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Tryptic digestion of peptides corresponding to modified fragments of human growth hormone-releasing hormone.

100%
Witkowska E., Orłowska A., Izdebski J.
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vol. 51
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issue 1
51-56
EN
The objective of this study was to examine the degradation of short peptides corresponding to modified fragments of human growth hormone-releasing hormone by trypsin. Six analogues of pentapeptide 9-13 of human growth hormone-releasing hormone containing homoarginine, ornithine, glutamic acid, glycine, leucine or phenylalanine residue in position 11, two analogues of hexapeptide 8-13 of human growth hormone-releasing hormone and two analogues of heptapeptide 7-13 of human growth hormone-releasing hormone containing homoarginine or glycine residue in position 11 were obtained. The peptides were subjected to digestion by trypsin and the course of reaction was monitored using HPLC. It was found that the rate of hydrolysis of the Lys12-Val13 peptide bond depends on the amino-acid residue preceding Lys12. The extension of the peptide chain towards the N-terminus by introduction of consecutive amino-acid residues corresponding to the human growth hormone-releasing hormone sequence accelerates the hydrolysis process. These results may be of assistance in designing new analogues of human growth hormone-releasing hormone, more resistant to the activity of proteolytic enzymes.
2
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Conformational analysis of a novel cyclic enkephalinanalogue using NMR and EDMC calculations

88%
Sidor M., Wójcik J., Pawlak D., Izdebski J.
Acta Biochimica Polonica
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1999
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vol. 46
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issue 3
641-650
3
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Cyclic enkephalin-deltorphin hybrids containing a carbonyl bridge: structure and opioid activity

64%
Ciszewska M., Ruszczyńska K., Oleszczuk M., Chung N., Witkowska E., Schiller P., Wójcik J., Izdebski J.
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2011
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vol. 58
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issue 2
225-230
EN
Six hybrid N-ureidoethylamides of octapeptides in which an N-terminal cyclic structure related to enkephalin was elongated by a C-terminal fragment of deltorphin were synthesized on MBHA resin. The synthetic procedure involved deprotection of Boc groups with HCl/dioxane and cleavage of the peptide resin with 45 % TFA in DCM. d-Lys and d-Orn were incorporated in position 2, and Lys, Orn, Dab, or Dap in position 5. The side chains of the dibasic amino function were protected with the Fmoc group. This protection was removed by treatment with 55 % piperidine in DMF, and cyclization was achieved by treatment with bis-(4-nitrophenyl)carbonate. Using various combinations of dibasic amino acids, peptides containing a 17-, 18-, 19- or 20-membered ring structure were obtained. The peptides were tested in the guinea-pig ileum (GPI) and mouse vas deferens (MVD) assays. Diverse opioid activities were observed, depending on the size of the ring. Extension of the enkephalin sequence at the C-terminus by a deltorphin fragment resulted in a change of receptor selectivity in favor of the δ receptor. The conformational propensities of selected peptides were determined using the EDMC method in conjunction with data derived from NMR experiments carried out in water. This approach allowed proper examination of the dynamical behavior of these small peptides. The results were compared with those obtained earlier with corresponding N-(ureidoethyl)pentapeptide amides.
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