Fluorescence spectra of human neuroglobin

The fluorescence quenching spectra of neuroglobin by cesium ion, iodide and acrylamide, synchronous fluorescence spectra, and 8-anilino-1-naphthalene-sulfonic acid binding property were investigated. The intrinsic fluorescence of neuroglobin cannot be effectively quenched by cesium ion, with a Stern–Volmer constant of 0.23?±?0.01. However, it can be significantly quenched by iodide and acrylamide with Stern–Volmer constants of 1.30?±?0.04 and 4.56?±?0.10, respectively. The results of synchronous fluorescence spectra indicate that tryptophan residues are distributed on both the surface and interior of neuroglobin molecule, but most of them are buried in the hydrophobic interior. The neuroglobin molecule has different conformational states in various pH solutions.     

The three-dimensional structure of aspergilloglutamic peptidase from Aspergillus niger

Aspergilloglutamic peptidase from Aspergillus niger is a novel pepstatin-insensitive acid endopeptidase distinct from the well-studied aspartic peptidases, and thus is an interesting target for protein structure/function studies. In the present study, we have determined the three-dimensional structure of the enzyme by X-ray crystallography to a 1.4-Å resolution. The results revealed that the enzyme has a unique structure, composed of two seven-stranded anti-parallel β-sheets which form a β-sandwich structure and appear to have a partial two-fold symmetry, suggesting its possible evolution by gene duplication and that the glutamic acid-110 and glutamine-24 in the heavy chain form a catalytic dyad, consistent with our results obtained by site-directed mutagenesis.     

Coupling of the heme and an internal disulfide bond in human neuroglobin

Neuroglobin displays a hexacoordination His-Fe-His in the absence of external ligands such as oxygen. The observed oxygen affinity therefore depends on the binding rates of both oxygen and the competing distal histidine. Furthermore, the binding properties depend on the presence of an internal disulfide bond. In the case of human neuroglobin, cysteines at positions CD7 and D5 are sufficiently close to form an internal disulfide bond. For cytoglobin, the cysteine residues at positions A7 and GH4 may also form a disulfide bond. Mass spectrometry, ligand binding, and thiol accessibility studies were used to study the role influence of these disulfide bonds. Mutation of specific cysteines, or reduction to break the S-S bond, led to a large decrease in the observed oxygen affinity of human neuroglobin, mainly due to a decrease in the histidine dissociation rate. This suggests a novel mechanism for the oxygen binding; reduction of the disulfide bond would provoke the release of oxygen.     

Direct-writing organic three-dimensional nanofibrous structure

Direct-writing technology based on Near-Field Electrospinning (NFES) was used to fabricate an organic three-dimensional nanofibrous circle on the patterned silicon substrate. In NFES, straight jet without splitting and chaotic motion was utilized to direct-write orderly nanofiber. When the collector movement speed was lower than electrospinning rate, the relaxed nanofiber would be lead into the pendulum motion by the electrical field force and Coulomb repulsion force from the residual charges on the collector. When the relative air humidity is lower than 35%, individual nanofiber with larger elastic resistance would reveal a good self-assembly performance. Owing to the guidance of the electric field force at the edge of the micro-pattern, a nanofiber was deposited layer by layer to format a 3D nanofibrous circle on the top surface of the micro-pattern. The dimension scale of 3D nanofibrous circle was smaller than 30 μm. With the help of a microscope, a 3D nanofibrous circle can be deposited precisely on the strip micro-pattern with width of 4 μm. Furthermore, a 3D nanofibrous circle in different shapes can be obtained by using special micro-patterns. This organic three-dimensional nanofibrous circle has created a new aspect for the fabrication of organic micro/nanosystems.     

Electronic structure of three-dimensional quantum dots

We study the electronic structure of three-dimensional quantum dots using the Hartree-Fock approximation. The confining potential of the electrons in the quantum dot is assumed to be spatially isotropic and harmonic. For up to 40 interacting electrons the ground-state energies and ground-state wavefunctions are calculated at various interaction strengths. The quadrupole moments and electron densities in the quantum dot are computed. Hund's rule is confirmed and a shell structure is identified via the addition energies and the quadrupole moments. While most of the shell structure can be understood on the basis of the unperturbed non-interacting problem, the interplay of an avoided crossing and the Coulomb interaction results in an unexpected closed shell for 19 electrons. Received 5 November 2001 / Received in final form 12 November 2002 Published online 1st April 2003 RID="a" ID="a"e-mail: vorrath@physnet.uni-hamburg.de     

Surface structure for three-dimensional percolation clusters abovep c

We study the surface behaviour of very large percolation clusters above the critical concentrationp _c by considering the width and the analogue of surface tension of the interface separating the interior of the cluster from the outside region. Our Monte Carlo simulation techniques, which are described in detail, are applied to a quadraticL ×L surface layer on the simple cubic lattice, withL up to 200. They give clearly a rough surface even for the highest concentrationsp. The data forp=1 suggest a logarithmic divergence for the interface width in the thermodynamic limitL.     

