ABSTRACT
With the aid of stimulus-responsive hydrogel substrates composed of ABA triblock copolymer micelles, we monitored the morphological dynamics of myoblast (C2C12) cells in response to an abrupt change in the substrate elasticity by live cell imaging. The remodeling of actin cytoskeletons could be monitored by means of transient transfection with LifeAct-GFP. Dynamic changes in the orientational order of actin filaments were characterized by an order parameter, which enables one to generalize the mechanically induced actin cytoskeletons as a break of symmetry. The critical role that acto-myosin complexes play in the morphological transition was verified by the treatment of cells with myosin II inhibitor (blebbistatin) and the fluorescence localization of focal adhesion contacts. Such dynamically tunable hydrogels can be utilized as in vitro cellular micro-environments that can exert time-dependent stimuli to mechanically regulate target cells.
Subject(s)
Actin Cytoskeleton/chemistry , Myoblasts/chemistry , Myosin Type II/chemistry , Actin Cytoskeleton/metabolism , Cell Adhesion , Cell Line , Cell Tracking , Elasticity , Myoblasts/cytology , Myosin Type II/metabolism , Optical Imaging , TransfectionABSTRACT
Electrochemically formed hydrogen nanobubbles at a platinum rotating disk electrode (RDE) were detected by re-oxidation charge. The dissolution time course of the hydrogen nanobubbles was measured by AFM tapping topography under open-circuit conditions at stationary platinum and gold single-crystal electrodes. The bubble dissolution at platinum was much faster than that at gold because two types of diffusion, bulk and surface diffusion, proceeded at the platinum surface, whereas surface diffusion was prohibited at the gold electrode. These findings indicated that the electrochemical reaction of normal hydrogen electrode partly proceeded heterogeneously on the three-phase boundary around the hydrogen nanobubble.
Subject(s)
Electrochemistry , Electrodes , Hydrogen/chemistry , Microbubbles , Nanoparticles , Gold/chemistry , Microscopy, Atomic Force , Models, Chemical , Oxidation-Reduction , Platinum/chemistry , Surface PropertiesABSTRACT
To investigate quantitatively the effects of stirring on protein crystallization, a new stirring system which can agitate a protein solution, approximately 100 nl, by providing Hagen-Poiseuille flow has been successfully developed. In addition, this new stirring system provides flow with a well defined pattern and velocity. Using this system, hen egg-white lysozyme was crystallized in 100-200 nl solutions while being stirred. The optimum stirring conditions for lysozyme crystals have been explored by evaluating the Reynolds (Re) number and the crystals obtained. Intermittent flow, as well as a low Re number, was found to contribute significantly to the growth of a smaller number of larger crystals.
