Similarity of fluorescence lifetime distributions for single tryptophan proteins in the random coil state.

AUTOR(ES)

Swaminathan, R

RESUMO

The picosecond time-resolved fluorescence decay data of nine single-tryptophan (trp) proteins and two multi-trp proteins in their native and denatured states were analyzed by the maximum entropy method (MEM). In the denatured state (6 M guanidine hydrochloride) a majority of the single-trp proteins show bimodal (at 25 degrees C) and trimodal (at 85 degrees C) distributions with similar patterns and similar values for average lifetimes. In the native state of the proteins the lifetime distributions were bimodal or trimodal. These results (multimodal distributions) are contradictory to the unimodal Lorentzian distribution of lifetimes reported for some proteins in the native and denatured states. MEM analysis gives a unimodal distribution of lifetimes only when the signal-to-noise ratio is poor in the time-resolved fluorescence decay data. The unimodal distribution model is therefore not realistic for proteins in the native and denatured states. The fluorescence decay components of the bi- or trimodal distribution are associated with the rotamer structures of the indole moiety when the protein is in the random coil state.

Documentos Relacionados

• Reassessing random-coil statistics in unfolded proteins
• Random-coil behavior and the dimensions of chemically unfolded proteins
• A model for multiexponential tryptophan fluorescence intensity decay in proteins.
• Direct laser trapping of single DNA molecules in the globular state.
• Time-resolved fluorescence of the single tryptophan of Bacillus stearothermophilus phosphofructokinase.