A differential lithium isotope effect on amorphous calcium phosphate formation at the nanoscale

Calcium phosphate plays an important and multi-faceted role in biological systems, ranging from mitochondrial signaling pathways to biomineralization processes such as bone growth. More recently, symmetric calcium phosphate nanoparticles known as Posner molecules have been theorized to serve as a putative ‘neural qubit’ via protected phosphorus nuclear spin states in a biological environment. Thus, understanding calcium phosphate nucleation and aggregation is key to testing the theory for Posner-mediated quantum activity in the brain. Here, we demonstrate using a combination of in vitro experimental methods that the prenucleation and aggregation behavior of amorphous calcium phosphate is differentially influenced by two isotopes of lithium, ⁶Li and ⁷Li. The two isotopes have nearly identical chemical behavior in solution, suggesting a quantum mechanical effect on calcium phosphate nucleation and aggregation. We situate this differential isotope effect within the context of calcium phosphate phase behavior, which helps to isolate pathways in which quantum mechanics may be at play. We expect that our results will help explain lithium isotope effects seen in vivo in various contexts, and advance our understanding of a wider range of nonclassical isotope effects in biology.