Influence of supramolecular forces on the linear viscoelasticity of gluten

Stress relaxation behavior of hydrated gluten networks was investigated by means of rheometry combined with μ-computed tomography (μ-CT) imaging. Stress relaxation behavior was followed over a wide temperature range (0–70 °C). Modulation of intermolecular bonds was achieved with urea or ascorbic acid in an effort to elucidate the presiding intermolecular interactions over gluten network relaxation. Master curves of viscoelasticity were constructed, and relaxation spectra were computed revealing three relaxation regimes for all samples. Relaxation commences with a well-defined short-time regime where Rouse-like modes dominate, followed by a power law region displaying continuous relaxation concluding in a terminal zone. In the latter zone, poroelastic relaxation due to water migration in the nanoporous structure of the network also contributes to the stress relief in the material. Hydrogen bonding between adjacent protein chains was identified as the determinant force that influences the relaxation of the networks. Changes in intermolecular interactions also resulted in changes in microstructure of the material that was also linked to the relaxation behavior of the networks

On the behaviour, mechanistic modelling and interaction of biochar and crop fertilizers in aqueous solutions

AbstractAlthough the benefits of applying biochar for the purposes of soil conditioning and crop productivity enhancement have been demonstrated, relatively few studies have elaborated on its causal mechanisms, especially on the biochar–fertilizer interaction. Thus, in the present study, the ex-situ adsorptive potential of base activated biochar (BAB) towards plant nutrient immobilization and removal from aqueous solutions was investigated. Napier grass (Pennisetum purpureum) was utilized as the precursor to prepare slow vacuum pyrolysed char and its affinity towards adsorption of urea was examined at various process conditions. Low sorption temperatures, moderate agitation speeds and high initial concentration were seen to favour greater urea uptake by BAB. The sorption was exothermic, physical, spontaneous and had a pseudo-second order kinetic fit. Both surface and intra-particle diffusion governed the removal and immobilization of urea. Furthermore, process mass transfer was limited by film diffusion of urea to the external surface of the BAB. Equilibrium studies suggested that Dubinin–Radushkevich is the most appropriate model to describe the urea-BAB behaviour with maximum uptake, estimated to be 1115 mg⋅g−1. Through such ex-situ analysis, it could be possible to have prior knowledge, quantification and differentiation of the potential of chars manufactured from various feedstocks. This could then be used as an effective screening step in designing appropriate biochar–fertilizer systems for soil conditioning and help reduce the time and effort spent otherwise in long-term field studies

Molecular mechanisms of the non-coenzyme action of thiamin in brain. Biochemical, structural and pathway analysis

Thiamin (vitamin B1) is a pharmacological agent boosting central metabolism through the action of the coenzyme thiamin diphosphate (ThDP). However, positive effects, including improved cognition, of high thiamin doses in neurodegeneration may be observed without increased ThDP or ThDPdependent enzymes in brain. Here, we determine protein partners and metabolic pathways where thiamin acts beyond its coenzyme role. Malate dehydrogenase, glutamate dehydrogenase and pyridoxal kinase were identified as abundant proteins binding to thiamin- or thiazolium-modified sorbents. Kinetic studies, supported by structural analysis, revealed allosteric regulation of these proteins by thiamin and/or its derivatives. Thiamin triphosphate and adenylated thiamin triphosphate activate glutamate dehydrogenase. Thiamin and ThDP regulate malate dehydrogenase isoforms and pyridoxal kinase. Thiamin regulation of enzymes related to malate-aspartate shuttle may impact on malate/citrate exchange, responsible for exporting acetyl residues from mitochondria. Indeed, bioinformatic analyses found an association between thiamin- and thiazolium-binding proteins and the term acetylation. Our interdisciplinary study shows that thiamin is not only a coenzyme for acetyl-CoA production, but also an allosteric regulator of acetyl-CoA metabolism including regulatory acetylation of proteins and acetylcholine biosynthesis. Moreover, thiamin action in neurodegeneration may also involve neurodegeneration-related 14-3-3, DJ-1 and β-amyloid precursor proteins identified among the thiamin- and/or thiazolium-binding proteins

