人肝癌细胞HepG2与正常肝细胞L02的Ο-糖链的比较分析

以培养的原发性肝细胞癌HepG2细胞和正常肝细胞L02为研究对象,用细胞裂解液提取总蛋白,然后采用Carlson还原性β-消除法释放O-糖链,以阳离子交换柱结合C18柱纯化分离O-糖链,用电喷雾电离质谱( ESI-MS)和串联质谱( MS/MS)对O-糖链进行序列鉴定,以β-环糊精为内标对2种细胞系的O-糖链进行定量比较分析.结果表明,在肝癌细胞系HepG2中检测到10种O-糖链,正常细胞系L02中检测到9种O-糖链,其中9种O-糖链是2种细胞系中共有的,但HepG2中存在癌细胞中特有的缩短的O-糖链N1A1( NeuAc-GalNAc, sialyl Tn 抗原). t检验结果表明, HepG2与L02相比,在检测到的10种O-糖链中有5种的含量具有极显著性差异(P<0.01),2种的含量具有显著性差异(P<0.05).     

基于质谱的蛋白质O-糖基化分析

蛋白质的O-糖基化是一种重要的蛋白质翻译后修饰,它和N-糖基化一样是蛋白质糖基化修饰的主要形式。蛋白质的O-糖基化对蛋白质的结构功能有重要的影响,因此分析蛋白质的O-糖基化具有重要的生物学意义。蛋白质O-糖基化分析包含4个方面的内容:(1)鉴定O-糖基化蛋白质的种类;(2)鉴定糖基化位点;(3)鉴定糖链结构;(4)糖链的定量分析。由于缺少保守的O-糖基化氨基酸特征序列,缺乏通用的糖苷酶以及O-糖链结构的复杂性等原因,基于质谱的蛋白质O-糖基化的分析目前仍处于方法开发阶段。本文主要介绍基于质谱的O-糖基化蛋白质的分析方法学在近期取得的一些进展,包括以下4个方面:O-糖蛋白/多肽的富集、O-糖链的解离、O-糖链的结构分析及O-糖基化定量分析。     

基于质谱的蛋白质O-糖基化分析研究进展

蛋白质的O-糖基化是一种重要的蛋白质翻译后修饰,它和N-糖基化一样是蛋白质糖基化修饰的主要形式。蛋白质的O-糖基化对蛋白质的结构功能有重要的影响,因此分析蛋白质的O-糖基化具有重要的生物学意义。蛋白质O-糖基化分析包含4个方面的内容:(1)鉴定O-糖基化蛋白质的种类; (2)鉴定糖基化位点; (3)鉴定糖链结构; (4)糖链的定量分析。由于缺少保守的O-糖基化氨基酸特征序列,缺乏通用的糖苷酶以及O-糖链结构的复杂性等原因,基于质谱的蛋白质O-糖基化的分析目前仍处于方法开发阶段。本文主要介绍基于质谱的O-糖基化蛋白质的分析方法学在近期取得的一些进展,包括以下4个方面:O-糖蛋白/多肽的富集、O-糖链的解离、O-糖链的结构分析及O-糖基化定量分析。     

基于寡糖代谢工程的正常和肿瘤细胞中Mucin型O-糖链的质谱定性定量比较分析

基于寡糖代谢工程结合质谱技术(MS结合MS/MS),对4种肿瘤细胞系和1种正常细胞系中的O-糖链进行了定性和相对定量比较分析.结果表明,4种肿瘤细胞系HeLa,SMMC-7721,HepG2和MCF-7中分别检测到19,11,6和5条O-糖链;在正常肝细胞系L02中检测到10条O-糖链.在对肿瘤和正常细胞系中表达的O-糖链进行定性和相对定量比较中发现,结构组成为N1,H1N1A1和H1N1A2的3种糖链在5种细胞系中均有表达;肿瘤细胞系表达的O-糖链的种类比正常细胞多,且岩藻糖基化和唾液酸化程度均高于正常细胞组.肿瘤细胞系中特有的O-糖链主要有岩藻糖化和唾液酸化修饰的Mucin型Core2结构糖链.MS/MS分析表明,其中岩藻糖基化修饰的O-糖链结构组成为H3N3F1A2,H4N4F1A2和H5N5F1A1,唾液酸化修饰的O-糖链结构组成为H5N4A1,H4N4A2和H5N5A2.     

