The organization and dynamics of chromatin are critical for genome functions such as transcription and DNA replication/repair. Historically, chromatin was assumed to fold into the 30-nm fiber and progressively arrange into larger helical structures, as described in the textbook model. However, over the past 15 years, extensive evidence including our studies has dramatically transformed the view of chromatin from a static, regular structure to one that is more variable and dynamic. In higher eukaryotic cells, chromatin forms condensed yet liquid-like domains, which appear to be the basic unit of chromatin structure, replacing the 30-nm fiber. These domains maintain proper accessibility, ensuring the regulation of DNA reaction processes. During mitosis, these domains assemble to form more gel-like mitotic chromosomes, which are further constrained by condensins and other factors. Based on the available evidence, I discuss the physical properties of chromatin in live cells, emphasizing its viscoelastic nature—balancing local fluidity with global stability to support genome functions.

Structural studies of natural products have been a driving force in the development of organic chemistry throughout its long history, especially in the early years. Recently, structure determination based on new concepts has also gained momentum. In this review we will mainly discuss the functional structures of natural products that account for the mechanisms of action largely from our studies. The topics include marine natural products, amphidinols, and ladder-shaped polyether compounds, which are known as potent antifungal agents and important marine biotoxins, respectively. Nuclear magnetic resonance studies for determining the stereochemistry of amphidinol 3 and its conformation in lipid-bilayer membranes will be presented in detail.

In Japan, serious food poisoning among individuals who took supplement tablets for lowering plasma cholesterol levels have been publicized since late March 2024. The tablets were prepared from red yeast rice (RYR), a product of Monascus pilosus. Puberulic acid (PA) was detected as an unexpected compound in tablets that caused food poisoning. We conducted an on-site investigation at the RYR production factory to determine the cause of PA contamination of the tablets. Fungi capable of producing PA were detected in wipe samples from the factory and were identified as Penicillium adametzioides. To understand the route through which P. adametzioides contaminated RYR and produced PA, coculture experiments with M. pilosus and P. adametzioides were performed. P. adametzioides grew on rice covered with M. pilosus and produced PA. These results suggest that PA-producing P. adametzioides inhabited the RYR production factory and accidently contaminated the culture of M. pilosus. Consequently, RYR tablets contaminated with PA were manufactured and caused the food poisoning outbreak.