Determination of the hapten density of immuno-conjugates by matrix-assisted uv laser desorption/ionization mass spectrometry

I. Wengatz, R. D. Schmid, S. KreisZig, C. Wittmann, B. Hock, A. Ingendoh, F. Hillenkamp

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Abstract

Information on the hapten densities of immunoconjugates, that is the number of couled haptens, is important for the production of antibodies directed towards the respective hapten, e.g. a pesticide. Matrix-assisted UV laser desorption mass spectrometry (MALDI) provides a sensitive method for the measurement of the molecular weight of large bioorganic compounds. The mass resolution of approx. 100, currently achievable with this technique in conjunction with a careful centroiding procedure of the peaks, is sufficient for the determination of the hapten density. Different immunoconjugates and labeled enzymes used in enzyme irnrnunoassays were investigated in order to evaluate the hapten density, as inferred from the measured differences in mass between the conjugated and nonconjugated carrier molecule. The pesticides methabenzthiazuron, phenoxybenzoic acid and derivatives of atrazine and pyrethroids were used as haptens. Hapten densities determined from mass spectra were compared to those based on UV spectra. Values determined by MALDI were considerably lower than those indicated by the UV spectra. This is most probably due to the fact that MALDI detects only covalently bound haptens whereas haptens bound by adsorption may also contribute to the signal in the UV-spectrum. The consequences of the MALDI results for immunization are discussed.

Original languageEnglish
Pages (from-to)1983-1997
Number of pages15
JournalAnalytical Letters
Volume25
Issue number11
DOIs
StatePublished - 1 Nov 1992

Keywords

  • Atrazine
  • Hapten Density
  • Immunoconjugate
  • MALDI
  • Methabenzthiazuron
  • Pesticides
  • Pyrethroids

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