 certain phenyl - substituted hydrocarbons of environmental concern have the potential to disrupt the endocrine system of animals , apparently in association with their estrogenic properties . 
 competition with natural estrogens for the estrogen receptor is a possible mechanism by which such effects could occur . 
 we used comparative molecular field analysis ( comfa ) , a three - dimensional quantitative structure - activity relationship ( qsar ) paradigm , to examine the underlying structural properties of ortho - chlorinated hydroxybiphenyl analogs known to bind to the estrogen receptor . 
 the cross - validated and conventional statistical results indicate a high degree of internal predictability for the molecules included in the training data set . 
 in addition to the phenolic ( a ) ring system , conformational restriction of the overall structure appears to play an important role in estrogen receptor binding affinity . 
 hydrophobic character as assessed using hydropathic interaction fields also contributes in a positive way to binding affinity . 
 the comfa - derived qsars may be useful in examining the estrogenic activity of a wider range of phenyl - substituted hydrocarbons of environmental concern.imagesfigure 1.figure 2 . 
Images