A new tripodal receptor for molecular recognition of monosaccharides. A paradigm for assessing glycoside binding affinities and selectivities by 1H NMR spectroscopy.
A new tripodal receptor for the recognition of monosaccharides is described. The prototypical host 1 features a 1,3,5-substituted 2,4,6-triethylbenzene scaffold bearing three convergent H-bonding units. The binding ability of the t-octyl derivative 1a toward a set of octylglycosides of biologically relevant monosaccharides, including Glc, Gal, Man, and GlcNAc, was investigated by 1H NMR in CDCl3. A protocol for the correct evaluation of binding affinities was established, which can be generally applied for the recognition of monosaccharides by 1H NMR spectroscopy. A three-constant equilibrium model, including 1:1 and 2:1 host-guest association and dimerization of the receptor, was ascertained for the interaction of 1a with all the investigated glycosides. An affinity index, which we defined median binding concentration BC50 in analogy to the IC50 parameter, intended to address the general issue of comparing dimensionally heterogeneous binding data, and a limiting BC0(50)quantity describing intrinsic binding affinities were developed for evaluating the results. BC0(50) values for 1a range from 1 to 6 mM, indicating an intrinsic binding affinity in the millimolar range and a selectivity factor of 5 toward the investigated glycosides. The treatment has been extended to include any generic host-guest system involved in single or multiple binding equilibria.
Vacca
Alberto
A
Dipartimento di Chimica, CNR, Istituto di Chimica dei Composti Organometallici, Università di Firenze, Polo Scientifico, I-50019 Sesto Fiorentino, Firenze, Italy.
Nativi
Cristina
C
Cacciarini
Martina
M
Pergoli
Roberto
R
Roelens
Stefano
S
D001555:Benzene Derivatives / Q000737:chemistry / Q000378:metabolism; D002240:Carbohydrate Sequence; D006027:Glycosides / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008956:Models, Chemical; D008969:Molecular Sequence Data; D009005:Monosaccharides / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000378:metabolism
D001555:Benzene Derivatives; D006027:Glycosides; D009005:Monosaccharides; D011956:Receptors, Cell Surface