A Temperature-Jump Optical Trap for Single-Molecule Manipulation

Abstract

[EN] 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 temper- atures 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 experi- ments 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. ; The authors thank J. Camunas and S. Frutos for contributing the molecules used in the experiments, and J.M. Huguet for helpful discussion. F.R. is supported by grant Institucio Catalana de Recerca i Estudis Avancats Academia 2013 and J.R. A.-G. by an Explora grant from MINECO (MAT2013-49455-EXP). The research that led to the results presented here was funded by the European Union Seventh Framework Programme (FP7/2007-2013) under grant 308850 INFERNOS and European Research Council grant MagReps (No. 267862). ; De Lorenzo, S.; Ribezzi-Crivellari, M.; Arias-Gonzalez, JR.; Smith, S.; Ritort, F. (2015). A Temperature-Jump Optical Trap for Single-Molecule Manipulation. Biophysical Journal. 108(12):2854-2864. https://doi.org/10.1016/j.bpj.2015.05.017 ; S ; 2854 ; 2864 ; 108 ; 12