Identification of organogermanium compounds as matrix complexes in fast‐atom bombardment mass spectrometry

Organogermanium compounds: XI. The stereochemistry of the reactions of optically active ethyl(1-naphthyl)phenylgermyllithium with some carbonyl compounds

Solution and gas phase hydrogen/deuterium exchange of oligoamide complexes by nanoelectrospray mass spectrometry

This paper describes preparation of carboxymethylated and carboxylated cellulosic fibers from waste paper. Chemical properties of the product were distinguished by Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) spectral analysis. To produce carboxylated and crosslinked fibers and also to increase the anionic surface charge of the fibers, maleic anhydride was used in three different batches; 0, 1%, and 5%. The treatment condition for producing carboxymethylated fibers also involved the use of isopropanol, sodium hydroxide solution, and monochloroacetic acid. The product was purified with 70/30 methanol/ water. Then one sample was neutralized with acetic acid and the other was considered as a sample without having been neutralized. Effects of these treatments were evaluated by FTIR and XRD analysis. The results of FTIR analysis indicated that the carboxyl and methyl functional groups had increased in the carboxymethylated fibers and that just carboxyl groups had increased in carboxylated fibers. The results of XRD analysis showed that the crystallinity of cellulose had decreased in both the carboxymethylated and carboxylated fibers.

Selective Detection of Specific Protein–Ligand Complexes by Electrosonic Spray–Precursor Ion Scan Tandem Mass Spectrometry

Purification method for the isolation of monophosphate nucleotides from Champagne wine and their identification by mass spectrometry

Natural products (NPs) obtained from plants and microorganisms often exhibit biological activities of interest for the discovery of new drugs as well as pharmaceutical and agrochemical products (Fredenhagen et al., 2005; Konishi et al., 2007; Lang et al., 2008). For instance, over 60% of the anticancer drugs have been discovered directly from NPs or are semi-synthetic derivatives of these compounds (Butler, 2008; Costa-Lotufo et al., 2010; Harvey, 2008; Newman & Cragg, 2007). However, the research for new bioactive compounds is usually laborious and slow, once the biological evaluation processes are preceded by isolation, purification, and structural elucidation steps, which are usually expensive and time-consuming (Konishi et al., 2007). This fact, in combination with the large number of known compounds, has led the scientific community to develop new techniques for the direct identification of NPs from extracts and natural broths, thus avoiding reisolation of already known compounds (Bindseil et al., 2001; Konishi et al., 2007; Lee, 2004; Newman et al., 2000; Newman et al., 2003; Shu, 1998). Dereplication is the process that allows for the rapid identification of bioactive metabolites in crude extracts by distinguishing previously identified compounds from novel ones (Crotti et al., 2006). This technique avoids repetitive work of isolation of already known NPs (Wolf & Siems, 2007), promoting chemical screening or metabolite profiling (Crotti et al., 2006). The dereplication process involves separation of single metabolites by chromatographic methods, identification of these compounds by spectroscopic methods, bioassays for evaluation of the biological activity, and searches in databases for verification of the novelty of these compounds (Konishi et al., 2007; Wolf & Siems, 2007). Hyphenated techniques have played a key role in the identification of NPs and other organic compounds (Crotti et al., 2006; Prasain et al., 2003). These techniques combine a separation method (i.e., gas chromatography, GC; liquid chromatography, LC) with a structural identification technique (i.e., mass spectrometry, MS; ultraviolet-visible spectroscopy, UV-vis; nuclear magnetic resonance, NMR). Although a number of

Ionospheric escape from Mars is an important process for the erosion of the Martian atmosphere. The heavy ion outflow is dominated by and O+, however, the Martian ionosphere consists of many more ion species. In the dayside ionosphere below roughly 220 km altitude, is the second most dominant ion, and higher up and in the nightside ionosphere other ions species with a mass near but below that of (28–30 Atomic Mass Unit [AMU], e.g., CO+, , HCO+, NO+, etc.) gain in importance. However, their contribution to the ionospheric outflow is often obscured by the dominant ions and O+. Therefore, we perform a peak fitting to the mass spectrum of SupraThermal and Thermal Ion Composition onboard Mars Atmosphere and Volatile EvolutioN. This method is validated against the mass spectrum given by Neutral Gas and Ion Mass Spectrometer, and results in the ionosphere agree qualitatively very well. A statistical study is then performed to study the low‐energy (<100 eV) heavy ion outflow. We find that can be seen throughout the Martian magnetosphere, but it escapes only in small amounts at a mean rate of less than 1% of the rate. On the other hand, we find that the ions with a mass from 28 to 30 AMU, which were previously unknown in the Martian ion escape, are an important part of the ionospheric outflow, with a mean escape rate that reaches 32% of the rate.

