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1.
Biotechnol Adv ; 31(3): 369-74, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-22634017

RESUMO

In this paper, we will employ two microscopy techniques, transmission electron microscopy and infrared nanospectromicroscopy, to study the production of polyhydroxybutyrate in Rhodobacter capsulatus and to evaluate the influence of glucose and acetone on the production yield. The results overlap which leads us to a consistent conclusion, highlighting that each technique brings specific and complementary information. By using electron microscopy and infrared nanospectromicroscopy we have proved that both glucose and acetone had a positive effect on the biopolymer production, although the first study done by Fourier transform infrared spectroscopy only identified the effect of acetone. In conclusion, we have now established a method to be able to perform fast diagnostic for PHB production.


Assuntos
Hidroxibutiratos/análise , Hidroxibutiratos/metabolismo , Processamento de Imagem Assistida por Computador/métodos , Microscopia de Força Atômica/métodos , Nanotecnologia/métodos , Poliésteres/análise , Poliésteres/metabolismo , Rhodobacter capsulatus/metabolismo , Acetona/metabolismo , Acetona/farmacologia , Técnicas Bacteriológicas , Meios de Cultura , Desenho de Equipamento , Glucose/metabolismo , Glucose/farmacologia , Microscopia de Força Atômica/instrumentação , Microscopia Eletrônica de Transmissão , Rhodobacter capsulatus/efeitos dos fármacos , Espectroscopia de Infravermelho com Transformada de Fourier
3.
Analyst ; 135(10): 2540-5, 2010 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-20820491

RESUMO

We have employed atomic force microscope-based infrared spectroscopy (AFM-IR) to spatially map energy storage polymers inside individual bacteria Rhodobacter capsulatus. AFM-IR allows chemical mapping of sub-cellular features with a spatial resolution of <100 nm. We have used key absorption bands of the energy storage polymer polyhydroxybutyrate (PHB) known from FTIR to spatially map the molecular distribution of PHB inside bacteria. We have also compared FTIR measurements on bulk PHB with AFM-IR measurements of PHB inside bacteria. We observe a shift in the location of the carbonyl absorption peak between bulk PHB and PHB inside bacteria. We have also used finite element analysis to model AFM-IR measurements of PHB granules, allowing for estimation of the real size of the granules. We have also performed transmission electron microscopy (TEM) of R. capsulatus to determine the size distribution of the PHB granules. Sizes measured by AFM-IR correspond well to TEM measurements.


Assuntos
Hidroxibutiratos/química , Microscopia de Força Atômica/métodos , Nanopartículas/química , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Microscopia Eletrônica de Transmissão , Tamanho da Partícula , Polímeros/química , Rhodobacter capsulatus/química
4.
J Am Chem Soc ; 131(36): 13009-19, 2009 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-19705830

RESUMO

Dinuclear gold(III) clusters with a rhombic Au(2)O(2) core and 2,2'-bipyridyl ligands substituted in the 6-position (bipy(R)) are examined by tandem mass spectrometry. Electrospray ionization of the hexafluorophosphate salts affords the complexes [(bipy(R))Au(mu-O)(2)Au(bipy(R))](2+) as free dications in the gas phase. The fragmentation behavior of the mass-selected dications is probed by means of collision-induced dissociation experiments which reveal an exceptionally pronounced effect of substitution. Thus, for the parent compound with R = H, i.e., [(bipy)Au(mu-O)(2)Au(bipy)](2+), fragmentation at the dicationic stage prevails to result in a loss of neutral H(2)O concomitant with an assumed rollover cyclometalation of the bipyridine ligands. In marked contrast, all complexes with alkyl substituents in the 6-position of the ligands (bipy(R) with R = CH(3), CH(CH(3))(2), CH(2)C(CH(3))(3), and 2,6-C(6)H(3)(CH(3))(2)) as well as the corresponding complex with 6,6'-dimethyl-2,2'-dipyridyl as a ligand exclusively undergo Coulomb explosion to produce two monocationic fragments. It is proposed that the additional steric strain introduced to the central Au(2)O(2) core by the substituents on the bipyridine ligand, in conjunction with the presence of oxidizable C-H bonds in the substituents, crucially affects the subtle balance between dication dissociation under maintenance of the 2-fold charge and Coulomb explosion into two singly charged fragments.


