The trio of protein segment repeats called spectrins diverges by more than 2 orders of magnitude in their folding and unfolding rates, despite having very similar stabilities and almost coincidental topologies. Experimental studies revealed that the mutation of five particular residues dramatically alters the kinetic rates in the slow folders, making them similar to the rates of the fast folder. This is considered to be an exceptional behavior which seems in principle to challenge the current understanding of the protein folding process. In this work, we analyze this scenario, using a simplified computational model, combined with state-of-theart kinetic analysis techniques. Our model faithfully separates the kinetics of the fast and slow folders and captures the effect of the five mutations. We show that the inclusion of electrostatics in the model is necessary to explain the experimental findings. Article pubs.acs.org/JPCB
We sought to determine whether the messages conveyed in the spike trains of individual retinal ganglion cells are unique or whether, as has been reported for other neurons, they depend in some way on a neuron's state. Our data show convincingly that the messages are unique.
Low salinity water flooding has shown great promise due to its cost-effectiveness and low environmental impact for improving and sustaining oil production. It is believed that injecting water with ionic strength lower than that of the reservoir changes the reservoir from less to more water-wet and enhances oil recovery. This alteration phenomenon is not well understood, due to complex interactions between oil, water, and rock. Here we use molecular simulations to characterize the wettability of the 10.4-face of calcite in a calcite/brine/oil system, and address how wettability is altered by changing ionic strength and salt type (NaCl vs. CaCl<sub>2</sub>). Using the test area method we calculate the superficial tension of the fluids against the solid and the surface tension between the two fluid phases. As the salinity is decreased, the wetting of calcite by brine is progressively less favored, contrary to what might be expected based on low salinity flooding. However, as salinity is decreased, forming the oil-brine interface is more favored. On balance, it is the latter effect that leads to the enhanced wetting of calcite by brine in the oil-brine-calcite system, and it is suggested as an important element in the physics underlying low-salinity flooding. <br>
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