微量生物样品中糖蛋白N-糖链电喷雾电离质谱分析前处理方法的建立

基于电喷雾电离质谱检测技术,建立了一种可靠、高效、简单,适合于微量糖蛋白N-糖链解离、富集纯化的方法.以糖蛋白牛胰核糖核酸酶(Rib B)和卵清白蛋白(OVA)为模型蛋白直接酶解,比较了4种方法纯化酶解样品的效果.比较了直接酶解和经过聚偏氟乙烯(PVDF)膜富集后酶解微量复杂生物来源样品胎牛血清的酶解效果,最终建立了微量生物样品中糖蛋白N-糖链的质谱分析前处理方法.采用PVDF膜吸附复杂生物样品中的糖蛋白,N-糖苷酶F(PNGase F)酶直接在膜上完成糖链释放(37℃,24 h),采用微晶纤维素柱结合石墨碳柱对糖链进行富集纯化,用于微克级胎牛血清和健康人血清中N-糖链质谱分析的前处理.本方法通用性好,在微量生物样品糖链质谱分析检测的前处理方面具有一定应用价值.     

基于电喷雾电离质谱的人肝癌细胞HepG2与正常肝细胞L02的N-糖链的定性定量比较

以培养的原发性肝癌细胞HepG2和正常肝细胞L02为研究对象,采用细胞裂解液提取总蛋白,用PNGase F酶解释放N-糖链,以微晶纤维素柱结合石墨碳柱纯化分离N-糖链,通过电喷雾电离质谱(ESI-MS)和串联质谱(MS/MS)对N-糖链进行序列鉴定,以β-环糊精为内标对2种细胞系的N-糖链进行了定量比较分析.结果表明,在肝癌细胞系HepG2和正常细胞系L02中共检测到26种N-糖链,与L02相比,HepG2的大多数高甘露糖型糖链、唾液酸化糖链和岩藻糖基化糖链的数量都明显升高,其中有15种糖链在数量上具有极显著性差异(p0.01),1种糖链具有显著性差异(p0.05).本研究为进一步探索肝癌中各类N-糖链的表达特点及发现早期肝癌糖链标志物提供了参考.     

当归多糖ASP3的甲基化分析

通过部分酸水解和甲基化分析, 结合GC-MS测试手段, 对当归多糖ASP3的糖链结构进行了研究. 采用0.2 mol/L三氟乙酸(Trifluoroacetic acid, TFA)对ASP3进行了部分酸水解, 对水解前后的多糖组分进行甲基化分析. 结果显示: ASP3的糖残基主要由D-GalpA, D-Galp, L-Araf和L-Rhap组成, 主链由1,4-D-GalpA连接, 形成“光滑区”半乳糖醛酸聚糖, 由1,4-D-GalpA通过O-4位与1,2-; 1,2,4-L-Rhap的O-2位交替连接形成含有较多分支的“毛发区”鼠李半乳糖醛酸聚糖. 58.8%的Rhap残基发生O-4位取代(1,2,4-L-Rhap). 由T-, 1,5-, 1,3,5-Araf和T-, 1,3-, 1,3,6-, 1,4-, 1,4,6-D-Galp聚合形成的阿拉伯半乳聚糖、半乳聚糖以及阿拉伯聚糖是ASP3侧链的主要组成, 通过Rhap残基的O-4位与主链相连.     

