Export 1423 results:
Sort by: Author Title Type [ Year  (Desc)]
2004
Fernandez, D, Parola AJ, Branco LC, Afonso CAM, Pina F.  2004.  Thermal and photochemical properties of 4 '-hydroxyflavylium in water-ionic liquid biphasic systems, 2004. Journal of Photochemistry and Photobiology a-Chemistry. 168:185-189. AbstractWebsite

The multistate/multifunctional properties of 4'-hydroxyflavylium in a water/ I -n-butyl-3 -methyl-imidazolium hexalluorophosphate (fbmim][PF6]) biphasic system are described. The kinetics and thermodynamics of this flavylium salt have been fully characterised in aqueous solutions and compared to those obtained in [bmim][PF6]. The trans-chalcone is thermally more stable in the ionic liquid but shows efficient photoisomerisation to the cis-chalcone, allowing to define write-read-erase cycles in this biphasic system. (C) 2004 Elsevier B.V. All rights reserved.

Fernandez, D, Folgosa F, Parola AJ, Pina F.  2004.  Two coupled photochromic systems of 3 ',4 '-(methylenedioxy)flavylium: kinetic and thermodynamic characterization, 2004. New Journal of Chemistry. 28:1221-1226. AbstractWebsite

The chemistry and photochemistry of 3',4'-(methylenedioxy)flavylium was studied by means of UV-Vis spectrophotometry, H-1 NMR, stopped flow, and continuous irradiation, in acidic and basic aqueous solutions. Six species were identified: the flavylium cation, AH(+); the hemiketal, B; the cis- and the trans-chalcones, Cc and Ct, and their ionized forms, Cc(-) and Ct(-). These species de. ne a multiequilibria network whose kinetics and thermodynamics were completely characterized. The two pairs of chalcones de. ne two coupled photochromic systems, respectively in acidic and basic media, both allowing cycles capable of writing, reading and erasing to be defined.

Sherratt, DJ, Soballe B, Barre F-X, Filipe SR, Massey T, Lau I, Yates J.  2004.  Recombination and chromosome segregation. Phil. Trans. R. Soc. Lond. B. 359:61-69.
Gardete, S, Ludovice AM, Sobral RG, Filipe SR, de Lencastre H, Tomasz A.  2004.  The role of murE in the expression of b-lactam antibiotic resistance in Staphylococcus aureus. J. Bacteriol. 186:1705-1713.
Alexandre, J, Feio G, Marvao MR, Figueiredo J.  2004.  Correlation between high power proton T(2) NMR relaxation and macroscopic viscoelastic properties. Advanced Materials Forum Ii. 455-456(R. Martins, E. Fortunato, Ferreira, I., Dias, C., Eds.).:459-462. Abstract
n/a
Carvalho, AL, Goyal A, Prates JAM, Bolam DN, Gilbert HJ, Pires VMR, Ferreira LMA, Planas A, Romao MJ, Fontes C.  2004.  The family 11 carbohydrate-binding module of Clostridium thermocellum Lic26A-Cel5E accommodates beta-1,4- and beta-1,3-1,4-mixed linked glucans at a single binding site. Journal of Biological Chemistry. 279:34785-34793., Number 33 AbstractWebsite
n/a
Faustino, P, Miranda A, Silva MD, Alves C, Pinanco I, Ferreira C, Seixas MT, Pina F, Romao L.  2004.  Hb Yaounde beta 134(H12)Val -> Ala in association with Hb C beta 6(A3)Glu -> Lys in a Caucasian Portuguese family. Hemoglobin. 28:229-235., Number 3 AbstractWebsite
n/a
Moncada, MC, Fernandez D, Lima JC, Parola AJ, Lodeiro C, Folgosa F, Melo MJ, Pina F.  2004.  Multistate properties of 7-(N,N-diethylamino)-4 '-hydroxyflavylium. An example of an unidirectional reaction cycle driven by pH. Organic & Biomolecular Chemistry. 2:2802-2808., Number 19 AbstractWebsite
n/a
Hettmann, T, Siddiqui RA, Frey C, Santos-Silva T, Romao MJ, Diekmann S.  2004.  Mutagenesis study on amino acids around the molybdenum centre of the periplasmic nitrate reductase from Ralstonia eutropha. Biochemical and Biophysical Research Communications. 320:1211-1219., Number 4 AbstractWebsite
n/a
Gago, S, Zhang YM, Santos AM, Kohler K, Kuhn FE, Fernandes JA, Pillinger M, Valente AA, Santos TM, Ribeiro-Claro PJA, Goncalves IS.  2004.  Synthesis and characterization of a manganese(II) acetonitrile complex supported on functionalized MCM-41. Microporous and Mesoporous Materials. 76:131-136., Number 1-3 AbstractWebsite
n/a
Ferrer, M, Rodriguez L, Rossell O, Lima JC, Gomez-Sal P, Martin A.  2004.  Unexpected alkyne transfer between gold and rhenium atoms and its application to the synthesis of alkynyl rhenium(I) compounds. Organometallics. 23:5096-5099., Number 21 Abstract
n/a
2003
Banci, L, Bertini I, Felli IC, Krippahl L, Kubicek K, Moura JJ, Rosato A.  2003.  A further investigation of the cytochrome b5-cytochrome c complex, Sep. J Biol Inorg Chem. 8:777-86., Number 7 AbstractWebsite

