Publications (40) View all
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Article: Fundamental questions and concepts about photoreception and the case of Euglena gracilis.
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ABSTRACT: The ability to sense light can be considered the most fundamental and presumably the most ancient property of visual systems. This ability is the basis of phototaxis, one of the most striking behavioral responses of motile photosynthetic microorganisms (i.e. microalgae) to light stimuli, which allows them to move toward or away directional light. In order to fully exploit the information content of light (intensity, direction, distribution) microorganisms need proper perceiving devices, termed photoreceptors, which must act as sensors, to perceive wavelength and direction of light, as transducers, to convert the light signal into chemical and/or electrical information, but also as amplifiers and eventually as transmitters. This review describes the universal structural, behavioral and physiological features necessary for the proper functioning of these devices in algae, and how these features have been investigated by means of different analytical techniques such as for example microspectroscopy, digital fluorescence microscopy, two photons FLIM. The insight of the photoreceptive response mechanism is explained using the unicellular alga Euglena gracilis, in which the different structural, behavioral and physiological features combine to achieve a concerted, efficient response to light stimuli.Integrative Biology 11/2011; 4(1):22-36. · 4.51 Impact Factor -
Article: Chemistry, physico-chemistry and applications linked to biological activities of β-glucans.
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ABSTRACT: β-Glucans is the common name given to a group of chemically heterogeneous polysaccharides. They are long- or short-chain polymers of (1-->3)-β-linked glucose moieties which may be branched, with the branching chains linked to the backbone by a (1-->6)-β linkage. β-(1-->3)-Glucans are widely distributed in bacteria, algae, fungi and plants, where they are involved in cell wall structure and other biological function. β-Glucans have been shown to provide a remarkable range of health benefits, and are especially important against the two most common conventional causes of death in industrialized countries, i.e. cardiovascular diseases (where they promote healthy cholesterol and blood glucose levels) and cancer (where they enhance immune system functions). This Highlight provides a comprehensive and up-to-date commentary on β-glucans, their chemistry, physico-chemistry, functional role in immunological responses, and possible applications as therapeutic tools. In addition, we discuss the mechanism behind their health benefits, which are not yet fully understood.Natural Product Reports 01/2011; 28(3):457-66. · 9.79 Impact Factor -
Article: A rhodopsin-like protein in Cyanophora paradoxa: gene sequence and protein immunolocalization.
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ABSTRACT: Here, we report the DNA sequence of the rhodopsin gene in the alga Cyanophora paradoxa (Glaucophyta). The primers were designed according to the conserved regions of prokaryotic and eukaryotic rhodopsin-like proteins deposited in the GenBank. The sequence consists of 1,272 bp comprised of 5 introns. The correspondent protein, named Cyanophopsin, showed high identity to rhodopsin-like proteins of Archea, Bacteria, Fungi, and Algae. At the N-terminal, the protein is characterized by a region with no transmembrane alpha-helices (80 aa), followed by a region with 7alpha-helices (219 aa) and a shorter 35-aa C-terminal region. The DNA sequence of the N-terminal region was expressed in E. coli and the recombinant purified peptide was used as antigen in hens to obtain polyclonal antibodies. Indirect immunofluorescence in C. paradoxa cells showed a marked labeling of the muroplast (aka cyanelle) membrane.Cellular and Molecular Life Sciences CMLS 12/2009; 67(6):965-71. · 6.57 Impact Factor -
Article: MICROSPECTROPHOTOMETRY AS A METHOD TO IDENTIFY KLEPTOPLASTIDS IN THE NAKED FRESHWATER DINOFLAGELLATE GYMNODINIUM ACIDOTUM1
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ABSTRACT: A relatively small number of freshwater dinoflagellates are involved in symbiotic association with cryptophytes. The chloroplasts of the cryptophytes are retained by the dinoflagellate and give it the characteristic phycobilin pigmentation, either phycoerythrin or phycocyanin. The pigment characterization of the retained chloroplasts can give precise and accurate information about the type of cryptophyte preyed upon by the dinoflagellate. For this purpose, we performed microspectrophotometric evaluation of the pigments of Gymnodinium acidotum Nygaard and three different cryptophytes present in samples collected from a tributary of the river Arno, in Tuscany (Italy). The comparison of the different spectroscopic data allowed us to discriminate effectively among the cryptophytes preyed upon by the dinoflagellate.Journal of Phycology 09/2009; 45(6):1304 - 1309. · 2.07 Impact Factor -
Article: Intramolecular photo-switching and intermolecular energy transfer as primary photoevents in photoreceptive processes: the case of Euglena gracilis.
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ABSTRACT: In this paper we report the results of measurements performed by FLIM on the photoreceptor of Euglenagracilis. This organelle consists of optically bistable proteins, characterized by two thermally stable isomeric forms: A(498,) non fluorescent and B(462), fluorescent. Our data indicate that the primary photoevent of Euglena photoreception upon photon absorption consists of two contemporaneous different phenomena: an intramolecular photo-switch (i.e., A(498) becomes B(462)), and a intermolecular and unidirectional Forster-type energy transfer. During the FRET process, the fluorescent B(462) form acts as donor for the non-fluorescent A(498) form of the protein nearby, which acts as acceptor. We hypothesize that in nature these phenomena follow each other with a domino progression along the orderly organized and closely packed proteins in the photoreceptor layer(s), modulating the isomeric composition of the photoreceptive protein pool. This mechanism guarantees that few photons are sufficient to produce a signal detectable by the cell.Biochemical and Biophysical Research Communications 06/2009; 385(2):176-80. · 2.48 Impact Factor
