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Drug molecule affinity

Each of these individual conformational states represents a unique opportunity for high-affinity interactions with drug molecules. [Pg.21]

Since lipophilic molecules have affinity for both the membrane lipid and the serum proteins, membrane retention is expected to decrease, by the extent of the relative lipophilicities of the drug molecules in membrane lipid versus serum proteins, and by the relative amounts of the two competitive-binding phases [see Eqs. (7.41)-(7.43)]. Generally, the serum proteins cannot extract all of the sample molecules from the phospholipid membrane phase at equilibrium. Thus, to measure permeability under sink conditions, it is still necessary to characterize the extent of membrane retention. Generally, this has been sidestepped in the reported literature. [Pg.197]

The affinity of the designed drug molecule for its site is governed by the free energy of interaction AG. AG can be determined experimentally from the equation... [Pg.152]

The polar character of the liposomal core makes the encapsulation of polar drug molecules possible. Amphiphilic and lipophilic molecules are solubilized within the phospholipid bilayer according to their affinity toward the phospholipids. Participation of nonionic surfactants instead of phospholipids in the bilayer formation results in Niosomes . The term sphingosomes is suggested for vesicles from sphingolipids. However, the nomenclature is not consistent, and the term liposomes is used as a general term, although vesicles would be the better choice. [Pg.123]

The volume of distribution of a drug molecule is, as described previously, a theoretical number that assumes the drug is at equal concentration in the tissue and in the circulation and represents what volume (or mass) of tissue is required to give that concentration. Volume of distribution, therefore, provides a term that partially reflects tissue affinity. However, it is important to remember that affinity may vary between different tissues and a moderate volume of distribution may reflect moderate concentrations in many tissues or high concentrations in a few. For an illustration of... [Pg.52]

In order to elicit their effect, drug molecules must be bound to the cells of the effector organ. Binding commonly occurs at specific cell structures, namely, the receptors. The analysis of drug binding to receptors aims to determine the affinity of ligands, the kinetics of interaction, and the characteristics of the binding site itself. [Pg.56]

There are two components to consider in the interaction of a drug with a protein. One is the capacity of the protein for binding drug molecules and this is related to the number of binding sites (n). The other is the affinity, or strength of binding, which is usually expressed as an apparent association constant (fc). [Pg.53]

Another simplification can be made if all binding sites are independent (noncooperative binding) and they can be attributed to classes of identical sites. In protein-drug affinity studies the fraction of drug molecules bound (D4) per protein molecule (P) is given by... [Pg.49]

This chapter focuses on computational studies which employ a combination of structure-based and 3D QSAR methods as a mean to predict the affinity of a ligand for its receptor. The comprehensive utility of this approach is exemplified by case studies published in the last few years and from our laboratory. Special emphasis will be placed on a detailed description of the combined structure-ligand-based approach and the successful application of this procedure to the design of novel drug molecules. [Pg.225]

Consider a polymorphic site, S, for which there are a set of positions P P , P2, P3, Pk,.. . Pr where protein polymorphisms are possible, at each position, Pk, there is a set of possible residues R (Rx, R2, R3, Rk,... Rs if a particular residue, Rk, at position, Pk, is absent or replaced within a patient and that residue is believed to contribute significantly to the activity of the current drug molecule, then that patient will show a marked difference in affinity for the drug. In a crude... [Pg.30]

The eventual distribution of drug molecules across plasma, however, is determined not only by the specific affinities and binding constants of dmg molecules to isolated lipoprotein fractions but also to the concentration of each lipoprotein fraction in the plasma. Consequently, because the relative concentrations of plasma lipoprotein fractions increase from VLDL (=0.1 pM) < LDL (=1 pM) < HDL (=11 pM) [142, 148, 150], the plasma distribution profiles of lipophilic drugs often reflect the relative lipoprotein concentrations and not the specific binding affinities. [Pg.119]

For a large range of phospholipid concentrations, the broadening linearly depends on the lipid concentration. The slope of such plots is proportional to the affinity of the drug molecules or molecular substructures to the phospholipid. It can be taken as a measure of the degree of interaction. [Pg.106]


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See also in sourсe #XX -- [ Pg.806 ]




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