| 1. |
- Engelmark Cassimjee, Karim
(författare)
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Tools in biocatalysis : enzyme immobilisation on silica and synthesis of enantiopure amines
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents two techniques in the field of biocatalysis: An enzyme immobilisation method based on the His6-tag for attachment on modified silica oxide beads, and it’s employment in aqueous and organic medium for synthesis applications. The method functions as a one step extraction and immobilisation protocol. An equilibrium displacement system which enables complete conversion in reactions with ω-transaminases where isopropylamine is the donor, a route for synthesis of pharmaceutically interesting enantiopure amines. Biocatalysis is predicted to be a paramount technology for an environmentally sustainable chemical industry, to which every newly developed method represents a small but important step. The work done here is aimed to be a part of this development.
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| 2. |
- Berglund, Torkel, et al.
(författare)
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Nicotinamide; antioxidative and DNA hypomethylation effects in plant cells
- 2017
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Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier. - 0981-9428 .- 1873-2690. ; 118, s. 551-560
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Tidskriftsartikel (refereegranskat)abstract
- The effects of nicotinamide (NIC) and its natural plant metabolites nicotinic acid (NIA) and trigonelline (TRIG) were studied with respect to defense in plant cell cultures. NIC and NIA could protect against oxidative stress damage caused by 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH), which generates free radicals. Damage was analyzed as DNA strand breaks in cell cultures of Pisum sativum (garden pea), Daucus carota (carrot), Populus tremula L. × P. tremuloides (hybrid aspen) and Catharanthus roseus (Madagascar periwinkle), monitored by single cell gel electrophoresis (comet assay), and assays of cell leakage in C. roseus. The activities of aconitase and fumarase enzymes, which have key roles in energy metabolism, were analyzed in P. sativum cultures after treatment with NIC or NIA. Aconitase activity was increased by NIA, and fumarase activity was increased by both compounds. These compounds were shown to promote glutathione metabolism in P. sativum cultures, and NIC was shown to have a global DNA hypomethylating effect. Neither TRIG nor poly(ADP-ribose) polymerase (PARP) inhibitor 3-aminobenzamide offered any protection against DNA damage or cell leakage, nor did they promote aconitase or fumarase activities, or glutathione metabolism. By this broad approach addressing multiple biochemical factors and different plant species, we demonstrate that NIC and NIA protect plant cells from oxidative stress, and that NIC clearly exerts an epigenetic effect; decreased DNA methylation. This indicates that these compounds have important roles in the regulation of metabolism in plant cells, especially in connection to stress.
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| 3. |
- Berglund, Torkel, et al.
(författare)
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Protection of spruce seedlings against pine weevil attacks by treatment of seeds or seedlings with nicotinamide, nicotinic acid and jasmonic acid
- 2016
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Ingår i: Forestry (London). - : Oxford University Press. - 0015-752X .- 1464-3626. ; 89:2, s. 127-135
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Tidskriftsartikel (refereegranskat)abstract
- Sustainable methods are required to protect newly planted tree seedlings from insect herbivore attack. To this end, here Norway spruce (Picea abies (L.) Karst.) seeds were treated with 2.5 mM nicotinamide (NIC), 2.5 mM nicotinic acid (NIA), 3 mM jasmonic acid (JA) or 0.2 mM 5-azacytidine (5-Aza), and 6-month-old seedlings grown from these seeds were planted at a reforestation area in central Sweden. Attack by pine weevils (Hylobius abietis) was reduced by 50 per cent by NIC treatment, 62.5 per cent by JA treatment and 25 per cent by 5-Aza treatment, when compared with seedlings grown from untreated seeds. Watering 18-month-old spruce seedlings with 2 mM NIC or 2 mM NIA did reduce attack during the first season in the field by 40 and 53 per cent, respectively, compared with untreated plants. Girdling was also reduced by the different treatments. Analysis of conifer seedlings treated with 5-Aza points at a possible involvement of epigenetic mechanisms in this defensive capacity. This is supported by a reduced level of DNA methylation in the needles of young spruce seedlings grown in a greenhouse from NIC-treated seeds. Seed treatment for seedling defense potentiation is simple, inexpensive and also a new approach for forestry with many potential applications.
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| 4. |
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| 5. |
- Christiernin, Maria, et al.
