Diffusion of flexible, charged, nanoscopic molecules in solution: Size and pH dependence for PAMAM dendrimer


Autoria(s): Maiti, Prabal K; Bagchi, Biman
Data(s)

07/12/2009

Resumo

In order to understand self-diffusion (D) of a charged, flexible, and porous nanoscopic molecule in water, we carry out very long, fully atomistic molecular dynamics simulation of PAMAM dendrimer up to eight generations in explicit salt water under varying pH. We find that while the radius of gyration (R-g) varies as N-1/3, the self-diffusion constant (D) scales, surprisingly, as N-alpha, with alpha=0.39 at high pH and 0.5 at neutral pH, indicating a dramatic breakdown of Stokes-Einstein relation for diffusion of charged nanoscopic molecules. The variation in D as a function of radius of gyration demonstrates the importance of treating water and ions explicitly in the diffusion process of a flexible nanoscopic molecule. In agreement with recent experiments, the self-diffusion constant increases with pH, revealing the importance of dielectric friction in the diffusion process. The shape of a dendrimer is found to fluctuate on a nanosecond time scale. We argue that this flexibility (and also the porosity) of the dendrimer may play an important role in determining the mean square displacement of the dendrimer and the breakdown of the Stokes-Einstein relation between diffusion constant and the radius.

Formato

application/pdf

Identificador

http://eprints.iisc.ernet.in/25994/1/23.pdf

Maiti, Prabal K and Bagchi, Biman (2009) Diffusion of flexible, charged, nanoscopic molecules in solution: Size and pH dependence for PAMAM dendrimer. In: Journal of Chemical Physics, 131 (21).

Publicador

American Institute of Physics.

Relação

http://jcp-beta.aip.org/jcpsa6/v131/i21/p214901_s1

http://eprints.iisc.ernet.in/25994/

Palavras-Chave #Physics
Tipo

Journal Article

PeerReviewed