Abstract
Photothermal cantilever excitation provides a fast and easy to implement means to control the deflection of standard atomic force microscopy cantilevers. Minute heat pulses yield deflections on the order of several tens of nanometers or when the deflection is kept constant, forces of several hundreds of piconewton can be applied. In our case these pulses resulted in less than 1 K temperature changes at the sample position. Here we present and characterize the implementation of photothermal actuation for single-molecule force-spectroscopy experiments. When molecules are stretched under force-clamp conditions, fast control cycles that re-establish the pulling force after the rupture of molecular domains are essential for detecting the complete unfolding pattern with high precision. By combining the fast response of photothermal cantilever excitation with a conventional piezoactuator, a fast force-clamp with high accuracy and large working distances is reached. Simple feedback mechanisms and standard cantilever geometries lead to step response times of less than 90 μs, which is more than one order of magnitude faster than those of conventional force-clamp systems that are based only on piezo feedback. We demonstrate the fast and accurate performance of the setup by unfolding a protein construct consisting of one green fluorescent protein and eight surrounding immunoglobulin domains at constant force.
Original language | English (US) |
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Article number | 073702 |
Journal | Review of Scientific Instruments |
Volume | 80 |
Issue number | 7 |
DOIs | |
State | Published - 2009 |
Bibliographical note
Funding Information:We thank Ann Fornof and Mathias Strackharn for discussions. This work was supported by the Nanosystems Initiative Munich (NIM), Center for Integrated Protein Science Munich (CIPSM) and the Deutsche Forschungsgemeinschaft Grant No. SFB 486.