排序方式: 共有66条查询结果,搜索用时 15 毫秒
31.
Zilma Escobar Carlos Solano Rikard Larsson Martin Johansson Efrain Salamanca Alberto Gimenez Eduardo Muñoz Olov Sterner 《Tetrahedron》2014
A synthesis of poinsettifolin A (1), a prenylated flavonol isolated from Dorstenia poinsettifolia, is described. Two routes starting from quercetin were explored, and 1 could be prepared if a prenyl group first was incorporated at C-6 of the protected quercetin followed by a condensation with citral at C-8. The key synthetic steps are a Mitsunobu reaction, an europium (III)-catalysed Claisen rearrangement coupled with cross-metathesis, and a benzopyran-forming geranylation. The two geranylated 3,5,3′,4′-tetrahydroxyflavonols prepared, 1 and 3, were assayed for antileishmanial activity against Leishmania amazonensis and Leishmania braziliensis, and found to be active. Compound 3 showed cytotoxic activity against leukaemia and lung cancer cells while 1 lacked cytotoxicity. 相似文献
32.
Guldan H Matysik FM Bocola M Sterner R Babinger P 《Angewandte Chemie (International ed. in English)》2011,50(35):8188-8191
An archaea-type ether lipid in bacteria: PcrB, the bacterial homologue of the archaea-specific geranylgeranylglyceryl phosphate synthase, produces heptaprenylglyceryl phosphate in bacillales. The product becomes dephosphorylated and acetylated in?vivo. 相似文献
33.
Almanza GR Quispe R Mollinedo P Rodrigo G Fukushima O Villagomez R Akesson B Sterner O 《Natural product communications》2011,6(9):1269-1274
Dichloromethane extract of the stem bark of Rheedia acuminata yielded three benzophenones with antioxidant activity, the new one named acuminophenone A (1), guttiferone K (2) and isoxanthochymol (3), along with the known xanthones formoxanthone C (4) and macluraxanthone (5). The structures were established through interpretation of their spectroscopic data, the stereochemistry of compounds (1) and (2) were resolved by experimental and computational experiments and their antioxidant activities were measured using the DPPH, ABTS and TEAC assays. The antioxidant results showed that metabolites 1, 4 and 5 had a better antioxidant activity than the reference compound quercetin. In addition, we evaluate the mutagenicity and antimutagenicity of the CH2Cl2 extract as well as of the free radical scavenger compounds 1, 4 and 5 by the AMES Salmonella/microsomal test. No mutagenicity was found in the CH2Cl2 extract using Salmonella typhimurium strains TA98, TA100, TA102, TA1537 and TA1538, with or without S9 metabolic activation. The pure compounds neither showed mutagenicity in TA 102 strain and the most important result was the strong reduction of mutagenic effect induced by hydrogen peroxide in S. typhimurium TA102, with or without S9, showed by the compounds 1 (more than 93%) and 4 (more than 88%) at 0.02 microg/plate. 相似文献
34.
Paola Terrazas Efrain Salamanca Marcelo Dvila Sophie Manner Alberto Gimenez Olov Sterner 《Molecules (Basel, Switzerland)》2021,26(13)
The natural products pulchrol and pulchral, isolated from the roots of the Mexican plant Bourreria pulchra, have previously been shown to possess antiparasitic activity towards Trypanosoma cruzi, Leishmania braziliensis and L. amazonensis, which are protozoa responsible for Chagas disease and leishmaniasis. These infections have been classified as neglected diseases, and still require the development of safer and more efficient alternatives to their current treatments. Recent SARs studies, based on the pulchrol scaffold, showed which effects exchanges of its substituents have on the antileishmanial and antitrypanosomal activity. Many of the analogues prepared were shown to be more potent than pulchrol and the current drugs used to treat leishmaniasis and Chagas disease (miltefosine and benznidazole, respectively), in vitro. Moreover, indications of some of the possible interactions that may take place in the binding sites were also identified. In this study, 12 analogues with modifications at two or three different positions in two of the three rings were prepared by synthetic and semi-synthetic procedures. The molecules were assayed in vitro towards T. cruzi epimastigotes, L. braziliensis promastigotes, and L. amazonensis promastigotes. Some compounds had higher antiparasitic activity than the parental compound pulchrol, and in some cases even benznidazole and miltefosine. The best combinations in this subset are with carbonyl functionalities in the A-ring and isopropyl groups in the C-ring, as well as with alkyl substituents in both the A- and C-rings combined with a hydroxyl group in position 1 (C-ring). The latter corresponds to cannabinol, which indeed was shown to be potent towards all the parasites. 相似文献
35.
Alaa Alhadad Michael Åkesson Leena Lehti Peter Leander Gunnar Sterner Per Åkeson Johan Wassélius 《Magnetic resonance imaging》2014
Purpose
The purpose of this retrospective study was to systematically search for acute adverse reactions and long-term complications in all patients that had been administered gadofosveset at our hospital.Materials and methods
We identified 67 gadofosveset administrations during 2006–2009 in 62 patients from 8 to 84 years of age. Radiological information system (RIS) and clinical patient records were analyzed for suspected acute adverse reactions and long-term complications including nephrogenic systemic fibrosis (NSF).The gadofosveset doses ranged between 0.024 and 0.060 mmol/kg bodyweight with a mean dose of 0.031-mmol/kg bodyweight. Follow-up time of the patients ranged from less than 1 year up to 4 years with a mean follow-up time of 2.1 years.Results
No acute adverse events or technical failures related to the contrast medium were recorded in the RIS. No dermatological and nephrological diseases related to the gadofosveset administration were found in the clinical patient records. Four patients died during follow-up without any apparent relation to the gadofosveset exposure.Conclusions
Based on our clinical material we conclude that gadofosveset is safe for a mixed patient population with no acute adverse events or any indications of long-term complications during the follow-up time up to four years. 相似文献36.
