Conformational changes in molecular

Chemical, electrochemical and/or photochemical stimuli can be used, for instance, to effect co-conformational changes in molecular devices. 

Scheme 6.5 Conformational change in molecular tweezers 6.44 upon aromatic guest binding.29...

A molecular dynamics simulation used for a conformational search can provide a quick assessment of low energy conformers suitable for further analysis. Plot the average potential energy of the molecule at each geometry. This plot may also suggest conformational changes in a molecule. 

In the case of liganded NRs, ligand binding is the first and ciucial molecular event that switches the function of these transcription factors from inactive to active state by inducing a conformational change in the LBD of the receptor (Fig. 1). This specific conformation allows the second step of NR activation that corresponds to the recruitment of coregulatoiy complexes, which contain chromatin-modifying enzymes required for transcription. The transcriptional coactivators are very diverse and have expanded to more than hundred in number. These include the pi 60 family of proteins,... 

Rotations around torsional barriers induce changes in chain conformation. For conjugated systems like polydiacetylenes, flow-induced changes in chain conformation can have a profound influence on the photon absorption and electronic conductivity properties of the material [73]. Flow-induced changes in molecular conformation form the basis for several technically important processes, the best known examples are the production of oriented fibers by gel spinning [74], the compatibility enhancement [75] and the shear-induced modification of polymer morphology [76]. 

The advent of a commercial 220 MHz NMR instrument has permitted the application of high resolution NMR to many larger molecules and the B 12-system is no exception. This technique has allowed more detailed assignments to be made thus permitting the study of more subtle chemical effects such as changes in molecular conformation. 

Typical examples are the conversion of the neutral form of an amino acid into its zwitterionic form, the helix-coil transitions in polypeptides and polynucleotides, and other conformational changes in biopolymers. Reactions of higher molecularity in which reactants and products have different dipole moments are subject to the same effect (association of the carboxylic acids to form hydrogen-bonded dimers). Equilibrium involving ions are often more sensitive to the application of an electric field ... 

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