the wild-type protein, face the apolar environment of the lipid bilayer. We then measured the thermodynamic stability of the wild-type protein and of each of the sequence variants by chemical denaturation. We only made these measurements when the proteins appeared to be at reversible equilibrium between folded and denatured states. We also characterized the folded states of each protein by fluorescence spectroscopy and by a functional assay. Those characterizations revealed additional information about how the lipid bilayers may accommodate an arginine.
Synaptic transmission insures neuronal communication but relies on several random steps. Because synapse are still inaccessible to direct experimental recordings, to study synaptic reliability, we analyze synaptic transmission by constructing a biophysical model. This model accounts for the synaptic cleft geometry and several dynamical variables such as the position of vesicular release and the membrane trafficking AMPA receptors, which mostly mediate the synaptic current. These receptors are located in the postsynaptic terminal, but can be exchanged from the Post-Synaptic Density (PSD), a fundamental microdomain and the extra-synaptic space. We show that the synapse geometry controls the amplitude of the synaptic current, while receptor diffusional motion can replace desensitized receptors and thus prevents synaptic depression from receptor desensitization (significantly only after 6 to 7 successful spikes). Synaptic reliability is optimal when the active zone of vesicular release is apposed to a PSD, where AMPA receptors are concentrated. Change in this co-localization can lead to drastic effects on the synaptic current, which suggests that these changes can underlie a form of remodeling and plasticity. We finally demonstrate that fast temporal correlated spike lead to a reduced synaptic current. We conclude that although synapse should and are unreliable devices, at the neuronal level, reliability is restored due to the presence of multiple synaptic boutons.
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