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THE STRUCTURE IS FORMED OF FOUR EQUIVALENT TCC STRANDS DESIGNATED A, B, C, D. STRANDS A AND C, CONNECTED BY TWO HEMI-PROTONATED BASE PAIRS (C2.C2+ AND C3.C3+), FORM A PARALLEL-STRANDED DUPLEX. THE RELATION BETWEEN STRANDS B AND D IS THE SAME AS THAT BETWEEN STRANDS A AND C. THE STRANDS OF EACH DUPLEX ARE RELATED BY A LONGITUDINAL TWO-FOLD SYMMETRY AXIS. THE DUPLEXES HAVE THE SAME LONGITUDINAL AXIS, AND THEY ARE ANTI-PARALLEL. THEIR HEMI-PROTONATED C.C+ BASE PAIRS ARE INTERCALATED FACE-TO-FACE. THE DUPLEXES CAN BE TRANSFORMED INTO ONE ANOTHER BY A 180 DEGREE ROTATION AROUND A TWO-FOLD AXIS PERPENDICULAR TO THE LONGITUDINAL AXIS, AND CONSEQUENTLY AROUND A THIRD AXIS PERPENDICULAR TO THE FIRST TWO. THE H3 IMINO PROTONS OF THE HEMI-PROTONATED C.C+ PAIRS WERE NOT INCORPORATED IN THE COMPUTATIONS. |
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