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991.
Amino Acid Chirality and Ferrocene Conformation Guided Self‐Assembly and Gelation of Ferrocene–Peptide Conjugates
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Dr. Bimalendu Adhikari Charanpreet Singh Dr. Afzal Shah Dr. Alan J. Lough Prof. Dr. Heinz‐Bernhard Kraatz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(32):11560-11572
The self‐assembly and gelation behavior of a series of mono‐ and disubstituted ferrocene (Fc)–peptide conjugates as a function of ferrocene conformation and amino acid chirality are described. The results reveal that ferrocene–peptide conjugates self‐assemble into organogels by controlling the conformation of the central ferrocene core, through inter‐ versus intramolecular hydrogen bonding in the attached peptide chain(s). The chirality controlled assembling studies showed that two monosubstituted Fc conjugates FcCO–L FL FL A‐OMe and FcCO–L FL FD A‐OMe form gels with nanofibrillar network structures, whereas the other two diastereomers FcCO–D FL FL A‐OMe and FcCO–L FD FL A‐OMe exclusively produced straight nanorods and non‐interconnected small fibers, respectively. This suggests the potential tuning of gelation behavior and nanoscale morphology by altering the chirality of constituted amino acids. The current study confirms the profound effect of diastereomerism and no influence of enantiomers on gelation. Correspondingly, the diastereomeric and enantiomeric Fc[CO‐FFA‐OMe]2 were constructed for the study of chirality‐organized structures. 相似文献
992.
Formation of benzofuran and chlorobenzofuran from 1,3‐dichloropropene: A quantum chemical investigation
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Nwakamma Ahubelem Kalpit Shah Behdad Moghtaderi Alister J. Page 《International journal of quantum chemistry》2015,115(24):1739-1745
We present a quantum chemical investigation of benzofuran and cholorobenzofuran formation mechanisms during the combustion of 1,3‐dichloropropene. Density functional theory and Gaussian‐n thermochemical methods are used to propose detailed mechanistic reaction pathways. These calculations indicate that oxidation of phenylvinyl radical intermediates and subsequent ring closure are key mechanistic pathways in the formation of benzofuran and chlorobenzofuran. Thermochemical and kinetic parameters presented herein will assist in further elucidation of dioxin formation mechanisms from thermolyses of hydrocarbon moieties. © 2015 Wiley Periodicals, Inc. 相似文献
993.
We consider a system of processor-sharing queues with state-dependent service rates. These are allocated according to balanced fairness within a polymatroid capacity set. Balanced fairness is known to be both insensitive and Pareto-efficient in such systems, which ensures that the performance metrics, when computable, will provide robust insights into the real performance of the system considered. We first show that these performance metrics can be evaluated with a complexity that is polynomial in the system size if the system is partitioned into a finite number of parts, so that queues are exchangeable within each part and asymmetric across different parts. This in turn allows us to derive stochastic bounds for a larger class of systems which satisfy less restrictive symmetry assumptions. These results are applied to practical examples of tree data networks, such as backhaul networks of Internet service providers, and computer clusters. 相似文献
994.
M.?AhmadEmail author Z.?Perveen A.?J.?BortoluzziEmail author S.?Hameed M.?R.?Shah M.?Tariq G.?ud Din M.?Anwar 《Journal of Structural Chemistry》2017,58(2):297-303
Schiff bases and their metal complexes have a number of biological activities such as antidepressant, analgesic, antimicrobial, antiviral, and antitumor. In the present studies, the 1-((E)-(pentylimino)methyl)naphthalen-2-ol ligand is prepared by the reaction of 2-hydroxynaphthaldehyde with n-amyl amine. The ligand results in CoL3, NiL2 and CuL2 complexes when reacted with the cobalt acetate, nickel acetate, and copper acetate salts respectively. The complexes along with their ligand are fully characterized by X-ray diffraction studies and biologically screened. The ligand structure reveals that it is a zwitterion species where the iminic nitrogen atom is protonated and the C–O bond shows a high double bond character. The cobalt complex has an octahedral geometry around the metal center and each nitrogen atom is in the trans position to the oxygen donor site. On the other hand, the copper complex shows a centrosymmetric square planar coordination, and in this case, the nitrogen sites are trans to each other. The complexes and the ligand are found to be more potent than the standard drugs used against some microbes in their preliminary biological studies. 相似文献
995.
Distinct Role of Sesn2 in Response to UVB‐Induced DNA Damage and UVA‐Induced Oxidative Stress in Melanocytes
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Baozhong Zhao Palak Shah Lei Qiang Tong‐Chuan He Andrey Budanov Yu‐Ying He 《Photochemistry and photobiology》2017,93(1):375-381
Ultraviolet (UV) radiation, including both UVB and UVA irradiation, is the major risk factor for causing skin cancer including melanoma. Recently, we have shown that Sesn2, a member of the evolutionarily conserved stress‐inducible protein family Sestrins (Sesn), is upregulated in human melanomas as compared to melanocytes in normal human skin, suggesting an oncogenic role of Sesn2. However, the role of Sesn2 in UVB and UVA response is unknown. Here, we demonstrated that both UVB and UVA induce Sesn2 upregulation in melanocytes and melanoma cells. UVB induces Sesn2 expression through the p53 and AKT3 pathways. Sesn2 negatively regulates UVB‐induced DNA damage repair. In comparison, UVA induces Sesn2 upregulation through mitochondria but not Nrf2. Sesn2 ablation increased UVA‐induced Nrf2 induction and inhibits UVA‐induced ROS production, indicating that Sesn2 acts as an upstream regulator of Nrf2. These findings suggest previously unrecognized mechanisms in melanocyte response to UVB and UVA irradiation and potentially in melanoma formation. 相似文献
996.