丝胶蛋白源Tn和T抗原的释放制备及质谱分析

以蚕茧丝胶蛋白源Tn抗原和T抗原为研究对象,采用“一釜法”、氨水催化法和链霉蛋白酶E(Pronase E)水解法对丝胶蛋白O-糖链进行释放,并通过固相萃取柱进行分级纯化,以高效液相色谱仪(HPLC)进行分离制备;利用电喷雾质谱(ESI-MS)、串联质谱(MS/MS)及在线液相色谱-质谱联用仪(Online LC-MS)进行了结构鉴定和定量分析.结果表明,丝胶蛋白中O-GalNAc含量为1.58μg/g, O-GalNAcGal含量为0.54μg/g,二者丰度比约为5.3∶1;并且氨水可高效释放出其还原性O-连接单糖GalNAc,通过液相色谱法可实现其精细分离纯化,而以等量Pronase E对丝胶蛋白水解可有效释放出Tn抗原和T抗原.     

人肝癌细胞HepG2与正常肝细胞L02的O-糖链的比较分析

以培养的原发性肝细胞癌HepG2细胞和正常肝细胞L02为研究对象, 用细胞裂解液提取总蛋白, 然后采用Carlson还原性β-消除法释放O-糖链, 以阳离子交换柱结合C₁₈柱纯化分离O-糖链, 用电喷雾电离质谱(ESI-MS)和串联质谱(MS/MS)对O-糖链进行序列鉴定, 以β-环糊精为内标对2种细胞系的O-糖链进行定量比较分析. 结果表明, 在肝癌细胞系HepG2中检测到10种O-糖链, 正常细胞系L02中检测到9种O-糖链, 其中9种O-糖链是2种细胞系中共有的, 但HepG2中存在癌细胞中特有的缩短的O-糖链N1A1(NeuAc-GalNAc, sialyl Tn 抗原). t检验结果表明, HepG2与L02相比, 在检测到的10种O-糖链中有5种的含量具有极显著性差异(P<0.01), 2种的含量具有显著性差异(P<0.05).     

基于MALDI-TOF质谱技术分析人宫颈癌 HeLa细胞N-糖链结构轮廓

以微量HeLa细胞(10⁷个)为对象, 经细胞裂解、还原羧甲基化、胰酶降解和Oasis-HLB柱提取分离得到总糖肽后, 用PNGase F酶解释放N-糖链. 对所得N-糖链用Sep-Pak C₁₈柱纯化后进行完全甲基化衍生, 再采用基质辅助激光解吸电离-飞行时间质谱(MALDI-TOF MS)分析HeLa细胞表面N-糖链的结构轮廓. 结果表明, 在获得的34种N-糖链中, 除高甘露糖型、二天线、三天线、四天线和五天线等N-糖链外, 还出现了在某种程度上与肿瘤发生转移相关的特殊平分型和Lewis结构. 利用MALDI-TOF MS技术可快速分析微量癌细胞表面N-糖链的结构轮廓, 为进一步寻找肿瘤糖链标志物及肿瘤的早期预防诊断提供技术支持.     

Simultaneous determination of magnesium lithospermate B, rosmarinic acid, and lithospermic acid in beagle dog serum by liquid chromatography/tandem mass spectrometry

A rapid, sensitive and specific isocratic liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed for the simultaneous quantitative determination of magnesium lithospermate B (MLB), rosmarinic acid (RA), and lithospermic acid (LA) in beagle dog serum, with silibinin as internal standard. The serum samples were treated by liquid-liquid extraction and analyzed using LC/MS/MS with a TurboIonSpray source. A short run-time (3 min) fulfilled the need for monitoring serum levels of MLB, RA, and LA in large-scale studies. The calibration curves for MLB, RA, and LA were linear over the ranges 8-2048, 4-1024, and 4-1024 ng/mL, respectively, with coefficients of correlation >0.999. The intra- and inter-day precision (CV) of analysis was <10%, and accuracy ranged from 90-104%. This quantitation method was successfully applied to a pharmacokinetic study of salvianolate administrated by intravenous infusion with dosage of 6 mg/kg in beagle dogs.     

