We seek funding to continue our studies of the structural chemical basis of the """"""""high energy phosphate bond."""""""" All kinds of metabolic energy exchanges are based on the ATP-ADP bioenergetics cycle in which free energy is stored by condensation of ADP and Pi and then released as needed by hydrolysis of the terminal phosphate of ATP. We are studying a series of small, model phosphates that span the biological range of free energy of hydrolysis of """"""""phosphate group transfer potential."""""""" The series ranges from the high-energy phosphoenolpyruvate to the low-energy 3-phosphoglycerate, and includes inorganic orthophosphate and pyrophosphate as well as acyl-, guanidyl-, and sugar-phosphate species. Our principal studies are highly accurate single-crystal X-ray and neutron diffraction analyses that extend to detailed analyses of the terminal vibrations and electron density distributions in the crystals. These studies provide accurate molecular geometries, corrected for thermal vibration effects, and detailed experimental maps of the valence electron density redistributions due to chemical bonding and of the molecular electrostatic potentials. For microcrystalline compounds of interest that do not form suitable single crystal for these X-ray and neutron analyses, we propose new approaches based on a powerful combination of alternative crystallographic diffraction techniques: electron crystallography for unit cell and space group determination, state- of-the-art methods of X-ray powder diffraction for structure determination and refinement, time-of-flight neutron diffraction with powder samples and a pulsed neutron spallation source for hydrogen structure refinement, and synchrotron X-ray diffraction for very small single crystals and powder samples. Our studies will provide accurate experimental data on bond lengths, net atomic charges, and P Pi(o) to d Pi(P) partial double bond orders. Comparisons of these results for high-energy vs. low- energy and unhydrolyzed vs. hydrolyzed phosphates will clarify the roles of ionic charge delocalization and electronic resonance as determinants of the free energy changes accompanying biological phosphate hydrolyses. The very important role od hydration of the hydrolysis reactants and products will be explored by using our charge density distributions and electrostatic potentials to model structures and energetics of phosphate ion-water molecule association interactions.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM034073-08
Application #
3284522
Study Section
Molecular and Cellular Biophysics Study Section (BBCA)
Project Start
1985-08-01
Project End
1994-07-31
Budget Start
1992-08-01
Budget End
1994-07-31
Support Year
8
Fiscal Year
1992
Total Cost
Indirect Cost
Name
Hauptman-Woodward Medical Research Institute
Department
Type
DUNS #
074025479
City
Buffalo
State
NY
Country
United States
Zip Code
14203
Maniukiewicz, W; Kwiatkowski, W; Blessing, R H (1996) O-phospho-DL-threonine and O-phospho-L-threonine compared with their serine analogs. Acta Crystallogr C 52 ( Pt 7):1736-41
Souhassou, M; Schaber, P M; Blessing, R H (1996) Structure of tris(cyclohexylammonium) phosphoenolpyruvate monohydrate and crystal chemistry of phosphoenolpyruvates. Acta Crystallogr B 52 ( Pt 5):865-75
Blessing, R H (1995) An empirical correction for absorption anisotropy. Acta Crystallogr A 51 ( Pt 1):33-8
Moss, G R; Souhassou, M; Blessing, R H et al. (1995) Computational studies of crystalline H3PO4. Acta Crystallogr B 51 ( Pt 5):650-60
Souhassou, M; Espinosa, E; Lecomte, C et al. (1995) Experimental electron density in crystalline H3PO4. Acta Crystallogr B 51 ( Pt 5):661-8
Blessing, R H (1995) On the differences between X-ray and neutron thermal vibration parameters. Acta Crystallogr B 51 ( Pt 5):816-23
Guo, D Y; Blessing, R H; Hauptman, H A (1994) On integrating the techniques of direct methods with anomalous dispersion. III. Estimation of two-wavelength two-phase structure invariants. Acta Crystallogr A 50 ( Pt 3):307-11
Souhassou, M; Lecomte, C; Blessing, R H (1992) Crystal chemistry of Mg2P2O7.nH2O, n = 0, 2 and 6: magnesium-oxygen coordination and pyrophosphate ligation and conformation. Acta Crystallogr B 48 ( Pt 4):370-6
Langs, D A; Blessing, R H; Duax, W L (1992) Crystal structure of valinomycin-monohydrate cage complexes crystallized from dioxane. Int J Pept Protein Res 39:291-9
Souhassou, M; Lecomte, C; Blessing, R H et al. (1991) Electron distributions in peptides and related molecules. 1. An experimental and theoretical study of N-acetyl-L-tryptophan methylamide. Acta Crystallogr B 47 ( Pt 2):253-66

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