PMID:28079161

Synthesis, spectroscopic, biological activity and thermal characterization of ceftazidime with transition metals

NASA Astrophysics Data System (ADS)

Masoud, Mamdouh S.; Ali, Alaa E.; Elasala, Gehan S.; Kolkaila, Sherif A.

2018-03-01

Synthesis, physicochemical characterization and thermal analysis of ceftazidime complexes with transition metals (Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II)) were discussed. It's obtained that ceftazidime act as bidentate ligand. From magnetic measurement and spectral data, octahedral structures were proposed for all complexes except for cobalt, nickel and mercury had tetrahedral structural. Hyper chemistry program confirmed binding sites of ceftazidime. Ceftazidime complexes show higher activity than ceftazidime for some strains. From TG and DTA curves the thermal decomposition mechanisms of ceftazidime and their metal complexes were suggested. The thermal decomposition of the complexes ended with the formation of metal oxides as a final product except in case of Hg complex.

Thermal treatment of galactose-branched polyelectrolyte microcapsules to improve drug delivery with reserved targetability.

PubMed

Zhang, Fu; Wu, Qi; Liu, Li-Jun; Chen, Zhi-Chun; Lin, Xian-Fu

2008-06-05

A novel multilayered drug delivery system by LbL assembly of galactosylated polyelectrolyte, which is possible to have the potential in hepatic targeting by the presence of galactose residues at the microcapsule's surface, is designed. Thermal treatment was performed on the capsules and a dramatic thermal shrinkage up to 60% decrease of capsule diameter above 50 degrees C was observed. This thermal behavior was then used to manipulate drug loading capacity and release rate. Heating after drug loading could seal the capsule shell, enhancing the loading capacity and reducing the release rate significantly. Excellent affinity between galactose-binding lectin and heated galactose-containing microcapsules were observed, indicating a stable targeting potential even after high temperature elevating up to 90 degrees C.

Protein Binding: Do We Ever Learn?▿

PubMed Central

Zeitlinger, Markus A.; Derendorf, Hartmut; Mouton, Johan W.; Cars, Otto; Craig, William A.; Andes, David; Theuretzbacher, Ursula

2011-01-01

Although the influence of protein binding (PB) on antibacterial activity has been reported for many antibiotics and over many years, there is currently no standardization for pharmacodynamic models that account for the impact of protein binding of antimicrobial agents in vitro. This might explain the somewhat contradictory results obtained from different studies. Simple in vitro models which compare the MIC obtained in protein-free standard medium versus a protein-rich medium are prone to methodological pitfalls and may lead to flawed conclusions. Within in vitro test systems, a range of test conditions, including source of protein, concentration of the tested antibiotic, temperature, pH, electrolytes, and supplements may influence the impact of protein binding. As new antibiotics with a high degree of protein binding are in clinical development, attention and action directed toward the optimization and standardization of testing the impact of protein binding on the activity of antibiotics in vitro become even more urgent. In addition, the quantitative relationship between the effects of protein binding in vitro and in vivo needs to be established, since the physiological conditions differ. General recommendations for testing the impact of protein binding in vitro are suggested. PMID:21537013

Binding and thermodynamics of REV peptide-ctDNA interaction.

PubMed

Upadhyay, Santosh Kumar

2017-03-01

The thermodynamics of DNA-ligand binding is important as it provides useful information to understand the details of binding processes. HIV-1 REV response element (RRE) located in the env coding region of the viral genome is reported to be well conserved across different HIV-1 isolates. In this study, the binding characteristics of Calf thymus DNA (ctDNA) and REV peptide from HIV-1 were investigated using spectroscopic (UV-visible, fluorescence, and circular dichroism (CD)) and isothermal titration calorimetric (ITC) techniques. Thermal stability and ligand binding properties of the ctDNA revealed that native ctDNA had a T m of 75.5 °C, whereas the ctDNA-REV peptide complex exhibited an incremental shift in the T m by 8 °C, indicating thermal stability of the complex. CD data indicated increased ellipticity due to large conformational changes in ctDNA molecule upon binding with REV peptide and two binding stoichiometric modes are apparent. The ctDNA experienced condensation due to large conformational changes in the presence of REV peptide and positive B→Ψ transition was observed at higher molar charge ratios. Fluorescence studies performed at several ligand concentrations revealed a gradual decrease in the fluorescence intensity of EtBr-bound ctDNA in response to increasing ligand concentrations. The fluorescence data further confirmed two stoichiometric modes of binding for ctDNA-REV peptide complex as previously observed with CD studies. The binding enthalpies were determined using ITC in the temperature range of 293 K-308 K. The ITC binding isotherm was exothermic at all temperatures examined, with low ΔH values indicating that the ctDNA-REV peptide interaction is driven largely by entropy. The heat capacity change (ΔC p ) was insignificant, an unusual finding in the area of DNA-peptide interaction studies. The variation in the values obtained for ΔH, ΔS, and ΔG with temperature further suggests that ctDNA-REV peptide interaction is entropically driven. ITC based analysis of salt dependence of binding constant gave a charge value (Z) = +4.01, as determined for the δlnK/δln[Na + ] parameter, suggesting the participation of only 3-4 Arg out of 11 Arg charge from REV peptide. The stoichiometry observed for the complex was three molar charge of REV peptide binding per molar charge of ctDNA. ITC based analysis further confirmed that the binding between ctDNA and REV peptide is governed by electrostatic interaction. Molecular interactions including H-bonding, van der Waals forces, and solvent molecules rearrangement, underlie the binding of REV peptide to ctDNA. © 2016 Wiley Periodicals, Inc.

Studies on the interaction of apigenin with calf thymus DNA by spectroscopic methods

NASA Astrophysics Data System (ADS)

Zhang, Shufang; Sun, Xuejun; Kong, Rongmei; Xu, Mingming

2015-02-01

The interaction between apigenin and calf thymus deoxyribonucleic acid (ctDNA) in a pH 7.4 Tris-HCl buffer solution was investigated by UV-Vis spectroscopy, fluorescence spectroscopy, DNA melting techniques, and viscosity measurements. It was found that apigenin molecules could intercalate into the base pairs of DNA, forming a apigenin-DNA complex with a binding constant of K310K = 6.4 × 104 L mol-1. The thermodynamic parameters enthalpy change (ΔH), entropy change (ΔS) and Gibbs free energy (ΔG) were calculated to be 7.36 × 104 J mol-1, 329 J K-1 mol-1 and -2.84 × 104 J mol-1 at 310 K, respectively. Hydrophobic interaction was the predominant intermolecular force in stabilizing the apigenin-DNA complex. Thermal denaturation study suggested that the stabilization of the ctDNA helix was increased when the apigenin binding to ctDNA as indicated by the increase in thermal denaturation temperature of ctDNA at around 5.0 °C in the presence of apigenin. Spectroscopic techniques together with melting techniques and viscosity determination provided evidences of intercalation mode of binding for the interaction between apigenin and ctDNA.

ProbeZT: Simulation of transport coefficients of molecular electronic junctions under environmental effects using Büttiker's probes

NASA Astrophysics Data System (ADS)

Korol, Roman; Kilgour, Michael; Segal, Dvira

2018-03-01

We present our in-house quantum transport package, ProbeZT. This program provides linear response coefficients: electrical and electronic thermal conductances, as well as the thermopower of molecular junctions in which electrons interact with the surrounding thermal environment. Calculations are performed based on the Büttiker probe method, which introduces decoherence, energy exchange and dissipation effects phenomenologically using virtual electrode terminals called probes. The program can realize different types of probes, each introducing various environmental effects, including elastic and inelastic scattering of electrons. The molecular system is described by an arbitrary tight-binding Hamiltonian, allowing the study of different geometries beyond simple one-dimensional wires. Applications of the program to study the thermoelectric performance of molecular junctions are illustrated. The program also has a built-in functionality to simulate electron transport in double-stranded DNA molecules based on a tight-binding (ladder) description of the junction.

Basalt fiber insulating material with a mineral binding agent for industrial use

NASA Astrophysics Data System (ADS)

Drozdyuk, T.; Aizenshtadt, A.; Tutygin, A.; Frolova, M.

2016-04-01

The paper considers a possibility of using mining industry waste as a binding agent for heat insulating material on the basis of basalt fiber. The main objective of the research is to produce a heat-insulating material to be applied in machine building in high-temperature environments. After synthetic binder having been replaced by a mineral one, an environmentally sound thermal insulating material having desirable heat-protecting ability and not failing when exposed to high temperatures was obtained.

Thermal fluctuations enable rapid protein-protein associations in aqueous solution by lowering the reaction barrier

NASA Astrophysics Data System (ADS)

Sakaizawa, Honami; Watanabe, Hiroshi C.; Furuta, Tadaomi; Sakurai, Minoru

2016-01-01

In hydrophilic protein-protein associations, the dehydration penalty, which can cause the formation of a reaction barrier, must be canceled out; however, its mechanism has not been clarified. Here, we explored the possible mechanism through investigation of the dimerization of nucleotide binding domains (NBDs). We assessed the different dimerization processes by molecular dynamics simulations with and without thermal fluctuations in each NBD. Consequently, the reaction barriers of the former and latter were estimated to be ∼100 and ∼15 kcal/mol, respectively, suggesting that thermal fluctuations in the proteins facilitate the exclusion of water molecules from the interfacial region, thereby lowering the barrier.

Power Control and Monitoring Requirements for Thermal Vacuum/Thermal Balance Testing of the MAP Observatory

NASA Technical Reports Server (NTRS)

Johnson, Chris; Hinkle, R. Kenneth (Technical Monitor)

2002-01-01

The specific heater control requirements for the thermal vacuum and thermal balance testing of the Microwave Anisotropy Probe (MAP) Observatory at the Goddard Space Flight Center (GSFC) in Greenbelt, Maryland are described. The testing was conducted in the 10m wide x 18.3m high Space Environment Simulator (SES) Thermal Vacuum Facility. The MAP thermal testing required accurate quantification of spacecraft and fixture power levels while minimizing heater electrical emissions. The special requirements of the MAP test necessitated construction of five (5) new heater racks.

Thermal perturbation correlation of calcium binding Human centrin 3 and its structural changes

NASA Astrophysics Data System (ADS)

Pastrana-Rios, Belinda

2014-07-01

Perturbation-correlation moving-window two-dimensional (PCMW2D) correlation spectroscopy was applied for the determination of the individual transition temperatures of different vibrational modes located within structural components of a calcium binding protein known as Human centrin 3. This crucial information served to understand the contribution individual calcium binding sites made towards the stability of the EF-hand and therefore the protein without the use of probes. We are convinced that the general application of PCMW2D correlation spectroscopy can be applied to the study of proteins in general to ascertain the differences in the stability of structural motifs within proteins and its relationship to the actual transition temperature of unfolding.

21 CFR 862.1685 - Thyroxine-binding globulin test system.

Code of Federal Regulations, 2010 CFR

2010-04-01

... globulin test system is a device intended to measure thyroxine (thyroid)-binding globulin (TBG), a plasma protein which binds thyroxine, in serum and plasma. Measurements obtained by this device are used in the...

21 CFR 862.1685 - Thyroxine-binding globulin test system.

Code of Federal Regulations, 2012 CFR

2012-04-01

... globulin test system is a device intended to measure thyroxine (thyroid)-binding globulin (TBG), a plasma protein which binds thyroxine, in serum and plasma. Measurements obtained by this device are used in the...

21 CFR 862.1685 - Thyroxine-binding globulin test system.

Code of Federal Regulations, 2011 CFR

2011-04-01

... globulin test system is a device intended to measure thyroxine (thyroid)-binding globulin (TBG), a plasma protein which binds thyroxine, in serum and plasma. Measurements obtained by this device are used in the...

21 CFR 862.1685 - Thyroxine-binding globulin test system.

Code of Federal Regulations, 2013 CFR

2013-04-01

... globulin test system is a device intended to measure thyroxine (thyroid)-binding globulin (TBG), a plasma protein which binds thyroxine, in serum and plasma. Measurements obtained by this device are used in the...

21 CFR 862.1685 - Thyroxine-binding globulin test system.

Code of Federal Regulations, 2014 CFR

2014-04-01

... globulin test system is a device intended to measure thyroxine (thyroid)-binding globulin (TBG), a plasma protein which binds thyroxine, in serum and plasma. Measurements obtained by this device are used in the...

Solar panel thermal cycling testing by solar simulation and infrared radiation methods

NASA Technical Reports Server (NTRS)

Nuss, H. E.

1980-01-01

For the solar panels of the European Space Agency (ESA) satellites OTS/MAROTS and ECS/MARECS the thermal cycling tests were performed by using solar simulation methods. The performance data of two different solar simulators used and the thermal test results are described. The solar simulation thermal cycling tests for the ECS/MARECS solar panels were carried out with the aid of a rotatable multipanel test rig by which simultaneous testing of three solar panels was possible. As an alternative thermal test method, the capability of an infrared radiation method was studied and infrared simulation tests for the ultralight panel and the INTELSAT 5 solar panels were performed. The setup and the characteristics of the infrared radiation unit using a quartz lamp array of approx. 15 sq and LN2-cooled shutter and the thermal test results are presented. The irradiation uniformity, the solar panel temperature distribution, temperature changing rates for both test methods are compared. Results indicate the infrared simulation is an effective solar panel thermal testing method.

An HMM-based algorithm for evaluating rates of receptor–ligand binding kinetics from thermal fluctuation data

PubMed Central

Ju, Lining; Wang, Yijie Dylan; Hung, Ying; Wu, Chien-Fu Jeff; Zhu, Cheng

2013-01-01

Motivation: Abrupt reduction/resumption of thermal fluctuations of a force probe has been used to identify association/dissociation events of protein–ligand bonds. We show that off-rate of molecular dissociation can be estimated by the analysis of the bond lifetime, while the on-rate of molecular association can be estimated by the analysis of the waiting time between two neighboring bond events. However, the analysis relies heavily on subjective judgments and is time-consuming. To automate the process of mapping out bond events from thermal fluctuation data, we develop a hidden Markov model (HMM)-based method. Results: The HMM method represents the bond state by a hidden variable with two values: bound and unbound. The bond association/dissociation is visualized and pinpointed. We apply the method to analyze a key receptor–ligand interaction in the early stage of hemostasis and thrombosis: the von Willebrand factor (VWF) binding to platelet glycoprotein Ibα (GPIbα). The numbers of bond lifetime and waiting time events estimated by the HMM are much more than those estimated by a descriptive statistical method from the same set of raw data. The kinetic parameters estimated by the HMM are in excellent agreement with those by a descriptive statistical analysis, but have much smaller errors for both wild-type and two mutant VWF-A1 domains. Thus, the computerized analysis allows us to speed up the analysis and improve the quality of estimates of receptor–ligand binding kinetics. Contact: jeffwu@isye.gatech.edu or cheng.zhu@bme.gatech.edu PMID:23599504

The Regulatory Subunit of PKA-I Remains Partially Structured and Undergoes β-Aggregation upon Thermal Denaturation

PubMed Central

Dao, Khanh K.; Pey, Angel L.; Gjerde, Anja Underhaug; Teigen, Knut; Byeon, In-Ja L.; Døskeland, Stein O.; Gronenborn, Angela M.; Martinez, Aurora

2011-01-01

Background The regulatory subunit (R) of cAMP-dependent protein kinase (PKA) is a modular flexible protein that responds with large conformational changes to the binding of the effector cAMP. Considering its highly dynamic nature, the protein is rather stable. We studied the thermal denaturation of full-length RIα and a truncated RIα(92-381) that contains the tandem cyclic nucleotide binding (CNB) domains A and B. Methodology/Principal Findings As revealed by circular dichroism (CD) and differential scanning calorimetry, both RIα proteins contain significant residual structure in the heat-denatured state. As evidenced by CD, the predominantly α-helical spectrum at 25°C with double negative peaks at 209 and 222 nm changes to a spectrum with a single negative peak at 212–216 nm, characteristic of β-structure. A similar α→β transition occurs at higher temperature in the presence of cAMP. Thioflavin T fluorescence and atomic force microscopy studies support the notion that the structural transition is associated with cross-β-intermolecular aggregation and formation of non-fibrillar oligomers. Conclusions/Significance Thermal denaturation of RIα leads to partial loss of native packing with exposure of aggregation-prone motifs, such as the B' helices in the phosphate-binding cassettes of both CNB domains. The topology of the β-sandwiches in these domains favors inter-molecular β-aggregation, which is suppressed in the ligand-bound states of RIα under physiological conditions. Moreover, our results reveal that the CNB domains persist as structural cores through heat-denaturation. PMID:21394209

Effect of polyethylene glycol conjugation on conformational and colloidal stability of a monoclonal antibody antigen-binding fragment (Fab').

PubMed

Roque, Cristopher; Sheung, Anthony; Rahman, Nausheen; Ausar, S Fernando

2015-02-02

We have investigated the effects of site specific "hinge" polyethylene glycol conjugation (PEGylation) on thermal, pH, and colloidal stability of a monoclonal antibody antigen-binding fragment (Fab') using a variety of biophysical techniques. The results obtained by circular dichroism (CD), ultraviolet (UV) absorbance, and fluorescence spectroscopy suggested that the physical stability of the Fab' is maximized at pH 6-7 with no apparent differences due to PEGylation. Temperature-induced aggregation experiments revealed that PEGylation was able to increase the transition temperature, as well as prevent the formation of visible and subvisible aggregates. Statistical comparison of the three-index empirical phase diagram (EPD) revealed significant differences in thermal and pH stability signatures between Fab' and PEG-Fab'. Upon mechanical stress, micro-flow imaging (MFI) and measurement of the optical density at 360 nm showed that the PEG-Fab' had significantly higher resistance to surface-induced aggregation compared to the Fab'. Analysis of the interaction parameter, kD, indicated repulsive intermolecular forces for PEG-Fab' and attractive forces for Fab'. In conclusion, PEGylation appears to protect Fab' against thermal and mechanical stress-induced aggregation, likely due to a steric hindrance mechanism.

The 90-kDa Heat Shock Protein Hsp90 Protects Tubulin against Thermal Denaturation*

PubMed Central

Weis, Felix; Moullintraffort, Laura; Heichette, Claire; Chrétien, Denis; Garnier, Cyrille

2010-01-01

Hsp90 and tubulin are among the most abundant proteins in the cytosol of eukaryotic cells. Although Hsp90 plays key roles in maintaining its client proteins in their active state, tubulin is essential for fundamental processes such as cell morphogenesis and division. Several studies have suggested a possible connection between Hsp90 and the microtubule cytoskeleton. Because tubulin is a labile protein in its soluble form, we investigated whether Hsp90 protects it against thermal denaturation. Both proteins were purified from porcine brain, and their interaction was characterized in vitro by using spectrophotometry, sedimentation assays, video-enhanced differential interference contrast light microscopy, and native polyacrylamide gel electrophoresis. Our results show that Hsp90 protects tubulin against thermal denaturation and keeps it in a state compatible with microtubule polymerization. We demonstrate that Hsp90 cannot resolve tubulin aggregates but that it likely binds early unfolding intermediates, preventing their aggregation. Protection was maximal at a stoichiometry of two molecules of Hsp90 for one of tubulin. This protection does not require ATP binding and hydrolysis by Hsp90, but it is counteracted by geldanamycin, a specific inhibitor of Hsp90. PMID:20110359

Spectral, thermal and kinetic studies of charge-transfer complexes formed between the highly effective antibiotic drug metronidazole and two types of acceptors: σ- and π-acceptors

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Saad, Hosam A.; Adam, Abdel Majid A.

2015-04-01

Understanding the interaction between drugs and small inorganic or organic molecules is critical in being able to interpret the drug-receptor interactions and acting mechanism of these drugs. A combined solution and solid state study was performed to describe the complexation chemistry of drug metronidazole (MZ) which has a broad-spectrum antibacterial activity with two types of acceptors. The acceptors include, σ-acceptor (i.e., iodine) and π-acceptors (i.e., dichlorodicyanobenzoquinone (DDQ), chloranil (CHL) and picric acid (PA)). The molecular structure, spectroscopic characteristics, the binding modes as well as the thermal stability were deduced from IR, UV-vis, 1H NMR and thermal studies. The binding ratio of complexation (MZ: acceptor) was determined to be 1:2 for the iodine acceptor and 1:1 for the DDQ, CHL or PA acceptor, according to the CHN elemental analyses and spectrophotometric titrations. It has been found that the complexation with CHL and PA acceptors increases the values of enthalpy and entropy, while the complexation with DDQ and iodine acceptors decreases the values of these parameters compared with the free MZ donor.

Development of Advanced Thermal and Environmental Barrier Coatings Using a High-Heat-Flux Testing Approach

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.

2003-01-01

The development of low conductivity, robust thermal and environmental barrier coatings requires advanced testing techniques that can accurately and effectively evaluate coating thermal conductivity and cyclic resistance at very high surface temperatures (up to 1700 C) under large thermal gradients. In this study, a laser high-heat-flux test approach is established for evaluating advanced low conductivity, high temperature capability thermal and environmental barrier coatings under the NASA Ultra Efficient Engine Technology (UEET) program. The test approach emphasizes the real-time monitoring and assessment of the coating thermal conductivity, which initially rises under the steady-state high temperature thermal gradient test due to coating sintering, and later drops under the cyclic thermal gradient test due to coating cracking/delamination. The coating system is then evaluated based on damage accumulation and failure after the combined steady-state and cyclic thermal gradient tests. The lattice and radiation thermal conductivity of advanced ceramic coatings can also be evaluated using laser heat-flux techniques. The external radiation resistance of the coating is assessed based on the measured specimen temperature response under a laser- heated intense radiation-flux source. The coating internal radiation contribution is investigated based on the measured apparent coating conductivity increases with the coating surface test temperature under large thermal gradient test conditions. Since an increased radiation contribution is observed at these very high surface test temperatures, by varying the laser heat-flux and coating average test temperature, the complex relation between the lattice and radiation conductivity as a function of surface and interface test temperature may be derived.

A Colorimetric Microplate Assay for DNA-Binding Activity of His-Tagged MutS Protein.

PubMed

Banasik, Michał; Sachadyn, Paweł

2016-09-01

A simple microplate method was designed for rapid testing DNA-binding activity of proteins. The principle of the assay involves binding of tested DNA by his-tagged protein immobilized on a nickel-coated ELISA plate, following colorimetric detection of biotinylated DNA with avidin conjugated to horseradish peroxidase. The method was used to compare DNA mismatch binding activities of MutS proteins from three bacterial species. The assay required relatively low amounts of tested protein (approximately 0.5-10 pmol) and DNA (0.1-10 pmol) and a relatively short time of analysis (up to 60 min). The method is very simple to apply and convenient to test different buffer conditions of DNA-protein binding. Sensitive colorimetric detection enables naked eye observations and quantitation with an ELISA reader. The performance of the assay, which we believe is a distinguishing trait of the method, is based on two strong and specific molecular interactions: binding of a his-tagged protein to a nickel-coated microplate and binding of biotinylated DNA to avidin. In the reported experiments, the solution was used to optimize the conditions for DNA mismatch binding by MutS protein; however, the approach could be implemented to test nucleic acids interactions with any protein of interest.

Damage Accumulation and Failure of Plasma-Sprayed Thermal Barrier Coatings under Thermal Gradient Cyclic Conditions

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Choi, Sung R.; Ghosn, Louis J.; Miller, rober A.

2005-01-01

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. A fundamental understanding of the sintering and thermal cycling induced delamination of thermal barrier coating systems under engine-like heat flux conditions will potentially help to improve the coating temperature capability. In this study, a test approach is established to emphasize the real-time monitoring and assessment of the coating thermal conductivity, which can initially increase under the steady-state high temperature thermal gradient test due to coating sintering, and later decrease under the thermal gradient cyclic test due to coating cracking and delamination. Thermal conductivity prediction models have been established for a ZrO2-(7- 8wt%)Y2O3 model coating system in terms of heat flux, time, and testing temperatures. The coating delamination accumulation is then assessed based on the observed thermal conductivity response under the combined steady-state and cyclic thermal gradient tests. The coating thermal gradient cycling associated delaminations and failure mechanisms under simulated engine heat-flux conditions will be discussed in conjunction with the coating sintering and fracture testing results.

G-quadruplex induced stabilization by 2′-deoxy-2′-fluoro-d-arabinonucleic acids (2′F-ANA)

PubMed Central

Peng, Chang Geng; Damha, Masad J.

2007-01-01

The impact of 2′-deoxy-2′-fluoroarabinonucleotide residues (2′F-araN) on different G-quadruplexes derived from a thrombin-binding DNA aptamer d(G2T2G2TGTG2T2G2), an anti-HIV phosphorothioate aptamer PS-d(T2G4T2) and a DNA telomeric sequence d(G4T4G4) via UV thermal melting (Tm) and circular dichroism (CD) experiments has been investigated. Generally, replacement of deoxyguanosines that adopt the anti conformation (anti-guanines) with 2′F-araG can stabilize G-quartets and maintain the quadruplex conformation, while replacement of syn-guanines with 2′F-araG is not favored and results in a dramatic switch to an alternative quadruplex conformation. It was found that incorporation of 2′F-araG or T residues into a thrombin-binding DNA G-quadruplex stabilizes the complex (ΔTm up to ∼+3°C/2′F-araN modification); 2′F-araN units also increased the half-life in 10% fetal bovine serum (FBS) up to 48-fold. Two modified thrombin-binding aptamers (PG13 and PG14) show an approximately 4-fold increase in binding affinity to thrombin, as assessed via a nitrocellulose filter binding assay, both with increased thermal stability (∼1°C/2′F-ANA modification increase in Tm) and nuclease resistance (4–7-fold) as well. Therefore, the 2′-deoxy-2′-fluoro-d-arabinonucleic acid (2′F-ANA) modification is well suited to tune (and improve) the physicochemical and biological properties of naturally occurring DNA G-quartets. PMID:17636049

Ice-binding proteins that accumulate on different ice crystal planes produce distinct thermal hysteresis dynamics

PubMed Central

Drori, Ran; Celik, Yeliz; Davies, Peter L.; Braslavsky, Ido

2014-01-01

Ice-binding proteins that aid the survival of freeze-avoiding, cold-adapted organisms by inhibiting the growth of endogenous ice crystals are called antifreeze proteins (AFPs). The binding of AFPs to ice causes a separation between the melting point and the freezing point of the ice crystal (thermal hysteresis, TH). TH produced by hyperactive AFPs is an order of magnitude higher than that produced by a typical fish AFP. The basis for this difference in activity remains unclear. Here, we have compared the time dependence of TH activity for both hyperactive and moderately active AFPs using a custom-made nanolitre osmometer and a novel microfluidics system. We found that the TH activities of hyperactive AFPs were time-dependent, and that the TH activity of a moderate AFP was almost insensitive to time. Fluorescence microscopy measurement revealed that despite their higher TH activity, hyperactive AFPs from two insects (moth and beetle) took far longer to accumulate on the ice surface than did a moderately active fish AFP. An ice-binding protein from a bacterium that functions as an ice adhesin rather than as an antifreeze had intermediate TH properties. Nevertheless, the accumulation of this ice adhesion protein and the two hyperactive AFPs on the basal plane of ice is distinct and extensive, but not detectable for moderately active AFPs. Basal ice plane binding is the distinguishing feature of antifreeze hyperactivity, which is not strictly needed in fish that require only approximately 1°C of TH. Here, we found a correlation between the accumulation kinetics of the hyperactive AFP at the basal plane and the time sensitivity of the measured TH. PMID:25008081

Endocrine activity of alternatives to BPA found in thermal paper in Switzerland.

PubMed

Goldinger, Daniela M; Demierre, Anne-Laure; Zoller, Otmar; Rupp, Heinz; Reinhard, Hans; Magnin, Roxane; Becker, Thomas W; Bourqui-Pittet, Martine

2015-04-01

Alternatives to bisphenol A (BPA) are more and more used in thermal paper receipts. To get an overview of the situation in Switzerland, 124 thermal paper receipts were collected and analyzed. Whereas BPA was detected in most samples (n=100), some alternatives, namely bisphenol S (BPS), Pergafast® 201 and D-8 have been found in 4, 11 and 9 samples respectively. As no or few data on their endocrine activity are available, these chemicals and bisphenol F (BPF) were tested in vitro using the H295R steroidogenesis assay. 17β-Estradiol production was induced by BPA and BPF, whereas free testosterone production was inhibited by BPA and BPS. Both non-bisphenol substances did not show significant effects. The binding affinity to 16 proteins and the toxicological potential (TP) were further calculated in silico using VirtualToxLab™. TP values lay between 0.269 and 0.476 and the main target was the estrogen receptor β (84.4 nM to 1.33 μM). A substitution of BPA by BPF and BPS should be thus considered with caution, since they exhibit almost a similar endocrine activity as BPA. D-8 and Pergafast® 201 could be alternatives to replace BPA, however further analyses are needed to better characterize their effects on the hormonal system. Copyright © 2015 Elsevier Inc. All rights reserved.

Sensing of Double-Stranded DNA/RNA Secondary Structures by Water Soluble Homochiral Perylene Bisimide Dyes.

PubMed

Gershberg, Jana; Radić Stojković, Marijana; Škugor, Marko; Tomić, Sanja; Rehm, Thomas H; Rehm, Stefanie; Saha-Möller, Chantu R; Piantanida, Ivo; Würthner, Frank

2015-05-18

A broad series of homochiral perylene bisimide (PBI) dyes were synthesized that are appended with amino acids and cationic side chains at the imide positions. Self-assembly behavior of these ionic PBIs has been studied in aqueous media by UV/Vis spectroscopy, revealing formation of excitonically coupled H-type aggregates. The interactions of these ionic PBIs with different ds-DNA and ds-RNA have been explored by thermal denaturation, fluorimetric titration and circular dichroism (CD) experiments. These PBIs strongly stabilized ds-DNA/RNA against thermal denaturation as revealed by high melting temperatures of the formed PBI/polynucleotide complexes. Fluorimetric titrations showed that these PBIs bind to ds-DNA/RNA with high binding constants depending on the number of the positive charges in the side chains. Thus, spermine-containing PBIs with six positive charges each showed higher binding constants (logKs =9.2-9.8) than their dioxa analogues (logKs =6.5-7.9) having two positive charges each. Induced circular dichroism (ICD) of PBI assemblies created within DNA/RNA grooves was observed. These ICD profiles are strongly dependent on the steric demand of the chiral substituents of the amino acid units and the secondary structure of the DNA or RNA. The observed ICD effects can be explained by non-covalent binding of excitonically coupled PBI dimer aggregates into the minor groove of DNA and major groove of RNA which is further supported by molecular modeling studies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Acid-base properties of humic substances from composted and thermally-dried sewage sludges and amended soils as determined by potentiometric titration and the NICA-Donnan model.

PubMed

Fernández, José M; Plaza, César; Senesi, Nicola; Polo, Alfredo

2007-09-01

The acid-base properties of humic acids (HAs) and fulvic acids (FAs) isolated from composted sewage sludge (CS), thermally-dried sewage sludge (TS), soils amended with either CS or TS at a rate of 80 t ha(-1)y(-1) for 3y and the corresponding unamended soil were investigated by use of potentiometric titrations. The non-ideal competitive adsorption (NICA)-Donnan model for a bimodal distribution of proton binding sites was fitted to titration data by use of a least-squares minimization method. The main fitting parameters of the NICA-Donnan model obtained for each HA and FA sample included site densities, median affinity constants and widths of affinity distributions for proton binding to low and high affinity sites, which were assumed to be, respectively, carboxylic- and phenolic-type groups. With respect to unamended soil HA and FA, the HAs and FAs from CS, and especially TS, were characterized by smaller acidic functional group contents, larger proton binding affinities of both carboxylic- and phenolic-type groups, and smaller heterogeneity of carboxylic and phenolic-type groups. Amendment with CS or TS led to a decrease of acidic functional group contents and a slight increase of proton binding affinities of carboxylic- and phenolic-type groups of soil HAs and FAs. These effects were more evident in the HA and FA fractions from CS-amended soil than in those from TS-amended soil.

Modulation of the platelet serotonin transporter by thermal balneotherapy: a study in healthy subjects.

PubMed

Baroni, S; Marazziti, D; Consoli, G; Picchetti, M; Catena-Dell'Osso, M; Galassi, A

2012-05-01

Although the beneficial effects of balneotherapy have been recognized since a long time, a few information is available on the biological mechanisms underlying them and the subjective feelings of increased well-being and mood. The links between the serotonin (5-HT) system and mood prompted us to investigate the 5-HT platelet transporter (SERT), which is considered a reliable, peripheral marker of the same structure present in presynaptic neurons, in 30 healthy volunteers before (t0) and 30 minutes after (t1) thermal balneotherapy with ozonized water, as compared with a similar group who underwent a bath in non-mineral water. MATERIALS AN METHODS: The SERT was evaluated by means of the specific binding of 3H-paroxetine (3H-Par) to platelet membranes. Equilibrium-saturation binding data, the maximal binding capacity (Bmax) and the dissociation constant (Kd), were obtained by means of the Scatchard analysis. The results showed that, while Bmax values did not change in both groups, the Kd values decreased significantly at t1 only in those subjects who bathed in ozonized water. The results of this study, while showing a decrease of the dissociation constant (Kd) which is the inverse of affinity constant, of 3H-Par binding to SERT in all subjects after balneotherapy and not in those bathing in normal water, suggest that SERT modifications may be related to a specific effect of ozonized water and, perhaps, also to the increased sense of well-being.

Thermal balneotherapy induces changes of the platelet serotonin transporter in healthy subjects.

PubMed

Marazziti, Donatella; Baroni, Stefano; Giannaccini, Gino; Catena Dell'Osso, Mario; Consoli, Giorgio; Picchetti, Michela; Carlini, Marina; Massimetti, Gabriele; Provenzano, Serafina; Galassi, Antonio

2007-10-01

Although the beneficial effects of balneotherapy have been recognized since a long time, a few information is available on the biological mechanisms underlying them and the subjective feelings of increased well-being and mood. The links between the serotonin (5-HT) system and mood prompted us to investigate the 5-HT platelet transporter (SERT), which is considered a reliable, peripheral marker of the same structure present in presynaptic neurons, in 20 healthy volunteers before (t0) and 30 min after (t1) thermal balneotherapy with ozonized water of Montecatini spa, as compared with a similar group who underwent a bath in non-mineral water. The SERT was evaluated by means of the specific binding of (3)H-paroxetine ((3)H-Par) to platelet membranes. Equilibrium-saturation binding data, the maximal binding capacity (Bmax) and the dissociation constant (Kd), were obtained by means of the Scatchard analysis. The results showed that, while Bmax values did not change in both groups, the Kd values decreased significantly at t1 only in those subjects who bathed in ozonized water. The results of this study, while showing a decrease of the dissociation constant (Kd) which is the inverse of affinity constant, of (3)H-Par binding to SERT in all subjects after balneotherapy and not in those bathing in normal water, suggest that SERT modifications may be related to a specific effect of ozonized water and, perhaps, also to the increased sense of well-being.

Modeling the Role of Bulk and Surface Characteristics of Carbon Fiber on Thermal Conductance across the Carbon Fiber/Matrix Interface (Postprint)

DTIC Science & Technology

2015-11-09

Osguthorpe, D. J.; Wolff, J.; Genest, M.; Hagler, A. T. Structure and Energetics of Ligand Binding to Proteins: Escherichia Coli Dihydrofolate...available at DOI: 10.1021/acsami.5b08591 14. ABSTRACT (Maximum 200 words) The rapid heating of carbon-fiber-reinforced polymer matrix composites leads ...polymer matrix composites leads to complex thermophysical interactions which not only are dependent on the thermal properties of the constituents and

Cost effectiveness as applied to the Viking Lander systems-level thermal development test program

NASA Technical Reports Server (NTRS)

Buna, T.; Shupert, T. C.

1974-01-01

The economic aspects of thermal testing at the systems-level as applied to the Viking Lander Capsule thermal development program are reviewed. The unique mission profile and pioneering scientific goals of Viking imposed novel requirements on testing, including the development of a simulation technique for the Martian thermal environment. The selected approach included modifications of an existing conventional thermal vacuum facility, and improved test-operational techniques that are applicable to the simulation of the other mission phases as well, thereby contributing significantly to the cost effectiveness of the overall thermal test program.

Acoustic and Thermal Testing of an Integrated Multilayer Insulation and Broad Area Cooling Shield System

NASA Technical Reports Server (NTRS)

Wood, Jessica J.; Foster, Lee W.

2013-01-01

A Multilayer Insulation (MLI) and Broad Area Cooling (BAC) shield thermal control system shows promise for long-duration storage of cryogenic propellant. The NASA Cryogenic Propellant Storage and Transfer (CPST) project is investigating the thermal and structural performance of this tank-applied integrated system. The MLI/BAC Shield Acoustic and Thermal Test was performed to evaluate the MLI/BAC shield's structural performance by subjecting it to worst-case launch acoustic loads. Identical thermal tests using Liquid Nitrogen (LN2) were performed before and after the acoustic test. The data from these tests was compared to determine if any degradation occurred in the thermal performance of the system as a result of exposure to the acoustic loads. The thermal test series consisted of two primary components: a passive boil-off test to evaluate the MLI performance and an active cooling test to evaluate the integrated MLI/BAC shield system with chilled vapor circulating through the BAC shield tubes. The acoustic test used loads closely matching the worst-case envelope of all launch vehicles currently under consideration for CPST. Acoustic test results yielded reasonable responses for the given load. The thermal test matrix was completed prior to the acoustic test and successfully repeated after the acoustic test. Data was compared and yielded near identical results, indicating that the MLI/BAC shield configuration tested in this series is an option for structurally implementing this thermal control system concept.

Scrutinizing MHC-I binding peptides and their limits of variation.

PubMed

Koch, Christian P; Perna, Anna M; Pillong, Max; Todoroff, Nickolay K; Wrede, Paul; Folkers, Gerd; Hiss, Jan A; Schneider, Gisbert

2013-01-01

Designed peptides that bind to major histocompatibility protein I (MHC-I) allomorphs bear the promise of representing epitopes that stimulate a desired immune response. A rigorous bioinformatical exploration of sequence patterns hidden in peptides that bind to the mouse MHC-I allomorph H-2K(b) is presented. We exemplify and validate these motif findings by systematically dissecting the epitope SIINFEKL and analyzing the resulting fragments for their binding potential to H-2K(b) in a thermal denaturation assay. The results demonstrate that only fragments exclusively retaining the carboxy- or amino-terminus of the reference peptide exhibit significant binding potential, with the N-terminal pentapeptide SIINF as shortest ligand. This study demonstrates that sophisticated machine-learning algorithms excel at extracting fine-grained patterns from peptide sequence data and predicting MHC-I binding peptides, thereby considerably extending existing linear prediction models and providing a fresh view on the computer-based molecular design of future synthetic vaccines. The server for prediction is available at http://modlab-cadd.ethz.ch (SLiDER tool, MHC-I version 2012).

Probabilistic thermal-shock strength testing using infrared imaging

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

Wereszczak, A.A.; Scheidt, R.A.; Ferber, M.K.

1999-12-01

A thermal-shock strength-testing technique has been developed that uses a high-resolution, high-temperature infrared camera to capture a specimen's surface temperature distribution at fracture. Aluminum nitride (AlN) substrates are thermally shocked to fracture to demonstrate the technique. The surface temperature distribution for each test and AlN's thermal expansion are used as input in a finite-element model to determine the thermal-shock strength for each specimen. An uncensored thermal-shock strength Weibull distribution is then determined. The test and analysis algorithm show promise as a means to characterize thermal shock strength of ceramic materials.

Binding equilibrium and kinetics of membrane-anchored receptors and ligands in cell adhesion: Insights from computational model systems and theory.

PubMed

Weikl, Thomas R; Hu, Jinglei; Xu, Guang-Kui; Lipowsky, Reinhard

2016-09-02

The adhesion of cell membranes is mediated by the binding of membrane-anchored receptor and ligand proteins. In this article, we review recent results from simulations and theory that lead to novel insights on how the binding equilibrium and kinetics of these proteins is affected by the membranes and by the membrane anchoring and molecular properties of the proteins. Simulations and theory both indicate that the binding equilibrium constant [Formula: see text] and the on- and off-rate constants of anchored receptors and ligands in their 2-dimensional (2D) membrane environment strongly depend on the membrane roughness from thermally excited shape fluctuations on nanoscales. Recent theory corroborated by simulations provides a general relation between [Formula: see text] and the binding constant [Formula: see text] of soluble variants of the receptors and ligands that lack the membrane anchors and are free to diffuse in 3 dimensions (3D).

Binding equilibrium and kinetics of membrane-anchored receptors and ligands in cell adhesion: Insights from computational model systems and theory

PubMed Central

Weikl, Thomas R.; Hu, Jinglei; Xu, Guang-Kui; Lipowsky, Reinhard

2016-01-01

ABSTRACT The adhesion of cell membranes is mediated by the binding of membrane-anchored receptor and ligand proteins. In this article, we review recent results from simulations and theory that lead to novel insights on how the binding equilibrium and kinetics of these proteins is affected by the membranes and by the membrane anchoring and molecular properties of the proteins. Simulations and theory both indicate that the binding equilibrium constant K2D and the on- and off-rate constants of anchored receptors and ligands in their 2-dimensional (2D) membrane environment strongly depend on the membrane roughness from thermally excited shape fluctuations on nanoscales. Recent theory corroborated by simulations provides a general relation between K2D and the binding constant K3D of soluble variants of the receptors and ligands that lack the membrane anchors and are free to diffuse in 3 dimensions (3D). PMID:27294442

Binding of carbonyl flavours to canola, pea and wheat proteins using GC/MS approach.

PubMed

Wang, Kun; Arntfield, Susan D

2014-08-15

Interactions of homologous aldehydes (hexanal, heptanal, and octanal) and ketones (2-hexanone, 2-heptanone, and 2-octanone) to salt and alkaline-extracted canola and pea proteins and commercial wheat gluten were studied using GC/MS. Long-chain aldehyde flavours exhibited higher binding affinity, regardless of protein type and isolation method. Salt-extracted canola protein isolates (CPIs) revealed the highest binding capacity to all aldehydes followed by wheat gluten and salt-extracted pea protein isolates (PPIs), while binding of ketone flavours decreased in the order: PPIs>wheat gluten>CPIs. Two aldolisation products, 2-butyl-2-octenal and 2-pentyl-2-nonenal, were detected from the interactions between CPIs with hexanal and heptanal, respectively. Protein thermal behaviour in the presence of these compounds was analysed by differential scanning calorimeter, where decreased ΔH inferred potential conformational changes due to partial denaturation of PPIs. Compared to ketones, aldehyde flavours possessed much higher "unfolding capacity" (lower ΔH), which accounted for their higher binding affinities. Copyright © 2014 Elsevier Ltd. All rights reserved.

Allosteric Ligand Binding and Anisotropic Energy Flow in Albumin

NASA Astrophysics Data System (ADS)

Dyer, Brian

2014-03-01

Protein allostery usually involves propagation of local structural changes through the protein to a remote site. Coupling of structural changes at remote sites is thought to occur through anisotropic energy transport, but the nature of this process is poorly understood. We have studied the relationship between allosteric interactions of remote ligand binding sites of the protein and energy flow through the structure of bovine serum albumin (BSA). We applied ultrafast infrared spectroscopy to probe the flow of energy through the protein backbone following excitation of a heater dye, a metalloporphyrin or malachite green, bound to different binding sites in the protein. We observe ballistic flow through the protein structure following input of thermal energy into the flexible ligand binding sites. We also observe anisotropic heat flow through the structure, without local heating of the rigid helix bundles that connect these sites. We will discuss the implications of this efficient energy transport mechanism with regard to the allosteric propagation of binding energy through the connecting helix structures.

Size-dependent protein segregation at membrane interfaces

NASA Astrophysics Data System (ADS)

Schmid, Eva M.; Bakalar, Matthew H.; Choudhuri, Kaushik; Weichsel, Julian; Ann, Hyoung Sook; Geissler, Phillip L.; Dustin, Michael L.; Fletcher, Daniel A.

2016-07-01

Membrane interfaces formed at cell-cell junctions are associated with characteristic patterns of membrane proteins whose organization is critical for intracellular signalling. To isolate the role of membrane protein size in pattern formation, we reconstituted model membrane interfaces in vitro using giant unilamellar vesicles decorated with synthetic binding and non-binding proteins. We show that size differences between membrane proteins can drastically alter their organization at membrane interfaces, with as little as a ~5 nm increase in non-binding protein size driving its exclusion from the interface. Combining in vitro measurements with Monte Carlo simulations, we find that non-binding protein exclusion is also influenced by lateral crowding, binding protein affinity, and thermally driven membrane height fluctuations that transiently limit access to the interface. This sensitive and highly effective means of physically segregating proteins has implications for cell-cell contacts such as T-cell immunological synapses (for example, CD45 exclusion) and epithelial cell junctions (for example, E-cadherin enrichment), as well as for protein sorting at intracellular contact points between membrane-bound organelles.

Antinociception by the anti-oxidized phospholipid antibody E06.

PubMed

Mohammadi, Milad; Oehler, Beatrice; Kloka, Jan; Martin, Corinna; Brack, Alexander; Blum, Robert; Rittner, Heike L

2018-04-21

Reactive oxygen species (ROS) and their downstream molecules such as oxidized phospholipids (OxPL) and 4-hydroxynonenal (4-HNE) activate transient receptor potential ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1) ion channels in vivo and in vitro shaping thermal and mechanical hypersensitivity in inflammatory pain. E06/T15 is a monoclonal autoantibody against oxidized phosphatidylcholine (OxPC) used in diagnostics in arteriosclerosis. Recently, we provided evidence that E06 also ameliorates inflammatory pain. Here, we studied E06 for local treatment against hypersensitivity evoked by endogenous and exogenous TRPA1 and TRPV1 agonists. We utilized a combination of reflexive and complex behavioural pain measurements, live-cell calcium imaging, and OxPC-binding assays. Lipid peroxidation metabolite 4-HNE, hydrogen peroxide (H 2 O 2 ) as ROS source, allyl isothiocyanate (AITC) and capsaicin were used to activate respective receptors. All irritants induced thermal and mechanical hypersensitivity, spontaneous nocifensive and affective motivational behaviour, as well as calcium influx in HEK TRPA1 - or HEK TRPV1 -cells and dorsal root ganglion (DRG) neurons. E06 prevented prolonged mechanical hypersensitivity induced by all irritants except for H 2 O 2 . E06 did not alter immediate irritant-induced nocifensive or affective motivational behaviour. In vitro, E06 blocked only 4-HNE-induced calcium influx albeit 4-HNE did not bind to E06. After 1-3 h, all tested irritants elicited formation of OxPC in paw tissue. E06 ameliorates not only inflammatory pain but also prolonged hypersensitivity due to formation of OxPC. This supports the view that neutralizing certain OxPL as endogenous TRPA1/V1 activators may be valuable for pain therapy. This article is protected by copyright. All rights reserved.

Operationally Responsive Space Standard Bus Battery Thermal Balance Testing and Heat Dissipation Analysis

NASA Technical Reports Server (NTRS)

Marley, Mike

2008-01-01

The focus of this paper will be on the thermal balance testing for the Operationally Responsive Space Standard Bus Battery. The Standard Bus thermal design required that the battery be isolated from the bus itself. This required the battery to have its own thermal control, including heaters and a radiator surface. Since the battery was not ready for testing during the overall bus thermal balance testing, a separate test was conducted to verify the thermal design for the battery. This paper will discuss in detail, the test set up, test procedure, and results from this test. Additionally this paper will consider the methods taken to determine the heat dissipation of the battery during charge and discharge. It seems that the heat dissipation for Lithium Ion batteries is relatively unknown and hard to quantify. The methods used during test and the post test analysis to estimate the heat dissipation of the battery will be discussed.

Influence of some DNA-alkylating drugs on thermal stability, acid and osmotic resistance of the membrane of whole human erythrocytes and their ghosts.

PubMed

Ivanov, I T; Gadjeva, V

2000-09-01

Human erythrocytes and their resealed ghosts were alkylated under identical conditions using three groups of alkylating antitumor agents: mustards, triazenes and chloroethyl nitrosoureas. Osmotic fragility, acid resistance and thermal stability of membranes were changed only in alkylated ghosts in proportion to the concentration of the alkylating agent. All the alkylating agents decreased acid resistance in ghosts. The clinically used drugs sarcolysine, dacarbazine and lomustine all decreased osmotic fragility and thermal stability of ghost membranes depending on their lipophilicity. DM-COOH did not decrease osmotic fragility and thermal stability of ghost membranes, while NEM increased thermal stability of membranes. The preliminary but not subsequent treatment of ghosts with DM-COOH fully abolished the alkylation-induced thermal labilization of ghost membrane proteins while NEM had a partial effect only. The present study gives direct evidence that alkylating agents, having a high therapeutic activity against malignant growth, bind covalently to proteins of cellular membranes.

Binding of vitamin A by casein micelles in commercial skim milk.

