Changes in the structure of water deduced from the pressure dependence of the Raman OH frequency

We report on the Raman spectra of water under high temperature and pressure conditions and show a discontinuity in the pressure dependence of the OH stretching frequency. As pressure increases, the strength of hydrogen bonding increases rapidly in the pressure ranges up to 0.4+/-0.1 GPa at 25 degrees C, 1.0+/-0.1 GPa at 100 degrees C, and 1.3+/-0.1 GPa at 300 degrees C and slowly above these pressures. This finding clearly demonstrates the existence of discontinuities in the pressure response of the hydrogen bonds of water, which suggests a possible structural change under these conditions.     

Formation of flat, homogeneous surfaces of organized molecular films of three-armed polymerizable amphiphiles with metal-scavenging properties

Surface complexing (i.e., metal-bridged polymerization in this study) of a three-armed amphiphilic compound with metal-scavenging properties has been investigated using the surface pressure-area (π-A) isotherms of a Langmuir monolayer from the subphase. Inductively coupled plasma mass spectrometry (ICP-MS) was also carried out on eluted solutions from corresponding multilayers of the solid. Furthermore, the molecular arrangement and surface morphology of organized molecular films of the resultant comb polymer were estimated by in-plane and out-of-plane X-ray diffraction (XRD) and by atomic force microscopy. From an analysis of the wide-angle X-ray diffraction of the corresponding monomer in the bulk, the long hydrocarbon chains are observed to pack hexagonally in the solid state. Compared to their monolayer on distilled water as the subphase, a polymerized monolayer on a buffer solution containing Cd(2+) ions is remarkably expanded at 15 °C. From ICP-MS and IR measurements, it is found that this monolayer stoichiometrically contains Cd(2+) ions on the -SH group. It is found by XRD that highly ordered layer structures and regular 2D lattices are constructed in the organized molecular films of the Cd-bridged comb polymer. Furthermore, the surface morphology of Langmuir-Blodgett films fabricated from the monolayers on a buffer solution containing Cd(2+) and Pd(2+) shows flat and smooth domains upon metal scavenging and polymerization.     

CHANGES IN THE PATTERNS OF BIOSYNTHESIS and COMPOSITION OF AMINO ACIDS IN A MARINE PHYTOPLANKTER EXPOSED TO ULTRAVIOLET-B RADIATION: NITROGEN LIMITATION IMPLICATED

Abstract— The impact of ultraviolet-B radiation (UVBR) on the biosynthesis and the composition of intracellular dissolved free and combined amino acids was examined in nitrate-replete and nitrate-deficient cultures of Tetraselmis sp. Several similarities were observed in the response of Tetraselmis sp. to nitrogen deficiency and exposure to UVBR, in support of a view that UVBR affects amino acid synthesis in phytoplankton via its inhibitory effects on nitrogen assimilation into the cells. At levels that still permitted the uptake of carbon into the cells, both nitrogen deficiency and UVBR exposure resulted in a reduction in the overall rates of carbon incorporated into amino acids, an increase in the absolute concentrations of amino acids within the intracellular dissolved free amino acid (INDFAA) pool and a decrease in the total cellular amino acid (TCAA) pool. An examination of the patterns of carbon assimilation into individual amino acids in cells exposed to UVBR revealed similarities with the patterns in cells subject to nitrogen deficiency. The most conspicuous changes from the controls included an increased incorporation of ¹³C into glutamic' acid (glutamic acid + glutamine) and aspartic acid and a marked reduction into alanine and valine. Changes in the concentrations of amino acids within the INDFAA and TCAA pools were also similar in nitrate-deficient and UVBR-exposed cells and resembled the carbon assimilation patterns. These results strongly suggest that UVBR-induced changes in the biosynthesis and composition of amino acids are probably via its suppression of nitrogen assimilation into the cells.     

Stimulation of Microvascular Networks on Sulfonated Polyrotaxane Surfaces with Immobilized Vascular Endothelial Growth Factor

Modulation of material properties and growth factor application are critical in constructing suitable cell culture environments to induce desired cellular functions. Sulfonated polyrotaxane (PRX) surfaces with immobilized vascular endothelial growth factors (VEGFs) are prepared to improve network formation in vascular endothelial cells. Sulfonated PRXs, whereby sulfonated α‐cyclodextrins (α‐CDs) are threaded onto a linear poly(ethylene glycol) chain capped with bulky groups at both terminals, are coated onto surfaces. The molecular mobility of sulfonated PRX surfaces is modulated by tuning the number of threading α‐CDs. VEGF is immobilized onto surfaces with varying mobility. Low mobility and VEGF‐immobilization reinforce cell proliferation, yes‐associated protein activity, and rhoA, pdgf, ang‐1, and pecam‐1 gene expression. Highly mobile surfaces and soluble VEGF weakly affect these cell responses. Network formation is strongly stimulated in vascular endothelial cells only on low‐mobility VEGF‐immobilized surfaces, suggesting that molecular mobility and VEGF immobilization synergistically control cell function.     

