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