二硫-水自由基阳离子复合物中二中心三电子键的质谱研究

含硫二中心三电子（2c3e）键的研究一直是蛋白质中自由基传递领域的重要课题。本研究采用串联质谱和同位素标记方法研究不同位阻［RS-SR+H₂O］^+·的质谱碎裂模式,以探索位阻不同时这些自由基阳离子配合物内2c3e键的结构性质。结果表明,空间位阻低的［RS-SR+H₂O］^+·（R=甲基,乙基或丙基）碎裂时主要产生［RSH+H₂O］+·和［RSOH+H］⁺ 2种离子,而空间位阻高的［RS-SR+H₂O］^+·（R=异丙基或叔丁基）主要碎片离子是由母离子丢失H₂O而形成的［RS-SR］^+·。因此,在空间位阻低的［RS-SR+H₂O］^+·中2c3e键应以［S∴S］⁺的形式存在,而在空间位阻高的［RS-SR+H₂O］^+·中2c3e键应以［S∴O］+的形式存在。由此可见,结构环境的不同对自由基结构的性质有重要影响,这有助于理解与2c3e键有关的化学反应和生物体中自由基的传递过程机理。     

权威发布

1、以治疗用重组细胞因子为主的基因工程多肽药物:α-干扰素系列产品,促进人血小板生长因子、表皮生因子(EGF)、肿瘤坏死因子(TAF)、碱性成纤维细胞生长因子(BFGF)、干细胞因子(SCF)和人白细胞介素-11、胰岛素和葡激酶等已经用于临床治疗的国家一、二类新药;全面推广蛋白质纯化及后处理环节中的先进技术及先进生产工艺。     

多肽衍生物中自由基介导的选择性C—C键断裂及异构体区分

选择性C—C键断裂反应是化学领域的前沿课题,尤其对于生物大分子,该研究具有重要意义。由于化合物中活性相似的C—C键普遍存在,选择性断裂其中1个C—C键是一大难点。本文以非天然氨基酸组成的多肽衍生物为研究对象,采用TEMPO自由基引发剂策略,将邻甲基苯甲酰(Bz)自由基引入多肽分子(M),在气相中成功制备出［Bz-M+H］^·+自由基离子。通过串联质谱实验发现,该离子相对于质子化多肽分子［M+H］⁺显示出更高的反应活性,具有更丰富的气相解离反应路径,其特征碎片离子［Bz·-a1］⁺和［(Bz-M+H)-HCOOEt］^·+可作为异构体区分和选择性C—C键断裂的灵敏探针,为质谱法区分多肽异构体和选择性C—C键断裂提供了思路和方法。     

水相中酒石酸铀酰形态的电喷雾串联质谱研究

铀的水溶液化学形态是高放废物处置研究的重要内容之一。本实验采用电喷雾串联质谱（ESI-MS/MS）研究酒石酸-硝酸铀酰水溶液中铀酰形态,共分析出14种酒石酸铀酰和5种无机铀酰形态。每个铀酰基团可紧密结合1个酒石酸阴离子,并继续以较弱的形式络合1~2个酒石酸分子。实验中还发现了［(UO₂HTarH₂Tar)₂］²⁺、［(UO₂)₃Tar(HTar)₂(H₂Tar)₂］²⁺等酒石酸铀酰团簇形态。酒石酸铀酰形态中各络合键解离所需能量大小顺序为：铀酰间结合键＞酒石酸阴离子-铀酰结合键＞酒石酸分子-铀酰结合键。该研究对实际条件下铀与有机酸的水溶液形态研究具有指导意义。     

基质辅助激光解吸飞行时间质谱及毛细管电泳对基因工程产品─重组人表皮生长因子的质量控制研究

本文应用基质辅助激光解吸飞行时间质谱（ＭＡＬＤＩ－ＴＯＦ－ＭＳ）测定基因工程产品一重组人表皮生长因子（ｒｈＥＧＦ）的分子量，用毛细管电泳仪测定了其纯度，并得到用Ｇｌｕ－蛋白酶切后ｒｈＥＧＦ的质量肽图，其中８１％的肽段与理论值相符，无规则裂解只占８％。由此建立了一种对基因工程产品进行质量控制及研究蛋白质一级结构的新方法，此方法快速、简便，灵敏度极高，相对误差小于０．５％。     

肿瘤坏死因子诱生剂RT—A2的质谱研究

本文报导了描爪草有效成份RT－A2的EI谱。RT－A2对肿瘤坏死因子（TNF）有较强的诱生作用。RT－A2的分子式被推断为n－C15H31COOH，并讨论了特征碎片离子可能裂解方式。     

