Vibrational and thermal studies of essential oils derived from Cistus ladanifer and Erica arborea shrubs

Essential oils from the two most representative shrub species from the Iberian Peninsula (namely Cistus ladanifer L. and Erica arborea L.) have been characterized by Fourier transform infrared spectroscopy (FTIR) and thermoanalytical techniques (TG/DTG and DSC). Vibrational spectra have been compared with those of components of the plants, and with those of oils, gums and resins from other species. The different content in terpenoids of C. ladanifer oil (mainly mono-and sesquiterpenoids) and E. arborea oil (mainly triterpenoids) is reflected in the ATR-FTIR by the position of the bands at around 2873 cm-1, 1730 cm-1 and 1678 cm-1. As regards their thermal behavior, C. ladanifer-derived oil evinced higher thermal stability than that of obtained from E. arborea: The pyrolysis of the former was sensitized at 210°C, whereas for the later it occurred at 143°C. These temperatures are high enough to state that thermolabile constituents such as terpenoids are conserved in the hydrodistillation and that this extraction process ensures the recovery of the main constituents of both essential oils

Influence of sample covering on the polymorphic and solid-solid transitions of a chiral molecule: Diprophylline

International audienc

Characterization of S-layer proteins of Lactobacillus by FTIR spectroscopy and differential scanning calorimetry

FTIR spectroscopy was used for the characterization of S-layer proteins extracted from microorganisms isolated from kefir grains. S-layer from Lactobacillus brevis ATCC 8287 has been already characterized [G. Vidgren, I. Palva, R. Pakkanen, K. Lounatmaa, A. Palva, J. Bacteriol. 174 (1992) 7419] and therefore it was used for the validation of FTIR as a method to investigate the secondary structure of the S-layer proteins of the studied kefir strains. A correlation between the secondary structures of S-layer proteins with surface properties of Lactobacillus kefir strains was found: a high percentage of b-sheet contents (40?50%) was found for non-aggregating strains, whereas this percentage decreased to 25?30% for aggregating ones. A quantitative comparison of the S-layers was performed by means of cluster analysis based on the obtained spectroscopic data. This analysis enabled the strains to be grouped in clusters according to the spectral diversity in the Amide I region. The non-aggregating strains of L. kefir cluster at Ssm > 0.943 and the aggregating strains form another cluster, with Ssm > 0.769. L. brevis ATCC 8287 appears clearly separated from these two clusters: the similarity with the aggregating strains is 0.658 and the similarity with the non-aggregating ones, 0.665. The thermal analysis of the lyophilized S-layer proteins was performed by means of differential scanning calorimetry (DSC) and FTIR. DSC analysis within the 30? 130 8C range showed two phase transitions with maxima located at ca. 58 and 98 8C for L. brevis and in the 67?70 and 110?119 8C ranges for the different strains of L. kefir (CIDCA 8344 only shows the lowest temperature phase transition). FTIR spectra obtained reveal that for all the L. kefir S-layer proteins the major secondary structure modifications upon heating occur nearly at the first phase transitions observed by DSC, with the thermal stability increasing with the percentage of b-sheets structures. The Slayer protein of L. brevis ATICC 8287, which among all protein studied is that with maximum b-sheet contents (and no a-helix structure) was then found to be the protein showing a greater thermal stability.Fil: Mobili, Pablo. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Londero, Alejandra. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Maria, T.M.R.. Universidad de Coimbra. Facultad de Ciencias E Tecnología. Department Of Chemistry; PortugalFil: Eusébio, M.E.S.. Universidad de Coimbra. Facultad de Ciencias E Tecnología. Department Of Chemistry; PortugalFil: de Antoni, Graciela Liliana. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Fausto, R.. Universidad de Coimbra. Facultad de Ciencias E Tecnología. Department Of Chemistry; PortugalFil: Gomez Zavaglia, Andrea. Universidad de Coimbra. Facultad de Ciencias E Tecnología. Department Of Chemistry; Portugal. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentin

Permeation of sodium dodecyl sulfate through polyaniline-modified cellulose acetate membranes

