Hydrophobic Porphyrin Assemblies with Oxygen-Transporting Capability

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Hemoglobin is a protein containing iron porphyrin as an oxygen-binding site and uptakes and carries molecular oxygen from air selectively. Designing assemblies focused on hydrophobicity of the precisely synthesized porphyrin enables to realize novel oxygen-carrying materials which work under conditions that different from that of hemoglobin.The hydrophobic iron porphyrin was hybridized with the xylanase which Nakamura have previously reported its stability against temperature. The red-colored aqueous solution of porphyrin-xylanase hybrid displayed a reversible oxygen-binding to the iron porphyrin even at high temperature at ca. 90℃. The catalytic activity as the xylanase was not interfered because the coordination site is different from that of the catalytic activity. This simple strategy using hydrophobic interactions will be applicable to the other host-guest combinations, which could afford a totally new class of artificial hemoprotein architectures.Meso-tetra(2-pyridyl) porphyrin f … More orms a duplex with tetrahydroxylcalix[4]arene via triplicate or quadruple hydrogen bonds, to provide a capping structure on the porphyrin plane, which was accompanied by the spontaneous equilibrium shift of the atropisomers. This was the first example of a hydrogen-bonded porphyrin-calix[4]arene duplex.Polymeric cobalt tetraphenylporphyrin thin membrane was obtained with nanometer thickness (80nm from SEM). The homogeneous red membrane reversibly binds and releases molecular oxygen at room temperature under high pressure. Oxygen permeability coefficient was large and steeply increased with decrease in oxygen upstream pressure. Oxygen permselectivity at 1cmHg difference between upstream and downstream was over 150. This indicates that the fixed cobalt porphyrin in the solid membrane facilitated oxygen transport in the membrane. Compressed air was applied to the upstream in the same condition to give the oxygen concentration above 900% at downstream. This indicates weak oxygen-binding affinity is preferable for the efficient oxygen facilitated transport. Less