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1.
We present immunoassay-based desorption electrospray ionization mass spectrometry imaging (immuno-DESI-MSI) to visualize functional macromolecules such as drug targets and cascade signaling factors. A set of boronic acid mass tags (BMTs) were synthesized to label antibodies as MSI probes. The boronic ester bond is employed to cross-link the BMT with the galactosamine-modified antibody. The BMT can be released from its tethered antibody by ultrafast cleavage of the boronic ester bond caused by the acidic condition of sprayed DESI microdroplets containing water. The fluorescent moiety enables the BMT to work in both optical and MS imaging modes. The positively charged quaternary ammonium group enhances the ionization efficiency. The introduction of the boron element also makes mass tags readily identified because of its unique isotope pattern. Immuno-DESI-MSI provides an appealing strategy to spatially map macromolecules beyond what can be observed by conventional DESI-MSI, provided antibodies are available to the targeted molecules of interest.  相似文献   

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3.
Mass spectrometry imaging (MSI) of lipids in biological tissues is useful for correlating molecular distribution with pathological results, which could provide useful information for both biological research and disease diagnosis. It is well understood that the lipidome could not be clearly deciphered without tandem mass spectrometry analysis, but this is challenging to achieve in MSI due to the limitation in sample amount at each image spot. Here we develop a multiplexed MS2 imaging (MS2I) method that can provide MS2 images for 10 lipid species or more for each sampling spot, providing spatial structural lipidomic information. Coupling with on-tissue photochemical derivatization, imaging of 20 phospholipid C=C location isomers is also realized, showing enhanced molecular images with high definition in structure for mouse brain and human liver cancer tissue sections. Spatially mapped t-distributed stochastic neighbor embedding has also been adopted to visualize the tumor margin with enhancement by structural lipidomic information.  相似文献   

4.
芍药苷的电喷雾串联质谱研究   总被引:7,自引:1,他引:7  
采用电喷雾串联质谱(ESI-MSn)技术, 结合H/D交换方法, 在正、负离子检测模式下对白芍药材中主要成分芍药苷的质谱裂解规律进行了系统研究. 实验结果表明, 该化合物在正、负离子模式下均得到较好的质谱信息, 且在正离子模式下, 电喷雾质谱分析的灵敏度更高. 同时获得了其质谱裂解规律, 为白芍中其它化合物的分析鉴定提供了有效的质谱方法.  相似文献   

5.
有机异构体的质谱分析简介   总被引:1,自引:0,他引:1  
汪明  詹东亮 《分析化学》1994,22(2):200-205
本文介绍了用于有机异构体辨析的几种质谱方法,并综述了它们在五类异构体中的应用。  相似文献   

6.

The silver(I) complex of a 15-membered macrocyclic ligand with an N3S2 donor set (L1) has been prepared by the reaction of 2,6-diacetylpyridine with 1,8-diamino-3,6-dithiaoctane in the presence of silver(I) ions. A reduced form (L2) of the ligand, in which the imine groups are converted to amines, was prepared by the reduction of the silver(I) complex by sodium borohydride. The ligand L2 has been characterised by various spectroscopic techniques and the copper(II) complex has been prepared. The metal complexes of L1 and L2 have been characterised by electrospray mass spectrometry and UV-visible spectroscopy. The copper(II) complex of L1 has been synthesised from [AgL1]+ via metal exchange. [CuL1](ClO4)2 crystallises in the orthorhombic space group Pna21 with a = 14.374(5) Å, b = 12.947(3) Å, c = 11.824(3) Å with Z= 4. The geometry about the metal centre approximates trigonal bipyramidal with the pyridinyl nitrogen and the sulfur donors in the equatorial positions and the imine nitrogen donors in the axial positions. Metal ion exchange and the relative stabilities of metal complexes of the macrocyclic ligands were studied by electrospray mass spectrometry.  相似文献   

7.
The syntheses and characterization of new chiral tetrabenzoxazine and tetrakis-(dialkylaminomethyl) resorcinarenes can be achieved through the reaction of resorcinarene with chiral amines and formaldehyde. In order to examine their host–guest chemistry, chiral quaternary ammonium guests were synthesized by methylation of different amines and amino acid methyl esters through a reductive methylation followed by addition of methyl iodide. Subsequent anion exchange of the iodide against tetraphenylborate helps to improve solubility of the salts in organic solvents. After characterization in solution, mass spectrometry is used to examine the resorcinarenes’ chemistry in the gas phase. Interesting implications of the fragmentation behavior for their solution phase chemistry arise, for which a first example is presented. Ammonium ion binding is indicated by mass spectrometry. Nevertheless, chiral recognition between the chiral hosts and pseudoracemic 1:1 mixtures of appropriately deuterium-labeled chiral guest cations is however not observed.  相似文献   

