排序方式: 共有32条查询结果,搜索用时 15 毫秒
1.
KL Britton HF Rogers Y Asano T Dairi Y Kato TJ Stillman DW Rice 《Acta crystallographica. Section D, Biological crystallography》1998,53(4):124-126
The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres. 相似文献
2.
3.
Katie Greenman Adam Bauer Daniel Kool Jianzhao Liu Bingbing Li 《Colloid and polymer science》2014,292(9):2227-2240
The morphological evolution of poly(ε-caprolactone) (PCL)/octaisobutyl polyhedral oligomeric silsesquioxane (IBUPOSS) films was analyzed using scanning electron microscopy (SEM) and polarized optical microscopy (POM). The morphologies of the blend films with PCL/IBUPOSS mass ratios of 95:5 to 50:50 were discussed according to decomposition mechanism in relation to film composition and thickness. In addition to the morphological regime for films with lower IBUPOSS loadings, in which the growth of PCL spherulites was nearly independent on the presence of fine IBUPOSS aggregates, two new morphological regimes were observed for the films with higher IBUPOSS loadings: (1) thicker blend films exhibited a rich dynamics, giving rise to a trilayer structure and (2) the decomposition of thinner films was induced by the kinetically controlled growth of IBUPOSS aggregates. By varying the thickness and the composition of the blend films, the current study provides important new insight into the rich phase behavior of nanoparticle-filled polymer films. 相似文献
4.
Khan A Silversides JD Madden L Greenman J Archibald SJ 《Chemical communications (Cambridge, England)》2007,(4):416-418
The copper(II) complex of a novel rhodamine-azamacrocycle conjugate binds to the CXCR4 chemokine receptor and competes effectively against anti-CXCR4 monoclonal antibodies. The copper macrocycle unit adopts a trans-II configuration in the solid state. 相似文献
5.
Yuehua Dou Stephen Haswell John Greenman Jay Wadhawan 《Electrochemistry communications》2009,11(10):1976-1981
The detection of hydrogen peroxide is detailed using horseradish peroxidase and anthraquinone. Both species are immobilized on a glassy carbon electrode substrate. This dual immobilization gives rise to lower detection limits compared with the situation when either of the species is immobilized. Detection limits of 40 nM are reported within physiologically-relevant media. 相似文献
6.
Dioxetanone, a key component of the bioluminescence of firefly luciferin, is itself a chemiluminescent molecule due to two conical intersections on its decomposition reaction surface. While recent calculations of firefly luciferin have employed four electrons in four active orbitals [(4,4)] for the dioxetanone moiety, a study of dioxetanone [F. Liu et al., J. Am. Chem. Soc. 131, 6181 (2009)] indicates that a much larger active space is required. Using a variational calculation of the two-electron reduced-density-matrix (2-RDM) [D. A. Mazziotti, Acc. Chem. Res. 39, 207 (2006)], we present the ground-state potential energy surface as a function of active spaces from (4,4) to (20,17) to determine the number of molecular orbitals required for a correct treatment of the strong electron correlation near the conical intersections. Because the 2-RDM method replaces exponentially scaling diagonalizations with polynomially scaling semidefinite optimizations, we readily computed large (18,15) and (20,17) active spaces that are inaccessible to traditional wave function methods. Convergence of the electron correlation with active-space size was measured with complementary RDM-based metrics, the von Neumann entropy of the one-electron RDM as well as the Frobenius and infinity norms of the cumulant 2-RDM. Results show that the electron correlation is not correctly described until the (14,12) active space with small variations present through the (20,17) space. Specifically, for active spaces smaller than (14,12), we demonstrate that at the first conical intersection, the electron in the σ(?) orbital of the oxygen-oxygen bond is substantially undercorrelated with the electron of the σ orbital and overcorrelated with the electron of the carbonyl oxygen's p orbital. Based on these results, we estimate that in contrast to previous treatments, an accurate calculation of the strong electron correlation in firefly luciferin requires an active space of 28 electrons in 25 orbitals, beyond the capacity of traditional multireference wave function methods. 相似文献
7.
J. V. Greenman 《Communications in Mathematical Physics》1970,16(2):123-135
We find a Hölder Banach space in which the Bethe-Salpeter equation is a compact integral equation as it stands. We study the properties of the solution in preparation for an analysis of linear field theory models of 3-body amplitudes. In particular we study the properties of the Regge poles of the solution and prove the existence and uniqueness of on mass shell scattering amplitudes. 相似文献
8.
Kevin L. Greenman 《Tetrahedron》2005,61(26):6438-6441
Palladium can catalyze the insertion of ethyl diazoacetate into benzyl bromides. The key step in the catalytic cycle is the migratory insertion of a carbene, derived from ethyl diazoacetate, into a Pd-C bond. 相似文献
9.
The creation of superpositions of hole states via single-photon ionization using attosecond extreme-ultraviolet pulses is studied with the time-dependent configuration-interaction singles (TDCIS) method. Specifically, the degree of coherence between hole states in atomic xenon is investigated. We find that interchannel coupling not only affects the hole populations, but it also enhances the entanglement between the photoelectron and the remaining ion, thereby reducing the coherence within the ion. As a consequence, even if the spectral bandwidth of the ionizing pulse exceeds the energy splittings among the hole states involved, perfectly coherent hole wave packets cannot be formed. For sufficiently large spectral bandwidth, the coherence can only be increased by increasing the mean photon energy. 相似文献
10.
Microflow cytometry represents a promising tool for the investigation of diagnostic and prognostic cellular cancer markers, particularly if integrated within a device that allows primary cells to be freshly isolated from the solid tumour biopsies that more accurately reflect patient-specific in vivo tissue microenvironments at the time of staining. However, current tissue processing techniques involve several sequential stages with concomitant cell losses, and as such are inappropriate for use with small biopsies. Accordingly, we present a simple method for combined antibody-labelling and dissociation of heterogeneous cells from a tumour mass, which reduces the number of processing steps. Perfusion of ex vivo tissue at 4°C with antibodies and enzymes slows cellular activity while allowing sufficient time for the diffusion of minimally active enzymes. In situ antibody-labelled cells are then dissociated at 37°C from the tumour mass, whereupon hydrogel-filled channels allow the release of relatively low cell numbers (<1000) into a biomimetic microenvironment. This novel approach to sample processing is then further integrated with hydrogel-based electrokinetic transport of the freshly liberated fluorescent cells for downstream detection. It is anticipated that this integrated microfluidic methodology will have wide-ranging biomedical and clinical applications. 相似文献