New parameters for the refinement of nucleic acid-containing structures.

Area of Science:

• Structural biology
• Computational chemistry
• Biochemistry

Background:

• Accurate structural models of nucleic acids are crucial for understanding their biological functions.
• Existing structural dictionaries may not fully capture the diversity of DNA and RNA conformations.

Purpose of the Study:

• To develop a comprehensive nucleic acid dictionary using high-resolution X-ray crystallographic data.
• To improve the accuracy and efficiency of molecular modeling and structure refinement of nucleic acids.

Main Methods:

• Selected atomic resolution structures (up to 1.0 A) from the Nucleic Acid Database and Cambridge Structural Database.
• Calculated average values for bond distances, angles, and dihedral angles for bases, sugars, and phosphodiester linkages.
• Incorporated variance to estimate root-mean-square (r.m.s.) deviations of refined parameters.
• Constructed a dictionary for X-PLOR refinement, including RNA and DNA with C2'-endo and C3'-endo sugar puckers and backbone dihedral values.

Main Results:

• Developed a new nucleic acid dictionary containing average geometric parameters and variance information.
• Tested the dictionary on B-DNA, Z-DNA, and a protein-DNA complex during X-PLOR refinement.
• Observed significant improvements in r.m.s. deviations and R factors compared to a previous DNA dictionary.

Conclusions:

• The new nucleic acid dictionary provides a more accurate representation of nucleic acid geometry.
• Utilizing this dictionary in refinement protocols leads to enhanced structural models.
• This resource is valuable for computational studies involving DNA and RNA structures.