1. Department of Biological Sciences; University of Texas-Brownsville; Brownsville TX 78520 U.S.A.
2. National Institutes of Health, NIDDK, LMC, Section on Carbohydrates; Bethesda MD 20892 U.S.A.
3. Department of Microbiology and Immunology; Dartmouth Medical School; Lebanon NH 03756 U.S.A.