Effect of some metals and related metal-orgaic compounds on ALA-dehydratase activity of corn

Summary The activity of ALA-dehydratase from corn seedlings is affected by Mn⁺⁺, Fe⁺⁺, Pb⁺⁺, Cu⁺⁺, Zn⁺⁺ and Sn⁺⁴ ions, in vivo Mn⁺⁺ and Fe⁺⁺ are ativators while Pb⁺⁺ and Sn⁺⁴ are inhibitors; in vitro Cu⁺⁺ and Zn⁺⁺ are inhibitors. The kinetic parameters (V_max and K_M) support the hypothesis that Mn, Fe, Sn and Pb ions act on the biosynthesis of the enzyme and Zn and Cu ions on the enzyme-substrate affinity. Some related metal-organic compounds interrere in vivo on the ALA-dehydratase activity modifying the kinetic parameters, therefore the enzyme biogenesis and/or enzyme-sustrat affinity are affected.     

Flight tunnel response of codling moth Cydia pomonella to blends of codlemone,codlemone antagonists and pear ester

Upwind orientation flights of codling moth males Cydia pomonella L. to a single source of sex pheromone (E,E)‐8,10‐dodecadienol (codlemone) are significantly reduced when blending it with pheromone antagonists, either with codlemone acetate, (E,E)‐8,10‐dodecadienyl acetate, or with the codlemone isomer (E,Z)‐8,10‐dodecadienol. However, once activated by a pheromone stimulus, males no longer distinguish between a pheromone source and these antagonistic blend sources. This shows that the pheromone stimulus required for the initiation of an upwind flight response differs from the stimulus for maintaining upwind flight and landing at the source. In contrast to pheromone antagonists, males discriminate between pheromone alone and a blend source of pheromone and the plant volatile pear ester, ethyl (2E,4Z)‐2,4‐decadienoate. This indicates a difference in the detection and neural integration of pheromone and plant volatile stimuli.     

Isoselenocyanates derived from amino acid esters: an expedient synthesis and application to the assembly of selenoureidopeptidomimetics,unsymmetrical Selenoureas and selenohydantoins

An important class of organoselenium compounds‐α‐isoselenocyanato esters 4 hasbeen prepared by a reaction of α‐isocyano esters with elemental selenium powder. The reaction issimple, rapid and all the isoselenocyanates havebeen isolated as stable ones after chromatographic purification. These hitherto unreported classes of molecules would be useful building blocks for the preparation of variety of selenium containing peptidomimetics. In this study, the utility of the title molecules in the preparation of selenoureidopeptidomimetics 6, unsymmetrical selenoureas 8 and selenohydantoins 10 isdemonstrated. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.     

Antibacterial activity of sphagnum acid and other phenolic compounds found in Sphagnum papillosum against food-borne bacteria

Aims:  To identify the phenolic compounds in the leaves of Sphagnum papillosum and examine their antibacterial activity at pH appropriate for the undissociated forms.
Methods and Results:  Bacterial counts of overnight cultures showed that whilst growth of Staphylococcus aureus 50084 was impaired in the presence of milled leaves, the phenol-free fraction of holocellulose of S. papillosum had no bacteriostatic effect. Liquid chromatography–mass spectrometry analysis of an acetone–methanol extract of the leaves detected eight phenolic compounds. Antibacterial activity of the four dominating phenols specific to Sphagnum leaves, when assessed in vitro as minimal inhibitory concentrations (MICs), were generally >2·5 mg ml⁻¹. MIC values of the Sphagnum- specific compound 'sphagnum acid' [ p -hydroxy-β-(carboxymethyl)-cinnamic acid] were >5 mg ml⁻¹. No synergistic or antagonistic effects of the four dominating phenols were detected in plate assays.
Conclusions:  Sphagnum -derived phenolics exhibit antibacterial activity in vitro only at concentrations far in excess of those found in the leaves.
Significance and Impact of the Study:  We have both identified the phenolic compounds in S. papillosum and assessed their antibacterial activity. Our data indicate that phenolic compounds in isolation are not potent antibacterial agents and we question their potency against food-borne pathogens.     

