Dear Colleagues,

The deposition of the structures of nucleic acid and nucleic acid–protein complexes in the Protein Databank continues to grow due to improvements in the methods for synthesis, purification, crystallization, and structure determination. However, the ratio between the number of nucleic acid-containing structures and that of protein structures is 1:14. This ratio does not reflect the importance of nucleic acids, especially with the recent identification of new roles played in biology by noncoding RNAs. This Special Issue provides a platform for updates on the developments and trends in nucleic acid crystallography. The scope includes X-ray, neutron, and electron diffraction (microED) methods as well as small-angle scattering methods. We seek original research reports and review articles focused on specific aspects of nucleic acid crystallography, including but not limited to the following topics:

• New crystal structures containing nucleic acids, including complexes with drugs, proteins, or metals;
• Small angle scattering studies;
• Crystallization construct design;
• Large-scale chemical or enzymatic synthesis of nucleic acids;
• Nucleic acid purification for crystallographic studies;
• Crystallization screen design;
• Use of biophysical methods to screen crystallization constructs;
• Crystal size optimization;
• Optimization of diffraction quality;
• Crystal derivatization with heavy atoms;
• Heavy-atom incorporation in synthetic RNA and DNA;
• Engineering of nucleic acids to promote crystallization;
• The use of crystallization chaperones, including RNA nanobodies;
• The use of fusions to ease purification or promote crystallization;
• The use of ligands to promote crystallization;
• Post-crystallization crystal improvement (crystal hardening);
• Cryocrystallography;
• Room-temperature data collection with synchrotron radiation;
• New diffraction methods (e.g., serial crystallography, XFELS, radiation damage);
• Crystal twinning;
• Crystal packing disorder;
• Pseudosymmetry;
• Diffuse scattering;
• Phasing methods;
• Density map interpretation;
• Model building in electron density maps;
• Structure refinement method advancements;
• Error analysis of nucleic acid structures;
• Methods of comparing crystal structures;
• Molecular dynamics simulations in crystal lattices;
• Use of machine learning to facilitate crystallization;
• Integrative molecular modeling that includes crystal structures of nucleic acids;
• Use of modeling methods to improve the diffraction quality;
• Molecular visualization of RNA, DNA or both;
• Structural bioinformatics using crystal structures of nucleic acids;
• Use of crystallography in DNA and RNA nanotechnology;
• Nucleic acid–water interactions in crystal structures.

Prof. Dr. Blaine Mooers
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• nucleic acid synthesis and purification
• RNA and DNA crystallization
• RNA and DNA crystal improvement
• Nucleic acid diffraction studies
• RNA and DNA structure determination
• RNA and DNA model building
• nucleic acid structure analysis
• nucleic acid structural bioinformatics

• Nucleic Acid Crystallography in Crystals (9 articles)