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The molecular understanding of secondary transport, in particular how transport activity is regulated, is one of the cutting-edge questions in biological science. A number of secondary transporters show regulation of transport activity, which plays an important role in stress-induced cellular responses. Transport activity is regulated in response to various external stimuli, which often are difficult to identify. Therefore, only a few regulated transporters are described to date; one of the best characterized amongst them is the Na+-coupled betaine symporter from Corynebacterium glutamicum, BetPCg. The biochemical background of stimulus sensing by activity regulation of BetPCg has been elucidated in detail both in cells and proteoliposomes. First insight into a molecular mechanism of regulated transport in BetP was obtained by the combination of two-dimensional (2D) and three-dimensional (3D) crystallization, functional measurements, spectroscopy, and bioinformatics. In the last 5 years several atomic structures of trimeric BetP were solved in different conformational states and under both activating and inactivating conditions. Thereby, the transport cycle of BetP was described in molecular detail; however, the dynamics of osmoregulation is still far from being understood. One major limiting factor on the way to a molecular mechanism is restrictions imposed by the crystalline environment, which may populate or exclude some of the functional important conformations. The example of BetP demonstrates how difficult it is to trap activation and regulation of a transporter in a crystal structure. In this chapter we will critically discuss the efforts in obtaining meaningful structural and functional data and how they are combined in a dynamic description of transport and regulation of a secondary carrier. [ABSTRACT FROM AUTHOR]

Synthesis of medium-sized and macrocyclic rings by ring closing metathesis (RCM) reactions of dienes involves challenges not found in synthesis of the more common five- and six-membered rings. This review discusses factors that determine the probability and efficiency of cyclization, and experimental methods that have been used to increase selectivity for RCM products, with specific reference to the concentrations at which RCM can be achieved. These issues have important implications for the environmental and economic sustainability of large-scale synthetic processes utilizing RCM for assembly of rings larger than six members. [ABSTRACT FROM AUTHOR]

The `Click΄ chemistry was explored for low temperature snap cure and for possible use as an adhesion promoter in electronic applications. Several azide and alkyne resins were synthesized and their curing potential was evaluated with a special emphasis on exploring Cu(I) catalyst effect. The preliminary curing study in the absence of catalysts showed a strong dependence of cure temperatures on the electronic nature of alkynes. The cure temperatures showed a tendency to increase with decreasing electronegativity of the substituent on alkynes. The capability of Cu(I) catalysts to accelerate the `Click΄ chemistry was demonstrated for the first time in bulk phase. Using several Cu(I) catalysts, the cure temperatures could be lowered by as much as 40–100°C compared to the control, depending on the nature of catalyst and the catalyst loading. We discovered a novel synergistic effect between Cu(I) and silver filler in lowering the cure temperatures. Using this combination, lower cure temperatures could be obtained than using either alone. Among several resins screened, one resin system has shown promise for 80°C snap-cure in which the aforementioned synergistic effect is operative. Solution phase `Click΄ chemistry was employed for the synthesis of a hybrid triazole-epoxy resin system. This system was found to cure without added amine curative. The triazole group here serves as a linker as well as an internal adhesion promoter. To address the incompatibility and volatility issues, which arose during evaluation, a controlled oligomerization method has been developed using controlled heating of azides and alkynes in solution phase. [ABSTRACT FROM AUTHOR]

Over the past three decades the field of glycobiology has expanded beyond a basic understanding of the structure and biosynthesis of glycoprotein, proteoglycans, and glycolipids toward a more detailed picture of how these molecules afford communication through binding to mammalian lectins. Although the number of different mammalian lectin domains appears to be finite and even much smaller than early estimates predicated based on the diversity of glycan structures, nature appears capable of using these in numerous combinations to fine tune specificity. The following provides an overview of the major classes of mammalian lectins and discusses their glycan binding specificity. The review provides a snapshot of the field of glycobiology that continues to grow providing an increasing number of examples of biological processes that rely upon glycan-lectin binding. [ABSTRACT FROM AUTHOR]