十二烷基甜菜碱与聚乙烯吡咯烷酮相互作用的研究

通过表面张力测定和13CNMR、ESR波谱研究了十二烷基甜菜碱（C12BE）与聚乙烯吡咯烷酮（PVP）的相互作用．表面张力测定表明,在pH＝6．5及NaCI存在下,C12BE与PVP之间有明显的相互作用,可形成C12BE／PVP复合物,且C12BE－PVP混合溶液的β－lgc曲线出现2个转折点,第一个转折点时C12BE浓度c1（C12BE－PVP开始缔合）低于C12BE的cmc值;而第二个转折点时C12BE浓度c2（C12BE－PVP缔合达饱和）大于cmc值．（c2─c1）与PVP浓度呈线性关系．PVP降低C12BE胶束化标准自由能（△G0）随PVP浓度增加而增大．13CNMR测定表明,PVP骨架上α-CH、β-CH2和吡咯环上与N相连的亚甲基吸附于C12BE胶束表面的碳氢链部位,屏蔽了C12BE胶束表面碳氢链与水的接触．ESR波谱表明,PVP－C12BE聚集体"界面"的粘度高于C12BE胶束"界面"的粘度．     

稀土Invar合金热力学性质研究

制备了稀土Invar（因瓦）合金YFe_(12-x)V_x（x＝1.6，2.0；2.4，2.8，3.2）和SmFe_(12－x_V_x（x=2.4, 2.8）采用电动势法以CaF_2单晶作为固体电解质，测定了钇和钐在相应合金中的活度．计算了偏摩尔自由能等热力学性质．测定温度对两类合金分别为920－1020 K和900－1000 K．     

水中苯胺类化合物的分光光度法测定

提出3种测定水中苯胺类化合物的分光光度法，在氢氧化钠介质（PH＝12．2）中，邻甲氰基苯酚、8－羟基喹啉和1－萘酚均可与苯胺形成偶氮化合物，它们的最大吸收波长分别位于452、482和497nm处，与传统的N－（1－萘基）乙二胺光度法相比，这3种方法测定苯胺更方便，快速、灵敏，线性范围更宽；它们的检出下限分别为8．6、10、14μg/L；线性范围分别为0－5．6、0－4．8和0－3．2mg/L。这3种方法用于测定环境水样中的苯胺类化合物，均获得了满意的结果。     

[（2—砷酸基苯基）偶氮]—8氨基喹啉与钴的显色反应研究

在pH7．8－9．5的硼砂缓冲溶液中,在CTMAB的存在下,钴（Ⅱ）与新显色剂（2－胂酸基苯基偶氮）－8－氨基喹啉（o－APAQ）反应生成蓝 绿色络合物,在610nm处有吸收峰。显色剂本身在此条件下的吸收峰位于450nm处,对比度（△λ）达160nm。显色反应须在70－80℃的水浴中加热10min完成,可稳定至少12h,对常见的共存离子作了干扰试验,将此反应用于．维生素V12注射液及废水中微量钴的光度测定。经试验 测定的准确度和精密度较满意。     

氧氟沙星在胶束体系中的荧光特性及应用

研究发现十二烷基硫酸钠胶束对氧氟沙星荧光有明显的增敏作用，据此建立了直接测定人体尿液中氧氟沙星的等波长差同步荧光光谱法（△λ=90nm）。经样品测定，其线性范围为0．12－3．6mg/L，检出限为0．12mg/L，回收率为92．2％－97．8％，相对标准偏差为1．2％－2．7％。     

在线柱分离ICP-MS测定高纯Eu2O3中Tm

报道了一种在线柱分离ICP－MS快速测定高纯氧化铕中杂质铥的方法，采用一种新型膦酸类萃取剂，大大降低了林洗酸度，洗脱液中的Tm直接进入ICP－MS进行在线测定。整个分离测定周期为40min，方法检出限为0．12ng/mL，加示加收率为91．5％－98％，RSD为4．1％，该方法快速，简便。用于高纯氧化铕中杂质铥的测定，结果满意。     

