Analysis of the Formation Process of Gold Nanoparticles by Surface-Assisted Laser Desorption/Ionization Mass Spectrometry

Chemical reactions of reducing agents in the gold nanoparticle (AuNP) formation process were characterized using surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). As the reaction of the AuNPs progresses, the produced AuNPs can serve as an efficient SALDI substrate. SALDI-MS revealed that the reducing agents and their oxidation products can be determined in the mass spectra. With respect to the transmission electron microscopic and UV-Vis spectroscopic examination of AuNPs, SALDI-MS results confirm not only the tendency toward AuNPs formation, but also reflect the information of the redox reaction process. Our results provide useful information for developing SALDI-MS methods to explore the chemical information regarding the surface behavior between adsorbates and nanomaterials.      

基体辅助激光解吸电离飞行时间质谱用于寡糖的分析

将基体辅助激光解吸电离飞行时间质谱这种新兴的质谱方法用于植物中寡糖的分析。比较了不同的样品制备方法和检测方法对分析结果的影响,给出各寡糖样品的分子量分布,单体和端基基团的分子量。     

壳聚糖的基质辅助激光解吸电离飞行时间质谱分析

利用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)分析甲壳素脱乙酰化降解产物——壳聚糖,对基质、制样方法等影响MALDI-TOF-MS测定结果的因素进行了研究。实验发现,以2,5-二羟基苯甲酸(DHB)为基质,二次结晶法制样分析壳聚糖,既获得了壳聚糖的分子量信息,又可以推断壳聚糖的脱乙酰度,对壳聚糖的制备及其质量与性能控制有着十分重要的指导意义。     

Aerosol Matrix-Assisted Laser Desorption Ionization Mass Spectrometry

A new method of liquid sample introduction for a time-of-flight mass spectrometer (TOF-MS) has been developed by applying the method of matrix-assisted laser desorption ionization to aerosols. Analyte biomolecules are dissolved in a methanol solvent along with a UVabsorbing matrix and formed into an aerosol with a pneumatic nebulizer. The aerosol particles are dried in a heated skimmer tube before ionization by pulsed 355-nm UV laser radiation. Mass analysis is achieved in a linear TOF-MS. Results for the ionization of bovine insulin (5733.5 Mw) are reported.     

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.     

富勒醇的直接激光解吸飞行时间质谱分析

采用激光解吸电离飞行时间质谱对富勒醇样品进行研究,并与富勒烯标准品的质谱特征比较,以正负离子模式联合检测方法考察其特征结构。结果显示,正离子模式下,富勒醇碳笼易为规律性的碎裂峰,负离子模式下,则保留碳笼主体结构的特征峰,而富勒烯的碳笼结构在两种模式下不发生变化。表明该方法可以方便、快速地鉴别富勒醇的结构。采用该方法对富勒醇在二甲基亚砜(DMSO)中的稳定性进行分析,结果发现富勒醇可稳定存在于DMSO溶剂中,用于碱式反应条件下合成富勒醇的鉴别与条件筛选,选择反应碱的最佳浓度为1.0 g/mL。     

表面活性剂的基体辅助激光解吸电离/质谱分析表征

利用基体辅助激光解吸电离／质谱（MALDI－MS）技术对表面活性剂的分析表征进行了详细研究。以2，5－二羟基苯甲酸作为基体，考察MALDI样品制备方法如液滴干燥法、快速干燥法及三明治法对测定结果的影响，发现三明治方法更适合表面活性剂的分析。MALDI可以准确测定离子型表面活性剂的分子量，同时对于非离子型表面活性剂，还可以测定其平均聚合度和分子量的分布。     

Interrogation of Microporous Silica by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

Microporous sol-gels prepared from a tetramethyl orthosilicate precursor with 5-hydroxytryptophan, 5-HTPP, as a dopant were investigated by matrix-assisted laser desorption/ionization mass spectrometry (MALDI). Spectra of 5-HTPP and its oxidation products were obtained when (a) the matrix, -hydroxycinnamic acid, was included in the sol, (b) thin wafers of silica were used, and (c) the surface of the gel was abraded after mounting the sol-gel on the MALDI sample puck so that laser reflection was minimized. The methodology permitted elucidation of the 5-HTPP oxidation pathway. In microporous silica a low molecular product, the dione, was obtained whereas in a mesoporous matrix, dimeric products were formed.     

