Arginine improves protein elution in hydrophobic interaction chromatography. The cases of human interleukin-6 and activin-A

The effects of arginine on protein binding and elution in hydrophobic interaction chromatography (HIC) were examined using recombinant human interleukin-6 (IL-6) and activin-A. Binding of IL-6 in the presence of ammonium sulfate (AS) was tested using low- and high-substituted phenyl-sepharose. While inclusion of arginine during loading of IL-6 resulted in incomplete binding to the low-substituted phenyl-sepharose, binding was complete to the high-substituted phenyl-sepharose. Arginine facilitated elution of IL-6 from both columns. These results demonstrate that arginine weakens hydrophobic interactions between IL-6 and the phenyl-sepharose. More drastic results were obtained using activin-A, which showed undetectable recovery from phenyl-sepharose. Although no apparent elution of activin-A was observed from butyl-sepharose in aqueous buffer alone, the addition of arginine to the buffer resulted in partial elution recovery and, together with ethanol, resulted in greatly improved recovery of the protein. Two arginine derivatives, acetylarginine and agmatine, were also effective. These results show that arginine improves protein elution in HIC.     

Expression of a model peptide of a marine mussel adhesive protein in Escherichia coli and characterization of its structural and functional properties

An expression system for a chemically synthesized gene, encoding a model peptide of marine mussel adhesive protein, was constructed in Escherichia coli under regulation of the T7‐promoter. The model peptide consisted of six repeats of the decapeptide AKPSYPPTYK. Although the product was expressed as an inclusion body, we were able to solubilize it successfully, using acetic acid. The higher‐order structure of this model peptide was investigated using CD spectroscopy and NMR spectroscopy. Using the modified enzyme, mushroom tyrosinase, the tyrosine residue was hydroxylated to 3,4‐dihydoxyphenylalanine (Dopa), and the resulting modified peptide was polymerized, solidified, and insolubilized spontaneously. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 729–736, 1999     

Peptoid-based reprogrammable template for cell-permeable inhibitors of protein–protein interactions

The development of inhibitors of intracellular protein–protein interactions (PPIs) is of great significance for drug discovery, but the generation of a cell-permeable molecule with high affinity to protein is challenging. Oligo(N-substituted glycines) (oligo-NSGs), referred to as peptoids, are attractive as potential intracellular PPI inhibitors owing to their high membrane permeability. However, their intrinsically flexible backbones make the rational design of inhibitors difficult. Here, we propose a peptoid-based rational approach to develop cell-permeable PPI inhibitors using oligo(N-substituted alanines) (oligo-NSAs). The rigid structures of oligo-NSAs enable independent optimization of each N-substituent to improve binding affinity and membrane permeability, while preserving the backbone shape. A molecule with optimized N-substituents inhibited a target PPI in cells, which demonstrated the utility of oligo-NSA as a reprogrammable template to develop intracellular PPI inhibitors.

A peptoid-based modular approach using oligo(N-substituted alanine) as a reprogrammable template enables independent optimization of N-substituents and facile development of cell-permeable inhibitors of protein–protein interactions.     

Structure–activity relationship studies of atpenin A5 analogs with chemical modification of the side chain moiety

We designed and synthesized new atpenin A5 analogs for SAR study. Most of the analogs lacked one or several functional groups in the side chain of atpenin A5, and the stereoisomers proved to be weak nematode complex II inhibitors. However, we determined that 4-epi-atpenin A5 was a potent nematode complex II inhibitor comparable to atpenin A5. Therefore, 4-epi-atpenin A5 is expected to become a new lead compound in nematicide development.     

Chiral recognition in cucurbituril cavities

For the first time, achiral cucurbiturils (CBs) were endowed with significant enantiomeric and distereomeric discrimination by incorporating a strong chiral binder. Calorimetric, nuclear magnetic, light-scattering, and mass spectral studies revealed that (S)-2-methylbutylamine (as a strong binder) can be discriminated by two enantiomeric supramolecular hosts, composed of CB[6] and (R)- or (S)-2-methylpiperazine, with an unprecedented 95% enantioselectivity in aqueous NaCl solution. This is the highest enantioselectivity ever reported for a supramolecular system derived from an achiral host. Similarly, CB[7], with a larger cavity, exhibited diastereoselectivities up to 8 times higher for diastereomeric dipeptides, as demonstrated for L-Phe-L-Leu-NH3+ versus L-Phe-D-Leu-NH3+.     

Dirhodium(II) tetrakis(perfluorobutyrate)-catalyzed 1,4-hydrosilylation of alpha,beta-unsaturated carbonyl compounds

The use of dirhodium(II) catalysts in the 1,4-hydrosilylation of alpha,beta-unsaturated ketones and aldehydes was explored. Dirhodium(II) tetrakis(perfluorobutyrate), Rh2(pfb)4, proved to be the catalyst of choice for this process, providing the corresponding silyl enol ethers in high yields.     

Terahertz radiation by an ultrafast spontaneous polarization modulation of multiferroic BiFeO3 thin films

Terahertz (THz) radiation has been observed from multiferroic BiFeO3 thin films via ultrafast modulation of spontaneous polarization upon carrier excitation with illumination of femtosecond laser pulses. The radiated THz pulses from BiFeO3 thin films were clarified to directly reflect the spontaneous polarization state, giving rise to a memory effect in a unique style and enabling THz radiation even at zero-bias electric field. On the basis of our findings, we demonstrate potential approaches to ferroelectric nonvolatile random access memory with nondestructive readability and ferroelectric domain imaging microscopy using THz radiation as a sensitive probe.     

Synthesis and Fluorescence Properties of Pyrimidine‐Based Diboron Complexes with Donor–π–Acceptor Structures

Pyrimidine‐based diboron complexes bearing β‐iminoenolate ligands and phenyl groups as bulky substituents on the boron atoms were synthesized as novel fluorescent dyes, and their fluorescence properties were investigated in solution and in the solid state. The diboron complexes with donor–π–acceptor structures showed positive solvatochromism in the fluorescence spectra. The cyano derivative exhibited the most dramatic redshift of the fluorescence maximum F_max with increasing solvent polarity (from 551 nm in n‐hexane to 710 nm in acetonitrile). The diboron complexes showed solid‐state fluorescence in the range of 578–706 nm with fluorescence quantum yields of 0.06–0.28. Additionally, the trifluoromethyl derivative exhibited solvent‐inclusion solid‐state fluorescence. The trifluoromethyl derivative formed toluene‐inclusion and ethyl acetate‐inclusion crystals. The toluene‐inclusion crystal (F_max=668 nm, Φ_f=0.16) showed a blueshifted F_max and higher Φ_f value compared to the original trifluoromethyl derivative (F_max=694 nm, Φ_f=0.08) in the solid state. On the other hand, the F_max (709 nm) and Φ_f (0.04) values of the ethyl acetate‐inclusion crystal were redshifted and lower, respectively.