| AVS 65th International Symposium & Exhibition | |
| Biomaterial Interfaces Division | Thursday Sessions |
| Session BI-ThA |
| Session: | Biolubrication and Wear / Women in Bio-surface Science |
| Presenter: | Laila Moreno Ostertag, Vienna University of Technology, Austria |
| Authors: | L. Moreno Ostertag, Vienna University of Technology, Austria T. Utzig, Max Planck Institute for Iron Research, Germany C. Klinger, TU Bergakademie Freiberg, Germany M. Valtiner, Vienna University of Technology, Austria |
| Correspondent: | Click to Email |
The “fly-fishing” and breaking of single molecular bonds to study their properties has been extensively studied via Atomic Force Microscopy (AFM) and optical tweezers. A good example for this are various ligand-receptor bonds or surface to molecule bonds such as the gold-amine bond, for which a free energy of ~ 37 kBT has been determined. The experimental setup and design has evolved over the years, and so have the technology and analysis strategies involved. In the last 15 years, using Jarzynski‘s equality emerged as a powerful theoretical tool for estimating interaction free energies via the analysis of non-equilibrium work distributions from single-molecule pulling experiments with optical tweezers and AFM. [1] However, some of the questions remain the same and others appear as the field becomes broader. For example, what happens when the chemical model used to connect the probe with the interacting surface and head groups is varied? We recently tested the variation of linker lengths and changing pulling speeds [2] and found strong correlations that confirm the predictions of bias in such experiments by Gore et al. [3] in 2003. In particular, the longer the length of the polymeric chain, the more work dissipates during the retraction of the tip, and so does in turn the estimated ∆G0, which leads to an increasing bias between the average values and those calculated using Jarzynski’s equality. This is also reflected in the broadening of work distributions when using the same sample size. Longer polymeric chains show no convergence, unless millions or even billions of events were used. With this order of magnitude in mind, we started our very own “pitch drop experiment”: an ambitious project which aims to collect an ever-increasing number of single-molecular force runs for a single system, which will allow us to directly and step-by-step further evaluate equations, work-distributions, convergence behavior, and expected biases in single-molecule experiments. This work will continue along the PhD times of many students - first non-converged results will be discussed in detail and compared to systems that are well converged. Part of this mammoth task is the development of an automated single-molecule recognition algorithm that is capable of distinguishing with high reliability very low work single-molecule events from thermal noise. Some of our advances in this direction will be discussed in detail as well.
References:
[1] Jarzynski, C., JSMTE 2004, 2004 (09), P09005.
[2] Moreno Ostertag, L.; Utzig, T.; Klinger, C.; Valtiner, M., Langmuir 2018, 34 (3), 766-772.
[3] Gore, J.; Ritort, F.; Bustamante, C., PNAS 2003, 100 (22), 12564-12569.