Haydn E. Edwards

A fluorescence-probe study of the interaction of cycloheptaamylose arenes and amphiphillic molecules

Abstract The inclusion of the fluorescence probe pyrene within the void of cycloheptaamylose has been demonstrated by the nature of the fluorescence spectra of the arene, the lifetime of the fluorescence, and the rate of reaction of excited states of the arene with quencher molecules. The data suggest two equilibria processes, namely, an initial, fast inclusion of the arene, followed by a slower aggregation of the resulting cycloamylose-pyrene complexes. Addition of surfactant molecules, below the critical micelle concentration (c.m.c.), to the pyrene-cycloamylose solution leads to complexing of the three components of the system and thence to an increase in the hydrophobicity of the arene environment. Above the c.m.c., micelles of the surfactants are formed and the arene is transferred from the cycloamylose to the micelle. The fluorescence measurements establish conditions for varying the hydrophobicity of the arene environment. Preliminary kinetic data show that the rates of quenching of the excited states of the arene by such molecules as I - and CH 3 NO 2 are significantly decreased by inclusion in the dextrin. The data suggest systems that may be used to study molecular details of the reactions of excited states with quencher molecules.

The study of rous sarcoma virus-transformed baby hamster kidney cells using fluorescent probes

The fluorescent probes pyrene, pyrene butyric acid and N-phenyl 1-naphthylamine have been used to investigate the changes that accompany in vitro transformation of a baby hamster kidney cell line using Rous sarcoma virus. The fluorescent probes which reside in the membrane were used to compare the changes in microviscosity and polarity of the membranes of normal cells with two transformed cell lines. The spectrofluorimetric data indicate that following transformation the probe N-phenyl 1-naphthylamine resides in a more polar environment. However, using the probe pyrene, the yield of excimer indicates decreased mobility of this probe in the membrane of transformed cells. The data also indicate differences between the two transformed cell lines. Laser photolysis was used to study the lifetime of the pyrene probes and the quenching of the pyrene fluorescence in the membrane by several different quenching molecules. The data indicate differences between the three cell lines and suggest that transformation decreases movement within the membrane.

An evaluation of the oral administration of commercial and fractionated heparin samples in rats

The oral absorption of the anticoagulant, heparin, has been studied in rats Heparin fractions from various commercial sources and with differences in molecular weight, anticoagulant activity and the type of counterions present have been tested. The results show that none of the heparin samples were absorbed into the blood system under the experimental conditions employed. Further work by administering heparins in non-toxic acids and complexed to spermine and lysine did not produce any absorbability of the drug. The experiments also revealed inherent changes in clotting times of rat plasma related to the animals age between 8 and 16 weeks. For the activated partial thromboplastin time assay, clotting time (s) = 2.105 × age (weeks) + 7.18(P < 0.001) and for the thrombin- fibrinogen time assay, clotting time (s) = 0.483 × age (weeks) + 8.67 (P < 0.01).

An investigation of calcium ion binding to heparins

Using the line charge model of Manning and, where appropriate, a form of the empirical corrections to his limiting laws proposed by Wells, we have investigated the ion condensation phenomenon for four pure calcium heparin preparations and similar Ca-heparin/CaCl2 mixtures in aqueous solution. This has been expressed in terms of the single ion activity coefficient of the total calcium counter ion present. The results found for the single counter ion activity coefficient of pure Ca-heparin agree moderately well with the limiting law of Manning for a pure divalent counter ion polyanion salt in dilute solution. The results for Ca-heparin/CaCl2 mixtures when corrected for small ion-small ion interactions give a surprisingly good fit to the theoretical counter ion activity coefficient for a divalent counter ion/divalent cation simple electrolyte system, for values of X (X = the polyanion/co-ion ratio) up to 4, with slight deviations for values of X > 4. In the mixtures with the largest excess of polyelectrolyte, the single ion activity coefficients of the Ca2+ ion are in excess of the value predicted by Mannings theory. Ion exchange of sodium heparins to give the Ca-heparin samples used in the work did not appear to cause regular changes in the anticoagulant activity.

Some physicochemical and biological characteristics of heparin fractions prepared by gel chromatography

Abstract Heparins of defined molecular weights fractionated on gel chromatography in the presence of salt, have been assayed for their anticoagulant (B.P.) and anti-Xa activities, protamine neutralization and equivalent weight values as well as their abilities to release lipoprotein lipase. The anticoagulant activity and lipoprotein lipase releasing ability appears to decrease with molecular weight. In contrast the anti-Xa activity of the low molecular weight fraction showed an increase. No discernable trend was noted for equivalent weight and protamine neutralization values of the fractions.

Some of the biological properties of factor X-fractionated heparin

Abstract Heparin and heparin molecular fractions have been chromatographed using bovine factor X immobilised to Biogel A15. The eluted fractions were assayed chemically using azure A dye, and biologically using the activated partial thromboplastin time (APTT), and prothrombin activation inhibition (PAI) assays. On the basis of these assays, low-affinity (LA-FX) and high-affinity (HA-FX) fractions, with respect to factor X, were isolated and the anticoagulant activities (B.P., APTT and antifactor Xa) determined. Several of the heparins could be used as antithrombotic agents and showed similar characteristics to those previously reported for low-molecular-weight heparin preparations.