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991.
The preparation of the co-oligopeptides of the series H-Gly-Phe-(Gly)n-Trp-Gly-OH (n = 0, 1, 2) and of other free peptides of glycine, L -tryptophan, and L -phenylalanine is reported. The syntheses have been carried out by conventional methods, using N-hydroxysuccinimide esters for the coupling steps. The ultraviolet absorption properties of the free peptides have been investigated in water. No hypo- or hyperchromicity was found for the aromatic chromophores, with the exception of H-Gly-Phe-Trp-OH, which shows a small but significant hypochromicity. The contribution of the peptide bond to the molar absorptivity in the far ultraviolet has been separated from that of the side chain plus the ? COO? group by plotting the measured molar absorptivity ? of the farthest accessible uv maximum as a function of the number of peptide bonds (nA). The peptide bond contribution proved to be independent of nA in the range nA = 1–5, thus ruling out the onset of helical conformations in the longer chain peptides. 相似文献
992.
Luigi Sportelli Harald Neubacher Wolfgang Lohmann 《Radiation and environmental biophysics》1976,13(4):305-313
Electron spin resonance and optical absorption studies have been done in order to investigate the interaction between Cu2+ and aromatic amino acids in aqueous solution at 77 K and at room temperature as well. Depending on the concentration each aromatic amino acid can form two different kinds of complexes with Cu2+ which can be characterized by its ESR pattern. Additional information was obtained from optical d-d and CT transitions. 相似文献
993.
Monika Horn Peter Humphries Markus Kunisch Christiana Marchese Eckart Apfelstedt-Sylla Luigi Fugi Eberhart Zrenner Paul Kenna Andreas Gal Jane Farrar 《Human genetics》1992,90(3):255-257
By screening patients with autosomal dominant retinitis pigmentosa for mutations in the rhodopsin gene, two deletions (8bp and 1bp) have been identified in exon 5; these deletions cause a shift in the reading frame. The predicted proteins should be radically altered with translation continuing past the normal stop signal and resulting in a rhodopsin molecule that is, respectively, 1 and 10 amino acids longer. The clinical phenotype of the patients is described and is compared with that associated with other mutations in the same region of the gene. 相似文献
994.
Giuliana De Sanctis Vincenzo Bottari Alessandra Frezzolini Martina Ficcardi Giulio De Rossi Maria Concetta Petti Franco Mandelli Luigi Fontana 《Cancer immunology, immunotherapy : CII》1992,34(6):414-418
Summary In this study we analysed the in vitro effect of recombinant interferon on cytotoxic activities mediated by both lymphoid and polymorphonuclear cells from 16 patients with myelodysplastic syndromes. Our results indicate the inability of interferon to restore the defective natural killer activity, natural killer cells and lectin-induced cytotoxicity. On the contrary we detected a boosting effect on the depressed polymorphonuclear cell cytotoxic activities. In our view, the ability of interferon to potentiate polymorphonuclear cell lytic efficiency could support an alternative defensive pathway against either neoplastic or infectious agents. 相似文献
995.
Upon differentiation of embryonal carcinoma cells induced by retinoids (10−7 M) the ‘apparent’ membrane microviscosity increases dramatically. Only biologically active retinoids induce differentiation and cause an enhancement in microviscosity. Several embryonal carcinoma cell lines have a relatively lower ‘apparent’ microviscosity than their differentiated derivatives, suggesting that this may be a general property of these cells. At higher concentrations retinoids cause a reduction in ‘apparent’ membrane microviscosity of various cells. This change occurs whether the analogue is biologically active or not, indicating the non-specific nature of this action. 相似文献
996.
Maria Grazia Tozzi Roberta Catalani Pier Luigi Ipata Umberto Mura 《Analytical biochemistry》1982,123(2):265-269
Published assays for phosphopentomutase activity are based on acid lability differences between ribose 1-phosphate and ribose 5-phosphate. The present work describes a new method in which the isomerization of ribose 5-phosphate to ribose 1-phosphate is followed spectrophotometrically at 265 nm by coupling it with the following two-stage enzymatic conversion: ribose 1-phosphate + adenine ? phosphate + adenosine (adenosine phosphorylase); adenosine + H2O → inosine + NH3 (adenosine deaminase). The method has been used to show some properties of Escherichia coli phosphopentomutase. 相似文献
997.
