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41.
Shishir Ghosh Shariff E. Kabir Ebbe Nordlander Derek A. Tocher 《Journal of organometallic chemistry》2011,696(10):1982-1989
Oxidative-addition of PhTe2Ph to the furyne cluster [Ru3(CO)7(μ-H)(μ3-η2-C4H2O){μ-P(C4H3O)2}(μ-dppm)] (1) results in the isolation of four complexes; (i) the previously reported 54-electron cluster [Ru3(CO)6(μ3-Te)2(μ-TePh)2(μ-dppm)] (5) which results from elimination of trifuryl phosphine, (ii) the furenyl cluster [Ru3(CO)5(μ-η2-C4H3O){μ-P(C4H3O)2}(μ-TePh)2(μ-dppm)] (6) which results from carbon-hydrogen bond formation and (iii) two new 50-electron complexes [Ru3(CO)5(μ-H)(μ3-η2-C4H2O){μ-P(C4H3O)2}(μ-TePh)2(к2-dppm)] (7) and [Ru3(CO)4(μ-H){P(C4H3O)3}(μ3-η2-C4H2O){μ-P(C4H3O)2}(μ-TePh)2(к2-dppm)] (8) both containing unsymmetrical furyne ligands. The structures of all the new compounds have been unambiguously established by single crystal X-ray crystallography. Further reactivity studies have provided a clear understanding of the relative sequence of the key oxidative-addition and reductive-elimination processes, showing that 6 is an intermediate in the formation of 7. DFT calculations have been used to shed light on the unsymmetrical binding of the furyne ligand in 7 and also to show that the adopted position of the heteroatom within the furyne ring can vary within complexes of this type. 相似文献
42.
Chundawat SP Bellesia G Uppugundla N da Costa Sousa L Gao D Cheh AM Agarwal UP Bianchetti CM Phillips GN Langan P Balan V Gnanakaran S Dale BE 《Journal of the American Chemical Society》2011,133(29):11163-11174
Conversion of lignocellulose to biofuels is partly inefficient due to the deleterious impact of cellulose crystallinity on enzymatic saccharification. We demonstrate how the synergistic activity of cellulases was enhanced by altering the hydrogen bond network within crystalline cellulose fibrils. We provide a molecular-scale explanation of these phenomena through molecular dynamics (MD) simulations and enzymatic assays. Ammonia transformed the naturally occurring crystalline allomorph I(β) to III(I), which led to a decrease in the number of cellulose intrasheet hydrogen bonds and an increase in the number of intersheet hydrogen bonds. This rearrangement of the hydrogen bond network within cellulose III(I), which increased the number of solvent-exposed glucan chain hydrogen bonds with water by ~50%, was accompanied by enhanced saccharification rates by up to 5-fold (closest to amorphous cellulose) and 60-70% lower maximum surface-bound cellulase capacity. The enhancement in apparent cellulase activity was attributed to the "amorphous-like" nature of the cellulose III(I) fibril surface that facilitated easier glucan chain extraction. Unrestricted substrate accessibility to active-site clefts of certain endocellulase families further accelerated deconstruction of cellulose III(I). Structural and dynamical features of cellulose III(I), revealed by MD simulations, gave additional insights into the role of cellulose crystal structure on fibril surface hydration that influences interfacial enzyme binding. Subtle alterations within the cellulose hydrogen bond network provide an attractive way to enhance its deconstruction and offer unique insight into the nature of cellulose recalcitrance. This approach can lead to unconventional pathways for development of novel pretreatments and engineered cellulases for cost-effective biofuels production. 相似文献
43.
The performance of chemically modified papaya seed (CMPS) adsorbent with carboxyl and amino groups has been studied. Adsorption experiments were performed with respect to the changes in initial pH of the solution, contact time, initial Hg(II) concentration, and CMPS dosage. Kinetic data were fitted to the pseudo-second-order model. The maximum adsorption capacity calculated by Langmuir model was 18.34 mg/g. CMPS was characterized by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy. The results indicate that adsorption mechanism of CMPS involves ion exchange (2Na+/Hg2+) and carboxylic-group-dominated surface complexation. Regeneration study revealed that CMPS can be used successfully for four cycles with a small adsorption capacity loss (6.8%). 相似文献
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45.
Shishir Ghosh Daniel T. Haworth Tasneem A. Siddiquee Graeme Hogarth 《Journal of organometallic chemistry》2009,694(18):2941-202
Reaction of tri(2-furyl)phosphine (PFu3) with [Re2(CO)10−n(NCMe)n] (n = 1, 2) at 40 °C gave the substituted complexes [Re2(CO)10−n(PFu3)n] (1 and 2), the phosphines occupying axial position in all cases. Heating [Re2(CO)10] and PFu3 in refluxing xylene also gives 1 and 2 together with four phosphido-bridged complexes; [Re2(CO)8−n(PFu3)n(μ-PFu2)(μ-H)] (n = 0, 1, 2) (3-5) and [Re2(CO)6(PFu3)2(μ-PFu2)(μ-Cl)] (6) resulting from phosphorus-carbon bond cleavage. A series of separate thermolysis experiments has allowed a detailed reaction pathway to be unambiguously established. A similar reaction between [Re2(CO)10] and PFu3 in refluxing chlorobenzene furnishes four complexes which include 1, 2, 6 and the new binuclear complex [Re2(CO)6(η1-C4H3O)2(μ-PFu2)2] (7). All new complexes have been characterized by a combination of spectroscopic data and single crystal X-ray diffraction studies. 相似文献
46.
