Structure Of Adenine

Structure of guanine

Cytosine

Thymine

Uracil

Adenine nucleoside and nucleotide

Pyrimidine nucleoside

Primary structure of DNA

Secondary Structure of DNA

Secondary structure of DNA

Syn and anti form of nucleoside

FORCES THAT STABILIZE NUCLEIC ACID STRUCTURES SUGAR-PHOSPHATE CHAIN CONFORMATIONS BASE PAIRING BASE-STACKING,HYDROPHOBIC IONIC INTERACTIONS

BASE-PAIRING WATSON-CRICK GEOMETRY HOOGSTEEN GEOMETRY THE A-T PAIRS USE ADENINE’S N1 AS THE H-BOND ACCEPTOR HOOGSTEEN GEOMETRY N7 IS THE ACCEPTOR SEEN IN CRYSTALS OF MONOMERIC A-T BASE PAIRS IN DOUBLE HELICES, W-C IS MORE STABLE ALTHOUGH HOOGSTEIN IS MORE STABLE FOR A-T PAIRS, W-C IS MORE STABLE IN DOUBLE HELICES CO-CRYSTALLIZED MONOMERIC G-C PAIRS ALWAYS FOLLOW W-C GEOMETRY THREE H-BONDS

IN MOST DOUBLE-HELICAL STRUCTURES, ALL BASES IN ANTI FORM

Hydrogen bonding between A and T

Hydrogen bonding between G and C