Characterization of castor bean neutral lipids by mass spectrometry/mass spectrometry

A method has been developed for the characterization of intact neutral lipids isolated from castor bean (Ricinus communis L.) by mass spectrometry/mass spectrometry (MS/MS). The molecular weights of the trimethylsilyl (TMS) derivatives of the neutral lipids are determined by using both electron impact and chemical ionization (ammonia). Collision-induced dissociation daughter spectra of the (M-CH₃)⁺ ions yield fragment ions that allow easy determination of the acyloxy groups present. The chainlength and degree of unsaturation for each acyloxy group are indicated by R in the ion represented by the general formula (RCO + 74)⁺. Other ions of diagnostic value include (M-RCOO)⁺, (M-RCOOH)⁺, [(M-CH₃-RCOOH]⁺ and [(M-RCOOH)-16]⁺. The presence of a TMS group in any of these fragments results in the formation of ions representing the loss of OTMSH. Prior to MS/MS analysis, partial fractionation by high-performance liquid chromatography (according to degree of unsaturation in the neutral lipids) is useful because daughter spectra are generated free of any isotopic contamination, and minor components are concentrated in single fractions, which aids their characterization. By using this method, 11 neutral lipids were characterized in castor bean.     

Synthesis of G0 aminopolyol and aminosugar dendrimers,controlled by NMR and MALDI TOF mass spectrometry

Organic compounds designed to serve as stable dendrimer cores were developed. A series of aminosugar and amino polyol containing G0 dendrimers were synthesized. The reaction mixture composition was checked by MALDI TOF mass spectrometry, while that of purified products – by ¹H and ¹³C NMR combined with 2D NMR spectroscopy as well as MALDI TOF MSMS mass spectra. Mass spectrometric fragmentation experiments were performed in positive ion mode in order to determine common fragmentation patterns of [M+H]⁺ ions.     

Mass spectrometry/mass spectrometry: capabilities and applications to fuel-related materials

The expanding capabilities of mass spectrometry/mass spectrometry (m.s.-m.s.) in mixture analysis and its applications to fuel-related materials are illustrated. High and low collision energy m.s.-m.s. data obtained on reverse geometry and triple quadrupole spectrometers are given for coal-derived liquid (SRC II) and diesel particulate samples. The direct analysis capability of the m.s.-m.s. methodology and its limitations are illustrated for the identification of an aliphatic carboxylic acid in diesel paniculate. The selective ionization techniques of ammonia chemical ionization and negative chemical ionization are shown to be particularly useful in enhancing the specificity of m.s.-m.s. characterizations. Negative chemical ionization is used to confirm the presence of hydroxybenzoic acid in a diesel particulate sample. Combined laser desorption-chemical ionization is also demonstrated to be an effective ionization technique in m.s.-m.s. analysis. A variant of m.s.-m.s., in which selected anions fragment with charge inversion to give fragment cations, is also employed in the analysis of SRC II and used to identify thioaryl moieties. Functional group screening by an alternative m.s.—m.s. scan procedure, neutral loss scanning, is demonstrated for phenols in SRC II. A scan for all parent ions of a selected daughter ion provides a screening procedure for rapidly identifying all compounds of a given structural type in a complex mixture. The dependence of m.s.-m.s. spectra on collision energy and pressure is shown to add further detail to m.s.—m.s. analysis. The development of a library of m.s.—m.s. spectra of reference compounds to be used for the identification of individual constituents in fuel-related materials is described.     

Stereospecific analysis and mass spectrometry of triacylglycerols fromarabidopsis thaliana (L.) heynh. columbia seed

Arabidopsis thaliana continues to be an excellent model organism for studying plant molecular genetics and biochemistry. In particular, the generation and analysis of mutant lines has facilitated the study of fatty acid biosynthesis, lipid bioassembly and the regulation of these processes. In view of its importance in understanding the pathways specific to seed storage lipid biosynthesis, we report here, for the first time, stereospecific and mass spectral analyses of the triacylglycerols present inA. thaliana (L.) Heynh. Columbia wild-type seed. The use of NH ₄ ⁺ -chemical-ionization mass spectrometry/mass spectrometry is described as a powerful technique in analyzing even trace amounts of individual triacylglycerol species.     

Matrix-assisted laser desorption/ionization imaging mass spectrometry

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a powerful tool that enables the simultaneous detection and identification of biomolecules in analytes. MALDI-imaging mass spectrometry (MALDI-IMS) is a two-dimensional MALDI-mass spectrometric technique used to visualize the spatial distribution of biomolecules without extraction, purification, separation, or labeling of biological samples. MALDI-IMS has revealed the characteristic distribution of several biomolecules, including proteins, peptides, amino acids, lipids, carbohydrates, and nucleotides, in various tissues. The versatility of MALDI-IMS has opened a new frontier in several fields such as medicine, agriculture, biology, pharmacology, and pathology. MALDI-IMS has a great potential for discovery of unknown biomarkers. In this review, we describe the methodology and applications of MALDI-IMS for biological samples.     

测试所有光盘格式、母盘和DVD L0/L1层的偏心率

随着高速CD-R和DVD的应用,测量偏心率就变得日益重要.偏心值太大,将限制读取速度和光盘播放稳定度.