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  • 1
    Electronic Resource
    Electronic Resource
    X-ray absorption spectroscopic analysis of Fe(II) and Cu(II) forms of a herbicide-degrading α-ketoglutarate dioxygenase (1999)
    Springer
    JBIC 4 (1999), S. 122-129 
    Details
    ISSN: 1432-1327
    Keywords: Key words α-Ketoglutarate dioxygenase ; TfdA ; X-ray absorption spectroscopy ; Extended X-ray absorption fine structure ; 2 ; 4-Dichlorophenoxyacetic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The first step in the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) by Ralstonia eutropha JMP134 is catalyzed by the α-ketoglutarate (α-KG)-dependent dioxygenase TfdA. Previously, EPR and ESEEM studies on inactive Cu(II)-substituted TfdA suggested a mixture of nitrogen/oxygen coordination with two imidazole-like ligands. Differences between the spectra for Cu TfdA and α-KG- and 2,4-D-treated samples were interpreted as a rearrangement of the g–tensor principal axis system. Herein, we report the use of X-ray absorption spectroscopy (XAS) to further characterize the metal coordination environment of Cu TfdA as well as that in the active, wild-type Fe(II) enzyme. The EXAFS data are interpreted in terms of four N/O ligands (two imidazole-like) in the Cu TfdA sample and six N/O ligands (one or two imidazole-like) in the Fe TfdA sample. Addition of α-KG results in no significant structural change in coordination for Cu or Fe TfdA. However, addition of 2,4-D results in a decrease in the number of imidazole ligands in both Cu and Fe TfdA. Since this change is seen both in the Fe and Cu EXAFS, loss of one histidine ligand upon 2,4-D addition best describes the phenomenon. These XAS data clearly demonstrate that changes occur in the atomic environment of the metallocenter upon substrate binding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050295
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  • 2
    Electronic Resource
    Electronic Resource
    A transcription factor IIB homolog from the hyperthermophilic archaeon Pyrococcus furiosus binds Zn or Fe in an N-terminal Cys4 motif (1996)
    Springer
    JBIC 1 (1996), S. 162-168 
    Details
    ISSN: 1432-1327
    Keywords: Key words TFIIB ; Metalloprotein ; Zinc finger ; Gene transcription ; X-ray absorption spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The gene for an archaeal homolog of the eukaryotic transcription factor TFIIB has been cloned from the marine hyperthermophilic archaeon Pyrococcus furiosus and overexpressed in Escherichia coli. This TFB gene displays a sequence that is identical to a gene sequence in P. woesei. A gene for the 49-residue N-terminal domain of TFB that contains a putative C-X2-C-X15-C-X2-C metal-binding motif was subcloned and overexpressed as TFB-NTD. Purification of the TFB-NTD gene product yields Zn- and Fe-containing forms, which have been characterized by mass spectrometry and UV-visible, electron paramagnetic resonance, and X-ray absorption (XAS) spectroscopies. Only the Zn form of the TFB holoprotein has been (partially) purified, and it has been characterized by XAS. All spectroscopic characteristics are consistent with a nearly tetrahedral MS4 metal-binding site made up of the four cysteine residues in the N-terminal domain. The relatively greater thermal stability of the Zn form suggests that TFB may be a Zn-containing protein involved in archaeal transcription.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050035
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  • 3
    Electronic Resource
    Electronic Resource
    Structural evidence for a common zinc binding domain in archaeal and eukaryal transcription factor IIB proteins (2000)
    Springer
    JBIC 5 (2000), S. 276-283 
    Details
    ISSN: 1432-1327
    Keywords: Key words Transcription factor IIB ; Metalloprotein ; Zinc finger ; Gene transcription ; X-ray absorption spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract X-ray absorption spectroscopy has been used to compare the metal coordination of the N-terminal zinc binding domain of eukaryal human transcription factor (TF) IIB to the previously reported structure of archaeal Pyrococcus furiosus (Pf) TFB. Full length and N-terminal fragments for both PfTFBand human TFIIB were cloned, expressed, and purified. The [C10H] variant of PfTFB was constructed to resemble the metal binding motif of higher eukaryal TFIIB proteins by mutating the second cysteine ligand to a histidine. All five proteins bind zinc in a 1 :1 ratio. Zn X-ray absorption spectroscopy of human TFIIB and [C10H]PfTFB mutant are consistent with ZnS3(N,O) ligation, and further suggest that the N/O ligand is an imidazole.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050372
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  • 4
    Electronic Resource
    Electronic Resource
    Experimental and theoretical studies of the three-dimensional structure of human interleukin-4 (1991)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 11 (1991), S. 111-119 
    Details
    ISSN: 0887-3585
    Keywords: interleukin-4 ; circular dichroism spectroscopy ; site-directed mutagenesis ; protein structure modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The structure of human interleukin 4 (IL-4) was predicted utilizing a series of experimental and theoretical techniques. Circular Dichroism (CD) spectroscopy indicated that IL-4 belonged to the all α-helix class of protein structures. Secondary structure prediction, site-directed mutagenesis, and CD spectroscopy suggested a predominantly α-helical structure, consistent with a four-helix bundle structural motif. A human/mouse IL-4 chimera was constructed to qualitatively evaluate alternative secondary structure predictions. The four predicted helices were assembled into tertiary structures using established algorithms. The mapping of three disulfide bridges in IL-4 provided additional constraints on possible tertiary structures. Using accessible surface contact area as a criterion, the most suitable structures were right handed all antiparallel four-helix bundles with two overhand loop connections. Successful loop closure and incorporation of the three disulfide constraints were possible while maintaining the expected shape, solvent accessibility, and steric interactions between loops and helices. Lastly, energy minimization was used to regularize the chain.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340110204
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  • 5
    Electronic Resource
    Electronic Resource
    Assignment of absolute configuration to an improved enantioselective naproxen selector (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 615-622 
    Details
    ISSN: 0899-0042
