Single-Molecular Dissection of Liquid–Liquid Phase Transitions

Abstract

Interaction between peptides and nucleic acids is a ubiquitous process that drives many cellular functions, such as replications, transcriptions, and translations. Recently, this interaction has been found in liquid−liquid phase separation (LLPS), a process responsible for the formation of newly discovered membraneless organelles with a variety of biological functions inside cells. In this work, we studied the molecular interaction between the poly-L-lysine (PLL) peptide and nucleic acids during the early stage of an LLPS process at the singlemolecule level using optical tweezers. By monitoring the mechanical tension of individual nucleic acid templates upon PLL addition, we revealed a multistage LLPS process mediated by the long-range interactions between nucleic acids and polyelectrolytes. By varying different types (ssDNA, ssRNA, and dsDNA) and sequences (A-, T-, G-, or U-rich) of nucleic acids, we pieced together transition diagrams of the PLL−nucleic acid condensates from which we concluded that the propensity to form rigid nucleic acid−PLL complexes reduces the condensate formation during the LLPS process. We anticipate that these results are instrumental in understanding the transition mechanism of LLPS condensates, which allows new strategies to interfere with the biological functions of LLPS condensates inside cells.

Catalytic Relaxation of Kinetically Trapped Intermediates by DNA Chaperones

“…Streptavidin-coated polystyrene beads (diameter, 1.76 μm) and bare polystyrene beads (diameter, 2.32 μm) were purchased from Spherotech Inc., IL, USA. Antidigoxigenin antibody-coated beads were prepared in lab by coating the antibody on the bare polystyrene beads (diameter, 2.32 μm) …”

“…Antidigoxigenin antibody-coated beads were prepared in lab by coating the antibody on the bare polystyrene beads (diameter, 2.32 μm). 19 Synthesis of a Single-Molecule Dual Hairpin Construct. A detailed flowchart for the synthesis is shown in Figure S1.…”