A New Initiative in Chemistry Seeks to Clarify Molecular Machines Language
A significant new initiative has been launched to enhance understanding in the advanced field of nanotechnology: molecular machines. Over the years, scientists in this domain have developed remarkable nanoscale devices – including motors, ratchets, switches, and pumps – which emulate the mechanical functions of larger machines, all within the confines of individual molecules. While the innovation and scientific significance are extraordinary – recognized with a Nobel Prize in Chemistry in 2016 – a fundamental issue remains: there is a lack of agreement among scientists regarding the meanings of these terms.
Currently, an international project led by Carson Bruns, a nanomaterials researcher at the University of Colorado Boulder and backed by the International Union of Pure and Applied Chemistry (IUPAC), seeks to standardize the terminology in this field. By establishing clear definitions for what constitutes a “molecular machine” and other related terms, Bruns and his team aim to break down communication barriers, facilitate collaboration, and prepare the discipline for future legal and regulatory considerations.
The Importance of a Unified Language
Despite remarkable advancements in the synthesis and functionality of molecular devices, Bruns notes that the term “molecular machine” has inconsistent usage in published works. A 2022 paper he wrote spurred considerable discussion, highlighting significant disagreement throughout the scientific community – even among leading figures like Nobel laureates Ben Feringa, Jean-Pierre Sauvage, and Fraser Stoddart.
“There are indeed numerous definitions present in the literature,” Bruns states. “Even a single author may revise their stance over time.”
To tackle this, Bruns has gathered a diverse committee under the IUPAC framework, intentionally bringing together differing perspectives on foundational terminology. The ambition is significant: to reach a consensus on a standardized lexicon that benefits the molecular machine community while remaining applicable across evolving technologies.
David Leigh, a pioneer in molecular machines at the University of Manchester, has long championed clearer scientific language. Although not part of the IUPAC committee, Leigh supports the initiative’s objectives, urging caution against overly strict definitions. “It’s a delicate balance between not being too prescriptive,” he remarks, “and being too permissive, which can render the language meaningless.”
Defining the Domain
The term “molecular machine” usually refers to engineered molecular systems that exhibit controlled mechanical movement in response to external stimuli such as light, heat, or chemical energy. This category can encompass:
– Molecular motors: systems that can rotate in a specific direction
– Molecular pumps: molecules that transport substrates contrary to concentration gradients
– Molecular switches: compounds that alternate between at least two stable states
– Molecular ratchets: devices that facilitate unidirectional movement
However, these definitions can often overlap. For instance, should a light-sensitive switch that alters shape be classified as a machine? What about a molecular rotor that spins freely without performing any useful work?
Without a common understanding, there is a risk of miscommunication among researchers, hindering progress.
Bruns and the IUPAC committee are inviting community feedback on this matter: they are participating in major scientific conferences in Japan and the US to gather insights from molecular machine researchers and have initiated two online surveys on Chemistry World for wider input.
The committee’s initial emphasis is on the term “molecular machine” itself. “Since that’s the title of the field, it feels particularly significant,” Bruns clarifies. “If the definition of a molecular machine is ambiguous, then the status of all these other terms is also unclear.”
Legal and Ethical Implications
Aside from settling academic disagreements, Bruns underscores potential real-world situations where formal definitions could have legal implications. For instance, litigation surrounding per- and polyfluoroalkyl substances (PFAS) has relied on precise term definitions. Bruns anticipates that similar situations may arise concerning molecular machines in the future.
“That is likely to happen one day,” he predicts. “When there’s an artificial molecular machine impacting society, there will be lawsuits – and we must be very clear about what defines a molecular machine.”
Indeed, as real-world applications increase – such as nanomachines used for targeted drug delivery or environmental remediation – courts, regulatory bodies, and patent offices will depend on exact and recognized terminology.
Looking Ahead
The field of molecular machines, which emerged in the 1980s, is positioned to become a foundational aspect of future technologies. As synthetic molecular devices become increasingly intricate and their capabilities approach those of biological systems such as kinesin or myosin – proteins responsible for intracellular movement – linguistic clarity will become essential.
Nevertheless, the undertaking is challenging. As Leigh points out, biologists and physicists publish significantly more on molecular motors than chemists. Therefore, any definitions must resonate beyond the realm of synthetic molecular chemists and align with established conventions in other fields.
A unified terminology for molecular machines may not only bring researchers together under one vocabulary – it could solidify