76
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Ming ZJ, Hu Y, Qiu YH, Cao L, Zhang XG. Synergistic effects of beta-aescin and 5-fluorouracil in human hepatocellular carcinoma SMMC-7721 cells. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2010; 17:575-580. [PMID: 20106644 DOI: 10.1016/j.phymed.2009.12.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Revised: 10/23/2009] [Accepted: 12/14/2009] [Indexed: 05/28/2023]
Abstract
The effects and mechanisms of action of beta-aescin and 5-fluorouracil (5-FU), alone and in combination, were studied in human hepatocellular carcinoma SMMC-7721 cells. Growth inhibition, cell cycle distribution, apoptosis, Bcl-2 expression and caspase activity were assessed. The Isobole-method/interaction-index analysis was applied to evaluate the synergy, additivity or antagonism of these agents. The results indicate that mixtures of beta-aescin and 5-FU showed a synergistic effect on the 50% inhibitory effect when their ratio was 4:1 when compared with either agent alone. The mechanism of action could be through the synergistic arrest of the cell cycle, induction of apoptosis, activation of caspases-3, 8 and 9, and down-regulation Bcl-2 expression. The results suggest that mixtures of these two agents had a synergistic inhibitory effect on SMMC-7721 cells, an observation which might be useful for the further development of anti-cancer drugs.
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77
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Sun D, Yin L, Sun C, Guo H, Gai Z, Zhang XG, Ward TZ, Cheng Z, Shen J. Giant magnetoresistance in organic spin valves. PHYSICAL REVIEW LETTERS 2010; 104:236602. [PMID: 20867259 DOI: 10.1103/physrevlett.104.236602] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Indexed: 05/29/2023]
Abstract
Interfacial diffusion between magnetic electrodes and organic spacer layers is a serious problem in the organic spintronics which complicates attempts to understand the spin-dependent transport mechanism and hurts the achievement of a desirably high magnetoresistance (MR). We deposit nanodots instead of atoms onto the organic layer using buffer layer assist growth. Spin valves using this method exhibit a sharper interface and a giant MR of up to ∼300%. Analysis of the current-voltage characteristics indicates that the spin-dependent carrier injection correlates with the observed MR.
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78
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Zhang XG, Pantelides ST. Screening in nanowires and nanocontacts: field emission, adhesion force, and contact resistance. NANO LETTERS 2009; 9:4306-4310. [PMID: 19845331 DOI: 10.1021/nl902533n] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The explanations of several nanoscale phenomena such as the field enhancement factor in field emission, the large decay length of the adhesion force between a metallic tip and a surface, and the contact resistance in a nanowire break junction have been elusive. Here we develop an analytical theory of Thomas-Fermi screening in nanoscale structures. We demonstrate that nanoscale dimensions give rise to an effective screening length that depends on the geometry and physical boundary conditions. The above phenomena are shown to be manifestations of the effective screening length.
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79
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Liu F, Zhang XG, Armentrout PB. Activation of CH4 by gas-phase Ni+ and the thermochemistry of Ni-ligand complexes. Phys Chem Chem Phys 2009; 7:1054-64. [PMID: 19791399 DOI: 10.1039/b500639m] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The kinetic energy dependence of the reaction of Ni+ (2D) with methane has been studied using guided ion beam mass spectrometry. Formation of NiH+, NiCH2+ and NiCH3+ are all observed with thresholds near 2 eV, and NiCH+ is observed at higher kinetic energies. The dehydrogenation reaction is shown to proceed over a barrier in excess of the endothermicity by examining the reverse reaction of NiCH2(+) + D2. Collision-induced dissociation of NiCH2+ and NiCH4+ with Xe provides additional information on the products and reaction intermediates. Modeling of the endothermic reaction cross sections yields the 0 K bond dissociation energies (in eV) of D0(Ni( +)-H) = 1.60 +/- 0.08, D0(Ni(+)-CH) = 3.12 +/- 0.12, D0(Ni(+)-CH2) = 3.20 +/- 0.08, D0(Ni(+)-CH3) = 1.76 +/- 0.07, and D0(Ni(+)-CH4) = 1.00 +/- 0.05. The experimental thermochemistry is favorably compared with previous experimental results and density functional theory calculations (B3LYP), which also establish the electronic structures of these species and provide insight into the reaction mechanism. The results for Ni(+) are compared with those for the third-row transition metal congener Pt+ and the differences in behavior and mechanism are discussed.
