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Wednesday, October 10, 2012

Types of Qsar

Various Types of Qsar are now a days available. We can do 2D, 3D...etc.,now days list is available up to 7D.but popular Qsar Study are 2D and we will discuss about in brief  related them.
2D Qsar means two dimensional quantitative structure relationships. in this the Qsar study various physiochemical properties are calculated. Then regression analysis is done. Then validation model are generated. This is simple type of Qsar study. It cannot give more information regarding biological activity and other property but it gives one direction of our study8 9. So it will helpful in drug discovery and modeling. In 2D Qsar physiochemical properties are logP, MR, HA, HD…etc. these are also calculated in 3D .in 3D many parameters are calculated which are discuss later. in short 2D Qsar is first and primary step for Qsar study10.
3D Qsar is a well recognized method at a molecular level the interaction that produced an observed biological response are usually non covalent and that such steric and electrostatic interaction can account for many of the observed molecular properties Extension of the traditional QSAR approaches have been developed which explicitly uses the 3D geometry of structure during the development of the QSAR model. 3D QSAR are quantitative model that relate the biological activity of small molecules with their properties calculated in 3D space. Two techniques can broadly be used in 3D QSAR11:
1) Receptor dependent 3D QSAR analysis
2) Receptor independent 3D QSAR analysis

Based on dimensionality:
Most often the QSAR methods are categorized into following classes, based on the structural representation or the way by which the descriptor Values are derived:
1D-QSAR correlating activity with global molecular Properties like pKa, log P etc.
2D-QSAR correlating activity with structural patterns like connectivity indices, 2D-pharmacophores etc., without taking into account the 3D-representation of these properties.
3D-QSAR correlating activity with non-covalent interaction fields surrounding the molecules.
4D-QSAR additionally including ensemble of ligand configurations in 3D-QSAR.
5D-QSAR explicitly representing different induced-fit models in 4D-QSAR.
6D-QSAR further incorporating different solvation models in 5D-QSAR.
Based on the type of chemometric methods used:
Sometimes QSAR methods are also classified into following two categories, depending upon the type of correlation technique employed to establish a relationship between structural properties and biological activity.
Linear methods including linear regression (LR), multiple linear regression (MLR), partial least-squares (PLS), and principal component analysis/regression (PCA/ PCR).Non-linear methods consisting of artificial neural networks(ANN), k-nearest neighbors (kNN), and Bayesian


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