具有好的溶解性和高的热稳定性的富勒烯-苝化合物的合成

在氩气保护下,利用N-(正丁基)-N’(4-甲酰基苯氧戊基)-1．6,7,12-四-(4-叔丁基苯氧基)-3,4,9,10-苝酰亚胺和N-甲基甘氨酸产生的亚胺叶立德与富勒烯反应,合成了含富勒烯的苝化合物,用NMR、FT—IR、UV-Vis及TGA等方法对其结构和性能进行了表征和测试。研究结果表明此类化合物具有好的溶解性和高的热稳定性。     

基于钯催化的Catellani反应的Rhazinal的高效全合成

Rhazinal是Rhazinilam家族中的一员,其家族都含有一个因环张力而形成的吡咯-苯胺手性轴,一个高张力的九元内酰胺,一个全碳季碳手性中心以及[3.4]并环结构.Rhazinilam被发现是一个很好的多种癌细胞的抑制剂,具有诱导和促进微管蛋白的聚合、防止解聚、稳定微管的作用.自其被分离之后得到了有机和生物有机化学家的广泛重视,至今已有多个其家族成员的全合成的报道.中国科学技术大学化学系顾振华小组将Pd催化的Catellani反应首次成     

紫精的负离子对耐水的紫精－聚合物膜的光致变色性能的影响

将合不同负离子的苄基紫精分散在混合有ＰＶＰ的ＭＭＡ－ＨＥＭＡ共聚物基质中可制成耐水的光致变色膜。它们的光致变色速度的大小随紫精负离子的不同而有如下序列：这与这些紫精在ＤＭＦ中的溶解度以及在共聚物基质中的溶解性大小的序列相一致．负离子对这些光致变色膜在空气中的氧化退色速度没有很大影响，对这些膜的光疲劳性能的影响也不大。将Ｖ３～Ｖ６分散在不很有ＰＶＰ的ＭＭＡ－ＨＥＭＡ共聚物基质中制成的膜也表现出光致变色的特性，表明它们的多原子负离子本身在聚合物膜中也能充当电子给体的角色．     

酯的水解实验的改进

该文对现行的高中化学 (试验修订本 )第二册中关于乙酸乙酯水解实验的不足之处进行了分析,并提出了改进的方法,对其实验内容和实验效果进行了讨论。     

基于压力的速率方程的应用

通过具体实例说明对于气相反应,使用基于压力的速率方程解题比使用基于浓度的速率方程更直接﹑更简便。总结了具有简单级数的反应的基于压力的速率方程及其特征。     

地球的内部可能是湿润的

在地球的低层地幔下 ,可能存在着比现在的海洋还要多 4倍的水 ,这是日本工业大学的Ｍ .Ｍｕｒａｋａｍｉ和他的同事们最近估测出来的。日本地球科学家们利用了一种多功能钻探仪 ,通过对 3种据信包含低层地幔中在高温高压下生成的主要矿物组成的分析后 ,得到了这个结论。这 3种矿物是 :Ｍｇ ｐｅｒｏｖｓｋｉｔｅ ,Ｃａ ｐｅｒｏｖｓｋｉｔｅ和Ｍａｇｎｅｓｉｏｗ櫣ｓｔｉｔｅ。再利用ＳＩＭＳ对矿物中溶解的氢的含量进行测量 ,矿物学家认为氢是水的标记。发现这3种矿物的含水量都相当可观 ,大约在 0 .2 %至 0 .4 %(重量比率 )之间。用红外…     

铁的吸氧腐蚀实验的改进

正1问题的提出化学实验是化学教学的生命线,在课堂教学中发挥着重要的认识论功能、方法论功能和教学论功能[1]。笔者在利用教科书中铁的吸氧腐蚀实验[2]进行教学时,如图1,发现该实验仅能让学生体会吸氧腐蚀的吸氧过程,而更核心的电化学过程却无法感受到。通过查阅近年文献,发现同仁们对该实验的研究更多关注如何缩短实验所用时间[3-6]。即便     

