The positive and negative ESI-MS/MS spectra of N-ethoxy（phenyl） phosphoryl amino acids（EPP-AA） were investigated by electrospray ionization（ESI） ion trap mass spectrometry. The fragmentation pathways of [ M ＋ N...The positive and negative ESI-MS/MS spectra of N-ethoxy（phenyl） phosphoryl amino acids（EPP-AA） were investigated by electrospray ionization（ESI） ion trap mass spectrometry. The fragmentation pathways of [ M ＋ Na]^＋ and [ M - H]^- ions are proposed and rationalized. The observation may have some potential applications in the interpretation of the MS/MS spectra of novel N-phosphoryl compounds. The complexity of MS/MS spectra of EPP-AA [ M ＋ Na]^＋ ions is decreased compared with that of N-dialkyloxyphosphoryl amino acid. Therefore, the new phosphonamidate method may be considered one of the superior methods that can be used in sequencing peptides and proteins extensively.展开更多
The sequence analysis of peptides was performed by nano-electrospray ionization Fourier transform ion cyclotron resonance tandem mass spectrometry（Nano-ESI-FT-ICR-MSn） and several peptides were chosen as examples. W...The sequence analysis of peptides was performed by nano-electrospray ionization Fourier transform ion cyclotron resonance tandem mass spectrometry（Nano-ESI-FT-ICR-MSn） and several peptides were chosen as examples. With the aid of the collision induced dissociation（CID）, FT-ICR provides not only precise mass/charge ratio, but also structure information of the selected peptides. The fragment ions were identified according to the observed molecular weights and peptide sequence was determined successfully. So Nano-ESI-FT-ICR-MSn is a useful tool for identification of the amino acid sequence of peptides with high confidence. Besides, a pathway for the dehydration of y ions without amino acids containing carboxylic acid under sustained off-resonance irradiation collision-induced dissociation（SORI-CID） condition was proposed.展开更多
During the analysis of benziamidazole-class irreversible proton pump inhibitors,an unusual mass spectral response with the mass-to-charge ratio at[Mt10]t intrigued us,as it couldn't be assigned to any literature k...During the analysis of benziamidazole-class irreversible proton pump inhibitors,an unusual mass spectral response with the mass-to-charge ratio at[Mt10]t intrigued us,as it couldn't be assigned to any literature known relevant structure,intermediate or adduct ion.Moreover,this mysterious mass pattern of[Mt10]t has been gradually observed by series of marketed proton pump inhibitors,viz.omeprazole,pantoprazole,lansoprazole and rabeprazole.All the previous attempts to isolate the corresponding component were unsuccessful.The investigation of present work addresses this kind of signal to a pyridinium thiocyanate mass spectral intermediate(10),which is the common fragment ion of series of labile aggregates.The origin of such aggregates can be traced to the reactive intermediates formed by acid-promoted degradation.These reactive intermediates tend to react with each other and give raise series of complicated aggregates systematically in a water/acetonitrile solution by electrospray ionization.The structure of the corresponding pyridinium thiocyanate species of omeprazole(10a)has been eventually characterized with the help of synthetic specimen(10a′).Our structural proposal as well as its origin was supported by in situ nuclear magnetic resonance,chemical derivatization and colorimetric experiments.展开更多
Cancer cell spheroids(CCS) are a valuable three-dimensional cell model in cancer studies because they could replicate numerous characteristics of solid tumors. Increasing researches have used matrix-assisted laser des...Cancer cell spheroids(CCS) are a valuable three-dimensional cell model in cancer studies because they could replicate numerous characteristics of solid tumors. Increasing researches have used matrix-assisted laser desorption/ionization mass spectrometry imaging(MALDI-MSI) to investigate the spatial distribution of endogenous compounds(e.g., lipids) in CCS. However, only limited lipid species can be detected owing to a low ion yield by using MALDI. Besides, it is still challenging to fully characterize the structural diversity of lipids due to the existence of isomeric/isobaric species. Here, we carried out the initial application of MALDI coupled with laser-postionization(MALDI-2) and trapped ion mobility spectrometry(TIMS) imaging in HCT116 colon CCS to address these challenges. We demonstrated that MALDI-2 is capable of detecting more number and classes of lipids in HCT116 colon CCS with higher signal intensities than MALDI. TIMS could successfully separate numerous isobaric/isomeric species of lipids in CCS. Interestingly, we found that some isomeric/isobaric species have totally different spatial distributions in colon CCS. Further MS/MS imaging analysis was employed to determine the compositions of fatty acid chains for isomeric species by examining disparities in signal intensities and spatial distributions of product ions. This work stresses the robust ability of TIMS and MALDI-2 imaging in analyzing endogenous lipids in CCS, which could potentially become powerful tools for future cancer studies.展开更多
