Louie Slocombe and Sara Imari Walker
ACS Cent. Sci. 2024
In a scientific era focused on big data, it is easy to lose sight of the critical role of metrology─the science of measurement─in advancing fundamental science. However, most major scientific advances have been driven by progress in what we measure and how we measure it. An example is the invention of temperature, (1) where before it, we could say one thing was hotter than another but without a standardized, empirical measure we could not say how much hotter. This is not unlike the current state in discussing complexity in chemistry, (2,3) where we can say molecules are complex but lack an empirically validated standardization to confirm that one is more complex than another. In this issue of ACS Central Science, (4) a set of experiments by Leroy Cronin and co-workers conducted at the University of Glasgow aim to change this by providing a new kind of measurement with a well-defined scale, a significant step toward a metrology of complexity in chemistry. Although the concept of quantifying molecular complexity is not new itself, (3) the team leveraged principles from the recently developed theory of molecular assembly (MA) and related ideas (5) to define a rigorous concept of a scale for complexity, connected to a theory for how evolution builds complex molecules. (6,7) They show how the complexity of molecules on this scale can be inferred from standard laboratory spectroscopic techniques, including nuclear magnetic resonance (NMR), infrared (IR) spectroscopy, and tandem mass spectrometry (MS/MS). The robust validation of the inferred complexity across a multimodal suite of techniques instills confidence in the objectivity of the complexity scale proposed and the reliability of its resultant measurement.
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