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  • 1
    Electronic Resource
    Electronic Resource
    Mutant Met121Ala of Pseudomonas aeruginosa Azurin and Its Azide Derivative: Crystal Structures and Spectral Properties (1996)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 52 (1996), S. 950-958 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The crystal structures of the azurin mutant Met121Ala and its azide derivative Met121Ala-azide from Pseudomonas aeruginosa have been determined. The final crystallographic R values are 21.3 and 19.4% for the two structures, respectively. In the Met121Ala mutant, the distance between the copper ion and His117 increases by 0.34 Å compared with the wild-type structure. The removal of the methionine in the apical position induces a shortening of the distance from the copper ion to the carbonyl O atom of Gly45 from 2.97 to 2.74 Å. In the Met121Ala-azide structure, the azide anion occupies the cavity created by replacing the Met121 side chain with the smaller methyl group of Ala. The azide anion binds with a terminal N atom to the copper ion at a distance of about 2.04 Å. In addition, the copper ion has moved out of the trigonal plane by about 0.26 Å towards the azide anion. Thus, the copper site in this structure has a distorted tetrahedral arrangement. The spectroscopic characteristics show, in addition, that the copper sites in the two structures are distinctively different. The Met121Ala mutant still maintains the properties of an ordinary type 1 copper site while the Met121Ala-azide derivative has an absorption maximum at about 409 nm and the copper hyperfine coupling has increased to a value intermediate between those of type 2 copper and the wild-type azurin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444996004982
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  • 2
    Electronic Resource
    Electronic Resource
    Structure of Pseudomonas aeruginosai zinc azurin mutant Asn47Asp at 2.4 Å resolution (1993)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 449-457 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The Pseudomonas aeruginosa azurin mutant Asn47Asp has been isolated, its spectroscopic and kinetic properties characterized, and the X-ray crystal structure of its zinc derivative determined. While the optical and electron paramagnetic resonance spectra as well as the electron-transfer activity of the mutant are very similar to the wild-type values, the Asn47Asp reduction potential is slightly increased by 20 mV. The mutant crystallized in the orthorhombic space group P212121 with cell dimensions a = 57.8, b = 81.5 and c = 112.6 Å. There are four molecules in the asymmetric unit, packed as a tetramer which consists of two independent dimers. The zinc site of this mutant structure is similar to the wild-type zinc azurin and, in particular, the metal-binding site is almost identical to the site found in the wild-type zinc-azurin structure [Nar, Huber, Messerschmidt, Filippou, Barth, Jaquinod, Kamp & Canters (1992). Eur. J. Biochem. 205, 1123–1129]. The Asp47 side chain at that mutation site takes on a very similar orientation to Asn47 in the wild-type structure preserving the two hydrogen bonds with the neighbouring Thr113 NH and OγH. Therefore, the increased reduction potential of the mutant is probably a result of an altered charge distribution close to the metal site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444993005207
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  • 3
    Electronic Resource
    Electronic Resource
    Structure of the azurin mutant nickel–Trp48Met from Pseudomonas aeruginosa at 2.2 Å resolution (1995)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 51 (1995), S. 711-717 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The structure of the azurin mutant nickel-Trp48Met from Pseudomonas aeruginosa has been determined by difference Fourier synthesis using phases from the wild-type azurin model. The final crystallographic R value is 0.170 for 17 394 reflections to a resolution of 2.2 Å. The mutant crystallized in the orthorhombic space group P212121, a = 57.4, b = 80.4, c = 110.3 Å. The four molecules in the asymmetric unit are packed as a dimer of dimers. The nickel metal site of this mutant structure is similar to the zinc metal site in the azurin Asp47 mutant. The site-specific mutation was performed at residue Trp48, which is located in the center of the protein in a highly hydrophobic environment, to investigate its suggested role in the long-range electron-transfer pathway between the disulfide bond on one side of the protein to the Cu centre. The structure around the mutation site Met48 showed no significant change compared with the wild-type structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444995001041
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  • 4
    Electronic Resource
    Electronic Resource
    Structure of the azurin mutant Phe114Ala from Pseudomonas aeruginosa at 2.6 Å resolution (1995)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 51 (1995), S. 168-176 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The crystal structure of azurin mutant Phe114Ala from Pseudomonas aeruginosa has been solved by molecular replacement. The final crystallographic R value is 0.185 for 9832 reflections to a resolution of 2.6 Å. The root-mean-square deviation for main-chain atom positions is 0.020 Å between the four independent monomers in the asymmetric unit. The mutant Ala114 crystallized from PEG 4000 in a new crystal form and the crystals are monoclinic, P21, a= 51.0, b = 83.6, c= 66.4 Å and β = 110.5°. The four molecules in the asymmetric unit are packed as a dimer of dimers and are related by an approximate twofold axis. The dimer packing and the dimer contact region are very similar to that of the Alcaligenes denitrificans azurin dimer. The mutation was performed at residue Phe114, which exhibits a π-electron overlap with the copper ligand His117, to investigate its suggested role in the electron self-exchange reaction. Removal of steric constrains from the phenylalanine side chain created a somewhat different geometry around the copper site with an increased mobility of His117 resulting in an enlarged Cu—N length which may be responsible for the slight differences obtained in the spectral properties of the mutant versus the wild-type protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444994005627
