| 1. |
- Björup, Peter, et al.
(författare)
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Reaction medium engineering in enzymatic peptide fragment condensation : Synthesis of eledoisin and LH-RH
- 1998
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Ingår i: Bioorganic and Medicinal Chemistry. - 0968-0896. ; 6:7, s. 891-901
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Tidskriftsartikel (refereegranskat)abstract
- The influence of different reaction systems on α-chymotrypsin-catalyzed synthesis of eledoisin and LH-RH peptides from (7+4) and (5+5) fragments was investigated. The peptide yield was determined in the following systems: buffered aqueous media, frozen solutions, organic media, and cosolvent mixtures. The experimental set up was tailored to allow the screening of an array of conditions with minimum consumption of peptide fragments (2.1 and 2.5mM). The best yields (22% yield for eledoisin and 68% yield for LH-RH) were obtained in buffered aqueous solutions. It was found that the choice of buffer had a strong influence on the peptide yield; boric-borate and ammonium acetate buffers at pH 9, gave the best results. In buffered aqueous systems, both syntheses were scaled up by using a 10-fold increase in fragment concentration (21 and 25mM). Under these conditions the yields rose to 57% and 80% of eledoisin and LH-RH, respectively. Moreover, during the synthesis of eledoisin and in the presence of boric-borate buffer pH 9, the peptide precipitated from the reaction medium preventing a secondary hydrolysis and facilitating the in situ product purification. Copyright (C) 1998 Elsevier Science Ltd.
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| 2. |
- Clapés, Pere, et al.
(författare)
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Enzymatic peptide synthesis in low water content systems : Preparative enzymatic synthesis of [Leu]- and [Met]-enkephalin derivatives
- 1995
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Ingår i: Bioorganic and Medicinal Chemistry. - 0968-0896. ; 3:3, s. 245-255
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Tidskriftsartikel (refereegranskat)abstract
- A novel total enzymatic synthesis of [Leu]- and [Met]-enkephalin derivatives was accomplished in low-water content systems at a preparative scale. α-Chymotrypsin, papain, thermolysin and bromelain adsorbed on Celite were used as catalysts. Organic solvents such as acetonitrile and ethyl acetate with small amounts of buffer added or at specific water activity were used as reaction media. Simple readily available amino acid ester derivatives were used as starting building blocks. This feature allowed the possibility of using the products in one step directly as acyl-donor ester, without any chemical or enzymatic modification, in the next enzymatic coupling. The optimal strategy for the synthesis of the enkephalin derivatives was different depending on the carboxy terminal group. The preparation of the carboxy-terminal amide derivatives (R-Tyr-Gly-Gly-Phe-Leu[Met]-NH2) was achieved via 4 + 1 fragment condensation catalyzed by α-chymotrypsin. The carboxy-terminal ethyl ester derivatives (R-Tyr-Gly-Gly-Phe-Leu[Met]-OEt) were obtained via 2 + 3 condensation catalyzed by bromelain, a quite unusual protease for peptide synthesis but more effective than papain in this coupling. Both syntheses were carried out in four enzymatic steps and one or two chemical deprotection steps routinely used in peptide synthesis. The overall yields of pentapeptide derivatives were between 40-54% of pure product.
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| 3. |
- Nilsson, Ulf, et al.
(författare)
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PapG adhesin from E. coli J96 recognizes the same saccharide epitope when present on whole bacteria and as isolated protein
- 1996
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Ingår i: Bioorganic and Medicinal Chemistry. - 0968-0896. ; 4:11, s. 1809-1817
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Tidskriftsartikel (refereegranskat)abstract
- Purified PapG adhesin from the genetically well-defined uropathogenic Escherichia coli strain J96, as well as whole bacteria, were bound to microtiter plates that carried covalently bound globotetraose and galabiose. The binding was inhibited by soluble saccharide derivatives corresponding to the globoseries of glycolipids, including all di-, tri-, tetra-, and pentasaccharide fragments of the Forssman antigen and all monodeoxy analogues of galabiose. Analysis of the inhibition pattern showed no significant difference between purified adhesin and whole bacteria. The glucose unit at the reducing end of the natural saccharides was detrimental to PapG binding since deletion of the glucose unit increased the inhibitory power 10-20 fold. The five hydroxyl groups HO-6, -2', -3', -4', -6' of the galabiose unit were shown to be important for PapG binding, presumably via intermolecular hydrogen bonds.
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| 4. |
- Persson, Tina, et al.
(författare)
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Synthesis of 2'-Deoxyuridine 5'-(α,β-Imido)triphosphate: A Substrate Analogue and Potent Inhibitor of dUTPase
- 1996
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Ingår i: Bioorganic & Medicinal Chemistry. - : Elsevier BV. - 0968-0896. ; 4:4, s. 553-556
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Tidskriftsartikel (refereegranskat)abstract
- The dUDP analogue, 2'-deoxyuridine 5'-(α,β-imido)diphosphate (dUPNP) was synthesized. The corresponding triphosphate analogue (dUPNPP) was prepared by enzymic phosphorylation of dUPNP using the enzyme pyruvate kinase and phosphoenolpyruvate as the phosphate donor. This method was successful in phosphorylating the imidodiphosphate analogue of 2'-deoxythymidine (dTPNP) to 2'-deoxythymidine 5'-(α,β-imido)triphosphate (dTPNPP), in contradiction to a previous report. The properties of dUPNPP have been tested using the enzyme dUTPase from Escherichia coli. This enzyme, having a crucial role in nucleotide metabolism, is strictly specific for its substrate (dUTP) and catalyzes the hydrolysis of the α,β-bridge, resulting in dUMP and pyrophosphate. Replacement of the α,β-bridging oxygen in dUTP with an imido group resulted in a nonhydrolyzable substrate analogue and a potent competitive inhibitor of dUTPase (Ki=5μM). The analogue prepared (dUPNPP) may be utilized in crystallographic studies of the active site of dUTPase to provide knowledge about specific interactions involved in substrate binding and as a parental compound in design of dUTPase inhibition for medical purposes.