8.
Steroid 5-α reductase (5AR) is responsible for the reduction of steroids to 5-α reduced metabolites, such as the reduction of testosterone to 5-α dihydrotestosterone (DHT). A new adverse outcome pathway (AOP) for 5AR inhibition to reduce female reproduction in fish (AOP 289) is under development to clarify the antiestrogenic effects of 5AR inhibitors in female fish. A sensitive method for the DHT analysis using chemical derivatization and liquid chromatography–tandem mass spectrometry was developed. A cell-based 5AR inhibition assay that utilizes human cell lines, a transient overexpression system, and fish cell lines was developed. The measured IC50 values of two well-known 5AR inhibitors, finasteride and dutasteride, were comparable in the different systems. However, the IC50 of dutasteride in the fish cell lines was lower than that in the human cell lines. Finasteride showed a higher IC50 against the RTG-2 cell line. These results demonstrated that 5ARs inhibition could differ in terms of structural characteristics among species. The assay has high sensitivity and reproducibility and is suitable for the application in 5AR inhibition screening for various endocrine disruption chemicals (EDCs). Future studies will continue to evaluate the quantitative inhibition of 5AR by EDCs to compare the endocrine-disrupting pathway in different species.  相似文献   

9.
采用电喷雾萃取电离质谱(EESI-MS)分析致癌性环境有机污染物多环芳烃(PAHs)生物标志物1-羟基芘(1-OHP),探究1-OHP在EESI源中电离的可行性,考察ESI溶剂和样品溶液组成对方法灵敏度的影响,初步建立I-OHP的EESI MS半定量分析方法.结果表明,溶液中1-OHP能够在EES1源中有效电离,生成准分子离子[M-H]- (m/z 217),并得到其二级质谱特征碎片离子[M- H- CO]- (m/z 189);水、甲醇、乙醇、正丙醇和正丁醇5种ESI溶剂中,使用甲醇时,离子峰m/z 217信噪比最大.样品溶液中甲醇含量越高,离子峰m/z 217强度越强.离子峰m/z 217强度与1-OHP浓度在10~200 μg/L内的线性相关性相对最好;相关系数(R)0.982;相对标准偏差(RSD)为3.4%~14.0%(n=5);定量下限约为10 μg/L(S/N=10);单次检测时间小于0.5 min.  相似文献   

10.
Matrix Assisted Laser Desorption Ionization (MALDI) Time of Flight (TOF) Mass Spectrometry (MS) was used to study the molecular weight distribution (MWD) and the number of α-methyl styrene (α-MeSty) repeat units in SRM 1487, a narrow MWD poly(methyl methacrylate) (PMMA) standard reference material of about 6300 g/mol, which was initiated with α-MeSty. It was found that each PMMA polymer chain had from zero to seven α-MeStys per chain. The MWD of the polymer chains containing a fixed number of α-MeStys was obtained. The MWD, Mw, and the average number of α-MeSty at a given molecular weight from MALDI TOF MS compare well with those obtained from more traditional methods such as ultracentrifugation and Size Exclusion Chromatography (SEC). The implications of the number of α-MeStys per chain is discussed in terms of the chemistry of anionic polymerization. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2409–2419, 1997  相似文献   

11.
以花生种子总蛋白及其主要致敏糖蛋白Ara h1为研究对象,采用"一釜法"对蛋白上的糖链进行释放并同时进行衍生化标记,通过C18固相萃取柱纯化,以电喷雾质谱(ESI-MS)、多级串联质谱(MSn)和亲水性液相色谱-质谱联用(HILIC-MS)进行结构解析和定量分析.结果表明,蛋白Ara h1共有10条N-糖链,其中7条为高甘露糖型,2条为木糖修饰,另外1条为与过敏原相关的核心α1,3-Fuc修饰N-糖链,其含量约占总糖链的12.45%.  相似文献   

12.
HIV‐1 nucleocapsid (NCp7) is a two Cys2HisCys zinc knuckle (N‐Zn and C‐Zn) protein that plays a key role in viral replication. NCp7 conformational dynamics is characterized by NMR relaxation dispersion and chemical exchange saturation transfer measurements. While the N‐Zn knuckle is conformationally stable, the C‐Zn knuckle interconverts on the millisecond timescale between the major state, in which the zinc is coordinated by three cysteines and a histidine, and two folded minor species (with populations around 1 %) in which one of the coordination bonds (Cys413‐Sγ‐Zn or His421‐N?2‐Zn) is hydrolyzed. These findings explain why antiretroviral thioesters specifically disrupt the C‐Zn knuckle by initial acylation of Cys413, and show that transient, sparsely‐populated (“dark”), excited states of proteins can present effective targets for rational drug design.  相似文献   

