Hydrophobicity coefficient

Zf Method This method developed by Rekker and Mannhold [36] uses fragmental hydrophobicity coefficients and correction factors obtained via a reductionist approach, deriving the constants for each fragment from Free-Wilson type... 

Wilce, M.C J., Aguilar, M.-L, and Heam, T.W. 1995. Physicochemical basis of amino acid hydrophobicity scales Evaluation of four new scales of amino acid hydrophobicity coefficients derived from RP-HPLC of peptides. Anal. Chem. 67 1210-1219. 

Liu, J. and C. Qian (1995). Hydrophobic coefficients of s-triazine and phenylurea herbicides. Chemosphere, 31 3951-3959. 

Adsorbent Surface area (mVg) Hydrophobicity coefficient" Phenol uptake (mg/g)... 

The activity of the native and modified SC was also studied for the reaction methanolysis of APEE, using the substrate, methanol, itself as a solvent. This was done for three different salt-enzyme preparations, consisting of 99% salt, 50% salt, and no added salt (except that present in buffer). It was found that the PEG modification resulted in a six- to sevenfold increase in the initial rates of conversion for the cases with no surfactant and with T 20 (Table 2). AOT was found to reduce the activity of the enzyme preparations in all experiments conducted in the solvent methanol. Previous reports on enzymatic conversion in organic solvents have shown the effect of the solvent dielectric constant on enzyme activity for salt-free enzymes [22], Relationship between activity of AOT and PEG-modified SC to the hydrophobicity coefficient of various solvents has also been studied [20], however, only for the enzymes without salt-lyophilization. The decrease in activity of enzymes in organic solvents is attributed to the decreased water availability in organic media. Additionally, as the dielectric constant increases, the potential for removal of the... 

The relationship between peptide retention behaviour and hydrophobicity coefficients... 

Various amino acid hydrophobicity coefficient scales derived from both chromatographic and octanol-water partition studies are listed in Table 3. Comparison of the experimentally observed retention times with those predicted from the summated hydrophobicity coefficients suggests that these approaches can in some special circumstances provide a reasonably accurate estimation of the elution profile... 

The most widely used descriptor for the hydrophobicity term in toxicology is the distribution coefficient between octanol and water, log Pq< - (the environmental scientists would rather call it log The bulk solvent octanol is of course a... 

Salt Effects. The definition of a capacity factor k in hydrophobic interaction chromatography is analogous to the distribution coefficient, in gel permeation chromatography ... 

S. W. Karickhoff and D. S. Brown, determination of Octanol Water Distribution Coefficients, Water Solubilities, and Sediment/Water Partitions Coefficientsfor Hydrophobic Organic Pollutants, EPA-600/4-79-032, report, EPA, Washington, D.C., 1979. 

Note that the relative spatial arrangement of the phenyl, amine, and hydroxyl functionahties are identical for (R)-alprenolol and (5)-sotalol. In addition to P-blocking activities, some of these compounds also possess potent local anaesthetic activity (see Anesthetics). The membrane stabilizing activity, however, is not stereoselective and correlates directly with the partition coefficient (hydrophobicity) of the compound. 

In subsequent studies attempting to find a correlation of physicochemical properties and antimicrobial activity, other parameters have been employed, such as Hammett O values, electronic distribution calculated by molecular orbital methods, spectral characteristics, and hydrophobicity constants. No new insight on the role of physiochemical properties of the sulfonamides has resulted. Acid dissociation appears to play a predominant role, since it affects aqueous solubiUty, partition coefficient and transport across membranes, protein binding, tubular secretion, and reabsorption in the kidneys. An exhaustive discussion of these studies has been provided (10). 

For many modeling purposes, Nhas been assumed to be 1 (42), resulting in a simplified equation, S = C, where is the linear distribution coefficient. This assumption usually works for hydrophobic polycycHc aromatic compounds sorbed on sediments, if the equdibrium solution concentration is <10 M (43). For many pesticides, the error introduced by the assumption of linearity depends on the deviation from linearity. 

The partition coefficient P, defined as the equilibrium concentration of the compound in n-octanol divided by that in the aqueous phase, has been measured for pyrazole and indazole (B-79MI40416). It was found that log F = 0.13-0.26 for pyrazole and 1.82 for indazole, clearly showing the greater hydrophobicity (lipophilicity) of the indazole ring, due to the benzenoid moiety. 

Strkcttire inflkence. The specificity of interphase transfer in the micellar-extraction systems is the independent and cooperative influence of the substrate molecular structure - the first-order molecular connectivity indexes) and hydrophobicity (log P - the distribution coefficient value in the water-octanole system) on its distribution between the water and the surfactant-rich phases. The possibility of substrates distribution and their D-values prediction in the cloud point extraction systems using regressions, which consider the log P and values was shown. Here the specificity of the micellar extraction is determined by the appearance of the host-guest phenomenon at molecular level and the high level of stmctural organization of the micellar phase itself. 

On the basis of data obtained the possibility of substrates distribution and their D-values prediction using the regressions which consider the hydrophobicity and stmcture of amines was investigated. The hydrophobicity of amines was estimated by the distribution coefficient value in the water-octanole system (Ig P). The molecular structure of aromatic amines was characterized by the first-order molecular connectivity indexes ( x)- H was shown the independent and cooperative influence of the Ig P and parameters of amines on their distribution. Evidently, this fact demonstrates the host-guest phenomenon which is inherent to the organized media. The obtained in the research data were used for optimization of the conditions of micellar-extraction preconcentrating of metal ions with amines into the NS-rich phase with the following determination by atomic-absorption method. 

The comparison of predicting capabilities of two kinds of hydrophobicity evaluations is of interest. For these purpose partition coefficients P and P for a number of benzodiazepines gidazepam (I), medazepam (II), nitrazepam (III), oxazepam (IV), lorazepam (V) and diazepam (VI) were determined. 

The lipophilicity (7 m value) and specific hydrophobic surface area of pyrido[l,2-a]pyrazinium-l-olates 342 and -3-olate 343, and l-(4-chlorophe-nyl)-l-hydroxy-l,2-dihydropyrazino[2,l-a]isoquinolinium salt (344) has been measured by reversed-phase thin-layer chromatography (98MI13). Partition coefficient (log/ ) of 9-bromo-5-[(A-phenylaminocarbonyl)-methyl]-l,2,3,5,6,7-hexahydropyrido[l,2,3- fc]quinoxaline-2,3-dione was calculated to be 2.78 (97JMC4053). 

The pFL-dependent partitioning of the ionizable, cationic dye thymol blue has also been investigated [6]. In its neutral, zwitterionic, and monoanionic forms, the dye preferentially partitions into the IL phase (from acidic solution), the partition coefficient to the IL increasing with increasing IL hydrophobicity. Under basic conditions, the dye is in the dianionic form and partitions into water (Figure 3.3-9). 

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