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Results for “ligand orientation”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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3 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

The adsorption and reaction of adenine nucleotides on montmorillonite

The binding of AMP to Zn(2+)-montmorillonite is investigated in the presence of salts and Good's zwitterion buffers, PIPES and MES. The initial concentrations of nucleotide and the percent adsorbtion are used to calculate the adsorption isotherms, and the Langmuir adsorption equation is used for the analysis of data. The adsorption coefficient was found to be three times greater in the presence of 0.2 M PIPES than in its absence. In addition, basal spacings measured by X-ray diffraction were increased by the buffer. These results are interpreted in terms of a model in which the adsorption of AMP is mediated by a Zn(2+) complex of PIPES in different orientations in the interlamellar region of the montmorillonite. Mixed ligand complexes of this type are reminiscent of the complexes observed between metal ions and biological molecules in living systems.

Ferris, James P.↗
NASA NTRS1988

Molecular dynamics study of ion capture from water by a model ionophore, tetraprotonated cryptand SC24

The molecular dynamics of chloride capture from water by the tetraprotonated cryptand SC24 has been studied for the cases of 19 distances between the criptand and the chloride. The chloride capture is found to be characterized by a rapid cooperative change in the conformation of the cryptand when the Cl(-) begins to enter the ligand and just as it encounters the energy barrier. The conformational transition is associated with a shift of three N-H bonds from the pure endo orientation, such that they point toward the chloride.

Owenson, Brian↗
NASA NTRS1987

The bonding of FeN2, FeCO, and Fe2N2 - Model systems for side-on bonding of CO and N2

Qualitative calculations are performed to elucidate the nature of the side-on interaction of both N2 and CO with a single Fe atom. The systems are found to be quite similar, with bonding leading to an increase in the CO or N2 bond length and a decrease in the vibrational frequency. The CO or N2 stretching modes lead to a large dipole derivative along the metal-ligand bond axis. The populations show an almost identical, large donation from the Fe 3d orbitals into the CO or N2 Pi-asterisk. The larger system Fe2N2 is then considered, with the N2 bridging the Fe2, both parallel and perpendicular to the Fe2 bond axis for two different Fe-Fe distances. For FeN2, the shift in the observed N2 frequency is smaller than observed for the alpha state of N2/Fe(111). The shift in the N2 vibrational frequency increases when the N2 interacts with two Fe atoms, either at the Fe-Fe nearest neighbor distance or at the first layer Fe-Fe distance, when the side-on N2 axis is oriented perpendicular to an Fe-Fe bond.

Bauschlicher, Charles W., Jr.↗