Affinity Chromatography of Insulin with a Heptapeptide Ligand Selected from Phage Display Library

A heptapeptide phage display library was screened with insulin to find its ligands for affinity chromatography. The peptide was synthesized and coupled to EAH Sepharose 4B (5.4 mol mL^–1 bed). Then, insulin chromatography was carried out with mobile phases of different pH values and by the addition of urea and ethylene glycol. It was found that electrostatic interactions were predominant for the affinity binding, and hydrogen bonding might also contribute somewhat to the affinity. Finally, frontal analysis was performed and the dynamic binding capacity of the affinity column for insulin at 50% breakthrough was estimated at 60.6 mg mL^–1 bed, which was about two times higher than the theoretical binding capacity of the monomeric insulin. The result suggests that insulin was bound in dimer state in a stoichiometric relationship with the coupled peptide, indicating the high binding efficiency of the peptide ligand for insulin.     

Application of solid phase peptide synthesis to engineering PEO–peptide block copolymers for drug delivery

This work describes a simple, versatile solid-phase peptide-synthesis (SPPS) method for preparing micelle-forming poly(ethylene oxide)-block-peptide block copolymers for drug delivery. To demonstrate its utility, this SPPS method was used to construct two series of micelle-forming block copolymers (one of constant core-composition and variable length; the other of constant core length and variable composition). The block copolymers were then used to study in detail the effect of size and composition on micellization. The various block copolymers were prepared by a combination of SPPS for the peptide block, followed by solution–phase conjugation of the peptide block with a proprionic acid derivative of poly(ethylene oxide) (PEO) to form the PEO-b-peptide block copolymer. The composition of each block component was characterized by mass spectrometry (MALDI and ES-MS). Block copolymer compositions were characterized by ¹H NMR. All the block copolymers were found to form micelles as judged by transmission electron microscopy (TEM) and light scattering analysis. To demonstrate their potential as drug delivery systems, micelles prepared from one member of the PEO-b-peptide block copolymer series were physically loaded with the anticancer drug doxorubicin (DOX). Micelle static and dynamic stability were found to correlate strongly with micelle core length. In contrast, these same micellization properties appear to be a complex function of core composition, and no clear trends could be identified from among the set of compositionally varying, fixed length block copolymer micelles. We conclude that SPPS can be used to construct biocompatible block copolymers with well-defined core lengths and compositions, which in turn can be used to study and to tailor the behavior of block copolymer micelles.     

在肽库中进行小肽筛选的初步研究

以合成六肽ＤＧＧＳＡＡ为模型对在噬菌体肽库中进行小肽筛选做了初步研究。结果表明，含有可形成氢键和离子键残基的小肽能够在噬菌体肽库中进行筛选。并用明显提高了筛选的专一性。     

Analytical procedures for quantification of peptides in pharmaceutical research by liquid chromatography–mass spectrometry

Peptide quantification by liquid chromatography–mass spectrometry (LC–MS) combines the high resolving power of reversed-phase (RP) chromatography with the excellent selectivity and sensitivity of mass spectrometric detection. On the basis of comprehensive practical experience in the analysis of small molecules, pharmaceutical research is developing technologies for analysis of a growing number of peptidic drug candidates. This article is a detailed review of procedures based on LC–MS techniques for quantitative determination of peptides. With the focus on pharmaceutical applications several technologies for sample preparation, various aspects of peptide chromatography, important characteristics of ESI–MS, selectivity of MS-detection modes, the large variability of internal standards, and modern instrumentation are discussed. The demand for reliable, robust, sensitive, and accurate methods is discussed using numerous examples from the literature, complemented by experiments and results from our laboratory.     

Effect of hydrophobic amino acids on the conformational change of decapeptides in micellar environments

A series of peptides containing various hydrophobic amino acids [methionine (Met), leucine (Leu), norleucine (Nle), phenylalanine (Phe), 2-aminooctanoic acid (Aoc), and 2-aminodecanoic acid (Ade)] were synthesized and their conformations were studied using circular dichroism (CD) spectroscopy in different solvents such as water, methanol, and aqueous solution of ammonium tetradecanesulfonate. Peptides containing hydrophobic amino acids with linear side chains formed -sheets in water and methanol. Electrostatic interaction between the charged side chain (lysine) and a micelle consisting of an anionic surfactant, ammonium tetradecanesulfonate, is necessary for the formation of -helices in micellar environments. The conformational transition from -helix to -sheet structure required moderate hydrophobicity and linear side chains. This conformational transition depended on the surfactant concentration.     

1，2，4－三嗪类化合物的研究（ⅩⅫ）──咪唑并－（5，4－e）－1，2，4－三嗪衍生物的合成

１，２，４－三嗪类化合物的研究（ⅩⅫ）──咪唑并－（５，４－ｅ）－１，２，４－三嗪衍生物的合成沙耀武，蔡孟深（北京医科大学药学院，北京，１０００８３）关键词乙二脒腙，原甲酸三乙酯，１，２，４－三嗪，咪唑并－（５，４－ｅ）－１，２，４－三嗪天然碱基拮抗...     

Synthesis of stereo-defined α-trifluoromethyl (Tfm)-malic units

Aldol reactions of titanium enolates of N-acyl-1,3-oxazolidin-2-ones with ethyl trifluoropyruvate occurred with low to good stereoselectivity depending on the steric properties of the N-acyl group. Attempts to transform the resulting aldols into peptidomimetics incorporating stereo-defined α-trifluoromethyl (Tfm)-malic units are described.     

High pressure FTIR study of intramolecular hydrogen bonding and conformation of a small peptide in solution

Effect of pressure on conformational equilibria of a small peptide N-acetyl-l-Pro-l-Leu-Gly-NH₂ in a chloroform solution has been studied by FTIR spectroscopy. Absorption in the NH stretching region was measured at pressures in the 1–1080 bar range and at 296 K, and decomposed into component bands by least-squares fitting. Intensity ratios of bands which were assigned to a hydrogen-bond-free conformer and intramolecularly hydrogen-bonded conformers with 10- and 13-membered hydrogen bonded rings, respectively, were examined as a function of pressure. It was found that the conformer with the 13-membered ring has definitely smaller partial molar volume than the other two conformers which have nearly the same volume with each other. On the basis of a simple dielectric model, we have shown that the conformer with the 13-membered hydrogen-bonded ring has a considerably large dipole moment which is consistent with the α-helical structure suggested by the previous variable-temperature FTIR study.     

Synthesis of Novel Dendrimers Containing Amino Acids and Peptides

Dendrimers are known for their well-defined, regular, highly branched architectures with a large number of functional groups1. Recently, dendrimers have been widely researched in different fields, such as molecular light havesting, catalysts, liquid cryst…     

Synthesis of peptides and oligosaccharides by using a recyclable fluorous tag

A hexakis(fluorous chain)-type alcohol was used in the synthesis of oligosaccharides and peptides through connection with a linker suitable for the particular type of target compound. After the preparation of the desired compound, the fluorous alcohol was easily recovered in good yields under basic conditions. It appears that the fluorous alcohol can be recovered, recycled, and reused.