Phoretic self-assembly of active colloidal molecules

We simulate the self-assembly of active colloidal molecules from binary mixtures of spherical particles using a Brownian dynamics algorithm.These particles interact via phoretic interactions,which are determined by two independently tunable parameters,surface activity and surface mobility.In systems composed of equal-size particles,we observe the formation of colloidal molecules with well-defined coordination numbers and spatial arrangement,which also display distinct dynamic functions,such as resting,translating,and rotating.By changing the size ratio to 2:1 between the two species,we further observe the formation of colloidal molecules with new structures arising from breaking the size symmetry.By tuning the mutual interactions between the smaller species via their surface mobility,we are able to control their spacing as well as the coordination number of the colloidal molecules.This study highlights the importance of tuning surface parameters and size asymmetry in controlling the structure and the active dynamics of colloidal molecules.

Emergent phenomena in chiral active matter

In recent years,there has been growing interest in the study of chiral active materials,which consist of building blocks that show active dynamics featuring chiral symmetry breaking,e.g.,particles that rotate in a common direction.These materials exhibit fascinating phenomena such as odd viscosity,odd diffusivity,active turbulence in fluids,vivid dislocation dynamics or odd elasticity in crystals or elastic materials,and hyperuniform states.The systematic study of soft chiral active matter systems is relatively new,starting around 2017,but has already shown promising applications in robust cargo transport,segregation and mixing dynamics,or manipulation of metamaterials.In this review,we summarize recent experimental and theoretical advances in this field,highlighting the emergence of anti-symmetric and odd stresses and ensuring effects such as odd viscosity or topologically protected edge modes.We further discuss the underlying mechanisms and provide insights into the potential of chiral active matter for various applications.

Morphology-Tailored Dynamic State Transition in Active-Passive Colloidal Assemblies

Mixtures of active self-propelled and passive colloidal particles promise rich assembly and dynamic states that are beyond reach via equilibrium routes.Yet,controllable transition between different dynamic states remains rare.Here,we reveal a plethora of dynamic behaviors emerging in assemblies of chemically propelled snowman-like active colloids and passive spherical particles as the particle shape,size,and composition are tuned.For example,assembles of one or more active colloids with one passive particle exhibit distinct translating or orbiting states while those composed of one active colloid with 2 passive particles display persistent“8”-like cyclic motion or hopping between circling states around one passive particle in the plane and around the waist of 2 passive ones out of the plane,controlled by the shape of the active colloid and the size of the passive particles,respectively.These morphology-tailored dynamic transitions are in excellent agreement with state diagrams predicted by mesoscale dynamics simulations.Our work discloses new dynamic states and corresponding transition strategies,which promise new applications of active systems such as micromachines with functions that are otherwise impossible.

Chemical inhibition of Arabidopsis PIN-FORMED auxin transporters by the anti-inflammatory drug naproxen

The phytohormone auxin plays central roles in many growth and developmental processes in plants.Development of chemical tools targeting the auxin pathway is useful for both plant biology and agriculture.Here we reveal that naproxen,a synthetic compound with anti-inflammatory activity in humans,acts as an auxin transport inhibitor targeting PIN-FORMED(PIN)transporters in plants.Physiological experiments indicate that exogenous naproxen treatment affects pleiotropic auxin-regulated developmental processes.Additional cellular and biochemical evidence indicates that naproxen suppresses auxin transport,specifically PIN-mediated auxin efflux.Moreover,biochemical and structural analyses confirm that naproxen binds directly to PIN1 protein via the same binding cavity as the indole-3-acetic acid substrate.Thus,by combining cellular,biochemical,and structural approaches,this study clearly establishes that naproxen is a PIN inhibitor and elucidates the underlying mechanisms.Further use of this compound may advance our understanding of the molecular mechanisms of PIN-mediated auxin transport and expand our toolkit in auxin biology and agriculture.

Defining A Global Map of Functional Group-based 3D Ligand-binding Motifs

Uncovering conserved 3D protein–ligand binding patterns on the basis of functional groups(FGs)shared by a variety of small molecules can greatly expand our knowledge of protein–ligand interactions.Despite that conserved binding patterns for a few commonly used FGs have been reported in the literature,large-scale identification and evaluation of FG-based 3D binding motifs are still lacking.Here,we propose a computational method,Automatic FG-based Three-dimensional Motif Extractor(AFTME),for automatic mapping of 3D motifs to different FGs of a specific ligand.Applying our method to 233 naturally-occurring ligands,we define 481 FG-binding motifs that are highly conserved across different ligand-binding pockets.Systematic analysis further reveals four main classes of binding motifs corresponding to distinct sets of FGs.Combinations of FG-binding motifs facilitate the binding of proteins to a wide spectrum of ligands with various binding affinities.Finally,we show that our FG–motif map can be used to nominate FGs that potentially bind to specific drug targets,thus providing useful insights and guidance for rational design of small-molecule drugs.