| 1. |
- Andersson, Mikael, et al.
(författare)
-
The Influence of the Degree of Cross-linking, Type of Ligand and Support on the Chemical Stability of Chromatography Media Intended for protein Purification
- 1998
-
Ingår i: Process Biochemistry. - 1359-5113 .- 1873-3298. ; 33:1, s. 47-55
-
Tidskriftsartikel (refereegranskat)abstract
- The release of organic compounds from different liquid chromatography media in static conditions has been analysed with a total organic carbon (TOC) analyser. TOC results show that chemical stability increases with the degree of cross-linking in agarose beaded chromatography media and thus extend the working pH-range of the media. Of the unsubstituted chromatography media investigated, Sepharose® 6B, Sepharose CL-6B, Sepharose 4 Fast Flow, Sepharose 6 Fast Flow and Sepharose High Performance, the latter was the most stable medium. Sepharose High Performance releases only about 0·06% of its total carbon content after 1 week in 0·01 m HCl. Agarose beads are more stable to basic conditions (pH 14) compared with acidic conditions (pH 2). From UV spectroscopic and gel filtration results it was found that all Sepharose media release low amounts of 5-(hydroxymethyl)-2-furaldehyde and agarose fragments in acidic conditions. To investigate the effect of different ligands on chemical stability Q Sepharose 6 Fast Flow, DEAE Sepharose 6 Fast Flow, SP Sepharose 6 Fast Flow, CM Sepharose 6 Fast Flow, Phenyl Sepharose 6 Fast Flow, Octyl Sepharose 4 Fast Flow media were also studied under static conditions. In basic conditions it was found that all these chromatography media release carbon compounds to a higher extent than the unsubstituted Sepharose support. In addition, Hofmann elimination of Q and DEAE groups contributes to the decrease in the carbon content of the corresponding anion exchangers. During exposure to acidic conditions (pH 2) the release of carbon compounds was lower than the release from the support to which the ligands were coupled. The exceptions are Octyl Sepharose 4 Fast Flow and SP Sepharose 6 Fast Flow. In the case of Octyl Sepharose 4 Fast Flow, the ligand did not seem to influence chemical stability, whereas the SP group increases the degradation of the Sepharose support. In the case of SP Sepharose 6 Fast Flow the stability in acidic conditions can be improved by increasing the ionic strength. Anion exchangers based on different support polymers (agarose-, polystyrene-, methacrylate- and polyvinyl-based matrixes) were studied under static conditions. Agarose-based anion exchanger was the most stable in basic conditions (pH 14). In acidic conditions (pH 2) the chemical stability was about the same for many different anion exchangers.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Christiansson, Marie-Therese, et al.
(författare)
-
En inter-organisatorisk förändringsanalys : utveckling av kund-/leverantörsprocessen
- 1997
-
Konferensbidrag (refereegranskat)abstract
- Dagens sätt att göra affärer innebär ett ökat partnerskap och ett ökat datautbyte mellan organisationer i sökandet efter effektivitet och konkurrensfördelar. Affärsrelationer mellan leverantörer och kunder är beroende av att informationen flödar på ett strukturerat sätt mellan deras organisationer för att tillgodose respektive parts informationsbehov, dvs inter-organisatoriska informationssystem (IOIS). En metodutveckling pågår inom VINST-projektet där målet är att utveckla kunskap om och utforma en användbar metod som stöd vid verksamhetsutveckling av inter-organisatorisk karaktär. Denna rapport bygger på en metodprövande aktionsforskning vid en gemensam förändringsanalys som PartnerTech AB och en av deras kunder bedrivit med stöd av FA/SIMMetoden. Den metodtillämpning och metodutveckling som skett analyseras och diskuteras utifrån frågorna; hur en leverantör tillsammans med kunden kan utveckla den gemensamma kund-leverantörsprocessen och hur verksamhetsutvecklare kan använda FA/SIMM för att kartlägga och driva förbättring av inter-organisatoriska processer. Rapporten pekar bl a på behov av anpassade projektstrategier, arbetsformer och notation samt metodkomponenter för interaktionsanalys och uppföljning av åtgärder.
|
|
| 5. |
|
|
| 6. |
- Collin, Peter, et al.
