Matrix-assisted laser desorption/ionization time-of-flight mass spectrometric observation of a peptide triplet induced by thermal cleavage of cystine.

Heat-induced (90 degrees C, 30 min) beta-elimination of a cystine residue leads to cleavage of a disulfide bond and produces a set of three peptides with a cysteine residue, a thiocysteine residue (+32Da), and a dehydroalanine residue (-34Da). This characteristic feature was observed from somatostatin and insulin by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Mass spectrometric observation of this triplet is useful in identifying the presence of a cystine residue in a peptide, and could assist mass spectrometric identification of the peptide from a database.     

超声波处理对渣油加氢过程的影响

对四种减压渣油的超声波处理前后渣油加氢反应产物分布研究表明,超声波处理后渣油加氢反应的焦炭和>500℃残渣油收率降低,气体、汽油、柴油和VGO收率提高,轻油产率提高6~10个百分点,渣油转化率增大,轻质化性能明显增强;不同渣油经超声波处理后的加氢反应性能改变不同;利用超声波处理后渣油加氢的虹吸作用模型,从宏观层次解释了超声波改善渣油加氢效果的原因;超声波处理后杂原子的脱除效果均有不同程度的提高,尤其是对金属钒的脱除影响最为明显。超声波处理后加氢残渣油的饱和分和沥青质含量增加,芳香分和胶质的含量减少。     

煤直接液化残渣焦CO2气化反应的研究

比较了流化床条件下神华煤及其直接液化残渣焦在CO2气氛中的气化反应性，考察了添加液化催化剂、脱除矿物质以及脱除重质油对煤直接液化残渣气化反应的影响规律。结果表明，残渣焦的气化反应性比原煤焦好，残渣焦在1000℃和1100℃的气化反应性指数为0.135和0.290，而原煤焦的则为0.118和0.200。脱灰后残渣焦气化反应性低于脱灰后的煤焦，说明直接液化反应后剩余的难液化物质的气化反应性低于煤焦；未经脱灰处理的残渣焦气化反应性高于煤焦，反映了液化过程中富集的矿物质及铁系催化剂的催化气化活性。脱除残渣中的重质油会降低残渣焦的气化反应性。     

Metal-ion-assisted hydrolysis of dipeptides involving a serine residue in a neutral aqueous solution

Dipeptides having a serine residue at the C-terminus, X-Ser, where X is an appropriate amino acid residue, were efficiently hydrolyzed in the presence of ZnCl2 at pH 7.0. The rapid hydrolysis of X-Ser is due to an autocatalysis of the hydroxy group in the serine residue, and is found to be accelerated by a metal ion, in particular by ZnCl2. Roles of the metal ion in the hydrolysis of peptides involving a serine residue, in relation to the recently reported protein cleavages, are discussed.     

化学修饰法表征Bacillus smithii T7产耐热菊粉酶催化活性中心的必需氨基酸残基

采用化学修饰法研究了史氏芽胞杆菌Bacillus smithiiT7产耐热菊粉酶活性中心氨基酸残基,发现该酶活性中心存在一个组氨酸残基和一个谷氨酸(或天冬氨酸)残基.修饰前后的酶动力学参数变化表明组氨酸残基参与了底物的结合和催化过程,而谷氨酸(或天冬氨酸)的羧基亲核攻击促使底物分解.邹氏作图法证明酶活性中心存在两个必需的色氨酸残基,荧光和圆二色光谱研究表明色氨酸残基在酶的催化和酶的耐热性方面起重要作用.     

Analytical isolation, separation and identification of mutagens from nonvolatile organics of drinking water

