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Publication Abstract from PubMed

Unlike other known anti-fluorescein antibodies, the monoclonal antibody 43.1 is directed toward the fluorescein's carboxyl phenyl moiety. It demonstrates a very high affinity (KD approximately 70pM) and a fast association rate (kon approximately 2 x 107 M-1 s-1 ). The three-dimensional structure of the Fab 43.1 - fluorescein complex was resolved at 2.4A resolution. The antibody binding site is exclusively assembled by the CDR loops. It includes the14A groove-shaped entrance leading to the 9A by 7A binding pocket. The highly polar binding pocket complementary encloses the fluorescein's carboxyl phenyl moiety and tightly fixes it by multiple hydrogen bonds. The fluorescein's xanthenone ring is embedded in the more hydrophobic groove and stacked between the side chains of Tyr37L and of Arg99H providing conditions for an excited state electron transfer process. In comparison to fluorescein, the absorption spectrum of the complex in the visible region is shifted to the "red" by 23 nm. The complex demonstrates a very weak fluorescence (Phic = 0.0018) with two short lifetime components: 0.03 ns (47%) and 0.8 ns (24%), which reflects a 99.8% fluorescein emission quenching effect upon complex formation. The antibody 43.1 binds fluorescein with remarkable affinity, fast association rate and strongly quenches its emission. Therefore, it may present a practical interest in applications such as molecular sensors and switches. This article is protected by copyright. All rights reserved.

Three-Dimensional Structure, Binding and Spectroscopic Characteristics of the Monoclonal Antibody 43.1 Directed to the Carboxyl Phenyl Moiety of Fluorescein.,Gayda S, Longenecker KL, Judge RA, Swift KM, Manoj S, Linthicum DS, Tetin SY Biopolymers. 2016 Jan 12. doi: 10.1002/bip.22801. PMID:26756394^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.