Magnetic sensitivity of cryptochrome 4 from a migratory songbird

Nature Springer Nature 594:7864 (2021) 535-540

Authors:

Jingjing Xu, Lauren Jarocha, Tilo Zollitsch, Marcin Konowalczyk, Kevin Henbest, Sabine Richert, Matthew Golesworthy, Jessica Schmidt, Victoire Déjean, Daniel Sowood, Marco Bassetto, Jiate Luo, Jessica Walton, Jessica Fleming, Yujing Wei, Tommy Pitcher, Gabriel Moise, Maike Hermann, Hang Yin, Haijia Wu, Rabea Bartoelke, Stefanie Kaesehagen, Simon Horst, Glen Dautaj, Patrick Murton, Angela Gehrckens, Yogarany Chelliah, Joseph Takahashi, Karl-Wilhelm Koch, Stefan Weber, Ilia Solov'yov, Can Xie, Stuart Mackenzie, Christiane Timmel, Henrik Mouritsen, Peter Hore

Abstract:

Night-migratory songbirds are remarkably proficient navigators1. Flying alone and often over great distances, they use various directional cues including, crucially, a light-dependent magnetic compass2,3. The mechanism of this compass has been suggested to rely on the quantum spin dynamics of photoinduced radical pairs in cryptochrome flavoproteins located in the retinas of the birds4,5,6,7. Here we show that the photochemistry of cryptochrome 4 (CRY4) from the night-migratory European robin (Erithacus rubecula) is magnetically sensitive in vitro, and more so than CRY4 from two non-migratory bird species, chicken (Gallus gallus) and pigeon (Columba livia). Site-specific mutations of ErCRY4 reveal the roles of four successive flavin–tryptophan radical pairs in generating magnetic field effects and in stabilizing potential signalling states in a way that could enable sensing and signalling functions to be independently optimized in night-migratory birds.

ANIMATE: A PHASE II STUDY OF NIVOLUMAB IN TRANSPLANT ELIGIBLE PATIENTS WITH RELAPSED/REFRACTORY CLASSIC HODGKIN LYMPHOMA

Hematological Oncology Wiley 39:S2 (2021)

Authors:

S Booth, A Kirkwood, P Johnson, S Barrington, E Gallop‐Evans, K Peggs, V Warbey, C Burton, A Ardavan, B Phillips, E Lawrie, L Pike, M Northend, L Clifton‐Hadley, R Jenner, GP Collins

EPR of photoexcited triplet state acceptor porphyrins

Journal of Physical Chemistry C American Chemical Society 125:21 (2021) 11782-11790

Authors:

Ashley Redman, Gabriel Moise, Sabine Richert, Erin Viere, William Myers, Michael Therien, Christiane Timmel

Abstract:

The photoexcited triplet states of porphyrin architectures are of significant interest in a wide range of fields including molecular wires, non-linear optics and molecular spintronics. Electron paramagnetic resonance (EPR) is a key spectroscopic tool in the characterization of these transient paramagnetic states singularly well suited to quantify spin delocalization. Previous work proposed a means of extracting the absolute sign of zero-field splitting (ZFS) parameters, D and E, and triplet sublevel populations by transient continuous wave, hyperfine measurements, and magnetophotoselection. Here, we present challenges of this methodology for a series of meso-perfluoroalkyl substituted zinc porphyrin monomers with orthorhombic symmetries, where interpretation of experimental data must proceed with caution and the validity of the assumptions used in the analysis must be scrutinized. The EPR data are discussed alongside quantum chemical calculations, employing both DFT and CASSCF methodologies. Despite some success of the latter in quantifying the magnitude of the ZFS interaction, the results clearly provide motivation to develop improved methods for ZFS calculations of highly delocalized organic triplet states.

Coherent electric field manipulation of Fe3+-spins in PbTiO3

Science Advances American Association for the Advancement of Science 7:10 (2021) eabf8103

Authors:

junjie Liu, Valentin Laguta, Katherine Inzani, Weichuan Huang, Sujit Das, Ruchira Chatterjee, Evan Sheridan, Sinead Griffin, Arzhang Ardavan, Ramamoorthy Ramesh

Abstract:

Magnetoelectrics, materials which exhibit coupling between magnetic and electric degrees of freedom, not only offer a rich environment for studying the fundamental materials physics of spin-charge coupling, but also present opportunities for future information technology paradigms. We present results of electric field manipulation of spins in a ferroelectric medium using dilute Fe3+-doped PbTiO3 as a model system. Combining first-principles calculations and electron paramagnetic resonance (EPR), we show that the Fe3+ spins are preferentially aligned perpendicular to the ferroelectric polar axis, which we can manipulate using an electric field. We also demonstrate coherent control of the phase of spin superpositions by applying electric field pulses during time-resolved EPR measurements. Our results suggest a new pathway towards the manipulation of spins for quantum and classical spintronics.

Probing resonating valence bond states in artificial quantum magnets

Nature Communications Springer Nature 12 (2021) 993

Authors:

Kai Yang, Soo-Hyon Phark, Yujeong Bae, Taner Esat, Arzhang Ardavan, Philip Willke, Andreas Heinrich, Christopher Lutz

Abstract:

Designing and characterizing the many-body behaviors of quantum materials represents a prominent challenge for understanding strongly correlated physics and quantum information processing. We constructed artificial quantum magnets on a surface by using spin-1/2 atoms in a scanning tunneling microscope (STM). These coupled spins feature strong quantum fluctuations due to antiferromagnetic exchange interactions between neighboring atoms. To characterize the resulting collective magnetic states and their energy levels, we performed electron spin resonance on individual atoms within each quantum magnet. This gives atomic-scale access to properties of the exotic quantum many-body states, such as a finite-size realization of a resonating valence bond state. The tunable atomic-scale magnetic field from the STM tip allows us to further characterize and engineer the quantum states. These results open a new avenue to designing and exploring quantum magnets at the atomic scale for applications in spintronics and quantum simulations.