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The influence of pH and the concentration of sodium chloride on the strength and selectivity of the interaction of twelve 8-substituted-2'-deoxyadenosine and sixteen 5-substituted-2'-deoxyuridine derivatives with gamma-cyclodextrin (GCD) have been studied by the spectral mapping technique (SPM). The potency values of the spectral map were regarded as indicators of the capability of antisense nucleosides and GCD to interact simultaneously taking into consideration all relevant data. It has been established that the strength of interaction is highest in acetic and lowest in alkaline solutions, and the selectivities of acidic, alkaline and salt solutions are markedly different. The length of hydrophobic alkyl substituents in antisense molecules influenced both the strength and selectivity of the interaction. The character of the base structure affected only the selectivity., (Copyright 2003 Elsevier Science B.V.)

The activity of manganese-dependent and manganese-independent peroxidases produced by Pleurotus ostreatus in culture media composed of agro-residues was measured by visible spectrophotometry. The overall enzyme activity and its selectivity were separated by using spectral mapping technique followed by nonlinear mapping. The relationships between the parameters of enzyme production and the composition of culture media and fermentation time was assessed by stepwise regression analysis. Calculations proved that the addition of extract of straw to the culture media significantly decreased the overall production of both enzymes, whereas the selectivity of enzyme production was influenced by amount of potato extract and the concentration of total sugar in the culture media. Enzyme activity depended quadratically on the fermentation time.

Silica gel, aluminium oxide, diatomaceous earth, polyamide, cyano, diol and amino plates have been tested for their capacity to separate the color pigments of six chili powders of different origin by both adsorption and reversed-phase thin-layer chromatography. The plates were evaluated at 340 and 440 nm wavelengths. Best separation of color pigments was obtained on impregnated diatomaceous earth layer using acetone-water 17:3 v/v eluent. It was found that the pigment composition of chili powders showed marked differences. Principal component analysis employed for the classification of the chili powders according to their pigment composition indicated that these differences can be used for the determination of the similarity or dissimilarity of the chili powders.

The lipophilicity and specific hydrophobic surface area of 12 8-substituted 2'-deoxyadenosine and 17 5-substituted-2'-deoxyuridine derivatives were determined by reversed-phase thin-layer chromatography in ion-free eluents and in eluents containing sodium chloride, sodium acetate and acetic acid. The strength and selectivity of the effect of eluent additives were separated by use of spectral mapping technique followed by two-dimensional nonlinear mapping. The relationship between the structural characteristics and hydrophobicity parameters was elucidated by stepwise regression analysis. Eluent additives exert a considerable influence on both hydrophobicity parameters. The effect of sodium chloride and acetic acid was higher than that of sodium acetate. The strength and selectivity of the sensitivity of nucleosides towards eluent additives significantly depended on the character of the ring structure and on the length of the apolar alkyl chain. The influence of the degree of unsaturation and the branching of the alkyl substituent was negligible.

The lipophilicity and specific hydrophobic area of 56 surfactants having different hydrophobic moiety and different length of ethylene oxide chain were determined by reversed-phase thin-layer chromatography and the strength and selectivity of the effect of sodium chloride and pH on the hydrophobicity parameters was elucidated using spectral mapping technique followed by two-dimensional nonlinear mapping. In each instance significant linear correlations were found between the lipophilicity and specific hydrophobic surface area of surfactants suggesting that from a chromatographic point of view they behave as a homologous series of solutes. It was established that the strength of the effect of both salt concentration and pH is relatively low and the selectivity of their influence on the hydrophobicity parameters is markedly different.

The retention of 7 monotetrazolium and 9 ditetrazolium salts was determined on alumina and reversed-phase (RP) alumina layers using n-hexane-1-propanol and water-1-propanol mixtures as eluents. The retention capacity and the specific surface area of solutes in contact with the stationary phases were calculated. The relationship between retention characteristics and physicochemical parameters of solutes was elucidated by canonical correlation analysis and partial least-square regression analysis. Both methods found significant relationships between the chromatographic and physicochemical parameters, however, the results were different according to the method applied. Calculations suggested that the retention on both alumina and RP alumina layers is of mixed character, hydrophobic, electronic and steric parameters are equally involved in the retention.

The adsorption of tributylphenol ethylene oxide isomers containing various lengths of ethylene oxide chain and positional isomers of tributylphenol on a riverine sediment was studied by thin-layer chromatography combined with high-performance liquid chromatography. The adsorption capacity of the sediment was compared with that of silica, alumina and diatomaceous earth. It was established that the adsorption capacity of the riverine sediment is similar to that of silica. The adsorption of surfactants on the sediment surface is not selective. Neither the length of the ethylene oxide chain nor the position of the butyl substituents on the phenol ring influence significantly the adsorption.

