Biomedical subjects

Lee Fielding

Publications and source records attributed to Lee Fielding.

5 recordsLinked to original sources

PubMed2005

Mutual induced fit in cyclodextrin-rocuronium complexes.

The binding of rocuronium bromide to 6-perdeoxy-6-per(4-carboxyphenyl)thio-gamma-cyclodextrin sodium salt, displays biphasic behaviour characteristic of the formation of a binary and 2 : 1 ternary guest-host complex in aqueous solution. Thermodynamic and structural data on this sequential complexation process can be rationalised within a single model involving switching of the conformational equilibria of both the rocuronium bromide and cyclodextrin molecules. Isothermal titration calorimetry (ITC), NMR and fluorescence experiments in solution, together with X-ray crystallography and molecular modelling, suggest that in order to induce encapsulation both rocuronium bromide and the modified cyclodextrin undergo conformational changes. Ring A of rocuronium bromide 'switches' from the more sterically encumbered chair to the sterically less demanding twist-boat, whilst the modified cyclodextrin "opens" its cavity to allow the steroid to enter. The recognition and mutual induced fit between cyclodextrin and steroid represents a classic example of dynamic host-guest chemistry.

Androstanols↗

PubMed2005

Determination of protein-ligand binding affinity by NMR: observations from serum albumin model systems.

The usefulness of bovine serum albumin (BSA) as a model protein for testing NMR methods for the study of protein-ligand interactions is discussed. Isothermal titration calorimetry established the binding affinity and stoichiometry of the specific binding site for L-tryptophan, D-tryptophan, naproxen, ibuprofen, salicylic acid and warfarin. The binding affinities of the same ligands determined by NMR methods are universally weaker (larger KD). This is because the NMR methods are susceptible to interference from additional non-specific binding. The L-tryptophan-BSA and naproxen-BSA systems were the best behaved model systems.

Animals↗

PubMed2003

Exploring the active site of human factor Xa protein by NMR screening of small molecule probes.

A collection of small molecules (MW < 350 Da) was screened for binding to human factor Xa using saturation transfer difference NMR spectroscopy to detect binding. The NMR screening experiments identified four hits. Binding isotherms constructed from NMR linewidth data showed that the binding affinities of the hits were all in the 30-210 microM range. Competition binding experiments showed that three of the ligands were displaced by a known microM inhibitor of factor Xa. The success of the method for identifying new ligands and the relevance of this information to the design of new factor Xa inhibitors are discussed.

Binding Sites↗

PubMed2003

NMR methods for the determination of protein-ligand dissociation constants.

This article is a review with 83 references of the application of NMR to the measurement of the dissociation constants of protein-ligand complexes. After briefly discussing some general concepts of molecular stability, the text turns to consider which NMR parameters are reporters of complex formation. The available data treatments required to translate observed NMR effects into quantitative measurements of the stability of the complex in the form of the dissociation constant (KD) are introduced. Linearisation methods and curve fitting methods are explained in detail and are illustrated with examples drawn from recent reports of protein-small molecule interactions. Throughout the text examples of the commonly observed NMR parameters , 1 / T1 and 1 / T2 are drawn from biological studies of 1H, 31P, 19F 15N (and other nuclei). The advantages of NMR diffusion experiments as a measure of KD are considered. Some less frequently used NMR approaches, some new ideas and some non-general methods are grouped together in a miscellaneous section. The major sources of errors in the determination of KD are identified. This allows recommendations for optimal experimental set up. Options for dealing with strong binding are reviewed. Finally, the implications of abstracting KD data from high throughput screening experiments are considered and several different approaches to generate this data are discussed.

Animals↗

PubMed2002

Anionic cyclophanes as potential reversal agents of muscle relaxants by chemical chelation.

A series of carboxyl-containing cyclophanes have been designed and synthesised as chemical chelators (or host molecules) of cationic muscle relaxant drugs (or guest molecules). Three of these cyclophane derivatives, 1-3, have been shown by NMR to form 1:1 complexes with the muscle relaxants pancuronium, and gallamine, in D(2)O, with association constants up to 10(4) M(-1). When tested in an in vitro chick biventer muscle preparation, the cyclophanes reversed the neuromuscular block induced by pancuronium and gallamine, with having the most effective reversal against pancuronium (EC(50) 40 microM.

Animals↗