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51.
A core-shell structure was found in AM SURE™ resin, in which most amino groups were located at the skin layer. The AM SURE™ resin revealed better synthetic efficiency, compared to the noncore-shell type resin in the synthesis of the fragment 65-74 of acyl carrier protein, the fragment 27-35 of HIV (human immunodeficiency virus) fusion inhibitor (T-20) and the Jung-Redemann 10-mer. 相似文献
52.
Functional-based screening of crude β-galactosidase activities from 42 yeast strains resulted in the selection of a single
enzyme of potential interest as a digestive supplement. β-Galactosidase produced by Kluyveromyces marxianus DSM5418 was purified to homogeneity by a combination of gel filtration, ion-exchange, and hydroxylapatite chromatographies.
The denatured (123 kDa) and native molecular masses (251 kDa) suggest that the enzyme is a homodimer. The optimum pH and temperature
of the purified enzyme were 6.8 and 37°C, respectively. The unpurified β-galactosidase in particular displayed a high level
of stability when exposed to simulated intestinal conditions in vitro for 4 h. Matrix-assisted laser desorption ionization
mass sectrometry analysis revealed that the enzyme's trypsin-generated peptide mass fingerprint shares several peptide fragment
hits with β-galactosidases from Kluyveromyces lactis. This confirms the enzyme's identity and indicates that significant sequence homology exists between these enzymes. 相似文献
53.
We present a series of conformational search calculations on the aggregation of short peptide fragments that form fibrils similar to those seen in many protein mis-folding diseases. The proteins were represented by a face-centered cubic lattice model with the conformational energies calculated using the Miyazawa-Jernigan potential. The searches were performed using algorithms based on the Metropolis Monte Carlo method, including simulated annealing and replica exchange. We also present the results of searches using the tabu search method, an algorithm that has been used for many optimization problems, but has rarely been used in protein conformational searches. The replica exchange algorithm consistently found more stable structures then the other algorithms, and was particularly effective for the octamers and larger systems. 相似文献
54.
We report the synthesis of Fmoc protected single amino acid chelates (SAAC) and their metal complexes. The modified amino acids are suitable for solid-phase peptide synthesis. The use of 4-hydroxymethylbenzoic acid AM (HMBA-AM) resin allows the nucleophilic cleavage of the peptide-metal complexes from the resin without decomplexation. 相似文献
55.
磷酰化肽链中电子转移的ESR研究 总被引:1,自引:0,他引:1
当前生命科学正以前所未有的速度向前发展,从对核酸的深入研究开始过渡到对蛋白质结构与功能的注意,尤其是近年来基因调控研究的重大进展是发现非组蛋白具有高度的磷酸化的特性[1],研究证明,核内蛋白磷酸化和去磷酸化则是基因表达调控的重要方式之一[2,3],它是酶活性调节、基因表达调控、细胞转化恶变的关键环节;同时在解决肿瘤的发生和治疗、病毒的感染和诊治、辐射损伤、抗衰老等实际问题上有突出意义,如1992年Krebus和Fisher因为在蛋白的可逆磷酸化方面的突出贡献而获得诺贝尔生理和医学奖.而电子转移是一切化学变化的基础… 相似文献
56.
57.
The conformational change of the 39-43 residues of the amyloid beta-peptide (Abeta) toward a beta-sheet enriched state promotes self-aggregation of the peptide molecules and constitutes the major peptide component of the amyloid plaques in Alzheimer patients. The crucial question behind the self-aggregation of Abeta is related to the different pathways the peptide may take after cleavage from the amyloid precursor proteins at cellular membranes. This work is aiming at determining the conformation of the Abeta (1-40) adsorbed on hydrophobic Teflon and hydrophilic silica particles, as model sorbent surfaces mimicking the apolar transmembrane environment and the polar, charged membrane surface, respectively. The mechanism by which the Abeta interacts with solid surfaces strongly depends on the hydrophobic/hydrophilic character of the particles. Hydrophobic and electrostatic interactions contribute differently in each case, causing a completely different conformational change of the adsorbed molecules on the two surfaces. When hydrophobic interactions between the peptide and the sorbent prevail, the adsorbed Abeta (1-40) mainly adopts an alpha-helix conformation due to H-bonding in the apolar part of the peptide that is oriented towards the surface. On the other hand, when the peptide adsorbs by electrostatic interactions beta-sheet formation is promoted due to intermolecular association between the apolar parts of the adsorbed peptide. Irrespective of the characteristics of the solid sorbent, crowding the surface results in intermolecular association between adsorbed molecules leading to a strong aggregation tendency of the Abeta (1-40). [Diagram: see text] CD spectra of Abeta (1-40) at pH 7: A) in solution ([Abeta]=0.2 mg.ml(-1)) freshly prepared (line) and after overnight incubation (symbols);B) on Teflon (Gamma=0.5 mg.m(-2)). 相似文献
58.
Enduracidin and ramoplanin belong to the large family of cyclodepsipeptide antibiotics, highly effective against Gram-positive bacteria. The primary and 3D solution structure of ramoplanin is already well known, and the primary structure of enduracidin has been determined by a combination of chemical and NMR spectroscopic methods. Both antibiotics share a similar peptide core of 17 amino acids and differ mainly in the length of the acyl chain and the presence of two D-mannose moieties in ramoplanin. Based on the high sequence homology with ramoplanin, the structure in solution of enduracidin is modeled as a cyclic peptide. The tertiary structure thus obtained was refined through molecular dynamics (MD) simulation, in which the interatomic NOE-derived distance restraints were imposed. MD simulations yielded a family of representative 3D structures (RMSD = 0.89), which highlighted a backbone geometry similar to that of ramoplanin in its beta-hairpin arrangement. In contrast, enduracidin displays a different arrangement of the side-chain and of the residues forming the hydrophobic core. 相似文献
59.
60.
Antonella Leggio 《Tetrahedron》2007,63(34):8164-8173
A highly efficient and practical synthesis of peptides in solution phase has been developed. The procedure is based on the use of p-nitrobenzenesulfonyl (nosyl) group for the protection of the amino function of α-amino acids. Every step of the procedure, protection of the amino function by the nosyl group, formation of the peptide bond, and removal of the sulfonamide group, is characterized by high yields and excellent purity of the final products. The described strategy allows the preparation of short peptide sequences keeping the chiral integrity of amino acid precursors. Compatibility of nosyl group with the side-chain protecting groups used in Fmoc-based strategy is demonstrated. The method here presented is an alternative strategy that could provide advantages for future peptide synthesis. 相似文献