Ignore my last message. I found the molecular weight calculation tool I was looking for at http://www.expasy.ch/tools/pi_tool.html Jeff Cohlberg -- Jeffrey A. Cohlberg, Professor Department of Chemistry and Biochemistry California State University, Long Beach 1250 Bellflower Blvd. Long Beach, CA 90840 phone (562) 985-4944 fax (209) 821-4471