The Interaction of Polyvinylpyrrolidone with Aromatic Compounds in Aqueous Solution. Part II.¹ The Effect of the Interaction on the Molecular Size of the Polymer²

The interaction of polyvinylpyrrolidone with aromatic compounds in aqueous solution Part IV. Evaluation of the co-operativity parameter, and the methylene-group contribution to the binding strength, for the alkyl parahydroxybenzoates

“…This isotherm corresponds to binding onto a linear sequence of a fixed number of sites which are equivalent (i.e., all have the same intrinsic value of K) and independent (i.e., the value of K for any one site is unaffected by variations in the degree of occupation of other sites on the chain); this leads therefore to a one-dimensional ideal localised monolayer, using the systematic nomenclature for surface layers proposed by Fowler and Guggenheim (18). It is clear from figures 2 and 3 that the PVP/alkyl parabens systems do not conform to this behaviour, for the binding isotherms are in each case curved upwards, rather than downwards as must be the case with the Langmuir form [3].…”

“…We note, firstly, that one commonly encountered effect that would give deviations from the simple Langmuir form [3] is heterogeneity of the binding sites, that is, when there are different values of K for different sites or groups of sites. However, by itself this effect leads to a "flattening" in the shape of the isotherm (rather the "sharpening" observed in the present cases) since the more active sites tend to be filled firstly, i.e., at the lower cosolute concentrations, and the less active ones only later on.…”

“…There are three main types of graphical method commonly used to convert equation [3] into a linear form so that the values of K and n may be obtained. have been divided by the ordinate intercept for that cosolute; with a few already noted exceptions, the points for the four cosolutes lie close to a common straight line with ordinate intercept of 1.03 4-0.05 (compared with the expected value of unity exactly).…”

“…This demonstrates quite clearly that the four compounds conform to a closely similar pattern of binding behaviour. For simple-site binding governed by equation [3], the rearranged form of equation which i) The straight lines drawn in figure 4 and in the subsequent similar figures (figs. 5-7) containing linear plots have in each case been fitted to the plotted data using unweighted least-squares linear regression of "y" upon "x"; the broken-line bands represent the estimated limits of uncertainty (i. e. 1 standard deviation).…”

Effect of Polyvinyl Pyrrolidone on the Thermal Phase Transition of 1,2 Dipalmitoyl-sn-glycero-3-phosphocholine Bilayer

“…Dwyer et al (2), reported the use of PVP as a protective agent during the freezing and preservation of red blood cells. Molyneux et al (3,4) studied the extent of the binding affinity of PVP toward small molecules in aqueous solution. Others (5), taking advantage of certain PVP properties, e.g., water solubility, formation of complexes with anion and neutral organic molecules, presence of amide, and absence of hydrogen donor group, studied the thermodynamics of PVP in a number of different solvents, in the presence or absence of urea, hoping to understand the process of protein denaturation.…”