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Conformational Switching of a Foldamer in a Multicomponent System by pH-Filtered Selection between Competing Noncovalent Interactions.

Brioche J, Pike SJ, Tshepelevitsh S, Leito I, Morris GA, Webb SJ, Clayden J - J. Am. Chem. Soc. (2015)

Bottom Line: As a consequence of this noncovalent interaction, a global absolute screw sense preference, detectable by (13)C NMR, is induced in the foldamer.Addition of base, or acid, to the mixture of ligands competitively modulates their interaction with the binding site, and reversibly switches the foldamer chain between its left and right-handed conformations.As a result, the foldamer-ligand mixture behaves as a biomimetic chemical system with emergent properties, functioning as a "proton-counting" molecular device capable of providing a tunable, pH-dependent conformational response to its environment.

View Article: PubMed Central - PubMed

Affiliation: †School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom.

ABSTRACT
Biomolecular systems are able to respond to their chemical environment through reversible, selective, noncovalent intermolecular interactions. Typically, these interactions induce conformational changes that initiate a signaling cascade, allowing the regulation of biochemical pathways. In this work, we describe an artificial molecular system that mimics this ability to translate selective noncovalent interactions into reversible conformational changes. An achiral but helical foldamer carrying a basic binding site interacts selectively with the most acidic member of a suite of chiral ligands. As a consequence of this noncovalent interaction, a global absolute screw sense preference, detectable by (13)C NMR, is induced in the foldamer. Addition of base, or acid, to the mixture of ligands competitively modulates their interaction with the binding site, and reversibly switches the foldamer chain between its left and right-handed conformations. As a result, the foldamer-ligand mixture behaves as a biomimetic chemical system with emergent properties, functioning as a "proton-counting" molecular device capable of providing a tunable, pH-dependent conformational response to its environment.

No MeSH data available.


Switching induction onor off by use of acid or base. Portionsof the 13C spectra in CDCl3 at 296 K of F4 in the presence of ligand HA, HA+NH3, and HA+NH3+HCl.
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fig4: Switching induction onor off by use of acid or base. Portionsof the 13C spectra in CDCl3 at 296 K of F4 in the presence of ligand HA, HA+NH3, and HA+NH3+HCl.

Mentions: Importantly, screw sense induction by HA1 and HA4 (Figure 4b,f) was dramaticallyreduced or turned off when the pH80 wasraised by addition of ammonia (1 equiv relative to HA) to the mixture (Figure 4c,g). In the caseof HA1, this additional equivalent of NH3 presumablydisrupts the HA1↔F4 pair by forminga stronger hydrogen bonded complex HA1↔NH3, because ammonia is more basic than pyridinein all solvents where data are available and thus most probably alsoin chloroform. For HA4, the disruption of the HA4↔F4 pair may be rationalized by deprotonationof the partially or fully formed pyridinium ion F4H+, replacing the interaction of A4– and F4H+ by a tight ion pair between A4– and NH4+. Addition of anequivalent of HCl led to precipitation of NH4Cl, restoringthe conformational induction in both cases. The lower level of controlin the case of HA1 possibly results from competing interactionswith Cl– ions remaining in solution (Figure 4d and 4h).


Conformational Switching of a Foldamer in a Multicomponent System by pH-Filtered Selection between Competing Noncovalent Interactions.

Brioche J, Pike SJ, Tshepelevitsh S, Leito I, Morris GA, Webb SJ, Clayden J - J. Am. Chem. Soc. (2015)

Switching induction onor off by use of acid or base. Portionsof the 13C spectra in CDCl3 at 296 K of F4 in the presence of ligand HA, HA+NH3, and HA+NH3+HCl.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4520694&req=5

fig4: Switching induction onor off by use of acid or base. Portionsof the 13C spectra in CDCl3 at 296 K of F4 in the presence of ligand HA, HA+NH3, and HA+NH3+HCl.
Mentions: Importantly, screw sense induction by HA1 and HA4 (Figure 4b,f) was dramaticallyreduced or turned off when the pH80 wasraised by addition of ammonia (1 equiv relative to HA) to the mixture (Figure 4c,g). In the caseof HA1, this additional equivalent of NH3 presumablydisrupts the HA1↔F4 pair by forminga stronger hydrogen bonded complex HA1↔NH3, because ammonia is more basic than pyridinein all solvents where data are available and thus most probably alsoin chloroform. For HA4, the disruption of the HA4↔F4 pair may be rationalized by deprotonationof the partially or fully formed pyridinium ion F4H+, replacing the interaction of A4– and F4H+ by a tight ion pair between A4– and NH4+. Addition of anequivalent of HCl led to precipitation of NH4Cl, restoringthe conformational induction in both cases. The lower level of controlin the case of HA1 possibly results from competing interactionswith Cl– ions remaining in solution (Figure 4d and 4h).

Bottom Line: As a consequence of this noncovalent interaction, a global absolute screw sense preference, detectable by (13)C NMR, is induced in the foldamer.Addition of base, or acid, to the mixture of ligands competitively modulates their interaction with the binding site, and reversibly switches the foldamer chain between its left and right-handed conformations.As a result, the foldamer-ligand mixture behaves as a biomimetic chemical system with emergent properties, functioning as a "proton-counting" molecular device capable of providing a tunable, pH-dependent conformational response to its environment.

View Article: PubMed Central - PubMed

Affiliation: †School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom.

ABSTRACT
Biomolecular systems are able to respond to their chemical environment through reversible, selective, noncovalent intermolecular interactions. Typically, these interactions induce conformational changes that initiate a signaling cascade, allowing the regulation of biochemical pathways. In this work, we describe an artificial molecular system that mimics this ability to translate selective noncovalent interactions into reversible conformational changes. An achiral but helical foldamer carrying a basic binding site interacts selectively with the most acidic member of a suite of chiral ligands. As a consequence of this noncovalent interaction, a global absolute screw sense preference, detectable by (13)C NMR, is induced in the foldamer. Addition of base, or acid, to the mixture of ligands competitively modulates their interaction with the binding site, and reversibly switches the foldamer chain between its left and right-handed conformations. As a result, the foldamer-ligand mixture behaves as a biomimetic chemical system with emergent properties, functioning as a "proton-counting" molecular device capable of providing a tunable, pH-dependent conformational response to its environment.

No MeSH data available.