Structural Characterisation of Acetaldehyde Adducts Formed by a Synthetic Peptide Mimicking the N‐Terminus of the Hemoglobin β‐Chain Under Reducing and Nonreducing Conditions
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Media type:
E-Article
Title:
Structural Characterisation of Acetaldehyde Adducts Formed by a Synthetic Peptide Mimicking the N‐Terminus of the Hemoglobin β‐Chain Under Reducing and Nonreducing Conditions
Published in:
European Journal of Biochemistry, 240 (1996) 1, Seite 30-36
Language:
English
DOI:
10.1111/j.1432-1033.1996.0030h.x
ISSN:
0014-2956;
1432-1033
Origination:
Footnote:
Description:
This work was carried out to elucidate the structures resulting from acetaldehyde‐induced modifications at the haemoglobin β‐chain N‐terminal residues under different experimental conditions. A synthetic peptide (Val‐His‐Leu‐Thr‐Pro‐Glu‐Cys) of m/z 798, which represents the six N‐terminal residues of the haemoglobin β‐chain N‐terminus with an additional C‐terminal cysteine, was used as a model compound. Peptide–acetaldehyde adducts were separated by reverse‐phase HPLC. Fast‐atom‐bombardment MS and linked‐scan (B/E) spectra were used to study adduct structures. Under nonreducing conditions at pH 7.4 (1:10 peptide/acetaldehyde molar ratio), two types of adducts of m/z 824 were formed, both with modifications at the N‐terminal valine. These two adducts were shown to be a Schiff base, and a cyclic 2‐methyl‐imidazolidine‐4‐one. The 2‐methyl‐imidazolidine‐4‐one adduct was demonstrated to be formed via the Schiff base and to undergo dissociation gradually after 24 h. Reducing conditions at pH 7.4 (peptide/acetaldehyde molar ratio of 1:1 with 20 mM NaCNBH3) resulted in the formation of an adduct of m/z 826, which was shown to be an N‐ethylated adduct of valine. A small amount of nonreduced adducts were also formed under these conditions. Reducing conditions at pH 9.0 (1:10 peptide/acetaldehyde molar ratio with 20 mM NaCNBH3) yielded two secondary, i.e. diethylated (m/z 854), products very rapidly. The cysteine residue of the peptide was not found to form an adduct with acetaldehyde under physiological pH.