Several migratory animal species use the magnetic field of the earth to navigate during migration. In particular, this includes birds which migrate nocturnally, some species of fish, and the North American monarch butterfly. These species are less able to use visual navigation. However, there is debate about the mechanism by which this internal compass works.
The two leading theories of magnetoreception can be categorised as a magnetite-based system which has been found to be involved most significantly in bacteria.The second, more complex proposed mechanism suggests that select biological molecules can generate radical pairs which are sensitive to the Earth’s magnetic field . Suggested by Thorsten Ritz et al. , this was posited as a theoretical model that has since been inspiration for several in vivo studies.
Behavioural experiments by Wolfgang and Roswitha Wiltschko in the European robin model seems to complement this proposed mechanism of the radical pair mechanism of the avian compass . However, though theoretically compelling, this mechanism still lacks the conclusive empirical biological evidence of the fundamental understanding of the mechanism behind the avian compass.
Magnetosensing of the cryptochrome molecule
Cryptochrome, the putative magnetosensor molecule, has been studied in the fields of chronobiology and circadian rhythmicity, but recently gained popularity for its blue-light receptor function and subsequent production of a radical pair. At the Leverhulme Quantum Biology Doctoral Training Centre, Edeline will be investigating the role of cryptochrome in magnetoreception and investigating the mechanism and interactions through which cryptochrome conveys its magnetosensor function and if this differs between species-specific variants of the protein via in vivo and in vitro characterisation.
Future scope may lead to the use of cryptochrome as a potential (magneto-)optogenetic tool in biotechnology applications.
Spin dynamics of radical pairs in protein systems
Spin dynamics is the study of the evolution of the quantum property of matter known as spin angular momentum (often simply 'spin'). I am interested in studying the spin dynamics of radical pair systems, where two 'lone' electrons attached to different atoms/molecules interact with one another. In the context of quantum biology, this type of research has been used to model the avian magnetic compass via the radical pair mechanism; this is probably the largest growing field within the discipline.
My project is interdisciplinary, here are some ways my interests go across different subjects:
- Physically, I am interested in the evolution of these systems in a general sense: the effect of noise on coherence, non-Markovianity, and thermal effects that arise from such a system being embedded in a biochemical background. I probe this using methods of open quantum systems
- Chemically, I am particularly interested in the activation of the pro-drug isoniazid. Isoniazid is an antitubercular drug whose precise activation mechanism is unknown, one suggested pathway being via the formation of radical pairs. It is thought that specific isotopic substitutions could enhance the singlet-triplet interconversion of such radical pairs due to their large hyperfine coupling. I investigate this with a varied combination of computational chemistry techniques.
Mycobacterium tuberculosis (TB) is a system of interest as it is responsible for the deaths of 1-2 million people worldwide annually and, for example, HIV sufferers are 15-21 times more likely to develop active TB. There are also increased instances of mutations causing drug resistance, thus this study may not only develop the field of quantum biology but also help to combat this problem.
- Primary supervisor: Dr Brendan Howlin
- Co-supervisors: Professor Johnjoe McFadden (University of Surrey) and Dr Daniel Kattnig (University of Exeter).
Tuberculosis tackled by quantum physics: Spin dynamics in isoniazid
Spin physics is central to the radical pair mechanism of the avian compass and is probably the fastest-growing field within quantum biology. However, progress with the avian compass model has been slow, dogged by the difficulties of working with birds as the standard in vivo model. The system described here appears to have quantum biology features that can be measured by one of the simplest measurements in biology: antibiotic resistance. Moreover, the live model system will be in E. coli, which is the simplest and most easily manipulated model organism and the one of which vastly more is known than any other organism. The project will study the radical pair mechanism that has been proposed to be responsible for the action of the antibiotic isoniazid. Isoniazid (INH) is one of the key drugs for treatment of tuberculosis, which affects about 10 million in the world today and kills about 1.5 million of them annually. The target of isoniazid is the catalase-peroxidase, KatG. Complexes of KatG:INH complexes have been crystallized and structure determined (Kamachi et al., 2015) allowing the construction of detailed molecular models of the RPM of INH action. This project will use these resources to test various models of RPM action of isoniazid.
The experimental work of this project will be complemented with a theoretical project to build an RPM model for INH action and generate predictions that will be tested in this experimental project. The theoretical project will be conducted in close collaboration with Dr Daniel Kattnig at the University of Exeter, one of the UK’s experts on the RPM.
University of Surrey
 Hore PJ, Mouritsen H. The radical-pair mechanism of magnetoreception. Annual review of biophysics. 2016 Jul 5;45:299-344.
 Ritz T, Adem S, Schulten K. A model for photoreceptor-based magnetoreception in birds. Biophysical journal. 2000 Feb 1;78(2):707-18.
 Ritz T, Wiltschko R, Hore PJ, Rodgers CT, Stapput K, Thalau P, Timmel CR, Wiltschko W. Magnetic compass of birds is based on a molecule with optimal directional sensitivity. Biophysical journal. 2009 Apr 22;96(8):3451-7.