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Molecular Movements (molecular + movement)
Selected AbstractsRoom-Temperature Self-Organizing Characteristics of Soluble Acene Field-Effect Transistors,ADVANCED FUNCTIONAL MATERIALS, Issue 4 2008Wi Hyoung Lee We report on the room-temperature self-organizing characteristics of thin films of the organic small-molecule semiconductor triethylsilylethynyl-anthradithiophene (TES-ADT) and its effect on the electrical properties of TES-ADT-based field-effect transistors (FETs). The morphology of TES-ADT films changed dramatically with time, and the field-effect mobility of FETs based on these films increased about 100-fold after seven days as a result of the change in molecular orientation from a tilted structure in the as-prepared film to a well-oriented structure in the final film. We found that the molecular movement is large enough to induce a conformational change to an energetically stable state in spin-coated TES-ADT films, because TES-ADT has a low glass-transition temperature (around room temperature). Our findings demonstrate that organic small-molecule semiconductors that exhibit a low crystallinity immediately after spin-coating can be changed into highly crystalline structures by spontaneous self-organization of the molecules at room temperature, which results in improved electrical properties of FETs based on these semiconductors. [source] Hydrogen-deuterium exchange in membrane proteins monitored by IR spectroscopy: A new tool to resolve protein structure and dynamicsBIOPOLYMERS, Issue 1-2 2004C. Vigano Abstract As more and more high-resolution structures of proteins become available, the new challenge is the understanding of these small conformational changes that are responsible for protein activity. Specialized difference Fourier transform infrared (FTIR) techniques allow the recording of side-chain modifications or minute secondary structure changes. Yet, large domain movements remain usually unnoticed. FTIR spectroscopy provides a unique opportunity to record 1H/2H exchange kinetics at the level of the amide proton. This approach is extremely sensitive to tertiary structure changes and yields quantitative data on domain/domain interactions. An experimental setup designed for attenuated total reflection and a specific approach for the analysis of the results is described. The study of one membrane protein, the gastric H+,K+ -ATPase, demonstrates the usefulness of 1H/2H exchange kinetics for the understanding of the molecular movement related to the catalytic activity. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004 [source] The translocation of signaling molecules in dark adapting mammalian rod photoreceptor cells is dependent on the cytoskeletonCYTOSKELETON, Issue 10 2008Boris Reidel Abstract In vertebrate rod photoreceptor cells, arrestin and the visual G-protein transducin move between the inner segment and outer segment in response to changes in light. This stimulus dependent translocation of signalling molecules is assumed to participate in long term light adaptation of photoreceptors. So far the cellular basis for the transport mechanisms underlying these intracellular movements remains largely elusive. Here we investigated the dependency of these movements on actin filaments and the microtubule cytoskeleton of photoreceptor cells. Co-cultures of mouse retina and retinal pigment epithelium were incubated with drugs stabilizing and destabilizing the cytoskeleton. The actin and microtubule cytoskeleton and the light dependent distribution of signaling molecules were subsequently analyzed by light and electron microscopy. The application of cytoskeletal drugs differentially affected the cytoskeleton in photoreceptor compartments. During dark adaptation the depolymerization of microtubules as well as actin filaments disrupted the translocation of arrestin and transducin in rod photoreceptor cells. During light adaptation only the delivery of arrestin within the outer segment was impaired after destabilization of microtubules. Movements of transducin and arrestin required intact cytoskeletal elements in dark adapting cells. However, diffusion might be sufficient for the fast molecular movements observed as cells adapt to light. These findings indicate that different molecular translocation mechanisms are responsible for the dark and light associated translocations of arrestin and transducin in rod photoreceptor cells. Cell Motil. Cytoskeleton 65: 785,800, 2008. © 2008 Wiley-Liss, Inc. [source] Space-demanding intramolecular isomerizations in the solid stateJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 3 2002G. Kaupp Abstract The thermal isomerizations of meso - and rac -3,4-dibromo-1,6-diphenyl-1,6-bis(p -tolyl)-1,2,4,5-hexatetraene (1) to give stereospecifically the 3,4-bis(phenyl- p -tolylmethylene)-1,2-dibromocyclobutenes 3 and 5,+,6 were studied in the solid state using atomic force microscopy (AFM) and interpreted on the basis of known crystal structural data. These isomerizations run to completion in the bulk and include highly space-demanding internal rotations around the central bond. Far-reaching anisotropic molecular movements are detected on the major faces that align the surface features along cleavage planes in the initial phase rebuilding stage. Only one of three identified cleavage planes of meso - 1 is successful, owing to closer interactions of the bromine substituents in the non-used cleavage planes. Thus, very fine details can be correlated and predicted for the occurrence of internal rotations and molecular movements in the crystal lattice. The second stage in these intramolecular isomerizations, the phase transformation, produces very high features up to 100,nm and still parallel to the preferred cleavage plane of meso - 1 but in the,µm range without relation to the initial crystal structure in the case of rac - 1. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||