Eleftherios Touloupakis

Technological applications of chlorophyll a fluorescence for the assessment of environmental pollutants.

Chlorophyll a fluorescence has been extensively studied over the last few years. As demonstrated, this phenomenon is closely related to the state of photosystem II, which plays a leading role in the photosynthetic process, and therefore it has become a powerful tool to investigate this complex and any damage occurring in it as a result of physical or chemical stresses. This means that by using photosynthetic organisms as biological probes, one can consider chlorophyll a fluorescence as one of the techniques of choice to reveal the presence of some hazardous toxicants widely spread in the environment. Herbicides, pesticides, and heavy metals, whose concentration in water and food products is generally subject to extremely severe restrictions, are a concrete example of compounds detectable by chlorophyll a fluorescence. These dangerous substances react with the photosystem II, modifying the fluorescence emitted and giving responses which vary in a concentration-dependent manner. The possibility of performing easy, fast, and direct measurements of the fluorescence, even under light conditions, has opened new frontiers for the analysis in situ of pollutants. The aim of this review is to give an overview of the different techniques based on chlorophyll a fluorescence spectrometry, focusing in particular on those which represented the starting point for applications addressed to the assessment of toxic compounds in environmental samples.

Development of a photosystem II-based optical microfluidic sensor for herbicide detection.

Herbicides are highly toxic for both human and animal health. The increased application of herbicides in agriculture during the last decades has resulted in the contamination of both soil and water. Herbicides, under illumination, can inhibit photosystem II electron transfer. Photosynthetic membranes isolated from higher plants and photosynthetic micro-organisms, immobilized and stabilized, can serve as a biorecognition element for a biosensor. The inhibition of photosystem II causes a reduced photoinduced production of hydrogen peroxide, which can be measured by a chemiluminescence reaction with luminol and the enzyme horseradish peroxidase. In the present work, a compact and portable sensing device that combines the production and detection of hydrogen peroxide in a single flow assay is proposed for herbicide detection.

Direct laser immobilization of photosynthetic material on screen printed electrodes for amperometric biosensor

This letter demonstrates the direct laser printing of photosynthetic material onto low cost nonfunctionalized screen printed electrodes for the fabrication of photosynthesis-based amperometric biosensors. The high kinetic energy of the transferred material induces direct immobilization of the thylakoids onto the electrodes without the use of linkers. This type of immobilization is able to establish efficient electrochemical contact between proteins and electrode, stabilizing the photosynthetic biomolecule and transporting electrons to the solid state device with high efficiency. The functionality of the laser printed biosensors was evaluated by the detection of a common herbicide such as Linuron.

Intercalation of the herbicide atrazine in layered double hydroxides for controlled‐release applications

BACKGROUND The herbicide atrazine was intercalated in the interlayer region of Mg/Al layered double hydroxides in order to produce a nanohybrid that could be used in controlled-release applications. RESULTS The hydrophobic herbicide was incorporated in artificial membranes formed in the interlayer of the inorganic host by using palmitic acid. The synthetic nanohybrid material was characterised by various techniques, and release studies were carried out. In addition, the photosynthetic alga Chlamydomonas reinhardtii Dang. was treated with the atrazine-containing nanohybrid, which exerted an herbicidal efficacy similar to that of the free herbicide. CONCLUSION The herbicide containing nanohybrid could enable a controlled release of the herbicide. In addition, the herbicide would be delivered close to its site of uptake, enhancing efficiency and reducing the required doses.

Isolation, characterization, sequencing and crystal structure of charybdin, a type 1 ribosome-inactivating protein from Charybdis maritima agg.

A novel, type 1 ribosome‐inactivating protein designated charybdin was isolated from bulbs of Charybdis maritima agg. The protein, consisting of a single polypeptide chain with a molecular mass of 29 kDa, inhibited translation in rabbit reticulocytes with an IC50 of 27.2 nm. Plant genomic DNA extracted from the bulb was amplified by PCR between primers based on the N‐terminal and C‐terminal sequence of the protein from dissolved crystals. The complete mature protein sequence was derived by partial DNA sequencing and terminal protein sequencing, and was confirmed by high‐resolution crystal structure analysis. The protein contains Val at position 79 instead of the conserved Tyr residue of the ribosome‐inactivating proteins known to date. To our knowledge, this is the first observation of a natural substitution of a catalytic residue at the active site of a natural ribosome‐inactivating protein. This substitution in the active site may be responsible for the relatively low in vitro translation inhibitory effect compared with other ribosome‐inactivating proteins. Single crystals were grown in the cold room from PEG6000 solutions. Diffraction data collected to 1.6 Å resolution were used to determine the protein structure by the molecular replacement method. The fold of the protein comprises two structural domains: an α + β N‐terminal domain (residues 4–190) and a mainly α‐helical C‐terminal domain (residues 191–257). The active site is located in the interface between the two domains and comprises residues Val79, Tyr117, Glu167 and Arg170.

Preventive or Potential Therapeutic Value of Nutraceuticals against Ionizing Radiation-Induced Oxidative Stress in Exposed Subjects and Frequent Fliers

Humans are constantly exposed to ionizing radiation deriving from outer space sources or activities related to medical care. Absorption of ionizing radiation doses over a prolonged period of time can result in oxidative damage and cellular dysfunction inducing several diseases, especially in ageing subjects. In this report, we analyze the effects of ionizing radiation, particularly at low doses, in relation to a variety of human pathologies, including cancer, and cardiovascular and retinal diseases. We discuss scientific data in support of protection strategies by safe antioxidant formulations that can provide preventive or potential therapeutic value in response to long-term diseases that may develop following exposure.

Synthesis, RNA binding and nuclease activity of porphyrin-hydroxamic acid derivatives

The interaction modes and nuclease activity against RNA of methylpyridiniumyl/phenyl-hydroxamic acid porphyrin adducts have been investigated. These compounds are derived from the tetracationic meso-tetrakis(N-methyl-4-pyridiniumyl)porphyrin (H2TMPyP-4) by replacing one or two pyridinium rings with a phenyl group. This group is bearing an aliphatic chain of three carbon atoms in the para position to a hydroxamic acid. A different interaction mode is observed depending on the number of charges and hydroxamic acid function. The nuclease activity of the porphyrin adducts against RNA has been demonstrated. Also the effect of the presence of various lanthanide ions on the porphyrin nuclease activity has been tested.

Successes in the Development and Application of Innovative Techniques

Up to now research centres and companies have developed their scientific disciplines and technologies within disparate sectors. Today, the trend is to combine these individual disciplines to meet a common goal. Converging technology represents the application and integration of complementary disciplines towards new fields. The technologies applied in various scientific fields often overlap; however, their union can result in much more than the sum of the single component, leading to unexpected and novel solutions.