In fact, with the establishment of high-throughput analytical methodologies, the amount of physicochemical data is growing rapidly, allowing hundreds of compounds to be measured rapidly and precisely each day. The availability of large datasets covering a sufficiently broad structural diversity increases the chances that improved schemes for reasonably successful predictions of physicochemical properties can be developed. Both databases and chemoinformatics tools aim at enhancing the capacity of medicinal chemists to design compounds with desired physicochemical and pharmacological properties. Physicochemical prediction with computational approaches plays a crucial role in the drug-discovery research.
In research and drug discovery, the common values are pKa and octanol/water partition coefficients (logD and logP values) for physicochemical properties. For example, it is important not only to know the pKa value of an amine-containing compound, but even more so, to be able to modulate its basicity in a rational, structure-based fashion. Furthermore, the analysis of the relationship of logD and molecular weight (MW) with in vitro measures of compound metabolic stability and permeability concluded that the chances of achieving acceptable permeability and stability in a single molecule were highest when logD was between 1 and 2 and MW350-450. Therefore, study on physicochemical properties of drugs is very important in drug discovery.
Melting point is an important property which can indicate whether a chemical compound is solid or liquid at particular temperatures. The melting point of a crystalline compound is controlled largely by intermolecular interactions and molecular symmetry. There are two approaches that have been used in the prediction of melting point-the physicochemical or structural descriptor approach and the group contribution approach.
Boiling point is an important property since it is an indicator of volatility, and can be used to predict vapour pressure. At BOC Sciences, many studies based on QSPR research for boiling point prediction have dealt with specific chemical classes and good correlations have generally been obtained.
The vapour pressure (VP) of a chemical controls its release into the atmosphere, and thus is an important factor in environmental distribution of chemicals. The variation of vapour pressure with temperature is given by the Clausius-Clapeyron equation:
ln (VP2/VP1) =- (L/R)((1/T2) – (1/T1))
Where L = latent heat of vaporisation, and R = universal gas constant.
Aqueous solubility depends not only on the affinity of a solute for water, but also on its affinity for its own crystal structure. We have created various ways in which aqueous solubilities can be predicted: in pure water, at a specified pH, at a specified ionic strength, as the intrinsic solubility undissociated species, or in the presence of other solvents or solutes.
The octanol-water partition coefficient is the ratio of concentrations of a chemical in n-octanol and in water at equilibrium at a specified temperature (typically 25oC). Partition coefficient is a good surrogate for partitioning of chemicals through lipid membranes, and is the most important physicochemical descriptor of biological activity.
Within a congeneric series of chemicals, pKa is often closely correlated with the Hammett substituent constant, and this is the basis for a number of attempts at pKa prediction. There are a number of software programs that can predict multiple pKa values of organic chemicals.
We can provide prediction services for other properties, such as density, refractive index, viscosity, surface tension, thermal conductivity and Henry’s law constant.
BOC Sciences has the advanced analytical and computational technology. Besides, our researchers are always concerned about the development of drug physicochemical prediction field. Our experienced scientists will predict the physicochemical property such as the pKa and logD values of drugs with the appropriate methods.