Intramolecular bond parameters determination

Direct methods. The charge per molecule is measured either directly (e.g., very accurate structural determination, x-ray photoelectron spectroscopy) or through the relative change of an intramolecular parameter sensitive to the charge (e.g., intramolecular bond length, intramolecular vibration frequency). The accuracy is relatively poor ( 10%). 

Elevated pressures can induce functional and structural alterations of proteins. The effects of pressure are governed by Le Chatelier s principle. According to this principle, an increase in pressure favours processes which reduce the overall volume of the system, and conversely increases in pressure inhibit processes which increase the volume. The effects of pressure on proteins depend on the relative contribution of the intramolecular forces which determine their stability and functions. Ionic interactions and hydrophobic interactions are disrupted by pressure. On the other hand, stacking interactions between aromatic rings and charge-transfer interactions are reinforced by pressure. Hydrogen bonds are almost insensitive to pressure. Thus, pressure acts on the secondary, tertiary, and quaternary structure of proteins. The extent and the reversibility, or irreversibility, of pressure effects depend on the pressure range, the rate of compression, and the duration of exposure to increased pressures. These effects are also influenced by other environmental parameters, such as the temperature, the pH, the solvent, and the composition of the medium. 

The heavy-atom parameters obtd agree with those from X-ray determinations except for slight position shifts of a few atoms. The study also concludes that all hydrogen atoms are located close to nearby oxygen atoms, a few of which form intramolecular or intermolecular hydrogen bonds of the type C—H.. . O. An R value of 0.059 was found]... 

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