Synthesis and binding properties of carboxylphenyl-modified calixarenes and cytochrome c.
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Talanta, ISSN: 1873-3573, Vol: 79, Issue: 1, Page: 54-61
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- Chemistry; Calixarene carboxylphenyl derivatives; Cytochrome c; Fluorescence spectroscopy; Protein binding; Synthesis
Two novel carboxylphenyl-modified calixarenes, tetrakis-carboxylphenylcalixarene (TCPC) and 1,3-bis-carboxylphenylcalixarene (BCPC), as well as a corresponding analogue for comparison, tetrakis-phenylcalixarene (TPC), have been synthesized by palladium-catalyzed Suzuki cross-coupling of arylboronic acid and tetrabromocalixarene as a key step. The binding properties of these calixarene derivatives with bovine heart cytochrome c (cyt c) in dimethylformamide (DMF) was investigated by fluorescence spectroscopy. The binding affinity in the order of TCPC>BCPC>>TPC reflects a clear dependence on the number of carboxyl ligating groups attached onto a receptor and suggests the electrostatic force may be the predominant factor driving the complexing process. The stable 1:1 complexes of TCPC and BCPC with cyt c were evidenced with the binding constants of 3.15 x 10(6) and 5.85 x 10(5)L mol(-1), respectively. Due to a large overlap between the emission spectrum of TCPC and the absorption spectrum of cyt c, and a short interaction distance (estimated to be 5.6 nm) between them, the fluorescence quenching of TCPC upon complexation with cyt c is attributed to an efficient energy transfer.