5003 DNA-A Set 5004 DNA-B Set
5005 DNA-Z Set 5008 Double Helices RNA
5009 Triple Helices DNA
Page 5

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5) Conformation of Furanose Ring The Sugar forming a 5-membered ring, such as Deoxyribose, Ribose etc called Furanose Ring, takes special conformations, since the pentagon shaped ring has an inside angle of 108, where carbons forming the pentagon have bonding angles 10928' causing C2' to raise upwards from the plane of 5-ring in some cases and C3' to raise in other cases. This plays an important role when assembling DNA, tRNA models. C3'-endo: Twist Deoxyribose (or Ribose) with both hands so that C3' toward Viewer is raised while C2' is lowered when three atom-balls C4' -O1' -C1' are horizontally viewed on a line. Fig. 16 C3'-end applies to : = �@ �› Deoxyribose DNA-A / DNA-Z Form-G �@ �@ Triple Helices DNA �@ �› Ribose Double Helices RNA C2'-endo : Twist Deoxyribose (or Ribose) to reverse direction, i,e., C3' lower and C2' raised. Fig. 17 C2'-endo applies to: = �@ �› Deoxyribose DNA-B / DNA-Z Form-C Note : Base Pairs DNA-Z are alternately arraged CGCGCG �c�c and conformation of Deoxyribose should be alternate C2' -C3' -C2' -C3' �c�c You may regard all the furanose ring confomations simply either as C3' -end or as C2' -end to simplify your assembling work. When the model is almost completed, make corrections, if any, faithfully according to the above.

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