基于Matlab的二元共聚合反应的竞聚率的求解

以直线交叉法为依据,根据最小二乘原理,采用Matlab GUI工具设计了一款用于计算二元共聚合反应竞聚率的图形用户程序。与传统的求解竞聚率方法相比,该图形用户程序具有设计原理简单、计算快捷的特点;同时程序提供界面简洁、交互友好的数据输入平台,实用性强。实际应用表明:采用该款图形用户程序所测得的数据与微机动态搜索法、Tidwell-Mortimer法相近,而比采用斜率截距法计算竞聚率的最小差方和更小,并且也避免了采用斜率截距法由于所用方程的非对称性造成的计算结果的不一致性。     

糖基修饰的氨基酸类化合物的合成

通过对5种氨基酸酯化和氨基保护得到苄氧羰基氨基酸甲酯, 经肼解制备苄氧羰基氨基酸酰肼, 然后分别与3种不同的糖基异硫氰酸酯反应, 制备了相应的目标化合物15个, 且产率均在60%以上. 所有新化合物均经元素分析, IR, MS和¹H NMR确证. 同时探索了苄氧羰基氨基酸甲酯肼解的最佳反应条件.     

基于环糊精的新材料的研究进展

从纳米粒子、水凝胶、纤维材料和环糊精高分子等方面介绍了近年来以环糊精为基础研制的新材料的研究进展。目前以环糊精为基础的纳米粒子材料有核壳结构的纳米粒子、环糊精的化学接枝与共聚、环糊精与无机非金属材料的复合和含环糊精的囊泡材料;以环糊精为基础的凝胶材料有水凝胶和有机凝胶两种材料;此外还有以环糊精为基础的纤维材料、环糊精高...     

A spider toxin binding protein from bovine brain: its purification and N-terminal amino acid sequence determination.

A 60kDa spider toxin binding protein from bovine brain was solubilized with digitonin and purified up to 5800-folds over starting crude homogenate. The purification procedure entailed DEAE-cellulose, concanavalin-A affinity, 1-naphthylacetyl spermine affinity and high performance liquid chromatography. The purified protein owned a very high affinity for ligand 125I-JSTX-3 binding Kd 15.6nM and Bmax 6.5nM. The amino acid composition of the protein was determined. The N-terminal amino acid sequence analysis yielded a unique sequence: NH2-X-Pro-X-Val-Tyr-Phe-Lys-Glu-Gln-Phe-Leu-Asp-Gly-Asp-X.     

Successive cleavage of pepsin with trypsin and cyanogen bromide isolation of a peptide fragment belonging to the C-terminal region of pepsin

Conclusions 1. The peptide TB has been isolated from the C-terminal fragment of pepsin.2. The amino acid composition of this region of pepsin has been refined.3. The sequence of nine amino acids in the peptide TB has been established.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 6, pp. 540–545, 1969     

An alignment-free method to find similarity among protein sequences via the general form of Chou’s pseudo amino acid composition

In this paper, we propose a method to create the 60-dimensional feature vector for protein sequences via the general form of pseudo amino acid composition. The construction of the feature vector is based on the contents of amino acids, total distance of each amino acid from the first amino acid in the protein sequence and the distribution of 20 amino acids. The obtained cosine distance metric (also called the similarity matrix) is used to construct the phylogenetic tree by the neighbour joining method. In order to show the applicability of our approach, we tested it on three proteins: 1) ND5 protein sequences from nine species, 2) ND6 protein sequences from eight species, and 3) 50 coronavirus spike proteins. The results are in agreement with known history and the output from the multiple sequence alignment program ClustalW, which is widely used. We have also compared our phylogenetic results with six other recently proposed alignment-free methods. These comparisons show that our proposed method gives a more consistent biological relationship than the others. In addition, the time complexity is linear and space required is less as compared with other alignment-free methods that use graphical representation. It should be noted that the multiple sequence alignment method has exponential time complexity.     