    Keywords: absolute configuration ; chiral stationary phase ; enantiomer ; chiral recognition ; NSAID ; HPLC ; NMR ; CD ; X-ray ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Assignment of absolute configuration to a recently developed chiral selector useful in the separation of the underivatized enantiomers of naproxen and other nonsteroidal anti-inflammatory drugs (NSAIDs) is described. Circular dichroism, 1H NMR, and X-ray diffraction have been used to confirm the original assignment which was based solely upon elution orders from HPLC chiral stationary phases. All of these techniques agree in the assignment of the (S,S) absolute configuration to the enantiomer of the chiral selector which associates preferentially with (S)-naproxen. © 1994 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530060803
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  • 6
    Electronic Resource
    Electronic Resource
    Fast liquid chromatography for the resolution of chiral compounds (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 188-195 
    Details
    ISSN: 0899-0042
    Keywords: fast analysis times ; enantiomers ; chiral stationary phase ; Pirkle-concept ; achiral derivatization ; rapid screening ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Pirkle-concept chiral stationary phase (CSP) derived from N-(1-naphthyl)leucine was evaluated for developing methods to reduce analysis times and investigating techniques in the rapid screening of a variety of chiral compounds over a given chiral selector. The effects of reduced column lengths and elevated temperatures were studied to shorten analysis times.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030309
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  • 7
    Electronic Resource
    Electronic Resource
    Optimization of capillary parameters for gas chromatography (1984)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 7 (1984), S. 382-388 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary columns ; HETP equation ; Optimum column parameters ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An HETP equation for the capillary column is developed that takes into account the dependence of gaseous diffusion on pressure, the compressibility of the mobile phase, together with the unique relationship between mobile phase velocity, and the resistance to mass transfer in the stationary phase. The equation is used to develop a procedure for column optimization and expressions are derived that allow the optimum column radius and optimum column length to be calculated for a given fixed inlet pressure. It is shown that fast, simple separations are optimally achieved using relatively short small diameter columns. Conversely, optimum performance for the separation of complex mixtures requiring higher efficiencies requires the use of long columns with relatively large diameters.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240070708
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  • 8
    Electronic Resource
    Electronic Resource
    Adsorption of collagenase to particulate titanium: A possible mechanism for collagenase localization in periprosthetic tissue (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 353-360 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Osteolysis is a central feature of aseptic loosening of orthopaedic joint prostheses. This destructive process is believed to result from phagocytosis of implant wear debris by periprosthetic and synovial macrophages and the subsequent release of proinflammatory mediators, including collagenase. Isolated murine macrophages were cultured in vitro with particulate titanium in order to explore the mechanism of macrophage activation by particulate wear debris. The results, in which the amount of secreted, soluble collagenase in culture supernatants was inversely proportional to titanium concentration, suggested that titanium strongly adsorbed secreted collagenase. This inference was confirmed by direct binding assays in which particulate titanium coated with adsorbed collagenase bound an alkaline phosphatase conjugated anticollagenase antibody, but not a conjugated anti-IgG antibody. Adsorption of collagenase was not influenced by preincubation of titanium particles with albumin. The adsorbed collagenase remained enzymatically active as indicated by its ability to hydrolyze a synthetic peptide substrate. These results demonstrate that particulate titanium stimulates collagenase production by macrophages and then strongly adsorbs the secreted proinflammatory enzyme. The process of macrophage stimulation, collagenase secretion, and adsorption may represent an important mechanism for localization and concentration of collagenase in periprosthetic and synovial tissue, a mechanism that ultimately triggers bone resorption through osteoclast activation. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050411
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  • 9
    Electronic Resource
    Electronic Resource
    Solution and solid-state structures of lithiated cyclic phosphonatesDedicated to Prof. William E. McEwen on the occasion of his seventy-fifth birthday. (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 9 (1998), S. 209-218 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Spectroscopic analysis of lithiated cyclic phospho-nates belonging to the 1,3,2-dioxaphosphorinane 2-oxide class have been examined by NMR spectroscopy in THF and by single-crystal X-ray crystallography. Lithio P-benzyl-1,3,2-dioxaphosphorinane 2-oxide (Li+7-) and lithio P-isopropyl-1,3,2-dioxaphosphorinane 2-oxide (Li+8-) are characterized by freely rotating, sp2-hybridized anions devoid of lithium-carbon contacts. The anions are most likely dimers linked through oxygen-lithium bridges. The P-isopropyl compound crystallized from TMEDA/THF as a C-lithiated dimer in which each lithium bridges a carbon and an oxygen and is solvated by one TMEDA molecule. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:209-218, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of chloro-functional molecules on the ammonia plasma treatment of silicone elastomers (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 44 (1992), S. 401-407 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Attenuated total reflectance (ATR) FTIR spectroscopy was utilized for surface studies of ammonia/plasma-modified poly(dimethylsiloxane) (PDMS) elastomer networks containing residual chloro-functional molecules. Ammonia/plasma modification of PDMS containing chloro-functional molecules causes the formation of surface amide groups, but due to the parallel formation of surface ammonium chloride, amide groups are not chemically bonded to the PDMS surface. The two primary sources of chlorine-containing species are residual traces of freon and cross-linking initiators present in the network. In the absence of chloro-functional molecules, ammonia/plasma surface modifications of PDMS leads to the formation of stable surface amide groups.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070440304
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