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80
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Ward TZ, Zhang XG, Yin LF, Zhang XQ, Liu M, Snijders PC, Jesse S, Plummer EW, Cheng ZH, Dagotto E, Shen J. Time-resolved electronic phase transitions in manganites. PHYSICAL REVIEW LETTERS 2009; 102:087201. [PMID: 19257781 DOI: 10.1103/physrevlett.102.087201] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2008] [Indexed: 05/27/2023]
Abstract
The dynamics of first-order electronic phase transitions in complex transition metal oxides are not well understood but are crucial in understanding the emergent phenomena of electronic phase separation. We show that a manganite system reduced to the scale of its inherent electronic charge-ordered insulating and ferromagnetic metal phase domains allows for the direct observation of single electronic phase domain fluctuations within a critical regime of temperature and magnetic field at the metal-insulator transition.
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81
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Zhang XG, Teng DY, Wu ZM, Wang X, Wang Z, Yu DM, Li CX. PEG-grafted chitosan nanoparticles as an injectable carrier for sustained protein release. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2008; 19:3525-3533. [PMID: 18622769 DOI: 10.1007/s10856-008-3500-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2008] [Accepted: 06/06/2008] [Indexed: 05/26/2023]
Abstract
The development of injectable nanoparticulate "stealth" carriers for protein delivery is a major challenge. The objective of this work was to investigate the possibility of achieving the controlled release of a model protein, insulin, from PEG-grafted chitosan (PEG-g-chitosan) nanoparticles (mean diameter 150-300 nm) prepared by the ion gelation method. Insulin was efficiently incorporated into the nanoparticles, and reached as high as 38%. In vitro release showed that it could control the insulin release by choosing the composition, loading and release temperature. We observed that the composition of the nanoparticle surface (C/O ratio) increased from 2.40 to 3.23, with an increase in the incubation time. Therefore, we concluded that during this time, insulin release from PEG-g-chitosan nanoparticles followed a diffusion mechanism in which erosion was negligible. The experiments also demonstrated that PEG-g-chitosan helped to maintain the natural structure of the protein entrapped in the nanoparticles.
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82
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Zhang XG, Yan H, Shen YL, Zhang XM. Decreased thrombospondin-I (TSP-I) expression in the hippocampus of streptozotocin-induced diabetic rats. Exp Clin Endocrinol Diabetes 2008; 116:309-14. [PMID: 18700275 DOI: 10.1055/s-2008-1042407] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Diabetes mellitus (DM) may give rise to cognitive impairment, but the pathological mechanism involved was still unknown. We investigated the thrombospondin-I (TSP-I) expression level in hippocampus of streptozotocin-induced diabetic rats, which, as a matricellular, calcium-binding protein that participates in cellular responses to growth factors, cytokines and injury, has been indicated as important synaptogenic components recently. We employed 20 streptozotocin (STZ)-induced diabetic rats. The weight, blood sugar and urine sugar were measured before and after model induction in diabetes and normal groups. We did immunohistochemical localization of TSP-I and RT-PCR was applied to determine TSP-I mRNA level in the hippocampus of both groups. Moreover, transmission electron microscope (TEM) was used to study the ultrastuctural changes of the hippocampus. All data were analyzed by the independent samples t-test. We found that the expression of TSP-I markedly decreased in the hippocampal neuronal cells. Moreover, TEM results showed the ultrastructures of diabetic hippocampus, including area CA1 and DG, neurons were characterized by mitochondria swelling, increased heterochromatin accumulation and reduced synaptic contacts. The present study provides experimental evidences that decreased TSP-I expression may help to explain the reduced synaptogenesis and altered hippocampal ultrastucture, both of which may contribute to the pathogenesis of diabetic dementia.
