Energy transfer tryptophan

The intramolecular distances measured at room temperature with the AEDANS FITC pair were similar in the Ca2Ei and E2V states [297]. Ca and lanthanides are expected to stabilize the Ej conformation of the Ca -ATPase, since they induce a similar crystal form of Ca -ATPase [119,157] and have similar effects on the tryptophan fluorescence [151] and on the trypsin sensitivity of Ca -ATPase [119,120]. It is also likely that the vanadate-stabilized E2V state is similar to the p2 P state stabilized by Pi [418]. Therefore the absence of significant difference in the resonance energy transfer distances between the two states implies that the structural differences between the two conformations at sites recorded by currently available probes, fall within the considerable error of resonance energy transfer measurements. Even if these distances would vary by as much as 5 A the difference between the two conformations could not be established reliably. 

Liao F, Xie Y, Yang X et al (2009) Homogeneous noncompetitive assay of protein via Forster-resonance-energy-transfer with tryptophan residue(s) as intrinsic donor(s) and fluorescent ligand as acceptor. Biosens Bioelectron 25 112-117... 

Visser NV, Borst JW, Hink MA, van Hoek A, Visser AJWG (2005) Direct observation of resonance tryptophan-to-chromophore energy transfer in visible fluorescent proteins. Biophys Chem 116 207-212... 

Weber G. (1960) Fluorescence Polarization Spectrum and Electronic Energy Transfer in Tyrosine, Tryptophan and Related Compounds, Biochem. J. 75, 335-345. 

Eisinger(55) also noted that it is difficult to obtain accurate data with phenylalanine as the donor and either tryptophan or tyrosine as the acceptor. The source of this problem is the weak S, - S0 absorption of phenylalanine compared to that of tyrosine or tryptophan, which leads to considerable experimental uncertainty in measuring the sensitized acceptor emission. This error may account for the finding of Kupryszewska et al.<56> that the sensitization of the acceptor fluorescence was less than the quenching of the donor fluorescence in their study of phenylalanine-to-tyrosine energy transfer... 

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. 

In order to avoid complications caused by excitation energy transfer between tryptophan residues, most investigations have been performed with proteins containing one tryptophan residue per molecule. When studying protein solutions, there are difficulties in separating the effects of rotation of entire protein molecules and of the chromophores themselves relative to their environment in the protein matrix. It is usually assumed that intramolecular motions are more rapid and manifest themselves as short-lived components of anisotropy decay curves or in depolarization at short emission lifetimes. 

Several routes are possible to populate the triplet state. The triplet excited state can, in principle, be directly excited from the ground state, but a low extinction coefficient associated with the S0 to T, transition (reflected in the long lifetime) makes direct excitation an inefficient process for tryptophan. The triplet state can be thermally populated, but for tryptophan the large energy gap between the ground state and the triplet state makes this process unfavorable. Energy transfer from a higher state can also populate the... 

Thus, the efficiency of energy transfer between donors and acceptors randomly distributed in a plane depends on R0, a, and a, and the transfer efficiency is independent of a. The important point was made that surface density of the acceptor could be 1 per 500 phospholipids for R0 > 30 A. Using these equations for different donor and acceptor concentrations, the data were matched against the different theoretical curves to obtain the R0. An example of the application of the method of Fung and Stryer(81) is the study of energy transfer between the tryptophan of a membrane protein (or peptide models of proteins) and DPH,(83) in which it was shown that efficient energy transfer can occur without any special interaction being required between DPH and the proteins in specific areas of the membrane. 

T. Le Doan, M. Takasugi, I. Aragon, G. Boudet, T. Montenay-Garestier, and C. Helene, Excitation energy transfer from tryptophan residues of peptides and intrinsic proteins to diphenylhexatriene in phospholipid vesicles and biological membranes, Biochim. Biophys. Acta 735, 259-270 (1983). 

As the investigation of the interactions between H DAC inhibitors and the enzymes are an important issue, competition assay systems are helpful implements in facilitating the characterization of inhibitor binding. Such a competition binding assay that has been developed for histone deacetylases is based on fluorescence resonance energy transfer (FRET) between tryptophan residues of the histone deacetylase and a fluorescent HDAC inhibitor [38]. In competition with other... 

INTRINSIC AND EXTRINSIC FLUORESCENCE. Intrinsic fluorescence refers to the fluorescence of the macromolecule itself, and in the case of proteins this typically involves emission from tyrosinyl and tryptopha-nyl residues, with the latter dominating if excitation is carried out at 280 nm. The distance for tyrosine-to-tryp-tophan resonance energy transfer is approximately 14 A, suggesting that this mode of tyrosine fluorescence quenching should occur efficiently in most proteins. Moreover, tyrosine fluorescence is quenched whenever nearby bases (such as carboxylate anions) accept the phenolic proton of tyrosine during the excited state lifetime. To examine tryptophan fluorescence only, one typically excites at 295 nm, where tyrosine weakly absorbs. [Note While the phenolate ion of tyrosine absorbs around 293 nm, its high pXa of 10-11 in proteins typically renders its concentration too low to be of practical concern.] The tryptophan emission is maximal at 340-350 nm, depending on the local environment around this intrinsic fluorophore. 

Deeble DJ, Schuchmann MN, Steenken S, von Sonntag C (1990) Direct evidence for the formation of thymine radical cations from the reaction of SO/" with thymine derivatives a pulse radiolysis study with optical and conductance detection. J Phys Chem 94 8186-8192 DeFelippis MR, Murthy CP, Faraggi M, Klapper MH (1989) Pulse radiolytic measurement of redox potentials the tyrosine and tryptophan radicals. Biochemistry 28 4847-4853 Delatour T, Douki T, D Ham C, Cadet J (1998) Photosensitization of thymine nucleobase by benzo-phenone through energy transfer, hydrogen abstraction and one-electron oxidation. J Photo-chem Photobiol 44 191-198... 

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