Open AccessLight scattered by model phantom bacteria reveals molecular interactions at their surface
Author(s) -
A. Ghetta,
Davide Prosperi,
Francesco Mantegazza,
Luigi Panza,
Sergio Riva,
Tommaso Bellini
Publication year - 2005
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0505877102
Subject(s) - binding constant , ligand (biochemistry) , tripeptide , imaging phantom , biophysics , scattering , materials science , chemistry , molecular binding , colloid , chemical physics , light scattering , receptor , crystallography , molecule , binding site , peptide , optics , biology , biochemistry , physics , organic chemistry
Testing molecular interactions is an ubiquitous need in modern biology and molecular medicine. Here, we present a qualitative and quantitative method rooted in the basic properties of the scattering of light, enabling detailed measurement of ligand-receptor interactions occurring on the surface of colloids. The key factor is the use of receptor-coated nanospheres matched in refractive index with water and therefore optically undetectable (“phantom”) when not involved in adhesion processes. At the occurrence of ligand binding at the receptor sites, optically unmatched material adsorbs on the nanoparticle surface, giving rise to an increment in their scattering cross section up to a maximum corresponding to saturated binding sites. The analysis of the scattering growth pattern enables extracting the binding affinity. This label-free method has been assessed through the determination of the binding constant of the antibiotic vancomycin with the tripeptidel -Lys-d -Ala-d -Ala and of the vancomycin dimerization constant. We shed light on the role of chelate effect and molecular hindrance in the activity of this glycopeptide.