Low-energy collision-induced dissociation of protonated polyamino alcohol derivatives of peptides and N-terminal blocked peptides

This investigation reports the low-energy collision-induced dissociation of the protonated molecules of polyamino alcohols, formed by chemical reduction of synthetic peptides and N-terminal blocked peptides, in order to evaluate its potential for peptide sequence determination. The --CH2--NH-- cleavage with charge retention on the N-terminus was prominent, and the entire sequence of ions produced in this manner was observed. Some of the sequence ions arising from --CH2--NH-- cleavage accompanied by migration of two hydrogens, and --NH--C alpha H-- cleavage with charge retention on the C-terminus, also occurred prominently. In addition, a great number of internal fragment ions were produced in relatively high abundance; these provided supplementary sequence information and were, in some cases, critical in determining the sequence. The usefulness of this method was exemplified by its application to the sequence determination of bacterial lipopeptides.

Characterization of an alkylated dinucleotide by desorption chemical ionization and tandem mass spectrometry

A highly sensitive (subpicomole level), structure-specific method of analysis has been developed for characterizing and quantitating the dinucleotide thymidylyl(3'----5')thymidine methyl phosphotriester by desorption chemical ionization tandem mass spectrometry. The methodology can be applied to related compounds such as the parent dinucleotide and employs either positive or negative ionization mass spectra or daughter spectra. The procedure allows specification of the site of methyl attachment.

Modification of calf thymus DNA by methyl methanesulfonate. Quantitative determination of 7-methyldeoxyguanosine by mass spectrometry

Quantitation of 7-methyldeoxyguanosine (m7dG) produced in the in vitro methyl methanesulfonate (MeMS) action on calf-thymus DNA is achieved by enzymatic degradation, liquid chromatographic separation and chemical ionization mass spectrometry. The total degree of methylation, measured by uptake of [14C]MeMS was 0.35%. Mass spectral analysis shows that m7dG constitutes 84% of the total methylated product. It is also shown that tandem mass spectrometry allows detection of m7dG, as the protonated base, down to 1 pmol level, suggesting that MS/MS analysis can be the method of choice in quantitation of the adducts of in vivo DNA modifications.

Fast atom bombardment mass spectrometry of metal nucleotide complexes

The fast atom bombardment mass spectrometry of the beta-gamma complexes of ATP and GTP with cobalt and chromium are reported. Spectra were recorded in the positive ion mode. Ions in the molecular weight region allow identification of the complexes to be made.

Systematic analysis of desorption chemical ionization (DCI) mass spectra of nucleic acids--7

The positive ion and negative ion pyrolysis mass spectra of the herring sperm DNA have been studied using desorption chemical ionization. The positive ion desorption chemical ionization spectra have been produced with CH4, i-C4H10, NH3, HCl and Cl2; the negative ones with N2O/CH4, N2O/i-C4H10, Cl2, CCl4, HCl and via electron capture. These spectra have been compared with the electron impact ionization spectra. We have observed an important increase of sensitivity when negative ionization has replaced the positive ionization mode. The series of diagnostic ions resulting from direct chemical ionization belong to the family of base + reagent ion X [BH + X] and base + X - HX ion [B]. Their abundance has increased considerably compared to the electron impact spectra. The application of these new diagnostic ions in nucleic acid studies is interesting especially for the much higher abundance of the usually weak dG fragment ion obtained in the negative ionization mode. The dG-base segment of the DNA is the most nucleophilic centre of the whole nucleic acid and is implicated in numerous important biochemical reactions involving, for example, proteins.