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121.
Carlos E. M. Carvalho Solange M. S. V. Wardell James L. Wardell Janet M. S. Skakle John N. Low Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(1):o28-o32
Molecules of the title compounds N2‐(benzoyloxy)benzamidine, C14H12N2O2, (I), N2‐(2‐hydroxybenzoyloxy)benzamidine, C14H12N2O3, (II), and N2‐benzoyloxy‐2‐hydroxybenzamidine, C14H12N2O3, (III), all have extended chain conformations, with the aryl groups remote from one another. In (I), the molecules are linked into chains by a single N—H⋯N hydrogen bond [H⋯N = 2.15 Å, N⋯N = 3.029 (2) Å and N—H⋯N = 153°] and these chains are linked into sheets by means of aromatic π–π stacking interactions. There is one intramolecular O—H⋯O hydrogen bond in (II), and a combination of one three‐centre N—H⋯(N,O) hydrogen bond [H⋯N = 2.46 Å, H⋯O = 2.31 Å, N⋯N = 3.190 (2) Å, N⋯O = 3.146 (2) Å, N—H⋯N = 138° and N—H⋯O = 154°] and one two‐centre C—H⋯O hydrogen bond [H⋯O = 2.46 Å, C⋯O = 3.405 (2) Å and C—H⋯O = 173°] links the molecules into sheets. In (III), an intramolecular O—H⋯N hydrogen bond and two N—H⋯O hydrogen bonds [H⋯O = 2.26 and 2.10 Å, N⋯O = 2.975 (2) and 2.954 (2) Å, and N—H⋯O = 138 and 163°] link the molecules into sheets. 相似文献
122.
Larissa R. Cohen Laura A. Pe?a Anton J. Seidl Janet M. Olsen Jennifer Wekselbaum Patrick E. Hoggard 《Monatshefte für Chemie / Chemical Monthly》2009,34(2):1159-1165
Abstract
Near-UV irradiation of solutions of (Bu4N)AuCl4 in aerated ethanol-stabilized chloroform causes the continuous decomposition of chloroform, as evidenced by the production of many equivalents of HCl and peroxides. At the outset of irradiation, most of the AuCl4 − is reduced to AuCl2 −, but the reduction stops and is reversed. The same experiments done in ethanol-free chloroform cause chloroform decomposition only until the irreversible reduction of the gold is complete. In deoxygenated ethanol-free chloroform, irreversible reduction to AuCl2 − is accompanied by the formation of HCl and CCl4, while the main decomposition products in deoxygenated ethanol-stabilized chloroform are HCl and C2Cl6. It is proposed that, in ethanol-free chloroform, photoreduction of AuCl4 − begins with the concerted elimination of HCl from an association complex of CHCl3 with AuCl4 −, and that ethanol suppresses { \textCHCl3 ·\textAuCl4 - } \{ {\text{CHCl}}_{3} \cdot {\text{AuCl}}_{4}^{ - } \} complex formation, leaving a slower radical process to carry out the photoreduction of AuCl4 − in ethanol-stabilized chloroform. In the presence of oxygen, the radical process causes a build-up of CCl3OOH, which reoxidizes AuCl2 − to AuCl4 − and allows the photodecomposition of CHCl3 to continue indefinitely. 相似文献123.
Julita K. Grzeskowiak Anne Tscheliessnig Poh Choo Toh Janet Chusainow Yih Yean Lee Niki Wong Alois Jungbauer 《Journal of chromatography. A》2009,1216(24):4902-4912
Although Staphylococcus Protein A (SpA) affinity chromatography is the state of the art capture step for antibody purification, non-affinity methods are more economical. We used two-dimensional fluorescence difference gel electrophoresis (2-D DIGE) to evaluate the purification of a recombinant IgG1 antibody from cultured cells, with two different processes: (1) SpA capture followed by cation-exchange chromatography (CEX); and (2) CEX capture, followed by anion exchanger, then hydrophobic interaction chromatography. Efficiencies were similar in sodium dodecylsulphate polyacrylamide gel electrophoresis and size-exclusion chromatography; however, 2-D DIGE revealed higher efficiency with SpA than with CEX capture. Thus, 2-D DIGE is a valuable tool for downstream process development. 相似文献
124.
