Aphids harbouring different endosymbionts exhibit differences in cuticular hydrocarbon profiles that can be recognized by ant mutualists

Cuticular hydrocarbons (CHCs) have important communicative functions for ants, which use CHC profiles to recognize mutualistic aphid partners. Aphid endosymbionts can influence the quality of their hosts as ant mutualists, via effects on honeydew composition, and might also affect CHC profiles, suggesting that ants could potentially use CHC cues to discriminate among aphid lines harbouring different endosymbionts. We explored how several strains of Hamiltonella defensa and Regiella insecticola influence the CHC profiles of host aphids (Aphis fabae) and the ability of aphid-tending ants (Lasius niger) to distinguish the profiles of aphids hosting different endosymbionts. We found significant compositional differences between the CHCs of aphids with different infections. Some endosymbionts changed the proportions of odd-chain linear alkanes, while others changed primarily methyl-branched compounds, which may be particularly important for communication. Behavioural assays, in which we trained ants to associate CHC profiles of endosymbiont infected or uninfected aphids with food rewards, revealed that ants readily learned to distinguish differences in aphid CHC profiles associated with variation in endosymbiont strains. While previous work has documented endosymbiont effects on aphid interactions with antagonists, the current findings support the hypothesis that endosymbionts also alter traits that influence communicative interactions with ant mutualists.

Hormonal modulation of reproduction and fertility signaling in polistine wasps

In social insects, it has been suggested that reproduction and the production of particular fertility-linked cuticular hydrocarbons (CHC) may be under shared juvenile hormone (JH) control, and this could have been key in predisposing such cues to later evolve into full-fledged queen pheromone signals. However, to date, only few studies have experimentally tested this “hormonal pleiotropy” hypothesis. Here, we formally test this hypothesis using data from four species of Polistine wasps, Polistes dominula, Polistes satan, Mischocyttarus metathoracicus, and Mischocyttarus cassununga, and experimental treatments with JH using the JH analogue methoprene and the anti-JH precocene. In line with reproduction being under JH control, our results show that across these four species, precocene significantly decreased ovary development when compared with both the acetone solvent-only control and the methoprene treatment. Consistent with the hormonal pleiotropy hypothesis, these effects on reproduction were further matched by subtle shifts in the CHC profiles, with univariate analyses showing that in P. dominula and P. satan the abundance of particular linear alkanes and mono-methylated alkanes were affected by ovary development and our hormonal treatments. The results indicate that in primitively eusocial wasps, and particularly in Polistes, reproduction and the production of some CHC cues are under joint JH control. We suggest that pleiotropic links between reproduction and the production of such hydrocarbon cues have been key enablers for the origin of true fertility and queen signals in more derived, advanced eusocial insects.

Oxidation of Organic Compounds with Peroxides Catalyzed by Polynuclear Metal Compounds

The review describes articles that provide data on the synthesis and study of the properties of catalysts for the oxidation of alkanes, olefins, and alcohols. These catalysts are polynuclear complexes of iron, copper, osmium, nickel, manganese, cobalt, vanadium. Such complexes for example are: [Fe2(HPTB)(m-OH)(NO3)2](NO3)2·CH3OH·2H2O, where HPTB-¼N,N,N0,N0-tetrakis(2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane; complex [(PhSiO1,5)6]2[CuO]4[NaO0.5]4[dppmO2]2, where dppm-1,1-bis(diphenylphosphino)methane; (2,3-η-1,4-diphenylbut-2-en-1,4-dione)undecacarbonyl triangulotriosmium; phenylsilsesquioxane [(PhSiO1.5)10(CoO)5(NaOH)]; bi- and tri-nuclear oxidovanadium(V) complexes [{VO(OEt)(EtOH)}2(L2)] and [{VO(OMe)(H2O)}3(L3)]·2H2O (L2 = bis(2-hydroxybenzylidene)terephthalohydrazide and L3 = tris(2-hydroxybenzylidene)benzene-1,3,5-tricarbohydrazide); [Mn2L2O3][PF6]2 (L = 1,4,7-trimethyl-1,4,7-triazacyclononane). For comparison, articles are introduced describing catalysts for the oxidation of alkanes and alcohols with peroxides, which are simple metal salts or mononuclear metal complexes. In many cases, polynuclear complexes exhibit higher activity compared to mononuclear complexes and exhibit increased regioselectivity, for example, in the oxidation of linear alkanes. The review contains a description of some of the mechanisms of catalytic reactions. Additionally presented are articles comparing the rates of oxidation of solvents and substrates under oxidizing conditions for various catalyst structures, which allows researchers to conclude about the nature of the oxidizing species. This review is focused on recent works, as well as review articles and own original studies of the authors.

Selective Terminal Functionalization of Linear Alkanes

Selective undirected functionalization of strong primary C-H bonds of linear alkanes, that do not possess directing groups, historically stands as one of the most challenging transformation in chemistry. In this Article, we report a two-step sequential strategy involving a biocatalytic dehydrogenation / remote hydrofunctionalization, as a unified and versatile approach to selectively convert linear alkanes into a large array of valuable functionalized aliphatic derivatives. The dehydrogenation is carried out by a mutant strain of Rhodococcus and the produced alkenes are subsequently engaged in a remote functionalization through a metal-catalyzed hydrometalation/migration sequence that subsequently react with a large variety of electrophiles. The judicious implementation of this combined biocatalytic and organometallic approach enabled us to develop a high-yielding protocol to site-selectively functionalize unreactive primary C–H bonds.

