Conformational changes, energetic

A prototype of such phenomena can be seen in even the simplest carboxylic acid, acetic acid (CH3CHOOH). Acidity is determined by the energy or free energy difference between the dissociated and nondissociated forms, whose energetics usually depend significantly on their conformation, e.g., the syn/anti conformational change of the carboxyl-ate group in the compound substantially affects the acid-base equilibrium. The coupled conformation and solvent effects on acidity is treated in Ref. 20. 

Ionophores such as A-23187 and X-14885A are flexible, so despite the need for conformational change, established for A-23187 by a 1H and 13C NMR solution study (556), their complex formation reactions can take place quite quickly as they can change their conformations rapidly as required for sequential bonding to the cation, and thus proceed in a series of energetically not-too-demanding steps. Formation rate constants for the Ca2+ complexes of A-23187 and X-14885A are 6 x 105 and... 

An important hypothesis related to interface energetics is that of Nyilas, who said that the free energy of adsorption basically drives conformational change 132>. He probed this approach by measuring the enthalpy of adsorption using micro calorimetry and attempted to relate surfaces with low heats of protein adsorption with increased blood compatibility. 

When the torsion angle around the O - Cp bond is driven, the system responds differently depending on which conformational change is energetically more favourable adjacent ring flip, conformational orientation change of the carbonate group, or a combination of the two. The intermolecular... 

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