 using two independent analyses , it is demonstrated that natural ( e.g. , estradiol ) and some xenoestrogens ( e.g. , methoxychlor metabolite ) are characterized by a lipophilic region that is absent in nonestrogens as well as in phytoestrogens . 
 it is suggested that this lipophilic region affects binding to specific receptors and may , in fact , differentiate harmful from beneficial estrogens.imagesfigure 1 . 
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