1. Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, Departamento de Biologia Molecular e Biotecnologia, Universidade Federal do Rio Grande do Sul, Avenida Bento Gonçalves 9500, Porto Alegre-RS 91501-970, Brazil, and Carbohydrate Chemistry Team, Industrial Research, Ltd., Lower Hutt, New Zealand