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definitions

mercapto-

combining form
  1. (in chemical compounds) indicating the presence of an HS- group
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
mercapto- in Medicine

mercapto-

pref.
  1. Containing the univalent radical SH:mercaptopurine.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.