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Sheet Formation (sheet + formation)
Selected AbstractsPotential implications of endogenous aldehydes in ,-amyloid misfolding, oligomerization and fibrillogenesisJOURNAL OF NEUROCHEMISTRY, Issue 5 2006Kun Chen Abstract Aldehydes are capable of inducing protein cross-linkage. An increase in aldehydes has been found in Alzheimer's disease. Formaldehyde and methylglyoxal are produced via deamination of, respectively, methylamine and aminoacetone catalyzed by semicarbazide-sensitive amine oxidase (SSAO, EC 1.4.3.6. The enzyme is located on the outer surface of the vasculature, where amyloidosis is often initiated. A high SSAO level has been identified as a risk factor for vascular disorders. Serum SSAO activity has been found to be increased in Alzheimer's patients. Malondialdehyde and 4-hydroxynonenal are derived from lipid peroxidation under oxidative stress, which is also associated with Alzheimer's disease. Aldehydes may potentially play roles in ,-amyloid aggregation related to the pathology of Alzheimer's disease. In the present study, thioflavin-T fluorometry, dynamic light scattering, circular dichroism spectroscopy and atomic force microscopy were employed to reveal the effect of endogenous aldehydes on ,-amyloid at different stages, i.e. ,-sheet formation, oligomerization and fibrillogenesis. Formaldehyde, methylglyoxal and malondialdehyde and, to a lesser extent, 4-hydroxynonenal are not only capable of enhancing the rate of formation of ,-amyloid ,-sheets, oligomers and protofibrils but also of increasing the size of the aggregates. The possible relevance to Alzheimer's disease of the effects of these aldehydes on ,-amyloid deposition is discussed. [source] Proteins can convert to ,-sheet in single crystalsPROTEIN SCIENCE, Issue 5 2004Run Zheng TC: transcarboxylase; 5S: a subunit of TC that carboxylates pyruvate; 12S: a subunit of TC that transfers carboxylate from methylmalonyl-CoA to biotin; Ni-NTA: a nickel-charged agarose resin Abstract Raman microscopy was used to follow conformational changes in single protein crystals. Crystals of native insulin and of the 5S and 12S subunits of the enzyme transcarboxylase showed a mixture of Raman marker bands signifying ,-helix, ,-sheet and nonordered secondary structure. However, by reducing the S,S bonds in the insulin crystal, or by lowering the pH for the 5S crystal, or by soaking substrates into the 12S crystal, the secondary structure in each crystal became predominantly ,-sheet. The ,-form crystals could be dissolved only with difficulty and yielded high,molecular weight protein aggregates, indicating that the ,-sheet formation involves intermolecular contacts. Although their morphology appeared unchanged, the crystals no longer diffracted X-rays. Using crystals that had not been exposed to laser light, the dye thioflavin T formed highly fluorescent complexes with the ",-transformed" crystals but not with the native crystals. [source] Hydrogen-bonding patterns in 3-alkyl-3-hydroxyindolin-2-onesACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2010Diana Becerra The molecules of racemic 3-benzoylmethyl-3-hydroxyindolin-2-one, C16H13NO3, (I), are linked by a combination of N,H...O and O,H...O hydrogen bonds into a chain of centrosymmetric edge-fused R22(10) and R44(12) rings. Five monosubstituted analogues of (I), namely racemic 3-hydroxy-3-[(4-methylbenzoyl)methyl]indolin-2-one, C17H15NO3, (II), racemic 3-[(4-fluorobenzoyl)methyl]-3-hydroxyindolin-2-one, C16H12FNO3, (III), racemic 3-[(4-chlorobenzoyl)methyl]-3-hydroxyindolin-2-one, C16H12ClNO3, (IV), racemic 3-[(4-bromobenzoyl)methyl]-3-hydroxyindolin-2-one, C16H12BrNO3, (V), and racemic 3-hydroxy-3-[(4-nitrobenzoyl)methyl]indolin-2-one, C16H12N2O5, (VI), are isomorphous in space group P. In each of compounds (II),(VI), a combination of N,H...O and O,H...O hydrogen bonds generates a chain of centrosymmetric edge-fused R22(8) and R22(10) rings, and these chains are linked into sheets by an aromatic ,,, stacking interaction. No two of the structures of (II),(VI) exhibit the same combination of weak hydrogen bonds of C,H...O and C,H...,(arene) types. The molecules of racemic 3-hydroxy-3-(2-thienylcarbonylmethyl)indolin-2-one, C14H11NO3S, (VII), form hydrogen-bonded chains very similar to those in (II),(VI), but here the sheet formation depends upon a weak ,,, stacking interaction between thienyl rings. Comparisons are drawn between the crystal structures of compounds (I),(VII) and those of some recently reported analogues having no aromatic group in the side chain. [source] Secondary structural formation of ,-synuclein amyloids as revealed by g -factor of solid-state circular dichroismBIOPOLYMERS, Issue 3 2006Xiao-Jing Lin Abstract ,-Synuclein (,-Syn) has been identified as a component of intracellular fibrillar deposits in Parkinson's disease. Though the real pathogenesis is still unknown, many investigations have revealed that conformational alteration and fibril formation of ,-Syn protein have an important role in causing the disease. In this work, we introduced the g -factor spectra of solid-state circular dichroism to estimate the secondary structure contents of ,-Syn fragments in amyloids. Fourier-transform infrared (FTIR) was also applied to confirm the structural formation. The results suggest that the central hydrophobic region is critical for ,-sheet formation and the conformational alteration is the foundation of protein abnormal aggregation. The research provides a practical approach to estimate the secondary structure contents of protein amyloids and further insight into the relevance of structural transformation and amyloidogenesis. © 2006 Wiley Periodicals, Inc. Biopolymers 83: 226,232, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Self-Assembly of Amylin(20,29) Amide-Bond Derivatives into Helical Ribbons and Peptide Nanotubes rather than FibrilsCHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2006Ronald C. Elgersma Abstract Uncontrolled aggregation of proteins or polypeptides can be detrimental for normal cellular processes in healthy organisms. Proteins or polypeptides that form these amyloid deposits differ in their primary sequence but share a common structural motif: the (anti)parallel , sheet. A well-accepted approach for interfering with ,-sheet formation is the design of soluble ,-sheet peptides to disrupt the hydrogen-bonding network; this ultimately leads to the disassembly of the aggregates or fibrils. Here, we describe the synthesis, spectroscopic analysis, and aggregation behavior, imaged by electron microscopy, of several backbone-modified amylin(20,29) derivatives. It was found that these amylin derivatives were not able to form fibrils and to some extent were able to inhibit fibril growth of native amylin(20,29). However, two of the amylin peptides were able to form large supramolecular assemblies, like helical ribbons and peptide nanotubes, in which ,-sheet formation was clearly absent. This was quite unexpected since these peptides have been designed as soluble ,-sheet breakers for disrupting the characteristic hydrogen-bonding network of (anti)parallel , sheets. The increased hydrophobicity and the presence of essential amino acid side chains in the newly designed amylin(20,29) derivatives were found to be the driving force for self-assembly into helical ribbons and peptide nanotubes. This example of controlled and desired peptide aggregation may be a strong impetus for research on bionanomaterials in which special shapes and assemblies are the focus of interest. [source] | ||||||||||