Nagaraju M. Patro Azmi Sultana Keiji Terao Daisuke Nakata Ayako Jo Akihito Urano Yoshiyuki Ishida Raghu N. Gorantla Vinay Pandit Kshama Devi Shishir Rohit Baljinder K. Grewal Elizabeth M. Sophia Anand Suresh Vineeth K. Ekbote Sarasija Suresh 《Journal of inclusion phenomena and macrocyclic chemistry》2014,78(1-4):471-483
In the present study investigated the effect of curcumin (CUR) alpha (α), beta (β) and gamma (γ) cyclodextrin (CD) complexes on its solubility and bioavailability. CUR the active principle of turmeric is a natural antioxidant agent with potent anti-inflammatory activity along with chemotherapeutic and chemopreventive properties. Poor solubility and poor oral bioavailability are the main reasons which preclude CUR use in therapy. Extent of complexation was β-CD complex (82 %) > γ-CD (71 %) > α-CD (65 %). Pulverization method resulted in significant enhancement of CUR (0.002 mg/ml) solubility with CUR α-CD complex (0.364 mg/ml) > CUR β-CD complex (0.186 mg/ml) > CUR γ-CD complex (0.068 mg/ml). Gibbs-free energy and in silico molecular docking studies favour formation of α-CD complex > β-CD complex > γ-CD complex. With reference to CUR, relative bioavailability of CUR α-CD, CUR β-CD and CUR γ-CD complexes were 460, 365 and 99 % respectively. CUR–CD complexes exhibited increased bioavailability with an increase in t½, tmax, Cmax, AUC, Ka, and MRT; and a decrease in Ke, clearance and Vd values. AUC increase was CUR α-CD complex > CUR β-CD complex > CUR γ-CD complex. Significant difference (p < 0.05) was observed between CUR α-CD complex and CUR γ-CD complex by one-way ANOVA and Dunnett’s post hoc test for multiple comparison analysis. Correlation observed between in vitro, in vivo and in silico methods indicates potential of in silico and in vitro methods in CD selection. 相似文献
47.
Kurian A Prasad S Dhinojwala A 《Langmuir : the ACS journal of surfaces and colloids》2010,26(23):17804-17807
We have studied acid-base interactions at solid-liquid and solid-solid interfaces using interface-sensitive sum frequency generation (SFG) spectroscopy. The shift of the sapphire hydroxyl peak in contact with several polar and nonpolar liquids and polymers was used to determine the interaction energy. The trend in the interaction energies cannot be explained by measuring only water contact angles. Molecular rearrangements at the sapphire interface, to maximize the interaction of the acid-base groups, play a dominant role, and these effects are not accounted for in the current theoretical models. These results provide important insights into understanding adhesion, friction, and wetting on solid interfaces. 相似文献
48.
Shishir Ghosh Shariff E. Kabir Farzana K. Camellia Md. Kamal Hossain Daniel T. Haworth Sergey V. Lindeman Tasneem A. Siddiquee Dennis W. Bennett 《Journal of chemical crystallography》2010,40(8):712-715
Abstract
Treatment of [Mo(CO)3(NCMe)3] with bis(diphenylphosphino)methane (dppm) and triphenylphosphine (PPh3) at 50 °C afforded mer-[Mo(CO)3(PPh3)(κ 2-dppm)] (1) in 55% yield which has been characterized by single crystal X-ray diffraction studies and spectroscopic measurements. Compound 1 crystallizes in the triclinic space group P−1 with a = 10.3449(6), b = 11.1570(6), c = 17.8961(10) ?, β = 80.8400(10)°, Z = 2 and V = 1959.8(2) ?3. 相似文献49.
Shishir Gupta Sumit Kumar Vishwakarma Dinesh Kumar Majhi Santimoy Kundu 《Applied Mathematical Modelling》2013,37(10-11):6652-6660
The present paper investigates the Love wave propagation in an anisotropic porous layer under the effect of rigid boundary. Effect of initial stresses on the propagation of Love waves in a fluid saturated, anisotropic, porous layer having linear variation in directional rigidities lying in contact over a pre-stressed, inhomogeneous elastic half-space has also been considered. The dispersion equation of phase velocity has been derived and the influence of medium characteristic such as porosity, rigid boundary, initial stress, anisotropy and inhomogeneity over it has been discussed. The velocities of Love waves have been calculated numerically as a function of KH (where K is the wave number and H is the thickness of the layer) and are presented in a number of graphs. 相似文献
50.
R. C. Srivastava P. V. Chacko Shishir Srivastava Saroj Yadav 《Journal of membrane science》1978,3(1):39-46
The formalism of network thermodynamics has been utilised to calculate the relaxation time for composite membranes, consisting of a prallel and a series arrangement of two constituent membrane elements, as a function of relaxation times for the constituent membrane elements. 相似文献