TAILIEUCHUNG - Báo cáo khóa học: Conformational changes of b-lactoglobulin in sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles A fluorescence and CD study

The effect ofb-lactoglobulin encapsulation in sodium bis (2-ethylhexyl) sulfosuccinate reverse micelles on the envi-ronment of protein and on Trp was analysed at different water contents (x0).CDdataunderlined thedistortionof the b-sheet and a less constrained tertiary structure as the x0 increased, in agreement with a concomitant red shift and a decrease in the signal intensity obtained in steady-state fluorescence measurements. | Eur. J. Biochem. 271 734-744 2004 FEBS 2004 doi Conformational changes of b-lactoglobulin in sodium bis 2-ethylhexyl sulfosuccinate reverse micelles A fluorescence and CD study Suzana M. Andrade Teresa I. Carvalho M. Isabel Viseu and Silvia M. B. Costa Centro de Quimica Estrutural Complexo 1 Instituto Superior Tecnico Lisboa Portugal The effect of b-lactoglobulin encapsulation in sodium bis 2-ethylhexyl sulfosuccinate reverse micelles on the environment of protein and on Trp was analysed at different water contents x . CD data unde dined the distortion of the b-sheet and a less constrained tertiary structure as the ro0 increased in agreement with a concomitant red shift and a decrease in the signal intensity obtained in steady-state fluorescence measurements. Fluorescence lifetimes evaluated by biexponential analysis were s1 ns and s2 ns in neutral water. In reverse micelles decay-associated spectra indicated the occurrence of important environmental changes associated with x0. Bimolecular fluorescence quenching by CCl4 and acrylamide was employed to analyse alterations in the accessibility of the two Trp residues in b-lactoglobulin induced by changes in ro0. The average bimolecular quenching constant kqCCl4 was found not to depend on ro0 confirming the insolubility of this quencher in the aqueous interface while kqacrylamide increases with ro0. The drastic decrease with ro0 of kq associated with the longest lifetime kq2CCl4 comparatively to the increase of kq2acrylamide emphasizes the location of b-lacto-globulin in the aqueous interfacial region especially at X0 10. The fact that kq2acrylamide X0 30 kq2acrylamide water also confirms the important conformational changes of encapsulated b-lactoglobulin. Keywords b-lactoglobulin conformation quenching reverse micelles. Many biological phenomena occur at interfaces rather than in homogeneous solution and protein-surfactant interactions play a key role in the reactions .

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