Chemo-enzymatic synthesis of 4-methylumbelliferyl beta-(1-->4)-D-xylooligosides: new substrates for beta-D-xylanase assays

Transglycosylation catalyzed by a beta-D-xylosidase from Aspergillus sp. was used to synthesize a set of 4-methylumbelliferyl (MU) beta-1-->4-D-xylooligosides having the common structure [beta-D-Xyl-(1-->4)]2-5-beta-D-Xyl-MU. MU xylobioside synthesized chemically by the condensation of protected MU beta-D-xylopyranoside with ethyl 2,3,4-tri-O-acetyl-1-thio-beta-D-xylopyranoside was used as a substrate for transglycosylation with the beta-D-xylosidase from Aspergillus sp. to produce higher MU xylooligosides. The structures of oligosaccharides obtained were established by 1H and 13C NMR spectroscopy and electrospray tandem mass spectrometry. MU beta-D-xylooligosides synthesized were tested as fluorogenic substrates for the GH-10 family beta-D-xylanase from Aspergillus orizae and the GH-11 family beta-D-xylanase I from Trichoderma reesei. Both xylanases released the aglycone from MU xylobioside and the corresponding trioside. With substrates having d.p. 4 and 5, the enzymes manifested endolytic activities, splitting off MU, MUX, and MUX2 primarily.     

Conformational equilibria and photoinduced tautomerization in 2-(2′-pyridyl)pyrrole

Depending on the polarity and protic abilities of the solvent, 2-(2′-pyridyl)pyrrole can exist in either syn or anti rotameric forms. In nonpolar solvents, intramolecular excited state single proton transfer is observed, manifested by the appearance of low-energy tautomeric emission. The solvent-assisted excited state double proton transfer reaction is also detected. DFT calculations confirm low barriers for both single and double proton transfer processes in the lowest excited singlet state and show different character of the tautomerization in both cases: in the intramolecular reaction, mutual approach of two nitrogen atoms plays an important role.     

Polystyrene prepared by reactive extrusion: kinetics and effect of processing parameters

The conversion and residence time were investigated during the bulk polymerization of styrene in a twin screw extruder. It was found that polymerization mainly occurred in the zone between 400 and 1000 mm along the screw axis in the extruder, corresponding to the residence time of the reactants ranging from 1 to 4 min in the extruder. Furthermore, the processing conditions (feed rate, screw rotation rate) and average molecular weight of the polymer have a great effect on the residence time. Based on dimensionless analysis, a model of the residence time has been built‐up, which has been confirmed by the results of realistic measurements. A kinetic model of the polymerization has also been established under the assumption that the screw extruder can be regarded as an ideal plug flow reactor. Copyright © 2004 John Wiley & Sons, Ltd.     

Catalytic activity of silica in ozone formation in electrical discharges

The catalytic action of granular silica packing on ozone formation has been observed under discharge conditions. Using a glass ozonizer with a metal high-voltage electrode, at a frequency of 400 Hz it was possible to obtain much higher ozone concentrations in the presence q( silica than without packing, with the same total energy consumption. The dependence between ozone production and energy efficiency is considered, and conditions of the optimum ozonizer run are discussed. It is shown that in the all-glass ozonizer with a narrow discharge gap, the ozone concentration may be as high as 6.5% (ca. 130g O₃/m³) when silica packing is applied.     

Synthesis of fused purinoquinazolines. Three new heterocyclic ring systems

The Ullmann reaction of 8-aminotheophylline or 8-aminocaffeine with 2-chlorobenzoic acid and of 8-bromotheophylline with ethyl-2-aminobenzoate afforded derivatives of three new heterocyclic systems: purino[7,8-α]quinazoline-5,9,11(6H,8H,10H)-trione, purino[8,9-b]quinazoline-2,4,11(1H,3H,5H)-trione and purino[8,7-b]quinazoline-2,4,6(1H,3H,11H)-trione, respectively.     

Biosynthesis of aglajnes, polypropionate allomones of the opisthobranch mollusc Bulla striata

The biogenesis of aglajnes, polypropionate allomones of the cephalaspidean mollusc Bulla striata, has been investigated in vivo by feeding experiments. Incorporation of the committed precursor, [1-¹⁴C]-propionate, into aglajne-1 (1) and -3 (3) established the de novo origin of these compounds in B. striata. In the letter we also discuss briefly the ecological meaning of the origin of polypropionates in B. striata and in other cephalaspidean molluscs.     

