Synthetic Processes toward Nitriles without the Use of Cyanide: A Biocatalytic Concept Based on Dehydration of Aldoximes in Water

While belonging to the most fundamental functional groups, nitriles represent a class of compound that still raises challenges in terms of an efficient, cost-effective, general and, at the same time, sustainable way for their synthesis. Complementing existing chemical routes, recently a cyanide-free enzymatic process technology based on the use of an aldoxime dehydratase (Oxd) as a biocatalyst component has been developed and successfully applied for the synthesis of a range of nitrile products. In these biotransformations, the Oxd enzymes catalyze the dehydration of aldoximes as readily available substrates to the nitrile products. Herein, these developments with such enzymes are summarized, with a strong focus on synthetic applications. It is demonstrated that this biocatalytic technology has the potential to “cross the bridge” between the production of fine chemicals and pharmaceuticals, on one hand, and bulk and commodity chemicals, on the other.     

Picosecond protein response to the chromophore isomerization of photoactive yellow protein: selective observation of tyrosine and tryptophan residues by time-resolved ultraviolet resonance Raman spectroscopy

Picosecond time-resolved ultraviolet resonance Raman (UVRR) spectra of photoactive yellow protein (PYP) were measured. UVRR bands attributed to the vibration of tyrosine and tryptophan residues showed a spectral change upon photoreaction. It was found that the hydrogen-bond strength between the chromophore and Y42 increases in the pG* state. The ultrafast change in the tryptophan band revealed that a photoinduced structural change of the chromophore had propagated to the W119 region, located 12 A from the chromophore, within picoseconds.     

Single-nanometer focusing of hard x-rays by Kirkpatrick-Baez mirrors

We have constructed an extremely precise optical system for hard-x-ray nanofocusing in a synchrotron radiation beamline. Precision multilayer mirrors were fabricated, tested, and employed as Kirkpatrick-Baez mirrors with a novel phase error compensator. In the phase compensator, an at-wavelength wavefront error sensing method based on x-ray interferometry and an in situ phase compensator mirror, which adaptively deforms with nanometer precision, were developed to satisfy the Rayleigh criterion to achieve diffraction-limited focusing in a single-nanometer range. The performance of the optics was tested at BL29XUL of SPring-8 and was confirmed to realize a spot size of approximately 7 nm.     

Highly fluorescent slipped-cofacial phthalocyanine dimer as a shallow inclusion complex with α-cyclodextrin

Supramolecular control of the π-stacked configuration of aqueous phthalocyanine (Zn[Pc(SO(3))(4)]) was achieved, allowing organization of a J-type slipped-cofacial dimer with per-O-methylated α-cyclodextrin (TMe-α-CDx) by the aid of host-guest interactions. Pristine Zn[Pc(SO(3))(4)] forms nonfluorescent face-to-face aggregates in water. The π-stacked configuration was controlled in the slipped-cofacial dimer, which was formed as a shallow inclusion complex with TMe-α-CDx, giving remarkably enhanced fluorescence with a very small Stokes shift. Organization of the J-type slipped-cofacial dimer as a 2:2 Zn[Pc(SO(3))(4)]-TMe-α-CDx complex was achieved through π-stacking of the unencapsulated segment of Zn[Pc(SO(3))(4)] shallowly encapsulated by a small TMe-α-CDx cavity.     

Structural basis for oxygen sensing and signal transduction of the heme-based sensor protein Aer2 from Pseudomonas aeruginosa

The crystal structure of a truncated Aer2, a signal transducer protein from Pseudomonas aeruginosa, consisting of the heme-containing PAS and di-HAMP domains revealed that a distal tryptophan residue (Trp283) plays an important role in stabilizing the heme-bound O(2) and intra-molecular signal transduction upon O(2) binding.     

Protein dynamics of heme–heme oxygenase‐1 complex following carbon monoxide dissociation

Structural changes of heme‐heme oxygenase‐1 complex following carbon monoxide (CO) dissociation were studied by time‐resolved resonance Raman spectroscopy. We observed temporal changes for resonance Raman bands of the Fe–His stretch and the heme propionate bends in the subnanosecond and microsecond time regimes. These changes suggest structural rearrangements in the Fe–His linkage and the salt bridges of the heme propionates following CO dissociation. The present data supports the model proposed by an X‐ray crystallographic study. The Fe–His stretching mode exhibited an upshift until 30 µs after dissociation as the delay time increased. This is the first example of a CO‐dissociation‐induced strengthening of the Fe‐His linkage in hemeproteins. Copyright © 2010 John Wiley & Sons, Ltd.     

Magnetic and Raman Scattering Studies on Intercalation Compounds FexNbS2

Abstract

Raman scattering spectra and magnetic susceptibility are measured in intercalation compounds Fe^xNbS² (0.159≤x≤0.325). A strong modification of Raman spectra is observed in a sample with x=0.239 (～ 0.25) which is accompanied by 2a × 2a structural change and antiferromagnetic ordering. Some correlations between magnetic ordering (antiferromagnetic or spin glass) and structural change are also discussed for wide range of Fe contents x.     

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.     

Self-assembled monolayer and multilayer formation using redox-active Ru complex with phosphonic acids on silicon oxide surface

The formation of self-assembled monolayer and multilayer using redox-active Ru complex molecules with phosphonic acids on SiO₂ surface has been examined using X-ray photoelectron spectroscopy (XPS), ellipsometry, and time of flight secondary mass-ion spectroscopy (TOF-SIMS). We found that an introduction of a Zr adlayer leads to higher surface molecular density of Ru complex SAMs on the SiO₂ surface, compared to that of obtained from the direct adsorption of Ru complex monolayer on the SiO₂ surface. We further tried to fabricate a multilayer film using this molecule with Zr(IV) ion acting as a chemical glue by a successive immersion process. The XPS data revealed that the molecular densities of the multilayers were also higher for the immobilization with Zr adlayer between Ru complex and SiO₂ surface than those without the Zr adlayer, suggesting that Zr adlayer is effective in forming highly packed molecular layer of phosphonic acids on SiO₂ surface. We found the film growth reached a saturation point after 6 layers on the SiO₂ surface. The film growth saturation can be explained by a molecular domain boundary effect encountered due to the large tilt angle of the molecular layer.     

Physicochemical studies on cross-linked thorium(IV)–alginate complex especially the electrical conductivity and chemical equilibrium related to the coordination geometry

The electrical conductivity of cross-linked thorium(IV)–alginate complex in the form of circular disc has been investigated as a function of temperature. The Arrhenius plot of log σ vs. 1/T showed a simple parabolic shape at the early stages, followed by a sharply increase in o values with raising the temperature at the final stages. This behaviour was interpreted by the formation of free-radicals at the initial stages, followed by the degradation of the complex at elevated temperatures to give rise to thorium oxide product. The heterogeneous chemical equilibrium for exchange of Th⁴⁺ counter ions in the complex by H⁺ ions has been investigated by titrimetric and complexometric techniques. The thermodynamic equilibrium constant was found to be 26 ± 0.25 dm⁹ mol^?3 at 25 °C. The X-ray diffraction pattern indicated that thorium(IV)–alginate complex is amorphous in nature. Infrared absorption spectra indicated that Th⁴⁺ is chelated to alginate macromolecular chains and displayed υ_s OCO^? and υ_as OCO^? in the ranges of 1419 and 1635 cm^?1, respectively. A geometrical structure for chelation of thorium(IV) to the functional groups of alginate macromolecule is suggested and discussed in terms of complex stability.