Functional architecture of higher plant photosystem II supercomplexes

Photosystem II (PSII) is a large multiprotein complex, which catalyses water splitting and plastoquinone reduction necessary to transform sunlight into chemical energy. Detailed functional and structural studies of the complex from higher plants have been hampered by the impossibility to purify it to homogeneity. In this work, homogeneous preparations ranging from a newly identified particle composed by a monomeric core and antenna proteins to the largest C₂S₂M₂ supercomplex were isolated. Characterization by biochemical methods and single particle electron microscopy allowed to relate for the first time the supramolecular organization to the protein content. A projection map of C₂S₂M₂ at 12 Å resolution was obtained, which allowed determining the location and the orientation of the antenna proteins. Comparison of the supercomplexes obtained from WT and Lhcb‐deficient plants reveals the importance of the individual subunits for the supramolecular organization. The functional implications of these findings are discussed and allow redefining previous suggestions on PSII energy transfer, assembly, photoinhibition, state transition and non‐photochemical quenching.     

<Emphasis Type="Italic">N</Emphasis>-vanillylnonanamide tested as a non-toxic antifoulant,applied to surfaces in a polyurethane coating

The potential on N-vanillylnonanamide (NVN) in preventing the attachment of Pseudomonas stutzeri and a Bacillus cereus-group strain was investigated. NVN up to 852 μM was not toxic, nor was it an energy source for either organism. Microbial attachment assays were carried out on glass and polylysine slides. with NVN being dispersed in or applied to the surfaces using a polyurethane coating. NVN at 205 μM inhibited Bacillus adhesion on glass slides by 48% and the percentage did not significantly increase at 852 μM. NVN blended into or sprayed onto the coating at 205 μmol/kg did not prevent adhesion. The compound is therefore not useful as an antifouling product under the tested coating conditions.     

Synthesis of 6-deoxy-6-chloro and 6-deoxy-6-bromo derivatives of scleroglucan as intermediates for conjugation with methotrexate and other carboxylate containing compounds

Polysaccharides are widely used as carriers in the field of drug delivery. We present a methodology to obtain water soluble drug-conjugates based on scleroglucan. Selective C-6 halogenation gives access to C-6 esters; conjugates between methotrexate and scleroglucan are described, potentially useful for antitumour therapy or in rheumatoid arthritis treatment.     

Evaluation of 59Fe-lignosulfonates complexes as Fe-sources for plants

Iron chlorosis is a wide-spread limiting factor of production in agriculture. To cope with this problem, synthetic chelates (like EDTA or EDDHA) of Fe are used in foliar-spray or in soil treatments; however, these products are very expensive. Therefore paper-production byproducts, like Lignosulfonates (LS), with varying content of carboxylate and sulfonate groups, were tested with respect to their ability to maintain Fe in the solution of soils and to feed plants grown in hydroponics with Fe through foliar sprays or application to the nutrient solution. Results show that LS had a low capability to solubilize ⁵⁹Fe-hydroxide and that preformed ⁵⁹Fe(III)-LS complexes had poor mobility through a soil column (pH 7.5) and scarce stability when interacting with soils compared to ⁵⁹Fe(III)-EDDHA. However when ⁵⁹Fe(III)-LS were supplied to roots in a hydroponic system, they demonstrated an even higher capability to fed Fe-deficient tomato plants than ⁵⁹Fe(III)-EDDHA. Hence, data here presented indicate that the low Fe use efficiency from Fe-LS observed in soil-applications is due to interactions of these Fe-sources with soil colloids rather than to the low capability of roots to use them. Foliar application experiments of ⁵⁹Fe(III)-LS or ⁵⁹Fe(III)-EDTA to Fe-deficient cucumber plants show that uptake and reduction rates of Fe were similar between all these complexes; on the other hand, when ⁵⁹Fe(III)-LS were sprayed on Fe-deficient tomato leaves, they showed a lower uptake rate, but a similar reduction rate, than ⁵⁹Fe(III)-EDTA did. In conclusion, Fe-LS may be a valid, eco-compatible and cheap alternative to synthetic chelates in dealing with Fe chlorosis when applied foliarly or in the nutrient solution of hydroponically grown plants.     

