| 1. |
- Ohlson, Sten, et al.
(author)
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Weak affinity chromatography
- 1993. - 1
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In: Handbook of affinity chromatography. - New York : Marcel Dekker. - 0824789393 ; , s. 299-314
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Book chapter (other academic/artistic)
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| 3. |
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| 6. |
- Adlercreutz, P., et al.
(author)
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Catalytic properties of α-chymotrypsin in organic media
- 1991
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In: Biomedica Biochimica Acta. - 0232-766X. ; 50:10-11, s. 55-60
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Journal article (peer-reviewed)abstract
- α-Chymotrypsin was deposited on Celite and the resulting immobilized preparations were used to carry out peptide synthesis reactions in organic media with only small amounts of water present. The influence of different parts of the donor ester and acceptor nucleophile substrate molecules on the kinetics of the enzymatic reactions was studied. The specificity of α-chymotrypsin in organic media was a combination of its substrate specificity in aqueous media and solvent effects. The kinetics of peptide synthesis can thus be modulated by using suitable solvents and protecting groups.
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| 7. |
- Adlercreutz, Patrick
(author)
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On the Importance of the Support Material for Enzymatic Synthesis in Organic Media. Support Effects at Controlled Water Activity
- 1992. - C
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In: Progress in Biotechnology. - 0921-0423. ; 8:C, s. 55-61
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Book chapter (peer-reviewed)abstract
- Enzymes adsorbed or deposited on porous support materials have been succesfully used as catalysts in organic media. However, the support must be chosen with great care. The support can affect the partitioning of substrates, products and water in the reaction mixture and thereby indirectly influence the catalytic properties of the enzyme. Furthermore, the support can influence both the enzyme kinetics and the number of catalytically active enzyme molecules. The effects of the support on water partitioning in the system can be interpreted by measurements of the aquaphilicity (water attracting capacity) of the supports. Normally, high reaction rates are obtained with supports having low aquaphilicity. Even in experiments carried out at fixed enzyme hydration (fixed water activity) the support influences both the total activity of the enzyme and the relative rates of different reactions catalyzed by the same enzyme.
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| 8. |
- Axelsson, Anders, et al.
(author)
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Performance of batch and continuous reactors with co-immobilized yeast and beta-galactosidase
- 1991
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In: Journal of Chemical Technology and Biotechnology. - : Wiley. - 0268-2575 .- 1097-4660. ; 52:2, s. 227-241
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Journal article (peer-reviewed)abstract
- The anaerobic fermentation of deproteinized whey with beta-galactosidase coimmobilized with Saccharomyces cerevisiae in calcium alginate gel beads for the production of ethanol has been studied in a continuous horizontal packed bed reactor (HPBR). The results are compared with batch experiments in a stirred tank reactor. The immobilized yeast cells are exposed to conditions that vary with time and location in the reactor, making a true steady state impossible. In spite of a very low specific growth rate-of the order of 0.01 h-1 in the first section of the HPBR-the yeast cell growth, accompanied by bead expansion in this section, was high enough to create a cell concentration gradient along the reactor. The continuous reactor is preferable to the batch reactor as the galactose conversion is more efficient. The highest volumetric productivity obtained in the HPBR was 125 mol ethanol m-3 h-1 (6 g ethanol dm-3 h-1) at a substrate concentration of 164 mol m-3 lactose (56 g dm-3) and a dilution rate of 0.21 h-1, corresponding to a space velocity of 0.51 dm3 dm-3 gel h-1. The ethanol yield from consumed glucose and galactose was 80%. The ethanol yield from lactose was only 70%, as only 75% of the galactose was consumed while all the lactose and glucose were converted.
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| 9. |
- Gololobov, M. Yu, et al.
(author)
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Influence of Organic Solvents on the Specificity of α-Chymotrypsin and Subtilisin from B. Subtilis Strain 72 in Acyl Transfer Reactions
- 1992. - C
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In: Progress in Biotechnology. - 0921-0423. ; 8:C, s. 435-442
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Book chapter (peer-reviewed)abstract
- Nucleophilic properties of amino acid amides were studied systematically in acyl-transfer reactions catalyzed by α-chymotrypsin and subtilisin from Bacillus subtilis strain 72 (subtilisin 72) using Mal-L-Ala-L-Ala-L-PheOMe and Bz-L-TyrOme as the acyl group donors. In α-chymotrypsin-catalyzed reactions in water the reactivity of the amino acid amides increases with hydrophobicity of the nucleophiles. Hydrophobic interactions in this case are responsible for the differences between the reactivity of the nucleophiles for amides of all the amino acids tested with the exception of D-AlaNH2 and L-ArgNH2. In a low water system (4% of H2O, 47.5% of acetonitrile, 47.5% of dimethyl formamide, 1% of (C2H5)3N) the specificity of α-chymotrypsin towards the amino acid amides in acyl transfer reactions decreases and does not depend on the amino acid side chain hydrophobicity. The specificity in this case correlates with the bulk characteristics of the amino acid side chains (normalized van der Waals volume, polarizability, molecular weight). The bulky amino acid amides are less efficient nucleophiles. In reactions catalyzed by subtilisin 72, amino acid side chain characteristics do not correlate with the nucleophile reactivities. The data obtained show that different factors may be responsible for the specificity of enzymes in water and in low water systems and in general, specificity patterns obtained in water can not be used for low water systems.
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| 10. |
- Hober, Sophia, et al.
(author)
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Disulfide exchange folding of insulin-like growth factor I.
- 1992
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In: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 31:6
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Journal article (peer-reviewed)abstract
- The disulfide exchange folding properties of insulin-like growth factor I (IGF-I) have been analyzed in a redox buffer containing reduced (10 mM) and oxidized (1 mM) glutathione. Under these conditions, the 3 disulfide bridges of the 70 amino acid peptide were not quantitatively formed. Instead, five major forms of IGF-I were detected, and these components were concluded to be in equilibrium as their relative amounts were similar starting from either reduced, native, or a mismatched variant of IGF-I containing two non-native disulfides. The different components in the mixtures were trapped by thiol alkylation using vinylpyridine and subsequently isolated by reverse-phase HPLC. The purified variants were further characterized using plasma desorption mass spectrometry and peptide mapping. Two of the five different forms were identified as native and mismatched IGF-I. One form was a variant with only one disulfide bond, and the other two major components had two disulfides formed. In a separate experiment, early refolding intermediates were trapped by pyridylethylation after only 90 s of refolding in the glutathione buffer, starting from reduced IGF-I. The intermediates were identical to the components observed at equilibrium, but at different relative concentrations. On the basis of the disulfide bond patterns of the different components in the equilibrium mixtures, we conclude that the disulfide between cysteines-47 and -52 in IGF-I is an unfavorable high-energy bond that may exist in the native molecule in a strained configuration.
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