Lipidic affinity constants

The pharmacokinetic constants of nimodipine have been carefully determined strong protein affinity (98%), hepatic elimination (clearance 850 ml/ min), half-life elimination (60 min), hepatic metabolism, and plasma concentration at equilibrium (27 2 ng/ml). Compared with other dihydropyridines, it is important to recall its high lipid affinity and slow renal elimina-... 

The cellular uptake and release of glucose and other monosaccharides is a protein-mediated process. Such proteins are embedded into the cell membrane and can be regarded as hydrophilic pores within the hydrophobic lipid bilayer. Monosaccharide transporters are substrate specific and stereospecific their action is saturable and can be inhibited by specific competitors. Like an enzymatic reaction, the kinetic characteristics can be described by affinity constants and the number of transporter protein molecules determines maximal transport velocity (Vmax)-... 

Our results for Ca " binding and their interpretation may be compared with those of Goerke et al. [19] for stearic or oleic acid monolayers. The affinity constant for one Ca ion bound to one lipid site is deduced using a Donnan type of treatment. 

Lipophilicity is a molecular property expressing the relative affinity of solutes for an aqueous phase and an organic, water-immiscible solvent. As such, lipophilicity encodes most of the intermolecular forces that can take place between a solute and a solvent, and represents the affinity of a molecule for a lipophilic environment. This parameter is commonly measured by its distribution behavior in a biphasic system, described by the partition coefficient of the species X, P. Thermodynamically, is defined as a constant relating the activity of a solute in two immiscible phases at equilibrium [111,112]. By convention, P is given with the organic phase as numerator, so that a positive value for log P reflects a preference for the lipid phase ... 

Keller and coworkers341 proposed that tunicamyein is a reversible, tight-binding, and, therefore, competitive inhibitor of the GlcNAc 1-P transferase. The association rate-constant was 7 x 104 M s 1 (at 23°). Inhibition can be overcome by increasing the proportion of enzyme, and, because preincubation of the enzyme with UDP-GlcNAc prevented inhibition by tunicamyein,341 some experimental support for competitive inhibition was obtained. The known affinity of the antibiotic for phosphonolipids323 may facilitate its access to the membrane-bound enzyme, but the lipids do not prevent inhibition of the enzyme by tunicamyein.340... 

The additional type of motion observed for both aPLAl (71 = 0.7 x 10 cm s ) and iPLAl D = 2.3 x 10" cm s ) on top of the layer most likely results from activated enzymes with an open lid. These enzymes are able to penetrate into the lipid phase (parts c and d of Fig. 25.8). The slight differences in the diffusion constants can be attributed to the structural differences originating from the S146A mutation, which results in a different lid mobility and different binding affinities [44]. 

Lactoferrin is a glycoprotein found in mammalian milk that tightly binds two ferric ions producing an iron complex more physically and chemically stable than the uncomplexed protein. Bovine lactoferrin inhibited oxidation in com oil-in-water emulsions and lecithin liposome systems (Table 10.8). At the same molar concentration, lactoferrin was less effective than EDTA in inhibiting hydroperoxide formation in a com oil emulsion. This lower antioxidant activity of lactoferrin may be explained by its partial iron saturation and lower affinity for ferric ions. The formation constant for ferric-EDTA is 1.3 x 10 compared to 10 ° for the ferric-lactoferrin complex. Lactoferrin was a better iron chelator in the liposome than in the emulsion systems. Inhibition in liposomes with iron-lactoferrin mixtures was in the order 1 2 > 1 1 > 2 1. This order suggested that lactoferrin also chelated metal impurities as well as added iron to inhibit lipid oxidation. Lactoferrin did not inhibit the copper-catalysed... 

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