This is in response to Dale's message about pseudorotation. While he is correct that the Cremer and Pople form is more general and would apply to all flexible rings, the Altona and Sundaralingam formalism is widely used by the nucleic acid community. I suggest that it be included in the struct_mon_nucl section. I am not exactly sure where the Cremer and Pople one should go but I do agree that it too deserves a place. I have written up the S and A ones for now. ----------------------------------------------------------------------- save__struct_mon_nucl.tau2 _item_description.description ; The value in degrees of the sugar torsion angle tau2 C1'_C2'_C3'_C4'. ; _item.name '_struct_mon_nucl.tau2' _item.category_id struct_mon_nucl _item.mandatory_code no _item_type.code float _item_units.code 'degrees' save_ save__struct_mon_nucl.tau3 _item_description.description ; The value in degrees of the sugar torsion angle tau2 C2'_C3'_C4'_O4'. ; _item.name '_struct_mon_nucl.tau3' _item.category_id struct_mon_nucl _item.mandatory_code no _item_type.code float _item_units.code 'degrees' save_ save__struct_mon_nucl.tau4 _item_description.description ; The value in degrees of the sugar torsion angle tau4 C3'_C4'_O4'_C1'. ; _item.name '_struct_mon_nucl.tau4' _item.category_id struct_mon_nucl _item.mandatory_code no _item_type.code float _item_units.code 'degrees' save_ save__struct_mon_nucl.tau0 _item_description.description ; The value in degrees of the sugar torsion angle tau0 C4'_O4'_C1'_C2'. ; _item.name '_struct_mon_nucl.tau0' _item.category_id struct_mon_nucl _item.mandatory_code no _item_type.code float _item_units.code 'degrees' save_ save__struct_mon_nucl.tau1 _item_description.description ; The value in degrees of the sugar torsion angle tau1 O4'_C1'_C2'_C3'. ; _item.name '_struct_mon_nucl.tau1' _item.category_id struct_mon_nucl _item.mandatory_code no _item_type.code float _item_units.code 'degrees' save_ save__struct_mon_nucl.taum _item_description.description ; The maximum amplitide of puckering. It is derived from the the pseudorotation value, P, and the torsion angles in the ribose ring. Tau2= Taum cosP Tau3= Taum cos(P+144) Tau4= Taum cos(P+288) Tau0= Taum cos(P+ 72) Tau1= Taum cos(P+216) ; _item.name '_struct_mon_nucl.taum' _item.category_id struct_mon_nucl _item.mandatory_code no _item_type.code float _item_units.code 'degrees' save_ save__struct_mon_nucl.P _item_description.description ; P is the phase angle of pseudorotation for five membered rings. This formulation is used for ribo and deoxyribo sugars in nucleic acids. (tau4 +tau1)-(tau3+tau0) P = ATAN (-------------------------) 2tau2 (sin 36+sin 72) If tau2 is <0, then P=P+180 This formulation is by Altona and Sundaralingam (1972), J.A.C.S., 94, 8205-8212. ; _item.name '_struct_mon_nucl.taum' _item.category_id struct_mon_nucl _item.mandatory_code no _item_type.code float _item_units.code 'degrees' save_ --PART-BOUNDARY=.19512131748.ZM5561.rutgers.edu--