用UVM-2型声速仪测定冻土弹性波速

利用ＵＶＭ－２型声速仪和自行研制的超声换能器对冻结兰州黄土进行了测定,在不同温度（－１℃、－２℃、－４℃、－６℃、－８℃、－１０℃、－１２℃、－１４℃、－１６℃、－１８℃和－２０℃）下测定了冻土的纵波速度和横波速度,测定结果显示,ＵＶＭ－２仪具有较高的测量精度,延时精度１０ｎｓ,而且具有自动化程度高、人为测量延时误差小和测量结果重复性好的特点。     

荧光猝灭法测定痕量六价铬

基于六价铬与碘化钾反应生产了单质碘，碘可以使2′，7′－二氯荧光素（DCF）发生荧光猝来，从而间接测定六价铬。六价铬浓度在0．20－2．50μg/25ml范围内，荧光强度差值与六价铬浓度呈线性关系，线性回归方程△F=12．12 0．19，相关系数r=0.9993，检出限为0．10μg/ml。方法简便，灵敏度较高，已用于合成样中六价铬的测定。回收率在100％－103％，结果满意。     

α-腈基阿魏酸基体在MALDI-TOFMS测定中的应用研究

在基体辅助激光解吸电离飞行时间质谱（MALDI－TOFMS）测定中基体的作用举足轻重。有效或特效基体的发现和应用不仅可提高测试灵敏度和分辨率,加大分子量测定范围,还能扩增测试样品的种类,推动MALDI－TOFMS应用的发展。目前MALDI－TOFMS分析的常用基体^[1,2]测定多肽、蛋白质的α-腈基－4－羟基肉桂酸（4HCCA）和介子酸（SA）效果比较理想;而测定糖类物质的2,5－二羟基苯甲酸（DHB）则不能完全适用于在组成、结构、序列以及连接方式上存在多样性的碳水化合物的分子;测定DNA的3－羟基吡啶甲酸（3－HPA）使用时必须对样品、溶剂甚至基体本身进行严格纯化,较为烦琐,测定含百个碱基以上大分子量DNA的灵敏度和分辨率还不理想。本文考察研究α-腈基阿魏酸（CFA）旨在寻找MALDI－TOFMS测定的有效新基体,为MALDI－TOFMS测定提供更多的基体选择。     

硼氢及客体二十面体簇合物的结构和稳定性

在(n=0、－1、－2、－3、－4)簇合物几何构型及稳定性研究的基础上,进一步对它的各种内含式和外 接式二十面体簇合物(X@B12H122－和XB12H122－,X=H0/＋、Li0/＋、He、Ne、Be0/2＋、Na＋、Mg2＋)进行了优化和 计 算.发现在内含式结构X@ B12H122－中,当X=Li＋、Be2＋、Mg2＋时,构型较稳定;在外接式结构中, XB12H122－(C3v)结构比XB12H122－(C2v)的结构稳定.通过IRC计算,确定XB12H122－(C2v)是X与B12H122－作用生成产物XB12H122－(C3v)的一种过渡态.     

Exclusive Use of High Pressure Liquid Chromatography for the Determination of the Complete Amino Acid Sequence of the 12K Fragment of Avian Sarcoma Virus Structural Protein p27

Abstract

Using exclusively high pressure liquid chromatography for the protein and peptide separation complete primary structure of the 12,000 molecular weight (12K) amino terminal (1–87 residues) fragment obtained by mild acid hydrolysis of p27 (Avian Sarcoma Virus structural protein) has been determined. The sequence was established by direct degradation of the native molecule and its (12K) peptides isolated by molecular exclusion and reverse phase HPLC.     

Evaluation of temperature,excipients impact on the primary structure of Ganirelix in an injectable formulation,and comparison with Orgalutran® using MALDI‐TOF/TOF‐MS

Ganirelix is a linear polypeptide consisting of covalently bonded 10 amino acid residues. The amino acid sequence in a peptide determines the properties of the molecule. The slightest change in the primary structure (amino acid sequence) of therapeutic peptides can significantly impact its safety, efficacy, and immunogenicity. Hence, the primary structure analysis of therapeutic peptides is regarded as a critical quality attribute (CQA). A vast array of analytical techniques can be used to capture the primary structure of the peptide. In this study, we applied matrix‐assisted laser desorption ionization (MALDI)/tandem time of flight mass spectroscopic (TOF/TOF MS) method to demonstrate the primary structure of Ganirelix in an injectable formulation. The apparent monoisotopic molecular mass of Ganirelix is 1,568.9 Da. The attained primary amino acid sequence of Ganirelix in temperature‐stressed generic product matched with the theoretical sequence and showed homology with those of the reference listed drug (RLD).     

