Temperature dependence of tryptophan photophysics in rabbit skeletal myosin rod

Yoke-chen Chang; Richard D. Ludescher

doi:10.1117/12.182721

17 August 1994 Temperature dependence of tryptophan photophysics in rabbit skeletal myosin rod

Yoke-chen Chang, Richard D. Ludescher

Proceedings Volume 2137, Time-Resolved Laser Spectroscopy in Biochemistry IV; (1994) https://doi.org/10.1117/12.182721
Event: OE/LASE '94, 1994, Los Angeles, CA, United States

Abstract

The fluorescence intensity decays of the two tryptophans in rabbit skeletal myosin rod were fit to double exponential functions at six temperatures ranging from 5 to 62 degree(s)C. The radiative decay rate (kf) was estimated from the ratio of the average lifetime and quantum yield (0.11) at 23 degree(s)C. This value (0.024 ns^-1 was used to calculate the non-radiative decay rates (equals knr) for each lifetime species at each temperature. Plots of log (knr) versus 1/T for each species showed distinctive breaks at 45 degree(s)C. The Arrhenius activation energies (Ea) for non-radiative quenching of the two lifetime species were significantly different below 45 degree(s)C, with values of 85 J/mole for the long and 31 J/mole for the short lifetime species, while the values were similar, 210 J/mole for the long and 230 J/mole for the short species, above 45 degree(s)C. The thermal unfolding of rod is known to be complex with transitions at 43 degree(s), 47 degree(s), and 53 degree(s)C; only the 43 degree(s) and 53 degree(s)C transitions involve the tryptophan-containing light meromyosin region (LMM) (King & Lehrer (1989) Biochemistry 28, 3498). Our results indicate that the two lifetime components are quenched by different mechanisms below, and similar mechanisms above, 45 degree(s)C. Although the environment of the two pairs of tryptophans differ in the folded protein, they have similar environments in the unfolded protein.

Citation Download Citation

Yoke-chen Chang and Richard D. Ludescher "Temperature dependence of tryptophan photophysics in rabbit skeletal myosin rod", Proc. SPIE 2137, Time-Resolved Laser Spectroscopy in Biochemistry IV, (17 August 1994); https://doi.org/10.1117/12.182721

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