The second article was published in Biotechniques (1994);16(6):1006-8 Good luck V. -- Dr. Volker Blaschke Dept. of Biochemistry Georg-August-University, Goettingen, Germany CompuServe: 74740,50 Email: vblasch at gwdg.de Tel: xx49 551 39 5959 / 5978 Fax: /5960