纳升电喷雾串联质谱"序列对接法"确定多肽的加钠位点

用QuattroM icro三级四极串联质谱分析常见的20种氨基酸的加钠效果。结果表明,绝大多数氨基酸与钠离子的非共价键结合力很弱甚至没有,但脯氨酸和苯丙氨酸很容易形成加钠离子峰。采用“序列对接法”测出重组人酸性纤维细胞生长因子(rh-a FGF)C-端肽段的全序列,并确定钠离子的加成位点为该肽段的第6位脯氨酸(6Pro)。通过酸化样品溶液获得无加钠、无序列间隙的该肽全序列,与加钠肽段的序列一致。     

Characterization of recombinant human serum albumin using matrix-assisted laser desorption ionization time-of-flight mass spectrometry

Chromatographically purified recombinant human serum albumin (rHSA), produced in genetically transformed yeast cells, was characterized using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) MS techniques. The molecular mass of the intact protein was determined to be 66671, in good agreement with that of purified HSA which was used as a standard. The identity of rHSA to its natural counterpart was established with high precision using peptide mass fingerprinting of tryptic peptides. Partial amino acid sequence data for rHSA were obtained using Ettan CAF MALDI Sequencing Kit and post-source decay on the tryptic peptides. The results achieved provide strong evidence that MALDI-TOF-MS is an important analytical technique for characterising gene products and for establishing the identity and bio-compatibility of recombinant proteins relative to their natural counterparts.     

Effect of sodium dodecyl sulfate micelles on peptide mass fingerprinting by matrix-assisted laser desorption/ionization mass spectrometry

Here we have examined the effect of sodium dodecyl sulfate (SDS) at various concentrations on matrix-assisted laser desorption/ionization (MALDI) peptide mass fingerprinting experiments. Several model proteins were digested with trypsin and then various amounts of SDS were added prior to MALDI mass spectrometry. Evaluation of the data was made by calculating the amino acid sequence coverage within each analysis. It was found that addition of 0.1-0.3% w/v SDS prior to MALDI analysis results in an increase in the number of tryptic peptides detected thereby improving the total sequence coverage of the analysis. The use of SDS at concentrations near its critical micelle concentration can improve sequence coverage from MALDI peptide mass fingerprinting analyses allowing for increased confidence in protein identification or additional opportunities to identify putative regions of posttranslational modification.     

梅花鹿茸多肽的化学结构及生物活性

在马鹿茸活性多肽结构与功能研究基础上, 从新鲜梅花鹿茸中分离纯化了活性单体多肽, 确定了其化学结构, 并与马鹿茸多肽进行结构与活性比较. 利用离子交换层析、 凝胶过滤层析及反相高效液相色谱层析等生物化学技术, 从梅花鹿茸中分离得到1个新多肽, SDS-PAGE电泳显示为一条带, HPLC图谱为单一峰, MALDI-TOF MS给出该多肽的精确分子量为3263.4, 其等电点pI=8.15. 一级结构研究表明, 该多肽是由32个氨基酸残基组成的直链多肽, 不含半胱氨酸, 富含缬氨酸、 赖氨酸、 亮氨酸和甘氨酸, 氨基酸序列为VLSATDKTNVLAAWGKVGGNAPAFGAEALERM. 生物活性检测结果表明, 该多肽可促进原代培养的表皮细胞和软骨细胞增殖, 也能刺激NIH3T3成纤维细胞株的分裂. 梅花鹿茸多肽与马鹿茸多肽在结构上均为32个氨基酸残基组成的直链多肽, 但第5, 8, 11和30位氨基酸残基不同. 2种多肽结构上的变化并未影响其促细胞增殖生物活性.     