A general procedure has been developed for the concentration/fractionation of mutagenic residue organics from small, less than 50L, and large, to 1200L, volumes of drinking water obtained from a variety of sources. This procedure features concentration of the residue organics chromatographically by passage of the water through XAD-2 and XAD-7 resins in specially designed columns, details of which are given. The residue organics are eluted from the resins via organic solvents, followed by solvent removal and subsequent bioassay for mutagenicity. Then the residue organics are fractionated via a coupled bioassay/analytical fractionation method which progressively focuses to the bioactive constituents of the complex mixture of residue organics. In this report, results for the optimal operation and validation of the concentration system are given, using drinking water derived from an industrially polluted river system, a wilderness river system and a major aquifer system. The predominant type of mutagenesis observed for the residue organics isolated from these samples was direct-acting to the Salmonella tester strain, TA98, which was decreased by the addition of the metabolic activation system from the livers of rats previously treated with Arochlor 1254. Some TA100 direct-acting mutagenesis was observed for all samples. Fractionation of the residue organics indicated the mutagens to be nonpolar. Samples of residue organics collected over a period of a year from each type of drinking water showed no discernable pattern of mutagenesis versus season. The methodologies described in this paper provide a comprehensive approach for the concentration/isolation of residue organics from drinking water for studies to identify biohazardous compounds and to characterize these compounds biologically.     

渣油加氢处理过程中硫的分布与脱除规律研究

硫是石油中质量分数最多的杂原子,国内外对硫化合物的研究甚多,但大多数是对轻质馏分的研究[1].原油中70%以上的硫集中在渣油中[2],由于减压渣油分子量大,组成和结构复杂,硫化物的分离和鉴定困难[3].含硫化合物的危害主要表现在严重影响石油产品的使用性能和污染环境,在石油加工过程中腐蚀设备[4,5].随着中国中东高硫原油进口量的增加和环保法规对硫质量分数要求越来越严格,加氢处理成为渣油深加工的主要手段之一[6].脱硫受多种因素的影响[7],如催化剂性能、工艺条件等,而且硫在渣油中的存在类型和分布也严重影响到硫的脱除效果.……     

球状蛋白质分子中氨基酸紧密接触对性质的研究

采用CSU软件 (Contactsofstructuralunits) ,对 61种球状蛋白质分子中氨基酸紧密接触对 (Residue residuecontact)进行了研究 .重点研究了不同氨基酸在形成远程紧密接触对 (Long rangecontact)和近程紧密接触对 (Short rangecontact)时的不同能力 .发现氨基酸Leu,Val,Ile,Met,Phe,Tyr,Cys,Trp(疏性氨基酸 ,H)比较容易形成远程紧密接触对 ,氨基酸Glu,Gln ,Asp ,Asn,Lys,Ser,Arg,Pro(亲水氨基酸 ,P)比较难形成远程紧密接触对 ,而氨基酸Ala,Gly,Thr,His(中性氨基酸 ,N)在形成远程紧密接触对时能力一般 .它们平均每个氨基酸可形成 6 0 3 ,3 64和 4 43个远程紧密接触对 .同时它们在形成近程紧密接触对时能力非常接近 ,平均每个氨基酸可形成的近程紧密接触对数目在 2 3 4～ 2 85变化 ,差别非常小 .亲水氨基酸 (P) ,中性氨基酸 (N)和疏水性氨基酸 (H)在蛋白质分子结构稳定性上起着不同的作用     

Mineralogical and Geochemical Characteristics of the Human Body Ash Residue

The article is devoted to the element composition of the human body ash residue of some Russian cities. It presents the element composition of the human body ash residue, the distribution of elements in the ash residue depending on age and sex. The specific elements of different cities, showing the possible influence of the environmental conditions on the element composition of the human body ash residue. The main objective of this paper is to study the element composition of the human body ash residue and determine the regional characteristics. The methods of instrumental neutron activation analysis and inductively coupled plasma mass spectrometry were applied, an electronic microscope being used as a tool. The result of the research is 63 elements identified within in the human body ash residue. The issue is topical as it expands the knowledge of rare and radioactive elements within the human body and contributes to medicine, for example, by identifying the chemical elements to be included in a person's diet.     

Research progress on pesticide residue detection based on microfluidic technology

The problem of pesticide residue contamination has attracted widespread attention and poses a risk to human health. The current traditional pesticide residue detection methods have difficulty meeting rapid and diverse field screening requirements. Microfluidic technology integrates functions from sample preparation to detection, showing great potential for quick and accurate high-throughput detection of pesticide residues. This paper reviews the latest research progress on microfluidic technology for pesticide residue detection. First, the commonly used microfluidic materials are summarized, including silicon, glass, paper, polydimethylsiloxane, and polymethyl methacrylate. We evaluated their advantages and disadvantages in pesticide residue detection applications. Second, the current pesticide residue detection technology based on microfluidics and its application to real samples are summarized. Finally, we discuss this technology's present challenges and future research directions. This study is expected to provide a reference for the future development of microfluidic technology for pesticide residue detection.     

