A Hybrid Water–Chloride Structure with Discrete Undecameric Water Moieties Self‐Assembled in a Heptaprotonated Octaamino Cryptand

Lakshminarayanan, P. S.; Suresh, Eringathodi; Ghosh, Pradyut

doi:10.1002/ange.200600254

Cited by 11 publications

(3 citation statements)

References 55 publications

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“…Central to these studies is the notion that the displacement of a high-energy water cluster from a receptor drives guest association, and in some cases, subsequent catalysis. However, despite the abundance of structural data documenting diverse water clusters encapsulated in various host cavities, mechanistic descriptions of the dynamic processes between water and host are rare (24)(25)(26)(27)(28)(29)(30)(31)(32).…”

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confidence: 99%

Protein-like proton exchange in a synthetic host cavity

Hart‐Cooper

Sgarlata

Perrin

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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The mechanism of proton exchange in a metal-ligand enzyme active site mimic (compound 1) is described through amide hydrogendeuterium exchange kinetics. The type and ratio of cationic guest to host in solution affect the rate of isotope exchange, suggesting that the rate of exchange is driven by a host whose cavity is occupied by water. Rate constants for acid-, base-, and watermediated proton exchange vary by orders of magnitude depending on the guest, and differ by up to 200 million-fold relative to an alanine polypeptide. These results suggest that the unusual microenvironment of the cavity of 1 can dramatically alter the reactivity of associated water by magnitudes comparable to that of enzymes.W ater-mediated proton transfer in molecular cavities plays an essential role in the function of nature's remarkable metabolic machinery (1, 2). Of the broad diversity of enzymecatalyzed reactions, those involving transfer of hydrogen are ubiquitous and of high fundamental importance (3). For instance, ATP synthase employs an internal chain of water molecules to mediate proton transfer across an electrochemical gradient (4, 5). This process drives ATP synthesis, which allows organisms to broadly meet their basic energy needs. Recent studies of tunneling in enzymatic hydron transfer reactions have other far-reaching and broad implications, namely the importance of the dynamic enzyme motions in driving catalysis (6, 7).Of the methods used to study hydron transfer, kinetic studies of the mechanisms of amide hydrogen-deuterium exchange (HDX) have helped to elucidate the dynamic interactions between water and protein surfaces that are central to the unique capabilities of enzymes (8-13). Noncovalent interactions, such as electrostatic effects and hydrogen bonding, have also been shown to exert a significant influence on amide HDX rates. These properties are manifest in amide HDX rate constants that can vary by a factor of a billion for residues on the same protein (8). How these variations arise, and how such a property could be harnessed to drive enzyme-like reactivity, remain challenging questions.In a growing effort to emulate the efficacy of biological receptors and enzymes, studies of the preparative, guest-binding, and catalytic properties of synthetic assemblies have been pursued (14-21). Whereas guest encapsulation has been reported in a variety of media, association processes of organic guests are generally more thermodynamically favorable in water (22, 23). Central to these studies is the notion that the displacement of a high-energy water cluster from a receptor drives guest association, and in some cases, subsequent catalysis. However, despite the abundance of structural data documenting diverse water clusters encapsulated in various host cavities, mechanistic descriptions of the dynamic processes between water and host are rare (24-32).As part of the broader field of synthetic hosts previously mentioned, our group has developed a class of biologically inspired, anionic K 12 Ga 4 L 6 assemblies that exhibit cat...

