Structures of dimethylammonium metal(III) sulfate hexahydrates (metal = Al, Cr)

Summary The TolC protein of Escherichia coli comprises an outer membrane β‐barrel channel and a contiguous α‐helical tunnel spanning the periplasm, providing an exit duct for protein export and multidrug efflux. It forms a single transmembrane pore that is open to the outside of the cell but constricted at the peri‐plasmic tunnel entrance. This sole constriction is lined by a ring of six aspartate residues, two in each of the three identical monomers. When these were replaced by alanines, the resulting TolCDADA protein reconstituted normally in black lipid membranes but showed altered electrophysiological characteristics. In particular, it had lost the strong pH dependence of the wild type and had switched ion selectivity from cations to anions. The function of wild‐type TolC as a membrane pore was severely inhibited by divalent and trivalent cations entering the channel tunnel from the channel (‘extracellular’) side. Divalent cations bound reversibly to effect complete blocking of the transmembrane ion flux. Trivalent cations were more potent. Hexamminecobalt bound at nanomolar concentrations allowed visualization of single blocking events, whereas the smaller Cr3+ cation bound irreversibly and could also access the cation binding site via the tunnel entrance. The inhibitory cations had no effect on the mutant TolCDADA, supporting the view that the aspartate ring is the cation binding site. The electronegative entrance is widely conserved throughout the TolC family, which is essential for efflux and export by Gram‐negative bacteria, suggesting that it could present a general target for drugs.

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“… b. Cr 3+ exists in water as Cr(H 2 O) 6 3+ with a Cr–O distance of between 1.94 and 1.98 Å (Galesic and Jordanovska, 1992). …”

Section: Resultsmentioning

confidence: 99%

An aspartate ring at the TolC tunnel entrance determines ion selectivity and presents a target for blocking by large cations

Andersen

Koronakis

Hughes

et al. 2002

Molecular Microbiology

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“…A great interest has been shown in some double sulphates of trivalent metal with monovalent aliphatic ammonium cations because of their ferroelastic and ferroelectric properties [1][2][3][4][5]. So far, there are few data on double sulphates of divalent metal cation with mono or divalent organic cations [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Synthesis, crystal structure, phase transition and thermal behaviour of a new dabcodiium hexaaquanickel(II) bis(sulphate), (C6H14N2)[Ni(H2O)6](SO4)2

Rekik¹,

Naı̈li²,

Bataille³

et al. 2006

Journal of Organometallic Chemistry

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Section: Introductionmentioning

confidence: 99%

“…In particular a detailed structural investigation was undertaken in order to explain the occurrence of macroscopic polarization in this compound [8][9]. It has been ascertained that DMAAS in the paraelectric phase is monoclinic, P2 1 /n with lattice constants a = 6.408 Å, b = 10.752 Å, c = 11.134 Å and β = 100.44° [8]. In this structure, aluminum atoms are coordinated octahedrally by six water molecules which form strong hydrogen bonds O-H...O (length 2.55-2.70 Å) with the oxygen's of the sulfate anion, and dimethylammonium cations are disordered [9].…”

Section: Introductionmentioning

confidence: 99%

Dielectric and spectral properties of DMAAS ferroelectric crystals doped with chromium

Kapustianik

Czapla

Tchukvinskyi

et al. 2004

phys. stat. sol. (a)

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This paper presents the results of investigations of the dielectric and spectral properties of NH 2 (CH 3 ) 2 Al(SO 4 ) 2 × 6 H 2 O crystals doped with chromium. In particular, it is shown that the dopant noticeably changes the temperature of ferroelectric phase transition and corresponding thermal dipole relaxation with a critical slowing-down at T c1 . The Cr 3+ ions were used as a convenient probe for investigations of crystalline structure. On the basis of absorption and luminescence spectroscopy and resonance Raman scattering study it has been shown that the metal-hydrate complexes in the investigated crystals possess the considerably distorted octahedral shape.

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Structures of dimethylammonium metal(III) sulfate hexahydrates (metal = Al, Cr)

Abstract: Introduction. Trivalent metal cations (most often A13+ and Cr 3+) form not only a variety of double sulfates with univalent alkaline and ammonium cations, but also with univalent guanidinium and

Cited by 18 publications

References 8 publications

An aspartate ring at the TolC tunnel entrance determines ion selectivity and presents a target for blocking by large cations

An aspartate ring at the TolC tunnel entrance determines ion selectivity and presents a target for blocking by large cations

Synthesis, crystal structure, phase transition and thermal behaviour of a new dabcodiium hexaaquanickel(II) bis(sulphate), (C6H14N2)[Ni(H2O)6](SO4)2

Dielectric and spectral properties of DMAAS ferroelectric crystals doped with chromium

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