Figure 6.

Definitions used in the analysis of hydrogen bonds. (a) Geometric definition of hydrogen bond; D ≡ Donor, A ≡ Acceptor, r < 3.5 Å, θ < 30°. (b) Various degrees of ssDNA wrapping described by the COM-distance, dCOM. The SWCNT and its axis are viewed on end and are denoted by the black circle and dot. The red line represents the ssDNA strand and the blue dot its center-of-mass. The dashed line is the measure dCOM for the relevant conformation. Small values of dCOM (less than the tube radius) are a necessary measure in order to characterize an intra-strand HB as stabilizing.