Yasuo Nagaoka

Molecular bases of cyclodextrin adapter interactions with engineered protein nanopores

Engineered protein pores have several potential applications in biotechnology: as sensor elements in stochastic detection and ultrarapid DNA sequencing, as nanoreactors to observe single-molecule chemistry, and in the construction of nano- and micro-devices. One important class of pores contains molecular adapters, which provide internal binding sites for small molecules. Mutants of the α-hemolysin (αHL) pore that bind the adapter β-cyclodextrin (βCD) ∼104 times more tightly than the wild type have been obtained. We now use single-channel electrical recording, protein engineering including unnatural amino acid mutagenesis, and high-resolution x-ray crystallography to provide definitive structural information on these engineered protein nanopores in unparalleled detail.

Novel histone deacetylase inhibitors: N-hydroxycarboxamides possessing a terminal bicyclic aryl group.

Utilizing tranexamic acid as a starting material, a series of N-hydroxycarboxamides were synthesized in order to seek new histone deacetylase (HDAC) inhibitors. Further structure optimization involving the replacement of the 1,4-cyclohexylene group with the 1,4-phenylene group yielded the promising HDAC inhibitors which possess a terminal bicyclic aryl amide.

The conjugate addition-aldol tandem reaction of α,β-unsaturated esters catalyzed by lithium benzenethiolate

Abstract Reactions of α,β-unsaturated esters with aldehydes were catalyzed by 0.2 equiv of lithium benzenethiolate in the presence of phenyl trimethylsilyl sulfide to afford the conjugate addition-aldol tandem reaction products in the anti stereoselectivity and good to high yields.

Enantioselective conjugate addition of diethylzinc to cyclohexenone catalyzed by a chiral aminophosphine–copper(II) triflate

Abstract Enantioselective conjugate addition of diethylzinc to cyclohexenone and 4,4-dimethylcyclohexenone was catalyzed by the combination of 0.1 equiv. of a chiral monodentate aminophosphine 3 and 0.05 equiv. of copper(II) triflate to give the corresponding adducts 4 in up to 70% ee.

Catalytic Enantioselective Protonation of Lithium Ester Enolates Generated by Conjugate Addition of Arylthiolate to Enoates

A chiral ligand, a catalytic amount of lithium cation, and no chiral proton source: These are features of the present asymmetric addition-protonation of propenoates with 2-trimethylsilylbenzenethiol. The reaction is catalyzed by a combination of lithium 2-trimethylsilylbenzenethiolate and the chiral ligand 1. Desulfurization of the product affords 2-substituted propanoates with high ee values and without racemization. Furthermore, 1 can be recovered quantitatively for reuse.

An external chiral amidophosphine ligand for asymmetric conjugate addition of organocopper

Abstract Two types of external, chiral amidophosphine ligands, 1–5, were prepared. Examination of their behavior in an asymmetric conjugate addition reaction of organocuprate revealed the possibility for steric tuning to realize high selectivity.

Efficient cyclization of ω-oxo-α,β-unsaturated esters using lithium thiolate-initiated Michael-aldol tandem reaction

Abstract The reaction of ω-oxo-α,β-unsaturated esters with lithium thiolates afforded the Michael-aldol tandem cyclization products in good to perfect stereoselectivity depending on the nature of thiolates.

Involvement of SIK3 in Glucose and Lipid Homeostasis in Mice

Salt-inducible kinase 3 (SIK3), an AMP-activated protein kinase-related kinase, is induced in the murine liver after the consumption of a diet rich in fat, sucrose, and cholesterol. To examine whether SIK3 can modulate glucose and lipid metabolism in the liver, we analyzed phenotypes of SIK3-deficent mice. Sik3 −/− mice have a malnourished the phenotype (i.e., lipodystrophy, hypolipidemia, hypoglycemia, and hyper-insulin sensitivity) accompanied by cholestasis and cholelithiasis. The hypoglycemic and hyper-insulin-sensitive phenotypes may be due to reduced energy storage, which is represented by the low expression levels of mRNA for components of the fatty acid synthesis pathways in the liver. The biliary disorders in Sik3 −/− mice are associated with the dysregulation of gene expression programs that respond to nutritional stresses and are probably regulated by nuclear receptors. Retinoic acid plays a role in cholesterol and bile acid homeostasis, wheras ALDH1a which produces retinoic acid, is expressed at low levels in Sik3 −/− mice. Lipid metabolism disorders in Sik3 −/− mice are ameliorated by the treatment with 9-cis-retinoic acid. In conclusion, SIK3 is a novel energy regulator that modulates cholesterol and bile acid metabolism by coupling with retinoid metabolism, and may alter the size of energy storage in mice.

Ion Channels of Alamethicin Dimer N-Terminally Linked by Disulfide Bond

A covalent dimer of alamethicin Rf30 was synthesized by linking the N-termini by a disulfide bond. When the dimer peptides were added to the cis-side of a diphytanoyl PC membrane, macroscopic channel current was induced only at cis positive voltages. The single-channel recordings showed several conductance levels that were alternately stabilized. These results indicate that the dimer peptides form stable channels by N-terminal insertion like alamethicin and that most of the pores are assembled from even numbers of helices. Taking advantages of the long open duration of the dimer peptide channels, the current-voltage (I-V) relations of the single-channels were obtained by applying fast voltage ramps during the open states. The I-V relations showed rectification, such that current from the cis-side toward the trans-side is larger than that in the opposite direction. The intrinsic rectification is mainly attributed to the macro dipoles of parallel peptide helices surrounding a central pore.

Structural requirements of a chiral ligand for the catalytic asymmetric addition of thiophenol to α,β-unsaturated esters

The tridentate amino ether ligands 1 and 14 were developed through systematic structural modification of the bidentate diether ligand 2. The reaction of thiophenol with methyl crotonate was catalyzed by 14 and lithium thiophenolate to afford (S)-methyl 3-phenylthiobutanoate in 75% ee and 95% yield.