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Showing papers on "Chemical binding published in 1984"


Journal ArticleDOI
TL;DR: Two methods for the chemical binding of biomolecules to silicon surfaces are described and it was found that an increasing time of incubation and higher concentration resulted in a more complete coverage of the silicon wafer surfaces.

75 citations


Journal ArticleDOI
01 Jan 1984-Analyst
TL;DR: By immobilisation of the enzymes, mainly by chemical binding to Eupergit, a considerable increase in their stability could be achieved, and electrodes were obtained with a half-life of 8.5 d, a response time, τ½, of 3.5 min and linear responses over four orders of magnitude.
Abstract: In the context of the development of enzyme electrodes for the determination of the substrates of dehydrogenases, different systems for the oxidation of NADH were tested. In a homogeneous system with the dehydrogenase, NAD+ and phenazine methosulphate, the oxygen consumption caused by oxidation of the substrate was determined with a Clark electrode. Satisfactory sensitivity and reproducibility were obtained in the range 0.04–1 mM for several substrates, but the enzyme was rapidly denatured by the mediator. The physical entrapment of dehydrogenases together with a water-forming NADH oxidase on a Clark electrode yielded enzyme electrodes for different substrates with linear responses in the range 0.1–10 mM and a response time of 2 min. Owing to the instability of the NADH oxidase, the half-life of the electrodes was less than 5 h. The most promising systems were obtained by the coupling of the dehydrogenases to 3-β-naphthoyl-Nile Blue-modified graphite electrodes leading to oxygen-independent catalysed electrochemical NADH oxidation. The systems were optimised with regard to the NAD+ concentration in the solution and the pore size of the membranes covering the electrodes. By immobilisation of the enzymes, mainly by chemical binding to Eupergit, a considerable increase in their stability could be achieved, and electrodes were obtained with a half-life of 8.5 d, a response time, τ½, of 3.5 min and linear responses over four orders of magnitude.

53 citations


Patent
06 Dec 1984
TL;DR: In this article, chondroitin was used to covalently bond chondrin to proteins, polypeptides, proteins, proteinaceous hormones, and enzymes to increase their stability toward in vivo degradation.
Abstract: Peptides, polypeptides, proteins, proteinaceous hormones, and enzymes are modified by covalently bonding chondroitin thereto, whereby their stability toward in vivo degradation is increased.

51 citations


Journal ArticleDOI
TL;DR: The metabolic activation and deactivation of fusarin C, a mutagen produced by Fusarium moniliforme strain MRC 826, was studied by the Salmonella typhimurium mutagenicity assay using tester strain TA 100.

26 citations


Journal ArticleDOI
TL;DR: On peut incorporer dans des films de polystyrene chlorosulfone, formes sur les surfaces des electrodes de platine ou de carbone vitreux des couples redox, correspondant a des complexes polypyridyles de fer, de ruthenium et d'osmium, un complexe ammino de Ru and des complexes de Ni avec une porphyrine or un autre macrocycle.
Abstract: On peut incorporer dans des films de polystyrene chlorosulfone, formes sur les surfaces des electrodes de platine ou de carbone vitreux des couples redox, correspondant a des complexes polypyridyles de fer, de ruthenium et d'osmium, un complexe ammino de Ru et des complexes de Ni avec une porphyrine ou un autre macrocycle

21 citations


Journal ArticleDOI
TL;DR: In this paper, a new simple form for the atomic kinetic energy density functional (t ) is proposed as a sum of the Thomas-Fermi term and a radial correction term, namely, t [ p ] = (3/10) (3π 2 ) 2/3 p 5/3 - ( 1/40 )( r ·▽ p )/r 2, where the first term is the Thomas Fermi terms and p ( r ) is the Hartree-Fock atomic density.

17 citations


Book ChapterDOI
01 Jan 1984
TL;DR: Far-infrared spectra in the 20 – 500 cm-1region are presented for solid layers of L-alanine and several proteins for investigating the chemical binding of this strong denaturing agent to the biomolecules.
Abstract: Far-infrared spectra in the 20 – 500 cm-1region are presented for solid layers of L-alanine and several proteins. A special study is devoted to the spectroscopy of films of amino- acids, homopolypeptides and proteins which were cast from solutions of trifluoro-acetic acid for investigating the chemical binding of this strong denaturing agent to the biomolecules.

