| 1. |
- Andresen Bergström, Moa, 1978, et al.
(författare)
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Oximes: Metabolic Activation and Structure−Allergenic Activity Relationships
- 2008
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Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 51:8, s. 2541-2550
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Tidskriftsartikel (refereegranskat)abstract
- Metabolic activation of chemicals (prohaptens) in the skin can cause allergic contact dermatitis. We have explored structure−allergenic activity relationships for seven potential oxime prohaptens using the local lymph node assay and a GSH trapping screen with liver microsomes. The general structure−allergenic activity relationships found were that an α,β-unsaturation is necessary for an oxime to be a prohapten and that increased steric hindrance around this double bond leads to reduction in sensitizing capacity. We also found that sensitizing oximes can be distinguished in vitro from nonsensitizers by monitoring of mono-oxidized (+16 Da) GSH conjugates in the GSH trapping screen. However, care should be taken when interpreting data from GSH trapping screens, as nonsensitizers may also form GSH conjugates via alternative mechanisms. This investigation emphasizes the importance of considering cutaneous bioactivation in toxicity assessment of chemicals used in contact with the skin.
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| 2. |
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| 3. |
- Hederos, Sofia, et al.
(författare)
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A promiscuous glutathione transferase transformed into a selective thiolester hydrolase
- 2006
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Ingår i: Organic & Biomolecular Chemistry. - 1477-0520. ; 4:1, s. 90-97
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Tidskriftsartikel (refereegranskat)abstract
- Human glutathione transferase A1-1 (hGST A1-1) can be reengineered by rational design into a catalyst for thiolester hydrolysis with a catalytic proficiency of 1.4 × 107 M–1. The thiolester hydrolase, A216H that was obtained by the introduction of a single histidine residue at position 216 catalyzed the hydrolysis of a substrate termed GSB, a thiolester of glutathione and benzoic acid. Here we investigate the substrate requirements of this designed enzyme by screening a thiolester library. We found that only two thiolesters out of 18 were substrates for A216H. The A216H-catalyzed hydrolysis of GS-2 (thiolester of glutathione and naphthalenecarboxylic acid) exhibits a kcat of 0.0032 min–1 and a KM of 41 µM. The previously reported catalysis of GSB has a kcat of 0.00078 min–1 and KM of 5 µM. The kcat for A216H-catalyzed hydrolysis of GS-2 is thus 4.1 times higher than for GSB. The catalytic proficiency (kcat/KM)/kuncat for GS-2 is 3 × 106 M–1. The promiscuous feature of the wt protein towards a range of different substrates has not been conserved in A216H but we have obtained a selective enzyme with high demands on the substrate.
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| 4. |
- Niklasson, Ida, 1982, et al.
(författare)
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Reduced Sensitizing Capacity of Epoxy Resin Systems: A Structure-Activity Relationship Study.
- 2009
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Ingår i: Chemical research in toxicology. - : American Chemical Society (ACS). - 1520-5010 .- 0893-228X.
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Tidskriftsartikel (refereegranskat)abstract
- Epoxy resins can be prepared from numerous chemical compositions. Until recently, alternatives to epoxy resins based on diglycidyl ethers of bisphenol A (DGEBA) or bisphenol F (DGEBF) monomers have not received commercial interest, but are presently doing so, as epoxy resins with various properties are desired. Epoxy resin systems are known to cause allergic contact dermatitis because of contents of uncured monomers, reactive diluents, and hardeners. Reactive diluents, for example, glycidyl ethers, which also contain epoxide moieties, are added to reduce viscosity and improve polymerization. We have investigated the contact allergenic properties of a series of six analogues to phenyl glycidyl ether (PGE), all with similar basic structures but with varying carbon chain lengths and degrees of saturation. The chemical reactivity of the compounds in the test series toward the hexapeptide H-Pro-His-Cys-Lys-Arg-Met-OH was investigated. All epoxides were shown to bind covalently to both cysteine and proline residues. The percent depletion of nonreacted peptide was also studied resulting in 88% depletion when using PGE and 46% when using butyl glycidyl ether (5) at the same time point, thus revealing a large difference between the fastest and the slowest reacting epoxide. The skin sensitization potencies of the epoxides using the murine local lymph node assay (LLNA) were evaluated in relation to the observed physicochemical and reactivity properties. To enable determination of statistical significance between structurally closely related compounds, a nonpooled LLNA was performed. It was found that the compounds investigated ranged from strong to weak sensitizers, congruent with the reactivity data, indicating that even small changes in chemical structure result in significant differences in sensitizing capacity.
