Using Monte Carlo simulations, we demonstrate that the shape of the intramolecular density
profile of dendritic polyelectrolytes in solution can be tailored by varying the ionic strength of the solvent.
Further, we find that a reversible transition between a “dense core” and a “dense shell” dendritic structure
may be observed as the ionic strength is cycled from high to low. We present the necessary conditions
in terms of salt concentration and various molecular variables such as generation number, spacer length,
and number of charges, for realizing the potential of dendrimers as hosts in controlled-release and similar
applications.
We present a unified continuum-level model for bilayer energetics that includes the effects of bending, compression, lipid orientation (tilting relative to the monolayer surface normal), and microscopic noise (protrusions). Expressions for thermal fluctuation amplitudes of several physical quantities are derived. These predictions are shown to be in good agreement with molecular simulations.
Our simulations of polymer crystallization from solutions show that (1) entropic barriers control the selection of the initial lamellar thickness, (2) growth at the crystalline interface is chain adsorption followed by crystallographic registry, and (3) lamellar thickening is a highly cooperative process requiring the mobility of all chains in the crystal. These results, especially the latter, challenge the conventional Lauritzen-Hoffman theory and its generalizations.
Thermal fluctuations of lipid orientation are analyzed to infer the bending rigidity of lipid bilayers directly from molecular simulations. Compared to the traditional analysis of thermal membrane undulations, the proposed method is reliable down to shorter wavelengths and allows for determination of the bending rigidity using smaller simulation boxes. The requisite theoretical arguments behind this analysis are presented and verified by simulations spanning a diverse range of lipid models from the literature.
Much experimental effort to realize possible uses of dendrimers has focused on the complexation of charged dendrimers to oppositely charged polyelectrolytes to form controlled delivery systems. Employing computer simulation and theory, we present a molecular-level picture of these guesthost aggregates and the conditions necessary for forming them. Specifically, we examine the equilibrium and dynamic complexation behavior of a monocentric dendrimer with charged terminal groups to a flexible, oppositely charged polyelectrolyte. Three different types of complexes are noted depending upon the solution ionic strength and the sizes of the dendrimer and chain. We find that a dendrimer may encapsulate a chain, a chain and a dendrimer may mutually interpenetrate, or a unique "chain-walking" phenomenon may be observed. The critical conditions for complexation, density profiles of the polyelectrolyte and the dendrimer in the complex, and the curious dynamics observed are discussed. A closed formula is proposed to describe the critical conditions for complexation between a dendrimer and a polyelectrolyte.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.