Symmetry-Broken Reactant Motion upon Phase-Related Symmetrically Modulated Excitations: Application to Highly Selective Molecular Sorting

Laboratoire de Physique Théorique des Liquides, Université Pierre et Marie Curie, C.N.R.S. U.M.R. 7600, 4, place Jussieu, 75252 Paris Cedex 05, France.
The Journal of Physical Chemistry A (Impact Factor: 2.69). 07/2005; 109(25):5770-6. DOI: 10.1021/jp0509156
Source: PubMed


This paper introduces a separation protocol relying on affinity chromatography that exhibits unprecedented selectivities. We submit the mixture contained in the separative medium to the simultaneous action of two symmetrically modulated excitations. The first is a uniform periodic field (e.g., electric field) with zero mean value, whereas the second is the periodic modulation of a thermodynamic parameter such as the temperature. Under appropriate tuning of the modulations with the dynamics of the discriminating chemical reaction, we predict a symmetry breaking of molecular motion: the mixture components that are addressed by their rate constants exhibit an oriented motion for a particular phase relation between the modulations of the field and the thermodynamic parameter. The resulting velocity of the mixture components depends on the rate constants and on a conjugated thermodynamic value such as the standard enthalpy of the discrimination process in the case of a temperature modulation. In particular, it may be possible to separate mixture components with identical rate constants. We use the present approach to design a protocol to sort nucleic acids by their sequence.

7 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: This theoretical paper introduces an experimental protocol derived from the concept of Brownian motors in order to selectively confer an oriented motion to given charged reactants. Instead of maintaining permanently the system in nonequilibrium conditions, we propose a simple experimental trick to restore periodically a transient out-of-equilibrium regime: the reactive medium is alternately submitted to a sawtooth potential and to a potential ramp. The model provides approximate analytical expressions for the operating conditions allowing us to design the extraction from a mixture of any desired reactant characterized by its rate constants. The orders of magnitude suggest a possible implementation in microsystems where the present approach could be used for separation and analysis.
    No preview · Article · Apr 2007 · The Journal of Physical Chemistry B
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We consider n reactive species involved in unimolecular reactions and submitted to a temperature modulation of small amplitude. We determine the conditions on the rate constants for which the deviations from the equilibrium concentrations of each species can be optimized and find the analytical expression of the frequency associated with an extremum of concentration shift in the case n=3. We prove that the frequency dependence of the displacement of equilibrium gives access to the number n of species involved in the mechanism. We apply the results to the case of the transformation of a reactant into a product through a possible reactive intermediate and find the order relation obeyed by the activation energies of the different barriers. The results typically apply to enzymatic catalysis with kinetics of Michaelis-Menten type.
    Full-text · Article · Dec 2007 · Physical Review E
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Biological samples exhibit huge molecular diversity over large concentration ranges. Titrating a given compound in such mixtures is often difficult, and innovative strategies emphasizing selectivity are thus demanded. To overcome limitations inherent to thermodynamics, we here present a generic technique where discrimination relies on the dynamics of interaction between the target of interest and a probe introduced in excess. Considering an ensemble of two-state exchanging reactants submitted to temperature modulation, we first demonstrate that the amplitude of the out-of-phase concentration oscillations is maximum for every compound involved in a reaction whose equilibrium constant is equal to unity and whose relaxation time is equal to the inverse of the excitation angular frequency. Taking advantage of this feature, we next devise a highly specific detection protocol and validate it using a microfabricated resistive heater and an epifluorescence microscope, as well as labeled oligonucleotides to model species displaying various dynamic properties. As expected, quantification of a sought for strand is obtained even if interfering reagents are present in similar amounts. Moreover, our approach does not require any separation and is compatible with imaging. It could then benefit some of the numerous binding assays performed every day in life sciences.
    Full-text · Article · Feb 2011 · Analytical Chemistry