PubMed

Mohan, M S; Jurat-Fuentes, J L; Harte, F

2013-02-01

Recent studies have shown that reassembled micelles formed by caseinates and purified casein fractions (α(s)- and β-casein) bind to hydrophobic compounds, including curcumin, docosahexaenoic acid, and vitamin D. However, limited research has been done on the binding of hydrophobic compounds by unmodified casein micelles in skim milk. In the present study, we investigated the ability of casein micelles in commercial skim milk to associate with vitamin A (retinyl palmitate), a fat-soluble vitamin commonly used to fortify milk. Milk protein fractions from different commercially available skim milk samples subjected to different processing treatments, including pasteurized, ultrapasteurized, organic pasteurized, and organic ultrapasteurized milks, were separated by fast protein liquid chromatography. The fractions within each peak were combined and freeze-dried. Sodium dodecyl sulfate-PAGE with silver staining was used to identify the proteins present in each of the fractions. The skim milk samples and fractions were extracted for retinyl palmitate and quantified against a standard using normal phase-HPLC. Retinyl palmitate was found to associate with the fraction of skim milk containing caseins, whereas the other proteins (BSA, β-lactoglobulin, α-lactalbumin) did not show any binding. The retinyl palmitate content in the various samples ranged from 1.59 to 2.48 µg of retinyl palmitate per mL of milk. The casein fractions contained between 14 and 40% of total retinyl palmitate in the various milks tested. The variation in the retention of vitamin A by caseins was probably explained by differences in the processing of different milk samples, including thermal treatment, the form of vitamin A emulsion used for fortification, and the point of fortification during processing. Unmodified casein micelles have a strong intrinsic affinity toward the binding of vitamin A used to fortify commercially available skim milks. Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Similarity tests of turbine vanes, effects of ceramic thermal barrier coatings

NASA Technical Reports Server (NTRS)

Gladden, H. J.

1980-01-01

The role of material thermal conductivity was analyzed for its effect on the thermal performance of air-cooled gas turbine components coated with a ceramic thermal barrier material when tested at reduced temperatures and pressures. It is shown that the thermal performance can be evaluated reliably at reduced gas and coolant conditions; however, thermal conductivity corrections are required for the data at reduced conditions. Corrections for a ceramic thermal barrier coated vane are significantly different than for an uncoated vane. Comparison of uncorrected test data, therefore, would show erroneously that the thermal barrier coating was ineffective. When thermal conductivity corrections are applied to the test data these data are then shown to be representative of engine data and also show that the thermal barrier coating increases the vane cooling effectiveness by 12.5 percent.

Detection of DNA damage in individual cells by flow cytometric analysis using anti-DNA monoclonal antibody

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

Frankfurt, O.S.

A new method for the measurement of DNA damage in individual cells treated with alkylating agents is described. The method is based on the binding of anti-DNA monoclonal antibody to DNA in situ. Binding of antibody was evaluated by flow cytometry with indirect immunofluorescence. No binding of antibody to DNA in non-treated HeLa S3 cells was detected. Treatment of cells with HN2 or L-phenylalanine mustard induced binding of antibody to DNA in situ. Binding of antibody was observed after treating cells with doses of drugs which reduced the surviving fraction below 20%. Intensity of binding increased in proportion to themore » drug dose. In HN2-treated cells a cell subset with the lowest antibody binding was observed among cells in G1 phase. Binding of antibody to DNA in HN2-treated cells was eliminated by single-strand (ss) specific S1 nuclease. In competition assay, antibody was inhibited by thermally denatured DNA, but not by native double-stranded (ds) DNA, RNA, nucleosides and deoxyribohomopolymers. Immunoreactivity of cells with the monoclonal antibody F7-26 may be a useful probe for the assessment of cell damage induced by alkylating agents, especially in heterogeneous cell populations.« less

James Webb Space Telescope Integrated Science Instrument Module Thermal Vacuum Thermal Balance Test Campaign at NASA's Goddard Space Flight Center

NASA Technical Reports Server (NTRS)

Glazer, Stuart; Comber, Brian (Inventor)

2016-01-01

The James Webb Space Telescope is a large infrared telescope with a 6.5-meter primary mirror, designed as a successor to the Hubble Space Telescope when launched in 2018. Three of the four science instruments contained within the Integrated Science Instrument Module (ISIM) are passively cooled to their operational temperature range of 36K to 40K with radiators, and the fourth instrument is actively cooled to its operational temperature of approximately 6K. Thermal-vacuum testing of the flight science instruments at the ISIM element level has taken place in three separate highly challenging and extremely complex thermal tests within a gaseous helium-cooled shroud inside Goddard Space Flight Centers Space Environment Simulator. Special data acquisition software was developed for these tests to monitor over 1700 flight and test sensor measurements, track over 50 gradients, component rates, and temperature limits in real time against defined constraints and limitations, and guide the complex transition from ambient to final cryogenic temperatures and back. This extremely flexible system has proven highly successful in safeguarding the nearly $2B science payload during the 3.5-month-long thermal tests. Heat flow measurement instrumentation, or Q-meters, were also specially developed for these tests. These devices provide thermal boundaries o the flight hardware while measuring instrument heat loads up to 600 mW with an estimated uncertainty of 2 mW in test, enabling accurate thermal model correlation, hardware design validation, and workmanship verification. The high accuracy heat load measurements provided first evidence of a potentially serious hardware design issue that was subsequently corrected. This paper provides an overview of the ISIM-level thermal-vacuum tests and thermal objectives; explains the thermal test configuration and thermal balances; describes special measurement instrumentation and monitoring and control software; presents key test thermal results; lists problems encountered during testing and lessons learned.

Identification and properties of steroid-binding proteins in nesting Chelonia mydas plasma.

PubMed

Ikonomopoulou, M P; Bradley, A J; Whittier, J M; Ibrahim, K

2006-11-01

We report for the first time the presence of a sex steroid-binding protein in the plasma of green sea turtles Chelonia mydas, which provides an insight into reproductive status. A high affinity, low capacity sex hormone steroid-binding protein was identified in nesting C. mydas and its thermal profile was established. In nesting C. mydas testosterone and oestradiol bind at 4 degrees C with high affinity (K (a) = 1.49 +/- 0.09 x 10(9) M(-1); 0.17 +/- 0.02 x 10(7) M(-1)) and low binding capacity (B (max) = 3.24 +/- 0.84 x 10(-5) M; 0.33 +/- 0.06 x 10(-4) M). The binding affinity and capacity of testosterone at 23 and 36 degrees C, respectively were similar to those determined at 4 degrees C. However, oestradiol showed no binding activity at 36 degrees C. With competition studies we showed that oestradiol and oestrone do not compete for binding sites. Furthermore, in nesting C. mydas plasma no high-affinity binding was observed for adrenocortical steroids (cortisol and corticosterone) and progesterone. Our results indicate that in nesting C. mydas plasma temperature has a minimal effect on the high-affinity binding of testosterone to sex steroid-binding protein, however, the high affinity binding of oestradiol to sex steroid-binding protein is abolished at a hypothetically high (36 degrees C) sea/ambient/body temperature. This suggests that at high core body temperatures most of the oestradiol becomes biologically available to the tissues rather than remaining bound to a high-affinity carrier.

Unexpected DNA affinity and sequence selectivity through core rigidity in guanidinium-based minor groove binders.

PubMed

Nagle, Padraic S; McKeever, Caitriona; Rodriguez, Fernando; Nguyen, Binh; Wilson, W David; Rozas, Isabel

2014-09-25

In this paper we report the design and biophysical evaluation of novel rigid-core symmetric and asymmetric dicationic DNA binders containing 9H-fluorene and 9,10-dihydroanthracene cores as well as the synthesis of one of these fluorene derivatives. First, the affinity toward particular DNA sequences of these compounds and flexible core derivatives was evaluated by means of surface plasmon resonance and thermal denaturation experiments finding that the position of the cations significantly influence the binding strength. Then their affinity and mode of binding were further studied by performing circular dichroism and UV studies and the results obtained were rationalized by means of DFT calculations. We found that the fluorene derivatives prepared have the ability to bind to the minor groove of certain DNA sequences and intercalate to others, whereas the dihydroanthracene compounds bind via intercalation to all the DNA sequences studied here.

Detection of protein-small molecule binding using a self-referencing external cavity laser biosensor.

PubMed

Meng Zhang; Peh, Jessie; Hergenrother, Paul J; Cunningham, Brian T

2014-01-01

High throughput screening of protein-small molecule binding interactions using label-free optical biosensors is challenging, as the detected signals are often similar in magnitude to experimental noise. Here, we describe a novel self-referencing external cavity laser (ECL) biosensor approach that achieves high resolution and high sensitivity, while eliminating thermal noise with sub-picometer wavelength accuracy. Using the self-referencing ECL biosensor, we demonstrate detection of binding between small molecules and a variety of immobilized protein targets with binding affinities or inhibition constants in the sub-nanomolar to low micromolar range. The demonstrated ability to perform detection in the presence of several interfering compounds opens the potential for increasing the throughput of the approach. As an example application, we performed a "needle-in-the-haystack" screen for inhibitors against carbonic anhydrase isozyme II (CA II), in which known inhibitors are clearly differentiated from inactive molecules within a compound library.

Finite temperature magnon spectra in yttrium iron garnet from a mean field approach in a tight-binding model

NASA Astrophysics Data System (ADS)

Shen, Ka

2018-04-01

We study magnon spectra at finite temperature in yttrium iron garnet using a tight-binding model with nearest-neighbor exchange interaction. The spin reduction due to thermal magnon excitation is taken into account via the mean field approximation to the local spin and is found to be different at two sets of iron atoms. The resulting temperature dependence of the spin wave gap shows good agreement with experiment. We find that only two magnon modes are relevant to the ferromagnetic resonance.

Precise determination of neutron binding energy of 64Cu

NASA Astrophysics Data System (ADS)

Telezhnikov, S. A.; Granja, C.; Honzatko, J.; Pospisil, S.; Tomandl, I.

2016-05-01

The neutron binding energy in 64Cu has been accurately measured in thermal neutron capture. A composite target of natural Cu and NaCl was used on a high flux neutron beam using a large measuring time. The γ-ray spectrum emitted in the ( n, γ) reaction was measured with a HPGe detector in large statistics (up to 106 events per channel). Intrinsic limitations of HPGe detectors, which restrict the accuracy of energy calibration, were determined. The value B n of 64Cu was determined as 7915.867(24) keV.

CO2-Binding-Organic-Liquids-Enhanced CO2 Capture using Polarity-Swing-Assisted Regeneration

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

Zhang, Jian; Kutnyakov, Igor; Koech, Phillip K.

A new solvent-based CO2 capture process couples the unique attributes of non-aqueous, CO2-binding organic liquids (CO2BOLs) with the newly discovered polarity-swing-assisted regeneration (PSAR) process that is unique to switchable ionic liquids. Laboratory measurements with PSAR indicate the ability to achieve a regeneration effect at 75°C comparable to that at 120°C using thermal regeneration only. Initial measurements also indicate that the kinetic behavior of CO2 release is also improved with PSAR. Abstract cleared PNWD-SA-9743

Targeting TMPRSS2 ERG in Prostate Cancer

DTIC Science & Technology

2016-09-01

Assay development for surface Plasmon resonance with purified ERG protein (months 31-36, completed July 2016) 7c. Perform thermal shift and...surface Plasmon resonance on compounds and determine binding constants (months 37-42, completed July 2016) Task 8. Identify FDA approved drugs that

Single well thermal tracer test, a new experimental set up for characterizing thermal transport in fractured media

NASA Astrophysics Data System (ADS)

de La Bernardie, Jérôme; Bour, Olivier; Guihéneuf, Nicolas; Chatton, Eliot; Labasque, Thierry; Longuevergne, Laurent; Le Lay, Hugo; Koch, Floriant; Gerard, Marie-Françoise; Le Borgne, Tanguy

2017-04-01

Thermal transport in fractured media depends on the hydrological properties of fractures and thermal characteristics of rock. Tracer tests using heat as tracer can thus be a good alternative to characterize fractured media for shallow geothermal needs. This study investigates the possibility of implementing a new thermal tracer test set up, the single well thermal tracer test, to characterize hydraulic and thermal transport properties of fractured crystalline rock. The experimental setup is based on injecting hot water in a fracture isolated by a double straddle packer in the borehole while pumping and monitoring the temperature in a fracture crossing the same borehole at greater elevation. One difficulty comes from the fact that injection and withdrawal are achieved in the same borehole involving thermal losses along the injection tube that may disturb the heat recovery signal. To be able to well localize the heat influx, we implemented a Fiber-Optic Distributed Temperature Sensing (FO-DTS) which allows the temperature monitoring with high spatial and temporal resolution (29 centimeters and 30 seconds respectively). Several tests, at different pumping and injection rates, were performed in a crystalline rock aquifer at the experimental site of Ploemeur (H+ observatory network). We show through signal processing how the thermal breakthrough may be extracted thanks to Fiber-Optic distributed temperature measurements. In particular, we demonstrate how detailed distributed temperature measurements were useful to identify different inflows and to estimate how much heat was transported and stored within the fractures network. Thermal breakthrough curves of single well thermal tracer tests were then interpreted with a simple analytical model to characterize hydraulic and thermal characteristics of the fractured media. We finally discuss the advantages of these tests compared to cross-borehole thermal tracer tests.

Multidimensional Tests of Thermal Protection Materials in the Arcjet Test Facility

NASA Technical Reports Server (NTRS)

Agrawal, Parul; Ellerby, Donald T.; Switzer, Mathew R.; Squire, Thomas H.

2010-01-01

Many thermal protection system materials used for spacecraft heatshields have anisotropic thermal properties, causing them to display significantly different thermal characteristics in different directions, when subjected to a heating environment during flight or arcjet tests. This paper investigates the effects of sidewall heating coupled with anisotropic thermal properties of thermal protection materials in the arcjet environment. Phenolic Impregnated Carbon Ablator (PICA) and LI-2200 materials (the insulation material of Shuttle tiles) were used for this study. First, conduction-based thermal response simulations were carried out, using the Marc.Mentat finite element solver, to study the effects of sidewall heating on PICA arcjet coupons. The simulation showed that sidewall heating plays a significant role in thermal response of these models. Arcjet tests at the Aerodynamic Heating Facility (AHF) at NASA Ames Research Center were performed later on instrumented coupons to obtain temperature history at sidewall and various radial locations. The details of instrumentation and experimental technique are the prime focus of this paper. The results obtained from testing confirmed that sidewall heating plays a significant role in thermal response of these models. The test results were later used to verify the two-dimensional ablation, thermal response, and sizing program, TITAN. The test data and model predictions were found to be in excellent agreement

Cooperative unfolding of apolipoprotein A-1 induced by chemical denaturation.

PubMed

Eckhardt, D; Li-Blatter, X; Schönfeld, H-J; Heerklotz, H; Seelig, J

2018-05-25

Apolipoprotein A-1 (Apo A-1) plays an important role in lipid transfer and obesity. Chemical unfolding of α-helical Apo A-1 is induced with guanidineHCl and monitored with differential scanning calorimetry (DSC) and CD spectroscopy. The unfolding enthalpy and the midpoint temperature of unfolding decrease linearly with increasing guanidineHCl concentration, caused by the weak binding of denaturant. At room temperature, binding of 50-60 molecules guanidineHCl leads to a complete Apo A-1 unfolding. The entropy of unfolding decreases to a lesser extent than the unfolding enthalpy. Apo A-1 chemical unfolding is a dynamic multi-state equilibrium that is analysed with the Zimm-Bragg theory modified for chemical unfolding. The chemical Zimm-Bragg theory predicts the denaturant binding constant K D and the protein cooperativity σ. Chemical unfolding of Apo A-1 is two orders of magnitude less cooperative than thermal unfolding. The free energy of thermal unfolding is ~0.2 kcal/mol per amino acid residue and ~1.0 kcal/mol for chemical unfolding at room temperature. The Zimm-Bragg theory calculates conformational probabilities and the chemical Zimm-Bragg theory predicts stretches of α-helical segments in dynamic equilibrium, unfolding and refolding independently and fast. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Calcium Binding and Disulfide Bonds Regulate the Stability of Secretagogin towards Thermal and Urea Denaturation

PubMed Central

Weiffert, Tanja; Ní Mhurchú, Niamh; O’Connell, David; Linse, Sara

2016-01-01

Secretagogin is a calcium-sensor protein with six EF-hands. It is widely expressed in neurons and neuro-endocrine cells of a broad range of vertebrates including mammals, fishes and amphibia. The protein plays a role in secretion and interacts with several vesicle-associated proteins. In this work, we have studied the contribution of calcium binding and disulfide-bond formation to the stability of the secretagogin structure towards thermal and urea denaturation. SDS-PAGE analysis of secretagogin in reducing and non-reducing conditions identified a tendency of the protein to form dimers in a redox-dependent manner. The denaturation of apo and Calcium-loaded secretagogin was studied by circular dichroism and fluorescence spectroscopy under conditions favoring monomer or dimer or a 1:1 monomer: dimer ratio. This analysis reveals significantly higher stability towards urea denaturation of Calcium-loaded secretagogin compared to the apo protein. The secondary and tertiary structure of the Calcium-loaded form is not completely denatured in the presence of 10 M urea. Reduced and Calcium-loaded secretagogin is found to refold reversibly after heating to 95°C, while both oxidized and reduced apo secretagogin is irreversibly denatured at this temperature. Thus, calcium binding greatly stabilizes the structure of secretagogin towards chemical and heat denaturation. PMID:27812162

Radiation Analysis Program

DTIC Science & Technology

2018-02-28

qualification testing to include vibrational, thermal bake and thermal cycling to ensure the experiment would perform as expected during operation on...series of tests for flight qualification. These tests included bake and thermal cycling. In addition, vibrational testing was also accomplished

Effects of Co doping on the metamagnetic states of the ferromagnetic fcc Fe-Co alloy.

PubMed

Ortiz-Chi, Filiberto; Aguayo, Aarón; de Coss, Romeo

2013-01-16

The evolution of the metamagnetic states in the ferromagnetic face centered cubic (fcc) Fe(1-x)Co(x) alloy as a function of Co concentration has been studied by means of first-principles calculations. The ground state properties were obtained using the full-potential linear augmented plane wave method and the generalized gradient approximation for the exchange-correlation functional. The alloying was modeled using the virtual crystal approximation and the magnetic states were obtained from the calculations of the total energy as a function of the spin moment, using the fixed spin moment method. For ferromagnetic fcc Fe, the binding-energy curve shows metamagnetic behavior, with two minima corresponding to a small-volume, low-spin (LS) state and a large-volume, high-spin (HS) state, which are separated by a small energy (E(LS) ≲ E(HS)). The evolution of the magnetic moment, the exchange integral (J), and the binding-energy curve is analyzed in the whole range of Co concentrations (x). The magnetic moment corresponding to the HS state decreases monotonically from 2.6 μ(B)/atom in fcc Fe to 1.7 μ(B)/atom in fcc Co. In contrast, the exchange integral for the HS state shows a maximum at around x = 0.45. The thermal dependence of the lattice parameter is evaluated with a method based on statistical mechanics using the binding-energy curve as an effective potential. It is observed that the behavior of the lattice parameter with temperature is tuned by Co doping, from negative thermal expansion in fcc Fe to positive thermal expansion in fcc Co, through the modification of the energetics of the metamagnetic states.

26th Space Simulation Conference Proceedings. Environmental Testing: The Path Forward

NASA Technical Reports Server (NTRS)

Packard, Edward A.

2010-01-01

Topics covered include: A Multifunctional Space Environment Simulation Facility for Accelerated Spacecraft Materials Testing; Exposure of Spacecraft Surface Coatings in a Simulated GEO Radiation Environment; Gravity-Offloading System for Large-Displacement Ground Testing of Spacecraft Mechanisms; Microscopic Shutters Controlled by cRIO in Sounding Rocket; Application of a Physics-Based Stabilization Criterion to Flight System Thermal Testing; Upgrade of a Thermal Vacuum Chamber for 20 Kelvin Operations; A New Approach to Improve the Uniformity of Solar Simulator; A Perfect Space Simulation Storm; A Planetary Environmental Simulator/Test Facility; Collimation Mirror Segment Refurbishment inside ESA s Large Space; Space Simulation of the CBERS 3 and 4 Satellite Thermal Model in the New Brazilian 6x8m Thermal Vacuum Chamber; The Certification of Environmental Chambers for Testing Flight Hardware; Space Systems Environmental Test Facility Database (SSETFD), Website Development Status; Wallops Flight Facility: Current and Future Test Capabilities for Suborbital and Orbital Projects; Force Limited Vibration Testing of JWST NIRSpec Instrument Using Strain Gages; Investigation of Acoustic Field Uniformity in Direct Field Acoustic Testing; Recent Developments in Direct Field Acoustic Testing; Assembly, Integration and Test Centre in Malaysia: Integration between Building Construction Works and Equipment Installation; Complex Ground Support Equipment for Satellite Thermal Vacuum Test; Effect of Charging Electron Exposure on 1064nm Transmission through Bare Sapphire Optics and SiO2 over HfO2 AR-Coated Sapphire Optics; Environmental Testing Activities and Capabilities for Turkish Space Industry; Integrated Circuit Reliability Simulation in Space Environments; Micrometeoroid Impacts and Optical Scatter in Space Environment; Overcoming Unintended Consequences of Ambient Pressure Thermal Cycling Environmental Tests; Performance and Functionality Improvements to Next Generation Thermal Vacuum Control System; Robotic Lunar Lander Development Project: Three-Dimensional Dynamic Stability Testing and Analysis; Thermal Physical Properties of Thermal Coatings for Spacecraft in Wide Range of Environmental Conditions: Experimental and Theoretical Study; Molecular Contamination Generated in Thermal Vacuum Chambers; Preventing Cross Contamination of Hardware in Thermal Vacuum Chambers; Towards Validation of Particulate Transport Code; Updated Trends in Materials' Outgassing Technology; Electrical Power and Data Acquisition Setup for the CBER 3 and 4 Satellite TBT; Method of Obtaining High Resolution Intrinsic Wire Boom Damping Parameters for Multi-Body Dynamics Simulations; and Thermal Vacuum Testing with Scalable Software Developed In-House.

Characterization of local polarity and hydrophobic binding sites of beta-lactoglobulin by using N-terminal specific fluorescence labeling.

PubMed

Dong, Su-Ying; Zhao, Zhen-Wen; Ma, Hui-Min

2006-01-01

Because of wide ligand-binding ability and significant industrial interest of beta-lactoglobulin (beta-LG), its binding properties have been extensively studied. However, there still exists a controversy as to where a ligand binds, since at least two potential hydrophobic binding sites in beta-LG have been postulated for ligand binding: an internal one (calyx) and an external one (near the N-terminus). In this work, the local polarity and hydrophobic binding sites of beta-LG have been characterized by using N-terminal specific fluorescence labeling combined with a polarity-sensitive fluorescent probe 3-(4-chloro-6-hydrazino- 1,3,5-triazinylamino)-7-(dimethylamino)-2-methylphenazine (CHTDP). The polarity within the calyx is found to be extremely low, which is explained in terms of superhydrophobicity possibly resulting from its nanostructure, and the polarity is increased with the destruction of the calyx by heat treatment. However, the polarity of the N-terminal domain in native beta-LG is decreased after thermal denaturation. This polarity trend toward decreasing instead of increasing shows that beta-LG may have no definite external hydrophobic binding site. The hydrophobic binding of a ligand such as CHTDP at the surface of the protein is probably achieved via appropriate assembling of corresponding hydrophobic residues rather than via a fixed external hydrophobic binding site. Also, the ligand-binding location in beta-LG is found to be relevant to not only experimental conditions (pH < or = 6.2 or pH > 7.1) but also binding mechanisms (hydrophobic affinity or electrostatic interaction).

Thermal decomposition study of manganese sulfide (MnS) nanoparticles

NASA Astrophysics Data System (ADS)

Tailor, Jiten P.; Khimani, Ankurkumar J.; Chaki, Sunil H.; Deshpande, M. P.

2018-05-01

The as-synthesized manganese sulfide (MnS) nanoparticles were used for the thermal study. The nanoparticles were synthesized by simple wet chemical route at ambient temperature. The photoelectron binding energy and chemical composition of MnS nanoparticles was analyzed by X-ray photoelectron spectroscopy (XPS). The thermogravimetric (TG), differential thermogravimetric (DTG) and differential thermal analysis (DTA) were carried out on the as-synthesized MnS nanoparticles. The thermocurves were recorded in inert N2 atmosphere in the temperature range of ambient to 1173 K. The heating rates employed were 5, 10, 15 and 20 K/min. The thermodynamic parameters like activation energy (Ea), enthalpy change (ΔH), entropy change (ΔS) and change in Gibbs free energy (ΔG) of as-synthesized MnS nanoparticles were determined using Kissinger method. The obtained XPS and thermal results are discussed.

Advanced Thermal Simulator Testing: Thermal Analysis and Test Results

NASA Technical Reports Server (NTRS)

Bragg-Sitton, Shannon M.; Dickens, Ricky; Dixon, David; Reid, Robert; Adams, Mike; Davis, Joe

2008-01-01

Work at the NASA Marshall Space Flight Center seeks to develop high fidelity, electrically heated thermal simulators that represent fuel elements in a nuclear reactor design to support non-nuclear testing applicable to the development of a space nuclear power or propulsion system. Comparison between the fuel pins and thermal simulators is made at the outer fuel clad surface, which corresponds to the outer sheath surface in the thermal simulator. The thermal simulators that are currently being tested correspond to a SNAP derivative reactor design that could be applied for Lunar surface power. These simulators are designed to meet the geometric and power requirements of a proposed surface power reactor design, accommodate testing of various axial power profiles, and incorporate imbedded instrumentation. This paper reports the results of thermal simulator analysis and testing in a bare element configuration, which does not incorporate active heat removal, and testing in a water-cooled calorimeter designed to mimic the heat removal that would be experienced in a reactor core.

10.2 Thermal-Structural Testing

NASA Technical Reports Server (NTRS)

Hudson, Larry D.

2008-01-01

Objective: Test a C/SiC Ruddervator Subcomponent under relevant thermal, mechanical & dynamic loading a) Thermal-structural mission cycling for re-entry and hypersonic cruise conditions; b) High-temperature modal survey to study the effect of heating on mode shapes, natural frequencies and damping. Supports NASA ARMD Hypersonics Material & Structures Program. Partners: NASA Dryden / Langley / Glenn, Lockheed-Martin, Materials Research & Design, GE CCP Test Phases - Phase 1: Acoustic-Vibration Testing (LaRC) completed - Phase 2: Thermal-Mechanical Testing (DFRC) in assembly - Phase 3: Mechanical Testing (DFRC) in assembly

Stereoselective L-(3H)quinuclidinyl benzilate-binding sites in nervous tissue of Aplysia californica: evidence for muscarinic receptors

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

Murray, T.F.; Mpitsos, G.J.; Siebenaller, J.F.

The muscarinic antagonist L-(/sup 3/H)quinuclidinyl benzilate (L-(/sup 3/H)QNB) binds with a high affinity (Kd = 0.77 nM) to a single population of specific sites (Bmax = 47 fmol/mg of protein) in nervous tissue of the gastropod mollusc, Aplysia. The specific L-(/sup 3/H)QNB binding is displaced stereoselectively by the enantiomers of benzetimide, dexetimide, and levetimide. The pharmacologically active enantiomer, dexetimide, is more potent than levetimide as an inhibitor of L-(/sup 3/H)QNB binding. Moreover, the muscarinic cholinergic ligands, scopolamine, atropine, oxotremorine, and pilocarpine are effective inhibitors of the specific L-(/sup 3/H)QNB binding, whereas nicotinic receptor antagonists, decamethonium and d-tubocurarine, are considerably lessmore » effective. These pharmacological characteristics of the L-(/sup 3/H)QNB-binding site provide evidence for classical muscarinic receptors in Aplysia nervous tissue. The physiological relevance of the dexetimide-displaceable L-(/sup 3/H)QNB-binding site was supported by the demonstration of the sensitivity of the specific binding to thermal denaturation. Specific binding of L-(/sup 3/H)QNB was also detected in nervous tissue of another marine gastropod, Pleurobranchaea californica. The characteristics of the Aplysia L-(/sup 3/H)QNB-binding site are in accordance with studies of numerous vertebrate and invertebrate tissues indicating that the muscarinic cholinergic receptor site has been highly conserved through evolution.« less

The test facility requirements for the thermal vacuum thermal balance test of the Cosmic Background Explorer Observatory

NASA Technical Reports Server (NTRS)

Milam, Laura J.

1990-01-01

The Cosmic Background Explorer Observatory (COBE) underwent a thermal vacuum thermal balance test in the Space Environment Simulator (SES). This was the largest and most complex test ever conducted at this facility. The 4 x 4 m (13 x 13 ft) spacecraft weighed approx. 2223 kg (4900 lbs) for the test. The test set up included simulator panels for the inboard solar array panels, simulator panels for the flight cowlings, Sun and Earth Sensor stimuli, Thermal Radio Frequency Shield heater stimuli and a cryopanel for thermal control in the Attitude Control System Shunt Dissipator area. The fixturing also included a unique 4.3 m (14 ft) diameter Gaseous Helium Cryopanel which provided a 20 K environment for the calibration of one of the spacecraft's instruments, the Differential Microwave Radiometer. This cryogenic panel caused extra contamination concerns and a special method was developed and written into the test procedure to prevent the high buildup of condensibles on the panel which could have led to backstreaming of the thermal vacuum chamber. The test was completed with a high quality simulated space environment provided to the spacecraft. The test requirements, test set up, and special fixturing are described.

Test facility requirements for the thermal vacuum thermal balance test of the Cosmic Background Explorer Observatory

NASA Technical Reports Server (NTRS)

Milam, Laura J.

1991-01-01

The Cosmic Background Explorer Observatory (COBE) underwant a thermal vacuum thermal balance test in the Space Environment Simulator (SES). This was the largest and most complex test ever conducted at this facility. The 4 x 4 m (13 x 13 ft) spacecraft weighed approx. 2223 kg (4900 lbs) for the test. The test set up included simulator panels for the inboard solar array panels, simulator panels for the flight cowlings, Sun and Earth Sensor stimuli, Thermal Radio Frequency Shield heater stimuli and a cryopanel for thermal control in the Attitude Control System Shunt Dissipator area. The fixturing also included a unique 4.3 m (14 ft) diameter Gaseous Helium Cryopanel which provided a 20 K environment for the calibration of one of the spacecraft's instruments, the Differential Microwave Radiometer. This cryogenic panel caused extra contamination concerns and a special method was developed and written into the test procedure to prevent the high buildup of condensibles on the panel which could have led to backstreaming of the thermal vacuum chamber. The test was completed with a high quality simulated space environment provided to the spacecraft. The test requirements, test set up, and special fixturing are described.

Lost time: Bindings do not represent temporal order information.

PubMed

Moeller, Birte; Frings, Christian

2018-06-04

Many accounts of human action control assume bindings between features of stimuli and responses of individual events. One widely accepted assumption about these bindings is that they do not contain temporal-order representations regarding the integrated elements. Even though several theories either explicitly or implicitly include it, this assumption has never been tested directly. One reason for this lack of evidence is likely that typical stimulus-response binding paradigms are inapt for such a test. Adapting a new paradigm of response-response binding to include order switches between response integration and retrieval, we were able to analyze possible representation of order information in bindings for the first time. Binding effects were identical for intact and switched response orders, indicating that bindings indeed include no temporal-order information.

Multivalency at Interfaces: Supramolecular Carbohydrate-Functionalized Graphene Derivatives for Bacterial Capture, Release, and Disinfection.

PubMed

Qi, Zhenhui; Bharate, Priya; Lai, Chian-Hui; Ziem, Benjamin; Böttcher, Christoph; Schulz, Andrea; Beckert, Fabian; Hatting, Benjamin; Mülhaupt, Rolf; Seeberger, Peter H; Haag, Rainer

2015-09-09

A supramolecular carbohydrate-functionalized two-dimensional (2D) surface was designed and synthesized by decorating thermally reduced graphene sheets with multivalent sugar ligands. The formation of host-guest inclusions on the carbon surface provides a versatile strategy, not only to increase the intrinsic water solubility of graphene-based materials, but more importantly to let the desired biofunctional binding groups bind to the surface. Combining the vital recognition role of carbohydrates and the unique 2D large flexible surface area of the graphene sheets, the addition of multivalent sugar ligands makes the resulting carbon material an excellent platform for selectively wrapping and agglutinating Escherichia coli (E. coli). By taking advantage of the responsive property of supramolecular interactions, the captured bacteria can then be partially released by adding a competitive guest. Compared to previously reported scaffolds, the unique thermal IR-absorption properties of graphene derivatives provide a facile method to kill the captured bacteria by IR-laser irradiation of the captured graphene-sugar-E. coli complex.

Free Energy Perturbation Calculations of the Thermodynamics of Protein Side-Chain Mutations.

PubMed

Steinbrecher, Thomas; Abel, Robert; Clark, Anthony; Friesner, Richard

2017-04-07

Protein side-chain mutation is fundamental both to natural evolutionary processes and to the engineering of protein therapeutics, which constitute an increasing fraction of important medications. Molecular simulation enables the prediction of the effects of mutation on properties such as binding affinity, secondary and tertiary structure, conformational dynamics, and thermal stability. A number of widely differing approaches have been applied to these predictions, including sequence-based algorithms, knowledge-based potential functions, and all-atom molecular mechanics calculations. Free energy perturbation theory, employing all-atom and explicit-solvent molecular dynamics simulations, is a rigorous physics-based approach for calculating thermodynamic effects of, for example, protein side-chain mutations. Over the past several years, we have initiated an investigation of the ability of our most recent free energy perturbation methodology to model the thermodynamics of protein mutation for two specific problems: protein-protein binding affinities and protein thermal stability. We highlight recent advances in the field and outline current and future challenges. Copyright © 2017 Elsevier Ltd. All rights reserved.

Influence of enzymatic hydrolysis on the allergenic reactivity of processed cashew and pistachio.

PubMed

Cuadrado, Carmen; Cheng, Hsiaopo; Sanchiz, Africa; Ballesteros, Isabel; Easson, Michael; Grimm, Casey C; Dieguez, M Carmen; Linacero, Rosario; Burbano, Carmen; Maleki, Soheila J

2018-02-15

Cashew and pistachio allergies are considered a serious health problem. Previous studies have shown that thermal processing, pressurization and enzymatic hydrolysis may reduce the allergenic properties of food by changing the protein structure. This study assesses the allergenic properties of cashew and pistachio after thermal treatment (boiling and autoclaving), with or without pressure (autoclaving), and multiple enzymatic treatments under sonication, by SDS-PAGE, western blot and ELISA, with serum IgE of allergic individuals, and mass spectroscopy. Autoclaving and enzymatic hydrolysis under sonication separately induced a measurable reduction in the IgE binding properties of pastes made from treated cashew and pistachio nuts. These treatments were more effective with pistachio allergens. However, heat combined with enzymatic digestion was necessary to markedly lower IgE binding to cashew allergens. The findings identify highly effective simultaneous processing conditions to reduce or even abolish the allergenic potency of cashew and pistachio. Copyright © 2017 Elsevier Ltd. All rights reserved.

Molecular dynamics simulations of AP/HMX composite with a modified force field.

PubMed

Zhu, Wei; Wang, Xijun; Xiao, Jijun; Zhu, Weihua; Sun, Huai; Xiao, Heming

2009-08-15

An all-atom force field for ammonium perchlorate (AP) is developed with the framework of pcff force field. The structural parameters of AP obtained with the modified force field are in good agreement with experimental values. Molecular dynamics (MD) simulations have been performed to investigate AP/HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane) composite at different temperatures. The binding energies, thermal expansion coefficient, and the trigger bond lengths of HMX in the AP/HMX composite have been obtained. The binding energies of the system increase slightly with temperature increasing, peak at 245K, and then gradually decrease. The volume thermal expansion coefficient of the AP/HMX composite has been derived from the volume variation with temperature. As the temperature rises, the maximal lengths of the trigger bond N-NO(2) of HMX increase gradually. The simulated results indicate that the maximal length of trigger bond can be used as a criterion for judging the sensitivity of energetic composite.

Diagnostic power of laboratory tests for hereditary spherocytosis: a comparison study in 150 patients grouped according to molecular and clinical characteristics

PubMed Central

Bianchi, Paola; Fermo, Elisa; Vercellati, Cristina; Marcello, Anna P.; Porretti, Laura; Cortelezzi, Agostino; Barcellini, Wilma; Zanella, Alberto

2012-01-01

Background The laboratory diagnosis of hereditary spherocytosis commonly relies on NaCl-based or glycerol-based red cell osmotic fragility tests; more recently, an assay directly targeting the hereditary spherocytosis molecular defect (eosin-5′-maleimide-binding test) has been proposed. None of the available tests identifies all cases of hereditary spherocytosis. Design and Methods We compared the performances of the eosin-5′-maleimide-binding test, NaCl-osmotic fragility studies on fresh and incubated blood, the glycerol lysis test, the acidified glycerol lysis test, and the Pink test on a series of 150 patients with hereditary spherocytosis grouped according to clinical phenotype and the defective protein, with the final aim of finding the combination of tests associated with the highest diagnostic power, even in the mildest cases of hereditary spherocytosis. Results The eosin-5′-maleimide-binding test had a sensitivity of 93% and a specificity of 98% for detecting hereditary spherocytosis: the sensitivity was independent of the type and amount of molecular defect and of the clinical phenotype. The acidified glycerol lysis test and Pink test showed comparable sensitivity (95% and 91%). The sensitivity of NaCl osmotic fragility tests, commonly considered the gold standard for the diagnosis of hereditary spherocytosis, was 68% on fresh blood and 81% on incubated blood, and further decreased in compensated cases (53% and 64%, respectively). The combination of the eosin-5′-maleimide-binding test and acidified glycerol lysis test enabled all patients with hereditary spherocytosis to be identified. The eosin-5′-maleimide-binding test showed the greatest disease specificity. Conclusions Each type of test fails to diagnose some cases of hereditary spherocytosis. The association of an eosin-5′-maleimide-binding test and an acidified glycerol lysis test enabled identification of all patients with hereditary spherocytosis in this series and, therefore, represents a currently effective diagnostic strategy for hereditary spherocytosis including mild/compensated cases. PMID:22058213

46 CFR 61.30-5 - Preparation of thermal fluid heater for inspection and test.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Preparation of thermal fluid heater for inspection and test. 61.30-5 Section 61.30-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PERIODIC TESTS AND INSPECTIONS Tests and Inspections of Fired Thermal Fluid Heaters § 61.30-5 Preparation of thermal fluid heater for...

Multidimensional Testing of Thermal Protection Materials in the Arcjet Test Facility

NASA Technical Reports Server (NTRS)

Agrawal, Parul; Ellerby, Donald T.; Switzer, Matt R.; Squire, Thomas Howard

2010-01-01

Many thermal protection system materials used for spacecraft heatshields have anisotropic thermal properties, causing them to display significantly different thermal characteristics in different directions, when subjected to a heating environment during flight or arcjet tests. The anisotropic effects are enhanced in the presence of sidewall heating. This paper investigates the effects of anisotropic thermal properties of thermal protection materials coupled with sidewall heating in the arcjet environment. Phenolic Impregnated Carbon Ablator (PICA) and LI-2200 materials (the insulation material of Shuttle tiles) were used for this study. First, conduction-based thermal response simulations were carried out, using the Marc.Mentat finite element solver, to study the effects of sidewall heating on PICA arcjet coupons. The simulation showed that sidewall heating plays a significant role in thermal response of these models. Arcjet tests at the Aerodynamic Heating Facility (AHF) at NASA Ames Research Center were performed later on instrumented coupons to obtain temperature history at sidewall and various radial locations. The details of instrumentation and experimental technique are the prime focus of this paper. The results obtained from testing confirmed that sidewall heating plays a significant role in thermal response of these models. The test results were later used to validate the two-dimensional ablation, thermal response, and sizing program, TITAN. The test data and model predictions were found to be in excellent agreement

Thermodynamic effects of proline introduction on protein stability.

PubMed

Prajapati, Ravindra Singh; Das, Mili; Sreeramulu, Sridhar; Sirajuddin, Minhajuddin; Srinivasan, Sankaranarayanan; Krishnamurthy, Vaishnavi; Ranjani, Ranganathan; Ramakrishnan, C; Varadarajan, Raghavan

2007-02-01

The amino acid Pro is more rigid than other naturally occurring amino acids and, in proteins, lacks an amide hydrogen. To understand the structural and thermodynamic effects of Pro substitutions, it was introduced at 13 different positions in four different proteins, leucine-isoleucine-valine binding protein, maltose binding protein, ribose binding protein, and thioredoxin. Three of the maltose binding protein mutants were characterized by X-ray crystallography to confirm that no structural changes had occurred upon mutation. In the remaining cases, fluorescence and CD spectroscopy were used to show the absence of structural change. Stabilities of wild type and mutant proteins were characterized by chemical denaturation at neutral pH and by differential scanning calorimetry as a function of pH. The mutants did not show enhanced stability with respect to chemical denaturation at room temperature. However, 6 of the 13 single mutants showed a small but significant increase in the free energy of thermal unfolding in the range of 0.3-2.4 kcal/mol, 2 mutants showed no change, and 5 were destabilized. In five of the six cases, the stabilization was because of reduced entropy of unfolding. However, the magnitude of the reduction in entropy of unfolding was typically several fold larger than the theoretical estimate of -4 cal K(-1) mol(-1) derived from the relative areas in the Ramachandran map accessible to Pro and Ala residues, respectively. Two double mutants were constructed. In both cases, the effects of the single mutations on the free energy of thermal unfolding were nonadditive. Copyright 2006 Wiley-Liss, Inc.

Process for the production of metal nitride sintered bodies and resultant silicon nitride and aluminum nitride sintered bodies

NASA Technical Reports Server (NTRS)

Yajima, S.; Omori, M.; Hayashi, J.; Kayano, H.; Hamano, M.

1983-01-01

A process for the manufacture of metal nitride sintered bodies, in particular, a process in which a mixture of metal nitrite powders is shaped and heated together with a binding agent is described. Of the metal nitrides Si3N4 and AIN were used especially frequently because of their excellent properties at high temperatures. The goal is to produce a process for metal nitride sintered bodies with high strength, high corrosion resistance, thermal shock resistance, thermal shock resistance, and avoidance of previously known faults.

Reversibly bound chloride in the atrial natriuretic peptide receptor hormone-binding domain: possible allosteric regulation and a conserved structural motif for the chloride-binding site.

PubMed

Ogawa, Haruo; Qiu, Yue; Philo, John S; Arakawa, Tsutomu; Ogata, Craig M; Misono, Kunio S

2010-03-01

The binding of atrial natriuretic peptide (ANP) to its receptor requires chloride, and it is chloride concentration dependent. The extracellular domain (ECD) of the ANP receptor (ANPR) contains a chloride near the ANP-binding site, suggesting a possible regulatory role. The bound chloride, however, is completely buried in the polypeptide fold, and its functional role has remained unclear. Here, we have confirmed that chloride is necessary for ANP binding to the recombinant ECD or the full-length ANPR expressed in CHO cells. ECD without chloride (ECD(-)) did not bind ANP. Its binding activity was fully restored by bromide or chloride addition. A new X-ray structure of the bromide-bound ECD is essentially identical to that of the chloride-bound ECD. Furthermore, bromide atoms are localized at the same positions as chloride atoms both in the apo and in the ANP-bound structures, indicating exchangeable and reversible halide binding. Far-UV CD and thermal unfolding data show that ECD(-) largely retains the native structure. Sedimentation equilibrium in the absence of chloride shows that ECD(-) forms a strongly associated dimer, possibly preventing the structural rearrangement of the two monomers that is necessary for ANP binding. The primary and tertiary structures of the chloride-binding site in ANPR are highly conserved among receptor-guanylate cyclases and metabotropic glutamate receptors. The chloride-dependent ANP binding, reversible chloride binding, and the highly conserved chloride-binding site motif suggest a regulatory role for the receptor bound chloride. Chloride-dependent regulation of ANPR may operate in the kidney, modulating ANP-induced natriuresis.

Reversibly Bound Chloride in the Atrial Natriuretic Peptide Receptor Hormone Binding Domain: Possible Allosteric Regulation and a Conserved Structural Motif for the Chloride-binding Site

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

Ogawa, H.; Qiu, Y; Philo, J

2010-01-01

The binding of atrial natriuretic peptide (ANP) to its receptor requires chloride, and it is chloride concentration dependent. The extracellular domain (ECD) of the ANP receptor (ANPR) contains a chloride near the ANP-binding site, suggesting a possible regulatory role. The bound chloride, however, is completely buried in the polypeptide fold, and its functional role has remained unclear. Here, we have confirmed that chloride is necessary for ANP binding to the recombinant ECD or the full-length ANPR expressed in CHO cells. ECD without chloride (ECD(-)) did not bind ANP. Its binding activity was fully restored by bromide or chloride addition. Amore » new X-ray structure of the bromide-bound ECD is essentially identical to that of the chloride-bound ECD. Furthermore, bromide atoms are localized at the same positions as chloride atoms both in the apo and in the ANP-bound structures, indicating exchangeable and reversible halide binding. Far-UV CD and thermal unfolding data show that ECD(-) largely retains the native structure. Sedimentation equilibrium in the absence of chloride shows that ECD(-) forms a strongly associated dimer, possibly preventing the structural rearrangement of the two monomers that is necessary for ANP binding. The primary and tertiary structures of the chloride-binding site in ANPR are highly conserved among receptor-guanylate cyclases and metabotropic glutamate receptors. The chloride-dependent ANP binding, reversible chloride binding, and the highly conserved chloride-binding site motif suggest a regulatory role for the receptor bound chloride. Chloride-dependent regulation of ANPR may operate in the kidney, modulating ANP-induced natriuresis.« less

Reversibly bound chloride in the atrial natriuretic peptide receptor hormone-binding domain: Possible allosteric regulation and a conserved structural motif for the chloride-binding site

PubMed Central

Ogawa, Haruo; Qiu, Yue; Philo, John S; Arakawa, Tsutomu; Ogata, Craig M; Misono, Kunio S

2010-01-01

The binding of atrial natriuretic peptide (ANP) to its receptor requires chloride, and it is chloride concentration dependent. The extracellular domain (ECD) of the ANP receptor (ANPR) contains a chloride near the ANP-binding site, suggesting a possible regulatory role. The bound chloride, however, is completely buried in the polypeptide fold, and its functional role has remained unclear. Here, we have confirmed that chloride is necessary for ANP binding to the recombinant ECD or the full-length ANPR expressed in CHO cells. ECD without chloride (ECD(−)) did not bind ANP. Its binding activity was fully restored by bromide or chloride addition. A new X-ray structure of the bromide-bound ECD is essentially identical to that of the chloride-bound ECD. Furthermore, bromide atoms are localized at the same positions as chloride atoms both in the apo and in the ANP-bound structures, indicating exchangeable and reversible halide binding. Far-UV CD and thermal unfolding data show that ECD(−) largely retains the native structure. Sedimentation equilibrium in the absence of chloride shows that ECD(−) forms a strongly associated dimer, possibly preventing the structural rearrangement of the two monomers that is necessary for ANP binding. The primary and tertiary structures of the chloride-binding site in ANPR are highly conserved among receptor-guanylate cyclases and metabotropic glutamate receptors. The chloride-dependent ANP binding, reversible chloride binding, and the highly conserved chloride-binding site motif suggest a regulatory role for the receptor bound chloride. Chloride-dependent regulation of ANPR may operate in the kidney, modulating ANP-induced natriuresis. PMID:20066666

ONE-DIMENSIONAL TIME TO EXPLOSION (THERMAL SENSITIVITY) TESTS ON PETN, PBX-9407, LX-10, AND LX-17

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

Hsu, Peter C.; Strout, Steve; McClelland, Matthew

Incidents caused by fire and combat operations can heat energetic materials that may lead to thermal explosion and result in structural damage and casualty. Some explosives may thermally explode at fairly low temperatures (< 100 C) and the violence from thermal explosion may cause a significant damage. Thus it is important to understand the response of energetic materials to thermal insults. The One Dimensional Time to Explosion (ODTX) system at the Lawrence Livermore National Laboratory has been used for decades to measure times to thermal explosion, threshold thermal explosion temperature, and determine the kinetic parameters of thermal decomposition of energeticmore » materials. Samples of different configurations (pressed part, powder, paste, and liquid) can be tested in the system. The ODTX testing can also provide useful data for assessing the thermal explosion violence of energetic materials. This report summarizes the results of our recent ODTX experiments on PETN powder, PBX-9407 pressed part, LX-10 pressed part, LX-17 pressed part and compares the test data that were obtained decades ago with the older version of ODTX system. Test results show the thermal sensitivity of various materials tested in the following order: PETN> PBX-9407 > LX-10 > LX-17.« less

Thermal Gradient Cyclic Behavior of a Thermal/Environmental Barrier Coating System on SiC/SiC Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Lee, Kang N.; Miller, Robert A.

2002-01-01

Thermal barrier and environmental barrier coatings (TBCs and EBCs) will play a crucial role in future advanced gas turbine engines because of their ability to significantly extend the temperature capability of the ceramic matrix composite (CMC) engine components in harsh combustion environments. In order to develop high performance, robust coating systems for effective thermal and environmental protection of the engine components, appropriate test approaches for evaluating the critical coating properties must be established. In this paper, a laser high-heat-flux, thermal gradient approach for testing the coatings will be described. Thermal cyclic behavior of plasma-sprayed coating systems, consisting of ZrO2-8wt%Y2O3 thermal barrier and NASA Enabling Propulsion Materials (EPM) Program developed mullite+BSAS/Si type environmental barrier coatings on SiC/SiC ceramic matrix composites, was investigated under thermal gradients using the laser heat-flux rig in conjunction with the furnace thermal cyclic tests in water-vapor environments. The coating sintering and interface damage were assessed by monitoring the real-time thermal conductivity changes during the laser heat-flux tests and by examining the microstructural changes after the tests. The coating failure mechanisms are discussed based on the cyclic test results and are correlated to the sintering, creep, and thermal stress behavior under simulated engine temperature and heat flux conditions.

