Near-identical macromolecules spontaneously partition into concentric circles.

Area of Science:

• Biochemistry
• Materials Science
• Chemical Engineering

Background:

• Separation of similar macromolecules like deoxyribonucleic acids (DNAs) is crucial for life sciences but remains challenging.
• Existing methods struggle with separating molecules with minor structural differences, such as single nucleotide variants.

Purpose of the Study:

• To investigate a novel liquid-liquid phase separation (LLPS) phenomenon at a solid-liquid interface for separating nearly identical DNAs.
• To develop a method for isolating specific DNA sequences, including disease-related variants, with high purity.

Main Methods:

• Drop-casting an aqueous ammonium sulfate dispersion of phase-separated poly(ethylene glycol) (PEG) droplets onto a glass plate.
• Observing competitive spreading and partitioning of terminally different PEGs into concentric circles.
• Applying the LLPS mechanism to partition and selectively extract DNAs using the salting-in effect.

Main Results:

• Identical molecular weight but terminally different PEGs partitioned into micrometre-scale concentric circles at the solid-liquid interface.
• A spontaneous ammonium sulfate layer on the glass surface induced competitive spreading.
• Successfully isolated a human cancer-causing single nucleotide variant from a 1:1 mixture with original DNA at 97% purity.

Conclusions:

• The discovered LLPS at a solid-liquid interface enables the separation of structurally similar DNAs.
• This method offers a promising approach for high-purity isolation of specific DNA sequences, including single nucleotide variants.
• The technique has significant implications for advancing life sciences and diagnostics.