捆绑SM社区

How macromolecules behave in nanoconfined spaces, such as what conformations DNA polymers adopt and how they interact with other DNA and protein molecules, is of immense fundamental as well as applied interest, warranting new biophysical explorations. In the context of cellular biophysics, compact coiled DNA molecules are squeezed within a nucleus, presenting open questions regarding their properties and interactions. In the context of genomics, nanofluidic tools often work by squeezing polymers into long nano pipes, with the hope of directly unraveling the sequence of our genetic code, using small numbers of intact DNA segments. One holy grail of modern biotechnology is reading, assembling and understanding single-cell genomes with minimal fragmentation. However, handling and visualizing long and delicate strands of genomic DNA represent key technological challenges, typically breaking DNA into tiny pieces.

In this talk, we harness capabilities of a novel single-molecule manipulation and microscopy platform we have developed called 鈥淐onvex Lens-induced Confinement (CLiC)鈥� for two explorations in biophysics. First, we demonstrate a new and gentle approach to directly manipulate and visualize long, purified strands of DNA for genomic analysis which is high-throughput, compatible with in-situ reagent exchange and controlled chemistry in nanofluidic environments, and relies on tiny entropic forces (Berard et al, PNAS 2014). We precisely explore the polymer physics underlying the DNA polymers鈥� behaviour as a function of applied confinement, and compare results to theory, which we consequently extend. Second, using more complex supercoiled DNA systems, closer to physiological conditions, we study how their conformational fluctuations mediate invasion into spontaneous unwinding sites by small oligonucleotides. Motivated by open questions on transcriptional initiation and dynamics, and beginning with model systems, our single-molecule reaction and trajectory visualizations can provide new mechanistic insights. The overarching vision of this talk is that by 鈥済etting into that room at the bottom鈥� of nanobiophysics by innovative technologies, we open doors to complementary biophysical discovery and biomedical diagnostics which can act hand in hand.