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Hu SZ, Zhou ZH, Robertson BE. Consistent approaches to van der Waals radii for the metallic elements. ACTA ACUST UNITED AC 2009. [DOI: 10.1524/zkri.2009.1158] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
AbstractDue to the paucity of data on non-bonding interactions for metal atoms, no complete tabulation is available for crystallographic van der Waals radii for metallic elements. In this work several sets of van der Waals radii for metal atoms are derived indirectly. Unique data resources used for the derivation are (i) average volumes of elements in crystals, (ii) single covalent radii, (iii) Allinger´s van der Waals radii, as well as (iv) bond valence parameters formetal-oxygenbonds. The van der Waals radii for metal atoms deduced from these various approaches are basically comparable with each other, but are strikingly different from those from Bondi’s system of van der Waals radii. A complete set of new values for metallic elements up to Am, derived from bond valence parameters, are recommended.
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Guttormson RJ, Rutherford JS, Robertson BE, Russell DB. Nitrosodisulfonates and hydroxylamine-N,N-disulfonates. II. Crystal structure of a rubidium hydroxylamine-N,N-disulfonate. Inorg Chem 2002. [DOI: 10.1021/ic50139a004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Brown KC, Nelson BR, Quail JW, Robertson BE, Weil JA, Zimpel Z. The structure and some molecular properties of acetone-picrylhydrazone. CAN J CHEM 1999. [DOI: 10.1139/v99-121] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Various physical measurements and quantum-mechanical computations to characterize molecular 2-propanone(2,4,6-trinitrophenyl)hydrazone, alias acetone-picrylhydrazine (AH), are reported, including an X-ray diffraction structural determination, an1H and13C NMR study of its internal hindered reorientation, and a theoretical (SCF-MO) interpretation of these observations. The structure of AH was determined by X-ray crystallography. The space group is Pbar over 1, with a = 10.1768(9) Å, b = 7.7968(18) Å, c = 8.0018(5) Å, α = 92.102(6)°, β = 99.919(7)°, γ = 105.926(6)°, Z = 2, wR2(F2) = 0.1995 based on all 2748 unique reflections. The (picryl) proton NMR thermal work yielded a Gibbs activation energy ΔG= 46.9 ± 0.4 kJ mol-1in acetone-d6and 48.1 ± 0.2 kJ mol-1in chloroform-d, whereas13C NMR (two pairs in the picryl ring) yielded 46.6 ± 1.0 and 46.4 ± 1.0 kJ mol-1in acetone-d6. The SCF-MO computations yielded a detailed model of the conformerization path. Various model conformations and tautomers of AH have been considered, as has removal of H+or of H0from its hydrazinic linkage.Key words: dynamic NMR, picrylhydrazone, hindered rotation, activation parameters, SCF-MO model.
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Robertson BE. Inhibition of calcium-activated chloride channels by niflumic acid dilates rat cerebral arteries. ACTA PHYSIOLOGICA SCANDINAVICA 1998; 163:417-8. [PMID: 9789585 DOI: 10.1046/j.1365-201x.1998.t01-1-00366.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Barton RJ, Major Q, Mihichuk LM, Robertson BE, Seip C. trans-Chlorobis(diphenylglyoximato)(tri-n-butylphosphine)cobalt(III). Acta Crystallogr C 1997. [DOI: 10.1107/s010827019601565x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Robertson BE, Bonev AD, Nelson MT. Inward rectifier K+ currents in smooth muscle cells from rat coronary arteries: block by Mg2+, Ca2+, and Ba2+. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 271:H696-705. [PMID: 8770113 DOI: 10.1152/ajpheart.1996.271.2.h696] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Inward rectifier K+ channels have been implicated in the control of membrane potential and external K(+)-induced dilations of small coronary arteries. To identify and characterize inward rectifier K+ currents in coronary artery smooth muscle, whole cell K+ currents in smooth muscle cells enzymatically isolated from rat coronary (septal) arteries (diameters, 100-150 microns) were measured in the conventional and perforated configurations of the patch-clamp technique. Ba(2+)-sensitive, whole cell K+ current-voltage relationships exhibited inward rectification. Blockers of Ca(2+)-activated K+ channels (1 mM tetraethylammonium ion), ATP-sensitive K+ channels (10 microM glibenclamide), and voltage-dependent K+ channels (1 mM 4-aminopyridine) in smooth muscle did not affect inward rectifier K+ currents. The nonselective K+ channel inhibitor phencyclidine (100 microM) reduced inward rectifier K+ currents by approximately 50%. External Ba2+ reduced inward currents, with membrane potential hyperpolarization increasing inhibition. The half-inhibition constant for Ba2+ was 2.1 microM at -60 mV, decreasing e-fold for a 25-mV hyperpolarization. External Cs+ also blocked inward rectifier K+ currents, with the half-inhibition constant for Cs+ of 2.9 mM at -60 mV. External Ca2+ and Mg2+ reduced inward rectifier K+ currents. At -60 mV, Ca2+ and Mg2+ (1 mM) reduced inward currents by 33 and 21%, respectively. Inward rectification was not affected by dialysis of the cell's interior with a nominally Ca(2+)- and Mg(2+)-free solution. These findings indicate that inward rectifier K+ channels exist in coronary artery smooth muscle and that Ba2+ may be a useful probe for the functional role of inward rectifier K+ channels in coronary arteries.