Insight into the mechanism of galactokinase: role of a critical glutamate residue and helix/coil transitions

Galactokinase, the enzyme which catalyses the first committed step in the Leloir pathway, has attracted interest due to its potential as a biocatalyst and as a possible drug target in the treatment of type I galactosemia. The mechanism of the enzyme is not fully elucidated. Molecular dynamics (MD) simulations of galactokinase with the active site residues Arg-37 and Asp-186 altered predicted that two regions (residues 174-179 and 231-240) had different dynamics as a consequence. Interestingly, the same two regions were also affected by alterations in Arg-105, Glu-174 and Arg- 228. These three residues were identified as important in catalysis in previous computational studies on human galactokinase. Alteration of Arg-105 to methionine resulted in a modest reduction in activity with little change in stability. When Arg-228 was changed to methionine, the enzyme’s interaction with both ATP and galactose was affected. This variant was significantly less stable than the wild-type protein. Changing Glu-174 to glutamine (but not to aspartate) resulted in no detectable activity and a less stable enzyme. Overall, these combined in silico and in vitro studies demonstrate the importance of a negative charge at position 174 and highlight the critical role of the dynamics in to key regions of the protein. We postulate that these regions may be critical for mediating the enzyme’s structure and function.

USSR Space Life Sciences Digest, issue 31

This is the thirty first issue of NASA's Space Life Sciences Digest. It contains abstracts of 55 journal papers or book chapters published in Russian and of 5 Soviet monographs. Selected abstracts are illustrated with figures and tables from the original. The abstracts in this issue have been identified as relevant to 18 areas of space biology and medicine. These areas include: adaptation, biological rhythms, cardiovascular and respiratory systems, endocrinology, enzymology, genetics, group dynamics, habitability and environmental effects, hematology, life support systems, metabolism, microbiology, musculoskeletal system, neurophysiology, nutrition, operational medicine, psychology, radiobiology, and space biology and medicine

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 336)

This bibliography lists 111 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during April 1990. Subject coverage includes: aerospace medicine and psychology, life support systems and controlled environments, safety equipment, exobiology and extraterrestrial life, and flight crew behavior and performance

Role of the Bifunctional Aminoacyl-tRNA Synthetase EPRS in Human Disease

Aminoacyl-tRNA synthetases (AARS) are a class of enzymes that catalyze the charging of tRNAs with cognate amino acids, a critical step that contributes to the fidelity of protein synthesis. Many AARSs also possess noncanonical functions such as regulation of apoptosis, mRNA translation, and RNA splicing. Some AARSs have evolved new domains with no apparent connection to their charging functions. For example, WHEP domains were originally identified in tryptophanyl-tRNA synthetase (WRS), histidyl-tRNA synthetase (HRS), and glutamyl-prolyl-tRNA synthetase (EPRS). EPRS is a unique bifunctional AARS, found only in higher eukaryotes, and consists of glutamyl-tRNA synthetase (ERS) and prolyl-tRNA synthetase (PRS) joined by a non-catalytic linker containing three WHEP domains in humans. Two compound heterozygous point mutations within human ERS (P14R and E205G) have been identified in the genomes of two patients with type 1 diabetes and bone disease. However, the mechanism by which these mutations contribute to disease is unknown. Our goal is to determine whether the point mutations affect the canonical catalytic activity of EPRS responsible for tRNA charging or noncanonical functions. Both P14 and E205 are highly conserved residues located in the GST and catalytic domain, respectively. An ERS variant appended to 2.5 WHEP domains (ERS 2.5W) has been purified and shown to display robust tRNA binding and aminoacylation activity in vitro. The P14R and E205G single mutants display the same binding affinity for tRNAGlu as WT ERS 2.5W, suggesting that the observed defect is at the catalytic step. Whereas the ERS 2.5W P14R mutant has near wild-type (WT) aminoacylation activity, the ERS 2.5W E205G variant has a severe aminoacylation defect. Both mutations, however, lead to reduced amino acid activation. Together with a collaborator, we are currently characterizing the effect of these two mutations on cell proliferation and the integrated stress response. Taken together, this work has important implications for the understanding of AARS-related human disease mechanisms and development of new therapeutics.College of Arts & SciencesOffice of Undergraduate Research & Creative InquiryNo embargoAcademic Major: Biochemistr

