Apolar Forces Research Articles

Structures and anti-inflammatory properties of 4-halogenated -mofebutazones

The crystal structures of the 4-halogenated (hal: F, Cl, Br)-4-butyl-1-phenyl-1,3-pyrolidine-dione (mofebutazone) are determined, and compared with their solution structures. The racemic 4-halogenated mofebutazone approximants crystallize in a monoclinic space group with four molecules in the unit cell. The 4-hal-mofebutazone molecules reveal strong hydrogen bonding between the hydrogen atom located at the N-2 nitrogen atom and a carbonyl oxygen atom of an adjacent 4-hal-mofebutazone molecule. The hydrogen bond angle for 4-Br-mifebutazone N (2)H (1)⋯O (1) is 173(3) °, so that the hydrogen bond is essentially linear indicating an infinite chain hydrogen bond network. The 3d and 2d structures are stabilized by π-π and σ-π interactions, short intermolecular distances, and apolar forces between adjacently stacked phenyl rings. Small-angle-X-ray scattering (SAXS) experiments and osmometric measurements reveal the presence of dimers for the 4-hal-mofebutazone molecules. Molecular simulations indicate similar solution structure factors for the 4-hal-mofebutazones solutions, S(Q), and in the solid state. There is a strong indication that the [1,1,0], [1,0,0], and [1,0,0] periodicities of the 4-Br, 4-Cl and 4-F-mofebutazone in the crystalline solid state were also present in the solution phase. The biochemical and cellular activities of the different 4-hal-mofebutazones were monitored by the magnitude of their inhibition of the PGE2 biosynthesis through the cyclo-oxygenase (COX-1) in macrophages, and on the inhibition of LTD4 (5-lipoxygenase) in polymorphonuclear leukocytes.

The isolation of large molecular mass procyanidins from grain sorghum and their interaction with [ 14c]methyl bovine serum albumins

1. 1. Three protein-free procyanidin fractions with molecular masses of 4000, 8000 and 10,000–50,000 were isolated from a bird resistant sorghum grain. 2. 2. The interaction between the largest procyanidin and 88 or 1% methylated bovine serum albumin ( 14C labelled) is stronger with the more methylated protein over a range of 0–2.75 ionic stength at pH 5. This indicates the involvement of apolar forces throughout the range though apolar forces were more pronounced from 0.7–2.75 ionic strength. 3. 3. In the interaction between procyanidins of different molecular masses and 88% 14C-methylated bovine serum albumin the smaller procyanidins exhibited a more pronounced sigmoidal precipitation pattern than the larger with an increase in their concentrations.

Solute characterization in gas chromatography by an extension of kováts retention index system : Dispersion and selectivity indices

Kováts retention index system is extended by the introduction of new retention parameters, namely the dispersion and selectivity indices. The former is calculated from the molecular weight of an analyte and reflects the contribution to the overall retention of apolar forces, whilst the latter reveals the contribution of polar interactions, moderated by steric factors. Preliminary results are presented that indicate the potential value of the new parameters for the study of molecular structure—retention relationships, the prediction of retention data and the characterization of stationary phases.

Interactions of band 3-protein from human erythrocyte membranes with phospholipid monolayers at the air-water interface.

Lipid monolayers at the air-water interface were used as a model system to study the interactions of solubilized band 3-protein of the human erythrocyte membrane with phospholipids. The changes in monolayer surface pressure accompanying protein incorporation were used as a measure of the strength of the protein-lipid interactions. The following results were obtained: (1) Both polar and apolar forces contribute to the protein-lipid interactions, the latter being predominant. (2) The interactions strongly depend on the pH of the monolayer subphase. They are much stronger at acid than at neutral or alkaline pH. (3) The influence of pH on the band 3-phospholipid interactions is mainly due to a pH-induced conformational change of the protein, the pK value of which is near 5.0. (4) At all pH values studied, band 3 shows the highest affinity for phosphatidic acid and phosphatidylglycerol, the lowest for sphingomyelin and phosphatidylcholine.

Differences in the binding of methylated albumin to non-replicating, replicating and denatured DNA from Ehrlich ascites cells

The binding of methylated albumin to DNA, the basis of the chromatography on columns of kieselguhr coated with methylated albumin (MAK chromatography), was investigated. Scatchard plots revealed only one mode of interaction with fully double-stranded DNA. The complexes should be completely dissociated by raising the NaCl concentration of the solution to 0.8 M, indicating a binding by electrostatic attraction between the oppositely charged protein and DNA molecules. In complexes with denatured and partially single-stranded replicating DNA an additional kind of binding was found which made these complexes more stable against salt dissociation. These secondary interactions were stronger at 23°C than at 0°C and could be weakened by the addition of 6 M urea. It was therefore concluded that apolar forces were involved in these interactions.

Micromorphologic consequences following perturbation of erythrocyte membranes by trypsin, phospholipase A, lysolecithin, sodium dodecyl sulfate and saponin A correlated freeze-etching and biochemical study

1. 1. Treatment of erythrocyte membranes with phospholipase A and low levels of saponin induces alternation in the fracture plane of freeze-etch preparations in such a way, that exposed membrane faces are covered with an array of plaques made up of adherent membrane material. 2. 2. Increasing levels of saponin, lysolecithin and sodium dodecyl sulfate lower the number of membranes fracturing tangentially, presumably because the altered balance between polar and apolar forces in the membranes allows the fracture plane, normally guided by hydrophobic regions in the membrane, to follow directions other than along the membrane plane. 3. 3. Trypsin also generates new polar groups at its site of action, but does not influence the plane of fracture. 4. 4. Our data suggest that alternations of the fracture plane occur preferentially in lipid domains.