(författare)
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Lignin isolated from primary walls of hybrid aspen cell cultures indicates significant differences in lignin structure between primary and secondary cell wall
- 2005
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Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 43:8, s. 777-785
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid aspen (Populus tremula x tremuloides) cell cultures were grown for 7, 14 and 21 days. The cell cultures formed primary cell walls but no secondary cell wall according to carbohydrate analysis and microscopic characterization. The primary walls were lignified, increasingly with age, according to Klason lignin analysis. Presence of lignin in the primary walls, with a higher content in 21-day old cells than in 7-day old cells, was further Supported by phloroglucinol/HCI reagent test and confocal microscopy after both immunolocalization and staining with acriflavin. Both laccase and peroxidase activity were found in the cultures and the activity increased during lignin formation. The lignin from the cell culture material was compared to lignin from mature aspen wood, where most of the lignin originates in the secondary cell wall, and which served as our secondary cell wall control. Lignin from the cell walls was isolated and characterized by thioacidolysis followed by gas chromatography and mass spectrometry. The lignin in the cell cultures differed from lignin of mature aspen wood in that it consisted exclusively of guaiacyl units, and had a more condensed structure. Five lignin structures were identified by mass spectrometry in the cell suspension cultures. The results indicate that the hybrid aspen cell culture used in this investigation may be a convenient experimental system for studies of primary cell wall lignin.
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| 6. |
- Colombani, A., et al.
(författare)
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In vitro synthesis of (1→3)-β-D-glucan (callose) and cellulose by detergent extracts of membranes from cell suspension cultures of hybrid aspen
- 2004
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Ingår i: Cellulose. - 0969-0239 .- 1572-882X. ; 11:3-4, s. 313-327
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to optimize the conditions for in vitro synthesis of (1 --> 3)-beta-D-glucan (callose) and cellulose, using detergent extracts of membranes from hybrid aspen (Populus tremula x tremuloides) cells grown as suspension cultures. Callose was the only product synthesized when CHAPS extracts were used as a source of enzyme. The optimal reaction mixture for callose synthesis contained 100 mM Mops buffer pH 7.0, 1 mM UDP-glucose, 8 mM Ca2+, and 20 mM cellobiose. The use of digitonin to extract the membrane-bound proteins was required for cellulose synthesis. Yields as high as 50% of the total in vitro products were obtained when cells were harvested in the stationary phase of the growth curve, callose being the other product. The optimal mixture for cellulose synthesis consisted of 100 mM Mops buffer pH 7.0, 1 mM UDP-glucose, 1 mM Ca2+, 8 mM Mg2+, and 20 mM cellobiose. The in vitro beta-glucans were identified by hydrolysis of radioactive products, using specific enzymes. C-13-Nuclear magnetic resonance spectroscopy and transmission electron microscopy were also used for callose characterization. The (1-->3)-beta-D-glucan systematically had a microfibrillar morphology, but the size and organization of the microfibrils were affected by the nature of the detergent used for enzyme extraction. The discussion of the results is included in a short review of the field that also compares the data obtained with those available in the literature. The results presented show that the hybrid aspen is a promising model for in vitro studies on callose and cellulose synthesis.
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| 7. |
- Gärdin, Anna, et al.
(författare)
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T2 * relaxation time in Achilles tendinosis and controls and its correlation with clinical score
- 2016
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Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 43:6, s. 1417-1422
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To investigate if the T2 * of Achilles tendons can discriminate between chronic Achilles tendinosis and healthy controls; to correlate with clinical score; to evaluate its short-term repeatability; and to estimate minimal detectable change.MATERIALS AND METHODS: Twenty patients, with chronic mid-portion Achilles tendinosis, and 10 controls without history of Achilles tendon symptoms, were examined with a 3T MR scanner with a 3D flash ultrashort time to echo sequence with five different echo times. The sequence was run twice to test repeatability. The tendon border was delineated on axial slices at three different levels in the calculated T2 * maps. The clinical severity of Achilles tendinosis was measured by a VISA-A questionnaire.RESULTS: There was a significant difference in mean T2 * between symptomatic and control tendons (P < 0.001). In patients with unilateral symptoms no significant difference in T2 * was found between symptomatic and contralateral asymptomatic tendons (P = 0.19). There was no significant correlation between clinical severity and T2 * (r = -0.28, P = 0.22). The short-term repeatability of T2 * showed a coefficient of variation of 18%, a least significant change of 50%, and the intraclass correlation coefficient had an average consistency of 0.99.CONCLUSION: T2 * may help to differentiate between chronic Achilles tendinosis and healthy controls but was not associated with the clinical score. However, and notably, the reproducibility of the method was low and the number of patients was small.
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| 8. |
- Kalbin, Georgi, et al.