The interaction of reduced rabbit cytochrome b(5) with reduced yeast iso-1 cytochrome c has been studied through the analysis of (1)H-(15)N HSQC spectra, of (15)N longitudinal ( R(1)) and transverse ( R(2)) relaxation rates, and of the solvent exchange rates of protein backbone amides. For the first time, the adduct has been investigated also from the cytochrome c side. The analysis of the NMR data was integrated with docking calculations. The result is that cytochrome b(5) has two negative patches capable of interacting with a single positive surface area of cytochrome c. At low protein concentrations and in equimolar mixture, two different 1:1 adducts are formed. At high concentration and/or with excess cytochrome c, a 2:1 adduct is formed. All the species are in fast exchange on the scale of differences in chemical shift. By comparison with literature data, it appears that the structure of one 1:1 adduct changes with the origin or primary sequence of cytochrome b(5).

Anda, C, Bazzicalupi C, Bencini A, Bianchi A, Fornasari P, Giorgi C, Valtancoli B, Lodeiro C, Parola AJ, Pina F.  2003.  Cu(II) and Ni(II) complexes with dipyridine-containing macrocyclic polyamines with different binding units, 2003. Dalton Transactions. :1299-1307. AbstractWebsite

The coordination features of the two dipyridine-containing polyamine macrocycles 2,5,8,11,14-pentaaza[ 15][ [15](2,2')[1,15]-bipyridylophane (L1) and 4,4'-(2,5,8,11,14-pentaaza[15]-[15](2,2')-bipyridylophane) (L2) toward Cu(II) and Ni(II) have been studied by means of potentiometric and spectrophotometric UV-vis titrations in aqueous solutions. While in L1 all the nitrogen donor atoms are convergent inside the macrocyclic cavity, in L2 the heteroaromatic nitrogen atoms are located outside. Ligands L1 and L2 form stable mono- and dinuclear complexes with Cu(II). In the case of Ni(II) coordination, only L1 gives dinuclear complexes, while L2 can form only mononuclear species. In the Cu(II) or Ni(II) complexes with L1 the metal(s) are lodged inside the macrocyclic cavity, coordinated to the heteroaromatic nitrogens. As shown by the crystal structure of the [CuL1](2+) and [NiL1](2+) cations, at least one of the two benzylic nitrogens is not coordinated and facile protonation of the complex takes place at neutral or slightly acidic pH values. The particular molecular architecture of L2, which displays two well-separated binding moieties, strongly affects its coordination behavior. In the mononuclear [ CuL2](2+) complex, the metal is encapsulated inside the cavity, not coordinated by the dipyridine unit. Protonation of the complex, however, occurs on the aliphatic polyamine chain and gives rise to translocation of the metal outside the cavity, bound to the heteroaromatic nitrogens. In the [NiL2](2+) complex the metal is coordinated by the dipyridine nitrogens, outside the macrocyclic cavity. Thermodynamic and/or kinetic considerations may explain the different behavior with respect to the corresponding Cu(II) complex.

Fiser, A, Filipe SR, Tomasz A.  2003.  Cell wall branches, penicillin resistance and the secrets of the MurM protein. Trends Microbiol. 11:547-553.
Lau, IF, Filipe SR, Soballe B, Okstad O-A, Barre F-X, Sherratt DJ.  2003.  Spatial and temporal organization of replicating Escherichia coli chromosomes. Mol Microbiol. 49:731-743.
Carvalho, AL, Dias FMV, Prates JAM, Nagy T, Gilbert HJ, Davies GJ, Ferreira LMA, Romao MJ, Fontes C.  2003.  Cellulosome assembly revealed by the crystal structure of the cohesin-dockerin complex. Proceedings of the National Academy of Sciences of the United States of America. 100:13809-13814., Number 24 AbstractWebsite
n/a
Ferrer, M, Rodriguez L, Rossell O, Pina F, Lima JC, Bardia MF, Solans X.  2003.  Linear ditopic acetylide gold or mercury complexes: synthesis and photophysic studies X-ray crystal structure of PPh4[Au(C CC5H4N)(2)]. Journal of Organometallic Chemistry. 678:82-89., Number 1-2 Abstract
n/a
Hettmann, T, Siddiqui RA, van Langen J, Frey C, Romao MJ, Diekmann S.  2003.  Mutagenesis study on the role of a lysine residue highly conserved in formate dehydrogenases and periplasmic nitrate reductases. Biochemical and Biophysical Research Communications. 310:40-47., Number 1 AbstractWebsite
n/a
2002
Maximo, P, Lourenco A, Feio SS, Roseiro JC.  2002.  A new prenylisoflavone from Ulex jussiaei, JUL-AUG. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION C-A JOURNAL OF BIOSCIENCES. 57:609-613., Number 7-8 Abstract
n/a
Lu, Y, Sousa A, Franco R, Mangravita A, Ferreira GC, Moura I, Shelnutt JA.  2002.  Binding of protoporphyrin IX and metal derivatives to the active site of wild-type mouse ferrochelatase at low porphyrin-to-protein ratios, Jul 2. Biochemistry. 41:8253-8262., Number 26 AbstractWebsite

