Crystal structure of the DNA sequence d(CGTGAATTCACG)₂ with DAPI

Area of Science:

• Structural Biology
• Biochemistry
• Crystallography

Background:

• The fluorescent dye 4',6-diamidine-2-phenylindole (DAPI) is widely used for DNA staining.
• Understanding DAPI's binding mechanism at a molecular level is crucial for its accurate application.

Purpose of the Study:

• To elucidate the precise structural interactions between DAPI and a synthetic B-DNA oligonucleotide.
• To compare the DNA structure with and without DAPI bound.

Main Methods:

• Single-crystal X-ray diffraction was employed to determine the structure.
• The study utilized a synthetic B-DNA oligonucleotide d(CGTGAATTCACG).
• Resolution of the diffraction data was 2.2 Å.

Main Results:

• The crystal structure of DAPI bound to B-DNA was solved in space group P212121.
• DAPI was observed to bind within the narrow minor groove of the DNA, primarily over A-T base pairs.
• DAPI binding displaced ordered water molecules from the minor groove, a phenomenon attributed to its hydrophobic nature.

Conclusions:

• DAPI binding induces structural changes in the DNA minor groove, including the displacement of water molecules.
• The observed interactions involve hydrogen bonding and van der Waals forces.
• The findings provide atomic-level insights into DAPI-DNA complex formation.