Competition between counterions and active protein sites to bind bisquaternary ammonium groups. A combined mass spectrometry and quantum chemistry model studyV. Pashynska, O. Boryak, M. V. Kosevich, S. Stepanian and L. AdamowiczEur. Phys. J. D, 58 3 (2010) 287-296DOI: https://doi.org/10.1140/epjd/e2010-00125-5