Exploitation of saturated macrocyclic polyamines has led to a discovery of numerous novel functions and new molecules such as (1) unique proton sponge properties ; (2) uptake of biological polyanions ; (3) peptide-like metal uptake properties ; (4) stabilization of unusual oxidation states of metal ions (e.g. CuIII, NiIII) ; (5) novel uptake and activation of O2 by a new NiII-macrocyclic complex ; (6) a new synthetic pathway to functionalyze polyamines ; (7) the first gold (III) complex that is a new candidate for gold-plating agents ; (8) intrinsic zinc (II) properties pertinent to zinc enzymes ; and (9) selective recognition of thymine by ZnII complexes. These newly discovered properties have created a way to a new type of supramolecular science.
Since the diversity of the immune response permits antibodies to be generated against virtually any substance, catalytic antibodies have the potential to provide catalysts for many chemical transformations. Such catalysts could be tailored by immunization with rationally designed transition state analogs, which is the main attraction of the catalytic antibody research field. However, when mice are immunized with a hapten conjugated to a carrier protein, a few, and occasionally several, of the dozens of antibodies that bind the hapten are characterized as catalytic. The diversity of the immune response can provide a panel of catalytic antibodies that possess varying degrees of catalytic activity and substrate specificity. These results have raised the following fundamental questions : how different are catalytic antibodies which were generated by immunization with a single hapten on a structural or mechanistic basis? We want to study the correlation between the antigen combining site structures and the chemical properties within a panel of catalytic antibodies elicited against a single hapten, which can potentially provide a more global understanding of the molecular mechanisms by which catalytic antibodies are generated in immune responses. We have demonstrated prodrug activation via catalytic antibodies that catalyze the hydrolysis of the nonbioactive chloramphenicol monoester derivative (1) to generate chloramphenicol (2). Immunization with a KLH conjugate of the transition state analog (3), designed on the basis of the transition state stabilization concept, yielded twelve immunoglobulin G (Ig G) proteins binding to 3, six of which were found to catalyze the hydrolysis with varying degrees of activity. This antibody system seems to be a suitable model for studies of the diversity of catalytic antibodies. Therefore, we have examined the biochemical and structural properties of these catalytic and non-catalytic antibodies, to enhance our understanding of the active site structure and function relationship assignments.
The ligand binding properties and esterase-like activity of recombinant human serum albumin (rHSA) expressed by Pichia pastoris were compared with those of plasma derived human albumin (pHSA). The binding of long fatty acid ions was detemined by the equilibrium partition method using radiolabeled palmitate. The association constants and the number of binding sites of diazepam, salicylate and warfarin were determined by specific and nonspecific binding models. The high affinity binding of bilirubin was kinetically determined from the oxidation rate of free bililubin in the binding mixture. The binding parameters of these five ligands obtained with rHSA were within the same range observed with pHSA preparations. The kinetic parameters for hydrolytic activity of rHSA toward p-nitrophenyl acetate was also similar to pHSA. These results indicate that rHSA and pHSA have the same functional property.
The binding properties to human serum albumin (HSA) and the transport of drugs through human erythrocyte membranes were examined with benzoic acid or its twenty-five derivatives (o-, m-, or p-hydroxybenzoic acid, o-, m-, or p-aminobenzoic acid, o-, m-, or p-nitrobenzoic acid, o-, m-, or p-toluic acid, o-, m-, or p-fluorobenzoic acid, o-, m-, or p-chlorobenzoic acid, o-, m-, or p-bromobenzoic acid, aspirin, salicyluric acid, α-resorcylic acid and γ-resorcylic acid) and with glycosides (arbutin, salicin, glycyrrhizin and four p-nitrophenylglycosides) or their aglycons (hydroquinone, saligenin, glycyrretinic acid and p-nitrophyenol). The drugs having hydroxyl group and amino group to o-site and those having nitro group, methyl group and halogen group to m- or p-site showed higher affinity with HSA and the plasma hindered the permeability of these drugs. The glycosides bind to each site (1, 2, and 3) of HSA more weakly than do their aglycons and they were difficult for plasma to hinder membrane permeation. The binding constants of each drug to HSA (Kb-site 1, Kb-site 2, Kb-site 3 and Kb-total) and the inhibition ratio (IR) related to the partition coefficient (P) : Kb-site 1 (M-1)=2.1479×103·√(P)-5.2824·P+2.0985×103 (R=0.9371), Kb-site 2 (M-1)=4.3741×103·√(P)-15.2068·P+6.5660×103 (R=0.6788), Kb-site 3 (M-1)=2.2176×104·logP+1.2022×104 (R=0.5227), Kb-total (M-1)=1.0214×104·√(P)-33.3721·P+1.6919×104 (R=0.7413), IR (%)=19.885·logP+17.916 (R=0.8605). IR obtained from predictive equations (IR=17.837·logP-13.286·logKb-site 1+0.175·√<Kb-site 2+0.074·√<Kb-site 3+37.355, R=0.9642, F=71.4937***, *** ; p<0.001) by multiple regression analysis was compatible with experimental IR.
Polymorphs of (R)-1-[2, 3-dihydro-1-(2'-methylphenacyl)-2-oxo-5-phenyl-1H-1, 4-benzodiazepin-3-yl]-3-(3-methylphenyl) urea (YM022) were investigated. Two crystalline forms (α-and β-forms) of YM022 were confirmed by powder X-ray diffractometry and differential scanning calorimetry. α-And β-forms were obtained by recrystallization from ethanol and ethanol : water (5 : 1), respectively. Amorphous YM022 was obtained by spray drying of YM022 methanol solution. Since both crystalline and amorphous YM022 were sparingly soluble in water, solubilization of YM022 by solid dispersion and wet grinding methods were performed. In vitro dissolution study and in vivo absorption study in dogs were carried out using spray-dried solid dispersion, heat-treated solid dispersion and mechanical mixture. Spray-dried solid dispersion, heat-treated solid dispersion and mechanced mixture. Spray-dried solid dispersion and heat-treated solid dispersion showed enhanced bioavailability, whereas mechanical mixture showed no improvement.
A number of naphthyl sulfone derivatives were synthesized and tested for cholecystokinin A (CCK-A) receptor inhibitory activity in order to study structure-activity relationships. Significant CCK-A receptor inhibitory activities were found in sulfone-carboxylic acid derivatives (7) having very hydrophobic sidechains. As the most preferred compound, (R)-4-[N-(3-methoxypropyl)-N-pentylcarbamoyl]-5-(2-naphthylsulfonyl) pentanoic acid ((R)-7c) was selected.
Monosodium 2-[(R*s, 9S*)-(4-methoxy-6, 7, 8, 9-tetrahydro-5H-cyclohepta-[b] pyridin-9-yl) sulfinyl]-1H-benzimidazole (3A), a novel antiulcer agent previously reported by us, was found to be easily decomposed in weakly acidic solutions. In order to improve the stability of the parent compound, 3A, the preparation of 1-substituted benzimidazoles (4A) was attempted. However, the inhibitory effect of 4A against gastric acid secretion was less potent than that of 3A. Then 3A was solvated by EtOH or H2O to afford 5A or 6A, respectively. On the other hand, an another diastereoisomer, (R*s, 9R*)-3B, was not solvated by EtOH or H2O under the same conditions. The thus obtained solvates (5A, 6A) are much more stable than that of 3A. The antiulcer activities of 5A and 6A were found to be similar to that of the parent compound (3A). Consequently, 6A was selected as an antiulcer agent for the development.