血清代谢轮廓分析在评估乙肝肝硬化病程中的应用

采用高效液相色谱-质谱联用(HPLC-MS)作为代谢组学研究平台,分析不同Child-Pugh分级肝硬化病人和健康人群的血清标本,获取代谢轮廓.对数据进行主成分分析(PCA)和正交偏最小二乘判别分析(OPLS-DA),用各组病例的80%作为训练数据构建疾病的OPLS-DA区分模型,以剩余的20%作为检测数据,观察模型对...     

液相色谱同位素稀释串联质谱法测定人血清中17β-雌二醇含量

研究建立了以人血清中E2-16,16,17-d3为内标测定17β-雌二醇的液相色谱/串联质谱(ID-LC/MS/MS)方法。血清样品经固相萃取装置(SPE)提取雌二醇,乙酸乙酯萃取净化,吹干复溶后用10-乙基吖啶酮-2-磺酰氯(EASC)进行衍生。以Agilent Eclipse XDB-C18色谱分离柱,乙腈、水梯度洗脱,使用电喷雾三重四极杆串联质谱的多重反应监测模式测定,以校准曲线法进行定量。所建立的液相色谱同位素稀释串联质谱法(ID-LC/MS/MS)对于分析血清17β-雌二醇的批内、批间RSD分别为0.29%～0.73%和0.18%～0.28%,回收率为99.6%～100.2%,采用IFCC RELA比对(JCTLM比对)样品进行了方法比较,测定结果与其他实验室相比偏差在0.8%范围内。方法可作为人血清中17β-雌二醇含量测量参考方法。     

Pharmacokinetics of salvianolic acid B,rosmarinic acid and Danshensu in rat after pulmonary administration of Salvia miltiorrhiza polyphenolic acid solution

A sensitive and accurate LC–MS/MS method was established for quantifying salvianolic acid B (Sal B), rosmarinic acid (Ros A) and Danshensu (DA) in rat plasma. Salvia miltiorrhiza polyphenolic acid (SMPA), active water‐soluble ingredients isolated and purified from Salvia miltiorrhiza Bge included Sal B, Ros A and DA. The pharmacokinetic analysis of Sal B, Ros A and DA after pulmonary administration of SMPA solution to rat was performed by LC–MS/MS. Results from the pharmacokinetic studies showed that the peak concentration of DA was 21.85 ± 6.43 and 65.39 ± 3.83 ng/mL after pulmonary and intravenous administration, respectively. DA was not detected at 2 h after administration. The absolute bioavailabilities of Sal B and Ros A were respectively 50.37 ± 27.04 and 89.63 ± 12.16% after pulmonary administration of 10 mg/kg SMPA solution in rats. The absolute bioavailability of Sal B increased at least 10‐fold after pulmonary administration, compared with oral administration. It was concluded that the newly established LC–MS/MS method was suitable for describing the pharmacokinetic characteristics of Sal B, Ros A and DA in rat after pulmonary administration of SMPA solution. The data from this study will provide a preclinical insight into the feasibility of pulmonary administration of SMPA.     

Detection and identification of carcinogen-peptide adducts by nanoelectrospray tandem mass spectrometry

