Weighing Molecules with Light | The Royal Society
•February 5, 2026
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Why It Matters
Accurate molecular weighing transforms security screening, doping control, and the development of complex biologics, making mass spectrometry indispensable for both public safety and cutting‑edge medicine.
Key Takeaways
- •Mass spectrometry measures individual molecular masses with extreme precision
- •Light‑based techniques enable detection of trace explosives and steroids
- •Advances allow mass analysis of large biologics like antibodies
- •Native mass spectrometry keeps fragile biomolecules in solution
- •Accurate molecular weighing drives drug development and personalized medicine
Summary
Professor Philip Kukura’s Royal Society lecture explored how modern light‑based methods, especially mass spectrometry, let scientists weigh individual molecules— from tiny explosives to massive therapeutic viruses. He began by tracing the historical need for standardized mass, from barley‑based pounds to Dalton’s atomic theory, showing that precise molecular weight acts like a unique QR code for chemical identity.
Kukura explained the physics of a mass spectrometer: vaporising a sample, ionising it, and steering charged particles through electric fields so that heavier ions take broader turns, landing at distinct detector positions. This simple “ski‑turn” analogy underpins the ability to differentiate compounds such as RDX explosives from the metabolite 3‑hydroxystanozol, enabling airport security and anti‑doping tests.
The talk then highlighted how the technology scales. Traditional small‑molecule drugs like aspirin are easily profiled, but newer biologics—antibody therapies such as Keytruda and gene‑delivery vectors like Zolgensma—contain thousands to millions of atoms and are water‑soluble, challenging conventional gas‑phase analysis. Pioneers like Carol Robinson introduced native mass spectrometry, preserving native conformations and extending accurate mass measurement to these complex therapeutics.
Kukura concluded that as medicines become larger and more sophisticated, precise molecular weighing remains essential for purity verification, regulatory compliance, and the development of next‑generation treatments, cementing mass spectrometry as a cornerstone of modern life‑science research.
Original Description
Join us for the Royal Society Clifford Paterson Prize Lecture delivered by Professor Philipp Kukura FRS.
The Clifford Paterson Medal and Lecture 2026 is awarded to Professor Philipp Kukura FRS for pioneering and democratising mass photometry, a novel means of mass measurement for single biomolecules.
Professor Kukura will cover how the development and use of scales was critical to trade, the creation of money and thus the development of human society. Weight and mass are used somewhat interchangeably for day-to-day objects, but need to be differentiated as objects become smaller and smaller. Once we reach scales much smaller than the width of human hair, gravity is no longer the dominant force experienced by objects and can thus not be used to quantify objects by ‘weighing’ them. Instead, we need to measure their mass, which corresponds to the amount of matter in an object. Due to the difficulty of operating on the microscopic scale, only a very small number of methods have been developed to measure the mass of molecules over the past century. Professor Kukura will describe the development of mass photometry – a method that measures the mass of molecules and viruses by shining light at them, effectively ‘looking at them’. Professor Kukura will explain the principles of operation, and show how this technique is being used broadly in academia and industry to understand the basis of disease and aid in the development of next generation therapeutics.
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