Multiple diffusion mechanisms due to nanostructuring in crowded environments.

Full Abstract

One of the key questions regarding intracellular diffusion is how the environment affects molecular mobility. Mostly, intracellular diffusion has been described as hindered, and the physical reasons for this behavior are:
immobile barriers, molecular crowding, and binding interactions with immobile or mobile molecules. Using results from multi-photon fluorescence correlation spectroscopy, we describe how immobile barriers and crowding agents affect translational mobility. To study the hindrance produced by immobile barriers, we used sol-gels (silica nanostructures) that consist of a continuous solid phase and aqueous phase in which fluorescently tagged molecules diffuse. In the case of molecular crowding, translational mobility was assessed in increasing concentrations of 500 kDa dextran solutions. Diffusion of fluorescent tracers in both sol-gels and dextran solutions shows clear evidence of anomalous subdiffusion. In addition, data from the autocorrelation function were analyzed using the maximum entropy method as adapted to fluorescence correlation spectroscopy data and compared with the standard model that incorporates anomalous diffusion. The maximum entropy method revealed evidence of different diffusion mechanisms that had not been revealed using the anomalous diffusion model. These mechanisms likely correspond to nanostructuring in crowded environments and to the relative dimensions of the crowding agent with respect to the tracer molecule. Analysis with the maximum entropy method also revealed information about the degree of heterogeneity in the environment as reported by the behavior of diffusive molecules.

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Author information

Author/s: Sanabria, Hugo (H); Kubota, Yoshihisa (Y); Waxham, M Neal (MN);

Affiliation: Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA. hugo.sanabria(-atsign-)uth.tmc.edu

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: Biophysical journal (Biophys J), published in United States. (Language: eng)

Reference: 2007-Jan; vol 92 (issue 1) : pp 313-22

Dates: Created 2006/12/12; Completed 2007/04/23; Revised 2008/11/20;

PMID: 17040979, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Biophysics - methods
Calmodulin - chemistry
Dextrans - chemistry
Diffusion
Entropy
Green Fluorescent Proteins - chemistry
Macromolecular Substances
Models, Chemical

Associated Chemicals: Calmodulin (0) ; Macromolecular Substances (0) ; Green Fluorescent Proteins (147336-22-9) ; Dextrans (9004-54-0)

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