Four Specific Hapten Conformations Dominating Antibody Specificity: Quantitative Structure–Activity Relationship Analysis for Quinolone Immunoassay

Abstract

Antibody-based immunoassay methods have been important tools for monitoring drug residues in animal foods. However, because of limited knowledge about the quantitative structure-activity relationships between a hapten and its resultant antibody specificity, antibody production with the desired specificity is still a huge challenge. In this study, the three-dimensional quantitative structure-activity relationship (3D QSAR) was analyzed in accordance with the cross-reactivity of quinolone drugs reacting with the antibody raised by pipemidic acid as the immunizing hapten and compared with the reported cross-reactivity data and their hapten structures. It was found that the specificity of a quinolone antibody was strongly related to the conformation of the hapten used and that hapten conformations shaped like the letters "I", "P", and "Φ" were essential for the desired high specificity with low cross-reactivity, but that the hapten conformation shaped like the letter "Y" led to an antibody with broad specificity and high cross-reactivity. Almost all of the antibodies against quinolones could result from these four hapten conformations. It was first found that the concrete conformations dominated the specificity of the antibody to quinolone, which will be of significance for the accurate hapten design, predictable antibody specificity, and better understanding the recognition mechanism between haptens and the antibodies for immunoassays.

Application of quantitative structure‐activity relationship analysis on an antibody and alternariol‐like compounds interaction study

“…The 33 compounds that had CR with the antibody were used for conformational optimization and molecular alignment . In view of the optimized molecular 3‐D structure, all molecules had similar bond lengths and bond angles with the parent nucleus structure lying in the same plane.…”

“…The aligned molecules showed how different substituents affected molecular structures . The alignment root‐mean‐square (RMS) value was introduced to measure the degree of molecular superposition in each group …”

“…The Partial Least Squares (PLS) with a leave‐one‐out (LOO) cross‐validation was applied to build the model. The contour maps were finally generated according to the non–cross‐validated model . The favored and disfavored contour maps can be visually investigated.…”

“…More and more studies have shown that the specificity of the antibody is of great significance for improving immunoassays . An antibody with high specificity (low cross‐reactivity [CR]) is suitable to be used in the immunoassay detecting a single compound, while an antibody with broad specificity (high CR) is suitable to be used in the immunoassay detecting multiple compounds . However, because of the lack of knowledge about the antibody recognition and the ambiguous structure‐activity relationship, artificial control of the specificity of the antibody remains a huge challenge …”

“…Wang et al prepared an antibody that can recognize 31 β‐agonists and analogues, thoroughly analyzing the key factors affecting hapten design and antibody recognition through 3D‐QSAR . Chen et al explained the effect of quinolone hapten conformation on the specificity of antibody through 3D‐QSAR, proposing a hapten design strategy for developing the class specificity immunoassay . In addition, the structure‐activity relationship between sulfonamides, organophosphorus pesticides, and antibodies has been reported, but there are few studies on the structure‐activity relationship between mycotoxin and antibodies …”