Unfolded annealing molecular dynamics conformers for wild-type and disease-associated variants of alpha-synuclein show no propensity for beta-sheetformation

Aggregation of alpha-synuclein leads to the formation of Lewy bodies in the brains of patients affected by Parkinson's disease (PD). Native human alpha-synuclein is unfolded in solution but assumes a partial alpha-helical conformation upon transient binding to lipid membranes. Annealing Molecular Dynamics (AMD) was used to generate a diverse set of unfolded conformers of free monomeric wild-type alpha-synuclein and PD-associated mutants A30P and A53T. The AMD conformers were compared in terms of secondary structure, hydrogen bond network, solvent-accessible surface per residue, and molecular volume. The objective of these simulations was to identify structural properties near mutation sites and the non-amyloid component (NAC) region that differ between wild- type and disease-associated variants and may be associated to aggregation of alpha- synuclein. Based on experimental evidence, a hypothesis exists that aggregation involves the formation of intermolecular beta sheets. According to our results, disease-associated mutants of alpha-synuclein are no more propense to contain extended beta regions than wild-type alpha-synuclein. Moreover, extended beta structures (necessary for beta sheet formation) were not found at or around positions 30 and 53, or the NAC region in any unfolded conformer of wild-type, A30P or A53T alpha-synuclein, under the conditions of the simulations. These results do not support the hypothesis that the mutant's higher propensity to aggregation results solely from changes in amino acid sequence leading to changes in secondary structure folding propensity.

Interactive association between processing induced molecular structure changes and nutrient delivery on a molecular basis,revealed by cutting-edge vibrational biomolecular spectroscopy

Background:This study was conducted to determine protein molecular structure profiles and quantify the relationship between protein structural features and protein metabolism and bioavailability of blend pel eted products(BPP)based on co-products(canola or carinata)from processing with different proportions of pulse pea screenings and lignosulfonate chemical compound.Method:The protein molecular structures were determined using the non-invasive advanced vibrational molecular spectroscopy(ATR-FT/IR)in terms of chemical structure and biofunctional groups of amides(ⅠandⅡ),α-helix andβ-sheet.Results:The results showed that increasing the level of the co-products in BPP significantly increased the spectral intensity of the amide area and amide height.The products exhibited similar protein secondaryα-helix toβ-sheet ratio.The protein molecular structure profiles(amidesⅠandⅡ,α-helix toβ-sheet)were highly associated with protein degradation kinetics and intestinal digestion.In conclusion,the non-invasive vibrational molecular spectroscopy(ATR-FT/IR)could be used to detect inherent structural make-up characteristics in BPP.Conclusion:The molecular structural features related to protein biopolymer were highly associated with protein utilization and metabolism.

β片层阻断肽对淀粉样β蛋白聚集和毒性的抑制作用

目的比较6种(K7,L5,H100,H101,H102,H103)β片层阻断肽对淀粉样β蛋白(Aβ)纤维形成及细胞毒性作用的影响,并进行药物筛选。方法运用硫黄素T(ThT)荧光法、电子显微镜技术(EM)以及噻唑蓝(MTT)法分析6种β片层阻断肽对Aβ_(1-42)聚集和毒性的影响。结果6种β片层阻断肽对Aβ_(1-42)的聚集和纤维抑制率分别为:(0.620±0.020)%、(25.740±0.011)%、(-0.470±0.020)%、(24.790±0.010)%、(27.840±0.009)%、(14.910±0.022)%,EM和MTT结果也以H102效果最佳。结论H102对淀粉样β蛋白聚集和毒性抑制效果最佳。

Geometrical criteria for left-handed twists within protein beta-strands

Using a statistical analysis on beta-sheet structures from the Protein Data Bank, characteristic angles within beta-strands were correlated to the nature of the side chains. The twists were computed from the atomic coordinates of five consecutive amino acids’ alpha carbons from single beta-strand sequences. Conditions on the angles for twists to be mainly left-handed are given together with the frequency of occurrence for these non-standard geometrical properties within protein beta-strands. Applications in protein structure prediction and CASP challenges in particular are envisioned by making use of the probabilities of occurrence in protein structures of angle value ranges for given amino acids.

隐藏高分子界面及生物界面分子结构的和频振动光谱研究(英文)

界面的分子结构决定界面的性质.为了以优化界面的结构来改进材料的性质,原位实时地研究界面的分子结构是很重要的.近年来和频振动光谱已发展成为一个很有效及独特的手段来研究隐藏界面的分子结构,例如液/液界面、固/液界面及固/固界面等.这篇综述讨论了和频振动光谱在研究高分子界面及生物界面等复杂界面的分子结构上的应用.具体说来,本文论述了高分子表面在水里的分子结构变化,高分子及模型粘合促进剂硅烷在界面相互作用的分子机理和隐藏的高分子/高分子及高分子/金属界面的结构.另外,此文还将介绍不同二级结构的多肽及几个有代表性的蛋白分子在界面的结构.界面在诸如化学、生物、物理、材料科学及工程和纳米技术等许多领域都很重要.发展一个独特的能原位研究隐藏界面的分子结构的技术会有力地促进这些领域的研究及跨学科研究的发展.

β-环糊精-荧光包合色谱法测定氧氟哌酸、甲氟哌酸和司帕氟哌酸

采用荧光包合色谱法测定痕量的氧氟哌酸(ofloxacin,OFLX)、甲氟哌酸(pefloxacin,PFLX)和司帕氟哌酸(sparfloxacin,SPLX)。实验采用聚酰胺膜为固定相,β环糊精(βcyclodextrin,βCD)水溶液为流动相,并在流动相中直接加入EDTA消除金属离子的干扰,使混合物得到较好的分离。实验表明,氟哌酸化合物在βCD和EDTA的浓度比为0.005∶0.1(mol/L)时最为适宜。在此条件下,OFLX、PFLX、和SPLX的Rf值分别为0.74、0.60和0.25。试样斑点用薄层荧光色谱法扫描测定,激发波长为280nm(OFLX)、278nm(PFLX)和282(SPLX)。各化合物的线性范围分别0～110ng/斑点(OFLX)、0～90ng/斑点(PFLX)和0～93ng/斑点(SPLX);相对标准偏差为2.7%～6.9%;在血样和尿样中的回收率为98.2%～104.6%。

H102衍生物对β淀粉样蛋白聚集的抑制作用

目的:比较6种β片层阻断肽(H102、H102-1、H102-2、H102-3、DH102、LD-7)对β淀粉样蛋白(Aβ)聚集及纤维形成的影响,并进行药物筛选。方法:运用硫磺素T(ThT)荧光法以及傅里叶变换红外光谱法(FT-IR)分析6种β片层阻断肽对Aβ1-42聚集的影响。结果:6种β片层阻断肽及对照组维生素E对Aβ1-42聚集和纤维抑制率分别为:(14.168±0.038)%、(9.725±0.023)%、(22.535±0.013)%、(8.586±0.035)%、(5.37±0.019)%、(9.599±0.012)%、(12.736±0.026)%,提示H102-2的效果最佳;FT-IR结果也以H102-2的效果最佳。结论:H102-2对β淀粉样蛋白聚集和纤维抑制效果最佳。