This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: While lithium has been used as a first-line treatment for the long-term management of bipolar disorder for more than 70 years, scientists still do not fully understand how it produces its therapeutic effects in the brain.In a new study published in PLOS ONE, Surrey researchers used computational chemistry and quantum simulations to investigate whether part of the answer could lie in "nuclear spin"—a quantum property that makes an atom's nucleus behave like a tiny magnet, allowing it to influence nearby electrons and potentially change the outcome of chemical reactions. The study focused on the two stable isotopes of lithium—lithium-6 and lithium-7.
Although chemically almost identical, their atomic nuclei have different quantum spins, and previous in vivo studies have found that this means they can produce different biological effects, including differences in their ability to reduce hyperactivity in rats. The team modeled whether this difference could influence a chemical reaction involving flavin, a vitamin B2–derived molecule that helps proteins transfer electrons, and a radical derived from vitamin C (a form of the molecule with an unpaired electron). Vitamin C is abundant in brain cells called neurons and helps protect the brain against oxidative stress, while its radical can retain its spin state for relatively long periods, giving quantum effects more time to potentially influence the reaction.
Simulations showed that lithium-6 and lithium-7 could affect the reaction differently because of their different nuclear spins. The size of the predicted isotope effect was similar to that derived from previous animal studies comparing the behavioral effects of lithium-6 and lithium-7. "What fascinated us was the possibility that two almost chemically identical forms of lithium could influence biology differently because of a quantum property of their nuclei.
"If this difference could affect chemical reactions and ultimately contribute to changes in behavior, it would demonstrate a remarkable link across scales, from atomic nuclei to biological processes. That possibility remains to be tested experimentally. Confirming such a link could open a new avenue for treatment design: fine-tuning how a medicine works by changing its isotopic composition," said Amina Mouhamed, a Ph.D. researcher at the University of Surrey and first author of the study.
While the study does not show that quantum effects are responsible for lithium's therapeutic action, it identifies a possible mechanism that researchers can now test experimentally. "Lithium is an extraordinary drug. It has transformed the treatment of bipolar disorder, yet after decades of clinical use we still do not completely understand what it does at the molecular level.
"Our results do not show that quantum spin effects are responsible for lithium's therapeutic action. What they do show is that such a mechanism is physically plausible in a biologically relevant molecular system and can generate an isotope effect of the right order of magnitude. That gives us a hypothesis we can now begin to test experimentally," said Dr.
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