INFLUENCE OF THE LOCATION OF TRYPTOPHANYL RESIDUES IN PROTEINS ON THEIR PHOTOSENSITIVITY

The environmental effect on Trp residues photolysis was investigated on four proteins containing a single Trp residue in environments of various polarities: glucagon (exposed residue), nuclease (partially buried residue), RNase T₁ (fully buried residue) and melittin (exposed or partially buried residue depending on the salt concentration). Direct photolysis was performed in neutral N₂-saturated phosphate solution at 20°C using 302 nm monochromatic light. Tryptophan loss was monitored by both absorption and fluorescence spectroscopy and by amino acid analysis. The results suggest that tryptophan photodegradation depends on the location of the residue in the protein, with regard to the exposure to the aqueous medium and to the neighbouring amino acids in the primary amino acid sequence and in the three dimensional structure. Photochemical products were not analysed but fluorescence spectra indicate that they vary with protein.     

食用菌中SO2残留的分析调查及检测方法的研究

采用副玫瑰苯胺比色法对14种食用菌产品的SO2残留量进行了测定,并对SO2残留的检测方法进行了比较研究。结果显示,2种食用菌鲜品和2种罐头的SO2残留为20~27 mg/kg,低于国家标准(50 mg/kg)。食用菌干品的SO2残留标准可设定为小于500 mg/kg,有6种干品的SO2残留低于这一标准,为175~291 mg/kg;另外4种干品的SO2残留为1588~2 920 mg/kg,超标情况非常严重,它们都是些白色的食用菌(如银耳、金针菇、竹荪)。副玫瑰苯胺比色法是检测SO2残留最准确、最灵敏的方法,适合于各种SO2浓度的样品;改良的副玫瑰苯胺比色法只适合于高SO2残留的样品;碘量法不适宜检测深颜色的食用菌,而且在检测低SO2残留样品时准确度不高;快速测定法可用于食用菌产品中SO2残留的定性检测和半定量分析。     

神华煤直接液化残渣萃取残渣焦气化动力学研究

在热天平上分别考察了甲苯、苯及乙醇萃取液化残渣热解焦在水蒸气和CO2气氛下的气化动力学,并对比了液化残渣热解焦在相同条件下的气化反应性。结果表明,温度是影响残渣焦气化反应速率的重要因素;超临界溶剂对残渣的萃取使得残渣焦中碳基质的有序度有所降低,并在一定程度上增加了残渣焦的孔结构,因此,提高了残渣焦的气化反应性;残渣焦孔结构不发达,可以使用化学反应控制未反应收缩核模型预测残渣焦的气化反应过程。     

Tryptic hydrolysis of inorcanic pyrophosphate modified by phosphate and O-phosphoethanolamine

By the peptide map method, a phosphorylated peptide has been isolated from a tryptic hydrolysate of phosphorylated yeast inorganic pyrophosphatase (I), and this is a direct proof of the formation of a covalent bond between (I) and phosphate in the course of this reaction. The isolation and analysis of the peptide from the tryptic hydrolysate shows that the phosphate acceptor is probably the aspartic acid residue 240 or 248. Analysis of a tryptic hydrolysate of (I) modified with O-phosphoethanolamine has shown that O-phosphoethanolamine forms an amide bond with the carboxy group of the same aspartic acid residue. In an alkaline medium, the phosphate residue migrates to the imidazole ring of a histidine residue, apparently that present in position 222.     

PHOTOLYSIS OF THE SINGLE TRYPTOPHAN RESIDUE OF EEL TROPONIN C

Abstract— The tryptophan (TRP) residue of eel troponin C was selectively degraded by direct UV irradiation, at 302 nm, in Ar-saturated solution. Depending on the absence or presence of calcium ions, this TRP residue is exposed to aqueous medium or buried in a hydrophobic environment. Tryptophan loss was determined by both absorption and fluorescence spectroscopy and by amino acid analysis. The photodegradation yield was significantly higher for the exposed TRP residue than for the buried ones. These results give more detail on previous observations on several other proteins and corroborate the predominant influence of the polarity on the photosensitivity of a TRP residue in polypeptidic structures.     

