[1] Kings Coll London, London WC2R 2LS, England
[2] Duke Univ, Durham, NC USA
[3] Inst J Paoli I Calmettes, F-13009 Marseille, France
[4] Vion Pharmaceut Inc, New Haven, CT USA
[5] Johns Hopkins Univ, Baltimore, MD USA
[6] Univ Texas Hlth Sci Ctr San Antonio, CTRC, San Antonio, TX 78229 USA