17 August 1994 Time-resolved fluorescence of thioredoxin single-tryptophan mutants: modeling experimental results with minimum perturbation mapping
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Abstract
The time-resolved fluorescence decay of single tryptophan (Trp) proteins is typically described using either a distribution of lifetimes or a sum of two or more exponential terms. A possible interpretation for this fluorescence decay heterogeneity is the existence of different isomeric conformations of Trp about its (chi) +1) and (chi) +2) dihedral angles. Are multiple Trp conformations compatible with the remainder of the protein in its crystallographic configuration or do they require repacking of neighbor side chains? It is conceivable that isomers of the neighbor side chains interconvert slowly on the fluorescence timescale and contribute additional lifetime components to the fluorescence intensity. We have explored this possibility by performing minimum perturbation mapping simulations of Trp 28 and Trp 31 in thioredoxin (TRX) using CHARMm 22. Mappings of Trp 29 and Trp 31 give the TRX Trp residue energy landscape as a function of (chi) +1) and (chi) +2) dihedral angles. Time-resolved fluorescence intensity and anisotropy decay of mutant TRX (W28F and W31F) are measured and interpreted in light of the above simulations. Relevant observables, like order parameters and isomerization rates, can be derived from the minimum perturbation maps and compared with experiment.
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Norberto D. Silva, Norberto D. Silva, Christopher Haydock, Christopher Haydock, Franklyn G. Prendergast, Franklyn G. Prendergast, } "Time-resolved fluorescence of thioredoxin single-tryptophan mutants: modeling experimental results with minimum perturbation mapping", Proc. SPIE 2137, Time-Resolved Laser Spectroscopy in Biochemistry IV, (17 August 1994); doi: 10.1117/12.182723; https://doi.org/10.1117/12.182723
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