Alessio Spepi

Exploring the Binding Ability of Phenanthroline-Based Polyammonium Receptors for Anions: Hints for Design of Selective Chemosensors for Nucleotides

The synthesis of receptor 2,6,10,14,18-pentaaza[20]-21,34-phenanthrolinophane (L1), containing a pentaamine chain linking the 2,9 positions of a phenanthroline unit, is reported. The protonation features of L1 and of receptor 2,6,10,14,18,22-hexaaza[23]-24,37-phenanthrolinophane (L2) have been studied by means of potentiometric, (1)H NMR, and spectrofluorimetric measurements; this study points out that the fluorescent emission of both receptors depends on the protonation state of the polyamine chain. In fact, the receptors are emissive only at neutral or acidic pH values, where all the aliphatic amine groups are protonated. Potentiometric titrations show that L2 is able to bind selectively ATP over TTP, CTP, and GTP. This selectivity is lost in the case of L1. (1)H and (31)P NMR measurements and molecular mechanics calculations show that the phosphate chains of nucleotides give strong electrostatic and hydrogen-bonding interactions with the ammonium groups of the protonated receptors, while the nucleobases interact either via pi-stacking with phenanthroline or via hydrogen bonding with the ammonium groups. Of note, MM calculations suggest that all nucleotides interact in an inclusive fashion. In fact, in all adducts the phosphate chain is enclosed within the receptor cavities. This structural feature is confirmed by the crystal structure of the [(H(6)L2)(2)(TTP)(2)(H(2)O)(2)](4+) adduct. Fluorescence emission measurements at different pH values show that L2 is also able to ratiometrically sense ATP in a narrow pH range, thanks to emission quenching due to a photoinduced electron transfer (PET) process from an amine group of the receptor to the excited phenanthroline.

A Novel Manganese Complex Effective as Superoxide Anion Scavenger and Therapeutic Agent against Cell and Tissue Oxidative Injury

Two cyclic polyamine-polycarboxylate ligands, 1,4,7,10-tetraazacyclododecane-1,7-diacetic acid (H(2)L3) and 4,10-dimethyl-1,4,7,10-tetraazacyclododecane-1,7-diacetic acid (H(2)L4), and two noncyclic scaffolds, N-(2-hydroxyethyl)ethylenediamine-N,N,N-triacetic acid (H(3)L1) and ethylene-bisglycol-tetracetic acid (H(4)L2), form stable complexes with Mn(II) in aqueous solutions. Cyclic voltammograms show that the complexes with the most hydrophobic ligands, [MnL2](2-) and [MnL4], are oxidized at higher potential than [MnL1](-) and [MnL3]. The pharmacological properties of these molecules were evaluated as superoxide ion scavengers and anti-inflammatory compounds. Among the four complexes, [MnL4] was the most bioactive, being effective in the nanomolar/micromolar range. It abates the levels of key markers of oxidative injury on cultured cells and ameliorates the outcome parameters in animal models of acute and chronic inflammation. [MnL4] toxicity was very low on both cell cultures in vitro and mice in vivo. Hence, we propose [MnL4] as a novel stable oxygen radical scavenging molecule, active at low doses and with a low toxicity.

FTIR study of ageing of fast drying oil colour (FDOC) alkyd paint replicas

We propose ATR-FTIR spectroscopy for the characterization of the spectral changes in alkyd resin from the Griffin Alkyd Fast Drying Oil Colour range (Winsor & Newton), occurring over 550 days (∼18 months) of natural ageing and over six months of artificial ageing under an acetic acid atmosphere. Acetic acid is one of the atmospheric pollutants found inside museums in concentrations that can have a significant effect on the works exhibited. During natural ageing we observed an increase and broadening of the OH group band around 3300 cm(-1) and an increase in bands in the region 1730-1680 cm(-1) due to carbonyl stretching. We found a broad band around 1635 cm(-1) likely due to CO stretching vibrations of β dichetons. These spectral changes are the result of autooxidation reactions during natural ageing and crosslinking, which then form f alcohols and carbonyl species. The increase in absorbance at 1635 cm(-1) was selected as a parameter to monitor the ageing process of paintings prepared with FDOC, without the need for any extractive procedure. FTIR spectra of paint replicas kept under an acetic acid atmosphere indicated the chemical groups involved in the reaction with acid, thus suggesting which spectral FTIR regions could be investigated in order to follow any degradation in real paintings. A red paint sample from a hyper-realistic artwork (Racconta storie, 2003) by the Italian painter Patrizia Zara was investigated by FTIR in order to evaluate the effects of 10 years natural ageing on alkyd colours. The results obtained suggested that after the end of chemical drying (autooxidation), alkyd colours are very stable.

