Photoinduced Charge-Separation in DNA

DNA-Histone Cross-Link Formation via Hole Trapping in Nucleosome Core Particles

Radical cations (holes) produced in DNA by ionizing radiation and other oxidants yield DNA-protein cross-links (DPCs). Detailed studies of DPC formation in chromatin via this process are lacking. We describe here a comprehensive examination of DPC formation within nucleosome core particles (NCPs), which are the monomeric component of chromatin. DNA holes are introduced at defined sites within NCPs that are constructed from the bottom-up. DPCs form at DNA holes in yields comparable to those of alkali-labile DNA lesions that result from water trapping. DPC-forming efficiency and site preference within the NCP are dependent on translational and rotational positioning. Mass spectrometry and the use of mutant histones reveal that lysine residues in histone N-terminal tails and amino termini are responsible for the DPC formation. These studies are corroborated by computational simulation at the microsecond time scale, showing a wide range of interactions that can precede DPC formation. Three consecutive dGs, which are pervasive in the human genome, including G-quadruplex-forming sequences, are sufficient to produce DPCs that could impact gene expression.

Subsystem density-functional theory: A reliable tool for spin-density based properties

Subsystem density-functional theory compiles a set of features that allow for efficiently calculating properties of very large open-shell radical systems such as organic radical crystals, proteins, or deoxyribonucleic acid stacks. It is computationally less costly than correlated ab initio wave function approaches and can pragmatically avoid the overdelocalization problem of Kohn-Sham density-functional theory without employing hard constraints on the electron-density. Additionally, subsystem density-functional theory calculations commonly start from isolated fragment electron densities, pragmatically preserving a priori specified subsystem spin-patterns throughout the calculation. Methods based on subsystem density-functional theory have seen a rapid development over the past years and have become important tools for describing open-shell properties. In this Perspective, we address open questions and possible developments toward challenging future applications in connection with subsystem density-functional theory for spin-dependent properties.

The mechanism and regularity of quenching the effect of bases on fluorophores: the base-quenched probe method

The base-quenched probe method for detecting single nucleotide polymorphisms (SNPs) relies on real-time PCR and melting-curve analysis, which might require only one pair of primers and one probe.

Photoinduced processes in nucleic acids

Photoinduced processes in nucleic acids are phenomena of fundamental interest in diverse fields, from prebiotic studies, through medical research on carcinogenesis, to the development of bioorganic photodevices. In this contribution we survey many aspects of the research across the boundaries. Starting from a historical background, where the main milestones are identified, we review the main findings of the physical-chemical research of photoinduced processes on several types of nucleic-acid fragments, from monomers to duplexes. We also discuss a number of different issues which are still under debate.