57 research outputs found
Chaotropic substances and their effects on the mechanical strength of Portland cement-based materials
The Effect of Macromolecular Crowding, Ionic Strength and Calcium Binding on Calmodulin Dynamics
The flexibility in the structure of calmodulin (CaM) allows its binding to
over 300 target proteins in the cell. To investigate the structure-function
relationship of CaM, we combined methods of computer simulation and experiments
based on circular dichroism (CD) to investigate the structural characteristics
of CaM that influence its target recognition in crowded cell-like conditions.
We developed a unique multiscale solution of charges computed from quantum
chemistry, together with protein reconstruction, coarse-grained molecular
simulations, and statistical physics, to represent the charge distribution in
the transition from apoCaM to holoCaM upon calcium binding. Computationally, we
found that increased levels of macromolecular crowding, in addition to calcium
binding and ionic strength typical of that found inside cells, can impact the
conformation, helicity and the EF hand orientation of CaM. Because EF hand
orientation impacts the affinity of calcium binding and the specificity of
CaM's target selection, our results may provide unique insight into
understanding the promiscuous behavior of calmodulin in target selection inside
cells.Comment: Accepted to PLoS Comp Biol, 201
Effect of line tension on axisymmetric nanoscale capillary bridges at the liquid-vapor equilibrium
Versatile Underwater Adhesive with Microarchitecture Triggered by Solvent Exchange
Polyelectrolyte complexation is critical to the formation and properties of many biological and polymeric materials, and is typically initiated by aqueous solution mixing that results in fluid-fluid phase separation, e.g., coacervation. Here we report a versatile and strong wet-contact adhesive inspired by sandcastle worm cement that enables both a triggered complexation of polyelectrolytes, and formation of a porous architecture. A catecholfunctionalized weak poly-anion was premixed with a poly-cation in dimethyl sulfoxide (DMSO). The polymer solution was applied underwater to substrates where electrostatic complexation, phase inversion, and rapid setting were actuated by water-DMSO solvent exchange. This process offers enhanced spatial and temporal control of complexation, thereby fostering rapid (??? 25 s) and robust underwater adhesion (Wad ??? 2 J/m2) of complexed catecholic polyelectrolytes to all tested surfaces including plastics, glasses, metals, and biological surfaces. The solvent exchange process is adaptable to diverse materials chemistry, supporting functionalities well beyond aqueous complex coacervates
In Situ Assembly of Hydrophilic and Hydrophobic Nanoparticles at Oil–Water Interfaces as a Versatile Strategy To Form Stable Emulsions
We report a conceptually new strategy
for forming particle-stabilized emulsions. We begin with stable, dilute
suspensions of highly hydrophilic nanoparticles in water and hydrophobic
nanoparticles in oil. When the two suspensions are mixed, attractive
interactions between the hydrophilic and hydrophobic particles cause
them to assemble at the oil–water interfaces into partially
wettable or Janus-like clusters that effectively stabilize emulsions.
By tuning the ratio of hydrophilic to hydrophobic particles in the
clusters, both water-in-oil as well as oil-in-water emulsions can
be formed. The van der Waals interaction energy between two particle
types across an aqueous–organic interface provide a systematic
guide to particle and liquid combinations that can form stable emulsions
using our strategy, or identify when emulsions will not form. Our
experiments and analysis provide a new platform for the formation
of particle-stabilized emulsions and can be used to combine particles
of different functionalities at emulsion droplet surfaces for generating
novel materials
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