The electrospray behaviors of saturated, substituted, and lacunary polyoxometalates(POMs) with classic Keggin and Dawson structures were investigated systematically by electrospray mass spectrometry(ESI-MS). The anion...The electrospray behaviors of saturated, substituted, and lacunary polyoxometalates(POMs) with classic Keggin and Dawson structures were investigated systematically by electrospray mass spectrometry(ESI-MS). The anions included Keggin [Si W12O40]4-, [Si W11O39]8-, [Si W10O36]8-, [Si W9O34]10-, Dawson [P2W18O62]6-, [P2W17O61]10-, and metal-substituted Keggin derivatives such as [PW11Mn O40]7-, [Si W10V2O40]6-, and [Ge W9Cu3O37]10-. Common species observed in the mass spectra arose from the protonation or cationization of either intact or dehydrated precursor ions. Compared to saturated and substituted POMs, lacunary POMs exhibited distinguished MS behaviors such as a much higher degree of cationization and dehydration of the bare polyoxoanions present in the mass spectra. In addition, some of these lacunary POMs were found to undergo subtle speciation change in solution. Freshly prepared solutions are suggested for synthetics for which lacunary POMs are starting materials. The advantages of the cation-exchange process which are prior to MS analysis are illustrated by an example.展开更多
In this study we systematically analyzed the elution condition of tryptic peptides and the characteristics of identi?ed peptides in reverse phase liquid chromatogra- phy and electrospray tandem mass spectrometry (RPLC...In this study we systematically analyzed the elution condition of tryptic peptides and the characteristics of identi?ed peptides in reverse phase liquid chromatogra- phy and electrospray tandem mass spectrometry (RPLC-MS/MS) analysis. Fol- lowing protein digestion with trypsin, the peptide mixture was analyzed by on-line RPLC-MS/MS. Bovine serum albumin (BSA) was used to optimize acetonitrile (ACN) elution gradient for tryptic peptides, and Cytochrome C was used to retest the gradient and the sensitivity of LC-MS/MS. The characteristics of identi?ed peptides were also analyzed. In our experiments, the suitable ACN gradient is 5% to 30% for tryptic peptide elution and the sensitivity of LC-MS/MS is 50 fmol. Analysis of the tryptic peptides demonstrated that longer (more than 10 amino acids) and multi-charge state (+2, +3) peptides are likely to be identi?ed, and the hydropathicity of the peptides might not be related to whether it is more likely to be identi?ed or not. The number of identi?ed peptides for a protein might be used to estimate its loading amount under the same sample background. Moreover, in this study the identi?ed peptides present three types of redundancy, namely iden- ti?cation, charge, and sequence redundancy, which may repress low abundance protein identi?cation.展开更多
The nitrogen-containing compounds in Changqing crude oil, its atmospheric residue(AR), and vacuum reside(VR) were characterized by negative and positive ion electrospray ionization(ESI) Fourier transform ion cyclotron...The nitrogen-containing compounds in Changqing crude oil, its atmospheric residue(AR), and vacuum reside(VR) were characterized by negative and positive ion electrospray ionization(ESI) Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS). The heteroatom compounds(N_1, N_2, N_1O_1, O_1, and O_2 class species) could be identified by the negative ESI analysis, while the positive mode could only detect the N_1, N_2, and N_1O_1 class species. Among them, the N_1 class species were found to be predominant in crude oil, as confirmed by either negative or positive ESI analyses,which were similar in composition to AR and VR. These compounds with higher abundance were characterized by double bond equivalent(DBE) values and carbon numbers. The composition of these compounds in crude oil and its AR as well as VR was correlated with their different boiling range, DBE values and carbon numbers. The negative ESI analysis showed that the abundant N_1 class species in crude oil and AR were centered at a DBE value of 12, and these species were likely benzocarbazoles, while the N_1 class species with the DBE value ranging from 13 to 16 having more complicated molecular structures were dominant in VR. And the positive ESI analysis gave the information of the abundant N_1 class species in crude oil, AR, and VR having the DBE values in the range of 10, 9―11, and 10―16, respectively, which were likely the compounds with the core of quinoline and benzoquinoline. The analysis confirmed that the distillation process in refinery preferentially removed the low DBE value and low molecular N-class species and brought them into the light and medium distillates, while those N-class species having a high molecular condensation in the molecules with large carbon number remained in the residual oil and could continually affect the downstream oil refining process.展开更多
基金Supported by the Education Department of Henan Province(No. 200510459015).