Nanoelectrospray (nanoES) tandem mass spectrometry was used to examine covalently modified peptides in crude enzymatic digests of human serum albumin (HSA) that had been exposed to either benzo[a]pyrene diol epoxide (B[a]PDE, 1), chrysene diol epoxide (CDE, 2), 5-methylchrysene diol epoxide (5MeCDE, 3), or benzo[g]chrysene diol epoxide (B[g]CDE, 4). The low flow rates of nanoES (～20 nL/min) allowed several MS/MS experiments to be optimized and performed on a single sample with very little sample consumption (～30 min analysis time/µL sample). Initially, nanoES was compared with conventional LC/MS/MS analysis of carcinogen-peptide adducts. For example, nanoES analysis of an unseparated digest of B[a]PDE-treated serum albumin revealed the same peptides (RRHPY and RRHPY-FYAPE) that were previously shown, by LC/MS/MS, to be adducted with B[a]PDE. In addition, nanoES could detect unstable peptide adducts that might not otherwise have been directly observable. Finally, nanoES was shown to be an effective way to screen mixtures of modified and unmodified peptides for which no chromatographic information is available.     

The application of ultra-performance liquid chromatography/tandem mass spectrometry to the detection and quantitation of apolipoproteins in human serum

The detection and quantitation of apolipoproteins, important markers for coronary heart disease, in serum by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using multiple reaction monitoring (MRM) is reported. A tryptic digest of depleted human serum was analysed by nanoflow LC/MS/MS at a flow rate of 300 nL/min and several apolipoproteins (Apo), including Apo A1, A2, A4, C1, C2, C3, D, F and M, were successfully identified. The analysis of the same depleted serum digest by ultra-performance (UP)LC/MS/MS operating at 700 microL/min resulted in comparable sensitivity and selectivity to the nanoflow method, but with a dramatic ( approximately 20-fold) reduction in run time. The potential of UPLC/MS/MS for the rapid quantitation of proteins in biological matrices by representative tryptic peptides was further investigated using Apo A1 and its corresponding stable isotopically labelled tryptic AQUA peptide (DYVSQFEGSALGK). A set of serum-based Apo A1 calibrators from a clinical analyser kit were digested without depletion following the addition of the AQUA peptide and analysed using UPLC/MS/MS. A linear calibration curve was generated from peak area ratios to the labelled peptide with a coefficient of correlation of 0.9989. Standard curves were also generated for other apolipoproteins together with Apo B100, Apo E, lecithin cholesterol acyltransferase and albumin, which were also detected in the standards. The concentration of Apo A1 in five fresh undepleted human serum samples and a quality control (QC) sample were determined using both the UPLC/MS/MS method and a clinical analyser. Results were comparable and the quantitative study, involving 80 injections which took hours rather than days to complete, demonstrates the high-throughput potential of UPLC/MS/MS to quantify multiple serum proteins without the need for antibodies, and thus provide an alternative to the use of clinical analysers for serum protein biomarkers.     

A Rapid Sample Preparation Procedure Using MonoSpin CBA and Amide Columns for Tetrodotoxin Detection in Serum and Urine Using LC–MS/MS Analysis

Clinical diagnosis of tetrodotoxin (TTX) poisoning can be difficult because of the lack of characteristic morphological findings and a screening test, such as an immunoassay. Here, we present a fully validated method for the analysis of TTX in serum and urine. In this method, serum and urine samples were extracted using MonoSpin CBA or amide columns, followed by LC–MS/MS analysis. The TTX was eluted from the column by 0.1 mL of 10 % acetic acid solution, and was directly injected into LC–MS/MS. An Agilent 1200 HPLC system equipped with a HILIC separation column (Zorbax HILIC Plus 2.1 × 100 mm, 3.5 μm) was used for isocratic elution, with a mobile phase of 10 mM ammonium formate with formic acid (95:5, v/v), along with 5 mM trifluoroacetic acid and 2 % acetonitrile. TTX was detected with an Agilent 6410 mass spectrometer utilizing positive electrospray ionization and multiple reaction monitoring. Limits of quantification for serum and urine were established to be 1 and 0.5 ng mL^?1, respectively. Limits of detection for serum and urine were 0.5 and 0.25 ng mL^?1, respectively. Intra-day and inter-day precision varied from 1.5 to 8.5 %. The recovery was >86.5 % for both matrices. In this method, the sample preparation process prior to injection into the LC–MS/MS takes approximately 10–15 min, which reduces the extraction time to one-tenth of that of previous methods. The application of this method was further verified by analysis of biological materials from a patient suffering from puffer fish poisoning.     

