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51.
Near-infrared absorption spectra of A2CoX4 (A = Cs, ethyl4N; X = Cl, Br) single crystals and from KBr pellets at low temperature are recorded by the Fourier transform technique. At 2 K a rich fine structure of v1(4A2→4T2) and v2(4A2→4T1) ligand field spectra is detected which can be assigned to low symmetry level splittings due to actual site symmetries superimposed by vibrational fine structure. Comparison of fundamental frequencies obtained from far-infrared spectra allows an assignment of all peaks measured in the vibronic spectra to vibrational modes of the MX4 complex. Zero-phonon bands are identified using the assistance of angular overlap calculations. 相似文献
52.
The beginning of a beautiful friendship: cross-linking/mass spectrometry and modelling of proteins and multi-protein complexes 总被引:1,自引:0,他引:1
Rappsilber J 《Journal of structural biology》2011,173(3):530-540
After more than a decade of method development, cross-linking in combination with mass spectrometry and bioinformatics is finally coming of age. This technology now provides improved opportunities for modelling by mapping structural details of functional complexes in solution. The structure of proteins or protein complexes is ascertained by identifying amino acid pairs that are positioned in close proximity to each other. The validity of this technique has recently been benchmarked for large multi-protein complexes, by comparing cross-link data with that from a crystal structure of RNA polymerase II. Here, the specific nature of this cross-linking data will be discussed to assess the technical challenges and opportunities for model building. We believe that once remaining technological challenges of cross-linking/mass spectrometry have been addressed and cross-linking/mass spectrometry data has been incorporated into modelling algorithms it will quickly become an indispensable companion of protein and protein complex modelling and a corner-stone of integrated structural biology. 相似文献
53.
Weiqiao Zhou Zihao Zhang Lixiang Li Jing Xu Yongyang Gong Song Guo Yuanli Liu 《Luminescence》2024,39(3):e4700
Three new neutral and ionic phosphorescent iridium(III) complexes were successfully prepared using 1-(6-methoxynaphthalen-2-yl)isoquinoline as the main ligand, while the auxiliary ligand was 2-(2-1H-imidazolyl)pyridine. Three complexes (Ir1, Ir2, Ir3) showed red emission, peaking at 610, 609, and 615 nm, respectively, and they exhibited good solubility and excellent photophysical properties in different solvents, which is suitable to prepare organic light-emitting diodes (OLEDs) by solution method. Among the three OLEDs prepared by iridium(III) complexes using the solution method, the device based on Ir2 possessed better electroluminescent properties, and its maximum brightness, current efficiency (CE), power efficiency (PE), and the maximum external quantum efficiency (EQE) were 507.2 cd m−2, 0.14 cd A−1, 0.06 lm W−1, and 0.14%. respectively, proving that the three complexes have a certain of potential for OLEDs applications and are expected to expand the applications of iridium(III) complexes for OLEDs. 相似文献
54.
Two new Co(II) coordination polymers with mixed ligands, {[Co(BTA)0.5(DBI)2]·DBI·H2O}n (1) and [Co(PDA)(DBI)(H2O)]n (2) (H4BTA = benzene-1,2,4,5-tetracarboxylic acid; H2PDA = 2,2′-(1,2-phenylene)diacetic acid; DBI = 5,6-dimethyl-1H-benzoimidazole) have been synthesized under hydrothermal conditions, respectively. Both of them are characterized by elemental analyses, powder X-ray diffraction, thermogravimetric analysis, single-crystal X-ray diffraction, and magnetic susceptibilities. In 1, the Co(II) ions are four-coordinated and lie in distorted tetrahedron coordination environment. 1D ladder-like chain structure is formed by the bridging BTA4− ligand. In 2, the Co(II) ions are in slightly distorted octahedral coordination geometry, and linked by PDA2− ligand exhibiting a 2D layer structure. Temperature-dependent magnetic susceptibility measurements of 1 and 2 revealed that there are antiferromagnetic interactions between Co(II) ions. 相似文献
55.
When classical, Nuclear Overhauser Effect (NOE)-based approaches fail, it is possible, given high-resolution structures of the free molecules, to model the structure of a complex in solution based solely on chemical shift perturbation (CSP) data in combination with orientational restraints from residual dipolar couplings (RDCs) when available. RDCs can be incorporated into the docking following various strategies: as direct restraints and/or as intermolecular intervector projection angle restraints (Meiler et al., J Biomol NMR 2000;16:245-252). The advantage of the latter for docking is that they directly define the relative orientation of the molecules. A combined protocol in which RDCs are first introduced as intervector projection angle restraints and at a later stage as direct restraints is shown here to give the best performance. This approach, implemented in our information-driven docking approach HADDOCK (Dominguez et al., J Am Chem Soc 2003;125:1731-1737), is used to determine the solution structure of the Lys48-linked di-ubiquitin, for which chemical shift mapping, RDCs, and (15)N-relaxation data have been previously obtained (Varadan et al., J Mol Biol 2002;324:637-647). The resulting structures, derived from CSP and RDC data, are cross-validated using (15)N-relaxation data. The solution structure differs from the crystal structure by a 20 degrees rotation of the two ubiquitin units relative to each other. 相似文献
56.
