Indole fluorescence quenching studies on proteins and model systems: use of the inefficient quencher succinimide

• Published in: Biochemistry (Easton) Vol. 23; no. 17; pp. 3891 - 3899
• Main Authors: Eftink, Maurice R, Ghiron, Camillo A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01-08-1984
• Subjects: acrylamide; adrenocorticotropin; Biological and medical sciences; fluorescence; fructose-bisphosphate aldolase; Fundamental and applied biological sciences. Psychology; glucagon; Molecular biophysics; parvalbumin; ribonuclease; Spectroscopy : techniques and spectras; succinimide; Proteins; Fluorescence; Tryptophan; Deexcitation; Enzyme; Molecular accessibility
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00312a016

The author have compared the quenching of the fluorescence of proteins by acrylamide and succinimide, two chemically similar quenchers. they find that the ratio of the apparent rate constants for succinimide and acrylamide quenching, gamma sub(S/A), ranges from -6 0.1 to similar to 0.7. Proteins having relatively buried tryptophan residues, such as ribonclease T sub(1), cod parvalbumin, and aldolase, are found to have small values of gamma sub(S/A); proteins with relatively solvent-exposed tryptophan residues, such as glucagon and adrenocorticotropin, are found to have larger values of gamma sub(S/A). The authors interpret this range of gamma sub(S/A) values as being due to either a critical size dependence of the dynamic penetration of quencher through a protein matrix (succinimide being larger than acrylamide) and/or an inherent dependence of the succinimide quenching reaction on the microenvironment of the indole ring. The latter interpretation is supported by studies of the solvent dependence of the quenching of the fluorescence of indole and 5-methoxyindole by succinimide and acrylamide. These studies show that whereas acrylamide is an efficient quencher in all solvents investigated, succinimide is a relatively inefficient quencher in aprotic solvents.