Nuclear magnetic resonance studies of p-fluorocinnamate-.alpha.-chymotrypsin complexes

Structure and dynamics of α-chymotrypsin-N-trifluoroacetyl-4-fluorophenylalanine complexes

“…Collection and analysis of spin-lattice relaxation data were carried out to provide further information about the structure and local dynamics of IV as it is bound to the enzyme. Regardless of system examined or model chosen for analysis of data the overall correlation time ~c for the fluoroaromatic ring in the complex of the D-isomer of IV is about 14 ns, a value in agreement with the results from ESR and fluorescence studies (Vaz and Schoellman, 1976), as well as values for 9 c found for the 4-fluorophenyl group in the acylchymotrypsin III (Gerig and Hammond, 1984) or for the4-fluorophenyl group in the 4-fluorocinnamic acid complex of chymotrypsin (Gerig, Halley and Ortiz, 1977). The correlation time (~i) used to characterize internal rotation of the aromatic ring in this complex is about 0.2 ns whether rotation is considered to be diffusive or to take place by 180 ~ ring flips.…”

Biological Magnetic Resonance

“…These types of experiments are not easily adapted to signal averaging. An alternate technique that can be used with dilute samples is the spin echo method first proposed by Allerhand and Gutowsky (1964), and this method has also been utilized to measure dissociation rates of chymotrypsin-fluorinated inhibitor complexes (Gerig and Stock, 1975;Gerig et al, 1977a).…”

“…Proton-proton NOEs have been used in studies of peptides and proteins (for examples see Gibbons et aI., 1972;Balaram et al, 1973;Campbell et al, 1974;Glickson et al, 1976) but have not found wide application in fluorinated biological systems. Computational studies of the 19F{lH} NOE indicate that this technique will provide useful structural information only when a macromolecular system has Tc < 10 ns and thus is limited to molecules of molecular weights less than about 20,000 (Gerig, 1977a). For situations involving the CF 3 group, internal rotation of the CF 3 does not appear to greatly change this limit (Gerig, 1977b).…”

Binding Interaction of Organofluorine–Serum Albumin: A Comparative Ligand-Detected 19F NMR Analysis

“…Dalvit et al, have worked on developing widely used 19 F ligand-detected screening methods, that is, fluorine chemical shift anisotropy and exchange for screening (FAXS) and Fluorine atoms for biochemical screening (FABS) for high throughput screening − besides theoretical analysis of 19 F competition-based experiments quantifying and expressing relationships between equilibrium parameters − relaxation, − molecular diffusion, , and magnetization transfer-based effects, that is, saturation transfer difference (STD), , nuclear overhauser enhancement, and so forth have been used extensively by several other groups for quantitative assessment of ligand binding in terms of determination of binding constant, understanding kinetics, and exchange dynamics. , These parameters have proven to be a quick probe of ligand–protein interactions.…”