Home About us Contact
|
Home About us Contact | ||
|
|
||
Coil Structure (coil + structure)
Selected AbstractsCurrent density mapping approach for design of clinical magnetic resonance imaging magnetsCONCEPTS IN MAGNETIC RESONANCE, Issue 3 2002Stuart Crozier Abstract Novel current density mapping (CDM) schemes are developed for the design of new actively shielded, clinical magnetic resonance imaging (MRI) magnets. This is an extended inverse method in which the entire potential solution space for the superconductors has been considered, rather than single current density layers. The solution provides an insight into the required superconducting coil pattern for a desired magnet configuration. This information is then used as an initial set of parameters for the magnet structure, and a previously developed hybrid numerical optimization technique is used to obtain the final geometry of the magnet. The CDM scheme is applied to the design of compact symmetric, asymmetric, and open architecture 1.0,1.5 T MRI magnet systems of novel geometry and utility. A new symmetric 1.0-T system that is just 1 m in length with a full 50-cm diameter of the active, or sensitive, volume (DSV) is detailed, as well as an asymmetric system in which a 50-cm DSV begins just 14 cm from the end of the coil structure. Finally a 1.0-T open magnet system with a full 50-cm DSV is presented. These new designs provide clinically useful homogeneous regions and have appropriately restricted stray fields but, in some of the designs, the DSV is much closer to the end of the magnet system than in conventional designs. These new designs have the potential to reduce patient claustrophobia and improve physician access to patients undergoing scans. © 2002 Wiley Periodicals, Inc. Concepts in Magnetic Resonance (Magn Reson Engineering) 15: 208,215, 2002 [source] Molecular characterization of Ciona sperm outer arm dynein reveals multiple components related to outer arm docking complex protein 2CYTOSKELETON, Issue 10 2006Akiko Hozumi Abstract Using proteomic and immunochemical techniques, we have identified the light and intermediate chains (IC) of outer arm dynein from sperm axonemes of the ascidian Cionaintestinalis. Ciona outer arm dynein contains six light chains (LC) including a leucine-rich repeat protein, Tctex1- and Tctex2-related proteins, a protein similar to Drosophila roadblock and two components related to Chlamydomonas LC8. No LC with thioredoxin domains is included in Ciona outer arm dynein. Among the five ICs in Ciona, three are orthologs of those in sea urchin dynein: two are WD-repeat proteins and the third one, unique to metazoan sperm flagella, contains both thioredoxin and nucleoside diphosphate kinase modules. The remaining two Ciona ICs have extensive coiled coil structure and show sequence similarity to outer arm dynein docking complex protein 2 (DC2) that was first identified in Chlamydomonas flagella. We recently identified a third DC2-like protein with coiled coil structure, Ci-Axp66.0 that is also associated in substoichiometric amounts with Ciona outer arm dynein. In addition, Oda5p, a component of an additional complex required for assembly of outer arm dynein in Chlamydomonas flagella, also groups with this family of DC2-like proteins. Thus, the assembly of outer arm dynein onto doublet microtubules involves multiple coiled-coil proteins related to DC2. Cell Motil. Cytoskeleton 2006. © 2006 Wiley-Liss, Inc. [source] Lipid-induced conformational transition of the amyloid core fragment A,(28,35) and its A30G and A30I mutantsFEBS JOURNAL, Issue 10 2008Sureshbabu Nagarajan The interaction of the ,-amyloid peptide (A,) with neuronal membranes could play a key role in the pathogenesis of Alzheimer's disease. Recent studies have focused on the interactions of A, oligomers to explain the neuronal toxicity accompanying Alzheimer's disease. In our study, we have investigated the role of lipid interactions with soluble A,(28,35) (wild-type) and its mutants A30G and A30I in their aggregation and conformational preferences. CD and Trp fluorescence spectroscopic studies indicated that, immediately on dissolution, these peptides adopted a random coil structure. Upon addition of negatively charged 1,2-dipalmitoyl- syn -glycero-3-phospho- rac -(glycerol) sodium salt (PG) lipid, the wild-type and A30I mutant underwent reorganization into a predominant ,-sheet structure. However, no conformational changes were observed in the A30G mutant on interaction with PG. In contrast, the presence of zwitterionic 1,2-dipalmitoyl- syn -glycero-3-phosphatidylcholine (PC) lipid had no effect on the conformation of these three peptides. These observations were also confirmed with atomic force microscopy and the thioflavin-T assay. In the presence of PG vesicles, both the wild-type and A30I mutant formed fibrillar structures within 2 days of incubation in NaCl/Pi, but not in their absence. Again, no oligomerization was observed with PC vesicles. The Trp studies also revealed that both ends of the three peptides are not buried deep in the vesicle membrane. Furthermore, fluorescence spectroscopy using the environment-sensitive probe 1,6-diphenyl-1,3,5-hexatriene showed an increase in the membrane fluidity upon exposure of the vesicles to the peptides. The