Spectroscopic and microcalorimetric studies on the molecular binding of food colorant acid red 27 with deoxyribonucleic acid.

PubMed

Basu, Anirban; Kumar, Gopinatha Suresh

2016-08-01

Interaction of the food colorant acid red 27 with double stranded DNA was investigated using spectroscopic and calorimetric methods. Absorbance and fluorescence studies suggested an intimate binding interaction between the dye and DNA. The quantum efficiency value testified an effective energy transfer from the DNA base pairs to the dye molecules. Minor groove displacement assay with Hoechst 33258 revealed that the binding occurs in the minor groove of DNA. Circular dichroism studies revealed that acid red 27 induces moderate conformational perturbations in DNA. Results of calorimetric studies suggested that the complexation process was driven largely by positive entropic contribution with a smaller favorable enthalpy contribution. The equilibrium constant of the binding was calculated to be (3.04 ± 0.09) × 10(4)  M(-1) at 298.15 K. Negative heat capacity value along with the enthalpy-entropy compensation phenomenon established the involvement of dominant hydrophobic forces in the binding process. Differential scanning calorimetry studies presented evidence for an increased thermal stability of DNA on binding of acid red 27. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Experimental and DFT studies on DNA binding and photocleavage of two cationic porphyrins. Effects of the introduction of a carboxyphenyl into pyridinium porphyrin.

PubMed

Zhao, Ping; Xu, Lian-Cai; Huang, Jin-Wang; Liu, Jie; Yu, Han-Cheng; Zheng, Kang-Cheng; Ji, Liang-Nian

2008-12-15

The DNA-binding affinities and DNA photocleavage abilities of cationic porphyrin, 5-(4-carboxyphenyl)-10,15,20-tris(4-methylpyridiniumyl)porphyrin (CTMPyP), and its reference compound meso-tetrakis(N-methyl-4-pyridiniumyl)porphyrin (H2TMPyP) have been investigated. The DNA-binding behaviors of the two compounds in NaH2PO4 buffer were compared systematically by using absorption, fluorescence and circular dichroism (CD) spectra, thermal denaturation as well as viscosity measurements. The experimental results show that CTMPyP binds to DNA in an outside binding mode, while H2TMPyP in an intercalative mode. Photocleavage experiments reveal that both two compounds employ 1O2-mediated mechanism in cleaving DNA and H2TMPyP can cleave DNA more efficiently than CTMPyP. Theoretical calculations were carried out with the density functional theory (DFT), and the calculated results indicate that the character and energies of some frontier orbitals of CTMPyP are quite different from those of H2TMPyP. These theoretical results can be used to explain their different DNA-binding modes and affinities to a certain extent.

A Prediction Method of Binding Free Energy of Protein and Ligand

NASA Astrophysics Data System (ADS)

Yang, Kun; Wang, Xicheng

2010-05-01

Predicting the binding free energy is an important problem in bimolecular simulation. Such prediction would be great benefit in understanding protein functions, and may be useful for computational prediction of ligand binding strengths, e.g., in discovering pharmaceutical drugs. Free energy perturbation (FEP)/thermodynamics integration (TI) is a classical method to explicitly predict free energy. However, this method need plenty of time to collect datum, and that attempts to deal with some simple systems and small changes of molecular structures. Another one for estimating ligand binding affinities is linear interaction energy (LIE) method. This method employs averages of interaction potential energy terms from molecular dynamics simulations or other thermal conformational sampling techniques. Incorporation of systematic deviations from electrostatic linear response, derived from free energy perturbation studies, into the absolute binding free energy expression significantly enhances the accuracy of the approach. However, it also is time-consuming work. In this paper, a new prediction method based on steered molecular dynamics (SMD) with direction optimization is developed to compute binding free energy. Jarzynski's equality is used to derive the PMF or free-energy. The results for two numerical examples are presented, showing that the method has good accuracy and efficiency. The novel method can also simulate whole binding proceeding and give some important structural information about development of new drugs.

Calculation of Relative Binding Free Energy in the Water-Filled Active Site of Oligopeptide-Binding Protein A.

PubMed

Maurer, Manuela; de Beer, Stephanie B A; Oostenbrink, Chris

2016-04-15

The periplasmic oligopeptide binding protein A (OppA) represents a well-known example of water-mediated protein-ligand interactions. Here, we perform free-energy calculations for three different ligands binding to OppA, using a thermodynamic integration approach. The tripeptide ligands share a high structural similarity (all have the sequence KXK), but their experimentally-determined binding free energies differ remarkably. Thermodynamic cycles were constructed for the ligands, and simulations conducted in the bound and (freely solvated) unbound states. In the unbound state, it was observed that the difference in conformational freedom between alanine and glycine leads to a surprisingly slow convergence, despite their chemical similarity. This could be overcome by increasing the softness parameter during alchemical transformations. Discrepancies remained in the bound state however, when comparing independent simulations of the three ligands. These difficulties could be traced to a slow relaxation of the water network within the active site. Fluctuations in the number of water molecules residing in the binding cavity occur mostly on a timescale larger than the simulation time along the alchemical path. After extensive simulations, relative binding free energies that were converged to within thermal noise could be obtained, which agree well with available experimental data.

Calculation of Relative Binding Free Energy in the Water-Filled Active Site of Oligopeptide-Binding Protein A

PubMed Central

Maurer, Manuela; de Beer, Stephanie B. A.; Oostenbrink, Chris

2018-01-01

The periplasmic oligopeptide binding protein A (OppA) represents a well-known example of water-mediated protein-ligand interactions. Here, we perform free-energy calculations for three different ligands binding to OppA, using a thermodynamic integration approach. The tripeptide ligands share a high structural similarity (all have the sequence KXK), but their experimentally-determined binding free energies differ remarkably. Thermodynamic cycles were constructed for the ligands, and simulations conducted in the bound and (freely solvated) unbound states. In the unbound state, it was observed that the difference in conformational freedom between alanine and glycine leads to a surprisingly slow convergence, despite their chemical similarity. This could be overcome by increasing the softness parameter during alchemical transformations. Discrepancies remained in the bound state however, when comparing independent simulations of the three ligands. These difficulties could be traced to a slow relaxation of the water network within the active site. Fluctuations in the number of water molecules residing in the binding cavity occur mostly on a timescale larger than the simulation time along the alchemical path. After extensive simulations, relative binding free energies that were converged to within thermal noise could be obtained, which agree well with available experimental data. PMID:27092480

Osmoregulation in Methanogens (and Other Interesting Organisms)

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

Roberts, Mary Fedarko

2014-12-03

Our research has been aimed at (i) identifying, (ii) determining mode of regulation, and (iii) understanding how different classes of compatible solutes (also termed osmolytes) affect macromolecular stability in response to osmotic and thermal stress. For solutes we have identified (e.g., di-inositol-1,1’-phosphate (DIP)), we used NMR to elucidate biosynthetic pathways and then cloned suspected enzymes in the pathway to explore how they are regulated. Compatible solutes are thought to protect proteins from thermal and osmotic stresses by being excluded from the surface, allowing critical water molecules to interact with the protein. This implies there are no specific binding interactions betweenmore » osmolytes and proteins. However, we and others have often observed very specific solute effects for proteins that suggest a more direct interaction between solute and protein is likely can occur. Measuring such a weak interaction is extremely difficult. We have developed a solution NMR method, high-resolution field cycling relaxometry, that can measure spin-lattice relaxation rates as a function of magnetic field from 11.7 (the field of a 500 MHz spectrometer) to 0.003 T. The methodology is ideal for nuclei in small molecules with moderately long relaxation times at high fields – phosphate groups (31P), enriched carbonyls (13C), or methyl groups (1H). The protein of interest is spin-labeled to introduce a large dipole on it that will dominate the relaxation of nuclei on any small molecules that bind transiently. The key is to measure relaxation below 1-2 T (and extract nuclei-spin label distances in the bound complex) where the small molecule relaxation will be dominated by dipolar mechanisms with a correlation time indicative of the large protein complex. Our explorations of an inositol monophosphatase (the last step in DIP generation) localized four discrete binding sides for the thermoprotectant α-glutamate. This is a novel approach, and while the work did not fully explain how this solute protected the IMPase from thermal denaturation, it did showcase a new and exciting method to monitor weak binding in biological systems.« less

Differential binding of RhoA, RhoB, and RhoC to protein kinase C-related kinase (PRK) isoforms PRK1, PRK2, and PRK3: PRKs have the highest affinity for RhoB.

PubMed

Hutchinson, Catherine L; Lowe, Peter N; McLaughlin, Stephen H; Mott, Helen R; Owen, Darerca

2013-11-12

Protein kinase C-related kinases (PRKs) are members of the protein kinase C superfamily of serine-threonine kinases and can be activated by binding to members of the Rho family of GTPases via a Rho-binding motif known as an HR1 domain. Three tandem HR1 domains reside at the N-terminus of the PRKs. We have assessed the ability of the HR1a and HR1b domains from the three PRK isoforms (PRK1, PRK2, and PRK3) to interact with the three Rho isoforms (RhoA, RhoB, and RhoC). The affinities of RhoA and RhoC for a construct encompassing both PRK1 HR1 domains were similar to those for the HR1a domain alone, suggesting that these interactions are mediated solely by the HR1a domain. The affinities of RhoB for both the PRK1 HR1a domain and the HR1ab didomain were higher than those of RhoA or RhoC. RhoB also bound more tightly to the didomain than to the HR1a domain alone, implicating the HR1b domain in the interaction. As compared with PRK1 HR1 domains, PRK2 and PRK3 domains bind less well to all Rho isoforms. Uniquely, however, the PRK3 domains display a specificity for RhoB that requires both the C-terminus of RhoB and the PRK3 HR1b domain. The thermal stability of the HR1a and HR1b domains was also investigated. The PRK2 HR1a domain was found to be the most thermally stable, while PRK2 HR1b, PRK3 HR1a, and PRK3 HR1b domains all exhibited lower melting temperatures, similar to that of the PRK1 HR1a domain. The lower thermal stability of the PRK2 and PRK3 HR1b domains may impart greater flexibility, driving their ability to interact with Rho isoforms.

Thermal Vacuum/Balance Test Results of Swift BAT with Loop Heat Pipe Thermal System

NASA Technical Reports Server (NTRS)

Choi, Michael K.

2004-01-01

The Swift Burst Alert Telescope (BAT) Detector Array is thermally well coupled to eight constant conductance heat pipes (CCHPs) embedded in the Detector Array Plate PAP), and two loop heat pipes (LHPs) transport heat from the CCHPs to a radiator. The CCHPs have ammonia as the working fluid and the LHPs have propylene as the working fluid. Precision heater controllers, which have adjustable set points in flight, are used to control the LHP compensation chamber and Detector Array xA1 ASIC temperatures. The radiator has AZ-Tek's AZW-LA-II low solar absorptance white paint as the thermal coating, and is located on the anti-sun side of the spacecraft. A thermal balance (T/B) test on the BAT was successfully completed. It validated that the thermal design satisfies the temperature requirements of the BAT in the flight thermal environments. Instrument level and observatory level thermal vacuum (TN) cycling tests of the BAT Detector Array by using the LHP thermal system were successfully completed. This paper presents the results of the T/B test and T N cycling tests.

Response of Staphylococcus aureus isolates from bovine mastitis to exogenous iron sources.

PubMed

Diarra, M S; Petitclerc, D; Lacasse, P

2002-09-01

Staphylococcus aureus can survive in conditions of extremely low iron concentration. The ability of S. aureus to use two exogenous hydroxamate types of siderophores (desferrioxamine and ferrichrome) and four iron-containing proteins found in cattle (hemin, hemoglobin, ferritin, and lactoferrin) were tested on 16 reference and clinical isolates. For all strains tested, ferrichrome and desferrioxamine showed strong growth-promoting activities in a disk diffusion assay and in liquid medium. The heme proteins hemin and hemoglobin were also found to support growth in culture media lacking other iron sources, while lactoferrin failed to do so. On media containing the iron chelator dipyridyl, ferritin induced a growth inhibition effect that was further enhanced in the presence of lactoferrin in seven of the 13 tested strains. Staphylococcus aureus was able to bind hemin and the level of binding activity was not increased after growth in iron-rich or -poor media. Dot-blot competition tests showed that biotin-labeled lactoferrin binds to S. aureus, and this binding can be inhibited by unlabeled lactoferrin. Expression of lactoferrin-binding activity was independent of the level of iron in the medium and the iron saturation status of lactoferrin. For each strain tested, ligand blots showed lactoferrin-binding proteins of molecular weights ranging from 32 to 92 kDa. Possible functions of these lactoferrin-binding proteins could not be related to iron acquisition mechanism in S. aureus.

Vapor deposition process provides new method for fabricating high temperature thermocouples

NASA Technical Reports Server (NTRS)

Remley, G. A.; Zellner, G. J.

1967-01-01

Fabrication techniques for high temperature thermocouples bind all components so that differential thermal expansion and contraction do not result in mechanical slippage and localized stress concentrations. Installation space is reduced or larger thermoelements and thicker insulation can be used to improve temperature measurement accuracy.

Identification of Maillard reaction induced chemical modifications on Ara h 1

USDA-ARS?s Scientific Manuscript database

The Maillard reaction is a non-enzymatic glycation reaction between proteins and reducing sugars that can modify nut allergens during thermal processing. These modifications can alter the structural and immunological properties of these allergens, and may result in increased IgE binding. Here, we ...

Cryogenic Optical Performance of a Light-weight Mirror Assembly for Future Space Astronomical Telescopes: Optical Test Results and Thermal Optical Model

NASA Technical Reports Server (NTRS)

Eng, Ron; Arnold, William; Baker, Markus A.; Bevan, Ryan M.; Carpenter, James R.; Effinger, Michael R.; Gaddy, Darrell E.; Goode, Brian K.; Kegley, Jeffrey R.; Hogue, William D.;

A substitutional mutation in the DNA binding domain of the androgen receptor causes complete androgen insensitivity syndrome.

PubMed

Komori, S; Sakata, K; Kasumi, H; Tsuji, Y; Hamada, K; Koyama, K

1999-10-01

DNA analysis of the androgen receptor gene in a patient with complete androgen insensitivity syndrome identified a substitutional mutation (tyrosine converted to cysteine at position 571) in the DNA binding domain. In vitro transfection experiments with the patients' androgen receptor gene, indicated normal expression of the androgen receptor in transfected COS-7 cells compared to the wild type gene. There was also no evidence of impaired thermal stability of the 5 alpha-dihydrotestosterone-androgen receptor complex. However, the capacity of the androgen receptor to activate target gene transcription was found to be completely disrupted in a luciferase assay. These results confirmed that only one substitutional mutation in the DNA binding domain was related to the pathogenesis of the complete androgen insensitivity syndrome.

IRIS thermal balance test within ESTEC LSS

NASA Technical Reports Server (NTRS)

Messidoro, Piero; Ballesio, Marino; Vessaz, J. P.

1988-01-01

The Italian Research Interim Stage (IRIS) thermal balance test was successfully performed in the ESTEC Large Space Simulator (LSS) to qualify the thermal design and to validate the thermal mathematical model. Characteristics of the test were the complexity of the set-up required to simulate the Shuttle cargo bay and allowing IRIS mechanism actioning and operation for the first time in the new LSS facility. Details of the test are presented, and test results for IRIS and the LSS facility are described.

Methods of Testing Thermal Insulation and Associated Test Apparatus

NASA Technical Reports Server (NTRS)

Fesmire, James E. (Inventor); Augustynowicz, Stanislaw D. (Inventor)

2004-01-01

The system and method for testing thermal insulation uses a cryostatic insulation tester having a vacuum chamber and a cold mass including a test chamber and upper and lower guard chambers adjacent thereto. The thermal insulation is positioned within the vacuum chamber and adjacent the cold mass. Cryogenic liquid is supplied to the test chamber, upper guard and lower guard to create a first gas layer in an upper portion of the lower guard chamber and a second gas layer in an upper portion of the test chamber. Temperature are sensed within the vacuum chamber to test the thermal insulation.

Comparative surface studies on wet and dry sacrificial thermal oxidation on silicon carbide

NASA Astrophysics Data System (ADS)

Koh, A.; Kestle, A.; Wright, C.; Wilks, S. P.; Mawby, P. A.; Bowen, W. R.

2001-04-01

A comparative study on the effect of wet and dry thermal oxidation on 4H-silicon carbide (SiC) and on sacrificial silicon (Si) thermal oxidation on 4H-SiC surface has been conducted using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The AFM images show the formation of 'nano-islands' of varying density on the SiC surface after the removal of thermal oxide using hydrofluoric (HF) acid etch. These nano-islands are resistant to HF acid and have been previously linked to residual carbon [1-3] resulting from the oxidation process. This paper presents the use of a sacrificial silicon oxidation (SSO) step as a form of surface preparation that gives a reproducible clean SiC surface. XPS results show a slight electrical shift in binding energy between the wet and dry thermal oxidation on the standard SiC surface, while the surface produced by the SSO technique shows a minimal shift.

Antifreeze and cryoprotective activities of ice-binding collagen peptides from pig skin.

PubMed

Cao, Hui; Zhao, Ying; Zhu, Yu Bing; Xu, Fei; Yu, Jing Song; Yuan, Min

2016-03-01

A novel "hyperactive" ice-binding peptide from porcine collagen was prepared by alkaline protease hydrolysis and a series of column chromatography separations, and then its antifreeze and cryoprotective properties were reported. Using differential scanning calorimetry (DSC), the thermal hysteresis (TH) of ice-binding collagen peptides was closely related to their concentration and crystal fraction. Collagen hydrolysates with maximal TH were obtained by hydrolysis at pH 8.0, DH 15.0%, and 5% alkaline protease at 55°C. After purification by column chromatography, the AP-3 ice-binding collagen peptide (GLLGPLGPRGLL) with 1162.8Da molecular weights exhibited the highest TH (5.28°C), which can be classified as "hyperactive". Recrystallisation and melt-resistance of ice cream were improved by AP-3 ice-binding collagen peptide at 0.2% (w/v) in a similar manner to natural antifreeze proteins. Moreover, the addition of AP-3 collagen peptides in ice cream greatly elevated the glass transition temperature (Tg) to -17.64°C. Copyright © 2015 Elsevier Ltd. All rights reserved.

Intrinsic thermodynamics of ethoxzolamide inhibitor binding to human carbonic anhydrase XIII

PubMed Central

2012-01-01

Background Human carbonic anhydrases (CAs) play crucial role in various physiological processes including carbon dioxide and hydrocarbon transport, acid homeostasis, biosynthetic reactions, and various pathological processes, especially tumor progression. Therefore, CAs are interesting targets for pharmaceutical research. The structure-activity relationships (SAR) of designed inhibitors require detailed thermodynamic and structural characterization of the binding reaction. Unfortunately, most publications list only the observed thermodynamic parameters that are significantly different from the intrinsic parameters. However, only intrinsic parameters could be used in the rational design and SAR of the novel compounds. Results Intrinsic binding parameters for several inhibitors, including ethoxzolamide, trifluoromethanesulfonamide, and acetazolamide, binding to recombinant human CA XIII isozyme were determined. The parameters were the intrinsic Gibbs free energy, enthalpy, entropy, and the heat capacity. They were determined by titration calorimetry and thermal shift assay in a wide pH and temperature range to dissect all linked protonation reaction contributions. Conclusions Precise determination of the inhibitor binding thermodynamics enabled correct intrinsic affinity and enthalpy ranking of the compounds and provided the means for SAR analysis of other rationally designed CA inhibitors. PMID:22676044

Insights into structural features determining odorant affinities to honey bee odorant binding protein 14.

PubMed

Schwaighofer, Andreas; Pechlaner, Maria; Oostenbrink, Chris; Kotlowski, Caroline; Araman, Can; Mastrogiacomo, Rosa; Pelosi, Paolo; Knoll, Wolfgang; Nowak, Christoph; Larisika, Melanie

2014-04-18

Molecular interactions between odorants and odorant binding proteins (OBPs) are of major importance for understanding the principles of selectivity of OBPs towards the wide range of semiochemicals. It is largely unknown on a structural basis, how an OBP binds and discriminates between odorant molecules. Here we examine this aspect in greater detail by comparing the C-minus OBP14 of the honey bee (Apis mellifera L.) to a mutant form of the protein that comprises the third disulfide bond lacking in C-minus OBPs. Affinities of structurally analogous odorants featuring an aromatic phenol group with different side chains were assessed based on changes of the thermal stability of the protein upon odorant binding monitored by circular dichroism spectroscopy. Our results indicate a tendency that odorants show higher affinity to the wild-type OBP suggesting that the introduced rigidity in the mutant protein has a negative effect on odorant binding. Furthermore, we show that OBP14 stability is very sensitive to the position and type of functional groups in the odorant. Copyright © 2014 Elsevier Inc. All rights reserved.

Universal binding energy relations in metallic adhesion

NASA Technical Reports Server (NTRS)

Ferrante, J.; Smith, J. R.; Rose, J. J.

1984-01-01

Rose, Smith, and Ferrante have discovered scaling relations which map the adhesive binding energy calculated by Ferrante and Smith onto a single universal binding energy curve. These binding energies are calculated for all combinations of Al(111), Zn(0001), Mg(0001), and Na(110) in contact. The scaling involves normalizing the energy by the maximum binding energy and normalizing distances by a suitable combination of Thomas-Fermi screening lengths. Rose et al. have also found that the calculated cohesive energies of K, Ba, Cu, Mo, and Sm scale by similar simple relations, suggesting the universal relation may be more general than for the simple free electron metals for which it was derived. In addition, the scaling length was defined more generally in order to relate it to measurable physical properties. Further this universality can be extended to chemisorption. A simple and yet quite accurate prediction of a zero temperature equation of state (volume as a function of pressure for metals and alloys) is presented. Thermal expansion coefficients and melting temperatures are predicted by simple, analytic expressions, and results compare favorably with experiment for a broad range of metals.

Exciton size and binding energy limitations in one-dimensional organic materials.

PubMed

Kraner, S; Scholz, R; Plasser, F; Koerner, C; Leo, K

2015-12-28

In current organic photovoltaic devices, the loss in energy caused by the charge transfer step necessary for exciton dissociation leads to a low open circuit voltage, being one of the main reasons for rather low power conversion efficiencies. A possible approach to avoid these losses is to tune the exciton binding energy to a value of the order of thermal energy, which would lead to free charges upon absorption of a photon, and therefore increase the power conversion efficiency towards the Shockley-Queisser limit. We determine the size of the excitons for different organic molecules and polymers by time dependent density functional theory calculations. For optically relevant transitions, the exciton size saturates around 0.7 nm for one-dimensional molecules with a size longer than about 4 nm. For the ladder-type polymer poly(benzimidazobenzophenanthroline), we obtain an exciton binding energy of about 0.3 eV, serving as a lower limit of the exciton binding energy for the organic materials investigated. Furthermore, we show that charge transfer transitions increase the exciton size and thus identify possible routes towards a further decrease of the exciton binding energy.

Feature binding in visual short-term memory is unaffected by task-irrelevant changes of location, shape, and color.

PubMed

Logie, Robert H; Brockmole, James R; Jaswal, Snehlata

2011-01-01

Three experiments used a change detection paradigm across a range of study-test intervals to address the respective contributions of location, shape, and color to the formation of bindings of features in sensory memory and visual short-term memory (VSTM). In Experiment 1, location was designated task irrelevant and was randomized between study and test displays. The task was to detect changes in the bindings between shape and color. In Experiments 2 and 3, shape and color, respectively, were task irrelevant and randomized, with bindings tested between location and color (Experiment 2) and location and shape (Experiment 3). At shorter study-test intervals, randomizing location was most disruptive, followed by shape and then color. At longer intervals, randomizing any task-irrelevant feature had no impact on change detection for bindings between features, and location had no special role. Results suggest that location is crucial for initial perceptual binding but loses that special status once representations are formed in VSTM, which operates according to different principles, than do visual attention and perception.

Significance of Landsat-7 Spacecraft Level Thermal Balance and Thermal Test for ETM+Instrument

NASA Technical Reports Server (NTRS)

Choi, Michael K.

1999-01-01

The thermal design and the instrument thermal vacuum (T/V) test of the Landsat-7 Enhanced Thematic Mapper Plus (ETM+) instrument were based on the Landsat-4, 5 and 6 heritage. The ETM+ scanner thermal model was also inherited from Landsat-4, 5 and 6. The temperature predictions of many scanner components in the original thermal model had poor agreement with the spacecraft and instrument integrated sun-pointing safehold (SPSH) thermal balance (T/B) test results. The spacecraft and instrument integrated T/B test led to a change of the Full Aperture Calibrator (FAC) motor stack "solar shield" coating from MIL-C-5541 to multi-layer insulation (MLI) thermal blanket. The temperature predictions of the Auxiliary Electronics Module (AEM) in the thermal model also had poor agreement with the T/B test results. Modifications to the scanner and AEM thermal models were performed to give good agreement between the temperature predictions and the test results. The correlated ETM+ thermal model was used to obtain flight temperature predictions. The flight temperature predictions in the nominal 15-orbit mission profile, plus margins, were used as the yellow limits for most of the ETM+ components. The spacecraft and instrument integrated T/B and TN test also revealed that the standby heater capacity on the Scan Mirror Assembly (SMA) was insufficient when the Earth Background Simulator (EBS) was 1 50C or colder, and the baffle heater possibly caused the coherent noise in the narrow band data when it was on. Also, the cooler cool-down was significantly faster than that in the instrument T/V test, and the coldest Cold Focal Plane Array (CFPA) temperature achieved was colder.

Use of thermal sieve to allow optical testing of cryogenic optical systems.

PubMed

Kim, Dae Wook; Cai, Wenrui; Burge, James H

2012-05-21

Full aperture testing of large cryogenic optical systems has been impractical due to the difficulty of operating a large collimator at cryogenic temperatures. The Thermal Sieve solves this problem by acting as a thermal barrier between an ambient temperature collimator and the cryogenic system under test. The Thermal Sieve uses a set of thermally controlled baffles with array of holes that are lined up to pass the light from the collimator without degrading the wavefront, while attenuating the thermal background by nearly 4 orders of magnitude. This paper provides the theory behind the Thermal Sieve system, evaluates the optimization for its optical and thermal performance, and presents the design and analysis for a specific system.

Thermal actuation in TRPV1: Role of embedded lipids and intracellular domains.

PubMed

Melnick, Corey; Kaviany, Massoud

2018-05-07

The transient response potential cation channel TRPV1 responds to high temperature, but many of the mechanisms driving its thermal actuation remain unclear. Its recently resolved structure has enabled a number of molecular dynamics (MD) studies focused on illuminating these mechanisms. We add to these efforts by performing the first all-atom MD simulations of its most recently resolved structure at different temperatures. While the complete, thermally induced transition of TRPV1 from its closed to open configuration remains elusive, our analysis of the hydrogen bonding networks, thermodynamics, hydration, and principal components of motion provide a wealth of information on the mechanisms which initiate or influence the thermal opening in TRPV1. In particular, we (i) support the previously proposed mechanism driving thermal actuation in the extracellular pore of TRPV1, (ii) present new hypotheses regarding the thermal actuation in the C-terminal and adjacent linker domains, and (iii) support and build upon the existing hypothesis regarding the role of the vanilloid binding pocket and lipids embedded therein. Copyright © 2018 Elsevier Ltd. All rights reserved.

Energetic Materials Center Report--Small-Scale Safety and Thermal Testing Evaluation of Butyl Nitrate

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

Hsu, Peter C.; Reynolds, John G.

2013-04-26

Butyl Nitrate (BN) was examined by Small-Scale Safety and Thermal (SSST) Testing techniques to determine its sensitivity to impact, friction, spark and thermal exposure simulating handling and storage conditions. Under the conditions tested, the BN exhibits thermal sensitivity above 150 °C, and does not exhibit sensitive to impact, friction or spark.

Flexible thermal cycle test equipment for concentrator solar cells

DOEpatents

Hebert, Peter H [Glendale, CA; Brandt, Randolph J [Palmdale, CA

2012-06-19

A system and method for performing thermal stress testing of photovoltaic solar cells is presented. The system and method allows rapid testing of photovoltaic solar cells under controllable thermal conditions. The system and method presents a means of rapidly applying thermal stresses to one or more photovoltaic solar cells in a consistent and repeatable manner.

Heavy-Duty Vehicle Thermal Management | Transportation Research | NREL

Science.gov Websites

Heavy-Duty Vehicle Thermal Management Heavy-Duty Vehicle Thermal Management Infrared image of a and meet more stringent idling regulations. NREL's HDV thermal management program, CoolCab, focuses on thermal management technologies undergo assessment at NREL's Vehicle Testing and Integration Facility test

Intrinsic Thermodynamics and Structure Correlation of Benzenesulfonamides with a Pyrimidine Moiety Binding to Carbonic Anhydrases I, II, VII, XII, and XIII

PubMed Central

Kišonaitė, Miglė; Zubrienė, Asta; Čapkauskaitė, Edita; Smirnov, Alexey; Smirnovienė, Joana; Kairys, Visvaldas; Michailovienė, Vilma; Manakova, Elena; Gražulis, Saulius; Matulis, Daumantas

2014-01-01

The early stage of drug discovery is often based on selecting the highest affinity lead compound. To this end the structural and energetic characterization of the binding reaction is important. The binding energetics can be resolved into enthalpic and entropic contributions to the binding Gibbs free energy. Most compound binding reactions are coupled to the absorption or release of protons by the protein or the compound. A distinction between the observed and intrinsic parameters of the binding energetics requires the dissection of the protonation/deprotonation processes. Since only the intrinsic parameters can be correlated with molecular structural perturbations associated with complex formation, it is these parameters that are required for rational drug design. Carbonic anhydrase (CA) isoforms are important therapeutic targets to treat a range of disorders including glaucoma, obesity, epilepsy, and cancer. For effective treatment isoform-specific inhibitors are needed. In this work we investigated the binding and protonation energetics of sixteen [(2-pyrimidinylthio)acetyl]benzenesulfonamide CA inhibitors using isothermal titration calorimetry and fluorescent thermal shift assay. The compounds were built by combining four sulfonamide headgroups with four tailgroups yielding 16 compounds. Their intrinsic binding thermodynamics showed the limitations of the functional group energetic additivity approach used in fragment-based drug design, especially at the level of enthalpies and entropies of binding. Combined with high resolution crystal structural data correlations were drawn between the chemical functional groups on selected inhibitors and intrinsic thermodynamic parameters of CA-inhibitor complex formation. PMID:25493428

Calcium-dependent antigen binding as a novel modality for antibody recycling by endosomal antigen dissociation

PubMed Central

Hironiwa, N; Ishii, S; Kadono, S; Iwayanagi, Y; Mimoto, F; Habu, K; Igawa, T; Hattori, K

2016-01-01

The pH-dependent antigen binding antibody, termed a recycling antibody, has recently been reported as an attractive type of second-generation engineered therapeutic antibody. A recycling antibody can dissociate antigen in the acidic endosome, and thus bind to its antigen multiple times. As a consequence, a recycling antibody can neutralize large amounts of antigen in plasma. Because this approach relies on histidine residues to achieve pH-dependent antigen binding, which could limit the epitopes that can be targeted and affect the rate of antigen dissociation in the endosome, we explored an alternative approach for generating recycling antibodies. Since calcium ion concentration is known to be lower in endosome than in plasma, we hypothesized that an antibody with antigen-binding properties that are calcium-dependent could be used as recycling antibody. Here, we report a novel anti-interleukin-6 receptor (IL-6R) antibody, identified from a phage library that binds to IL-6R only in the presence of a calcium ion. Thermal dynamics and a crystal structure study revealed that the calcium ion binds to the heavy chain CDR3 region (HCDR3), which changes and possibly stabilizes the structure of HCDR3 to make it bind to antigen calcium dependently (PDB 5AZE). In vitro and in vivo studies confirmed that this calcium-dependent antigen-binding antibody can dissociate its antigen in the endosome and accelerate antigen clearance from plasma, making it a novel approach for generating recycling antibody. PMID:26496237

Simulation of Reversible Protein–Protein Binding and Calculation of Binding Free Energies Using Perturbed Distance Restraints

PubMed Central

2017-01-01

Virtually all biological processes depend on the interaction between proteins at some point. The correct prediction of biomolecular binding free-energies has many interesting applications in both basic and applied pharmaceutical research. While recent advances in the field of molecular dynamics (MD) simulations have proven the feasibility of the calculation of protein–protein binding free energies, the large conformational freedom of proteins and complex free energy landscapes of binding processes make such calculations a difficult task. Moreover, convergence and reversibility of resulting free-energy values remain poorly described. In this work, an easy-to-use, yet robust approach for the calculation of standard-state protein–protein binding free energies using perturbed distance restraints is described. In the binding process the conformations of the proteins were restrained, as suggested earlier. Two approaches to avoid end-state problems upon release of the conformational restraints were compared. The method was evaluated by practical application to a small model complex of ubiquitin and the very flexible ubiquitin-binding domain of human DNA polymerase ι (UBM2). All computed free energy differences were closely monitored for convergence, and the calculated binding free energies had a mean unsigned deviation of only 1.4 or 2.5 kJ·mol–1 from experimental values. Statistical error estimates were in the order of thermal noise. We conclude that the presented method has promising potential for broad applicability to quantitatively describe protein–protein and various other kinds of complex formation. PMID:28898077

Thermal-Mechanical Fatigue Testing of a Titanium-Aluminide Alloy.

DTIC Science & Technology

1987-12-01

DIMSTRIBUTION STA Approved for pubi robing e% dQ *- AFIT/GAB/AA/87D-18 THERMAL-MECHANICAL FATIGUE TESTING OF A TITANIUM - ALUMINIDE ALLOY THESIS John J...THERMAL-MECHANICAL FATIGUE TESTING OF A TITANIUM - ALUMINIDE ALLOY THESIS Presented to the Faculty of the School of Engineering of the Air Force Institute...develop a Thermal-Mechanical Fatigue (TMF) testing system for titanium - aluminide compact tension specimens. I could not have accomplished this without the

Analysis of protein stability and ligand interactions by thermal shift assay.

PubMed

Huynh, Kathy; Partch, Carrie L

2015-02-02

Purification of recombinant proteins for biochemical assays and structural studies is time-consuming and presents inherent difficulties that depend on the optimization of protein stability. The use of dyes to monitor thermal denaturation of proteins with sensitive fluorescence detection enables rapid and inexpensive determination of protein stability using real-time PCR instruments. By screening a wide range of solution conditions and additives in a 96-well format, the thermal shift assay easily identifies conditions that significantly enhance the stability of recombinant proteins. The same approach can be used as an initial low-cost screen to discover new protein-ligand interactions by capitalizing on increases in protein stability that typically occur upon ligand binding. This unit presents a methodological workflow for small-scale, high-throughput thermal denaturation of recombinant proteins in the presence of SYPRO Orange dye. Copyright © 2015 John Wiley & Sons, Inc.

EV space suit gloves (passive)

NASA Technical Reports Server (NTRS)

Fletcher, E. G.; Dodson, J. D.; Elkins, W.; Tickner, E. G.

1975-01-01

A pair of pressure and thermal insulating overgloves to be used with an Extravehicular (EV) suit assembly was designed, developed, fabricated, and tested. The design features extensive use of Nomex felt materials in lieu of the multiple layer insulation formerly used with the Apollo thermal glove. The glove theoretically satisfies all of the thermal requirements. The presence of the thermal glove does not degrade pressure glove tactility by more than the acceptable 10% value. On the other hand, the thermal glove generally degrades pressure glove mobility by more than the acceptable 10% value, primarily in the area of the fingers. Life cycling tests were completed with minimal problems. The thermal glove/pressure glove ensemble was also tested for comfort; the test subjects found no problems with the thermal glove although they did report difficulties with pressure points on the pressure glove which were independent of the thermal glove.

Three holes bound to a double acceptor - Be(+) in germanium

NASA Technical Reports Server (NTRS)

Haller, E. E.; Mcmurray, R. E., Jr.; Falicov, L. M.; Haegel, N. M.; Hansen, W. L.

1983-01-01

A double acceptor binding three holes has been observed for the first time with photoconductive far-infrared spectroscopy in beryllium-doped germanium single crystals. This new center, Be(+), has a hole binding energy of about 5 meV and is only present when free holes are generated by ionization of either neutral shallow acceptors or neutral Be double acceptors. The Be(+) center thermally ionizes above 4 K. It disappears at a uniaxial stress higher than about a billion dyn/sq cm parallel to (111) as a result of the lifting of the valence-band degeneracy.

Synthesis, characterization, molecular modeling and biological activity of metal complexes derived from (E)-N'-(furan-2-ylmethylene)morpholine-4-carbothiohydrazide

NASA Astrophysics Data System (ADS)

El-Samanody, El-Sayed A.; Emam, Sanaa M.; Emara, Esam M.

2017-10-01

A new series of some biologically active Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes was synthesized from the novel thiosemicarbazone ligand; (E)-N'-(furan-2-ylmethylene)morpholine-4-carbothiohydrazide (HL). Elemental, spectral, thermal analyses, magnetic susceptibility and molar conductivity measurements were used to elucidate the structure of separated compounds. The data prove that the ligand reacts with all metal ions in a neutral thione form. The electrolytic tetra-coordinate Cu(II); Zn(II) complexes (5, 6; 10) bind through the thione sulfur, furfural oxygen and azomethine nitrogen atoms of the ligand (NSO type) to construct fused five membered rings. However, the rest non-electrolyte octahedral complexes chelate via the furfural oxygen and azomethine nitrogen atoms of the ligand (NO type). Molecular modeling was conducted for the ligand and two representative complexes (1, 5) in order to substantiate their chemical structures. Thermal analyses are compatible with molecular modeling studies to support the proposed thermal decomposition pathways of metal complexes which start with the rupture of the long and weak N-NH bond. The thermal stability of metal complexes varies according to the number of solvents of crystallization, ionic radii and steric effect of anions. The ESR spectra of Cu(II) complexes are compatible with a primarily (dx2-y2)1 ground state with axial symmetry. The ligand and its Co(II); Cu(II); Cd(II) complexes (1; 5, 8; 11) along with their mixtures with metaldehyde were screened in vitro for their molluscicidal activity against Eobania vermiculata. Combination with metaldehyde enhances the toxicity effect of the tested compounds through reducing the period required for mortality and increasing the percentage of mortality after 24 h of treatments. The tested compounds gathered with metaldehyde are strongly affecting on the activity of ACP and ALP enzymes and TP content which are very important factors in the mucous secretion of Eobania vermiculata. These effects lead to excess mucous secretion, causing dryness and death for the snails.

Sequencing-based gene network analysis provides a core set of gene resource for understanding thermal adaptation in Zhikong scallop Chlamys farreri.

PubMed

Fu, X; Sun, Y; Wang, J; Xing, Q; Zou, J; Li, R; Wang, Z; Wang, S; Hu, X; Zhang, L; Bao, Z

2014-01-01

Marine organisms are commonly exposed to variable environmental conditions, and many of them are under threat from increased sea temperatures caused by global climate change. Generating transcriptomic resources under different stress conditions are crucial for understanding molecular mechanisms underlying thermal adaptation. In this study, we conducted transcriptome-wide gene expression profiling of the scallop Chlamys farreri challenged by acute and chronic heat stress. Of the 13 953 unique tags, more than 850 were significantly differentially expressed at each time point after acute heat stress, which was more than the number of tags differentially expressed (320-350) under chronic heat stress. To obtain a systemic view of gene expression alterations during thermal stress, a weighted gene coexpression network was constructed. Six modules were identified as acute heat stress-responsive modules. Among them, four modules involved in apoptosis regulation, mRNA binding, mitochondrial envelope formation and oxidation reduction were downregulated. The remaining two modules were upregulated. One was enriched with chaperone and the other with microsatellite sequences, whose coexpression may originate from a transcription factor binding site. These results indicated that C. farreri triggered several cellular processes to acclimate to elevated temperature. No modules responded to chronic heat stress, suggesting that the scallops might have acclimated to elevated temperature within 3 days. This study represents the first sequencing-based gene network analysis in a nonmodel aquatic species and provides valuable gene resources for the study of thermal adaptation, which should assist in the development of heat-tolerant scallop lines for aquaculture. © 2013 John Wiley & Sons Ltd.

Validation of NASA Thermal Ice Protection Computer Codes. Part 1; Program Overview

NASA Technical Reports Server (NTRS)

Miller, Dean; Bond, Thomas; Sheldon, David; Wright, William; Langhals, Tammy; Al-Khalil, Kamel; Broughton, Howard

1996-01-01

The Icing Technology Branch at NASA Lewis has been involved in an effort to validate two thermal ice protection codes developed at the NASA Lewis Research Center. LEWICE/Thermal (electrothermal deicing & anti-icing), and ANTICE (hot-gas & electrothermal anti-icing). The Thermal Code Validation effort was designated as a priority during a 1994 'peer review' of the NASA Lewis Icing program, and was implemented as a cooperative effort with industry. During April 1996, the first of a series of experimental validation tests was conducted in the NASA Lewis Icing Research Tunnel(IRT). The purpose of the April 96 test was to validate the electrothermal predictive capabilities of both LEWICE/Thermal, and ANTICE. A heavily instrumented test article was designed and fabricated for this test, with the capability of simulating electrothermal de-icing and anti-icing modes of operation. Thermal measurements were then obtained over a range of test conditions, for comparison with analytical predictions. This paper will present an overview of the test, including a detailed description of: (1) the validation process; (2) test article design; (3) test matrix development; and (4) test procedures. Selected experimental results will be presented for de-icing and anti-icing modes of operation. Finally, the status of the validation effort at this point will be summarized. Detailed comparisons between analytical predictions and experimental results are contained in the following two papers: 'Validation of NASA Thermal Ice Protection Computer Codes: Part 2- The Validation of LEWICE/Thermal' and 'Validation of NASA Thermal Ice Protection Computer Codes: Part 3-The Validation of ANTICE'

Indoor test for thermal performance of the Sunmaster evacuated tube (liquid) solar collector

NASA Technical Reports Server (NTRS)

1979-01-01

The test procedures used to obtain the thermal performance data for a solar collector under simulated conditions are presented. Tests included a stagnation test, a time constant test, a thermal efficiency test, an incident angle modifier test, and a hot fill test. All tests were performed at ambient conditions and the transient effect and the incident angle effect on the collector were determined. The solar collector is a water working fluid type.

A Survey of Methods for Measuring Thermally Induced Distortions of Test Articles Undergoing Solar Thermal Vacuum Test

NASA Technical Reports Server (NTRS)

Rempt, R. D.

1982-01-01

Various methods of measuring the small thermally induced distortions experienced either by various points on the space vehicles or by deviations of surfaces from a known shape during solar thermal vacuum tests are examined. State-of-the-art application of both photographic and real time observation are discussed. The relative merits of each of the methods are compared and evaluated in their applications to different types of test articles and situations. Magnitudes of thermally induced distortions which may be expected to be routinely measurable by the various methods are presented and compared.

Binding site feature description of 2-substituted benzothiazoles as potential AcrAB-TolC efflux pump inhibitors in E. coli.

PubMed

Yilmaz, S; Altinkanat-Gelmez, G; Bolelli, K; Guneser-Merdan, D; Ufuk Over-Hasdemir, M; Aki-Yalcin, E; Yalcin, I

2015-01-01

The resistance-nodulation-division (RND) family efflux pumps are important in the antibiotic resistance of Gram-negative bacteria. However, although a number of bacterial RND efflux pump inhibitors have been developed, there has been no clinically available RND efflux pump inhibitor to date. A set of BSN-coded 2-substituted benzothiazoles were tested alone and in combinations with ciprofloxacin (CIP) against the AcrAB-TolC overexpressor Escherichia coli AG102 clinical strain. The results indicated that the BSN compounds did not show intrinsic antimicrobial activity when tested alone. However, when used in combinations with CIP, a reversal in the antibacterial activity of CIP with up to 10-fold better MIC values was observed. In order to describe the binding site features of these BSN compounds with AcrB, docking studies were performed using the CDocker method. The performed docking poses and the calculated binding energy scores revealed that the tested compounds BSN-006, BSN-023, and BSN-004 showed significant binding interactions with the phenylalanine-rich region in the distal binding site of the AcrB binding monomer. Moreover, the tested compounds BSN-006 and BSN-023 possessed stronger binding energies than CIP, verifying that BSN compounds are acting as the putative substrates of AcrB.

Rapid CE-UV binding tests of environmentally hazardous compounds with polymer-modified magnetic nanoparticles.

PubMed

Iqbal, Zafar; Alsudir, Samar; Miah, Musharraf; Lai, Edward P C

2011-08-01

Hazardous compounds and bacteria in water have an adverse impact on human health and environmental ecology. Polydopamine (or polypyrrole)-coated magnetic nanoparticles and polymethacrylic acid-co-ethylene glycol dimethacrylate submicron particles were investigated for their fast binding kinetics with bisphenol A, proflavine, naphthalene acetic acid, and Escherichia coli. A new method was developed for the rapid determination of % binding by sequential injection of particles first and compounds (or E. coli) next into a fused-silica capillary for overlap binding during electrophoretic migration. Only nanolitre volumes of compounds and particles were sufficient to complete a rapid binding test. After heterogeneous binding, separation of the compounds from the particles was afforded by capillary electrophoresis. % binding was influenced by applied voltage but not current flow. In-capillary coating of particles affected the % binding of compounds. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cryogenic Optical Performance of a Lightweighted Mirror Assembly for Future Space Astronomical Telescopes: Correlating Optical Test Results and Thermal Optical Model

NASA Technical Reports Server (NTRS)

Eng, Ron; Arnold, William R.; Baker, Marcus A.; Bevan, Ryan M.; Burdick, Gregory; Effinger, Michael R.; Gaddy, Darrell E.; Goode, Brian K.; Hanson, Craig; Hogue, William D.;

Prediction of Carbohydrate Binding Sites on Protein Surfaces with 3-Dimensional Probability Density Distributions of Interacting Atoms

PubMed Central

Tsai, Keng-Chang; Jian, Jhih-Wei; Yang, Ei-Wen; Hsu, Po-Chiang; Peng, Hung-Pin; Chen, Ching-Tai; Chen, Jun-Bo; Chang, Jeng-Yih; Hsu, Wen-Lian; Yang, An-Suei

2012-01-01

Non-covalent protein-carbohydrate interactions mediate molecular targeting in many biological processes. Prediction of non-covalent carbohydrate binding sites on protein surfaces not only provides insights into the functions of the query proteins; information on key carbohydrate-binding residues could suggest site-directed mutagenesis experiments, design therapeutics targeting carbohydrate-binding proteins, and provide guidance in engineering protein-carbohydrate interactions. In this work, we show that non-covalent carbohydrate binding sites on protein surfaces can be predicted with relatively high accuracy when the query protein structures are known. The prediction capabilities were based on a novel encoding scheme of the three-dimensional probability density maps describing the distributions of 36 non-covalent interacting atom types around protein surfaces. One machine learning model was trained for each of the 30 protein atom types. The machine learning algorithms predicted tentative carbohydrate binding sites on query proteins by recognizing the characteristic interacting atom distribution patterns specific for carbohydrate binding sites from known protein structures. The prediction results for all protein atom types were integrated into surface patches as tentative carbohydrate binding sites based on normalized prediction confidence level. The prediction capabilities of the predictors were benchmarked by a 10-fold cross validation on 497 non-redundant proteins with known carbohydrate binding sites. The predictors were further tested on an independent test set with 108 proteins. The residue-based Matthews correlation coefficient (MCC) for the independent test was 0.45, with prediction precision and sensitivity (or recall) of 0.45 and 0.49 respectively. In addition, 111 unbound carbohydrate-binding protein structures for which the structures were determined in the absence of the carbohydrate ligands were predicted with the trained predictors. The overall prediction MCC was 0.49. Independent tests on anti-carbohydrate antibodies showed that the carbohydrate antigen binding sites were predicted with comparable accuracy. These results demonstrate that the predictors are among the best in carbohydrate binding site predictions to date. PMID:22848404

Thermal Performance Testing of EMU and CSAFE Liquid Cooling Garments

NASA Technical Reports Server (NTRS)

Rhodes, Richard; Bue, Grant; Hakam, Mark; Radford, Tamara

2013-01-01

Future exploration missions require the development of a new liquid cooling garment (LCG) that offers greater system reliability, is more comfortable, and maximizes thermal performance. To inform the development of a future LCG a thermal performance test was conducted to evaluate three factors: (1) the effect of the thermal comfort undergarment (TCU) on tactile and thermal comfort, (2) the comparable thermal performance of an CSAFE developed engineering evaluation unit (EEU) LCG, which uses a commercial-off-the-shelf (COTS) wicking garment as the base, and (3) the performance of a torso or upper body only LCG configuration to evaluate a proposed auxiliary loop configuration. To evaluate the thermal performance of each configuration a metabolic suit test was conducted, utilizing suited subjects to generate metabolic heat by walking on a treadmill at various speeds. Three (3) test subjects of similar height and weight produced a metabolic load for five tests by either resting (300-600 BTU/hr), walking at a slow pace (1200 BTU/hr), and walking at a brisk pace (2200 BTU/hr). During the test, data was collected that would allow us to track the heat transfer to the LCG and ventilation system to determine the thermal performance of the LCG configurations. Four different test configurations were tested, with one configuration tested twice. The test results show that the CSAFE EEU LCG and EMU LCG had comparable performance. The testing also showed that an auxiliary loop LCG, sized similarly to the shirt-only configuration, should provide adequate cooling for contingency scenarios. Finally, the testing showed the previous analysis that assumed a UA deterioration from the TCU was too conservative and the TCU may prove to be acceptable for future development with additional analysis and testing.