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| 5. |
- Redeby, Theres, 1973, et al.
(författare)
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Specific Adducts Formed through a Radical Reaction between Peptides and Contact Allergenic Hydroperoxides
- 2010
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Ingår i: Chemical Research in Toxicology. - : American Chemical Society (ACS). - 0893-228X .- 1520-5010. ; 23:1, s. 203-210
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Tidskriftsartikel (refereegranskat)abstract
- The first step in the development of contact allergy (allergic contact dermatitis) includes the penetration of an allergy-causing chemical (hapten) into the skin, where it binds to macromolecules such as proteins. The protein-hapten adduct is then recognized by the immune system as foreign to the body. For hydroperoxides, no relevant hapten target proteins or protein-hapten adducts have so far been identified. In this work, bovine insulin and human angiotensin I were used as model peptides to investigate the haptenation mechanism of three hydroperoxide haptens: (5R)-5-isopropenyl-2-methyl-2-cyclohexene-1-hydroperoxide (Lim-2-OOH), cumene hydroperoxide (CumOOH), and 1-(1-hydroperoxy-1-methylethyl) cyclohexene (CycHexOOH). These hydroperoxides are expected to react via a radical mechanism, for which 5,10,15,20-tetraphenyl-21H,23H-porphine iron(III) chloride (Fe(III)TPPCl) was used as a radical initiator. The reactions were carried out in 1:1 ethanol/10 mM amonium acetate buffer pH 7.4, for 3 h at 37 T, and the reaction products were either enzymatically digested or analyzed directly by MALDI/TOF-MS, HPLC/MS/MS, and 2D gel electrophoresis. Both hydroperoxide-specific and unspecific reaction products were detected, but only it) the presence of the iron catalyst. In the absence of catalyst, the hydroperoxides remained unreacted. This suggests that the hydroperoxides call enter into the skin and remain inert until activated. Through the detection of a Lim-2-OOH adduct bound at the first histidine (of two) of angiotensin I, it was confirmed that hydroperoxides have the potential to form specific antigens in contact allergy.
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| 8. |
- Viljanen, Johan, et al.
(författare)
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Surface-assisted delivery of fluorescent groups to hGST A1-1 and a lysine mutant
- 2006
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Ingår i: Bioconjugate Chemistry. - : American Chemical Society (ACS). - 1043-1802 .- 1520-4812. ; 17:2, s. 429-437
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Tidskriftsartikel (refereegranskat)abstract
- Human glutathione transferase (hGST) Al-l and a lysine mutant(A216K) can both be rapidly and site-specifically acylated on Y9 and K216, respectively, using a range of thiolesters of glutathione (GS-thiolesters) as modifying reagents. The present investigation was aimed at developing a method with which to deliver a fluorescent acyl group from a solid support under conditions compatible with standard protein purification schemes. A number of fluorescent GS-thiolesters with modified peptide backbones were therefore prepared and tested for reactivity toward hGST Al-l and the A216K mutant. Substitutions at the alpha-NH2 part of the glutathione backbone were not tolerated by the proteins. However, two fluorescent reagents that carry a biotin moiety at the C-terminal part of glutathione were found through MALDI-MS experiments to react in solution with Y9 of the wild-type protein and one reagent with K216 of A216K. The reaction can take place in the presence of glutathione and even in a crude E. coli lysate of cells expressing A216K. Delivery of the fluorescent group to Y9 or K216 was possible using, NeutrAvidin (NA) beads that had been preincubated with biotinylated reagent. Alternatively, excess reagent can be removed by a brief incubation with NA beads. We have thus now developed a system for protein labeling with easy removal of excess and used up low-molecular weight reagent. This strategy can conceivably be utilized in future protein purification and labeling experiments.
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