Why Nature is Chiral: The role of chirality in making processes essential for life efficient

Living organisms rely on chiral molecules, such as nucleic acids and proteins. A chiral molecule is not superimposable on its mirror image, also known as its enantiomer, just like our right hand cannot be superimposed on our left hand. Organisms contain only one enantiomeric form of a molecule, a selectivity that has prevailed through evolution. The proposed research examines whether the chiral induced spin selectivity (CISS) effect can explain why enantiomeric purity might provide an advantage in biology. CISS is an electronic phenomenon in which electron transmission through chiral molecules depends on the direction of the electron spin, a quantum mechanical property associated with its magnetic moment. Thus charge displacement and transmission in chiral molecules generates a spin-polarized electron distribution.
Electron transfer and charge separation processes are essential for life, occurring in respiration, photosynthesis, and other processes. By elucidating how electron transfer is linked to the electrons’ spin in a chiral potential, we can reveal an advantage for preserving enantiomeric purity. The proposed research will expose the role of chirality for three fundamental processes: 1) electron transfer, by quantifying the spin dependence of long-range electron transfer in chiral molecules, 2) charge separation, by examining how chirality inhibits charge recombination, and 3) biorecognition, by examining how spin polarization affects enantioselectivity. The research will also address the questions: ‘What is the role of electron spin in biological charge transport?’ and ‘To what extent is electron transfer through peptides coherent?’. These questions will be answered first for simple model systems and then by measurements using peptides and proteins. Also, we will demonstrate our understanding and control of these principles by developing new types of biomimetic devices that exploit these hitherto unknown properties of chiral molecules.