Physicochemical parameters and indicator

Physicochemical Parameters and Indicator Variables in Position 7 of Set A (Table III)... 

Set B. The structures and in vitro antibacterial activity of 1,6,7-trisubstituted-l,4-dihydro-4-oxo-l,8-naphthyridine-3-carboxylic acids against S. aureus 209 PJC-l, E. coll NIHJ JC-2, and Ps. aeruginosa Tsuchijima are shown in Table VII.f241 Minimum inhibitory concentrations of B3A - B3C and nalidixic acid (BNA) which are unsubstituted at position 6 are included for comparison. The 18 compoimds represented by BnA, BnB, and BnC where n = 3, 15, 18, and 22 - 24 constitute a set where ethyl is constant at position 1 and the substituent at position 7 is varied consistently (A = pyrrolidinyl, B = piperazinyl, and C - N-methylpiperazinyl) for three different substituents at position 7. This set permits a comparison of both the LFER and de novo approaches. The physicochemical parameters and indicator variables of this set of compounds for the substituents at positions 1, 6 and 7 listed in Tables VIII - X. 

Set C. The antibacterial activities for a series of l,4-dihydro-4-oxo-l,8-naphthyridine-3-carboxylic acids with substituted azetidinyl (C28 - C32), pyrrolidinyl (C33 - C48), and piperidinyl (C49 - C56) rings at position 7, fluorine at position 6, and ethyl (series A), vinyl (series B) or 2-fluoroethyl (series C) at position 1 are listed in Table XI. The antibacterial activity was measured against the same microorganisms as in Set B.(25) The data for enoxacin (C2) are included for comparison. The physicochemical parameters and indicator variables of this set of compoimds for each of the substituents at positions 1 and 7 (fluorine only at position 6) are listed in Tables XII -XIII. 

A classical Hansch approach and an artificial neural networks approach were applied to a training set of 32 substituted phenylpiperazines characterized by their affinity for the 5-HTiA-R and the generic arAR [91]. The study was aimed at evaluating the structural requirements for the 5-HTiA/ai selectivity. Each chemical structure was described by six physicochemical parameters and three indicator variables. As electronic descriptors, the field and resonance constants of Swain and Lupton were used. Furthermore, the vdW volumes were employed as steric parameters. The hydrophobic effects exerted by the ortho- and meta-substituents were measured by using the Hansch 7t-ortho and n-meta constants [91]. The resulting models provided a significant correlation of electronic, steric and hydro-phobic parameters with the biological affinities. Moreover, it was inferred that the... 

The applicability of Eq. (45) to a broad range of biological (i.e., toxic, geno-toxic) structure-activity relationships has been demonstrated convincingly by Hansch and associates and many others in the years since 1964 [60-62, 80, 120-122, 160, 161, 195, 204-208, 281-285, 289, 296-298]. The success of this model led to its generalization to include additional parameters in attempts to minimize residual variance in such correlations, a wide variety of physicochemical parameters and properties, structural and topological features, molecular orbital indices, and for constant but for theoretically unaccountable features, indicator or dummy variables (1 or 0) have been employed. A widespread use of Eq. (45) has provided an important stimulus for the review and extension of established scales of substituent effects, and even for the development of new ones. It should be cautioned here, however, that the general validity or indeed the need for these latter scales has not been established. 

The chromatographic characteristics of 14 peptides have been determined on a PGC column, using acetonitrile-water mixtures as eluents.The majority of peptides showed irregular retention behavior their retention decreased with increasing concentration of acetonitrile, reached a minimum, and increased again with increasing concentration of acetonitrile. For the elucidation of the relationship between the various physicochemical parameters and retention characteristics, principal component analysis (PCA) was employed. Calculations indicated that... 

Nonspecific parameters, physicochemical parameters, and topological indices are the main parameters used in QSRR studies in TLC. The establishment of QSRR equations in TLC are reviewed according to these parameters. 

The conditions for production of TTX and STX by bacteria are unknown. The low levels of TTX and STX observed in laboratory cultures may indicate that the host environment has not been duplicated. Likely, the composition of culture medium and other physicochemical parameters for TTX and STX production have not yet been defined in vitro. Conversely, bacteria may actually produce only small amounts of TTX and STX in vivo that accumulate in host tissues over long time intervals. 

This equation suggests that the Fe content of tetrahedrite-tennantite positively correlates with that of sphalerite at constant temperature and pressure, indicating Fe and Zn contends of tetrahedrite-tennantite are useful to estimate physicochemical parameters (/sj, /02 etc.) as well as Fe content of sphalerite, although detailed study on thermochemical properties of tennantite-tetrahedrite solid solution is still needed. 

Cavaretta, G., Gianelli, G. and Puxeddu, M. (1982) Formation of authigenic minerals and their use as indicators of the physicochemical parameters of the fluid in the Larderello-Travale geothermal field. Econ. Geoi, 77, 1071-1084. 

The lipophilicity and specific surface area of a similar set of synthetic dyes was also determined on an alumina-based RP-TLC stationary phase and the linear relationship between the two hydrophobicity parameters was calculated. The result of the calculation is depicted in Fig. 3.6. The good correlation between these physicochemical parameters indicated that from the chromatographic point of view these compounds behave as a homologous series of analytes, however, their chemical structures are markedly different [87],... 

The influence of various structural and physicochemical parameters of the stationary and mobile phases on the tailing of a cationic dye in reversed-phase chromatography has been studied in detail. Measurements were performed in a C8 reversed-phase column (80 X 4.6 mm). The isocratic mobile phase was ACN-0.01 M aqueous HC1 (90 10, v/v). Analyses were carried out at 20°C and the flow rate was 1-5 ml/min. The concentration of the cationic dye, l,l -didodecyl-3,3,3, 3 -tetramethylindocarbocyanine perchlorate (Dil) in the model solutions varied between 0.9-309 pM. The dependence of the chromatographic profile of the dye on the injected concentration is illustrated in Fig. 3.112. Calculations and mathematical modelling indicated that the peak tailing of the dye can be... 

As indicated earlier (Section 3.1.1) the sorption of organic compounds onto dissolved matter can significantly increase the solubility of the compound. This can in turn affect the fate of these chemicals in the environment. We can use physicochemical parameters such as distribution coefficients (log D), aqueous acid dissociation constants (pAia), and octanol-water partition coefficients (p/to )-These attributes are also linked to the acidity and alkalinity of the environment as well as lipohilicity of the compound. The mathematical relationships between these attributes are outlined below to explore how each of these impacts the fate of PPCPs in the environment. 

There are no differences between the physicochemical parameters of the methyl and the ethyl derivatives, indicating that only steric effects produce differences in their chemical properties. 

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