5种甜味添加剂的反相高效液相色谱法同时测定

建立了同时测定5种人工合成甜味剂阿斯巴甜、糖精钠、甜蜜素、安赛蜜、纽甜的反相高效液相色谱分析方法.以Synergi Fusion-RP柱为分离柱,20mmol/L硫酸铵缓冲溶液(pH 4.4)-乙腈为流动相,梯度洗脱.采用二极管阵列检测器进行检测,整个分离过程在9min内完成.样品加标回收率为89%～107%;相对标准偏差小于3.2%.该法可用于食品和饮料中5种甜味剂的同时测定.     

味觉电化学传感器的研究：甜味物质对模拟生物膜电位振荡的影响

本文以十六基三甲基溴化铵＋乙醇／含苦味酸的硝基苯／蔗糖溶液为研究体系，对影响该体电位振荡的各因进行了探讨，观察到各种甜味物质均能影该体系的振动波形和频率，并发现振荡频率的对数与各甜味物质浓度在一定范围内呈线性关系，初步建立了利用该体系测定甜味物的定笥，定量，工对该味觉电化学传感器的响应机理进行了。     

甜味分子和人工合成甜味剂的结构化学

为了开发多品种食品调味料,本文按有机化学中官能团分类讨论了合成甜味剂及有关呈味分子的结构与味道的相互关系。     

L-天门冬氨酸二肽的结构与甜味的一些关系

本文报导了一系列L-天门冬氨酸二肽衍生物,NH_2CH(CH_2COOH)CONHCH(COOCH_3)-(COX)(X为烷氧基,烷氨基,邻位取代苯胺基及N-甲基苯胺基)的合成和它们的甜度。这些二肽尾部的电性能、憎水性、以及整个分子的链长(在满足一定立体要求的条件下)都影响着二肽的甜度。     

蛋白质的离子交换平衡

一、引言蛋白质是由肽键将氨基酸这一化学单位连接起来而组成的高分子量化合物,具有许多可解离基,它们主要来自侧链上的羧基、胺基、咪唑     

蛋白质的离子交换平衡及动力学

众所周知,离子交换色层是蛋白质分离的有效方法,而离子交换平衡及动力学是决定分离效果的重要因素。本文介绍了蛋白质在离子交换剂及水溶液之间分配的平衡关系式以及离子交换速度方程。此外,还讨论了实验方法。     

超高效液相色谱-电化学检测法测定饮料中爱德万甜和5种二氢查耳酮类甜味剂的含量

取10 g饮料样品,加水稀释并定容至50 mL,混合均匀,取少量混合液以转速10000 r·min^-1离心10 min,上清液经0.22μm滤膜过滤后,以ACQUITY UPLC~?BEH C₁₈色谱柱为固定相,电化学检测器(ECD)检测,检测池电压为650 mV,采用超高效液相色谱法测定其中爱德万甜、根皮苷、柚皮苷二氢查耳酮、三叶苷、新橙皮苷二氢查耳酮、根皮素的含量。结果表明,爱德万甜和5种二氢查耳酮类甜味剂在9.0 min内可以完全分离,其质量浓度在一定范围内与其对应的峰面积呈线性关系,检出限(3S/N)为2.1~6.8μg·L^-1。按标准加入法进行回收试验,回收率为97.1%~105%,测定值的相对标准偏差(n=6)为1.4%~5.1%。与二极管阵列检测器(DAD)比较,使用ECD时,灵敏度高、检出限低。与其他文献方法相比,本方法的灵敏度、分析时间均具有明显优势。     

蛋白质二级结构预测的综合分析

本文提出了一个蛋白质二级结构预测结果的综合分析方法, 它综合了常用的几种二级结构预测法(Chou-Fasman方法、Garnier方法, Cohen方法、疏水性分析法), 取各方法之长, 对由每种方法得到的有差别的结果进行综合分析, 经过这样处理, 可使蛋白质二级结构预测精度提高7%左右。     

蛋白质的结构预测和分子设计

蛋白质的结构预测及分子设计是适应基因工程的需要发展起来的对蛋白质的空间结构进行研究并在此基础上提供蛋白质改造方案的方法。通过对已知的蛋白质结构数据进行总结、分析,结合分子力学、分子动力学等计算方法可以进行某些种类的结构预测。在对蛋白质的结构与功能研究的基础上可以提出改造方案,从而进行有目的的分子设计。     

蛋白质与人类

蛋白质是组成人体的主要固态成分,是生命活动的基础。近年来,由于蛋白质供给数量不足、质量低劣、资源严重浪费等问题的出现,人们更加注重对蛋白质的研究和开发,并通过利用传统资源和扩大开发传统资源等途径获得了大量质优价廉的蛋白质。本文简要介绍了蛋白质与人类的密切关系、新蛋白食品以及蛋白质新资源等。     

Proteins and polymers

Proteins, chain molecules of amino acids, behave in ways which are similar to each other yet quite distinct from standard compact polymers. We demonstrate that the Flory theorem, derived for polymer melts, holds for compact protein native state structures and is not incompatible with the existence of structured building blocks such as alpha helices and beta strands. We present a discussion on how the notion of the thickness of a polymer chain, besides being useful in describing a chain molecule in the continuum limit, plays a vital role in interpolating between conventional polymer physics and the phase of matter associated with protein structures.     

