ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Holographic relaxation techniques (HRS) were used to study dynamics in solutions of bovine serum albumin (BSA) labeled with azobenzene-p-isothiocyanate (ABITC). The ionic strengths ranged from 0.5 to 100 mM and the protein concentrations were 3 to 50 g/L. A single diffusive component was observed above 25 mM salt, but at lower ionic strengths two components were resolved. Also, electrophoresis combined with holographic relaxation spectroscopy (EHRS) showed two components. A photoionization model, in which the net charge of the BSA-ABITC molecule is altered by the writing laser pulse, is proposed to explain the results. The coupled diffusion problem for the bleached and unbleached macroions and the counter and coions is solved to obtain the concentration and ionic strength dependences of the diffusion coefficients. Also, effective diffusion coefficients for the components in EHRS are obtained. Overall, there is good agreement between this simple model and experiment; however, the macroion charges required in the theory are roughly a factor of two lower than those found by titration and electrolysis.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.452954
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