文摘The positive and negative ESI-MS/MS spectra of N-ethoxy（phenyl） phosphoryl amino acids（EPP-AA） were investigated by electrospray ionization（ESI） ion trap mass spectrometry. The fragmentation pathways of [ M ＋ Na]^＋ and [ M - H]^- ions are proposed and rationalized. The observation may have some potential applications in the interpretation of the MS/MS spectra of novel N-phosphoryl compounds. The complexity of MS/MS spectra of EPP-AA [ M ＋ Na]^＋ ions is decreased compared with that of N-dialkyloxyphosphoryl amino acid. Therefore, the new phosphonamidate method may be considered one of the superior methods that can be used in sequencing peptides and proteins extensively.
基金Supported by the National Natural Science Foundation of China(No.20675079)
文摘The sequence analysis of peptides was performed by nano-electrospray ionization Fourier transform ion cyclotron resonance tandem mass spectrometry（Nano-ESI-FT-ICR-MSn） and several peptides were chosen as examples. With the aid of the collision induced dissociation（CID）, FT-ICR provides not only precise mass/charge ratio, but also structure information of the selected peptides. The fragment ions were identified according to the observed molecular weights and peptide sequence was determined successfully. So Nano-ESI-FT-ICR-MSn is a useful tool for identification of the amino acid sequence of peptides with high confidence. Besides, a pathway for the dehydration of y ions without amino acids containing carboxylic acid under sustained off-resonance irradiation collision-induced dissociation（SORI-CID） condition was proposed.
基金supported by the National Natural Science Foundation of China(Grant Nos.:82030107 and 81872831)the National Science and Technology Major Projects for significant new drugs creation of the 13th five-year plan(Grant Nos.:2017ZX09101001 and 2018ZX09721002007).
文摘During the analysis of benziamidazole-class irreversible proton pump inhibitors,an unusual mass spectral response with the mass-to-charge ratio at[Mt10]t intrigued us,as it couldn't be assigned to any literature known relevant structure,intermediate or adduct ion.Moreover,this mysterious mass pattern of[Mt10]t has been gradually observed by series of marketed proton pump inhibitors,viz.omeprazole,pantoprazole,lansoprazole and rabeprazole.All the previous attempts to isolate the corresponding component were unsuccessful.The investigation of present work addresses this kind of signal to a pyridinium thiocyanate mass spectral intermediate(10),which is the common fragment ion of series of labile aggregates.The origin of such aggregates can be traced to the reactive intermediates formed by acid-promoted degradation.These reactive intermediates tend to react with each other and give raise series of complicated aggregates systematically in a water/acetonitrile solution by electrospray ionization.The structure of the corresponding pyridinium thiocyanate species of omeprazole(10a)has been eventually characterized with the help of synthetic specimen(10a′).Our structural proposal as well as its origin was supported by in situ nuclear magnetic resonance,chemical derivatization and colorimetric experiments.
基金supported by the National Natural Science Foundation of China (Nos.22036001, 22276034 and 22106130)。
文摘Cancer cell spheroids(CCS) are a valuable three-dimensional cell model in cancer studies because they could replicate numerous characteristics of solid tumors. Increasing researches have used matrix-assisted laser desorption/ionization mass spectrometry imaging(MALDI-MSI) to investigate the spatial distribution of endogenous compounds(e.g., lipids) in CCS. However, only limited lipid species can be detected owing to a low ion yield by using MALDI. Besides, it is still challenging to fully characterize the structural diversity of lipids due to the existence of isomeric/isobaric species. Here, we carried out the initial application of MALDI coupled with laser-postionization(MALDI-2) and trapped ion mobility spectrometry(TIMS) imaging in HCT116 colon CCS to address these challenges. We demonstrated that MALDI-2 is capable of detecting more number and classes of lipids in HCT116 colon CCS with higher signal intensities than MALDI. TIMS could successfully separate numerous isobaric/isomeric species of lipids in CCS. Interestingly, we found that some isomeric/isobaric species have totally different spatial distributions in colon CCS. Further MS/MS imaging analysis was employed to determine the compositions of fatty acid chains for isomeric species by examining disparities in signal intensities and spatial distributions of product ions. This work stresses the robust ability of TIMS and MALDI-2 imaging in analyzing endogenous lipids in CCS, which could potentially become powerful tools for future cancer studies.