Item-location binding in working memory: is it hippocampus-dependent?

PubMed

Allen, Richard J; Vargha-Khadem, Faraneh; Baddeley, Alan D

2014-07-01

A general consensus is emerging that the hippocampus has an important and active role in the creation of new long-term memory representations of associations or bindings between elements. However, it is less clear whether this contribution can be extended to the creation of temporary bound representations in working memory, involving the retention of small numbers of items over short delays. We examined this by administering a series of recognition and recall tests of working memory for colour-location binding and object-location binding to a patient with highly selective hippocampal damage (Jon), and groups of control participants. Jon achieved high levels of accuracy in all working memory tests of recognition and recall binding across retention intervals of up to 10s. In contrast, Jon performed at chance on an unexpected delayed test of the same object-location binding information. These findings indicate a clear dissociation between working memory and long-term memory, with no evidence for a critical hippocampal contribution to item-location binding in working memory. Copyright © 2014 Elsevier Ltd. All rights reserved.

Synthesis, spectroscopic characterization, DNA interaction and biological activities of Mn(II), Co(II), Ni(II) and Cu(II) complexes with [(1H-1,2,4-triazole-3-ylimino)methyl]naphthalene-2-ol

NASA Astrophysics Data System (ADS)

Gaber, Mohamed; El-Wakiel, Nadia A.; El-Ghamry, Hoda; Fathalla, Shaimaa K.

2014-11-01

Manganese(II), cobalt(II), nickel(II) and copper(II) complexes of [(1H-1,2,4-triazole-3-ylimino)methyl]naphthalene-2-ol have been synthesized. The structure of complexes have been characterized by elemental analysis, molar conductance, magnetic moment measurements and spectral (IR, 1H NMR, EI-mass, UV-Vis and ESR), and thermal studies. The results showed that the chloro and nitrato Cu(II) complexes have octahedral geometry while Ni(II), Co(II) and Mn(II) complexes in addition to acetato Cu(II) complex have tetrahedral geometry. The possible structures of the metal complexes have been computed using the molecular mechanic calculations using the hyper chem. 8.03 molecular modeling program to confirm the proposed structures. The kinetic and thermodynamic parameters of the thermal decomposition steps were calculated from the TG curves. The binding modes of the complexes with DNA have been investigated by UV-Vis absorption titration. The results showed that the mode of binding of the complexes to DNA is intercalative or non-intercalative binding modes. Schiff base and its metal complexes have been screened for their in vitro antimicrobial activities against Gram positive bacteria (Staphylococcus aureus), Gram negative bacteria (Escherichia coli and Pesudomonas aeruginosa), fungi (Asperigllus flavus and Mucer) and yeast (Candida albicans and Malassezia furfur).

Inhibition of Mammalian 15-Lipoxygenase by Three Ebselen-like Drugs. A QM/MM and MM/PBSA Comparative Study.

PubMed

Cebrián-Prats, Anna; Rovira, Tiffani; Saura, Patricia; González-Lafont, Àngels; Lluch, José M

2017-12-28

Ebselen is a potent competitive inhibitor of the active form of rabbit 15-lipoxygenase, an enzyme involved in many inflammatory diseases. Light-induced Z-to-E isomerization of the ebselen-like 2-(3-benzylidene)-3-oxo-2,3-dihydrobenzo[b]thiophene-7-carboxylic acid methyl ester (BODTCM) molecule was used to convert the weak (Z)-BOTDCM inhibitor into the (E)-isomer with much higher inhibitory capacity. In this study, the binding modes of ebselen, (E)-BOTDCM and (Z)-BOTDCM, have been analyzed to provide molecular insights on the inhibitory potency of ebselen and on the geometric-isomer specificity of (E)- and (Z)-BOTDCM inhibitors. The inhibitor-enzyme structures obtained from docking and molecular dynamics simulations as well as from QM/MM calculations show that the inhibitor molecules are not coordinated to the nonheme iron in the active site. Thermal motion allows ebselen and (E)-BOTDCM to visit a wide range of the configurational space competing with the polyunsaturated fatty acid for binding at the active site. Both molecules present similar MM/PBSA binding free energies. The energy penalty for the bigger geometric deformation undergone by (E)-BODTCM would explain its lower inhibitor potency. The (Z)-isomer is the weakest inhibitor because thermal motion moves it to a region very far from the first coordination sphere of Fe, where it could not compete with the fatty acid substrate.

Thermal cycle testing of Space Station Freedom solar array blanket coupons

NASA Technical Reports Server (NTRS)

Scheiman, David A.; Schieman, David A.

1991-01-01

Lewis Research Center is presently conducting thermal cycle testing of solar array blanket coupons that represent the baseline design for Space Station Freedom. Four coupons were fabricated as part of the Photovoltaic Array Environment Protection (PAEP) Program, NAS 3-25079, at Lockheed Missile and Space Company. The objective of the testing is to demonstrate the durability or operational lifetime of the solar array welded interconnect design within the durability or operational lifetime of the solar array welded interconnect design within a low earth orbit (LEO) thermal cycling environment. Secondary objectives include the observation and identification of potential failure modes and effects that may occur within the solar array blanket coupons as a result of thermal cycling. The objectives, test articles, test chamber, performance evaluation, test requirements, and test results are presented for the successful completion of 60,000 thermal cycles.

Coupled diffusion processes and 2D affinities of adhesion molecules at synthetic membrane junctions

NASA Astrophysics Data System (ADS)

Peel, Christopher; Choudhuri, Kaushik; Schmid, Eva M.; Bakalar, Matthew H.; Ann, Hyoung Sook; Fletcher, Daniel A.; Journot, Celine; Turberfield, Andrew; Wallace, Mark; Dustin, Michael

A more complete understanding of the physically intrinsic mechanisms underlying protein mobility at cellular interfaces will provide additional insights into processes driving adhesion and organization in signalling junctions such as the immunological synapse. We observed diffusional slowing of structurally diverse binding proteins at synthetic interfaces formed by giant unilamellar vesicles (GUVs) on supported lipid bilayers (SLBs) that shows size dependence not accounted for by existing models. To model the effects of size and intermembrane spacing on interfacial reaction-diffusion processes, we describe a multistate diffusion model incorporating entropic effects of constrained binding. This can be merged with hydrodynamic theories of receptor-ligand diffusion and coupling to thermal membrane roughness. A novel synthetic membrane adhesion assay based on reversible and irreversible DNA-mediated interactions between GUVs and SLBs is used to precisely vary length, affinity, and flexibility, and also provides a platform to examine these effects on the dynamics of processes such as size-based segregation of binding and non-binding species.

The effects of linear assembly of two carbazole groups on acid-base and DNA-binding properties of a ruthenium(II) complex.

PubMed

Chen, Xi; Xue, Long-Xin; Ju, Chun-Chuan; Wang, Ke-Zhi

2013-07-01

A novel Ru(II) complex of [Ru(bpy)2(Hbcpip)](ClO4)2 {where bpy=2,2-bipyridine, Hbcpip=2-(4-(9H-3,9'-bicarbazol-9-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline} is synthesized and characterized. Calf-thymus DNA-binding properties of the complex were studied by UV-vis absorption and luminescence titrations, steady-state emission quenching by [Fe(CN)6](4-), DNA competitive binding with ethidium bromide, thermal denaturation and DNA viscosity measurements. The results indicate that the complex partially intercalated into the DNA with a binding constant of (5.5±1.4)×10(5) M(-1) in buffered 50 mM NaCl. The acid-base properties of the complex were also studied by UV-visible and luminescence spectrophotometric pH titrations, and ground- and excited-state acidity ionization constant values were derived. Copyright © 2013 Elsevier B.V. All rights reserved.

An overview of current activities at the National Solar Thermal Test Facility

NASA Astrophysics Data System (ADS)

Cameron, C. P.; Klimas, P. C.

This paper is a description of the United States Department of Energy's National Solar Thermal Test Facility, highlighting current test programs. In the central receiver area, research underway supports commercialization of molten nitrate salt technology, including receivers, thermal energy transport, and corrosion experiments. Concentrator research includes large-area, glass-metal heliostats and stretched-membrane heliostats and dishes. Test activities in support of dish-Stirling systems with reflux receivers are described. Research on parabolic troughs includes characterization of several receiver configurations. Other test facility activities include solar detoxification experiments, design assistance testing of commercially-available solar hardware, and non-DOE-funded work, including thermal exposure tests and testing of volumetric and PV central receiver concepts.

Thermal design and TDM test of the ETS-VI

NASA Astrophysics Data System (ADS)

Yoshinaka, T.; Kanamori, K.; Takenaka, N.; Kawashima, J.; Ido, Y.; Kuriyama, Y.

The Engineering Test Satellite-VI (ETS-VI) thermal design, thermal development model (TDM) test, and evaluation results are described. The allocation of the thermal control materials on the spacecraft is illustrated. The principal design approach is to minimize the interactions between the antenna tower module and the main body, and between the main body and the liquid apogee propulsion system by means of multilayer insulation blankets and low conductance graphite epoxy support structures. The TDM test shows that the thermal control subsystem is capable of maintaining the on-board components within specified temperature limits. The heat pipe network is confirmed to operate properly, and a uniform panel temperature distribution is accomplished. The thermal analytical model is experimentally verified. The validity of the thermal control subsystem design is confirmed by the modified on-orbit analytical model.

Space tug thermal control follow-on

NASA Technical Reports Server (NTRS)

Ward, T. L.

1975-01-01

The Space Tug Thermal Control Follow-On program was conducted to further explore some of the thermal control concepts proposed for use in space tug in a breadboard test program. The objectives were to demonstrate the thermal control capabilities of a louver/battery configuration and a thermal conditioning panel/heat pipe radiator configuration. An additional objective was added to model the header pipe and radiator of the second test and correlate the analysis with the test results. These three objectives were achieved and are discussed within this report.

Design manual: Oxygen Thermal Test Article (OTTA)

NASA Technical Reports Server (NTRS)

Chronic, W. L.; Baese, C. L.; Conder, R. L.

1974-01-01

The characteristics of a cryogenic tank for storing liquid hydrogen, nitrogen, oxygen, methane, or helium for an extended period of time with minimum losses are discussed. A description of the tank and control module, assembly drawings and details of major subassemblies, specific requirements controlling development of the system, thermal concept considerations, thermal analysis methods, and a record of test results are provided. The oxygen thermal test article thermal protection system has proven that the insulation system for cryogenic vessels is effective.

Transient Thermal Testing and Analysis of a Thermally Insulating Structural Sandwich Panel

NASA Technical Reports Server (NTRS)

Blosser, Max L.; Daryabeigi, Kamran; Bird, Richard K.; Knutson, Jeffrey R.

2015-01-01

A core configuration was devised for a thermally insulating structural sandwich panel. Two titanium prototype panels were constructed to illustrate the proposed sandwich panel geometry. The core of one of the titanium panels was filled with Saffil(trademark) alumina fibrous insulation and the panel was tested in a series of transient thermal tests. Finite element analysis was used to predict the thermal response of the panel using one- and two-dimensional models. Excellent agreement was obtained between predicted and measured temperature histories.

Thermal Cyclic Behavior of Thermal and Environmental Barrier Coatings Investigated Under High-Heat-Flux Conditions

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Lee, Kang N.; Miller, Robert A.

2002-01-01

Environmental barrier coatings (EBC's) have been developed to protect silicon-carbide- (SiC) based ceramic components in gas turbine engines from high-temperature environmental attack. With continuously increasing demands for significantly higher engine operating temperature, future EBC systems must be designed for both thermal and environmental protection of the engine components in combustion gases. In particular, the thermal barrier functions of EBC's become a necessity for reducing the engine-component thermal loads and chemical reaction rates, thus maintaining the required mechanical properties and durability of these components. Advances in the development of thermal and environmental barrier coatings (TBC's and EBC's, respectively) will directly impact the successful use of ceramic components in advanced engines. To develop high-performance coating systems, researchers must establish advanced test approaches. In this study, a laser high-heat-flux technique was employed to investigate the thermal cyclic behavior of TBC's and EBC's on SiC-reinforced SiC ceramic matrix composite substrates (SiC/SiC) under high thermal gradient and thermal cycling conditions. Because the laser heat flux test approach can monitor the coating's real-time thermal conductivity variations at high temperature, the coating thermal insulation performance, sintering, and delamination can all be obtained during thermal cycling tests. Plasma-sprayed yttria-stabilized zirconia (ZrO2-8 wt% Y2O3) thermal barrier and barium strontium aluminosilicate-based environmental barrier coatings (BSAS/BSAS+mullite/Si) on SiC/SiC ceramic matrix composites were investigated in this study. These coatings were laser tested in air under thermal gradients (the surface and interface temperatures were approximately 1482 and 1300 C, respectively). Some coating specimens were also subject to alternating furnace cycling (in a 90-percent water vapor environment at 1300 C) and laser thermal gradient cycling tests (in air), to investigate the water vapor effect. All cyclic tests were conducted using a 60-min hot-time temperature.

49 CFR 173.65 - Exceptions for Division 1.4G consumer fireworks.

Code of Federal Regulations, 2014 CFR

2014-10-01

...) The device must pass a thermal stability test. The test must be performed by maintaining the device... thermal stability test; (3) The manufacturer of the Division 1.4G consumer firework applies in writing to... thermal stability test; and (iv) Signed certification declaring that the device for which certification is...

49 CFR 173.65 - Exceptions for Division 1.4G consumer fireworks.

Code of Federal Regulations, 2013 CFR

2013-10-01

...) The device must pass a thermal stability test. The test must be performed by maintaining the device... thermal stability test; (3) The manufacturer of the Division 1.4G consumer firework applies in writing to... thermal stability test; and (iv) Signed certification declaring that the device for which certification is...

Computer assisted thermal-vacuum testing

NASA Technical Reports Server (NTRS)

Petrie, W.; Mikk, G.

1977-01-01

In testing complex systems and components under dynamic thermal-vacuum environments, it is desirable to optimize the environment control sequence in order to reduce test duration and cost. This paper describes an approach where a computer is utilized as part of the test control operation. Real time test data is made available to the computer through time-sharing terminals at appropriate time intervals. A mathematical model of the test article and environmental control equipment is then operated on using the real time data to yield current thermal status, temperature analysis, trend prediction and recommended thermal control setting changes to arrive at the required thermal condition. The data acquisition interface and the time-sharing hook-up to an IBM-370 computer is described along with a typical control program and data demonstrating its use.

Design and Test of Advanced Thermal Simulators for an Alkali Metal-Cooled Reactor Simulator

NASA Technical Reports Server (NTRS)

Garber, Anne E.; Dickens, Ricky E.

2011-01-01

The Early Flight Fission Test Facility (EFF-TF) at NASA Marshall Space Flight Center (MSFC) has as one of its primary missions the development and testing of fission reactor simulators for space applications. A key component in these simulated reactors is the thermal simulator, designed to closely mimic the form and function of a nuclear fuel pin using electric heating. Continuing effort has been made to design simple, robust, inexpensive thermal simulators that closely match the steady-state and transient performance of a nuclear fuel pin. A series of these simulators have been designed, developed, fabricated and tested individually and in a number of simulated reactor systems at the EFF-TF. The purpose of the thermal simulators developed under the Fission Surface Power (FSP) task is to ensure that non-nuclear testing can be performed at sufficiently high fidelity to allow a cost-effective qualification and acceptance strategy to be used. Prototype thermal simulator design is founded on the baseline Fission Surface Power reactor design. Recent efforts have been focused on the design, fabrication and test of a prototype thermal simulator appropriate for use in the Technology Demonstration Unit (TDU). While designing the thermal simulators described in this paper, effort were made to improve the axial power profile matching of the thermal simulators. Simultaneously, a search was conducted for graphite materials with higher resistivities than had been employed in the past. The combination of these two efforts resulted in the creation of thermal simulators with power capacities of 2300-3300 W per unit. Six of these elements were installed in a simulated core and tested in the alkali metal-cooled Fission Surface Power Primary Test Circuit (FSP-PTC) at a variety of liquid metal flow rates and temperatures. This paper documents the design of the thermal simulators, test program, and test results.

A selective chemosensor for fluoride ion and its interaction with Calf Thymus DNA

NASA Astrophysics Data System (ADS)

Ghosh, Soumen; Al Masum, Abdulla; Ganguly, Aniruddha; Islam, Md. Maidul; Alam, Md. Akhtarul; Guchhait, Nikhil

2017-05-01

The amido-Schiff base 1 (N1, N3-bis (2-nitrobenzylidene)benzene-1,3-dicabohydrazide) containing a sbnd CONHsbnd group and sbnd CHdbnd Nsbnd linkage has been synthesized by the condensation between isophthalic acid dihydrazide and o-nitrobenzaldehyde. This molecule can act as a fluoride ion sensor with high selectivity and sensitivity. Presence of nitro group in the phenyl ring may be responsible for the detection of fluoride ion visually with a dramatic color change from colorless to deep red in aqueous dimethyl sulphoxide solution. This Schiff base can be used as test kit for sensing of fluoride ion in the solid state. Compound 1 can detect fluoride also in commercially available toothpaste. As the compound has adequate solubility in DMSO-water mixture (7:93, v/v) and having some hydrogen bond donor and acceptor centers, we have investigated its nature of binding with Calf Thymus-DNA (CT-DNA) using theoretical molecular modelling and other experimental methods like UV-vis spectroscopy, circular dichroic and thermal melting studies. Thermodynamic parameters have been obtained using the well known Van't Hoff's equation. From both theoretical and experimental findings it has been observed that it can interact effectively with CT-DNA with binding energy - 7.55 kcal/mol to - 7.50 kcal/mol.

Molecular and Biochemical Characterization of Opisthorchis viverrini Calreticulin.

PubMed

Chaibangyang, Wanlapa; Geadkaew-Krenc, Amornrat; Vichasri-Grams, Suksiri; Tesana, Smarn; Grams, Rudi

2017-12-01

Calreticulin (CALR), a multifunctional protein thoroughly researched in mammals, comprises N-, P-, and C-domain and has roles in calcium homeostasis, chaperoning, clearance of apoptotic cells, cell adhesion, and also angiogenesis. In this study, the spatial and temporal expression patterns of the Opisthorchis viverrini CALR gene were analyzed, and calcium-binding and chaperoning properties of recombinant O. viverrini CALR (OvCALR) investigated. OvCALR mRNA was detected from the newly excysted juvenile to the mature parasite by RT-PCR while specific antibodies showed a wide distribution of the protein. OvCALR was localized in tegumental cell bodies, testes, ovary, eggs, Mehlis' gland, prostate gland, and vitelline cells of the mature parasite. Recombinant OvCALR showed an in vitro suppressive effect on the thermal aggregation of citrate synthase. The recombinant OvCALR C-domain showed a mobility shift in native gel electrophoresis in the presence of calcium. The results imply that OvCALR has comparable function to the mammalian homolog as a calcium-binding molecular chaperone. Inferred from the observed strong immunostaining of the reproductive tissues, OvCALR should be important for reproduction and might be an interesting target to disrupt parasite fecundity. Transacetylase activity of OvCALR as reported for calreticulin of Haemonchus contortus could not be observed.

Thermal and Alignment Analysis of the Instrument-Level ATLAS Thermal Vacuum Test

NASA Technical Reports Server (NTRS)

Bradshaw, Heather

2012-01-01

This paper describes the thermal analysis and test design performed in preparation for the ATLAS thermal vacuum test. NASA's Advanced Topographic Laser Altimeter System (ATLAS) will be flown as the sole instrument aboard the Ice, Cloud, and land Elevation Satellite-2 (ICESat-2). It will be used to take measurements of topography and ice thickness for Arctic and Antarctic regions, providing crucial data used to predict future changes in worldwide sea levels. Due to the precise measurements ATLAS is taking, the laser altimeter has very tight pointing requirements. Therefore, the instrument is very sensitive to temperature-induced thermal distortions. For this reason, it is necessary to perform a Structural, Thermal, Optical Performance (STOP) analysis not only for flight, but also to ensure performance requirements can be operationally met during instrument-level thermal vacuum testing. This paper describes the thermal model created for the chamber setup, which was used to generate inputs for the environmental STOP analysis. This paper also presents the results of the STOP analysis, which indicate that the test predictions adequately replicate the thermal distortions predicted for flight. This is a new application of an existing process, as STOP analyses are generally performed to predict flight behavior only. Another novel aspect of this test is that it presents the opportunity to verify pointing results of a STOP model, which is not generally done. It is possible in this case, however, because the actual pointing will be measured using flight hardware during thermal vacuum testing and can be compared to STOP predictions.

Image based performance analysis of thermal imagers

NASA Astrophysics Data System (ADS)

Wegner, D.; Repasi, E.

2016-05-01

Due to advances in technology, modern thermal imagers resemble sophisticated image processing systems in functionality. Advanced signal and image processing tools enclosed into the camera body extend the basic image capturing capability of thermal cameras. This happens in order to enhance the display presentation of the captured scene or specific scene details. Usually, the implemented methods are proprietary company expertise, distributed without extensive documentation. This makes the comparison of thermal imagers especially from different companies a difficult task (or at least a very time consuming/expensive task - e.g. requiring the execution of a field trial and/or an observer trial). For example, a thermal camera equipped with turbulence mitigation capability stands for such a closed system. The Fraunhofer IOSB has started to build up a system for testing thermal imagers by image based methods in the lab environment. This will extend our capability of measuring the classical IR-system parameters (e.g. MTF, MTDP, etc.) in the lab. The system is set up around the IR- scene projector, which is necessary for the thermal display (projection) of an image sequence for the IR-camera under test. The same set of thermal test sequences might be presented to every unit under test. For turbulence mitigation tests, this could be e.g. the same turbulence sequence. During system tests, gradual variation of input parameters (e. g. thermal contrast) can be applied. First ideas of test scenes selection and how to assembly an imaging suite (a set of image sequences) for the analysis of imaging thermal systems containing such black boxes in the image forming path is discussed.

In Vitro Binding Capacity of Bile Acids by Defatted Corn Protein Hydrolysate

PubMed Central

Kongo-Dia-Moukala, Jauricque Ursulla; Zhang, Hui; Irakoze, Pierre Claver

2011-01-01

Defatted corn protein was digested using five different proteases, Alcalase, Trypsin, Neutrase, Protamex and Flavourzyme, in order to produce bile acid binding peptides. Bile acid binding capacity was analyzed in vitro using peptides from different proteases of defatted corn hydrolysate. Some crystalline bile acids like sodium glycocholate, sodium cholate and sodium deoxycholate were individually tested using HPLC to see which enzymes can release more peptides with high bile acid binding capacity. Peptides from Flavourzyme defatted corn hydrolysate exhibited significantly (p < 0.05) stronger bile acid binding capacity than all others hydrolysates tested and all crystalline bile acids tested were highly bound by cholestyramine, a positive control well known as a cholesterol-reducing agent. The bile acid binding capacity of Flavourzyme hydrolysate was almost preserved after gastrointestinal proteases digestion. The molecular weight of Flavourzyme hydrolysate was determined and most of the peptides were found between 500–180 Da. The results showed that Flavourzyme hydrolysate may be used as a potential cholesterol-reducing agent. PMID:21541043

Direct Binding of the Corrector VX-809 to Human CFTR NBD1: Evidence of an Allosteric Coupling between the Binding Site and the NBD1:CL4 Interface.

PubMed

Hudson, Rhea P; Dawson, Jennifer E; Chong, P Andrew; Yang, Zhengrong; Millen, Linda; Thomas, Philip J; Brouillette, Christie G; Forman-Kay, Julie D

2017-08-01

Understanding the mechanism of action of modulator compounds for the cystic fibrosis transmembrane conductance regulator (CFTR) is key for the optimization of therapeutics as well as obtaining insights into the molecular mechanisms of CFTR function. We demonstrate the direct binding of VX-809 to the first nucleotide-binding domain (NBD1) of human CFTR. Disruption of the interaction between C-terminal helices and the NBD1 core upon VX-809 binding is observed from chemical shift changes in the NMR spectra of residues in the helices and on the surface of β -strands S3, S9, and S10. Binding to VX-809 leads to a significant negative shift in NBD1 thermal melting temperature (T m ), pointing to direct VX-809 interaction shifting the NBD1 conformational equilibrium. An inter-residue correlation analysis of the chemical shift changes provides evidence of allosteric coupling between the direct binding site and the NBD1:CL4 interface, thus enabling effects on the interface in the absence of direct binding in that location. These NMR binding data and the negative T m shifts are very similar to those previously reported by us for binding of the dual corrector-potentiator CFFT-001 to NBD1 (Hudson et al., 2012), suggesting that the two compounds may share some aspects of their mechanisms of action. Although previous studies have shown an important role for VX-809 in modulating the conformation of the first membrane spanning domain (Aleksandrov et al., 2012; Ren et al., 2013), this additional mode of VX-809 binding provides insight into conformational dynamics and allostery within CFTR. Copyright © 2017 by The Author(s).

Analytical Methodology Used To Assess/Refine Observatory Thermal Vacuum Test Conditions For the Landsat 8 Data Continuity Mission

NASA Technical Reports Server (NTRS)

Fantano, Louis

2015-01-01

Thermal and Fluids Analysis Workshop Silver Spring, MD NCTS 21070-15 The Landsat 8 Data Continuity Mission, which is part of the United States Geologic Survey (USGS), launched February 11, 2013. A Landsat environmental test requirement mandated that test conditions bound worst-case flight thermal environments. This paper describes a rigorous analytical methodology applied to assess refine proposed thermal vacuum test conditions and the issues encountered attempting to satisfy this requirement.

Surge current and electron swarm tunnel tests of thermal blanket and ground strap materials

NASA Technical Reports Server (NTRS)

Hoffmaster, D. K.; Inouye, G. T.; Sellen, J. M., Jr.

1977-01-01

The results are described of a series of current conduction tests with a thermal control blanket to which grounding straps have been attached. The material and the ground strap attachment procedure are described. The current conduction tests consisted of a surge current examination of the ground strap and a dilute flow, energetic electron deposition and transport through the bulk of the insulating film of this thermal blanket material. Both of these test procedures were used previously with thermal control blanket materials.

A radiant heating test facility for space shuttle orbiter thermal protection system certification

NASA Technical Reports Server (NTRS)

Sherborne, W. D.; Milhoan, J. D.

1980-01-01

A large scale radiant heating test facility was constructed so that thermal certification tests can be performed on the new generation of thermal protection systems developed for the space shuttle orbiter. This facility simulates surface thermal gradients, onorbit cold-soak temperatures down to 200 K, entry heating temperatures to 1710 K in an oxidizing environment, and the dynamic entry pressure environment. The capabilities of the facility and the development of new test equipment are presented.

Creating the Thermal Environment for Safely Testing the James Webb Space Telescope at the Johnson Space Center's Chamber A

NASA Technical Reports Server (NTRS)

Homan, Jonathan L.; Lauterbach, John; Garcia, Sam

2016-01-01

Chamber A is the largest thermal vacuum chamber at the Johnson Space Center and is one of the largest space environment chambers in the world. The chamber is 19.8 m (65 ft) in diameter and 36.6 m (120 ft) tall and is equipped with cryogenic liquid nitrogen panels (shrouds) and gaseous helium shrouds to create a simulated space environment. The chamber was originally built to support testing of the Apollo Service and Command Module for lunar missions, but underwent major modifications to be able to test the James Webb Space Telescope in a simulated deep space environment. To date seven tests have been performed in preparation of testing the flight optics for the James Webb Space Telescope (JWST). Each test has had a uniquie thermal profile and set of thermal requirements for cooling down and warming up, controlling contamination, and releasing condensed air. These range from temperatures from 335K to 15K, with tight uniformity and controllability for maintining thermal stability and pressure control. One unique requirement for two test was structurally proof loading hardware by creating thermal gradients at specific temperatures. This paper will discuss the thermal requirements and goals of the tests, the original requirements of the chamber thermal systems for planned operation, and how the new requirements were met by the team using the hardware, system flexiblilty, and engineering creativity. It will also discuss the mistakes and successes to meet the unique goals, especially when meeting the thermal proof load.

Effect of temperature acclimation on red blood cell oxygen affinity in Pacific bluefin tuna (Thunnus orientalis) and yellowfin tuna (Thunnus albacares).

PubMed

Lilly, Laura E; Bonaventura, Joseph; Lipnick, Michael S; Block, Barbara A

2015-03-01

Hemoglobin-oxygen (Hb-O2) binding properties are central to aerobic physiology, and must be optimized for an animal's aerobic requirements and environmental conditions, both of which can vary widely with seasonal changes or acutely with diving. In the case of tunas, the matter is further complicated by large regional temperature differences between tissues within the same animal. This study investigates the effects of thermal acclimation on red blood cell Hb-O2 binding in Pacific bluefin tuna (T. orientalis) and yellowfin tuna (T. albacares) maintained in captive tanks at acclimation temperatures of 17°, 20° and 24 °C. Oxygen binding properties of acclimated tuna isolated red blood cells were examined under varying experimental temperatures (15°-35 °C) and CO2 levels (0%, 0.5% and 1.5%). Results for Pacific bluefin tuna produced temperature-independence at 17 °C- and 20 °C-acclimation temperatures and significant reverse temperature-dependence at 24 °C-acclimation in the absence of CO2, with instances of reverse temperature-dependence in 17 °C- and 24 °C-acclimations at 0.5% and 1.5% CO2. In contrast, yellowfin tuna produced normal temperature-dependence at each acclimation temperature at 0% CO2, temperature-independence at 0.5% and 1.5% CO2, and significant reverse temperature-dependence at 17 °C-acclimation and 0.5% CO2. Thermal acclimation of Pacific bluefin tuna increased O2 binding affinity of the 17 °C-acclimation group, and produced a significantly steeper oxygen equilibrium curve slope (nH) at 24 °C-acclimation compared to the other acclimation temperatures. We discuss the potential implications of these findings below. Copyright © 2014 Elsevier Inc. All rights reserved.

Segregation of O2 and CO on the surface of dust grains determines the desorption energy of O2

NASA Astrophysics Data System (ADS)

Noble, J. A.; Diana, S.; Dulieu, F.

2015-12-01

Selective depletion towards pre-stellar cores is still not understood. The exchange between the solid and gas phases is central to this mystery. The aim of this paper is to show that the thermal desorption of O2 and CO from a submonolayer mixture is greatly affected by the composition of the initial surface population. We have performed thermally programmed desorption (TPD) experiments on various submonolayer mixtures of O2 and CO. Pure O2 and CO exhibit almost the same desorption behaviour, but their desorption differs strongly when mixed. Pure O2 is slightly less volatile than CO, while in mixtures, O2 desorbs earlier than CO. We analyse our data using a desorption law linking competition for binding sites with desorption, based on the assumption that the binding energy distribution of both molecules is the same. We apply Fermi-Dirac statistics in order to calculate the adsorption site population distribution, and derive the desorbing fluxes. Despite its simplicity, the model reproduces the observed desorption profiles, indicating that competition for adsorption sites is the reason for lower temperature O2 desorption. CO molecules push-out or `dislodge' O2 molecules from the most favourable binding sites, ultimately forcing their early desorption. It is crucial to consider the surface coverage of dust grains in any description of desorption. Competition for access to binding sites results in some important discrepancies between similar kinds of molecules, such as CO and O2. This is an important phenomenon to be investigated in order to develop a better understanding of the apparently selective depletion observed in dark molecular clouds.

Structural characterization of more potent alternatives to HAMLET, a tumoricidal complex of α-lactalbumin and oleic acid.

PubMed

Nemashkalova, Ekaterina L; Kazakov, Alexei S; Khasanova, Leysan M; Permyakov, Eugene A; Permyakov, Sergei E

2013-09-10

HAMLET is a complex of human α-lactalbumin (hLA) with oleic acid (OA) that kills various tumor cells and strains of Streptococcus pneumoniae. More potent protein-OA complexes were previously reported for bovine α-lactalbumin (bLA) and β-lactoglobulin (bLG), and pike parvalbumin (pPA), and here we explore their structural features. The concentration dependencies of the tryptophan fluorescence of hLA, bLA, and bLG complexes with OA reveal their disintegration at protein concentrations below the micromolar level. Chemical cross-linking experiments provide evidence that association with OA shifts the distribution of oligomeric forms of hLA, bLA, bLG, and pPA toward higher-order oligomers. This effect is confirmed for bLA and bLG using the dynamic light scattering method, while pPA is shown to associate with OA vesicles. Like hLA binding, OA binding increases the affinity of bLG for small unilamellar dipalmitoylphosphatidylcholine vesicles, while pPA efficiently binds to the vesicles irrespective of OA binding. The association of OA with bLG and pPA increases their α-helix and cross-β-sheet content and resistance to enzymatic proteolysis, which is indicative of OA-induced protein structuring. The lack of excess heat sorption during melting of bLG and pPA in complex with OA and the presence of a cooperative thermal transition at the level of their secondary structure suggest that the OA-bound forms of bLG and pPA lack a fixed tertiary structure but exhibit a continuous thermal transition. Overall, despite marked differences, the HAMLET-like complexes that were studied exhibit a common feature: a tendency toward protein oligomerization. Because OA-induced oligomerization has been reported for other proteins, this phenomenon is inherent to many proteins.

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

Kubouchi, Masatoshi; Hojo, Hidemitsu

The thermal shock resistance of epoxy resin specimens toughened with carboxy-terminated poly(butadiene-acrylonitrile) (CTBN) and poly-glycol were tested using a new notched disk-type specimen. The new thermal shock testing method consists of quenching a notched disk-type specimen and applying a theoretical analysis to the test results to determine crack propagation conditions. For both toughened epoxy resins, this test method evaluated improvements in thermal shock resistance. The thermal shock resistance of epoxy resin toughened with CTBN exhibited a maximum at a 35 parts per hundred resin content of CTBN. The epoxy resin toughened with polyglycol exhibited improved thermal shock resistance with increasingmore » glycol content. 7 refs., 14 figs., 1 tab.« less

Thermal Error Test and Intelligent Modeling Research on the Spindle of High Speed CNC Machine Tools

NASA Astrophysics Data System (ADS)

Luo, Zhonghui; Peng, Bin; Xiao, Qijun; Bai, Lu

2018-03-01

Thermal error is the main factor affecting the accuracy of precision machining. Through experiments, this paper studies the thermal error test and intelligent modeling for the spindle of vertical high speed CNC machine tools in respect of current research focuses on thermal error of machine tool. Several testing devices for thermal error are designed, of which 7 temperature sensors are used to measure the temperature of machine tool spindle system and 2 displacement sensors are used to detect the thermal error displacement. A thermal error compensation model, which has a good ability in inversion prediction, is established by applying the principal component analysis technology, optimizing the temperature measuring points, extracting the characteristic values closely associated with the thermal error displacement, and using the artificial neural network technology.

Measurement of single crystal surface parameters

NASA Technical Reports Server (NTRS)

Swanson, L. W.; Bell, A. E.; Strayer, R. W.

1972-01-01

The sticking coefficient and thermal desorption spectra of Cs from the (110) plane of W was investigated. A sticking coefficient of unity for the monolayer region was measured for T 250 K. Several distinct binding states were observed in the thermal desorption spectrum. Work function and electron reflection measurements were made on the (110) and (100) crystal faces of Mo. Both LEED and Auger were used to determine the orientation and cleanliness of the crystal surfaces. The work function values obtained for the (110) and (100) planes of Mo were 4.92 and 4.18 eV respectively.

A thermal scale modeling study for Apollo and Apollo applications, volume 1

NASA Technical Reports Server (NTRS)

Shannon, R. L.

1972-01-01

The program is reported for developing and demonstrating the capabilities of thermal scale modeling as a thermal design and verification tool for Apollo and Apollo Applications Projects. The work performed for thermal scale modeling of STB; cabin atmosphere/spacecraft cabin wall thermal interface; closed loop heat rejection radiator; and docked module/spacecraft thermal interface are discussed along with the test facility requirements for thermal scale model testing of AAP spacecraft. It is concluded that thermal scale modeling can be used as an effective thermal design and verification tool to provide data early in a spacecraft development program.

Study of skin model and geometry effects on thermal performance of thermal protective fabrics

NASA Astrophysics Data System (ADS)

Zhu, Fanglong; Ma, Suqin; Zhang, Weiyuan

2008-05-01

Thermal protective clothing has steadily improved over the years as new materials and improved designs have reached the market. A significant method that has brought these improvements to the fire service is the NFPA 1971 standard on structural fire fighters’ protective clothing. However, this testing often neglects the effects of cylindrical geometry on heat transmission in flame resistant fabrics. This paper deals with methods to develop cylindrical geometry testing apparatus incorporating novel skin bioheat transfer model to test flame resistant fabrics used in firefighting. Results show that fabrics which shrink during the test can have reduced thermal protective performance compared with the qualities measured with a planar geometry tester. Results of temperature differences between skin simulant sensors of planar and cylindrical tester are also compared. This test method provides a new technique to accurately and precisely characterize the thermal performance of thermal protective fabrics.

Two-Dimensional Finite Element Ablative Thermal Response Analysis of an Arcjet Stagnation Test

NASA Technical Reports Server (NTRS)

Dec, John A.; Laub, Bernard; Braun, Robert D.

2011-01-01

The finite element ablation and thermal response (FEAtR, hence forth called FEAR) design and analysis program simulates the one, two, or three-dimensional ablation, internal heat conduction, thermal decomposition, and pyrolysis gas flow of thermal protection system materials. As part of a code validation study, two-dimensional axisymmetric results from FEAR are compared to thermal response data obtained from an arc-jet stagnation test in this paper. The results from FEAR are also compared to the two-dimensional axisymmetric computations from the two-dimensional implicit thermal response and ablation program under the same arcjet conditions. The ablating material being used in this arcjet test is phenolic impregnated carbon ablator with an LI-2200 insulator as backup material. The test is performed at the NASA, Ames Research Center Interaction Heating Facility. Spatially distributed computational fluid dynamics solutions for the flow field around the test article are used for the surface boundary conditions.

Isolation of anti-toxin single domain antibodies from a semi-synthetic spiny dogfish shark display library.

PubMed

Liu, Jinny L; Anderson, George P; Goldman, Ellen R

2007-11-19

Shark heavy chain antibody, also called new antigen receptor (NAR), consists of one single Variable domain (VH), containing only two complementarity-determining regions (CDRs). The antigen binding affinity and specificity are mainly determined by these two CDRs. The good solubility, excellent thermal stability and complex sequence variation of small single domain antibodies (sdAbs) make them attractive alternatives to conventional antibodies. In this report, we construct and characterize a diversity enhanced semi-synthetic NAR V display library based on naturally occurring NAR V sequences. A semi-synthetic shark sdAb display library with a complexity close to 1e9 was constructed. This was achieved by introducing size and sequence variations in CDR3 using randomized CDR3 primers of three different lengths. Binders against three toxins, staphylococcal enterotoxin B (SEB), ricin, and botulinum toxin A (BoNT/A) complex toxoid, were isolated from panning the display library. Soluble sdAbs from selected binders were purified and evaluated using direct binding and thermal stability assays on the Luminex 100. In addition, sandwich assays using sdAb as the reporter element were developed to demonstrate their utility for future sensor applications. We demonstrated the utility of a newly created hyper diversified shark NAR displayed library to serve as a source of thermal stable sdAbs against a variety of toxins.

Biophysical Characterization and Thermal Stability of Pneumococcal Histidine Triad Protein D in the Presence of Zinc and Manganese.

PubMed

Ausar, Salvador F; Jayasundara, Kavisha; Akawi, Lamees; Roque, Cristopher; Sheung, Anthony; Hu, Jian; Kirkitadze, Marina; Rahman, Nausheen

2017-10-01

The pneumococcal histidine triad protein D (PhtD) is believed to play a central role in pneumococcal metal ion homeostasis and has been proposed as a promising vaccine candidate against pneumococcal disease. To investigate for potential stabilizers, a panel of physiologically relevant metals was screened using the thermal shift assay and it was found that only Zn 2+ and Mn 2+ were able to increase PhtD melting temperature. Differential scanning calorimetry analysis revealed a sequential unfolding of PhtD and the presence of at least 3 independent folding domains that can be stabilized by Zn 2+ and Mn 2+ . UV spectroscopy and fluorescence quenching studies showed significant Zn 2+ -induced tertiary structure changes in PhtD characterized by decreased accessibility of inner tryptophan residues to the aqueous solvent. Isothermal titration calorimetry data show no apparent binding to Mn 2+ but revealed a Zn 2+ :PhtD exothermic interaction stoichiometry of 3:1 with strong enthalpic contribution, suggesting that 3 of the 5 histidine triads are accessible binding sites for Zn 2+ . Only Zn +2 , but not Mn +2 , was able to increase the thermal stability of PhtD in the presence of aluminum hydroxide adjuvant, making it a promising stabilizer excipient candidate in vaccine products containing PhtD. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Design and structure of an equilibrium protein folding intermediate: a hint into dynamical regions of proteins.

PubMed

Ayuso-Tejedor, Sara; Angarica, Vladimir Espinosa; Bueno, Marta; Campos, Luis A; Abián, Olga; Bernadó, Pau; Sancho, Javier; Jiménez, M Angeles

2010-07-23

Partly unfolded protein conformations close to the native state may play important roles in protein function and in protein misfolding. Structural analyses of such conformations which are essential for their fully physicochemical understanding are complicated by their characteristic low populations at equilibrium. We stabilize here with a single mutation the equilibrium intermediate of apoflavodoxin thermal unfolding and determine its solution structure by NMR. It consists of a large native region identical with that observed in the X-ray structure of the wild-type protein plus an unfolded region. Small-angle X-ray scattering analysis indicates that the calculated ensemble of structures is consistent with the actual degree of expansion of the intermediate. The unfolded region encompasses discontinuous sequence segments that cluster in the 3D structure of the native protein forming the FMN cofactor binding loops and the binding site of a variety of partner proteins. Analysis of the apoflavodoxin inner interfaces reveals that those becoming destabilized in the intermediate are more polar than other inner interfaces of the protein. Natively folded proteins contain hydrophobic cores formed by the packing of hydrophobic surfaces, while natively unfolded proteins are rich in polar residues. The structure of the apoflavodoxin thermal intermediate suggests that the regions of natively folded proteins that are easily responsive to thermal activation may contain cores of intermediate hydrophobicity. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Isolation of anti-toxin single domain antibodies from a semi-synthetic spiny dogfish shark display library

PubMed Central

Liu, Jinny L; Anderson, George P; Goldman, Ellen R

2007-01-01

Background Shark heavy chain antibody, also called new antigen receptor (NAR), consists of one single Variable domain (VH), containing only two complementarity-determining regions (CDRs). The antigen binding affinity and specificity are mainly determined by these two CDRs. The good solubility, excellent thermal stability and complex sequence variation of small single domain antibodies (sdAbs) make them attractive alternatives to conventional antibodies. In this report, we construct and characterize a diversity enhanced semi-synthetic NAR V display library based on naturally occurring NAR V sequences. Results A semi-synthetic shark sdAb display library with a complexity close to 1e9 was constructed. This was achieved by introducing size and sequence variations in CDR3 using randomized CDR3 primers of three different lengths. Binders against three toxins, staphylococcal enterotoxin B (SEB), ricin, and botulinum toxin A (BoNT/A) complex toxoid, were isolated from panning the display library. Soluble sdAbs from selected binders were purified and evaluated using direct binding and thermal stability assays on the Luminex 100. In addition, sandwich assays using sdAb as the reporter element were developed to demonstrate their utility for future sensor applications. Conclusion We demonstrated the utility of a newly created hyper diversified shark NAR displayed library to serve as a source of thermal stable sdAbs against a variety of toxins. PMID:18021450

Persistent Graves' hyperthyroidism despite rapid negative conversion of thyroid-stimulating hormone-binding inhibitory immunoglobulin assay results: a case report.

PubMed

Ohara, Nobumasa; Kaneko, Masanori; Kitazawa, Masaru; Uemura, Yasuyuki; Minagawa, Shinichi; Miyakoshi, Masashi; Kaneko, Kenzo; Kamoi, Kyuzi

2017-02-06

Graves' disease is an autoimmune thyroid disorder characterized by hyperthyroidism, and patients exhibit thyroid-stimulating hormone receptor antibody. The major methods of measuring circulating thyroid-stimulating hormone receptor antibody include the thyroid-stimulating hormone-binding inhibitory immunoglobulin assays. Although the diagnostic accuracy of these assays has been improved, a minority of patients with Graves' disease test negative even on second-generation and third-generation thyroid-stimulating hormone-binding inhibitory immunoglobulins. We report a rare case of a thyroid-stimulating hormone-binding inhibitory immunoglobulin-positive patient with Graves' disease who showed rapid lowering of thyroid-stimulating hormone-binding inhibitory immunoglobulin levels following administration of the anti-thyroid drug thiamazole, but still experienced Graves' hyperthyroidism. A 45-year-old Japanese man presented with severe hyperthyroidism (serum free triiodothyronine >25.0 pg/mL; reference range 1.7 to 3.7 pg/mL) and tested weakly positive for thyroid-stimulating hormone-binding inhibitory immunoglobulins on second-generation tests (2.1 IU/L; reference range <1.0 IU/L). Within 9 months of treatment with oral thiamazole (30 mg/day), his thyroid-stimulating hormone-binding inhibitory immunoglobulin titers had normalized, but he experienced sustained hyperthyroidism for more than 8 years, requiring 15 mg/day of thiamazole to correct. During that period, he tested negative on all first-generation, second-generation, and third-generation thyroid-stimulating hormone-binding inhibitory immunoglobulin assays, but thyroid scintigraphy revealed diffuse and increased uptake, and thyroid ultrasound and color flow Doppler imaging showed typical findings of Graves' hyperthyroidism. The possible explanations for serial changes in the thyroid-stimulating hormone-binding inhibitory immunoglobulin results in our patient include the presence of thyroid-stimulating hormone receptor antibody, which is bioactive but less reactive on thyroid-stimulating hormone-binding inhibitory immunoglobulin assays, or the effect of reduced levels of circulating thyroid-stimulating hormone receptor antibody upon improvement of thyroid autoimmunity with thiamazole treatment. Physicians should keep in mind that patients with Graves' disease may show thyroid-stimulating hormone-binding inhibitory immunoglobulin assay results that do not reflect the severity of Graves' disease or indicate the outcome of the disease, and that active Graves' disease may persist even after negative results on thyroid-stimulating hormone-binding inhibitory immunoglobulin assays. Timely performance of thyroid function tests in combination with sensitive imaging tests, including thyroid ultrasound and scintigraphy, are necessary to evaluate the severity of Graves' disease and treatment efficacy.

Thermal Testing of Ablators in the NASA Johnson Space Center Radiant Heat Test Facility

NASA Technical Reports Server (NTRS)

Del Papa, Steven; Milhoan, Jim; Remark, Brian; Suess, Leonard

2016-01-01

A spacecraft's thermal protection system (TPS) is required to survive the harsh environment experienced during reentry. Accurate thermal modeling of the TPS is required to since uncertainties in the thermal response result in higher design margins and an increase in mass. The Radiant Heat Test Facility (RHTF) located at the NASA Johnson Space Center (JSC) replicates the reentry temperatures and pressures on system level full scale TPS test models for the validation of thermal math models. Reusable TPS, i.e. tile or reinforced carbon-carbon (RCC), have been the primary materials tested in the past. However, current capsule designs for MPCV and commercial programs have required the use of an ablator TPS. The RHTF has successfully completed a pathfinder program on avcoat ablator material to demonstrate the feasibility of ablator testing. The test results and corresponding ablation analysis results are presented in this paper.

Thermal Performance Comparison of Glass Microsphere and Perlite Insulation Systems for Liquid Hydrogen Storage Tanks

NASA Astrophysics Data System (ADS)

Sass, J. P.; Fesmire, J. E.; Nagy, Z. F.; Sojourner, S. J.; Morris, D. L.; Augustynowicz, S. D.

2008-03-01

A technology demonstration test project was conducted by the Cryogenics Test Laboratory at the Kennedy Space Center (KSC) to provide comparative thermal performance data for glass microspheres, referred to as bubbles, and perlite insulation for liquid hydrogen tank applications. Two identical 1/15th scale versions of the 3,200,000 liter spherical liquid hydrogen tanks at Launch Complex 39 at KSC were custom designed and built to serve as test articles for this test project. Evaporative (boil-off) calorimeter test protocols, including liquid nitrogen and liquid hydrogen, were established to provide tank test conditions characteristic of the large storage tanks that support the Space Shuttle launch operations. This paper provides comparative thermal performance test results for bubbles and perlite for a wide range of conditions. Thermal performance as a function of cryogenic commodity (nitrogen and hydrogen), vacuum pressure, insulation fill level, tank liquid level, and thermal cycles will be presented.

Infrared Heater Used in Qualification Testing of International Space Station Radiators

NASA Technical Reports Server (NTRS)

Ziemke, Robert A.

2004-01-01

Two heat rejection radiator systems for the International Space Station (ISS) have undergone thermal vacuum qualification testing at the NASA Glenn Research Center (GRC), Plum Brook Station, Sandusky, Ohio. The testing was performed in the Space Power Facility (SPF), the largest thermal vacuum chamber in the world. The heat rejection system radiator was tested first; it removes heat from the ISS crew living quarters. The second system tested was the photovoltaic radiator (PVR), which rejects heat from the ISS photovoltaic arrays and the electrical power-conditioning equipment. The testing included thermal cycling, hot- and cold-soaked deployments, thermal gradient deployments, verification of the onboard heater controls, and for the PVR, thermal performance tests with ammonia flow. Both radiator systems are orbital replacement units for ease of replacement on the ISS. One key to the success of these tests was the performance of the infrared heater system. It was used in conjunction with a gaseous-nitrogen-cooled cryoshroud in the SPF vacuum chamber to achieve the required thermal vacuum conditions for the qualification tests. The heater, which was designed specifically for these tests, was highly successful and easily met the test requirements. This report discusses the heating requirements, the heater design features, the design approach, and the mathematical basis of the design.

