title: Oxidation versus carboxamidomethylation of S-S bond in ranid frog peptides: pro and contra for de novo MALDI-MS sequencing.
abstract: Five natural peptides isolated from ranid skin secretions of European frog species of Rana ridibunda and Rana arvalis (molecular masses 3516, 2674, 2636, 1874, and 1810 Da) were studied by MALDI-TOF/TOF to compare two procedures of disulfide bond cleavage: (1) performic oxidation and (2) reduction/carboxamidomethylation. The processes are relevant for the elucidation of the amino acid sequence inside the seven-member cystine ring at the C-terminus. The results clearly demonstrated that oxidation of the disulfide bond led to notably higher abundances of b- and y-ions, corresponding to the C-terminal peptide bonds, than reduction/carboxamidomethylation. This conclusion is true for all five peptides studied. Besides that, the oxidation procedure is simpler than carboxamidomethylation, as it is a one-step process with no purification required. The oxidation is more reproducible. The results were similar each time the peptide was subjected to the process. It was successfully applied to all five peptides while reduction/carboxamidomethylation failed in the case of brevinin-1Ra, despite all variations of reaction conditions.
authors.affiliation: Chemistry Department, Moscow State University, Moscow, Russia.
authors.forename: Tatiana Y
authors.initials: TY
authors.lastname: Samgina
authors.forename: Konstantin A
authors.initials: KA
authors.lastname: Artemenko
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Gorshkov
authors.forename: Nikita B
authors.initials: NB
authors.lastname: Poljakov
authors.forename: Albert T
authors.initials: AT
authors.lastname: Lebedev
mesh_terms: D000577:Amides / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D029845:Amphibian Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000378:metabolism; D002264:Carboxylic Acids / Q000737:chemistry* / Q000378:metabolism; D004220:Disulfides / Q000737:chemistry* / Q000378:metabolism; D008745:Methylation; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000737:chemistry; D010449:Peptide Mapping; D011485:Protein Binding; D011898:Ranidae / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D000577:Amides; D029845:Amphibian Proteins; D023181:Antimicrobial Cationic Peptides; D002264:Carboxylic Acids; D004220:Disulfides; D010446:Peptide Fragments; C078413:brevinin-1 protein, Rana