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101.
Dr. Agnese Marcelli Dr. Barbara Patrizi Prof. Alessandra Bonamore Prof. Alberto Boffi Prof. Maurizio Becucci Prof. Paolo Foggi 《Chemphyschem》2021,22(11):1134-1140
Flavohemoglobins have the particular capability of binding unsaturated and cyclopropanated fatty acids as free acids or phospholipids. Fatty acid binding to the ferric heme results in a weak but direct bonding interaction. Ferrous and ferric protein, in presence or absence of a bound lipid molecule, have been characterized by transient absorption spectroscopy. Measurements have been also carried out both on the ferrous deoxygenated and on the CO bound protein to investigate possible long-range interaction between the lipid acyl chain moiety and the ferrous heme. After excitation of the deoxygenated derivatives the relaxation process reveals a slow dynamics (350 ps) in lipid-bound protein but is not observed in the lipid-free protein. The latter feature and the presence of an extra contribution in the absorption spectrum, indicates that the interaction of iron heme with the acyl chain moiety occurs only in the excited electronic state and not in the ground electronic state. Data analysis highlights the formation of a charge-transfer complex in which the iron ion of the lipid-bound protein in the expanded electronic excited state, possibly represented by a high spin Fe III intermediate, is able to bind to the sixth coordination ligand placed at a distance of at 3.5 Å from the iron. A very small nanosecond geminate rebinding is observed for CO adduct in lipid-free but not in the lipid-bound protein. The presence of the lipid thus appears to inhibit the mobility of CO in the heme pocket. 相似文献
102.
The structure and properties of optimal networks depend on the cost functional being minimized and on constraints to which the minimization is subject. We show here two different formulations that lead to identical results: minimizing the dissipation rate of an electrical network under a global constraint is equivalent to the minimization of a power-law cost function introduced by Banavar et al. [Phys. Rev. Lett. 84, 4745 (2000)10.1103/PhysRevLett.84.4745]. An explicit scaling relation between the currents and the corresponding conductances is derived, proving the potential flow nature of the latter. Varying a unique parameter, the topology of the optimized networks shows a transition from a tree topology to a very redundant structure with loops; the transition corresponds to a discontinuity in the slope of the power dissipation. 相似文献
103.
104.
Dr. Sankar Mohan Dr. Philip S. Kerry Nicole Bance Prof. Dr. Masahiro Niikura Prof. Dr. B. Mario Pinto 《Angewandte Chemie (International ed. in English)》2014,53(4):1076-1080
We have previously reported a potent neuraminidase inhibitor that comprises a carbocyclic analogue of zanamivir in which the hydrophilic glycerol side chain is replaced by the hydrophobic 3‐pentyloxy group of oseltamivir. This hybrid inhibitor showed excellent inhibitory properties in the neuraminidase inhibition assay (Ki=0.46 nM ; Ki (zanamivir)=0.16 nM ) and in the viral replication inhibition assay in cell culture at 10?8 M . As part of this lead optimization, we now report a novel spirolactam that shows comparable inhibitory activity in the cell culture assay to that of our lead compound at 10?7 M . The compound was discovered serendipitously during the attempted synthesis of the isothiourea derivative of the original candidate. The X‐ray crystal structure of the spirolactam in complex with the N8 subtype neuraminidase offers insight into the mode of inhibition. 相似文献
105.
Enzymatic Desymmetrising Redox Reactions for the Asymmetric Synthesis of Biaryl Atropisomers 下载免费PDF全文
Samantha Staniland Bo Yuan Nelson Giménez‐Agulló Dr. Tommaso Marcelli Dr. Simon C. Willies Dr. Damian M. Grainger Prof. Nicholas J. Turner Prof. Jonathan Clayden 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13084-13088
Atropisomeric biaryls carrying ortho‐hydroxymethyl and formyl groups were made enantioselectively by desymmetrisation of dialdehyde or diol substrates. The oxidation of the symmetrical diol substrates was achieved using a variant of galactose oxidase (GOase), and the reduction of the dialdehydes using a panel of ketoreductases. Either M or P enantiomers of the products could be formed, with absolute configurations assigned by time‐dependent DFT calculations of circular dichroism spectra. The differing selectivities observed with different biaryl structures offer an insight into the detailed structure of the active site of the GOase enzyme. 相似文献
106.
A Deadly Organometallic Luminescent Probe: Anticancer Activity of a ReI Bisquinoline Complex 下载免费PDF全文
Dr. Igor Kitanovic Suzan Can Dr. Hamed Alborzinia Dr. Ana Kitanovic Vanessa Pierroz Anna Leonidova Dr. Antonio Pinto Priv. Doz. Dr. Bernhard Spingler Priv. Doz. Dr. Stefano Ferrari Roberto Molteni Dr. Andreas Steffen Prof. Dr. Nils Metzler‐Nolte Prof. Dr. Stefan Wölfl Prof. Dr. Gilles Gasser 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(9):2496-2507
The photophysical properties of [Re(CO)3(L ‐N3)]Br (L ‐N3=2‐azido‐N,N‐bis[(quinolin‐2‐yl)methyl]ethanamine), which could not be localized in cancer cells by fluorescence microscopy, have been revisited in order to evaluate its use as a luminescent probe in a biological environment. The ReI complex displays concentration‐dependent residual fluorescence besides the expected phosphorescence, and the nature of the emitting excited states have been evaluated by DFT and time‐dependent (TD) DFT methods. The results show that fluorescence occurs from a 1LC/MLCT state, whereas phosphorescence mainly stems from a 3LC state, in contrast to previous assignments. We found that our luminescent probe, [Re(CO)3(L ‐N3)]Br, exhibits an interesting cytotoxic activity in the low micromolar range in various cancer cell lines. Several biochemical assays were performed to unveil the cytotoxic mechanism of the organometallic ReI bisquinoline complex. [Re(CO)3(L ‐N3)]Br was found to be stable in human plasma indicating that [Re(CO)3(L ‐N3)]Br itself and not a decomposition product is responsible for the observed cytotoxicity. Addition of [Re(CO)3(L ‐N3)]Br to MCF‐7 breast cancer cells grown on a biosensor chip micro‐bioreactor immediately led to reduced cellular respiration and increased glycolysis, indicating a large shift in cellular metabolism and inhibition of mitochondrial activity. Further analysis of respiration of isolated mitochondria clearly showed that mitochondrial respiratory activity was a direct target of [Re(CO)3(L ‐N3)]Br and involved two modes of action, namely increased respiration at lower concentrations, potentially through increased proton transport through the inner mitochondrial membrane, and efficient blocking of respiration at higher concentrations. Thus, we believe that the direct targeting of mitochondria in cells by [Re(CO)3(L ‐N3)]Br is responsible for the anticancer activity. 相似文献
107.
