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The synthesis of a new bis(2,2′-bipyridine), bridged by a Schiff base cyclohexane moiety is described. Surprisingly, this compound does not appear to form discrete oligonuclear metal complexes on the addition of zinc(II) and iron(II) cations. In order to rationalise this behaviour, the compound’s conformation has been explored using a combination of circular dichroism, X-ray crystallography and DFT calculations, indicating that at least two energy barriers need to be overcome to orientate the ligand in a suitable conformation to permit the formation of coordination helicates with control over the metal centred stereochemistry.

DFT calculations at the B3LYP/6-31G(d) level were carried out for the ground and excited triplet states of free base meso-tetraphenylporphyrin, H2TPP, and its d2, d8, d10, d20, d22, and 13C4 isotopomers. The agreement between experimental and calculated (scaled with a single factor of 0.973) band positions for the ground state was acceptable (rms = 9.9 cm-1). In addition, although the shifts on isotopic substitution were frequently of the same order as this rms error in the absolute positions, it was found that the cancellation of errors in the calculations meant that the direction and magnitude of even small isotope shifts < 10 cm-1 were also calculated correctly. In the D2 symmetry of the calculations the lowest lying triplet state corresponded to a one-electron transition from the b1 HOMO to a b3 LUMO. It was found that the calculated changes in cm-1 of the vibrational modes on excitation to this triplet (ΔS-T) reproduced the ΔS-T values of the seven bands found in the experimental spectra. Three of th...

The free-base form of tetra-tert-butyl porphine (TtBP), which has extremely bulky meso substituents, is severely distorted from planarity, with a ruffling angle of 65.5°. The resonance Raman spectrum of TtBP (λex = 457.9 nm) and its d2, d8, and d10 isotopomers have been recorded, and while the spectra show high-frequency bands similar to those observed for planar meso-substituted porphyrins, there are several additional intense bands in the low-frequency region. Density functional calculations at the B3-LYP/6-31G(d) level were carried out for all four isotopomers, and calculated frequencies were scaled using a single factor of 0.98. The single factor scaling approach was validated on free base porphine where the RMS error was found to be 14.9 cm-1. All the assigned bands in the high-frequency (>1000 cm-1) region of TtBP were found to be due to vibrations similar in character to the in-plane skeletal modes of conventional planar porphyrins. In the low-frequency region, two of the bands, assigned as ν8 (ca....

Herein, we show a comprehensive experimental, theoretical, and computational study aimed at designing macromolecules able to adsorb a cargo at the nanoscale. Specifically, we focus on the adsorption properties of star diblock copolymers, i.e., macromolecules made by a number f of H-T diblock copolymer arms tethered on a central core; the H monomeric heads, which are closer to the tethering point, are attractive toward a specific target, while the T monomeric tails are neutral to the cargo. Experimentally, we exploited the adaptability of poly(2-oxazoline)s (POxs) to realize block copolymer-coated nanoparticles with a proper functionalization able to interact with heavy metals and show or exhibit a thermoresponsive behavior in aqueous solution. We here present the synthesis and analysis of the properties of a high molecular mass block copolymer featured by (i) a polar side chain, capable of exploiting electrostatic and hydrophilic interaction with a predetermined cargo, and (ii) a thermoresponsive scaffold, able to change the interaction with the media by tuning the temperature. Afterward, the obtained polymers were grafted onto iron oxide nanoparticles and the thermoresponsive properties were investigated. Through isothermal titration calorimetry, we then analyzed the adsorption properties of the synthesized superparamagnetic nanoparticles for heavy metal ions in aqueous solution. Additionally, we use a combination of scaling theories and simulations to link equilibrium properties of the system to a prediction of the loading properties as a function of size ratio and effective interactions between the considered species. The comparison between experimental results on adsorption and theoretical prediction validates the whole design process.

Background Meloidae (blister beetles) are known to synthetize cantharidin (CA), a toxic and defensive terpene mainly stored in male accessory glands (MAG) and emitted outward through reflex-bleeding. Recent progresses in understanding CA biosynthesis and production organ(s) in Meloidae have been made, but the way in which self-protection is achieved from the hazardous accumulation and release of CA in blister beetles has been experimentally neglected. To provide hints on this pending question, a comparative de novo assembly transcriptomic approach was performed by targeting two tissues where CA is largely accumulated and regularly circulates in Meloidae: the male reproductive tract (MRT) and the haemolymph. Differential gene expression profiles in these tissues were examined in two blister beetle species, Lydus trimaculatus (Fabricius, 1775) (tribe Lyttini) and Mylabris variabilis (Pallas, 1781) (tribe Mylabrini). Upregulated transcripts were compared between the two species to identify conserved genes possibly involved in CA detoxification and transport. Results Based on our results, we hypothesize that, to avoid auto-intoxication, ABC, MFS or other solute transporters might sequester purported glycosylated CA precursors into MAG, and lipocalins could bind CA and mitigate its reactivity when released into the haemolymph during the autohaemorrhaging response. We also found an over-representation in haemolymph of protein-domains related to coagulation and integument repairing mechanisms that likely reflects the need to limit fluid loss during reflex-bleeding. Conclusions The de novo assembled transcriptomes of L. trimaculatus and M. variabilis here provided represent valuable genetic resources to further explore the mechanisms employed to cope with toxicity of CA in blister beetle tissues. These, if revealed, might help conceiving safe and effective drug-delivery approaches to enhance the use of CA in medicine.

New dihydroxytyrosyl esters 2a, 2c&ndash, 2j of dicarboxylic acids were synthesized from methyl orthoformate protected hydroxytyrosol 3 and diacyl chlorides. New compounds were characterized (HRMS, FT-IR, 1H- and 13C-NMR), and tested for antioxidant activity both in vitro (ABTS) and on L6 myoblasts and THP1 leukemic monocytes cell culture by DCF assay. According to the ABTS assay, compounds 2a, 2c&ndash, 2j showed a TEAC value of antioxidant capacity up to twice that of Trolox. Very high or complete ROS protections were obtained in the cell environment where lipophilicity and rigidity of dicarboxylic structure seem to facilitate the antioxidant effect. MTT assay and proliferation test were used for assessment of cell viability. These compounds can be envisaged as a new class of preservatives for food or cosmetic products.

Cantharidin (CA), a toxic terpene produced by blister beetles (Coleoptera: Meloidae), attracts the interest of many researchers for its renowned medical properties. The CA content in blister beetles has been mainly quantified in some Oriental species, due to their use in traditional Chinese medicine, or in few other species of toxicological importance. As CA quantification has been largely ignored in many other members of this family, we aimed at estimating CA content in natural populations of two of the most abundant species in central Italy, Mylabris variabilis and Lydus trimaculatus. Nearly 100 individuals for each species were collected in the field, identified and reared in fauna-boxes until CA collection. Available protocols were optimized for CA extraction from both dried-body tissues and exuded hemolymph collected from leg joints using capillary tubes. The CA content was quantified in a gas chromatography system coupled to a mass spectrometer using a calibration curve with diethyl-ester of norcantharidin as the internal standard. We observed: (i) high variability in CA content among specimens, which was positively related to individual dry-weight; and (ii) slightly larger (though non-significant) amount of CA in males than in females for both species. Our data are consistent with the available published reports about CA content, transfer and distribution in blister beetles and suggest a conserved biological role of this terpene in Meloidae.