Investigation of the temperature dependence of single molecule biomolecular interactions

Lone, Mudasir (2008) Investigation of the temperature dependence of single molecule biomolecular interactions. MRes thesis, University of Nottingham.

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Abstract

Weak non-covalent interactions such as hydrogen bonds, van der Waals forces and hydrophobic interactions form the basis of biomolecular interactions, and hence govern the function of many biological processes such as ligand-receptor interactions (cell adhesion), DNA replication and transcription. Measurement of such forces is important as it enables an understanding of the physio-biochemical properties of biological macromolecules. Single molecule forces and interactions can be measured with the help of ultra high sensitive force measurement devices such as the atomic force microscope (AFM), magnetic tweezers (MT), optical tweezers (OT) and the bio-membrane force probe (BFP). In this study, AFM has been employed over a range of temperatures to study the forced unbinding of streptavidin-biotin and complementary DNA oligonucleotides (30mer). With regards to the DNA based experiments, recently developed dendron immobilization chemistry was employed with the aim of improving sample immobilization and hence force spectroscopy data. At room temperature, the dynamic force spectroscopic measurements of the streptavidin-biotin complex showed two regimes of strength, consistent with previous studies. The unbinding strength of complementary DNA oligonucleotides immobilized via the dendron approach was also investigated at room temperature and found to be consistent with previous studies.

Several factors such as load, temperature and attachment chemistry have the potential to influence unbinding forces in single molecule measurements. Most single molecule force spectroscopic studies within the literature have investigated bonding strength on the basis of loading rate (which can be varied through measurement rate and the mechanical properties of the immobilization chemistry). Few studies have taken into account the critical effect of an increase in temperature. In this work, the temperature dependence of single molecule force spectroscopy measurements has been explored. It was observed that the unbinding forces of both streptavidin-biotin and complementary DNA oligonucleotides decrease with temperature. The decrease in the unbinding force of both molecular species was attributed to the increase in the thermal energy of the system, which tilts the energy binding energy landscape in the direction of applied force besides decreasing the thermal force scale. Moreover increase in thermal energy decreases thermal off rate exponentially. The combined effect of all these factors reduces the unbinding forces of both the studied systems. However, for DNA, temperature increases are also known to decrease the average fraction of bonded pairs in hybridised DNA duplexes, which in these experiments would result in an additional reduction in force.

The presented data hence provide new insight into the effect of temperature on single molecule force spectroscopy data and the opportunities presented by a novel dendron based immobilization strategy.

Item Type:Thesis (MRes)
Supervisors:Roberts, Clive
Allen, Stephanie
Uncontrolled Keywords:Dynamic Force Spectroscopy, Molecular Force Probe, Silanization, Dendrimers, Loading Rate, Thermal Off Rate, Mesospacing, Adhesion Force
Faculties/Schools:UK Campuses > Faculty of Science > School of Pharmacy
ID Code:2031
Deposited By:Mr Mudasir Lone
Deposited On:11 Jul 2011 10:25
Last Modified:11 Jul 2011 10:48

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