Tiago A. Chimenez Marcelo H. Gehlen Karen Marabezi Antonio A. S. Curvelo 《Cellulose (London, England)》2014,21(1):653-664
The spatial distribution of chemical compounds in sugarcane bagasse is an important issue in its use as a raw material for second generation ethanol production from cellulose hydrolysis. Lignocellulosic materials including whole bagasse, fiber, pith, and respective samples obtained after chemical bleaching were investigated using confocal fluorescence microscopy and spectroscopy with one and two-photon excitation. Autofluorescence from unbleached samples revealed that emission from fiber walls containing the lignin fraction was longitudinally oriented. After bleaching treatment, the oriented emission was partially disrupted. Autofluorescence from bleached samples with a residual lignin content of about 1 % was ascribed to improved dispersion of remaining fluorophores throughout the samples inducing a concomitant reduction of fluorescence self-quenching in the samples. The combination of autofluorescence images with spectral emission and lifetime measurements provides a tool for microscopic characterization of natural bagasse samples. Moreover, the technique allows monitoring bleaching processes related to lignin removal. 相似文献
108.
Perini Nickson Delmonde Marcelo V. F. Ranjan Chinmoy Varela Hamilton 《Journal of Solid State Electrochemistry》2020,24(8):1811-1818
Journal of Solid State Electrochemistry - The characteristics of the electrochemical oscillations that emerge along the catalytic oxidation of small organic molecules critically depend on the... 相似文献
109.
Fernanda R. Santana Liany Luna-Dulcey Víctor U. Antunes Claudio F. Tormena Marcia R. Cominetti Marcelo C. Duarte 《Natural product research》2020,34(1):102-109
AbstractHyptis pectinata is a herb popularly used in Brazil for the treatment of inflammations, pain, bacterial infections and cancer. In the present study, inflorescences (MPIn), leaves (MPL), branches (MPB), root (MPR) extracts and three compounds isolated from MPIn were assayed against breast tumor cell lines. The structures of the three compounds (pectinolide J, hyptolide and pectinolide E) were determined by means of spectroscopic analysis. Pectinolide J was isolated for the first time. The MPIn, MPL and MPR exhibited specific antiproliferative activity on tumor cell lines when compared to normal cell lines with IC50 of 52.01?±?0.64, 45.91?±?0.02?μg/mL and 82.84?±?0.03?μg/mL, respectively. Although the isolated substances did not present good antiproliferative activity, when the three were associated, a greater biological effect was observed, suggesting a synergistic effect. Hyptolide (5.6?±?0.4?μg/mL) showed IC50 sufficiently low to be considered as a drug prototype. 相似文献
110.
Manoel Raimundo dos Santos Junior Elinia Castro Costa Caio Campos Ferreira Lucas Pinto Bernar Marcilene Paiva da Silva Andria de Andrade Mncio Marcelo Costa Santos Sílvio Alex Pereira da Mota Douglas Alberto Rocha de Castro Sergio Duvoisin Junior Luiz Eduardo Pizarro Borges Marilena Emmi Araújo Nlio Teixeira Machado 《Molecules (Basel, Switzerland)》2022,27(7)
In this work, the deoxygenation of organic liquid products (OLP) obtained through the thermal catalytic cracking of palm oil at 450 °C, 1.0 atmosphere, with 10% (wt.) Na2CO3 as a catalyst, in multistage countercurrent absorber columns using supercritical carbon dioxide (SC-CO2) as a solvent, with an Aspen-HYSYS process simulator, was systematically investigated. In a previous study, the thermodynamic data basis and EOS modeling necessary to simulate the deoxygenation of OLP was presented. This work addresses a new flowsheet, consisting of 03 absorber columns, 10 expansions valves, 10 flash drums, 08 heat exchanges, 01 pressure pump, and 02 make-ups of CO2, aiming to improve the deacidification of OLP. The simulation was performed at 333 K, 140 bar, and (S/F) = 17; 350 K, 140 bar, and (S/F) = 38; 333 K, 140 bar, and (S/F) = 25. The simulation shows that 81.49% of OLP could be recovered and that the concentrations of hydrocarbons in the extracts of absorber-01 and absorber-02 were 96.95 and 92.78% (wt.) on a solvent-free basis, while the bottom stream of absorber-03 was enriched in oxygenated compounds with concentrations of up to 32.66% (wt.) on a solvent-free basis, showing that the organic liquid products (OLP) were deacidified and SC-CO2 was able to deacidify the OLP and obtain fractions with lower olefin contents. The best deacidifying condition was obtained at 333 K, 140 bar, and (S/F) = 17. 相似文献