1,720,963 research outputs found
Reversible Binding of Metal Ions onto Bacterial Layers Revealed by Protonation-Induced ATR-FTIR Difference Spectroscopy
No full textThe ability of microorganisms to adhere to abiotic surfaces and the potentialities of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy have been exploited to study protonation and heavy metal binding events onto bacterial surfaces. This work represents the first attempt to apply on bacteria the recently developed method known as perfusion-induced ATR-FTIR difference spectroscopy.(1,2) Such a technique allows measurement of even slight changes in the infrared spectrum of the sample, deposited as a thin layer on an ATR crystal, while an aqueous solution is perfused over its surface. Solutions at different pH have been used for inducing protonation/deprotonation of functional groups lying on the surface of Rhodobacter sphaeroides cells, chosen as a model system. The interaction of Ni2+ with surface protonable groups of this microorganism has been investigated with a double-difference approach exploiting competition between nickel cations and protons. Protonation-induced difference spectra of simple model compounds have been acquired to guide band assignment in bacterial spectra, thus allowing identification of major components involved in proton uptake and metal binding. The data collected reveal that carboxylate moieties on the bacterial surface of R. sphaeroides play a role in extracellular biosorption of Ni2+, establishing with this ion relatively weak coordinative bonds
X-ray photoelectron spectroscopy as a non-conventional analytical technique for bio-organic materials characterization: the example of Arbacia lixula.
No full textPurple photosynthetic bacteria and sea urchin coelomocytes examination by X‐ray photoelectron spectroscopy as a non‐conventional analytical technique for bio‐organic materials
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The phototrophic bacterium Rhodobacter sphaeroides as a bio-catalyst for the reduction of Chromate to Chromium(III)
No full textBacterial phototrophic biomass as biosorbent for the removal of Nickel(II) from waste-waters
No full textXPS AND FTIR spectroscopic characterization of phototrophic bacterial cells interacting with Nickel ions.
No full textLipid/detergent mixed micelles as a tool for transferring antioxidant power from hydrophobic natural extracts into bio-deliverable liposome carriers: the case of lycopene rich oleoresins
No full textThis work demonstrates that lipid-detergent mixed micelles can be employed successfully in order to achieve and modulate the transfer of bio-active hydrophobic compounds into lipid carriers by means of a simple and bio-safe procedure. In our specific investigation, liposome preparations incorporating mixtures of natural carotenoids with high lycopene content were developed and characterized, aiming to obtain formulations of potential nutraceutical and pharmaceutical interest. The starting material was a solvent-free high-quality lycopene rich oleoresin (LRO) obtained by extracting a freeze-dried tomato matrix with supercritical carbon dioxide (SC-CO2). Mixed micelles containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and cholate were loaded with LRO antioxidants by means of two slightly different procedures, which surprisingly resulted in significant differences in both quality and quantity of incorporated carotenoids. In particular, the selective incorporation of (all-E)-lycopene was achieved by extracting the oleoresin with a pre-formed cholate/POPC micelle suspension whilst (Z)-isomers were preferentially integrated when treating a POPC/LRO mixed film with cholate. The micelle to vesicle transition (MVT) method was employed in order to produce vesicles of well-defined lamellarity and size. Visible and infrared (IR) spectroscopy as well as Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) measurements allowed the extensive characterization of LRO-loaded micelles and liposomes. The antioxidant potential of preparations was assessed by measuring the radical scavenging activity towards the coloured radical cation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonate) (ABTS). Important information about the reliability of different approaches for antioxidant capacity evaluation of micelle and liposome preparations was gained and the successful incorporation of LRO antioxidant power in a bio-deliverable water-dispersed form was demonstrated
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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