13.
《Analytical letters》2012,45(18):2828-2834
The endogenous neurotoxin, 1-acetyl-6,7-dihydroxyl-1,2,3,4 –tetrahydro isoquinoline (ADTIQ), is acatecholamine isoquinoline, indicating its possible involvement in Parkinson's disease. Moreover, it has been assumed to be a bridge between diabetes and Parkinson's disease because metabolic synthesis resembles glucose metabolism. Therefore, the accurate determination of ADTIQ could play an important role in diagnosis of diabetes and Parkinson's disease. Herein, a sensitive and precise method was established to determine ADTIQ by high performance liquid chromatography-electrospray ionization-tandem mass spectrometry in multiple reaction monitoring mode. The [M+H]+ precursor product ions for ADTIQ were 208.1/190.1 and linear range of calibration curve was from 1.0 to 250.0 nM. The limit of detection and limit of quantification of the developed method were 0.2 nM and 1 nM, respectively. The inter-day, intra-day precision, accuracy, and recoveries were acceptable for biological samples. Furthermore, the reported method was used to determine ADTIQ levels in the substantia nigra of rats. The results indicated that the developed method was highly sensitive and accurate for the determination of ADTIQ.  相似文献   

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15.
The mass spectrometric fragmentation of 2a, 4-disubstituted 5-benzoyl-2a, 3,4, 5-tetrahydro-2-phenoxy-azeto[1,2-α] [ 1,5 ] benzodiazepin-I (2H)-ones has been investigated by means of mass-analyzed ion kinetic energy spectrometry under electron impact ionization conditions. All compounds tend to lose different moieties, such as phenoxy, phenoxy and H, and phenoxyketene. Both [ M^ - PhO ] and [ M^ - PhOH ] ions could further lose CO, and the [ M^ - PhOCH = C = O] ions could lose propene or styrene, PhCON, PhCOHN, and other fragments.  相似文献   

16.
17.
建立了植物源产品茶叶、粮谷、中药材中阿维菌素B1a残留量的液相色谱-串联质谱(LC-MS/MS)测定方法。样品用丙酮-二氯甲烷(体积比1:1)微波辅助提取,提取液经石墨化炭黑/氨基(Carb/NH2)固相萃取小柱净化。采用Hypersil Gold C18色谱柱(150mm×2.1mm,5μm),乙腈-2.5mmol/L乙酸铵水溶液为流动相,以电喷雾电离正离子(ESI+)、多反应监测模式(MRM)定性、定量测定阿维菌素B1a,采用基质标准曲线外标法定量。在5—100μg/L范围内,阿维菌素B1a的峰面积与质量浓度呈线性关系,相关系数大于0.998,方法的检出限(S/N〉3)为5μg/k,定量限(S/N〉10)为10μg/kg。取有代表性的绿茶、小麦、丹参阴性样品进行加标回收试验,在10,50μg/kg加标水平下,回收率为75%-87%,相对标准偏差为4.04%-6.38%(n=5)。该法提取效果好、净化较彻底,灵敏度满足国内外限量标准的要求,适合复杂基质植物源产品中阿维菌素B1a残留量的测定。  相似文献   