基于同位素标记的唑菌酯水解和光解动态及其降解产物质谱分析研究

为深入探究唑菌酯在水中的降解特性，研究了不同温度和pH值下唑菌酯的水解动态和不同光照下的光解动态，并以¹³C-唑菌酯为对照，采用质谱分析研究唑菌酯的水解和光解产物及途径。结果表明，唑菌酯的水解和光解均符合一级动力学方程。在酸性至弱碱性（pH 8.0）水溶液中，唑菌酯较难水解；在碱性水溶液（pH 10.0~13.0）中，唑菌酯的水解速率随温度升高而加快。水解反应为碱基催化反应，唑菌酯的水解速率常数对数值与pH值成线性正相关，且温度越高，反应速率常数越大。在室内模拟太阳光、30 ℃下，唑菌酯易光解，光解反应速率随着光强和紫外强度增加而增加；在室外自然光、13~19 ℃下，唑菌酯难光解。由质谱分析结果推测，唑菌酯水解过程可能是未标记C原子上的酯键断裂脱去1个烷基后加氢，形成(E)-2-［2-［［3-(4-氯苯基)-1-甲基-1H-吡唑-5-氧基］甲基］苯基］-3-甲氧基丙烯酸（C₂₁H₁₉ClN₂O₄），光解过程可能是未标记C原子上的羰基加氢、脱水后成环形成3-(4-氯苯基)-5-［［2-(4-甲氧基呋喃-3-基)苯基］甲氧基］-1-甲基-1H-吡唑（C₂₂H₁₉ClN₂O₃）。本研究对唑菌酯在水环境中的安全评价具有重要的参考价值。     

［C_7H_5O］~（2＋·）双电荷离子的解离反应研究

本文研究了由苯甲酰氨产生的［Ｃ_７Ｈ_５Ｏ］~（２＋·）双电荷离子的单分子解离反应及碰撞诱导解离（ＣＩＤ）和电子捕获诱导解离（ＥＣＩＤ）反应，讨论了离子的结构及电荷分离过渡态的结构，该离子主要以保持苯环或苯环上Ｈ迁移到侧链的结构存在。用在碰撞室上加电压的方法，排除了ＣＩＤ和ＥＣＩＤ谱中单分子解离产物的干扰。     

货车和公共汽车齿轮箱的发展趋势

开发商用车辆齿轮箱的特征是其主要部件不断进一步的发展以及新的变速箱概念的探讨［１］。部件的开发包括努力降低噪音，增加齿轮和同步器的承载能力以及延长使用寿命和改善润滑剂的环境适应性。在手动齿轮箱中增加电子换挡系统在今后商用车辆齿轮箱概念将具有重要的作用。目前还不清楚是否要改变设计，比如机械无级变速器，液力机械功率分支变速箱和电动变速箱将获得重视。     

质子化胞嘧啶碰撞诱导解离的实验和理论研究

在较高的去簇电压(DP)下,使用三重四极杆质谱仪通过电喷雾胞苷的甲醇-水溶液产生了质子化的胞嘧啶［C+H］⁺。［C+H］⁺的碰撞诱导解离过程共有4个相互竞争的解离通道,分别为脱去NH₃分子（-17 u）形成相对强度较高的碎片离子m/z 95;脱去异氢氰酸HNCO（-43 u）和H₂O（-18 u）分别形成m/z 69 和m/z 94;脱去C₂NH₃（-41 u）产生相对强度较低的碎片离子m/z 71,随后对这些碎片离子进行了结构确定。通过量化计算对该过程进行了模拟：首先,对9种质子化胞嘧啶的异构体进行了优化,并给出了它们之间异构化过程的势能面曲线; 其次,基于质子化胞嘧啶的初始结构对这4个解离通道进行了详细的模拟和推导。模拟结果表明,丢失NH₃、HNCO、H₂O和 C₂NH₃这4个解离通道的势垒分别为292.2、355.0、586.6和838.6 kJ/mol,此结果与质子化胞嘧啶碰撞诱导解离过程中产生的离子m/z 95、69、94和71的丰度大小基本一致。     

基于质谱技术的二硫键定位分析方法研究进展

蛋白质中的二硫键是一种常见的重要翻译后修饰,对稳定蛋白质的三维空间结构、维持正确的折叠构象、保持和调节生物活性具有重要意义。因此,分析蛋白质中的二硫键对理解生命过程和药物研发至关重要。质谱既可断裂二硫键和肽键,又可作为检测终端,在二硫键定位分析中发挥了重要作用。本文根据断裂二硫键所处介质以及断裂机理进行分类整理,综述了基于质谱技术的主流二硫键定位方法,通过对比各方法的优缺点,为选择合适的质谱分析方式提供参考。最后,提出了二硫键分析领域面临的挑战和方法学研究的发展方向,以促进方法学相关研究者开发更有效的质谱方法。     

