NMR and crystallographic studies of a p-sulfonatocalix[4]arene-guest complex

Proposed cation‐π mediated binding by factor Xa: a novel enzymatic mechanism for molecular recognition

“…Recently the cation-Tr interaction has received considerable attention as a new type of binding interaction. Besides the extensive investigations on artificial host-guest systems [16,18,[27][28][29][30], computational studies of several biolog- Table 1 c ND: no experimental data ical systems have postulated an important role in molecular recognition for such systems as ion selectivity of the potassium channel [31], binding of acetylcholine to acetylcholinesterase [16,32], and binding of choline derivatives to phospholipases A 2 [33]. The most direct evidence for biological importance has been the X-ray crystallographic determination of such an interaction in the immunoglobulin Fab McPC603-phosphocholine complex [34].…”

Complexation of basic amino acids by water-soluble calixarene sulphonates as a study of the possiblemechanisms of recognition of calixarene sulphonates by proteins

“…In addition, the electrostatic binding of quaternary amines to water-soluble calixarene sulphonate derivatives has been investigated by Morozumi and Shinkai; 5 in particular, the inclusion complex formed from p-sulphonated calix [4]arene and trimethylanilinium was studied by 1 H and 13 C NMR spectroscopy. 6 However, in spite of extensive early work of the biological properties of the p-sulphonated calixarenes, 7 it is only very recently that interest in their biomedical potential has come to the fore again. 8 The charge density and size of the p-sulphonated calixarenes make them excellent candidates as heparin mimics, particularly in view of the difference in the synthetic pathways to the sulphonated derivatives (three steps) 9 as compared with the heparin pentasaccharide (over 50 steps).…”

“…10 We have noted this heparin mimicry with respect to peptide folding and even protein-protein interactions. 11 In this work, we investigated the fundamental bases of the interactions between p-sulphonated calix [4]arene (1), calix [6]arene (2) and calix [8]arene (3) with the basic amino acid residues arginine (4) and lysine (5), known for their electrostatic anchoring of the heparin fragment 12 ( Fig. 1).…”

Water-Soluble Calix[4]arene Derivatives: Binding Stoichiometry and Spectroscopic Evaluation of the Host-Guest Recognition Mechanism

“…33 For cations derived from amines, the organic moiety introduces a significant steric factor, with the ammonium cation included in the host cavity. 34,35,36 A closely related www.intechopen.com Water-Soluble Calix [4]arene Derivatives: Binding Stoichiometry and Spectroscopic Evaluation of the Host-Guest Recognition Mechanism 37 study 37 involving a variety of ammonium guests, including acetylcholine and Nmethylquinuclidinium, reached the same conclusion that the guest is in the cavity and that its ammonium portion is closely associated with the calixarene aromatic rings. This interaction was discussed as a π-cation interaction.…”

“…12. Aromatic neutral guests (34)(35)(36)(37), and cationic guests 38, 39. The new water-soluble aminocalix [4]arene hosts 11 and 12 with deep hydrophobic cavity facilitate hydrophilic mouth and hydrophobic mouth, respectively.…”