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

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