18.
Arsenic is a type 1 carcinogen and its toxicity is critically dependent on chemical speciation. However, after decades of research, the biogenesis of at least fifty naturally occurring arsenic species is still not well understood.Here, based on experimental work, it is proposed a set of pathways for the formation of multiple arsenic species that might help to clarify the present situation.These are focused on the thiol protein arsenic bond and on its interaction with reactive metabolites. In fact, arsenic bound to glutathione interacting with sulfur adenosyl methionine (SAM), MethylCB12 and AdoCB12, forms a number of complexes that might be key intermediates in arsenic biochemistry. These include dimethylarsino glutathione (DMAG) m/z 412 [M + H]+, synthesized non-enzymatically from glutathione and cacodylate. Trimethylarsonio glutathione (TMAG) m/z 426 [M]+ synthesized from DMA, GSH and SAM, apparently by a classical Challenger methylcarbonium attack. Tetramethyl arsonium ion m/z 135 [M]+ is formed in a third step, apparently by carbanion methylation. The presence of trimethylarsine oxide (TMAO) m/z 137 [M + H]+ is attributed to the hydrolysis of TMAG or TMA, or to carbanion methylation of dimethylarsinoyl glutathione (m/z 428 [M]+) formed from cacodylate and GSH. Cantoni type attacks of DMAG on SAM were unsuccessful, eventually due to competition of the trivalent S+ atom of SAM for the AsIII atom attack. The presence of dimethylarsonio diglutathione (DMADG m/z 717 [M]+), is suggested to result from a GS- attack on dimethylarsenoyl glutathione (m/z 428 [M + H]+). The presence of dimethylarsenoyladenosine (m/z 372 [M + H]+), trimethylarsenosugar adenine (m/z 370 [M]+), and dimethylthioarsenosugar adenine (m/z 388 [M + H]+), is explained by the synthesis of the pecursor dimethylarsonio-adenosine glutathione DMAAG (m/z 661 [M]+), a likely source of oxo-and trimethylated arsenosugars, as well as of thio-arsenosugars by the cleavage of its S-C bond. The results gathered suggest that cell vacuoles might play a major role in arsenic metabolism, and that the dominance of oxo-As sugars, in algae extracts, may be supported by a mechanism of synthesis independent of DMAAG (m/z 661).They also offer an explanation for the reason why arsenobetaine, and tetramethylarsonium are loosely bound to biotic tissues. Four arsenic species new to science, to the best of our knowledge, and a number of known arsenic compounds were synthesized in this work, identified by HPLC–ESI-MSn and FTICR–ESI-MS, and suggestions regarding their mechanisms of synthesis were advanced. These results provide a framework for arsenic biochemistry which may explain the origin of a significant part of arsenic known metabolites.  相似文献   

19.
Multiple processing by means of successive injection cycles was used to simulate the thermo-mechanical degradation effects on the oligomeric distribution of PLA under mechanical recycling. Likewise, an accelerated thermal ageing over PLA glass transition was performed in order to simulate its service life. MALDI-TOF MS was used for the analysis and the sample preparation procedure was assessed by means of a statistical Design of Experiments (DoE). The quality effects in use for the analysis were signal-to-noise ratio and Resolution. Different matrixes, analyte/matrix proportions and the use of NaTFA as cationization agent were considered. A deep inspection of the statistical results provided a better understanding of the influence of the different factors, individually or in combination, to the signal. The application of DoE for the improvement of the MALDI measurement of PLA stated that the best combination of factors (levels) was the following: matrix (s-DHB), proportion analyte/matrix (1/5 V/V), and no use of cationization agent. Degradation primarily affected the initially predominant cyclic [LAC]n and linear H[LAL]nOH species, where LA stands for a PLA repeating unit. Intramolecular and intermolecular transesterifications as well as hydrolytic and homolytic reactions took place during the formation and disappearance of oligomeric species. In both degradation mechanisms induced by thermal ageing and thermo-mechanical degradation, the formation of H[LAL]nOCH3 by intermolecular transesterifications was highlighted.  相似文献   

20.
The continuous development of resistance to antibiotic drugs by microorganisms causes high mortality and morbidity. Pathogens with distinct features and biochemical abilities make them destructive to human health. Therefore, early identification of the pathogen is of substantial importance for quick ailments and healthcare outcomes. Several phenotype methods are used for the identification and resistance determination but most of the conventional procedures are time-consuming, costly, and give qualitative results. Recently, great focus has been made on the utilization of advanced techniques for microbial identification. This review is focused on the research studies performed in the last five years for the identification of microorganisms particularly, bacteria using advanced spectroscopic techniques including mass spectrometry (MS), infrared (IR) spectroscopy, Raman spectroscopy (RS), and nuclear magnetic resonance (NMR) spectroscopy. Among all the techniques, MS techniques, particularly MALDI-TOF/MS have been widely utilized for microbial identification. A total of 44 bacteria i.e., 6 Staphylococcus spp., 3 Enterococcus spp., 6 Bacillus spp., 4 Streptococcus spp., 6 Salmonella spp., and one from each genus including Escherichia, Acinetobacter, Pseudomonas, Proteus, Clostridioides, Candida, Brucella, Burkholderia, Francisella, Yersinia, Moraxella, Vibrio, Shigella, Serratia, Citrobacter, and Haemophilus (spp.) were discussed in the review for their identification using the above-mentioned techniques. Among all the identified microorganisms, 21% of studies have been conducted for the identification of E. coli, 14% for S. aureus followed by 37% for other microorganisms.  相似文献   

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