富勒烯与纳米二硫化钨极压抗磨协同性能研究

为探讨富勒烯与纳米二硫化钨的极压抗磨协同性能,利用四球试验机考察富勒烯与纳米二硫化钨复配后在PAO基础油中的摩擦学性能;采用扫描电子显微镜对试验钢球磨痕形貌进行分析,探究富勒烯与纳米二硫化钨的协同作用机制。结果表明:富勒烯与纳米二硫化钨单剂对PAO基础油减摩抗磨效果的改善不明显,而富勒烯与纳米二硫化钨复配后可明显提高油样的减摩抗磨性能,其中质量分数0.01%富勒烯与0.005%二硫化钨复配后减摩抗磨协同效果最优,这是因为富勒烯能够实现滚动摩擦,而纳米二硫化钨能够沉淀到磨损处,起到修复的作用,两者的协同作用,提高了基础油的抗磨减摩性能;富勒烯与纳米二硫化钨复配并不能提高基础油极压性能,这是因为富勒烯不能与纳米二硫化钨生成新的物质来提高基础油的承载能力。     

纳米WS2作为润滑油添加剂的分散稳定性及摩擦学性能

将纳米二硫化钨微粒作为低温切削油CTY-B的添加剂,制备不同质量分数的纳米二硫化钨油样,考察Span-80、十二烷基苯磺酸钠及聚乙二醇6000作为表面活性剂对油样分散稳性能的影响,采用HRS-2M型高速往复摩擦试验机研究纳米二硫化钨对低温切削油CTY-B摩擦学性能的影响,使用扫描电子显微镜观察磨损表面的形貌,利用能谱仪测定磨损表层的元素含量,并对润滑机制进行分析。试验结果显示:Span-80作为表面活性剂对纳米二硫化钨的分散效果最优;纳米二硫化钨能够有效提升低温切削油CTY-B的摩擦学性能,当添加的质量分数为2%时,摩擦因数以及磨痕宽度相比基础油润滑条件下分别降低了24. 8%和16. 4%;在摩擦过程中纳米二硫化钨易沉积在磨损表面的低凹处,形成一层不连续的保护薄膜,从而降低接触面的损伤并起到一定的修复作用。     

含二硫键的蛋白质/多肽的MALDI-TOF MS源内裂解研究

应用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)法研究含二硫键的人胰岛素与甘精胰岛素酶解液的源内裂解(ISD)。比较了不同基质种类及不同结晶状态对含二硫键的人胰岛素与甘精胰岛素酶解液的源内裂解的影响。结果表明,含二硫键的蛋白质的ISD发生受激光点照射位置的影响,在不同基质与结晶形态的条件下,含二硫键的蛋白质的ISD碎片信息不同。通过分析比较,含二硫键的蛋白质的ISD较容易控制,并且其基质的种类及结晶状态作用很关键。需要获得大量碎片时,使激光照射在样品和阿魏酸(FA)基质形成的大结晶处;不希望出现碎片时,可使用2,4,6-三羟基苯乙酮(THAP)为基质,或使激光照射在样品和其他基质形成的细小均匀结晶处。     

Extreme Pressure Lubrication and Wear. The Chemical Reactivity and the Extreme Pressure Action of Two Aliphatic Disulfides

Reaction rates were studied for the action of di-tert-octyl disulfide and di-n-cetyl disulfide in white oil on iron powder over the temperature range 165–250 C. The data were fitted to the Arrhenius equation, and the tertiary disulfide was found to be 1500 times as reactive as the normal disulfide. White oil solutions of the two disulfides were subjected to the Falex test and to the four-ball extreme-pressure test, and the tertiary disulfide was found to be the more effective lubricant additive in these tests. Wear studies were carried out with a pin and disk apparatus under conditions which approximated the above bench tests as regards specimen material, rubbing speed and pressure. The complex nature of the course of wear made it difficult to compare the two disulfides quantitatively. It was found that the tertiary disulfide was 2 to 20 times as efficacious as the normal disulfide in reducing the terminal steady-state wear rate. By treating the additive action of the disulfides as a competition between the rate of metallic adhesion and the rate of chemical reaction with iron, it is possible to reconcile the wide discrepancy between the relative chemical reactivity and the relative additive action of the two disulfides in a quantitative fashion.     

