THE EFFECT OF pH ON THE AEROBIC and ANAEROBIC PHOTOLYSIS OF TRYPTOPHAN AND SOME TRYPTOPHAN‐CONTAINING DIPEPTIDES

Hibbard, Lisa; Kirk, Nancy Jo; Borkman, Raymond F.

doi:10.1111/j.1751-1097.1985.tb01545.x

Cited by 21 publications

(12 citation statements)

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“…Consequently, the photochemistry and photophysics of free tryptophan and tryptophan residues in model peptides have been studied extensively in an effort to understand their behavior under UV excitation (Borkman, 1977;Dillon, 1980. 1981: Tassin and Borkman, 1980: Robbins et al, 1980Hibbard et al, 1985;Grossweiner, 1976;Walrant and Santus, 1974). These studies have almost always been performed with UV excitation in the range 25G310 nm, i.e.…”

Section: Introductionmentioning

confidence: 99%

THE PHOTOLYSIS OF TRYPTOPHAN WITH 337.1 nm LASER RADIATION

Borkman

Hibbard

Dillon

1986

Photochem & Photobiology

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Abstract— Aqueous solutions of L‐tryptophan were photolyzed by exposure to 337.1 nm radiation from a pulsed nitrogen laser. These data were compared with results for the 290 nm conventional‐source photolysis of tryptophan. The progress of photolysis was monitored by fluorescence analysis of tryptophan. UV absorption spectroscopy, HPLC, TLC, and proton NMR spectroscopy. The loss of Trp was observed to be first order for 290 nm photolysis but of mixed order for 337.1 nm photolysis. Five photolysis products were detected by TLC analysis, including: N‐formylkynurenine. kynurenine, tryptamine (detected after 290 nm photolysis but not 337.1 nm photolysis) and two unknown products. The tryptophan‐containing peptides N‐acetyl‐tryptophanamide (NATA) and tryptophylglycine (Trp‐Gly) were also observed to photolyze upon 337.1 nm laser radiation demonstrating that this phenomenon is not restricted to free tryptophan monomer. Since Trp is not ordinarily thought to absorb U V radiation at wavelengths as long as 337.1 nm. a number of experiments were performed in an effort to determine the mechanism of photolysis at this wavelength. Evidence is presented which indicates that the 337.1 nm laser photolysis of Trp does not result from two photon absorption, dielectric breakdown, or other laser‐specific processes. Instead. it is concluded that this photolysis results either from a very weak absorption tail extending to 337.1 nm in tryptophan itself or from a reaction involving an impurity sensitizer which absorbs the 337.1 nm radiation. The sensitizing impurity. if present, could not. however, be removed by preparative HPLC and could not be detected by TLC or fluorescence analysis.

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Section: Introductionmentioning

confidence: 99%

THE PHOTOLYSIS OF TRYPTOPHAN WITH 337.1 nm LASER RADIATION

Borkman

Hibbard

Dillon

1986

Photochem & Photobiology

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“…The excited species is reactive, and may deactivate by transformation into a stable, covalently modified product. The identity of these products and their probability of formation depend upon many factors, including the wavelength of the UV light (Setlow and Doyle, 1957), the nature of the excited electronic state (Creed, 1984a), the identity and location of other reactive groups in the vicinity of the chromophore (Tallmadge and Borkman, 1990), the temperature (Setlow and Doyle, 1954), and the pH and concentration of dissolved oxygen in the preparation (McLaren and Pearson, 1949;Hibbard et al, 1985). UV irradiation of tryptophan in aerated aqueous solution at neutral pH generates five major stable products: kynurenine, serine, tryptamine, aspartic acid, and N -formyl kynurenine (Creed, 1984a).…”

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Modification of Cyclic Nucleotide–Gated Ion Channels by Ultraviolet Light

