A21978C, produced by Streptomyces roseosporus, NRRL 11379, is a complex of new acidic lipopeptolide antibiotics which inhibits Gram-positive bacteria. HPLC separation of the various components from the purified complex resulted in the isolation of A21978C1, -C2 and -C3 (major components) and -C4, -C5, and -C0 (minor components). Each of these components was fermented with cultures of Actinoplanes utahensis (NRRL 12052) to give the identical inactive peptide ("A21978C nucleus") by removal of the fatty acid acyl groups from the N-terminus. This peptide was composed of 13 amino acids: L-kynurenine, L-threo-3-methylglutamic acid, L-asparagine, L-aspartic acid (3 residues), glycine (2 residues), L-tryptophan, L-ornithine, D-alanine, D-serine and L-threonine. The amino acid sequence was determined using a combination of the Edman degradation and gas chromatography mass spectrum (GC-MS) analysis of appropriately derivatized peptides obtained from partial hydrolysis. Each major component was shown to be acylated with a branched chain fatty acid at the N-terminus and the structure of this fatty acid was determined by 1H NMR and mass spectral methods. A structure for A21978C was assigned on the basis of this degradative and physico-chemical information.

https://www.jstage.jst.go.jp/article/antibiotics1968/40/6/40_6_761/_pdf

A21978C, a complex of new acidic peptide antibiotics: isolation, chemistry, and mass spectral structure elucidation.

The sequence of 102 amino acid residues from the NH2 terminus and that of 39 amino acid residues from the COOH terminus of bacteriorhodopsin have been determined. These results are in agreement with those recently published by Ovchinnikov and coworkers [Ovchinnikov, Y.A., Abdulaey, N.G., Feigina, M.Y., Kiselev, A.V. & Lobanov, N.A. (1977) FEBS Lett. 84, 1-4]. Chymotryptic cleavage of bacteriorhodopsin produced two fragments, C-1 (Mr 19,000) and C-2 (Mr 6900), the latter containing the blocked NH2 terminus (pyroglutamic acid). Further fragmentation with CNBr gave mostly hydrophobic fragments, which were separated by gel permeation and reverse-phase high-pressure liquid chromatography in formic acid/ethanol/water mixtures. The fragments were sequenced by a judicious combination of mass spectrometric peptide sequencing and automated Edman degradation. The C-2 fragments were ordered on the basis of methionine-containing peptides identified by gas chromatographic mass spectrometry, while C-1 and C-2 were arranged by analysis of an overlapping CNBr fragment.

Partial primary structure of bacteriorhodopsin: sequencing methods for membrane proteins

Twenty-fifth anniversary of the retention index system in gas—liquid chromatography

The mode of ionization of a molecule has a strong influence on its behavior in the mass spectrometer and thus on the information that can be obtained from its mass spectrum. In chemical ionization a reagent gas, e.g. methane, is first ionized by electron impact. The ions formed in ion-molecule reactions, in particular [CH5]+, [C2H5]+, and [C3H5]+, then react “chemically” with the substrate M in fast acid/base type reactions to form ions of the type [MH]+, [M(C2H5)]+, etc., which subsequently fragment to various extents. Alternatively, chemical ionization can be effected by charge exchange, in that ions of a reagent gas, e.g. [He]+•, react with the substrate M to form molecular ions [M]+·. Chemical ionization can thus be conducted in a more or less mild fashion and the extent of the fragmentation can be controlled over a very wide range.

Chemical Ionization—A Mass‐Spectrometric Analytical Procedure of Rapidly Increasing Importance

Amino acid sequence information in proteins and complex proteinaceous material revealed by pyrolysis-capillary gas chromatography-low and high resolution mass spectrometry

A generally applicable strategy for polypeptide sequencing has been developed which involves cleavage of a large peptide (for example, primary degradation peptides obtained by tryptic or cyanogen bromide cleavage of a protein) to a mixture of small peptides whose individual amino acid sequences are then determined without their prior isolation. This is accomplished by conversion of the peptide mixture into the corresponding mixture of O-trimethylsilylated polyamino alcohols through reduction of the N-acetylated peptide esters with lithium aluminum deuteride, followed by treatment with trimethylsilyldiethylamine. The conditions for the enzymatic or chemical cleavage were optimized to yield mixtures of peptides best suited for this technique and which represented complete overlap. Limited acid hydrolysis combined with a second experimen utilizing either an enzyme with broad specificity, a set of enzymes, or dipeptidyl aminopeptidase I on the original and/or Edman-degraded molecule was found to be the best choice. This sequencing strategy was evaluated using 0.4 to 1.4 μmol of peptides with known structures (ribonuclease S-peptide, glucagon) and then applied to primary degradation peptides of rabbit skeletal muscle actin up to twenty amino acids long (0.4 to 1 μmol per experiment).

Polypeptide sequencing by a gas chromatograph mass spectrometer computer system: I—generation and derivatization of complex mixtures of oligopeptides†

Complex mixtures of O-trimethylsilylated polyamino alcohols, which have been generated by either acid or enzymatic hydrolysis of polypeptides and subsequent derivatization, are completely characterized by a gas chromatograph mass spectrometer computer system. These peptide derivatives possess excellent gas chromatographic properties; a wide range of derivatives from di- to hexapeptides may be separated in a single chromatographic experiment. The identification of these compounds, either manually or with the assistance of the computer, is based on three sets of data which are automatically generated after the g.c.m.s. computer experiment: (1) mass spectra, which exhibit sequence-determining ions of high abundance; (2) selected ion records, which allow efficient location of peptide derivatives in the gas chromatogram as well as resolution of incompletely separated fractions; (3) retention indices, which can be calculated from values which have been assigned to each amino acid residue.

Polypeptide sequencing by a gas chromatograph mass spectrometer computer system: II—characterization of complex mixtures of oligopeptides as trimethylsilylated polyamino alcohols

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Polypeptide sequencing by a gas chromatograph mass spectrometer computer system: I—generation and derivatization of complex mixtures of oligopeptides†

Polypeptide sequencing by a gas chromatograph mass spectrometer computer system: II—characterization of complex mixtures of oligopeptides as trimethylsilylated polyamino alcohols