AFM based characterization of fuel-driven materials

Media type: E-Book

Title: AFM based characterization of fuel-driven materials

Contributor: Lallemang, Max [Verfasser]; Hugel, Thorsten [Akademischer Betreuer]; Walther, Andreas [Reviewer]; Balzer, Bizan N. [Reviewer]

Corporation: Albert-Ludwigs-Universität Freiburg, Fakultät für Chemie und Pharmazie

imprint: Freiburg: Universität, 2023

Extent: Online-Ressource

Language: English

DOI: 10.6094/UNIFR/236090

Identifier:

Keywords: Verbundverhalten ; Rasterkraftmikroskopie ; Adaptiver Werkstoff ; (local)doctoralThesis

Origination:

University thesis: Dissertation, Universität Freiburg, 2023

Footnote:

Description: Abstract: Due to their programmability, deoxyribonucleic acid (DNA) and peptide structures have emerged as promising and ideal candidates to mediate response and adaptivity in material science. In contrast to classic materials, which strive equilibrium conditions, we design and engineer dissipative non-equilibrium materials like, e.g., microtubules in the cytoskeleton of the cells. Here, the thermodynamic system is in constant exchange of energy with its environment. To study this kind of structures, an Atomic Force Microscope (AFM) is applied. In order to monitor and investigate dynamic processess and rupture forces of single molecules at the nanoscale and mesoscale, imaging and single molecule force spectroscopy (SMFS) are used. Here, we will start with simple responsive systems at the nanoscale and later on, we will move towards complex responsive system at the nanoscale and macroscale, compromising molecular fuel. In the third chapter, the interaction between poly-(T) single stranded DNA (ssDNA) and mica in different ion solutions, namely Li+, Na+, K+ and Cs+ was investigated using AFM based SMFS. The highest detachment force was found for Na+ and the lowest for Cs+. The binding is mainly based on sharing a cation between the phosphate O of the ssDNA and negatively charged mica. In addition, k0 and x‡ were calculated for Na+ using Bell- Evans model. Finally, among all kinds of interactions (mica-cation, cation-phosphate O, mica-nucleobase), breaking the contact between mica and the cation required the highest pulling force. In summary, we demonstrated the response of ssDNA towards changes in the ionic environment. In the fourth chapter, N3-PG110-b-P(Cat5-Ph5-A2), compromising an azide group, five cat- echolic groups, five phenyl groups and two amine groups, was covalently bound to an AFM cantilever tip in order to study the multivalent interactions by SMFS on a crosslinked and non-crosslinked catechol-based N3-PG110-b-P(Cat5-Ph5-A2) coating. We finally could designate our detachment forces to certain type of interactions, including covalent bonds, π-π-stacking, van-der-Waals (vdW) interactions, hydrogen bonds (H-bonds) and coordination bonds. In addition, we didn’t only find the highest frequency of occurence for bonds of intermediate strength but we also showed increased detachment forces for the interaction between the N3-PG110-b-P(Cat5-Ph5-A2) and a fully crosslinked N3-PG110-b-P(Cat5-Ph5- A2) coating, reaching nearly 3000 pN for a single polymer. Our findings pave the way for the design of coatings with increased adhesion. In summary, we could demonstrate how our polymers respond reversibly to changes in the pH. In the fifth chapter, AFM based imaging was used to study the influence of heat shock protein 90 (Hsp90) and adenosine triphosphate (ATP) on the amyloid-beta 40 (Aβ40) fibrillation which plays a key role in curing Alzheimer’s disease. The imaging of Aβ40 only revealed major fibrils, while in the presence of Hsp90, only oligomers emerged. Finally, the incubation of Aβ40 together with Hsp90 and ATP showed oligomers with several fibrils. The inhibitory effect of Hsp90 on the fibrillation of Aβ40 is also reduced by ATP, mainly due to the diminution of its hydrophobic surface. With our result, we come a small step closer towards understanding Alzheimer’s disease. In the sixth chapter, the in situ and ex situ monitoring of the polymerization and de- polymerization of rigid and circual double stranded DNA (dsDNA) was performed using terminal deoxynucleotidyl transferase (TdT) and Exonuclease-I (Exo-I) as enzymes and deoxynucleoside triphosphate (dNTP) as fuel. As a first step, the different structures were imaged to determine their height, width and diameter. Next, enzymes and fuel were applied. Both processes, the polymerization as well as the depolymerization were observed and studied quantitatively and qualitatively. In summary, the first steps towards imaging transient steady-states with an AFM were performed. The self-assembly of various homo-and heteromultimers of phosphate activated amino acids into peptides and subsequently into supramolecular structures was monitored on highly ori- ented pyrolytic graphite (HOPG) in chapter 7. Equilibrium structures could be observed in the absence of molecular fuel, as well as out-of-equilibrium structures upon refueling with phosphate activated amino acids. The last chapter compromises the bottom-up design of a single DNA hairpin loop towards a hydrogel. Besides, an hierarchical mechanical transduction could be demonstrated by implementing programmable units into a single DNA chain and the DNA hydrogel network. We characterized the DNA hairpin loop with SMFS, while the hydrogel was characterized using rheology and SMFS to identify its mechanical properties like stretchability, elastic modulus and energy dissipation. We demonstrate a transduction of the non-linear response of the single DNA hairpin loop to the macroscopic hydrogel. As a next step, the non-linear response of the DNA hairpin loop was modified using a 7-(diethylamino)- 4-(hydroxymethyl)-coumarin (DEACM) based phosphoramidite, which was implemented in the stem region of the DNA hairpin loop and can be cleaved upon irradiation with light (400 nm). Altogether, we have shown that a bottom-up design of hydrogels or materials with novel properties by programming and understanding its constituting molecular units is possible. In summary, this work paves the way for the design and construction of novel energy- autonomous, living, active and adaptive materials made out of peptides or DNA. We could demonstrate the response of different biopolymers on various length scales towards several external triggers. Such materials already compromise energy and can easily be refueled

Access State: Open Access

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