The use of chromium(III) to supercharge peptides by protonation at low basicity sites.

ABSTRACT: The addition of chromium(III) nitrate to solutions of peptides with seven or more residues greatly increases the formation of doubly protonated peptides, [M + 2H](2+), by electrospray ionization. The test compound heptaalanine has only one highly basic site (the N-terminal amino group) and undergoes almost exclusive single protonation using standard solvents. When Cr(III) is added to the solution, abundant [M + 2H](2+) forms, which involves protonation of the peptide backbone or the C-terminus. Salts of Al(III), Mn(II), Fe(III), Fe(II), Cu(II), Zn (II), Rh(III), La(III), Ce(IV), and Eu(III) were also studied. Although several metal ions slightly enhance protonation, Cr(III) has by far the greatest ability to generate [M + 2H](2+). Cr(III) does not supercharge peptide methyl esters, which s

SUBMITTER: Feng C 

PROVIDER: S-EPMC4323856 | biostudies-literature | 2015 Feb

REPOSITORIES: biostudies-literature