Calculation of Absolute Molecular Entropies and Heat Capacities Made Simple

We propose a fully automated composite scheme for the calculation of molecular entropies efficiently, accurately and numerically stable by a combination of DFT, semiempirical quantum chemical (SQM) and force-field (FF) levels. A modified rigid-rotor-harmonic-oscillator (msRRHO) approximation and the Gibbs-Shannon formula for extensive conformer ensembles (CEs) are applied and <br>efficiently account for effects of anharmonicity. CEs of systematically increasing quality are generated by a modified metadynamics search algorithm and extrapolated to completeness. Variations of the ro-vibrational entropy over the CE are accounted for by a Boltzmann population average for the first time consistently. The proposed procedure was extensively tested with two standard DFT methods (B97-3c and B3LYP) and at GFN-SQM/FF levels for the conformation term in comparison with experimental gas phase entropies and heat capacities. Excellent performance is observed with mean deviations <1 cal/mol K (about < 1-2%) for the total molecular entropy. Even for extremely flexible linear alkanes (C₁₄H₃₀-C₁₆H₃₄),<br>unprecedentedly small errors of about 3 cal/mol K are obtained. For 25 typical drug molecules, the conformational entropy depends weakly to strongly on the underlying theory level revealing the complex potential energy surfaces as main source of error. The approach is systematically expandable and moreover can be applied straightforward together with continuum solvation models.<br><br>

Calculation of Absolute Molecular Entropies and Heat Capacities Made Simple

We propose a fully automated composite scheme for the calculation of molecular entropies efficiently, accurately and numerically stable by a combination of DFT, semiempirical quantum chemical (SQM) and force-field (FF) levels. A modified rigid-rotor-harmonic-oscillator (msRRHO) approximation and the Gibbs-Shannon formula for extensive conformer ensembles (CEs) are applied and <br>efficiently account for effects of anharmonicity. CEs of systematically increasing quality are generated by a modified metadynamics search algorithm and extrapolated to completeness. Variations of the ro-vibrational entropy over the CE are accounted for by a Boltzmann population average for the first time consistently. The proposed procedure was extensively tested with two standard DFT methods (B97-3c and B3LYP) and at GFN-SQM/FF levels for the conformation term in comparison with experimental gas phase entropies and heat capacities. Excellent performance is observed with mean deviations <1 cal/mol K (about < 1-2%) for the total molecular entropy. Even for extremely flexible linear alkanes (C₁₄H₃₀-C₁₆H₃₄),<br>unprecedentedly small errors of about 3 cal/mol K are obtained. For 25 typical drug molecules, the conformational entropy depends weakly to strongly on the underlying theory level revealing the complex potential energy surfaces as main source of error. The approach is systematically expandable and moreover can be applied straightforward together with continuum solvation models.<br><br>

Thermal and Catalytic Fast Pyrolysis of Oily Extracts of Microalgae: Production of Biokerosene

Three different microalgae species, Desmodesmus sp., Nannochloropsis oculata and Halamphora coffeaeformis were grown under controlled conditions. The resulting dry biomass was characterized by TG-DTA (thermogravimetry-differential thermal analysis) and extracted with three solvents having different polarities. The extracts gross mass yields varied from 2% using n-hexane to 23% (or 74% when subtracting the volatiles and ashes) when using methanolchloroform whatever the microalgae species. Fourier transform infrared (FTIR) spectra of all extracts suggested the presence of fatty esters and acids. The extracts were pyrolyzed at 600 °C, using a micro pyrolizer coupled to a gas chromatograph-mass spectrometer (GC-MS), without and with γ-alumina as catalyst. Hydrocarbons concentrations varied respectively from 92% in the better case to 46% in the worst case. The C9-C15 fraction of these hydrocarbons, potentially useful for biokerosene formulation, was object of detailed analysis. In this fraction, nitrogenous products had concentrations always lower than 0.1%. The main hydrocarbons produced were linear 1-alkenes for thermal pyrolysis whereas for pyrolysis with γ-alumina, linear 1-alkenes and also alkenes isomers and linear alkanes, together with cyclic and aromatic compounds were observed for all microalgae species, but in different proportions. The C9-C15 fraction of pyrolyzed extracts can be considered as precursor for biokerosene or direct “drop in” fuel for kerosene petroleum fraction.

The Exocrine Chemistry of the Parasitic Wasp Sphecophaga orientalis and Its Host Vespa orientalis: A Case of Chemical Deception?

The main challenge facing a parasite of social insects lies in deceiving its host’s detection and defense systems in order to enter and survive within the host colony. Sphecophaga orientalis is an ichneumonid wasp that parasitizes the pupae of the Oriental hornet Vespa orientalis. In Israel’s Mediterranean region, this parasitoid infects on average 23.48% (8–56%) of the host pupal cells. Observation of colonies brought to the laboratory revealed that the parasite moves around within the colony without being aggressed by the host workers. To assess how the parasite evades host detection and defense, we compared the cuticular hydrocarbon (CHC) profiles of both species. There was little similarity between the parasite and the host workers’ CHC, refuting the hypothesis of chemical mimicry. The parasite’s CHCs were dominated by linear alkanes and alkenes with negligible amounts of branched alkanes, while the host workers’ CHCs were rich in branched alkanes and with little or no alkenes. Moreover, the parasite cuticular wash was markedly rich in oleic acid, previously reported as a cue eliciting necrophoric behavior. Since nests of Oriental hornets are typified by large amounts of prey residues, we suggest that, due to its unfamiliar CHCs and the abundance of oleic acid, the parasite is considered as refuse by the host. We also detected rose oxide in the parasitoid head extracts. Rose oxide is a known insect repellent, and can be used to repel and mitigate aggression in workers. These two factors, in concert, are believed to aid the parasite to evade host aggression.