Nonlinear Broensted correlations: The roles of resonance, solvation, and changing transition-state structure

Jencks, William P.; Brant, Steven R.; Gandler, Joseph R.; Fendrich, Gabriele; Nakamura, Charles E.

doi:10.1021/ja00389a027

Cited by 106 publications

(79 citation statements)

References 2 publications

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“…Hupe and Wu's [29] conclusion is that most of the curvatures in Brönsted plots of oxygen anions depends on the basicity of the oxygen bases rather than the difference in energies of the reactants and products. The same curvature is observed for correlations of several reactions of oxygen anions and elimination reactions [28,30].…”

Section: Reaction With Hydroxide Ion and Alkoxidessupporting

confidence: 73%

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Kinetics and mechanism of the reaction of N‐chlorosuccinimide with I⁻ and OH⁻

Agulla

Antelo

Arce

et al. 2005

Int J of Chemical Kinetics

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In this kinetic study of the reaction between the iodide ion and the Nchlorosuccinimide, we have found that the reaction is first order in N-chlorosuccinimide: namely, first order with respect to the iodide ion and first order with respect to the proton concentration. Based on the experimental results, we propose a mechanism consistent in Cl + transfer from the N-chlorosuccinimide to the iodide ion. We have found that the reaction presents general acid catalysis with a Brönsted exponent value of 0.10. In addition, given that the N-chlorocompounds are not stable in aqueous solution, we have carried out a study on the influence of bases in the presence of N-chlorosuccinimide. We have found that the reaction is first order in hydroxide ion, as well as in the 1,1,1,3,3,3-hexafluoroisopropanoxide ion and the 2,2,2-trifluorethoxide ion, which shows that the reaction is general-base catalyzed. C 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: [243][244][245][246][247][248][249][250][251][252] 2005

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Section: Reaction With Hydroxide Ion and Alkoxidessupporting

confidence: 73%

“…The study has been carried out in acidic solutions at five different temperatures: 16,20,25,30, and 40…”

mentioning

confidence: 99%

Kinetics and mechanism of the reaction of N‐chlorosuccinimide with I⁻ and OH⁻

Agulla

Antelo

Arce

et al. 2005

Int J of Chemical Kinetics

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“…What is not clear, however, is the extent to which this phenomenon accounts for the experimentallyobserved changes in transition-state Φ-values. A Hammond-postulate behavior has been invoked frequently (e.g., refs 27,30,32,53-58), perhaps improperly in many cases (23,52,59,60), in the context of organic-chemistry and protein-folding reactions.…”

Section: Discussionmentioning

confidence: 99%

Free-Energy Landscapes of Ion-Channel Gating Are Malleable: Changes in the Number of Bound Ligands Are Accompanied by Changes in the Location of the Transition State in Acetylcholine-Receptor Channels

Grosman

2003

Biochemistry

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Acetylcholine-receptor channels (AChRs) are allosteric membrane proteins that mediate synaptic transmission by alternatively opening and closing ('gating') a cation-selective transmembrane pore. Although ligand binding is not required for the channel to open, the binding of agonists (for example, acetylcholine) increases the closed ⇌ open equilibrium constant because the ion-impermeable → ion-permeable transition of the ion pathway is accompanied by a low → high affinity change at the agonist-binding sites. The fact that the gating conformational change of muscle AChRs can be kinetically modeled as a two-state reaction has paved the way to the experimental characterization of the corresponding transition state, which represents a snapshot of the continuous sequence of molecular events separating the closed and open states. Previous studies of fully (di-) liganded AChRs, combining single-channel kinetic measurements, site-directed mutagenesis, and data analysis in the framework of the linear free-energy relationships of physical organic chemistry, have suggested a transition-state structure that is consistent with channel opening being an asynchronous conformational change that starts at the extracellular agonist-binding sites and propagates towards the intracellular end of the pore. In this paper, I characterize the gating transition state of unliganded AChRs, and report a remarkable difference: unlike that of diliganded gating, the unliganded transition state is not a hybrid of the closed-and open-state structures but, rather, is almost indistinguishable from the open state itself. This displacement of the transition state along the reaction coordinate † This work was supported by grants from the National Institutes of Health (NS042169 to Claudio Grosman and NS23513 to Anthony Auerbach). 1 AChR acetylcholine receptor channelACh acetylcholine M2second transmembrane segment M3 third transmembrane segment 2 'Brönsted plot' is actually a misnomer. In the original work (15), the plotted rate and equilibrium constants correspond to two different reactions. However, the name is so widely used now to designate the rate-equilibrium type of plot used in this paper (rate and equilibrium constants correspond to the same reaction) that I decided to keep it.

