Semiconductor photocatalysis has attracted great interest because it provides a promising pathway for solving energy supply and environmental pollution problems. To date, various kinds of semiconductor materials, including metal oxides, 1 sulfides, 2 nitrides, 3 and their mixed solid solutions, 4,5 have been exploited as photocatalysts responsive to both the UV and visible light ranges. However, their applications are usually restricted by photocorrosion, short lifetimes of photogenerated electronÀhole pairs, and limited visible-light responses. 6 It is, therefore, of considerable significance to develop an efficient strategy toward producing catalysts with high photoactivity and high stability for practical applications.Although narrow-band-gap semiconductors are able to capture visible light in the solar spectrum, their photogenerated electronÀhole pairs suffer from fast recombination. Thus, tailoring semiconductor properties by fabricating designed structures is indispensable to improving the overall charge-transfer efficiency. For instance, reducing doping defects can suppress the recombination of photogenerated charge carriers, resulting in an improved photocatalytic activity. 7 In addition, combining a semiconductor with a metal or coupling two different semiconductors to form a heterostructure is another way to promote the separation of photogenerated charge carriers and thus increase their lifetime. 8,9 Heterostructure construction between two different semiconductors has been extensively exploited in many fields such as photocatalysis and solar energy conversion to enhance the performance of photovoltaic devices, 10,11 because heterojunctions dominate some behaviors of photogenerated charges, such as the direction of transportation, the distance for separation, and the recombination rate. 12,13 Furthermore, the internal electric field built at a heterojunction interface can greatly decrease the photogenerated charge-carrier recombination and increase the charge-carrier lifetimes, thus enhancing the photocatalytic activity. Therefore, heterostructure construction is not only a feasible approach for developing highly active photocatalysts response to visible light, but also a rational route to studying the relationship between photogenerated charge-carrier transfer and photocatalytic properties.Bismuth oxyhalides (BiOX, X = Cl, Br, and I) are well-known layered compounds that have a crystal structure of [Bi 2 O 2 ] 2+ layers interleaved by slabs comprising halide atoms. Owing to strong intralayer bonding and weak interlayer van der Waals interactions, these unique layered structures usually exhibit fascinating properties (e.g., anisotropic structural, electrical, optical, and mechanical properties) and have promising applications in cosmetics, pigments, catalysis, and photoelectrochemical devices. 14 In particular, bismuth oxyhalides are interesting as they offer the possibility to manipulate the electronic structure by choosing different halide atoms in the crystal structure, which is highly desirable fro...

Iron is an essential nutrient for most bacterial pathogens, but is restricted by the host immune system. Mycobacterium tuberculosis (Mtb) utilizes two classes of small molecules, mycobactins and carboxymycobactins, to capture iron from the human host. Here, we show that an Mtb mutant lacking the mmpS4 and mmpS5 genes did not grow under low iron conditions. A cytoplasmic iron reporter indicated that the double mutant experienced iron starvation even under high-iron conditions. Loss of mmpS4 and mmpS5 did not change uptake of carboxymycobactin by Mtb. Thin layer chromatography showed that the ΔmmpS4/S5 mutant was strongly impaired in biosynthesis and secretion of siderophores. Pull-down experiments with purified proteins demonstrated that MmpS4 binds to a periplasmic loop of the associated transporter protein MmpL4. This interaction was corroborated by genetic experiments. While MmpS5 interacted only with MmpL5, MmpS4 interacted with both MmpL4 and MmpL5. These results identified MmpS4/MmpL4 and MmpS5/MmpL5 as siderophore export systems in Mtb and revealed that the MmpL proteins transport small molecules other than lipids. MmpS4 and MmpS5 resemble periplasmic adapter proteins of tripartite efflux pumps of Gram-negative bacteria, however, they are not only required for export but also for efficient siderophore synthesis. Membrane association of MbtG suggests a link between siderophore synthesis and transport. The structure of the soluble domain of MmpS4 (residues 52–140) was solved by NMR and indicates that mycobacterial MmpS proteins constitute a novel class of transport accessory proteins. The bacterial burden of the mmpS4/S5 deletion mutant in mouse lungs was lower by 10,000-fold and none of the infected mice died within 180 days compared to wild-type Mtb. This is the strongest attenuation observed so far for Mtb mutants lacking genes involved in iron utilization. In conclusion, this study identified the first components of novel siderophore export systems which are essential for virulence of Mtb.

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Large conductance, Ca(2+)-activated potassium (BK) channels play important roles in the regulation of neuronal excitability and the control of smooth muscle contractions. BK channels can be activated by changes in both the membrane potential and intracellular Ca(2+) concentrations. Here, we provide an overview of the structural and pharmacological properties of BK channel blockers. First, the properties of different venom peptide toxins from scorpions and snakes are described, with a focus on their characteristic structural motifs, including their disulfide bond formation pattern, the binding interface between the toxin and BK channel, and the functional consequence of the blockage of BK channels by these toxins. Then, some representative non-peptide blockers of BK channels are also described, including their molecular formula and pharmacological effects on BK channels. The detailed categorization and descriptions of these BK channel blockers will provide mechanistic insights into the blockade of BK channels. The structures of peptide toxins and non-peptide compounds could provide templates for the design of new channel blockers, and facilitate the optimization of lead compounds for further therapeutic applications in neurological disorders or cardiovascular diseases.

KCNQ1 channels play vital roles in cardiovascular, gastric and other systems. The conductance and dynamics of KCNQ1 could be modulated by different single transmembrane helical auxiliary proteins (such as KCNE1, KCNE2 and others). In this study, detail KCNQ1 function modulations by different regions of KCNE1 or KCNE2 were examined using combinational methods of electrophysiology, immunofluorescence, solution NMR and related backbone flexibility analysis. In the presence of KCNE2 N-terminus, decreased surface expression and consequent low activities of KCNQ1 were observed. The transmembrane domains (TMDs) of KCNE1 and KCNE2 were illustrated to associate with the KCNQ1 channel in different modes: Ile64 in KCNE2-TMD interacting with Phe340 and Phe275 in KCNQ1, while two pairs of interacting residues (Phe340-Thr58 and Ala244-Tyr65) in the KCNQ1/KCNE1 complex. The KCNE1 C-terminus could modulate gating property of KCNQ1, whereas KCNE2 C-terminus had only minimal influences on KCNQ1. All of the results demonstrated different KCNQ1 function modulations by different regions of the two auxiliary proteins.