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141.
Daniela Pinzani Anna Maria Papini Mario Chelli Mauro Ginanneschi Carlo Alberto Maggi Riccardo Patacchini Laura Quartara Gianfranco Rapi 《Letters in Peptide Science》1996,2(5):307-313
Summary The adamantane moiety was introduced in the tachykinin NK2 receptor-selective agonist [-Ala8]-NKA(4–10) (H-Asp-Ser-Phe-Val--Ala-Leu-Met-NH2, MEN 10210) and in different positions of the NK2 receptor antagonist MEN 10376 (H-Asp-Tyr-d-Trp-Val-d-Trp-d-Trp-Lys-NH2) in order to investigate how this substitution affects their biological activity at tachykinin NK1, NK2 and NK3 receptors. 1-Adamantaneacetic acid (1-Ada-CH2COOH) was directly conjugated in the solid phase as the preformed OBt active ester to the N-terminal position of MEN 10210, obtaining MEN 10586 (1-Ada-CH2CO-Asp-Ser-Phe-Val--Ala-Leu-Met-NH2). The Pfp ester of adamantaneacetic acid (1) was prepared and used for the acylation of the N-terminal position of MEN 10376, yielding MEN 10606 (1-Ada-CH2CO-Asp-Tyr-d-Trp-Val-d-Trp-d-Trp-Lys-NH2). Compound 1 was then used to obtain the building block Fmoc-Lys(1-Ada-CH2CO)-OH as a modified amino acid for the synthesis of MEN 10818 [H-Asp-Tyr-d-Trp-Val-d-Trp-d-Trp-Lys(1-Ada-CH2CO)-NH2]. In order to investigate the biological activity of the peptide bearing the adamantane group together with the free N-terminal amino function, we synthesised MEN 10676 [H-Asp(O-2-Ada)-Tyr-d-Trp-Val-d-Trp-d-Trp-Lys-NH2] using Fmoc-Asp(O-2-Ada)-OH, in which 2-adamantanole was the protecting group of the aspartate -COOH moiety during the peptide synthesis and survived the final peptide cleavage and deprotection carried out under controlled conditions. MEN 10586 showed an agonist activity comparable to that of the parent compound MEN 10210 at NK1 and NK2 receptors of guinea pig ileum, rabbit isolated pulmonary artery and hamster isolated trachea preparations, while it showed a 25-fold higher agonist activity at NK3 receptors of rat isolated portal vein. The three modified antagonist analogs displayed similar or reduced affinity at NK1, NK2 and NK3 receptors as compared to MEN 10376. The drop was particularly evident (>2 log units) at the NK2 receptors of the rabbit isolated pulmonay artery. 相似文献
142.
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144.
Oxidative stress and antioxidant content in Chlorella vulgaris after exposure to ultraviolet-B radiation 总被引:4,自引:0,他引:4
Growth of Chlorella vulgaris was measured in cultures irradiated with 0, 0.8, 2.0 and 4.4 kJ m2 UV-B. Growth expressed as chlorophyll content, declined significantly with increased UV-B dose. Ultraviolet-B irradiated cultures in log phase of growth showed a 284% increase in oxygen radical generation and a 145% increase in lipid peroxidation compared with unirradiated cultures, whereas cultures in the stationary growth phase showed no significant changes in these parameters. The activities of superoxide dismutase and catalase increased by 40 and 500%, respectively, after exposure to a UV-B dose of 4.4 kJ m−2 . Contents of the lipophilic antioxidants α-tocopherol and β-carotene increased by 180 and 63 amol cell−1 respectively, between log and stationary phases in unirradiated cultures; but in UV-B-irradiated cultures these increases were significantly depressed. Photoreducing capacities of chloroplasts were decreased following UV-B irradiation of both isolated chloroplasts and those isolated from irradiated algae. Cells exposed to UV-B exhibited increased size and starch accumulation. These results suggest that oxidative stress conditions related to UV-B exposure trigger an antioxidant response that includes an increase in the activity of the antioxidant enzymes (superoxide dismutase and catalase). 相似文献
145.
Phosphorylation and dephosphorylation of ribosomal proteins have been suggested to participate in the regulation of protein synthesis in eukaryotic organisms. The present research focuses on the purification and partial characterization of a protein kinase from maize ribosomes that specifically phosphorylates acidic ribosomal proteins. Ribosomes purified from maize axes were used as the enzyme source. Purification of ribosomes was performed by centrifugation through a 0.5 M sucrose, 0.8 M KCl cushion. A protein kinase activity present in this fraction was released by extraction with 1.5 M KCl and further purified by diethylaminoethyl cellulose column chromatography. A peak containing protein kinase activity was eluted around 400 m M KCl. Analysis of this fraction by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed one band of 38 kDa molecular mass, which cross-reacted in a western blot with antibodies raised against proteins from the large ribosomal subunit. This enzyme specifically phosphorylates one of the acidic ribosomal proteins (P2 ). Its activity is inhibited by Ca2+ and Zn2+ and is activated by Mg2+ , polylysine and spermine. The relevance of this protein kinase in reinitiating the protein synthesis process during germination is discussed. 相似文献
146.
