Hydrogen bonding continued intramolecular

Step 3. The hydrophobic environment of the membrane causes a conformational change to an a- (or 3io) helical conformation, in which intramolecular hydrogen bonding is maximized. As a result of this conformational change, a segment of the mature protein enters the membrane, provided that the basic residues continue to anchor the amino terminus on the inner surface of the membrane. In a helical conformation, the signal sequence spans the hydrophobic part of the bilayer, and the cleavage site falls on the opposite face of the membrane. 

A number of disaccharides with 1,3-, 1,4- and 1,6-linkages have been investigated in a continuing study on the use of hydroxy protons in conformational analysis of saccharides in aqueous solution by NMR. The intramolecular N-H-- 0 hydrogen bonds formed by a number of heteroconjugated systems (P-enaminones, ketohydrazones, and nitrosoenamines) were studied by X-ray, IR and NMR spectroscopic, and quantum-mechanical calculation. ... 

The spectra of intramolecularly hydrogen bonded enol systems continue to receive attention. In the case of )3-diketones and o-hydroxy-aromatic aldehydes and ketones, the width of the enolic proton peak is inversely related to the rate of intermolecular proton exchange. ... 

Indicator variables have also been used to account for other struetural features, e.g. for intramolecular hydrogen bonds, hydrogen bond donor and acceptor properties, ortho effects, cis/trans isomerism, different parent skeletons, different test models, etc. [22, 390]. Some precautions are necessary indicator variables should not describe a single compound (in this case the corresponding group contribution includes the experimental error of this one biological activity value) and the use of indicator variables should be justified from a theoretical point of view otherwise, continuous variables will be mixed with meaningless dummy variables, just to fit the data. 

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