Effects of rebinding rate and asymmetry in unbinding rate on cargo transport by multiple kinesin motors

Many intracellular transports are performed by multiple molecular motors in a cooperative manner.Here,we use stochastic simulations to study the cooperative transport by multiple kinesin motors,focusing mainly on effects of the form of unbinding rate versus force and the rebinding rate of single motors on the cooperative transport.We consider two forms of the unbinding rate.One is the symmetric form with respect to the force direction,which is obtained according to Kramers theory.The other is the asymmetric form,which is obtained from the prior studies for the single kinesin motor.With the asymmetric form the simulated results of both velocity and run length of the cooperative transport by two identical motors and those by a kinesin-1 motor and a kinesin-2 motor are in quantitative agreement with the available experimental data,whereas with the symmetric form the simulated results are inconsistent with the experimental data.For the cooperative transport by a faster motor and a much slower motor,the asymmetric form can give both larger velocity and longer run length than the symmetric form,giving an explanation for why kinesin adopts the asymmetric form of the unbinding rate rather than the symmetric form.For the cooperative transport by two identical motors,while the velocity is nearly independent of the rebinding rate,the run length increases linearly with the rebinding rate.For the cooperative transport by two different motors,the increase of the rebinding rate of one motor also enhances the run length of the cooperative transport.The dynamics of transport by N(N=3,4,5,6,7 and 8)motors is also studied.

Large family of two-dimensional ferroelectric metals discovered via machine learning

Ferroelectricity and metallicity are usually believed not to coexist because conducting electrons would screen out static internal electric fields.In 1965,Anderson and Blount proposed the concept of"ferroelectric metal",however,it is only until recently that very rare ferroelectric metals were reported.Here,by combining high-throughput ab initio calculations and data-driven machine learning method with new electronic orbital based descriptors,we systematically investigated a large family(2964)of two-dimensional(2D)bimetal phosphates,and discovered 60 stable ferroelectrics with out-of-plane polarization,including 16 ferroelectric metals and 44 ferroelectric semiconductors that contain seven multiferroics.The ferroelectricity origins from spontaneous symmetry breaking induced by the opposite displacements of bimetal atoms,and the full-d-orbital coinage metal elements cause larger displacements and polarization than other elements.For 2D ferroelectric metals,the odd electrons per unit cell without spin polarization may lead to a half-filled energy band around Fermi level and is responsible for the metallicity.It is revealed that the conducting electrons mainly move on a single-side surface of the 2D layer,while both the ionic and electric contributions to polarization come from the other side and are vertical to the above layer,thereby causing the coexistence of metallicity and ferroelectricity.Van der Waals heterostructures based on ferroelectric metals may enable the change of Schottky barrier height or the Schottky-Ohmic contact type and induce a dramatic change of their vertical transport properties.Our work greatly expands the family of 2D ferroelectric metals and will spur further exploration of 2D ferroelectric metals.