173 research outputs found
T-L SPLITTINGS FROM POLARIZED ATR SPECTRA OF UNIAXIAL CRYSTALS
No full textR. P. J. Cooney, C. Thayer, P. C. Li, and J. P. Devlin, J. Chem. Phys. 51, 302 (1969).""Author Institution: Chemistry Department, Oklahoma State University; Department of Chemistry, Oregon State UniversityOriented films of the trigonal alkali metal nitrates, which behave effectively as single crystals, can be grown in optical contact with silicon and Irtran 6 atr elements from the corresponding pure melts. Contrary to earlier spectra from such crystals are not strongly influenced by crystal distortion at the interface. Rather the unusual experimental curves, typified by a nearly complete lack of TE and TM band overlap for the mode of (II), have been found to be predictable using optical parameters generated from a damped oscillator model. Substitution of the empirically calibrated optical constants into Fresnel’s equations for the case in point (unique crystal axis perpendicular to the sample-element interface) yields nearly quantitative agreement with the experimental curves
The quaternary organization and dynamics of the molecular chaperone HSP26 are thermally regulated
No full textThe function of ScHSP26 is thermally controlled: the heat shock that causes the destabilization of target proteins leads to its activation as a molecular chaperone. We investigate the structural and dynamical properties of ScHSP26 oligomers through a combination of multiangle light scattering, fluorescence spectroscopy, NMR spectroscopy, and mass spectrometry. We show that ScHSP26 exists as a heterogeneous oligomeric ensemble at room temperature. At heat-shock temperatures, two shifts in equilibria are observed: toward dissociation and to larger oligomers. We examine the quaternary dynamics of these oligomers by investigating the rate of exchange of subunits between them and find that this not only increases with temperature but proceeds via two separate processes. This is consistent with a conformational change of the oligomers at elevated temperatures which regulates the disassembly rates of this thermally activated protein.Justin L.P. Benesch, J. Andrew Aquilina, Andrew J. Baldwin, Agata Rekas, Florian Stengel, Robyn A. Lindner, Eman Basha, Glyn L. Devlin, Joseph Horwitz, Elizabeth Vierling, John A. Carver, and Carol V. Robinsonhttp://www.cell.com/chemistry-biology/hom
The interaction of alphaB-crystallin with mature alpha-synuclein amyloid fibrils inhibits their elongation
No full textαB-Crystallin is a small heat-shock protein (sHsp) that is colocalized with α-synuclein (αSyn) in Lewy bodies—the pathological hallmarks of Parkinson's disease—and is an inhibitor of αSyn amyloid fibril formation in an ATP-independent manner in vitro. We have investigated the mechanism underlying the inhibitory action of sHsps, and here we establish, by means of a variety of biophysical techniques including immunogold labeling and nuclear magnetic resonance spectroscopy, that αB-crystallin interacts with αSyn, binding along the length of mature amyloid fibrils. By measurement of seeded fibril elongation kinetics, both in solution and on a surface using a quartz crystal microbalance, this binding is shown to strongly inhibit further growth of the fibrils. The binding is also demonstrated to shift the monomer-fibril equilibrium in favor of dissociation. We believe that this mechanism, by which a sHsp interacts with mature amyloid fibrils, could represent an additional and potentially generic means by which at least some chaperones protect against amyloid aggregation and limit the onset of misfolding diseases.Christopher A. Waudby, Tuomas P.J. Knowles, Glyn L. Devlin, Jeremy N. Skepper, Heath Ecroyd, John A. Carver, Mark E. Welland, John Christodoulou, Christopher M. Dobson and Sarah Meeha
Native disulphide-linked dimers facilitate amyloid fibril formation by bovine milk alpha(S2)-casein
No full textData source: Supplementary information, https://doi.org/10.1016/j.bpc.2020.106530Bovine milk α(S2)-casein, an intrinsically disordered protein, readily forms amyloid fibrils in vitro and is implicated in the formation of amyloid fibril deposits in mammary tissue. Its two cysteine residues participate in the formation of either intra- or intermolecular disulphide bonds, generating monomer and dimer species. X-ray solution scattering measurements indicated that both forms of the protein adopt large, spherical oligomers at 20 °C. Upon incubation at 37 °C, the disulphide-linked dimer showed a significantly greater propensity to form amyloid fibrils than its monomeric counterpart. Thioflavin T fluorescence, circular dichroism and infrared spectra were consistent with one or both of the dimer isomers (in a parallel or antiparallel arrangement) being predisposed toward an ordered, amyloid-like structure. Limited proteolysis experiments indicated that the region from Ala⁸¹ to Lys¹¹³ is incorporated into the fibril core, implying that this region, which is predicted by several algorithms to be amyloidogenic, initiates fibril formation of α(S2)-casein. The partial conservation of the cysteine motif and the frequent occurrence of disulphide-linked dimers in mammalian milks despite the associated risk of mammary amyloidosis, suggest that the dimeric conformation of α(S2)-casein is a functional, yet amyloidogenic, structure.David C. Thorn, Elmira Bahraminejad, Aidan B. Grosas, Tomas Koudelka, Peter Hoffmann, Jitendra P. Mata, Glyn L. Devlin, Margaret Sunde, Heath Ecroyd, Carl Holt, John A. Carve
ON THE CIRCULAR DICHROISM MEASUREMENTS IN THE 800-600 cm-1 RANGE
No full text P. L. Polavarapu, Appl. Spectrosc, 38, 26 (1984). P. Devlin and P.J. Stephens, Appl. Spectrose. 41, 1142 (1987).Author Institution: Department of Chemistry, Vanderbilt UniversityCircular dichroism measurements in the range were shown to be feasible about five years Some of these earlier results were 'misinterpreted' These differences will be clarified and new results will be presented