Specific detection of tetanus toxoid using an aptamer-based matrix.

PubMed

Modh, Harshvardhan B; Bhadra, Ankan K; Patel, Kinjal A; Chaudhary, Rajeev K; Jain, Nishant K; Roy, Ipsita

2016-11-20

Batch-to-batch variation of therapeutic proteins produced by biological means requires rigorous monitoring at all stages of the production process. A large number of animals are employed for risk assessment of biologicals, which has low ethical and economic acceptability. Research is now focussed on the validation of in vitro and ex vivo tests to replace live challenges. Among in vitro methods, enzyme-linked immunosorbent assay (ELISA) is considered to be the gold standard for estimation of integrity of tetanus toxoid. ELISA utilizes antibodies for detection, which, because of their biological origin and limited modifiability, may have low stability and result in irreproducibility. We have developed a method using highly specific and selective RNA aptamers for detection of tetanus toxoid. Using displacement assay, we first identified aptamers which bind to different aptatopes on the surface of the toxoid. Pairs of these aptamers were employed as capture-detection ligands in a sandwich-ALISA (aptamer-linked immobilized sorbent assay) format. The binding efficiency was confirmed by the fluorescence intensity in each microtire plate well. Using aptamers alone, detection of tetanus toxoid was possible with the same level of sensitivity as antibody. Aptamers were also used in the capture ALISA format. Adjuvanted tetanus toxoid was subjected to accelerated stress testing, including thermal, mechanical and freeze-thawing stress conditions. The loss in antigenicity of the preparation determined by ALISA in each case was found to be similar to that determined by conventional ELISA. Thus, it is possible to replace antibodies with aptamers to develop a more robust detection tool for tetanus toxoid. Copyright © 2016 Elsevier B.V. All rights reserved.

Thermal Vacuum Test Correlation of A Zero Propellant Load Case Thermal Capacitance Propellant Gauging Analytics Model

NASA Technical Reports Server (NTRS)

McKim, Stephen A.

2016-01-01

This thesis describes the development and test data validation of the thermal model that is the foundation of a thermal capacitance spacecraft propellant load estimator. Specific details of creating the thermal model for the diaphragm propellant tank used on NASA's Magnetospheric Multiscale spacecraft using ANSYS and the correlation process implemented to validate the model are presented. The thermal model was correlated to within plus or minus 3 degrees Centigrade of the thermal vacuum test data, and was found to be relatively insensitive to uncertainties in applied heat flux and mass knowledge of the tank. More work is needed, however, to refine the thermal model to further improve temperature predictions in the upper hemisphere of the propellant tank. Temperatures predictions in this portion were found to be 2-2.5 degrees Centigrade lower than the test data. A road map to apply the model to predict propellant loads on the actual MMS spacecraft toward its end of life in 2017-2018 is also presented.

Thermal shock testing for assuring reliability of glass-sealed microelectronic packages

NASA Technical Reports Server (NTRS)

Thomas, Walter B., III; Lewis, Michael D.

1991-01-01

Tests were performed to determine if thermal shocking is destructive to glass-to-metal seal microelectronic packages and if thermal shock step stressing can compare package reliabilities. Thermal shocking was shown to be not destructive to highly reliable glass seals. Pin-pull tests used to compare the interfacial pin glass strengths showed no differences between thermal shocked and not-thermal shocked headers. A 'critical stress resistance temperature' was not exhibited by the 14 pin Dual In-line Package (DIP) headers evaluated. Headers manufactured in cryogenic nitrogen based and exothermically generated atmospheres showed differences in as-received leak rates, residual oxide depths and pin glass interfacial strengths; these were caused by the different manufacturing methods, in particular, by the chemically etched pins used by one manufacturer. Both header types passed thermal shock tests to temperature differentials of 646 C. The sensitivity of helium leak rate measurements was improved up to 70 percent by baking headers for two hours at 200 C after thermal shocking.

Arcjet Testing of Micro-Meteoroid Impacted Thermal Protection Materials

NASA Technical Reports Server (NTRS)

Agrawal, Parul; Munk, Michelle M.; Glaab, Louis J.

2013-01-01

There are several harsh space environments that could affect thermal protection systems and in turn pose risks to the atmospheric entry vehicles. These environments include micrometeoroid impact, extreme cold temperatures, and ionizing radiation during deep space cruise, all followed by atmospheric entry heating. To mitigate these risks, different thermal protection material samples were subjected to multiple tests, including hyper velocity impact, cold soak, irradiation, and arcjet testing, at various NASA facilities that simulated these environments. The materials included a variety of honeycomb packed ablative materials as well as carbon-based non-ablative thermal protection systems. The present paper describes the results of the multiple test campaign with a focus on arcjet testing of thermal protection materials. The tests showed promising results for ablative materials. However, the carbon-based non-ablative system presented some concerns regarding the potential risks to an entry vehicle. This study provides valuable information regarding the capability of various thermal protection materials to withstand harsh space environments, which is critical to sample return and planetary entry missions.

Advanced Testing Method for Ground Thermal Conductivity

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

Liu, Xiaobing; Clemenzi, Rick; Liu, Su

A new method is developed that can quickly and more accurately determine the effective ground thermal conductivity (GTC) based on thermal response test (TRT) results. Ground thermal conductivity is an important parameter for sizing ground heat exchangers (GHEXs) used by geothermal heat pump systems. The conventional GTC test method usually requires a TRT for 48 hours with a very stable electric power supply throughout the entire test. In contrast, the new method reduces the required test time by 40%–60% or more, and it can determine GTC even with an unstable or intermittent power supply. Consequently, it can significantly reduce themore » cost of GTC testing and increase its use, which will enable optimal design of geothermal heat pump systems. Further, this new method provides more information about the thermal properties of the GHEX and the ground than previous techniques. It can verify the installation quality of GHEXs and has the potential, if developed, to characterize the heterogeneous thermal properties of the ground formation surrounding the GHEXs.« less

Thermal design and test results for SUNLITE ultra-stable reference cavity

NASA Technical Reports Server (NTRS)

Amundsen, Ruth M.

1991-01-01

SUNLITE (Stanford University-NASA Laser In-Space Technology Experiment) is a space-based experiment which uses a reference cavity to provide a stable frequency reference for a terahertz laser oscillator. Thermal stability of the cavity is a key factor in attaining a stable narrow-linewidth laser beam. The mount which is used to support and align the cavity will provide thermal isolation from the environment. The baseline requirement for thermal stability of the cavity is 0.025 C/min, but the design is directed toward achieving stability well beyond this requirement to improve the science data gained. A prototype of the cavity mount was fabricated and tested to characterize the thermal performance. The thermal vacuum test involved stable high-resolution temperature measurements and stable baseplate temperature control over long durations. Based on test data, the cavity mount design satisfies the severe requirement for the cavity thermal stability.

Manipulation of a DNA aptamer-protein binding site through arylation of internal guanine residues.

PubMed

Van Riesen, Abigail J; Fadock, Kaila L; Deore, Prashant S; Desoky, Ahmed; Manderville, Richard A; Sowlati-Hashjin, Shahin; Wetmore, Stacey D

2018-05-23

Chemically modified aptamers have the opportunity to increase aptamer target binding affinity and provide structure-activity relationships to enhance our understanding of molecular target recognition by the aptamer fold. In the current study, 8-aryl-2'-deoxyguanosine nucleobases have been inserted into the G-tetrad and central TGT loop of the thrombin binding aptamer (TBA) to determine their impact on antiparallel G-quadruplex (GQ) folding and thrombin binding affinity. The aryl groups attached to the dG nucleobase vary greatly in aryl ring size and impact on GQ stability (∼20 °C change in GQ thermal melting (Tm) values) and thrombin binding affinity (17-fold variation in dissociation constant (Kd)). At G8 of the central TGT loop that is distal from the aptamer recognition site, the probes producing the most stable GQ structure exhibited the strongest thrombin binding affinity. However, within the G-tetrad, changes to the electron density of the dG component within the modified nucleobase can diminish thrombin binding affinity. Detailed molecular dynamics (MD) simulations on the modified TBA (mTBA) and mTBA-protein complexes demonstrate how the internal 8-aryl-dG modification can manipulate the interactions between the DNA nucleobases and the amino acid residues of thrombin. These results highlight the potential of internal fluorescent nuclobase analogs (FBAs) to broaden design options for aptasensor development.

Interaction and inhibitory influence of the azo dye carmoisine on lysozyme amyloid fibrillogenesis.

PubMed

Basu, Anirban; Suresh Kumar, Gopinatha

2017-07-25

The binding of the common food colorant carmoisine and its inhibitory effect on amyloid fibrillation in lysozyme have been investigated. Since humans are increasingly exposed to various food colorants like carmoisine, such studies are highly relevant. In the presence of lysozyme, the carmoisine absorption spectrum exhibited hypochromic changes. The intrinsic fluorescence of lysozyme was also quenched on interaction. Time-resolved fluorescence results suggested that the binding mechanism involved ground state complexation. The binding was predominantly dominated by non-polyelectrolytic forces. The molecular distance between the donor (lysozyme) and the acceptor (carmoisine), calculated from FRET theory, was found to be 3.37 nm, indicating that carmoisine binds close to Trp-62/63 residues in the β-domain of the protein. Information on alterations in the microenvironment surrounding the Trp-residues was also obtained from synchronous fluorescence data. Carmoisine binding induced significant loss in the alpha helical organization of lysozyme. The binding, nevertheless, did not influence the thermal stability of lysozyme significantly. The binding reaction was exothermic and driven by large negative enthalpy and small but favourable entropic contributions. Thioflavin T assay, far-UV circular dichroism studies and AFM imaging profiles testified that carmoisine had a significant inhibitory effect on amyloid fibrillogenesis in lysozyme. Carmoisine also had a definitive defibrillating effect on existing fibrils. The results may provide new insights for designing new small molecule inhibitors for amyloid related diseases.

Specificity and kinetics of alpha-synuclein binding to model membranes determined with fluorescent excited state intramolecular proton transfer (ESIPT) probe.

PubMed

Shvadchak, Volodymyr V; Falomir-Lockhart, Lisandro J; Yushchenko, Dmytro A; Jovin, Thomas M

2011-04-15

Parkinson disease is characterized cytopathologically by the deposition in the midbrain of aggregates composed primarily of the presynaptic neuronal protein α-synuclein (AS). Neurotoxicity is currently attributed to oligomeric microaggregates subjected to oxidative modification and promoting mitochondrial and proteasomal dysfunction. Unphysiological binding to membranes of these and other organelles is presumably involved. In this study, we performed a systematic determination of the influence of charge, phase, curvature, defects, and lipid unsaturation on AS binding to model membranes using a new sensitive solvatochromic fluorescent probe. The interaction of AS with vesicular membranes is fast and reversible. The protein dissociates from neutral membranes upon thermal transition to the liquid disordered phase and transfers to vesicles with higher affinity. The binding of AS to neutral and negatively charged membranes occurs by apparently different mechanisms. Interaction with neutral bilayers requires the presence of membrane defects; binding increases with membrane curvature and rigidity and decreases in the presence of cholesterol. The association with negatively charged membranes is much stronger and much less sensitive to membrane curvature, phase, and cholesterol content. The presence of unsaturated lipids increases binding in all cases. These findings provide insight into the relation between membrane physical properties and AS binding affinity and dynamics that presumably define protein localization in vivo and, thereby, the role of AS in the physiopathology of Parkinson disease.

A generic approach to engineer antibody pH-switches using combinatorial histidine scanning libraries and yeast display.

PubMed

Schröter, Christian; Günther, Ralf; Rhiel, Laura; Becker, Stefan; Toleikis, Lars; Doerner, Achim; Becker, Janine; Schönemann, Andreas; Nasu, Daichi; Neuteboom, Berend; Kolmar, Harald; Hock, Björn

2015-01-01

There is growing interest in the fast and robust engineering of protein pH-sensitivity that aims to reduce binding at acidic pH, compared to neutral pH. Here, we describe a novel strategy for the incorporation of pH-sensitive antigen binding functions into antibody variable domains using combinatorial histidine scanning libraries and yeast surface display. The strategy allows simultaneous screening for both, high affinity binding at pH 7.4 and pH-sensitivity, and excludes conventional negative selection steps. As proof of concept, we applied this strategy to incorporate pH-dependent antigen binding into the complementary-determining regions of adalimumab. After 3 consecutive rounds of separate heavy and light chain library screening, pH-sensitive variants could be isolated. Heavy and light chain mutations were combined, resulting in 3 full-length antibody variants that revealed sharp, reversible pH-dependent binding profiles. Dissociation rate constants at pH 6.0 increased 230- to 780-fold, while high affinity binding at pH 7.4 in the sub-nanomolar range was retained. Furthermore, binding to huFcRn and thermal stability were not affected by histidine substitutions. Overall, this study emphasizes a generalizable strategy for engineering pH-switch functions potentially applicable to a variety of antibodies and further proteins-based therapeutics.

Intrinsic thermodynamics of inhibitor binding to human carbonic anhydrase IX.

PubMed

Linkuvienė, Vaida; Matulienė, Jurgita; Juozapaitienė, Vaida; Michailovienė, Vilma; Jachno, Jelena; Matulis, Daumantas

2016-04-01

Human carbonic anhydrase 9th isoform (CA IX) is an important marker of numerous cancers and is increasingly interesting as a potential anticancer drug target. Various synthetic aromatic sulfonamide-bearing compounds are being designed as potent inhibitors of CA IX. However, sulfonamide compound binding to CA IX is linked to several reactions, the deprotonation of the sulfonamide amino group and the protonation of the CA active site Zn(II)-bound hydroxide. These linked reactions significantly affect the affinities and other thermodynamic parameters such as enthalpies and entropies of binding. The observed and intrinsic affinities of compound binding to CA IX were determined by the fluorescent thermal shift assay. The enthalpies and entropies of binding were determined by the isothermal titration calorimetry. The pKa of CA IX was determined to be 6.8 and the enthalpy of CA IX-Zn(II)-bound hydroxide protonation was -24 kJ/mol. These values enabled the analysis of intrinsic thermodynamics of a library of compounds binding to CA IX. The most strongly binding compounds exhibited the intrinsic affinity of 0.01 nM and the observed affinity of 2 nM. The intrinsic thermodynamic parameters of compound binding to CA IX helped to draw the compound structure to thermodynamics relationship. It is important to distinguish the intrinsic from observed parameters of any disease target protein interaction with its inhibitors as drug candidates when drawing detailed compound structure to thermodynamics correlations. Copyright © 2016 Elsevier B.V. All rights reserved.

Interrelations of secondary structure stability and DNA-binding affinity in the bacteriophage SPO1-encoded type II DNA-binding protein TF1.

PubMed

Andera, L; Spangler, C J; Galeone, A; Mayol, L; Geiduschek, E P

1994-02-11

TF1, a homodimeric DNA-binding and -bending protein with a preference for hydroxymethyluracil-containing DNA is the Bacillus subtilis-encoded homolog of the bacterial HU proteins and of the E. coli integration host factor. A temperature-sensitive mutation at amino acid 25 of TF1 (L25-->A) and two intragenic second site revertants at amino acids 15 (E15-->G) and 32 (L32-->I) were previously identified and their effects on virus development were examined. The DNA-binding properties of these proteins and the thermal stability of their secondary structures have now been analyzed. Amino acids 15 and 32 are far removed from the putative DNA-binding domains of TF1 but changes there exert striking effects on DNA affinity that correlate with effects on structure. The double mutant protein TF1-G15I32 binds to a preferred site in hydroxymethyluracil-containing DNA 40 times more tightly, denatures at higher temperature (delta tm = 21 degrees C), and also exchanges subunits much more slowly than does the wild-type protein. The L25-->A mutation makes TF1 secondary structure and DNA-binding highly salt concentration-dependent. The E15-->G mutation partly suppresses this effect: secondary structure of TF1-A25G15 is restored at 21 degrees C by 1 M NaCl or, at low NaCl concentration, by binding to DNA.

Structure-based design of novel naproxen derivatives targeting monomeric nucleoprotein of Influenza A virus

PubMed Central

Tarus, Bogdan; Bertrand, Hélène; Zedda, Gloria; Di Primo, Carmelo; Quideau, Stéphane; Slama-Schwok, Anny

2015-01-01

The nucleoprotein (NP) binds the viral RNA genome as oligomers assembled with the polymerase in a ribonucleoprotein complex required for transcription and replication of influenza A virus. Novel antiviral candidates targeting the nucleoprotein either induced higher order oligomers or reduced NP oligomerization by targeting the oligomerization loop and blocking its insertion into adjacent nucleoprotein subunit. In this study, we used a different structure-based approach to stabilize monomers of the nucleoprotein by drugs binding in its RNA-binding groove. We recently identified naproxen as a drug competing with RNA binding to NP with antiinflammatory and antiviral effects against influenza A virus. Here, we designed novel derivatives of naproxen by fragment extension for improved binding to NP. Molecular dynamics simulations suggested that among these derivatives, naproxen A and C0 were most promising. Their chemical synthesis is described. Both derivatives markedly stabilized NP monomer against thermal denaturation. Naproxen C0 bound tighter to NP than naproxen at a binding site predicted by MD simulations and shown by competition experiments using wt NP or single-point mutants as determined by surface plasmon resonance. MD simulations suggested that impeded oligomerization and stabilization of monomeric NP is likely to be achieved by drugs binding in the RNA grove and inducing close to their binding site conformational changes of key residues hosting the oligomerization loop as observed for the naproxen derivatives. Naproxen C0 is a potential antiviral candidate blocking influenza nucleoprotein function. PMID:25333630

Structure-based design of novel naproxen derivatives targeting monomeric nucleoprotein of Influenza A virus.

PubMed

Tarus, Bogdan; Bertrand, Hélène; Zedda, Gloria; Di Primo, Carmelo; Quideau, Stéphane; Slama-Schwok, Anny

2015-09-01

The nucleoprotein (NP) binds the viral RNA genome as oligomers assembled with the polymerase in a ribonucleoprotein complex required for transcription and replication of influenza A virus. Novel antiviral candidates targeting the nucleoprotein either induced higher order oligomers or reduced NP oligomerization by targeting the oligomerization loop and blocking its insertion into adjacent nucleoprotein subunit. In this study, we used a different structure-based approach to stabilize monomers of the nucleoprotein by drugs binding in its RNA-binding groove. We recently identified naproxen as a drug competing with RNA binding to NP with antiinflammatory and antiviral effects against influenza A virus. Here, we designed novel derivatives of naproxen by fragment extension for improved binding to NP. Molecular dynamics simulations suggested that among these derivatives, naproxen A and C0 were most promising. Their chemical synthesis is described. Both derivatives markedly stabilized NP monomer against thermal denaturation. Naproxen C0 bound tighter to NP than naproxen at a binding site predicted by MD simulations and shown by competition experiments using wt NP or single-point mutants as determined by surface plasmon resonance. MD simulations suggested that impeded oligomerization and stabilization of monomeric NP is likely to be achieved by drugs binding in the RNA grove and inducing close to their binding site conformational changes of key residues hosting the oligomerization loop as observed for the naproxen derivatives. Naproxen C0 is a potential antiviral candidate blocking influenza nucleoprotein function.

Correleation of the SAGE III on ISS Thermal Models in Thermal Desktop

NASA Technical Reports Server (NTRS)

Amundsen, Ruth M.; Davis, Warren T.; Liles, Kaitlin, A. K.; McLeod, Shawn C.

2017-01-01

The Stratospheric Aerosol and Gas Experiment III (SAGE III) instrument is the fifth in a series of instruments developed for monitoring aerosols and gaseous constituents in the stratosphere and troposphere. SAGE III was launched on February 19, 2017 and mounted to the International Space Station (ISS) to begin its three-year mission. A detailed thermal model of the SAGE III payload, which consists of multiple subsystems, has been developed in Thermal Desktop (TD). Correlation of the thermal model is important since the payload will be expected to survive a three-year mission on ISS under varying thermal environments. Three major thermal vacuum (TVAC) tests were completed during the development of the SAGE III Instrument Payload (IP); two subsystem-level tests and a payload-level test. Additionally, a characterization TVAC test was performed in order to verify performance of a system of heater plates that was designed to allow the IP to achieve the required temperatures during payload-level testing; model correlation was performed for this test configuration as well as those including the SAGE III flight hardware. This document presents the methods that were used to correlate the SAGE III models to TVAC at the subsystem and IP level, including the approach for modeling the parts of the payload in the thermal chamber, generating pre-test predictions, and making adjustments to the model to align predictions with temperatures observed during testing. Model correlation quality will be presented and discussed, and lessons learned during the correlation process will be shared.

Cytoplasmic dynein binding, run length, and velocity are guided by long-range electrostatic interactions

PubMed Central

Li, Lin; Alper, Joshua; Alexov, Emil

2016-01-01

Dyneins are important molecular motors involved in many essential biological processes, including cargo transport along microtubules, mitosis, and in cilia. Dynein motility involves the coupling of microtubule binding and unbinding to a change in the configuration of the linker domain induced by ATP hydrolysis, which occur some 25 nm apart. This leaves the accuracy of dynein stepping relatively inaccurate and susceptible to thermal noise. Using multi-scale modeling with a computational focusing technique, we demonstrate that the microtubule forms an electrostatic funnel that guides the dynein’s microtubule binding domain (MTBD) as it finally docks to the precise, keyed binding location on the microtubule. Furthermore, we demonstrate that electrostatic component of the MTBD’s binding free energy is linearly correlated with the velocity and run length of dynein, and we use this linearity to predict the effect of mutating each glutamic and aspartic acid located in MTBD domain to alanine. Lastly, we show that the binding of dynein to the microtubule is associated with conformational changes involving several helices, and we localize flexible hinge points within the stalk helices. Taken all together, we demonstrate that long range electrostatic interactions bring a level of precision to an otherwise noisy dynein stepping process. PMID:27531742

Topex Microwave Radiometer thermal control - Post-system-test modifications and on-orbit performance

NASA Technical Reports Server (NTRS)

Lin, Edward I.

1993-01-01

The Topex Microwave Radiometer has had an excellent thermal performance since launch. The instrument, however, went through a hardware modification right before launch to correct for a thermal design inadequacy that was uncovered during the spacecraft thermal vacuum test. This paper reports on how the initially obscure problem was tracked down, and how the thermal models were revised, validated, and utilized to investigate the solution options and guide the hardware modification decisions. Details related to test data interpretation, analytical uncertainties, and model-prediction vs. test-data correlation, are documented. Instrument/spacecraft interface issues, where the problem originated and where in general pitfalls abound, are dealt with specifically. Finally, on-orbit thermal performance data are presented, which exhibit good agreement with flight predictions, and lessons learned are discussed.

Fabrication of titanium multi-wall Thermal Protection System (TPS) test panel arrays

NASA Technical Reports Server (NTRS)

Blair, W.; Meaney, J. E.; Rosenthal, H. A.

1980-01-01

Several arrays were designed and tested. Tests included vibrational and acoustical tests, radiant heating tests, and thermal conductivity tests. A feasible manufacturing technique was established for producing the protection system panels.

Characterization of the Heat Extraction Capability of a Compliant, Sliding, Thermal Interface for Use in a High Temperature, Vacuum, Microgravity Furnace

NASA Technical Reports Server (NTRS)

Bellomy-Ezell, Jenny; Farmer, Jeff; Breeding, Shawn; Spivey, Reggie

2001-01-01

A compliant, thermal interface material is tested to evaluate its thermal behavior at elevated temperatures, in vacuum conditions, and under varying levels of compression. Preliminary results indicate that the thermal performance of this polymer fiber-based, felt-like material is sufficient to meet thermal extraction requirements for the Quench Module Insert, a Bridgman furnace for microgravity material science investigation. This paper discusses testing and modeling approaches employed, gives of a status of characterization activities and provides preliminary test results.

3D thermography for improving temperature measurements in thermal vacuum testing

NASA Astrophysics Data System (ADS)

Robinson, D. W.; Simpson, R.; Parian, J. A.; Cozzani, A.; Casarosa, G.; Sablerolle, S.; Ertel, H.

2017-09-01

The application of thermography to thermal vacuum (TV) testing of spacecrafts is becoming a vital additional tool in the mapping of structures during thermal cycles and thermal balance (TB) testing. Many of the customers at the European Space Agency (ESA) test centre, European Space Research and Technology Centre (ESTEC), The Netherlands, now make use of a thermal camera during TB-TV campaigns. This complements the use of embedded thermocouples on the structure, providing the prospect of monitoring temperatures at high resolution and high frequency. For simple flat structures with a well-defined emissivity, it is possible to determine the surface temperatures with reasonable confidence. However, for most real spacecraft and sub-systems, the complexity of the structure's shape and its test environment creates inter-reflections from external structures. This and the additional complication of angular and spectral variations of the spacecraft surface emissivity make the interpretation of the radiation detected by a thermal camera more difficult in terms of determining a validated temperature with high confidence and well-defined uncertainty. One solution to this problem is: to map the geometry of the test specimen and thermal test environment; to model the surface temperatures and emissivity variations of the structures and materials; and to use this model to correct the apparent temperatures recorded by the thermal camera. This approach has been used by a team from NPL (National Physical Laboratory), Psi-tran, and PhotoCore, working with ESA, to develop a 3D thermography system to provide a means to validate thermal camera temperatures, based on a combination of thermal imaging photogrammetry and ray-tracing scene modeling. The system has been tested at ESTEC in ambient conditions with a dummy spacecraft structure containing a representative set of surface temperatures, shapes, and spacecraft materials, and with hot external sources and a high power lamp as a sun simulator. The results are presented here with estimated temperature measurement uncertainties and defined confidence levels according to the internationally accepted Guide to Uncertainty of Measurement as used in the IEC/ISO17025 test and measurement standard. This work is understood to represent the first application of well-understood thermal imaging theory, commercial photogrammetry software, and open-source ray-tracing software (adapted to realize the Planck function for thermal wavebands and target emission), and to produce from these elements a complete system for determining true surface temperatures for complex spacecraft-testing applications.

Development of a Cryogenic Thermal Distortion Measurement Facility for Testing the James Webb Space Telescope Instrument Support Integration Module 2-D Test Assemblies

NASA Technical Reports Server (NTRS)

Miller, Franklin; Bagdanove, paul; Blake, Peter; Canavan, Ed; Cofie, Emmanuel; Crane, J. Allen; Dominquez, Kareny; Hagopian, John; Johnston, John; Madison, Tim;

Different Results of IgE Binding- and Crosslinking-Based Allergy Tests Caused by Allergen Immobilization.

PubMed

Okamoto-Uchida, Yoshimi; Nakamura, Ryosuke; Matsuzawa, Yumiko; Soma, Megumi; Kawakami, Hiroshi; Ishii-Watabe, Akiko; Nishimaki-Mogami, Tomoko; Teshima, Reiko; Saito, Yoshiro

2016-01-01

The physicochemical nature of allergen molecules differ from the liquid phase to the solid phase. However, conventional allergy tests are based on the detection of immunoglobulin (Ig)E binding to immobilized allergens. We recently developed an in vitro allergy testing method using a luciferase-reporting humanized rat mast cell line to detect IgE crosslinking-induced luciferase expression (EXiLE test). The aim of the present study was to evaluate the effects of antigen immobilization on the results of different in vitro allergy tests using two anti-ovalbumin (OVA) antibodies (Abs), E-C1 and E-G5, with different properties in the OVA-induced allergic reaction. Both Abs showed clear binding to OVA with an enzyme-linked immunosorbent assay and by BIAcore analysis. However, only E-C1 potentiated EXiLE response for the liquid-phase OVA. On the other hand, OVA immobilized on solid-phase induced EXiLE responses in both E-C1 Ab- and E-G5 Ab-sensitized mast cells. Western blotting of OVA indicated that E-C1 Ab binds both to OVA monomers and dimers, unlike E-G5 Ab, which probably binds only to the OVA dimer. These results suggest that antigen immobilization enhanced IgE crosslinking ability through multimerization of allergen molecules in the solid phase, resulting in an increase in false positives in IgE binding-based conventional in vitro allergy tests. These findings shed light on the physicochemical nature of antigens as an important factor for the development and evaluation of in vitro allergy tests and suggest that mast cell activation-based allergy testing with liquid-phase allergens is a promising strategy to evaluate the physiological interactions of IgE and allergens.

Structural and functional characterization of solute binding proteins for aromatic compounds derived from lignin: p-coumaric acid and related aromatic acids.

PubMed

Tan, Kemin; Chang, Changsoo; Cuff, Marianne; Osipiuk, Jerzy; Landorf, Elizabeth; Mack, Jamey C; Zerbs, Sarah; Joachimiak, Andrzej; Collart, Frank R

2013-10-01

Lignin comprises 15-25% of plant biomass and represents a major environmental carbon source for utilization by soil microorganisms. Access to this energy resource requires the action of fungal and bacterial enzymes to break down the lignin polymer into a complex assortment of aromatic compounds that can be transported into the cells. To improve our understanding of the utilization of lignin by microorganisms, we characterized the molecular properties of solute binding proteins of ATP-binding cassette transporter proteins that interact with these compounds. A combination of functional screens and structural studies characterized the binding specificity of the solute binding proteins for aromatic compounds derived from lignin such as p-coumarate, 3-phenylpropionic acid and compounds with more complex ring substitutions. A ligand screen based on thermal stabilization identified several binding protein clusters that exhibit preferences based on the size or number of aromatic ring substituents. Multiple X-ray crystal structures of protein-ligand complexes for these clusters identified the molecular basis of the binding specificity for the lignin-derived aromatic compounds. The screens and structural data provide new functional assignments for these solute-binding proteins which can be used to infer their transport specificity. This knowledge of the functional roles and molecular binding specificity of these proteins will support the identification of the specific enzymes and regulatory proteins of peripheral pathways that funnel these compounds to central metabolic pathways and will improve the predictive power of sequence-based functional annotation methods for this family of proteins. Copyright © 2013 Wiley Periodicals, Inc.

Structural and functional characterization of solute binding proteins for aromatic compounds derived from lignin: p-coumaric acid and related aromatic acids

PubMed Central

Tan, Kemin; Chang, Changsoo; Cuff, Marianne; Osipiuk, Jerzy; Landorf, Elizabeth; Mack, Jamey C.; Zerbs, Sarah; Joachimiak, Andrzej; Collart, Frank R.

2013-01-01

Lignin comprises 15.25% of plant biomass and represents a major environmental carbon source for utilization by soil microorganisms. Access to this energy resource requires the action of fungal and bacterial enzymes to break down the lignin polymer into a complex assortment of aromatic compounds that can be transported into the cells. To improve our understanding of the utilization of lignin by microorganisms, we characterized the molecular properties of solute binding proteins of ATP.binding cassette transporter proteins that interact with these compounds. A combination of functional screens and structural studies characterized the binding specificity of the solute binding proteins for aromatic compounds derived from lignin such as p-coumarate, 3-phenylpropionic acid and compounds with more complex ring substitutions. A ligand screen based on thermal stabilization identified several binding protein clusters that exhibit preferences based on the size or number of aromatic ring substituents. Multiple X-ray crystal structures of protein-ligand complexes for these clusters identified the molecular basis of the binding specificity for the lignin-derived aromatic compounds. The screens and structural data provide new functional assignments for these solute.binding proteins which can be used to infer their transport specificity. This knowledge of the functional roles and molecular binding specificity of these proteins will support the identification of the specific enzymes and regulatory proteins of peripheral pathways that funnel these compounds to central metabolic pathways and will improve the predictive power of sequence-based functional annotation methods for this family of proteins. PMID:23606130

Freezable Radiator Coupon Testing and Full Scale Radiator Design

NASA Technical Reports Server (NTRS)

Lillibridge, Sean T.; Guinn, John; Cognata, Thomas; Navarro, Moses

2009-01-01

Freezable radiators offer an attractive solution to the issue of thermal control system scalability. As thermal environments change, a freezable radiator will effectively scale the total heat rejection it is capable of as a function of the thermal environment and flow rate through the radiator. Scalable thermal control systems are a critical technology for spacecraft that will endure missions with widely varying thermal requirements. These changing requirements are a result of the space craft s surroundings and because of different thermal loads during different mission phases. However, freezing and thawing (recovering) a radiator is a process that has historically proven very difficult to predict through modeling, resulting in highly inaccurate predictions of recovery time. This paper summarizes tests on three test articles that were performed to further empirically quantify the behavior of a simple freezable radiator, and the culmination of those tests into a full scale design. Each test article explored the bounds of freezing and recovery behavior, as well as providing thermo-physical data of the working fluid, a 50-50 mixture of DowFrost HD and water. These results were then used as a tool for developing correlated thermal model in Thermal Desktop which could be used for modeling the behavior of a full scale thermal control system for a lunar mission. The final design of a thermal control system for a lunar mission is also documented in this paper.

Thermal Conductivity and Elastic Modulus Evolution of Thermal Barrier Coatings under High Heat Flux Conditions

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.

1999-01-01

Laser high heat flux test approaches have been established to obtain critical properties of ceramic thermal barrier coatings (TBCs) under near-realistic temperature and thermal gradients that may he encountered in advanced engine systems. Thermal conductivity change kinetics of a thin ceramic coating were continuously monitored in real time at various test temperatures. A significant thermal conductivity increase was observed during the laser simulated engine heat flux tests. For a 0.25 mm thick ZrO2-8%Y2O3 coating system, the overall thermal conductivity increased from the initial value of 1.0 W/m-K to 1. 15 W/m-K, 1. 19 W/m-K and 1.5 W/m-K after 30 hour testing at surface temperatures of 990C, 1100C, and 1320C. respectively. Hardness and modulus gradients across a 1.5 mm thick TBC system were also determined as a function of laser testing time using the laser sintering/creep and micro-indentation techniques. The coating Knoop hardness values increased from the initial hardness value of 4 GPa to 5 GPa near the ceramic/bond coat interface, and to 7.5 GPa at the ceramic coating surface after 120 hour testing. The ceramic surface modulus increased from an initial value of about 70 GPa to a final value of 125 GPa. The increase in thermal conductivity and the evolution of significant hardness and modulus gradients in the TBC systems are attributed to sintering-induced micro-porosity gradients under the laser-imposed high thermal gradient conditions. The test techniques provide a viable means for obtaining coating data for use in design, development, stress modeling, and life prediction for various thermal barrier coating applications.

Structural, thermal, functional, antioxidant & antimicrobial properties of β-d-glucan extracted from baker's yeast (Saccharomyces cereviseae)-Effect of γ-irradiation.

PubMed

Khan, Asma Ashraf; Gani, Adil; Masoodi, F A; Amin, Furheen; Wani, Idrees Ahmed; Khanday, Firdous Ahmad; Gani, Asir

2016-04-20

This study was carried out to evaluate the effect of γ-irradiation (0, 5, 10, 20, 30 & 50kGy) on the structural, functional, antioxidant and antimicrobial properties of yeast β-d-glucan. The samples were characterized by ATR-FTIR, gel permeation chromatography (GPC) and the thermal properties were studied using DSC. There was a decrease in the average molecular weight of β-d-glucan as the irradiation dose increased. The functional properties of irradiated yeast β-d-glucan were largely influenced by the action of gamma radiation like swelling power and viscosity decreases with increase in the irradiation dose while as fat binding capacity, emulsifying properties, foaming properties and bile acid binding capacity shows an increasing trend. All the antioxidant properties carried out using six different assays increased significantly (p≤0.05) in a dose dependent manner. The antibacterial activity of yeast β-d-glucan also showed an increasing trend with increase in the irradiation dose from 5 to 50kDa. Copyright © 2016 Elsevier Ltd. All rights reserved.

A 45-Amino-Acid Scaffold Mined from the PDB for High-Affinity Ligand Engineering.

PubMed

Kruziki, Max A; Bhatnagar, Sumit; Woldring, Daniel R; Duong, Vandon T; Hackel, Benjamin J

2015-07-23

Small protein ligands can provide superior physiological distribution compared with antibodies, and improved stability, production, and specific conjugation. Systematic evaluation of the PDB identified a scaffold to push the limits of small size and robust evolution of stable, high-affinity ligands: 45-residue T7 phage gene 2 protein (Gp2) contains an α helix opposite a β sheet with two adjacent loops amenable to mutation. De novo ligand discovery from 10(8) mutants and directed evolution toward four targets yielded target-specific binders with affinities as strong as 200 ± 100 pM, Tms from 65 °C ± 3 °C to 80°C ± 1 °C, and retained activity after thermal denaturation. For cancer targeting, a Gp2 domain for epidermal growth factor receptor was evolved with 18 ± 8 nM affinity, receptor-specific binding, and high thermal stability with refolding. The efficiency of evolving new binding function and the size, affinity, specificity, and stability of evolved domains render Gp2 a uniquely effective ligand scaffold. Copyright © 2015 Elsevier Ltd. All rights reserved.

Transcriptional activity and DNA binding of heat shock factor-1 involve phosphorylation on threonine 142 by CK2.

PubMed

Soncin, Fabrice; Zhang, Xinfeng; Chu, Boyang; Wang, Xiaozhe; Asea, Alexzander; Ann Stevenson, Mary; Sacks, David B; Calderwood, Stuart K

2003-04-04

Heat shock factor-1 (HSF-1) is the regulator of hsp molecular chaperone transcription, although the intracellular mechanisms involved in HSF-1 activation have not been fully elucidated. As HSF1 is activated by heat shock simultaneously with the nuclear translocation of the protein kinase CK2, we have investigated the role of CK2 in HSF1 activation. We demonstrate that HSF-1 is phosphorylated by CK2 on both serine and threonine residues and has characterized a phosphorylation site at threonine 142. Mutation of Thr-142 to alanine (T142A) inhibits trans-activation of the HSP70 gene by HSF1 and in addition inhibits the accumulation of HSF-1 competent to bind heat shock elements in the nucleus. HSF1 activation by heat is correlated with the thermal activation of nuclear CK2 and overexpression of CK2 activates HSF1. Phosphorylation by CK2 on threonine 142 may therefore be an essential step in the thermal activation of latent HSF1 by stresses.

Thermal Design Overview of the Mars Exploration Rover Project

NASA Technical Reports Server (NTRS)

Tsuyuki, Glenn

2002-01-01

Contents include the following: Mission Overview. Thermal Environments. Driving Thermal Requirements. Thermal Design Approach. Thermal Control Block Diagram. Thermal Design Description. Thermal Analysis Results Summary. Testing Plans. Issues & Concerns.

Cyclic Failure Mechanisms of Thermal and Environmental Barrier Coating Systems Under Thermal Gradient Test Conditions

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Lee, Kang N.; Miller, Robert A.

2002-01-01

Plasma-sprayed ZrO2-8wt%Y2O3 and mullite+BSAS/Si multilayer thermal and environmental barrier coating (TBC-EBC) systems on SiC/SiC ceramic matrix composite (CMC) substrates were thermally cyclic tested under high thermal gradients using a laser high-heat-flux rig in conjunction with furnace exposure in water-vapor environments. Coating sintering and interface damage were assessed by monitoring the real-time thermal conductivity changes during the laser heat-flux tests and by examining the microstructural changes after exposure. Sintering kinetics of the coating systems were also independently characterized using a dilatometer. It was found that the coating failure involved both the time-temperature dependent sintering and the cycle frequency dependent cyclic fatigue processes. The water vapor environments not only facilitated the initial coating conductivity increases due to enhanced sintering and interface reaction, but also promoted later conductivity reductions due to the accelerated coating cracking and delamination. The failure mechanisms of the coating systems are also discussed based on the cyclic test results and are correlated to the sintering and thermal stress behavior under the thermal gradient test conditions.

21 CFR 862.1415 - Iron-binding capacity test system.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Iron-binding capacity test system. 862.1415 Section 862.1415 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Chemistry Test...

Design, fabrication and test of Load Bearing multilayer insulation to support a broad area cooled shield

NASA Astrophysics Data System (ADS)

Dye, S. A.; Johnson, W. L.; Plachta, D. W.; Mills, G. L.; Buchanan, L.; Kopelove, A. B.

2014-11-01

Improvements in cryogenic propellant storage are needed to achieve reduced or Zero Boil Off of cryopropellants, critical for long duration missions. Techniques for reducing heat leak into cryotanks include using passive multi-layer insulation (MLI) and vapor cooled or actively cooled thermal shields. Large scale shields cannot be supported by tank structural supports without heat leak through the supports. Traditional MLI also cannot support shield structural loads, and separate shield support mechanisms add significant heat leak. Quest Thermal Group and Ball Aerospace, with NASA SBIR support, have developed a novel Load Bearing multi-layer insulation (LBMLI) capable of self-supporting thermal shields and providing high thermal performance. We report on the development of LBMLI, including design, modeling and analysis, structural testing via vibe and acoustic loading, calorimeter thermal testing, and Reduced Boil-Off (RBO) testing on NASA large scale cryotanks. LBMLI uses the strength of discrete polymer spacers to control interlayer spacing and support the external load of an actively cooled shield and external MLI. Structural testing at NASA Marshall was performed to beyond maximum launch profiles without failure. LBMLI coupons were thermally tested on calorimeters, with superior performance to traditional MLI on a per layer basis. Thermal and structural tests were performed with LBMLI supporting an actively cooled shield, and comparisons are made to the performance of traditional MLI and thermal shield supports. LBMLI provided a 51% reduction in heat leak per layer over a previously tested traditional MLI with tank standoffs, a 38% reduction in mass, and was advanced to TRL5. Active thermal control using LBMLI and a broad area cooled shield offers significant advantages in total system heat flux, mass and structural robustness for future Reduced Boil-Off and Zero Boil-Off cryogenic missions with durations over a few weeks.

New Battery Testing Facility Could Boost Future of Electric Vehicles

Science.gov Websites

industry. The Battery Thermal Test Facility at the U.S. Department of Energy's (DOE) National Renewable , ambient heat sources that could effect thermal readings from the battery. The cycler can both charge and draw current from a battery, allowing for thermal testing of any voltage. It can also be used to test

Effects of Long-Term Thermal Exposure on Commercially Pure Titanium Grade 2 Elevated-Temperature Tensile Properties

NASA Technical Reports Server (NTRS)

Ellis, David L.

2012-01-01

Elevated-temperature tensile testing of commercially pure titanium (CP Ti) Grade 2 was conducted for as-received commercially produced sheet and following thermal exposure at 550 and 650 K (531 and 711 F) for times up to 5000 h. The tensile testing revealed some statistical differences between the 11 thermal treatments, but most thermal treatments were statistically equivalent. Previous data from room temperature tensile testing was combined with the new data to allow regression and development of mathematical models relating tensile properties to temperature and thermal exposure. The results indicate that thermal exposure temperature has a very small effect, whereas the thermal exposure duration has no statistically significant effects on the tensile properties. These results indicate that CP Ti Grade 2 will be thermally stable and suitable for long-duration space missions.

First Test Flight Thermal Performance of the Low Density Supersonic Decelerator (LDSD) Supersonic Flight Dynamics Test (SFDT) Vehicle

NASA Technical Reports Server (NTRS)

Mastropietro, A.J.; Kempenaar, Jason; Redmond, Matthew; Pauken, Michael; Ancarrow, Walt

2015-01-01

The thermal telemetry from the first test flight, an assessment of post-flight inspections of the recovered vehicle, and a review of the thermal design and model of the vehicle will be presented along with several lessons learned.

Thermal behavior of crumb-rubber modified asphalt concrete mixtures

NASA Astrophysics Data System (ADS)

Epps, Amy Louise

Thermal cracking is one of the primary forms of distress in asphalt concrete pavements, resulting from either a single drop in temperature to an extreme low or from multiple temperature cycles above the fracture temperature of the asphalt-aggregate mixture. The first mode described is low temperature cracking; the second is thermal fatigue. The addition of crumb-rubber, manufactured from scrap tires, to the binder in asphalt concrete pavements has been suggested to minimize both types of thermal cracking. Four experiments were designed and completed to evaluate the thermal behavior of crumb-rubber modified (CRM) asphalt-aggregate mixtures. Modified and unmodified mixture response to thermal stresses was measured in four laboratory tests. The Thermal Stress Restrained Specimen Test (TSRST) and the Indirect Tensile Test (IDT) were used to compare mixture resistance to low temperature cracking. Modified mixtures showed improved performance, and cooling rate did not affect mixture resistance according to the statistical analysis. Therefore results from tests with faster rates can predict performance under slower field rates. In comparison, predicted fracture temperatures and stresses (IDT) were generally higher than measured values (TSRST). In addition, predicted fracture temperatures from binder test results demonstrated that binder testing alone is not sufficient to evaluate CRM mixtures. Thermal fatigue was explored in the third experiment using conventional load-induced fatigue tests with conditions selected to simulate daily temperature fluctuations. Test results indicated that thermal fatigue may contribute to transverse cracking in asphalt pavements. Both unmodified and modified mixtures had a finite capacity to withstand daily temperature fluctuations coupled with cold temperatures. Modified mixtures again exhibited improved performance. The fourth experiment examined fracture properties of modified and unmodified mixtures using a common fracture toughness test. Results showed no effect from modification, but the small experiment size may have masked this effect. Reliability concepts were introduced to include risk and uncertainty in a comparison of mixture response measured in the laboratory and estimated environmental conditions. This comparison provided evidence that CRM mixtures exhibit improved resistance to both types of thermal cracking at high levels of reliability. In conclusion, a mix design and analysis framework for evaluating thermal behavior was recommended.

Studies on the interaction of a synthetic nitro-flavone derivative with DNA: A multi-spectroscopic and molecular docking approach.

PubMed

Mitra, A; Saikh, F; Das, J; Ghosh, S; Ghosh, R

2018-05-22

Interaction of a ligand with DNA is often the basis of drug action of many molecules. Flavones are important in this regard as their structural features confer them the ability to bind to DNA. 2-(4-Nitrophenyl)-4H-chromen-4-one (4NCO) is an important biologically active synthetic flavone derivative. We are therefore interested in studying its interaction with DNA. Absorption spectroscopy studies included standard and reverse titration, effect of ionic strength on titration, determination of stoichiometry of binding and thermal denaturation. Spectrofluorimetry techniques included fluorimetric titration, quenching studies and fluorescence displacement assay. Assessment of relative viscosity and estimation of thermodynamic parameters from CD spectral studies were also undertaken. Furthermore, molecular docking analyses were also done with different short DNA sequences. The fluorescent flavone 4NCO reversibly interacted with DNA through partial intercalation as well as minor-groove binding. The binding constant and the number of binding sites were of the order 10 4  M -1 and 1 respectively. The binding stoichiometry with DNA was found to be 1:1. The nature of the interaction of 4NCO with DNA was hydrophobic in nature and the process of binding was spontaneous, endothermic and entropy-driven. The flavone also showed a preference for binding to GC rich sequences. The study presents a profile for structural and thermodynamic parameters, for the binding of 4NCO with DNA. DNA is an important target for ligands that are effective against cell proliferative disorders. In this regard, the molecule 4NCO is important since it can exert its biological activity through its DNA binding ability and can be a potential drug candidate. Copyright © 2018 Elsevier B.V. All rights reserved.

Tradespace Assessment: Thermal Strain Modeling Comparison Of Multiple Clothing Configurations Based On Different Environmental Conditions

DTIC Science & Technology

2017-02-01

risks, by modeling thermal strain. Twenty clothing ensembles were tested for thermal and evaporative resistances according to American Society of...e.g., football, hockey, etc.) or during military, law enforcement, or first responder operations (e.g., body armor, flame resistant clothing, etc...Each clothing configuration was tested to American Society of Testing and Materials (ASTM) standards for “dry” thermal resistance (Rct) (ASTM F1291

Thermal balance testing of the MSAT spacecraft

NASA Technical Reports Server (NTRS)

Samson, Serge; Choueiry, Elie; Pang, Kenneth

1994-01-01

This paper reports on the recently completed thermal balance/thermal vacuum testing of an MSAT satellite, the first satellite to provide mobile communications service for all of continental North America. MSAT is a two-spacecraft program, using a three-axis-stabilized HUGHES HS-601 series bus as the vehicle for the Canadian-designed payload. The thermal tests performed at the Canadian Space Agency's David Florida Laboratory in Ottawa, Canada, lasted approximately 32 days.

Laser geodynamic satellite thermal/optical/ vibrational analyses and testing. Volume 2: Technical report, book 1. [retroreflector design

NASA Technical Reports Server (NTRS)

1974-01-01

The results of the LAGEOS thermal/optical/vibrational analysis and test program are reported. Through analyses and tests it is verified that the MSFC LAGEOS design provides a retroreflector thermal environment which maintains acceptable retroflector internal thermal gradients. The technical results of the study, organized by the major task areas are presented. The interrelationships of the major tasks are described and the major decisions are identified.

Isolation and characterisation of sericin antifreeze peptides and molecular dynamics modelling of their ice-binding interaction.

