Organisms can adapt to the environment robustly despite large heterogeneity of cellular response. Heterogeneity of cellular responses has been regarded as noise, which reduces accurate information transmission. The heterogeneity consists of intracellular variation caused by stochasticity of biochemical reactions, and intercellular variation caused by differences in amounts of molecules (cell-to-cell variability). We found that intercellular variation increases gradualness of the multi-cellular dose-response (response diversity effect), resulting in increase of accuracy of information transmission. This “response diversity effect” is a novel mechanism that enables multi-cellular organisms to utilize cell-to-cell variability as information not noise.
Chromatin fibers, as the substance of the genome, are biopolymers packed inside the cell nucleus. High-throughput chromosome conformation capture (Hi-C) techniques have revealed the 3D genome organization for over a decade. Meanwhile, live-cell imaging experiments have shown the dynamic nature of chromatin. To bridge the gap between genome 3D structure and dynamics, we have developed a computational method for deciphering Hi-C data by polymer modeling. Here we provide a way to uncover the rheological properties of the dynamic 3D genome organization.
Oxygen concentration of living cells is one of the key parameters in various metabolic processes. Phosphorescence imaging techniques allow estimation of intracellular oxygen levels, because the intensity and lifetime of phosphorescence are significantly dependent on the concentration (partial pressure) of molecular oxygen. We herein demonstrate that the phosphorescence lifetime measurements using a microscope equipped with a time correlated single photon counting system or a gated intensified charge-coupled device camera and intracellular oxygen probes based on phosphorescent iridium(III) complexes are very useful for visualization of heterogeneous oxygen distribution in monolayer cultured cells.
Construction of a living cell from molecules and genes widens our understanding of how life systems are organized. Among cell functions, energy production and self-reproduction are fundamental for sustaining life. Here, we constructed an artificial organelle producing ATP by light, through assembling bacteriorhodopsin and ATP synthase onto liposome membrane. The photo-synthesized ATP was consumed as an energy for protein synthesis, eventually drove the self-production of the component proteins of the organelle. The de novo photo-synthesized bacteriorhodopsin and parts of ATP synthase enhanced ATP production efficiency of the artificial organelle in the positive feedback loop.
Heat capacities of four ketohexoses, fructose, sorbose, psicose, and tagatose, were measured by adiabatic calorimetry in the temperature range from ca.10 to 330 K. For sorbose, thermal anomalies were detected: 199.5 K (main phase transition of order-disorder type), around 210 K (minor ones), and ca. 120 K (glass transition). Although no heat anomaly was observed for the other three ketohexoses, their standard thermodynamic functions were estimated from the measured molar heat capacities. A spectral analysis using Kieffer’s model was applied to the heat capacities to rationalize the relation among them in terms of intra- and intermolecular hydrogen bonds in crystal.
Proteins expressed in human cells contain about 50% intrinsically disordered regions (IDRs). An unexpectedly large content of IDRs in human proteins prompted exploring how IDRs exert elaborate functions that are not associated with the folded parts of proteins. This review reports the ultrasensitive change in the nucleosome binding of FACT, a nucleosome remodeler, according to the degree of phosphorylation: in which FACT binding ability to nucleosomal DNA changes in a sigmoidal manner along with the number of phosphorylation to the IDR in its DNA binding domain. This finding adds a new function exclusively achieved by IDRs.
Swimming bacteria display distinct motile patterns to explore their favorable environments, driven by bacterial flagella. A typical example of the flagellar motility is the run-tumble swimming in Escherichia coli: the CCW rotation of a flagellar bundle propels a cell forward. The cell undergoes reorientation (tumbling) upon the switching of flagellar rotation from CCW to CW. It has been characterized using chemotactic mutants for motility studies; however, the original E. coli strain’s motility mode remains unclear. In this review, we characterized the original E. coli K-12 strain’s forward and backward swimming based on the single-molecular techniques.