Chemical binding

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

Bandstruktur des Festkörpers – Interpretation der chemischen Bindung in einigen Übergangsmetallverbindungen aufgrund von Bandstrukturrechnungen

Abstract: Die chemischen Bindungsverhaltnisse einiger in der NaCl-Struktur kristallisierenden Ubergangsmetallverbindungen (ScN. ScO, TiC, TiN, TiO, VC, VN, VO) werden auf Grund von Bandstrukturrechnungen diskutiert. Grundlage der Betrachtungen bilden die nach der quasi-selbstkonsistenten APW-Methode berechneten Wellenfunktionen und Energieeigenwerte sowie die nach dem LCAO-TB-Inter-polationsverfahren von Slater und Koster ermittelten Energieeigenwerte und Eigenvektoren. Die partiellen LCAO-TB l-Zustandsdichten erlauben eine Analyse der Valenzbander, aus der hervorgeht, das das energetisch tiefstliegende Valenzband nahezu ausschlieslich s-Charakter besitzt. In den folgenden Bandern, die sich im wesentlichen von den Nichtmetall 2p-Atomzustanden herleiten, besitzt die LCAO-TB-Zustandsdichte neben einem hohen Anteil an partieller p-Zustandsdichte auch einen deutlichen Beitrag an partieller d-Zustandsdichte, der sich vom Karbid zum Oxid verringert. In der LCAO-TB-Zustandsdichte der funf Bander, die sich von den Metall-3d-Atomzustanden herleiten, findet man neben einem uberwiegenden Anteil an partieller d-Zustandsdichte auch einen kleineren Beitrag an partieller p-Zustandsdichte. Die partielle d-Zustandsdichte wird in den eg- und t2g-Anteil zerlegt und deren Verhalten diskutiert. Eine Analyse der APW-Kristallwellenfunktionen gibt Aufschlus uber die l-artigen Ladungen in den Atomspharen. Auf Grund eines Vergleichs der APW-Gesamtladungen in den Atmospharen mit den Ladungen, die sich durch die Uberlagerung der Ladungsdichten eines hypothetischen Kristalls neutraler Atome ergeben, wird auf eine Uberfuhrung von Elektronen geschlossen, die in allen Verbindungen aus der Metallatomsphare in die Nichtmetallatomsphare erfolgt. The nature of chemical binding for some transition metal compounds (ScN, ScO, TiC, TiN, TiO, VC, VN, VO) with NaCl structure is discussed in terms of energy band structure calculations. The discussion is based on the wave functions and energy eigenvalues, as calculated by the “Quasi self consistent APW method” as well as on the energy eigen values and eigen vectors resulting from the Slater-Koster LCAO-Tight binding interpolation scheme. The LCAO-TB l-like partial density of states can be used to analyse the valence bands. This analysis shows, that the deepest valence band has predominantly s-character. The following bands, which can be derived in essence from the atomic 2p states of the non metal are characterized not only by the partial p-like density of states but also by a substantial contribution from the d-like partial density of states, which is decreasing going from a particular Carbide to the corresponding Oxide. For the valence bands, which can be associated with the atomic 3d states of the metal, the density of states exhibits besides the partial d-density of states small contributions from the partial p-like density of states. The decomposition of the d-like partial density of states into an eg-like and a t2g-like contribution is discussed. By analyzing the APW crystal wave functions the partial l-like charges inside each atomic sphere can be obtained. If the APW total charges within the atomic spheres are compared with the charges of a hypothetical crystal, which correspond to a superposition of the charge densities of the neutral atoms, a transfer of electrons from the metal to the non-metal sphere is found for all compounds under investigation.

Immobilization of liposomes onto quartz crystal microbalance to detect interaction between liposomes and proteins.

Abstract: To study the interaction between liposomes and proteins, intact liposomes were immobilized on a metal planar support by chemical binding and/or bioaffinity using a quartz crystal microbalance (QCM) A large decrease in the resonance frequency of quartz crystal was observed when the QCM, modified by a self-assembled monolayer (SAM) of carboxythiol, was added to liposome solutions The stable chemical immobilization of intact liposomes onto SAM was judged according to the degree with which adsorbed mass depended on the prepared size of liposomes, as well as on the activation time of SAMs when amino-coupling was introduced, where the liposome coverage of electrodes was 69 ± 8 % in optimal conditions When avidin–biotin binding was used on amino-coupling liposome layers, liposome immobilization finally reached 168% coverage of the electrode surface Denatured protein was also successfully detected according to the change in the frequency of the liposome-immobilized QCM The adsorbed mass of denatured carbonic anhydrase from bovine onto immobilized liposomes showed a characteristic peak at a concentration of guanidine hydrochloride that corresponded to a molten globule-like state of the protein, although the mass adsorbed onto deactivated SAM increased monotonously

The theory of electron scattering from molecules. i. theoretical development

Abstract: The quantum theory of electron scattering from molecules in the gas phase was developed Expressions that include the effects of chemical binding are presented and the intensity averages to be expected for various types of experiments are discussed in terms of the theory The quantum mechanical average over the rotational states of the molecule is shown to be reducible to the classical method of averaging rotational motion except in the case of extremely high energy resolution of the scattered electrons (auth)

First evidence of octacalcium phosphate@osteocalcin nanocomplex as skeletal bone component directing collagen triple-helix nanofibril mineralization.

Abstract: Tibia trabeculae and vertebrae of rats as well as human femur were investigated by high-resolution TEM at the atomic scale in order to reveal snapshots of the morphogenetic processes of local bone ultrastructure formation By taking into account reflections of hydroxyapatite for Fourier filtering the appearance of individual alpha–chains within the triple–helix clearly shows that bone bears the feature of an intergrowth composite structure extending from the atomic to the nanoscale, thus representing a molecular composite of collagen and apatite Careful Fourier analysis reveals that the non–collagenous protein osteocalcin is present directly combined with octacalcium phosphate Besides single spherical specimen of about 2 nm in diameter, osteocalcin is spread between and over collagen fibrils and is often observed as pearl necklace strings In high-resolution TEM, the three binding sites of the γ-carboxylated glutamic acid groups of the mineralized osteocalcin were successfully imaged, which provide the chemical binding to octacalcium phosphate Osteocalcin is attached to the collagen structure and interacts with the Ca–sites on the (100) dominated hydroxyapatite platelets with Ca-Ca distances of about 95 A Thus, osteocalcin takes on the functions of Ca–ion transport and suppression of hydroxyapatite expansion