Imperial College London

ProfessorJanetPowell

Faculty of MedicineDepartment of Surgery & Cancer

Visiting Professor
 
 
 
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Contact

 

+44 (0)20 3311 7312j.powell

 
 
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Location

 

4E05Charing Cross HospitalCharing Cross Campus

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Summary

 

Publications

Publication Type
Year
to

447 results found

BREW K, POWELL JT, 1976, SUBSTRATE-DEPENDENT PROTEIN-PROTEIN INTERACTIONS IN REGULATION OF LACTOSE SYNTHASE, FEDERATION PROCEEDINGS, Vol: 35, Pages: 1892-1898, ISSN: 0014-9446

Journal article

POWELL JT, BREW K, 1976, COMPARISON OF INTERACTIONS OF GALACTOSYLTRANSFERASE WITH A GLYCOPROTEIN SUBSTRATE (OVALBUMIN) AND WITH ALPHA-LACTALBUMIN, JOURNAL OF BIOLOGICAL CHEMISTRY, Vol: 251, Pages: 3653-3663, ISSN: 0021-9258

Journal article

POWELL JT, BREW K, 1976, METAL-ION ACTIVATION OF GALACTOSYLTRANSFERASE, JOURNAL OF BIOLOGICAL CHEMISTRY, Vol: 251, Pages: 3645-3652, ISSN: 0021-9258

Journal article

SEBER JF, TOOMEY TP, POWELL JT, BREW K, AWAD WMet al., 1976, PROTEOLYTIC-ENZYMES OF K-1 STRAIN OF STREPTOMYCES-GRISEUS OBTAINED FROM A COMMERCIAL PREPARATION (PRONASE) - PURIFICATION AND CHARACTERIZATION OF CARBOXYPEPTIDASE, JOURNAL OF BIOLOGICAL CHEMISTRY, Vol: 251, Pages: 204-208, ISSN: 0021-9258

Journal article

POWELL JT, BREW K, 1975, INTERACTION OF ALPHA-LACTALBUMIN AND GALACTOSYLTRANSFERASE DURING LACTOSE SYNTHESIS, JOURNAL OF BIOLOGICAL CHEMISTRY, Vol: 250, Pages: 6337-6343, ISSN: 0021-9258

Journal article

SMITH CA, POWELL JT, BREW K, 1975, PUROMYCIN DOES NOT INACTIVATE GALACTOSYLTRANSFERASE OF GOLGI MEMBRANES, BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, Vol: 62, Pages: 621-626, ISSN: 0006-291X

Journal article

POWELL JT, BREW K, 1974, PREPARATION AND CHARACTERIZATION OF 2 FORMS OF BOVINE GALACTOSYL TRANSFERASE, EUROPEAN JOURNAL OF BIOCHEMISTRY, Vol: 48, Pages: 217-228, ISSN: 0014-2956

Journal article

POWELL JT, BREW K, 1974, GLYCOSYLTRANSFERASES IN GOLGI MEMBRANES OF ONION STEM, BIOCHEMICAL JOURNAL, Vol: 142, Pages: 203-&, ISSN: 0264-6021

Journal article

Powell JT, Richards EG, 1972, Specific effects of Li+ on stacking equilibria in polynucleotides., Biochim Biophys Acta, Vol: 281, Pages: 145-151, ISSN: 0006-3002

Journal article

Powell JT, Richards EG, Gratzer WB, 1972, The nature of stacking equilibria in polynucleotides., Biopolymers, Vol: 11, Pages: 235-250, ISSN: 0006-3525

Journal article

BRIGHT A, NICHOLSON JK, POWELL J, SHAW BL, MALONE JFet al., 1971, PRODUCTS FORMED FROM RHODIUM TRICHLORIDE TRIHYDRATE AND ALLYL ALCOHOL OR DIALLYL ETHER - CRYSTAL AND MOLECULAR STRUCTURE OF [RH2CL4(C6H11O)2], CH3OH, JOURNAL OF THE CHEMICAL SOCIETY D-CHEMICAL COMMUNICATIONS, Pages: 712-+

Journal article

Powell J, Shaw BL, 1968, Transition metal-carbon bonds. Part XVI. Cationic allylic complexes of palladium(II). A cationic allylic complex of platinum(II), Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 774-777, ISSN: 0022-4944