PubMed

Wu, Jinhong; Rong, Yuzhi; Wang, Zhengwu; Zhou, Yanfu; Wang, Shaoyun; Zhao, Bo

2015-05-01

This study aimed to isolate and characterise a novel sericin antifreeze peptide and investigate its ice-binding molecular mechanism. The thermal hysteresis activity of ice-binding sericin peptides (I-SP) was measured and their activity reached as high as 0.94 °C. A P4 fraction, with high hypothermia protective activity and inhibition activity of ice recrystallisation, was obtained from I-SP, and a purified sericin peptide, named SM-AFP, with the sequence of TTSPTNVSTT and a molecular weight of 1009.50 Da was then isolated from the P4 fraction. Treatment of Lactobacillus delbrueckii Subsp. bulgaricus LB340 LYO with 100 μg/ml synthetic SM-AFP led to 1.4-fold increased survival (p < 0.05). Finally, an SM-AFP/ice binding model was constructed and results of molecular dynamics simulation suggested that the binding of SM-AFP with ice and prevention of ice crystal growth could be attributed to hydrogen bond formation, hydrophobic interaction and non-bond interactions. Sericin peptides could be developed into beneficial cryoprotectants and used in frozen food processing. Copyright © 2014 Elsevier Ltd. All rights reserved.

Incorporating a guanidine-modified cytosine base into triplex-forming PNAs for the recognition of a C-G pyrimidine–purine inversion site of an RNA duplex

PubMed Central

Toh, Desiree-Faye Kaixin; Devi, Gitali; Patil, Kiran M.; Qu, Qiuyu; Maraswami, Manikantha; Xiao, Yunyun; Loh, Teck Peng; Zhao, Yanli; Chen, Gang

2016-01-01

RNA duplex regions are often involved in tertiary interactions and protein binding and thus there is great potential in developing ligands that sequence-specifically bind to RNA duplexes. We have developed a convenient synthesis method for a modified peptide nucleic acid (PNA) monomer with a guanidine-modified 5-methyl cytosine base. We demonstrated by gel electrophoresis, fluorescence and thermal melting experiments that short PNAs incorporating the modified residue show high binding affinity and sequence specificity in the recognition of an RNA duplex containing an internal inverted Watson-Crick C-G base pair. Remarkably, the relatively short PNAs show no appreciable binding to DNA duplexes or single-stranded RNAs. The attached guanidine group stabilizes the base triple through hydrogen bonding with the G base in a C-G pair. Selective binding towards an RNA duplex over a single-stranded RNA can be rationalized by the fact that alkylation of the amine of a 5-methyl C base blocks the Watson–Crick edge. PNAs incorporating multiple guanidine-modified cytosine residues are able to enter HeLa cells without any transfection agent. PMID:27596599

Demonstration and Characterization of Biomolecular Enrichment on Microfluidic Aptamer-Functionalized Surfaces

PubMed Central

Nguyen, Thai Huu; Pei, Renjun; Stojanovic, Milan; Lin, Qiao

2010-01-01

This paper demonstrates and systematically characterizes the enrichment of biomolecular compounds using aptamer-functionalized surfaces within a microfluidic device. The device consists of a microchamber packed with aptamer-functionalized microbeads and integrated with a microheater and temperature sensor to enable thermally controlled binding and release of biomolecules by the aptamer. We first present an equilibrium binding-based analytical model to understand the enrichment process. The characteristics of the aptamer-analyte binding and enrichment are then experimentally studied, using adenosine monophosphate (AMP) and a specific RNA aptamer as a model system. The temporal process of AMP binding to the aptamer is found to be primarily determined by the aptamer-AMP binding kinetics. The temporal process of aptamer-AMP dissociation at varying temperatures is also obtained and observed to occur relatively rapidly (< 2 s). The specificity of the enrichment is next confirmed by performing selective enrichment of AMP from a sample containing biomolecular impurities. Finally, we investigate the enrichment of AMP by either discrete or continuous introduction of a dilute sample into the microchamber, demonstrating enrichment factors ranging from 566 to 686×, which agree with predictions of the analytical model. PMID:21765612

Exciton size and binding energy limitations in one-dimensional organic materials

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

Kraner, S., E-mail: stefan.kraner@iapp.de; Koerner, C.; Leo, K.

2015-12-28

In current organic photovoltaic devices, the loss in energy caused by the charge transfer step necessary for exciton dissociation leads to a low open circuit voltage, being one of the main reasons for rather low power conversion efficiencies. A possible approach to avoid these losses is to tune the exciton binding energy to a value of the order of thermal energy, which would lead to free charges upon absorption of a photon, and therefore increase the power conversion efficiency towards the Shockley-Queisser limit. We determine the size of the excitons for different organic molecules and polymers by time dependent densitymore » functional theory calculations. For optically relevant transitions, the exciton size saturates around 0.7 nm for one-dimensional molecules with a size longer than about 4 nm. For the ladder-type polymer poly(benzimidazobenzophenanthroline), we obtain an exciton binding energy of about 0.3 eV, serving as a lower limit of the exciton binding energy for the organic materials investigated. Furthermore, we show that charge transfer transitions increase the exciton size and thus identify possible routes towards a further decrease of the exciton binding energy.« less

Hybrid k .p tight-binding model for intersubband optics in atomically thin InSe films

NASA Astrophysics Data System (ADS)

Magorrian, S. J.; Ceferino, A.; Zólyomi, V.; Fal'ko, V. I.

2018-04-01

We propose atomic films of n -doped γ -InSe as a platform for intersubband optics in the infrared and far-infrared range, coupled to out-of-plane polarized light. Depending on the film thickness (number of layers) and the amount of n -doping of the InSe film, these transitions span from ˜0.7 eV for bilayer to ˜0.05 eV for 15-layer InSe. We use a hybrid k .p theory and tight-binding model, fully parametrized using density-functional theory, to predict their oscillator strengths and thermal linewidths at room temperature.

Switching bonds in a DNA gel: an all-DNA vitrimer.

PubMed

Romano, Flavio; Sciortino, Francesco

2015-02-20

We design an all-DNA system that behaves like vitrimers, innovative plastics with self-healing and stress-releasing properties. The DNA sequences are engineered to self-assemble first into tetra- and bifunctional units which, upon further cooling, bind to each other forming a fully bonded network gel. An innovative design of the binding regions of the DNA sequences, exploiting a double toehold-mediated strand displacement, generates a network gel which is able to reshuffle its bonds, retaining at all times full bonding. As in vitrimers, the rate of bond switching can be controlled via a thermally activated catalyst, which in the present design is very short DNA strands.

Passive Gas-Gap Heat Switches for Use in Adiabatic Demagnetization Refrigerators

NASA Technical Reports Server (NTRS)

Shirron, P. J.; Canavan, E. R.; DiPirro, M. J.; Jackson, M.; Panek, J.; Tuttle, J. G.; Krebs, Carolyn (Technical Monitor)

2001-01-01

We have designed, built, and tested a gas gap heat switch that works passively, without the need for a separate, thermally activated getter. This switch uses He-3 condensed as a thin film on alternating plates of copper. The switch is thermally conductive at temperatures above about 0.2 K, and is insulating if either end of the switch is below about 0.15 K. The "on" conductance (7 mW/K at 0.25K) is limited by the surface area and gap between the copper leaves, the saturated vapor pressure of the He-3, and the Kapitza boundary resistance between the He-3 and the copper. The "off" conductance is determined by the helium containment shell which physically supports the two conductive ends. We have also designed and are building passive gas gap heat switches which will passively turn off near 1 K and 4 K. For these switches we rely on the rapidly changing vapor pressure of He-4 above neon or copper substrates, respectively, when the coverage is less than one monolayer. The different binding energies of the He-4 to the neon or copper give rise to the different temperatures where the switches transition between the on and off states.

Specific stabilization of CFTR by phosphatidylserine.

PubMed

Hildebrandt, Ellen; Khazanov, Netaly; Kappes, John C; Dai, Qun; Senderowitz, Hanoch; Urbatsch, Ina L

2017-02-01

The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR, ABCC7) is a plasma membrane chloride ion channel in the ABC transporter superfamily. CFTR is a key target for cystic fibrosis drug development, and its structural elucidation would advance those efforts. However, the limited in vivo and in vitro stability of the protein, particularly its nucleotide binding domains, has made structural studies challenging. Here we demonstrate that phosphatidylserine uniquely stimulates and thermally stabilizes the ATP hydrolysis function of purified human CFTR. Among several lipids tested, the greatest stabilization was observed with brain phosphatidylserine, which shifted the Tm for ATPase activity from 22.7±0.8°C to 35.0±0.2°C in wild-type CFTR, and from 26.6±0.7°C to 42.1±0.2°C in a more stable mutant CFTR having deleted regulatory insertion and S492P/A534P/I539T mutations. When ATPase activity was measured at 37°C in the presence of brain phosphatidylserine, Vmax for wild-type CFTR was 240±60nmol/min/mg, a rate higher than previously reported and consistent with rates for other purified ABC transporters. The significant thermal stabilization of CFTR by phosphatidylserine may be advantageous in future structural and biophysical studies of CFTR. Copyright © 2016. Published by Elsevier B.V.

Significant thermal conductivity reduction of silicon nanowire forests through discrete surface doping of germanium

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

Pan, Ying; Hong, Guo; Raja, Shyamprasad N.

2015-03-02

Silicon nanowires (SiNWs) are promising materials for the realization of highly-efficient and cost effective thermoelectric devices. Reduction of the thermal conductivity of such materials is a necessary and viable pathway to achieve sufficiently high thermoelectric efficiencies, which are inversely proportional to the thermal conductivity. In this article, vertically aligned forests of SiNW and germanium (Ge)-doped SiNW with diameters around 100 nm have been fabricated, and their thermal conductivity has been measured. The results show that discrete surface doping of Ge on SiNW arrays can lead to 23% reduction in thermal conductivity at room temperature compared to uncoated SiNWs. Such reduction canmore » be further enhanced to 44% following a thermal annealing step. By analyzing the binding energy changes of Ge-3d and Si-2p using X-ray photoelectron spectroscopy, we demonstrate that surface doped Ge interacts strongly with Si, enhancing phonon scattering at the Si-Ge interface as has also been shown in non-equilibrium molecular dynamics studies of single nanowires. Overall, our results suggest a viable pathway to improve the energy conversion efficiency of nanowire-forest thermoelectric nanomaterials.« less

Lysozyme immobilization onto PVC catheters grafted with NVCL and HEMA for reduction of bacterial adhesion

NASA Astrophysics Data System (ADS)

Guadarrama-Zempoalteca, Yesica; Díaz-Gómez, Luis; Meléndez-Ortiz, H. Iván; Concheiro, Angel; Alvarez-Lorenzo, Carmen; Bucio, Emilio

2016-09-01

The aim of the present work was to functionalize poly(vinyl chloride) (PVC) urinary catheters with grafted copolymers that can improve the biocompatibility and serve as binding points of lysozyme. PVC catheters were modified by grafting a mixture of N-vinylcaprolactam (NVCL) and 2-hydroxyethylmethacrylate (HEMA) applying a gamma-ray pre-irradiation method. The effect of absorbed dose, monomer concentration, temperature, and reaction time on the grafting percentage was evaluated. The grafted catheters were characterized regarding surface composition (FTIR-ATR spectroscopy), thermal properties (DSC and TGA) and swelling in aqueous medium. Lysozyme was directly coupled onto PVC-g-(NVCL/HEMA) previously activated using carbonyldiimidazole. Antimicrobial lytic activity of the modified catheters over time was tested against Micrococcus lysodeikticus. Lysozyme diminished the adhesion of Staphylococcus aureus onto the functionalized catheters, which may be suitable to prevent biofilm formation.

Comparative expression profile of NOD1/2 and certain acute inflammatory cytokines in thermal-stressed cell culture model of native and crossbred cattle

NASA Astrophysics Data System (ADS)

Bhanuprakash, V.; Singh, Umesh; Sengar, Gyanendra Singh; Raja, T. V.; Sajjanar, Basavraj; Alex, Rani; Kumar, Sushil; Alyethodi, R. R.; Kumar, Ashish; Sharma, Ankur; Kumar, Suresh; Bhusan, Bharat; Deb, Rajib

2017-05-01

Thermotolerance depends mainly on the health and immune status of the animals. The variation in the immune status of the animals may alter the level of tolerance of animals exposed to heat or cold stress. The present study was conducted to investigate the expression profile of two important nucleotide binding and oligomerization domain receptors (NLRs) (NOD1 and NOD2) and their central signalling molecule RIP2 gene during in vitro thermal-stressed bovine peripheral blood mononuclear cells (PBMCs) of native (Sahiwal) and crossbred (Sahiwal X HF) cattle. We also examined the differential expression profile of certain acute inflammatory cytokines in in vitro thermal-stressed PBMC culture among native and its crossbred counterparts. Results revealed that the expression profile of NOD1/2 positively correlates with the thermal stress, signalling molecule and cytokines. Present findings also highlighted that the expression patterns during thermal stress were comparatively superior among indigenous compared to crossbred cattle which may add references regarding the better immune adaptability of Zebu cattle.

Predicting protein-binding regions in RNA using nucleotide profiles and compositions.

PubMed

Choi, Daesik; Park, Byungkyu; Chae, Hanju; Lee, Wook; Han, Kyungsook

2017-03-14

Motivated by the increased amount of data on protein-RNA interactions and the availability of complete genome sequences of several organisms, many computational methods have been proposed to predict binding sites in protein-RNA interactions. However, most computational methods are limited to finding RNA-binding sites in proteins instead of protein-binding sites in RNAs. Predicting protein-binding sites in RNA is more challenging than predicting RNA-binding sites in proteins. Recent computational methods for finding protein-binding sites in RNAs have several drawbacks for practical use. We developed a new support vector machine (SVM) model for predicting protein-binding regions in mRNA sequences. The model uses sequence profiles constructed from log-odds scores of mono- and di-nucleotides and nucleotide compositions. The model was evaluated by standard 10-fold cross validation, leave-one-protein-out (LOPO) cross validation and independent testing. Since actual mRNA sequences have more non-binding regions than protein-binding regions, we tested the model on several datasets with different ratios of protein-binding regions to non-binding regions. The best performance of the model was obtained in a balanced dataset of positive and negative instances. 10-fold cross validation with a balanced dataset achieved a sensitivity of 91.6%, a specificity of 92.4%, an accuracy of 92.0%, a positive predictive value (PPV) of 91.7%, a negative predictive value (NPV) of 92.3% and a Matthews correlation coefficient (MCC) of 0.840. LOPO cross validation showed a lower performance than the 10-fold cross validation, but the performance remains high (87.6% accuracy and 0.752 MCC). In testing the model on independent datasets, it achieved an accuracy of 82.2% and an MCC of 0.656. Testing of our model and other state-of-the-art methods on a same dataset showed that our model is better than the others. Sequence profiles of log-odds scores of mono- and di-nucleotides were much more powerful features than nucleotide compositions in finding protein-binding regions in RNA sequences. But, a slight performance gain was obtained when using the sequence profiles along with nucleotide compositions. These are preliminary results of ongoing research, but demonstrate the potential of our approach as a powerful predictor of protein-binding regions in RNA. The program and supporting data are available at http://bclab.inha.ac.kr/RBPbinding .

Rapid thermal cycling of new technology solar array blanket coupons

NASA Technical Reports Server (NTRS)

Scheiman, David A.; Smith, Bryan K.; Kurland, Richard M.; Mesch, Hans G.

1990-01-01

NASA Lewis Research Center is conducting thermal cycle testing of a new solar array blanket technologies. These technologies include test coupons for Space Station Freedom (SSF) and the advanced photovoltaic solar array (APSA). The objective of this testing is to demonstrate the durability or operational lifetime of the solar array interconnect design and blanket technology within a low earth orbit (LEO) or geosynchronous earth orbit (GEO) thermal cycling environment. Both the SSF and the APSA array survived all rapid thermal cycling with little or no degradation in peak performance. This testing includes an equivalent of 15 years in LEO for SSF test coupons and 30 years of GEO plus ten years of LEO for the APSA test coupon. It is concluded that both the parallel gap welding of the SSF interconnects and the soldering of the APSA interconnects are adequately designed to handle the thermal stresses of space environment temperature extremes.

Thermal Analysis of Small Re-Entry Probe

NASA Technical Reports Server (NTRS)

Agrawal, Parul; Prabhu, Dinesh K.; Chen, Y. K.

2012-01-01

The Small Probe Reentry Investigation for TPS Engineering (SPRITE) concept was developed at NASA Ames Research Center to facilitate arc-jet testing of a fully instrumented prototype probe at flight scale. Besides demonstrating the feasibility of testing a flight-scale model and the capability of an on-board data acquisition system, another objective for this project was to investigate the capability of simulation tools to predict thermal environments of the probe/test article and its interior. This paper focuses on finite-element thermal analyses of the SPRITE probe during the arcjet tests. Several iterations were performed during the early design phase to provide critical design parameters and guidelines for testing. The thermal effects of ablation and pyrolysis were incorporated into the final higher-fidelity modeling approach by coupling the finite-element analyses with a two-dimensional thermal protection materials response code. Model predictions show good agreement with thermocouple data obtained during the arcjet test.

Performance Testing of Thermal Interface Filler Materials in a Bolted Aluminum Interface Under Thermal/Vacuum Conditions

NASA Technical Reports Server (NTRS)

Glasgow, S. D.; Kittredge, K. B.

2003-01-01

A thermal interface material is one of the many tools often used as part of the thermal control scheme for space-based applications. Historically, at Marshall Space Flight Center, CHO-THERM 1671 has primarily been used for applications where an interface material was deemed necessary. However, numerous alternatives have come on the market in recent years. It was decided that a number of these materials should be tested against each other to see if there were better performing alternatives. The tests were done strictly to compare the thermal performance of the materials relative to each other under repeatable conditions and do not take into consideration other design issues, such as off-gassing, electrical conduction, isolation, etc. The purpose of this Technical Memorandum is to detail the materials tested, test apparatus, procedures, and results of these tests. The results show that there are a number of better performing alternatives now available.

Differential age-related effects on conjunctive and relational visual short-term memory binding.

PubMed

Bastin, Christine

2017-12-28

An age-related associative deficit has been described in visual short-term binding memory tasks. However, separate studies have suggested that ageing disrupts relational binding (to associate distinct items or item and context) more than conjunctive binding (to integrate features within an object). The current study directly compared relational and conjunctive binding with a short-term memory task for object-colour associations in 30 young and 30 older adults. Participants studied a number of object-colour associations corresponding to their individual object span level in a relational task in which objects were associated to colour patches and a conjunctive task where colour was integrated into the object. Memory for individual items and for associations was tested with a recognition memory test. Evidence for an age-related associative deficit was observed in the relational binding task, but not in the conjunctive binding task. This differential impact of ageing on relational and conjunctive short-term binding is discussed by reference to two underlying age-related cognitive difficulties: diminished hippocampally dependent binding and attentional resources.

NASA's OSIRIS-REx Spacecraft In Thermal Vacuum Testing

NASA Image and Video Library

2017-12-08

The OSIRIS-REx spacecraft being lifted into the thermal vacuum chamber at Lockheed Martin for environmental testing. Credits: Lockheed Martin Read more: www.nasa.gov/feature/goddard/2016/osiris-rex-in-thermal-vac

Facilities | Geothermal Technologies | NREL

Science.gov Websites

research, development, analysis, and deployment. A photo of the Thermal Test Facility at NREL. Thermal Test development of building and thermal energy systems. For more information, read the fact sheet

Thermal Conductivity and Thermal Gradient Cyclic Behavior of Refractory Silicate Coatings on SiC/SiC Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Lee, Kang N.; Miller, Robert A.

2001-01-01

Plasma-sprayed mullite and BSAS coatings have been developed to protect SiC/SiC ceramic matrix composites from high temperature environmental attack. In this study, thermal conductivity and thermal barrier functions of these coating systems are evaluated using a laser high-heat-flux test rig. The effects of water vapor on coating thermal conductivity and durability are studied by using alternating furnace and laser thermal gradient cyclic tests. The influence of laser high thermal-gradient cycling on coating failure modes is also investigated.

Multi-Laboratory Study of Five Methods for the Determination of Brevetoxins in Shellfish Tissue Extracts.

PubMed

Dickey, Robert W; Plakas, Steven M; Jester, Edward L E; El Said, Kathleen R; Johannessen, Jan N; Flewelling, Leanne J; Scott, Paula; Hammond, Dan G; Van Dolah, Frances M; Leighfield, Tod A; Bottein Dachraoui, Marie-Yasmine; Ramsdell, John S; Pierce, Richard H; Henry, Mike S; Poli, Mark A; Walker, Calvin; Kurtz, Jan; Naar, Jerome; Baden, Daniel G; Musser, Steve M; White, Kevin D; Truman, Penelope; Miller, Aaron; Hawryluk, Timothy P; Wekell, Marleen M; Stirling, David; Quilliam, Michael A; Lee, Jung K

A thirteen-laboratory comparative study tested the performance of four methods as alternatives to mouse bioassay for the determination of brevetoxins in shellfish. The methods were N2a neuroblastoma cell assay, two variations of the sodium channel receptor binding assay, competitive ELISA, and LC/MS. Three to five laboratories independently performed each method using centrally prepared spiked and naturally incurred test samples. Competitive ELISA and receptor binding (96-well format) compared most favorably with mouse bioassay. Between-laboratory relative standard deviations (RSDR) ranged from 10 to 20% for ELISA and 14 to 31% for receptor binding. Within-laboratory (RSDr) ranged from 6 to 15% for ELISA, and 5 to 31% for receptor binding. Cell assay was extremely sensitive but data variation rendered it unsuitable for statistical treatment. LC/MS performed as well as ELISA on spiked test samples but was inordinately affected by lack of toxin-metabolite standards, uniform instrumental parameters, or both, on incurred test samples. The ELISA and receptor binding assay are good alternatives to mouse bioassay for the determination of brevetoxins in shellfish.

Targeted delivery of carbon nanotubes to cancer cells

NASA Astrophysics Data System (ADS)

Chakravarty, Pavitra

CD22 is broadly expressed on human B cell lymphomas. Monoclonal anti-CD22 antibodies (MAbs) alone, or coupled to toxins, have been used to selectively target these tumors both in severe combined immunodeficient (SCID) mice with xenografted human lymphomas and in patients. Single-walled carbon nanotubes (CNTs) attached to antibodies or peptides represent another approach to targeting cancer cells. CNTs convert absorbed near-infrared (NIR) light into heat, which can thermally ablate cells in the vicinity of the CNTs. We have made MAb-CNT constructs where the MAb was either noncovalently or covalently coupled to CNTs, and investigated their ability to bind specifically to cells and to thermally ablate them after exposure to NIR light. The specific binding of these MAb-CNT constructs to antigen-positive and antigen-negative cells was demonstrated in vitro by using CD22+CD25 - Daudi cells, CD22-CD25+ phytohemagglutinin (PHA)-activated normal human peripheral blood mononuclear cells (PBMCs) and CNTs coupled non-covalently or covalently to either anti-CD22 or anti-CD25. We then demonstrated that the MAb-CNTs could bind to tumor cells expressing the relevant antigen but not to cells lacking the antigen. Furthermore we showed that, following exposure to NIR light, the cells could be thermally ablated. We also determined the stability of the MAb-CNTs in conditions designed to mimic the in vivo environment, i.e. mouse serum at 37°C. We then use the intrinsic Raman signature of CNTs to study the circulation and tissue distribution of intravenously injected MAb-CNTs in a murine xenograft model of lymphoma in vivo over a period of 24 hrs. We demonstrated that the MAb-CNTs have a short half-life in blood and that most of them are cleared by the reticuloendothelial system (RES). In the current embodiment, these constructs would therefore be of limited effectiveness in vivo.

Data book for 12.5-inch diameter SRB thermal model water flotation test; 1.29 psia, series P022

NASA Technical Reports Server (NTRS)

Allums, S. L.

1974-01-01

Data acquired from tests conducted to determine how thermal conditions affect SRB (Space Shuttle Solid Rocket Booster) flotation at a scaled pressure of 1.29 psia are presented. Included are acceleration, pressure, and temperature data recorded from initial water impact to final flotation position using a 12.5-inch diameter thermal model of the SRB. Nineteen valid tests were conducted. These thermal tests indicated the following basic differences relative to the ambient temperature and pressure model tests: (1) more water was taken on board during penetration and (2) model flotation/sinking was temperature sensitive.

Thermography During Thermal Test of the Gaia Deployable Sunshield Assembly Qualification Model in the ESTEC Large Space Simulator

NASA Astrophysics Data System (ADS)

Simpson, R.; Broussely, M.; Edwards, G.; Robinson, D.; Cozzani, A.; Casarosa, G.

2012-07-01

The National Physical Laboratory (NPL) and The European Space Research and Technology Centre (ESTEC) have performed for the first time successful surface temperature measurements using infrared thermal imaging in the ESTEC Large Space Simulator (LSS) under vacuum and with the Sun Simulator (SUSI) switched on during thermal qualification tests of the GAIA Deployable Sunshield Assembly (DSA). The thermal imager temperature measurements, with radiosity model corrections, show good agreement with thermocouple readings on well characterised regions of the spacecraft. In addition, the thermal imaging measurements identified potentially misleading thermocouple temperature readings and provided qualitative real-time observations of the thermal and spatial evolution of surface structure changes and heat dissipation during hot test loadings, which may yield additional thermal and physical measurement information through further research.

Thermal certification tests of Orbiter Thermal Protection System tiles coated with KSC coating slurries

NASA Technical Reports Server (NTRS)

Milhoan, James D.; Pham, Vuong T.; Sherborne, William D.

1993-01-01

Thermal tests of Orbiter thermal protection system (TPS) tiles, which were coated with borosilicate glass slurries fabricated at Kennedy Space Center (KSC), were performed in the Radiant Heat Test Facility and the Atmospheric Reentry Materials & Structures Evaluation Facility at Johnson Space Center to verify tile coating integrity after exposure to multiple entry simulation cycles in both radiant and convective heating environments. Eight high temperature reusable surface insulation (HRSI) tiles and six low temperature reusable surface insulation (LRSI) tiles were subjected to 25 cycles of radiant heat at peaked surface temperatures of 2300 F and 1200 F, respectively. For the LRSI tiles, an additional cycle at peaked surface temperature of 2100 F was performed. There was no coating crack on any of the HRSI specimens. However, there were eight small coating cracks (less than 2 inches long) on two of the six LRSI tiles on the 26th cycle. There was practically no change on the surface reflectivity, physical dimensions, or weight of any of the test specimens. There was no observable thermal-chemical degradation of the coating either. For the convective heat test, eight HRSI tiles were tested for five cycles at a surface temperature of 2300 F. There was no thermal-induced coating crack on any of the test specimens, almost no change on the surface reflectivity, and no observable thermal-chemical degradation with an exception of minor slumping of the coating under painted TPS identification numbers. The tests demonstrated that KSC's TPS slurries and coating processes meet the Orbiter's thermal specification requirements.

Capabilities of the thermal acoustic fatigue apparatus

NASA Technical Reports Server (NTRS)

Clevenson, S. A.; Daniels, E. F.

1992-01-01

The Thermal Acoustic Fatigue Apparatus (TAFA) is a facility for applying intense noise and heat to small test panels. Modifications to TAFA have increased the heating capability to 44 BTU/(ft.-sec.), making it possible to heat test panels to 2000 F and concurrently apply 168 dB of noise. Results of acoustic and thermal surveys are shown. Two test items, a 0.09 in. steel panel and an insulated panel, were used in the thermal survey.

Accelerated Thermal Cycling Test of Microencapsulated Paraffin Wax/Polyaniline Made by Simple Preparation Method for Solar Thermal Energy Storage.

PubMed

Silakhori, Mahyar; Naghavi, Mohammad Sajad; Metselaar, Hendrik Simon Cornelis; Mahlia, Teuku Meurah Indra; Fauzi, Hadi; Mehrali, Mohammad

2013-04-29

Microencapsulated paraffin wax/polyaniline was prepared using a simple in situ polymerization technique, and its performance characteristics were investigated. Weight losses of samples were determined by Thermal Gravimetry Analysis (TGA). The microencapsulated samples with 23% and 49% paraffin showed less decomposition after 330 °C than with higher percentage of paraffin. These samples were then subjected to a thermal cycling test. Thermal properties of microencapsulated paraffin wax were evaluated by Differential Scanning Calorimeter (DSC). Structure stability and compatibility of core and coating materials were also tested by Fourier transform infrared spectrophotometer (FTIR), and the surface morphology of the samples are shown by Field Emission Scanning Electron Microscopy (FESEM). It has been found that the microencapsulated paraffin waxes show little change in the latent heat of fusion and melting temperature after one thousand thermal recycles. Besides, the chemical characteristics and structural profile remained constant after one thousand thermal cycling tests. Therefore, microencapsulated paraffin wax/polyaniline is a stable material that can be used for thermal energy storage systems.

Accelerated Thermal Cycling Test of Microencapsulated Paraffin Wax/Polyaniline Made by Simple Preparation Method for Solar Thermal Energy Storage

PubMed Central

Silakhori, Mahyar; Naghavi, Mohammad Sajad; Metselaar, Hendrik Simon Cornelis; Mahlia, Teuku Meurah Indra; Fauzi, Hadi; Mehrali, Mohammad

2013-01-01

Microencapsulated paraffin wax/polyaniline was prepared using a simple in situ polymerization technique, and its performance characteristics were investigated. Weight losses of samples were determined by Thermal Gravimetry Analysis (TGA). The microencapsulated samples with 23% and 49% paraffin showed less decomposition after 330 °C than with higher percentage of paraffin. These samples were then subjected to a thermal cycling test. Thermal properties of microencapsulated paraffin wax were evaluated by Differential Scanning Calorimeter (DSC). Structure stability and compatibility of core and coating materials were also tested by Fourier transform infrared spectrophotometer (FTIR), and the surface morphology of the samples are shown by Field Emission Scanning Electron Microscopy (FESEM). It has been found that the microencapsulated paraffin waxes show little change in the latent heat of fusion and melting temperature after one thousand thermal recycles. Besides, the chemical characteristics and structural profile remained constant after one thousand thermal cycling tests. Therefore, microencapsulated paraffin wax/polyaniline is a stable material that can be used for thermal energy storage systems. PMID:28809232

New NREL Research Facility Slashes Energy Use by 66 Percent

Science.gov Websites

Thermal Test Facility, which serves as a showcase of energy-saving features and the home of NREL's cutting technologies now being developed at the Thermal Test Facility will help us reach this goal." The facility energy-efficient building design, NREL's Thermal Test Facility houses sophisticated equipment for

Heater Development, Fabrication, and Testing: Analysis of Fabricated Heaters

NASA Technical Reports Server (NTRS)

Bragg-Sitton, S. M.; Dickens, R. E.; Farmer, J. T.; Davis, J. D.; Adams, M. R.; Martin, J. J.; Webster, K. L.

2008-01-01

Thermal simulators (highly designed heater elements) developed at the Early Flight Fission Test Facility (EFF-TF) are used to simulate the heat from nuclear fission in a variety of reactor concepts. When inserted into the reactor geometry, the purpose of the thermal simulators is to deliver thermal power to the test article in the same fashion as if nuclear fuel were present. Considerable effort has been expended to mimic heat from fission as closely as possible. To accurately represent the fuel, the simulators should be capable of matching the overall properties of the nuclear fuel rather than simply matching the fuel temperatures. This includes matching thermal stresses in the pin, pin conductivities, total core power, and core power profile (axial and radial). This Technical Memorandum discusses the historical development of the thermal simulators used in nonnuclear testing at the EFF-TF and provides a basis for the development of the current series of thermal simulators. The status of current heater fabrication and testing is assessed, providing data and analyses for both successes and failures experienced in the heater development and testing program.

CRYogenic Orbital TEstbed Ground Test Article Thermal Analysis

NASA Technical Reports Server (NTRS)

Piryk, David; Schallhorn, Paul; Walls, Laurie; Stopnitzky, Benny; Rhys, Noah; Wollen, Mark

2012-01-01

The purpose of this study was to anchor thermal and fluid system models to CRYOTE ground test data. The CRYOTE ground test artide was jointly developed by Innovative Engineering Solutions, United Launch Alliance and NASA KSC. The test article was constructed out of a titanium alloy tank, Sapphire 77 composite skin (similar to G10), an external secondary payload adapter ring, thermal vent system, multi layer insulation and various data acquisition instrumentation. In efforts to understand heat loads throughout this system, the GTA (filled with liquid nitrogen for safety purposes) was subjected to a series of tests in a vacuum chamber at Marshall Space Flight Center. By anchoring analytical models against test data, higher fidelity thermal environment predictions can be made for future flight articles which would eventually demonstrate critical cryogenic fluid management technologies such as system chilldown, transfer, pressure control and long term storage. Significant factors that influenced heat loads included radiative environments, multi-layer insulation performance, tank fill levels and pressures and even contact conductance coefficients. This report demonstrates how analytical thermal/fluid networks were established and includes supporting rationale for specific thermal responses.

Dryden Flight Research Center (DFRC) Thermal Capabilities and Status

NASA Technical Reports Server (NTRS)

Holguin, Andrew; Kostyk, Christopher B.

2010-01-01

This presentation provides an overview of the thermal analysis and test capabilities at the Dryden Flight Research Center (DFRC) as well as highlights from the thermal analysis and test efforts of the past year.

Thermal Vacuum Facility for Testing Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Daryabeigi, Kamran; Knutson, Jeffrey R.; Sikora, Joseph G.

2002-01-01

A thermal vacuum facility for testing launch vehicle thermal protection systems by subjecting them to transient thermal conditions simulating re-entry aerodynamic heating is described. Re-entry heating is simulated by controlling the test specimen surface temperature and the environmental pressure in the chamber. Design requirements for simulating re-entry conditions are briefly described. A description of the thermal vacuum facility, the quartz lamp array and the control system is provided. The facility was evaluated by subjecting an 18 by 36 in. Inconel honeycomb panel to a typical re-entry pressure and surface temperature profile. For most of the test duration, the average difference between the measured and desired pressures was 1.6% of reading with a standard deviation of +/- 7.4%, while the average difference between measured and desired temperatures was 7.6% of reading with a standard deviation of +/- 6.5%. The temperature non-uniformity across the panel was 12% during the initial heating phase (t less than 500 sec.), and less than 2% during the remainder of the test.

TOPEX Microwave Radiometer - Thermal design verification test and analytical model validation

NASA Technical Reports Server (NTRS)

Lin, Edward I.

1992-01-01

The testing of the TOPEX Microwave Radiometer (TMR) is described in terms of hardware development based on the modeling and thermal vacuum testing conducted. The TMR and the vacuum-test facility are described, and the thermal verification test includes a hot steady-state segment, a cold steady-state segment, and a cold survival mode segment totalling 65 hours. A graphic description is given of the test history which is related temperature tracking, and two multinode TMR test-chamber models are compared to the test results. Large discrepancies between the test data and the model predictions are attributed to contact conductance, effective emittance from the multilayer insulation, and heat leaks related to deviations from the flight configuration. The TMR thermal testing/modeling effort is shown to provide technical corrections for the procedure outlined, and the need for validating predictive models is underscored.

Investigation of Flash Fill{reg_sign} as a thermal backfill material

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

Ayers, P.H.; Charlton, C.B.; Frishette, C.W.

1995-09-01

Flash Fill{reg_sign} was created as a fast-setting, flowable backfill material made entirely from coal combustion by-products and water. Its quick-setting, self-leveling, self-compacting characteristics makes trench road repairs faster, easier, and more economical. Other uses include building foundations, fill around pipes, gas lines, and manholes, and replacement of weak subgrade beneath rooters. Flash Fill can be hand-excavated without the use of power assisted tools or machinery. To enhance thermal resistivity, the original Flash Fill mix was modified to include concrete sand. This resulted in a new Flash Fill, designated FSAND, with all of the aforementioned desirable characteristics of Flash Fill andmore » a thermal resistivity of approximately 50{degree} C-cm/watt. Thermal resistivity tests using conventional laboratory thermal probes, high-current thermal tests, and moisture migration tests have been performed to determine the properties of FSAND. As a result of these tests, FSAND has been approved for use as power cable thermal backfill on all AEP System distribution projects.« less

Thermal Design, Analysis, and Testing of the Quench Module Insert Bread Board

NASA Technical Reports Server (NTRS)

Breeding, Shawn; Khodabandeh, Julia

2002-01-01

Contents include the following: Quench Module Insert (QMI) science requirements. QMI interfaces. QMI design layout. QMI thermal analysis and design methodology. QMI bread board testing and instrumentation approach. QMI thermal probe design parameters. Design features for gradient measurement. Design features for heated zone measurements. Thermal gradient analysis results. Heated zone analysis results. Bread board thermal probe layout. QMI bread board correlation and performance. Summary and conclusions.

Results of shuttle EMU thermal vacuum tests incorporating an infrared imaging camera data acquisition system

NASA Technical Reports Server (NTRS)

Anderson, James E.; Tepper, Edward H.; Trevino, Louis A.

1991-01-01

Manned tests in Chamber B at NASA JSC were conducted in May and June of 1990 to better quantify the Space Shuttle Extravehicular Mobility Unit's (EMU) thermal performance in the cold environmental extremes of space. Use of an infrared imaging camera with real-time video monitoring of the output significantly added to the scope, quality and interpretation of the test conduct and data acquisition. Results of this test program have been effective in the thermal certification of a new insulation configuration and the '5000 Series' glove. In addition, the acceptable thermal performance of flight garments with visually deteriorated insulation was successfully demonstrated, thereby saving significant inspection and garment replacement cost. This test program also established a new method for collecting data vital to improving crew thermal comfort in a cold environment.

Thermal-environmental testing of a 30-cm engineering model thruster

NASA Technical Reports Server (NTRS)

Mirtich, M. J.

1976-01-01

An experimental test program was carried out to document all 30-cm electron bombardment Hg ion bombardment thruster functions and characteristics over the thermal environment of several proposed missions. An engineering model thruster was placed in a thermal test facility equipped with -196 C walls and solar simulation. The thruster was cold soaked and exposed to simulated eclipses lasting in duration from 17 to 72 minutes. The thruster was operated at quarter, to full beam power in various thermal configurations which simulated multiple thruster operation, and was also exposed to 1 and 2 suns solar simulation. Thruster control characteristics and constraints; performance, including thrust magnitude and direction; and structural integrity were evaluated over the range of thermal environments tested.

Thermal-environment testing of a 30-cm engineering model thruster

NASA Technical Reports Server (NTRS)

Mirtich, M. J.

1976-01-01

An experimental test program was carried out to document all 30-cm electron bombardment Hg ion bombardment thruster functions and characteristics over the thermal environment of several proposed missions. An engineering model thruster was placed in a thermal test facility equipped with -196 C walls and solar simulation. The thruster was cold soaked and exposed to simulated eclipses lasting in duration from 17 to 72 minutes. The thruster was operated at quarter, to full beam power in various thermal configurations which simulated multiple thruster operation, and was also exposed to 1 and 2 suns solar simulation. Thruster control characteristics and constraints; performance, including thrust magnitude and direction; and structural integrity were evaluated over the range of thermal environments tested.

On-Line, Self-Learning, Predictive Tool for Determining Payload Thermal Response

NASA Technical Reports Server (NTRS)

Jen, Chian-Li; Tilwick, Leon

2000-01-01

This paper will present the results of a joint ManTech / Goddard R&D effort, currently under way, to develop and test a computer based, on-line, predictive simulation model for use by facility operators to predict the thermal response of a payload during thermal vacuum testing. Thermal response was identified as an area that could benefit from the algorithms developed by Dr. Jeri for complex computer simulations. Most thermal vacuum test setups are unique since no two payloads have the same thermal properties. This requires that the operators depend on their past experiences to conduct the test which requires time for them to learn how the payload responds while at the same time limiting any risk of exceeding hot or cold temperature limits. The predictive tool being developed is intended to be used with the new Thermal Vacuum Data System (TVDS) developed at Goddard for the Thermal Vacuum Test Operations group. This model can learn the thermal response of the payload by reading a few data points from the TVDS, accepting the payload's current temperature as the initial condition for prediction. The model can then be used as a predictive tool to estimate the future payload temperatures according to a predetermined shroud temperature profile. If the error of prediction is too big, the model can be asked to re-learn the new situation on-line in real-time and give a new prediction. Based on some preliminary tests, we feel this predictive model can forecast the payload temperature of the entire test cycle within 5 degrees Celsius after it has learned 3 times during the beginning of the test. The tool will allow the operator to play "what-if' experiments to decide what is his best shroud temperature set-point control strategy. This tool will save money by minimizing guess work and optimizing transitions as well as making the testing process safer and easier to conduct.

Protein sequences bound to mineral surfaces persist into deep time

PubMed Central

Demarchi, Beatrice; Hall, Shaun; Roncal-Herrero, Teresa; Freeman, Colin L; Woolley, Jos; Crisp, Molly K; Wilson, Julie; Fotakis, Anna; Fischer, Roman; Kessler, Benedikt M; Rakownikow Jersie-Christensen, Rosa; Olsen, Jesper V; Haile, James; Thomas, Jessica; Marean, Curtis W; Parkington, John; Presslee, Samantha; Lee-Thorp, Julia; Ditchfield, Peter; Hamilton, Jacqueline F; Ward, Martyn W; Wang, Chunting Michelle; Shaw, Marvin D; Harrison, Terry; Domínguez-Rodrigo, Manuel; MacPhee, Ross DE; Kwekason, Amandus; Ecker, Michaela; Kolska Horwitz, Liora; Chazan, Michael; Kröger, Roland; Thomas-Oates, Jane; Harding, John H; Cappellini, Enrico; Penkman, Kirsty; Collins, Matthew J

2016-01-01

Proteins persist longer in the fossil record than DNA, but the longevity, survival mechanisms and substrates remain contested. Here, we demonstrate the role of mineral binding in preserving the protein sequence in ostrich (Struthionidae) eggshell, including from the palaeontological sites of Laetoli (3.8 Ma) and Olduvai Gorge (1.3 Ma) in Tanzania. By tracking protein diagenesis back in time we find consistent patterns of preservation, demonstrating authenticity of the surviving sequences. Molecular dynamics simulations of struthiocalcin-1 and -2, the dominant proteins within the eggshell, reveal that distinct domains bind to the mineral surface. It is the domain with the strongest calculated binding energy to the calcite surface that is selectively preserved. Thermal age calculations demonstrate that the Laetoli and Olduvai peptides are 50 times older than any previously authenticated sequence (equivalent to ~16 Ma at a constant 10°C). DOI: http://dx.doi.org/10.7554/eLife.17092.001 PMID:27668515

The Production of a Stable Infliximab Powder: The Evaluation of Spray and Freeze-Drying for Production.

PubMed

Kanojia, Gaurav; Have, Rimko Ten; Bakker, Arjen; Wagner, Koen; Frijlink, Henderik W; Kersten, Gideon F A; Amorij, Jean-Pierre

2016-01-01

In prospect of developing an oral dosage form of Infliximab, for treatment of Crohn's disease and rheumatoid arthritis, freeze-drying (vial vs Lyoguard trays) and spray-drying were investigated as production method for stable powders. Dextran and inulin were used in combination with sucrose as stabilizing excipients. The drying processes did not affect Infliximab in these formulations, i.e. both the physical integrity and biological activity (TNF binding) were retained. Accelerated stability studies (1 month at 60°C) showed that the TNF binding ability of Infliximab was conserved in the freeze-dried formulations, whereas the liquid counterpart lost all TNF binding. After thermal treatment, the dried formulations showed some chemical modification of the IgG in the dextran-sucrose formulation, probably due to Maillard reaction products. This study indicates that, with the appropriate formulation, both spray-drying and freeze-drying may be useful for (bulk) powder production of Infliximab.

Indoor test for thermal performance evaluation of Libbey-Owens-Ford solar collector. [using a solar simulator

NASA Technical Reports Server (NTRS)

Shih, K.

1977-01-01

The thermal performance of a flat plate solar collector that uses liquid as the heat transfer medium was investigated under simulated conditions. The test conditions and thermal performance data obtained during the tests are presented in tabular form, as well as in graphs. Data obtained from a time constant test and incident angle modifier test, conducted to determine transient effect and the incident angle effect on the collector, are included.

Thermal performance of MSFC hot air collectors under natural and simulated conditions

NASA Technical Reports Server (NTRS)

Shih, K., Sr.

1977-01-01

The procedures used and the results obtained from an evaluation test program conducted to determine the thermal performance and structural characteristics of selected MSFC--designed hot air collectors under both real and simulated environmental conditions are described. Five collectors were tested in the three phased program. A series of outdoor tests were conducted to determine stagnation temperatures on a typical bright day and to determine each collector's ability to withstand these temperatures. Two of the collectors experienced structural deformation sufficient to eliminate them from the remainder of the test program. A series of outdoor tests to evaluate the thermal performance of collector S/N 10 under certain test conditions were performed followed by a series of indoor tests to evaluate the thermal performance of the collector under closely controlled simulated conditions.

Use of Cold Radiometers in Several Thermal/Vacuum Tests

NASA Technical Reports Server (NTRS)

DiPirro, M.; Tuttle, J.; Canavan, E.; Shirron, P.

2011-01-01

We have developed a low cost low temperature broadband radiometer for use with low temperature tests as a diagnostic tool for measuring stray thermal radiation and remote measurement of material properties. So far these radiometers have been used in two large thermal/vacuum tests for the James Webb Space Telescope (JWST) Project. In the first test the radiometers measured stray radiation in a test of part of the JWST sunshield, and in the second test the radiometers were used to measure the reflectivity and specularity of black Z307 painted aluminum walls on a 25 K cooled shroud. These results will be presented as well as plans for future tests to measure the residual energy through a baffled aperture in the shroud and other stray thermal energy measurements.

Development of a plasma sprayed ceramic gas path seal for high pressure turbine applications

NASA Technical Reports Server (NTRS)

Shiembob, L. T.

1977-01-01

The plasma sprayed graded layered yittria stabilized zirconia (ZrO2)/metal(CoCrAlY) seal system for gas turbine blade tip applications up to 1589 K (2400 F) seal temperatures was studied. Abradability, erosion, and thermal fatigue characteristics of the graded layered system were evaluated by rig tests. Satisfactory abradability and erosion resistance was demonstrated. Encouraging thermal fatigue tolerance was shown. Initial properties for the plasma sprayed materials in the graded, layered seal system was obtained, and thermal stress analyses were performed. Sprayed residual stresses were determined. Thermal stability of the sprayed layer materials was evaluated at estimated maximum operating temperatures in each layer. Anisotropic behavior in the layer thickness direction was demonstrated by all layers. Residual stresses and thermal stability effects were not included in the analyses. Analytical results correlated reasonably well with results of the thermal fatigue tests. Analytical application of the seal system to a typical gas turbine engine application predicted performance similar to rig specimen thermal fatigue performance. A model for predicting crack propagation in the sprayed ZrO2/CoCrAlY seal system was proposed, and recommendations for improving thermal fatigue resistance were made. Seal system layer thicknesses were analytically optimized to minimize thermal stresses in the abradability specimen during thermal fatigue testing. Rig tests on the optimized seal configuration demonstrated some improvement in thermal fatigue characteristics.

Sustainable hemp-based composites for the building industry application

NASA Astrophysics Data System (ADS)

Schwarzova, Ivana; Stevulova, Nadezda; Junak, Jozef; Hospodarova, Viola

2017-07-01

Sustainability goals are essential driving principles for the development of innovative materials in the building industry. Natural plant (e.g. hemp) fibers represent an attractive alternative as reinforcing material due to its good properties and sustainability prerequisites. In this study, hemp-based composite materials, designed for building application as non-load bearing material, providing both thermal insulation and physico-mechanical properties, are presented. Composite materials were produced by bonding hemp hurds with a novel inorganic binder (MgO-based cement) and then were characterized in terms of physical properties (bulk density, water absorption), thermal properties (thermal conductivity) and mechanical properties (compressive and tensile strength). The composites exhibited promising physical, thermal and mechanical characteristics, generally comparable to commercially available products. In addition, the hemp-based composites have the advantage of a significantly low environmental impact (thanks to the nature of both the dispersed and the binding phase) and no negative effects on human health. All things considered, the composite materials seem like very promising materials for the building industry application.

Structural Basis for Intrinsic Thermosensing by the Master Virulence Regulator RovA of Yersinia*

PubMed Central

Quade, Nick; Mendonca, Chriselle; Herbst, Katharina; Heroven, Ann Kathrin; Ritter, Christiane; Heinz, Dirk W.; Dersch, Petra

2012-01-01

Pathogens often rely on thermosensing to adjust virulence gene expression. In yersiniae, important virulence-associated traits are under the control of the master regulator RovA, which uses a built-in thermosensor to control its activity. Thermal upshifts encountered upon host entry induce conformational changes in the RovA dimer that attenuate DNA binding and render the protein more susceptible to proteolysis. Here, we report the crystal structure of RovA in the free and DNA-bound forms and provide evidence that thermo-induced loss of RovA activity is promoted mainly by a thermosensing loop in the dimerization domain and residues in the adjacent C-terminal helix. These determinants allow partial unfolding of the regulator upon an upshift to 37 °C. This structural distortion is transmitted to the flexible DNA-binding domain of RovA. RovA contacts mainly the DNA backbone in a low-affinity binding mode, which allows the immediate release of RovA from its operator sites. We also show that SlyA, a close homolog of RovA from Salmonella with a very similar structure, is not a thermosensor and remains active and stable at 37 °C. Strikingly, changes in only three amino acids, reflecting evolutionary replacements in SlyA, result in a complete loss of the thermosensing properties of RovA and prevent degradation. In conclusion, only minor alterations can transform a thermotolerant regulator into a thermosensor that allows adjustment of virulence and fitness determinants to their thermal environment. PMID:22936808

Optimizing the Binding Energy of the Surfactant to Iron Oxide Yields Truly Monodisperse Nanoparticles.

