Complex forming ability of a family of isolated cyclosophoraoses with ergosterol and its Monte Carlo docking computational analysis

Neutral cyclosophoraoses (unbranched cyclic beta-1,2-D-glucans) produced by the Rhizobium meliloti 2011 were prepared by size exclusion and anion-exchange chromatographic techniques. The degree of polymerization (DP) of isolated cyclosophoraoses was determined by matrix associated laser desorption/ionization mass spectrometry (MALDI/MS) techniques. A family of purified neutral cyclosophoraoses (DP 17-27) was used as a host for the inclusion complexation with hardly soluble ergosterol. High performance liquid chromatographic (HPLC) analysis showed that it induced much enhanced solubility of ergosterol compared to beta-cyclodextrin. In order to understand the molecular basis of the complex forming ability of cyclosophoraoses, a Monte Carlo (MC) docking-minimization method was used for host-guest complex formation of cyclosophoraoses or beta-cyclodextrin with ergosterol. From the MC simulation we propose the 'hand-shake' mechanism for complexation of cyclosophoraoses with ergosterol.