Quadruply H Bonded Duplexes with Sequence-Independent Stability

QUADRUPLY H BONDED DUPLEXES WITH SEQUENCE-INDEPENDENT STABILITY 

The most conclusive evidence for the presence of duplexes la la and 2 2 came from 2-D H-NMR [nuclear Overhauser effect spectroscopy (NOESY)] and X-ray crystallography. The NOESY spectrum of lb in CDCI3 contains interstrand NOEs (Fig. 9.2a) between protons c and e, c and i, and c and j, which are consistent with an H bonded dimer. The crystal structures of la and 2 both revealed the expected dimeric stmctures held together by intermolecular H bonds (Fig. 9.2b). 

It was found that a-amino acid linkers other than glycine, or different alkoxy side chains did not affect the stability of each of the duplexes, which lies in the range of 10 M. Because of its ready availability, the glycine residue has been adopted in most of the subsequently designed duplexes. The similar stability of these duplexes 

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