A search algorithm for fixed-composition protein design

We present a computational protein design algorithm for finding low-energy sequences of fixed amino acid composition. The search algorithms used in protein design typically do not restrict amino acid composition. However, the random energy model of Shakhnovich suggests that the use of fixed-composition sequences may circumvent defects in the modeling of the denatured state. Our algorithm, FC_FASTER, links fixed-composition versions of Monte Carlo and the FASTER algorithm. As proof of principle, FC_FASTER was tested on an experimentally validated, full-sequence design of the beta1 domain of protein G. For the wild-type composition, FC_FASTER found a lower energy sequence than the experimentally validated sequence. Also, for a different composition, FC_FASTER found the hypothetical lowest-energy sequence in 14 out of 32 trials.     

Identification of mouse brain proteins after two-dimensional electrophoresis and electroblotting by microsequence analysis and amino acid composition analysis

Two-dimensional electrophoretic separation and immobilization of proteins onto inert membranes for subsequent amino acid sequence and amino acid composition analysis is described as a rapid procedure for the identification or characterization of proteins from complex mixtures. This method avoids the drawbacks of classical purification and isolation methods which involve time-consuming operations with low resolution and, often, insufficient yields. Excellent overall yields of minor amounts (in the low microgram range) using this method allow for sequence determination of yet inaccessible proteins. Solubilized cell proteins of mouse brain were separated by high resolution two-dimensional electrophoresis and electroblotted onto a siliconized glass fiber membrane. The immobilized proteins were stained with Coomassie Brilliant Blue R-250, and twelve proteins spots were then submitted to both Edman degradation and amino acid analysis. Proteins were identified by comparison of the experimentally determined amino acid composition with a dataset derived from the Protein Identification Resource (PIR) protein sequence database. Eight out of twelve proteins tested were identified by amino acid analysis and confirmed by N-terminal sequence determination.     

Characterization of native and recombinant peptidyl prolyl cis-trans isomerases derived from Methanococcus thermolithotrophicus based on cDNA sequence

It is important to establish whether a recombinant protein is an authentic copy of the predicted cDNA sequence. In this study, recombinant protein for native peptidyl prolyl cis-trans isomerase (N-PPIase) and double-labeled (13C- and 15N-) protein (DL-PPIase) appeared on the sodium dodecyl sulfate (SDS) electropherograms as two bands for N-PPIase and four bands for DL-PPIase. Since the N-terminal amino acid residues of all bands were the same, we characterized these bands using the peptide mapping method and amino acid composition analysis. Peptide mapping of the proteins seemed to be almost identical but they could not reflect the whole amino acid sequences of the protein. The bands on the polyvinylidene difluoride (PVDF) membrane, electroblotted after SDS-polyacrylamide gel electrophoresis (SDS-PAGE), were hydrolyzed and their amino acid composition was analyzed using a highly sensitive 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) amino acid analysis and compared with the cDNA sequences for proteins. The matching score (sigma(T%-E%)2) for similarity of proteins was calculated by summation of the square difference between the theoretical (T%) and the experimental (E%) amino acid composition of the recombinant protein. The amino acid composition of all bands of both proteins showed more than 93% of the theoretical values. The major molecular weights of both proteins were 16812 and 17694 by electrospray ionization (ESI)-mass spectrometry. However, the purified proteins also contained minor compounds with Mr of 3721 for N-PPIase and 5285 for DL-PPIase. These compounds were considered to be nonpeptidyl products that comigrated with the protein. Similarities of the amino acid composition of the four bands were more than 98%. Our results indicate that AQC amino acid analysis is the most suitable method for characterization of a recombinant protein.     

