NMR analysis of the ultraviolet photolytic behavior of several tryptophan-rich growth hormone releasing peptides

McKim, Steve; Hinton, James F.; Deghenghi, Romano

doi:10.1002/(sici)1520-6343(1997)3:4<317::aid-bspy7>3.0.co;2-0

Cited by 2 publications

(4 citation statements)

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“…Solvent exposure often facilitates fluorescence quenching, so it is reasonable to expect that hydrophobic residues might shield the chromophore. Also, tryptophan is known to generate fluorescent kynurenine derivatives at wavelengths above 300 nm. 8b, The results of sequencing were contrary to our initial expectations. The sequences were not hydrophobic, they were abundant in aspartic acid and serine, and every sequence contained at least one lysine.…”

Section: Resultsmentioning

confidence: 69%

“…Much is known about the oxidation and photooxidation of free tryptophan, but not peptides that contain tryptophan . Simat and co-workers have shown that, when Ala-Trp-Ala was oxidized by hydrogen peroxide, Ala-Oia-Ala was the major identifiable product along with N -formylkynurenine (NFK). 8g, Similarly, Holt and co-workers showed that when AlaGlyTrpVal was irradiated in the presence of oxygen under acidic conditions, the tryptophan residue was converted to Oia, NFK, and Asp, in nearly equal amounts (4−5% based on amino acid analysis) 8d. Because Oia is the predominant monooxygenation product of tryptophan under both photooxidative conditions and hydrogen peroxide conditions, it is the most plausible structure for photoproduct A .…”

Section: Resultsmentioning

confidence: 99%

“…A significant gap remains between the general knowledge that peptides form photoproducts and the structural elucidation of these photoproducts. Previous peptide oxidation studies of tryptophan have been unable to account for the majority of the oxidized tryptophan. 8d,g This study of fluorogenesis, in particular, the fluorogenesis of peptide 4 , has not closed that gap, but rather the elucidation of the structure of photoproduct B has increased our appreciation for the oxidative transformations of tryptophan. This focused study was biased by our choice of time, temperature, light source, and excitation wavelength.…”

Section: Discussionmentioning

confidence: 99%

“…We set out to identify fluorogenic peptides, particularly under conditions where light might play a catalytic role in the presence of molecular oxygen. Such photocatalytic conditions complement the photoreactivity studies that have been carried out on a relatively small number of tryptophan-containing peptides, usually using photosensitizers or high-intensity light. The aim of this study was to identify fluorogenic peptide sequences by exposing a bead-based peptide library to ambient photooxidative conditions, determine which peptides exhibit fluorogenesis as soluble peptides, and, where possible, elucidate the structure of the fluorophores that are formed.…”

Section: Introductionmentioning

confidence: 99%

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Fluorogenic Peptide Sequences − Transformation of Short Peptides into Fluorophores under Ambient Photooxidative Conditions

Tivitmahaisoon

et al. 2003

J. Am. Chem. Soc.

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Long-lived proteins are susceptible to nonenzymatic chemical reactions and the evolution of fluorescence; however, little is known about the sequence-dependence of fluorogenesis. We synthesized a library of over half a million octapeptides and exposed it to light and air in pH 7.4 buffer to identify fluorogenic peptides that evolve under mild oxidative conditions. The bead-based peptide library was composed of the general sequence H(2)N-Ala-(Xxx)(6)-Ala-resin, where Xxx was one of nine representative amino acids: Asp, Gly, His, Leu, Lys, Pro, Ser, Trp, and Tyr. Next, we selected five highly fluorescent beads from the library and subjected them to microsequencing, revealing the sequence of the unreacted peptide. All five of the fluorogenic sequences were ionic; lacked Tyr, His, and Leu; and most of the sequences contained only one Trp. We then synthesized the five soluble peptides corresponding to the fluorogenic peptide sequences and exposed them to photooxidative conditions. In general, the soluble peptides reacted slowly, generating nonfluorescent monooxygenated and dioxygenated products. However, one peptide (H(2)N-AlaLysProTrpGlyGlyAspAla-CONH(2)) evolved into a highly fluorescent photoproduct as well as a nonfluorescent monooxygenated photoproduct. The fluorescent photoproduct consisted of a 2-carboxy-quinolin-4-yl moiety fused to the N-terminus of GlyGlyAspAla. The formation of this photoproduct requires cleavage of the peptide backbone and a dramatic reorganization of tryptophan. This work demonstrates that sequencing unreacted peptide on beads can reveal sequences with unique nonenzymatic reactivity. The study also confirms that peptide fluorogenesis is dependent on sequence and not merely on the presence of tryptophan. The potential importance of fluorogenic peptide sequences is two-fold. First, fluorogenic sequences that arise through mutation could prove to be hot spots for human aging. Second, fluorogenic sequences, particularly those compatible with intracellular conditions, may serve as fluorescent tags for proteins or as fluorescent biomaterials.

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Section: Resultsmentioning

confidence: 69%