Crystal and molecular structure of l-valyl-l-lysine hydrochloride

l -Valyl-l -lysine hydrochloride, C₁₁N₃O₃H₂₃ HCl, crystallizes in the monoclinic space group P2, with a = 5.438(5), b = 14.188(5), c = 9.521(5) Å, β= 95.38(2)° and Z = 2. The crystal structure, solved by direct methods, refined to R = 0.036, using full matrix least-squares method. The peptide exists in a zwitterionic form, with the N atom of the lysine side-chain protonated. The two γ-carbons of the valine side-chain have positional disorder, giving rise to two conformations, χ¹¹₁= -67.3 and 65.9°, one of which (65.9°) is sterically less favourable and has been found to be less popular amongst residues branching at β-C. The lysine side-chain has the geometry of g^? tgt, not seen in crystal structures of the dipeptides reported so far. Interestingly, χ³₂ (63.6°) of lysine side-chain has a gauche⁺ conformation unlike in most of the other structures, where it is trans. The neighbouring peptide molecules are hydrogen bonded in a head-to-tail fashion, a rather uncommon interaction in lysine peptide structures. The structure shows considerable similarity with that of l -Lys-l -Val HO in conformational angles and H-bond interactions [4].     

Comparison of assays for determination of peptide content for lyophilized thymalfasin*

Abstract: Precise determination of the peptide content in drug substance samples depends highly upon the particular peptide compound and methodology used. Four independent methods were evaluated and compared to determine which would produce the best experimental precision for analysis of thymalfasin (thymosin α‐1). Four different methods were evaluated including elemental analysis (CHN), quantitative amino acid analysis (AAA), high‐performance liquid chromatography (HPLC), and Kjeldahl. This study demonstrates that the AAA method is highly variable in one laboratory while quite precise in another laboratory. Similarly, HPLC results depended on the laboratory conducting the study with more precise values obtained under cGMP. On the contrary, the CHN method yielded highly precise [i.e. <2% coefficient of variation (CV)] values. As precise knowledge of protein content is fundamental for the compounding of final pharmaceutical product of a specific potency, the CHN analysis is recommended for peptide content determination of the drug substance thymalfasin.     

背根神经节内P物质、降钙素基因相关肽免疫阳性神经元与阴茎包皮系带感觉信息的传递

目的:探讨背根神经节(DRG)内P物质(SP)、降钙素基因相关肽(CGRP)免疫阳性神经元与阴茎包皮系带感觉信息传递之间的关系。方法:通过荧光金(FG)逆行标记对大鼠阴茎包皮系带内神经末梢的来源作追踪定位,并结合SP、CGRP免疫荧光标记法,研究大鼠DRG内FG标记阳性神经元中SP、CGRP免疫阳性神经元的形态和分布。结果:FG逆行标记结果发现,大鼠阴茎包皮系带内的神经末梢起源于第6腰髓对应的背根神经节(L6-DRG)和第1骶髓对应的背根神经节(S1-DRG)的神经元。对这些神经元分别作SP、CGRP免疫荧光标记后发现,标记细胞大小不等,分别呈深红色和深绿色,沿神经束成行排列或散在分布。FG/SP、FG/CGRP双标记阳性细胞均为中小型,其数量分别占FG逆行标记阳性细胞总数的1/3和1/2,FG/SP/CGRP三标记阳性细胞占FG逆行标记阳性细胞总数的1/5。结论:大鼠L6-DRG和S1-DRG内的SP、CGRP免疫阳性神经元可能参与阴茎包皮系带感觉信息的传递。     

人源性多肽pCM-19抗菌机制的初步研究

目的：初步分析人源性多肽pCM-19的抗菌作用机制。方法：利用荧光素掺入破损细胞膜的原理，采用流式荧光激活细胞分析（FACScan）和扫描电子显微镜分析pCM-19对靶菌膜的作用机制。结果：FACS分析法结果显示pCM-19处理后的大肠杆菌PI着染细菌比例明显高于未处理组，并且随作用时间的延长，PI着染BL-21菌比例增大，20min时达最高水平，20min以后反而降低；扫描电子显微镜观察到pCM-19处理后的大肠杆菌有明显的表面形态学的改变，如细菌体积缩小、细菌表面出现皱缩、凹陷似有孔洞形成。结论：人源性多肽pCM-19可能作用于细菌细胞壁和（或）细胞膜，通过改变其通透性而发挥杀菌作用。     

心房纤颤病人B型利钠肽变化与护理要点

目的测定心房纤颤(房颤)病人血B型利钠肽(BNP)水平并探讨其护理要点。方法抽静脉血化验45例住院房颤病人的血B型利钠肽,并与35例非房颤病例对照;2组病人采取不同级别的护理措施。结果房颤组病人血BNP水平较对照组明显升高[(161±119)pg/ml和(89±64)pg/ml,t=4.87,P<0.01];2组病人对护理工作满意者分别有(43/45)例和(30/35)例,2组对比无显著性差异,(P>0.05)。结论房颤病人血BNP水平会增高,护理工作者应了解这些变化,并应用于护理实践中。     