(författare)
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Ultraviolet-B-radiation-induced changes in nicotinamide and glutathione metabolism and gene expression in plants
- 1997
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Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 249:2, s. 465-472
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Tidskriftsartikel (refereegranskat)abstract
- Pea (Pisum sativum L. cv. Greenfeast) plants were exposed to supplementary ultraviolet-B (UV-B) radiation (biologically effective dose rates normalised to 300 nm UV-B-BE,B-300: 0.18, 0.32 or 1.4 W m(-2)). Leaf nicotinamide, trigonelline, GSH(tot) (total glutathione) and (GSSG (oxidised glutathione) levels remained unchanged after exposure to the lowest dose rates. 1.4 W m(-2) UV-B-BE,B-300 gave rise to 60-fold and 4.5-fold increases in GSSG and GSH(tot), respectively. 3.5-fold and 9.5-fold increases were found in nicotinamide and trigonelline, respectively. cab (Chlorophyll-a/b-binding protein) transcript levels decreased and CHS (chalcone synthase) and PAL (phenylalanine ammonia-lyase) mRNA increased after shorter UV-B exposures (hours) to the higher dose rate of UV-B and after exposure to the intermediate dose rate. CHS and PAL mRNAs also increased after prolonged exposure to the lowest dose rate. cab transcripts completely disappeared. whereas CHS and PAL mRNA levels rose by 60-fold and 17-fold, respectively, after 12 h exposure at the highest dose rate and 12 h of development. Our results indicate that nicotinamide or trigonelline do not function as signalling compounds for CHS and PAL gene expression. Elevated nicotinamide and trigonelline levels occur in response to UV-B, but only at UV-B doses high enough to cause oxidative stress.
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| 9. |
- Laurell, Cecilia, et al.
(författare)
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Transcriptome analysis shows nicotinamide seed treatment alters expression of genes involved in defense and epigenetic processes in roots of seedlings of Picea abies
- 2021
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Ingår i: Journal of Forestry Research. - : Springer Nature. - 1007-662X .- 1993-0607.
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Tidskriftsartikel (refereegranskat)abstract
- Nicotinamide treatment of plants and plant cell cultures has been shown to promote defense and decrease levels of DNA methylation. In the present study, we used RNA-seq technology to study overall changes in gene expression induced in roots of 3-month-old spruce (Picea abies) seedlings grown from nicotinamide-treated seeds to examine the molecular mechanisms underlying the defense promotion. Approximately 350 genes were identi- fied as differentially expressed in roots after the seed treat- ment. Stress response genes, including transcription factors MYB77 and LHY and two chitinase enzymes, were gen- erally upregulated, whereas genes thought to be involved in epigenetic regulation such as DDM1, known to promote DNA methylation, were present at high frequency among the downregulated genes. Across all samples, the expression of downregulated epigenetic-related genes was highly cor- related with the nicotinamide treatment, indicating a com- mon regulation. Our results support an earlier hypothesis regarding a potential role of nicotinamide as a defense-signal mediator.
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| 10. |
- Ohlsson, Anna B., et al.
(författare)
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Cell suspension cultures of Populus tremula x P. tremuloides exhibit a high level of cellulose synthase gene expression that coincides with increased in vitro cellulose synthase activity.
- 2006
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Ingår i: Protoplasma. - : Springer Science and Business Media LLC. - 0033-183X .- 1615-6102. ; 228:4, s. 221-9
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Tidskriftsartikel (refereegranskat)abstract
- Compared to wood, cell suspension cultures provide convenient model systems to study many different cellular processes in plants. Here we have established cell suspension cultures of Populus tremula L. x P. tremuloides Michx. and characterized them by determining the enzymatic activities and/or mRNA expression levels of selected cell wall-specific proteins at the different stages of growth. While enzymes and proteins typically associated with primary cell wall synthesis and expansion were detected in the exponential growth phase of the cultures, the late stationary phase showed high expression of the secondary-cell-wall-associated cellulose synthase genes. Interestingly, detergent extracts of membranes from aging cell suspension cultures exhibited high levels of in vitro cellulose synthesis. The estimated ratio of cellulose to callose was as high as 50 : 50, as opposed to the ratio of 30 : 70 so far achieved with membrane preparations extracted from other systems. The increased cellulose synthase activity was also evidenced by higher levels of Calcofluor white binding in the cell material from the stationary-phase cultures. The ease of handling cell suspension cultures and the improved capacity for in vitro cellulose synthesis suggest that these cultures offer a new basis for studying the mechanism of cellulose biosynthesis.
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