Open Access1‐Anilinonaphthalene‐8‐sulphonate
Author(s) -
Penzer Geoffrey R.
Publication year - 1972
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1972.tb01687.x
Subject(s) - chemistry , aqueous solution , solvent , fluorescence , quenching (fluorescence) , excited state , quantum yield , photochemistry , crystallography , dimethylformamide , proton , organic chemistry , physics , quantum mechanics , nuclear physics
The conformations of 1‐anilinonaphthalene‐8‐sulphonate in 2 H 2 O and C 2 H 3 O 2 H have been determined by proton magnetic resonance spectroscopy, and its fluorescence spectra as a solid, in a methyl‐cellulose matrix, and in solution in water, methanol and aqueous MgCl 2 have been studied. The aromatic rings of anilinonaphthalene‐sulphonate are more nearly coplanar in C 2 H 3 O 2 H than in 2 H 2 O. The NH proton fails to exchange with 2 H from the solvent in C 2 H 3 O 2 H, and its chemical shift indicates that there is a strong interaction with the sulphonate group. The solvents in which rapid exchange of the NH proton occurs are those in which the quantum yield of fluorescence of anilinonaphthalene‐sulphonate is quenched. The fluorescence emission is enhanced and blue‐shifted in strong aqueous MgCl 2 solutions. Under some conditions the overall emission is composed of contributions from two separable spectra. It is argued that an efficient mechanism for quenching the first excited singlet of anilinonaphthalene‐sulphonate is through vibrations of bonds to the nitrogen, and that the shifts of emission maxima in non‐aqueous solvents may be partly a result of the molecule displaying different spectra in different conformations (rather than simply a solvent‐polarity‐induced change). There is no convincing reason for the assumption that when a fluorescence enhancement follows the binding of anilinonaphthalene‐sulphonate to a biological structure the site of interaction must be hydrophobic.