Haruki Ohkawa

Olefin metathesis and quadruple hydrogen bonding: A powerful combination in multistep supramolecular synthesis

We show that combining concepts generally used in covalent organic synthesis such as retrosynthetic analysis and the use of protecting groups, and applying them to the self-assembly of polymeric building blocks in multiple steps, results in a powerful strategy for the self-assembly of dynamic materials with a high level of architectural control. We present a highly efficient synthesis of bifunctional telechelic polymers by ring-opening metathesis polymerization (ROMP) with complementary quadruple hydrogen-bonding motifs. Because the degree of functionality for the polymers is 2.0, the formation of alternating, blocky copolymers was demonstrated in both solution and the bulk leading to stable, microphase-separated copolymer morphologies.

OXYGEN RELEASING FROM CELLULAR HEMOGLOBIN

The oxygen-releasing behavior of hemoglobin vesicles (HbV) was measured in order to study the difference in oxygen dynamics inside and outside the cellular Hb using a conventional stopped flow method and a newly developed stopped flow flash photolysis method. The partial pressure of oxygen in the solution outside the HbV was monitored with the lifetime of the triplet state of meso-tetraphenylporphinatozinc(II) bound to human serum albumin excited by the laser flash. The change in the partial pressure of oxygen outside the HbV showed a biphasic profile and was slower than that inside the HbV. The first phase shows the oxygen-releasing process from Hb near the phospholipid bilayer membrane, and the second phase is considered the process in which oxygen diffuses to the bulk aqueous region and reaches the equilibrium value.