应用动力髁螺钉联合骨肽注射液治疗股骨髁上骨不连疗效观察

目的观察应用动力髁螺钉联合骨肽注射液治疗股骨髁上骨不连的疗效。方法53例股骨髁上骨不连患者随机分为两组：对照组（26例）和治疗组（27例）,两组均应用动力髁螺钉治疗,治疗组加用骨肽注射液治疗。随访,进行疗效评价,记录骨愈合时间和测定疼痛指数。结果治疗组疗效优于对照组。结论应用动力髁螺钉联合骨肽注射液治疗股骨髁上骨不连可提高疗效。     

Use of Fmoc-N-(2-hydroxy-4-methoxybenzyl) amino acids in peptide synthesis

The use of N, O-bisFmoc-N-(2-hydroxy-4-methoxybenzyl) amino acid derivatives in the synthesis of peptides with difficult sequences has already been described. With these amino acid derivatives the reversible protecting group 2-hydroxy-4-methoxybenzyl (Hmb) for the backbone amide bonds of peptide chains is introduced, and thus the aggregation due to hydrogen-bond interchain association is inhibited. This paper describes the synthesis and use of Fmoc-N-(2-hydroxy-4-methoxybenzyl)amino acid derivatives as an alternative means of introducing Hmb backbone protection. These new monoFmoc derivatives were obtained in higher yield than the bisFmoc derivatives. Coupling yields to the amino peptide resin were the same as those obtained with bisFmoc derivatives, under the TBTU/HOBt/DIEA conditions. We also compared different syntheses of a difficult peptide with the Fmoc approach [triple coupling, capping, use of chaotropic agents, backbone protection using monoFmoc (Hmb)Ala] and with optimized Boc chemistry. Both the backbone protection and optimized Boc chemistry approaches gave the desired product in excellent yield and purity. © Munksgaard 1997.     

BIOCHEMICAL CORRECTION IN THE SYNDROME OF HYPERTENSION AND HYPERKALAEMIA BY SEVERE DIETARY SALT RESTRICTION SUGGESTS RENIN-ALDOSTERONE SUPPRESSION CRITICAL IN PATHOPHYSIOLOGY

1. Plasma potassium and chloride concentrations were raised and plasma renin activity, aldosterone, bicarbonate and arterial pH were reduced in two brothers with the syndrome of hypertension and hyperkalaemia with normal glomerular filtration rate (Gordon's syndrome), on unrestricted or moderately restricted sodium diets. 2. These abnormalities were corrected in both patients within 10 days of severe sodium restriction. 3. Pressor sensitivity to cold and angiotensin II decreased on low sodium diet, associated with a fall in blood pressure. 4. Increasing distal tubular sodium delivery by infusion of normal saline increased fractional excretion of potassium when aldosterone had been stimulated by severely restricted sodium diet, but not when aldosterone levels were low on unrestricted sodium diet. 5. These findings are consistent with excessive sodium reabsorption as the primary renal lesion in Gordon's syndrome, leading to volume expansion and suppression of renin and aldosterone. Severe dietary sodium restriction leading to volume contraction, by stimulating renin and aldosterone and promoting kaliuresis, corrects the abnormalities.     

Chemical shift differences between free and Fab-bound peptide correlate with a two-stage selection of peptide sequences from a random phage display library to delineate critical and non-critical residues for antibody recognition

Epitope libraries provide a method to identify peptide ligands for antibodies, receptors or other binding proteins. As such, they provide a powerful tool to rapidly identify lead ligands in the drug discovery process. In an attempt to correlate structural information with the results from peptide screening, we have used NMR spectroscopy of peptide/antibody complexes to demonstrate that core residues identified through a two-stage selection process undergo a larger structural change upon binding antibody than do positions in the peptide amenable to a variety of side chains. The model system used was the M2 monoclonal antibody/Flag? octapeptide epitope system. We have analyzed two peptides: Ac-Asp-Tyr-Lys-Leu-Gly-Asp-Asp-Leu-NH₂ (peptide l), which contains several non-core positions randomized, and Ac-Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Leu-NH₂ (peptide 2), which closely corresponds to the original Flag? sequence. Enrichment of the peptides with ¹⁵N facilitated the investigation by permitting spectral editing of the peptide resonances in the presence of antibody. For peptide 1 the absolute shifts for the free vs. Fab-bound peptide were found to be largest for the amide groups of Asp-1 and Asp-6, in agreement with classification of these residues as critical by the phage display library selection process. For peptide 2 the largest absolute shifts were observed for Asp-1 and Asp-4, with the other aspartic acid residues also showing significant but smaller changes. © Munksgaard 1995.