in crystal structure analyses of oligonucleotides , the free oxygen atoms of adjacent phosphate groups along the polynucleotide chain in b-dna are found at least 6.6 a apart and individually hydrated whereas they are as close as 5.3 a in a-dna and 4.4 a in z-dna , and bridged by water molecules .
C0028953
oligonucleotides
C0032550
polynucleotide