Solubility structural factors

The relationship between odour quality and chemical structure is of considerable practical and theoretical interest. A numt r of methods have been used to determine quantitatively the relationships between the structure of a molecule and its odour quality (7). Though quantitative results were not obtained, a number of interesting theories were present in that the intermolecular interaction in olfaction involved electrostatic attraction, hydrophobic bonding, van der Waals forces, hydrogen bonding, and dipole-dipole interactions. Hydrophobic interactions also appeared to be a major force for substrate binding in olfaction. It had previously been shown that lipophilicity and water solubility were factors diat significandy influenced the odour thresholds of the pyrazines (8),... 

The structural factors controlling a compound s lipid solubility are the opposite of those responsible for a compound s water solubility. Consequently, lipid solubility may be improved by replacing polar groups by nonpolar structures or groups that are significantly less polar in nature. 

This review article deals with aromatic polyimides that are processable from the melt or soluble in organic solvents. Conventional aromatic polyimides represent the most important family of heat resistant polymers, but they cannot be processed in the melt, and their application in the state of soluble intermediates always involves a hazardous step of cyclodehydration and elimination of a non-volatile polar solvent. A major effort has therefore been devoted to the development of novel soluble and/or melt-processable aromatic polyimides that can be applied in the state of full imidation. The structural factors conducive to better solubility and tractability are discussed, and representative examples of monomers showing favourable structural elements have been gathered and listed with the chemical criteria. Experimental and commercial aromatic polyimides are studied and evaluated by their solubility, transition temperatures and thermal resistance. An example is also given of the methods of computational chemistry applied to the study and design of polyimides with improved processability. 

Vitamin A (2) was first described as a fat-soluble growth factor by W. Stepp in 1909, and was later investigated in more detail by US research groups. Its structure was solved by P. Karrer and was published in 1931 1). 

Banner, D. W., D Arcy, A. D., Chene, C., Winkler, F. K., Guha, A., Konigsberg, W. H., Nermerson, Y, and Kirchhofer, D. (1996). The crystal structure of the complex of blood coagulation factor Vila with soluble tissue factor. Nature 380, 41-46. 

After suggestions on an iron-sulphur protein in the 6c, complex [215], this subunit was isolated and characterised by Rieske et al. [216,218], but in a form that was not active in reconstitution. Isolation in a reconstitutively active form was pioneered by Racker et al. [219], who showed that a soluble oxidation factor was required for activity. Subsequently, Trumpower and Edwards [220] purified oxidation factor and identified it as a form of the FeS protein that is active in reconstitution. An excellent review on the structure and function of the FeS protein is available [221]. 

W.D. Gao, Y. Liu and E. Marban, Mechanism of decreased myofilament Ca2 responsiveness in stunned rat ventricular myocardium relative roles of soluble cytosolic factors versus structural alterations, Circ. Res. 78, 455 165 (1996). 

The chemical structure of a drug determines its solubility and permeability profiles. In turn, the concentration at the intestinal lumen and the permeation of the drug across the intestinal mucosa are responsible for the rate and extent of absorption.39 Unfavorable physicochemical properties have been a limiting factor in the oral absorption of peptides and peptidomimetics.40 The structural factors involved in the permeation of peptides will be described here. 

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