Iron nuclearity in mineral fibres: Unravelling the catalytic activity for predictive modelling of toxicity

Chronic inflammation induced in vivo by mineral fibres, such as asbestos, is sustained by the cyclic formation of cytotoxic/genotoxic oxidant species that are catalysed by iron. High catalytic activity is observed when iron atoms are isolated in the crystal lattice (nuclearity=1), whereas the catalytic activity is expected to be reduced or null when iron forms clusters of higher nuclearity. This study presents a novel approach for systematically measuring iron nuclearity across a large range of iron-containing standards and mineral fibres of social and economic importance, and for quantitatively assessing the relation between nuclearity and toxicity. The multivariate curve resolution (MCR) empirical approach and density functional theory (DFT) calculations were applied to the analysis of UV-Vis spectra to obtain information on the nature of iron and nuclearity. This approach led to the determination of the nuclearity of selected mineral fibres which was subsequently used to calculate a toxicity-related index. High nuclearity-related toxicity was estimated for chrysotile samples, fibrous glaucophane, asbestos tremolite, and fibrous wollastonite. Intermediate values of toxicity, corresponding to a mean nuclearity of 2, were assigned to actinolite asbestos, amosite, and crocidolite. Finally, a low nuclearity-related toxicity parameter, corresponding to an iron-cluster with a lower catalytic power to produce oxidants, was assigned to asbestos anthophyllite.

Gaseous Heptanethiol Removal by a Fe3+-Phenanthroline-Kaolinite Hybrid Material

Kaolinite functionalized by the μ-oxo Fe³⁺-phenanthroline complex (Fe⁺³Phen) was selected to test its ability to efficiently remove and store gaseous heptanethiol (HPT). Spectroscopic techniques, elemental analysis, and thermal analysis coupled with evolved gas mass spectrometry were employed to characterize the material before and after the exposure to the gas and to define the adsorption process. The amount of HPT trapped by the functionalized kaolinite after 60 days is 0.10940 moles per 100 g of kaolinite which, considering the amount of adsorbed Fe⁺³Phen (0.00114 moles per 100 g of kaolinite), means a thiol/Fe³⁺Phen molar ratio of about 100:1, a value much higher than those found in the past for Fe⁺³Phen functionalized montmorillonite and sepiolite. In addition, the process was found to be efficient also beyond 60 days. This significant removal of the smelly gas was explained by considering a continuous catalytic activity of Fe³⁺ toward the oxidation of thiol to disulfide.

Electrochemical data on redox properties of human Cofilin-2 and its Mutant S3D

The reported data are related to a research paper entitled "Phosphorylated cofilin-2 is more prone to oxidative modifications on Cys39 and favors amyloid fibril formation" [1]. Info about the formation and redox properties of the disulfide bridge of a protein is quite difficult to obtain and only in a few cases was it possible to observe a cyclic voltammetry (CV) signal [2,3]. Human cofilin-2 contains two cysteines (Cys39 and Cys80) which can be oxidized in suitable conditions and form a disulfide bridge [1]. For this purpose, CV measurements were carried out on human cofilin-2 WT and its mutant S3D immobilized on a gold electrode coated by an anionic self-assembled monolayer (SAM), after a pre-oxidation time which was fundamental for observing a CV signal relating to the oxidation/reduction process of the disulfide bridge of the proteins. The data include CV curves obtained with and without electrochemical pre-oxidation and after oxidation with H₂O₂. In addition, the plot of the cathodic peak current vs. electrochemical pre-oxidation time and the pH dependence of the formal potential (E°') are reported. The data obtained by CV measurements were used to determine the time required to form the disulfide bridge for the immobilized proteins and, consequently, to observe the CV signal, to calculate the E°' values and analyse the pH dependence of E°'. The electrochemical data were provided which will be useful for further electrochemical investigations regarding proteins bearing disulfide bridge(s) or cysteines prone to oxidation.

Phosphorylated cofilin-2 is more prone to oxidative modifications on Cys39 and favors amyloid fibril formation

Cofilins are small protein of the actin depolymerizing family. Actin polymerization/depolymerization is central to a number of critical cellular physiological tasks making cofilin a key protein for several physiological functions of the cell. Cofilin activity is mainly regulated by phosphorylation on serine residue 3 making this post-translational modification key to the regulation of myofilament integrity. In fact, in this form, the protein segregates in myocardial aggregates in human idiopathic dilated cardiomyopathy. Since myofilament network is an early target of oxidative stress we investigated the molecular changes induced by oxidation on cofilin isoforms and their interplay with the protein phosphorylation state to get insight on whether/how those changes may predispose to early protein aggregation. Using different and complementary approaches we characterized the aggregation properties of cofilin-2 and its phosphomimetic variant (S3D) in response to oxidative stress in silico, in vitro and on isolated cardiomyocytes. We found that the phosphorylated (inactive) form of cofilin-2 is mechanistically linked to the formation of an extended network of fibrillar structures induced by oxidative stress via the formation of a disulfide bond between Cys39 and Cys80. Such phosphorylation-dependent effect is likely controlled by changes in the hydrogen bonding network involving Cys39. We found that the sulfide ion inhibits the formation of such structures. This might represent the mechanism for the protective effect of the therapeutic agent Na2S on ischemic injury.

