CH–π and π–π Interactions as Contributors to the Guest Binding in Reversible Inclusion and Encapsulation Complexes

Ballester, Pablo; Biros, Shannon M.

doi:10.1002/9781119945888.ch3

Cited by 7 publications

(4 citation statements)

References 72 publications

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“…van der Waals forces rangef rom 2t o4kJ mol À1 ,v alues of 2, 3, and 4w ere assigned for weak ( ), moderate (<), and strong (! )i nteractions, hydrogen bonds strengthr anges from 2t o4 0s o the average value of 21 wasa ssigned, and nitroÀp interactions rangef rom 10 to 52, so an average value of 31 was assigned;f or face-to-face pÀp interactions av alue of 6.7 kJ mol À1 [15] wasu sed] can be calculatedb ys umming the interactions per molecule. When this was plotted against published drop height data, an experimental measurement of stability, ar easonable relationship was observed ( Figure 2).…”

Section: Resultsmentioning

confidence: 99%

Stabilization of Nitro‐Aromatics

Deschamps

Parrish

2015

Propellants Explo Pyrotec

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For a variety of reasons, including U.S. Federal law and improved safety, it is desirable to have insensitive munitions (IM). Although a variety of methods are available to reduce the sensitivity of munitions only changes to the high explosive (HE) itself result in increased safety during storage, transportation, handling, and deployment. As a result of this IM are almost always filled with fire resistant, shock resistant insensitive HE such as triaminotrinitrobenzene (TATB). The high cost of TATB has limited its use. In this study we examine 28 nitro‐aromatics, including TATB and five previously unpublished structures, in the solid state in order to identify forces that stabilize the HE. We show that the sum of forces involved in crystal packing (i.e. the estimated energy of stabilization) has a direct relationship to the observed sensitivity of nitro‐aromatic explosives.

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Section: Resultsmentioning

confidence: 99%

Stabilization of Nitro‐Aromatics

Deschamps

Parrish

2015

Propellants Explo Pyrotec

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“…However, and as stated above, the occurrence of multiple CH-π interactions in a supramolecular assembly renders them quite important in terms of total energy and preferred structure. Consequently, CH-π interactions have been described to play important roles in a variety of phenomena including molecular recognition, crystal engineering and the structure of many biomolecules [4,5,6,7].…”

Section: Introductionmentioning

confidence: 99%

Quantification of CH-π Interactions Using Calix[4]pyrrole Receptors as Model Systems

et al. 2015

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Abstract:We describe the use of two series of aryl-extended calix [4]pyrrole receptors bearing two and four electronically tunable phenyl groups, respectively, in their meso-positions as model systems for the quantification of CH-π interactions in solution. The "four-wall" and the "two-wall" receptors formed thermodynamically stable 1:1 complexes in acetonitrile solution with both trimethylamine N-oxide and trimethylphosphine P-oxide as guests. The complexes were mainly stabilized by the formation of four convergent hydrogen bonds between the oxygen atom of the guests and the pyrrole NHs of the host. In general, the N-oxide produced thermodynamically more stable hydrogen bonding interactions than the P-oxide. Upon guest binding, the receptors adopted the cone conformation and the methyl groups of the included guests engaged in CH-π interactions with the aromatic walls. We show that the modification of the electronic properties of the aromatic surfaces, in any of the receptor series, did not have a significant impact in the measured binding affinities for a given guest. However, the larger binding affinities determined for the "four-wall" receptors in comparison to the "two-wall" counterparts supported the importance of CH-π interactions on guest complexation. The strength of the CH-π interactions present in the inclusion complexes was quantified employing the octamethyl calix[4]pyrrole as reference. We determined an average magnitude of ~1 kcal·mol

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“…The aryl plane of Phe427 from each protomer is parallel to the central axis of the PA pore. Neighboring Phe427 residues interact with each other by aromatic CH-π interaction in a tilted T-shaped configuration 27 and possibly by hydrophobic interaction, thus forming the Φ-clamp ( Fig. 4 , Extended Data Fig.…”

mentioning

confidence: 99%

Atomic structure of anthrax protective antigen pore elucidates toxin translocation

Jiang

Pentelute

Collier

et al. 2015

Nature

226

297

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SummaryAnthrax toxin, comprising protective antigen (PA), lethal factor (LF) and edema factor (EF), is the major virulence factor of Bacillus anthracis, an agent that causes high mortality in human and animals. PA forms oligomeric prepores that undergo conversion to membrane-spanning pores by endosomal acidification, and these pores translocate the enzymes LF and EF into the cytosol of target cells1. PA is not only a vaccine component and therapeutic target for anthrax infections but also an excellent model system for understanding the mechanism of protein translocation. Based on biochemical and electrophysiological results, researchers have proposed that a Φ-clamp composed of Phe427 residues of PA catalyzes protein translocation via a charge-state dependent Brownian ratchet2–9. Although atomic structures of PA prepores are available10–14, how PA senses low pH, converts to active pore and translocates LF and EF are not well defined without an atomic model of the PA pore. Here, by cryo electron microscopy (cryoEM) with direct electron counting, we have determined the PA pore structure at 2.9-Å resolution. The structure reveals the long-sought-after catalytic Φ-clamp and the membrane-spanning translocation channel, and supports the Brownian ratchet model for protein translocation. Comparisons of four structures reveal conformational changes in prepore to pore conversion that support a multi-step mechanism by which low-pH is sensed and the membrane-spanning channel is formed.

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CH–π and π–π Interactions as Contributors to the Guest Binding in Reversible Inclusion and Encapsulation Complexes

Cited by 7 publications

References 72 publications

Stabilization of Nitro‐Aromatics

Stabilization of Nitro‐Aromatics

Quantification of CH-π Interactions Using Calix[4]pyrrole Receptors as Model Systems

Atomic structure of anthrax protective antigen pore elucidates toxin translocation

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