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  • Determination of association constants between 5'-guanosine monophosphate gel and aromatic compounds by capillary electrophoresis.

Determination of association constants between 5'-guanosine monophosphate gel and aromatic compounds by capillary electrophoresis.

Journal of chromatography. A (2013-03-26)
Kaori Yamaguchi, Nobuyuki Takeyasu, Takashi Kaneta
ABSTRACT

Hydro gel formed by 5'-guanosine monophosphate (GMP) in the presence of a potassium ion is expected to exhibit interesting selectivity in capillary electrophoretic separations. Here, we estimated the conditional association constants between the hydro gel (G-gel) and aromatic compounds by capillary electrophoresis in order to investigate the separation selectivity that is induced by the G-gel. Several aromatic compounds were separated in a solution containing GMP and potassium ion at different concentrations. The association constants were calculated by correlating the electrophoretic mobilities of the analytes obtained experimentally using a concentration of G-gel. During semi-quantitative estimation, naphthalene derivatives had larger association constants (Kass=10.3-16.8) compared with those of benzene derivatives (Kass=3.91-5.31), which means that the binding sites of G-gel match better to a naphthalene ring than to a benzene ring. A hydrophobic interaction was also found when the association constants for alkyl resorcinol were compared with those of different hydrocarbon chains. The association constants of nucleobases and tryptophan ranged from 6.05 to 12.6, which approximated the intermediate values between benzene and naphthalene derivatives. Consequently, the selective interaction between G-gel and aromatic compounds was classified as one of three types: (1) an intercalation into stacked planar GMP tetramers; (2) a hydrophobic interaction with a long alkyl chain; or, (3) a small contribution of steric hindrance and/or hydrogen bonding with functional groups such as amino and hydroxyl groups.

MATERIALS
Product Number
Brand
Product Description

Supelco
Naphthalene solution, certified reference material, 5000 μg/mL in methanol
Supelco
Naphthalene, certified reference material, TraceCERT®, Manufactured by: Sigma-Aldrich Production GmbH, Switzerland
Supelco
Naphthalene, analytical standard
Sigma-Aldrich
Naphthalene, 99%
Sigma-Aldrich
Naphthalene, suitable for scintillation, ≥99%
Supelco
Melting point standard 79-81°C, analytical standard