Trapping at the Solid-Gas Interface: Selective Adsorption of Naphthalene by Montmorillonite Intercalated with a Fe(III)-Phenanthroline Complex

In this study, stable hybrid materials (Mt-Fe(III)Phen), made by the μ-oxo Fe(III)-phenanthroline complex [(OH₂)₃(Phen)FeOFe(Phen)(OH₂)₃]⁴⁺ (Fe(III)Phen) intercalated in different amounts into montmorillonite (Mt), were used as a trap for immobilizing gaseous benzene and naphthalene and their mono chloro-derivatives at 25 and 50 °C. The entrapping process was studied through elemental analysis, magic angle spinning NMR spectroscopy, thermal analysis, and evolved gas mass spectrometry. Naphthalene and 1-chloronaphthalene were found to be immobilized in large amount at both temperatures. Molecular modeling allowed designing of the structure of the interlayer in the presence of the immobilized aromatic molecules. Adsorption is affected by the amount of the Fe complex hosted in the interlayer of the entrapping hybrid materials. On the contrary, under the same conditions, benzene and chlorobenzene were not adsorbed. Thermal desorption of naphthalenes was obtained under mild conditions, and immobilization was found to be reversible at least for 20 adsorption/desorption cycles.

Effective and Selective Trapping of Volatile Organic Sulfur Derivatives by Montmorillonite Intercalated with a μ-oxo Fe(III)-Phenanthroline Complex

The μ-oxo Fe(III)-phenanthroline complex [(OH₂)₃(Phen)FeOFe(Phen) (OH₂)₃]⁺⁴ intercalated in montmorillonite provides a stable hybrid material. In this study, the ability and efficiency of this material to immobilize thiols in gas phase, acting as a trap at the solid-gas interface, were investigated. Aliphatic thiols containing both hydrophilic and hydrophobic end groups were chosen to test the selectivity of this gas trap. DR-UV-vis, IR, elemental analysis, thermal analysis and evolved gas mass spectrometry, X-ray powder diffraction, and X-ray absorption spectroscopy techniques were employed to characterize the hybrid material before and after thiol exposure and to provide information on the entrapping process. Thiol immobilization is very large, up to 21% w/w for heptanethiol. In addition, evidence was obtained that immobilization occurs through the formation of a covalent bond between the iron of the complex and the sulfur of the thiol. This provides an immobilization process characterized by a higher stability with respect to the methods based on physi-adsorption. Thiol immobilization resulted thermally reversible at least for 20 adsorption/desorption cycles. Unlike standard desulfurization processes like hydrotreating and catalytic oxidation which work at high temperatures and pressures, the present system is able to efficiently trap thiols at room temperature and pressure, thus saving energy. Furthermore, we found that the selectivity of thiol immobilization can be tuned acting on the amount of complex intercalated in montmorillonite. In particular, montmorillonite semisaturated with the complex captures both hydrophobic and hydrophilic thiols, while the saturated montmorillonite shows a strong selectivity toward the hydrophobic molecules.

Vertical jump performance in Italian male and female national team soccer players

The aim of this study was to examine the validity of vertical jump (VJ) performance variables in elite-standard male and female Italian soccer players. One hundred eighteen national team soccer players (n = 56 men and n = 62 women) were tested for countermovement (CMJ) and squatting jump (SJ) heights. The stretch-shortening cycle efficiency (SSCE) was assessed as percentage of CMJ gain over SJ ([INCREMENT]CMJ-SJ), difference (CMJ-SJ), and ratio (CMJ:SJ). Results showed significant sex difference in SJ and CMJ. Differences in SSCE were mainly in the absolute variables between sexes. Cutoff values for CMJ and SJ using sex as construct were 34.4 and 32.9 cm, respectively. No competitive level differences in VJ performance were detected in the male players. Female national team players showed VJ performance higher than the under 17 counterpart. The results of this study showed that VJ performance could not discriminate between competitive levels in male national team-selected soccer players. However, the use of CMJ and SJ normative data may help strength and conditioning coaches in prescribing lower limb explosive strength training in elite soccer players. In this, variations in VJ performance in the range of approximately 1 cm may be regarded as of interest in tracking noncasual variation in elite-standard soccer players.

