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- Lozinsky, Vladimir I, et al.
(författare)
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Synthesis and studies of N-vinylcaprolactam/N-vinylimidazole copolymers taht exhibit the ”proteinlike” behaviour in aquesous media
- 2003
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 36:19, s. 7308-7323
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Tidskriftsartikel (refereegranskat)abstract
- Proteinlike copolymers were first predicted by the computer-aided biomimetic design (Physica A 1998, 249, 253-261). These copolymers consist of comonomer units of differing hydrophilicity/hydrophobicity. Heterogeneous blockiness, characteristic for such copolymers, facilitates chain folding with the formation of specific spatial packing: a dense core consisting of hydrophobic units and a polar shell formed by hydrophilic units. This paper describes the synthesis of N-vinylcaprolactam/N-vinylimidazole copolymers via the redox-initiated radical copolymerization in the medium of 10% aqueous DMSO at the temperatures both below and above the phase separation threshold. The synthesized macromolecular products were separated into thermally precipitating and nonprecipitating fractions. Their molecular weight characteristics were evaluated using size-exclusion chromatography; their comonomer composition was determined from 1H NMR spectra of copolymers dissolved in DMSO-d6. The temperature-dependent behavior of copolymer macromolecules in water was investigated by thermonephelometry, high-sensitivity differential scanning calorimetry, and 1H NMR spectroscopy of the copolymers dissolved in D2O. It was shown that thermally nonprecipitating copolymer fractions obtained at initial comonomer molar ratios of 85:15 and 90:10 can be identified as proteinlike copolymers.
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| 2. |
- Anwaar, I., et al.
(författare)
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Intraplatelet cyclic 3'-5' guanosine monophosphate is related to serum cholesterol
- 1996
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Ingår i: International Angiology. - 0392-9590. ; 15:3, s. 201-206
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Tidskriftsartikel (refereegranskat)abstract
- Nitric oxide (NO) exerts its vasodilator and antiaggregatory effects through activation of soluble guanylate cyclase and the consequent increase in the concentration of cGMP in target cells. We conducted this study in order to evaluate relationships between intraplatelet cGMP levels and risk factors for atherosclerosis in middle aged subjects. Intraplatelet cGMP was determined by radioimmunoassay and related to age, BMI, blood pressure, antihypertensive treatment, total, LDL and HDL cholesterol, triglycerides, blood glucose, HbA1c, smoking habit and intimal thickness of the common carotid artery in 265 subjects participating in a health survey (age 59 ± 6 years, range 48-68 years, 121 females, 144 males). Intraplatelet cGMP concentration was inversely correlated with total serum cholesterol (r = -0.18; p < 0.01) and HDL cholesterol (r = -0.14, p < 0.05) as well as with platelet count (r = -0.29; p < 0.001). When platelet count was adjusted for, only the correlation between total serum cholesterol and cGMP remained significant. No significant correlations could be demonstrated between intraplatelet cGMP levels and measurable parameters of atherosclerosis. Lower levels of the vasodilating and antiaggregating mediator cGMP in platelets are related to higher levels of serum total cholesterol. These results favour the hypothesis of a relationship between lipid levels and NO associated vasodilator and antiaggregating fuction in atherosclerosis.
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| 3. |
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| 4. |
- Bernspång, Lars, et al.
(författare)
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Verification of an explicit finite-element code for the simulation of the press forming of rectangular boxes of coated sheet steels
- 1993
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 39:3-4, s. 431-453
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Tidskriftsartikel (refereegranskat)abstract
- The industrial aim for shorter lead times in the development process for new products has encouraged a fast development of finite-element procedures for the simulation of sheet-metal forming. These procedures can shorten the design stage for new sheet-forming tools and the try-out period. In order to reach these goals robust calculation procedures and extensive verification of results are required. This paper presents a detailed validation of one promising type of finite-element code, namely the explicit code DYNA3D. Experiments for verification were performed on a zinc-coated sheet steel with a hot-dip galvanized coating. Stretch forming and deep drawing of cylindrical cups were performed. Rectangular boxes were formed from rectangular blanks and blanks with cut corners. Dies both with and without draw beads were used. Punch forces, flange draw-in and strain distributions were measured. The pressings with cylindrical shape were used to determine coefficients of friction with a fitting procedure based on comparison of data from pressings and from the DYNA3D calculations. These tribological data and constitutive data of the steels were used in the simulation of pressings of rectangular boxes. The calculations with DYNA3D gave a good description of flange draw-in and the strain distributions in the pressings. In most of the cases studied the punch-force curves were well reproduced. It is concluded that the present code is well suited for the simulation of sheet-forming operations.
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| 7. |
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| 8. |
- Ivanov, Alexander, et al.
