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- Cruys-Bagger, Nicolaj, et al.
(author)
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An amperometric enzyme biosensor for real-time measurements of cellobiohydrolase activity on insoluble cellulose
- 2012
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In: Biotechnology and Bioengineering. - : Wiley. - 1097-0290 .- 0006-3592. ; 109:12, s. 3199-3204
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Journal article (peer-reviewed)abstract
- An amperometric enzyme biosensor for continuous detection of cellobiose has been implemented as an enzyme assay for cellulases. We show that the initial kinetics for cellobiohydrolase I, Cel7A from Trichoderma reesei, acting on different types of cellulose substrates, semi-crystalline and amorphous, can be monitored directly and in real-time by an enzyme-modified electrode based on cellobiose dehydrogenase (CDH) from Phanerochaete chrysosporium (Pc). PcCDH was cross-linked and immobilized on the surface of a carbon paste electrode which contained a mediator, benzoquinone. An oxidation current of the reduced mediator, hydroquinone, produced by the CDH-catalyzed reaction with cellobiose, was recorded under constant-potential amperometry at +0.5V (vs. Ag/AgCl). The CDH-biosensors showed high sensitivity (87.7 mu AmM-1cm-2), low detection limit (25nM), and fast response time (t95%similar to 3s) and this provided experimental access to the transient kinetics of cellobiohydrolases acting on insoluble cellulose. The response from the CDH-biosensor during enzymatic hydrolysis was corrected for the specificity of PcCDH for the beta-anomer of cello-oligosaccharides and the approach were validated against HPLC. It is suggested that quantitative, real-time data on pure insoluble cellulose substrates will be useful in attempts to probe the molecular mechanism underlying enzymatic hydrolysis of cellulose. Biotechnol. Bioeng. 2012; 109: 31993204. (C) 2012 Wiley Periodicals, Inc.
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| 2. |
- Rolstad, Jørund, et al.
(author)
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Genetic variation and reproductive mode in two epiphytic lichens of conservation concern: a transatlantic study of Evernia divaricata and Usnea longissima
- 2013
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In: Botany. - : Canadian Science Publishing. - 1916-2790 .- 1916-2804. ; 91, s. 69-81
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Journal article (peer-reviewed)abstract
- North European epiphytic lichens are often genetically impoverished compared with their North American counterparts.This has been hypothesized to impede sexual reproduction due to reduced chances of finding compatible mating typepartners. We compared genetic variation and reproductive mode in two threatened Scandinavian lichens, Evernia divaricata andUsnea longissima, with more viable populations in North America to see (i) if these species also show genetical depletion innorthern Europe and (ii) if the occurrence of sexual propagules (ascospores in apothecia) is more prevalent in genetically diversepopulations. Genetic variation of the fungal component was assessed by sequencing two nuclear rDNA gene regions (ITS and IGS)in 1005 and 1477 thalli, collected from 92 and 160 localities of E. divaricata and U. longissima, respectively. Scandinavian populationsof both species were almost devoid of genetic variation compared with much higher genetic diversity in North America.Wefound no support for the proposed relationship between genetic diversity and fertility. Fertile thalli were found in severalgenetically invariable populations. Fertility increased with population size and regional abundance in E. divaricata, but not inU. longissima. In Scandinavia, E. divaricata was more fertile than previously recorded, whereas all sampled populations ofU. longissima were sterile and possibly clonal.
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| 4. |
- Sosted, Heidi, et al.
(author)
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Contact allergy to common ingredients in hair dyes
- 2013
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In: Contact Dermatitis. - : Wiley. - 0105-1873. ; 69:1, s. 32-39
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Journal article (peer-reviewed)abstract
- Background p-Phenylenediamine (PPD) is the primary patch test screening agent for hair dye contact allergy, and approximately 100 different hair dye chemicals are allowed. Objectives To examine whether PPD is an optimal screening agent for diagnosing hair dye allergy or whether other clinically important sensitizers exist. Methods Two thousand nine hundred and thirty-nine consecutive patients in 12 dermatology clinics were patch tested with five hair dyes available from patch test suppliers. Furthermore, 22 frequently used hair dye ingredients not available from patch test suppliers were tested in subgroups of approximate to 500 patients each. Results A positive reaction to PPD was found in 4.5% of patients, and 2.8% reacted to toluene-2,5-diamine (PTD), 1.8% to p-aminophenol, 1% to m-aminophenol, and 0.1% to resorcinol; all together, 5.3% (n=156). Dying hair was the most frequently reported cause of the allergy (55.4%); so-called temporary henna' tattoos were the cause in 8.5% of the cases. p-Methylaminophenol gave a reaction in 20 patients (2.2%), 3 of them with clinical relevance, and no co-reaction with the above five well-known hair dyes. Conclusions Hair dyes are the prime cause of PPD allergy. PPD identifies the majority of positive reactions to PTD, p-aminophenol and m-aminophenol, but not all, which justifies additional testing with hair dye ingredients from the used product.
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