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83
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Lu JQ, Zhang XG, Pantelides ST. Standing Friedel waves: a quantum probe of electronic states in nanoscale devices. PHYSICAL REVIEW LETTERS 2007; 99:226804. [PMID: 18233314 DOI: 10.1103/physrevlett.99.226804] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Indexed: 05/25/2023]
Abstract
We report a theoretical study of the dynamic response of electrons in a metallic nanowire or a two-dimensional electron gas under a capacitively coupled "spot gate" driven by an ac voltage. A dynamic standing Friedel wave (SFW) is formed near the spot gate and near edges and boundaries, analogous to the static Friedel oscillations near defects. The SFW wavelength is controlled by the ac voltage frequency and the device's Fermi velocity, whereby the latter can be measured. In addition, the SFW amplitude exhibits resonant behavior at driving frequencies that are related to eigenenergy spacings in the device, allowing their direct measurement.
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84
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Zhou YH, Chen YJ, Ma ZY, Xu L, Wang Q, Zhang GB, Xie F, Ge Y, Wang XF, Zhang XG. 4IgB7-H3 is the major isoform expressed on immunocytes as well as malignant cells. ACTA ACUST UNITED AC 2007; 70:96-104. [PMID: 17610414 DOI: 10.1111/j.1399-0039.2007.00853.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Human B7-H3, a novel member of B7 family, has two isoforms (2IgB7-H3 and 4IgB7-H3). As costimulatory functions of both isoforms are not clarified, there has been much discussion on their expression patterns, T-cell responses, etc. This study generated two specific mouse anti-human 2IgB7-H3 monoclonal antibodies (mAbs) (7D7 and 10F1), whose specificities are quite different from those of the available B7-H3 mAb (21D4) by competition assay. The use of antibodies indicated that B7-H3 was found to have different expression patterns on monocyte-derived dendritic cells, that is the isoform 2IgB7-H3 is tended to express on immature dendritic cells (iDCs), whereas 4IgB7-H3 could be detected in the whole process of maturation of dendritic cells. The isoform 4IgB7-H3 was shown in the immunohistochemistry assay to be more widely expressed than 2IgB7-H3 in human benign and malignant hepatic tissues. Furthermore, flow cytometry and reverse transcription-polymerase chain reaction indicated that 4IgB7-H3 rather than 2IgB7-H3 was the major isoform on many human tumor cell lines. In addition, both 2IgB7-H3- and 4IgB7-H3-transfected cells could promote T-cell proliferation, which could be blocked by 7D7 mAb. These two novel antibodies may shed light on the function of the two B7-H3 isoforms.
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MESH Headings
- Animals
- Antibodies, Monoclonal/physiology
- Antigens, CD/biosynthesis
- Antigens, CD/genetics
- Antigens, CD/physiology
- B7 Antigens
- Cell Differentiation/immunology
- Cell Line, Tumor
- Cells, Cultured
- Coculture Techniques
- Dendritic Cells/cytology
- Dendritic Cells/immunology
- Dendritic Cells/metabolism
- Humans
- Liver Neoplasms/immunology
- Liver Neoplasms/metabolism
- Liver Neoplasms/pathology
- Mice
- Mice, Inbred BALB C
- Protein Isoforms/biosynthesis
- Protein Isoforms/genetics
- Protein Isoforms/physiology
- Receptors, Immunologic/biosynthesis
- Receptors, Immunologic/genetics
- Receptors, Immunologic/physiology
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85
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Zikic R, Krstić PS, Zhang XG, Fuentes-Cabrera M, Wells J, Zhao X. Reply to "Comment on 'Characterization of the tunneling conductance across DNA bases' ". PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:013902. [PMID: 17677521 DOI: 10.1103/physreve.76.013902] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2007] [Indexed: 05/16/2023]
Abstract
Lagerqvist 's Comment regarding the calculation of the transverse conductance of a single-strand DNA heteropolymer translocated through a nanogap between two metal electrodes fully confirms the main conclusions of our study [Phys. Rev. E 74, 011919 (2006)]. In the absence of resonant tunneling, the sensitivity to geometrical factors and the uncertainty in the density functional theory model, which is used in our study and is the basis for the parametrization of the model used by Lagerqvist , raises doubt about the utility of static-bias measurements for DNA sequencing. A possible scheme discussed by Lagerqvist , the stabilization of geometry by an applied strong transverse voltage (1V) , is outside the applicability range of the near-equilibrium theory they (and we) used. More advanced theories and precise gap measurements are needed to resolve these issues.
