Tyrosine triplet state

T.-T. Co, J. Hoover, and A. H. Maki, Dynamics of the tyrosine triplet state from magnetic resonance saturated phosphorescence decay measurements, Chem. Phys. Lett. 27, 5-9 (1974). 

Lu, C. Y. Lui, Y.Y. (2002). Electron transfer oxidation of tryptophan and tyrosine by triplet states and oxidized radicals of flavin sensitizers a laser flash photolysis study. Biochimica et Biophysica Acta (BBA) - General Subjects, Vol. 1571, No.l, (May 2002), pp. 71-76, ISSN 0304-4165... 

The Excited Singlet and Triplet States of Tyrosine and Tyrosinate... 

The triplet-state splittings of tyrosine were first observed by electron paramagnetic resonance (EPR) more than two decades ago.l30 32) The initial characterization of the splittings was limited to a measurement of >, a root-mean-square zfs defined by... 

D was determined by measuring the Ams = 2 EPR transition, where ms is the spin quantum number. Several years later, D and E were obtained directly by observation of the Ams = 1 EPR signals/33 1 In 1973, Zuclich et alP redetermined the triplet-state splitting parameters of tyrosine using optically detected magnetic resonance (ODMR) spectroscopy. 

The most direct demonstration of triplet-triplet energy transfer between the aromatic amino acids is the ODMR study by Rousslang and Kwiram on the tryptophanyl-tyrosinate dipeptide.(57) Since the first excited singlet state of tyrosinate is at lower energy than that of tryptophan, it is possible to excite tyrosinate preferentially. The phosphorescence of this dipeptide, however, is characteristic of tryptophan, which is consistent with the observation that the triplet state of tyrosinate is at higher energy than that of tryptophan, making tryptophan the expected triplet acceptor. 

K. W. Rousslang and A. L. Kwiram, Triplet state decay and spin-lattice relaxation rate constants in tyrosinate and tryptophan, Chem. Phys. Lett. 39, 226-230 (1976). 

K. Ugurbil, A. H. Maki, and R. Bersohn, Study of the triplet state properties of tyrosines and tryptophan in azurins using optically detected magnetic resonance, Biochemistry 16, 901-907 (1977). 

Work on indole, tryptophan, etc. continues because of their relevance to the complex field of protein photophysics. Creed has produced reviews of the photophysics and photochemistry of near-u.v.-absorbing amino-acids, viz. tryptophan and its simple derivatives, tyrosine and its simple derivatives, and cysteine and its simple derivatives. The nature of the fluorescent state of methylated indole derivatives has been examined in detail by Meech et al. Another investigation on indole derivatives deals particularly with solvent and temperature effects. Fluorescence quenching of indole by dimethylfor-mamide has also been examined in detail. Fluorescence excitation spectra of indoles and van der Waals complexes by supersonic jets give microscopic solvent shifts of electronic origin and prominent vibrational excitation of L(, states. Conventional flash photolysis of 1-methylindole in water shows R, e p, and a triplet state to be formed. " Changes in the steady-state fluores-... 

The quenching of chemically excited triplet acetone by biologically important compounds such as indoles, tyrosine derivatives, quinones, riboflavin, and xanthene dyes has been studied. Quenching occurs by electron and Forster transfer processes. Triplet-state parameters have been presented for the... 

The environmental sensitivity of the fluorescence and phosphorescence of phenylalanine, tryptophan and tyrosine, and their side chains, is often examined when considering the macromolecular luminescence of natural peptides and proteins. Therefore, lower-lying singlet and triplet states of toluene, aniline and phenol have been extensively studied as the simplest models of the proteins mentioned above, respectively. Knowledge of the various aspects of electronic spectra of the corresponding aromatic amino acids is often exploited to probe those of the proteins137. In other words, accurate information on both... 

Microwave-induced delayed fluorescence studies have provided information on the triplet states of toluene 230 and p-chloroaniline.231 Magnetic resonance saturated phosphorescence decay measurements on tyrosine,232 and cidnp studies on but-2-enone and pentan-3-one,233 1,4-benzoquinone in propanol,234 9-methylacridine,235 and the dye-sensitized photo-oxidation of phenols230 have been reported. 

The UV absorption spectra of tr3q)tophan, tyrosine and phenylalanine are virtually identical to those of indole 35), phenol 86) and benzene 27) respectively. Close similarities also exist between the fluorescence and phosphorescence spectra of each pair, as well as between the phosphorescence lifetimes 8.28,38). This and the electron spin resonance observations to be discussed in a later section indicate that the addition of a methyl group or other substituents of the type —CH2R does not have a large effect on the measurable properties of the phosphorescent triplet state of the compounds being discussed here. 

Dimers of t3n osine are readily formed as a photoproduct upon irradiation of poly-L-tyrosine Possibly the mechanism involves the initial formation of the t5o osine triplet state with subsequent photoejection of an electron, and the loss of a proton to form a neutral phenoxyl radical which attacks a neighboring t5n osine to form the 0—O -dihy-droxy diphenyl compound 28b),... 

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