Mass spectrometric characteristics and kinetics of iron release in visceral mass of Saccostrea cucullata

Ferritins with electrophoretic homogeneity were prepared from the visceral mass of Saccostrea cucullata in batch. The native PAGE approach showed similar electrophoretic mobility among pig pancreatic ferritin, liver ferritin of Dasyatis akajei, and visceral mass ferritin of Saccostrea cucullata. SDS-PAGE indicated that the Saccostrea cucullata visceral ferritin (SCVF) consisted of a single subunit type and had a molecular weight (MW) of approximately 20 kDa, suggesting that the protein shell in SCVF was composed of a single subunit. In addition, peptide mass fingerprinting and transmission electron microscopy were used to identify SCVF further, and to observe its molecular structure. We found that the molecular structure in SCVF was similar to that of most mammalian ferritins, which are composed of a protein shell and an iron core. The results of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry under the assistance of an acidic matrix, sinapic acid, also showed that SCVF was composed of a single subunit type and its subunit MW was calculated to be 19871.042 Da in the absence of heme. Kinetics analysis revealed that the complete process of iron release fitted the law of a first-order reaction, which is similar to that of most ferritins in mammals. Similar to bacterial ferritin, studies indicated that the shell consisted of a single subunit type and showed similar kinetics of iron release, suggesting that this subunit plays two important roles in iron release and storage, and that it shows different stability and intensity of interaction in carrying out its physiological functions in SCVF.     

Biochemical properties of Cu/Zn-superoxide dismutase from fungal strain Aspergillus niger 26

The fungal strain Aspergillus niger produces two superoxide dismutases, Cu/Zn-SOD and Mn-SOD. The primary structure of the Cu/Zn-SOD has been determined by Edman degradation of peptide fragments derived from proteolytic digests. A single chain of the protein, consisting of 153 amino acid residues, reveals a very high degree of structural homology with the amino acid sequences of other Aspergillus Cu/Zn-SODs. The molecular mass of ANSOD, measured by MALDI-MS and ESI-MS, and calculated by its amino acid sequence, was determined to be 15821 Da. Only one Trp residue, at position 32, and one disulfide bridge were identified. However, neither a Tyr residue nor a carbohydrate chain occupying an N-linkage site (-Asn-Ile-Thr-) were found. Studies on the temperature and pH dependence of fluorescence, and on the temperature dependence of CD spectroscopic properties, confirmed that the enzyme is very stable, which can be explained by the stabilising effect of the disulfide bridge. The enzyme retains about 53% of its activity after incubation for a period of 30 min at 60 degrees C, and 15% at 85 degrees C.     

Use of low-and high-energy collision-induced dissociation tandem mass spectrometry in the identification of an unusual amino acid in a semisynthetic polypeptide

During production of the semisynthetic eicosapeptide Phe-Pro-Arg-Pro-Gly-Gly-Gly-Gly-Asn-Gly-Asp-Phe-Glu-Glu-Ile-Pro-Glu-Glu-Tyr-Leu, two minor impurities were isolated in which Ile-15 had been replaced by other amino acids. The molecular weights of the two peptide minor products were 14 u lower and 14 u higher, respectively, than the major product with the foregoing amino acid sequence. It was determined that the first, lower molecular weight, impurity contained Val instead of Ile at position 15 of the sequence, whereas the second, higher molecular weight, impurity contained an unusual amino acid at the same position. This amino acid, which was characterized from the low-and high-energy collision-induced dissociation product ion tandem mass spectra of the second peptide impurity, is an α-amino acid with an asymmetric side chain branched at the β-carbon.     

A computer program (COMPOST) for predicting mass spectrometric information from known amino acid sequences

A computer program (COMPOST) is described that carries out predictive computations on known amino acid sequences. The program is designed to be of use to mass spectrometrists with an interest in protein and peptide sequencing. Mass values (monoisotopic and average) for protonated peptide and protein molecules and elemental compositions are calculated. COMPOST also calculates mass to charge ratio values for protonated peptides expected from specified digests, locates specified amino acid subsequences or peptides of a specifIed molecular weight within a longer sequence, and predicts mass to charge ratio values for fragment ions from high-energy collision-induced dissociation of protonated peptides.