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86
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Li S, Zhang ZQ, Wu LJ, Zhang XG, Li YD, Wang YY. Understanding ZHENG in traditional Chinese medicine in the context of neuro-endocrine-immune network. IET Syst Biol 2007; 1:51-60. [PMID: 17370429 DOI: 10.1049/iet-syb:20060032] [Citation(s) in RCA: 261] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Traditional Chinese medicine uses ZHENG as the key pathological principle to understand the human homeostasis and guide the applications of Chinese herbs. Here, a systems biology approach with the combination of computational analysis and animal experiment is used to investigate this complex issue, ZHENG, in the context of the neuro-endocrine-immune (NEI) system. By using the methods of literature mining, network analysis and topological comparison, it is found that hormones are predominant in the Cold ZHENG network, immune factors are predominant in the Hot ZHENG network, and these two networks are connected by neuro-transmitters. In addition, genes related to Hot ZHENG-related diseases are mainly present in the cytokine-cytokine receptor interaction pathway, whereas genes related to both the Cold-related and Hot-related diseases are linked to the neuroactive ligand-receptor interaction pathway. These computational findings were subsequently verified by experiments on a rat model of collagen-induced arthritis, which indicate that the Cold ZHENG-oriented herbs tend to affect the hub nodes in the Cold ZHENG network, and the Hot ZHENG-oriented herbs tend to affect the hub nodes in the Hot ZHENG network. These investigations demonstrate that the thousand-year-old concept of ZHENG may have a molecular basis with NEI as background.
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87
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Wang XF, Chen YJ, Wang Q, Ge Y, Dai Q, Yang KF, Zhou YH, Hu YM, Mao YX, Zhang XG. Distinct expression and inhibitory function of B and T lymphocyte attenuator on human T cells. ACTA ACUST UNITED AC 2007; 69:145-53. [PMID: 17257317 DOI: 10.1111/j.1399-0039.2006.00710.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
B and T lymphocyte attenuator (BTLA) has been recently identified as a new inhibitory receptor of the CD28 superfamily, with similarities to cytotoxic T lymphocyte activation antigen (CTLA)-4 and programmed death (PD)-1. Engagement of BTLA on T lymphocytes can profoundly reduce the T cell receptor (TCR)-mediated activation. In this study, we generated four monoclonal antibodies (mAbs) against human BTLA. Using the produced mAb 8H9, the BTLA molecule was found to distinctly express on many subgroups of immunocytes and show a regulatory expression, which was in accordance with its unique ligand herpes virus entry mediator (HVEM) in the process of T cell activation. In addition, the expression of BTLA was increased in the CD4(+) and CD8(+) T cells of pleural fluid in lung cancer patients. Furthermore, we showed that the BTLA-induced negative signals could be triggered by mAb 7D7. Cross-linking of BTLA with mAb 7D7 suppressed T lymphocyte proliferation, downregulated the expression of T cell activation marker CD25, and inhibited the production of interferon (IFN)-gamma, interleukin (IL)-2, IL-4, and IL-10.
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88
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Zhai HY, Ma JX, Gillaspie DT, Zhang XG, Ward TZ, Plummer EW, Shen J. Giant discrete steps in metal-insulator transition in perovskite manganite wires. PHYSICAL REVIEW LETTERS 2006; 97:167201. [PMID: 17155428 DOI: 10.1103/physrevlett.97.167201] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Indexed: 05/12/2023]
Abstract
Optical lithography is used to fabricate LPCMO wires starting from a single (La(5/8-0.3)Pr(0.3))Ca3/8MnO3 (LPCMO) film epitaxially grown on a LaAlO3(100) substrate. As the width of the wires is decreased, the resistivity of the LPCMO wires exhibits giant and ultrasharp steps upon varying temperature and magnetic field in the vicinity of the metal-insulator transition. The origin of the ultrasharp transitions is attributed to the effect of spatial confinement on the percolative transport in manganites.