PubMed

Sharifi Dehsari, Hamed; Harris, Richard Anthony; Ribeiro, Anielen Halda; Tremel, Wolfgang; Asadi, Kamal

2018-06-05

Despite the great progress in the synthesis of iron oxide nanoparticles (NPs) using a thermal decomposition method, the production of NPs with low polydispersity index is still challenging. In a thermal decomposition synthesis, oleic acid (OAC) and oleylamine (OAM) are used as surfactants. The surfactants bind to the growth species, thereby controlling the reaction kinetics and hence playing a critical role in the final size and size distribution of the NPs. Finding an optimum molar ratio between the surfactants oleic OAC/OAM is therefore crucial. A systematic experimental and theoretical study, however, on the role of the surfactant ratio is still missing. Here, we present a detailed experimental study on the role of the surfactant ratio in size distribution. We found an optimum OAC/OAM ratio of 3 at which the synthesis yielded truly monodisperse (polydispersity less than 7%) iron oxide NPs without employing any post synthesis size-selective procedures. We performed molecular dynamics simulations and showed that the binding energy of oleate to the NP is maximized at an OAC/OAM ratio of 3. The optimum OAC/OAM ratio of 3 is allowed for the control of the NP size with nanometer precision by simply changing the reaction heating rate. The optimum OAC/OAM ratio has no influence on the crystallinity and the superparamagnetic behavior of the Fe 3 O 4 NPs and therefore can be adopted for the scaled-up production of size-controlled monodisperse Fe 3 O 4 NPs.

Novel humic acid-bonded magnetite nanoparticles for protein immobilization.

PubMed

Bayrakci, Mevlut; Gezici, Orhan; Bas, Salih Zeki; Ozmen, Mustafa; Maltas, Esra

2014-09-01

The present paper is the first report that introduces (i) a useful methodology for chemical immobilization of humic acid (HA) to aminopropyltriethoxysilane-functionalized magnetite iron oxide nanoparticles (APS-MNPs) and (ii) human serum albumin (HSA) binding to the obtained material (HA-APS-MNPs). The newly prepared magnetite nanoparticle was characterized by using Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and elemental analysis. Results indicated that surface modification of the bare magnetite nanoparticles (MNPs) with aminopropyltriethoxysilane (APS) and HA was successfully performed. The protein binding studies that were evaluated in batch mode exhibited that HA-APS-MNPs could be efficiently used as a substrate for the binding of HSA from aqueous solutions. Usually, recovery values higher than 90% were found to be feasible by HA-APS-MNPs, while that value was around 2% and 70% in the cases of MNPs and APS-MNPs, respectively. Hence, the capacity of MNPs was found to be significantly improved by immobilization of HA. Furthermore, thermal degradation of HA-APS-MNPs and HSA bonded HA-APS-MNPs was evaluated in terms of the Horowitz-Metzger equation in order to determine kinetic parameters for thermal decomposition. Activation energies calculated for HA-APS-MNPs (20.74 kJmol(-1)) and HSA bonded HA-APS-MNPs (33.42 kJmol(-1)) implied chemical immobilization of HA to APS-MNPs, and tight interactions between HA and HA-APS-MNPs. Copyright © 2014 Elsevier B.V. All rights reserved.

Long Duration Life Test of Propylene Glycol Water Based Thermal Fluid Within Thermal Control Loop

NASA Technical Reports Server (NTRS)

Le, Hung; Hill, Charles; Stephan, Ryan A.

2010-01-01

Evaluations of thermal properties and resistance to microbial growth concluded that 50% Propylene Glycol (PG)-based fluid and 50% de-ionized water mixture was desirable for use as a fluid within a vehicle s thermal control loop. However, previous testing with a commercial mixture of PG and water containing phosphate corrosion inhibitors resulted in corrosion of aluminum within the test system and instability of the test fluid. This paper describes a follow-on long duration testing and analysis of 50% Propylene Glycol (PG)-based fluid and 50% de-ionized water mixture with inorganic corrosion inhibitors used in place of phosphates. The test evaluates the long-term fluid stability and resistance to microbial and chemical changes

Thermal and Fluid Modeling of the CRYogenic Orbital TEstbed (CRYOTE) Ground Test Article (GTA)

NASA Technical Reports Server (NTRS)

Piryk, David; Schallhorn, Paul; Walls, Laurie; Stopnitzky, Benny; Rhys, Noah; Wollen, Mark

2012-01-01

The purpose of this study was to anchor thermal and fluid system models to data acquired from a ground test article (GTA) for the CRYogenic Orbital TEstbed - CRYOTE. To accomplish this analysis, it was broken into four primary tasks. These included model development, pre-test predictions, testing support at Marshall Space Flight Center (MSFC} and post-test correlations. Information from MSFC facilitated the task of refining and correlating the initial models. The primary goal of the modeling/testing/correlating efforts was to characterize heat loads throughout the ground test article. Significant factors impacting the heat loads included radiative environments, multi-layer insulation (MLI) performance, tank fill levels, tank pressures, and even contact conductance coefficients. This paper demonstrates how analytical thermal/fluid networks were established, and it includes supporting rationale for specific thermal responses seen during testing.

Laboratories | NREL

Science.gov Websites

| Z A Accelerated Exposure Testing Laboratory Advanced Optical Materials Laboratory Advanced Thermal Laboratory Structural Testing Laboratory Surface Analysis Laboratory Systems Performance Laboratory T Thermal Storage Materials Laboratory Thermal Storage Process and Components Laboratory Thin-Film Deposition

Experimental thermal characterization of concrete to be used in CP5.2 packaging system

NASA Astrophysics Data System (ADS)

Lo Frano, R.; Maggini, A.; Aquaro, D.

2017-01-01

This work deals with the experimental evaluation of the thermal conductivity of a concrete matrix to be used for embedding LILW bituminised Wastes into the packaging system. Such a type of packaging, identified with the acronym CP5.2, has been also qualified by executing at the Lab. Scalbatraio of Dep. of Civil and Industrial Engineering of the University of Pisa, an experimental test campaign accordingly to the IAEA regulations. In particular, the knowledge of the thermal conductivity is important because of the fire or furnace test to carry out in oven at 800 °C for 30 minutes. These data allowed to simulate pre-test conditions and to set up safety and operational fire test procedures. The concrete thermal conductivity was obtained by performing hot wire tests on cylindrical concrete samples for temperatures ranging from 100° to about 800°C. Thermal conductivity is determined at steady state condition. Results indicate a monotonically reduction of the thermal conductivity as the temperature increases. The comparison with concrete thermal conductivity data available in literature indicates a quite good agreement. Finally, visual and X-ray inspection of sample did not highlight the presence of micro/macro damages that would have affected the thermal performance of the concrete under study.

High Reynolds Number Thermal Stability Experiments

NASA Technical Reports Server (NTRS)

Emens, Jessica M.; Brown, Sarah P.; Frederick Robert A., Jr.; Wood, A. John

2004-01-01

This work represents preliminary thermal stability results for liquid hydrocarbon fuels. High Reynolds Number Thermal Stability experiments with Jet A and RP-1 resulted in a quantitative measurement of the thermal stability. Each fuel flowed through a heated capillary tube that held the outlet temperature at 290 C. An optical pyrometer measured the surface temperature of the tube at 12 locations as a function of time. The High Reynolds Number Thermal Stability number was then determined using standards published by the American Society for Testing and Materials. The results for Jet A showed lower thermal stability than similar tests conducted at another facility. The RP-1 results are the first reported using this technique. Because the temperature rise on the capillary tube during testing for the RP-1 fuels was not significant, a new standard for the testing conditions should be developed for these types of fuels.

Thermal Performance Testing of EMU and CSAFE Liquid Cooling Gannents

NASA Technical Reports Server (NTRS)

Rhodes, Richard; Bue, Grant; Meginnis, Ian; Hakam, Mary; Radford, Tamara

2013-01-01

Future exploration missions require the development of a new liquid cooling garment (LCG) to support the next generation extravehicular activity (EVA) suit system. The new LCG must offer greater system reliability, optimal thermal performance as required by mission directive, and meet other design requirements including improved tactile comfort. To advance the development of a future LCG, a thermal performance test was conducted to evaluate: (1) the comparable thermal performance of the EMU LCG and the CSAFE developed engineering evaluation unit (EEU) LCG, (2) the effect of the thermal comfort undergarment (TCU) on the EMU LCG tactile and thermal comfort, and (3) the performance of a torso or upper body only LCG shirt to evaluate a proposed auxiliary loop. To evaluate the thermal performance of each configuration, a metabolic test was conducted using the Demonstrator Spacesuit to create a relevant test environment. Three (3) male test subjects of similar height and weight walked on a treadmill at various speeds to produce three different metabolic loads - resting (300-600 BTU/hr), walking at a slow pace (1200 BTU/hr), and walking at a brisk pace (2200 BTU/hr). Each subject participated in five tests - two wearing the CSAFE full LCG, one wearing the EMU LCG without TCUs, one wearing the EMU LCG with TCUs, and one with the CSAFE shirt-only. During the test, performance data for the breathing air and cooling water systems and subject specific data was collected to define the thermal performance of the configurations. The test results show that the CSAFE EEU LCG and EMU LCG with TCU had comparable performance. The testing also showed that an auxiliary loop LCG, sized similarly to the shirt-only configuration, should provide adequate cooling for contingency scenarios. Finally, the testing showed that the TCU did not significantly hinder LCG heat transfer, and may prove to be acceptable for future suit use with additional analysis and testing.

Mars Science Laboratory Rover System Thermal Test

NASA Technical Reports Server (NTRS)

Novak, Keith S.; Kempenaar, Joshua E.; Liu, Yuanming; Bhandari, Pradeep; Dudik, Brenda A.

2012-01-01

On November 26, 2011, NASA launched a large (900 kg) rover as part of the Mars Science Laboratory (MSL) mission to Mars. The MSL rover is scheduled to land on Mars on August 5, 2012. Prior to launch, the Rover was successfully operated in simulated mission extreme environments during a 16-day long Rover System Thermal Test (STT). This paper describes the MSL Rover STT, test planning, test execution, test results, thermal model correlation and flight predictions. The rover was tested in the JPL 25-Foot Diameter Space Simulator Facility at the Jet Propulsion Laboratory (JPL). The Rover operated in simulated Cruise (vacuum) and Mars Surface environments (8 Torr nitrogen gas) with mission extreme hot and cold boundary conditions. A Xenon lamp solar simulator was used to impose simulated solar loads on the rover during a bounding hot case and during a simulated Mars diurnal test case. All thermal hardware was exercised and performed nominally. The Rover Heat Rejection System, a liquid-phase fluid loop used to transport heat in and out of the electronics boxes inside the rover chassis, performed better than predicted. Steady state and transient data were collected to allow correlation of analytical thermal models. These thermal models were subsequently used to predict rover thermal performance for the MSL Gale Crater landing site. Models predict that critical hardware temperatures will be maintained within allowable flight limits over the entire 669 Sol surface mission.

Back reaction effects on the dynamics of heavy probes in heavy quark cloud

NASA Astrophysics Data System (ADS)

Chakrabortty, Shankhadeep; Dey, Tanay K.

2016-05-01

We holographically study the effect of back reaction on the hydrodynamical properties of {N}=4 strongly coupled super Yang-Mills (SYM) thermal plasma. The back reaction we consider arises from the presence of static heavy quarks uniformly distributed over {N}=4 SYM plasma. In order to study the hydrodynamical properties, we use heavy quark as well as heavy quark-antiquark bound state as probes and compute the jet quenching parameter, screening length and binding energy. We also consider the rotational dynamics of heavy probe quark in the back-reacted plasma and analyse associated energy loss. We observe that the presence of back reaction enhances the energy-loss in the thermal plasma. Finally, we show that there is no effect of angular drag on the rotational motion of quark-antiquark bound state probing the back reacted thermal plasma.

Current Protocols in Protein Science

PubMed Central

Huynh, Kathy

2015-01-01

The purification of recombinant proteins for biochemical assays and structural studies is time-consuming and presents inherent difficulties that depend on the optimization of protein stability. The use of dyes to monitor thermal denaturation of proteins with sensitive fluorescence detection enables the rapid and inexpensive determination of protein stability using real-time PCR instruments. By screening a wide range of solution conditions and additives in 96-well format, the thermal shift assay easily identifies conditions that significantly enhance the stability of recombinant proteins. The same approach can be used as a low cost, initial screen to discover new protein:ligand interactions by capitalizing on increases in protein stability that typically occur upon ligand binding. This unit presents a methodological workflow for the small-scale, high-throughout thermal denaturation of recombinant proteins in the presence of SYPRO Orange dye. PMID:25640896

Thermal balance testing of MSAT 2 spacecraft

NASA Technical Reports Server (NTRS)

Samson, Serge; Choueiry, Elie

1994-01-01

The present work reports on the recently completed infrared thermal balance/thermal vacuum testing of a MSAT satellite, the first satellite to provide mobile communications service for all of continental North America. MSAT is a two spacecraft program, using a three-axis stabilized Hughes HS-601 series Bus as the vehicle for the Canadian designed Payload. The thermal tests which were performed at the Canadian Space Agency's David Florida Laboratory in Ottawa, Canada, lasted approximately 35 days. The infrared (IR) heating rig was designed to provide radiant heat inputs into seven spacecraft zones during Thermal Vacuum (TV) testing. The TV test was divided into multiple phases. It began with a thermal balance cold phase, followed by a thermal cold cycle and a hot balance phase, complemented by a thermal hot cycle to finish with a thermal cycle with continuous monitoring of the Bus and Payload. The spacecraft's external heat fluxes were provided by IR lamp sources. To ensure flux uniformity, highly reflective baffles and IR East and West faces; the Earth facing (Nadir); and the inside of the thrust cylinder. The aft-end panel heat fluxes were provided by a heated LN2 shroud. The radiation flux intensity on the spacecraft zones from the various rig elements was measured using Monitored Background Radiometers (MBR's) and compared with direct calculations and with pretest predictions. The temperature measurement system was based on Uniform Temperature References (UTR's) located inside the chamber such that all feedthroughs were copper-copper. This system was devised to achieve a temperature measurement accuracy of plus/minus 0.5 C for over 850 thermocouples used in the test. A PC-(QNX-based) based real-time data acquisition system was utilized to provide continuous monitoring of all channels based on a 30-second time scan. In addition, the data acquisition system was able to retrieve telemetry stream from the Satellite Test Equipments (STE) station for real-time data manipulation. Preliminary results showed the test to be successful from both the thermal balance side and the electrical testing side.

Multi-Scale Thermal Heat Tracer Tests for Characterizing Transport Processes and Flow Channelling in Fractured Media: Theory and Field Experiments

NASA Astrophysics Data System (ADS)

de La Bernardie, J.; Klepikova, M.; Bour, O.; Le Borgne, T.; Dentz, M.; Guihéneuf, N.; Gerard, M. F.; Lavenant, N.

2017-12-01

The characterization of flow and transport in fractured media is particularly challenging because hydraulic conductivity and transport properties are often strongly dependent on the geometric structure of the fracture surfaces. Here we show how thermal tracer tests may be an excellent complement to conservative solute tracer tests to infer fracture geometry and flow channeling. We performed a series of thermal tracer tests at different scales in a crystalline rock aquifer at the experimental site of Ploemeur (H+ observatory network). The first type of thermal tracer tests are push-pull tracer tests at different scales. The temporal and spatial scaling of heat recovery, measured from thermal breakthrough curves, shows a clear signature of flow channeling. In particular, the late time tailing of heat recovery under channeled flow is shown to diverge from the T(t) α t-1,5 behavior expected for the classical parallel plate model and follow the scaling T(t) α 1/t(logt)2 for a simple channel modeled as a tube. Flow channeling is also manifested on the spatial scaling of heat recovery as flow channeling affects the decay of the thermal breakthrough peak amplitude and the increase of the peak time with scale. The second type of thermal tracer tests are flow-through tracer tests where a pulse of hot water was injected in a fracture isolated by a double straddle packer while pumping at the same flow rate in another fracture at a distance of about 10 meters to create a dipole flow field. Comparison with a solute tracer test performed under the same conditions also present a clear signature of flow channeling. We derive analytical expressions for the retardation and decay of the thermal breakthrough peak amplitude for different fracture geometries and show that the observed differences between thermal and solute breakthrough can be explained only by channelized flow. These results suggest that heat transport is much more sensitive to fracture heterogeneity and flow channeling than conservative solute transport. These findings, which bring new insights on the effect of flow channeling on heat transfer in fractured rocks, show how heat recovery in geothermal systems may be controlled by fracture geometry. This highlights the interest of thermal tracer tests as a complement to solute tracers tests to infer fracture aperture and geometry.

Mathematical Models of IABG Thermal-Vacuum Facilities

NASA Astrophysics Data System (ADS)

Doring, Daniel; Ulfers, Hendrik

2014-06-01

IABG in Ottobrunn, Germany, operates thermal-vacuum facilities of different sizes and complexities as a service for space-testing of satellites and components. One aspect of these tests is the qualification of the thermal control system that keeps all onboard components within their save operating temperature band. As not all possible operation / mission states can be simulated within a sensible test time, usually a subset of important and extreme states is tested at TV facilities to validate the thermal model of the satellite, which is then used to model all other possible mission states. With advances in the precision of customer thermal models, simple assumptions of the test environment (e.g. everything black & cold, one solar constant of light from this side) are no longer sufficient, as real space simulation chambers do deviate from this ideal. For example the mechanical adapters which support the spacecraft are usually not actively cooled. To enable IABG to provide a model that is sufficiently detailed and realistic for current system tests, Munich engineering company CASE developed ESATAN models for the two larger chambers. CASE has many years of experience in thermal analysis for space-flight systems and ESATAN. The two models represent the rather simple (and therefore very homogeneous) 3m-TVA and the extremely complex space simulation test facility and its solar simulator. The cooperation of IABG and CASE built up extensive knowledge of the facilities thermal behaviour. This is the key to optimally support customers with their test campaigns in the future. The ESARAD part of the models contains all relevant information with regard to geometry (CAD data), surface properties (optical measurements) and solar irradiation for the sun simulator. The temperature of the actively cooled thermal shrouds is measured and mapped to the thermal mesh to create the temperature field in the ESATAN part as boundary conditions. Both models comprise switches to easily establish multiple possible set-ups (e.g. exclude components like the motion system or enable / disable the solar simulator). Both models were validated by comparing calculated results (thermal balance temperatures for simple passive test articles) with measured temperatures generated in actual tests in these facilities. This paper presents information about the chambers, the modelling approach, properties of the models and their performance in the validation tests.

Creation of a Data Base on Energetic Materials

DTIC Science & Technology

1987-08-10

Examples of booster explosives are Tetryl, RDX , and HMX . Examples of bursting explosives are Amatols, TNT, Compositions A, B, & C, and Picatrol. Within...Test Thermal Shock Resistance Glass Transition Temperature Toxicity Grain Size Viscosity Hardness Volatility Heat Capacity Water Resistance Heat of...Tensile Strength Flammability Thermal Conductivity Flexural Strength Thermal Expansion Coefficient Gap Test Thermal Shock Resistance Glass Transition

Study on indoor thermal environment in winter for rural residences in Yulin region

NASA Astrophysics Data System (ADS)

Yanjun, Li; Weixiao, Han

2018-02-01

Yulin region is located in the northern part of Shaanxi Province, China. The winter here is very cold and it has a long duration. In this paper, a rural residence which was located in Yulin region was taken as a study object. Indoor thermal environment of the rural residence were tested, including indoor air temperature and air relative humidity. Then, test data were analyzed. It was summarized that indoor thermal environment of test room can not fully meet human thermal comfort needs, and some tactics of regulation building thermal environment were proposed. This research contributes to improvement of indoor thermal environment for local rural residences and it provides reference for rural residences in other cold regions.

Shuttle antenna radome technology test program. Volume 2: Development of S-band antenna interface design

NASA Technical Reports Server (NTRS)

Kuhlman, E. A.; Baranowski, L. C.

1977-01-01

The effects of the Thermal Protection Subsystem (TPS) contamination on the space shuttle orbiter S band quad antenna due to multiple mission buildup are discussed. A test fixture was designed, fabricated and exposed to ten cycles of simulated ground and flight environments. Radiation pattern and impedance tests were performed to measure the effects of the contaminates. The degradation in antenna performance was attributed to the silicone waterproofing in the TPS tiles rather than exposure to the contaminating sources used in the test program. Validation of the accuracy of an analytical thermal model is discussed. Thermal vacuum tests with a test fixture and a representative S band quad antenna were conducted to evaluate the predictions of the analytical thermal model for two orbital heating conditions and entry from each orbit. The results show that the accuracy of predicting the test fixture thermal responses is largely dependent on the ability to define the boundary and ambient conditions. When the test conditions were accurately included in the analytical model, the predictions were in excellent agreement with measurements.

[Immobilization of pectawamorine G10x by gel entrapment].

PubMed

Bogatskiĭ, A V; Davidenko, T I; Areshidze, I V; Gren', T A; Sevast'ianov, O V

1979-01-01

Polyacrylamide gel immobilization of pectawamorine G10x was investigated. Its pectinesterase and polygalacturonase activity and stability in storage were measured. The degree of pectawamorine binding during gel immobilization was 80--90%, 55% of initial activity being retained. Thermal stability of the immobilized and native preparations was equal. Pectinesterase activity of the gel immobilized enzyme increased during storage.

49 CFR Appendix B to Part 179 - Procedures for Simulated Pool and Torch-Fire Testing

Code of Federal Regulations, 2011 CFR

2011-10-01

... plate. (3) Before exposure to the pool-fire simulation, none of the thermocouples on the thermal... simulated pool fire. (5) A pool-fire simulation test must run for a minimum of 100 minutes. The thermal... three consecutive successful simulation fire tests must be performed for each thermal protection system...

49 CFR Appendix B to Part 179 - Procedures for Simulated Pool and Torch-Fire Testing

Code of Federal Regulations, 2010 CFR

2010-10-01

... plate. (3) Before exposure to the pool-fire simulation, none of the thermocouples on the thermal... simulated pool fire. (5) A pool-fire simulation test must run for a minimum of 100 minutes. The thermal... three consecutive successful simulation fire tests must be performed for each thermal protection system...

49 CFR Appendix B to Part 179 - Procedures for Simulated Pool and Torch-Fire Testing

Code of Federal Regulations, 2012 CFR

2012-10-01

... plate. (3) Before exposure to the pool-fire simulation, none of the thermocouples on the thermal... simulated pool fire. (5) A pool-fire simulation test must run for a minimum of 100 minutes. The thermal... three consecutive successful simulation fire tests must be performed for each thermal protection system...

A Space Acquisition Leading Indicator Based on System Interoperation Maturity

DTIC Science & Technology

2010-12-01

delivered hardware, improper use of soldering materials, improper installation of thermal blankets , and missing test procedure documentation A poor...office, the first GEO integrated payload and spacecraft successfully completed thermal vacuum (TVAC) testing in November 2009. Program officials...contamination in delivered hardware, improper use of soldering materials, improper installation of thermal blankets , and missing test procedure

Effect of glycosylation on hydration behavior at the ice-binding surface of the Ocean Pout type III antifreeze protein: a molecular dynamics simulation.

PubMed

Halder, Swagata; Mukhopadhyay, Chaitali

2017-12-01

Antifreeze proteins (AFPs), found in certain vertebrates, plants, fungi and bacteria have the ability to permit their survival in subzero environments by thermal hysteresis mechanism. However, the exact mechanism of ice growth inhibition is still not clearly understood. Here, four long explicit molecular dynamics (MD) simulations have been carried out at two different temperatures (277 and 298 K) with and without glycan to study the conformational rigidity of the Ocean pout type III antifreeze protein in aqueous medium and the structural arrangements of water molecules hydrating its ice-binding surface. It is found that irrespective of the temperature the ice-binding surface (IBS) of the protein is relatively more rigid than its non ice-binding surface (NonIBS) in its native and glycosylated form. Hydrophilic residues N14, T18 and Q44 are essential to antifreeze activity. Radial distribution, density distribution function and nearest neighbor orientation plots with respect to individual two surfaces confirm that density of water molecule near these binding surface in native and glycosylated form are relatively more than the nonbinding surface. The glycosylated form shows a strong peak than the native one. From rotational auto correlation function of water molecules around ice-binding sites, it is prominent that with increase in temperature, strong interaction between the water oxygen and the hydrogen bond acceptor group on the protein-binding surface decreases. This provides a possible molecular reason behind the ice-binding activity of ocean pout at the prism plane of ice.

Thermophysiological Responses of Human Volunteers to Whole Body RF Exposure at 220 MHz

DTIC Science & Technology

2005-05-19

could make judgments of sensations and the test. A Fiso temperature probe was also taped to the thermal comfort at intervals during the test (cf. Table...general trends in individual responses. These responses sensation, thermal comfort , perceived sweating, and included six skin temperatures and weighted...Tankle). similar fashion, mean judgments of thermal sensation, The two right panels of the figure show M (upper) and thermal comfort , thermal preference

An ice-binding and tandem beta-sandwich domain-containing protein in Shewanella frigidimarina is a potential new type of ice adhesin.

PubMed

Vance, Tyler D R; Graham, Laurie A; Davies, Peter L

2018-04-01

Out of the dozen different ice-binding protein (IBP) structures known, the DUF3494 domain is the most widespread, having been passed many times between prokaryotic and eukaryotic microorganisms by horizontal gene transfer. This ~25-kDa β-solenoid domain with an adjacent parallel α-helix is most commonly associated with an N-terminal secretory signal peptide. However, examples of the DUF3494 domain preceded by tandem Bacterial Immunoglobulin-like (BIg) domains are sometimes found, though uncharacterized. Here, we present one such protein (SfIBP_1) from the Antarctic bacterium Shewanella frigidimarina. We have confirmed and characterized the ice-binding activity of its ice-binding domain using thermal hysteresis measurements, fluorescent ice plane affinity analysis, and ice recrystallization inhibition assays. X-ray crystallography was used to solve the structure of the SfIBP_1 ice-binding domain, to further characterize its ice-binding surface and unique method of stabilizing or 'capping' the ends of the solenoid structure. The latter is formed from the interaction of two loops mediated by a combination of tandem prolines and electrostatic interactions. Furthermore, given their domain architecture and membrane association, we propose that these BIg-containing DUF3494 IBPs serve as ice-binding adhesion proteins that are capable of adsorbing their host bacterium onto ice. Submitted new structure to the Protein Data Bank (PDB: 6BG8). © 2018 Federation of European Biochemical Societies.

Development and Fatigue Testing of Ceramic Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dong-Ming; Choi, Sung R.; Miller, Robert A.

2004-01-01

Ceramic thermal barrier coatings will play an increasingly important role in future gas turbine engines because of their ability to effectively protect the engine components and further raise engine temperatures. Durability of the coating systems remains a critical issue with the ever-increasing temperature requirements. Thermal conductivity increase and coating degradation due to sintering and phase changes are known to be detrimental to coating performance. There is a need to characterize the coating thermal fatigue behavior and temperature limit, in order to potentially take full advantage of the current coating capability. In this study, thermal conductivity and cyclic fatigue behaviors of plasma-sprayed ZrO2-8wt%Y2O3 thermal barrier coatings were evaluated under high temperature, large thermal gradient and thermal cycling conditions. The coating degradation and failure processes were assessed by real-time monitoring of the coating thermal conductivity under the test conditions. The ceramic coating crack initiation and propagation driving forces and failure modes under the cyclic thermal loads will be discussed in light of the high temperature mechanical fatigue and fracture testing results.

Target Residence Time-Guided Optimization on TTK Kinase Results in Inhibitors with Potent Anti-Proliferative Activity.

PubMed

Uitdehaag, Joost C M; de Man, Jos; Willemsen-Seegers, Nicole; Prinsen, Martine B W; Libouban, Marion A A; Sterrenburg, Jan Gerard; de Wit, Joeri J P; de Vetter, Judith R F; de Roos, Jeroen A D M; Buijsman, Rogier C; Zaman, Guido J R

2017-07-07

The protein kinase threonine tyrosine kinase (TTK; also known as Mps1) is a critical component of the spindle assembly checkpoint and a promising drug target for the treatment of aggressive cancers, such as triple negative breast cancer. While the first TTK inhibitors have entered clinical trials, little is known about how the inhibition of TTK with small-molecule compounds affects cellular activity. We studied the selective TTK inhibitor NTRC 0066-0, which was developed in our own laboratory, together with 11 TTK inhibitors developed by other companies, including Mps-BAY2b, BAY 1161909, BAY 1217389 (Bayer), TC-Mps1-12 (Shionogi), and MPI-0479605 (Myrexis). Parallel testing shows that the cellular activity of these TTK inhibitors correlates with their binding affinity to TTK and, more strongly, with target residence time. TTK inhibitors are therefore an example where target residence time determines activity in in vitro cellular assays. X-ray structures and thermal stability experiments reveal that the most potent compounds induce a shift of the glycine-rich loop as a result of binding to the catalytic lysine at position 553. This "lysine trap" disrupts the catalytic machinery. Based on these insights, we developed TTK inhibitors, based on a (5,6-dihydro)pyrimido[4,5-e]indolizine scaffold, with longer target residence times, which further exploit an allosteric pocket surrounding Lys553. Their binding mode is new for kinase inhibitors and can be classified as hybrid Type I/Type III. These inhibitors have very potent anti-proliferative activity that rivals classic cytotoxic therapy. Our findings will open up new avenues for more applications for TTK inhibitors in cancer treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Biopanning and characterization of peptides with Fe3O4 nanoparticles-binding capability via phage display random peptide library technique.

PubMed

You, Fei; Yin, Guangfu; Pu, Ximing; Li, Yucan; Hu, Yang; Huang, Zhongbin; Liao, Xiaoming; Yao, Yadong; Chen, Xianchun

2016-05-01

Functionalization of inorganic nanoparticles (NPs) play an important role in biomedical applications. A proper functionalization of NPs can improve biocompatibility, avoid a loss of bioactivity, and further endow NPs with unique performances. Modification with vairous specific binding biomolecules from random biological libraries has been explored. In this work, two 7-mer peptides with sequences of HYIDFRW and TVNFKLY were selected from a phage display random peptide library by using ferromagnetic NPs as targets, and were verified to display strong binding affinity to Fe3O4 NPs. Fourier transform infrared spectrometry, fluorescence microscopy, thermal analysis and X-ray photoelectron spectroscopy confirmed the presence of peptides on the surface of Fe3O4 NPs. Sequence analyses revealed that the probable binding mechanism between the peptide and Fe3O4 NPs might be driven by Pearson hard acid-hard base specific interaction and hydrogen bonds, accompanied with hydrophilic interactions and non-specific electrostatic attractions. The cell viability assay indicated a good cytocompatibility of peptide-bound Fe3O4 NPs. Furthermore, TVNFKLY peptide and an ovarian tumor cell A2780 specific binding peptide (QQTNWSL) were conjugated to afford a liner 14-mer peptide (QQTNWSLTVNFKLY). The binding and targeting studies showed that 14-mer peptide was able to retain both the strong binding ability to Fe3O4 NPs and the specific binding ability to A2780 cells. The results suggested that the Fe3O4-binding peptides would be of great potential in the functionalization of Fe3O4 NPs for the tumor-targeted drug delivery and magnetic hyperthermia. Copyright © 2016 Elsevier B.V. All rights reserved.

Comparison of Thermal Performance Characteristics of Ammonia and Propylene Loop Heat Pipes

NASA Technical Reports Server (NTRS)

Kaya, Tarik; Baker, Charles; Ku, Jentung

2000-01-01

In this paper, experimental work performed on a breadboard Loop Heat Pipe (LHP) is presented. The test article was built by DCI for the Geoscience Laser Altimeter System (GLAS) instrument on the ICESat spacecraft. The thermal system requirements of GLAS have shown that ammonia cannot be used as the working fluid in this LHP because GLAS radiators could cool to well below the freezing point of ammonia. As a result, propylene was proposed as an alternative LHP working fluid since it has a lower freezing point than ammonia. Both working fluids were tested in the same LHP following a similar test plan in ambient conditions. The thermal performance characteristics of ammonia and propylene LHP's were then compared. In general, the propylene LHP required slightly less startup superheat 5nd less control heater power than the ammonia LHP, The thermal conductance values for the propylene LHP were also lower than the ammonia LHP. Later, the propylene LHP was tested in a thermal vacuum chamber. These tests demonstrated that propylene could meet the GLAS thermal design requirements. Design guidelines were proposed for the next flight-like Development Model (DM) LHP for thermal control of the GLAS instrument.

Biological variability of transferrin saturation and unsaturated iron binding capacity

PubMed Central

Adams, PC; Reboussin, DM; Press, RD; Barton, JC; Acton, RT; Moses, GC; Leiendecker-Foster, C; McLaren, GD; Dawkins, FW; Gordeuk, VR; Lovato, L; Eckfeldt, JH

2007-01-01

Background Transferrin saturation is widely considered the preferred screening test for hemochromatosis. Unsaturated iron binding capacity has similar performance at lower cost. However, the within-person biological variability of both these tests may limit their ability at commonly used cut points to detect HFE C282Y homozygous patients. Methods The Hemochromatosis and Iron Overload Screening (HEIRS) Study screened 101,168 primary care participants for iron overload using tansferrin saturation, unsaturated iron binding capacity, ferritin and HFE C282Y and H63D genotyping. Transferrin saturation and unsaturated iron binding capacity were performed at initial screening and again when selected participants and controls returned for a clinical examination several months later. A missed case was defined as a C282Y homozygote who had transferrin saturation below cut point (45 % women, 50 % men) or unsaturated iron binding capacity above cut point (150 μmol/L women, 125 μmol/L men) at either the initial screening or clinical examination, or both, regardless of serum ferritin. Results There were 209 C282Y previously undiagnosed homozygotes with transferrin saturation and unsaturated iron binding capacity testing done at initial screening and clinical examination. Sixty-eight C282Y homozygotes (33%) would have been missed at these transferrin saturation cut points (19 men, 49 women, median SF 170 μg/L, first and third quartiles 50 and 474 μg/L), and 58 homozygotes (28 %) would have been missed at the unsaturated iron binding capacity cut points (20 men, 38 women, median SF 168 μg/L, quartiles 38 and 454 μg/L). There was no advantage to using fasting samples. Conclusions The within-person biological variability of transferrin saturation and unsaturated iron binding capacity limit their usefulness as an initial screening test for expressing C282Y homozygotes. PMID:17976429

Rocket nozzle thermal shock tests in an arc heater facility

NASA Technical Reports Server (NTRS)

Painter, James H.; Williamson, Ronald A.

1986-01-01

A rocket motor nozzle thermal structural test technique that utilizes arc heated nitrogen to simulate a motor burn was developed. The technique was used to test four heavily instrumented full-scale Star 48 rocket motor 2D carbon/carbon segments at conditions simulating the predicted thermal-structural environment. All four nozzles survived the tests without catastrophic or other structural failures. The test technique demonstrated promise as a low cost, controllable alternative to rocket motor firing. The technique includes the capability of rapid termination in the event of failure, allowing post-test analysis.

On the Behavior of Different PCMs in a Hot Water Storage Tank against Thermal Demands.

PubMed

Porteiro, Jacobo; Míguez, José Luis; Crespo, Bárbara; de Lara, José; Pousada, José María

2016-03-21

Advantages, such as thermal storage improvement, are found when using PCMs (Phase Change Materials) in storage tanks. The inclusion of three different types of materials in a 60 l test tank is studied. Two test methodologies were developed, and four tests were performed following each methodology. A thermal analysis is performed to check the thermal properties of each PCM. The distributions of the water temperatures inside the test tanks are evaluated by installing four Pt-100 sensors at different heights. A temperature recovery is observed after exposing the test tank to an energy demand. An energetic analysis that takes into account the energy due to the water temperature, the energy due to the PCM and the thermal loss to the ambient environment is also presented. The percentage of each PCM that remains in the liquid state after the energy demand is obtained.

On the Behavior of Different PCMs in a Hot Water Storage Tank against Thermal Demands

PubMed Central

Porteiro, Jacobo; Míguez, José Luis; Crespo, Bárbara; de Lara, José; Pousada, José María

2016-01-01

Advantages, such as thermal storage improvement, are found when using PCMs (Phase Change Materials) in storage tanks. The inclusion of three different types of materials in a 60 𝓁 test tank is studied. Two test methodologies were developed, and four tests were performed following each methodology. A thermal analysis is performed to check the thermal properties of each PCM. The distributions of the water temperatures inside the test tanks are evaluated by installing four Pt-100 sensors at different heights. A temperature recovery is observed after exposing the test tank to an energy demand. An energetic analysis that takes into account the energy due to the water temperature, the energy due to the PCM and the thermal loss to the ambient environment is also presented. The percentage of each PCM that remains in the liquid state after the energy demand is obtained. PMID:28773339

TEXSYS. [a knowledge based system for the Space Station Freedom thermal control system test-bed

NASA Technical Reports Server (NTRS)

Bull, John

1990-01-01

The Systems Autonomy Demonstration Project has recently completed a major test and evaluation of TEXSYS, a knowledge-based system (KBS) which demonstrates real-time control and FDIR for the Space Station Freedom thermal control system test-bed. TEXSYS is the largest KBS ever developed by NASA and offers a unique opportunity for the study of technical issues associated with the use of advanced KBS concepts including: model-based reasoning and diagnosis, quantitative and qualitative reasoning, integrated use of model-based and rule-based representations, temporal reasoning, and scale-up performance issues. TEXSYS represents a major achievement in advanced automation that has the potential to significantly influence Space Station Freedom's design for the thermal control system. An overview of the Systems Autonomy Demonstration Project, the thermal control system test-bed, the TEXSYS architecture, preliminary test results, and thermal domain expert feedback are presented.

[11C]Harmine Binding to Brain Monoamine Oxidase A: Test-Retest Properties and Noninvasive Quantification.

PubMed

Zanderigo, Francesca; D'Agostino, Alexandra E; Joshi, Nandita; Schain, Martin; Kumar, Dileep; Parsey, Ramin V; DeLorenzo, Christine; Mann, J John

2018-02-08

Inhibition of the isoform A of monoamine oxidase (MAO-A), a mitochondrial enzyme catalyzing deamination of monoamine neurotransmitters, is useful in treatment of depression and anxiety disorders. [ 11 C]harmine, a MAO-A PET radioligand, has been used to study mood disorders and antidepressant treatment. However, [ 11 C]harmine binding test-retest characteristics have to date only been partially investigated. Furthermore, since MAO-A is ubiquitously expressed, no reference region is available, thus requiring arterial blood sampling during PET scanning. Here, we investigate [ 11 C]harmine binding measurements test-retest properties; assess effects of using a minimally invasive input function estimation on binding quantification and repeatability; and explore binding potentials estimation using a reference region-free approach. Quantification of [ 11 C]harmine distribution volume (V T ) via kinetic models and graphical analyses was compared based on absolute test-retest percent difference (TRPD), intraclass correlation coefficient (ICC), and identifiability. The optimal procedure was also used with a simultaneously estimated input function in place of the measured curve. Lastly, an approach for binding potentials quantification in absence of a reference region was evaluated. [ 11 C]harmine V T estimates quantified using arterial blood and kinetic modeling showed average absolute TRPD values of 7.7 to 15.6 %, and ICC values between 0.56 and 0.86, across brain regions. Using simultaneous estimation (SIME) of input function resulted in V T estimates close to those obtained using arterial input function (r = 0.951, slope = 1.073, intercept = - 1.037), with numerically but not statistically higher test-retest difference (range 16.6 to 22.0 %), but with overall poor ICC values, between 0.30 and 0.57. Prospective studies using [ 11 C]harmine are possible given its test-retest repeatability when binding is quantified using arterial blood. Results with SIME of input function show potential for simplifying data acquisition by replacing arterial catheterization with one arterial blood sample at 20 min post-injection. Estimation of [ 11 C]harmine binding potentials remains a challenge that warrants further investigation.

Recombinant spider silk genetically functionalized with affinity domains.

PubMed

Jansson, Ronnie; Thatikonda, Naresh; Lindberg, Diana; Rising, Anna; Johansson, Jan; Nygren, Per-Åke; Hedhammar, My

2014-05-12

Functionalization of biocompatible materials for presentation of active protein domains is an area of growing interest. Herein, we describe a strategy for functionalization of recombinant spider silk via gene fusion to affinity domains of broad biotechnological use. Four affinity domains of different origin and structure; the IgG-binding domains Z and C2, the albumin-binding domain ABD, and the biotin-binding domain M4, were all successfully produced as soluble silk fusion proteins under nondenaturing purification conditions. Silk films and fibers produced from the fusion proteins were demonstrated to be chemically and thermally stable. Still, the bioactive domains are concluded to be folded and accessible, since their respective targets could be selectively captured from complex samples, including rabbit serum and human plasma. Interestingly, materials produced from mixtures of two different silk fusion proteins displayed combined binding properties, suggesting that tailor-made materials with desired stoichiometry and surface distributions of several binding domains can be produced. Further, use of the IgG binding ability as a general mean for presentation of desired biomolecules could be demonstrated for a human vascular endothelial growth factor (hVEGF) model system, via a first capture of anti-VEGF IgG to silk containing the Z-domain, followed by incubation with hVEGF. Taken together, this study demonstrates the potential of recombinant silk, genetically functionalized with affinity domains, for construction of biomaterials capable of presentation of almost any desired biomolecule.

Essential slow degrees of freedom in protein-surface simulations: A metadynamics investigation.

PubMed

Prakash, Arushi; Sprenger, K G; Pfaendtner, Jim

2018-03-29

Many proteins exhibit strong binding affinities to surfaces, with binding energies much greater than thermal fluctuations. When modelling these protein-surface systems with classical molecular dynamics (MD) simulations, the large forces that exist at the protein/surface interface generally confine the system to a single free energy minimum. Exploring the full conformational space of the protein, especially finding other stable structures, becomes prohibitively expensive. Coupling MD simulations with metadynamics (enhanced sampling) has fast become a common method for sampling the adsorption of such proteins. In this paper, we compare three different flavors of metadynamics, specifically well-tempered, parallel-bias, and parallel-tempering in the well-tempered ensemble, to exhaustively sample the conformational surface-binding landscape of model peptide GGKGG. We investigate the effect of mobile ions and ion charge, as well as the choice of collective variable (CV), on the binding free energy of the peptide. We make the case for explicitly biasing ions to sample the true binding free energy of biomolecules when the ion concentration is high and the binding free energies of the solute and ions are similar. We also make the case for choosing CVs that apply bias to all atoms of the solute to speed up calculations and obtain the maximum possible amount of information about the system. Copyright © 2017 Elsevier Inc. All rights reserved.

Binding of Nickel to Testicular Glutamate–Ammonia Ligase Inhibits Its Enzymatic Activity

PubMed Central

SUN, YINGBIAO; OU, YOUNG; CHENG, MIN; RUAN, YIBING; VAN DER HOORN, FRANS A.

2016-01-01

SUMMARY Exposure to nickel has been shown to cause damage to the testis in several animal models. It is not known if the testis expresses protein(s) that can bind nickel. To test this, we used a nickel-binding assay to isolate testicular nickel-binding proteins. We identified glutamate–ammonia ligase (GLUL) as a prominent nickel-binding protein by mass spectrometry. Protein analysis and reverse transcriptase polymerase chain reaction showed that GLUL is expressed in the testis, predominantly in interstitial cells. We determined that GLUL has a higher affinity for nickel than for its regular co-factor manganese. We produced an enzymatically active, recombinant GLUL protein. Upon binding, nickel interferes with the manganese-catalyzed enzymatic activity of recombinant GLUL protein. We also determined that GLUL activity in testes of animals exposed to nickel sulfate is reduced. Our results identify testicular GLUL as the first testicular protein shown to be affected by nickel exposure. PMID:21254280

Contact thermal shock test of ceramics

NASA Technical Reports Server (NTRS)

Rogers, W. P.; Emery, A. F.

1992-01-01

A novel quantitative thermal shock test of ceramics is described. The technique employs contact between a metal-cooling rod and hot disk-shaped specimen. In contrast with traditional techniques, the well-defined thermal boundary condition allows for accurate analyses of heat transfer, stress, and fracture. Uniform equibiaxial tensile stresses are induced in the center of the test specimen. Transient specimen temperature and acoustic emission are monitored continuously during the thermal stress cycle. The technique is demonstrated with soda-lime glass specimens. Experimental results are compared with theoretical predictions based on a finite-element method thermal stress analysis combined with a statistical model of fracture. Material strength parameters are determined using concentric ring flexure tests. Good agreement is found between experimental results and theoretical predictions of failure probability as a function of time and initial specimen temperature.

Below-Ambient and Cryogenic Thermal Testing

NASA Technical Reports Server (NTRS)

Fesmire, James E.

2016-01-01

Thermal insulation systems operating in below-ambient temperature conditions are inherently susceptible to moisture intrusion and vapor drive toward the cold side. The subsequent effects may include condensation, icing, cracking, corrosion, and other problems. Methods and apparatus for real-world thermal performance testing of below-ambient systems have been developed based on cryogenic boiloff calorimetry. New ASTM International standards on cryogenic testing and their extension to future standards for below-ambient testing of pipe insulation are reviewed.

Performance Testing of Thermal Interface Filler Materials in a Bolted Aluminum Interface Under Thermal/Vacuum Conditions

NASA Technical Reports Server (NTRS)

Glasgow, Shaun; Kittredge, Ken

2003-01-01

A thermal interface material is one of the many tools that are often used as part of the thermal control scheme for space-based applications. These materials are placed between, for example, an avionics box and a cold plate, in order to improve the conduction heat transfer so that proper temperatures can be maintained. Historically at Marshall Space Flight Center, CHO-THERM@ 1671 has primarily been used for applications where an interface material was deemed necessary. However, there have been numerous alternatives come on the market in recent years. It was decided that a number of these materials should be tested against each other to see if there were better performing alternatives. The tests were done strictly to compare the thermal performance of the materials relative to each other under repeatable conditions and they do not take into consideration other design issues such as off-gassing, electrical conduction or isolation, etc. This paper details the materials tested, test apparatus, procedures, and results of these tests.

Investigation of thermal fatigue in fiber composite materials. [(thermal cycling tests)

NASA Technical Reports Server (NTRS)

Fahmy, A. A.; Cunningham, T. G.

1976-01-01

Graphite-epoxy laminates were thermally cycled to determine the effects of thermal cycles on tensile properties and thermal expansion coefficients of the laminates. Three 12-ply laminate configurations were subjected to up to 5,000 thermal cycles. The cumulative effect of the thermal cycles was determined by destructive inspection (electron micrographs and tensile tests) of samples after progressively larger numbers of cycles. After thermal cycling, the materials' tensile strengths, moduli, and thermal expansion coefficients were significantly lower than for the materials as fabricated. Most of the degradation of properties occurred after only a few cycles. The property degradation was attributed primarily to the progressive development of matrix cracks whose locations depended upon the layup orientation of the laminate.

Key issues in the thermal design of spaceborne cryogenic infrared instruments

NASA Astrophysics Data System (ADS)

Schember, Helene R.; Rapp, Donald

1992-12-01

Thermal design and analysis play an integral role in the development of spaceborne cryogenic infrared (IR) instruments. From conceptual sketches to final testing, both direct and derived thermal requirements place significant constraints on the instrument design. Although in practice these thermal requirements are interdependent, the sources of most thermal constraints may be grouped into six distinct categories. These are: (1) Detector temperatures, (2) Optics temperatures, (3) Pointing or alignment stability, (4) Mission lifetime, (5) Orbit, and (6) Test and Integration. In this paper, we discuss these six sources of thermal requirements with particular regard to development of instrument packages for low background infrared astronomical observatories. In the end, the thermal performance of these instruments must meet a set of thermal requirements. The development of these requirements is typically an ongoing and interactive process, however, and the thermal design must maintain flexibility and robustness throughout the process. The thermal (or cryogenic) engineer must understand the constraints imposed by the science requirements, the specific hardware, the observing environment, the mission design, and the testing program. By balancing these often competing factors, the system-oriented thermal engineer can work together with the experiment team to produce an effective overall design of the instrument.

Design of a thermal waist-pad

NASA Astrophysics Data System (ADS)

Kursun Bahadir, S.; Sahin, U. K.; Acikgoz Tufan, H.

2017-10-01

The objective of the current study is designing a thermal waist-pad for people who have backaches with a sandwich-like multi-layered structure. Two model is developed; one is three-layered and second is five-layered with waterproof woven outer layer fabric, Thermolite® knitted fabric (for five-layered structures), wool knitted, polyester nonwoven fabric, polypropylene nonwoven fabric and viscose nonwoven fabric for mid-layer. 10 different structures are designed and produced. All samples are tested for thermal comfort properties of waist-pad. Multi-layer structures were tested, and according to their thermal performance and thermal comfort criteria, all results are evaluated for identifying the best product. These three factors are examined by analysis of thermal conductivity, thermal resistance, thermal absorptivity, relative water vapour/air permeability, water absorption. Highest thermal resistance test result, 150,42 mK/Wm2, is achieved in five-layered sandwich structure with waterproof fabric, Thermolite® fabric, wool based knitted fabric, Thermolite® fabric and waterproof fabric, respectively. Thermal conductivity result of this structure is 46,2 mW/mK, which is one of the lowest results among the alternative structures. Structures with Thermolite® fabric show higher thermal comfort when compared to others.

