Simultaneously Capturing the Structure and Mechanical Properties of Chromosome using STED Nanoscopy and Optical Tweezers

Abstract

In our cells, DNA is organized in chromosomes, complex structures of DNA condensed by proteins. Over the last few decades, the fundamental structure of DNA and chromatin has been revealed by analyzing the mechanical responses of the molecules using optical tweezers. However, for investigating the higher-level structural organization, it still remains a major challenge to visualize and probe the dense and complex molecular architecture of chromosomes. In the present study, we combined optical tweezers with 3D stimulated emission depletion (STED) and confocal fluorescence microscopy for simultaneously capturing the structure and mechanical properties of chromosomes. Our previous 1D STED optical tweezers system was updated to 3D by employing a spatial light modulator as wave-front controlling element that enables both 3D STED nanoscopy and sensor-less adaptive optics. We present proof-of-principle results on force-extension analysis of optically trapped DNA/human chromosomes as well as their confocal/STED images. The proposed method can provide superior means to uncover the biological structure and kinetics of vital processes of chromosomes such as their spatial organization during replication.