In aqueous acetone [Pd2Cl2(2-methylallyl) 2] reacts with PPh3 to give the colourless cation [Pd(2-methylallyl)(PPh3)2]+, isolated as its tetraphenylborate salt. Similar complexes with PMe2Ph and AsMe 2Ph were prepared. Treatment of [PdCl2(PPh 3)2] with 2-methylallylmagnesium chloride followed by hydrolysis gave the hydrated chloride [Pd(2-methylallyl)(PPh3) 2]Cl·2H2O. Attempts to prepare analogous complexes with other allylic ligands were unsuccessful. N.m.r. data show the 2-methylallyl ligands in these cations to be symmetrically π-bonded to the palladium. Conductimetric studies on systems of the type [Pd2X2 all2] + x mol. of L have shown that the tendency to form ionic species decreases (1) for different ligands L in the order PMe2Ph ∼ PEt2Ph ∼ PEt3 > PPh3 > AsPh3 > SbPh3 > pyridine; (2) for different allyl ligands 'all' in the order 2-methylallyl > allyl > 1-methylallyl > 1,3-dimethylallyl > 1,1-dimethylallyl; and (3) for different halogens X in the order Cl > Br > I. Compounds of the type [Pd2Cl2 all2] react rapidly with an excess of PPh3 in aqueous acetone to give [Pd(PPh3)4] and [all PPh3] + Cl-. Treatment of [Pd(PPh3)4] with an excess of the allylic chloride gives [PdCl all PPh3]. Treatment of [PtCl2(AsMe2Ph)2] with 2- methylallylmagnesium chloride followed by water and NaBPh4 gave the salt [Pt(2-methylallyl)(AsMe2Ph)2]+ BPh 4-.

Journal article

Powell J, Shaw BL, 1968, Transition metal-carbon bonds. Part XV. A crotyl-butadiene-rhodium(III) complex and related complexes, Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 597-599, ISSN: 0022-4944

Butadiene reacts with rhodium trichloride in methanol to give a crotyl, butadiene-bridged, chloro-bridged complex, [C4H7RhCl 2(C4H6)RhCl2C4H 7]. The complex reacts with pyridine to give [RhCl 2(1-methylallyl)(py)2] and with cyclopentadienylthallium to give [RhCl(1-methylallyl)(C5H5)], both with evolution of butadiene. The complex [C4H7RhCl2(C 4H6)RhCl2(C4H7)] is also formed by the oxidative addition of 1-methyallyl chloride to [RhCl(C 4H6)2] or by treating [Rh2Cl 2(C2H4)4] successively with 1-methylallyl chloride then with butadiene; this method was also used to synthesise the corresponding allyl and 2-methylallyl complexes, [Rh 2Cl4(all)2(C4H6)] (all = allyl or 2-methylallyl). An allyl alcohol complex [Rh2Cl 4(Allyl)2(C3H5OH)2] has also been prepared. N.m.r. and infrared data are given.

Journal article

Powell J, Shaw BL, 1968, Transition metal-carbon bonds. Part XIV. Allylic complexes of rhodium, Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 583-596, ISSN: 0022-4944

A convenient synthesis of complexes of the type [Rh2Cl 2(all)4] (all = allyl, 1-methyl-, 2-methyl-, or 2-chloro-allyl) is described from the oxidative hydrolysis of [Rh 2Cl2(CO)4] in the presence of an allylic chloride (allCl) in aqueous methanol. If the synthesis is carried out in the presence of potassium hydroxide the reactions are much faster and the yields higher; [Rh2Cl2(1-phenylallyl)4] was prepared by this method. With 2-methylallyl chloride and [Rh2Cl 2(CO)4] reacting in aqueous methanol at ca. 0° the major product is [Rh2Cl2(2-methylallyl)4] but at 60° only [Rh2Cl2(2,5-dimethylhexa-1,5-diene) 2] was isolated. Deuteriation and other studies show that reversible protonation of the 2-methylallyl groups plays an essential part in the formation of the 2,5-dimethylhexa-1,5-diene ligand. Complexes of the type [Rh 2Cl2(all)4] contain asymmetrically bonded allylic groups, the nature of which is discussed. Some complexes of the type [Rh2Cl2(all)4] react with alcoholic potassium hydroxide to give an olefin (allH). They can also be used to prepare complexes of the types: [Rh2X2(all)4] (X = Br, I, or Ac); [RhCl(all)2L] and [Rh(all)2py2]+ (L = py, PR3, or AsR3); [RhCl(PPh3)3]; [Rh2Cl2(cyclo-octa-1,5-diene)]; [Rh(acac)(all) 2]; [Rh(σ-all)(π-all)(C5H5)]; [RhCl2(all)]x and [Rh(all)3]. [Rh(all) 3] reacts with Na2PdCl4 to give [Rh 2Cl2(all)4] and [Pd2Cl 2(all)2], or with PPh3 to give [Rh(all)(PPh3)2]. Complexes of the types [RhCl 2(all)L2] (L = py or PMe2Ph) and [Rh 2Cl4(all)2(CO)2], and the complex [RhCl2(C5H5)]x are described. Near-infrared, far-infrared, and nuclear magnetic resonace data are given and discussed.