Specific interaction between polyethylenimine and azo dyes carrying hydroxyl groups

The binding of acid azo dyes having phenolic hydroxyl groups such as orange I ( I ), orange II ( II ), chrome violet ( III ), 4-hydroxyazobenzene-4′-sulfonate ( IV ), and 2,4-dihydroxyazobenzene-4′-sulfonate ( V ) by polyethylenimine was studied by equilibrium dialysis and spectroscopic methods. The results obtained indicate that dyes ( III ) and ( V ) with two OH groups are bound much more strongly than dyes ( I ), ( II ), and ( IV ) with one OH group. Also polyethylenimine is far superior to any other polymers which have been examined, including bovine serum albumin, polyvinylpyrrolidone, and poly-L -lysine, in its ability to form complexes with these dyes ( III ) and ( V ). The OH groups involved participate preferentially in complex formation with polyethylenimine. The unusual affinity of polyethylenimine for the dyes carrying OH groups is discussed.     

Crystal Structures of Mono-, Di-, and Tri(p-tert-butyl)-thiacalix[4]arenes: Dimeric Self-inclusion Behavior

X-Ray crystal structures of the mono-, di-, and tri(p-tert-butyl)-substituted thiacalix[4]arenes (TC4As; 1, 2, and 3, respectively) have beendetermined. TC4As 1–3 adopt a cone conformation and form dimeric self-inclusion units in such a manner that phenol moieties are inserted into the cavity of each molecule. In all the crystal structures of 1–3, lateralface-to-face interactions exist between the phenol rings that do not bear a tert-butyl substituent, and seemingly, this molecular assembly stabilizes the formation of self-inclusion. TC4As 1 and 2 adopt a cone conformation with C₂ symmetry, leading to the formation of rim-to-rim intermolecular hydrogenbonds so as to link the dimeric units up and down. On the other hand, 3 adopts a regular cone conformation with C₄ symmetry to form cyclic hydrogen bonds withinthe rim part of TC4A.     

Reverse zymography using fluorogenic substrates for protease inhibitor detection

A novel, sensitive method for detecting protease inhibitors by using fluorescent protease substrates in gels is described. The protease inhibitors were separated on sodium dodecyl sulfate (SDS)-polyacrylamide gels containing a copolymerized peptide substrate, namely 4-methyl-coumaryl-7-amide (MCA). As the incorporated substrates in the gel, Boc-Phe Ser-Arg-MCA was used for trypsin, Suc-Ala-Ala-Pro-Phe-MCA for alpha-chymotrypsin, and Z-Phe-Arg-MCA for papain. After electrophoresis, washing and incubating the gel with the target protease solutions allowed the substrate to be cleaved by the protease, and the release of the fluorescent 7 amino-4 methyl-coumarin (AMC), which was detected under a UV transilluminator. The uncleaved peptide-MCA substrate remained where the inhibitors were present, and was visualized as dark blue bands on the light-green fluorescent background gel. This new method offers several advantages over other previous methods including: (i) greatly increased sensitivity can be achieved in a shorter period of time, which may be useful for discovering new protease inhibitors in small amounts of crude material; (ii) the procedure is quite simple and quick since the incubation period is very short and no time is needed for staining and destaining steps; (iii) since these probes using substrate specificity/target proteases, they are excellent tools for detection and discrimination of unknown protease inhibitors for various target proteases.     

Preconcentration of copper, cadmium, and lead with a thiacalix[4]arenetetrasulfonate-loaded Sephadex A-25 anion-exchanger for graphite-furnace atomic-absorption spectrometry

A rapid column-adsorption method has been developed for concentrating traces of copper, cadmium, and lead in water prior to their determinations by graphite-furnace atomic-absorption spectrometry. The adsorbent used was prepared by loading a strongly basic anion-exchanger QAE-Sephadex A-25 (50 mg) with thiacalix[4]arenetetrasulfonate (20 mol). Two-hundredfold preconcentration of the analyte elements was achieved by passing 100 mL of sample solution (pH 8.0) through a column packed with the adsorbent (6 mm i.d.×7 mm high) at a flow rate of 10 mL min^–1 and by the subsequent elution with 500 L of aqueous nitric acid solution (1 mol L^–1). The practical applicability of the proposed method was evaluated by analyzing certified reference seawater samples.