Structure and Function of Molecular Assembly. A Personal Reminiscence

In this account is described an outline of research the author has conducted over the last 35 years. Depending on the type of molecular assemblies dealt with, the whole work is divided into four pails, i.e., small host-guest systems in organic media, infinite solid systems, huge but finite nano systems in aqueous media, and manipulated biological systems. The essence of the host-guest systems (Section 2) is molecular recognition based on convergent multiple interactions involving O-H center dot center dot center dot O hydrogen bonds, where sugar binding and detailed thermodynamic analysis of multipoint recognition may be taken as highlights. A couple of new fields arise from the host-guest chemistry by paradigm shift. One is in the direction of multiple interactions, from convergent to divergent. Section 3 thus concerns molecular alignment control in crystals using orthogonal aromatic triad and diad building blocks. Catalysis by microporous metallo-organic frameworks as organic zeolites is also described. The other shift in paradigm is in the media, from organic to aqueous, and also in the significance of sugar binding, from sugars as a guest to sugars as a probe. Section 4 is devoted to the highly adhesive (hydrogen bonding) nature of glycocluster compounds and their micelle-like aggregates, focusing on the formation of glycoviruses and glycoviral gene delivery. With DNA and RNA manipulation techniques in hand, we became interested in in-cell gene sensing and transcription monitoring. The latest activity in this area is shown in Section 5. The entire work is design-based. The author, who is soon retiring from Kyoto University, now has mixed feelings about this apparently natural approach, as briefly referred to in the Closing Remark (Section 6).