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Analysis of nucleic acid double helix geometry

PDB code 2I7Z   (PDB summary)
Duplex length 43 base pairs

Only the nucleic acid double helix part of the structure is analysed here. Small ligands, proteins, and overhanging ends are not taken into account. Information on the complete structure is available at the Image Library Entry page and at the Sequence, Chains, Units page.

Strand 1    5' G1 G2 G3 A4 U5 A6 U7 G8 G9 A10 A11 G12 A13 A14 C15 C16 G17 G18 G19 G20 A21 A22 A23 C24 U25 U26 G27 G28 U29 U30 C31 U32 U33 C34 C35 U36 A37 A38 G39 U40 C41 C42 U43 3'
Strand 2    3' U86 C85 C84 U83 G82 A81 A80 U79 C78 C77 U76 U75 C74 U73 U72 G71 G70 U69 U68 C67 A66 A65 A64 G63 G62 G61 G60 C59 C58 A57 A56 G55 A54 A53 G52 G51 U50 A49 U48 A47 G46 G45 G44 5'

Warning
  1 base(s) in syn conformation detected.
  Helix parameters and curvilinear axis from CURVES are meaningless (see Help).


Side view 1 Top view
Side view 1 Top view
Side view 2 3-dimensional interactive models
(Help)
  

RASMOL, CHIME, VRML 2.0, PDB

Side view 2  

Figure 1   Three orthogonal views of the double helix (Help). Residues are colored according to the nucleotide type (Help: Color codes). The curvilinear helical axis (green) was calculated with CURVES. The double helix is oriented with respect to the principle axis of inertia of the curvilinear helical axis (see Help for further explanations). This drawing reveals immediately if there is any bending of the helical axis.


Backbone parameters

Table 1.  Selected torsional angles and sugar pucker phase angles describing the conformation of the sugar phosphate backbone. (See Help for further explanations.)


 gamma     epsilon-zeta       pucker        chi      Strand 1     Strand 2      chi        pucker       epsilon-zeta     gamma 

