these analogues contained a bulky , lipophilic group ( 2,2,2-trichloroethoxy or 2,2,2-trichloro-1,1-dimethylethoxy ) a small , uncharged hydrogen-bonding group ( amido ) , or a cationic phosphoramidate ( 2-aminoethylamido , protonated in neutral aqueous media ) in place of the anionic oxygen of the internucleotide phosphate .
C0003075
anionic
C0031603
phosphate