基于末端准等重同位素标记的肽段从头测序方法

蛋白质的从头测序在蛋白质生物功能的研究、疾病相关蛋白突变体的发现和抗体药物表征等领域具有关键作用,其主要方法是将蛋白质酶解成肽段,通过二级谱图中碎片离子的质量差异判断氨基酸残基的序列信息,进而实现肽段的从头测序。由于谱图中的碎片离子信号易受噪声和不能用于测序的离子的干扰,目前的从头测序算法准确度较低。本研究发展了一种基于肽段末端准等重同位素标记(Pseudo-isobaric peptide termini labeling,PIPTL)的从头测序方法,将肽段样品分成两份,对一份肽段使用甲醛进行N端二甲基化标记,使用H₂¹⁸O进行C端¹⁸O标记;对另一份样品使用氘代甲醛进行N端二甲基化标记,C端不做处理;两份样品等量混合后,相同序列的不同标记的肽段质量仅相差0.016 Da,这些准等重肽段可在质谱中同时碎裂,产生成对的碎片离子。通过发展基于碎片离子成对性的测序算法简化谱图,并有效提取和分辨b/y离子,实现对肽段快速从头测序。本方法对牛血清白蛋白酶解后肽段测序准确度达到95.51%,显著优于商品化测序软件PEAKS的测序准...     

2709碱性蛋白酶水解BSA蛋白肽谱变化的研究

以2709碱性蛋白酶酶解牛血清白蛋白为研究对象,采用液相色谱-飞行时间质谱联用分析方法和位点非特异性酶切肽谱鉴定方法,分析水解过程中肽谱的动态变化。蛋白电泳分析结果显示,2709碱性蛋白酶在0.1%的添加比例条件下,0.5 h内可将全部蛋白降解,表明其具有极强的水解能力。肽谱分析结果显示,该酶酶解BSA蛋白过程中肽谱变化复杂多样,不同序列多肽具有不同的动态变化特征。酶切位点分析结果显示,2709碱性蛋白酶几乎能在所有种类的氨基酸位点发生酶切,但酶切的频率并不相同,这表明该酶在水解位点上具有宽泛的选择性和一定的倾向性,其中在肽键C端氨基酸种类的选择上具有明显的亮氨酸倾向性。该文可为研究其他工业蛋白酶水解肽谱的规律提供借鉴,并有助于提高我国工业蛋白酶制剂的应用水平和蛋白质加工水平。     

依赖色谱保留时间的智能化选择反应监测质谱方法的建立及其初步应用

建立了依赖色谱保留时间的智能化选择反应监测质谱方法,并与非依赖色谱保留时间的智能化选择反应监测质谱分析方法对不同体系(牛血清白蛋白酶切物、6种标准蛋白质混合物酶切物、腾冲嗜热菌蛋白提取液酶切物)的分析结果进行了系统比较。结果表明,引入色谱保留时间后的智能化选择反应监测质谱方法能够显著提高肽段及蛋白质的鉴定量,并且在复杂体系（如腾冲嗜热菌蛋白提取液酶切物）中效果尤为明显,鉴定到的肽段及蛋白质的覆盖率可分别达到目标肽段和蛋白质数量的89.62%和92.41%,并且灵敏度高、重复性好,能够实现对质荷比相同但保留时间有差异的肽段的准确鉴定。该方法将在复杂生物样本目标蛋白质组高通量、高灵敏度的鉴定、验证和确认中发挥独特作用。     

基质辅助激光解析飞行时间质谱分析条件及准确度对蛋白质数据库搜索结果的影响

考察了基质辅助激光解析飞行时间质谱获得肽质量指纹谱(PMF)时主要分析条件及准确度对蛋白质数据库搜索结果的影响.将牛血清白蛋白(BSA)经聚丙烯酰胺凝胶电泳(SDS-PAGE)分离、酶解;肽段经质谱分析得PMF数据;用MS-Fit引擎在相同数据库及参数下搜索.得出:(1)激光脉冲击打次数在300次以前时,蛋白序列和肽段覆盖率逐步增加;当击打400次时,覆盖率呈下降趋势;(2)随着激光强度增加,目标蛋白得分、氨基酸序列和肽段的覆盖率逐步增加,但当强度增到1413时,则呈现降低趋势;(3)随延迟时间的增加,肽覆盖率呈递增趋势,但当达260 ns后呈下降趋势.按照优化的分析条件对同一位点重复3次,重复性良好.通过对质谱数据准确度的考察,发现以Mix2为外标,数据跟标准值差异越小时,则经其校正后的肽段数据所搜索目标蛋白的得分越高、排序靠前、检出预选蛋白个数越少,可信度越高;反之,难获得候选蛋白.结果表明:质谱准确度和分析条件对蛋白质数据库搜索影响显著.     

新型亲水聚合物修饰硅胶颗粒固定化酶的制备及在蛋白质组鉴定中的应用

采用原子转移自由基聚合法制备了亲水聚合物修饰的硅胶颗粒作为一种新型固定化酶载体,在实现胰蛋白酶高密度固定的同时,显著降低了载体材料非特异性吸附导致的样品损失。因此,该固定化酶材料兼具高酶解效率和高回收率的特性。以标准蛋白质牛血清白蛋白(BSA)为样本,使用该固定化酶1 min即可完成酶解,鉴定到肽段对BSA的氨基酸序列覆盖率可达90%以上。该固定化酶材料成功应用于酵母菌全蛋白质复杂样本的酶解,从3 min酶解产物中鉴定到666个蛋白质,超过同样条件下溶液酶解12 h的鉴定结果。     

