Open AccessDynamics of a protein matrix revealed by fluorescence quenching.
Author(s) -
Maurice R. Eftink,
Camillo A. Ghiron
Publication year - 1975
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.72.9.3290
Subject(s) - nanosecond , quenching (fluorescence) , reaction rate constant , chemistry , fluorescence , matrix (chemical analysis) , chemical physics , acrylamide , tryptophan , diffusion , viscosity , molecule , activation energy , biophysics , thermodynamics , photochemistry , crystallography , kinetics , organic chemistry , biochemistry , chromatography , physics , polymer , biology , laser , amino acid , quantum mechanics , optics , copolymer
The fluorescence of the supposedly buried tryptophan in ribonuclease T1 has been found to be collisionally quenched by acrylamide with a rate constant of 3 X 10(8) M--1 sec--1. Only a slight decrease in the quenching rate is observed upon a 5-fold increase in the viscosity of the solution. For this to be the case, the diffusion of the quencher must be limited by the protein matrix. To explain the process of diffusion through this complex material, the formation of "holes" in the lattice of a protein due to nanosecond fluctuations must be invoked. Thus, the dynamic character of a protein molecule is revealed. The quenching rate constant has an activation energy of 9 kcal/mol which can be used to characterize the nature of the cohesive forces in the microenvironment about the indole ring. The mechanical properties of a portion of a protein matrix can, therefore, be described as one would for a fluid.