上游充通大兽 1 A Nucleic Acid Consists of 4 Kinds of Bases SHANGHAI JIAO TONG UNIVERSITY Linked to a Sugar-Phosphate Backbone 核苷结构（8种)： NH2 阝-糖苷键 B-Glycosidic linkage H2 N 5 HO H 3 OH Figure 4.5 B-Glycosidic linkage in a nucleoside.1 A Nucleic Acid Consists of 4 Kinds of Bases Linked to a Sugar-Phosphate Backbone Figure 4.5 b-Glycosidic linkage in a nucleoside. 核苷结构（8种）： b -糖苷键 5’ 3’