Precise information regarding the transmembrane topology of mitochondrial porin is essential for understanding the mechanisms by which this protein functions. Porin acts as a channel in the outer membrane and interacts with small solutes and proteins to regulate mitochondrial function. The acquisition of high-resolution structural data requires a method of maintaining high concentrations of unaggregated, properly folded porin. In the current studies, several mixed detergent systems were analyzed for their ability to fold Neurospora mitochondrial porin expressed in and isolated from Escherichia coli. A mixture of sodium dodecyl sulfate and dodecyl-@b-D-maltopyranoside in a 1:6 molar ratio supports a @b-strand-rich conformation. In this state, the two tryptophan residues in the protein reside in hydrophobic environments, and about half of the nine tyrosines are solvent exposed. Most importantly, heat-labile tertiary contacts, as detected by near-UV circular dichroism spectropolarimetry, in the sodium dodecyl sulfate/dodecyl-@b-D-maltopyranoside-solubilized porin are very similar to those of the protein following functional reconstitution into liposomes. Similarly, both forms are protease resistant. Thus, a method has been identified with the potential to solubilize high concentrations of mitochondrial porin in a state virtually indistinguishable from the membrane-embedded form.
We review several parallel tempering schemes and examine their main
Ingredients for accuracy and efficiency. The present study covers two selection
Methods of temperatures and several choices for the exchange of replicas,
Including a recent novel all-pair exchange method. We compare the resulting
We present are a series of $m$ boundary layer potentials. We give
Explicit formulas for these layer potentials as linear combinations of powers
Of the Laplacian applied to the Dirichlet data, with coefficients determined by
Certain path counting problems....
General Relativity is extended into the quantum domain. A thought experiment
is explored to derive a specific topological build-up for Planckian space-time.
The presented arguments are inspired by Feynman's path integral for
superposition and Wheeler's quantum foam of Planck mass mini black
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