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Throughout nature, both free radicals and transient radical reaction intermediates are vital to many biological functions. Coenzyme B12 is a case in point. This organometallic cofactor generates a radical pair upon activation in its dependent enzymes by substrate binding and following photolysis. The resulting cob(ii)alamin/5′-deoxyadenosyl radical pair has unusual magnetic properties that present a challenge to detailed investigation at ambient temperatures. Here, we use femtosecond transient absorption spectroscopy adapted for magnetic field exposure to reveal that the spin dynamics of the B12 radical pair are sufficiently fast for magnetic field effects to be observed on the ultrafast reaction kinetics. Moreover, the large difference in g-values between the radicals of the pair means that effects of the Δg mechanism are observed for the first time for a radical pair system exposed to magnetic fields below 1 T. Spin dynamic simulations allow a value of the cob(ii)alamin radical g-value (2.105) at ambient temperature to be extracted and, because the spin dynamic time scale is faster than the diffusional rotation of the cob(ii)alamin radical, the observed value corresponds to the anisotropic g|| value for this radical. [ABSTRACT FROM AUTHOR]

Year 1 of the chemistry degree at the University of Leicester has been significantly changed by the integration of a problem based learning (PBL) component into the introductory inorganic/physical chemistry module, "Chemical Principles". Small groups of 5-6 students were given a series of problems with real world scenarios and were then given the responsibility of planning, researching and constructing solutions to the problem on a group wiki hosted on the University's Virtual Learning Environment (VLE). The introduction of PBL to the course was evaluated both quantitatively and qualitatively. Class test and exam results were analysed and compared with those achieved in previous years (i.e. before the introduction of PBL). It was found that student performance was at least as good as it had been before the introduction of PBL. Retention figures after PBL had risen sharply (not one PBL student dropped out of the course during the first term). Student and staff feedback was also collected for qualitative analysis of the impact of the change. Combining these findings showed that students appeared to show an improvement in, and recognition of the acquisition of, transferable skills and that group work on immediate arrival at university (representing an opportunity to use social skills within an academic exercise) led to high student retention within the PBL cohort. (Contains 3 notes, 2 tables, and 3 figures.)

It has been possible to identify three spin-polarized transient radical species by time-resolved EPR techniques. These species are .CH2SOCH3, (CH3)2SO(OH). and .CH3.

We demonstrate, by direct, single-cell imaging kinetic measurements, that endogenous autofluorescence in HeLa cells is sensitive to the application of external magnetic fields of 25 mT and less. We provide spectroscopic and mechanistic evidence that our findings can be explained in terms of magnetic field effects on photoinduced electron transfer reactions to flavins, through the radical pair mechanism. The observed magnetic field dependence is consistent with a triplet-born radical pair and a B1/2 value of 18.0 mT with a saturation value of 3.7%. [ABSTRACT FROM AUTHOR]

Due to the photobiology of the flavoproteins DNA photolyase and cryptochrome, electron transfer reactions between flavins and tryptophan are of significant biological relevance. In addition, electron transfer across vesicle membranes has also seen much attention. In this work, we study the electron transfer reaction between flavins and tryptophan across lipid bilayer membranes in 1,2-dipalmitoyl-sn-glycero-3-phosphocholine small unilamellar vesicles using time-resolved optical absorption microspectroscopy and magnetically affected reaction yield spectroscopy. We demonstrate that riboflavin tetrabutyrate is embedded in the vesicle bilayer and can undergo electron transfer with tryptophan molecules in either the inner water pool or the bulk solution. Remarkably, flavin mononucleotide encapsulated in the inner water pool can undergo electron transfer across the vesicle bilayer to generate a magnetically sensitive radical pair with tryptophan molecules located in the bulk solution. The observed kinetics suggest that back electron transfer occurs between radical pairs generated by diffusive reencounter, either in the vesicle surface water or via electron hopping through degenerate electron exchange. [ABSTRACT FROM AUTHOR]

