Intermittent Brownian Dynamics over Strands P. Levitz PMC, Ecole Polytechnique-CNRS, Route de Saclay, Palaiseau, 91128 France. E-mail: levitz@pmc.polytechnique.fr 1. Introduction Intermittent dynamics is intrinsically involved for particles or molecules exploring confining interfacial systems such as porous material, colloidal suspension and catalytic surfaces. Periods of relocation in the bulk phase or in the pore network (bridges) alternate with adsorption or trapping steps generally located nearby the interface (cf. Fig 1A). A representative example concerns the search for a specific target site on DNA by a protein, which alternates adsorption or scanning phases where the protein diffuses on the DNA strand and three-dimensional bulk excursions or relocations [1]. A better understanding of such dynamics is needed in order, for example, to optimize the intermittent search strategy [2]. Recently [3], we have proposed a theoretical analysis of field cycling NMR dispersion technique (NMRD) experiments allowing to probe the time/frequency dependence of relocation steps [4] and adsorption periods of an intermittent fluid dynamics near an interface. In this communication, we consider the Brownian dynamics of a fluid molecule over thin and very long mineral strands having a diameter of about 3 nm. Experiments are compared with numerical simulations and theoretical derivation. 2. Probing relocation statistics over strands by NMR relaxometry A B Fig.1: A: Intermittent Brownian dynamics over a strand. A and B stand for the Adsorption step and the Relocation (Brigde statistics). B: Frequency dependence of the spin-lattice relaxation rate in diluted suspension of imogolite. Full squares: experimental results. Dotted line: Brownian dynamics numerical simulation. In the following, we consider the case of imogolite particles in very diluted suspensions. Imogolite are thin and very long cylinders having a diameter similar to DNA 1 The Open-Access Journal for the Basic Principles of Diffusion Theory, Experiment and Application © 2007, P. Levitz Diffusion Fundamentals 6 (2007) 78.1 - 78.2