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| 5. |
- Tuite, Eimer, 1966, et al.
(författare)
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Intercalative interactions of ethidium dyes with triplex structures
- 1995
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Ingår i: Bioorganic and Medicinal Chemistry. - 0968-0896 .- 1464-3391. ; 3:6, s. 701-711
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Tidskriftsartikel (refereegranskat)abstract
- The binding of phenanthridine dyes to tripler poly(dT)*poly(dA). poly(dT) and its precursor duplex poly(dA). poly(dT) is characterized using linear dichroism and circular dichroism spectroscopy, and thermal denaturation. The two monomeric dyes ethidium bromide and propidium iodide are shown to behave similarly to each other in intercalating into and stabilizing both the duplex and the tripler structures. However, contrary to expectations, the extra cationic side-chain of propidium iodide provides no significant extra stabilization of tripler compared with ethidium bromide, although propidium does stabilize the duplex more than ethidium. The monomeric dyes appear to have somewhat different binding geometries with the duplex and tripler polymers. The dimeric dye ethidium homodimer is found to bis-intercalate in the tripler as well as the duplex but, in contrast to the monomers, no variation in geometry between duplex and tripler is observed. However, although dimer stabilizes the duplex, it has no effect on the thermal stability of the tripler. This lack of binding preferentiality of the dimer for tripler compared with the monomeric dyes indicates greater constraints on the accommodation of a bis-intercalator in the tripler structure than in the duplex.
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| 6. |
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| 7. |
- Marton, J., et al.
(författare)
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New nepenthone and thevinone derivatives
- 1997
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Ingår i: Bioorganic & Medicinal Chemistry. - : Elsevier BV. - 0968-0896 .- 1464-3391. ; 5:2, s. 369-382
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Tidskriftsartikel (refereegranskat)abstract
- The diastereoselective reaction of thevinone (2a) and nepenthone (2c) and their dihydro derivatives (2b and d) with Grignard reagents afforded new N-substituted (20S)- and (20R)-phenyI-6,14-ethenomorphinan derivatives (6a-y). The Grignard reaction of the N-substituted-N-demethyl derivatives 4a-f and 4m-r with methylmagnesium iodide resulted in the (20R)-phenyl tertiary alcohols 5a-f and 5m-r, respectively, but the conversion of 4g-l and that of the N-substituted-dihydrothevinone derivatives with phenylmagnesium bromide afforded the (20S)-phenyl derivatives 5g-l and 5s-y, respectively. The N-cyclopropylmethyl-, N-β-phenylethyl-, and N-propyl derivatives were prepared by the 3-O-demethylation of compounds 5. For the synthesis of the N-allyl-, N-dimethylallyl-, and N-propargyl compounds 2a-d were reacted with the corresponding Grignard reagent, and treatment of the products with cyanogen bromide gave the cyanamides 8a-d. These latter compounds were transformed into 10a,b,d, whose alkylation led to the target derivatives 6d-f, j-l, p-r, and w-y. The biochemical investigation of these substances showed that the affinities to the δ-opioid receptors were high, but the selectivity was low. Tn two cases (6c and 11d) a μ-opioid receptor specificity was observed.
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| 8. |
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| 9. |
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| 10. |
- Karlsson, Karl-Anders, 1935, et al.
(författare)
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Unexpected carbohydrate cross-binding by Escherichia coli heat-labile enterotoxin. Recognition of human and rabbit target cell glycoconjugates in comparison with cholera toxin.
- 1996
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Ingår i: Bioorganic & medicinal chemistry. - 0968-0896. ; 4:11, s. 1919-28
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Tidskriftsartikel (refereegranskat)abstract
- The bacterial protein enterotoxins, cholera toxin (CT) of Vibrio cholerae and heat-labile toxin (LT) of Escherichia coli, induce diarrhea by enhancing the secretory activity of the small intestine of man and rabbit (animal model). This physiological effect is mediated by toxin binding to a glycolipid receptor, the ganglioside GM1, Gal beta 3GalNAc beta 4(NeuAc alpha 3)GAl beta 4Glc beta 1Cer. However, LT, but not CT, was recently shown by us to bind also to paragloboside, Gal beta 4GlcNAc beta 3Gal beta 4Glc beta 1Cer, identified in the target cells. By molecular modeling of this tetrasaccharide in the known binding site of LT, the saccharide-peptide interaction was shown to be limited to the terminal disaccharide (N-acetyllactosamine). This sequence is expressed in many glycoconjugates, and we have therefore assayed glycolipids and glycoproteins prepared from the target tissues. In addition to paragloboside, receptor activity for LT was detected in glycoproteins of human origin and in polyglycosylceramides of rabbit. However, CT bound only to GM1. Two variants of LT with slightly different sequences, human (hLT) and porcine (pLT), were identical in their binding to target glycoproteins and polyglycosylceramides, but different regarding paragloboside, which was positive for pLT but negative for hLT. This difference is discussed on basis of modeling, taking in view the difference at position 13, with Arg in pLT and His in hLT. Although N-acetyllactosamine is differently recognized in form of paragloboside by the two toxin variants, we speculate that this sequence in human glycoproteins and rabbit polyglycosylceramides is the basis for the common binding. Much work remains, however, to clear up up this unexpected sophistication in target recognition.
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