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J Puls

Publications and source records attributed to J Puls.

At least 19 recordsLinked to original sources
PubMed2002

Laser action of trions in a semiconductor quantum well.

We report on the observation of optical gain and lasing at the trion transition of n-doped ZnSe quantum wells. Specifically, the (stimulated) emission-absorption net rate of this transition is controlled by the difference of trion and electron occupation in momentum space. As the mass of the trion is larger than that of the electron, gain occurs on the low-energy side of the line center without degeneracy and inversion in the total particle numbers. The scenario is reminiscent of a three-level system. At higher injection levels, carrier heating sets on and limits the available gain to values of about 10(4) cm(-1).

Journal Article↗
PubMed2001

Investigation on molar mass, solubility and enzymatic fragmentation of xylans by multi-detected SEC chromatography.

Four xylan samples from different origin were investigated, using a multi-detector, size exclusion, chromatographic system with two chromatographic column sets and mobile phases differing in the DMSO:water ratio. Molar mass distribution could be analysed best using a mobile phase of DMSO:water (90:10) with addition of 0.05 M LiBr, a system offering good solubilisation of the polymers and a proper chromatographic separation. SEC analysis in aqueous systems provided information on solubility and aggregation of xylans. A comparison of UV- and RI-signals in different systems gave further information on lignin impurities, which in some cases were involved in aggregation phenomena. Both analytical systems were applied to study the enzymatic fragmentation of xylans. Combining the information derived from the two systems can differentiate between the enzymatic degradation of the well-dissolved and the associated polymer fractions.

Bromides↗
PubMed1999

Purification and characterization of a low-molecular-weight xylanase produced by acrophialophora nainiana

A low-molecular-weight xylanase activity (XynI) was isolated from the fungus Acrophialophora nainiana after growth in a solid medium containing wheat bran. XynI was purified to apparent homogeneity by ultrafiltration and gel filtration chromatography. The purified enzyme had a molecular weight value of approx. 17 kDa, as determined by SDS-PAGE. This enzyme was most active at 50 degreesC and pH 6.0. At 50 degreesC the half-life was 150 min. The apparent Km value for birchwood xylan was much lower than the Km value for oat spelt xylan. XynI was activated by L-cysteine, DTE, beta-mercaptoethanol, and L-tryptophan. XynI did not show significant sequence homology with other xylanases. The analysis of hydrolysis products of xylans and wood pulps showed that XynI was able to release xylooligomers ranging from X2 to X3 and X2 to X6, respectively. The enzyme was not active against acetylated xylan. A small amount of xylose was released from deacetylated, birchwood, and oat spelt xylans. The results obtained with enzymatic treatment of Kraft pulp indicated a reduction in the amount of chlorine compounds required for the process and enhanced brightness gain.

Journal Article↗
PubMed1999

Hydrolysis of xylans by enzyme systems from solid cultures of Trichoderma harzianum strains.

Xylanase activity was isolated from crude extracts of Trichoderma harzianum strains C and 4 grown at 28 degree C in a solid medium containing wheat bran as the carbon source. Enzyme activity was demonstrable in the permeate after ultrafiltration of the crude extracts using an Amicon system. The hydrolysis patterns of different xylans and paper pulps by xylanase activity ranged from xylose, xylobiose and xylotriose to higher xylooligosaccharides. A purified ss-xylosidase from the Trichoderma harzianum strain released xylose, xylobiose and xylotriose from seaweed, deacetylated, oat spelt and birchwood xylans. The purified enzyme was not active against acetylated xylan and catalyzed the hydrolysis of xylooligosaccharides, including xylotriose, xylotetraose and xylopentaose. However, the enzyme was not able to degrade xylohexaose. Xylanase pretreatment was effective for hardwood kraft pulp bleaching. Hardwood kraft pulp bleached in the XEOP sequence had its kappa number reduced from 13.2 to 8.9 and a viscosity of 20. 45 cp. The efficiency of delignification was 33%.

Cell Culture Techniques↗
PubMed1996

Purification and characterization of two arabinofuranosidases from solid-state cultures of the fungus Penicillium capsulatum.

