Time-resolved optical absorption microspectroscopy of magnetic field sensitive flavin photochemistry

Abstract

The photochemical reactions of blue-light receptor proteins have received much attention due to their very important biological functions. In addition, there is also growing evidence that the one particular class of such proteins, the cryptochromes, may be associated with not only a biological photo-response but also a magneto-response, which may be responsible for the mechanism by which many animals can respond to the weak geomagnetic field. Therefore, there is an important scientific question over whether it is possible to directly observe such photochemical processes, and indeed the effects of weak magnetic fields thereon, taking place both in purified protein samples in vitro and in actual biochemical cells and tissues. For the former samples, the key lies in being able to make sensitive spectroscopic measurements on very small volumes of samples at potentially low protein concentrations, while the latter requires, in addition, spatially resolved measurements on length scales smaller than typical cellular components, i.e., sub-micron resolution. In this work, we discuss a two- and three-color confocal pump-probe microscopic approach to this question which satisfies these requirements and is thus useful for experimental measurements in both cases.

Cellular autofluorescence is magnetic field sensitive

“…In recent years, to address this problem and to directly investigate MFEs of RPs in biological systems, some research groups, including ours, have developed a number of microscope-based imaging approaches [transient absorption (TA) based (15,16) and fluorescence based (17)]. Some of our recent experiments have demonstrated that the photochemistry of FAD in aqueous solution is magnetic field sensitive, even at physiological pH, using our TA-based microscope (18).…”

Development of lock-in based overtone modulated MARY spectroscopy for detection of weak magnetic field effects

“…20 There are other, related, techniques which make use of the field-modulation and derivative detection. In recent years, field-modulation technique has been combined with laser scanning to yield both fluorescence 21 and absorptionbased ModMARY imaging 22,23 (referred to as magnetofluorescence imaging (MFI) and magnetic intensity modulation (MIM) imaging respectively). The general technique of stimulus-modulation can be seen in many fields of spectroscopy, most notably optical spectroscopy, for example in frequency (wavelength) modulation using tunable light sources, cavity spectroscopy and electron paramagnetic resonance (EPR).…”

Development of Lock-in Based Overtone Modulated MARY Spectroscopy for Detection of Weak Magnetic Field Effects

“…20 There are other, related, techniques which make use of the field-modulation and derivative detection. In recent years, field-modulation technique has been combined with laser scanning to yield both fluorescence 21 and absorptionbased ModMARY imaging 22,23 (referred to as magnetofluorescence imaging (MFI) and magnetic intensity modulation (MIM) imaging respectively). The general technique of stimulus-modulation can be seen in many fields of spectroscopy, most notably optical spectroscopy, for example in frequency (wavelength) modulation using tunable light sources, cavity spectroscopy and electron paramagnetic resonance (EPR).…”