Related Experiment Video
Updated: Jul 25, 2026

CD Spectroscopy to Study DNA-Protein Interactions
Published on: February 10, 2022
Role of the protein alpha helixes in histone-DNA interactions studied by vibrational spectroscopy
Abstract:
The localization of structurally important histone-DNA interactions has been investigated by vibrational spectroscopy. Histones H2A, H2B, and H4 and their fragments (H2A, 1-56, 1-89, 73-129; H2B, 1-59, 1-83; H4, 1-53, 1-67, 1-84, 69-84, 85-102) have been prepared, characterized, and used to reconstitute protein-DNA complexes. Evidence is given for the existence of a direct relationship between the presence of ordered alpha-helical structures in the histones and a stabilization of the DNA in a B geometry. Infrared linear and ultraviolet dichroism measurements indicate that the N-terminal fragments, rich in basic residues and mostly in a random conformation, remain without any influence on the secondary structure of the nucleic acid, leaving it free in the complexes to undergo a total B----A conformational transition. On the contrary, histone fragments that involve some alpha-helical parts of the protein partially stabilize the DNA in a B geometry. Histone fragments that contain all of the alpha helixes of the protein block the DNA in the same way as the whole corresponding histone. A model for histone-DNA interactions in the core particle is discussed.
Related Concept Videos
The Nucleosome Core Particle
The paradox
Nucleosomes, paradoxically, perform two opposite functions simultaneously. On the one hand, their main responsibility is to protect the delicate DNA strands from physical damage and help achieve a higher compaction ratio. While on the other hand, they must allow polymerase enzymes to access DNA...
Histone Modification
Acetylation
The enzyme histone acetyltransferase adds acetyl group to the histones. Another enzyme, histone deacetylase,...
IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
According to Hooke's law, the vibrational frequency is directly proportional to the...
NMR Spectroscopy Of Amines
The Nucleosome
In a chromosome, DNA is wound twice around a protein complex called a histone octamer core, which consists of 8 histone proteins. This...
The Nucleosome Core Particle
Nucleosomes, paradoxically, perform two opposite functions simultaneously. On the one hand, their primary aim is to protect the delicate DNA strands from physical damage and help achieve a higher compaction ratio. On the other hand, they must allow polymerase enzymes to access histone-bound DNA during...