RNAseq analysis of fast skeletal muscle in restriction-fed transgenic coho salmon (Oncorhynchus kisutch) : an experimental model uncoupling the growth hormone and nutritional signals regulating growth
No full textBackground Coho salmon (Oncorhynchus kisutch) transgenic for growth hormone (Gh) express Gh in multiple tissues which results in increased appetite and continuous high growth with satiation feeding. Restricting Gh-transgenics to the same lower ration (TR) as wild-type fish (WT) results in similar growth, but with the recruitment of fewer, larger diameter, muscle skeletal fibres to reach a given body size. In order to better understand the genetic mechanisms behind these different patterns of muscle growth and to investigate how the decoupling of Gh and nutritional signals affects gene regulation we used RNA-seq to compare the fast skeletal muscle transcriptome in TR and WT coho salmon. Results Illumina sequencing of individually barcoded libraries from 6 WT and 6 TR coho salmon yielded 704,550,985 paired end reads which were used to construct 323,115 contigs containing 19,093 unique genes of which >10,000 contained >90 % of the coding sequence. Transcripts coding for 31 genes required for myoblast fusion were identified with 22 significantly downregulated in TR relative to WT fish, including 10 (vaspa, cdh15, graf1, crk, crkl, dock1, trio, plekho1a, cdc42a and dock5) associated with signaling through the cell surface protein cadherin. Nineteen out of 44 (43 %) translation initiation factors and 14 of 47 (30 %) protein chaperones were upregulated in TR relative to WT fish. Conclusions TR coho salmon showed increased growth hormone transcripts and gene expression associated with protein synthesis and folding than WT fish even though net rates of protein accretion were similar. The uncoupling of Gh and amino acid signals likely results in additional costs of transcription associated with protein turnover in TR fish. The predicted reduction in the ionic costs of homeostasis in TR fish associated with increased fibre size were shown to involve multiple pathways regulating myotube fusion, particularly cadherin signaling.Peer reviewe
Protein Particulates: Another Generic Form of Protein Aggregation?
No full textAbstractProtein aggregation is a problem with a multitude of consequences, ranging from affecting protein expression to its implication in many diseases. Of recent interest is the specific form of aggregation leading to the formation of amyloid fibrils, structures associated with diseases such as Alzheimer’s disease. The ability to form amyloid fibrils is now regarded as a property generic to all polypeptide chains. Here we show that around the isoelectric point a different generic form of aggregation can also occur by studying seven widely different, nonrelated proteins that are also all known to form amyloid fibrils. Under these conditions gels consisting of relatively monodisperse spherical particulates are formed. Although these gels have been described before for β-lactoglobulin, our results suggest that the formation of particulates in the regime where charge on the molecules is minimal is a common property of all proteins. Because the proteins used here also form amyloid fibrils, we further propose that protein misfolding into clearly defined aggregates is a generic process whose outcome depends solely on the general properties of the state the protein is in when aggregation occurs, rather than the specific amino acid sequence. Thus under conditions of high net charge, amyloid fibrils form, whereas under conditions of low net charge, particulates form. This observation furthermore suggests that the rules of soft matter physics apply to these systems
Hundreds of variants clustered in genomic loci and biological pathways affect human height
No full textMost common human traits and diseases have a polygenic pattern of inheritance: DNA sequence variants at many genetic loci influence the phenotype. Genome-wide association (GWA) studies have identified more than 600 variants associated with human traits(1), but these typically explain small fractions of phenotypic variation, raising questions about the use of further studies. Here, using 183,727 individuals, we show that hundreds of genetic variants, in at least 180 loci, influence adult height, a highly heritable and classic polygenic trait(2,3). The large number of loci reveals patterns with important implications for genetic studies of common human diseases and traits. First, the 180 loci are not random, but instead are enriched for genes that are connected in biological pathways (P = 0.016) and that underlie skeletal growth defects (P<0.001). Second, the likely causal gene is often located near the most strongly associated variant: in 13 of 21 loci containing a known skeletal growth gene, that gene was closest to the associated variant. Third, at least 19 loci have multiple independently associated variants, suggesting that allelic heterogeneity is a frequent feature of polygenic traits, that comprehensive explorations of already-discovered loci should discover additional variants and that an appreciable fraction of associated loci may have been identified. Fourth, associated variants are enriched for likely functional effects on genes, being over-represented among variants that alter amino-acid structure of proteins and expression levels of nearby genes. Our data explain approximately 10% of the phenotypic variation in height, and we estimate that unidentified common variants of similar effect sizes would increase this figure to approximately 16% of phenotypic variation (approximately 20% of heritable variation). Although additional approaches are needed to dissect the genetic architecture of polygenic human traits fully, our findings indicate that GWA studies can identify large numbers of loci that implicate biologically relevant genes and pathways
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