(författare)
-
Lateral-torsional buckling of continuous bridge girders
- 1998
-
Ingår i: Journal of constructional steel research. - 0143-974X .- 1873-5983. ; 45:2, s. 217-235
-
Tidskriftsartikel (refereegranskat)abstract
- The resistance of bridge girders with respect to lateral-torsional buckling at support is strongly influenced by the moment gradient. In most design methods this influence is taken into account by the use of a correct critical bending moment in the slenderness parameter λ. This critical moment is influenced by the shape of the moment diagram as well as the distortion of the cross-section and the restraint from the web and stiffeners, if any. In this paper, a method for the calculation of the critical moment is presented. A further effect of the moment gradient is that the stresses due to lateral bending of the flange in connection with lateral-torsional buckling does not coincide with the maximum of stresses caused by bending in the vertical plane. This is taken into account by performing the check for lateral-torsional buckling in a design section at some distance from the support. A design procedure based on this concept has been introduced in Eurocode 3 Part 2: Steel Bridges
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Hedlund, Sven, et al.
(författare)
-
PWLTool - a Matlab Toolbox for Piecewise Linear System
- 1999
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This manual describes a Matlab toolbox for computational analysis of piecewise linear systems. Key features of the toolbox are modeling, simulation, analysis, and optimal control for piecewise linear systems. The simulation routines detect sliding modes and simulate equivalent dynamics. The analysis and design are based on computation of piecewise quadratic Lyapunov functions. The computations are performed using convex optimization in terms of linear matrix inequalities (LMIs).
|
|
| 10. |
- Johansson, Ann-Sofie, et al.
(författare)
-
Structure-activity relationships and thermal stability of human glutathione transferase P1-1 governed by the H-site residue 105
- 1998
-
Ingår i: Journal of Molecular Cell Biology. - : Elsevier BV. - 1674-2788 .- 1759-4685 .- 0022-2836. ; 278:3, s. 687-698
-
Tidskriftsartikel (refereegranskat)abstract
- Human glutathione transferase P1-1 (GSTP1-1) is polymorphic in amino acid residue 105, positioned in the substrate binding H-site. To elucidate the role of this residue an extensive characterization of GSTP1-1/Ile105 and GSTP1-1/Val105 was performed. Mutant enzymes with altered volume and hydrophobicity of residue 105, GSTP1-1/Ala105 and GSTP1-1/Trp105, were constructed and included in the study. Steady-state kinetic parameters and specific activities were determined using a panel of electrophilic substrates, with the aim of covering different types of reaction mechanisms. Analysis of the steady-state kinetic parameters indicates that the effect of the substitution of the amino acid in position 105 is highly dependent on substrate used. When 1-chloro-2,4-dinitrobenzene was used as substrate a change in the side-chain of residue 105 seemed primarily to cause changes in the KM value, while the kcat value was not distinctively affected. With other substrates, such as 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole and ethacrynic acid both kcat and KM values were altered by the substitution of amino acid 105. The constant for formation of the sigma-complex between 1,3, 5-trinitrobenzene and glutathione was shown to be dependent upon the volume of the amino acid in position 105. The nature of the amino acid in position 105 was also shown to affect the thermal stability of the enzyme at 50 degrees C, indicating an important role for this residue in the stabilization of the enzyme. The GSTP1-1/Ile105 variant was approximately two to three times more stable than the Val105 variant as judged by their half-lives. The presence of glutathione in the incubation buffer afforded a threefold increase in the half-lives of the enzymes. Thus, the thermal stability of the enzyme and depending on substrate, both KM values and turnover numbers are influenced by substitutions in position 105 of GSTP1-1.
|
|
