Force detection of high-frequency electron paramagnetic resonance spectroscopy of microliter solution sample

Abstract

Force detection of magnetic resonance is now able to attain extremely high spin sensitivity. In these setups, microcantilevers were usually used as a sensitive force sensor and, in most cases, have been applied to solid-state samples such as paramagnetic impurities in solids. On the other hand, there are now growing demands for their applications to liquid-state samples in the research areas of life science because many proteins and enzymes are biofunctionally active only in solutions, where they interact with the surrounding water molecules. In this letter, we present an electron paramagnetic resonance (EPR) technique for solution samples using a SiNx nanomembrane and report high-frequency EPR spectroscopy of a microliter-volume frozen solution sample of hemin and myoglobin at multiple frequencies up to 350 GHz. This technique would be particularly useful to obtain more detailed insight into the electronic structure of metalloproteins/metalloenzymes under biologically active conditions.

Force detection of high-frequency electron spin resonance near room temperature using high-power millimeter-wave source gyrotron

“…9 This technique achieved precise broadband spectroscopy of submillimeter-sized samples and microliter solution samples. 10 However, the ESR signal becomes smaller as the temperature increases, which hinders the practical application of this method.…”