Osaka team's nanogap sensor reads amino acid chirality one molecule at a time
Japanese researchers report a gold-wire nanogap and AI pipeline that distinguish L- and D-amino acids in single molecules with over 80 per cent accuracy, tested on meteorite and desert soil.
A team at the University of Osaka has demonstrated that an electrical sensor can distinguish the two mirror-image forms of amino acids one molecule at a time, reporting an accuracy above 80 per cent. The results appear in Nature Communications, with Takahito Oshiro and Masateru Taniguchi among the authors. The significance lies in chirality: proteins in terrestrial organisms are built almost entirely from L-amino acids, while non-biological synthesis generally produces both L- and D-forms in comparable proportions. That ratio can therefore serve as a biosignature — but not, on its own, as proof of life, since abiotic chemistry also generates amino acids.
The mechanism is a nanogap. A thin gold wire is broken to leave two nanoelectrodes separated by a minute gap; when a single amino acid molecule passes through, it alters the tunnel current and generates a characteristic current curve. An artificial-intelligence routine classifies those signals and assigns them to one of the two mirror forms, counting events at the single-molecule level rather than averaging a bulk measurement. Oshiro described the work as the first discrimination of amino acid chirality at the single-molecule level and, in the team's assessment, a fundamental advance in chemical sensing.
To test the approach under less tidy conditions, the group analysed natural samples: material from the Murchison meteorite in Australia and soil from Chile's Atacama Desert, a site treated as a Mars analogue because of its extreme dryness. Taniguchi said the method was comparable to traditional procedures in capturing the main features of amino acid composition. The technique extends an instrument concept called ELIE, a solid-state system using nanogap sensors that members of the same group had already examined as a possible biological sensor for planetary missions.
The practical case for flight hardware rests on two claimed advantages: electrical detection is expected to be less sensitive to vibration and is intended to operate without chemical reagents, both of which could reduce the effort of building a compact instrument. Against that, the Osaka team notes that an accuracy above 80 per cent is not error-free, and that such advantages must still be technically validated for specific missions. A future instrument would also need to quantify L- and D-fractions reliably across different mixtures and control interfering signals. The study presents a technological route to reading a possible biosignature; the composition it reveals would still have to be interpreted within its geological and chemical context. The linked coverage does not report the number of molecules or samples analysed. The next step to watch is technical validation of the sensor for concrete mission concepts.