Amino acids binding to Zn²⁺‐cyclen molecular receptor in aqueous solution

Abstract

Potentiometric titrations and (1) H NMR spectroscopic studies of amino acids binding to the [ZnL](2+) -complex where L=cyclen in aqueous solution provide information concerning complexing species identity, their stability, and coordination mode declaration. The amino acids form stable ternary [ZnL(HL(n))](2+) and [ZnL(L(n))](+) complexes. The observations indicate bidentate coordination mode of the deprotonated amino acids, involving both the amine and the carboxylate functions to the [ZnL](2+) complex in pH region of about 7.5-9.5. The determined stability constants indicate that [ZnL](2+) complex is a very efficient receptor for simple amino acids such as glycine and alanine.

Utilization of IR spectral detailed analysis for coordination mode determination in novel Zn–cyclen–aminoacid complexes

“…Pariya et al [17] isolated [Zn 2 ( 2 -imidazolato-N,N )(cyclen) 2 ](ClO 4 ) 3 complex in solid state and its crystal structure was solved. Therefore, our current interests are focused on recognition of aminoacids by above mentioned model receptor [18,19]. We pre- [18].…”

Dipeptide interactions with Zn(II)–cyclen artificial model for molecular recognition

“…In the neutral region, Zn(II) forms a very stable complex with cyclen (log β 0101 = log K Zn‐cyclen = 15.0) having the [Zn(H 2 O)( L )] 2+ stochiometry (Koike et al ., ; Martell et al ., , Vargová et al ., ; Vargová et al ., ), and this platform offers only one or two coordination sites for interaction with the dipeptides. To undertand the feasible dipeptide coordination modes, we have used two methods: 1 H NMR spectroscopy and potentiometric titrations.…”

“…To undertand the feasible dipeptide coordination modes, we have used two methods: 1 H NMR spectroscopy and potentiometric titrations. In addition, decomplexation/ligand exchange of cyclen in the [Zn(H 2 O)( L )] 2+ complex is slow, and thus, two methods were applied for potentiometric titrations: (i) out‐of‐cell method described previously (Vargová et al ., ) and (ii) direct titration of the preformed Zn(II)–cyclen complex in the presence of the dipeptide, starting at pH = 3. At this pH, [Zn( L )] 2+ and [Zn(H L )] 3+ complex species and cyclen and free Zn(II) are in equilibrium (Vargová et al ., ).…”

“…wileyonlinelibrary.com/journal/jmr stochiometry Martell et al, 2003, Vargová et al, 2007Vargová et al, 2011), and this platform offers only one or two coordination sites for interaction with the dipeptides. To undertand the feasible dipeptide coordination modes, we have used two methods: 1 H NMR spectroscopy and potentiometric titrations.…”

“…In our previous paper (Vargová et al ., ), we described an interaction of the Zn(II)‐cyclen complex with several amino acids. Here, we continue with investigation of the interaction with dipeptides (Gly‐Gly, Gly‐( S )‐Ala, Scheme) to better understand if the Zn(II)–cyclen complex can be also used for peptide recognition.…”