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Browsing by Author "Vaz, Winchil"

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  • Effects of domain connection and disconnection on the yields of in-plane bimolecular reactions in membranes
    Publication . Melo, E. C. C.; Lourtie, I. M. G.; Sankaram, M. B.; Thompson, T. E.; Vaz, Winchil
    It has recently been shown (Vaz, W.L.C., E.C.C. Melo, and T.E. ThomPson. 1989. Biophys. J. 56:869-875; 1990. Biophys. J. 58:273-275) that in lipid bilayer membranes in which ordered and disordered phases coexist, the ordered phase can form a two-dimensional reticular structure that subdivides the coexisting disordered phase into a disconnected domain structure. Here we consider theoretically the yields of bimolecular reactions between membrane-localized reactants, when both the reactants and products are confined to the disordered phase. It is shown that compartmentalization of reactants in disconnected domains can lead to significant reductions in reaction yields. The reduction in yield was calculated for classical bimolecular processes and for enzyme-catalyzed reactions. These ideas can be used to explain certain experimental observations.
    1992-12Journal article Open access Show more
  • Phase topology and percolation in two-component lipid bilayers: A Monte Carlo approach
    Publication . Coelho, FP; Vaz, Winchil; Melo, E
    Monte Carlo simulations of fluorescence recovery after photobleaching (FRAP) experiments on two-component lipid bilayers systems in the solid-fluid phase coexistence region were carried out to study the geometry and size of fluid domains in these bilayers. The gel phase was simulated by superposable elliptical domains, which were either of predetermined dimensions, increasing in number with increasing gel phase fraction, or of predetermined number, increasing in dimensions with increasing gel phase fraction. The simulations were done from two perspectives: 1) a time-independent analysis of fractional fluorescence recovery as a function of fractional fluid phase in the system; and 2) a time-dependent analysis of fractional fluorescence recovery as a function of time al a given fraction of fluid phase in the system. The time-dependent simulations result in recovery curves that are directly comparable to experimental FRAP curves and provide topological and geometrical models for the coexisting phases that are consistent with the experimental result.
    1997-04Journal article Open access Show more