The dimeric (gemini) surfactant 12-2-12 (dimethylene-1,2-bis(dodecyl dimethylammonium bromide)) has been known to form threadlike micelles at relatively low concentrations. We investigated the micellar growth of this in aqueous solutions by much-improved cryo-TEM technique (transmission electron microscopy cryogenic temperature) concentration range between 0.26 and 1.5 wt %. digitally acquired micrographs solutions, with concentrations up about 1 %, show coexistence spheroidal long,...

We used cryo-TEM and light scattering to study the micellar growth subsequent network formation in aqueous solutions of nonionic surfactant C12E5. Cryo-TEM shows first direct evidence for existence connected topology vicinity critical point two-phase separation curve C12E5/water system. The coexisting phases within region consist one concentrated dilute interconnected cylindrical micelles. These findings are consistent with recent theoretical explanation criticality phase certain systems as...

The actin cytoskeleton is an active gel which constantly remodels during cellular processes such as motility and division. Myosin II molecular motors are involved in this remodeling process therefore control the dynamic self-organization of cytoskeletal structures. Due to complexity vivo systems, it hard investigate role myosin reorganization determines resulting Here we use vitro model system show that actively reorganizes into a variety mesoscopic patterns, but only presence bundling...

Abstract The ESCRT machinery mediates membrane remodeling in numerous processes cells including cell division and nuclear reformation. identification of homologs Asgard archaea, currently considered the closest prokaryotic relative eukaryotes, implies a role for ESCRTs that occurred during eukaryogenesis. Yet, function these distant is mostly unresolved. Here we show ESCRT-III proteins Lokiarcheota self-assemble into helical filaments, hallmark system. We determined cryo-EM structure...

The cellular cytoskeleton is a complex dynamical network that constantly remodels as cells divide and move. This reorganization process occurs not only at the cell membrane, but also in interior (bulk). During locomotion, regulated actin assembly near plasma membrane produces lamellipodia filopodia. Therefore, most vitro experiments explore phenomena taking place vicinity of surface. To understand how molecular machinery self-organizes more general way, we studied bulk polymerization...

Active gels play an important role in biology and inspiring biomimetic active materials, due to their ability change shape, size, create own morphology. We study a particular class of gels, generated by polymerizing actin the presence cross-linkers clusters myosin as molecular motors, which exhibit large contractions. The relevant mechanics for these highly swollen is result interplay between activity liquid flow: gel yields structural reorganization network produces flow that eventually...

Living systems adopt a diversity of curved and highly dynamic shapes. These diverse morphologies appear on many length scales, from cells to tissues organismal scales. The common driving force for these shape changes are contractile stresses generated by myosin motors in the cell cytoskeleton, that converts chemical energy into mechanical work. A good understanding how cytoskeleton arise different three-dimensional (3D) shapes what selection rules determine their final configurations is...

Eukaryotic cells rely on their cytoskeleton to carry out coordinated motion, transport materials within them, and interact mechanically with environment. To adapt the changing requirements, cell's constantly remodels through action of myosin II motor clusters that numerous actin filaments simultaneously. Here we study various roles in formation evolution vitro actomyosin networks as a model system for cytoskeleton. In our experiments can vary size between 14 144 molecules apply forces...

Shape transitions in developing organisms can be driven by active stresses, notably, contractility generated myosin motors. The mechanisms generating tissue folding are typically studied epithelia. There, the interaction between cells is also coupled to an elastic substrate, presenting a major difficulty for studying contraction induced folding. Here we study and buckling of active, initially homogeneous, thin actomyosin networks isolated from bounding surfaces. network behaves as...

Direct evidence by cryogenic temperature transmission electron microscopy shows the existence of networks in microemulsions near two-phase closed loops. Networks formed interconnected oil-swollen cylinders were observed water-rich regions phase diagram C12E5 /water/n-octane system. The coexisting phases within loops shown to be concentrated and dilute networks. Similar micellar also found binary These observations substantiate suggested theoretical link between structural bicontinuity unique...

The viscoelastic response of complex fluids is length- and time-scale dependent, encoding information on intrinsic dynamic correlations mesoscopic structure. We study the length scale above which bulk viscoelasticity sets in, material that precedes it at shorter distances. show crossover between these two regimes may appear a surprisingly large distance. generalize framework microrheology to include both apply F-actin networks, thereby extracting their correlation from local properties.

During cellular migration, regulated actin assembly takes place at the cell leading edge, with continuous disassembly deeper in interior. Actin polymerization plasma membrane results extension of protrusions form lamellipodia and filopodia. To understand how cells regulate transformation into filopodia, to determine major factors that control their transition, we studied self-assembly presence Arp2/3 complex, WASp-VCA fascin, proteins participating We show early stages fascin is passive...

The structural reorganization of the actin cytoskeleton is facilitated through action motor proteins that crosslink filaments and transport them relative to each other. Here, we present a combined experimental-computational study probes dynamic evolution mixtures clusters myosin motors. While on small spatial temporal scales system behaves in very noisy manner, larger it evolves into several well distinct patterns such as bundles, asters networks. These are characterized by junctions with...

The microstructures in mixtures of two dimeric (gemini) surfactants, the dimethylene-1,2- and eicosamethylene-1,20-bis(dimethyldodecylammonium bromide), referred to as 12-2-12 12-20-12, have been investigated at 25 °C by electrical conductivity, spectrophotometry, digital light microscopy (DLM), transmission electron cryogenic temperature (cryo-TEM). This mixture was selected because 12-20-12 forms vesicles a wide range concentration whereas micelles that are spherical low then rapidly...

Microrheology is used to measure the length scale dependent mechanical response of F-actin gels. The dynamic correlation thus measured has a non-trivial dependence on actin filament length.

We study the effect of myosin concentration on mechanical properties actomyosin networks in steady state. find that fluctuations tracer particles embedded network decrease amplitude as motor increases, while networks' stiffness increases.