Novel chiral recognition beyond the limitation due to the law of mass action: highly enantioselective chiral sensing based on non-linear response in phase transition events

Based on non-linear response in phase transition events exhibiting a sharp transmittance change, an intelligent chiral sensor capable of chirality amplification in aqueous media was designed and constructed as poly(N-isopropylacrylamide) having chiral pseudo-18-crown-6. Both sensitivity and selectivity of the sensor surmount the limitation due to the law of mass action.     

Development of salt-tolerance interface for an high performance liquid chromatography/inductively coupled plasma mass spectrometry system and its application to accurate quantification of DNA samples

Accurate quantification of DNA is highly important in various fields. Determination of phosphorus by ICP-MS is one of the most effective methods for accurate quantification of DNA due to the fixed stoichiometry of phosphate to this molecule. In this paper, a smart and reliable method for accurate quantification of DNA fragments and oligodeoxythymidilic acids by hyphenated HPLC/ICP-MS equipped with a highly efficient interface device is presented. The interface was constructed of a home-made capillary-attached micronebulizer and temperature-controllable cyclonic spray chamber (IsoMist). As a separation column for DNA samples, home-made methacrylate-based weak anion-exchange monolith was employed. Some parameters, which include composition of mobile phase, gradient program, inner and outer diameters of capillary, temperature of spray chamber etc., were optimized to find the best performance for separation and accurate quantification of DNA samples. The proposed system could achieve many advantages, such as total consumption for small amount sample analysis, salt-tolerance for hyphenated analysis, high accuracy and precision for quantitative analysis. Using this proposed system, the samples of 20 bp DNA ladder (20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 300, 400, 500 base pairs) and oligodeoxythymidilic acids (dT_12–18) were rapidly separated and accurately quantified.     

Differences between protein dynamics of hemoglobin upon dissociation of oxygen and carbon monoxide

Protein dynamics of human adult hemoglobin (HbA) upon ligand photolysis of oxygen (O(2)) and carbon monoxide (CO) was investigated using time-resolved resonance Raman (TR(3)) spectroscopy. The TR(3) spectra of the both photoproducts at 1-ns delay differed from that of the equilibrium deligated form (deoxy form) in the frequencies of the iron-histidine stretching [ν(Fe-His)] and methine wagging (γ(7)) modes, and the band intensity of pyrrole stretching and substituent bending (ν(8)) modes. Spectral changes of the O(2) photoproduct in the submicrosecond region were faster than those of the CO photoproduct, indicating that the structural dynamics following the photodissociation is ligand dependent for HbA. In contrast, no ligand dependence of the dynamics was observed for myoglobin, which has a structure similar to that of the subunit of HbA. The structural dynamics and relevance to the functionality of HbA also are discussed.     

Degradation of Target Oligosaccharides by Anthraquinone–Lectin Hybrids with Light Switching

Anthraquinone–lectin hybrids were effectively synthesized using water‐soluble anthraquinone derivative 11 with concanavalin A (ConA) and hygrophorus russula lectin (HRL) to give anthraquinone–ConA ( 16 ) and anthraquinone–HRL ( 17 ) hybrids, respectively. These anthraquinone–lectin hybrids effectively and selectively degraded oligosaccharides containing a mannose residue as a non‐reducing terminal sugar, which has affinity for ConA and HRL, under photo‐irradiation with long‐wavelength UV light without additives and under neutral conditions. In addition, anthraquinone–HRL ( 17 ) selectively photo‐degraded only Man(α1,6)Man, which has a high affinity for HRL, among several mannosides by recognition of both the type and glycosidic linkage profile of the sugar in an oligosaccharide.     

Successive Chain‐Growth Condensation Polymerization for the Synthesis of Well‐Defined Diblock Copolymers of Aromatic Polyamide and Aromatic Polyether

Well‐defined diblock condensation copolymers composed of an aromatic polyamide and an aromatic polyether have been synthesized by means of successive chain‐growth condensation polymerizations. Polymerization of a polyamide monomer with an orthogonally difunctional initiator is accompanied with side reactions. On the other hand, polymerization with a monofunctional initiator afforded well‐defined polyamide, which has been converted into a macroinitiator by introduction of a terminal 4‐fluorobenzophenone unit. Well‐defined diblock copolymers are obtained by polymerization of a polyether monomer in the presence of this macroinitiator.

