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. 2018 Jan 1;74(Pt 1):52–64. doi: 10.1107/S2059798318000050

Table 1. The 12 letters of the CANA DNA structural alphabet based on the NtC step-conformer classes and their presence in the 58 069 analyzed steps.

A brief annotation and other characteristics of all 44 NtC classes are given in Supplementary Table S1.

    Protein–DNA Naked DNA  
The main features of the CANA letters CANA letter No. % No. % NtC classes merged into the CANA letter
A-form conformers AAA 1942 3.8 1063 14.6 AA00 + AA01 + AA02 + AA03 + AA04
Conformers bridging A-form to B-form A-B 2393 4.7 368 5 AB01 + AB02 + AB03
Conformers bridging B-form to A-form B-A 3530 7 616 8.4 BA01–BA10, BA13–BA17
The most frequent ‘canonical’ B-form BBB 17513 34.5 1561 21.4 BB00
Less populated BI conformer 2B1 3076 6.1 486 6.7 BB01
Less populated BI conformers with switched α11 values 3B1 2696 5.3 52 0.7 BB02 + BB03
Conformers bridging BI-form to BII-form B12 3286 6.5 213 2.9 BB04 + BB05
BII conformers BB2 2521 5 603 8.3 BB07 + BB08
Various minor B conformers miB 2610 5.1 192 2.6 BB10–BB16
Conformers with bases in syn orientation, may occur in quadruplexes and other nonduplexes SQX 214 0.4 248 3.4 AB1S + BBS1 + BB1S + BB2S + NS1S + NS02 + NS03 + NS04 + NS05
Z-forms ZZZ 154 0.3 175 2.4 ZZ1S + ZZ2S + ZZS1 + ZZS2
All assigned steps   39935 78.7 5577 76.4  
Non-assigned steps NAN 10839 21.3 1718 23.6  
All steps   50774 100.0 7295 100.0