Molecular Mechanisms of Sweet Taste 1: Sweet and Non-Sweet Tasting Amino Acids

ABSTRACT

A novel mechanism is proposed for the AH/B interaction of sweet molecules, such as D-α-amino acids with the L-asparagine unit at the N-terminus of a receptor protein which has a right-handed α-helical conformation. The lipophilic, dispersive bonding occurs between the side chain of the fifth amino acid residue, from the N-terminus, and either the side chain of the α-amino acid or its methine group at the carbon 2. The sequence of AH, B and X groups on the sweet amino acids occurs in a clockwise orientation, when viewed from the receptor.     

Sweet like chocolate

A new crystalline form of αβ‐d ‐lactose prepared by oven drying a concentrated aqueous solution of d ‐lactose is a lesson in the power of observation and the rigorous analysis of powder samples.     

Immobilized Proteins and Peptides

In recent years a great deal has been learned about the structure and function of proteins and about the roles they play in the complex process of a living organism. The classical approach of the biochemist in studying a given protein is to free it from the cellular species. The properties and structure of the protein in solution are then examined and analyzed. While this approach is logical and has yielded much information about proteins, one should always keep in mind that in natureagreat many proteins function not in solution, but at an interface or within solid state assemblages in cells. The protein removed from a surface is thus often not in its natural environment and can display an altered reactivity and stability.     

Pharmaceutical Proteins

There is currently great interest in pharmaceutical proteins, and work in this area, from basic research to drug marketing, is expanding vigorously. The starting points of these developments are genetic engineering and biotechnology, which contribute to the discovery of new proteins and allow them to be produced on a worthwhile scale. Ever since the commercial introduction of insulin in 1923, of thyroid hormone in 1934, of factor VIII in 1948, and of calcitonin in 1970, hormones, serum proteins, and enzymes have been firmly established as therapeutic agents. Immunomodulators and various tissue proteins are in a turbulent phase of development as a new approach to the therapy of tumors. Increasingly, diagnostic aids now take the form of enzymes and monoclonal antibodies, and recently there has even been development of vaccines based on defined single proteins and oligopeptides. Of the more than 200 pharmaceutical proteins which have been investigated to date, more than half are undergoing research and development, about 100 are in clinical trials, and a dozen or so have already been marketed. The most important indications for them are cardiovascular disorders, tumors, autoimmune diseases, and infections. Genetically engineered proteins can be used as active substances, which are chemically and biologically exactly defined, for new drug products and in research to acquire new information on therapeutic use, based on the concept of therapy with endogenous proteins. Very recent developments have shown that proteins, either in their natural form or modified, are becoming of increasing importance for research into active substances.     

Electroactivity of Nonconjugated Proteins and Peptides. Towards Electroanalysis of All Proteins

Present proteomics and biomedicine require sensitive analytical methods for all proteins. Recent progress in electrochemical analysis of peptides and proteins based on their intrinsic electroactivity is reviewed. Tyrosine and/or tryptophan‐containing proteins are oxidizable at carbon electrodes. At mercury electrodes all peptides and proteins (about 13 peptides and >25 proteins were tested) produce chronopotentiometric peak H at nanomolar concentrations. This peak is sensitive to changes in protein structure. Microliter sample volumes are sufficient for the analysis. Electrochemical methods can be used in studies of nucleic acid‐protein interactions and can be applied in biomedicine. Examples of such applications in neurogenerative diseases and cancer are presented.     

二十面体病毒及其衣壳蛋白质

许多病毒具有二十面体结构。本文对已经发现的各种二十面体病毒进行了分类,分析了二十面体病毒衣壳的结构特征,阐述了二十面体病毒的结构蛋白。     

Moco Carrier and Binding Proteins

The molybdenum cofactor (Moco) is the active site prosthetic group found in numerous vitally important enzymes (Mo-enzymes), which predominantly catalyze 2 electron transfer reactions. Moco is synthesized by an evolutionary old and highly conserved multi-step pathway, whereby the metal insertion reaction is the ultimate reaction step here. Moco and its intermediates are highly sensitive towards oxidative damage and considering this, they are believed to be permanently protein bound during synthesis and also after Moco maturation. In plants, a cellular Moco transfer and storage system was identified, which comprises proteins that are capable of Moco binding and release but do not possess a Moco-dependent enzymatic activity. The first protein described that exhibited these properties was the Moco carrier protein (MCP) from the green alga Chlamydomonas reinhardtii. However, MCPs and similar proteins have meanwhile been described in various plant species. This review will summarize the current knowledge of the cellular Moco distribution system.