The retention of 17 propargylamine derivatives was determined on a beta-cyclodextrin polymer (beta-CDP)-coated silica column using tetrahydrofuran-0.05 M K2HPO4 (6:4, v/v) as eluent. The inclusion complex formation between the propargylamine derivatives and a water-soluble beta-CDP was studied by charge-transfer chromatography carried out on reversed-phase TLC layers. The capacity factors were correlated with the various measured and calculated physicochemical parameters of the solutes using principal component analysis followed by non-linear mapping, varimax rotation and cluster analysis. Calculations proved that the hydrophobicity and steric parameters have the highest influence on the retention of propargylamine derivatives. It has been established that each statistical method can be used for the evaluation of similar retention data matrices, however, the results can be slightly different according to the method applied.

The interaction of 12 anti-hypoxia drugs with hydroxypropyl-beta-cyclodextrin (HPBCD) and the influence of LiCl, NaCl and KCl on the strength of interaction was studied by charge transfer chromatography. Most of the drugs form inclusion complexes with HPBCD and the relative strength of interaction varies markedly according to the structure of the drugs. Salts exert a considerable influence on the inclusion complex formation and the effect depends on the radii of the cation. The significant correlations between the lipophilicity of drugs and their capacity to form inclusion complexes with HPBCD indicate the involvement of hydrophobic forces in the interaction.

The lipophilicity and specific hydrophobic surface area of 22 nonionic surfactants having different hydrophobic moieties have been determined by reversed-phase thin-layer chromatography using methanol as an organic modifier. RM values decreased linearly with increasing concentration of methanol. Both the lipophilicity and specific hydrophobic surface area of the surfactants decreased with increasing numbers of ethylene oxide groups per molecule. The significant correlation between the RM0 value and the specific hydrophobic surface area indicates that these surfactants can be considered as a homologous series of solutes independently of their structural inhomogeneity. Stepwise regression analysis suggested that the hydrophobic moieties are not entirely solvated and they are in a folded state in the eluents.

The absorption capacity, the specific hydrophilic surface area, the lipophilicity and the specific hydrophobic surface area of 17 monoamine oxidase inhibitory drugs were determined by means of adsorptive and reversed-phase thin-layer chromatography for future application of these molecular parameters in quantitative structure-activity relationship studies. Principal component analysis suggests that most of the physicochemical parameters have a different information content, and their application in the elucidation of their mode of action is therefore justified.

The effect of chlorhexidine and its molecular complexes with some nonionic tenzides (Tween and Myrj series) on the phase transfer parameters of dipalmitoylphosphatidylcholine has been studied by differential scanning calorimetry. The application of principal component analysis facilitated the evaluation of the experimental data matrix. It was found that both the lipophilicity of the tenzide and the strength of interaction between chlorhexidine and nonionic tenzide had a considerable impact on some of the phase transition parameters of dipalmitoylphosphatidylcholine. These findings indicate the possible existence of ternary complexes. This ternary complex formation may cause a decrease of chlorhexidine activity in the presence of nonionic tenzides.

The adsorption capacity, the specific adsorptive surface, the lipophilicity and the specific hydrophobic surface of 59 natural and synthetic nucleoside derivatives were determined by means of adsorptive chromatography and reversed-phase thin-layer chromatography for the future application of these molecular parameters in quantitative structure-activity relationship studies. Stepwise regression analysis and principal component analysis proved that each of the physico-chemical parameters has a different information content, and their application in the design of new bioactive derivatives is therefore justified.

The effect of ion strength and pH value of the eluent on the determination of the lipophilicity of chlorhexidine was studied by reversed-phase thin-layer chromatography. The method has been improved by using various buffers: aqueous solutions of formic, acetic and propionic acids and their sodium salts in different ratios and in various concentrations. Stepwise regression analysis separated the effect of pH value, ion strength and acid type on the lipophilicity of chlorhexidine and proved that the ion strength exerted a higher impact than the pH value did. The effect of alkyl chain length of the acids was of secondary importance.

The interaction between 8 synthetic phospholipids and the nonionic tenzide nonylphenyl-nonylglycolate was studied by charge transfer chromatography. The method has been improved by carrying out the determination at different organic phase concentrations of eluent and by extrapolating the interactive strength back to pure water. It was suggested that two types of interaction of commensurable strength may exist between the tenzide and the phospholipids; hydrophil-hydrophil interactions between the polar head groups of phospholipids and the hydrophilic ethylene-oxide chain of tenzide; hydrophob-hydrophob interactions between the fatty acid chains of phospholipids and the alkyl chain of tenzide. This last effect strongly depends on the length of the fatty acid chain, but it is independent of the presence of double bonds in the lipophilic region of phospholipid.