RESUMEN
In recent years, it was found that current passing through chiral molecules exhibits spin preference, an effect known as Chiral Induced Spin Selectivity (CISS). The effect also enables the reduction of scattering and therefore enhances delocalization. As a result, the delocalization of an exciton generated in the dots is not symmetric and relates to the electronic and hole excited spins. In this work utilizing fast spectroscopy on hybrid multilayered QDs with a chiral polypeptide linker system, we probed the interdot chiral coupling on a short time scale. Surprisingly, we found strong coherent coupling and delocalization despite having long 4-nm chiral linkers. We ascribe the results to asymmetric delocalization that is controlled by the electron spin. The effect is not measured when using shorter nonchiral linkers. As the system mimics light-harvesting antennas, the results may shed light on a mechanism of fast and efficient energy transfer in these systems.
RESUMEN
Partially charged chiral molecules act as spin filters, with preference for electron transport toward one type of spin ("up" or "down"), depending on their handedness. This effect is named the chiral induced spin selectivity (CISS) effect. A consequence of this phenomenon is spin polarization concomitant with electric polarization in chiral molecules. These findings were shown by adsorbing chiral molecules on magnetic surfaces and investigating the spin-exchange interaction between the surface and the chiral molecule. This field of study was developed using artificial chiral molecules. Here we used such magnetic surfaces to explore the importance of the intrinsic chiral properties of proteins in determining their stability. First, proteins were adsorbed on paramagnetic and ferromagnetic nanoparticles in a solution, and subsequently urea was gradually added to induce unfolding. The structural stability of proteins was assessed using two methods: bioluminescence measurements used to monitor the activity of the Luciferase enzyme, and fast spectroscopy detecting the distance between two chromophores implanted at the termini of a Barnase core. We found that interactions with magnetic materials altered the structural and functional resilience of the natively folded proteins, affecting their behavior under varying mild denaturing conditions. Minor structural disturbances at low urea concentrations were impeded in association with paramagnetic nanoparticles, whereas at higher urea concentrations, major structural deformation was hindered in association with ferromagnetic nanoparticles. These effects were attributed to spin exchange interactions due to differences in the magnetic imprinting properties of each type of nanoparticle. Additional measurements of proteins on macroscopic magnetic surfaces support this conclusion. The results imply a link between internal spin exchange interactions in a folded protein and its structural and functional integrity on magnetic surfaces. Together with the accumulating knowledge on CISS, our findings suggest that chirality and spin exchange interactions should be considered as additional factors governing protein structures.