(författare)
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Conjugation of penicillin acylase with the reactive copolymer of N-isopropylacrylamide: a step towards thermosensitive industrial biocatalyst.
- 2003
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Ingår i: Biotechnology Progress. - : Wiley. - 1520-6033 .- 8756-7938. ; 19:4, s. 1167-1175
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Tidskriftsartikel (refereegranskat)abstract
- Conjugation of penicillin acylase (PA) to poly-N-isopropylacrylamide (polyNIPAM) was studied as a way to prepare a thermosensitive biocatalyst for industrial applications to antibiotic synthesis. Condensation of PA with the copolymer of NIPAM containing active ester groups resulted in higher coupling yields of the enzyme (37%) compared to its chemical modification and copolymerization with the monomer (9% coupling yield) at the same NIPAM:enzyme weight ratio of ca. 35. A 10-fold increase of the enzyme loading on the copolymer resulted in 24% coupling yield and increased by 4-fold the specific PA activity of the conjugate. Two molecular forms of the conjugate were found by gel filtration on Sepharose CL 4B: the lower molecular weight fraction of ca. 106 and, presumably, cross-linked protein-polymer aggregates of MW > 107. Michaelis constant for 5-nitro-3-phenylacetamidobenzoic acid hydrolysis by the PA conjugate (20 M) was found to be slightly higher than that of the free enzyme (12 M), and evaluation of Vmax testifies to the high catalytic efficiency of the conjugated enzyme. PolyNIPAM-cross-linked PA retained its capacity to synthesize cephalexin from D-phenylglycin amide and 7-aminodeacetoxycephalosporanic acid. The synthesis-hydrolysis ratios of free and polyNIPAM-cross-linked enzyme in cephalexin synthesis were 7.46 and 7.49, respectively. Thus, diffusional limitation, which is a problem in the industrial production of -lactam antibiotics, can be successfully eliminated by cross-linking penicillin acylase to a smart polymer (i.e., polyNIPAM).
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| 9. |
- Khattab, R. A., et al.
(författare)
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Biodegradation of 17-β-estradiol in water
- 2019
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Ingår i: International Journal of Environmental Science and Technology. - : Springer Science and Business Media LLC. - 1735-1472 .- 1735-2630. ; 16:8, s. 4935-4944
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Tidskriftsartikel (refereegranskat)abstract
- This study reports a potential biotechnical method of 17-β-estradiol removal in aquatic systems. The different bacterial strains isolated from sewage water samples were Bacillus sp., Enterobacter sp. I, Enterobacter sp. II, Klebsiella sp., Aeromonas veronii and Aeromonas punctate. These isolates were characterized on the basis of a single PCR reaction from the 5′ end of the PCR fragment to obtain > 700 bp of high-quality sequence. The adjoining lineages of each organism were obtained by BLAST searches. The identified bacterial species were incubated in a saline media under different concentrations of 17-β-estradiol in both aerobic and anaerobic conditions. The concentrations of CO2 and 17-β-estradiol were measured by GC and HPLC, respectively. The percentage degradations of 17-β-estradiol in aerobic and anaerobic conditions were 100 and 91.56%, respectively, using Klebsiella and Bacillus species. The developed and reported method is an inexpensive, selective and economic. This method may be used to remove 17-β-estradiol in any water resource.
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| 10. |
- Kumar, Ashok, et al.
(författare)
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Affinity binding of cells to cryogel adsorbents with immobilized specific ligands : effect of ligand coupling and matrix architecture
- 2005
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Ingår i: Journal of Molecular Recognition. - : Wiley. - 0952-3499 .- 1099-1352. ; 18:1, s. 84-93
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Tidskriftsartikel (refereegranskat)abstract
- The capture of human acute myeloid leukemia KG-1 cells expressing the CD34 surface antigen and the fractionation of human blood lymphocytes were evaluated on polyvinyl alcohol (PVA)-cryogel beads and dimethyl acrylamide (DMAAm) monolithic cryogel with immobilized protein A. The affinity ligand (protein A) was chemically coupled to the reactive PVA-cryogel beads and epoxy-derivatized monolithic cryogels through different immobilization techniques and the binding efficiency of the cell surface receptors specific antibody-labeled cells to the gels/beads was determined. The binding of cells to monolithic cryogel was higher (90-95%) compared with cryogel beads (76%). B-lymphocytes, which bound to the protein A-cryogel beads, were separated from T-lymphocytes with yields for the two cell types 74 and 85%, respectively. About 91% of the bound B-cells could be recovered without significantly impairing their viability. Our results show differences in the percentage of cell-binding to the immunosorbents caused by ligand density, flow shear forces and bond strength between the cells and the affinity surface once distinct chemical coupling of protein A, size of beads, sequence of antibody binding to protein A adsorbents, morphology and geometry of surface matrices were compared.
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