Ashie Y Hosaka J Ishihara K Itow Y Kameda J Koshio Y Minamino A Mitsuda C Miura M Moriyama S Nakahata M Namba T Nambu R Obayashi Y Shiozawa M Suzuki Y Takeuchi Y Taki K Yamada S Ishitsuka M Kajita T Kaneyuki K Nakayama S Okada A Okumura K Ooyabu T Saji C Takenaga Y Desai S Kearns E Likhoded S Stone JL Sulak LR Walter CW Wang W Goldhaber M Casper D Cravens JP Gajewski W Kropp WR Liu DW Mine S Smy MB Sobel HW Sterner CW Vagins MR Ganezer KS Hill J Keig WE Jang JS Kim JY Lim IT Ellsworth RW 《Physical review letters》2004,93(10):101801
Muon neutrino disappearance probability as a function of neutrino flight length L over neutrino energy E was studied. A dip in the L/E distribution was observed in the data, as predicted from the sinusoidal flavor transition probability of neutrino oscillation. The observed L/E distribution constrained nu(micro)<-->nu(tau) neutrino oscillation parameters; 1.9x10(-3)0.90 at 90% confidence level. 相似文献
37.
Conversion of Anthranilate Synthase into Isochorismate Synthase: Implications for the Evolution of Chorismate‐Utilizing Enzymes 下载免费PDF全文
Maximilian G. Plach Patrick Löffler Prof. Dr. Rainer Merkl Prof. Dr. Reinhard Sterner 《Angewandte Chemie (International ed. in English)》2015,54(38):11270-11274
Chorismate‐utilizing enzymes play a vital role in the biosynthesis of metabolites in plants as well as free‐living and infectious microorganisms. Among these enzymes are the homologous primary metabolic anthranilate synthase (AS) and secondary metabolic isochorismate synthase (ICS). Both catalyze mechanistically related reactions by using ammonia and water as nucleophiles, respectively. We report that the nucleophile specificity of AS can be extended from ammonia to water by just two amino acid exchanges in a channel leading to the active site. The observed ICS/AS bifunctionality demonstrates that a secondary metabolic enzyme can readily evolve from a primary metabolic enzyme without requiring an initial gene duplication event. In a general sense, these findings add to our understanding how nature has used the structurally predetermined features of enzyme superfamilies to evolve new reactions. 相似文献
38.
Smith JR McNeil RR Breedon RE Kim GN Ko W Lander RL Maeshima K Malchow RL Rowe J Stuart D Imlay R Kirk P Lim J Metcalf W Myung SS Cheng CP Gu P Li J Li YK Ye MH Zhu YC Abashian A Gotow K Hu KP Low EH Mattson ME Piilonen L Sterner KL Lusin S Rosenfeld C Wang AT Wilson S Frautschi M Kagan H Kass R Trahern CG Abe K Fujii Y Higashi Y Kim SK Kurihara Y Maki A Nozaki T Omori T Sagawa H Sakai Y Sugimoto Y Takaiwa Y Terada S Walker R Kajino F Perticone D Poling R Thomas T Ishi Y Miyano K Miyata H 《Physical review D: Particles and fields》1990,42(3):949-951
39.
J. L. Sterner M. V. Johnston G. R. Nicol D. P. Ridge 《Journal of the American Society for Mass Spectrometry》1999,10(6):483-491
The apparent proton affinities (PA) of various charge states of three highly basic peptides [(KAP)10, (KAP)8, (KAA)8] were measured by the “bracketing” method. For all three peptides the apparent PA decreases as the charge state increases and the magnitude of the decrease is consistent with an increase in coulombic repulsion in the highly protonated species. Based on a simple electrostatic model, theoretical PAs were predicted for each charge state and the values for (KAP)10 and (KAP)8 were within 10 kcal/mol of the experimental values. The maximum charge state of these peptides was observed in all cases even when the most volatile solvent was sufficiently basic to deprotonate that charge state in the gas phase. In solution (KAP)8 exhibits a random coil secondary structure while (KAA)8 exhibits an α-helix structure. Comparison of measured and calculated apparent PAs suggests that (KAP)8 retains its solution random coil structure in the gas phase and (KAA)8 retains the solution compact α-helix structure in the lower charge states but opens up to a β structure in the gas phase to minimize electrostatic repulsions in higher charge states. 相似文献
40.
Miguel V. Drummond Rogério N. Nogueira Manuel Violas Carola Sterner Pierre-Yves Fonjallaz 《Optics Communications》2010,283(12):2492-2495
In this work, we demonstrate a reliable all-optical technique for performing optical double sideband (ODSB) to single sideband (OSSB) format conversion of a 40 Gb/s non-return-to-zero signal. It is based on the optimization of a detuned optical filter, which was implemented on a fiber Bragg grating (FBG) with a complex apodization profile. An OSSB signal with negligible distortion was obtained, as the FBG presented a nearly ideal frequency response. Higher tolerance to chromatic dispersion enabled by the OSSB signal in comparison to the ODSB signal was demonstrated on both simulation and experimental results. 相似文献