A myxobacterium strain Sorangium cellulosum AHB125 producing epothilone B and other anticancer substances

A myxobacterium strain AHB125 belonging to genus Sorangium cellulosum was isolated from Anhui area in China and identified with morphological analysis by electron microscopy and phase contrast microscope according to Bergey's manual of systematic bacteriology (8th Ed.). Its high-antitumor bioactivity metabolites was evaluated by bioassay-directed screening technique with B16 tumor cell line etc. Research results showed that it exhibited not only strong antitumor ability bioactivities and broad-spectrum antitumor abilities to B16, Bel7402, H446, SGC7901 cell lines, but also has selectivity and pertinence to B16 and SGC7901 cell lines. The compound was confirmed as epothilone B by HPLC and LC/MS analysis, compared to the epothilone B standard sample. Bioassay indicated that there were other high-bioactive substances in the metabolites.     

Analysis of aflatoxin B1-lysine adduct in serum using isotope-dilution liquid chromatography/tandem mass spectrometry

A method for quantitative analysis of aflatoxin B1-lysine adduct (B1-Lys) in serum by liquid chromatography using tandem mass spectrometry (LC/MS/MS) is presented. The protein in a 250-microL sample was digested in the presence of a stable-isotope internal standard during a 4-h incubation at 37 degrees C with Pronasetrade mark. B1-Lys and the internal standard were extracted using mixed-mode solid-phase extraction cartridges and eluted with 2% formic acid in methanol. Following evaporation and reconstitution, extracts were injected onto a Luna C-18(2) column and eluted with a step gradient of acetonitrile and 0.06% formic acid. The B1-Lys and the internal standard were detected in a positive ionization selective reaction monitoring mode with a ThermoFinnigan TSQ Quantum triple quadrupole mass spectrometer. Calibration curves were linear for concentrations from 0.05-8.0 ng/mL. The method was validated with aflatoxin B1 dosed rat serum diluted to anticipated high and low concentrations. Total imprecision determined from 30 measurements over 15 days was 5.6% and 9.1%, respectively. Recoveries of 78.8 +/- 6.4% for B1-Lys and 85.4 +/- 12.4% for the internal standard were based on the full extraction and reconstitution processes. The method can be used to quantitate B1-Lys at the 0.5 pg/mg albumin level and is suitable for routine analysis.     

Development and validation of a liquid chromatography–tandem mass spectrometry method for the simultaneous analysis of androgens,estrogens, glucocorticoids and progestagens in human serum

We present a liquid chromatography tandem mass spectrometry method for the simultaneous analysis of 16 endogenous steroids (androgens, estrogens, glucocorticoids and progestogens) in human serum. Samples (250 μl of matrix) were extracted with t-butylmethyl ether prior to LC–MS/MS analysis. The chromatographic separation was achieved on a reversed-phase column using a methanol–water gradient. The HPLC was coupled to a triple quadrupole mass spectrometer equipped with an electrospray ionization source with acquisition in multiple reaction monitoring mode. The method was validated using surrogate matrices and human serum samples. The specificity of the method was confirmed for all of the considered steroids; linearity was also assessed (R² > 0.99, lack-of-fit test) in the ranges of concentrations investigated. The lower limits of quantification were in the range 10–400 pg/ml depending on the target steroid. Accuracy was in the range 85–115% for all target steroids except for the lower limit of quantitation levels where it was 80–120%. The extraction recovery was always >65%. No significant matrix effects were observed. To test the reliability of the method, the analysis of serum samples collected from 10 healthy subjects (5 M/5F) was performed. The present method can be used to identify the trajectories of deviation from the concentration normality ranges applied to disorders of the gonadal and adrenal axes.