Static quenching of tryptophan fluorescence by oxidized dithiothreitol.
The quenching of fluorescence of 5-methoxyindole, N-acetyl-L-tryptophanamide and two single tryptophan containing peptides, melittin and mastoparan X, by oxidized dithiothreitol was studied. The slopes of the Stern-Volmer plots for steady-state fluorescence quenching were 133 M-1, 71.2 M-1, 75.5 M-1 and 35.0 M-1 at 21 degrees C and pH 7.0 for 5-methyoxyindole, N-acetyl-L-tryptophanamide, melittin and mastoparan X respectively. Fluorescence lifetimes of indole or tryptophan in these compounds, as determined by multifrequency phase fluorometry, were decreased by 15% or less at concentrations that produced 50% or more quenching of steady-state fluorescence. Thus, quenching of fluorescence by oxidized dithiothreitol for these derivatives of indole appears to be largely static in nature, suggesting a ground-state interaction.
Sanyal
G
G
Department of Chemistry, Hamilton College, Clinton, New York 13323.
Kim
E
E
Thompson
F M
FM
Brady
E K
EK
D004229:Dithiothreitol; D007700:Kinetics; D010084:Oxidation-Reduction; D013050:Spectrometry, Fluorescence / Q000379:methods; D013997:Time Factors; D014364:Tryptophan / Q000031:analogs & derivatives
D014364:Tryptophan; D004229:Dithiothreitol