Molecular recognition by gold, silver and copper nanoparticles

The intrinsic physical properties of the noble metal nanoparticles,which are highly sensitive to the nature of their local molecular environment,make such systems ideal for the detection of molecular recognition events.The current review describes the state of the art concerning molecular recognition of Noble metal nanoparticles.In the first part the preparation of such nanoparticles is discussed along with methods of capping and stabilization.A brief discussion of the three common methods of functionalization:Electrostatic adsorption;Chemisorption;Affinity-based coordination is given.In the second section a discussion of the optical and electrical properties of nanoparticles is given to aid the reader in understanding the use of such properties in molecular recognition.In the main section the various types of capping agents for molecular recognition;nucleic acid coatings,protein coatings and molecules from the family of supramolecular chemistry are described along with their numerous applications.Emphasis for the nucleic acids is on complementary oligonucleotide and aptamer recognition.For the proteins the recognition properties of antibodies form the core of the section.With respect to the supramolecular systems the cyclodextrins,calix[n]arenes,dendrimers,crown ethers and the cucurbitales are treated in depth.Finally a short section deals with the possible toxicity of the nanoparticles,a concern in public health.     

Modular design of Cys-loop ligand-gated ion channels: functional 5-HT3 and GABA rho1 receptors lacking the large cytoplasmic M3M4 loop

Cys-loop receptor neurotransmitter-gated ion channels are pentameric assemblies of subunits that contain three domains: extracellular, transmembrane, and intracellular. The extracellular domain forms the agonist binding site. The transmembrane domain forms the ion channel. The cytoplasmic domain is involved in trafficking, localization, and modulation by cytoplasmic second messenger systems but its role in channel assembly and function is poorly understood and little is known about its structure. The intracellular domain is formed by the large (>100 residues) loop between the alpha-helical M3 and M4 transmembrane segments. Putative prokaryotic Cys-loop homologues lack a large M3M4 loop. We replaced the complete M3M4 loop (115 amino acids) in the 5-hydroxytryptamine type 3A (5-HT(3A)) subunit with a heptapeptide from the prokaryotic homologue from Gloeobacter violaceus. The macroscopic electrophysiological and pharmacological characteristics of the homomeric 5-HT(3A)-glvM3M4 receptors were comparable to 5-HT(3A) wild type. The channels remained cation-selective but the 5-HT(3A)-glvM3M4 single channel conductance was 43.5 pS as compared with the subpicosiemens wild-type conductance. Coexpression of hRIC-3, a protein that modulates expression of 5-HT(3) and acetylcholine receptors, significantly attenuated 5-HT-induced currents with wild-type 5-HT(3A) but not 5-HT(3A)-glvM3M4 receptors. A similar deletion of the M3M4 loop in the anion-selective GABA-rho1 receptor yielded functional, GABA-activated, anion-selective channels. These results imply that the M3M4 loop is not essential for receptor assembly and function and suggest that the cytoplasmic domain may fold as an independent module from the transmembrane and extracellular domains.     

Genetic variability in Tunisian populations of faba bean (<Emphasis Type="Italic">Vicia faba</Emphasis> L. var. <Emphasis Type="Italic">major</Emphasis>) assessed by morphological and SSR markers

The genetic diversity of 21 faba bean populations was examined using morphological and molecular markers. DNA was extracted from 189 individuals and 8 microsatellite markers were genotyped individually in these 21 populations. A total of 53 alleles were obtained in all populations, with an average of 6.62 alleles per locus. The expected and observed heterozygosity was 0.38 and 0.62 respectively. The average polymorphism index content of SSR markers was 0.61, ranging from 0.31 to 0.81. The unweighted pair group method with arithmetic mean dendrogram clustered all the populations into two groups, each for them subdivided into 3 sub-groups according to geographical origin. Morphological variation showed that the populations were not grouped according to their geographical origin. Therefore, patterns of differentiation of morphological traits did not coincide with molecular differentiation, indicating that morphological variation does not reflect genetic subdivision in studied faba bean populations. Analysis of molecular variance revealed high levels of genetic variation (83%) within population and provides a good base for designing genetic improvement programs. The result of Principal Component Analysis (PCA) revealed that three dimensional principal components (PC1, PC2 and PC3) contributed 40.56% of the total variability and accounted with values of 20.64, 11.22 and 8.70%, respectively. Cluster analysis based on PCA indicated three separate groups of populations. The genetic relationships found between the 21 populations samples were the same in both the PCA and STRUCTURE analysis which support the results observed. These data may serve as a foundation for the development of faba bean breeding programs.     

Nodule conductance varied among common bean (Phaseolus vulgaris) genotypes under phosphorus deficiency

Common bean genotypes BAT477, COCOT, DOR364, Flamingo, and NAG310 were inoculated with Rhizobium tropici CIAT899 and grown under phosphorus deficiency. This treatment induced a significant decrease in shoot and nodule growth that varied among genotypes from 35% to 57% and from 45% to 61%, respectively, whereas root biomass was less affected. Phosphorus deficiency affected differently the genotypes for nodule number and size, and the responses of nodulated-root O2 uptake (Conr) to raising rhizospheric PO2. From the later data, nodule conductance could be computed by dividing the slope of the regression of Conr as a function of external pO2 by nodule surface area. It is concluded that differences in nodule conductance are related to genotypic tolerance to P deficiency.     

