No abstract

We study the effects of strong magnetic fields on the neutron star structure. If the interior field of a star is on the same order of the surface field currently observed, the influences of the magnetic field on the star mass and radius are negligible. If one assumes that the internal magnetic field can be as large as that estimated from the scalar virial theorem, considerable effects can be induced. The maximum mass of stars is arisen substantially while the central density is largely suppressed. For two equal-mass stars the radius of the magnetic star can be larger by about 10% ∼ 20% than the nonmagnetic star.

E. coli YbgH belongs to the family of proton-dependent oligopeptide transporters (POTs), a subfamily of the major facilitator superfamily (MFS) of secondary active transporters. Like other MFS transporters, POT proteins switch between two major conformations during substrate transport. Apart from possessing a canonical 12-helix, two-domain transmembrane (TM) core, prokaryotic POT proteins usually have two TM helices inserted between the two domains. Here we determined the crystal structure of YbgH in its inward-facing conformation. Our structure-based functional studies investigated the roles of both the POT signature motif 2 and the inserted interdomain TM helix pair in the stabilization and regulation of the major conformational change in MFS/POT transporters. Furthermore, of all the proton-titratable amino acid residues, Glu21 is the only conserved one (among POTs) located in the central cavity and is critical for in vivo transport. Together, our results support the notion that MFS symporters utilize a transport mechanism based on substrate-protonation coupling.