Structural descriptors, examples chemical names

During the bioconcentration process, chemical compounds accumulate in, for example, fish, by absorption through skin or respiratory surface. The steady-state ratio between the concentration of a compound in an aquatic organism and its concentration in the aquatic environment defines the bioconcentration factor (BCF). To determine the environmental fate of chemicals released from industrial, agricultural, or residential sources, it is essential to determine or predict their BCF. Because the experimental determination of BCF is time consuming and expensive, various QSAR models have been developed for the BCF prediction using structural descriptors. " Gramatica and Papa proposed a BCF QSAR model for 238 diverse chemicals, based on five theoretical descriptors, namely deg n ean information content of the dis-... 

In computational chemistry, the main use of PLS is to model the relationship between, on the one hand, computed and measured variables that together characterize the structural variation of a set of N compounds and, on the other hand, biological response variables or other interesting properties measured on the same N substances. " The former comprise the matrix X-of predictor variables, and the latter the matrix Y of response variables. These matrices have dimensions N x K and N X M, respectively. We note that the X variables are usually not independent, and hence they should not be called by that name, but rather predictors or simply X variables. The example used here to illustrate PLS is of this type, where the structural variation of iV = 15 compounds is translated to iV = 15 rows of an X matrix using X = 8 measured and calculated quantum chemical descriptors. The biological response of these compounds is described by a Y matrix comprising M = S aquatic toxicity responses. 

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