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  • 5
    Electronic Resource
    Electronic Resource
    Examination of a blue copper site
    Amsterdam : Elsevier
    Journal of Inorganic Biochemistry 43 (1991), S. 173 
    Details
    ISSN: 0162-0134
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0162-0134(91)84165-6
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  • 6
    Electronic Resource
    Electronic Resource
    Positive and negative persistent photoconductivities in semimetallic AlxGa1−xSb/InAs quantum wells (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 3152-3158 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a detailed investigation of the "positive" persistent photoconductivity (PPC) and "negative" persistent photoconductivity (NPPC) in semimetallic AlxGa1−xSb/InAs quantum wells. The studies of the NPPC and PPC effects have been performed under various conditions, such as different photon energy of excitation, different temperature, different Al composition x, and different well width. It is found that all the previously proposed mechanisms fail to explain several of our observations. We suggest that the NPPC and PPC effects are produced principally by two competing processes. At a high temperature, the photoconduction is dominated by the photogenerated electrons in the InAs well, in which the relaxation of the excess electrons is prohibited by an energy barrier due to the trapping of photoexcited holes by deep defects in the InAs well. As a result, the PPC is observed. At low temperature, electrons in the InAs layer are photoexcited into the local potential minima induced by compositional fluctuations at the AlGaSb and InAs interface, the number of electrons in the InAs well decreases, thus the NPPC occurs. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371182
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  • 7
    Electronic Resource
    Electronic Resource
    Persistent photoconductivity in SiGe/Si quantum wells (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 877-880 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Persistent photoconductivity (PPC) has been observed in boron-doped Si1−xGex/Si quantum wells. The decay kinetics of the PPC effect can be well described by a stretched-exponential function, Ippc(t)=Ippc(0)exp[−(t/τ)β](0〈β〈1), which is usually observed in many disorder materials. Through the studies of the PPC effect under various conditions, such as different temperature, different photon energy of photoexcitation, and different Ge content, we identify that the alloy potential fluctuations induced by compositional disorder are the origin of the PPC effect in Si1−xGex/Si quantum wells. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368150
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  • 8
    Electronic Resource
    Electronic Resource
    Crystallization and preliminary crystallographic data for the azurin mutant Ala 114 from Pseudomonas aeruginosa (1992)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 48 (1992), S. 107-109 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768191007292
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  • 9
    Electronic Resource
    Electronic Resource
    Antimutagenicity of a partially fractionated Maillard reaction product
    Amsterdam : Elsevier
    Food Chemistry 47 (1993), S. 11-15 
    Details
    ISSN: 0308-8146
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0308-8146(93)90295-Q
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  • 10
    Electronic Resource
    Electronic Resource
    Cytokeratin-19 associated with apoptosis and chemosensitivity in human cervical cancer cells (1997)
    Springer
    Apoptosis 2 (1997), S. 101-105 
    Details
    ISSN: 1573-675X
    Keywords: Apoptosis ; cytokeratin ; drug resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Cytokeratins are one group of intermediate filament proteins responsible for the integrity of cell structure, and have been recently reported to play a role in conferring a drug resistance phenotype. MAb Cx-99 is a monoclonal antibody exhibiting the specificity toward its corresponding antigen which was recently identified as the cytokeratin-19 protein. In the present study, we found that the level of cytokeratin-19 in cervical cancer cells could be decreased by incubation of cancer cells with MAb Cx-99. The reduction of cytokeratin-19 level had a killing effect on cervical carcinoma SIHA and HeLa S3 cell lines. The DNA ladder pattern, convoluted nuclei and blebbing morphology were observed with these cells after exposure to MAb Cx-99 for 72 h, suggesting that the cytotoxic mechanism of reduced cytokeratin-19 was mediated by induction of apoptosis. Moreover, the MAb Cx-99 treatment could increase the cytotoxicities of cancer chemotherapeutic agents such as cisplatin and vinblastine to both cervical carcinoma cell lines. The LD80 values were at least 15-fold reduced when cancer cells were treated with cisplatin or vinblastine in the presence of MAb Cx-99. These results suggest that the functional role of cytokeratin-19 was associated with the apoptosis prevention and drug resistance of cervical cancer cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026448027870
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