Phase transitions in linear polymers

Kolbeck, Pauline Julika (2024): Phase transitions in linear polymers: fundamental mechanisms and biotechnological & biomedical applications = Phasenübergänge in linearen Polymeren. Dissertation, LMU München: Fakultät für Physik

Abstract

Phase transition are ubiquitous and have long been studied in physics. In recent years, phase transitions in biological systems have attracted growing interest and are more and more established as an important regulatory principle. In this thesis, I will present three research projects investigating phase transitions in linear polymers, how we can understand them in a biological context, and demonstrate their use for biotechnological and biomedical applications. In addition, I will introduce and apply newly established methods that are essential for quantitative measurements at the nanoscale. The first part focuses on a newly developed selective and switchable nanopore system for biomacromolecules. By exploiting the influence of different polymer graftings inside artificial nanopores on the translocation of biomolecules, I will demonstrate the creation of a thermally switchable nanogate. The system is based on a polymer phase transition of the polymers grafted in the nanopore which is tunable via temperature. This thermoswitch opens up new perspectives for controlling transport and filtration of macromolecules and, particularly, viral particles. In the second part, I will present a novel method for atomic force microscopy (AFM) tip characterization and image reconstruction based on a DNA origami reference structure. The method allows to characterize AFM tips in detail and then use this information to obtain precise 3D AFM images and accurate size estimates of biomolecules as well as other types of (non-)biological nanostructures. This versatile and easy-to-use system greatly improves current AFM imaging and has broad applications in improving imaging results for samples ranging from biological macromolecules and their complexes to synthetic nanoparticles. Finally, in the third part, I will analyze and characterize the interaction of the protein HIV integrase (IN) with DNA. Using AFM imaging, AFM-based elasticity mapping, and single-molecule magnetic tweezers measurements, I show that IN can play an additional, previously unknown role beyond viral integration catalysis, namely in DNA compaction. Intriguingly, compaction occurs in two distinct concentration regimes and results in the formation of biphasic condensates with a rigid core and a softer outer layer which are held together by two mechanically and thermodynamically distinct types of interaction forces. The results of the following work highlight the importance of phase transitions in linear polymers and pave the way for new applications of these systems and techniques in nanotechnology, biomedicine, and beyond.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: DNA, single molecule, phase transition, polymer, AFM, Magnetic tweezers, ZMW, nano pore, HIV
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 530 Physik
• Fakultäten: Fakultät für Physik
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 20. Februar 2024
• 1. Bericht­erstatter:in: Lipfert, Jan