P. Rostam-Khani

Publications (3)2.88 Total impact

• Article: Determination of metal-cofactors in respiratory chain complexes by total-reflection X-ray fluorescence spectrometry (TXRF)

  A. Wittershagen, P. Rostam-Khani, V. Zickermann, I. Zickermann, S. Gemeinhardt, B. Ludwig, B. O. Kolbesen
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  ABSTRACT: Total Reflection X-Ray Fluorescence Spectrometry (TXRF) offers many advantages for the detection of trace elements in enzymes as compared to other well known analytical techniques like flame-AAS or ICP-AES because of the significantly smaller amounts of sample required. Without any decomposition, elements like Fe, Ni, Cu, Zn, Mn and Mo could be determined with high accuracy, in spite of the large bio-organic matrix. Besides the metals also sulfur can be determined in protein samples. The two terminal oxidases, cytochrome c oxidase and quinol oxidase, isolated from the soil bacterium Paracoccus denitrificans, were transferred from their usual salt buffer into a solution of 100 mmol/L tris(hydroxymethyl)aminomethane (TRIS) acetate containing an appropriate detergent. By this procedure an improved signal/noise ratio is attained. The data for cytochrome c oxidase are in good agreement with values obtained by ICP-AES. Further results of quinol oxidase, which has different element ratios, also fit the expected values. The investigations lead to the conclusion that the method is well suited for the quantitative determination of metals in enzymes, and in particular their molar ratios, and requires only small amounts of the biological sample without any extensive pretreatment.
  Fresenius Journal of Analytical Chemistry 04/1998; 361(3):326-328.
• Article: Determination of metal-cofactors in enzyme complexes by total-reflection X-ray fluorescence spectrometry

  A. Wittershagen, P. Rostam-Khani, O. Klimmek, R. Groß, V. Zickermann, I. Zickermann, S. Gemeinhardt, A. Kröger, B. Ludwig, B.O. Kolbesen
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  ABSTRACT: The determination of metal-cofactors and their molar concentrations is an important requirement for the characterisation of metalloproteins and a challenge regarding the capabilities of trace analytical methods. In this respect, total-reflection X-ray fluorescence spectrometry offers many advantages for the determination of trace elements in enzymes, as compared to other well known analytical techniques such as flame atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry (ICP-AES), because of the significantly smaller amounts of sample required. Without any decomposition, elements like P, S, Fe, Ni, Cu, Zn, Mn and Mo could be determined with high accuracy, in spite of the large bio-organic matrix. The enzymes (polysulphide reductase and hydrogenase of the rumen bacterium Wolinella succinogenes, and the cytochrome c oxidase and quinol oxidase of the soil bacterium Paracoccus denitrificans) were transferred from their usual salt-buffer into a solution of 100 mmol l−1 tris(hydroxymethyl)aminomethane (tris)-acetate containing an appropriate detergent. By this procedure, an improved signal-to-noise ratio is obtained. The polysulphide reductase was found to contain copper as a hitherto existing unknown cofactor. The enzyme contains a stretch of amino acids that are typical of copper proteins and thus confirm the presence of this element. Furthermore, the data concerning cytochrome c oxidase from Paracoccus denitrificans are in good agreement with published values obtained by ICP-AES. Also, results from measurements with the quinol oxidase from the same bacterium agree with the expected values. The investigations lead to the conclusion that the method is well suited to the quantitative determination of metals in enzymes, in particular their molar fractions, and requires only small amounts of the biological sample without any extensive pretreatment. © 1997 Elsevier Science B.V.
  Spectrochimica Acta Part B Atomic Spectroscopy 52(7):1033-1038. · 2.88 Impact Factor
• Article: Trace element determination in drugs by total-reflection X-ray fluorescence spectrometry

  M. Wagner, P. Rostam-Khani, A. Wittershagen, Claudia Rittmeyer, B.O. Kolbesen, H. Hoffmann
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  ABSTRACT: The capability of total-reflection X-ray fluorescence spectrometry (TXRF) for the determination of trace elements in drugs is described. Various samples of lecithin, insulin, procaine and tryptophan of different origin were investigated. The element concentrations provide element fingerprints which offer the possibility to discriminate between different batches of the analysed substances originating from different production or purification processes. TXRF facilitates the characterization of such samples without extensive pre-treatment, and provides fast multi-element determination of elements with atomic numbers 14<Z<92 based on matrix-independent quantification by means of an internal standard. © 1997 Elsevier Science B.V.
  Spectrochimica Acta Part B: Atomic Spectroscopy.