酰肼类抗结核病药物的3D-QSAR研究

采用三维全息原子场作用矢量(3D-HoVAIF)对115个酰肼类抗结核病药物进行定量构效关系(QSAR)研究.运用多元线性回归(MLR)和偏最小二乘回归(PLS)建模,同时采用内部及外部双重验证的办法对所得模型稳定性能进行了深入分析和检验.MLR建模和PLS建模的复相关系数(R2cum)、留一法交互校验复相关系数(Q2LOO)以及外部样本校验复相关系数(Q2ext)分别为0.766、0.663、0.748和0.733、0.614、0.715.结果表明,3D-HoVAIF能较好表征抗结核药物分子结构信息,所建QSAR模型具有良好稳定性和预测能力,为抗结核病药物的研发提供一定的理论基础.     

Photonic band structure of three-dimensional colloidal crystals with field-induced lattice structure transformation

By utilizing the electrorheological effect, three-dimensional colloidal crystals can be produced, whose lattice structure can be changed from the body-centered-tetragonal lattice to other lattices under the application of electric fields. This paper calculates photonic band structures of such crystals with lattice structure transformation, and demonstrates the existence of complete band gaps for some intermediate lattices. Thus, it becomes possible to use the electrorheological effect to achieve photonic crystals with desired photonic gap properties resulting from tunable structures.     

Synchronization tomography: a method for three-dimensional localization of phase synchronized neuronal populations in the human brain using magnetoencephalography

We present a noninvasive technique which allows the anatomical localization of phase synchronized neuronal populations in the human brain with magnetoencephalography. We study phase synchronization between the reconstructed current source density (CSD) of different brain areas as well as between the CSD and muscular activity. We asked four subjects to tap their fingers in synchrony with a rhythmic tone, and to continue tapping at the same rate after the tone was switched off. The phase synchronization behavior of brain areas relevant for movement coordination, inner voice, and time estimation changes drastically when the transition to internal pacing occurs, while their averaged amplitudes remain unchanged. Information of this kind cannot be derived with standard neuroimaging techniques like functional magnetic resonance imaging or positron emission tomography.     

New family of three-dimensional topological insulators with antiperovskite structure

All known topological insulators are crystallographically related to either the noncentrosymmetric zinc-blende HgTe-type family or to the hexagonal centrosymmetric Bi2Se3 one. Through first-principles calculations, here we show evidence that under a proper uniaxial strain cubic ternary centrosymmetric antiperovskite compounds (M3N)Bi (M=Ca, Sr, and Ba) are three-dimensional topological insulators. This proposed family of materials is chemically inert and the lattice structure is well matched to important semiconductors, which provides a rich platform to easily integrate with electronic devices.     

Broadband visible metamaterial absorber based on a three-dimensional structure

In this paper, a broadband metamaterial absorber is successfully designed by a three-dimensional structure. And the three-dimensional absorber is just obtained by a two-dimensional structure which rotates 90°along x-axis. The simulated results show that the absorption of the three-dimensional metamaterial absorber is much better than the two-dimensional absorber. Moreover, the absorber is polarization-sensitive for the incident electromagnetic waves due to the asymmetry of the structure. Compared with the Y-polarization wave, the proposed absorber can realize broadband absorption with greater than 90% from 355.6 to 737.7 THz for X-polarized wave. Finally, based on the analysis of the electric field and surface current distributions, it can demonstrate that the localized surface plasmons and dipoles resonances will play an important role in the broadband absorption. And we believe that the metamaterial absorber will have many potential applications in emitter and energy harvesting.     