Exploring the Use of Thermal Infrared Imaging in Human Stress Research

PubMed Central

Grant, Joshua A.; Cardone, Daniela; Tusche, Anita; Singer, Tania

2014-01-01

High resolution thermal infrared imaging is a pioneering method giving indices of sympathetic activity via the contact-free recording of facial tissues (thermal imprints). Compared to established stress markers, the great advantage of this method is its non-invasiveness. The goal of our study was to pilot the use of thermal infrared imaging in the classical setting of human stress research. Thermal imprints were compared to established stress markers (heart rate, heart rate variability, finger temperature, alpha-amylase and cortisol) in 15 participants undergoing anticipation, stress and recovery phases of two laboratory stress tests, the Cold Pressor Test and the Trier Social Stress Test. The majority of the thermal imprints proved to be change-sensitive in both tests. While correlations between the thermal imprints and established stress markers were mostly non-significant, the thermal imprints (but not the established stress makers) did correlate with stress-induced mood changes. Multivariate pattern analysis revealed that in contrast to the established stress markers the thermal imprints could not disambiguate anticipation, stress and recovery phases of both tests. Overall, these results suggest that thermal infrared imaging is a valuable method for the estimation of sympathetic activity in the stress laboratory setting. The use of this non-invasive method may be particularly beneficial for covert recordings, in the study of special populations showing difficulties in complying with the standard instruments of data collection and in the domain of psychophysiological covariance research. Meanwhile, the established stress markers seem to be superior when it comes to the characterization of complex physiological states during the different phases of the stress cycle. PMID:24675709

Exploring the use of thermal infrared imaging in human stress research.

PubMed

Engert, Veronika; Merla, Arcangelo; Grant, Joshua A; Cardone, Daniela; Tusche, Anita; Singer, Tania

2014-01-01

High resolution thermal infrared imaging is a pioneering method giving indices of sympathetic activity via the contact-free recording of facial tissues (thermal imprints). Compared to established stress markers, the great advantage of this method is its non-invasiveness. The goal of our study was to pilot the use of thermal infrared imaging in the classical setting of human stress research. Thermal imprints were compared to established stress markers (heart rate, heart rate variability, finger temperature, alpha-amylase and cortisol) in 15 participants undergoing anticipation, stress and recovery phases of two laboratory stress tests, the Cold Pressor Test and the Trier Social Stress Test. The majority of the thermal imprints proved to be change-sensitive in both tests. While correlations between the thermal imprints and established stress markers were mostly non-significant, the thermal imprints (but not the established stress makers) did correlate with stress-induced mood changes. Multivariate pattern analysis revealed that in contrast to the established stress markers the thermal imprints could not disambiguate anticipation, stress and recovery phases of both tests. Overall, these results suggest that thermal infrared imaging is a valuable method for the estimation of sympathetic activity in the stress laboratory setting. The use of this non-invasive method may be particularly beneficial for covert recordings, in the study of special populations showing difficulties in complying with the standard instruments of data collection and in the domain of psychophysiological covariance research. Meanwhile, the established stress markers seem to be superior when it comes to the characterization of complex physiological states during the different phases of the stress cycle.

Thermal test of the insulation structure for LH 2 tank by using the large experimental apparatus

NASA Astrophysics Data System (ADS)

Kamiya, S.; Onishi, K.; Konshima, N.; Nishigaki, K.

Conceptual designs of large mass LH 2 (liquid hydrogen) storage systems, whose capacity is 50,000 m3, have been studied in the Japanese hydrogen project, World Energy Network (WE-NET) [K. Fukuda, in: WE-NET Hydrogen Energy Symposium, 1999, P1-P41]. This study has concluded that their thermal insulation structures for the huge LH 2 tanks should be developed. Their actual insulation structures comprise not only the insulation material but also reinforced members and joints. To evaluate their thermal performance correctly, a large test specimen including reinforced members and joints will be necessary. After verifying the thermal performance of a developed large experimental apparatus [S. Kamiya, Cryogenics 40 (1) (2000) 35] for measuring the thermal conductance of various insulation structures, we tested two specimens, a vacuum multilayer insulation (MLI) with a glass fiber reinforced plastic (GFRP) support and a vacuum solid insulation (microtherm ®) with joints. The thermal background test for verifying the thermal design of the experimental apparatus showed that the background heat leak is 0.1 W, small enough to satisfy apparatus performance requirement. The thermal conductance measurements of specimens also showed that thermal heat fluxes of MLI with a GFRP support and microtherm ® are 8 and 5.4 W/m2, respectively.

Determination of total arsenic using a novel Zn-ferrite binding gel for DGT techniques: Application to the redox speciation of arsenic in river sediments.

PubMed

Gorny, Josselin; Lesven, Ludovic; Billon, Gabriel; Dumoulin, David; Noiriel, Catherine; Pirovano, Caroline; Madé, Benoît

2015-11-01

A new laboratory-made Zn-ferrite (ZnFe2O4) binding gel is fully tested using Diffusive Gradient in Thin films (DGT) probes to measure total As [including inorganic As(III) and As(V), as well as MonoMethyl Arsenic Acid (MMAA(V)) and DiMethyl Arsenic Acid (DMAA(V))] in river waters and sediment pore waters. The synthesis of the binding gel is easy, cheap and its insertion into the acrylamide gel is not problematic. An important series of triplicate tests have been carried out to validate the use of the Zn-ferrite binding gel in routine for several environmental matrixes studies, in order to test: (i) the effect of pH on the accumulation efficiency of inorganic As species; (ii) the reproducibility of the results; (iii) the accumulation efficiency of As species; (iv) the effects of the ionic strength and possible competitive anions; and (v) the uptake and the elution efficiency of As species after accumulation in the binding gel. All experimental conditions have been reproduced using two other existing binding gels for comparison: ferrihydrite and Metsorb® HMRP 50. We clearly demonstrate that the Zn-ferrite binding gel is at least as good as the two other binding gels, especially for pH values higher than 8. In addition, by taking into consideration the diffusion rates of As(III) and As(V) in the gel, combining the 3-mercaptopropyl [accumulating only As(III)] with the Zn-ferrite binding gels allows for performing speciation studies. An environmental study along the Marque River finally illustrates the ability of the new binding gel to be used for field studies. Copyright © 2015. Published by Elsevier B.V.

Environmental qualification testing of the prototype pool boiling experiment

NASA Technical Reports Server (NTRS)

Sexton, J. Andrew

1992-01-01

The prototype Pool Boiling Experiment (PBE) flew on the STS-47 mission in September 1992. This report describes the purpose of the experiment and the environmental qualification testing program that was used to prove the integrity of the prototype hardware. Component and box level vibration and thermal cycling tests were performed to give an early level of confidence in the hardware designs. At the system level, vibration, thermal extreme soaks, and thermal vacuum cycling tests were performed to qualify the complete design for the expected shuttle environment. The system level vibration testing included three axis sine sweeps and random inputs. The system level hot and cold soak tests demonstrated the hardware's capability to operate over a wide range of temperatures and gave the project team a wider latitude in determining which shuttle thermal altitudes were compatible with the experiment. The system level thermal vacuum cycling tests demonstrated the hardware's capability to operate in a convection free environment. A unique environmental chamber was designed and fabricated by the PBE team and allowed most of the environmental testing to be performed within the project's laboratory. The completion of the test program gave the project team high confidence in the hardware's ability to function as designed during flight.

Simulator with integrated HW and SW for prediction of thermal comfort to provide feedback to the climate control system

NASA Astrophysics Data System (ADS)

Pokorný, Jan; Kopečková, Barbora; Fišer, Jan; JÍcha, Miroslav

2018-06-01

The aim of the paper is to assemble a simulator for evaluation of thermal comfort in car cabins in order to give a feedback to the HVAC (heating, ventilation and air conditioning) system. The HW (hardware) part of simulator is formed by thermal manikin Newton and RH (relative humidity), velocity and temperature probes. The SW (software) part consists of the Thermal Comfort Analyser (using ISO 14505-2) and Virtual Testing Stand of Car Cabin defining the heat loads of car cabin. Simulator can provide recommendation for the climate control how to improve thermal comfort in cabin by distribution and directing of air flow, and also by amount of ventilation power to keep optimal temperature inside a cabin. The methods of evaluation of thermal comfort were verified by tests with 10 test subjects for summer (summer clothing, ambient air temperature 30 °C, HVAC setup: +24 °C auto) and winter conditions (winter clothing, ambient air temperature -5 °C, HVAC setup: +18 °C auto). The tests confirmed the validity of the thermal comfort evaluation using the thermal manikin and ISO 14505-2.

Thermal testing by internal IR heating of the FEP module

NASA Technical Reports Server (NTRS)

Nathanson, D. M.; Efromson, R. A.; Lee, E. I.

1986-01-01

A spacecraft module, to be integrated with the FLTSATCOM spacecraft, was tested in a simulated orbit environment separate from the host spacecraft. Thermal vacuum testing of the module was accomplished using internal IR heating rather than conventional external heat sources. For this configuration, the technique produced boundary conditions expected for flight to enable verification of system performance and thermal design details.

Thermomechanical and Environmental Durability of Environmental Barrier Coated Ceramic Matrix Composites Under Thermal Gradients

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Bhatt, Ramakrishna T.; Harder, Bryan

2016-01-01

This paper presents the developments of thermo-mechanical testing approaches and durability performance of environmental barrier coatings (EBCs) and EBC coated SiCSiC ceramic matrix composites (CMCs). Critical testing aspects of the CMCs will be described, including state of the art instrumentations such as temperature, thermal gradient, and full field strain measurements; materials thermal conductivity evolutions and thermal stress resistance; NDE methods; thermo-mechanical stress and environment interactions associated damage accumulations. Examples are also given for testing ceramic matrix composite sub-elements and small airfoils to help better understand the critical and complex CMC and EBC properties in engine relevant testing environments.

THE MECHANISM OF ACTION OF COLCHICINE

PubMed Central

Wilson, Leslie; Meza, Isaura

1973-01-01

The thermal depolymerization procedure of Stephens (1970. J. Mol. Biol. 47:353) has been employed for solubilization of Strongylocentrotus purpuratus sperm tail outer doublet microtubules with the use of a buffer during solubilization which is of optimal pH and ionic strength for the preservation of colchicine binding activity of chick embryo brain tubulin. Colchicine binding values were corrected for first-order decay during heat solubilization at 50°C (t½ = 5.4 min) and incubation with colchicine at 37°C in the presence of vinblastine sulfate (t½ = 485 min). The colchicine binding properties of heat-solubilized outer doublet tubulin were qualitatively identical with those of other soluble forms of tubulin. The solubilized tubulin (mol wt, 115,000) bound 0.9 ± 0.2 mol of colchicine per mol of tubulin, with a binding constant of 6.3 x 105 liters/mol at 37°C. The colchicine binding reaction was both time and temperature dependent, and the binding of colchicine was prevented in a competitive manner by podophyllotoxin (Ki = 1.3 x 10-6 M). The first-order decay of colchicine binding activity was substantially decreased by the addition of the vinca alkaloids, vinblastine sulfate or vincristine sulfate, thus demonstrating the presence of a vinca alkaloid binding site(s) on the outer doublet tubulin. Tubulin contained within the assembled microtubules did not decay. Intact outer doublet microtubules bound less than 0.001 mol of colchicine per mol of tubulin contained in the microtubules, under conditions where soluble tubulin would have bound 1 mol of colchicine per mol of tubulin (saturating concentration of colchicine, no decay of colchicine binding activity). The presence of colchicine had no effect on the rate of solubilization of outer doublet microtubules during incubation at 37°C. Therefore, the colchicine binding site on tubulin is blocked (not available to bind colchicine) when the tubulin is in the assembled outer doublet microtubules. PMID:4747924

Structural and Biophysical Characterization of the Mycobacterium tuberculosis Protein Rv0577, a Protein Associated with Neutral Red Staining of Virulent Tuberculosis Strains and Homologue of the Streptomyces coelicolor Protein KbpA [Structural and Biophysical Characterization of Rv0577, a Protein Associated with Neutral Red Staining of Virulent Strains of Mycobacterium tuberculosis and homolog of the Streptomyces coelicolor protein KbpA

DOE PAGES

Buchko, Garry W.; Echols, Nathaniel; Flynn, E. Megan; ...

2017-07-10

Mycobacterium tuberculosis protein Rv0577 is a prominent antigen in tuberculosis patients, the component responsible for neutral red staining of virulent strains of M. tuberculosis, a putative component in a methylglyoxal detoxification pathway, and an agonist of toll-like receptor 2. It also has an amino acid sequence that is 36% identical to that of Streptomyces coelicolor AfsK-binding protein A (KbpA), a component in the complex secondary metabolite pathways in the Streptomyces genus. To gain insight into the biological function of Rv0577 and the family of KpbA kinase regulators, the crystal structure for Rv0577 was determined to a resolution of 1.75 Å,more » binding properties with neutral red and deoxyadenosine were surveyed, backbone dynamics were measured, and thermal stability was assayed by circular dichroism spectroscopy. The protein is composed of four approximate repeats with a βαβββ topology arranged radially in consecutive pairs to form two continuous eight-strand β-sheets capped on both ends with an α-helix. The two β-sheets intersect in the center at roughly a right angle and form two asymmetric deep “saddles” that may serve to bind ligands. Nuclear magnetic resonance chemical shift perturbation experiments show that neutral red and deoxyadenosine bind to Rv0577. Binding to deoxyadenosine is weaker with an estimated dissociation constants of 4.1 ± 0.3 mM for saddle 1. Heteronuclear steady-state { 1H}– 15N nuclear Overhauser effect, T 1, and T 2 values were generally uniform throughout the sequence with only a few modest pockets of differences. As a result, circular dichroism spectroscopy characterization of the thermal stability of Rv0577 indicated irreversible unfolding upon heating with an estimated melting temperature of 56 °C.« less

Structural and Biophysical Characterization of the Mycobacterium tuberculosis Protein Rv0577, a Protein Associated with Neutral Red Staining of Virulent Tuberculosis Strains and Homologue of the Streptomyces coelicolor Protein KbpA [Structural and Biophysical Characterization of Rv0577, a Protein Associated with Neutral Red Staining of Virulent Strains of Mycobacterium tuberculosis and homolog of the Streptomyces coelicolor protein KbpA

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

Buchko, Garry W.; Echols, Nathaniel; Flynn, E. Megan

Mycobacterium tuberculosis protein Rv0577 is a prominent antigen in tuberculosis patients, the component responsible for neutral red staining of virulent strains of M. tuberculosis, a putative component in a methylglyoxal detoxification pathway, and an agonist of toll-like receptor 2. It also has an amino acid sequence that is 36% identical to that of Streptomyces coelicolor AfsK-binding protein A (KbpA), a component in the complex secondary metabolite pathways in the Streptomyces genus. To gain insight into the biological function of Rv0577 and the family of KpbA kinase regulators, the crystal structure for Rv0577 was determined to a resolution of 1.75 Å,more » binding properties with neutral red and deoxyadenosine were surveyed, backbone dynamics were measured, and thermal stability was assayed by circular dichroism spectroscopy. The protein is composed of four approximate repeats with a βαβββ topology arranged radially in consecutive pairs to form two continuous eight-strand β-sheets capped on both ends with an α-helix. The two β-sheets intersect in the center at roughly a right angle and form two asymmetric deep “saddles” that may serve to bind ligands. Nuclear magnetic resonance chemical shift perturbation experiments show that neutral red and deoxyadenosine bind to Rv0577. Binding to deoxyadenosine is weaker with an estimated dissociation constants of 4.1 ± 0.3 mM for saddle 1. Heteronuclear steady-state { 1H}– 15N nuclear Overhauser effect, T 1, and T 2 values were generally uniform throughout the sequence with only a few modest pockets of differences. As a result, circular dichroism spectroscopy characterization of the thermal stability of Rv0577 indicated irreversible unfolding upon heating with an estimated melting temperature of 56 °C.« less

Aero-Thermal Calibration of the NASA Glenn Icing Research Tunnel (2012 Test)

NASA Technical Reports Server (NTRS)

Pastor-Barsi, Christine M.; Arrington, E. Allen; VanZante, Judith Foss

2012-01-01

A major modification of the refrigeration plant and heat exchanger at the NASA Glenn Icing Research Tunnel (IRT) occurred in autumn of 2011. It is standard practice at NASA Glenn to perform a full aero-thermal calibration of the test section of a wind tunnel facility upon completion of major modifications. This paper will discuss the tools and techniques used to complete an aero-thermal calibration of the IRT and the results that were acquired. The goal of this test entry was to complete a flow quality survey and aero-thermal calibration measurements in the test section of the IRT. Test hardware that was used includes the 2D Resistive Temperature Detector (RTD) array, 9-ft pressure survey rake, hot wire survey rake, and the quick check survey rake. This test hardware provides a map of the velocity, Mach number, total and static pressure, total temperature, flow angle and turbulence intensity. The data acquired were then reduced to examine pressure, temperature, velocity, flow angle, and turbulence intensity. Reduced data has been evaluated to assess how the facility meets flow quality goals. No icing conditions were tested as part of the aero-thermal calibration. However, the effects of the spray bar air injections on the flow quality and aero-thermal calibration measurements were examined as part of this calibration.

Thermal Performance of Cryogenic Piping Multilayer Insulation in Actual Field Installations

NASA Technical Reports Server (NTRS)

Fesmire, J.; Augustnynowicz, S.; Thompson, K. (Technical Monitor)

2002-01-01

A standardized way of comparing the thermal performance of different pipelines in different sizes is needed. Vendor data for vacuum-insulated piping are typically given in heat leak rate per unit length (W/m) for a specific diameter pipeline. An overall k-value for actual field installations (k(sub oafi)) is therefore proposed as a more generalized measure for thermal performance comparison and design calculation. The k(sub oafi) provides a direct correspondence to the k-values reported for insulation materials and illustrates the large difference between ideal multilayer insulation (MLI) and actual MLI performance. In this experimental research study, a section of insulated piping was tested under cryogenic vacuum conditions, including simulated spacers and bending. Several different insulation systems were tested using a 1-meter-long cylindrical cryostat test apparatus. The simulated spacers tests showed significant degradation in the thermal performance of a given insulation system. An 18-meter-long pipeline test apparatus is now in operation at the Cryogenics Test Laboratory, NASA Kennedy Space Center, for conducting liquid nitrogen thermal performance tests.

A low cost imaging displacement measurement system for spacecraft thermal vacuum testing

NASA Technical Reports Server (NTRS)

Dempsey, Brian

2006-01-01

A low cost imaging displacement technique suitable for use in thermal vacuum testing was built and tested during thermal vacuum testing of the space infrared telescope facility (SIRTF, later renamed Spitzer infrared telescope facility). The problem was to measure the relative displacement of different portions of the spacecraft due to thermal expansion or contraction. Standard displacement measuring instrumentation could not be used because of the widely varying temperatures on the spacecraft and for fear of invalidating the thermal vacuum testing. The imaging system was conceived, designed, purchased, and installed in approximately 2 months at very low cost. The system performed beyond expectations proving that sub millimeter displacements could be measured from over 2 meters away. Using commercial optics it was possible to make displacement measurements down to 10 (mu)m. An automated image processing tool was used to process the data, which not only speeded up data reduction, but showed that velocities and accelerations could also be measured. Details of the design and capabilities of the system are discussed along with the results of the test on the observatory. Several images from the actual test are presented.

Microelectronics Instrument Products Shock and Vibration Electro-optics: C-Qualification Test Report

NASA Technical Reports Server (NTRS)

1994-01-01

In this test report all measurements made during testing are recorded in ATP 20049 DS data sheets and are included in the log. The motor/encoder (henceforth referred to as the UUT) test sequence began with a baseline functional evaluation, which demonstrated that the motor satisfied the operating torque, cogging torque, winding resistance, and mechanical requirements of SOW. In addition, the encoder electrical requirements were verified, as well as the alignment of the encoder outputs relative tc, the motor shaft position. There were no discrepancies observed in this portion of the test. The UUT was then exposed to a number of environments, including thermal vacuum, thermal cycling, random and sine vibration, and mechanical shock. During the thermal environments, the performance of the UUT under load was verified at specified points in the cycles, as described in ATP 20049. In addition, the UUT was bench tested between the two thermal environments. No anomalies were observed during the thermal tests. The load attachment method was subsequently corrected, and vibration of S/N 0002 began while 0003 was being repaired.

Generator of the low-temperature heterogeneous plasma flow

NASA Astrophysics Data System (ADS)

Yusupov, D. I.; Gadzhiev, M. Kh; Tyuftyaev, A. S.; Chinnov, V. F.; Sargsyan, M. A.

2018-01-01

A generator of low-temperature dc plasma with an expanding channel of an output electrode for gas-thermal spraying was designed and constructed. The delivery of the sprayed powder into the cathode and anode arc-binding zones or into the plasma jet below the anode binding was realized. The electrophysical characteristics of both the plasma torch and the heterogeneous plasma flow with Al2O3 powder are studied. It is shown that the current-voltage characteristic (CVC) of a plasma torch depends on the gas flow rate. If the flow rate varies from 1 to 3 g/s, the falling CVC becomes gradually increasing. The speed and temperature of the sprayed powder are determined.

FAST TRACK COMMUNICATION: Finite-temperature magnetism in bcc Fe under compression

NASA Astrophysics Data System (ADS)

Sha, Xianwei; Cohen, R. E.

2010-09-01

We investigate the contributions of finite-temperature magnetic fluctuations to the thermodynamic properties of bcc Fe as functions of pressure. First, we apply a tight-binding total-energy model parameterized to first-principles linearized augmented plane-wave computations to examine various ferromagnetic, anti-ferromagnetic, and noncollinear spin spiral states at zero temperature. The tight-binding data are fit to a generalized Heisenberg Hamiltonian to describe the magnetic energy functional based on local moments. We then use Monte Carlo simulations to compute the magnetic susceptibility, the Curie temperature, heat capacity, and magnetic free energy. Including the finite-temperature magnetism improves the agreement with experiment for the calculated thermal expansion coefficients.

Rupture of DNA aptamer: New insights from simulations

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

Mishra, Rakesh Kumar; Nath, Shesh; Kumar, Sanjay

2015-10-28

Base-pockets (non-complementary base-pairs) in a double-stranded DNA play a crucial role in biological processes. Because of thermal fluctuations, it can lower the stability of DNA, whereas, in case of DNA aptamer, small molecules, e.g., adenosinemonophosphate and adenosinetriphosphate, form additional hydrogen bonds with base-pockets termed as “binding-pockets,” which enhance the stability. Using the Langevin dynamics simulations of coarse grained model of DNA followed by atomistic simulations, we investigated the influence of base-pocket and binding-pocket on the stability of DNA aptamer. Striking differences have been reported here for the separation induced by temperature and force, which require further investigation by single moleculemore » experiments.« less

On the origin of the decrease in stability of the DNA hairpin d(GCGAAGC) on complexation with aromatic drugs.

PubMed

Kostjukov, V V; Lantushenko, A O; Davies, D B; Evstigneev, M P

2007-08-01

Molecular dynamics simulations of drug-DNA complexes have been carried out in order to explain the experimentally observed decrease in thermal stability of the DNA hairpin d(GCGAAGC) on binding the aromatic drug molecules, daunomycin, ethidium bromide, novantrone and proflavine. This complexation behavior is in contrast to the stabilizing effect of the same aromatic drug molecules on DNA duplexes. Analysis of the energy parameters and the hydration properties of the complexes shows that the main factor correlating with the decrease in melting temperatures of the drug-hairpin complexes is the number of water bridges, with a reduction of at least 40% on ligand binding.

Nucleation time of nanoscale water bridges.

PubMed

Szoszkiewicz, Robert; Riedo, Elisa

2005-09-23

Water capillaries bind together grains of sand. They also can bind an atomic force microscope tip to a substrate. The kinetics of capillary condensation at the nanoscale is studied here using friction force microscopy. At 40% relative humidity we find that the meniscus nucleation times increase from 0.7 to 4.2 ms when the temperature decreases from 332 to 299 K. The nucleation times grow exponentially with the inverse temperature 1/T obeying an Arrhenius law. We obtain a nucleation energy barrier of 7.8 x 10(-20) J and an attempt frequency ranging between 4 and 250 GHz, in excellent agreement with theoretical predictions. These results provide direct experimental evidence that capillary condensation is a thermally activated phenomenon.

Early thermal testing of type B radioactive material packages in USA to environments beyond regulatory package thermal test standards

DOE PAGES

Yoshimura, H. R.; Pope, R. B.; Kubo, M.

2007-06-01

Three separate fire test programmes exposing casks beyond the regulatory thermal test requirements were performed by Sandia National Laboratories during the late 1970s and mid 1980s. The results of these test programmes can be used to assist in addressing the adequacy of the regulatory thermal test of fully engulfing exposure at 800°C for 30 min and how that test might relate to real accident thermal environments. The test programmes were undertaken on obsolete and new casks on behalf of the US Department of Energy (DOE), the US Department of Transportation (DOT) and the Japanese Power Reactor and Nuclear Fuel Developmentmore » Corporation (PNC), currently known as the Japan Atomic Energy Agency. Two of the tests involved exposure of casks in damaged transport vehicles to fully engulfing fires for 72–125 min, and the other test involved four exposures of a cask to torch environments for 30 min. Much of the original documentation regarding these tests and their results is no longer readily available. The documents relating to these tests have been surveyed; this paper presents summaries from this survey of the tests and their results. Specifically, for the pool fire exposures, the temperatures measured in the flames of both exceeded the flame temperature required by the Transport Regulations; yet an obsolete 67 t cask endured 90 min of exposure before evidence of failure was detected, and a new cask endured the 72 min exposure while retaining its containment integrity. For the exposure of a modified obsolete cask to four different torch environments, the integrity of the cask was retained and the relative temperature increases within the cask were well within acceptable limits and well below the values that could be expected if the cask was exposed to the regulatory thermal test. In this paper, a review of these three thermal test programmes, establishes that the two older cask designs and one new cask design have the ability to survive environments that were different from (the torch environments) or more severe than the environment specified by the existing thermal test requirement in the Transport Regulations. Finally, these results can be extrapolated to apply to modern casks that generally have more robust designs as well as better quality assurance applied during the manufacturing process.« less

Development of NASA's Sample Cartridge Assembly: Summary of GEDS Design, Development Testing, and Thermal Analyses

NASA Technical Reports Server (NTRS)

O'Connor, Brian; Hernandez, Deborah; Hornsby, Linda; Brown, Maria; Horton-Mullins, Kathryn

2017-01-01

Outline: Background of ISS (International Space Station) Material Science Research Rack; NASA SCA (Sample Cartridge Assembly) Design; GEDS (Gravitational Effects in Distortion in Sintering) Experiment Ampoule Design; Development Testing Summary; Thermal Modeling and Analysis. Summary: GEDS design development challenging (GEDS Ampoule design developed through MUGS (Microgravity) testing; Short duration transient sample processing; Unable to measure sample temperatures); MUGS Development testing used to gather data (Actual LGF (Low Gradient Furnace)-like furnace response; Provided sample for sintering evaluation); Transient thermal model integral to successful GEDS experiment (Development testing provided furnace response; PI (Performance Indicator) evaluation of sintering anchored model evaluation of processing durations; Thermal transient model used to determine flight SCA sample processing profiles).

Industry tests of NASA ceramic thermal barrier coating. [for gas turbine engine applications

NASA Technical Reports Server (NTRS)

Liebert, C. H.; Stepka, F. S.

1979-01-01

Ceramic thermal barrier coating (TBC) system was tested by industrial and governmental organizations for a variety of aeronautical, marine, and ground-based gas turbine engine applications. This TBC is a two-layer system with a bond coating of nickel-chromium-aluminum-yttrium (Ni-16Cr-6Al-0.6Y, in wt. percent) and a ceramic coating of yttria-stabilized zirconia (ZrO2-12Y2O3, in wt. percent). Seven tests evaluated the system's thermal protection and durability. Five other tests determined thermal conductivity, vibratory fatigue characteristics, and corrosion resistance of the system. The information presented includes test results and photographs of the coated parts. Recommendations are made for improving the coating procedures.

Pyrrole-indolinone SU11652 targets the nucleoside diphosphate kinase from Leishmania parasites.

PubMed

Vieira, Plínio Salmazo; Souza, Tatiana de Arruda Campos Brasil; Honorato, Rodrigo Vargas; Zanphorlin, Letícia Maria; Severiano, Kelven Ulisses; Rocco, Silvana Aparecida; de Oliveira, Arthur Henrique Cavalcante; Cordeiro, Artur Torres; Oliveira, Paulo Sérgio Lopes; de Giuseppe, Priscila Oliveira; Murakami, Mário Tyago

2017-07-01

Nucleoside diphosphate kinases (NDKs) are key enzymes in the purine-salvage pathway of trypanosomatids and have been associated with the maintenance of host-cell integrity for the benefit of the parasite, being potential targets for rational drug discovery and design. The NDK from Leishmania major (LmNDK) and mutants were expressed and purified to homogeneity. Thermal shift assays were employed to identify potential inhibitors for LmNDK. Calorimetric experiments, site-directed mutagenesis and molecular docking analysis were performed to validate the interaction and to evaluate the structural basis of ligand recognition. Furthermore, the anti-leishmanial activity of the newly identified and validated compound was tested in vitro against different Leishmania species. The molecule SU11652, a Sunitinib analog, was identified as a potential inhibitor for LmNDK and structural studies indicated that this molecule binds to the active site of LmNDK in a similar conformation to nucleotides, mimicking natural substrates. Isothermal titration calorimetry experiments combined with site-directed mutagenesis revealed that the residues H50 and H117, considered essential for catalysis, play an important role in ligand binding. In vitro cell studies showed that SU11652 had similar efficacy to Amphotericin b against some Leishmania species. Together, our results indicate the pyrrole-indolinone SU11652 as a promising scaffold for the rational design of new drugs targeting the enzyme NDK from Leishmania parasites. Copyright © 2017 Elsevier Inc. All rights reserved.

Qualification of Fiber Optic Cables for Martian Extreme Temperature Environments

NASA Technical Reports Server (NTRS)

Ramesham, Rajeshuni; Lindensmith, Christian A.; Roberts, William T.; Rainen, Richard A.

2011-01-01

Means have been developed for enabling fiber optic cables of the Laser Induced Breakdown Spectrometer instrument to survive ground operations plus the nominal 670 Martian conditions that include Martian summer and winter seasons. The purpose of this development was to validate the use of the rover external fiber optic cabling of ChemCam for space applications under the extreme thermal environments to be encountered during the Mars Science Laboratory (MSL) mission. Flight-representative fiber optic cables were subjected to extreme temperature thermal cycling of the same diurnal depth (or delta T) as expected in flight, but for three times the expected number of in-flight thermal cycles. The survivability of fiber optic cables was tested for 600 cumulative thermal cycles from -130 to +15 C to cover the winter season, and another 1,410 cumulative cycles from -105 to +40 C to cover the summer season. This test satisfies the required 3 times the design margin that is a total of 2,010 thermal cycles (670 x 3). This development test included functional optical transmission tests during the course of the test. Transmission of the fiber optic cables was performed prior to and after 1,288 thermal cycles and 2,010 thermal cycles. No significant changes in transmission were observed on either of the two representative fiber cables subject through the 3X MSL mission life that is 2,010 thermal cycles.

Residual Tensile Property of Plain Woven Jute Fiber/Poly(Lactic Acid) Green Composites during Thermal Cycling

PubMed Central

Katogi, Hideaki; Takemura, Kenichi; Akiyama, Motoki

2016-01-01

This study investigated the residual tensile properties of plain woven jute fiber reinforced poly(lactic acid) (PLA) during thermal cycling. Temperature ranges of thermal cycling tests were 35–45 °C and 35–55 °C. The maximum number of cycles was 103 cycles. The quasi-static tensile tests of jute fiber, PLA, and composite were conducted after thermal cycling tests. Thermal mechanical analyses of jute fiber and PLA were conducted after thermal cycling tests. Results led to the following conclusions. For temperatures of 35–45 °C, tensile strength of composite at 103 cycles decreased 10% compared to that of composite at 0 cycles. For temperatures of 35–55 °C, tensile strength and Young’s modulus of composite at 103 cycles decreased 15% and 10%, respectively, compared to that of composite at 0 cycles. Tensile properties and the coefficient of linear expansion of PLA and jute fiber remained almost unchanged after thermal cycling tests. From observation of a fracture surface, the length of fiber pull out in the fracture surface of composite at 103 cycles was longer than that of composite at 0 cycles. Therefore, tensile properties of the composite during thermal cycling were decreased, probably because of the decrease of interfacial adhesion between the fiber and resin. PMID:28773694

Genetic ablation or chemical inhibition of phosphatidylcholine transfer protein attenuates diet-induced hepatic glucose production.

PubMed

Shishova, Ekaterina Y; Stoll, Janis M; Ersoy, Baran A; Shrestha, Sudeep; Scapa, Erez F; Li, Yingxia; Niepel, Michele W; Su, Ya; Jelicks, Linda A; Stahl, Gregory L; Glicksman, Marcie A; Gutierrez-Juarez, Roger; Cuny, Gregory D; Cohen, David E

2011-08-01

Phosphatidylcholine transfer protein (PC-TP, synonym StARD2) is a highly specific intracellular lipid binding protein that is enriched in liver. Coding region polymorphisms in both humans and mice appear to confer protection against measures of insulin resistance. The current study was designed to test the hypotheses that Pctp-/- mice are protected against diet-induced increases in hepatic glucose production and that small molecule inhibition of PC-TP recapitulates this phenotype. Pctp-/- and wildtype mice were subjected to high-fat feeding and rates of hepatic glucose production and glucose clearance were quantified by hyperinsulinemic euglycemic clamp studies and pyruvate tolerance tests. These studies revealed that high-fat diet-induced increases in hepatic glucose production were markedly attenuated in Pctp-/- mice. Small molecule inhibitors of PC-TP were synthesized and their potencies, as well as mechanism of inhibition, were characterized in vitro. An optimized inhibitor was administered to high-fat-fed mice and used to explore effects on insulin signaling in cell culture systems. Small molecule inhibitors bound PC-TP, displaced phosphatidylcholines from the lipid binding site, and increased the thermal stability of the protein. Administration of the optimized inhibitor to wildtype mice attenuated hepatic glucose production associated with high-fat feeding, but had no activity in Pctp-/- mice. Indicative of a mechanism for reducing glucose intolerance that is distinct from commonly utilized insulin-sensitizing agents, the inhibitor promoted insulin-independent phosphorylation of key insulin signaling molecules. These findings suggest PC-TP inhibition as a novel therapeutic strategy in the management of hepatic insulin resistance. Copyright © 2011 American Association for the Study of Liver Diseases.

Thermal Testing and Model Correlation of the Magnetospheric Multiscale (MMS) Observatories

NASA Technical Reports Server (NTRS)

Kim, Jong S.; Teti, Nicholas M.

2015-01-01

International Conference on Envronmental Systems (ICES), Seattle WA NCTS 20964-15. The Magnetospheric Multiscale (MMS) mission is a Solar Terrestrial Probes mission comprising four identically instrumented spacecraft that will use Earths magnetosphere as a laboratory tostudy the microphysics of three fundamental plasma processes: magnetic reconnection, energetic particle acceleration, and turbulence. This paper presents the complete thermal balance (TB) test performed on the first of four observatories to go through thermal vacuum (TV) and the minibalance testing that was performed on the subsequent observatories to provide a comparison of all four. The TV and TB tests were conducted in a thermal vacuum chamber at the Naval Research Laboratory (NRL) in Washington, D.C. with the vacuum level higher than 1.3 x 10-4 Pa (10-6 torr)and the surrounding temperature achieving -180 C. Three TB test cases were performed that included hot operational science, cold operational science and a cold survival case. In addition to the three balance cases a two hour eclipse and a four hour eclipse simulation was performed during the TV test to provide additional transient data points that represent the orbit in eclipse (or Earth's shadow) The goal was to perform testing such that the flight orbital environments could be simulated as closely as possible. A thermal model correlation between the thermal analysis and the test results was completed. Over 400 1-Wire temperature sensors, 200 thermocouples and 125 flight thermistor temperature sensors recorded data during TV and TB testing. These temperatureversus time profiles and their agreements with the analytical results obtained using Thermal Desktop and SINDAFLUINT are discussed. The model correlation for the thermal mathematical model (TMM) is conducted based on the numerical analysis results and the test data. The philosophy of model correlation was to correlate the model to within 3 C of the test data using the standard deviation and mean deviation error calculation. Individual temperature error goal is to be within 5 C and the heater power goal is to be within 5 of test data. The results of the model correlation are discussed and the effect of some material and interface parameters on the temperature profiles are presented.

Thermal Testing and Model Correlation of the Magnetospheric Multiscale (MMS) Observatories

NASA Technical Reports Server (NTRS)

Kim, Jong S.; Teti, Nicholas M.

2015-01-01

The Magnetospheric Multiscale (MMS) mission is a Solar Terrestrial Probes mission comprising four identically instrumented spacecraft that will use Earth's magnetosphere as a laboratory to study the microphysics of three fundamental plasma processes: magnetic reconnection, energetic particle acceleration, and turbulence. This paper presents the complete thermal balance (TB) test performed on the first of four observatories to go through thermal vacuum (TV) and the minibalance testing that was performed on the subsequent observatories to provide a comparison of all four. The TV and TB tests were conducted in a thermal vacuum chamber at the Naval Research Laboratory (NRL) in Washington, D.C. with the vacuum level higher than 1.3 x 10 (sup -4) pascals (10 (sup -6) torr) and the surrounding temperature achieving -180 degrees Centigrade. Three TB test cases were performed that included hot operational science, cold operational science and a cold survival case. In addition to the three balance cases a two hour eclipse and a four hour eclipse simulation was performed during the TV test to provide additional transient data points that represent the orbit in eclipse (or Earth's shadow) The goal was to perform testing such that the flight orbital environments could be simulated as closely as possible. A thermal model correlation between the thermal analysis and the test results was completed. Over 400 1-Wire temperature sensors, 200 thermocouples and 125 flight thermistor temperature sensors recorded data during TV and TB testing. These temperature versus time profiles and their agreements with the analytical results obtained using Thermal Desktop and SINDA/FLUINT are discussed. The model correlation for the thermal mathematical model (TMM) is conducted based on the numerical analysis results and the test data. The philosophy of model correlation was to correlate the model to within 3 degrees Centigrade of the test data using the standard deviation and mean deviation error calculation. Individual temperature error goal is to be within 5 degrees Centigrade and the heater power goal is to be within 5 percent of test data. The results of the model correlation are discussed and the effect of some material and interface parameters on the temperature profiles are presented.

JT9D ceramic outer air seal system refinement program

NASA Technical Reports Server (NTRS)

Gaffin, W. O.

1982-01-01

The abradability and durability characteristics of the plasma sprayed system were improved by refinement and optimization of the plasma spray process and the metal substrate design. The acceptability of the final seal system for engine testing was demonstrated by an extensive rig test program which included thermal shock tolerance, thermal gradient, thermal cycle, erosion, and abradability tests. An interim seal system design was also subjected to 2500 endurance test cycles in a JT9D-7 engine.

Thermal Design, Test and Analysis of PharmaSat, a Small Class D Spacecraft with a Biological Experiment

NASA Technical Reports Server (NTRS)

Diaz-Aguado, Millan F.; VanOutryve, Cassandra; Ghassemiah, Shakib; Beasley, Christopher; Schooley, Aaron

2009-01-01

Small spacecraft have been increasing in popularity because of their low cost, short turnaround and relative efficiency. In the past, small spacecraft have been primarily used for technology demonstrations, but advances in technology have made the miniaturization of space science possible [1,2]. PharmaSat is a low cost, small three cube size spacecraft, with a biological experiment on board, built at NASA (National Aeronautics and Space Administration) Ames Research Center. The thermal design of small spacecraft presents challenges as their smaller surface areas translate into power and thermal constraints. The spacecraft is thermally designed to run colder in the Low Earth Orbit space environment, and heated to reach the temperatures required by the science payload. The limited power supply obtained from the solar panels on small surfaces creates a constraint in the power used to heat the payload to required temperatures. The pressurized payload is isolated with low thermally conductance paths from the large ambient temperature changes. The thermal design consists of different optical properties of section surfaces, Multi Layer Insulation (MLI), low thermal conductance materials, flexible heaters and thermal spreaders. The payload temperature is controlled with temperature sensors and flexible heaters. Finite Element Analysis (FEA) and testing were used to aid the thermal design of the spacecraft. Various tests were conducted to verify the thermal design. An infrared imager was used on the electronic boards to find large heat sources and eliminate any possible temperature runaways. The spacecraft was tested in a thermal vacuum chamber to optimize the thermal and power analysis and qualify the thermal design of the spacecraft for the mission.

Formation and characterization of iron-binding phosphorylated human-like collagen as a potential iron supplement.

PubMed

Deng, Jianjun; Chen, Fei; Fan, Daidi; Zhu, Chenhui; Ma, Xiaoxuan; Xue, Wenjiao

2013-10-01

Iron incorporated into food can induce precipitation and unwanted interaction with other components in food. Iron-binding proteins represent a possibility to avoid these problems and other side effects, as the iron is protected. However, there are several technical problems associated with protein-iron complex formation. In this paper, the iron-binding phosphorylated human-like collagen (Fe-G6P-HLC) was prepared under physiological conditions through phosphorylated modification. One molecule of Fe-G6P-HLC possesses about 24 atoms of Fe. Spectroscopy analysis, differential scanning calorimetry (DSC) and equilibrium dialysis techniques were employed to investigate the characteristics of the Fe-G6P-HLC. The binding sites (nb) and apparent association constant (Kapp) between iron and phosphorylated HLC were measured at nb=23.7 and log Kapp=4.57, respectively. The amount of iron (Fe(2+) sulfate) binding to phosphorylated HLC was found to be a function of pH and phosphate content. In addition, the solubility and thermal stability of HLC were not significantly affected. The results should facilitate the utilization of HLC as a bioactive iron supplement in the food and medical industry and provide an important theoretical evidence for the application of HLC chelates. © 2013.

Multiplexed target detection using DNA-binding dye chemistry in droplet digital PCR.

PubMed

McDermott, Geoffrey P; Do, Duc; Litterst, Claudia M; Maar, Dianna; Hindson, Christopher M; Steenblock, Erin R; Legler, Tina C; Jouvenot, Yann; Marrs, Samuel H; Bemis, Adam; Shah, Pallavi; Wong, Josephine; Wang, Shenglong; Sally, David; Javier, Leanne; Dinio, Theresa; Han, Chunxiao; Brackbill, Timothy P; Hodges, Shawn P; Ling, Yunfeng; Klitgord, Niels; Carman, George J; Berman, Jennifer R; Koehler, Ryan T; Hiddessen, Amy L; Walse, Pramod; Bousse, Luc; Tzonev, Svilen; Hefner, Eli; Hindson, Benjamin J; Cauly, Thomas H; Hamby, Keith; Patel, Viresh P; Regan, John F; Wyatt, Paul W; Karlin-Neumann, George A; Stumbo, David P; Lowe, Adam J

2013-12-03

Two years ago, we described the first droplet digital PCR (ddPCR) system aimed at empowering all researchers with a tool that removes the substantial uncertainties associated with using the analogue standard, quantitative real-time PCR (qPCR). This system enabled TaqMan hydrolysis probe-based assays for the absolute quantification of nucleic acids. Due to significant advancements in droplet chemistry and buoyed by the multiple benefits associated with dye-based target detection, we have created a "second generation" ddPCR system compatible with both TaqMan-probe and DNA-binding dye detection chemistries. Herein, we describe the operating characteristics of DNA-binding dye based ddPCR and offer a side-by-side comparison to TaqMan probe detection. By partitioning each sample prior to thermal cycling, we demonstrate that it is now possible to use a DNA-binding dye for the quantification of multiple target species from a single reaction. The increased resolution associated with partitioning also made it possible to visualize and account for signals arising from nonspecific amplification products. We expect that the ability to combine the precision of ddPCR with both DNA-binding dye and TaqMan probe detection chemistries will further enable the research community to answer complex and diverse genetic questions.

Impact of the alkyl chain length on binding of imidazolium-based ionic liquids to bovine serum albumin

NASA Astrophysics Data System (ADS)

Zhang, Mengyue; Wang, Ying; Zhang, Hongmei; Cao, Jian; Fei, Zhenghao; Wang, Yanqing

2018-05-01

The effects of six imidazolium-based ionic liquids (ILs) with different alkyl chain length ([CnMim]Cl, n = 2, 4, 6, 8, 10, 12) on the structure and functions of bovine serum albumin (BSA) were studied by multi-spectral methods and molecular docking. ILs with the longer alkyl chain length have the stronger binding interaction with BSA and the greater conformational damage to protein. The effects of ILs on the functional properties of BSA were further studied by the determination of non-enzyme esterase activity, β-fibrosis and other properties of BSA. The thermal stability of BSA was reduced, the rate of the formation of beta sheet structures of BSA was lowered, and the esterase-like activity of BSA were decreased with the increase of ILs concentration. Simultaneous molecular modeling technique revealed the favorable binding sites of ILs on protein. The hydrophobic force and polar interactions were the mainly binding forces of them. The calculated results are in a good agreement with the spectroscopic experiments. These studies on the impact of the alkyl chain length on binding of imidazolium-based ionic liquids to BSA are of great significance for understanding and developing the application of ionic liquid in life and physiological system.

Structure of the human factor VIII C2 domain in complex with the 3E6 inhibitory antibody

DOE PAGES

Wuerth, Michelle E.; Cragerud, Rebecca K.; Spiegel, P. Clint

2015-11-24

Blood coagulation factor VIII is a glycoprotein cofactor that is essential for the intrinsic pathway of the blood coagulation cascade. Inhibitory antibodies arise either spontaneously or in response to therapeutic infusion of functional factor VIII into hemophilia A patients, many of which are specific to the factor VIII C2 domain. The immune response is largely parsed into “classical” and “non-classical” inhibitory antibodies, which bind to opposing faces cooperatively. In this study, the 2.61 Å resolution structure of the C2 domain in complex with the antigen-binding fragment of the 3E6 classical inhibitory antibody is reported. The binding interface is largely conservedmore » when aligned with the previously determined structure of the C2 domain in complex with two antibodies simultaneously. Further inspection of the B factors for the C2 domain in various X-ray crystal structures indicates that 3E6 antibody binding decreases the thermal motion behavior of surface loops in the C2 domain on the opposing face, thereby suggesting that cooperative antibody binding is a dynamic effect. Furthermore, understanding the structural nature of the immune response to factor VIII following hemophilia A treatment will help lead to the development of better therapeutic reagents.« less

Integrated photovoltaic-thermal solar energy conversion systems

NASA Technical Reports Server (NTRS)

Samara, G. A.

1975-01-01

A combined photovoltaic/thermal collector has been built and is now being tested. Initial tests have concentrated on evaluating the thermal efficiency of the collector before and after the silicon cells are mounted. With likely improvements in bonding between cells and receiver and in the absorptivity of the cells, thermal efficiencies greater than 50% can be expected for the combined receiver operating at 100 C.

Lessons Learned from the Wide Field Camera 3 TV1 and TV2 Thermal Vacuum Test Campaigns

NASA Technical Reports Server (NTRS)

Peabody, Hume; Stavely, Richard; Bast, William

2008-01-01

The Wide Field Camera 3 (WFC3) instrument has undergone two complete thermal vacuum tests (TV1 and TV2), during which valuable lessons were learned regarding test configuration, test execution, model capabilities, and modeling practices. The very complex thermal design of WFC3 produced a number of challenging aspects to ground testing with numerous ThermoElectric Coolers and heat pipes, not all of which were functional. Lessons learned during TV1 resulted in significant upgrades to the model capabilities and a change in the test environment approach for TV2. These upgrades proved invaluable during TV2 when pretest modeling assumptions proved to be false. Each of the lessons learned relate to one of two following broad statements: 1. Ensure the design can be tested and that the effect of non-flight like conditions is well understood, particularly with respect to non passive devices (TECs, Heat Pipes, etc) 2. Ensure that the model is sufficiently detailed and is capable of predicting off-nominal behavior and the power dissipation of any thermal devices, especially TECs This paper outlines a number of the lessons learned over these two test campaigns with respect to the thermal design, model, and test configuration and presents recommendations for future tests.

S-2 stage 1/25 scale model base region thermal environment test. Volume 1: Test results, comparison with theory and flight data

NASA Technical Reports Server (NTRS)

Sadunas, J. A.; French, E. P.; Sexton, H.

1973-01-01

A 1/25 scale model S-2 stage base region thermal environment test is presented. Analytical results are included which reflect the effect of engine operating conditions, model scale, turbo-pump exhaust gas injection on base region thermal environment. Comparisons are made between full scale flight data, model test data, and analytical results. The report is prepared in two volumes. The description of analytical predictions and comparisons with flight data are presented. Tabulation of the test data is provided.

Basic thermal-mechanical properties and thermal shock, fatigue resistance of swaged + rolled potassium doped tungsten

NASA Astrophysics Data System (ADS)

Zhang, Xiaoxin; Yan, Qingzhi; Lang, Shaoting; Xia, Min; Ge, Changchun

2014-09-01

The potassium doped tungsten (W-K) grade was achieved via swaging + rolling process. The swaged + rolled W-K alloy exhibited acceptable thermal conductivity of 159.1 W/m K and ductile-to-brittle transition temperature of about 873 K while inferior mechanical properties attributed to the coarse pores and small deformation degree. Then the thermal shock, fatigue resistance of the W-K grade were characterized by an electron beam facility. Thermal shock tests were conducted at absorbed power densities varied from 0.22 to 1.1 GW/m2 in a step of 0.22 GW/m2. The cracking threshold was in the range of 0.44-0.66 GW/m2. Furthermore, recrystallization occurred in the subsurface of the specimens tested at 0.66-1.1 GW/m2 basing on the analysis of microhardness and microstructure. Thermal fatigue tests were performed at 0.44 GW/m2 up to 1000 cycles and no cracks emerged throughout the tests. Moreover, recrystallization occurred after 1000 cycles.