Two arabinofuranosidases, termed Ara I and Ara II, from solid-state cultures of Penicillium capsulatum were purified to apparent homogeneity as judged by electrophoresis and isoelectric focusing. Each enzyme is a single subunit glycoprotein, and they have M(r)s and pIs of 64,500 and 4.15 (Ara I) and 62,700 and 4.54 (Ara II), respectively. Ara I is most active at pH 4.0 and 60 degrees C, while Ara II exhibits optimal activity at pH 4.0 and 55 degrees C. Ara I is the more thermostable, with its half-life at 70 degrees C and pH 4.0 being 17.5 min. By contrast, the half-life of Ara II is only 9 min at 60 degrees C and pH 4.0. Ara I has the lower Km and higher catalytic constant values with p-nitrophenyl-alpha-L-arabinofuranoside being used as the substrate. Arabinose, a competitive inhibitor (Ki, 16.4 mM) of Ara II, has no effect on Ara I activity at concentrations of up to 40 mM. Each enzyme catalyzes the release of arabinose from pectin, araban, and certain arabinose-containing xylans. The last activity is enhanced by pretreatment of the relevant substrates with xylanase, ferulic acid esterase, or combinations of these enzymes. Thus, arabinoxylooligosaccharides in which arabinose is the sole side chain substituent appear to be the preferred substrates. On the basis of the evidence cited above, each enzyme has been classified as an alpha-L-arabinofuranoside arabinofuranohydrolase (EC 3.2.1.79).

Arabinose↗
PubMed1995

Purification and Characterization of the (alpha)-Glucuronidase from Thermoanaerobacterium sp. Strain JW/SL-YS485, an Important Enzyme for the Utilization of Substituted Xylans.

A cell-associated (alpha)-glucuronidase was purified to gel electrophoretic homogeneity from the thermophilic anaerobic bacterium Thermoanaerobacterium sp. strain JW/SL-YS485. This enzyme had a pI of 4.65, a molecular weight of 130,000, and two subunits; the molecular weight of each subunit was 74,000. The enzyme exhibited the highest level of activity at pH 5.4 and 60(deg)C, as determined by a 5-min assay. The K(infm) and k(infcat) values of the enzyme for 4-methylglucuronosyl xylobiose were 0.76 mM and 1,083 IU/(mu)mol, respectively. The Arrhenius energy was 26.4 kJ/mol. The specific activities of the enzyme with 4-O-methylglucuronosyl xylobiose, 4-O-methylglucuronosyl xylotriose, and 4-O-methylglucuronosyl xylotetraose were 8.4, 4.8, and 3.9 IU/mg, respectively. The purified (alpha)-glucuronidase and a (beta)-xylosidase purified from the same organism interacted synergistically to hydrolyze 4-methylglucuronosyl xylotetraose.

Journal Article↗
PubMed1993

The xylan-degrading enzyme system of Talaromyces emersonii: novel enzymes with activity against aryl beta-D-xylosides and unsubstituted xylans.

Talaromyces emersonii, a thermophilic aerobic fungus, produces a complete xylan-degrading enzyme system when grown on appropriate substrates. In this paper we present the physicochemical and catalytic properties of three enzymes, xylosidase (Xyl) I (M(r) 181,000; pI 8.9), II (M(r) 131,000; pI 5.3) and III (M(r) 54,200; pI 4.2). Xyl I and II appear to be dimeric and Xyl III is a single-subunit protein. All three enzymes catalyse the hydrolysis of aryl beta-D-xylosides and xylo-oligosaccharides. Xyl I is a classic beta-xylosidase (1,4-beta-D-xylan xylohydrolase; EC 3.2.1.37), and Xyl II and III are novel xylanases (endo-1,4-beta-D-xylan xylanohydrolase; EC 3.2.1.8) which we believe have not hitherto been reported. In addition to the above substrates, they also catalyse the extensive hydrolysis of unsubstituted xylans, and may have considerable biotechnological potential. The hydrolysis product profiles and bond-cleavage frequencies with various substrates are presented.

Ascomycota↗
PubMed1993

Matrix isolation applied to the 252Cf plasma-desorption mass spectrometry of underivatized oligosaccharides.

A number of different low molecular weight and volatile compounds have been tested and compared as matrices in 252Cf plasma-desorption mass spectrometry (PDMS) measurements of oligosaccharides. Some heteroaromatic amines (2-aminothiazole and 3-aminopyridine), hydroxyanthraquinones (alizarin and quinalizarin) and phthaleins (fluorescein) proved to be especially suited to enhancing the quasimolecular ion intensity of oligosaccharides. Discrimination effects could be reduced by matrix addition and thus, quantitative results of PDMS could be improved. Oligosaccharides with broad molecular weight distribution (dextrin 10 and dextran T 1.5) have been successfully analyzed by PDMS. The mass spectra obtained compared quite well with ion chromatograms of the respective oligosaccharides.