latter effect may result from the lipid head group interactions with the peptides. Fluorescence resonance energy transfer experiments revealed that these peptides undergo a random coil-to-sheet conversion in solution on aging and that this process is accelerated by negatively charged lipid vesicles. These results indicate that aggregation depends on hydrophobicity and propensity to form ,-sheets of the amyloid peptide, and thus offer new insights into the mechanism of amyloid neurodegenerative disease. [source] Switching the Solubility of PMMA Bearing Attached Cyclodextrin-Moieties by Supramolecular Interactions with Ionic LiquidsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2009Sadik Amajjahe Abstract Methacrylate-modified , -cyclodextrin (, -CD) and methyl methacrylate (MMA) have been radically copolymerized to obtain hydrophobic CD copolymers. The water-insoluble copolymers are able to form highly stable inclusion complexes with anions of ionic liquids. Surprisingly, the inclusion of the anions in the CD cavity results in a significant change of thermal and solution properties. Furthermore, it can be shown that the structure of the ionic liquid anions influences the coil structure of the copolymers. The obtained results could be proven by means of microcalorimetry, differential scanning calorimetry, and dynamic light scattering. [source] Solution structure of a novel T-cell adhesion inhibitor derived from the fragment of ICAM-1 receptor: Cyclo(1,8)-Cys-Pro-Arg-Gly-Gly-Ser-Val-CysBIOPOLYMERS, Issue 8 2009Bimo A. Tejo Abstract This study is aimed at elucidating the structure of a novel T-cell adhesion inhibitor, cyclo(1,8)-CPRGGSVC using one- and two-dimensional (2D) 1H NMR and molecular dynamics (MD) simulation. The peptide is derived from the sequence of its parent peptide cIBR (cyclo(1,12)-PenPRGGSVLVTGC), which is a fragment of intercellular adhesion molecule-1 (ICAM-1). Our previous results show that the cyclo(1,8)-CPRGGSVC peptide binds to the LFA-1 I-domain and inhibits heterotypic T-cell adhesion, presumably by blocking the LFA-1/ICAM-1 interactions. The structure of the peptide was determined using NMR and MD simulation in aqueous solution. Our results indicate that the peptide adopts type-I ,-turn conformation at the Pro2-Arg3-Gly4-Gly5 (PRGG) sequence. The ,-turn structure at the PRGG motif is well conserved in cIBR peptide and ICAM-1 receptor, which suggests the importance of the PRGG motif for the biological activity of cyclo(1,8)-CPRGGSVC peptide. Meanwhile, the Gly5-Ser6-Val7-Cys8-Cys1 (GSVCC) sequence forms a "turn-like" random coil structure that does not belong to any structured motif. Therefore, cyclo(1,8)-CPRGGSVC peptide has only one structured region at the PRGG sequence, which may play an important role in the binding of the peptide to the LFA-1 I-domain. The conserved ,-turn conformation of the PRGG motif in ICAM-1, cIBR, and cyclo(1,8)-CPRGGSVC peptides can potentially be used to design peptidomimetics. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 633,641, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Studies on the conformational properties of CP-1042,55, the hinge region of CP-10, using circular dichroism and RP-HPLCCHEMICAL BIOLOGY & DRUG DESIGN, Issue 6 2000E. Lazoura Abstract: The conformational properties of CP-1042,55, a peptide corresponding to the hinge region of CP-10, were investigated using circular dichroism spectroscopy and reverse-phase high-performance liquid chromatography (RP-HPLC). The circular dichroism studies indicated that CP-1042,55 formed considerable secondary structure in the presence of hydrophobic solution environments including 50% acetonitrile, 50% trifluoroethanol and 200 mm sodium dodecyl sulfate, which comprised a mixture of ,-helix and ,-sheet. The effect of temperature on the conformation of CP-1042,55 was investigated between 5 and 40°C, with very small changes in the spectra being observed.RP-HPLC was then used to investigate the effect of temperature on the conformation of CP-1042,55 in the presence of a hydrophobic surface. Using a C18 -adsorbent, CP-1042,55 exhibited a conformational transition at 25°C, which was associated with an increase in the chromatographic contact area and the binding affinity of the peptide for the stationary phase. In addition, near-planar bandbroadening behaviour indicated that conformational species interconverted with rapid rate constants compared with the chromatographic time scale. These results indicated that the conformational change at 25°C in theRP-HPLC system most likely corresponds to the unfolding of an ,-helical and/or ,-sheet structure to an extended coil structure. Therefore, the strong chemotactic properties of this peptide may be attributed to its ability to form considerable secondary structure in the presence of a hydrophobic environment. [source] Novel Secondary Structure of Calcitonin in Solid State as Revealed by Circular Dichroism SpectroscopyCHINESE JOURNAL OF CHEMISTRY, Issue 7 2002Hai-Ning Du Abstract The solid-state circular dichroic study reveals that salmon calcitonin presents a typical ,-helical structure while human calcitonin appears to form a ,-sheet in solid state, although both of them adopt random coil structures in aqueous solution. [source] | |||||||||||||