Non-Fickian Interdiffusion of Dynamically Asymmetric Species: A Molecular Dynamics Study

We use Molecular Dynamics combined with Dissipative Particle Dynamics to construct a model of a binary mixture where the two species differ only in their dynamic properties (friction coefficients). For an asymmetric mixture of slow and fast particles we study the interdiffusion process. The relaxation of the composition profile is investigated in terms of its Fourier coefficients. While for weak asymmetry we observe Fickian behavior, a strongly asymmetric system exhibits clear indications of anomalous diffusion, which occurs in a crossover region between the Cases I (Fickian) and II (sharp front moving with constant velocity), and is close to the Case II limit.Comment: to appear in J. Chem. Phy

Polymer nano-doplets forming liquid bridges in chemically structured slit pores: A computer simulation

Using a coarse-grained bead-spring model of flexible polymer chains, the structure of a polymeric nanodroplet adsorbed on a chemically decorated flat wall is investigated by means of Molecular Dynamics simulation. We consider sessile drops on a lyophilic (attractive for the monomers) region of circular shape with radius R_D while the remaining part of the substrate is lyophobic. The variation of the droplet shape, including its contact angle, with R_D is studied, and the density profiles across these droplets also are obtained. In addition, the interaction of droplets adsorbed on two walls forming a slit pore with two lyophilic circular regions just opposite of one another is investigated, paying attention to the formation of a liquid bridge between both walls. A central result of our study is the measurement of the force between the two substrate walls at varying wall separation as well as the kinetics of droplet merging. Our results are compared to various phenomenological theories developed for liquid droplets of mesoscopic rather than nanoscopic size.Comment: 8 pages, 9 figures, accepted in J. Chem. Phys. 200

SPRTN patient variants cause global-genome DNA-protein crosslink repair defects

DNA-protein crosslinks (DPCs) are toxic DNA lesions which threaten genome stability. Here, the authors develop a method to track the fate of DPCs in cells and identify a role for the SPRTN protease in replication-independent DPC repair