Californium↗
PubMed1992

Essential fatty acid status during early human development.

Preliminary studies indicated that the EFA status of normal neonates is marginal, if not insufficient. Since a better knowledge of the physiology of maternal-fetal essential fatty acid transfer is relevant for nutritional recommendations during pregnancy, we investigated the course of the fetal EFA status during fetal development by analysing the absolute (micrograms/g dry fetal tissue) and relative (% of total fatty acids) fatty acid composition of phospholipids in human fetal tissue, (n = 40, gestational age 5-15.2 weeks). The total content of fatty acids (mg/g dry fetal tissue) increased with gestational age. The absolute amount of virtually all fatty acids increased with maturation. Linoleic acid (18:2n-6, LA), however, was an exception. A highly significant, negative correlation between gestational age and the relative amount of LA in fetal tissue was observed during this first trimester of pregnancy. Our results show that the fetal-maternal difference in linoleic acid content observed at birth, initiates early in pregnancy. Since the fetus completely depends on the mother for its EFA supply, the maternal EFA status was measured simultaneously by analysing the fatty acid composition of phospholipids, isolated from plasma and red blood cells. Significant positive correlations between maternal rbc and fetal tissue were found for the relative amounts of LA. Similar relationships were observed between maternal plasma and fetal tissue for the relative amounts of cervonic acid (22:6n-3), the most abundant essential fatty acid in brain and retina. The relation between maternal and fetal EFA in phospholipids is significantly more pronounced after 10 weeks of gestation than before. This might be connected with the increased importance of the placenta with respect to maternal-fetal fatty acid transfer after 10 weeks of gestation.

Embryonic and Fetal Development↗
PubMed1985

Differences in Xylan Degradation by Various Noncellulolytic Thermophilic Anaerobes and Clostridium thermocellum.

Hemicellulose fractions with a predetermined distribution of xylose, xylooligomers, and xylan fractions were obtained through steam explosion of wood by the steam explosion-extraction process of BFA-Hamburg, Hamburg, Federal Republic of Germany. A differential utilization of various molecular-weight fractions by several thermophilic anaerobic bacteria was determined during their growth on the hemicellulose preparations. Clostridium thermocellum (60 degrees C) first utilized the high-molecular-weight fractions (polymerization degree of 15 to 40 xylose units). Xylose and xylooligomers of n = 2 to 5 accumulated while C. thermocellum was not growing, as evident from the fermentation products formed. Whereas the xylan was hydrolyzed and the small oligoxylans were utilized after more than 100 h of incubation, xylose was not significantly utilized. In contrast to this, C. thermohydrosulfuricum (70 degrees C) and Thermoanaerobium brockii (70 degrees C) utilized xylose first and then xylooligomers of n = 2 to 5, but xylooligomers of n greater than 6 were only slowly utilized. Thermoanaerobacter ethanolicus (70 degrees C), Thermobacteroides acetoethylicus (70 degrees C), and C. thermosaccharolyticum (60 degrees C) utilized xylose preferentially. Xylooligomers of n = 2 to 5 and n = 6 and greater were apparently concomitantly utilized without significant differences. In contrast to C. thermocellum, the non-cellulolytic organisms grew during xylan hydrolysis, producing ethanol, lactate, acetate, CO(2), and H(2).

Journal Article↗
PubMed1984

Epiglottitis due to ampicillin-tolerant Haemophilus influenzae type b.

Tolerance to beta-lactam antibiotics has been described with staphylococci and enterococci, but this phenomenon and its clinical significance in Haemophilus influenzae has not been reported. We have reported a case of bacteremic epiglottitis due to an ampicillin-tolerant, beta-lactamase-negative strain of Haemophilus influenzae type b which was cured with ampicillin therapy alone. The organism was not tolerant to moxalactam, cefotaxime, or rifampin. Rifampin therapy eliminated pharyngeal carriage.

Ampicillin↗
PubMedDate not supplied

Computer recognition of ectocervical cells. Classification accuracy and spatial resolution.

The effect of a relaxation of the spatial resolution of images of ectocervical cells on classification accuracy by computer has been studied. The discriminatory capabilities of optical density, texture and shape features have been evaluated. Comparable computer classifications have been derived. The differences in the discriminating power of .5 and 1 mu resolution are found to be smaller than the differences corresponding to 1 and 2 mu resolution. While 2 mu resolution may be marginally acceptable in certain situations, the 4 mu resolution did not render acceptably good classification rates.

Computers↗