    C2'-exo -172° G1 U86 -149° C4'-exo    
 57°   -105° (BI)             -108° (BI)   49° 
    C3'-endo -158° G2 C85 -145° C3'-endo    
 42°   -51° (BI)             -80° (BI)   53° 
    C3'-endo -145° G3 C84 -147° C3'-endo    
 44°   -76° (BI)             -61° (BI)   59° 
    C3'-endo -140° A4 U83 -153° C3'-endo    
 76°   -101° (BI)             -69° (BI)   172° 
    C3'-endo -144° U5 G82 -170° C2'-exo    
 -165°   51° (BII)             -56° (BI)   114° 
    C2'-endo -139° A6 A81 -172° C3'-endo    
 48°   -76° (BI)             101° (BII)   163° 
    C4'-exo -21° U7 A80 -129° C3'-exo    
 34°   169° (BII)             -104° (BI)   172° 
    C3'-endo -148° G8 U79 -167° C3'-endo    
 153°   175° (BII)             144° (BII)   73° 
    C2'-exo 180° G9 C78 -146° C3'-endo    
 67°   -24° (BI)             -103° (BI)   -177° 
    C3'-endo -168° A10 C77 -165° C3'-endo    
 68°   -69° (BI)             -77° (BI)   55° 
    C3'-endo -157° A11 U76 -146° C3'-endo    
 64°   -50° (BI)             -47° (BI)   61° 
    C3'-endo -158° G12 U75 -156° C4'-exo    
 33°   -68° (BI)             -39° (BI)   66° 
    C3'-endo -142° A13 C74 -148° C3'-endo    
 61°   -93° (BI)             -102° (BI)   50° 
    C3'-endo -143° A14 U73 -147° C3'-endo    
 63°   -77° (BI)             -85° (BI)   54° 
    C3'-endo -145° C15 U72 -149° C3'-endo    
 40°   -69° (BI)             -77° (BI)   57° 
    C4'-exo -140° C16 G71 -153° C3'-endo    
 65°   -78° (BI)             -65° (BI)   50° 
    C3'-endo -163° G17 G70 -145° C4'-exo    
 35°   -99° (BI)             -91° (BI)   42° 
    C4'-exo -161° G18 U69 -143° C3'-endo    
 53°   -109° (BI)             -85° (BI)   41° 
    C3'-endo -140° G19 U68 -145° C3'-endo    
 156°   -166° (BII)             -88° (BI)   68° 
    C2'-exo -173° G20 C67 -152° C3'-endo    
 84°   -38° (BI)             -50° (BI)   105° 
    C2'-exo -152° A21 A66 -148° C2'-exo    
 143°   -169° (BII)             -82° (BI)   137° 
    C2'-exo 176° A22 A65 -176° C2'-exo    
 100°   -72° (BI)             178° (BII)   84° 
    C2'-exo -149° A23 A64 -152° C2'-exo    
 68°   -37° (BI)             -33° (BI)   164° 
    C3'-endo -155° C24 G63 -175° C2'-exo    
 53°   -83° (BI)             153° (BII)   43° 
    C3'-endo -153° U25 G62 -144° C4'-exo    
 28°   -73° (BI)             -99° (BI)   33° 
    C3'-endo -138° U26 G61 -151° C3'-endo    
 67°   -101° (BI)             -106° (BI)   61° 
    C4'-exo -148° G27 G60 -156° C3'-endo    
 51°   -50° (BI)             -70° (BI)   55° 
    C3'-endo -147° G28 C59 -144° C4'-exo    
 60°   -82° (BI)             -92° (BI)   59° 
    C3'-endo -149° U29 C58 -145° C3'-endo    
 65°   -86° (BI)             -80° (BI)   48° 
    C3'-endo -148° U30 A57 -144° C3'-endo    
 67°   -87° (BI)             -64° (BI)   55° 
    C4'-exo -150° C31 A56 -153° C3'-endo    
 54°   -62° (BI)             -61° (BI)   67° 
    C3'-endo -144° U32 G55 -157° C3'-endo    
 67°   -97° (BI)             -50° (BI)   68° 
    C3'-endo -145° U33 A54 -157° C3'-endo    
 -162°   -90° (BI)             -70° (BI)   66° 
    C3'-endo -171° C34 A53 -168° C3'-endo    
 158°   -72° (BI)             -26° (BI)   153° 
    C2'-exo -170° C35 G52 -176° C2'-exo    
 150°   -86° (BI)             -147° (BI)   48° 
    C2'-exo -170° U36 G51 -163° C3'-endo    
 171°   -83° (BI)             -94° (BI)   78° 
    C3'-exo -128° A37 U50 -31° C2'-endo    
 57°   29° (BII)             -68° (BI)   168° 
    C3'-endo -171° A38 A49 -124° C2'-endo    
 158°   -73° (BI)             -50° (BI)   68° 
    C2'-exo -170° G39 U48 -145° C3'-endo    
 67°   -77° (BI)             -89° (BI)   57° 
    C3'-endo -154° U40 A47 -145° C3'-endo    
 57°   -66° (BI)             -65° (BI)   54° 
    C3'-endo -148° C41 G46 -150° C3'-endo    
 46°   -73° (BI)             -50° (BI)   56° 
    C3'-endo -145° C42 G45 -163° C3'-endo    
 68°   -113° (BI)             -86° (BI)   60° 
    C4'-exo -147° U43 G44 -170° C2'-exo    


Groove width

Plot of minor groove width:   PDF,   GIF
Plot of major groove width:   PDF,   GIF
(See Help for further explanations.)

Further information

Full output from CURVES  (helical parameters with respect to global and local axes)

Full output from FREEHELIX  (helical parameters with respect to local axis, angles between normal vectors)

Chirality of ribose and phosphate atoms
Check the naming of phosphate and ribose substituents. Recommended for phosphate oxygens and for ribose hydrogens in NMR structures.


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Perl script:    helixparameter.pl  (15 Sep 2016)
Author:    Peter Slickers  (slickers@leibniz-fli.de),  IMB Jena,  Germany