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confidence: 99%

Protein-like proton exchange in a synthetic host cavity

Hart‐Cooper

Sgarlata

Perrin

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Currently, its importance has been well documented by the over 355,000 references in the chemical abstracts and by numerous monographs [4]. Moreover, many papers describing unusual 1D, 2D or 3D water chains, sheets or clusters, respectively, formed by hydrogen bonds have been reported [5]. Although, there are not many reports on the acceptor properties of sulfur atoms, the hydrogen bonds dealing with sulfur as the acceptor atom have proven to be determinant in the tuning of the reactivity of the ZnÁ Á Ácystein thiolate moiety and the Fe-S clusters in proteins [6,7].…”

Section: Introductionmentioning

confidence: 98%

2D hydrogen bond networks in the crystals of [(NH4·H2O)2][(RO)(Fc)P(S)2]2 (R=3-(BzO)-Bz, 4-(n-Bu)-Bz, Bz=benzyl)

Hernández-Galindo

Jancik

Moya‐Cabrera

et al. 2007

Journal of Organometallic Chemistry

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“…1 ) forms a fluoride-based cascade complex [ 9 ], whilst for chloride/bromide encapsulation inside the cavity of hexaprotonated L 1 , [H 6 L 1 ] 6+ leads to both monohydrated complexes [ 10 ] and monotopic chloride/bromide complexes [ 11 ]. Protonated ligand [H 7 L 1 ] 7+ leads to monotopic encapsulation of chloride via hydrogen bonding with external undecameric water clusters [ 12 ] whilst iodide encapsulation has been observed in the case of [H 8 L 1 ] 8+ [ 13 ]. Whereas there are a large number of reports on halide encapsulation in different protonated states for L 1 , encapsulation of polyatomic anions such as tetrahedral (ClO 4 − , HSO 4 − , H 2 PO 4 − ), and octahedral (SiF 6 2− , PF 6 − ) anions etc.…”

Section: Introductionmentioning

confidence: 99%

Structural studies on encapsulation of tetrahedral and octahedral anions by a protonated octaaminocryptand cage

Ravikumar¹,

Lakshminarayanan²,

Suresh³

et al. 2009

Beilstein J. Org. Chem.

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SummaryStructural aspects of the binding of inorganic anions such as perchlorate, hydrogen sulfate, and hexafluorosilicate with the proton cage of octaaminocryptand L 1, N(CH2CH2NHCH2-p-xylyl-CH2NHCH2CH2)3N), are examined thoroughly. Crystallographic results for a hexaprotonated perchlorate complex of L 1, [(H6L1)6+(ClO4 −)]5(ClO4 −)·11H2O·CH3CN (1), an octaprotonated hydrogen sulfate complex of L 1, [(H8 L 1)8+(HSO4 −)]7(HSO4 −)·3H2O·CH3OH (2) and an octaprotonated fluorosilicate complex of L 1, [(H8 L 1)8+(HSiF6 −)]3(SiF6 2−)·(HSiF6 −)·15H2O (3), show encapsulation of one perchlorate, hydrogen sulfate and hexafluorosilicate, respectively inside the cage of L 1 in their protonated states. Further, detailed structural analysis on complex 1 reveals that the hexaprotonated L 1 encapsulates a perchlorate via two N–H···O and five O–H···O hydrogen bonds from protonated secondary nitrogen atoms of L 1 and lattice water molecules, respectively. Encapsulated hydrogen sulfate in complex 2 is “glued” inside the octaprotonated cage of L 1 via four N–H···O and six C–H···O hydrogen bonds whereas encapsulated HSiF6 − in complex 3 has short contacts via six N–H···F and three C–H···F hydrogen bonds with [H8 L 1]8+. In the cases of complexes 2 and 3, the cryptand L 1 in octaprotonated state shows monotopic encapsulation of the guest and the final conformation of these receptors is spherical in nature compared to the elongated shape of hexaprotonated state of L 1 in complex 1.

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A Hybrid Water–Chloride Structure with Discrete Undecameric Water Moieties Self‐Assembled in a Heptaprotonated Octaamino Cryptand

Cited by 11 publications

References 55 publications

Protein-like proton exchange in a synthetic host cavity

Protein-like proton exchange in a synthetic host cavity

2D hydrogen bond networks in the crystals of [(NH4·H2O)2][(RO)(Fc)P(S)2]2 (R=3-(BzO)-Bz, 4-(n-Bu)-Bz, Bz=benzyl)

Structural studies on encapsulation of tetrahedral and octahedral anions by a protonated octaaminocryptand cage

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