Synthesis of Glycosylrifamycins,a new type of semisynthetic rifamycins

Glycosylrifamycins, a new type of semisynthetic rifamycin derivatives, can be easily obtained by reaction of 3-(2-aminoethylthio)rifamycin SV ( 2 ) with a glycosyl compound carrying a coupling group, such as isothicyanate or carboxy. We prepared O-acetylated and free glucopyranosyl and arabinopyranosyl derivatives of rifamycin S and SV (see 3–10 ). Additionally, derivatives with D -saccharo-1,4-lactone and with shikimic acid were obtained (see 11–15 ). Glycosylrifamycins show an interesting inhibitory power on Gram-positive bacteria (Table).     

High-density lipoproteins contribute to the alpha-1-globulin zone in capillary electrophoresis of human serum proteins

Alpha-1-antitrypsin (AAT) and alpha-1-acid glycoprotein (AAG) are reported to be the main proteins contributing to the alpha-1-globulin capillary zone electrophoresis (CZE) zone, but the sum (AAT + AAG) showed lower than the alpha-1-globulin. We investigated the role of high-density lipoprotein (HDL), an additional protein migrating in the alpha-1-globulin zone, as a possible cause for such a gap. In a set of 98 sera we measured the alpha-1-globulin with a dedicated clinical capillary electrophoresis system, and AAT, AAG and apolipoprotein A-1 (ApoA) by immunonephelometry. The alpha-1-globulin were consistently higher than the sum (AAT + AAG), by (mean value +/- standard deviation) 1.70 +/- 0.88 g/L in 49 sera with low ApoA, and by 3.59 +/- 0.75 g/L in 49 sera with high ApoA. Corresponding figures in the comparison alpha-1-globulin/(AAT + AAG + ApoA) were reduced to 1.08 +/- 0.77 g/L and 1.67 +/- 0.70 g/L. It is concluded that HDL significantly contribute to the CZE alpha-1-globulin zone, but do not completely explain the differences between the electrophoretic and the immunochemical measurements. However, CZE alpha-1-globulin measurements give information about increases of the two major acute phase proteins comparable to specific protein measurements.     

Antioxidant activity of novel indole derivatives and protection of the myocardial damage in rabbits

Novel indole derivatives containing a triazole moiety (1a-d, 2a-c) were synthesized as lead compounds with interesting pharmacological profiles. Their antioxidant activity was investigated on in vitro non-enzymatic rat hepatic microsomal lipid peroxidation. All compounds showed significant effect in the above assay. The effect depended mainly on the attachment position of the triazole moiety on the indole nucleus. The most potent antioxidant derivatives la, 1c and 1d were tested for their protective ability against the oxidative damage of the myocardium after ischemia-reperfusion, in male rabbits which were subjected to 30 min regional ischemia followed by reperfusion. The tested antioxidant compounds 1a, 1c and 1d were continuously infused for 30 min starting at 10th min of ischemia and lasted at 10th min of reperfusion. The concentration of malondialdehyde (MDA, a marker of lipid peroxidation) and hemodynamic parameters (blood pressure and heart rate) were measured in the baseline, at 20th min of the sustained ischemia, 1st and 20th min of reperfusion. It was found that the examined compounds la, 1c and 1d reduced significantly the level of MDA in rabbits under ischemia-reperfusion and proved to be promising substances for further evaluation of anti-ischemic properties.     

Study of the winter and summer changes of the air composition in the church of Szalowa, Poland, related to conservation

The St. Michael Archangel’s Church in Szalowa, Poland, was selected for closer investigation with respect to the indoor/outdoor air exchange and its influence on the air quality and work arts preservation. Chemical composition, size and abundance of particulate matter and concentration of gases NO₂, SO₂, O₃ inside and outside the church were determined. To study seasonal variation of the weather condition (temperature, inversion level, wind direction) and the influence of seasonal sources of the air pollution (like heating of the nearby houses), samples were collected in winter and summer time. It was stated that suspended particulate matter inside the wooden church has in general an outdoor source. Several groups of particles were distinguished such as the organic ones, soil dust, nitrates and sulphates. In case of organic and soil dust particles, the concentration inside was higher than outside. From the results, in comparison to literature data, one can conclude that accumulation of particulate suspended matter in the church is more intense than in other types of buildings. Gaseous pollutants were detected but their concentration was negligible.