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    Negative SPR Signals during Low Molecular Weight Analyte Recognition

    Year: 2021

    Journal: Anal. Chem., Volume 93, MAR 2, page 4134–4140

    Authors: Bonnet, H.; Coche-Guerente, L.; Defrancq, E.; Spinelli, N.; Van der Heyden, A.; Dejeu, J.

    Organizations: French National Agency (ANR) [ANR-10-blan-1517, ANR-17-EURE-0003]; University Grenoble Alpes; ICMG (UAR2607) Chemistry Nanobio Platform, Grenoble

    Surface plasmon resonance (SPR) is a powerful technique for studying biomolecular interactions mainly due to its sensitivity and real-time and label free advantages. While SPR signals are usually positive, only a few studies have reported sensorgrams with negative signals. The aim of the present work is to investigate and to explain the observation of negative SPR signals with the hypothesis that it reflects major changes in ligand conformation resulting from target binding. We demonstrated that these negative unconventional signals were due to the negative complex (ligand/analyte) refractive index increment (RH) deviation from the sum of the RII of the individual entities which counterbalanced the theoretical increase of the signal triggered by the target recognition and the ligand folding. We also found that the conformation change of biomolecules can induce a negative or a positive complex RH deviation depending on its sequence and immobilization mode.
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