Novel configurations for a citrus waste based biorefinery: from solventless to simultaneous ultrasound and microwave assisted extraction

Innovative extraction configurations for the biorefining of a biomass waste (citrus peel) were developed in this work. Non-conventional energies, such as microwaves (MW) and ultrasounds (US), were directly irradiated to the fresh orange peel using a versatile MW coaxial dipole antenna. This particular MW configuration enabled us to build two new extraction systems: (1) a coaxial solventless MW-assisted extraction (SMWAE) approach and, (2) a simultaneous ultrasound coaxial MW-assisted hydrodistillation (US-MWHD) method. The yield and chemical composition of the essential oils (EOs) of the orange peel obtained by the two innovative approaches were analyzed as a function of the extraction time and compared with those from coaxial microwave hydrodistillation (MWHD) and conventional hydrodistillation (CH). The EOs were chemically characterized by GC and GC-MS analysis. The residue mash was then used to extract pectin by a MW-assisted procedure. The structure and thermal stability of the pectin were investigated by FTIR and TG. The biorefining of EOs and pectin from a citrus waste maximises the benefits of our proposed green methodologies, which involve safe operability, faster processing and easy scalability. Furthermore, the energy consumed per unit mass of products in each step of the orange peel biorefining clearly showed that the most promising approach is SMWAE (since it is around 27 times lower than the CH approach). MWHD and US-MWHD also showed more than 60% energy savings compared to CH.

Loading of halloysite nanotubes with BSA, α-Lac and β-Lg: A Fourier transform infrared spectroscopic and thermogravimetric study

Halloysite nanotubes (HNTs) are considered as ideal materials for biotechnological and medical applications. An important feature of halloysite is that it has a different surface chemistry on the inner and outer sides of the tubes. This property means that negatively-charged molecules can be selectively loaded inside the halloysite nanoscale its lumen. Loaded HNTs can be used for the controlled or sustained release of proteins, drugs, bioactive molecules and other agents. We studied the interaction between HNTs and bovine serum albumin, α lactalbumin and β -lactoglobulin loaded into HTNs using Fourier transform infrared spectroscopy and thermogravimetry. These techniques enabled us to study the protein conformation and thermal stability, respectively, and to estimate the amount of protein loaded into the HNTs. TEM images confirmed the loading of proteins into HTNs.

A simple and versatile solvothermal configuration to synthesize superparamagnetic iron oxide nanoparticles using a coaxial microwave antenna

Magnetic iron oxide nanoparticles (IONs) with controllable physicochemical and magnetic properties were synthesized by a fast and simple solvothermal microwave (MW) assisted approach. The MW-assisted synthesis using a coaxial microwave antenna was carried out in different routes: (i) a fast one-step solvothermal approach, and (ii) a non-aqueous sol–gel system. This innovative configuration obtained IONs maghemite crystal phase, in a very short reaction time (from 5 to 15 min), with a small size (6 nm) and narrow particle size distribution. Magnetization as a function of the applied magnetic field revealed that all the samples showed superparamagnetisms, with a saturation magnetization ranging from 60 to 68 emu g−1 (T = 300 K). TEM, XRD, FTIR, TG, and magnetic measurements were used to fully characterize the IONs. Not only did the proposed methodologies using the coaxial MW configuration produce IONs with similar or improved physicochemical and magnetic properties, but they also overcame the classical drawbacks of oven-type MW configurations.

Thermal decomposition of metal N,N-dialkylcarbamates A TG-FTIR study

Thermogravimetric analysis coupled with IR spectroscopy was used to investigate the thermal stability and decomposition products of N,N-dialkylcarbamates of zirconium(IV), hafnium(IV), and niobium(IV), M(O2CNR2)4. The niobium derivatives were less stable than the corresponding Zr(IV) and Hf(IV) derivatives, and the thermal stability was in the order of Rxa0=xa0Etxa0>xa0iPrxa0>xa0Me. XRD analysis of the residue showed the formation of the oxides ZrO2 (tetragonal, P42/nmc), HfO2, (monoclinic, P21/c), and Nb2O5 (orthorhombic, Pbam). TEM analysis showed that all the oxides were obtained as nanopowders with a crystal size below 30xa0nm.

Vaporization kinetic study of lavender and sage essential oils

The thermal behavior of lavender and sage essential oils (EOs) and also that of their main components (camphor and 1,8-cineole) were studied by thermogravimetry (TG) at different scan rates under inert gas atmosphere up to about 140xa0°C. All the samples investigated undergo a single-step evaporation starting from ambient temperature without evidence of side decomposition processes. On the basis of the onset temperatures (Ton) extrapolated from the TG curves, the following increasing stability trend is assessed:

A highly pH-sensitive Zn(II) chemosensor

1{,}8{text{-cineole}} < {text{sage}} < {text{lavender}} < {text{camphor}}.