Photophysics, excited-state tryptophan

Several reviews have been written concerning the phosphorescence of intrinsic indole probes [201] and the use of triplet excited states to probe proteins [202]. Triplet tryptophan can be used to probe proteins, but its photophysics is complex, because in a homogeneous solution, the decays of the excited triplet tryptophan or indole derivatives do not usually follow first-order kinetics, due to protonation, triplet-triplet annihilation, or self-quenching [203,204]. In ad-... 

Table 3. The photophysical parameters of the LDA p irs in mRFPl by LTV excitation. In the table (1) ctd( x=266) and <7A(Aez=266) are the absorption cross section of the donor (tryptophan) and the acceptor (chromophore) at the wavelength of 266 nm (2) Rda and E=Kd//(Kda+1/td) are the rate and efficiency of the energy transfer from the excited donor to the unexcited acceptor (3) td and Ta are the excited state lifetimes of the donor (in the absence of the acceptor) and the acceptor.

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-... 

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