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Robertson BE, Nelson MT. Aminopyridine inhibition and voltage dependence of K+ currents in smooth muscle cells from cerebral arteries. THE AMERICAN JOURNAL OF PHYSIOLOGY 1994; 267:C1589-97. [PMID: 7810600 DOI: 10.1152/ajpcell.1994.267.6.c1589] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Voltage-dependent K+ currents were characterized using the patch-clamp technique in smooth muscle cells isolated from rabbit cerebral (basilar) arteries. This study focused on the voltage dependence and the pharmacology of these K+ currents, since this information will be useful for the investigation of the role of the voltage-dependent K+ channels in arterial function. Currents through Ca(2+)-activated K+ (KCa) channels were minimized by buffering intracellular Ca2+ to low levels and by blockers (tetraethylammonium and iberiotoxin) of these channels. Membrane depolarization increased K+ currents, independent of changes in the driving force for K+ movement. With 140 mM internal and external K+, activation of K+ currents by membrane depolarization was half maximal at about -10 mV and increased as much as e-fold per 11 mV. Inactivation also depended on voltage, with a midpoint at -44 mV. 3,4-Diaminopyridine (3,4-DAP),4-aminopyridine(4-AP),3-amino-pyridine(3-AP), and 2-aminopyridine (2-AP) inhibited voltage-dependent K+ currents. At 0 mV, 3,4-DAP, 4-AP, 3-AP, and 2-AP (5 mM) inhibited the K+ currents by 84, 66, 36, and 8%, respectively. Phencyclidine (100 microM) inhibited the current by 53% at 0 mV. Steady-state whole cell currents through these channels were measured at physiological membrane potentials. At -40 mV, 4-AP (5 mM) reduced the steady-state outward current by 2.5 pA. These results are consistent with the idea that voltage-dependent K+ channels are involved in the regulation of the membrane potential of arterial smooth muscle.
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Albarwani S, Robertson BE, Nye PC, Kozlowski RZ. Biophysical properties of Ca(2+)- and Mg-ATP-activated K+ channels in pulmonary arterial smooth muscle cells isolated from the rat. Pflugers Arch 1994; 428:446-54. [PMID: 7838666 DOI: 10.1007/bf00374564] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A novel class of Ca(2+)-activated K+ channel, also activated by Mg-ATP, exists in the main pulmonary artery of the rat. In view of the sensitivity of these "KCa,ATP" channels to such charged intermediates it is possible that they may be involved in regulating cellular responses to hypoxia. However, their electrophysiological profile is at present unknown. We have therefore characterised the sensitivity of KCa,ATP channels to voltage, intracellular Ca2+ ([Ca2+]i) and Mg-ATP. They have a conductance of 245 pS in symmetrical K+ and are approximately 20 times more selective for K+ ions than Na+ ions, with a K+ permeability (PK) of 4.6 x 10(-13) cm s-1.Ca2+ ions applied to the intracellular membrane surface of KCa,ATP channels causes a marked enhancement of their activity. This activation is probably the result of simultaneous binding of at least two Ca2+ ions, determined using Hill analysis, to the channel or some closely associated protein. This results in a shift of the voltage activation threshold to more hyperpolarized membrane potentials. The activation of KCa,ATP channels by Mg-ATP has an EC50 of approximately 50 microM. Although the EC50 is unaffected by [Ca2+]i, channel activation by Mg-ATP is enhanced by increasing [Ca2+]i. One possible interpretation of these data is that Mg-ATP increases the sensitivity of KCa,ATP channels to Ca2+. It is therefore possible that under hypoxic conditions, where lower levels of Mg-ATP may be encountered, the sensitivity of KCa,ATP channels to Ca2+ and therefore voltage is reduced.(ABSTRACT TRUNCATED AT 250 WORDS)
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Robertson BE, Schubert R, Hescheler J, Nelson MT. cGMP-dependent protein kinase activates Ca-activated K channels in cerebral artery smooth muscle cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 265:C299-303. [PMID: 8338137 DOI: 10.1152/ajpcell.1993.265.1.c299] [Citation(s) in RCA: 490] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Guanosine-3',5'-cyclic monophosphate (cGMP)-dependent protein kinase (cGMP-PK) plays a central role in the mediation of the vasodilator response to nitric oxide (NO) and other nitrovasodilators. It is unclear whether cGMP-PK affects calcium-activated potassium channels (KCa channels) or any other type of ion channel in smooth muscle. We provide here the first direct evidence that cGMP-PK can activate KCa channels in arterial smooth muscle cells. We demonstrate that NO and a membrane-permeable analogue of cGMP can activate KCa channels in on-cell patches approximately twofold. Furthermore, cGMP-PK, in the presence of ATP and cGMP added directly to the intracellular surface of inside-out patches, increases channel activity by approximately eightfold. These results suggest that cGMP-PK-mediated activation of KCa channels may contribute to the actions of NO and other nitrovasodilators.