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“…Thus, at pH 7.1, the concentration of alkoxide ions will decrease in the order 2'(3') > internal 2' > 5'. The Bronsted-type coefficient (flnuc) for attack on the Boc-Ala-Im by alkoxide is likely to be much less than 1.0 (Jencks et al 1982), so the observed rates of acylation by this mechanism at pH 7.1 should decrease in the same order. Buffer catalysis of attack by the 5' and internal-2' hydroxyl groups is not strong enough, even in 1.0 M imidazole, to raise the yield of either of these esters above that of the 2'(3') ester.…”

Section: Discussionmentioning

confidence: 99%

Stereoselective aminoacylation of a dinucleoside monophosphate by the imidazolides ofDl-alanine and N-(tert-butoxycarbonyl)-Dl-alanine

Profy

Usher

1984

J Mol Evol

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The aminoacylation of diinosine monophosphate (IpI) was studied. When the acylating agent was the imidazolide of N-(tert-butoxycarbonyl)-DL-alanine, a 40% enantiomeric excess of the L isomer was incorporated at the internal 2' site and the positions of equilibrium for the 2' in equilibrium with 3' migration reaction differed for the D and L enantiomers. The reactivity of the nucleoside hydroxyl groups decreased in the order 2'(3') greater than internal 2' greater than 5', and the extent of reaction was affected by the concentration of the imidazole buffer (pH 7.1). In contrast, reaction of IpI with the imidazolide of unprotected DL-alanine led to an excess of the D isomer at the internal 2' site, while reaction with the N-carboxy anhydride of DL-alanine proceeded without detectable stereoselection. The relevance of these results to the evolution of optical activity and the origin of genetically directed protein synthesis is discussed.

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Nonlinear Broensted correlations: The roles of resonance, solvation, and changing transition-state structure

Cited by 106 publications

References 2 publications

Kinetics and mechanism of the reaction of N‐chlorosuccinimide with I⁻ and OH⁻

Kinetics and mechanism of the reaction of N‐chlorosuccinimide with I⁻ and OH⁻

Free-Energy Landscapes of Ion-Channel Gating Are Malleable: Changes in the Number of Bound Ligands Are Accompanied by Changes in the Location of the Transition State in Acetylcholine-Receptor Channels

Stereoselective aminoacylation of a dinucleoside monophosphate by the imidazolides ofDl-alanine and N-(tert-butoxycarbonyl)-Dl-alanine

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Nonlinear Broensted correlations: The roles of resonance, solvation, and changing transition-state structure

Cited by 106 publications

References 2 publications

Kinetics and mechanism of the reaction of N‐chlorosuccinimide with I− and OH−

Kinetics and mechanism of the reaction of N‐chlorosuccinimide with I− and OH−

Free-Energy Landscapes of Ion-Channel Gating Are Malleable: Changes in the Number of Bound Ligands Are Accompanied by Changes in the Location of the Transition State in Acetylcholine-Receptor Channels

Stereoselective aminoacylation of a dinucleoside monophosphate by the imidazolides ofDl-alanine and N-(tert-butoxycarbonyl)-Dl-alanine

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Kinetics and mechanism of the reaction of N‐chlorosuccinimide with I⁻ and OH⁻

Kinetics and mechanism of the reaction of N‐chlorosuccinimide with I⁻ and OH⁻