10 citations


Journal ArticleDOI
TL;DR: In this paper, a density diagram of real space and density-of-states histograms are presented that visualise and confirm the existing theories of chemical binding in titanium carbide, derived from band-structure calculations which have been performed previously by the modified augmented plane-wave method.
Abstract: Electron density diagrams in real space and density-of-states histograms are presented that visualise and confirm the existing theories of chemical binding in titanium carbide. The data are derived from band-structure calculations which have been performed previously by the modified augmented plane-wave method.

9 citations


Journal ArticleDOI
TL;DR: The effect of nuclear motion on chemical binding is described by proposing a definition of the force acting on a nucleus which remains valid when all the nuclei in the molecule are quantum mechanically described and modifications of the Berlin's binding and antibinding regions are examined.
Abstract: We have used nuclear coordinate scalings to treat the problem of forces in molecular systems in such a way that nuclei are quantum mechanically described throughout. We first examined the case in which only one of the nuclei is considered to occupy successive fixed positions. We have shown that the force acting on such a nucleus can be exactly described in terms of an electrostatic field which results from the electronic charge density and from the nuclear charge density of all other nuclei. We propose a definition of the force acting on a nucleus which remains valid when all the nuclei in the molecule are quantum mechanically described and we examined modifications of the Berlin’s binding and antibinding regions due to the effect of quantum motion of the nuclei. Thus, we describe the effect of nuclear motion on chemical binding.

8 citations


Journal ArticleDOI
TL;DR: The electron structure of the cluster NTi6N12; and the cluster Ti 6N12 is calculated by the self-consistent scattered-wave method as discussed by the authors, making allowance for the electric neutrality of the unit cell in the crystal.

4 citations


Dissertation
01 Jan 1984
TL;DR: On the other hand, in this article, the authors examined the fluoride budget of euphausiids and found that more than 99% of the total fluoride in an individual is bound in the cuticle.
Abstract: On the fluoride budget of euphausiids. Investigations on Meganyctiphanes norvegica (M. Sars) and Euphausia superba Dana various aspects of the fluoride occurrence in euphausiids were chiefly examined in maintenance experiments: Fluoride uptake, release, toxicity, accumulation, dynamics during the mault cycle and function. Krill takes up dissolved fluoride quantitatively from seawater. A potential uptake via food can be neglected as a model calculation shows. The fluoride uptake was quantified for norvegica by F- analysis of experimental water. Fluoride was released rapidly from dissected cuticle and exuviae, respectively (70% and 50% of the initial value in the course of 4 hours, resp.). In dead individuals, however, the F- release was strongly delayed (40% in the course of 4 hours). The loss of the organic portion in any case proceeded more slowly and therefore reveals no direct connection with the F- liberation. The possible chemical binding in the cuticle is discussed. A raised amount of fluoride in the experimental tanks from 5 mg/1 up caused significant mortality. Dependent on the exposure time an additional fluoride accumulation took place which more than doubled the normal F- values of the carapace. More than 99% of the total fluoride in an individual is bound in the cuticle, as a balance estimation shows. The p- content of the cuticle only changes for a short period directly before (F- decrease) and after exuviation, during the synthesis of the new shell F- increase), and otherwise remains constant. Maintenance for several weeks in fluoride-free artificial seawater did not affect survival rates of experimental animals as compared to controls. Accordingly, fluoride appears not to have a vital function for krill. It is hypothesized that the significance of fluoride for euphausiids is its functional property as a structural element of a common type of skeletal construction in marine invertebrates to which high contents of phosphate and protein are characteristic.

DOI
01 Jan 1984
TL;DR: In this article, the one-particle density, the interference density at the midpoint of the bond axis and the kinetic part of the interference energy calculated through the deorthogonalized density matrices over a wide range of intermolecular separation between the donor and the acceptor were analyzed.
Abstract: A cndo/2D study of the charge distribution obtained through Mulliken population analysis in the ground state of the title compounds shows that the features of charge distribution found by severalab initio calculations are fairly well reproduced by this method. The one-particle density, the interference density at the mid-point of the bond axis and the kinetic part of the interference energy calculated through the deorthogonalized density matrices over a wide range of intermolecular separation between the donor and the acceptor show that the one-particle density and the interference density steadily grow with decreasing internuclear separation, while the kinetic interference energy starts with negative value at large distance, then decreases and passes through a minima near but above the equilibrium distance and then increases rapidly below it conforming to the characteristic general behaviour of the kinetic component of Morse curve. The orbital pairwise interference density and the corresponding kinetic energy components reveal that the orbitals involved in the covalent binding are σ2p AO of B and 2S and σ2p AO of N and C atoms in H3B-NH3 and H3B-CO respectively.