Mototsugu Doi

Highly oriented aragonite nanocrystal–biopolymer composites in an aragonite brick of the nacreous layer of Pinctada fucata

13C CP/MAS NMR and FE/TEM measurements of the aragonite brick of the nacreous layer of Pinctada fucata indicate that it assembles with highly oriented aragonite nanocrystals, which are regulated by biopolymers.

Direct Interaction between Amphotericin B and Ergosterol in Lipid Bilayers As Revealed by 2H NMR Spectroscopy

Although amphotericin B (AmB) is thought to exert its antifungal activity by forming transmembrane ion-permeable self-assemblies together with ergosterol, no previous study has directly proven AmB-ergosterol interaction. To establish the interaction, we measured (2)H NMR using deuterium-labeled sterols and AmB. The (2)H NMR spectra of deuterated ergosterol in palmitoyloleoylphosphatidylcholine (POPC) bilayers showed that fast axial diffusion of erogosterol was almost completely inhibited by the coexistence of AmB. Conversely, cholesterol mobility in POPC membrane was essentially unchanged with or without AmB. These results unequivocally demonstrate that ergosterol has significant interaction with AmB in POPC bilayers. In addition, we examined the mobility of AmB using deuterium-labeled AmB, and found that, although AmB is almost immobilized in sterol-free and cholesterol-containing POPC membranes, a certain ratio of AmB molecules acquires mobility in the presence of ergosterol. The similar mobility of AmB and ergosterol in POPC bilayers confirmed the idea of the direct intermolecular interaction between ergosterol and AmB.

Restriction of CaCO3 polymorph by NH...O hydrogen-bonded poly(methacryloylaminocarboxylate) ligands : induced polymorph change by strength and/or formation manner of hydrogen bond

Novel poly(methacryloylaminocarboxylate) ligands were synthesized as models for an acidic peptide in CaCO3 biominerals. Syndiotactic poly[3-methyl-2-(methacryloylamino)butyrate], isotactic-rich poly[3-(methacryloylamino)propionate], and syndiotactic poly[4-(methacryloylamino)butyrate] form 5-, 6-, and 7-membered-ring intra-side-chain NH⋯O hydrogen bonds, respectively, between a carboxylate oxyanion and the neighboring amide NH proton, while syndiotactic poly[3-(methacryloylamino)propionate] forms intermolecular NH⋯O hydrogen bonds. These polymer ligands strongly bind to CaCO3 crystals because of the NH⋯O hydrogen bonds. In polymer ligand–CaCO3 composites, the strength and/or mode of hydrogen bonding in the polymer ligands affects the CaCO3 polymorphs. Five-membered-ring intra-side-chain and intermolecular hydrogen-bonded polymers have weak hydrogen bonds and produce calcite crystals, whereas other ligands with 6- and 7-membered-ring intra-side-chain hydrogen bonds have strong hydrogen bonds and yield vaterite crystals. Polymorph change of CaCO3 crystal is induced by differences of strength and/or mode of the NH⋯O hydrogen bond.