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Zhan Y, Barton RJ, Robertson BE. Structure of 2,3-naphthalenediamine dihydrochloride dihydrate. Acta Crystallogr C 1993. [DOI: 10.1107/s0108270192004736] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Robertson BE, Kozlowski RZ, Nye PC. Opposing actions of tolbutamide and glibenclamide on hypoxic pulmonary vasoconstriction. ACTA ACUST UNITED AC 1993; 102:459-62. [PMID: 1360355 DOI: 10.1016/0742-8413(92)90143-u] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
1. We show that cromakalin and diazoxide, drugs that activate ATP-sensitive potassium (KATP) channels, abolish hypoxic pulmonary vasoconstriction (HPV) of isolated, perfused rat lungs. 2. Glibenclamide, an inhibitor of these channels, does not affect HPV, but it reverses the relaxation caused by cromakalim and diazoxide. 3. Tolbutamide, which has effects similar to glibenclamide in other tissues, paradoxically abolishes HPV, an effect reversed by glibenclamide. 4. These results suggest that: (i) pulmonary vessels contain KATP channels which are normally closed and are not opened by levels of hypoxia that cause constriction, (ii) tolbutamide acts on the pulmonary vasculature by a mechanism which differs from that of glibenclamide.
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Robertson BE, Corry PR, Nye PC, Kozlowski RZ. Ca2+ and Mg-ATP activated potassium channels from rat pulmonary artery. Pflugers Arch 1992; 421:94-6. [PMID: 1528724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have observed a novel class of calcium-activated potassium channel which is activated by physiological levels of intracellular ATP. These KCa,ATP channels are found on smooth muscle cells isolated from the pulmonary artery. Since their activation by ATP is Mg2+ dependent and is poorly evoked by non- or slowly-hydrolyzed ATP analogues, we conclude that it involves phosphorylation. We suggest that in hypoxia a reduction of intracellular ATP may reduce KCa,ATP channel activity and thereby tend to depolarize the cells. This effect would increase Ca2+ entry through voltage-activated Ca2+ channels and contribute to vasoconstriction.
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Manocha SK, Mihichuk LM, Barton RJ, Robertson BE. Synthesis and structure of (CH3)2AsC(CF3)=C(CF3)As(CH3)2W(CO)2Br2P(C6H5)3. Erratum. Acta Crystallogr C 1992. [DOI: 10.1107/s0108270191013070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Warren JB, Donnelly LE, Cullen S, Robertson BE, Ghatei MA, Bloom SR, MacDermot J. Pituitary adenylate cyclase-activating polypeptide: a novel, long-lasting, endothelium-independent vasorelaxant. Eur J Pharmacol 1991; 197:131-4. [PMID: 1915565 DOI: 10.1016/0014-2999(91)90511-n] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The vasoactivity of the 27- and 38-amino acid forms of the novel peptide pituitary adenylate cyclase-activating polypeptide (PACAP) was tested in vitro. Both forms of PACAP caused endothelium-independent vasodilation (assayed by their vasodilator action on rabbit aorta). When superfused for 1 min the relaxation EC50 of PACAP27 was 23 +/- 8 nM and of PACAP38 was 152 +/- 66 nM. PACAP was 100-fold more potent than vasoactive intestinal polypeptide (VIP) (PACAP27 shows 68% amino acid sequence homology with VIP), and had a prolonged duration of action, a 1 min exposure to 1 microM PACAP27 lasting 135 +/- 7 min and to 1 microM PACAP38 108 +/- 3 min. Adenylate cyclase activity in homogenates of rabbit aortic smooth muscle cells was increased by PACAP27 and PACAP38 with EC50s of 4.4 and 0.73 nM, respectively. PACAP27 and PACAP38 are potent, long-lasting, endothelium-independent vasodilators.