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89
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Zeng ZM, Feng JF, Wang Y, Han XF, Zhan WS, Zhang XG, Zhang Z. Probing spin-flip scattering in ballistic nanosystems. PHYSICAL REVIEW LETTERS 2006; 97:106605. [PMID: 17025839 DOI: 10.1103/physrevlett.97.106605] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2006] [Indexed: 05/12/2023]
Abstract
Because spin-flip length is longer than the electron mean-free path in a metal, past studies of spin-flip scattering are limited to the diffusive regime. We propose to use a magnetic double barrier tunnel junction to study spin-flip scattering in the nanometer sized spacer layer near the ballistic limit. We extract the voltage and temperature dependence of the spin-flip conductance Gs in the spacer layer from magnetoresistance measurements. In addition to spin scattering information including the mean-free path (70 nm) and the spin-flip length (1.0-2.6 microm) at 4.2 K, this technique also yields information on the density of states and quantum well resonance in the spacer layer.
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90
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Zhang XM, Zhong JM, Tang MZ, Zhang XG, Liao J, Zheng YM, Deng H, Zeng Y. [Comparison of IgA/VCA, IgA/EA, IgG/EA in immunoenzyme methods and ZEBRA ELISA in early diagnosis of nasopharyngeal carcinoma.]. ZHONGHUA SHI YAN HE LIN CHUANG BING DU XUE ZA ZHI = ZHONGHUA SHIYAN HE LINCHUANG BINGDUXUE ZAZHI = CHINESE JOURNAL OF EXPERIMENTAL AND CLINICAL VIROLOGY 2006; 20:263-5. [PMID: 17086289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
BACKGROUND To develop an ELISA method using Herpesvirus hominis type 4 (EBV) IgG/Zebra as capture antigen for large population screening. METHODS The ELISA method used purified ZEBRA antigen to detect the IgG/ZEBRA antibody from serum in nasopharyngeal carcinoma (NPC) and normal healthy subjects. RESULTS Of 288 NPC sera, 262 were detected positive, the sensitivity was 91%, while 5 of 96 normal sera were detected positive, the specificity was 94.8% and the results of NPC group and healthy group displayed significant difference (P less than 0.001). IgA/VCA, IgA/EA, IgG/EA in immunoenzyme methods and ZEBRA ELISA were compared during the NPC screening in two cities: Huizhou, Guangdong and Guiping, Guangxi, 5463 and 2017 samples respectively were tested and 5 earlier NPC patients were found. CONCLUSION The results indicate that this method has high specificity and sensitivity, and can be used for large population screening to assist early phase NPC diagnosis.
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91
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Wang Y, Lu ZY, Zhang XG, Han XF. First-principles theory of quantum well resonance in double barrier magnetic tunnel junctions. PHYSICAL REVIEW LETTERS 2006; 97:087210. [PMID: 17026335 DOI: 10.1103/physrevlett.97.087210] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2006] [Indexed: 05/12/2023]
Abstract
Quantum well (QW) resonances in Fe(001)/MgO/Fe/MgO/Fe double barrier magnetic tunnel junctions are calculated from first principles. By including the Coulomb blockade energy due to the finite size islands of the middle Fe film, we confirm that the oscillatory differential resistance observed in a recent experiment [T. Nozaki, Phys. Rev. Lett. 96, 027208 (2006)10.1103/PhysRevLett.96.027208] originates from the QW resonances from the Delta1 band of the Fe majority-spin channel. The primary source of smearing at low temperatures is shown to be the variation of the Coulomb blockade energy.