原子转移自由基聚合修饰银丝固定化酶反应器的制备及在蛋白质组鉴定中的应用

针对传统溶液酶解存在的酶解时间较长、酶自切物干扰以及蛋白酶不能重复使用等缺陷,通过电子转移生成催化剂的原子转移自由基聚合法修饰银丝,并以其为载体制备了一种新型的固定化酶反应器。用质谱考察了银丝固定化酶反应器(SW-Trypsin)的酶解效率、重复性和回收率。结果表明:绒毛状聚合物修饰的SW-Trypsin的酶解效率较高,酶解标准蛋白牛血清白蛋白(BSA)20 min后,肽段的氨基酸序列覆盖率可达93%,高于传统溶液酶解方法酶解16 h所得79%的覆盖率。使用该固定化酶反应器于一个月内8次酶解BSA所得的氨基酸序列覆盖率在89%到97%之间,平均覆盖率为94%,显示出良好的稳定性。另外,该固定化酶反应器酶解马心肌红蛋白(MYO)的回收率为87.67%。最后,用SW-Trypsin酶解腾冲嗜热菌全蛋白20 min,所鉴定到的氨基酸序列覆盖率和蛋白数量与同样条件下溶液酶解16 h的结果接近,且零漏切位点肽段的比例更高。加之容易分离的优点,SW-Trypsin在蛋白质组学的应用中具有良好的前景。     

基于四极杆-飞行时间质谱的非标记蛋白定量检测方法学研究

以四极杆飞行时间质谱检测的蛋白肽段的质谱信息为基础,开发了一种简单、准确的蛋白定性、定量检测方法,并用于牛血清白蛋白的定性、定量检测。对酶解肽段的梯度洗脱条件和流速等液相色谱条件进行了优化;进行蛋白样品的酶解及质谱检测,利用MassHunter定量软件对数据进行分析;为减少假阳性结果的出现,实验优化了数据处理软件中的设置参数,并对方法的重现性进行了考察。结果显示,重复检测的8个肽段峰面积的RSD均在3.0%以下。该方法对牛血清白蛋白的检出限为100 ng。实验发现,样品中蛋白的含量与检测到的肽段匹配率呈对数关系,并从检测到的丰度较高的8个肽段中确定可用于BSA蛋白定性检测的肽段为:HLVDEPQNLIK,定量检测的肽段为:ATEEQLK,方法的回收率为106%。该方法操作简便,检测快速,成本较低,专一性强,可用于蛋白特异性肽段的筛选及复杂生物样品中蛋白的检测。     

栝楼蛋白 2: 栝楼蛋白部分化学结构的初步测定

栝楼蛋白(Trichobitacin)是从栝楼(Trichosanthes kirilowiiMaxim, Cucurbitaceae)中新发现的核糖体失活蛋白, 分子量为27,228; pI为9.6。应用基质辅助的激光解析飞行时间质谱(MALDI-TOF-MS)和快原子轰击质谱法(FAB-MS)分别测定胰蛋白酶酶解栝楼蛋白和天花粉蛋白(Trichosanthin)的混合肽质谱, 通过比较发现了一些分子量相同的肽。由于这两种蛋白质都来源于栝楼块根, 同源性比较强, 所以这些肽序列在两种蛋白质中基本一样; 再结合蛋白N-端自动顺序仪测定栝楼蛋白N-端的结果, 确定了栝楼蛋白N-端38个氨基酸的顺序, 栝楼蛋白经胰蛋白酶酶解后所得肽段用HPLC分离纯化, 再用蛋白质自动顺序仪, DABITC/PITC双偶合手工法和质谱法共确定了栝楼蛋白N-端, C-端等100多个氨基酸残基的序列。     

栝楼蛋白 2: 栝楼蛋白部分化学结构的初步测定

栝楼蛋白(Trichobitacin)是从栝楼(Trichosanthes kirilowiiMaxim, Cucurbitaceae)中新发现的核糖体失活蛋白, 分子量为27,228; pI为9.6。应用基质辅助的激光解析飞行时间质谱(MALDI-TOF-MS)和快原子轰击质谱法(FAB-MS)分别测定胰蛋白酶酶解栝楼蛋白和天花粉蛋白(Trichosanthin)的混合肽质谱, 通过比较发现了一些分子量相同的肽。由于这两种蛋白质都来源于栝楼块根, 同源性比较强, 所以这些肽序列在两种蛋白质中基本一样; 再结合蛋白N-端自动顺序仪测定栝楼蛋白N-端的结果, 确定了栝楼蛋白N-端38个氨基酸的顺序, 栝楼蛋白经胰蛋白酶酶解后所得肽段用HPLC分离纯化, 再用蛋白质自动顺序仪, DABITC/PITC双偶合手工法和质谱法共确定了栝楼蛋白N-端, C-端等100多个氨基酸残基的序列。     

赖氨酸C端内切酶/胰蛋白酶顺序酶切在蛋白质组学样本制备中的评估

采用胰蛋白酶(Trypsin)单独酶切与不同酶量的赖氨酸C端内切酶(Lys-C/trypsin)顺序酶切两种方法,对293T细胞全蛋白样本进行酶解消化,系统评估Lys-C/trypsin顺序酶切与Trypsin单一酶切在蛋白质组学样本制备中的差别.实验结果表明,Lys-C/trypsin顺序酶切不仅能显著提高肽段和蛋白质的鉴定数目,同时降低遗漏K酶切位点的数目及比例,而且得到的肽段长度有利于质谱鉴定,蛋白质覆盖率明显提升.通过对酶的用量进行优化对比,最终确定了Lys-C/trypsin顺序酶切时酶的合理用量.本研究结果对提高蛋白质组学样本的制备质量以及蛋白质的序列鉴定覆盖度具有指导意义.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.