The Importance of Variable Speeds under Extreme Pressure Loading in Molybdenum Disulfide Greases Using Four-Ball Wear Tests

There is recent concern regarding grease behavior in extreme pressure applications. The research described here is aimed at providing good friction and wear performance while optimizing rotational speeds under extreme loading conditions. A design of experiment (DOE) was used to analyze molybdenum disulfide (MoS₂) greases and their importance in reducing wear under extreme loading and various speeds conditions (schedule 1 and schedule 2 speeds). The lamellar structure of MoS₂ provides very good weld protection by forming a layer that can be easily sheared under the applications of extreme pressures. An extreme load of 785 N was used in conjunction with different schedules of various rotational speeds to examine lithium-based grease with and without MoS₂ for an equal number of revolutions. A four-ball wear tester was utilized to run a large number of experiments randomly selected by the DOE software. The grease was heated to 75°C and the wear scar diameters were collected at the end of each test.

The results indicated that wear was largely dependent on the speed condition under extreme pressure loading, and thus a lower MoS₂ concentration is needed to improve the wear resistance of lithium-based greases. The response surface diagram showed that the developed molybdenum disulfide greases exhibited both extreme pressure as well as good wear properties under various rotational speeds when compared to steady-state speed. It is believed that MoS₂ greases under schedule 1 speeds perform better and provide an antiwear film that can resist extreme pressure loadings.     

Tribological properties of nickel-based self-lubricating composite at elevated temperature and counterface material selection

Solid lubricating materials are necessary for development of new generation gas turbine engines. Nickel-based self-lubricating composites with graphite and molybdenum disulfide as lubricant were prepared by powder metallurgy (P/M) method. Their tribological properties were tested by a MG-2000 high-temperature tribometer from room temperature to 600 °C. The structure of the composite was analyzed by XRD and worn surface morphologies were observed by optical microscope. The effects of counterface materials on tribological behavior of composites were investigated. It was found that chromium sulfide and tungsten carbide were formed in the composite by adding molybdenum disulfide and graphite, which were responsible for low-friction and high wear-resistance at elevated temperatures, respectively. The average friction coefficients (0.14–0.27) and wear rates (1.0–3.5 × 10⁻⁶ mm³/(N m)) were obtained for Ni–Cr–W–Fe–C–MoS₂ composite when rubbed against silicon nitride from room temperature to 600 °C due to a synergetic lubricating action of graphite and molybdenum disulfide. The optimum combination of Ni–Cr–W–Fe–C–MoS₂/Ni–Cr–W–Al–Ti–C showed lower friction than other counter pairs. The graphite played the main role of lubrication at room temperature, while sulfides were responsible for low friction at high temperature.     

二硫化钼锂基润滑脂的老化性能预测

对二硫化钼锂基润滑脂进行加速老化试验,获得其质量变化率与老化温度及老化时间的变化规律。运用阿累尼乌斯方程和性能变化的时温关系式,采用线性回归方法推导出以二硫化钼锂基润滑脂质量变化率为性能指标的时温等效关系式。运用该模型可以推算不同贮存温度及不同贮存时间下二硫化钼润滑脂的质量变化情况,实现其老化性能的预测与评估。     

Formation of Adsorbed and Chemically Reacted Sulfur Films on Steel Surfaces During Sliding

Neat thiophene, dimethyl disulfide and dibenzyl disulfide environments were tested for friction and wear with a pin-on-disk apparatus on two steels, 1045 and 4142, the former not containing chromium and the latter containing chromium. In general, friction and wear were changed on introduction of the sulfur compound. Thiophene reduced wear and friction at room temperature while dimethyl disulfide was prowear under similar test conditions. Flow rate of the vaporous lubricant proved to be a dominant factor. Wear tracks were analyzed by SEM, AES, and EDAX. Significant sulfur could only only be found in the wear tracks and only once a surface layer was removed. Interestingly enough, the maximum sulfur concentration was located about 50 Å below the surface. This depth of 50 Å corresponds to the oxide layer. Hardly any sulfur was detectable above the oxide layer. The sulfur concentration decreased exponentially at depths greater than 50 Å.     

二硫化钨发动机油的摩擦学性能研究

采用矿物油和合成油调配成半合成发动机油基础油,同时,通过表面化学修饰和吸附修饰表面改性超细二硫化钨颗粒,使其作为固体润滑添加剂稳定悬浮于基础油中,并加入一定量的功能添加剂,研制了一种二硫化钨发动机油。与国内外品牌发动机油进行摩擦学性能对比实验,发现该种发动机油的油膜强度分别是壳牌超凡喜力发动机油和国产长城发动机油的1.06倍和1.38倍,烧结载荷分别是它们的1.75倍和2.33倍,并且在392N、1450r/min、30min下长时间作用时,摩擦副的摩擦因数随时间的增长而减少,磨斑直径小,磨斑表面光滑,没有明显的犁沟出现。实验表明二硫化钨发动机油具有比国内外品牌发动机油更加优良的抗磨、减摩和极压性能。