Effect of T3 on metabolic response and oxidative stress in skeletal muscle from sedentary and trained rats

We investigated whether swim training modifies the effect of T₃-induced hyperthyroidism on metabolism and oxidative damage in rat muscle. Respiratory capacities, oxidative damage, levels of antioxidants, and susceptibility to oxidative challenge of homogenates were determined. Mitochondrial respiratory capacities, H₂O₂ release rates, and oxidative damage were also evaluated. T₃-treated rats exhibited increases in muscle respiratory capacity, which were associated with enhancements in mitochondrial respiratory capacity and tissue mitochondrial protein content in sedentary and trained animals, respectively. Hormonal treatment induced muscle oxidative damage and GSH depletion. Both effects were reduced by training, which also attenuated tissue susceptibility to oxidative challenge. The changes in single antioxidant levels were slightly related to oxidative damage extent, but the examination of parameters affecting the susceptibility to oxidants indicated that training was associated with greater effectiveness of the muscle antioxidant system. Training also attenuated T₃-induced increases in H₂O₂ production and, therefore, oxidative damage of mitochondria by lowering their content of autoxidizable electron carriers. The above results suggest that moderate training is able to reduce hyperthyroid state-linked tissue oxidative damage, increasing antioxidant protection and decreasing the ROS flow from the mitochondria to the cytoplasmic compartment.     

Highly selective single nucleotide polymorphism recognition by a chiral (5S) PNA beacon

A chiral peptide nucleic acid (PNA) beacon containing a C-5 modified monomer based on L-lysine was synthesized. The terminal amino group of the lysine side chain was linked to a spacer for future applications on surfaces. The PNA beacon bears a carboxyfluorescein fluorophore and a dabcyl quencher at opposite ends. The DNA binding properties were compared with those of a homologous PNA beacon containing only achiral monomers. Both beacons underwent a fluorescence increase in the presence of complementary DNA, with higher efficiency and higher selectivity (evaluated using single mismatched DNA sequences) observed for the chiral monomer containing PNA. Ion exchange (IE) HPLC with fluorimetric detection was used in combination with the beacon for the selective detection of complementary DNA. A fluorescent peak corresponding to the PNA beacon:DNA duplex was observed at a very low detection limit (1 nM). The discriminating capacity of the chiral PNA beacon for a single mismatch was found to be superior to those observed with the unmodified one, thus confirming the potency of chirality for increasing the affinity and specificity of DNA recognition.     

Improving the spatial orientation of human teeth using a virtual 3D approach

Since teeth are resistant to decomposition processes, they provide important and at times unique sources of information about fossil humans. Fortunately, dental remains reflect significant evolutionary changes. These changes make a very important and often exclusive contribution to the definition of new taxa or the attribution of fossil specimens to existing taxa.The traditional approach to dental morphometric analyses usually focuses on the recording of several measures of the tooth with calipers, especially the two basic crown diameters (buccolingual and mesiodistal). However, since these measures do not adequately represent the complex morphology of the tooth, 2D images and 3D digital models of dental morphology have been used. For both types of analysis, the possibility of correctly comparing homologous teeth depends on the adoption of a common orientation system. The lack of such a system makes it difficult to compare the results of different studies.Here we describe a new method for orienting teeth specifically devised for the upper and lower first molar (M1). Samples of unworn maxillary (n = 15) and mandibular (n = 15) first molars of modern humans were scanned with a Roland Picza 3D digitizer. The 3D virtual models were used to compare our new orientation method with those proposed in the literature. The new orientation system, which meets a geometric criterion, is based on three points identified on the cervical line and ensures acceptable repeatability of the spatial positioning and orientation independent of the shape and wear of the first molar under investigation. This orientation system is a first step toward the creation of a virtual set of hominid and fossil human first molars, which will allow us to make comparisons via a sophisticated and noninvasive approach. This pilot study also provides guidelines to extend the new methodology to the other types of teeth.