Chirality in Resonance Energy Transfer: Donor-Imprinted Ellipticity in Achiral Acceptor Emission

Chirality pervades chemistry, yet the Förster mechanism of resonance energy transfer (RET), widely applied in biostructure analysis, is blind to molecular handedness. Through a quantum-electrodynamical analysis that restores the magnetic-dipole contributions neglected in the Förster picture, we identify two ways in which a chiral donor imprints its handedness on energy transfer. The transfer rate becomes handedness-dependent but only in a genuinely chiral environment. Additionally, a chiral donor imprints a circularly polarized signature onto the fluorescence of an otherwise achiral acceptor, a signal that survives in isotropic solution and reverses for the opposite enantiomer of the donor. Compact orientation maps convert these effects into design rules linking geometry to handedness-dependent output, peaking in complementary arrangements. The results may help explain recent chirality-transfer experiments and pave the way for circularly polarized light sources and chirality sensors in which brightness and handedness originate in different molecules.