| 1. |
- Ademark, Pia, et al.
(författare)
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Hydrolytic properties of a beta-mannosidase purified from Aspergillus niger. J. Biotechnol. 75: 281-289.
- 1999
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Ingår i: Journal of Biotechnology. - 1873-4863. ; 75:2-3, s. 281-289
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Tidskriftsartikel (refereegranskat)abstract
- A β-mannosidase was purified to homogeneity from the culture filtrate of Aspergillus niger. A specific activity of 500 nkat mg−1 and a 53-fold purification was achieved using ammonium sulfate precipitation, anion-exchange chromatography, and gel filtration. The isolated enzyme has an isoelectric point of 5.0 and appears to be a dimer composed of two 135-kDa subunits. It is a glycoprotein and contains 17% N-linked carbohydrate by weight. Maximal activity was observed at pH 2.4–5.0 and at 70°C. The β-mannosidase hydrolyzed β-1,4-linked manno-oligosaccharides of degree of polymerization (DP) 2–6 and also released mannose from polymeric ivory nut mannan and galactomannan. The Km and Vmax values for p-nitrophenyl-β-Image-mannopyranoside were 0.30 mM and 500 nkat mg−1, respectively. Hydrolysis of Image-galactose substituted manno-oligosaccharides showed that the β-mannosidase was able to cleave up to, but not beyond, a side group. An internal peptide sequence of 15 amino acids was highly similar to that of an Aspergillus aculeatus β-mannosidase belonging to family 2 of glycosyl hydrolases.
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| 2. |
- Alp, Dennis, et al.
(författare)
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The 30 Year Search for the Compact Object in SN 1987A
- 2018
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Ingår i: Astrophysical Journal. - : Institute of Physics Publishing (IOPP). - 0004-637X .- 1538-4357. ; 864:2
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Tidskriftsartikel (refereegranskat)abstract
- Despite more than 30 years of searching, the compact object in Supernova (SN) 1987A has not yet been detected. We present new limits on the compact object in SN 1987A using millimeter, near-infrared, optical, ultraviolet, and X-ray observations from ALMA, VLT, HST, and Chandra. The limits are approximately 0.1 mJy (0.1 x 10(-26) erg s(-1) cm(-2) Hz(-1)) at 213 GHz, 1 L-circle dot (6 x 10(-29) erg s(-1) cm(-2) Hz(-1)) in the optical if our line of sight is free of ejecta dust, and 10(36) erg s(-1) (2 x 10(-30) erg s(-1) cm(-2) Hz(-1) ) in 2-10 keV X-rays. Our X-ray limits are an order of magnitude less constraining than previous limits because we use a more realistic ejecta absorption model based on three-dimensional neutrino-driven SN explosion models. The allowed bolometric luminosity of the compact object is 22 L-circle dot if our line of sight is free of ejecta dust, or 138L(circle dot) if dust-obscured. Depending on assumptions, these values limit the effective temperature of a neutron star (NS) to <4-8 MK and do not exclude models, which typically are in the range 3-4 MK. For the simplest accretion model, the accretion rate for an efficiency 77 is limited to <10(-11) eta(-1) M-circle dot yr(-1), which excludes most predictions. For pulsar activity modeled by a rotating magnetic dipole in vacuum, the limit on the magnetic field strength (B) for a given spin period (P) is B less than or similar to 10(14) P-2 G s(-2), which firmly excludes pulsars comparable to the Crab. By combining information about radiation reprocessing and geometry, we infer that the compact object is a dust-obscured thermally emitting NS, which may appear as a region of higher-temperature ejecta dust emission.
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| 3. |
- Bose, Subhash, et al.
