Evaporation as a new approach to understand early evolution
The team, led by Professor Anderson Shum (Croucher Senior Research Fellowship 2020), Professor in the Department of Mechanical Engineering at the University of Hong Kong, discovered that evaporation could facilitate compartmentalisation of biochemical compounds relevant to the living cells, providing an environment within which early evolution could have started.
Life is envisaged to have emerged through a series of complex prebiotic reactions and processes. Concentration and compartmentalisation of early functional biomolecules and their precursors were essential to the formation of the first living cells, which were believed to have evolved from the hypothetical primordial soup — the liquid substance that existed on the Early Earth around 4.0 to 3.7 billion years ago.
Liquid-liquid phase separation (LLPS), a mechanism by which membrane-less organelles form inside cells, has been hypothesised as a potential mechanism for prebiotic compartmentalisation.
It has been hypothesised that liquid-liquid phase separation (LLPS), a mechanism by which membrane-less organelles form inside cells, is the potential mechanism for prebiotic compartmentalisation. The mechanism is difficult to trigger in the lab settings as lab-made primordial soup is stochastic. In particular, ingredients involved in LLPS need to be concentrated and sufficient for phase separation.
Shum found that LLPS can be triggered and maintained through evaporation. By evaporating all-aqueous droplet containing polyethylene glycol (PEG) and dextran, the concentration of biomolecules needed for LLPS can be increased thus enhancing reactions and compartmentalisation.
“With evaporation the water content in the droplet decreased, leading to an increase in polymer concentration,” explained PhD student Wei Guo, who witnessed the process with excitement, where the initially homogeneous, clear droplet dissolved into two phases.
“The dissolution of a bigger droplet into smaller ones could be useful for future study on living cells." Guo said the finding laid a very strong foundation in understanding physical phenomena in terms of fluid dynamics.
Shum said the latest finding was an example of how curiosity fostered scientific discovery. “Aqueous two-phase system had been studied previously but this is the first time evaporation was used to initiate this kind of phase separation.”
The technique could also be used for the purpose of diagnostics or making droplets in a controlled manner. More can be found on molecular reactions if controlling factors, such as controlling for the temperature or rate of evaporation, are put in place.
The research paper published in Nature Communications, entitled “Non-associative phase separation in an evaporating droplet as a model for prebiotic compartmentalization”.
Professor Anderson Shum Ho Cheung is a Professor in the Department of Mechanical Engineering at HKU. He received his B.S.E. degree, summa cum laude, in Chemical Engineering from Princeton University, S.M. and Ph.D. in Applied Physics from Harvard University. He has made pioneering contributions to the fields of soft matter and microfluidics by introducing and elucidating all-aqueous multiphase microfluidics. His multidisciplinary works find applications in materials and biomedical engineering. He received his Croucher Senior Research Fellowship in 2020.
To view Shum’s Croucher profile, please click here.