Sterilization of Semiconductive Nanomaterials: The Case of Water-Suspended Poly-3-Hexylthiophene Nanoparticles.

In this work, the feasibility of sterilizing a water suspension of poly-3-hexylthiophene nanoparticles (P3HT-NPs) is investigated using ionizing radiation, either γ-rays or high-energy electrons (e-beam). It is found that regardless of the irradiation source, the size, polydispersity, aggregation stability, and morphology of the NPs are not affected by the treatment. Furthermore, the impact of ionizing radiation on the physicochemical properties of NPs at different absorbed radiation doses (10-25 kGy) and dose rates (kGy time ) is evaluated through different spectroscopic techniques.

The Interaction of Hypotaurine and Other Sulfinates with Reactive Oxygen and Nitrogen Species: A Survey of Reaction Mechanisms.

Considerable strides have been made in understanding the oxidative mechanisms involved in the final steps of the cysteine pathway leading to taurine. The oxidation of sulfinates, hypotaurine and cysteine sulfinic acid, to the respective sulfonates, taurine and cysteic acid, has never been associated with any specific enzyme. Conversely, there is strong evidence that in vivo formation of taurine and cysteic acid is the result of sulfinate interaction with a variety of biologically relevant oxidants.

Hierarchical Growth of Supramolecular Structures Driven by Pimerization of Tetrahedrally Arranged Bipyridinium Units.

A shape-persistent molecule, featuring four bipyridinium units, has been synthesized that upon reduction undergoes intermolecular pimerization because of the rigid architecture of the molecule. The pimerization process has been investigated by a variety of techniques, such as absorption measurements, EPR spectroscopy, as well as gamma and pulse radiolysis, and compared with the behavior of a model compound. Computational studies have also been performed to support the experimental data.

A fluorine 1,2-migration via aryl cation/radical/radical anion/radical sequence.

Irradiation of a 7-piperazino-8-fluoroquinolone causes formal 1,2-fluorine migration, piperazine loss and reduction, or nucleophile addition in 8. Product study, laser flash photolysis, and computational modeling support F(-) detachment to yield a triplet 8-quinolyl cation that either inserts intramolecularly or is trapped by Cl(-), Br(-). However, iodide and pyrrole reduce it to the radical that continues the 'redox tour' (aryl cation→ radical→ radical anion→ radical and then again radical or radical anion) leading to the rearranged products.

New insights into the reaction paths of hydroxyl radicals with 2'-deoxyguanosine.

The reaction of HO(•) radical with 2'-deoxyguanosine is intensively studied as a model for DNA damage. Several aspects related to the reaction paths responsible for the most relevant lesions are not well understood. We have reinvestigated the reaction of HO(•) with 2'-deoxyguanosine by pulse radiolysis and extended our studies to a variety of substituted derivatives.

Comparison of isoelectronic 8-HO-G and 8-NH2-G derivatives in redox processes.

8-Oxo-7,8-dihydroguanine (8-oxo-G) is the major lesion of oxidatively generated DNA damage. Despite two decades of intense study, several fundamental properties remain to be defined. Its isoelectronic 8-aminoguanine (8-NH(2)-G) has also received considerable attention from a biological point of view, although its chemistry involving redox processes remains to be discovered.

A reevaluation of the ambident reactivity of the guanine moiety towards hydroxyl radicals.

Radically different: Contrary to previous proposals, the main reaction of the HO(*) radical with guanosine or 2'-deoxyguanosine is the hydrogen abstraction from the NH(2) moiety to give a guanyl radical. This radical, characterized by a broad band in the visible region (around 610 nm), undergoes tautomerization to the most stable isomer.

Reaction of hydrated electrons with guanine derivatives: tautomerism of intermediate species.

Here, we show that two tautomers are produced by the protonation of the guanine-electron adduct. The fate of electron adducts of a variety of substituted guanosines was investigated by radiolytic methods and addressed computationally by means of time-dependent DFT (TD-B3LYP/6-311G**//B1B95/6-31+G**) calculations. The reaction of e(aq-) with guanosine and 1-methylguanosine produces two transient species, whereas the reaction with N2-ethylguanosine and N2,N2-diethylguanosine produces only one.

One-electron reduction of 8-bromo-2-aminoadenosine in the aqueous phase: radiation chemical and DFT studies of the mechanism.

Two tautomeric forms of one-electron oxidized 2-aminoadenosine (2AA) have been produced by reactions of hydrated electrons (e aq-) with 8-bromo-2-aminoadenosine (8-Br-2AA) at natural pH, whereas only one tautomer is formed by oxidation of 2AA. Tailored experiments by pulse radiolysis and time-dependent DFT (TD-B3LYP/6-311G**//B1B95/6-31+G**) calculations allowed the definition of the reaction mechanism in some detail. The electron adducts of 8-Br-2AA protonated at C8 eject Br- and produce the two short-lived tautomers (8 and 9).

Chemical radiation studies of 8-bromo-2'-deoxyinosine and 8-bromoinosine in aqueous solutions.

The reactions of hydrated electrons (e(aq) (-)) with 8-bromo-2'-deoxyinosine (8) and 8-bromoinosine (12) have been investigated by radiolytic methods coupled with product studies and have been addressed computationally by means of BB1K-HMDFT calculations. Pulse radiolysis revealed that one-electron reductive cleavage of the C--Br bond gives the C8 radical 9 or 13 followed by a fast radical translocation to the sugar moiety. Selective generation of a C5' radical occurs in the 2'-deoxyribo derivative, whereas in the ribo analogue the reaction is partitioned between the C5' and C2' positions with similar rates.