(författare)
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Gaia17biu/SN 2017egm in NGC 3191 : The Closest Hydrogen-poor Superluminous Supernova to Date Is in a Normal, Massive, Metal-rich Spiral Galaxy
- 2018
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 853:1
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen-poor superluminous supernovae (SLSNe-I) have been predominantly found in low-metallicity, star-forming dwarf galaxies. Here we identify Gaia17biu/SN 2017egm as an SLSN-I occurring in a normal spiral galaxy (NGC 3191) in terms of stellar mass (several times 10(10) M-circle dot) and metallicity (roughly solar). At redshift z = 0.031, Gaia17biu is also the lowest-redshift SLSN-I to date, and the absence of a larger population of SLSNe-I in dwarf galaxies of similar redshift suggests that metallicity is likely less important to the production of SLSNe-I than previously believed. With the smallest distance and highest apparent brightness for an SLSN-I, we are able to study Gaia17biu in unprecedented detail. Its pre-peak near-ultraviolet to optical color is similar to that of Gaia16apd and among the bluest observed for an SLSN-I, while its peak luminosity (M-g = -21 mag) is substantially lower than that of Gaia16apd. Thanks to the high signal-to-noise ratios of our spectra, we identify several new spectroscopic features that may help to probe the properties of these enigmatic explosions. We detect polarization at the similar to 0.5% level that is not strongly dependent on wavelength, suggesting a modest, global departure from spherical symmetry. In addition, we put the tightest upper limit yet on the radio luminosity of an SLSN-I with < 5.4 x 10(26) erg s(-1) Hz(-1) at 10 GHz, which is almost a factor of 40 better than previous upper limits and one of the few measured at an early stage in the evolution of an SLSN-I. This limit largely rules out an association of this SLSN-I with known populations of gamma-ray-burst-like central engines.
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| 4. |
- Ekstrand, Jan, 1944-, et al.
(författare)
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Is there a correlation between coaches' leadership styles and injuries in elite football teams? A study of 36 elite teams in 17 countries
- 2018
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Ingår i: British Journal of Sports Medicine. - London, United Kingdom : BMJ. - 0306-3674 .- 1473-0480. ; 52:8, s. 527-531
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Tidskriftsartikel (refereegranskat)abstract
- Background Do coaches' leadership styles affect injury rates and the availability of players in professional football? Certain types of leadership behaviour may cause stress and have a negative impact on players' health and well-being. Aim To investigate the transformational leadership styles of head coaches in elite men's football and to evaluate the correlation between leadership styles, injury rates and players' availability. Methods Medical staff from 36 elite football clubs in 17 European countries produced 77 reports at four postseason meetings with a view to assessing their perception of the type of leadership exhibited by the head coaches of their respective teams using the Global Transformational Leadership scale. At the same time, they also recorded details of individual players' exposure to football and time-loss injuries. Results There was a negative correlation between the overall level of transformational leadership and the incidence of severe injuries (rho=-0.248; n=77; p=0.030); high levels of transformational leadership were associated with smaller numbers of severe injuries. Global Transformational Leadership only explained 6% of variation in the incidence of severe injuries (r 2 =0.062). The incidence of severe injuries was lower at clubs where coaches communicated a clear and positive vision, supported staff members and gave players encouragement and recognition. Players' attendance rates at training were higher in teams where coaches gave encouragement and recognition to staff members, encouraged innovative thinking, fostered trust and cooperation and acted as role models. Conclusions There is an association between injury rates and players' availability and the leadership style of the head coach.
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| 5. |
- Jacobs, Anna, Ph. D., et al.
(författare)
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Characterization of water-soluble hemicelluloses from spruce and aspen employing SEC/MALDI mass spectroscopy
- 2002
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Ingår i: Carbohydrate Research. - 1873-426X .- 0008-6215. ; 337:8, s. 711-717
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Tidskriftsartikel (refereegranskat)abstract
- Partly depolymerized hemicelluloses isolated from wood chips of spruce and aspen employing microwave treatment were resolved using size-exclusion chromatography (SEC) into oligo- and polysaccharide fractions containing components with a narrow range of sizes, as determined by MALDI mass spectroscopy. The degree of substitution with acetyl moieties (DS) was also calculated on the basis of the MALDI-MS spectra obtained prior to and following deacetylation. For spruce hemicelluloses, the low molecular mass fraction contained small arabino-4-O-methylglucuronoxylan oligosaccharides, with DP values ranging from 4 to ~20, separated primarily on the basis of their charge density. The fraction eluted last consisted of an O-acetyl-(galacto)glucomannan polysaccharide of peak-average DP value (DPp) 14. The degree of substitution with acetyl groups (DS) decreased with decreasing DP, a value DS of 0.39 being obtained for the fraction with DPp 12. For the aspen hemicelluloses, the SEC fractions eluted first contained an acidic O-acetyl-4-O-methylglucuronoxylan polysaccharide with DP ranging from 10 to ~28 and an average DS of ~0.75. The fractions eluted last consisted of oligosaccharide mixtures composed primarily of small neutral O-acetyl-xylooligosaccharides (DPp 6, DS 0.41), together with minor quantities of an O-acetyl-glucomannan.
