Amine
RNH2, R2NH,R3N
Thiol
-SH
Ether
ROR
Ester
RCOOR
Thioester
RCOSR
Amide
RCONH2
Imine
R=NR
Disulfide
R-S-S-R
Phosphate Ester
ROP(O2)OH
Carboxyl group
COOH
Carboxylate group
COO-
Phosphoanhydride group
O O
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P - O - P - O-
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O- OH
Phosphodiester linkage
: O
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O - P - O
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O-