Convolution-based modelling of the stimulus modulation broadening in derivative spectroscopy

This dataset contains the supplementary data to the manuscript under the name "Development of lock-in based overtone Modulated MARY spectroscopy for detection of weak magnetic field effects", as well as demonstration and data analysis scripts

High-sensitivity measurements of weak magnetic field effects

The study of spin chemistry and, in specific, magnetosensitivity has been growing in importance in recent years. Not only has there been great advances in the field of magnetic field effects (MFEs) on biological reactions, but also on their applications in semiconductor and polymer science. Many chemical systems exhibit sensitivity to comparatively weak magnetic fields by a variety of mechanisms. The most prevalent of such magnetic field effect (MFE) mechanisms in solution is the radical pair (RP) mechanism, which will be investigated in this work. Chapter 1 will introduce ideas behind the RP-based magnetosensitivity: the quantum mechanics of spin, the theory of long-range electron transfer, chemical kinetics and finally the RP-mechanism itself. The chapter will conclude by describing the magnetosensitivity of flavin-based systems investigated in this work. A significant part of this work revolved around the understanding, using and development of the methodology involved. Chapter 2 will discuss some of the mathematical and computational methods used throughout this work. The methods covered are the time-frequency analysis, fitting, numerical solutions to differential equations and analysis of uncertainty. The examples used throughout this chapter have been selected to illustrate important points of their respective subjects, but also to be relevant to understanding other parts of this work. Chapter 3 will make use of some of the methodology described in the previous chapter and talk about the development and theoretical treatment of a modulated fluorescence experiment - ModMARY. The chapter will conclude by showcasing the methodology developed to measure a fluorescent exciplex-based system traditionally investigated by ModMARY pyrene / 1,3-dicyanobenzene. The work done in this chapter is the basis of a publication led by the author. The flavin-based system often used in magnetosensitivity studies of biological systems is the solution of flavin mononucleotide (FMN) and hen egg-white lysozyme (HEWL). This system is well known, but not fully understood. The interactions of freely diffusing FMN within a crystal lattice of HEWL has been investigated in Chapter 4, by confocal laser-scanning microscopy (CLSM). The principle of CLSM, as well as the data analysis methodology developed, will be discussed. Then, the spatiotemporal evolution of the MFE of FMN in HEWL crystals will be explored. The work in this chapter is part of a joined publications with Dejéan et al. MFEs can be probed optically not only by fluorescence, as investigated in the aforementioned chapters, but also by absorption techniques. The understanding and development of broadband cavity-enhanced absorption spectroscopy (BBCEAS), and its application to measurements of solution-based cryptochrome samples will be discussed in Chapter 5. The systems of most interest in the field of magnetoreception are the cryptochrome molecules - flavin-binding proteins proposed as the source of the avian magnetic sense. The methodology from previous chapter will be used in Chapter 6 to measure the samples of cryptochrome proteins from five different animal species and their selected mutants. This data will be compared and its implications will be discussed. The work is a part of a joined publications with Xu et al.</p

Detection of Magnetic Field Effects by Confocal Microscopy

This dataset contains raw data and accompanying analysis used in the publication 'Detection of Magnetic Field Effects by Confocal Microscopy' by Dejean et al. The data was recorded using a Zeiss inverted confocal microscope - Exciter 5. The analysis scripts are written in Matlab (R2017b). Please note that the analysis shown here is a simplified version of the code used for the publication and is only meant to showcase the methods used. Pairs of paramagnetic species generated under conservation of total spin angular momentum can undergo magnetosensitive processes. Two prominent examples of systems exhibiting these so-called magnetic field effects (MFEs) are photogenerated radical pairs created from molecular precursors and pairs of triplets generated by singlet fission. Here, we showcase confocal microscopy as a powerful technique for the investigation of such phenomena. We first characterise the instrument studying the field-sensitive chemistry of two systems in solution: radical pairs formed in the protein cryptochrome and the flavin mononucleotide/hen-egg white lysozyme model system. We then extend these studies to single crystals. Firstly, we report temporally- and spatially-resolved MFEs in flavin-doped lysozyme single crystals. Anisotropic magnetic field effects are then reported in tetracene single crystals. Finally, we discuss the future applications of confocal microscopy for the study of magnetosensitive processes with a particular focus on the cryptochrome-based chemical compass believed to lie at the heart of animal magnetoreception

Detection of magnetic field effects by confocal microscopy

Certain pairs of paramagnetic species generated under conservation of total spin angular momentum are known to undergo magnetosensitive processes. Two prominent examples of systems exhibiting these so-called magnetic field effects (MFEs) are photogenerated radical pairs created from either singlet or triplet molecular precursors, and pairs of triplet states generated by singlet fission. Here, we showcase confocal microscopy as a powerful technique for the investigation of such phenomena. We first characterise the instrument by studying the field-sensitive chemistry of two systems in solution: radical pairs formed in a cryptochrome protein and the flavin mononucleotide/hen egg-white lysozyme model system. We then extend these studies to single crystals. Firstly, we report temporally and spatially resolved MFEs in flavin-doped lysozyme single crystals. Anisotropic magnetic field effects are then reported in tetracene single crystals. Finally, we discuss the future applications of confocal microscopy for the study of magnetosensitive processes with a particular focus on the cryptochrome-based chemical compass believed to lie at the heart of animal magnetoreception

Magnetic sensitivity of cryptochrome 4 from a migratory songbird

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