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: The truth is out there—but identifying signs of life in space involves an intense search for biosignatures within our solar system and beyond. However, developing sensitive yet compact technologies capable of detection has proven to be an out-of-this-world challenge.
That may be set to change, as researchers at the University of Osaka have developed an electrical method that could be used to detect extraterrestrial life. This discovery is set to be published in Nature Communications. Distinguishing living beings from nonliving chemicals and processes relies on amino acids, the building blocks of proteins.
The two mirror-image forms of an amino acid have the same chemical formula but can help distinguish the living from the nonliving. For living creatures, almost all amino acids are exclusively in the L-form, with sugars existing in the D-form. By contrast, nonliving chemical and physical processes produce both L- and D-forms in equal abundance.
Consequently, the L/D ratio is a potential biosignature of life, making amino acids an ideal target for astrobiology research. Traditional methods distinguish samples by measuring large groups of molecules, presenting researchers with practical challenges. It has been suggested that an alternative method involving electrical detection would be simpler, less sensitive to vibrations and circumvent the use of chemical reagents.
Recent developments in nanotechnology were harnessed to electrically detect single molecules of biological relevance. To do this, the team measures molecules passing through a gap between two gold nanowires, which generates an electrical tunneling current. As the current waveforms of each form of amino acid are different from one another, the team could directly count the number of molecules passing through the gap.
"By combining our nanogap tunneling technique with artificial intelligence, we were able to distinguish between the L- and D-forms of amino acids with over 80% accuracy," says lead author Takahito Oshiro. "This is the first discrimination of amino acid chirality at the single-molecule level and constitutes a fundamental advance in chemical sensing." As astrobiological samples typically contain many types of molecules, the team tested whether the technique could be used to identify amino acids in complex mixtures. "We analyzed natural samples from the Murchison meteorite in Australia and soil samples from the Atacama Desert in Chile," explains senior author Masateru Taniguchi.
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