Renormalization of myoglobin-ligand binding energetics by quantum many-body effects

C. Weber, D. J. Cole, D. D. O’Regan, and M. C. Payne

Apr. 22, 2014

Abstract: We carry out a first-principles atomistic study of the electronic mechanisms of ligand binding and discrimination in the myoglobin protein. Electronic correlation effects are taken into account using one of the most advanced methods currently available, namely a linear-scaling density functional theory (DFT) approach wherein the treatment of localized iron 3d electrons is further refined using dynamical mean-field theory. This combination of methods explicitly accounts for dynamical and multireference quantum physics, such as valence and spin fluctuations, of the 3d electrons, while treating a significant proportion of the protein (more than 1,000 atoms) with DFT. The computed electronic structure of the myoglobin complexes and the nature of the Fe–O2 bonding are validated against experimental spectroscopic observables. We elucidate and solve a long-standing problem related to the quantum-mechanical description of the respiration process, namely that DFT calculations predict a strong imbalance between O2 and CO binding, favouring the latter to an unphysically large extent. We show that the explicit inclusion of the many-body effects induced by the Hund’s coupling mechanism results in the correct prediction of similar binding energies for oxy- and carbonmonoxymyoglobin. [1]

[1] C. Weber, et al“Renormalization of myoglobin-ligand binding energetics by quantum many-body effects”, Proc. Natl. Acad. Sci. USA, 2014 111 (16) 5790-5795.

Importance of many body effects in the kernel of hemoglobin for ligand binding

C. Weber, D. D. O’Regan, N. D. M. Hine, P. B. Littlewood, G. Kotliar, and M. C. Payne

Mar. 6, 2013

Abstract: We propose a mechanism for binding of diatomic ligands to heme based on a dynamical orbital selection process. This scenario may be described as bonding determined by local valence fluctuations. We support this model using linear-scaling first-principles calculations, in combination with dynamical mean-field theory, applied to heme, the kernel of the hemoglobin metalloprotein central to human respiration. We find that variations in Hund’s exchange coupling induce a reduction of the iron 3d density, with a concomitant increase of valence fluctuations. We discuss the comparison between our computed optical absorption spectra and experimental data, our picture accounting for the observation of optical transitions in the infrared regime, and how the Hund’s coupling reduces, by a factor of 5, the strong imbalance in the binding energies of heme with CO and O_2 ligands. [1]

[1] C. Weber et al“Importance of many body effects in the kernel of hemoglobin for ligand binding”, Phys. Rev. Lett., 110, 106402 (2013).

Self-assembled quantum dots in a nanowire system for quantum photonics

M. Heiss, Y. Fontana, A. Gustafsson, G. Wüst, C. Magen, D. D. O’Regan, J. W. Luo, B. Ketterer, S. Conesa-Boj, A. V. Kuhlmann, J. Houel, E. Russo- Averchi, J. R. Morante, M. Cantoni, N. Marzari, J. Arbiol, A. Zunger, R. J. Warburton, and A. Fontcuberta i Morral

Feb. 3, 2013

Abstract: Quantum dots embedded within nanowires represent one of the most promising technologies for applications in quantum photonics. Whereas the top-down fabrication of such structures remains a technological challenge, their bottom-up fabrication through self-assembly is a potentially more powerful strategy. However, present approaches often yield quantum dots with large optical linewidths, making reproducibility of their physical properties difficult. We present a versatile quantum-dot-in-nanowire system that reproducibly self-assembles in core–shell GaAs/ AlGaAs nanowires. The quantum dots form at the apex of a GaAs/AlGaAs interface, are highly stable, and can be positioned with nanometre precision relative to the nanowire centre. Unusually, their emission is blue-shifted relative to the lowest energy continuum states of the GaAs core. Large-scale electronic structure calculations show that the origin of the optical transitions lies in quantum confinement due to Al-rich barriers. By emitting in the red and self-assembling on silicon substrates, these quantum dots could therefore become building blocks for solidstate lighting devices and third-generation solar cells. [1]

[1] M. Heiss et. al, “Self-assembled quantum dots in a nanowire system for quantum photonics”, Nature Materials, 12, 439–444 (2013).

Vanadium dioxide: A Peierls-Mott insulator stable against disorder

C. Weber, D. D. O’Regan, N. D. M. Hine, M. C. Payne, G. Kotliar, and P. B. Littlewood

June 20, 2012

Abstract: Vanadium dioxide undergoes a first order metal-insulator transition at 340 K. In this Letter, we develop and carry out state-of-the-art linear scaling density-functional theory calculations refined with nonlocal dynamical mean-field theory. We identify a complex mechanism, a Peierls-assisted orbital selection Mott instability, which is responsible for the insulating M_1 phase, and which furthermore survives a moderate degree of disorder. [1]

[1] C. Weber, et al“Vanadium dioxide: A Peierls-Mott insulator stable against disorder”, Phys. Rev. Lett. 108, 256402 (2012)