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92
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Zikic R, Krstić PS, Zhang XG, Fuentes-Cabrera M, Wells J, Zhao X. Characterization of the tunneling conductance across DNA bases. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 74:011919. [PMID: 16907139 DOI: 10.1103/physreve.74.011919] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2006] [Indexed: 05/11/2023]
Abstract
Characterization of the electrical properties of the DNA bases (adenine, cytosine, guanine, and thymine), in addition to building the basic knowledge on these fundamental constituents of a DNA, is a crucial step in developing a DNA sequencing technology. We present a first-principles study of the current-voltage characteristics of nucleotidelike molecules of the DNA bases, placed in a 1.5 nm gap formed between gold nanoelectrodes. The quantum transport calculations in the tunneling regime are shown to vary strongly with the electrode-molecule geometry and the choice of the density-functional theory exchange-correlation functionals. Analysis of the results in the zero-bias limit indicates that distinguishable current-voltage characteristics of different DNA bases are dominated by the geometrical conformations of the bases and nanoelectrodes.
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93
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Zhang C, Wang LL, Cheng HP, Zhang XG, Xue Y. Spin-dependent transport through a magnetic carbon nanotube-molecule junction. J Chem Phys 2006; 124:201107. [PMID: 16774310 DOI: 10.1063/1.2202739] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The electronic structure and spin-dependent conductance of a magnetic junction consisting of two Fe-doped carbon nanotubes and a C60 molecule are investigated using a first-principles approach that combines the density functional theory with the nonequilibrium Greens function technique. The tunneling magnetoresistance ratio is found to be 11%. The density of states and transmission coefficient through the molecular junction are analyzed and compared to layered magnetic tunneling junctions. Our findings suggest new possibilities for experiments and for future technology.
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94
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Zhang XG, Krstić PS, Zikić R, Wells JC, Fuentes-Cabrera M. First-principles transversal DNA conductance deconstructed. Biophys J 2006; 91:L04-6. [PMID: 16679371 PMCID: PMC1479083 DOI: 10.1529/biophysj.106.085548] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
First-principles calculation of the transverse conductance across DNA fragments placed between gold nanoelectrodes reveals that such conductance describes electron tunneling that depends critically on geometrical rather than electronic-structure properties. By factoring the first-principles result into two simple and approximately independent tunneling factors, we show that the conductances of the A, C, G, and T fragments differ only because of their sizes: the larger is the DNA base, the smaller its distance to the electrode, and the larger its conductance. Because the geometrical factors are difficult to control in an experiment, the direct-current measurements across DNA with gold contact electrodes may not be a convenient approach to DNA sequencing.
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95
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Zhang GB, Zhou H, Chen YJ, Ge Y, Xie F, Shi Q, Ma HB, Fei M, Zhang XG. Characterization and application of two novel monoclonal antibodies against 2IgB7-H3: expression analysis of 2IgB7-H3 on dendritic cells and tumor cells. ACTA ACUST UNITED AC 2005; 66:83-92. [PMID: 16029427 DOI: 10.1111/j.1399-0039.2005.00449.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
2IgB7-H3 has recently been identified as a new member of the B7 family. Its expression at the protein level remains largely unknown due to the lack of the specific monoclonal antibody (mAb). To characterize the expression of 2IgB7-H3, we newly generated two mouse antihuman 2IgB7-H3 mAbs (4H7 and 21D4). We found the constitutive expression of 2IgB7-H3 on a series of tumor cell lines. Furthermore, the expression was examined on monocyte-derived dendritic cells (Mo-DCs) and DCs from CD34(+) hematopoietic progenitor cells (HPC) by means of mAb staining. The results showed that 2IgB7-H3 was expressed on Mo-DCs at a high and stable level during differentiation in vitro. With the maturation of DCs from CD34(+) HPCs, the expression of the molecule was upregulated. However, the 2IgB7-H3 was not expressed on fresh isolated T and B lymphocytes, monocytes, or CD34(+) HPCs. These results suggested that 2IgB7-H3 may be a valuable surface antigen for the detection of DCs.
