ISSN:
1432-1017
Keywords:
Fluorescence of proteins
;
red-edge-excitation spectroscopy
;
nanosecond dynamics
;
dipolereorientational relaxation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Physics
Notes:
Abstract With the aim of finding non-equilibrium dipole-relaxational electronic excited states of tryptophan residues in proteins the dependence of the fluorescence emission maximum on excitation wavelength was studied for several proteins containing a single tryptophan residue per molecule. Spectral shifts upon red-edge excitation are not observed for short wavelength-emitting proteins (azurin, two-calcium form of whiting parvalbumin, ribonucleases C 2 and T 1). This may be because of the non-polar environment of the tryptophan residues in these proteins or because of the absence of dipole-orientational broadening of spectra. The effect was also not found for proteins emitting at long wavelengths (max. at 341–350 nm) —melittin at low ionic strength, IT-Aj1 protease inhibitor, myelin basic protein. In these proteins, the tryptophan residues are exposed to the rapidly relaxing aqueous solvent. Spectral shifts associated with red-edge excitation are observed for proteins emitting in the medium spectral range — human serum albumin in the N and F forms, IT-Aj1 protease inhibitor at pH 2.9, melittin at high ionic strength as well as the albumin-dodecylsulfate complex. This suggests the existence in these proteins of a distribution of microstates for tryptophan environment with various orientation of dipoles and of slow (on the nanosecond time scale) mobility of the field of these dipoles. As a result the emission proceeds from electronic excited states which are not at equilibrium.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00255522
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