C. Dale Keefe Janet E. Pickup 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,72(5):947-953
Previous studies have been done in this laboratory focusing on the optical properties of several liquid aromatic and aliphatic hydrocarbons in the infrared. The current study reports the infrared and absorption Raman spectra of liquid cyclohexane. Infrared spectra were recorded at 25 °C over a wavenumber range of 7400–490 cm−1. Infrared measurements were taken using transmission cells with pathlengths ranging from 3 to 5000 μm. Raman spectra were recorded between 3700 and 100 cm−1 at 25 °C using a 180° reflection geometry. Ab initio calculations of the vibrational wavenumbers at the B3LYP/6311G level of theory were performed and used to help assign the observed IR and Raman spectra. Extensive assignments of the fundamentals and binary combinations observed in the infrared imaginary molar polarizability spectrum are reported. The imaginary molar polarizability spectrum was curve fitted to separate the intensity from the various transitions and used to determine the transition moments and magnitudes of the derivatives of the dipole moment with respect to the normal coordinates for the fundamentals. 相似文献
125.
Ibon Alkorta Janet E. Del Bene José Elguero Otilia Mó Manuel Yáñez 《Theoretical chemistry accounts》2009,124(3-4):187-195
Ab initio calculations were carried out to investigate the structures, binding energies, bonding, and NMR spin–spin coupling constants of complexes HLB=BLH, for L=CO, NH3, OH2, PH3, SH2, and ClH. Both B–B and B–H bonds lengthen on complex formation relative to singlet HBBH, and except for L=CO, the B–B bonds are double bonds. The order of stability of the trans isomers correlates with the ordering of ligands in the spectrochemical series of ligand field theory. The trans isomer is always more stable than the corresponding cis. Inverse correlations are found between 1 J(B–B) and 1 J(B–H) and the corresponding B–B and B–H distances. For the trans isomers, 1 J(B–B) appears to be related to the ordering of ligands in the spectrochemical series, while 1 J(B–H) is related to the protonation energy of the ligand L. 相似文献
126.
Based on the notion of predictive influence functions, the paper develops multivariate limited translation hierarchical Bayes estimators of the normal mean vector which serve as a compromise between the hierarchical Bayes and maximum likelihood estimators. The paper demonstrates the superiority of the limited translation estimators over the usual hierarchical Bayes estimators in terms of the frequentist risks when the true parameter to be estimated departs widely from the grand average of all the parameters. 相似文献
127.
Rosenfeld A Morgan J Goswami LN Ohulchanskyy T Zheng X Prasad PN Oseroff A Pandey RK 《Photochemistry and photobiology》2006,82(3):626-634
The effects of an additional keto group on absorption wavelength and the corresponding metal complexes Zn(II), Cu(II) In(III) on singlet oxygen production and photodynamic efficacy were examined among the alkyl ether analogs of pyropheophorbide-a. For the preparation of the desired photosensitizers, the methyl 13(2)-oxo-pyropheophorbide-a obtained by reacting methyl pyropheophorbide-a with aqueous LiOH-THF was converted into a series of alkyl ether analogs. These compounds were evaluated for photophysical properties and in vitro (by means of the MTT assay and intracellular localization in RIF cells) and in vivo (in C3H mice implanted with RIF tumors) photosensitizing efficacy. Among the alkyl ether derivatives, the methyl 3-decyloxyethyl-3-devinyl-13(2)-oxo-pyropheophorbide-a was found to be most effective and the insertion of In(III) into this analog further enhanced its in vitro and in vivo photosensitizing efficacy. Fluorescence microscopy showed that, in contrast to the hexyl and dodecyl ether derivatives of HPPH (which localize in mitochondria and lysosomes, respectively), the diketo-analogs and their In(III) complexes localized in Golgi bodies. The preliminary in vitro and in vivo results suggest that, in both free-base and metalated analogs, the introduction of an additional keto group at the five-member exocyclic ring in pyropheophorbide-a diminishes its photosensitizing efficacy. This may be due to a shift in subcellular localization from mitochondria to the Golgi bodies. The further introduction of In(III) enhances photoactivity, but not by shifting the localization of the photosensitizer. 相似文献
128.