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96
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Evans MH, Zhang XG, Joannopoulos JD, Pantelides ST. First-principles mobility calculations and atomic-scale interface roughness in nanoscale structures. PHYSICAL REVIEW LETTERS 2005; 95:106802. [PMID: 16196951 DOI: 10.1103/physrevlett.95.106802] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2005] [Indexed: 05/04/2023]
Abstract
Calculations of mobilities have so far been carried out using approximate methods that suppress atomic-scale detail. Such approaches break down in nanoscale structures. Here we report the development of a method to calculate mobilities using atomic-scale models of the structures and density functional theory at various levels of sophistication and accuracy. The method is used to calculate the effect of atomic-scale roughness on electron mobilities in ultrathin double-gate silicon-on-insulator structures. The results elucidate the origin of the significant reduction in mobility observed in ultrathin structures at low electron densities.
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97
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Lu ZY, Zhang XG, Pantelides ST. Spin-dependent resonant tunneling through quantum-well states in magnetic metallic thin films. PHYSICAL REVIEW LETTERS 2005; 94:207210. [PMID: 16090286 DOI: 10.1103/physrevlett.94.207210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2004] [Indexed: 05/03/2023]
Abstract
Quantum-well (QW) states in nonmagnetic metal films between magnetic layers are known to be important in spin-dependent transport, but QW states in magnetic films remains elusive. Here we identify the conditions for resonant tunneling through QW states in magnetic films and report first principles calculations of Fe/MgO/FeO/Fe/Cr and Co/MgO/Fe/Cr. We show that, at resonance, the current increases by 1 to 2 orders of magnitude. The tunneling magnetoresistance ratio is much larger than in simple spin tunnel junctions and is positive (negative) for majority- (minority-) spin resonances, with a large asymmetry between positive and negative biases. The results can serve as a basis for novel spintronic devices.
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98
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Zhang XG, Hou XG. Evidence for a single median fin-fold and tail in the Lower Cambrian vertebrate, Haikouichthys ercaicunensis. J Evol Biol 2004; 17:1162-6. [PMID: 15312089 DOI: 10.1111/j.1420-9101.2004.00741.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this study, we illustrate an exceptionally well-preserved Haikouichthys ercaicunensis from the Lower Cambrian Chengjiang fauna that displays complete single dorsal, ventral and caudal fins. This 530-million-year old vertebrate is fish-shaped and characterized by a single median fin-fold, which is an essential trait of the initial vertebrate chordates. The radially orientated ray-like structures in its dorsal fin somewhat resemble but are probably not real radials seen in basal vertebrates, such as hagfishes and lampreys. The unique design of primitive fins and fin structures provides additional insights into the early evolution of vertebrates.
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Zhang C, Du MH, Cheng HP, Zhang XG, Roitberg AE, Krause JL. Coherent electron transport through an azobenzene molecule: a light-driven molecular switch. PHYSICAL REVIEW LETTERS 2004; 92:158301. [PMID: 15169322 DOI: 10.1103/physrevlett.92.158301] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2003] [Indexed: 05/24/2023]
Abstract
We apply a first-principles computational approach to study a light-sensitive molecular switch. The molecule that comprises the switch can convert between a trans and a cis configuration upon photoexcitation. We find that the conductance of the two isomers varies dramatically, which suggests that this system has potential application as a molecular device. A detailed analysis of the band structure of the metal leads and the local density of states of the system reveals the mechanism of the switch.
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100
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Zhang XG, Shi YL, Li HL. The Effect of the Water Content of Acetonitrile on the Electrochemistry of Ferrocenyl Thiol Self-Assembled Monolayers. J Colloid Interface Sci 2002; 246:296-301. [PMID: 16290414 DOI: 10.1006/jcis.2001.8067] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2001] [Accepted: 10/29/2001] [Indexed: 11/22/2022]
Abstract
A novel kind of ethylene-ferrocenyl dodecyl thiol bearing an electron-withdrawing pyridium group (FcCH=CH-Py(CH2)10SH) was synthesized and mixed with HOOCC(10)SH on an Au electrode to form mixed self-assembled monolayers (SAMs) in ethanol solution. The influence of the water content of acetonitrile on the electrochemistry of the SAMs was studied by cyclic voltammetry and ac voltammetry measurement. The results showed that the current decreased and the oxidation potential of the ferrocene group shifted negatively with increasing water content of acetonitrile.
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