147.
Carbonera Daniela; Rovati Laura; Guano Fulvio; Balestrazzi Alma 《Journal of experimental botany》1995,46(3):347-354
Topoisomerase II was partially purified from Daucus carota cellsby a procedure including ammonium sulphate fractionation, ion-exchange,and affinity chromatography steps. The type II enzyme, identifiedfor its ability to unknot knotted P4 DNA and decatenate Trypanosomacruzi kDNA, requires ATP and Mg2+ for activity. The unknottingactivity was sensitive to an inhibitor of the mammalian typeII enzyme, the drug VP16 (IC50 32 mmol m3), whereas inhibitorsof DNA gyrase showed a limited effect on activity. The SDS-PAGEanalysis of the dsDNA cellulose fraction revealed the presenceof four polypeptides of apparent molecular masses of 72, 71,34, and 33 kDa among which only a polypeptide of about 70 kDacrossreacted with antibodies against yeast topoisomerase II.Immunoprecipitation experiments with monoclonal antibodies tothe and ß isoforms of the human enzyme confirmedthe recognition of a polypeptide of 70 kDa. The sedimentationcoefficient (S) of the topoisomerase II in the phosphocellulosefraction, calculated by analytical glycerol gradient, was 6.1corresponding to a molecular mass of about 123 kDa. Resultssuggest the presence in carrot of a protein of molecular massof 70 kDa having the typical properties of an eukaryotic topoisomeraseII and carrying epitopes recognized by MoAbs to both human and ß enzymes. The 70 kDa polypeptide might then representthe monomer of a homodimer enzyme of 123 kDa. Key words: Daucus carota, topoisomerase II, immunoprecipitation 相似文献
148.
Laura Chiarantini Luigia Rossi Alessandra Fraternale Mauro Magnani 《Molecular and cellular biochemistry》1995,144(1):53-59
Human and murine blood cells treated with ZnCl2 and bis(sulfosuccinimidyl)suberate (BS3) (a cross linking agent) undergo band 3 clustering and binding of hemoglobin to red blood cell membrane proteins. These clusters induce autologous IgG binding and complement fixation, thus favouring the phagocytosis of ZnCl2/BS3 treated cells by macrophages. The extension of red blood cell opsonization can be easily modulated by changing the ZnCl2 concentration in the 0.1–1.0 mM range thus providing an effective way to affect blood cell recognition by macrophages. In fact, murine erythrocytes treated with increasing ZnCl2 concentrations have proportionally reduced survivals when reinjected into the animal. Furthermore, the organ sequestration of ZnCl2/BS3 treated cells strongly resembles the typical distribution of the senescent cells. Since the ZnCl2/BS3 treatment can also be performed on red blood cells loaded with drugs or other substances, this procedure is an effective drug-targeting system to be used for the delivery of molecules to peritoneal, liver and spleen macrophages. 相似文献
149.
Paul G. Braunschweiger Vathsala S. Basrur Dayna Cameron Laura Sharpe Octavio Santos James P. Perras Bernd-Uwe Sevin Arnold M. Markoe 《Biotherapy》1997,10(2):129-137
The modulation of cisPlatin cytotoxicity by interleukin-1 (IL-1α) was studied in cultures of SCC-7 tumor cells with and without
tumor macrophages to examine potential mechanisms for the synergistic antitumor activity of cisPlatin and IL-1α in SCC-7 solid
tumors. Neither IL-1α nor tumor macrophages affected the survival of clonogenic tumor cells and IL-1α had no direct effect
on tumor cell growthin vitro. Macrophages had no direct effect on cisPlatin sensitivity (IC90=6.0 μM), but, the addition of IL-1α (500–2000U/ml) to co-cultures of cisPlatin pretreated tumor cells and resident tumor
macrophages increased cell killing (IC90=3.1 μM). Similar responses were seen in primary cultures treated with cisPlatin before IL-1α. The modulation of cisPlatin
cytotoxicity by IL-1α exhibited a biphasic dose response that paralleled the IL-1α dose dependent release of H2O2by resident tumor macrophages. Further, IL-1α modification of cisPlatin cytotoxicity was prompt and inhibited by catalase.
CisPlatin and exogenous H2O2 (50 μM) produced more than additive SCC-7 clonogenic cell kill and hydroxyl radicals played an important role in the response.
Interleukin-1 modulation of cisPlatin cytotoxicity was schedule dependent. IL-1α treatment for 24 hrs, before cisPlatin, produced
drug resistance (IC90=11.1 μM). Our study shows that IL-1α can stimulate tumor macrophages to release pro-oxidants that modify cellular chemosensitivity
in a schedule and dose dependent fashion. Our findings may also provide a mechanistic explanation for the synergistic antitumor
activity of cisPlatin and IL-1αin vivo. 相似文献
150.