title: Thermodynamics and kinetics of amphotericin B self-association in aqueous solution characterized in molecular detail.
abstract: Amphotericin B (AmB) is a potent but toxic drug commonly used to treat systemic mycoses. Its efficiency as a therapeutic agent depends on its ability to discriminate between mammalian and fungal cell membranes. The association of AmB monomers in an aqueous environment plays an important role in drug selectivity, as oligomers formed prior to membrane insertion - presumably dimers - are believed to act differently on fungal (ergosterol-rich) and mammalian (cholesterol-rich) membranes. In this work, we investigate the initial steps of AmB self-association by studying the structural, thermodynamic and spectral properties of AmB dimers in aqueous medium using molecular dynamics simulations. Our results show that in water, the hydrophobic aggregation of AmB monomers yields almost equiprobable populations of parallel and antiparallel dimers that rapidly interconvert into each other, and the dipole-dipole interaction between zwitterionic head groups plays a minor role in determining the drug's tendency for self-aggregation. A simulation of circular dichroism (CD) spectra indicates that in experimental measurements, the signature CD spectrum of AmB aggregates should be attributed to higher-order oligomers rather than dimers. Finally, we suggest that oligomerization can impair the selectivity of AmB molecules for fungal membranes by increasing their hydrophobic drive for non-specific membrane insertion.
authors.affiliation: Department of Pharmaceutical Chemistry, Medical University of Gdańsk, Gdańsk, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Zielińska
authors.affiliation: Department of Physical Chemistry, Gdańsk University of Technology, Gdańsk, Poland.
authors.forename: Miłosz
authors.initials: M
authors.lastname: Wieczór
authors.affiliation: Department of Pharmaceutical Chemistry, Medical University of Gdańsk, Gdańsk, Poland.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Bączek
authors.affiliation: Department of Radiological Informatics and Statistics, Medical University of Gdańsk, Gdańsk, Poland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Gruszecki
authors.affiliation: Department of Physical Chemistry, Gdańsk University of Technology, Gdańsk, Poland.
authors.forename: Jacek
authors.initials: J
authors.lastname: Czub
mesh_terms: D000666:Amphotericin B / Q000737:chemistry*; D000935:Antifungal Agents / Q000737:chemistry*; D001692:Biological Transport; D002462:Cell Membrane / Q000737:chemistry; D002784:Cholesterol / Q000737:chemistry*; D002942:Circular Dichroism; D004875:Ergosterol / Q000737:chemistry*; D005658:Fungi; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D012996:Solutions; D013045:Species Specificity; D055672:Static Electricity; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D000935:Antifungal Agents; D008051:Lipid Bilayers; D012996:Solutions; D014867:Water; D000666:Amphotericin B; D002784:Cholesterol; D004875:Ergosterol