Tuning Single-Polymer Growth via Hydrogen Bonding in Conformational Entanglements

Stochastic dynamics of hairballs in single-polymer growth

Real-time monitoring of the single-chain growth of synthetic polymers shows that their end-to-end extension during polymerization in living conditions does not increase continuously. Instead, it remains in a non-equilibrium state, exhibiting stochastic wait-and-jump events when one end of the polymer is subjected to a constant force and the other end is clamped. This wait-and-jump observation was attributed to the stochastic formation and unwinding of conformational entanglements, referred to as hairballs, which result from intrachain and non-bonded interactions within the polymer. In this work, we propose a new theoretical approach to investigate the microscopic dynamics of a single hairball formation and unravelling process during single-chain polymerisation. A discrete state stochastic approach is adopted to analyse the respective wait-and-jump events, which provides fully analytical solutions for all dynamic properties under non-equilibrium conditions. Our theory suggests that dynamic conformation fluctuations of the hairball may be responsible for the experimentally observed complex non-exponential behaviour in the waiting times. Excellent quantitative agreements with existing experimental data provide strong support for our theory. Further, using a Monte Carlo simulation approach, we analysed the correlations between the waiting time and extension of polymer in a single jump, which indicates the possibility of more complex dynamics of polymer growth.

From Molecules to Classrooms: A Comprehensive Guide to Single-Molecule Localization Microscopy

Single-molecule localization microscopy (SMLM) has revolutionized our ability to visualize cellular structures, offering unprecedented detail. However, the intricate biophysical principles that underlie SMLM can be daunting for newcomers, particularly undergraduate and graduate students. To address this challenge, we introduce the fundamental concepts of SMLM, providing a solid theoretical foundation. In addition, we have developed an intuitive graphical interface APP that simplifies these core concepts, making them more accessible for students. This APP clarifies how super-resolved images are fitted and highlights the crucial factors determining image quality. Our approach deepens students' understanding of SMLM by combining theoretical instruction with practical learning. This development equips them with the skills to carry out single-molecule super-resolved experiments and explore the microscopic world beyond the diffraction limit.