Binding of homoserine lactone (HSL) signaling molecules used by Gram-negative bacteria with native and substituted cyclodextrin (CD) host molecules was mapped. Between differently substituted HSLs with different alkyl chain lengths, chain length governed binding affinity. Between α-CD and β-CDs, the wider β-CD cavity was found to be more tolerant of substitutions in terms of binding constant.
In this work, the binding ability of different CDs against HSLs with three different tail lengths (C4, C8, C12) and three different 3-site substitutions (oxo, hydroxyl, and unsubstituted) was systematically probed using 1H NMR host–guest titrations, isothermal titration calorimetry (ITC) measurements UV–Vis or fluorescence-based indicator displacement assay (IDA). Comparisons were drawn between the native α- and β-CD, as well as different substituted forms of the two. The HSL tail length was found to govern the binding affinity, albeit a slight difference between different substitution motifs may be present — particularly for the shortest-tailed autoinducers (C4), where the relative alkyl chain length is most affected. Between different diameter α- and β-CD, substitution was more likely to impair the former’s binding affinity toward HSLs. The results present a chemical toolbox for informing the design of new macrocyclic hosts for the binding of HSLs in therapeutic applications, as well as in designing bioengineered systems that make use of reversible modulation of the QS system for, for example, biotechnological processes or synthetic biology.
Otso I. V. Luotonen, Rasmus Rantanen, Lijo George, Sandra Kaabel, Eduardo Anaya-Plaza, Mauri A. Kostiainen (2025) Systematic Mapping of Homoserine Lactone and Cyclodextrin Binding Strengths — Effects of Structural Features. Chemistry – A European Journal e01916. https://doi.org/10.1002/chem.202501916