Science & Technology, Singapore (Commonwealth Union) – Scientists hailing from the Department of Biological Sciences at the National University of Singapore (NUS), in collaboration with the French Centre for Scientific Research (CNRS), have orchestrated a groundbreaking feat. Their team has triumphantly synthesized a distinctive protein-mimicking entity capable of autonomous self-assembly into a structural configuration resembling pores. Once embedded within a lipid membrane, these pores exhibit a unique ability to facilitate the exclusive passage of water through the membrane while repelling salt ions. These artificial protein-mimics, termed ‘oligourea foldamers,’ introduce an entirely novel category of artificial water channels (AWC) that hold potential to revolutionize contemporary techniques of industrial water purification.
Current methodologies for water purification primarily rely on reverse osmosis and membrane distillation technologies. However, the reverse osmosis technique entails a notable drawback, as it mandates substantial energy consumption due to the necessity for elevated pressures to drive seawater or wastewater through semi-permeable membranes for the elimination of salts and other contaminants. Given the pressing concerns of climate change and the escalating demand for freshwater resources, the drive to devise energy-efficient membranes capable of selective water filtration for large-scale desalination endeavors has intensified. This recent breakthrough stands as a commendable stride towards this objective. The elevated water permeability exhibited by the pores sculpted by these oligourea foldamers hints at the prospect of substantial energy reduction in the broader context of water purification requirements.
Extensive research efforts within this domain have predominantly concentrated on the fabrication of membranes integrating aquaporins, naturally-occurring proteins boasting pores that enable the passage of water molecules in a singular procession. These proteinaceous ‘water channels’ are ubiquitous, gracing the cell membranes of various life forms, encompassing microbes, plants, and animals alike. However, the intricate architecture of aquaporins poses a challenge in the endeavor to synthesize substantial quantities of these sizeable proteins for application in water purification membranes, resulting in a process that is both expensive and time-intensive.
In a publication in May this year within the scientific journal Chem, a cohort of National University of Singapore (NUS) scientists, under the guidance of Professor Prakash Kumar, unveiled a significant breakthrough in the realm of simplifying molecular constituents. These components possess the remarkable ability to autonomously assemble, generating structures akin to transmembrane channels, complete with pores. These engineered structures emulate the functionalities of aquaporins, exclusively permitting the passage of water molecules through the membrane, while steadfastly rejecting salts and other impurities. Notably, the individual building blocks of these structures, known as ‘oligourea foldamers,’ are notably smaller in scale, comprising a mere 10 amino acid-residues. This compact size confers advantages, rendering them more amenable to modification, synthesis, and purification when juxtaposed with the challenges posed by aquaporins or alternative classes of artificial water channels (AWC).
The foldamers exhibit amphiphilic properties, signifying the presence of distinct charges that facilitate their assembly into intricate configurations. This assembly mechanism is reminiscent of the way magnets aggregate into a sphere when in close proximity. The resultant intricate, quaternary structures feature pore-like conduits akin to water channels, their stability bolstered by robust bonds like hydrophobic and electrostatic interactions.
Professor Kumar, having a joint appointment with the NUS Environment Research Institute, says, “The discovery of this new class of artificial water channels is significant because the individual foldamer molecules do not contain any pores, unlike other AWCs where the pores are found within their larger molecular structure. In our novel design, the water-selective pores only emerge when the individual units self-assemble. The high-water permeability coupled with resistance to proteolytic degradation makes these foldamers excellent candidates for industrial water purification applications.”
Research for obtaining clean water has been a key focus in the last few years, making this new finding extremely significant.
