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Abstract: The mechanism by which nucleotide-binding domains (NBDs) of ABC transporters power the transport of substrates across cell membranes is currently unclear. Here we report the crystal structure of an NBD, FbpC, from the Neisseria gonorrhoeae ferric iron uptake transporter with an unusual and substantial domain swap in the C-terminal regulatory domain. This entanglement suggests that FbpC is unable to open to the same extent as the homologous protein MalK. Using molecular dynamics we demonstrate that this is not the case: both NBDs open rapidly once ATP is removed. We conclude from this result that the closed structures of FbpC and MalK have higher free energies than their respective open states. This result has important implications for our understanding of the mechanism of power generation in ABC transporters, because the unwinding of this free energy ensures that the opening of these two NBDs is also powered.

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Abstract: We have determined the structure of a complex rhodium carbonyl chloride [Rh(CO)2Cl] molecule adsorbed on the TiO2(110) surface by the normal incidence x-ray standing wave technique. The data show that the technique is applicable to reducible oxide systems and that the dominant adsorbed species is undissociated with Rh binding atop bridging oxygen and to the Cl found close to the fivefold coordinated Ti ions in the surface. A minority geminal dicarbonyl species, where Rh-Cl bond scission has occurred, is found bridging the bridging oxygen ions forming a high-symmetry site.

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Abstract: The group 13 monoalkoxometallanes [Me_{2}Ga(OC(CH_{3})_{2}CH_{2}OMe)]_{2} (1) and [Me_{2}In(OCH(CH_{3})CH_{2}OMe)]_{2} (2), incorporating donor functionalised alkoxides, were synthesised from the reaction of GaMe_{3} or InMe_{3} with ROH (R=C(CH_{3})_{2}CH_{2}OMe (1); R=CH(CH_{3})CH_{2}OMe (2)) in toluene. X-ray crystallography showed that both compounds adopt dimeric structures with a planar M_{2}O_{2} ring, and each group 13 atom is coordinated in a distorted trigonal bipyramidal geometry. The AACVD reaction of GaMe_{3} and ROH (R =C(CH_{3})_{2}CH_{2}OMe, CH_{2}CH_{2}OMe, CH_{2}CH_{2}NMe_{2}) resulted in the formation of thin films of Ga_{2}O_{3} on glass substrates at 450°C. The gallium oxide films were analyzed by scanning electron microscopy, X-ray powder diffraction, energy dispersive analysis of X-rays, wavelength dispersive analysis of X-rays and X-ray photoelectron spectroscopy. This CVD technique offers a rapid, convenient route to Ga_{2}O_{3}, which involves the in situ formation of dimethylgallium alkoxides, of the type [Me_{2}Ga(?-OR)]_{2} similar to compound 1.

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Abstract: Enterococcus hirae vacuolar ATPase (V-ATPase) is composed of a soluble catalytic domain (V1; NtpA3-B3-D-G) and an integral membrane domain (V0; NtpI-K10) connected by a central and peripheral stalk(s) (NtpC and NtpE-F). Here we examined the nucleotide binding of NtpA monomer, NtpB monomer or NtpD-G heterodimer purified by using Escherichia coli expression system in vivo or in vitro, and the reconstitution of the V1 portion with these polypeptides. The affinity of nucleotide binding to NtpA was 6.6 ?M for ADP or 3.1 ?M for ATP, while NtpB or NtpD-G did not show any binding. The NtpA and NtpB monomers assembled into NtpA3-B3 heterohexamer in nucleotide binding-dependent manner. NtpD-G bound NtpA3-B3 forming V1 (NtpA3-B3-D-G) complex independent of nucleotides. The V1 formation from individual NtpA and NtpB monomers with NtpD-G heterodimer was absolutely dependent on nucleotides. The ATPase activity of reconstituted V1 complex was as high as that of native V1-ATPase purified from the V0V1 complex by EDTA treatment of cell membrane. This in vitro reconstitution system of E. hirae V1 complex will be valuable for characterizing the subunit-subunit interactions and assembly mechanism of the V1-ATPase complex.

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Abstract: Controlling a phase of matter by coherently manipulating specific vibrational modes has long been an attractive (yet elusive) goal for ultrafast science. Solids with strongly correlated electrons, in which even subtle crystallographic distortions can result in colossal changes of the electronic and magnetic properties, could be directed between competing phases by such selective vibrational excitation. In this way, the dynamics of the electronic ground state of the system become accessible, and new insight into the underlying physics might be gained. Here we report the ultrafast switching of the electronic phase of a magnetoresistive manganite via direct excitation of a phonon mode at 17-THz. A prompt, five-order-of-magnitude drop in resistivity is observed, associated with a non-equilibrium transition from the stable insulating phase to a metastable metallic phase. In contrast with light-induced1, 2, 3 and current-driven4 phase transitions, the vibrationally driven bandgap collapse observed here is not related to hot-carrier injection and is uniquely attributed to a large-amplitude Mn-O distortion. This corresponds to a perturbation of the perovskite-structure tolerance factor, which in turn controls the electronic bandwidth via inter-site orbital overlap5, 6. Phase control by coherent manipulation of selected metal-oxygen phonons should find extensive application in other complex solids-notably in copper oxide superconductors, in which the role of Cu-O vibrations on the electronic properties is currently controversial.