Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Henry's constants at zero solute pressure have been determined by the gas chromatographic peak shape method for twenty-two solutes on four adsorbents (Rohm and Haas Ambersorb XE-348F carbonaceous adsorbent at 323 and 373 K, Sutcliffe Speakman 207A and 207C at 323 K, and Calgon Filtrasorb activated carbon at 323 K). The limiting values of log KH have been analysed in terms of solute dipolarity (pi 2*), solute hydrogen-bond acidity (alpha 2), and basicity (beta 2), and a new solute parameter (log L16), the solute Ostwald absorption coefficient on eta-hexadecane. The multiple linear regression equation, SP = SP0 + l.log L16 + s(pi 2* + d delta 2) + a alpha 2 + b beta 2 where in this instance SP = -log KH, can be used to identify the nature of the solute-adsorbent interactions, and to predict further values of log KH. For the solutes and solids we have studied, only the l.log L16 term is statistically significant, and hence--log KH is proportional to l.log L16. It is concluded that interactions between the gaseous solutes (that include alcohols and amines) and the four adsorbents involve just general dispersion forces.
 ...
PMID:Solubility properties in polymers and biological media. II. A new method for the characterisation of the adsorption of gases and vapours on solids. 369 80

The general solvation equation log L = c + rR2 + pi H2 + a alpha H2 + b beta H2 + l log L16 has been used to analyze the solubility of solute gases and vapors, as log L values, in water, blood, and a variety of other biological fluids and tissues. The explanatory variables are R2, the solute excess molar refraction; pi H2, the solute dipolarity/polarizability; alpha H2 and beta H2, the solut hydrogen-bond acidity and basicity; and log L16, where L16 is the solute Ostwald solubility coefficient of hexadecane. The obtained coefficients then serve to characterize the biological phase as follows: r + s is the phase dipolarity/polarizability, a is the phase hydrogen-bond basicity, b is the phase hydrogen-bond acidity, ald l is the phase lipophilicity. In addition to characterization of phases, the equation can be used to determine quantitatively solute/phase interactions and predict further log L values. A similar equation in which McGowan's characteristic volume, Vx, replaces the log L16 descriptor can be used to analyze partitions between phases. For example, water/phase and blood/phase partition coefficients are analyzed, and the analysis leads again to coefficients that characterize phases and to the prediction of partition coefficients.
 ...
PMID:Hydrogen bonding. 30. Solubility of gases and vapors in biological liquids and tissues. 788 68

Nasal pungency thresholds (NPT) in man have been determined by Cometto-Muniz and Cain for 44 varied compounds, including esters, aldehydes, ketones, alcohols, carboxylic acids, aromatic hydrocarbons and pyridine. With the exclusion of acetic acid, 43 of these NPT values are well correlated through the general linear free energy equation of Abraham, leading to the algorithm, log(1/NPT) = -8.519 + 2.154 pi(2)H + 3.522 sigma alpha(2)H + 1.397 sigma beta(2)H + 0.860 logL16. N = 43, r2 = 0.955, SD = 0.27, F = 201 (i) where the independent variables are solute descriptors: pi(2)H is the dipolarity/polarizability, sigma alpha(2)H and sigma beta(2)H are the overall or effective hydrogen-bond acidity and basicity, and L16 is the solute Ostwald solubility coefficient on hexadecane at 25 degrees C. Surprisingly, the aliphatic aldehydes and carboxylic acids fit the correlation and with respect to nasal pungency thresholds in man for brief (1-3 s) presentations must be regarded as 'nonreactive' compounds. It is suggested mere transport of the compound from the air stream to the receptor area largely determines the potency to produce pungency. Various chemical properties of the receptor area are deduced from the coefficients in Eq. i.
 ...
PMID:An algorithm for nasal pungency thresholds in man. 958 18

Draize eye scores (DES) of 37 pure organic liquids have been converted into scores for the corresponding vapors, DES/P0, where P0 is the liquid vapor pressure in atmospheres at 298 K. It is shown that there is a constant difference of 6.7 between values of log(DES/P0) and log (1/EIT), where EIT is the eye irritation threshold in parts per million (ppm, by volume) of eight vapors for human subjects. The 37 log(DES/P0) values can be combined with log(1/EIT) values for 17 vapors into one quantitative structure-activity relationship (QSAR) for sensory potency (SP) using our general solvation equation, [formula: see text] where R2 is an excess molar refraction, pi 2H is the compound polarizability/dipolarity, sigma alpha 2H and sigma beta 2H are the compound hydrogen-bond acidity and basicity, and L16 is the gas-hexadecane partition coefficient at 298 K. n is the number of data points, r the correlation coefficient, SD the standard deviation, and F the F-statistic. LogSP is then either [log(DES/P0) - 0.66] or log (1/EIT), confirming the result for the eight common compounds. It is suggested that the equation can be used to predict eye irritancy of organic vapors and pure liquids. It is further suggested that for the compounds in the data set, the main process in eye irritation is transfer of the compound from the vapor or pure liquid to a biological phase, and a number of chemical properties of the biological phase have been mapped out through the equation. These properties are consistent with corresponding properties for a number of organic liquid phases.
 ...
PMID:Draize eye scores and eye irritation thresholds in man can be combined into one QSAR. 992 67

