Vigorous trimethylsilylation of dihydropyrimidine and dihydro-s-triazine bases and nucleosides results in their dehydrogenation to the analogous aromatic derivatives. This transformation, which cannot be effected by conventional dehydrogenating reagents, has been studied in detail using gas chromatographic and mass spectrometric methods. For 5,6-dihydro-5-azacytidine (2a) the oxidation is quantitative, requires molecular oxygen as well as reagents capable of both N- and O-silylation, is accelerated by heat and selected free radiacal initiators, and is inhibited by diethyldithiocarbamate and galvinoxyl free radical. This anomalous silylation reaction occurs on both an analytical and preparative scale. Silylation-mediated oxidation also exhibits a substantial deuterium isotope effect with preferential retention of deuterium at the new site of unsaturation. The potential of this new reaction for the synthesis of aromatic systems and for the insertion of non-exchangeable isotopic labels in suitable reduced precursors is illustrated. 相似文献
Strongyloides stercoralis is a human intestinal parasite which may lead to complicated strongyloidiasis in immunocompromised. Here, a case of complicated strongyloidiasis in a patient with chronic lymphocytic leukemia is reported. Presence of numerous S. stercoralis larvae in feces and sputum confirmed the diagnosis of hyperinfection syndrome in this patient. Following recovery of filariform larvae from agar plate culture of the stool, the isolate was characterized for the ITS1 region of ribosomal DNA gene by nested-PCR and sequencing. Albendazole therapy did not have cure effects; and just at the beginning of taking ivermectin, the patient died. The most important clue to prevent such fatal consequences is early diagnosis and proper treatment. 相似文献
AbstractNickel oxide nanoparticles (NiO NPs) have received great interests in medical and biotechnological applications. However, their adverse impacts against biological systems have not been well-explored. Herein, the influence of NiO NPs on structural changes, heme degradation and aggregation of hemoglobin (Hb) was evaluated by UV-visible (Vis) spectroscopy, circular dichroism (CD) spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), and molecular modeling investigations. Also, the morphological changes and expression of Bax/Bcl-2 mRNA in human lymphocyte cell exposed to NiO NPs were assayed by DAPI staining and quantitative real-time PCR (qPCR), respectively. The UV-Vis study depicted that NiO NPs resulted in the displacement of aromatic residues and heme groups and production of the pro-aggregatory species. Intrinsic and Thioflavin T (ThT) fluorescence studies revealed that NiO NPs resulted in heme degradation and amorphous aggregation of Hb, respectively, which the latter result was also confirmed by TEM study. Moreover, far UV-CD study depicted that NiO NPs lead to substantial secondary structural changes of Hb. Furthermore, near UV-CD displayed that NiO NPs cause quaternary conformational changes of Hb as well as heme displacement. Molecular modelling study also approved that NiO NPs resulted in structural alterations of Hb and heme deformation. Moreover, morphological and genotoxicity assays revealed that the DNA fragmentation and expression ratio of Bax/Bcl-2 mRNA increased in lymphocyte cells treated with NiO NPs for 24?hr. In conclusion, this study indicates that NiO NPs may affect the biological media and their applications should be limited.Communicated by Ramaswamy H. Sarma 相似文献
Biomechanics and Modeling in Mechanobiology - The bronchial tree plays a main role in the human respiratory system because the air distribution throughout the lungs and gas exchange with blood... 相似文献
Molecular Biology Reports - Malignant tumors have become the most dangerous disease in recent years. Chemotherapy is the most effective treatment for this disease; however, the problem of drug... 相似文献
Ocimum basilicum L. var. purpurascens is an enriched reservoir of pharmaceutically important compounds with plenty of health and therapeutic attributes such as phenolic acids and anthocyanins. However, the inefficient production of aforementioned metabolites in wild has restricted its commercial utilization. Herein, commercially viable phytochemicals have been enhanced through elicitation of in-vitro cultures of O. basilicum using yeast extract.The impact of various concentrations (YE 1 mg/L,YE 10 mg/L, YE 25 mg/L, YE 50 mg/L, YE 100 mg/L, YE 200 mg/L and YE 400 mg/L) of yeast extract on biomass accumulation, phytochemical production, and antioxidant activities were assessed in callus cultures. Moderate concentration of yeast extract (100 mg/L) enhanced biomass accumulation i.e. fresh weight (FW 216.28 g/L) and dry weight (DW 15.49 g/L) up to 1.5 folds as compared to control (FW 167.14 g/L and DW 10.25 g/L). Similarly, yeast extract (100 mg/L) increased total phenolic and flavonoid contents as well as enhanced antioxidant activities such as ABTS (2,2 azinobis 3-ethylbenzthiazoline-6-sulphonic acid), FRAP (ferric reducing antioxidant power) and DPPH (2,2-diphenyl-1-picryhydrazyl). High performance liquid chromatography (HPLC) analysis was elucidated for further phytochemical investigation. HPLC analysis showed an increase of almost 1.9 folds as compared to control in rosmarinic acid (15.19 mg/g DW), chicoric acid (2.13 mg/g DW), peonidin (2.70 mg/g DW) and cyanidin (1.57 mg/g DW). Likewise, 1.8 fold and 2.4 folds increase was observed in eugenol essential oils (0.25 mg/g DW) and chavicol (0.037 mg/g DW), respectively. For cellular antioxidant activity, reactive oxygen specie or reactive nitogen specie (ROS/RNS) was induced in yeast cells and the effect of O. basilicum callus culture was further investigated in stressed yeast cells. A positive correlation exists between the antioxidant activities, TPC and TFC analysis. In short, these results showed that yeast extract could act as an efficient elicitor to enhance pharmacologically important metabolites in callus cultures of Ocimum basilicum.
