CUSB

Abstract: The Escherichia coli periplasmic proteins CusF and CusB, as part of the CusCFBA efflux system, aid in the resistance of elevated levels of copper and silver by direct metal transfer between the metallochaperone CusF and the membrane fusion protein CusB before metal extrusion from the periplasm to the extracellular space Although previous in vitro experiments have demonstrated highly specific interactions between CusF and CusB that are crucial for metal transfer to occur, the structural details of the interaction have not been determined Here, the interactions between CusF and CusB are mapped through nuclear magnetic resonance (NMR) spectroscopy and chemical cross-linking coupled with high-resolution mass spectrometry to better understand how recognition and metal transfer occur between these proteins The NMR 1H−15N correlation spectra reveal that CusB interacts with the metal-binding face of CusF In vitro chemical cross-linking with a 77 A homobifunctional amine-reactive cross-linker, BS2G, was used

Abstract: We present local probe results on the honeycomb lattice antiferromagnet Ba(3)CuSb(2)O(9). Muon spin relaxation measurements in a zero field down to 20 mK show unequivocally that there is a total absence of spin freezing in the ground state. Sb NMR measurements allow us to track the intrinsic susceptibility of the lattice, which shows a maximum at around 55 K and drops to zero in the low-temperature limit. The spin-lattice relaxation rate shows two characteristic energy scales, including a field-dependent crossover to exponential low-temperature behavior, implying gapped magnetic excitations.