Resonance Raman (RR) spectroscopy is used to examine porphyrin substrate, product, and inhibitor interactions with the active site of murine ferrochelatase (EC 4.99.1.1), the terminal enzyme in the biosynthesis of heme. The enzyme catalyzes in vivo Fe2+ chelation into protoporphyrin IX to give heme. The RR spectra of native ferrochelatase show that the protein, as isolated, contains varying amounts of endogenously bound high- or low-spin ferric heme, always at much less than 1 equiv. RR data on the binding of free-base protoporphyrin IX and its metalated complexes (Fe(III), Fe(II), and Ni(II)) to active wild-type protein were obtained at varying ratios of porphyrin to protein. The binding of ferric heme, a known inhibitor of the enzyme, leads to the formation of a low-spin six-coordinate adduct. Ferrous heme, the enzyme's natural product, binds in the ferrous high-spin five-coordinate state. Ni(II) protoporphyrin, a metalloporphyrin that has a low tendency toward axial ligation, becomes distorted when bound to ferrochelatase. Similarly for free-base protoporphyrin, the natural substrate of ferrochelatase, the RR spectra of porphyrin-protein complexes reveal a saddling distortion of the porphyrin. These results corroborate and extend our previous findings that porphyrin distortion, a crucial step of the catalytic mechanism, occurs even in the absence of bound metal substrate. Moreover, RR data reveal the presence of an amino acid residue in the active site of ferrochelatase which is capable of specific axial ligation to metals.

Maximo, P, Lourenco A, Feio SS, Roseiro JC.  2002.  Flavonoids from Ulex airensis and Ulex europaeus ssp europaeus, FEB. JOURNAL OF NATURAL PRODUCTS. 65:175-178., Number 2 Abstract
n/a
Carepo, M, Baptista JF, Pamplona A, Fauque G, Moura JJ, Reis MA.  2002.  Hydrogen metabolism in Desulfovibrio desulfuricans strain New Jersey (NCIMB 8313)--comparative study with D. vulgaris and D. gigas species, Dec. Anaerobe. 8:325-32., Number 6 AbstractWebsite

This article aims to study hydrogen production/consumption in Desulfovibrio (D.) desulfuricans strain New Jersey, a sulfate reducer isolated from a medium undergoing active biocorrosion and to compare its hydrogen metabolism with two other Desulfovibrio species, D. gigas and D. vulgaris Hildenborough. Hydrogen production was followed during the growth of these three bacterial species under different growth conditions: no limitation of sulfate and lactate, sulfate limitation, lactate limitation, pyruvate/sulfate medium and in the presence of molybdate. Hydrogen production/consumption by D. desulfuricans shows a behavior similar to that of D. gigas but a different one from that of D. vulgaris, which produces higher quantities of hydrogen on lactate/sulfate medium. The three species are able to increase the hydrogen production when the sulfate became limiting. Moreover, in a pyruvate/sulfate medium hydrogen production was lower than on lactate/sulfate medium. Hydrogen production by D. desulfuricans in presence of molybdate is extremely high. Hydrogenases are key enzymes on production/consumption of hydrogen in sulfate reducing organisms. The specific activity, number and cellular localization of hydrogenases vary within the three Desulfovibrio species used in this work, which could explain the differences observed on hydrogen utilization.

Viciosa, MT, Nunes AM, Fernandes A, Almeida PL, Godinho MH, Dionísio MD.  2002.  Dielectric studies of the nematic mixture E7 on a hydroxypropylcellulose substrate. Liquid Crystals. 29(3):429-441.Website
Filipe, SR, Severina E, Tomasz A.  2002.  The murMN operon: a functional connection between antibiotic resistance and antibiotic tolerance in Streptococcus pneumoniae. Proc. Natl. Acad. Sci. USA. 99:1550-1555.
loading