Six alkyl alcohols were studied using thermospray mass Spectrometry. Whereas the dominant ion in the spectrum up to a repeller potential of 120 V was [M + NH4]+, above that potential [M + H]+ and fragment ions appeared. The fragments observed were largely due to hydrogen release from alkyl ions ([CnH2n+1]+ – H2 → [CnH2n‐1]+) and loss of water or some other stable molecule from the same species. The results are compared with those from ionization of the same alcohols under electron impact and photoionization conditions and with results obtained for methanol under thermospray conditions.

Accurate and reliable identification of chemical compounds is the ultimate goal of mass spectrometry analyses. Currently, identification of compounds is usually based on the measurement of the accurate mass and fragmentation spectrum, chromatographic elution time, and collisional cross section. Unfortunately, despite the growth of databases of experimentally measured MS/MS spectra (such as MzCloud and Metlin) and developing software for predicting MS/MS fragments in silico from SMILES patterns (such as MetFrag, CFM-ID, and Ms-Finder), the problem of identification is still unsolved. The major issue is that the elution time and fragmentation spectra depend considerably on the equipment used and are not the same for different LC-MS systems. It means that any additional descriptors depending only on the structure of the chemical compound will be of big help for LC-MS/MS-based omics. Our approach is based on the characterization of compounds by the number of labile hydrogen and oxygen atoms in the molecule, which can be measured using hydrogen/deuterium and 16O/18O-exchange approaches. The number of labile atoms (those from -OH, -NH, ═O, and -COOH groups) can be predicted from SMILES patterns and serves as an additional structural descriptor when performing a database search. In addition, distribution of isotope labels among MS/MS fragments can be roughly predicted by software such as MetFrag or CFM-ID. Here, we present an approach utilizing the selection of structural candidates from a database on the basis of the number of functional groups and analysis of isotope labels distribution among fragments. It was found that our approach allows reduction of the search space by a factor of 10 and considerably increases the reliability of the compound identification.

Screening and identification of unknown contaminants in water with liquid chromatography and quadrupole-orthogonal acceleration-time-of-flight tandem mass spectrometry

Identification and relative quantification of hundreds to thousands of proteins within complex biological samples have become realistic with the emergence of stable isotope labeling in combination with high throughput mass spectrometry. However, all current chemical approaches target a single amino acid functionality (most often lysine or cysteine) despite the fact that addressing two or more amino acid side chains would drastically increase quantifiable information as shown by in silico analysis in this study. Although the combination of existing approaches, e.g. ICAT with isotope-coded protein labeling, is analytically feasible, it implies high costs, and the combined application of two different chemistries (kits) may not be straightforward. Therefore, we describe here the development and validation of a new stable isotope-based quantitative proteomics approach, termed aniline benzoic acid labeling (ANIBAL), using a twin chemistry approach targeting two frequent amino acid functionalities, the carboxylic and amino groups. Two simple and inexpensive reagents, aniline and benzoic acid, in their (12)C and (13)C form with convenient mass peak spacing (6 Da) and without chromatographic discrimination or modification in fragmentation behavior, are used to modify carboxylic and amino groups at the protein level, resulting in an identical peptide bond-linked benzoyl modification for both reactions. The ANIBAL chemistry is simple and straightforward and is the first method that uses a (13)C-reagent for a general stable isotope labeling approach of carboxylic groups. In silico as well as in vitro analyses clearly revealed the increase in available quantifiable information using such a twin approach. ANIBAL was validated by means of model peptides and proteins with regard to the quality of the chemistry as well as the ionization behavior of the derivatized peptides. A milk fraction was used for dynamic range assessment of protein quantification, and a bacterial lysate was used for the evaluation of relative protein quantification in a complex sample in two different biological states.

In an effort to identify the anticoagulant region of venom phospholipases A2, we have systematically compared the amino acid sequences of strong, weak and non-anticoagulant phospholipases. The comparison disclosed several significant substitutions in the region between residues 54 and 77 (homology numbers). This proposed anticoagulant region is positively charged in strong, but negatively charged in weak and non-anticoagulant phospholipases. The microenvironment of a tryptophan residue falls within the proposed region, accounting for the differential characteristics of intrinsic fluorescence changes observed at 335 nm after the binding of phospholipid vesicles to strong and weak anticoagulants. Four lysine residues are located in specific positions in the "anticoagulant" region of strong anticoagulants, and should form a cationic surface, based on analogy with the available crystallographic structures. The chemical modification of lysine, arginine, tyrosine, and tryptophan residues and carboxylate groups, performed by other investigators, not only provides added support for the predicted site, but also confirms the essentiality of the positive charges in the site. This region may participate in the formation of a specific preferential hydrolytic complex leading to the strong anticoagulant effect. The anticoagulant region is distinct and separate from the predicted neurotoxic and myotoxic sites, and is located on the opposite surface of the phospholipase molecule.

