Observation of water molecules bound to a protein using cold-spray ionization mass spectrometry.

The characterization of water molecules bound to ribonuclease T1 (RNase T1) was carried out using cold-spray ionization mass spectrometry (CSI-MS). CSI-MS is a variant of electrospray ionization mass spectrometry (ESI-MS) operating at low temperature, and is particularly suitable for investigating the weaker molecular associations, since the temperature at the spray interface is much lower than that in the conventional ESI-MS. In this approach, ion peaks due to the addition of nine water molecules were identified at a spray temperature of 48 degrees C. This result showed good agreement with that inferred by the combinational analysis of NMR and X-ray crystallography, indicating that CSI-MS is capable of rapidly providing reliable information to characterize the number of water molecules bound to a macromolecule.     

Hydrogen‐bond‐assisted stereocontrol in the radical polymerization of N‐isopropylacrylamide with secondary alkyl phosphate: The effect of the bulkiness of the ester group

The radical polymerization of N‐isopropylacrylamide (NIPAAm) in toluene at low temperatures was investigated in the presence of triisopropyl phosphate (TiPP). The addition of TiPP induced a syndiotactic specificity that was enhanced by the polymerization temperature being lowered, whereas atactic polymers were obtained in the absence of TiPP, regardless of the temperature. Syndiotactic‐rich poly(NIPAAm) with a racemo dyad content of 65% was obtained at ?60 °C with a fourfold amount of TiPP, but almost atactic poly(NIPAAm)s were obtained by the temperature being lowered to ?80 °C. This result contrasted with the result in the presence of primary alkyl phosphates, such as tri‐n‐propyl phosphate: the stereospecificity varied from syndiotactic to isotactic as the polymerization temperature was lowered. NMR analysis at ?80 °C revealed that TiPP predominantly formed a 1:1 complex with NIPAAm, although primary alkyl phosphates preferentially formed a 1:2 complex with NIPAAm. Thus, it was concluded that a slight increase in the bulkiness of the added phosphates influenced the stoichiometry of the NIPAAm–phosphate complex at lower temperatures, and consequently a drastic change in the effect on the stereospecificity of NIPAAm polymerization was observed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3899–3908, 2005     

Z‐Shaped Pentaleno‐Acene Dimers with High Stability and Small Band Gap

Acene‐based materials have promising applications for organic electronics but the major constrain comes from their poor stability. Herein a new strategy to stabilize reactive acenes, by fusion of an anti‐aromatic pentalene unit onto the zigzag edges of two acene units to form a Z‐shaped acene dimer, is introduced. The Z‐shaped acene dimers are extremely stable and show a small energy gap resulting from intramolecular donor–acceptor interactions. X‐ray crystallographic analysis revealed their unique geometry and one‐dimensional slip‐stack columnar structure. Besides optical and electrochemical characterizations, solution‐processed field‐effect transistors were also fabricated.     

Presence of rhodopsin and porphyropsin in the eyes of 164 fishes, representing marine, diadromous, coastal and freshwater species--a qualitative and comparative study

There are two types of visual pigments in fish eyes; most marine fishes have rhodopsin, while most freshwater fishes have porphyropsin. The biochemical basis for this dichotomy is the nature of the chromophores, retinal (A1) and 3-dehydroretinal (A2), each of which is bound by an opsin. In order to study the regional distribution of these visual pigments, we performed a new survey of the visual pigment chromophores in the eyes of many species of fish. Fish eyes from 164 species were used to examine their chromophores by high-performance liquid chromatography--44 species of freshwater fish, 20 of peripheral freshwater fish (coastal species), 10 of diadromous fish and 90 of seawater fish (marine species) were studied. The eyes of freshwater fish, limb freshwater fish and diadromous fish had both A1 and A2 chromophores, whereas those of marine fish possessed only A1 chromophores. Our results are similar to those of previous studies; however, we made a new finding that fish which live in freshwater possessed A1 if living near the sea and A2 if living far from the sea if they possessed only one type of chromophore.     

Selective synthesis of 5-alkenyl-15-alkynyl-porphyrin and 5,15-dialkynyl-porphyrin by 2+2 acid-catalyzed condensation of dipyrrylmethane and TMS propynal

One of 5-alkenyl-15-alkynyl-porphyrin and 5,15-dialkynyl-porphyrin was prepared selectively by 2+2 acid-catalyzed condensation of bicyclo[2.2.2]octadiene-fused dipyrrylmethane and TMS propynal in the presence of BF₃·OEt₂ only by the choice of the solvent. The alkenyl group was expected to be obtained by a protonation followed by intramolecular 1,2-hydride transfer from methine position of porphyrinogen.     

Temperature-swing adsorption of aromatic compounds in water using polyampholyte gel

The adsorption property of the polyampholyte gel composed of sodium styrene sulfate (SSS) and vinylbenzyl trimethylammonium chloride (VBTA) has been investigated with several hydrophobic aromatic compounds as adsorbate. Using the N-isopropylacrylamide (NIPA) gel, the corresponding experiments were also performed for comparison. At room temperature, the NIPA gel hardly adsorbed the aromatic compounds, while it adsorbed them at higher temperatures. As for the SSS-VBTA gel, the adsorption amounts of the polyaromatic compounds decreased with increasing temperature, while the adsorption amounts of the monoaromatic compounds were almost independent of temperature and smaller than those of the polyaromatic compounds. These results indicate that the aromatic rings in the SSS-VBTA gel may play an important role in the adsorption of the aromatic compounds. Also, it has been demonstrated that the SSS-VBTA gel can repeatedly adsorb bisphenol-A at room temperature and desorb it at higher temperature by the temperature-swing operation: this behavior is diametrically opposite to that of the NIPA gel. This shows that the SSS-VBTA gel is much more suitable for the adsorption removal of the hydrophobic aromatic compounds from very dilute aqueous solutions, because a vast amount of energy is required for heating a large amount of water when using the NIPA gel.     

Soluble precursors of 2,3-naphthalocyanine and phthalocyanine for use in thin film transistors

Soluble precursors of 2,3-naphthalocyanine (Nc) and phthalocyanine (Pc) were prepared and were converted into insoluble semiconducting thin films of Pc and Nc by heating after fabrication via spin-coating.     

3D coordination metal-organic frameworks of octacyanometalate bridging between Cu4 magnetic units

Magnetic Cu4 clusters with S = 2 are bridged by octacyanometaltate(IV) to form two 3D cluster arrays of metal-organic frameworks. Magnetic investigation shows the ferromagnetic coupling between Cu(II) ions and very weak antiferromagnetic interaction between clusters.     

Quantitative determination of amino acids in functional foods by microchip electrophoresis

Microchip electrophoresis (MCE), a first-generation micrototal analysis system, has emerged during the miniaturization phase of food analysis. Based on the micellar electrokinetic chromatography mode, a simple and fast MCE method with light emitting diode-induced fluorescence detection was developed for quantitative analysis of amino acids in three different kinds of functional foods, viz. sports beverages, jelly-form beverages, and tablet-form functional foods. In contrast to the glass microchip, we improved the separation of amino acids on a poly(methyl methacrylate) (PMMA) chip by addition of cationic starch derivatives. 4-fluoro-7-nitro-2,1,3-benzoxadiazole, which has a short labeling time for amino acids, was used as the fluorescently labeled dye. This MCE method takes less than 10 min of total analysis time including sample preparation and analysis of amino acids in functional foods on a PMMA chip. The results show that this approach has the potential to be a fast and simple method for amino acid analysis in functional foods.