Photoactive assemblies of organic compounds and biomolecules: drug-protein supramolecular systems

[EN] The properties of singlet and triplet excited states are strongly medium-dependent. Hence, these species constitute valuable tools as reporters to probe compartmentalised microenvironments, including drug@protein supramolecular systems. In the present review, the attention is focused on the photophysical properties of the probe drugs (rather than those of the protein chromophores) using transport proteins (serum albumins and 1-acid glycoproteins) as hosts. Specifically, fluorescence measurements allow investigating the structural and dynamic properties of biomolecules or their complexes. Thus, the emission quantum yields and the decay kinetics of the drug singlet excited states provide key information to determine important parameters such as the stoichiometry of the complex, the binding constant, the relative degrees of occupancy of the different compartments, etc. Application of the FRET concept allows determining donor-acceptor interchromophoric distances. In addition, anisotropy measurements can be related to the orientation of the drug within the binding sites, where the degrees of freedom for conformational relaxation are restricted. Transient absorption spectroscopy is also a potentially powerful tool to investigate the binding of drugs to proteins, where formation of encapsulated triplet excited states is favoured over other possible processes leading to ionic species (i. e. radical ions), and their photophysical properties are markedly sensitive to the microenvironment experienced within the protein binding sites. Even under aerobic conditions, the triplet lifetimes of protein-complexed drugs are remarkably long, which provides a broad dynamic range for identification of distinct triplet populations or for chiral discrimination. Specific applications of the laser flash photolysis technique include the determination of drug distribution among the bulk solution and the protein binding sites, competition of two types of proteins to bind a 3 drug, occurrence of drug-drug interactions within protein binding sites, enzymatic-like activity of the protein or determination of enantiomeric compositions. The use of proteins as supramolecular hosts modifies the photoreactivity of encapsulated substrates by providing protection against oxygen or other external reagents, by imposing conformational restrictions in the binding pockets, or by influencing the stereochemical outcome. In this review, a selected group of examples is presented including decarboxylation, dehalogenation, nucleophilic addition, dimerisation, oxidation, Norrish type II reaction, photo-Fries rearrangement and 6 electrocyclisationFinancial support from the Spanish Government (CTQ2010-14882, JCI-2011-09926, RyC-2007-00476), from the EU (PCIG12-GA-2012-334257), from the Universitat Politènica de València (SP20120757) and from the Consellería de Educació, Cultura i Esport (PROMETEOII/2013/005, GV/2013/051) is gratefully acknowledged.Vayá Pérez, I.; Lhiaubet-Vallet, VL.; Jiménez Molero, MC.; Miranda Alonso, MÁ. (2014). Photoactive assemblies of organic compounds and biomolecules: drug-protein supramolecular systems. Chemical Society Reviews. 43:4102-4122. https://doi.org/10.1039/C3CS60413FS410241224

Sorption and release of cadmium by some sewage sludges

Sorption and release of Cd were determined in nine sewage sludges from Tuscany, Italy. The Cd adsorption data were in agreement with both the linear sorption isotherm and the Langmuir equation. The average of calculated adsorption maxima was about 50% of the mean CEC value, indicating that exchangeable cations present in the sludges were more effective in competing with the Cd ion for exchange sites. The calculated Langmuir adsorption maxima were found significantly correlated with fulvic acid C content and carboxyl and phenolic hydroxyl groups of fulvic acids. The release of Cd retained at two initial concentrations as a function of different extraction solutions was indicated. Extraction experiments showed that Cd may be held in sludges by more than one type of site and that the strength of bonding decreases as the total Cd increases. Cadmium was retained mainly by exchange and complexing sites, the former assuming a relatively more important role as cadmium adsorption increased. The effect of different exchangeable cations on the sorption of Cd by sludges was also studied. The amounts of Cd sorbed on the sludge surfaces decreased in the order: Ca-sludge > untreated sludge > Fe-sludge = Al-sludge. Sorption and release of Cd were determined in nine sewage sludges from Tuscany, Italy. The Cd adsorption data were in agreement with both the linear sorption isotherm and the Langmuir equation. The average of calculated adsorption maxima indicated that exchangeable cations present in the sludges were more effective in competing with the Cd ion for exchange sites. The calculated Langmuir adsorption maxima were found significantly correlated with fulvic acid C content and carboxyl and phenolic hydroxyl groups of fulvic acids. Extraction experiments showed that Cd may be held in sludges by more than one type of site and that the strength of bonding decreases as the total Cd increases. Cadmium was retained mainly by exchange and complexing sites. The effect of different exchangeable cations on the sorption of Cd by sludges was also studied

Evaluating garbage compost: 1. Solid phase

Describes the results of Italian research which aimed to evaluate different chemical methods of assessing the degree of stabilisation of composted municipal waste. The city refuse in this study was produced at a composting facility in Tuscany; the paper outlines composting techniques and percentage changes of organic constituents and humic characteristics. The conclusion summarises which techniques are most successful, and the type of applications for which the compost produced is suitable. -P.Hardima

The influence of Metam Sodium on soil respiration

A laboratory experiment was performed in order to evaluate the extent to which metam sodium (MS) applied at two different recommended rates and its degradation product, methyl isothiocyanate (MITC), affect soil respiration. Results suggest that MS degradation to MITC was complete within 4 hours and that MITC decomposed quickly in a few days, except in the soil containing high organic matter where it was still present after 15 days. Following the addition of MS, a lag phase appeared in CO 2-C evolution in the soil. It was longer for the higher dose of MS added and for the two soils with low organic C content. The dynamics of the process was described by the Bonde and Rosswall model and by the Gompertz RS E model for the untreated and the MS- treated soils, respectively

Role playing as a measure of program effectiveness

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