Two-way packing model for ribonuclease T1 fluorescence

Christopher Haydock; Salah S. Sedarous; Franklyn G. Prendergast; Teresa A. Felmlee

doi:10.1117/12.182724

17 August 1994 Two-way packing model for ribonuclease T1 fluorescence

Christopher Haydock, Salah S. Sedarous, Franklyn G. Prendergast, Teresa A. Felmlee

Author Affiliations +

Proceedings Volume 2137, Time-Resolved Laser Spectroscopy in Biochemistry IV; (1994) https://doi.org/10.1117/12.182724
Event: OE/LASE '94, 1994, Los Angeles, CA, United States

Abstract

The fluorescence intensity decay of ribonuclease T1 is biexponential at neutral pH. The lifetimes in nsec and preexponential factors of the exponential components are 3.9 (81%) and 1.7 (19%). The mutations A22L, G23A, L26A, V67G, and V67D, which all neighbor tryptophan-59, have a fairly small effect on this biexponential decay. The lifetime of the long lived component varies from 3.7 to 4.2 nsec and the preexponential varies from 75% to 92%. The emission maximum varies from 319 to 328 nm and the acrylamide quenching rate constant varies from 2.0 to 4.0 x 10⁸ M₁s₁ for these mutations. Minimum perturbation mapping simulations of the tryptophan-59 side chain in wild type ribonuclease T1 show that the (chi) ² side chain dihedral angle may adopt either a perpendicular or an antiperpendicular conformation. These computational and spectroscopic results lead us to propose a two- way packing model for tryptophan-59. This model predicts the relative free energies of the perpendicular and antiperpendicular conformations and acrylamide interaction site to indole ring distances for the wild type and mutant ribonucleases.

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Christopher Haydock, Salah S. Sedarous, Franklyn G. Prendergast, and Teresa A. Felmlee "Two-way packing model for ribonuclease T1 fluorescence", Proc. SPIE 2137, Time-Resolved Laser Spectroscopy in Biochemistry IV, (17 August 1994); https://doi.org/10.1117/12.182724

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