基体辅助激光解吸—电离飞行时间质谱法分析衍生化的寡链糖

以２，５－二羟基苯甲酸（ＤＨＢ）＋间硝基苄醇（ＮＢＡ）混合基体辅助激光解吸电离飞行时间质谱法（ＭＡＬＤＩ）分析甲壳素降解并衍生化的寡链糖，获得了满意的结果。对比其它基体，如：芥子酸（ＳＡ）、α－氰基－４－羟基肉桂酸等（α＿ＣＨＣＡ），２，５＿ＤＨＢ＋ＮＢＡ混合基体解吸电离效果最好：信号强、信噪比高。甲壳素降解产物的质谱分析至今未见报道。     

单分散聚苯胺齐聚物的激光解吸电离质谱

采用基质辅助激光解吸电离飞行时间质谱（ＭＡＬＤＩ－ＴＯＦ－ＭＳ）技术分别对８个单分散的聚苯胺齐聚物进行了分析研究。实验结果表明,ＭＡＬＤＩ－ＴＯＦ－ＭＳ不但可以作为分析单分散聚苯胺齐聚物的直观、准确、快速的分析工具,而且可以为合成路线的确定提供有利的证据。     

基体辅助激光解吸电离质谱法对DNA样品的高分辨率测定

基体辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)法因其具有测定质量范围大、灵敏度高、速度快及精确度好等优点,近年来已成为测定多肽、蛋白质、核酸、多糖等生物大分子分子量及其一级结构的有力工具.     

Minimization of Fragmentation and Aggregation by Laser Desorption Laser Ionization Mass Spectrometry

Measuring average quantities in complex mixtures can be challenging for mass spectrometry, as it requires ionization and detection with nearly equivalent cross-section for all components, minimal matrix effect, and suppressed signal from fragments and aggregates. Fragments and aggregates are particularly troublesome for complex mixtures, where they can be incorrectly assigned as parent ions. Here we study fragmentation and aggregation in six aromatic model compounds as well as petroleum asphaltenes (a naturally occurring complex mixture) using two laser-based ionization techniques: surface assisted laser desorption ionization (SALDI), in which a single laser desorbs and ionizes solid analytes; and laser ionization laser desorption mass spectrometry (L²MS), in which desorption and ionization are separated spatially and temporally with independent lasers. Model compounds studied include molecules commonly used as matrices in single laser ionization techniques such as matrix assisted laser desorption ionization (MALDI). We find significant fragmentation and aggregation in SALDI, such that individual fragment and aggregate peaks are typically more intense than the parent peak. These fragment and aggregate peaks are expected in MALDI experiments employing these compounds as matrices. On the other hand, we observe no aggregation and only minimal fragmentation in L²MS. These results highlight some advantages of L²MS for analysis of complex mixtures such as asphaltenes.

基质辅助激光解析电离质谱和电喷雾质谱共同快速确证达托霉素结构

运用基质辅助激光解析电离-飞行时间串联质谱(MALDI-TOF/TOF MS)和电喷雾-四级杆-飞行时间质谱(ESI-Q-TOF MS)快速确证环脂肽达托霉素的结构。首先,ESI检测达托霉素相对分子量为1619.7107,与理论值偏差0.0007。选择其双电荷峰m/z 809.848作为母离子进行ESI串联质谱(MS/MS)测定,成功匹配了达托霉素环外氨基酸序列C9H19CO-Trp-Asn-Asp。其次,优化Li OH裂解达托霉素的实验条件,以MALDITOF/TOF MS监测开环效果,获得95%以上的开环样本后,分别运用MALDI和ESI进行MS/MS测定,达托霉素开环产物的b+和y+全部被匹配,达托霉素全部氨基酸序列得到确证。最后,对开环产物的ESI-MS/MS条件进一步优化,获得了丰富的低端碎片离子,解析了脂肪酸链结构,并绘制了脂肪酸链的裂解图。本方法快速、简便、准确,是确证环脂肽类化合物结构的可靠方法。     

