A Temperature-Jump Optical Trap for Single-Molecule Manipulation |
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| Authors: | Sara de?Lorenzo Marco Ribezzi-Crivellari J.?Ricardo Arias-Gonzalez Steven?B. Smith Felix Ritort |
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| Affiliation: | 1.Departament de Física Fonamental, Universitat de Barcelona, Barcelona, Spain;2.Ciber-BBN de Bioingenería, Biomateriales y Nanomedicina, Instituto de Salud Carlos III, Madrid, Spain;3.Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanociencia), Cantoblanco, Madrid, Spain;4.CNB-CSIC-IMDEA Nanociencia Associated Unit “Unidad de Nanobiotecnología”, Madrid, Spain;5.Steven B. Smith Engineering, Los Lunas, New Mexico |
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| Abstract: | To our knowledge, we have developed a novel temperature-jump optical tweezers setup that changes the temperature locally and rapidly. It uses a heating laser with a wavelength that is highly absorbed by water so it can cover a broad range of temperatures. This instrument can record several force-distance curves for one individual molecule at various temperatures with good thermal and mechanical stability. Our design has features to reduce convection and baseline shifts, which have troubled previous heating-laser instruments. As proof of accuracy, we used the instrument to carry out DNA unzipping experiments in which we derived the average basepair free energy, entropy, and enthalpy of formation of the DNA duplex in a range of temperatures between 5°C and 50°C. We also used the instrument to characterize the temperature-dependent elasticity of single-stranded DNA (ssDNA), where we find a significant condensation plateau at low force and low temperature. Oddly, the persistence length of ssDNA measured at high force seems to increase with temperature, contrary to simple entropic models. |
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