Affinity capillary electrophoresis and quantum mechanical calculations applied to investigation of [Gly⁶]‐antamanide binding with sodium and potassium ions

Abstract

ACE in a free solution and quantum mechanical density functional theory have been applied to the investigation of interactions of glycine-6-antamanide ([Gly ]AA), a synthetic derivative of cyclic decapeptide antamanide isolated from the highly poisonous mushroom Amanita phalloides, with sodium or potassium ions in methanol. First, from the dependence of effective electrophoretic mobility of [Gly ]AA on Na or K ions concentration in the BGE (methanolic solution of 20 mM chloroacetic acid, 10 mM Tris, pH 7.8, containing 0-50 mM NaCl or 0-40 mM KCl), the apparent binding (stability) constants of [Gly ]AA-Na and [Gly ]AA-K complexes were evaluated as 26 ± 1 and 14 ± 1 L/mol, respectively. The employed ACE method included correction of the effective mobilities measured at ambient temperature and at variable ionic strength of the BGEs to the mobilities related to the reference temperature 25°C and to the constant ionic strength 10 mM. Second, the interaction energies of the [Gly ]AA-Na and [Gly ]AA-K complexes (-466.3 and -345.2 kJ/mol, respectively) and the structural details of these complexes, such as position of the Na and K ions in the cavity of the [Gly ]AA molecule and the interatomic distances within these complexes, were determined by the density functional theory calculations.

Recent developments in capillary and microchip electroseparations of peptides (2015–mid 2017)

“…ACN or methanol (MeOH), or CZE in hydro‐organic solvents, are suitable for analysis of water insoluble or poorly soluble peptides and peptidomimetics and/or for modification of selectivity of CE separations of peptides exhibiting identical or close mobilities in aqueous BGEs. NACE analysis of water insoluble cyclic peptide [Gly 6 ]‐antamanide and its complexes with sodium and potassium ions in methanolic BGE (20 mM chloroacetic acid, 10 mM Tris, pH MeOH 7.8) can be mentioned as an example here .…”

“…ACE is now widely used for determination of association or dissociation constants of biomolecular complexes with different types of both low and high‐molecular mass ligands including peptides, for a review see . Binding constant of the complexes of glycine‐6‐antamanide ([Gly 6 ]AA), a synthetic derivative of cyclic decapeptide antamanide isolated from the highly poisonous mushroom Amanita phalloides , with sodium and potassium ions in MeOH was determined from the dependence of effective mobility of this peptide on the concentration of Na + or K + ions in the BGE , see Fig. .…”

Affinity capillary electrophoresis and density functional theory study of noncovalent interactions of cyclic peptide [Gly6]‐antamanide with small cations

“…The obtained apparent stability constants K ML and the ionic mobilities m ML of the [Gly 6 ]AA‐Rb + and [Gly 6 ]AA‐Cs + complexes were found to be equal to 13 ± 4 L/mol for the former and 22 ± 3 L/mol for the latter. These constants and ionic mobilities are presented in Table where they are compared with the stability constants and ionic mobilities of the [Gly 6 ]AA complexes with Na + and K + ions determined in our previous study . The stability constants of all these four complexes are relatively low in the range 13–26 L/mol, decreasing in the order Na + > Cs + > K + > Rb + .…”

“…of the [Gly 6 ]AA-Rb + and [Gly 6 ]AA-Cs + complexes were found to be equal to 13 ± 4 L/mol for the former and 22 ± 3 L/mol for the latter. These constants and ionic mobilities are presented in Table 1 where they are compared with the stability constants and ionic mobilities of the [Gly 6 ]AA complexes with Na + and K + ions determined in our previous study [22].…”

Affinity capillary electrophoresis employed for determination of stability constants of antamanide complexes with univalent and divalent cations in methanol

“…Circular dichroism spectroscopy and conductivity measurements were applied to study binding of AA with Mg 2+ and Ca 2+ ions. Recently, affinity capillary electrophoresis (ACE) has been applied to study noncovalent interactions of AA derivative ([Gly 6 ]antamanide) with small cations.…”