基质辅助激光解吸附飞行时间质谱方法分析山竹果皮缩合单宁

在反射模式(Reflectron modes)下,去离子处理后, 引入Cs+(CsCl, 1.52 g/L) 作为阳离子化试剂,得到清晰的山竹果皮缩合单宁的MALDI-TOF质谱图.解析该质谱图能得到完整的山竹果皮缩合单宁的结构信息:山竹果皮缩合单宁是从三聚体(m/z 999)到十一聚体(m/z 3303)分布的多聚物,离子峰最强的为五聚体(m/z 1575);同时存在3种结构单元:(表)儿茶素(C/EC)、(表)棓儿茶素(GC/EGC)和(表)阿福豆素(AC/EAC),且C/EC、AC/EAC和 GC/EGC的离子峰强度依次降低,同时在四聚体(m/z 1440)到七聚体(m/z 2303)均存在棓酰基;从四聚体(m/z 1285)到八聚体(m/z 2436),不同的聚合物中普遍存在A型连接.本研究优化了获取植物缩合单宁结构信息的基质辅助激光解吸附飞行时间质谱方法.     

Probing of Metabolites in Finely Powdered Plant Material by Direct Laser Desorption Ionization Mass Spectrometry

Natural products continue to serve as an important source of novel drugs since the beginning of human history. High-throughput techniques, such as MALDI-MS, can be techniques of choice for the rapid screening of natural products in plant materials. We present here a fast and reproducible matrix-free approach for the direct detection of UV active metabolites in plant materials without any prior sample preparation. The plant material is mechanically ground to a fine powder and then sieved through different mesh sizes. The collected plant material is dispersed using 1 μL solvent on a target plate is directly exposed to Nd:YAG 335 nm laser. The strategy was optimized for the analysis of plant metabolites after study of the different factors affecting the reproducibility and effectiveness of the analysis, including particle sizes effects, types of solvents used to disperse the sample, and the part of the plant analyzed. Moreover, several plant species, known for different classes of metabolites, were screened to establish the generality of the approach. The developed approach was validated by the characterization of withaferin A and nicotine in the leaves of Withania somnifera and Nicotiana tabacum, respectively, through comparison of its MS/MS data with the standard compound. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques were used for the tissue imaging purposes. This approach can be used to directly probe small molecules in plant materials as well as in herbal and pharmaceutical formulations for fingerprinting development.      

聚芳醚砜环状低聚物的基质辅助激光解吸电离质谱分析

采用基质辅助激光解吸电离飞行时间质谱技术分别对两种合成的聚芳醚砜环状低聚物进行了分析研究，并讨论了低聚物中不同聚合度离子组份的分布规律。     

基体辅助激光解吸/电离质谱法对核酸分子的分析测定

基体辅助激光解吸／电离质谱（ＭＡＬＤＩＭＳ）法自８０年代末由Ｋａｒａｓ,Ｈｉｌｅｎｋａｍｐ报道以来,已获得极大的发展．近几年来,其应用范围迅速扩大,各种生物大分子如蛋白质,核酸（ＤＮＡ）,多糖等都已能用ＭＡＬＤＩＭＳ法进行分子量测定．１９９３年,...     

重组人FK506结合蛋白12的基体辅助激光解析电离飞行时间质谱分析

用MALDI－TOF－MS测定了具有生物活性的重组人FK506结合蛋白12(rhFKBP12)的分子量和胰蛋白酶酶解的肽质量指纹谱,实验测定结果与理论计算值一致。证明其一级结构是正确的,在表达、复性和纯化过程中没有氨基酸的丢失、变异和修饰。     

应用基质辅助激光解吸电离飞行时间质谱法测定牛甲状腺球蛋白的分子量

应用基质辅助激光解吸电离飞行时间质谱法测定了牛甲状腺球蛋白的纯度与相对分子量.选择芥子酸为适宜的基质,并对所得的结果进行了讨论.实验结果表明分析方法具有灵敏度高、重现性好、信息直观等特点,明显优于其他传统测定蛋白质的方法.