The preparation of polyaniline (PANi)-cellulose acetate (CA) blends by casting films from a suspension, is reported. Two membranes were prepared from different solvents, one with a homogeneous and the other a heterogeneous dispersion of PANi in CA matrices. The membranes were characterized by X-ray diffraction, SEM, DSC, and FTIR, and the results were compared with those obtained for pure CA and PANi films. The transport properties of water and sodium dodecyl sulfate (SDS) in membranes of the PANi-CA blends and of CA were analysed. The transport of SDS and water depends on both the bulk/polymer density and the PANi content. In the homogeneous blend, the interaction between SDS and the polymer plays an important role in the transport mechanism. An irreversible interaction is observed, which can be monitored by UV-vis spectroscopy. The spectra of homogeneous, highly transparent PANi-CA blends show a pronounced sensitivity to SDS concentration, with detection limits [SDS]>=0.1 mM for films with a PANi concentration of 0.05% w/v.http://www.sciencedirect.com/science/article/B6TXW-4GCX1K6-C/1/14a4cf07e9dd93654b4cba319350f27

First observation of Chapman rearrangement of a pseudosaccharyl ether in the solid state: the thermal isomerization of 3-(methoxy)-1,2-benzisothiazole 1,1-dioxide revisited

3-(Methoxy)-1,2-benzisothiazole 1,1-dioxide, a pseudosaccharyl ether, was long ago known to undergo a thermal Chapman-like [1,3′]-isomerization to the corresponding N-methyl pseudosaccharin at temperatures above its melting point (ca. 184 °C) [Hettler H., Tetrahedron Lett.1968, 15, 1793]. In the present study, it is shown that this rearrangement can also take place in the solid state, at temperatures as low as 150 °C. This was the first observation of a Chapman-like [1,3′]-isomerization in pseudosaccharyl ethers in the solid state. The study has been carried out by a multidisciplinary approach using temperature dependent infrared spectroscopy, differential scanning calorimetry (DSC), and polarized light thermomicroscopy, complemented by theoretical methods. Graphical abstrac

Characterization of S-layer proteins of Lactobacillus by FTIR spectroscopy and differential scanning calorimetry

FTIR spectroscopy was used for the characterization of S-layer proteins extracted from microorganisms isolated from kefir grains. S-layer from Lactobacillus brevis ATCC 8287 has been already characterized [G. Vidgren, I. Palva, R. Pakkanen, K. Lounatmaa, A. Palva, J. Bacteriol. 174 (1992) 7419] and therefore it was used for the validation of FTIR as a method to investigate the secondary structure of the S-layer proteins of the studied kefir strains. A correlation between the secondary structures of S-layer proteins with surface properties of Lactobacillus kefir strains was found: a high percentage of β-sheet contents (40–50%) was found for non-aggregating strains, whereas this percentage decreased to 25–30% for aggregating ones. A quantitative comparison of the S-layers was performed by means of cluster analysis based on the obtained spectroscopic data. This analysis enabled the strains to be grouped in clusters according to the spectral diversity in the Amide I region. The non-aggregating strains of L. kefir cluster at Ssm > 0.943 and the aggregating strains form another cluster, with Ssm > 0.769. L. brevis ATCC 8287 appears clearly separated from these two clusters: the similarity with the aggregating strains is 0.658 and the similarity with the non-aggregating ones, 0.665. The thermal analysis of the lyophilized S-layer proteins was performed by means of differential scanning calorimetry (DSC) and FTIR. DSC analysis within the 30–130 °C range showed two phase transitions with maxima located at ca. 58 and 98 °C for L. brevis and in the 67–70 and 110–119 °C ranges for the different strains of L. kefir (CIDCA 8344 only shows the lowest temperature phase transition). FTIR spectra obtained reveal that for all the L. kefir S-layer proteins the major secondary structure modifications upon heating occur nearly at the first phase transitions observed by DSC, with the thermal stability increasing with the percentage of β-sheets structures. The S-layer protein of L. brevis ATICC 8287, which among all protein studied is that with maximum β-sheet contents (and no α-helix structure) was then found to be the protein showing a greater thermal stability