Synthesis and multi‐spectroscopic study on DNA‐binding,cleavage and biological properties of M(II) complexes based on N2O2 donor Schiff base ligand 下载免费PDF全文
A novel Schiff base, (S,Z)‐4‐(methylthio)‐2‐((3‐oxo‐2,3‐dihydro‐1H‐inden‐1‐ylidene)amino)butanoic acid (L) and four M(II) complexes (where M = Co, Cu, Ni and Zn) were synthesized and characterized. The DNA‐binding characteristics of the complexes were investigated using various spectroscopic methods and viscosity measurements. Analysis of the results suggests that all the complexes bind to calf thymus DNA via intercalation. Among the four, Cu(II) complex was found to promote the photocleavage of plasmid DNA pBR322 under irradiation at 365 nm. These complexes also exhibit good antioxidant activities against 2,2‐diphenyl‐1‐picrylhydrazyl radical. In vitro antibacterial and antifungal assay indicates that these complexes are good antimicrobial agents. 相似文献
57.
《Bioorganic & medicinal chemistry》2016,24(18):4108-4119
The natural antioxidant flavonoid diosmin, found in citric fruits, showed low antioxidant properties among other flavonoids due to its structural characteristics and low cytotoxicity against lung (A549) and breast (T47D, SKBR3 and MDAMB231) cancer cell lines. The anticancer behavior has been improved by the metal complex generated with the flavonoid and the oxidovanadium(IV) ion. This new complex, [VO(dios)(OH)3]Na5·6H2O (VOdios), has been synthesized and characterized both in solid and solution states. The interaction of the metal ion through the sugar moiety of diosmin precluded the improvement of the antioxidant effects. However, the cell-killing effects tested in human lung A549 and breast T47D, SKBR3 and MDAMB231 cancer cell lines, were enhanced by complexation. The anti-proliferative effects on the human lung cancer cell line were accompanied by cellular ROS generation and an increase in cytoplasm condensation. The breast cancer cell lines did not produce caspase3/7 activation, mitochondrial potential reduction and ROS generation. Therefore, a non-apoptotic form of cell death in a caspase- and oxidative stress-independent manner has been proposed. The protein binding ability has been monitored by the quenching of tryptophan emission in the presence of the compounds using bovine serum albumin (BSA) as a model protein. Both compounds could be distributed and transported in vivo and the complex displayed stronger binding affinity and higher contributions to the hydrogen bond and van der Waals forces. 相似文献
58.
Daniel R. Vlock Beth Arnold Jeannette Humpierres Donald R. Schwartz Shan R. Baker Charles J. Krause Neil Swanson Thomas E. Carey 《Cancer immunology, immunotherapy : CII》1992,34(5):329-336
Summary In previous studies we evaluated the incidence and specificity of autologous antibody reactivity against squamous cell carcinoma of the head and neck (SCCHN). We were able to demonstrate that autologous antibody reactivity is present in native sera but was usually of too low a titer to allow further analysis. Dissociation of immune complexes by acidification and ultrafiltration of serum augmented autologous antibody reactivity in nine out of nine autologous systems tested. Native antibody and antibody derived from immune complexes produced by the host and reactive with autologous tumor cells may be directed against physiologically relevant antigens. Therefore, correlations of antibody titers with clinical course may provide insight into the nature of the host response to cancer. In the present analysis, serological studies of six patients with SCCHN were performed with serum samples obtained over many months. Results of serial serological assays were correlated to tumor progression and clinical course. Fluctuations in autologous antibody reactivity were noted over time. In four cases, rises in autologous antibody titers preceded the clinical diagnosis of recurrence by several months. Drops in autologous antibody reactivity were noted in two cases following surgery or radiation therapy. In two cases of long-term survivors, no correlation between antibody reactivity and clinical course was noted. Specificity analysis of the six autologous systems demonstrated reactivity against autologous and allogeneic SCCHN as well as melanoma cell lines. These sera did not react with glioma, neuroblastoma, renal cell, breast, bladder and colon carcinoma cell lines nor with fetal calf serum, pooled lymphocytes, red blood cells and platelets. Autologous serial serological studies may provide a means by which to evaluate the host/tumor relationship in patients with SCCHN. 相似文献
59.
Enzymes of Direct,Excision, and Mismatch DNA Repair in Pro- and Eukaryotes and Their Biological Role
DNA repair is of paramount importance to protect the integrity of the cell genome. Over the last decade, DNA repair enzymes have been intensely studied owing to their role in mutagenesis, carcinogenesis, and aging. This led to discoveries of novel enzymes, protein factors as well as their intermolecular complexes involved in the repair process. Alternative pathways of cell response to the same type of damage were identified. Data on the tertiary structure of a number of enzymes and mechanisms of their molecular interaction were obtained. This paper is an overview of latest advances in the research of cell response to DNA damage via direct, base and nucleotide excision, and mismatch DNA repair. 相似文献
60.
Deepali Gupta 《Inorganica chimica acta》2007,360(7):2379-2386
1-Methylisocytosine (1-MeIC) can be protonated at the endocyclic N(3) position (pKa of 1-MeICH+, 4.02 ± 0.04) or complexed at this position with (dien)MII (M = Pt, Pd). X-ray crystal structures of the protonated species 1 as well as the Pd (2) and Pt (3) complexes are reported, and gas phase structures of the cation 2 and 3 have been calculated by ab initio methods. These results are compared with results from X-ray crystallography. At high pH, the Pt complex 3 undergoes deamination of the exocyclic N(2)H2 group to the 1-methyluracilate complex. As compared to the situation with 1-methylcytosine (1-MeC), the accelerating effect of (dien)PtII is much less pronounced, however. 相似文献