Fluctuation-induced transport of two coupled particles: Effect of the interparticle interaction

Abstract

We consider a system of two coupled particles fluctuating between two states, with different interparticle interaction potentials and particle friction coefficients. An external action drives the interstate transitions that induces reciprocating motion along the internal coordinate x (the interparticle distance). The system moves unidirectionally due to rectification of the internal motion by asymmetric friction fluctuations and thus operates as a dimeric motor that converts input energy into net movement. We focus on how the law of interaction between the particles affects the dimer transport and, in particular, the role of thermal noise in the motion inducing mechanism. It is argued that if the interaction potential behaves at large distances as x(α), depending on the value of the exponent α, the thermal noise plays a constructive (α > 2), neutral (α = 2), or destructive (α < 2) role. In the case of α = 1, corresponding piecewise linear potential profiles, an exact solution is obtained and discussed in detail.

Chromatin remodelers as active Brownian dimers

“…Obviously, the model we present is extremely reduced. It can, however, easily be extended in both more microscopic and macroscopic directions: in order to include detail of nucleosome structure and coupling it to the proper ATP-cycle, modeling approaches such as cited before in terms of ratchet models [33], or very recent novel active models [34] can be applied. In this way, more information about the force-generation leading to the inchworm motion would be built in.…”

“…For chromatin remodelers such models have been developed for the case of a remodeler from the ISWI family which is capable to position nucleosomes on DNA; this could be demonstrated experimentally in single-molecule positioning assays [4,5]. For the present case in which the motion is that of a motor with two footprints, a ratchet model has been discussed in the literature [33]. The other modeling philosophy relies on active Brownian dimer models [21,26], which is the approach we follow here.…”

Фотоуправляемые Возвратно-Поступательные Молекулярные Машины Типа “Гость-Хозяин”

“…Заметим, что система уравнений (4) и ее решения ( 6)-( 8) не зависят от температуры. Это полностью согласуется с выводами нашей работы [22], в которой было показано, что если константы скоростей переходов не зависят от координаты, а потенциальные энергии U j (x) на больших расстояниях ведут себя как x α , то тепловой шум играет конструктивную (α > 2) или деструктивную (α < 2) роль, а при α = 2, т.е. при параболических потенциалах, как в нашем случае, играет нейтральную роль.…”

“…Подчеркнем, что зависимость обсуждаемых величин от температуры появляется исключительно из-за координатной зависимости константы скорости распада Γ(x). Как отмечалось выше, если Γ(x) = const, то характеристики возвратнопоступательного движения в параболических потенциалах не зависят от температуры в полном согласии с нашими прежними результатами [22]. Таким образом, в настоящей работе механизм функционирования управляемых светом возвратнопоступательных молекулярных машин (light-driven molecular machines) схематически рассмотрен на примере броуновского фотомотора.…”