Journal article

Powell J, Shaw BL, 1968, The relative rates of neutral ligand exchange reactions in some complex iridium(III) hydrides and halides. Iridium(III) hydrido- and halogeno-complexes containing two different tertiary phosphine and/or tertiary arsine ligands, Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 617-622, ISSN: 0022-4944

The tertiary phosphine or tertiary arsine ligands (L) in trans-position to hydride in complexes of the type [IrHCl2L3] configuration (I), is labile towards substitution by the strongly bonding phosphine, PMe 2Ph, the other two neutral ligands (L) being inert. Complexes of the type [IrHCl2L2(PMe2Ph)], configuration (II) (L = tertiary phosphine or tertiary arsine; X = Cl), can thus be readily prepared. The reaction goes through a dissociative mechanism, being independent of PMe2Ph concentration. The relative rates of substitution of the ligand L (studied by a 1H n.m.r. method) are in the order L = AsEt3 ≫ PEt3 > PBun3 ≫ PEt2Ph > PBu2Ph, and substitution is faster in [IrHBr2(PEt3)3] than in [IrHCl 2(PEt3)3]. The monohydride-complex [IrHCl 2(PEt2Ph)3], configuration (III), undergoes general displacement of the PEt2Ph ligands by PMe2Ph but the dihydrido-complexes [IrH2X(PEt2Ph)3] [X = Cl, Br, or I] are inert to substitution by PMe2Ph. Treatment of complexes of the type mer-[IrCl3Ars3] (Ars = AsEt 3 or AsEt2Ph) with PMe2Ph gave complexes of the type [IrCl3(Ars)(PMe2Ph)2], configuration (VI), but similar treatment of the corresponding phosphine complexes mer-[IrCl3Phos3] (Phos = PEt3 or PEt 2Ph) gave complexes of type [IrCl3(Phos)(PMe 2Ph)2], configuration (VII). Infrared and n.m.r. data are given and discussed.

Journal article

Powell J, Shaw BL, 1968, Transition metal-carbon bonds. Part XIII. Di-μ-chlorodicarbonyldi- (ethylene)dirhodium(I), Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 211-212, ISSN: 0022-4944

[Rh2Cl2(CO)4] and [Rh2Cl 2(C2H4)4] react in benzene solution to give [Rh2Cl2(CO)2(C2H 4)2] in good yield. [Rh2Cl2(CO) 2(C2H4)2] reacts with hydrogen chloride to given an ethylrhodium(III) complex [RhCl2Et(CO)] x which in turn reacts with dimethylphenylphosphine to give [RhCl2Et(CO)(PMe2Ph)2]. Nuclear magnetic resonance and infrared data are given.

Journal article

Day AC, Powell JT, 1968, Some reactions of trismethylenemethyl from the photolysis of tricarbonyltrismethylenemethyliron, Chemical Communications (London), Pages: 1241-1243, ISSN: 0009-241X

Journal article

Powell J, Shaw BL, 1968, Transition metal-carbon bonds. Part XII. Allylic complexes of ruthenium(II), Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 159-161, ISSN: 0022-4944

New allylic complexes of ruthenium(II) of the type [Ru(all) 2(diolefin)] (all = allyl or 2-methylallyl; diolefin = cyclo-octa-1,5-diene or norbornadiene) are described. The allylic ligands in these complexes are asymmetrically bonded. The complexes react with allyl halides to give halogeno-bridged complexes of the type [Ru2X 2(all)2(diolefin)2] (X = Cl or Br). On treatment with triphenylphosphine cyclo-octa-1,5-diene is displaced from [Ru(2-methylallyl)2C8H12] giving [Ru(2-methylallyl)2(PPh3)2]. This in turn reacts with carbon monoxide to give [Ru(CO)3(PPh3) 2] and 2,5-dimethylhexa-1,5-diene. Nuclear magnetic resonance and far-infrared data are given.

Journal article

Powell J, Shaw BL, 1968, Transition metal-carbon bonds. Part XVII. Some allylic complexes of iridium(III), Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 780-783, ISSN: 0022-4944

Treatment of complexes of type mer-[IrCl3P3] (P = PEt3, PMe2Ph, or PEt2Ph) with 2-methylallylmagnesium chloride gives complexes of the type [IrCl 2(π-2-methylallyl)P2]. Similarly, treatment of mer-[IrCl3(PEt3)3] with allylmagnesium chloride gives [IrCl2(π-allyl)(PEt3)2] but mer-[IrCl3(PMe2Ph)3] with allylmagnesium chloride gives [IrCl2(σ-allyl)(PMe2Ph)3]. This σ-allyl complex with KOH in methanol gave [IrCl2(π- allyl)(PMe2Ph)2]. Treatment of [IrCl2(π-2- methylallyl) (PMe2Ph)2] with dilute hydrochloric acid gives a bridged chloro-complex, [Ir2Cl6(PMe 2Ph)4]. Treatment of [IrCl2(π-2-methylallyl) (PMe2Ph)2] with carbon monoxide gives the σ-2-methylallyl complex [IrCl2(C4H7) (CO) (PMe2Ph)2]. Treatment of mer-[IrCl3(PEt 3)3] with 2-methylallylmagnesium chloride gave [Ir(π-2-methylallyl)2(PEt3)2]+ isolated as its tetraphenylborate salt.