Application of a probabilistic double-fibre structure model to diffusion-weighted MR images of the human brain

A Markov chain Monte Carlo (MCMC) algorithm has been reported which is capable of determining the probabilistic orientation of two-fibre populations from high angular resolution diffusion-weighted data (HARDI). We present and critically discuss the application of this algorithm to in vivo human datasets acquired in clinically realistic times. We show that by appropriate model selection areas of multiple fibre populations can be identified that correspond with those predicted from known anatomy. Quantitative maps of fibre orientation probability are derived and shown for one- and two-fibre models of neural architecture. Fibre crossings in the pons, the internal capsule and the corona radiata are shown. In addition, we demonstrate that the relative proportion of anisotropic signal may be a more appropriate measure of anisotropy than summary measures derived from the tensor model such as fractional anisotropy in areas with multi-fibre populations.     

The study of the reconstructed three-dimensional structure of a solid-oxide fuel-cell cathode by X-ray nanotomography

The microstructure and morphology of solid‐oxide fuel‐cell electrodes are very complex but important because they strongly affect the electrical performance of the cell. In this work the high‐resolution X‐ray nanotomography technique is applied to reconstruct the three‐dimensional microstructure of a (La_0.8Sr_0.2)_0.95MnO₃ yttria‐stabilized zirconia composite cathode. Some key microstructural parameters, such as the porosity, representative elementary volume, connected pore volume and pore phase tortuosity, were obtained based on the three‐dimensional reconstruction volume data with a spatial resolution of sub‐60 nm. These parameters bear intimate correlation with the efficiency of the electrochemical conversion process, and provide valuable information for optimizing the manufacturing processes and improving the device's reliability.     

Preoperative fast MRI of brain tumors using three-dimensional segmented echo planar imaging compared to three-dimensional gradient echo technique

The purpose of this study was to compare the diagnostic efficacy of a newly developed T(1)-weighted three-dimensional segmented echo planar imaging (3D EPI) sequence versus a conventional T(1)-weighted three dimensional spoiled gradient echo (3D GRE) sequence in the evaluation of brain tumors. Forty-four patients with cerebral tumors and infections were examined on a 1.0 T MR unit with 23 mT/m gradient strength. The total scan time for the T(1) 3D EPI sequence was 2 min 12 s, and for a conventional 3D GRE sequence it was 4 min 59 s. Both sequences were performed after administration of a contrast agent. The images were analyzed by three radiologists. Image assessment criteria included lesion conspicuity, contrast between different types of normal tissue, and image artifacts. In addition, signal-to-noise and contrast-to-noise-ratio (C/N) were calculated. The gray-white differentiation and C/N ratio of 3D EPI were found to be inferior to conventional 3D GRE images, but the difference was not statistically significant. In the qualitative comparison, lesion detection and conspicuity of 3D EPI images and conventional 3D GRE images were similar, but a tow-fold reduction of the scanning time was obtained. With the 3D EPI technique, a 50% scan time reduction could be achieved with acceptable image quality compared to conventional 3D GRE. Thus, the 3D EPI technique could replace conventional 3D GRE in the preoperative imaging of brain.     

A method of moments solution to a three-dimensional whisker structure

A method of moments solution to a three-dimensional whisker structure in a rectangular waveguide is presented. Theoretical results are compared with and verified by corresponding experimental measurements. As a result, it is shown that the orientation of the whisker with typical dimensions is not significant for the impedance tuning.     

Phase structure of the three-dimensional radially active Abelian Higgs model

The phase diagram of the 3-D U(1) gauge-Higgs models withq=1 andq=2 are derived without freezing the Higgs field length. The models are studied for several values of λ, the Higgs self-coupling. When λ is sufficiently small, new phase transitions appear, due to the radial fluctuations.     

苯并噁嗪酮衍生物类抗艾滋病药物3D-QSAR研究

摘要：采用三维全息原子场作用矢量（3D-HoVAIF）对36个苯并噁嗪酮衍生物类抗艾滋病药物进行定量构效关系(QSAR)研究.运用偏最小二乘回归（partial least square regression, PLS）建模,同时采用内部及外部双重验证的办法对所得模型稳定性能进行了深入分析和检验.PLS建模的复相关系数（Rcum）、留一法（leave-one-out, LOO）交互校验（cross-validation, CV）复相关系数（QCV）和外部样本校验复相关系数（Qext）分别为0.906、0.865、0.815.结果表明,3D-HoVAIF能较好表征类苯并噁嗪酮衍生物抗艾滋病药物分子结构信息,因而能建立具有良好稳定性和预测能力的QSAR模型,为抗艾滋病药物的研发提供一定的理论基础.