Free radical chemistry of disinfection byproducts. 2. Rate constants and degradation mechanisms of trichloronitromethane (chloropicrin)

Absolute rate constants for the free-radical-induced degradation of trichloronitromethane (TCNM, chloropicrin) were determined using electron pulse radiolysis and transient absorption spectroscopy. Rate constants for hydroxyl radical, *OH, and hydrated electron, e(aq)-, reactions were (4.97 +/- 0.28) x 10(7) M(-1) s(-1) and (2.13 +/- 0.03) x 10(10) M(-1) s(-1), respectively. It appears that the *OH adds to the nitro-group, while the e(aq)- reacts via dissociative electron attachment to give two carbon centered radicals. The mechanisms of these free radical reactions with TCNM were investigated, using 60Co gamma irradiation at various absorbed doses, measuring the disappearance of TCNM and the appearance of the product nitrate and chloride ions. The rate constants and mechanistic data were combined in a kinetic computer model that was used to describe the major free radical pathways for the destruction of TCNM in solution. These data are applicable to other advanced oxidation/reduction processes.     

Hide tanning with modified natural tannins

Tannin from “Acacia Mearnsii” usually called Mimosa, is largely employed in vegetal tanning of hide even if the quality of the leather is poorer than that obtained using chromium as tanning agents. However, taking into account the natural resources of this product and its reduced environmental impact, mimosa tannin has been modified to obtain leather having improved properties. Tannin was modified using formaldehyde, urea, a sulfonic acid and a sulfiting agent: The new products show a higher molecular weight than mimosa tannin but maintain a good solubility in water. Modified tannins were characterized through physicochemical and technological tests and evaluated as tanning agents. The properties of tanned leathers obtained using the new tannin products and mimosa were compared. Some of the polymers containing phenolsulfonic acid are good tannin agents, especially those with a suitable molecular weight. The technological and sensorial properties of the leather obtained using modified tannins (distension and strength of grain, tensile strength, elongation, and tear load) are better than those obtained using mimosa when an appropriate ratio of the reagents were employed. At the same time the feeling of the tanned leather was improved and the final products show fullness, elasticity, fluency, reactivity, and a thin and fine grain. Some of the tannins modified with naphtalensulfonic acid show poor tanning properties but good penetration in the leather suggesting their use as auxiliary sintans in the pretanning process. A simple procedure to prepare these modified tanning agents in the course of the tannin extraction is suggested. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Biomarkers in Prostate Cancer Diagnosis: From Current Knowledge to the Role of Metabolomics and Exosomes

Early detection of prostate cancer (PC) is largely carried out using assessment of prostate-specific antigen (PSA) level; yet it cannot reliably discriminate between benign pathologies and clinically significant forms of PC. To overcome the current limitations of PSA, new urinary and serum biomarkers have been developed in recent years. Although several biomarkers have been explored in various scenarios and patient settings, to date, specific guidelines with a high level of evidence on the use of these markers are lacking. Recent advances in metabolomic, genomics, and proteomics have made new potential biomarkers available. A number of studies focused on the characterization of the specific PC metabolic phenotype using different experimental approaches has been recently reported; yet, to date, research on metabolomic application for PC has focused on a small group of metabolites that have been known to be related to the prostate gland. Exosomes are extracellular vesicles that are secreted from all mammalian cells and virtually detected in all bio-fluids, thus allowing their use as tumor biomarkers. Thanks to a general improvement of the technical equipment to analyze exosomes, we are able to obtain reliable quantitative and qualitative information useful for clinical application. Although some pilot clinical investigations have proposed potential PC biomarkers, data are still preliminary and non-conclusive.     

Unfolding under Pressure: An NMR Perspective

This review aims to analyse the role of solution nuclear magnetic resonance spectroscopy in pressure-induced in vitro studies of protein unfolding. Although this transition has been neglected for many years because of technical difficulties, it provides important information about the forces that keep protein structure together. We first analyse what pressure unfolding is, then provide a critical overview of how NMR spectroscopy has contributed to the field and evaluate the observables used in these studies. Finally, we discuss the commonalities and differences between pressure-, cold- and heat-induced unfolding. We conclude that, despite specific peculiarities, in both cold and pressure denaturation the important contribution of the state of hydration of nonpolar side chains is a major factor that determines the pressure dependence of the conformational stability of proteins.     

