Chemical binding

About: Chemical binding is a research topic. Over the lifetime, 1822 publications have been published within this topic receiving 52516 citations.

Cytochrome c-induced increase of motionally restricted lipid in reconstituted cytochrome c oxidase membranes, revealed by spin-label ESR spectroscopy.

Abstract: Cytochrome c oxidase isolated from beef heart mitochondria was reconstituted in bilayer membranes of the anionic lipid dimyristoylphosphatidylglycerol (DMPG) with varying enzyme/DMPG ratio. Lipid-protein interactions in the reconstituted membrane complexes were studied in the presence and absence of saturating amounts of bound cytochrome c, by both chemical binding assays and spin- label ESR spectroscopy. The ESR spectra from a phosphatidylglycerol probe spin-labeled on C-14 of the sn-2 chain revealed two distinct lipid populations differing in their rotational mobility. The stoichiometry of lipids that were restricted in their rotational motion by direct interaction with the integral protein was 50-60 lipids/cytochrome c oxidase monomer, in the absence of cytochrome c, independent of the total lipid/protein ratio. Cytochrome c alone did not induce a motionally restricted population in the lipid ESR spectra, when bound to bilayers of negatively charged DMPG alone, in the fluid phase (at 36 °C). However, the motionally restricted lipid population associated with reconstituted cytochrome c oxidase/ DMPG membranes increased on binding cytochromec, indicating structural/dynamic changes taking place in the membrane. Depending on the DMPG/cytochrome c oxidase ratio, apparent stoichiometries of up to 115 motionally restricted lipid molecules/cytochrome c oxidase monomer were found, when saturating amounts of cytochrome c were bound. Under these conditions, cytochrome c binds to 9 negatively charged DMPG molecules, independent of the cytochrome c oxidase content in the reconstituted system. A likely explanation for these results is that the surface binding of cytochrome c propagates the motional restriction of the lipid chains beyond the first boundary shell of cytochrome c oxidase, possibly creating microscopic in-plane domains.

Nondestructive Speciation Depth Profiling of Complex TiOx Nanolayer Structures by Grazing Incidence X-ray Fluorescence Analysis and Near Edge X-ray Absorption Fine Structure Spectroscopy.

Abstract: An important challenge of modern material science is the depth-sensitive and nondestructive analysis of the chemical binding state of complex structures consisting of multiple thin layers. In general, the correlation of the material functionality and underlying chemical and physical properties is the key question in view of directed device development, performance, and quality control. It has been shown that the combined method grazing incidence X-ray fluorescence analysis (GIXRF) and near edge X-ray absorption fine structure spectroscopy (NEXAFS) can significantly contribute to the nondestructive chemical analysis of buried thin films and interface structures regarding chemical speciation. Recently, we have enhanced the method to allow for a depth-resolved analysis of multilayered nanoscaled thin film structures. By means of appropriate model systems, the methodology has been developed and successfully validated. The model systems basically consist of a carbon cap layer, two titanium layers differing in ...

Preparation of novel fibre–silica–Ag composites: the influence of fibre structure on sorption capacity and antimicrobial activity

Abstract: Novel fibre–silica–Ag composites with biocidal activity were successfully produced by chemical modifying cotton (CO), wool (WO), silk (SE), polyamide (PA) and polyester (PES) fabrics and CO/PES and WO/PES fabric blends A silica–Ag coating was prepared using a two-step procedure that included the creation of a silica matrix on the fibre surface via the application of an inorganic–organic hybrid sol–gel precursor [reactive binder (RB)] using a pad-dry-cure method, followed by the in situ synthesis of AgCl particles within the RB-treated fibres from solutions of 010 mM and 050 mM AgNO3 and NaCl The presence of the coating on the fibres was verified by scanning electron microscopy and energy-dispersive X-ray spectroscopy The bulk concentration of Ag in the coated fibres was determined using inductively coupled plasma mass spectroscopy The antimicrobial activity was determined for the bacteria Escherichia coli and Staphylococcus aureus and the fungus Aspergillus niger The results show that the chemical and morphological structures of the fibres directly influenced their absorptivity and affinity for the Ag compound particles As the amorphous molecular structure of the fibres and the amount of functional groups available as binding sites for Ag+ were increased, both the silver solution uptake and the concentration of the absorbed Ag compound particles increased The chemical binding of Ag to the fibres significantly reduced the effectiveness of the antimicrobial activity of the Ag compound particles Accordingly, an increase in the concentration of absorbed Ag was required to achieve a biocidal effect