The unusual transfer ribonucleic acid (RNA) anticodon adjacent modified nucleoside N-[(9-beta-D-ribofuranosylpurin-6-yl)carbamoyl]threonine, t6A, and its N6-methyl (mt6A) and 5'-phosphate (pt6A) derivatives are efficient ligands for magnesium and manganese ions, as demonstrated by potentiometry and nuclear magnetic resonance spectroscopy. Analysis of the 1H and 13C NMR spectra of t6A in the presence of paramagnetic Mn (II) at 32-34 degrees C has shown that the metal ion binds to the carboxyl group and probably N6 of the side chain as well as the N1 or N7 atom of the adenine ring. A more specific and stronger metal-ligand complex between Mn(II) and pt6A is evident from the 1H, 13C, and 31P NMR data. In this case, the metal forms a complex involving phosphate, N7 of the adenine and the carboxyl group, and N6 of the side chain. Blocking the N6 site as in mt6A attenuates the interaction, as revealed in the proton spectra. Potentiometric titrations at 30 degree C and in 0.1 M KNO3 have produced findings parallel to the NMR data on the interaction of Mn(II) with these ligands and have allowed a quantitative comparisup, and N6 of the side chain. Blocking the N6 site as in mt6A attenuates the interaction, as revealed in the proton spectra. Potentiometric titrations at 30 degree C and in 0.1 M KNO3 have produced findings parallel to the NMR data on the interaction of Mn(II) with these ligands and have allowed a quantitative comparisup, and N6 of the side chain. Blocking the N6 site as in mt6A attenuates the interaction, as revealed in the proton spectra. Potentiometric titrations at 30 degree C and in 0.1 M KNO3 have produced findings parallel to the NMR data on the interaction of Mn(II) with these ligands and have allowed a quantitative comparison between them as well as a comparison of the binding between Mg(II) and Mn(II). The stability constants (log K) for 1:1 metal-ligand complexes between Mg(II) and t6A, mt6A, and pt6A are respectively 5.5, 4.3, and 7.1. For Mn(II), the respective values are 6.0, 4.5, and 7.9. In the case of pt6A, the stability constants are about 5 log K units larger than those obtained for Mg(II) and Mn(II) binding to 5'-AMP [Khan, M. M. T., & Martell, A. E. (1967) J. Am. Chem. Soc. 89, 5585]. Thus the threonine side chain is an important determinant in the interaction between the modified nucleosides and metal ions, and these results are supportive of the idea that a facet of the function of this type of unusual nucleoside in transfer RNA is as a specific ligand for magnesium ion, a postulate promulgated earlier [Miller, J. P., Hussain, Z., & Schweizer, M. P. (1976) Nucleic Acids Res. 3, 1185].

In this contribution RF excited atmospheric pressure glow discharges are investigated in He–water mixtures in a parallel metal plate reactor by mass spectrometry. Positive and negative ion fluxes to the electrode are investigated as a function of varying water concentration and discharge power. The dominant positive ions are H3O+ (and its clusters), OH+, O+, , , HeH+, and . Negative ions are detectable from a concentration of 900 ppm water in He onwards. Coinciding with the emergence of the negative ions, there is a drop in positive ion flux to the mass spectrometer and a significant increase in applied voltage indicating increasing electron loss by attachment and ion loss by mutual (three and two body) positive–negative ion recombination. The dominant negative ions are OH− and its clusters. The negative ion flux increases with increasing water concentration. Positive and negative ion cluster formation increases with decreasing discharge power and increasing concentration of water vapour at constant power. It is shown that the size of the sampling orifice of the inlet of the mass spectrometer is important for sampling atmospheric pressure active plasmas due to the presence of the narrow sheath.

Triacetone triperoxide (TATP), which is used as an explosive in acts of terrorism, was measured by means of gas chromatography/multiphoton ionization/time-of-flight mass spectrometry using a deep-ultraviolet (deep-UV) femtosecond laser as an ionization source. The fragmentation process was investigated by changing the intensity of the laser at the center axis of a molecular beam. A molecular ion was observed using a femtosecond laser, and the ratio of the intensities of the molecular and fragment ions decreased as the intensity of the laser increased. These results suggest that TATP can be efficiently ionized using a deep-UV, ultrashort optical pulse. Furthermore, fragmentation was accelerated by excess energy supplied through higher-order multiphoton processes under a strong radiation field. The detection limits obtained using the molecular ion and two dominant fragment ions, C(2)H(3)O(+) and CH(3) (+), were determined to be 670, 83 and 150 pg, respectively.