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| 6. |
- Karp, Johan, et al.
(författare)
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Clostridioides difficile incidence related to in-hospital cephalosporin use: a tale of two highly comparable hospitals.
- 2019
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Ingår i: The Journal of antimicrobial chemotherapy. - : Oxford University Press (OUP). - 1460-2091 .- 0305-7453. ; 74:1, s. 182-189
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Tidskriftsartikel (refereegranskat)abstract
- Antibiotic treatment is a well-known risk factor for healthcare facility-associated Clostridioides (Clostridium) difficile infection (HCF-CDI). Antibiotic stewardship programmes (ASPs) targeting high-risk antibiotics have been shown to decrease HCF-CDI incidence. HCF-CDI incidence is high in Nordic countries despite relatively low antibiotic use in hospital.To determine if HCF-CDI incidence was modified by a hospital ASP that restricted cephalosporin use.The effects of an ASP on HCF-CDI incidence were evaluated in a two-centre setting using a retrospective design. We exploited a strategy of both individual case ascertainment based on chart reviews and aggregated data from the hospitals. Cases were attributed to the antibiotics given prior to disease onset, in proportion to the number of DDDs used. Three periods were studied: 2007 (before the ASP), 2012 and 2015.At the ASP hospital, cephalosporin use decreased by 87% and the number of HCF-CDI/1000 hospital admissions decreased significantly from 2.25 (2007) to 1.16 (2015) (P=0.0014). The corresponding results at the non-ASP hospital showed a non-significant increase from 2.09 to 2.38. A high number of cases could be attributed to cephalosporins at both hospitals. The increased use of other broad-spectrum antibiotics, e.g. piperacillin/tazobactam, at the ASP hospital was not associated with offsetting increases in attributable HCF-CDI cases.Decreased use of cephalosporins is an effective strategy to decrease HCF-CDI incidence over time in a setting with high incidence and low antibiotic use.
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| 7. |
- Lundqvist, Jon, et al.
(författare)
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Characterization of galactoglucomannan extracted from spruce (Picea abies) by heat-fractionation at different conditions
- 2003
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 51:2, s. 203-211
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Tidskriftsartikel (refereegranskat)abstract
- Water-soluble hemicelluloses were extracted from spruce chips by microwave heat-fractionation. The galactoglucomannan (GGM) extraction was evaluated on the basis of weight-average molecular weight (MW), yield and carbohydrate composition of the GGM. The MW was determined by size-exclusion chromatography with column calibration using off-line MALDI-MS analysis, and determination of mannan content in the fractions collected. Water impregnated spruce chips were heat-fractionated at three different temperatures (180, 190, and 200oC). The spruce chips were also impregnated in NaOH solutions of different concentrations, and then heat-fractionated at 190oC for 5min. The highest mannan yield (78% based on the amount in the raw material) was obtained from water impregnated spruce chips heat-fractionated at 190oC for 5min (MW of 3800). The highest MW (14,000) was obtained from impregnation with 2% NaOH (190oC, 5min), but the yield of mannan was very low (3%). Impregnation with 0.025% NaOH and heat-fractionation at 190oC for 5min resulted in extraction of GGM with MW of 9500 and a mannan yield of 31%. When the spruce chips were impregnated with =<0.05% NaOH an O-acetyl-galactoglucomannan was extracted, whereas when higher NaOH charges were used in the impregnation, the extracted GGM lacked acetyl groups.
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| 8. |
- Lundqvist, Jon, et al.