明胶与Ag+相互作用的XPS研究

X射线光电子能谱(XPS)技术是一种高灵敏、高分辨的元素定性定量和结构分析技术.本文用该技术研究了照相明胶中S原子与Ag⁺相互作用的本质.研究结果表明,照相明胶中的蛋氨酸、蛋氨酸亚砜残基均能通过S原子与Ag⁺作用,而且在所研究的明胶中蛋氨酸亚砜残基的含量远高于蛋氨酸残基的含量,这意味着在与Ag⁺键合过程中前者占有更重要的地位.此外,本文还比较了不同原料制成的明胶与Ag⁺的作用情况.     

神华煤直接液化残渣超临界溶剂萃取研究

利用甲苯、苯和乙醇三种溶剂在反应釜中对神华煤直接液化残渣进行了超临界溶剂萃取,考察了压力、温度、萃取时间、溶剂/残渣比等对萃取产物收率和重质液体萃取组成的影响。结果表明,以甲苯为溶剂进行萃取时,萃取时间对重质液体产率及HS和A收率的影响不大,而温度、压力以及溶剂/残渣质量比都会影响萃取产物的产率及组成。溶剂超临界萃取过程中,有其他组分向HS组分转化,提高了HS的收率。三种溶剂中,苯显示了和甲苯相似的萃取性能,而乙醇的萃取性能相比苯和甲苯则较差,但乙醇萃取得到的重质液体中轻质组分含量高于苯和甲苯。萃取过程中,残渣中的灰分和硫分主要富集至萃取残渣中。     

尖吻蝮蛇蛇毒中纤溶组分与铽的相互作用

利用平衡析,原子吸收,荧光滴定和荧光寿命测定等方法确定了皖南尖吻蝮蛇蛇毒纤溶组分中Ｃａ＾２＋含量,并利用荧光光谱研究了Ｔｂ＾３＋与ＦＰ中色氨酸残基之间能量转移和ＦＰ中的微区结构。     

Mass spectrometry analysis of in vitro nitration of a recombinant human IgG1 monoclonal antibody

Nitration of a recombinant human monoclonal antibody was carried out in vitro by incubating the antibody with the nitrating reagent tetranitromethane (TNM). The susceptible sites of nitration were identified using high-performance liquid chromatography/mass spectrometry (HPLC/MS). In general, tyrosine residues in the variable domains of the antibody are more susceptible to nitration, while tyrosine residues in the constant domains are relatively resistant to nitration. However, one tyrosine residue in the CH1 domain and one tyrosine residue in the CH2 domain are highly susceptible to nitration. Interestingly, the susceptible tyrosine residue in the CH2 domain is followed by the conserved asparagine residue that is glycosylated.     

神华煤直接液化残渣热解特性研究

通过热重分析技术考察了神华煤直接液化残渣的热解特性。结果表明,和煤热解相比,在相同条件下残渣热解具有更大的失重率和失重速率。残渣热失重分为三个阶段,在173℃以前为残渣热解第一阶段;从173℃～510℃是残渣热解第二阶段,此阶段为残渣的主要失重阶段;510℃以后是残渣热解的第三阶段,在这个阶段残渣继续失重,此阶段的失重是由于残渣的二次分解和残渣中的矿物质分解造成的。通过比较脱油前后残渣热失重曲线发现,残渣主要失重是由于残渣中重质油、沥青烯以及前沥青烯的热解以及挥发造成的。通过脱灰残渣的热解发现,与原残渣相比,脱灰后残渣的失重量变小,矿物质的分解和残渣中有机组分的缩聚是温度高于649℃以后残渣失重的主要原因。由热解特征参数看出,脱油残渣的初始热解温度、最大失重温度以及剧烈热解终温均高于原煤,说明和原煤相比,脱油后残渣中惰性组分不易热解。与原煤和四氢呋喃脱油渣相比,残渣具有最大的失重速率,这是由于残渣中含有大量重质油、沥青烯以及前沥青烯造成的。