Parasitoids of chickpea leafminer Liriomyza cicerina (Diptera: Agromyzidae) and their parasitism rate on chickpea fields in North Tunisia

In recent years, as a consequence of climatic changes, the leafminer Liriomyza cicerina had emerged as a serious pest in chickpea crops causing considerable damage in Tunisia. Thus, the search of control methods is necessary. The aim of this research was to monitor and identify the naturally occurring parasitoids of the chickpea leafminer Liriomyza cicerina in insecticide-free chickpea-growing areas located in North-Western Tunisia. Chickpea leaves with mines were weekly sampled from Beja and Kef sites during 2016 and 2017 and kept to observe and count emerging leafminer and parasitoid adults in the laboratory. Results revealed that L. cicerina parasitoids complex species included three hymenopteran parasitoids namely Opius monilicornis (Fisher, 1962) (Braconidae); Diglyphus isaea (Walker, 1838) (Eulophidae) and Diaulinopsis arenaria (Erdös, 1951) (Eulophidae). These parasitoids were identified and recorded for the first time in Tunisia on L. cicerina with parasitism rate varied between 13% and 52.5%. The most common species was O. monilicornis. The correlation between infestation rate on chickpea plants and number of emerged three parasitoids was calculated revealing high significant and positive correlations. The diversity index (H′) was also calculated. The three parasitoids were found in two sites Beja and Kef; while the diversity differed during the developmental stage of chickpea crops.     

The Calcitonin Gene-Related Peptide Activates Both cAMP and NO Pathways to Induce Relaxation of Circular Smooth Muscle Cells of Guinea-Pig Ileum

Rekik, M., M. Delvaux, J. Frexinos, and L. Bueno. Calcitonin gene-related peptide activates both cAMP and NO pathways to induce relaxation of circular smooth muscle cells of guinea-pig ileum. Peptides 18(10) 1517–1522, 1997.—The direct effects and the intracellular pathways of rCGRP were investigated on smooth muscle cells (SMC) isolated by enzymatic digestion from the circular and longitudinal layers of guinea-pig ileum. In circular SMC, rCGRP inhibited CCK8-induced contraction in a concentration-dependent manner (Cmax = 100 μM and EC₅₀ = 0.7 ± 0.4 nM). Preincubation of SMC with 1 μM Rp-cAMPs, a cAMP antagonist, abolished the relaxing effect of rCGRP; moreover, preincubation of SMC with 100 μM L-NAME, an inhibitor of NOS, inhibited the relaxing effect of rCGRP. hCGRP(8-37), a selective antagonist of rCGRP receptors, inhibited the rCGRP-induced relaxation in a concentration dependent manner whereas the vasoactive intestinal polypeptide (VIP) antagonist had no significant effect. In longitudinal SMC, rCGRP-induced relaxation was abolished by Rp-cAMPs, whereas L-NAME had no effect. In conclusion, rCGRP triggers different intracellular pathways to induce relaxation of circular or longitudinal intestinal SMC; cAMP is involved in cells from both layers while nitric oxide (NO) is involved only in relaxation of circular SMC.     

The secretion of the bacterial phytase PHY‐US417 by Arabidopsis roots reveals its potential for increasing phosphate acquisition and biomass production during co‐growth

Phytic acid (PA) is a major source of inorganic phosphate (Pi) in the soil; however, the plant lacks the capacity to utilize it for Pi nutrition and growth. Microbial phytases constitute a group of enzymes that are able to remobilize Pi from PA. Thus, the use of these phytases to increase the capacity of higher plants to remobilize Pi from PA is of agronomical interest. In the current study, we generate transgenic Arabidopsis lines (ePHY) overexpressing an extracellular form of the phytase PHY‐US417 of Bacillus subtilis, which are characterized by high levels of secreted phytase activity. In the presence of PA as sole source of Pi, while the wild‐type plants show hallmark of Pi deficiency phenotypes, including the induction of the expression of Pi starvation‐induced genes (PSI, e.g. PHT1;4) and the inhibition of growth capacity, the ePHY overexpressing lines show a higher biomass production and no PSI induction. Interestingly, when co‐cultured with ePHY overexpressors, wild‐type Arabidopsis plants (or tobacco) show repression of the PSI genes, improvement of Pi content and increases in biomass production. In line with these results, mutants in the high‐affinity Pi transporters, namely pht1;1 and pht1;1‐1;4, both fail to accumulate Pi and to grow when co‐cultured with ePHY overexpressors. Taken together, these data demonstrate the potential of secreted phytases in improving the Pi content and enhancing growth of not only the transgenic lines but also the neighbouring plants.     

Rational design of Bacillus stearothermophilus US100 l-arabinose isomerase: Potential applications for d-tagatose production

l-Arabinose isomerases catalyze the bioconversion of d-galactose into d-tagatose. With the aim of producing an enzyme optimized for d-tagatose production, three Bacillus stearothermophilus US100 l-arabinose isomerase mutants were constructed, purified and characterized. Our results indicate that mutant Q268K was significantly more acidotolerant and more stable at acidic pH than the wild-type enzyme. The N175H mutant has a broad optimal temperature range from 50 to 65 °C. With the aim of constructing an acidotolerant mutant working at relatively low temperatures we generated the Q268K/N175H construct. This double mutant displays an optimal pH in the range 6.0–7.0 and an optimal activity around 50–65 °C, temperatures at which the enzyme was stable without addition of metal ions.