Biology subjects

Antill, L. M.

Publications and source records attributed to Antill, L. M..

6 recordsLinked to original sources

bioRxiv2026

Organelle-Specific pH Quantification Using a Protein-Based Quantum Sensor

Quantum sensing enables measurements of physicochemical changes within living cells at the organelle level. Conventional nanoparticle-based sensors, however, face limitations in subcellular targeting, intracellular tracking, and following dynamic biological processes across distinct intracellular environments. Here, we investigate MagLOV2, a genetically encoded quantum sensor, by examining its organelle-specific localization, magnetic field effects (MFEs) during mitophagy, and pH dependent response kinetics. MagLOV2 retained magnetic responsiveness in the cytoplasm, nucleus, and mitochondria, with fluorescence contrasts of 17.1%, 12.3%, and 28.0%, respectively. Optimization of mitochondrial targeting increased fluorescence 2.7 fold. During CCCP induced mitophagy, lysosomal colocalization of MagLOV2 increased from 20.75% to 89.73%, accompanied by slower MFE responses in acidic compartments. Purified MagLOV2 showed response times ranging from 8.27 s at pH 4.5 to 1.56 s at pH 9.5. Structural, spectral, and kinetic analyses suggested that protonation dependent flavin photochemistry and the surrounding protein environment contribute to this behavior. These measurements demonstrate that genetically targeted MagLOV2 can follow organelle transport and report local acidification through changes in magnetic-response kinetics.

biophysics↗

bioRxiv2026

Structure-defined amplification of spin-dependent radical-pair reactivity in mitochondrial complex I

Mitochondrial complex I generates reactive oxygen species (ROS), but whether radical pair spin dynamics shape these reactions is unknown. We combined cryo-electron microscopy-guided oxygen sampling with radical pair quantum dynamics to examine how the protein environment around flavin mononucleotide (FMN) shapes spin-dependent reaction outcomes. Sterically accessible oxygen positions clustered near FMN, and spin sensitivity concentrated in a narrow region about 3.3 angstroms away, where magnetic coupling between radicals is strong. This hotspot was robust across varying reaction rates, although its magnitude fell sharply with faster spin dephasing, implying observable effects require unusually slow dephasing. Magnetic sensitivity itself showed no sharp peak near FMN, rising instead to a plateau farther away, indicating the hotspot reflects accessibility rather than a localized maximum. Structural fluctuations produced greater yield variability within the hotspot, suggesting the FMN pocket amplifies small geometric changes into heterogeneous ROS outcomes, linking structure to spin-dependent chemistry in complex I.

biophysics↗

bioRxiv2026

Revealing properties for enhanced quantum sensing in engineered proteins

Genetically encoded flavoproteins have emerged as optically readable radical pair quantum sensors, but the molecular basis of the differing magnetic responses of closely related variants remains unresolved. Here, we analyse parental AsLOV2 and three evolved MagLOV variants using molecular dynamics, quantum chemical hyperfine calculations, Marcus electron transfer theory, and trajectory-based spin relaxation analysis. The mutations preserve the LOV fold and FMN-binding core but progressively reshape the conformational landscape of the W89 electron donor, with broader rigid-body libration yet increasingly restricted internal torsional motion and predominant occupation of a single rotameric basin in MagLOV2f. These distinct motions have different magnetic consequences: dipolar coupling modulation increases strongly in the later variants, whereas hyperfine modulation rates vary non-monotonically and decrease from MagLOV2 to MagLOV2f. The mutations also alter the radical pair free energy landscape and donor-acceptor orientation, producing variant-dependent back electron transfer rates, with MagLOV2f combining comparatively fast calculated recombination with reduced hyperfine relaxation relative to MagLOV2. Thus, directed evolution redistributes competing recombination and relaxation pathways rather than optimising a single kinetic parameter. This molecular picture rationalises the distinct magnetic-response amplitudes and saturation dynamics of closely related MagLOV proteins and identifies donor conformational control as a practical design variable for protein-based radical pair quantum sensors.

biophysics↗

bioRxiv2026

Magnetic sensitivity of cryptochrome 4a in domesticated quail with migratory origins

Magnetoreception, the ability of animals to sense the Earths magnetic field, is a fascinating biological phenomenon. Cryptochromes, in particular cryptochrome 4a (CRY4a), have emerged as potential key players in mediating magnetic sensing in various bird species. Building on an earlier investigation of magnetic field effects on European robin (Erithacus rubecula) CRY4a, we focus here on CRY4a from the common/Japanese quail (Coturnix coturnix/japonica). Japanese quail is one of the very small number of domesticated bird species whose wild forms are migratory. A detailed spectroscopic study of purified quail CRY4a shows that it has magnetic properties similar to robin CRY4a, suggesting that the quail could be a promising additional experimental model with which to unravel the intricacies of magnetoreception in migratory birds.

biophysics↗

bioRxiv2024

Quantum Correlations in Engineered Magneto-Sensitive Fluorescent Proteins Enables Multi-Modal Sensing in Living Cells

Quantum mechanical phenomena have been identified as fundamentally significant to an increasing number of biological processes. Simultaneously, quantum sensing is emerging as a cutting-edge technology for diverse applications across materials and biological science. However, until recently, biological based candidates for quantum sensors have been limited to in vitro systems, were prone to light induced degradation, and the experimental setups involved are typically not amenable to high-throughput study as would enable further engineering e.g. via directed evolution. We recently created a new class of magneto-sensitive fluorescent proteins (MFPs), which we show overcome these challenges and represent a new form of engineered biological quantum sensors that function both at physiological conditions and in living cells. Through directed evolution, we demonstrate the possibility of engineering these proteins to alter properties of their response to magnetic fields and radio frequencies. These effects are explained in terms of the radical pair mechanism (RPM), involving the protein backbone and a bound flavin cofactor. Using this engineered system we demonstrate the first observation of a fluorescent protein exhibiting Optically Detected Magnetic Resonance (ODMR) in living bacterial cells at room temperature, at sufficiently high signal-to-noise to be detected in a single cell. These magnetic resonance and magnetic field effects measured via fluorescence enable novel technologies; examples we demonstrate include spatial localisation of fluorescence signals using gradient fields (i.e. Magnetic Resonance Imaging (MRI) using a genetically encoded probe), sensing of the molecular microenvironment, multiplexing of bio-imaging, and lock-in detection, overcoming typical fluorescence imaging challenges of light scattering and autofluorescence. Taken together, our results represent a new range of sensing modalities for engineered biological systems, based on and designed around understanding the quantum mechanical properties of MFPs.

bioengineering↗

bioRxiv2023

Dimerisation of European robin cryptochrome 4a

Homo-dimer formation is important for the function of many proteins. Although dimeric forms of cryptochromes (Cry) have been found by crystallography and were recently observed in vitro for European robin Cry4a, little is known about the dimerisation of avian cryptochromes and the role it could play in the mechanism of magnetic sensing in migratory birds. Here we present a combined experimental and computational investigation of the dimerisation of robin Cry4a resulting from covalent and non-covalent interactions. Experimental studies using native mass spectrometry, mass spectrometric analysis of disulphide bonds, chemical cross-linking and photometric measurements show that disulphide-linked dimers are routinely formed, the most likely cysteines being C317 and C412. Computational modelling and molecular dynamics simulations were used to generate and assess a number of possible dimer structures. The relevance of these findings to the proposed role of Cry4a in avian magnetoreception is discussed.

biochemistry↗