Molecular basis of phospholipase A2 inhibition by petrosaspongiolide M

Petrosaspongiolide M (PM) is an anti-inflammatory marine metabolite that displays a potent inhibitory activity toward group II and III secretory phospholipase A(2) (PLA(2)) enzymes. The details of the mechanism, which leads to a covalent adduct between PLA(2) and gamma-hydroxybutenolide-containing molecules such as PM, are still a matter of debate. In this paper the covalent binding of PM to bee venom PLA(2) has been investigated by mass spectrometry and molecular modeling. The mass increment observed for the PM-PLA(2) adduct is consistent with the formation of a Schiff base by reaction of a PLA(2) amino group with the hemiacetal function (masked aldehyde) at the C-25 atom of the PM gamma-hydroxybutenolide ring. Proteolysis of the modified PLA(2) by the endoprotease LysC followed by HPLC MS analysis allowed us to establish that the PLA(2) alpha-amino terminal group of the Ile-1 residue was the only covalent binding site for PM. The stoichiometry of the reaction between PM and PLA(2) was also monitored and results showed that even with excess inhibitor, the prevalent product is a 1:1 (inhibitor:enzyme) adduct, although a 2:1 adduct is present as a minor component. The 2:1 adduct was also characterized, which showed that the second site of reaction is located at the epsilon -amino group of the Lys-85 residue. Similar results in terms of the reaction profile, mass increments, and location of the PLA(2) binding site were obtained for manoalide, a paradigm for irreversible PLA(2) inhibitors, which suggests that the present results may be considered of more general interest within the field of anti-inflammatory sesterterpenes that contain the gamma-hydroxybutenolide pharmacophore. Finally, a 3D model, constrained by the above experimental results, was obtained by docking the inhibitor molecule into the PLA(2) binding site through AFFINITY calculations. The model provides an interesting insight into the PM-PLA(2) inhibition process and may prove useful in the design of new anti-inflammatory agents that target PLA(2) secretory enzymes.     

Atom transfer radical polymerization synthesis and association properties of amphiphilic pullulan copolymers grafted with poly(methyl methacrylate)

Amphiphilic copolymers of pullulan grafted with poly(methyl methacrylate) (PMMA) were synthesized by atom transfer radical polymerization under homogeneous mild conditions without using protecting group chemistry. The hydroxyl groups of pullulan were reacted with 2‐bromoisobutyryl bromide to prepare pullulan macroinitiators with various degrees of substitution. Kinetic study showed that the polymerization was first order. The copolymers were characterized using ¹H NMR spectroscopy and gel permeation chromatography. The molecular weights of the grafted chains were controlled and polydispersities were low. Association properties in aqueous solution were studied using ¹H NMR spectroscopy, dynamic light scattering and transmission electron microscopy. Spherical nanoparticles with size and size distribution significantly affected by the number and length of the grafted chains were formed. Graft copolymers with a degree of substitution of 5.3% and length of PMMA grafted chains from 5 to 35 repeating units formed well‐defined quite monodisperse spherical nanoparticles with hydrodynamic diameters in the range 20–40 nm. This means that nanoparticle size can be tuned by changing the length of the grafted chains for this degree of substitution. Less control of aggregate size was obtained for a degree of substitution of 1.0%. Copyright © 2010 Society of Chemical Industry     

Cellulose as a renewable resource for the synthesis of wood consolidants

Crosslinkable cellulose ethers as allyl cellulose, allyl carboxymethyl cellulose, and allyl n‐hydroxypropyl cellulose were synthesized and characterized, and their use as consolidating agents for waterlogged wood was studied. For this kind of application, structural properties similar to those of wood's polysaccharide components are desired in the design stage of new consolidants. The choice to synthesize cellulose ethers was determined from the possibility of using cellulose as the starting material because of its large availability in nature, biocompatibility, and low cost. In addition, cellulose ethers are quite easy to obtain, and they can have different properties, depending on the nature and the amount of the functional groups introduced. For this purpose, a cellulose with a lower degree of polymerization was also used for the synthesis of related cellulose ethers. By means of Fourier transform infrared spectroscopy, the affinity of the cellulose derivatives for degraded lignin flours was detected. The preliminary results of this study show that these polysaccharide compounds may be proposed as wood consolidating agents. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Recycling of waste glasses into partially crystallized glass foams

Waste soda-lime glass, alone or mixed with wastes from the manufacturing of glass fibers, was successfully converted into partially crystallized glass foams by a particularly simple and economic processing, consisting of a direct heating of glass powders at temperatures from 900 to 1050 °C. The foaming operated by the oxidation of SiC, inserted as powder additive, was found to depend on a complex combination of processing temperature, soaking time, tendency of the investigated glasses toward devitrification, and amount of MnO₂, acting as oxidation promoter. Selected combinations led to foams with a good microstructural homogeneity and mechanical strength, suitable for application as aggregates in lightweight concrete.