Journal article

Powell J, Shaw BL, 1967, Transition metal-carbon bonds. Part X. Reactions between allylic palladium halides and tertiary phosphines, triphenylarsine, triphenylstibine, or carbon monoxide, Journal of the Chemical Society A: Inorganic, Physical, and Theoretical Chemistry, Pages: 1839-1851, ISSN: 0022-4944

A series of complexes of the type [PdX(all)L] (X = halogen, all = allylic ligand, and L = tertiary phosphine, triphenylarsine, or triphenylstibine) is described and the asymmetric bonding of the allylic ligand discussed. Several fast rate processes occur in solutions containing allylic palladium halides [Pd2X2(all)2] and neutral ligands L (e.g., phosphines) as the ratio L/Pd is varied from 0 to ca. 2 and these have been studied by n.m.r. spectroscopy at 34°. These fast rate processes involve the conversion of the π-allylic complexes into dynamic σ-allylic systems in which various rotations about carbon-carbon and palladium-carbon bonds and also exchange of the co-ordinated ligand L with free ligand occur. Co-ordination of dimethylphenylphosphine to the palladium atom of [Pd2Cl 2(2-methylallyl)2] has been studied both by n.m.r. and by osmometry and at least two dimethylphenylphosphine ligands can become co-ordinated to the palladium, with the probable formation of [PdCl(σ-2-methylallyl)-(PMe2Ph)2] in solution. Carbon monoxide will also co-ordinate to the palladium atom of [Pd 2Cl2(2-methylallyl)2], the n.m.r. spectrum in chloroform solution corresponding to that of a 'dynamic' σ-2-methylallylic system.

Journal article

Lupin MS, Powell J, Shaw BL, 1966, Transition metal-carbon bonds. Part VII. The formation of π-allylic-palladium complexes from allenes and palladium halides and the reversed reactions, Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 1687-1691, ISSN: 0022-4944

The formation of bridged-chloro- 2-chloroprop-2-enyl- and β-(3-chloroprop-1-en-2-yl)allyl-palladium(II) complexes by reacting allene with palladium(II) chloride complexes are described. Similar reactions of methylallene and 1,1-dimethylallene are also described. The resultant bridged-chloro-π-allylic complexes undergo reactions such as metathesis and conversion to monomeric acetylacetonates and also bridged splitting reactions with amines or tertiary phosphines. Under certain conditions, the β-halo π-allylic complexes can eliminate allenes on reaction with ammonia or tertiary phosphines. The mechanisms of the formation of π-allylic complexes from allenes and palladium(II) halide complexes are discussed as are the reversed reactions, e.g., elimination of allene from β-haloallyl complexes. Nuclear magnetic resonance data are given.

Journal article

Lupin MS, Powell J, Shaw BL, 1966, The palladium-chlorine stretching frequencies of bridged chloro-π-allylic palladium(II) complexes, Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 1410-1411, ISSN: 0022-4944

Two extremely strong absorption bands at ca. 250 cm.-1 in the infrared absorption spectra of di-μ-chloro-diallyldipalladium(II) and its 1-methylallyl and 2-methylallyl analogues are assigned to palladium-chlorine stretching modes of vibration. Previously a band of ca. 360 cm.-1 had been incorrectly assigned to these modes.

Journal article

Powell J, Shaw BL, 1966, Triallylrhodium(III) and a crotyl-butadiene complex of rhodium, Chemical Communications (London), Pages: 323-325, ISSN: 0009-241X

Journal article

Powell J, Shaw BL, 1966, Allylic complexes of rhodium, Chemical Communications (London), Pages: 236-237, ISSN: 0009-241X

Journal article

Nicholson JK, Powell J, Shaw BL, 1966, The mechanism of formation of π-allylic palladium(II) chlorides from sodium chloropalladite, allylic chlorides, and carbon monoxide reacting in aqueous methanol, Chemical Communications (London), Pages: 174-175, ISSN: 0009-241X

Journal article

Powell J, Robinson SD, Shaw BL, 1965, Intermediates in the conversion of π- Into σ-allyic palladium(II) complexes, Chemical Communications (London), Pages: 78-79, ISSN: 0009-241X

Journal article

Powell J, Shaw BL, 1965, 715. The proton magnetic resonance spectra of some complex platinum hydrides, Journal of the Chemical Society (Resumed), Pages: 3879-3881, ISSN: 0368-1769

Journal article

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