Cryptochrome magnetoreception: four tryptophans could be better than three

The biophysical mechanism of the magnetic compass sensor in migratory songbirds is thought to involve photo-induced radical pairs formed in cryptochrome (Cry) flavoproteins located in photoreceptor cells in the eyes. In Cry4a—the most likely of the six known avian Crys to have a magnetic sensing function—four radical pair states are formed sequentially by the stepwise transfer of an electron along a chain of four tryptophan residues to the photo-excited flavin. In purified Cry4a from the migratory European robin, the third of these flavin–tryptophan radical pairs is more magnetically sensitive than the fourth, consistent with the smaller separation of the radicals in the former. Here, we explore the idea that these two radical pair states of Cry4a could exist in rapid dynamic equilibrium such that the key magnetic and kinetic properties are weighted averages. Spin dynamics simulations suggest that the third radical pair is largely responsible for magnetic sensing while the fourth may be better placed to initiate magnetic signalling particularly if the terminal tryptophan radical can be reduced by a nearby tyrosine. Such an arrangement could have allowed independent optimization of the essential sensing and signalling functions of the protein. It might also rationalize why avian Cry4a has four tryptophans while Crys from plants have only three.

Magnetic Functionalization of Scanning Probes by Focused Electron Beam Induced Deposition Technology

The fabrication of nanostructures with high resolution and precise control of the deposition site makes Focused Electron Beam Induced Deposition (FEBID) a unique nanolithography process. In the case of magnetic materials, apart from the FEBID potential in standard substrates for multiple applications in data storage and logic, the use of this technology for the growth of nanomagnets on different types of scanning probes opens new paths in magnetic sensing, becoming a benchmark for magnetic functionalization. This work reviews the recent advances in the integration of FEBID magnetic nanostructures onto cantilevers to produce advanced magnetic sensing devices with unprecedented performance.

Recent Reports of Magneto-Mechano-Electric Conversion Composites

Magneto-mechano-electric (MME) conversion composites composed of distinctive magnetostrictive and piezoelectric materials derive interfacial coupling of magnetoelectric conversion between magnetic and electric properties, thus enabling energy harvesting and magnetic sensing. To demonstrate high-performance MME composites and their applications, various research teams have studied tailoring device structures, enhancing material properties, and developing MME application system. This article reviews the recent research progress of MME composites for energy harvesting and magnetic sensing.