Chem. J. Chinese Universities ›› 2015, Vol. 36 ›› Issue (11): 2271.doi: 10.7503/cjcu20150651

• Physical Chemistry • Previous Articles     Next Articles

Metastable Hydrogen-bonds Featuring Negative Dissociation Energies in Protein-bound DNA in Hole Migration

WANG Mei1,2, WANG Jun1, BU Yuxiang1,*()   

  1. 1.School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
    2.Department of Physics, Qufu Normal University, Qufu 273165, China
  • Received:2015-08-14 Online:2015-11-10 Published:2015-10-21
  • Contact: BU Yuxiang E-mail:byx@sdu.edu.cn

Abstract:

We theoretically investigated the properties of hydrogen bonds in the protein-bound DNA trimer(protona-ted arginine…guanine…cytosine, ArgH+-GC) units as hole migration carriers using density functional theory calculations. Results suggest these hydrogen bonds are metastable and feature considerable negative dissociation energies upon hole migration through the ArgH+-GC units of the carriers. Normally, the ArgH+ group can H-bond with the guanine-cytosine(GC) base pair in the major/minor-groove face with positive dissociation energy. However, hole trapping weakens the H-bonds to being metastable with a mild dissociation barrier and considerable negative dissociation energy. This barrier-inhibited negative dissociation energy phenomenon implies that the trimer motif can store energy(ca.108.48 kJ/mol) in its ArgH+…N7/O6 bond zone due to hole-trapping. This H-bond dissociation channel is governed by a balance between electrostatic repulsion and H-bonding attraction in the two associated moieties and different attenuations of two opposite interactions with respect to the H-bond distance. The topological properties of electron densities and the Laplacian values at the bond critical points clarify that this energetic phenomenon mainly originates from additional electrostatic repulsions between two moieties linked via high-energy H-bonds(ArgH+…N7/O6). Proton transfer from G induced by hole-trapping can expand the negative dissociation energy zone to both the ArgH+…N7/O6 and Watson-Crick(WC) H-bond zones. In addition, the placement of ArgH+ at the major/minor grooves of DNA where ArgH+ could interact with the GC unit increases its ionization potential, and thus weakens its hole-relaying ability in different degrees, depending on the separation between ArgH+ and GC. Similar phenomena can be observed in the protonated lysine-GC and protonated histidine-GC cases. Clearly, such property-tunable metastable H-bonds can regulate the hole migration mechanism. This work provides some important energetic information for understanding the protein-regulated hole migration mechanism in DNA.

Key words: Metastable hydrogen bond, Negative dissociation energy, Protein-regulated DNA hole migration, Protonated arginine residue, Hole trapping

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