Some proline substituent effects in the tandem mass spectrum of protonated pentaalanine
✍ Scribed by Brenda L. Schwartz; Maurice M. Bursey
- Publisher
- John Wiley and Sons
- Year
- 1992
- Tongue
- English
- Weight
- 492 KB
- Volume
- 21
- Category
- Article
- ISSN
- 1076-5174
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✦ Synopsis
Tandem mass spectral effects of the replacement of alanine by proline in pentaalanine were studied. The principal difference when residue 3 or 4 is proline is the great enhancement of the y3 or yz ion, respectively. This is precisely the principal difference which thermochemical arguments predict, since a y-type ion with N-terminal proline is estimated to be 32 kJ mol-' more stable than with N-terminal alanine. When this proline effect and the effect of neutral diketopiperazine loss occur simultaneously, the y-type ion is not observed, as predicted from the additivity of substituent effects by the kinetic approach. No interpretation is offered for observations of btype ion intensities, since the pattern is not obvious to us.