In this work, we propose to extend the scope of single-molecule spectroscopy to spin chemistry investigations of single radical pairs. A consistent theory of single-molecule spectroscopy on single radical pairs is proposed, which allows one to show that bunching phenomena are affected by singlet–triplet interconversion in radical pairs, which is, in turn, affected by local and external magnetic fields. A detailed study on the feasibility of such experiments with single flavin adenine dinucleotide, FAD, molecules is presented. We conclude that the observation of magnetic field effects on single FAD molecules is feasible but experimentally challenging for measurements on integrated fluorescence intensity and fluorescence event statistics. [ABSTRACT FROM AUTHOR]

Continuous wave photolysis magnetic field effect (MFE) data has disclosed the ethanolamine ammonia lyase (EAL) active site to be an ideal microreactor for observing enhanced magnetic field sensitivity in the adenosylcobalamin radical pair. The results have shown that rapid radical quenching, through the coupling of homolysis and hydrogen abstraction steps, and subsequent radical pair stabilization has contributed to the rate acceleration of Co-C bond homolysis in adenosylcobalamin-dependent enzymes.

Time-resolved mid-infrared spectroscopy was used to study the radical recombination of radicals generated from the photolysis of alpha-HP on a micro-second time scale. The reaction exhibited opposite magnetic field dependencies at 2 and 21 mT, the effect at low-field being the first such observation for neutral free radicals in isotropic solution.

The case study method is nothing new: cases in their real-world context have been used not only for research but also for teaching in different disciplines for many decades. Multidisciplinary collaborative teaching and learning frameworks, however, can contribute to the development of sustainability case-based education in rather innovative ways. To exemplify this, the present paper will particularly examine the transformative potential of the introduction of a "legal perspective" to promote students' learning into a co-taught course based on a range of selected case studies about sustainability in industrial companies and whose main feature consists in involving instructors and students from various educational backgrounds and two different higher education institutions, namely Uppsala University in Sweden and the University of Tokyo in Japan. [ABSTRACT FROM AUTHOR]

The hydrogen abstraction reaction of benzophenone in micellar interiors were studied by the effect of a short, resonant microwave pulse on the recombination kinetics under magnetic fields of approximately 0.3 T. All kinetic parameters are extracted for each system using a combination of single pulse and pulse shift measurements.

A detailed reinvestigation of a reported magnetic field effect (MFE), in the haem-dependent enzyme horseradish peroxide (HRP) by the use of a stooped-flow device adapted to make high-precision single-wavelength measurements in the presence of a static magnetic field is presented. The results demonstrate the absence of MFE in the reductive half-reaction of HRP-catalyzed cycle and identify problems with the analysis of kinetic data in the original study.

Hydrogen-release by photoexcitation, excited-state-hydrogen-transfer (ESHT), is one of the important photochemical processes that occur in aromatic acids and is responsible for photoprotection of biomolecules. The mechanism is described by conversion of the initial state to a charge-separated state along the O(N)-H bond elongation, leading to dissociation. Thus ESHT is not a simple H-atom transfer in which a proton and a 1s electron move together. Here we show that the electron-transfer and the proton-motion are decoupled in gas-phase ESHT. We monitor electron and proton transfer independently by picosecond time-resolved near-infrared and infrared spectroscopy for isolated phenol-(ammonia)5, a benchmark molecular cluster. Electron transfer from phenol to ammonia occurred in less than 3 picoseconds, while the overall H-atom transfer took 15 picoseconds. The observed electron-proton decoupling will allow for a deeper understanding and control of of photochemistry in biomolecules. [ABSTRACT FROM AUTHOR]

Hydrogen-release by photoexcitation, excited-statehydrogen- transfer (ESHT), is one of the important photochemical processes that occur in aromatic acids and is responsible for photoprotection of biomolecules. The mechanism is described by conversion of the initial state to a chargeseparated state along the O(N)-H bond elongation, leading to dissociation. Thus ESHT is not a simple H-atom transfer in which a proton and a 1s electron move together Here we show that the electron-transfer and the proton-motion are decoupled in gas-phase ESHT. We monitor electron and proton transfer independently by picosecond time-resolved near-infrared and infrared spectroscopy for isolated phenol-(ammonia)5, a benchmark molecular cluster Electron transfer from phenol to ammonia occurred in less than 3 picoseconds, while the overall H-atom transfer took 15 picoseconds. The observed electron-proton decoupling will allow for a deeper understanding and control of of photochemistry in biomolecules. [ABSTRACT FROM AUTHOR]