Rate and Duration of Stimulation Determine Presynaptic Effects of Haloperidol on Dopaminergic Neurons 总被引:2,自引:1,他引:1
Abstract: Superfused rabbit neostriatal slices prelabeled with [3 H]dopamine ([3 H]DA) were depolarized with electrical pulses (12 V, 1 ms). Although transmitter release showed a proportional increase with a greater number of pulses (30-360 pulses), flat frequency-release curves were obtained. Haloperidol (0.03–0.3 μ m ) enhanced 3 H overflow without affecting its metabolism or time course, and antagonized apomorphine-induced inhibition of transmitter release. Maximal enhancement of release by haloperidol was obtained with 30–60 pulses delivered at a rate of 3 Hz, whereas much less facilitation of release was seen at 0.3 and 1 Hz (30–90 pulses) or with 360 pulses at either of the three frequencies. Therefore, the slope of the frequency-release curve was markedly increased by haloperidol. These results indicate that activation of presynaptic DA receptors, and thus facilitation of release by haloperidol was highly dependent on the rate and duration of stimulation of striatal dopaminergic terminals. In these neurons the feedback loop seems to act physiologically to depress the slope of the frequency-release curve. 相似文献
998.
Maria Luisa Vuotto Rocco De Luna Maria Teresa Lucia Ielpo Pasquale De Sole Vincenza Moscatiello Immacolata Simeone Luigi Gradoni Domenico Mancino 《Luminescence》2000,15(4):251-255
Dogs are the domestic reservoir of Leishmania infantum, a vector-borne intracellular protozoan agent of human visceral leishmaniasis. The role of polymorphonuclear leukocytes (PMNs) in the immune defence against this parasite has been poorly studied. We have investigated the function of peripheral blood PMNs in naive beagle dogs that have been naturally exposed to phlebotomine vectors in an area highly endemic for canine leishmaniasis, and found infected by Leishmania at the end of the transmission season. Whole blood phagocyte oxidative metabolism was assessed by a rapid method that determines a luminol-amplified chemiluminescence (CL) emission. This was evaluated using either a soluble stimulant, phorbol mirystate acetate (PMA), or phagocytic stimuli, such as zymosan unopsonized (ZYM) or opsonized with autologous serum (OPZ). In blood samples taken 2 months after exposure to Leishmania transmission, data on CL emission revealed a significant decrease of reactive oxygen intermediates (ROI) production in the presence of both PMA and ZYM, compared with blood samples obtained from dogs before exposure. On the contrary, no variations in CL emission were detected in presence of OPZ. Our data indicate that immunological changes occur early in canine leishmaniasis and confirm that the role of PMNs and their products need to be clarified. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
999.
Rossana Migheli Chiara Godani Luigi Sciola Maria R Delogu Pier Andrea Serra Danilo Zangani Guglielmo De Natale Egidio Miele & Maria S Desole 《Journal of neurochemistry》1999,73(3):1155-1163
L-DOPA and manganese both induce oxidative stress-mediated apoptosis in catecholaminergic PC12 cells. In this study, exposure of PC12 cells to 0.2 mM MnCl2 or 10-20 microM L-DOPA neither affected cell viability, determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, nor induced apoptosis, tested by flow cytometry, fluorescence microscopy, and the TUNEL technique. L-DOPA (50 microM) induced decreases in both cell viability and apoptosis. When 0.2 mM MnCl2 was associated with 10, 20, or 50 microM L-DOPA, a concentration-dependent decrease in cell viability was observed. Apoptotic cell death also occurred. In addition, manganese inhibited L-DOPA effects on dopamine (DA) metabolism (i.e., increases in DA and its acidic metabolite levels in both cell lysate and incubation medium). The antioxidant N-acetyl-L-cysteine significantly inhibited decreases in cell viability, apoptosis, and changes in DA metabolism induced by the manganese association with L-DOPA. An increase in autoxidation of L-DOPA and of newly formed DA is suggested as a mechanism of manganese action. These data show that agents that induce oxidative stress-mediated apoptosis in catecholaminergic cells may act synergistically. 相似文献
1000.
Diego Moraa Maria Grazia Fortinaa Carlo Parinia Pier Luigi Manachinia 《FEMS microbiology letters》1997,151(2):231-236
A multiplex PCR assay that can readily and unambiguously identify Pediococcus acidilactici and Pediococcus pentosaceus strains was developed to give an easy-to-read profile based on the amplification of a 16S rRNA gene fragment, specific for each species, and a d-lactate dehydrogenase gene fragment specific for Pediococcus acidilactici strains. 相似文献