基金financially supported by the National Natural Science Foundation of China(21371025)the 111 Project(B07012)a Fundamental Research Grant(20121942006)by the Beijing Institute of Technology
文摘The electrospray behaviors of saturated, substituted, and lacunary polyoxometalates(POMs) with classic Keggin and Dawson structures were investigated systematically by electrospray mass spectrometry(ESI-MS). The anions included Keggin [Si W12O40]4-, [Si W11O39]8-, [Si W10O36]8-, [Si W9O34]10-, Dawson [P2W18O62]6-, [P2W17O61]10-, and metal-substituted Keggin derivatives such as [PW11Mn O40]7-, [Si W10V2O40]6-, and [Ge W9Cu3O37]10-. Common species observed in the mass spectra arose from the protonation or cationization of either intact or dehydrated precursor ions. Compared to saturated and substituted POMs, lacunary POMs exhibited distinguished MS behaviors such as a much higher degree of cationization and dehydration of the bare polyoxoanions present in the mass spectra. In addition, some of these lacunary POMs were found to undergo subtle speciation change in solution. Freshly prepared solutions are suggested for synthetics for which lacunary POMs are starting materials. The advantages of the cation-exchange process which are prior to MS analysis are illustrated by an example.
基金This work was partially supported by grants fromthe National Basic Research Program (973) of China(2004CB520804), and National Natural Science Foun-dation of China (No. 30270657, 30230150, 3037030).
文摘In this study we systematically analyzed the elution condition of tryptic peptides and the characteristics of identi?ed peptides in reverse phase liquid chromatogra- phy and electrospray tandem mass spectrometry (RPLC-MS/MS) analysis. Fol- lowing protein digestion with trypsin, the peptide mixture was analyzed by on-line RPLC-MS/MS. Bovine serum albumin (BSA) was used to optimize acetonitrile (ACN) elution gradient for tryptic peptides, and Cytochrome C was used to retest the gradient and the sensitivity of LC-MS/MS. The characteristics of identi?ed peptides were also analyzed. In our experiments, the suitable ACN gradient is 5% to 30% for tryptic peptide elution and the sensitivity of LC-MS/MS is 50 fmol. Analysis of the tryptic peptides demonstrated that longer (more than 10 amino acids) and multi-charge state (+2, +3) peptides are likely to be identi?ed, and the hydropathicity of the peptides might not be related to whether it is more likely to be identi?ed or not. The number of identi?ed peptides for a protein might be used to estimate its loading amount under the same sample background. Moreover, in this study the identi?ed peptides present three types of redundancy, namely iden- ti?cation, charge, and sequence redundancy, which may repress low abundance protein identi?cation.
基金supported by the Young Talent Fund of University Association for Science and Technoloqy in Shaanxi, China (No. 20160222)The PetroChina Innovation Foundation (No. 2016D-5007-0404)the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2017JQ2034)
文摘The nitrogen-containing compounds in Changqing crude oil, its atmospheric residue(AR), and vacuum reside(VR) were characterized by negative and positive ion electrospray ionization(ESI) Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS). The heteroatom compounds(N_1, N_2, N_1O_1, O_1, and O_2 class species) could be identified by the negative ESI analysis, while the positive mode could only detect the N_1, N_2, and N_1O_1 class species. Among them, the N_1 class species were found to be predominant in crude oil, as confirmed by either negative or positive ESI analyses,which were similar in composition to AR and VR. These compounds with higher abundance were characterized by double bond equivalent(DBE) values and carbon numbers. The composition of these compounds in crude oil and its AR as well as VR was correlated with their different boiling range, DBE values and carbon numbers. The negative ESI analysis showed that the abundant N_1 class species in crude oil and AR were centered at a DBE value of 12, and these species were likely benzocarbazoles, while the N_1 class species with the DBE value ranging from 13 to 16 having more complicated molecular structures were dominant in VR. And the positive ESI analysis gave the information of the abundant N_1 class species in crude oil, AR, and VR having the DBE values in the range of 10, 9―11, and 10―16, respectively, which were likely the compounds with the core of quinoline and benzoquinoline. The analysis confirmed that the distillation process in refinery preferentially removed the low DBE value and low molecular N-class species and brought them into the light and medium distillates, while those N-class species having a high molecular condensation in the molecules with large carbon number remained in the residual oil and could continually affect the downstream oil refining process.
