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CMP
Credit: Jack Hobhouse

Gabriel Moise

Long Term Visitor

Sub department

  • Condensed Matter Physics

Research groups

  • Quantum spin dynamics
gabriel.moise@physics.ox.ac.uk
Clarendon Laboratory, room 262
  • About
  • Publications

Intersystem Crossing Outcompetes Triplet-Pair Separation from 1(TT) below 270 K in Anthradithiophene Films

Journal of the American Chemical Society American Chemical Society (ACS) (2025) jacs.5c00001

Authors:

Eman M Bu Ali, Arnau Bertran, Gabriel Moise, Shuangqing Wang, Rachel C Kilbride, John E Anthony, Claudia E Tait, Jenny Clark
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Spectroscopic Characterization of Radical Pair Photochemistry in Nonmigratory Avian Cryptochromes: Magnetic Field Effects in Gg Cry4a

Journal of the American Chemical Society American Chemical Society 147:28 (2025) 24286-24298

Authors:

Jamie Gravell, Patrick DF Murton, Tommy L Pitcher, Kevin B Henbest, Jessica Schmidt, Madeline M Buffett, Gabriel Moise, Angela S Gehrckens, Daniel R Cubbin, Ana Štuhec, Lewis M Antill, Olivier Paré-Labrosse, Marco Bassetto, Ghazaleh Saberamoli, Jingjing Xu, Corinna Langebrake, Miriam Liedvogel, Erik Schleicher, Stefan Weber, Rabea Bartölke, Henrik Mouritsen, PJ Hore, Stuart R Mackenzie, Christiane R Timmel

Abstract:

The magnetic compass sensor in night-migratory songbirds is thought to be a flavin-tryptophan radical pair formed by blue-light excitation of the protein cryptochrome-4a (Cry4a) localized in photoreceptor cells in the birds’ retinas. The effects of applied magnetic fields on the photochemistry of purified Cry4a from the migratory European robin are well characterized, but it is less clear what, if anything, distinguishes the magnetic responses of the Cry4a proteins from migratory and nonmigratory species. We present here a detailed study of the magnetic sensitivity of Cry4a from the nonmigratory chicken. The wild-type protein is compared with two mutants in which either Arg317 or Glu320, both close to the tryptophan radical, were replaced by the amino acids Cys and Lys, respectively, found in Cry4a from robins and other night-migratory passerines. These sites had previously been identified as probably facilitating the evolution of an optimized magnetic sensor for nocturnal orientation in songbirds. Neither of these mutations was found to affect the reaction kinetics or magnetic sensitivity of the radical pairs, suggesting that any differences in Cry4a between robin and chicken must stem from their ability to transmit magnetic information, for example via protein–protein interactions. In contrast, a Trp → Phe mutation at the end of the tryptophan-tetrad electron transfer chain in both cryptochromes led to a large increase in magnetic sensitivity, suggesting different sensing and signaling roles for the third and fourth tryptophans.
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The impact of spin–orbit coupling on fine-structure and spin polarisation in photoexcited porphyrin triplet states

Journal of Magnetic Resonance Elsevier 355 (2023) 107546

Authors:

Gabriel Moise, Ashley J Redman, Sabine Richert, William K Myers, Ibrahim Bulut, Pernille S Bolls, Michel Rickhaus, Jibin Sun, Harry L Anderson, Christiane R Timmel

Abstract:

The photoexcited triplet states of porphyrins show great promise for applications in the fields of opto-electronics, photonics, molecular wires, and spintronics. The magnetic properties of porphyrin triplet states are most conveniently studied by time-resolved continuous wave and pulse electron spin resonance (ESR). This family of techniques is singularly able to probe small yet essential details of triplet states: zero-field splittings, g-anisotropy, spin polarisation, and hyperfine interactions. These characteristics are linked to spin–orbit coupling (SOC) which is known to have a strong influence on photophysical properties such as intersystem crossing rates. The present study explores SOC effects induced by the presence of Pd2+ in various porphyrin architectures. In particular, the impact of this relativistic interaction on triplet state fine-structure and spin polarisation is investigated. These properties are probed using time-resolved ESR complemented by electron-nuclear double resonance. The findings of this study could influence the future design of molecular spintronic devices. The Pd2+ ion may be incorporated into porphyrin molecular wires as a way of controlling spin polarisation.
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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.
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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.
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