Photoswitching Affinity and Mechanism of Multivalent Lectin Ligands

Abstract

Multivalent receptor–ligand binding is a key principle in a plethora of biological recognition processes. Immense binding affinities can be achieved with the correct spatial orientation of the ligands. Accordingly, the incorporation of photoswitches, which can be used to reversibly change the spatial orientation of molecules, into multivalent ligands is a means to alter the binding affinity and possibly also the binding mode of such ligands. We report a divalent ligand for the model lectin wheat germ agglutinin (WGA) containing an arylazopyrazole photoswitch. This switch, which has recently been introduced as an alternative to the more commonly used azobenzene moiety, is characterized by almost quantitative E/Z photoswitching in both directions, high quantum yields, and high thermal stability of the Z isomer. The ligand was designed in a way that only one of the isomers is able to bridge adjacent binding sites of WGA leading to a chelating binding mode. Photoswitching induces an unprecedentedly high change in lectin binding affinity as determined by isothermal titration calorimetry (ITC). Furthermore, additional dynamic light scattering (DLS) data suggest that the binding mode of the ligand changes from chelating binding of the E isomer to crosslinking binding of the Z isomer.

Divergent approach to nanoscale glycomicelles and photo-responsive supramolecular glycogels. Implications for drug delivery and photoswitching lectin affinity

“…This result indicates for the first time, that after isomerization, the mannose within gel-1 in the cis form is no longer accessible and therefore cannot establish effective interactions with ConA. This observation is in line with previous research conducted by the Jayaraman group, 64 the Hartmann group, 65 and the Lindhorst group. 66,67 These studies have highlighted the critical role of carbohydrate ligand orientation in lectin recognition, mainly in solution.…”

“…64 Similarly, the Hartmann group reported changes in inhibitory concentrations upon photoswitching, underscoring the importance of ligand structure and orientation. 65 Additionally, the Lindhorst group demonstrated light-dependent differences in bacterial adhesion on immobilized glycosylated azo-benzene derivatives, both on microtiter plates 66 and human cell membranes. 67 Interestingly, in the second test, once the glycogel-1-ConA Texas Red aggregate was obtained (Fig.…”

Photoswitchable glycoligands targeting Pseudomonas aeruginosa LecA

“…-β-D-galactopyranoside (E-11): From 10 (200 mg, 0.53 mmol) and BocNHCH2CH2Br (475 mg, 2.12 mmol), K2CO3 (293 mg, 2.12 mmol) according to the General procedure I, compound 11 (220 mg, 80%) was isolated as an orange solid. Rf = 0.5 (CH2Cl2/MeOH = 5/1), mp: 90°C, [α] 23 D : -29.0 (c = 0.5 , MeOH); 1 H NMR (400 MHz, CD3OD): δ 7.66 (t, J = 2.4 Hz, 1H, HPh), 7.60 (ddd, J = 8.0, 1.6, 0.8 Hz, 1H, HPh), 7.53 (d, J = 8.4 Hz, 1H, HPh), 7.48-7.42 (m, 3H, HPh), 7.27 (ddd, J = 8.4, 2.4, 0.8 Hz, 1H, HPh), 7.10 (ddd, J = 8.0, 2.4, 0.8 Hz, 1H, HPh), 4.97 (d, J = 7.6 Hz, 1H, H1), 4.09 (t, J = 5.2 Hz, 2H, OCH2), 3.93 (d, J = 3.2 Hz, 1H, H4), 3.88-3.70 (m, 4H, H2,5,6,6'), 3.62 (dd, J = 9.6, 3.2 Hz, 1H, H3), 3.47 (t, J = 5.2 Hz, 2H, NCH2), 1.44 (s, 9H, 3×CH3); 13 C NMR (100 MHz, CD3OD): δ 160.9, 160.0, 158.5, 154.9 (Cq); 131.0, 130.9, 120.8, 119.1, 119.0, 118.2, 110.9, 107.8 (CHPh); 102.9 (C1); 80.…”

“…A variation of IC50 value by a factor up to 1.6 has been observed for the divalent ligand [21]; while almost no difference of inhibition was observed for LecA and LecB upon irradiation, probably due to the low photoisomerization of glycodentrimers [22]. Very recently, the group of Wittmann reported an arylazopyrazole-linked divalent N-acetylglucosamine targeting lectin wheat germ agglutinin [23]. The binding affinity kd evaluated by isothermal titration calorimetry (ITC) showed a variation by a factor of 12.5 upon the photoisomerization.…”

Deactivatable Bisubstrate Inhibitors of Protein Kinases

“…The attachment of a single nitrodibenzofuran (NDBF) photocage to a hot-spot position on the ATP-binding site-targeting fragment efficiently blocked the binding of ARC to the catalytic subunit type α of cAMP-dependent PK (PKAcα), as shown by the five orders of magnitude affinity difference between the photocaged ( K D = 1.9 µM) and active ( K D = 5 pM) forms of the inhibitor [ 22 ]. Furthermore, several examples of bivalent (and multivalent) ligands have been published whose multivalent binding is controlled by a photoswitch ( Figure 1 d) [ 24 , 25 , 26 , 27 , 28 ].…”