Ab initio equation-of-motion coupled cluster calculations have been carried out to evaluate one-, two-, and three-bond 13C-13C, 15N-13C, 31P-13C coupling constants in benzene, pyridine, pyridinium, phosphinine, and phosphininium. The introduction of N or P heteroatoms into the aromatic ring not only changes the magnitudes of the corresponding X-C coupling constants (J, for X = C, N, or P) but also the signs and magnitudes of corresponding reduced coupling constants (K). Protonation of the heteroatoms also produces dramatic changes in coupling constants and, by removing the lone pair of electrons from the sigma-electron framework, leads to the same signs for corresponding reduced coupling constants for benzene, pyridinium, and phosphininium. C-C coupling constants are rather insensitive to the presence of the heteroatoms and protonation. All terms that contribute to the total coupling constant (except for the diamagnetic spin-orbit (DSO) term) must be computed if good agreement with experimental data is to be obtained. 相似文献
129.
O'Donoghue A Pyun SY Yang MY Morrow JR Richard JP 《Journal of the American Chemical Society》2006,128(5):1615-1621
The cleavage of the diribonucleoside UpU (uridylyl-3'-5'-uridine) to form uridine and uridine (2',3')-cyclic phosphate catalyzed by the dinuclear Zn(II) complex of 1,3-bis(1,4,7-triazacyclonon-1-yl)-2-hydroxypropane (Zn(2)(1)(H(2)O)) has been studied at pH 7-10 and 25 degrees C. The kinetic data are consistent with the accumulation of a complex between catalyst and substrate and were analyzed to give values of k(c) (s(-)(1)), K(d) (M), and k(c)/K(d) (M(-)(1) s(-)(1)) for the Zn(2)(1)(H(2)O)-catalyzed reaction. The pH rate profile of values for log k(c)/K(d) for Zn(2)(1)(H(2)O)-catalyzed cleavage of UpU shows the same downward break centered at pH 7.8 as was observed in studies of catalysis of cleavage of 2-hydroxypropyl-4-nitrophenyl phosphate (HpPNP) and uridine-3'-4-nitrophenyl phosphate (UpPNP). At low pH, where the rate acceleration for the catalyzed reaction is largest, the stabilizing interaction between Zn(2)(1)(H(2)O) and the bound transition states is 9.3, 7.2, and 9.6 kcal/mol for the catalyzed reactions of UpU, UpPNP, and HpPNP, respectively. The larger transition-state stabilization for Zn(2)(1)(H(2)O)-catalyzed cleavage of UpU (9.3 kcal/mol) compared with UpPNP (7.2 kcal/mol) provides evidence that the transition state for the former reaction is stabilized by interactions between the catalyst and the C-5'-oxyanion of the basic alkoxy leaving group. 相似文献
130.
Woods M Woessner DE Zhao P Pasha A Yang MY Huang CH Vasalitiy O Morrow JR Sherry AD 《Journal of the American Chemical Society》2006,128(31):10155-10162
Paramagnetic lanthanide(III) complexes that contain hyperfine-shifted exchangeable protons offer considerable advantages over diamagnetic molecules as chemical exchange saturation transfer (CEST) agents for MRI. As part of a program to investigate avenues to improve the sensitivity of such agents, the CEST characteristics of europium(III) macrocyclic complexes having appended hydroxyethyl groups were investigated. The CEST spectrum of the asymmetrical complex, EuCNPHC3+, shows five distinct peaks for each magnetically nonequivalent exchangeable proton in the molecule. The CEST spectra of this complex were fitted to NMR Bloch theory to yield exchange rates between each of six exchanging proton pools (five on the agent plus bulk water). Exchange between the Eu3+-bound hydroxyl protons and bulk water protons was slow in dry acetonitrile but accelerated incrementally upon stepwise addition of water. In pure water, exchange was too fast to observe a CEST effect. The utility of this class of europium(III) complex for CEST imaging applications is ultimately limited by the small chemical shifts induced by the hydroxyl-appended ligands of this type and the resulting small Deltaomega values for the exchangeable hydroxyl protons. 相似文献