Parameters physicochemical

Reactions can be considered as composite systems containing reactant and product molecules, as well as reaction sites. The similarity of chemical structures is defined by generalized reaction types and by gross structural features. The similarity of reactions can be defined by physicochemical parameters of the atoms and bonds at the reaction site. These definitions provide criteria for searching reaction databases [23],... 

PETRA (calculation of physicochemical parameters) Molecular Networks GmbH, Nagelsbachstrasse 25, D-91052 Erlangen, Germany http //www.mol-net.de/ VolSurf Molecular Discovery Ltd., West Way House, Elms Parade, Oxford 0X2 9LL, UK http //www.moldiscovery.com/... 

K and G M Crippen 1986. Atomic Physicochemical Parameters for Three-dimensional Struc-directed Quantitative Structure-Activity Relationships. I. Partition Coefficients as a Measure ydrophobicity. Journal of Computational Chemistry 7 565-577. 

Because protein samples are actually ampholytes, when samples are loaded onto the gel and a current is appHed, the compounds migrate through the gel until they come to their isoelectric point where they reach a steady state. This technique measures an intrinsic physicochemical parameter of the protein, the pi, and therefore does not depend on the mode of sample appHcation. The highest sample load of any electrophoretic technique may be used, however, sample load affects the final position of a component band if the load is extremely high, ie, high enough to titrate the gradient ampholytes or distort the local electric field. 

The applications of quantitative structure-reactivity analysis to cyclodextrin com-plexation and cyclodextrin catalysis, mostly from our laboratories, as well as the experimental and theoretical backgrounds of these approaches, are reviewed. These approaches enable us to separate several intermolecular interactions, acting simultaneously, from one another in terms of physicochemical parameters, to evaluate the extent to which each interaction contributes, and to predict thermodynamic stabilities and/or kinetic rate constants experimentally undetermined. Conclusions obtained are mostly consistent with those deduced from experimental measurements. 

Cobo, M. G., Palacios, M. A., and Camara, C., Effect of Physicochemical Parameters on Trace Inorganic Selenium Stability, Analytica Chimica Acta, 286, 1994, 371-379. 

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. 

Summarizing the discussion above, we can only say that all the relations observed experimentally between the parameters of catalytic activity of metals and parameters of their physicochemical bulk properties are secondary. The primary factor influencing the catalytic activity of all metals and most of their physicochemical parameters are... 

Table 1 Biological and physicochemical parameters used to derive QSAR Eq. 3 ...

It is important to know the influence of the physicochemical parameters of the mobile phase (dipole moment, dielectric constant, and refractive index) on solvent strength and selectivity. The main interactions in planar chromatography between the molecules of the mobile phases and those of solutes are caused by dispersion forces related to the refractive index, dipole-dipole forces related to the dipole moment, induction forces related to a permanent dipole and an induced one, hydrogen bonding, and dielectric interactions related to the dielectric constant. Solvent strength depends mainly on the dipole moment of the mobile phase, whereas the solvent selectivity depends on the dielectric constant of the mobile phase. 

Prediction of physicochemical parameters by atomic contributions. J. Chem. Inf. Comput. Sci. 1999, 39, 868-873. 

Loidl-Stahlhofen, A., Eckert, A., Hartmann, T Schottner, M. Solid-supported lipid membranes as a tool for determination of membrane affinity high-throughput screening of a physicochemical parameter. J. Pharm. Sci. 2001, 90, 599-606. 

Faller, B., Wohnsland, F. Physicochemical parameters as tools in drug discovery and lead optimization. 

The solubility of chemicals, drugs or pollutants in water (S ), in octanol (S ), their saturation concentration in air Qii), as well as their partitioning in the corresponding two-phase systems [octanol-water (P /w = Q/Cw), air-water (Pair/w = C IC ) and air-octanol (Paij/ = C /Co)] are important physicochemical parameters in medicinal chemistry and in environmental research. The following correlahons of those properties with HYBOT descriptors have been published recently [54—58] ... 

E. P., McFarland, J. W., Schaper, K.-J. Quantitative estimation of drug absorption in human for passively transported compounds on the basis of their physicochemical parameters. Quant. Struct.-Act. Relat. 2000, 19, 355-374. 

Viswanadhan, V. N., Chose, A. K., Revankar, G. R., Robins, R. K. Atomic physicochemical parameters for three dimensional structure directed quantitative structure-activity relationships. 

Ghose, A. K., Pritchett, A., Crippen, G. M. Atomic physicochemical parameters for three-dimensional strucmre direded quantitative stmcmre-activity relationships III modeling hydrophobic interactions./ Comp. Chem. 1988, 9, 80-90. 

Wildman, S. A., Crippen, G. M. Prediction of physicochemical parameters by atomic contribution. 

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. 

The generalized sequence of alteration minerals from shallower to deeper portions and/or from lower to higher temperatures in active geothermal systems, which is constructed mainly based on the work by Henley and Ellis (1983), is given in Fig. 2.25. It is shown in Fig. 2.25 that the change in alteration and gangue minerals largely depends on temperature as well as on the other physicochemical parameters such as /s2, /o2> /c02> and pH. 

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