Two series of new oligo(p-phenyleneethynylene)s (OPEs) O1-O4 and O5-O8, which have been proven to be one of the chief classes of molecules mainly used as the wires and other potential backbones of molecular electronic devices, have been synthesized by stepwise synthetic approach. The characterization of these oligomers was performed on MALDI TOF MS. Different cationization salts have been applied to investigate the ionization processes of these series of oligomers under MALDI conditions. The experimental results show that these oligomers display a strong tendency to undergo radical cationization and varied ionization efficiency with different cationization agents attributable to their difference in cationic diameters. Furthermore, we found that these two series of oligomers differed in ionization properties because of their different end-groups even when the same cationization agent was used.
FAB mass spectra of sereral synthetic oligopeptides were improved by using various matrices. They provide imformation of both molecular weights and the sequence of amino acids in oligopeptides.An empirical formula B_n+Y_n=M+ 2 was found.From B or Y ion series,the sequence of amino acids in oligopeptides could be induced.
Abstract Electron impact‐induced fragmentations of isomeric dodecen‐1‐ols were investigated using mass‐analysed ion kinetic energy (MIKE) spectrometry and high‐resolution data. The principal fragmentation pathways of the positional isomers studied are dominated by the CC double bond and involve migration and radical‐site rearrangements along the carbon chain with the aid of consecutive rearrangements of hydrogen atoms.
Abstract The mass spectra of novel estra derivatives of amino acids and peptides were studied using electron impact and fast atom bombardment ionization, high‐resolution data and mass‐analysed ion kinetic energy spectrometry. The characteristic peaks of the basic nucleus of estrogenic steroids, the amino acid sequence of the peptide chain and partial skeletal rearrangement of some of these compounds were observed.
Rational design and modification of autotrophic bacteria to efficiently produce high-value chemicals and biofuels are crucial for establishing a sustainable and economically viable process for one-carbon (C1) source utilization, which, however, remains a challenge in metabolic engineering. In this study, autotrophic Clostridium ljungdahlii was metabolically engineered to efficiently co-produce three important bulk chemicals, isopropanol, 3-hydroxybutyrate (3-HB), and ethanol (together, IHE), using syngas (CO2/CO). An artificial isopropanol-producing pathway was first constructed and optimized in C. ljungdahlii to achieve an efficient production of isopropanol and an unexpected product, 3-HB. Based on this finding, an endogenous active dehydrogenase capable of converting acetoacetate to 3-HB was identified in C. ljungdahlii, thereby revealing an efficient 3-HB-producing pathway. The engineered strain was further optimized to reassimilate acetic acid and synthesize 3-HB by introducing heterologous functional genes. Finally, the best-performing strain was able to produce 13.4, 3.0, and 28.4 g/L of isopropanol, 3-HB, and ethanol, respectively, in continuous gas fermentation. Therefore, this work represents remarkable progress in microbial production of bulk chemicals using C1 gases.
Abstract The mass spectrometric behavior of some diene‐based sex pheromones of lepidopterous insects, under electron impact ionization conditions, was studied with the aid of mass‐analyzed ion kinetic energy spectroscopy and high‐resolution data. The similarity of the mass spectra of these dienes and their ability to distinguish double bond positional isomers and geometrical isomers was examined by a ‘minimum‐maximum’ similarity analysis.
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