Effect of Paclobutrazol Application on Plant Growth and Flower Quality in Herbaceous Peony

Herbaceous peony (Paeonia lactiflora Pall.) is an important ornamental plant worldwide. In its natural state, P. lactiflora often manifests traits like rapidly elongating internodal growth, loose plant types, and soft inflorescence stems. However, very little has been known about the measures for controlling these traits. This study investigated the effect of applying paclobutrazol (PBZ) on the plant growth and flower quality in P. lactiflora. The results indicated that PBZ application reduced the plant height (8.05%), plant crown width (14.72%), and leaf area (10.90%), but increased the leaf thickness (18.18%) and stem diameter (over 11%) in P. lactiflora. Meanwhile, PBZ application was also found to increase the chlorophyll (Chl) a (29.63%), Chl b (33.33%), Chl a+b (30.56%), SPAD (27.32%), relative water content (0.47%), soluble sugar (5.09%) and activities of three antioxidant enzymes (superoxide dismutase 169.66%, peroxidase 3.59%, catalase 319.30%), but decreased the relative electrical conductivity (18.52%). Additionally, the application of PBZ was found to affect the flowering quality of P. lactiflora, increasing the flower diameter and fresh weight only in the flower-bud stage. This initiates the bloom stage, where there was a decrease in the total content of the aromatic compounds except for the flower-bud stage, and faded the flower color by reducing the content of anthocyanin. These results demonstrated that the application of PBZ can regulate the P. lactiflora plant types with no significant decrease in its ornamental values. This might provide a theoretical basis for further applying PBZ in P. lactiflora for use in urban landscape spaces.     

Metal ion-N7 coordination in a ribozyme branch domain by NMR

The N7 of purine nucleotides presents one of the most dominant metal ion binding sites in nucleic acids. However, the interactions between kinetically labile metal ions like Mg²⁺ and these nitrogen atoms are inherently difficult to observe in large RNAs. Rather than using the insensitive direct ¹⁵N detection, here we have used ²J-[¹H,¹⁵N]-HSQC (Heteronuclear Single Quantum Coherence) NMR experiments as a fast and efficient method to specifically observe and characterize such interactions within larger RNA constructs. Using the 27 nucleotides long branch domain of the yeast-mitochondrial group II intron ribozyme Sc.ai5γ as an example, we show that direct N7 coordination of a Mg²⁺ ion takes place in a tetraloop nucleotide. A second Mg²⁺ ion, located in the major groove at the catalytic branch site, coordinates mainly in an outer-sphere fashion to the highly conserved flanking GU wobble pairs but not to N7 of the sandwiched branch adenosine.     

Cu(I) binding properties of a designed metalloprotein

The Cu(I) binding properties of the designed peptide C16C19-GGY are reported. This peptide was designed to form an α-helical coiled-coil but modified to incorporate a Cys-X-X-Cys metal-binding motif along its hydrophobic face. Absorption, emission, electrospray ionization mass spectrometry (ESI-MS), and circular dichroism (CD) experiments show that a 1:1 Cu-peptide complex is formed when Cu(I) is initially added to a solution of the monomeric peptide. This is consistent with our earlier study in which the emissive 1:1 complex was shown to exist as a peptide tetramer containing a tetranuclear copper cluster Kharenko et al. (2005) [11]. The presence of the tetranuclear copper center is now confirmed by ESI-MS which along with UV data show that this cluster is formed in a cooperative manner. However, spectroscopic titrations show that continued addition of Cu(I) results in the occupation of a second, lower affinity metal-binding site in the metallopeptide. This occupancy does not significantly affect the conformation of the metallopeptide but does result in a quenching of the 600 nm emission. It was further found that the exogenous reductant tris(2-carboxyethyl)phosphine (TCEP) can competitively inhibit the binding of Cu(I) to the low affinity site of the peptide, but does not interact with Cu(I) clusters.     

Predator pheromone elicits a temporally dependent non-consumptive effect in prey

1. The influence of predator cues on the behaviour of prey is well supported in the literature; however, a clear understanding of how predator cues affect prey in variable environmental conditions and over longer time scales is needed to better understand the underlying mechanisms. Here, we measure how predator odors affect herbivore colonization, abundance, oviposition, and plant damage across two growing seasons.
2. The study system consisted of Leptinotarsa decemlineata (Colorado potato beetle) as prey, and the aggregation pheromone of live Podisus maculiventris (spined soldier bug) as the predator cue in a potato field.
3. In 2016, the amount of feeding damage by early beetle colonists was lower in predator odor-treated plots, reducing plant damage by 22%. Larval abundance was also reduced in treated plots in 2016. Beetle abundance and damage in 2017 was similar in the treatment and control plots. Two mechanisms were investigated to better understand why prey response to the predator odor treatment weakened over the first season, including changes in predator odor cue strength and prey habituation. Predator odor cue strength emerged as a likely explanation, as dispensers, which released a synthetic predator pheromone over the entire season, reduced the probability of finding damage more consistently than the live predator treatment.
4. These results suggest that temporal patterns of predator cue release and strength may drive prey response across the season, underscoring the importance of cue release-rate and consistency in both species interactions and for the future application of modifying insect behaviour using non-consumptive effects in agricultural systems.