scholarly journals Inferring non-equilibrium interactions from tracer response near confined active Janus particles

2021 ◽  
Vol 7 (18) ◽  
pp. eabd0719
Author(s):  
Jaideep Katuri ◽  
William E. Uspal ◽  
Mihail N. Popescu ◽  
Samuel Sánchez
Keyword(s):  
Symmetry Axis ◽  
Coarse Grained ◽  
Janus Particles ◽  
Janus Particle ◽  
Indirect Methods ◽  
Effective Interactions ◽  
Coarse Grained Model ◽  
Direct Mapping ◽  
Tracer Particles ◽  
Non Equilibrium

Chemically active Janus particles sustain non-equilibrium spatial variations in the chemical composition of the suspending solution; these induce hydrodynamic flow and (self-)motility of the particles. Direct mapping of these fields has so far proven to be too challenging. Therefore, indirect methods are needed, e.g., deconvolving the response of “tracer” particles to the activity-induced fields. Here, we study experimentally the response of silica particles, sedimented at a wall, to active Pt/silica Janus particles. The latter are either immobilized at the wall, with the symmetry axis perpendicular or parallel to the wall, or motile. The experiments reveal complex effective interactions that are dependent on the configuration and on the state of motion of the active particle. Within the framework of a coarse-grained model, the behavior of tracers near an immobilized Janus particle can be captured qualitatively once activity-induced osmotic flows on the wall are considered.

scholarly journals Interactions Between Nucleosomes: From Atomistic Simulation to Polymer Model

2021 ◽  
Vol 8 ◽  
Author(s):  
Chengwei Zhang ◽  
Jing Huang
Keyword(s):  
Atomistic Simulation ◽  
Umbrella Sampling ◽  
Coarse Grained ◽  
Basic Unit ◽  
Time Dimension ◽  
Effective Interactions ◽  
Coarse Grained Model ◽  
Explicit Solvent ◽  
Chromatin Folding ◽  
Free Energy Landscapes

The organization of genomes in space and time dimension plays an important role in gene expression and regulation. Chromatin folding occurs in a dynamic, structured way that is subject to biophysical rules and biological processes. Nucleosomes are the basic unit of chromatin in living cells, and here we report on the effective interactions between two nucleosomes in physiological conditions using explicit-solvent all-atom simulations. Free energy landscapes derived from umbrella sampling simulations agree well with recent experimental and simulation results. Our simulations reveal the atomistic details of the interactions between nucleosomes in solution and can be used for constructing the coarse-grained model for chromatin in a bottom-up manner.

scholarly journals Non-equilibrium effects of molecular motors on polymers

Soft Matter ◽  
2019 ◽  
Vol 15 (29) ◽  
pp. 5995-6005 ◽  
Author(s):  
M. Foglino ◽  
E. Locatelli ◽  
C. A. Brackley ◽  
D. Michieletto ◽  
C. N. Likos ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Molecular Motors ◽  
Coarse Grained ◽  
Polymer Substrates ◽  
Coarse Grained Model ◽  
Non Equilibrium

We present a generic coarse-grained model to describe molecular motors acting on polymer substrates, mimicking, for example, RNA polymerase on DNA or kinesin on microtubules.

Insights Into Crowding Effects on Protein Stability From a Coarse-Grained Model

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Vincent K. Shen ◽  
Jason K. Cheung ◽  
Jeffrey R. Errington ◽  
Thomas M. Truskett
Keyword(s):  
Protein Stability ◽  
Coarse Grained ◽  
Protein Solutions ◽  
Native State ◽  
High Concentration ◽  
Coarse Grained Model ◽  
Excluded Volume Effects ◽  
Thermodynamic Phase ◽  
Broad Interest ◽  
Liquid Liquid Phase Separation

Proteins aggregate and precipitate from high concentration solutions in a wide variety of problems of natural and technological interest. Consequently, there is a broad interest in developing new ways to model the thermodynamic and kinetic aspects of protein stability in these crowded cellular or solution environments. We use a coarse-grained modeling approach to study the effects of different crowding agents on the conformational equilibria of proteins and the thermodynamic phase behavior of their solutions. At low to moderate protein concentrations, we find that crowding species can either stabilize or destabilize the native state, depending on the strength of their attractive interaction with the proteins. At high protein concentrations, crowders tend to stabilize the native state due to excluded volume effects, irrespective of the strength of the crowder-protein attraction. Crowding agents reduce the tendency of protein solutions to undergo a liquid-liquid phase separation driven by strong protein-protein attractions. The aforementioned equilibrium trends represent, to our knowledge, the first simulation predictions for how the properties of crowding species impact the global thermodynamic stability of proteins and their solutions.

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