Macro molecular parameters

The role of morphology in inhomogeneous networks is also not very clear. Is the mechanical behavior under the influence of molecular/macro-molecular parameters or is it controlled by stress concentration effects at the boundaries of dispersed domains ... 

Crystallographic refinement is a procedure which iteratively improves the agreement between structure factors derived from X-ray intensities and those derived from a model structure. For macro molecular refinement, the limited diffraction data have to be complemented by additional information in order to improve the parameter-to-observation ratio. This additional information consists of restraints on bond lengths, bond angles, aromatic planes, chiralities, and temperature factors. 

The possibility to carry out conformational studies of peptides at low concentrations and in the presence of complex biological systems represents a major advantage of fluorescence spectroscopy over other techniques. Fluorescence quantum yield or lifetime determinations, anisotropy measurements and singlet-singlet resonance energy transfer experiments can be used to study the interaction of peptides with lipid micelles, membranes, proteins, or receptors. These fluorescence techniques can be used to determine binding parameters and to elucidate conformational aspects of the interaction of the peptide with a particular macro-molecular system. The limited scope of this chapter does not permit a comprehensive review of the numerous studies of this kind that have been carried and only a few general aspects are briefly discussed here. Fluorescence studies of peptide interactions with macromolecular systems published prior to 1984 have been reviewed. 

Wales, J. L. S. Draft report. Working Party The relationship of performance characteristics to basic parameters of polymers, IUPAC Division of Macro-molecular Science. 

Non-ionic polymers are less dependent on parameters such as pH levels and electrolyte concentration of the surrounding fluids. The main mechanism of mucoadhesion seems to be just physical by interpenetration and subsequent chain entanglement. Some of the polymers such as polyethylene oxide can additionally form hydrogen bonds, but still play only a minor role in macro-molecular drug delivery due to less pronounced mucoadhesive properties than the above-described charged polymers. 

Finally, it should be remarked that proteins and enzymes, being macro-molecular, may not necessarily represent identical structures instead they may be composed of a range of closely related but slightly different molecules. In such a case we might expect to find that they would have to be characterized by additional parameters and that their sorption isotherms... 

These observations suggest two independent effects of macro-molecular chain branching on X and/or on F (X). The first, inherent in Eq. (2.6), represents a decrease in the effective intermolecular hydro-dynamic interaction parameter X resulting from the shrinkage of the... 

It was noted also that satisfactory compatibilization could be achieved by local miscibility (given by solubility parameters) rather than direct matching of the chemical and macro-molecular composition. This may require the copolymer to have several components, such as poly(styrene-co-ethylene)-b-poly(butene-co-styrene) (SEES), which has been found useful in compatibilization of HDPE and PET (Bonner and Hope, 1993). 

The reactions and properties of macromolecules are determined by chemical structure and molecular size. Consequently, it is convenient to use these parameters instead of, for example, mechanisms to classify macro-molecular reactions. Distinction is made among catalyses, isomerizations, polymer analog conversions, chain extension, and degradation reactions according to whether the chemical structure, the molar mass and/or the degree of polymerization are retained or changed. 

The effect of the heating rate and the degree of transformation on such kineti c parameters as the activation energy and reaction order in the thermal degradation of phenyl- or pyridyl-carbamoylmethyl cellulose, indicated that the degradation reaction was very complex. Amidation of carboxymethyl-cellulose decreased the heat resistance and favoured the breaking of macro-molecular chains so that the supramolecular structure affected the heat stability of the derivative and the mechanism of thermal degradation. 

Steric Parameters - The steric parameter, E, of Taft has been employed by Kutter and Hansch in the correlation of the molecular structure of some phenoxyethylcyclopropylamine monoamine oxidase inhibitors and diphenhydramine antihistamines with their activity. For the types of biological activity investigated it was found that the Taft Eg was more important in the correlation than was either the electronic parameter of Hammett, a, or the hydrophobic parameter of Hansch. Their results led Kutter and Hansch to conclude that the binding of substituent groups of moderate size into a macro-molecular pouch may well be, at least over a limited range, a continuous linear process. This would negate the all-or-none situation which sometimes arises from the "lock and key" theory of enzyme-substrate interaction. ... 

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