Angiotensin-converting enzyme/vitamin D receptor gene polymorphisms and bioelectrical impedance analysis in predicting athletic performances of Italian young soccer players

We evaluated the association between 2 genetic polymorphisms known to be involved in fitness and performance, and anthropometric features, body composition, and athletic performances in young male soccer players with the goal of identifying genetic profiles that can be used to achieve maximal results from training. One hundred twenty-five medium-high-level male soccer players were genotyped for angiotensin-converting enzyme (ACE) I/D, and vitamin D receptor (VDR) FokI gene polymorphisms and scored for anthropometric measurements, body composition, and athletic performance. Body mass index, fat mass, fat-free mass, resistance, reactance, impedance, phase angle (PA), and body cell mass were measured. Athletic performance was evaluated by squat jump, countermovement jump (CMJ), 2-kg medicine ball throw, 10- and 20-m sprint time. We observed that the homozygous ff genotype of the VDR gene was significantly more represented in young soccer players than in a matched sedentary population. Values of reactance and PA were differently distributed in ACE and VDR genotypes with high mean values in subjects with DD (ACE) and FF (VDR) genotypes. No correlation was observed between ACE or VDR genotypes and 2-kg medicine ball throw, 10- and 20-m sprint times. The ID genotype of ACE was associated with the best performances in squat jump and CMJ. Our results suggest that determination of ACE and VDR genotypes might help select those young athletes harboring the most favorable genetic potential to succeed in soccer.

pH-Dependent peroxidase activity of yeast cytochrome c and its triple mutant adsorbed on kaolinite

The peroxidase activity of wild-type yeast cytochrome c and its triple mutant K72AK73AK79A adsorbed onto kaolinite was investigated as a function of pH and temperature. Both adsorbed proteins displayed an appreciable catalytic activity, which remained constant from pH 7 to pH 10, decreased below pH 7, and showed a remarkable increase at pH values lower than 4. In the whole pH range investigated the catalytic activity of the adsorbed wild-type cytochrome c was higher than that of the mutant. Both diffuse-reflectance UV-vis and resonance Raman spectroscopies applied on solid samples were used to probe the structural features responsible for the catalytic activity of the immobilized proteins. At neutral and alkaline pH values a six-coordinate low-spin form of cytochrome c was observed, while at pH < 7 the formation of a high-spin species occurred whose population increased at decreasing pH. The orientation and exposure of the heme to the substrate-strictly dependent on adsorption-was found to affect the peroxidase activity.

Thermodynamic aspects of the adsorption of cytochrome c and its mutants on kaolinite

The adsorption of native, wild-type, and engineered cytochrome c on sodium-exchanged kaolinite was investigated by spectroscopic means. The variants of yeast cytochrome c were obtained replacing surface lysines in positions 72, 73, and 79 with alanine residues. All proteins are strongly adsorbed onto kaolinite. In particular, the presence of the lysine residue in position 73 remarkably favors adsorption. A detailed characterization of the thermodynamic aspects of the adsorption process has been performed. Most notably, adsorbed cytochrome c maintains its moderate peroxidase activity against guaiacol. This investigation is prodromal to the exploitation of the catalytic activity of engineered cytochrome c immobilized on a polydisperse system.

Thermodynamic aspects of the adsorption of hexametaphosphate on kaolinite

The adsorption of hexametaphosphate ion, an important deflocculant used in the ceramic industry, from aqueous solutions onto kaolinite has been studied at different temperatures. The adsorption isotherm follows the Langmuir model: the thermodynamic parameters DeltaG(ads)(0), DeltaH(ads)(0), and DeltaS(ads)(0) were calculated and found to be consistent with an interaction model involving the formation of an inner-sphere complex between HMP and aluminol groups. Also, the dependence of the adsorption behavior on the kaolinite volume fraction has been studied and discussed in term of association processes between the clay particles.

[Calcium antagonist vs diuretics. Doppler velocimetric monitoring of the carotid flow in patients with essential hypertension]

BACKGROUND

In the period from 1995 to 1996, 19 patients with a range of 180-200 mmHg and 95-110 mmHg respectively for systolic and diastolic pressure, have been examined by Doppler monitoring.

METHODS

Nine patients were treated with lacidipine (4 mg/die) and 10 were treated with idroclorotiazide + amiloride (50 mg every other day). The IPP and the IDC were end points to value the arterial compliance and the remodynamic flow in common carotid.

RESULTS

The humeral blood pressure was valued every morning and Doppler monitoring of common carotid 30 and 60 day after treatment. The carotid blood flow and cerebral perfusion had a significant amelioration with calcium antagonists and an increase of IDC with a decrease of IPP were found.

CONCLUSIONS

This study demonstrates the role of calcium antagonists not only as antihypertensive drug, but also to prevent, to check and to improve progression of ateromatic injury. The conclusions is drawn that Doppler monitoring is a satisfactory scientific method to obtain information on features of arterial wall without excessive cost.