(författare)
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Isolation and characterization of galactoglucomannan from spruce (Picea abies)
- 2002
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Ingår i: Carbohydrate Polymers. - 0144-8617. ; 48:1, s. 29-39
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Tidskriftsartikel (refereegranskat)abstract
- Water-soluble hemicelluloses were extracted from spruce chips by microwave heat fractionation. The chips were impregnated with water at different pH values. Screening of heat-fractionation conditions, i.e. impregnation medium, temperature and residence time was performed with the aim to extract O-acetyl-galactoglucomannan. The impregnation and heat fractionation conditions were evaluated on the basis of the yield of dissolved mannan (oligo- and polysaccharides), molecular weight of the carbohydrates and amount of dissolved lignin. Increasing temperature and residence time increases the yield of mannan and decreases the molecular weight of dissolved carbohydrates. For a structural study of the extracted carbohydrates the chips were impregnated with water and treated at 200oC for 2min. Oligo- and polysaccharides were fractionated with preparative size-exclusion chromatography from the filtered extract.The structure of the obtained saccharides in two fractions 8 and 9 was determined by 1H NMR spectroscopy. The polysaccharides in the fractions were O-acetyl-galactoglucomannan with a degree of polymerization ~20 and ~11 for fractions 8 and 9, respectively. The molar ratio for galactose:glucose:mannose was approximately 0.1:1:4. About one-third of the d-mannosyl units are substituted by O-acetyl groups almost equally distributed between C-2 and C-3.
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| 9. |
- Lundqvist, Jon
(författare)
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Isolation, characterization and enzymatic hydrolysis of water-soluble wood polysaccharides
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The need for new renewable products has enhanced the interest in cellulose and hemicellulose as raw material. The wood plant cell wall is a complex mixture of cellulose, hemicellulose, lignin and minor amounts of pectin, proteins and extractives. Several interactions between the compounds make them difficult to separate without modification. O-acetyl-galactoglucomannan (O-acetyl-GGM), the major hemicellulose in spruce, has been the main focus of this thesis. Heat-fractionation with microwave irradiation and size-fractionation with size exclusion chromatography have been used for the isolation of O-acetyl-GGM. HPLC, NMR and MALDI-MS were used as characterization methods. The structure of O-acetyl-GGM is sensitive to temperature, residence time and pH during the heat-fractionation. Considering MW, yield of GGM and sugar composition the best conditions for extracting O-acetyl-GGM using microwave irradiation were found to be a pH between 4-5, a temperature of 190°C and a residence time of 5 min. Cellulose- and hemicellulose-degrading enzymes are valuable tools for the investigation of O-acetyl-GGM. The possibility to characterize O-acetyl-GGM is improved by the purification and characterization of a beta-mannosidase (Man2A) from Aspergillus niger. Man2A has the capacity to catalyze the cleavage of mannosyl residues from the non-reducing end of manno-oligosaccharides, soluble and insoluble mannans and glucomannans. Man2A was shown to remove acetylated mannosyl units, but not galactosyl substituted mannosyl units from the substrate. The endoglucanase Cel7B and beta-mannanase Man5A from Trichoderma reesei have the ability to catalyze the cleavage of O-acetyl-GGM. Characterization methods were studied to determine the substitution pattern of ethyl(hydroxyethyl)cellulose (EHEC) by means of enzymatic degradation and chromatographic methods. The action of Cel7B and Cel12A from T. reesei on EHEC was found to be limited due to the high degree of substitution.
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| 10. |
- Richardson, Sara, et al.
(författare)
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Initial Characterization of Ethyl(hydroxyethyl) Cellulose Using Enzymic Degradation and Chromatographic Methods
- 2002
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 3:6, s. 1359-1363
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Tidskriftsartikel (refereegranskat)abstract
- Two different ethyl(hydroxyethyl) cellulose (EHEC) samples were characterized by size-exclusion chromatography (SEC) with multiangle light scattering (MALS) detection and high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD). The aim of the study was to investigate the molar mass distribution and the heterogeneity of the substituent distribution, factors that are thought to affect the functional properties of EHEC. The presence of blocks of unsubstituted glucose units was studied by enzymic degradation of EHEC by two different endoglucanases from Trichoderma reesei. The SEC-MALS analysis of the hydrolysis products showed that both enzymes were strongly inhibited by the large number of substituents along the cellulose chain. However, as the weight-average molar mass was reduced from approximately 360 000 to 80 000 g/mol in one of the polymers and from 770 000 to 60 000 g/mol in the other polymer, it was suggested that both samples were composed of some unsubstituted regions where the enzymes got access to the glucosidic bonds. The amount of glucose released upon endoglucanase hydrolysis was determined by HPAEC-PAD, which gave information on the homogeneity of the substituent distribution. The production of unsubstituted glucose units indicated that one of the polymers had a more uneven distribution compared with the other. It was demonstrated that chemical characterization of EHEC is a complex task, which requires an analytical approach involving numerous different methods and techniques.
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