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Manocha SK, Mihichuk LM, Barton RJ, Robertson BE. Synthesis and structure of (CH3)2AsC(CF3)=C(CF3)As(CH3)2W(CO)2Br2P(C6H5)3. Acta Crystallogr C 1991. [DOI: 10.1107/s0108270190010423] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Wang H, Barton RJ, Robertson BE. Structure of cis-diacetonitrile[ferrocenylbis(diphenylphosphine)]rhodium(I) perchlorate acetonitrile solvate. Acta Crystallogr C 1991. [DOI: 10.1107/s0108270190009386] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Dong N, Wang H, Barton RJ, Robertson BE. Synthesis, Structure and Spectroscopy of the Complexes Tetrakis μ-Trichloroacetato)Bis[Trichloroacetato-Ethanol-(1,10-Phenanthroline-N,N')LN(III)] (LN = Pr, Nd and Er). J COORD CHEM 1990. [DOI: 10.1080/00958979009408215] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Luo Y, Barton RJ, Robertson BE. Structure of 2-(1-hydroxyethyl)-1-ferrocenecarboxylic acid methyl ester. Acta Crystallogr C 1990. [DOI: 10.1107/s0108270189012539] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Robertson BE, Warren JB, Nye PC. Inhibition of nitric oxide synthesis potentiates hypoxic vasoconstriction in isolated rat lungs. Exp Physiol 1990; 75:255-7. [PMID: 2340164 DOI: 10.1113/expphysiol.1990.sp003399] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We have investigated the influence of endogenous nitric oxide (NO) on the vascular resistance of isolated rat lungs by inhibiting its synthesis with the false substrate N-monomethyl-L-arginine (L-NMMA). When perfused with blood at constant flow the addition of L-NMMA (10(-3) M) did not affect pulmonary arterial pressure in hyperoxia but did increase the response to hypoxia (PO2 25-35 mmHg) by 2.5 +/- 0.2 fold (mean +/- S.E.M.). The effect of L-NMMA was reversed by 3 x 10(-3) M-L-arginine, the true substrate for NO synthesis. Thus NO is an important pulmonary vasodilator but hypoxic vasoconstriction does not result from a reduction of its background release.
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Robertson BE, Paterson DJ, Peers C, Nye PC. Tolbutamide reverses hypoxic pulmonary vasoconstriction in isolated rat lungs. QUARTERLY JOURNAL OF EXPERIMENTAL PHYSIOLOGY (CAMBRIDGE, ENGLAND) 1989; 74:959-62. [PMID: 2594946 DOI: 10.1113/expphysiol.1989.sp003369] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We have investigated the effects of tolbutamide on the hypoxic vasoconstriction of isolated, perfused rat lungs. We did this because lowered ATP may link hypoxia and constriction, and tolbutamide mimics the effects of ATP in other tissues by blocking ATP-sensitive potassium (ATP-K) channels. Pulmonary vasoconstriction, induced by lowering the oxygen of the gas ventilating the lungs from 95 to 2%, was always reduced or abolished by tolbutamide (1.7 x 10(-4)-8.5 x 10(-3) M). High concentrations (greater than or equal to 10(-3) M) of diazoxide, a drug that opens ATP-K channels, dramatically constricted the pulmonary vasculature and this effect was also reversed by tolbutamide. The opening of ATP-K channels may therefore underlie hypoxic pulmonary vasoconstriction.
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Gopal R, Robertson BE, Rutherford JS. Adamantane inclusion complexes with thiourea and selenourea. Acta Crystallogr C 1989. [DOI: 10.1107/s010827018801114x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Schwarzenbach D, Abrahams SC, Flack HD, Gonschorek W, Hahn T, Huml K, Marsh RE, Prince E, Robertson BE, Rollett JS, Wilson AJC. Statistical descriptors in crystallography: Report of the IUCr Subcommittee on Statistical Descriptors. Acta Crystallogr A 1989. [DOI: 10.1107/s0108767388009596] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Zhan Y, Luo Y, Barton RJ, Robertson BE. Structure of 2-methylnaphthimidazolium chloride dihydrate. Acta Crystallogr C 1988. [DOI: 10.1107/s0108270188001635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Robertson BE, Schlemper EO, Ross FK, Fair CK, Rutherford JS. Nitrosodisulfonates and hydroxylamine-N,N-disulfonates. VI. A neutron diffraction study of the 'symmetry-free' very short hydrogen bonds in K5[H{ON(SO3)2}]2.H2O. ACTA CRYSTALLOGRAPHICA SECTION B: STRUCTURAL SCIENCE 1988. [DOI: 10.1107/s0108768188000461] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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