     

Morphology and properties of globular polymeric materials in the solid state: A composite material of DNA with a cationic surfactant

The aim of the present study was to control entanglements in order to regulate the properties of polymeric solids. Initially, fabrication of polymeric solids with few entanglements was attempted. Films of the DNA–cationic surfactant, cetyltrimethylammonium bromide (CTAB) (DNA–CTA), were cast from ethanol solution at room temperature. Morphological examination of DNA–CTA complex films using atomic force microscopy (AFM) revealed that these films were constructed by particle‐like substances. Geometrical analysis of AFM images showed that the particle‐like substances were the aggregates of several DNA–CTA globules. Mechanical characterization suggested that there were fewer entanglements than with normal plastic films. Small angle X‐ray scattering experiments during annealing indicated that molecular motions were highly excited in the surface region of each particle. In conclusion, a globular polymeric film with fewer entanglements was fabricated. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 730–738     

A new reagent, 2-[phenyl(methyl)sulfonio]ethyl-4-nitro-phenylcarbonate tetrafluoroborate (Pms-ONp), for preparing water-soluble N-protected amino acids

Peptide syntheses are performed in various organic solvents, the disposal of which is an environmental problem. To avoid this problem, peptide synthesis in water using reagents of low toxicity is desirable. For peptide synthesis in water, we previously reported the design of a water-soluble N-protecting group, 2-[phenyl(methyl)sulfonio]ethoxycarbonyl tetrafluoroborate (Pms) group, but the introduction of this group onto sulfur-containing amino acids was problematic. Here, a new reagent, 2-[phenyl(methyl)sulfonio]ethyl-4-nitrophenylcarbonate tetrafluoroborate (Pms-ONp), has been designed and used to prepare Pms derivatives of sulfur-containing amino acids. Pms-Met was prepared and tested for the solid-phase synthesis of Met-enkephalin amide in water using a crosslinked ethoxylate acrylate resin.     

A phytochrome-like protein AphC triggers the cAMP signaling induced by far-red light in the cyanobacterium Anabaena sp. strain PCC7120

In the filamentous, nitrogen-fixing cyanobacterium Anabaena sp. PCC7120, red light (630 nm) decreased, whereas far-red light (720 nm) increased cellular adenosine 3',5'-cyclic monophosphate (cAMP) content. To find a red and far-red light photoreceptor that triggers the cAMP signal cascade, we disrupted 10 open reading frame having putative chromophore-binding GAF domains. The response of the cellular cAMP concentration to red and far-red light in each open reading frame disruptant was determined. It was found that only the mutant of the gene all2699 failed to respond to far-red light. The open reading frame named as aphC encoded a protein with 920 amino acids including GAF domains similar to those involved in Cph2, a photoreceptor of Synechocystis sp. PCC6803. To determine which adenylate cyclase (AC) is responsible for far-red light signal, we disrupted all AC genes and found that CyaC was the candidate. The enzymatic activity of CyaC might be controlled by a far-red light photoreceptor through the phosphotransfer reaction. The site-specific mutant of the Asp59 residue of the receiver (R1) domain of CyaC lost its light-response capability. It was suggested that the far-red light signal was received by AphC and then transferred to the N-terminal response regulator domain of CyaC. Then its catalytic activity was stimulated, which increased the cellular cAMP concentration and drove the subsequent signal transduction cascade.     

Poly(α-amino acid)-immobilized polymer adsorbents for optical resolution. IV. Elucidation of chiral recognition mechanism of poly(N5-benzyl-L-glutamine)-immobilized resin

Various investigations have been carried out in order to further elucidate the chiral recognition mechanism of immobilized poly(N⁵-benzyl-L -glutamine) (PBLGN) for optical resolution. The shape and dimension of the chiral recognition site are determined by resolution of hydantoin derivatives, with substituents of varied bulkiness at the chiral center. The site of the hydrogen bonding association of the enantiomers responsible for chiral recognition is also elucidated. Several adsorbents with electron-donating/withdrawing substituents incorporated into the PBLGN side chain phenyl are synthesized and evaluated for the resolution of (RS)-5-isopropylhydantoin in order to elucidate the association site of PBLGN. Based on the experimental evidences obtained, a most plausible mechanism of chiral recognition is proposed. Additionally, adsorbents with several other poly(α-amino acid)s are also synthesized, and the effect of poly(α-amino acid) side chain length is discussed.     

Efficient synthesis of 3-cyano-6-(2-hydroxyphenyl)pyridines by multi-component condensations on beads

An efficient procedure to perform pyridine ring closure reactions has been developed on beads. A certain number of hydroxyacetophenones were immobilized on Wang resin and condensed with a variety of aldehydes and malononitrile in the presence of ammonium acetate to give 3-cyano-6-(2-hydroxyphenyl)pyridines in a suitable manner for a good example of combinatorial approaches. Chemical yields were better than the corresponding solution-phase chemistry except only a few examples and the best use of inherent advantage of solid-phase chemistry was successfully demonstrated.