Report of the 2004 Workshop on In Situ Iron Enrichment Experiments in the Eastern and Western Subarctic Pacific

Foreword 1. BACKGROUND AND OBJECTIVES (pdf, 0.1 Mb) 2. 2004 WORKSHOP SUMMARY (pdf, < 0.1 Mb) 2.1. What have we learned from the enrichment experiments? 2.2 What are the outstanding questions? 2.3 Recommendations for SEEDS-II 3. EXTENDED ABSTRACTS OF THE 2004 WORKSHOP 3.1 Synthesis of the Iron Enrichment Experiments: SEEDS and SERIES (pdf, 0.5 Mb) Iron fertilization experiment in the western subarctic Pacific (SEEDS) by Atsushi Tsuda The response of N and Si to iron enrichment in the Northeast Pacific Ocean: Results from SERIES by David Timothy, C.S. Wong, Yukihiro Nojiri, Frank A. Whitney, W. Keith Johnson and Janet Barwell-Clarke 3.2 Biological and Physiological Responses (pdf, 0.2 Mb) Zooplankton responses during SEEDS by Hiroaki Saito Phytoplankton community response to iron and temperature gradient in the NW and NE subarctic Pacific Ocean by Isao Kudo, Yoshifumi Noiri, Jun Nishioka, Hiroshi Kiyosawa and Atsushi Tsuda SERIES: Copepod grazing on diatoms by Frank A. Whitney, Moira Galbraith, Janet Barwell-Clarke and Akash Sastri The Southern Ocean Iron Enrichment Experiment: The nitrogen uptake response by William P. Cochlan and Raphael M. Kudela 3.3 Biogeochemical Responses (pdf, 0.5 Mb) What have we learned regarding iron biogeochemistry from iron enrichment experiments? by Jun Nishioka, Shigenobu Takeda and W. Keith Johnson Iron dynamics and temporal changes of iron speciation in SERIES by W. Keith Johnson, C.S. Wong, Nes Sutherland and Jun Nishioka Dissolved organic matter dynamics during SEEDS and SERIES experiments by Takeshi Yoshimura and Hiroshi Ogawa Formation of transparent exopolymer particles during the in-situ iron enrichment experiment in the western subarctic Pacific (SEEDS) by Shigenobu Takeda, Neelam Ramaiah, Ken Furuya and Takeshi Yoshimura Atmospheric measurement by Mitsuo Uematsu 3.4 Prediction from Models (pdf, 0.3 Mb) Modelling iron limitation in the North Pacific by Kenneth L. Denman and M. Angelica Peña A proposed model of the SERIES iron fertilization patch by Debby Ianson, Christoph Voelker and Kenneth L. Denman 4. LIST OF PARTICIPANTS FOR THE 2004 WORKSHOP (pdf, < 0.1 Mb) APPENDIX 1 Report of the 2000 Planning Workshop on Designing the Iron Fertilization Experiment in the Subarctic Pacific (pdf, 1 Mb) APPENDIX 2 Terms of Reference for the Advisory Panel on Iron fertilization experiment in the subarctic Pacific Ocean (pdf, < 0.1 Mb) APPENDIX 3 Historical List of Advisory Panel Members on Iron fertilization experiment in the subarctic Pacific Ocean (pdf, < 0.1 Mb) APPENDIX 4 IFEP-AP Annual Reports (pdf, 0.1 Mb) APPENDIX 5 PICES Press Articles (pdf, 0.6 Mb) (194 page document