Structure determination of glycopeptide of p-momorcharin

The structure of the N-linked oligosaccharide chain of β-momorcharin, a ribosome-inactivating protein from the seeds of Momordica charantia Linn (Cucurbitaceae) was determined. A glycopeptide liberated by pronase digestion of the glycoprotein was subjected to amino acid and neutral carbohydrate analysis to establish the composition of amino acid and sugar residues. The sequences and glycosylation linkages of the sugar and amino acid residues in the glycopeptide were determined as Manal-6(Xylβ1-2)-Manβ1-4GlcNAcβ1-4(Fucal-3)-GlcNAc-Asn-Leu by 2D-NMR spectroscopy and FAB-MS data.     

The synthesis of sterically demanding amino acid-derived cyclic phosphonamides

The preparation and utilization of C(2)-symmetric 1,4-diamines in the synthesis of amino acid-derived cyclic phosphonamides 1-3 are described. The 1,4-diamines are synthesized via three methods: (i) amino acid/fumaryl chloride coupling followed by amide reduction, (ii) amino acid/1,4-diamine coupling followed by amide reduction, and (iii) a template-supported ring-closing metathesis/hydrolysis sequence. The pseudo C(2)-symmetric cyclic phosphonamides 1-3 are prepared by condensation of the C(2)-symmetric 1,4-diamines to P(III) centers, followed by oxidation.     

Predicting protein folding rates using the concept of Chou's pseudo amino acid composition

One of the most important challenges in computational and molecular biology is to understand the relationship between amino acid sequences and the folding rates of proteins. Recent works suggest that topological parameters, amino acid properties, chain length and the composition index relate well with protein folding rates, however, sequence order information has seldom been considered as a property for predicting protein folding rates. In this study, amino acid sequence order was used to derive an effective method, based on an extended version of the pseudo-amino acid composition, for predicting protein folding rates without any explicit structural information. Using the jackknife cross validation test, the method was demonstrated on the largest dataset (99 proteins) reported. The method was found to provide a good correlation between the predicted and experimental folding rates. The correlation coefficient is 0.81 (with a highly significant level) and the standard error is 2.46. The reported algorithm was found to perform better than several representative sequence-based approaches using the same dataset. The results indicate that sequence order information is an important determinant of protein folding rates.     

抗菌肽SAMP1及其类似肽的构效关系

以人工合成抗菌肽1(Synthetic antimicrobial peptide 1, SAMP1)为研究模板, 采用氨基酸序列重排、 不同的带正电荷氨基酸残基和疏水性氨基酸残基取代等方法, 设计合成了8条SAMP1类似肽. 利用生物信息学软件预测了SAMP1及其类似肽的理化性质; 采用圆二色光谱(CD)技术测定其在不同环境下二级结构的变化; 采用噻唑蓝(MTT)法测定其抗菌活性; 通过红细胞溶血实验评估了这些多肽的溶血性. 结果表明, 大部分类似肽具有较低的溶血毒性和较高的广谱抗菌活性. CD光谱分析结果显示, 大部分类似肽二级结构以α螺旋和无规则卷曲为主, 在体积分数为50%的2,2,2-三氟乙醇(TFE)溶液中, α螺旋结构比例增加. 与母肽SAMP1相比, 经序列重排后得到的SAMP1-A1, SAMP1-A2和SAMP1-A3的抗菌活性变化不大, 但序列中正电荷氨基酸残基均匀分布的类似肽SAMP1-A2的溶血毒性增加. 用精氨酸(Arg)取代SAMP1序列中的赖氨酸(Lys)得到的类似肽SAMP1-A4的抗菌活性增强, 同时溶血毒性降低. 用疏水性较强的异亮氨酸(Ile)和缬氨酸(Val)取代SAMP1中的疏水性氨基酸残基, 得到的类似肽SAMP1-A5和SAMP1-A7的抗菌活性急剧降低; 用疏水性较弱的色氨酸(Trp)取代SAMP1中的疏水性氨基酸残基, 得到的类似肽SAMP1-A8的抗菌活性增强, 同时溶血毒性提高.