Online background cleanup followed by high‐performance liquid chromatography with tandem mass spectrometry for the analysis of perfluorinated compounds in human blood
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Liangpo Liu Jianwen She Jie Zhang Meiping Tian Qingyu Huang Syed Ali Musstjab Akber Shah Eqani Heqing Shen 《Journal of separation science》2015,38(2):247-253
In this study, a novel method for the analysis of perfluorinated compounds in whole blood has been developed and validated. The method was developed by using a conventional reversed‐phase C18 column as a trapping column for the elimination of background contamination and high‐performance liquid chromatography with tandem mass spectrometry for the target compounds analysis. The trapping column provided fast online separation of the background contamination of perfluorinated compounds. In this developed method, the limits of detection for different perfluorinated compounds ranged from 0.06 to 0.14 ng/mL. It is notable that the limit of detection (0.07 ng/mL) for perfluorooctanoic acid was improved significantly after the elimination of background contamination. The method was also validated in terms of sensitivity, accuracy, and precision. The recoveries ranged from 66.8 to 111.9%, with relative standard deviations from 2.1 to 15.3%. Our preliminary data suggest that the novel method based on trapping column cleanup followed by high‐performance liquid chromatography with tandem mass spectrometry could be applied in studies on the human exposure to perfluorinated compounds. 相似文献
997.
Jens Heber Gerhard Knieper Hemangi M. Shah 《Proceedings of the American Mathematical Society》2007,135(3):845-849
Let be a Hadamard manifold of dimension whose sectional curvature satisfies and whose curvature tensor satisfies for suitable constants and . We show that is of constant sectional curvature provided is asymptotically harmonic. This was previously only known if admits a compact quotient.
998.
Montenegro EC Shah MB Luna H Scully SW de Barros AL Wyer JA Lecointre J 《Physical review letters》2007,99(21):213201
Time-of-flight mass spectrometry was used to investigate fragmentation and energy transfer processes in water by C ions at the distal part of the Bragg peak. Measurements of the positive ion fragments from ionization, electron capture, electron loss, transfer-loss and loss-ionization channels have allowed us for the first time (a) to obtain a quantitative determination of the energy lost by C ions in water and (b) to show that total water fragment ion production has a much flatter profile with projectile energy than would be expected if the water radical formation was assumed to follow the energy-loss profile obtained from available stopping power models. 相似文献
999.
A comparative study of suitably functionalized, highly soluble tetraceno[2,3-b]thiophenes (1-3) and pentacenes (4-6) that show higher photoxidative stability than that of unfunctionalized corresponding acenes is reported. The absorption and emission of 1-3 (Amax = 624-656 nm, lambda max = 634-672 nm, PhiF approximately 10%) and 4-6 (Amax = 672-704 nm, lambda max = 682-718 nm, PhiF approximately 10%) were found to be systematically red-shifted by the substitution in the order of the tert-butylethynyl < triisopropylsilylethynyl < phenylethynyl groups. The oxidation potentials of these compounds were similar (E1/2 approximately 0.70 V), except for 4, which showed lower oxidation potential (E1/2 approximately 0.63 V). 相似文献
1000.
Proton-detected solid-state NMR spectroscopy of fully protonated proteins at 40 kHz magic-angle spinning 总被引:3,自引:0,他引:3
Zhou DH Shah G Cormos M Mullen C Sandoz D Rienstra CM 《Journal of the American Chemical Society》2007,129(38):11791-11801
Remarkable progress in solid-state NMR has enabled complete structure determination of uniformly labeled proteins in the size range of 5-10 kDa. Expanding these applications to larger or mass-limited systems requires further improvements in spectral sensitivity, for which inverse detection of 13C and 15N signals with 1H is one promising approach. Proton detection has previously been demonstrated to offer sensitivity benefits in the limit of sparse protonation or with approximately 30 kHz magic-angle spinning (MAS). Here we focus on experimental schemes for proteins with approximately 100% protonation. Full protonation simplifies sample preparation and permits more complete chemical shift information to be obtained from a single sample. We demonstrate experimental schemes using the fully protonated, uniformly 13C,15N-labeled protein GB1 at 40 kHz MAS rate with 1.6-mm rotors. At 500 MHz proton frequency, 1-ppm proton line widths were observed (500 +/- 150 Hz), and the sensitivity was enhanced by 3 and 4 times, respectively, versus direct 13C and 15N detection. The enhanced sensitivity enabled a family of 3D experiments for spectral assignment to be performed in a time-efficient manner with less than a micromole of protein. CANH, CONH, and NCAH 3D spectra provided sufficient resolution and sensitivity to make full backbone and partial side-chain proton assignments. At 750 MHz proton frequency and 40 kHz MAS rate, proton line widths improve further in an absolute sense (360 +/- 115 Hz). Sensitivity and resolution increase in a better than linear manner with increasing magnetic field, resulting in 14 times greater sensitivity for 1H detection relative to that of 15N detection. 相似文献