Rapid Separation of DNAs and Their Mutated Analogues: An Unexpected Phenomenon of Liquid–Liquid Phase Separation of Near-Identical Macromolecules at a Solid–Liquid Interface

Nucleic acids, such as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), carry the genetic information essential for life. For example, the substitution of a single base of approximately 2,300 bases in the human BRAF gene can lead to the development of multiple human cancers [1]. Therefore, the techniques to separate highly similar nucleic acids hold great potential for advancing life sciences. However, this cannot be achieved easily due to their near-identical structures. In this study, a team led by Dr. Hao Gong, a Project Researcher at the Department of Chemistry and Biotechnology, Graduate School of Engineering, the University of Tokyo and Prof. Takuzo Aida, a Distinguished University Professor at Tokyo College, the University of Tokyo (also Group Director at the RIKEN Center for Emergent Matter Science), successfully separated near-identical nucleic acids at the solid–liquid interface using just salt, water, and glass. When ammonium sulfate was added to a solution of nucleic acids, primary liquid–liquid phase separation (LLPS) (salting-out) occurred to generate an aqueous two-phase dispersion containing nucleic acid-enriched droplets in a salt-enriched continuous phase. When the resulting dispersion was drop-cast onto a glass plate, a secondary LLPS spontaneously occurred on the glass plate, partitioning the nucleic acid mixture into concentric circles. This finding led to the successful selective extraction of the concentrically partitioned human BRAF gene fragments with and without a single-point mutation by the "salting-in" effect. Remarkably, this discovery was made serendipitously during the partitioning a mixture of polyethylene glycols (PEGs) with different termini into concentric circles. This method is much faster and more cost-effective than the existing methods, and its underlying principles are also unprecedented. This technology has the potential to significantly advance life sciences, considering that it can certainly be automated by microfluidics. A patent (No. JP2024-188368) covering the concentric partitioning–extraction process described in this paper has been filed by the University of Tokyo, Japan.

Papers

Journal: Nature

Title: Near-identical macromolecules spontaneously partition into concentric circles

Authors: Hao Gong*, Yuriko Sakaguchi, Tsutomu Suzuki, Miho Yanagisawa, Takuzo Aida*

DOI: 10.1038/s41586-024-08203-4

Reference

[1] Davies, H. et al. Mutations of the BRAF gene in human cancer. Nature, 2002, 417, 949–954.