This presentation will describe our efforts in using magnetic tweezers, a type of single-molecule force spectroscopy, to track single polymer growth in real time from a single catalyst under living polymerization catalysis conditions. It will focus on the ring opening metathesis polymerization catalyzed by the Ru-based 2nd generation Grubbs catalyst. I will describe how the real-time growth dynamics of single linear polymers uncover the stochastic formation and unraveling of nonequilibrium conformational entanglements that were not known to exist and that appear to play key roles in the polymerization kinetics and kinetic dispersion among individual polymers. I will also cover more recent results on using inter- and intra-molecular hydrogen bonding to modulate the stability of these entanglements to alter polymerization kinetics, as well as results on the polymerization dynamics and mechanics of single conjugated polymers.

Phase separations involving biomolecular liquids are emerging as a fundamental mechanism of intracellular organization. Liquid-liquid phase separation (LLPS) of biomolecules compartmentalizes intracellular space into multiple coexisting condensates to facilitate spatio-temporal regulation of biological processes. The list of intracellular structures driven to form by LLPS is growing rapidly, and include canonical membrane-less organelles such as nucleoli, nuclear speckles and stress granules, as well as recently described structures such as transcriptional and synaptic clusters. In an effort to investigate biophysical mechanisms of intracellular condensation, I have been developing technologies to navigate intracellular phase space. In this talk, I will first discuss a strategy to control phase separation in living cells, in particular within nuclear space. We have developed an optogenetics-based technology where genome targeting capacity of the Cas9 system is combined with the optogenetic controllability. This approach enables targeted liquid-liquid phase separation at a specific genomic locus, and suggests the role of liquid condensates of transcriptional regulators in shaping genome structure. I will also briefly discuss an imaging technique enabling quantitative measurements of biomolecular concentrations in condensates.

Endoribonucleases play an essential role in processing and degradation of RNA molecules. Today, I will present data showing how endoribonucleases control mRNA stability and, consequently, modulate cellular physiology that includes bacterial pathogenesis and cancer development.

Mass spectrometry is acknowledged as one of the most important analytical tools for the understanding of biological phenomena by providing proteomics, metabolomics and imaging information. An introduction of mass spectrometry and a description of current progresses in the multiomics approaches will be presented. In particular, its enormous potential in biological sciences in complement to traditional research tools and its important role in the study of proteome and metabolome changes in various biological systems will be described. In this presentation, studies, including quantitative measurement of proteins and metabolites responsible for drug resistance in cancer and pathogenesis of diabetes, will be presented.

Many processes in biology, from antibody production to tissue differentiation, share a common fundamental step — establishing physical contact between distant genomic segments. A key outstanding question is then: How do genomic segments that are strung out over millions of base pairs along the DNA find each other in the crowded cell on a remarkably short timescale? This question, fundamental to biology, can be recognized as the physics problem of the first-passage time. I will show how concepts from statistical physics help reveal the physical principles by which cells solve this first-passage problem with astonishing efficiency. These ideas will be illustrated in the context of adaptive immunity – the system that enables the individual to respond to a great variety of pathogens through a diverse repertoire of antibodies.

Optical coherence tomography (OCT) is a three-dimensional (3-D) optical imaging technology that provides noninvasive, micrometer resolution (<7µm) images of structural interiors within biological samples with an approximately 1~2 mm penetration depth. Over the last decades, advances in OCT have revolutionized in biomedical imaging by demonstrating a potential of optical biopsy in preclinical and clinical settings. Recently, functional OCT imaging has shown a promise as angiography to visualize cell-perfused vasculatures in the tissue bed in vivo without requiring any exogenous contrast agents. This new technology termed OCT angiography (OCTA) possesses a unique imaging capability of delineating tissue morphology and blood or lymphatic vessels down to capillaries at a fast acquisition rate (>180 frames/s). For the past few years, OCTA has been proven being a useful tool to identify disorder or dysfunction in tissue microcirculation from experimental animal studies and clinical researches in ophthalmology and dermatology. In this presentation, we introduce OCTA and our OCTA works; a mechanism of OCTA is explained with simple optical physics, and its scan protocols and post-processing algorithms for angiography are introduced. Then, in vivo small animal studies aimed for investigating the changes in vessel networks under pathological challenges such as stroke in cerebral cortex of brain are presented with interesting findings measured. Furthermore, potential and challenge of OCTA for clinical settings are shown with outcomes of our small animal studies.