Middendorf

Aldrich²,

Baylor

2000

The Journal of General Physiology

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We irradiated cyclic nucleotide–gated ion channels in situ with ultraviolet light to probe the role of aromatic residues in ion channel function. UV light reduced the current through excised membrane patches from Xenopus oocytes expressing the α subunit of bovine retinal cyclic nucleotide–gated channels irreversibly, a result consistent with permanent covalent modification of channel amino acids by UV light. The magnitude of the current reduction depended only on the total photon dose delivered to the patches, and not on the intensity of the exciting light, indicating that the functionally important photochemical modification(s) occurred from an excited state reached by a one-photon absorption process. The wavelength dependence of the channels' UV light sensitivity (the action spectrum) was quantitatively consistent with the absorption spectrum of tryptophan, with a small component at long wavelengths, possibly due to cystine absorption. This spectral analysis suggests that UV light reduced the currents at most wavelengths studied by modifying one or more “target” tryptophans in the channels. Comparison of the channels' action spectrum to the absorption spectrum of tryptophan in various solvents suggests that the UV light targets are in a water-like chemical environment. Experiments on mutant channels indicated that the UV light sensitivity of wild-type channels was not conferred exclusively by any one of the 10 tryptophan residues in a subunit. The similarity in the dose dependences of channel current reduction and tryptophan photolysis in solution suggests that photochemical modification of a small number of tryptophan targets in the channels is sufficient to decrease the currents.

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“…These results suggest that solvent accessibility predominates over other factors. In photolysis studies of some Trp containing di-and tripeptides (Dillon, 1980;1981;Tassin and Borkman, 1980;Hibbard et al, 1985), the peptide sequence was shown to be important in determining Trp photoproducts and photolysis rates. It has also been suggested that the photolysis of Trp residues in proteins is affected by microenvironmental factors like energy transfer, quenching, diffusion of singlet oxygen and proximity of charged groups (Hibbard ef al., 1985;Dillon et al, 1987;Sponheim-Maurizot et al, 1985).…”

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The RATES OF PHOTOLYSIS OF THE FOUR INDIVIDUAL TRYPTOPHAN RESIDUES IN UV EXPOSED CALF Γ‐II CRYSTALLIN

Tallmadge

Borkman

1990

Photochem & Photobiology

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Aqueous buffer solutions of the lens protein bovine gamma-II crystallin were irradiated at 295 nm in the presence of dithiothreitol to determine the individual photolysis susceptibilities of the four tryptophan residues. Reverse-phase high performance liquid chromatography was utilized to compare the tryptic peptide maps before and after irradiation. Sequence analysis of collected tryptic peptides showed that the four tryptophans in calf gamma-II crystallin. TRP-42, TRP-68, TRP-131, and TRP-157 appeared in four distinct tryptic peptides. Fluorescence and absorption (diode array) monitoring of the eluting peptides allowed assessment of the changes in peptide absorbance and fluorescence following irradiation. Tryptophan fluorescence losses of (40 +/- 15)%, (17 +/- 4)%, (35 +/- 5)% and (15 +/- 4)% were observed for the peptides containing TRP-42, TRP-68, TRP-131 and TRP-157, respectively. Thus the four tryptophans in calf gamma-II crystallin did not all photolyze at the same rate. The rate differences are presumably related to the microenvironments of the individual tryptophan residues, and this is discussed in terms of the known crystal structure of calf gamma-II crystallin.

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THE EFFECT OF pH ON THE AEROBIC and ANAEROBIC PHOTOLYSIS OF TRYPTOPHAN AND SOME TRYPTOPHAN‐CONTAINING DIPEPTIDES

Cited by 21 publications

References 31 publications

THE PHOTOLYSIS OF TRYPTOPHAN WITH 337.1 nm LASER RADIATION

THE PHOTOLYSIS OF TRYPTOPHAN WITH 337.1 nm LASER RADIATION

Modification of Cyclic Nucleotide–Gated Ion Channels by Ultraviolet Light

The RATES OF PHOTOLYSIS OF THE FOUR INDIVIDUAL TRYPTOPHAN RESIDUES IN UV EXPOSED CALF Γ‐II CRYSTALLIN

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