Assuntos
2,2'-Dipiridil/análise , Compostos Organoáuricos/análise , 2,2'-Dipiridil/química , Ligantes , Estrutura Molecular , Compostos Organoáuricos/química , Espectrometria de Massas em Tandem
5.
Opt Express ; 17(13): 10887-94, 2009 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-19550489

RESUMO

Midinfrared absorption can be locally measured using a detection combining an atomic force microscope and a pulsed excitation. This is illustrated for the midinfrared bulk GaAs phonon absorption and for the midinfrared absorption of thin SiO(2) microdisks. We show that the signal given by the cantilever oscillation amplitude of the atomic force microscope follows the spectral dependence of the bulk material absorption. The absorption spatial resolution achieved with microdisks is around 50 nanometer for an optical excitation around 22 micrometer wavelength.


Assuntos
Microscopia de Força Atômica/instrumentação , Microscopia de Força Atômica/métodos , Espectrofotometria Infravermelho/métodos , Absorção , Acústica , Desenho de Equipamento , Oscilometria/métodos , Semicondutores , Dióxido de Silício/química , Propriedades de Superfície
6.
Chemphyschem ; 8(11): 1629-39, 2007 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-17600797

RESUMO

Coordination complexes of the magnesium nitrate cation with water [MgNO(3)(H(2)O)(n)](+) up to n=7 are investigated by experiment and theory. The fragmentation patterns of [MgNO(3)(H(2)O)(n)](+) clusters generated via electrospray ionization indicate a considerable change in stability between n=3 and 4. Further, ion-molecule reactions of mass-selected [MgNO(3)(H(2)O)(n)](+) cations with D(2)O reveal the occurrence of consecutive replacement of water ligands by heavy water, and in this respect the complexes with n=4 and 5 are somewhat more reactive than their smaller homologs with n=1-3 as well as the larger clusters with n=6 and 7. For the latter two ions, the theory suggests the existence of isomers, such as complexes with monodentate nitrato ligands as well as solvent-separated ion pairs with a common solvation shell. The reactions observed and the ion thermochemistry are discussed in the context of ab initio calculations, which also reveal the structures of the various hydrated cation complexes.

7.
Phys Rev Lett ; 99(21): 217404, 2007 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-18233255

RESUMO

We show that we can measure the room temperature ultraweak absorption of a single buried semiconductor quantum dot. This is achieved by monitoring the deformation field induced by the absorption of midinfrared laser pulses and locally detected with an atomic force microscope tip. The absorption is spectrally and spatially resolved around lambda approximately 10 microm wavelength with 60 nm lateral resolution (lambda/150). The electronic S-D intersublevel absorption of a single quantum dot is identified around 120 meV and exhibits a homogeneous linewidth of approximately 10 meV at room temperature.

8.
J Am Chem Soc ; 126(37): 11666-74, 2004 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-15366914

RESUMO

Infrared spectra in the mid-infrared region (800-1600 cm(-1)) of highly unsaturated Fe(+)-hydrocarbon complexes isolated in the gas phase are presented. These organometallic complexes were selectively prepared by ion-molecule reactions in a Fourier transform ion cycloton mass spectrometer (FTICR-MS). The infrared multiphoton dissociation (IRMPD) technique has been employed using the free electron laser facility CLIO (Orsay, France) to record the infrared spectra of the mass selected complexes. The experimental IRMPD spectra present the main features of the corresponding IR absorption spectra calculated ab initio. As predicted by these calculations, the experimental spectra of three selectively prepared isomers of Fe+(butene) present differences in the 800-1100 cm(-1) range. On the basis of the comparison with calculated IR spectra, the IRMPD spectrum of Fe(butadiene)(+) suggests that the ligand presents the s-trans isomeric form. This study further confirms the potentialities of IRMPD spectroscopy for the structural characterization of organometallic ionic highly reactive intermediates in the gas phase. In conjunction with soft ionization techniques such as electrospray, this opens the door to the gas-phase characterization of reactive intermediates associated with condensed phase catalysts.

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