Ostwald solubility coefficients of 74 compounds in dry octan-1-ol at 298 K have been determined, and have been combined with literature values and additional values we have calculated from solubilities in dry octan-1-ol and vapour pressures to yield a total of 161 log L(OctOH) values at 298 K. These L(OctOH) values are identical to gas-to-dry octan-1-ol partition coefficients, often denoted as K(OA). Application of the solvation equation of Abraham to 124 values as a training set yielded a correlation equation with n = 124, S.D. = 0.125, r2 = 0.9970 and F = 7731. This equation was then used to predict 32 values of log L(OctOH) as a test set, giving a standard deviation, S.D. of 0.131, an average absolute deviation of 0.085 and an average deviation of -0.009 log units. The solvation equation for the combined 156 log L(OctOH) values was log L(OctOH) = -0.120 - 0.203R2 + 0.560pi2(H) + 3.560 sum(alpha2(H)) + 0.702 sum(beta2(H)) + 0.939 logL16, n =156, r2 = 0.9972, S.D. = 0.125, F = 10573, where, n is the number of data points (solutes), r the correlation coefficient, S.D. the standard deviation and F is the F-statistic. The independent variables are solute descriptors as follows: R2 is an excess molar refraction, pi2(H) the dipolarity/polarisability, sum(alpha2(H)) the overall or summation hydrogen-bond acidity, sum(beta2(H)) the overall or summation hydrogen-bond basicity and L16 is the Ostwald solubility coefficient on hexadecane at 298 K. The equation is consistent with similar equations for the solubility of gases and vapours into methanol, ethanol and propan-1-ol. It is suggested that the equation can be used to predict further values of log L(OctOH), for which the solute descriptors are known, to within 0.13 log units.
 ...
PMID:The solubility of gases and vapours in dry octan-1-ol at 298 K. 1148 78

To fully utilize the sorption traits of organobentonites to control volatile organic compounds (VOCs) pollution, the sorption mechanisms of VOCs with organobentonites need to be understood adequately. The sorption of VOCs as vapors to a typical organobentonite, modified with cetyltrimethylammonium bromide (CTMAB-bentonite), was characterized using a linear solvation energy relationship (LSER) of the type log Kc = c + rR2 + s pi2H + a sigma(alpha2)H + b sigma(beta2)H + l log L16. The fitted LSER equation, log Kc = 0.434 + 0.968R2 - 0.0886pi2H + 2.170sigma(alpha2)H + 1.611sigma(beta2)H + 0.417 log L16, was obtained by a multiple regression of the partition coefficients of 22 probe solutes against the solvation parameters of the solutes. The coefficients of the LSER equation show that CTMAB-bentonite is a sorbent with nonsignificant dipolarity/polarizability, interacts with solutes partly through pi-/n-electron pairs, behaves both as hydrogen-bond donor and hydrogen-bond acceptor, and can interact with solutes by cavity/dispersion interactions. The related terms in LSER suggest that the potential factors governing the sorption of VOCs onto CTMAB-bentonite are dispersion interactions, hydrogen-bond acidity interactions, hydrogen-bond basicity interactions, and pi-/n-electron interactions. The dispersion interaction is recognized to be the predominant parameter for most solutes, whereas the contributions of the other parameters depend on specific solutes. The derived LSER equation successfully predicted the VOC partition coefficients and the selectivity of CTMAB-bentonite for the VOCs. The relationship between LSER and adsorption/partition model was compared. The classification of sorption mechanisms by LSER goes on the molecular interaction types between sorbate and sorbent, and classification by adsorption/partition model goes on the property difference among various components of sorbent. The LSER approach coupled with inverse gas chromatography (IGC) is a comparatively simple and reliable tool to rapidly characterize the sorption mechanism of VOCs with solid sorbents such as CTMAB-bentonite, and may potentially be applied to the design of an organoclay sorbent for control of VOCs.
 ...
PMID:Characterization of sorption mechanisms of VOCs with organobentonites using a LSER approach. 1475 Jul 24