NMR analysis of the ultraviolet photolytic behavior of several tryptophan-rich growth hormone releasing peptides
by McKim, S.; Hinton, J. F.; Deghenghi, R.
Aqueous solutions of three tryptophan-rich growth hormone releasing hexapeptides, GHRP-6 ( His-D-Trp-Ala-Trp-D-Phe-Lys-NH2), hexarelin (His-D-2-Me-Trp-Ala-Trp-D-Phe-Lys-NH2 ), and EP7458 ( His-D-Trp-Ala-2-Me-Trp-D-Phe-Lys-NH2), were exposed to varying durations of ultraviolet (UV) light. Using NMR spectroscopy, first-order rate constants for the UV photolytic degradation of the tryptophan(s)/2-methyl tryptophan residues within each peptide were obtained by plotting the decrease in the area of the indole N-H resonances with respect to UV photolysis time. A significant differential photolytic effect was observed between the two tryptophan residues of GHRP-6 and the tryptophan/2-methyl tryptophan residues of EP7458. A somewhat smaller differential photolytic effect was observed between the tryptophan/2-methyl tryptophan residues of hexarelin. In addition, the three peptides were degraded at different rates, suggesting that the effect of UV light on each peptide is dependent on whether a tryptophan or 2-methyl tryptophan is the second or fourth residue in the primary sequence.
- Journal
- Biospectroscopy
- Volume
- 3
- Issue
- 4
- Year
- 1997
- Start Page
- 317-323
- URL
- https://dx.doi.org/10.1002/(sici)1520-6343(1997)3:4<317::aid-bspy7>3.0.co;2-0
- ISBN/ISSN
- 1520-6343; 1075-4261
- DOI
- 10.1002/(sici)1520-6343(1997)3:4<317::aid-bspy7>3.0.co;2-0