Visser, A. and Vanengelen, J. and Visser, N.V and Vanhoek, A. and Hilhorst, R. and Freedman, R.B. (1994) Fluresence Dynamics of Staphylococcal Nulease in Aqueous-Solution and Reversed Micelles. Biochimica Et Biophysica Acta-Protein Structure and Molecular Enzymology, 1204 (2). pp. 225-234. ISSN 0167-4838.
The dynamical fluorescence properties of the sole tryptophan residue (Trp-140) in Staphylococcus aureus nuclease (EC 18.104.22.168) have been investigated in aqueous solution and reversed micelles composed of either sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in isooctane or cetyltrimethylammonium chloride (CTAC) in isooctane/hexanol (12:1 by volume). The fluorescence decay of nuclease in the different environments can be described by a trimodal distribution of fluorescence lifetimes at approx. 0.5, 1.5 and 5.0 ns. The relative amplitudes depend on the environment. For pH 9.0 solutions the contribution of the two shortest lifetime components in the distribution is largest for AOT and smallest for CTAC reversed micelles. There is reasonable agreement between the average fluorescence lifetime and the fluorescence quantum efficiency confirming a significant fluorescence quenching in AOT reversed micelles. Fluorescence anisotropy decay revealed that the tryptophan environment in aqueous nuclease solutions is rigid on a nanosecond timescale. When nuclease was entrapped into reversed micelles the tryptophan gained some internal flexibility as judged from the distinct presence of a shorter correlation time. The longer correlation time reflected the rotational properties of the protein-micellar system. Modulation of the overall charge of nuclease (isoelectric point pH 9.6) by using buffer of pH 9.0 and pH 10.4, respectively, and of the size of empty micelles by selecting two values of the water to surfactant molar ratio, had only a minor effect on the rotational properties of nuclease in the positively charged reversed micelles. Encapsulation of nuclease in anionic reversed micelles resulted in the development of protein bound to aggregated structures which are immobilised on a nanosecond timescale. According to far UV circular dichroism results the secondary structure of nuclease only followed the already published pH-dependent changes. Encapsulation had no major effect on the overall secondary structure.
|Uncontrolled keywords:||REVERSED MICELLE; FLUORESCENCE ANISOTROPY; MAXIMUM ENTROPY METHOD; LIFETIME DISTRIBUTION; CORRELATION TIME DISTRIBUTION|
|Subjects:||Q Science > QP Physiology (Living systems) > QP517 Biochemistry|
|Divisions:||Faculties > Science Technology and Medical Studies > School of Biosciences|
|Depositing User:||P. Ogbuji|
|Date Deposited:||10 Jun 2009 06:22|
|Last Modified:||30 May 2012 10:54|
|Resource URI:||http://kar.kent.ac.uk/id/eprint/20089 (The current URI for this page, for reference purposes)|
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