Study of chemical bond formation in oligodieneurethane epoxide in its interaction with encapsulated dicarboxylic acid

Interaction of an oligodieneurethane-epoxy oligomer with encapsulated glutaric acid was studied. The conditions that provide initiation of the mechanism of diffusion of the encapsulated component and formation of new chemical bonds between macromolecules of the copolymer were determined.     

Thermal analysis of hair treated with oxidative hair dye under influence of conditioners agents

This research aimed the effect on Caucasian hair tresses treated with oxidative hair dye, either incorporated or not with conditioners agents, analyzed by Differential Scanning Calorimetry (DSC) and Thermogravimetric analysis (TG). The formulations of hair dyes were emulsions oil-in-water with light blond color containing or not the conditioners agents: silanetriol and panthenol; PEG-12 dimethicone; hydrolyzed silk, hydrolyzed milk protein, and lactose. Each dye (1.5 g) was applied in the hair tress (2.0 g/20.0 cm of length of Caucasian light-brown), previously treated, more 1.5 g of hydrogen peroxide 20 vol during 40 min. Evaluation of mass loss of the different hair sample demonstrates that these chemical hair treatments impair the hair fibers, reduced their moisture content with respect to the untreated hair. The incorporation of conditioners agents (silanetriol and panthenol; PEG-12 dimethicone; hydrolyzed silk, hydrolyzed milk protein, and lactose) in oxidative hair dyes types did not decrease the damage caused on the tresses by the coloring process quantified by TG/DTG. However, the DSC curves demonstrated those conditioners agents (silanetriol and panthenol; PEG-12 dimethicone) dislocated the beginning of the third event in 20 °C and they inhibited the presence of the fourth event, having characterized thermal protection to the hair.     

Controlled radical polymerization of styrene mediated by the C‐phenyl‐N‐tert‐butylnitrone/AIBN pair: Kinetics and electron spin resonance analysis

Kinetics of the free radical polymerization of styrene at 110 °C has been investigated in the presence of C‐phenyl‐N‐tert‐butylnitrone (PBN) and 2,2′‐azobis(isobutyronitrile) (AIBN) after prereaction in toluene at 85 °C. The effect of the prereaction time and the PBN/AIBN molar ratio on the in situ formation of nitroxides and alkoxyamines (at 85 °C), and ultimately on the control of the styrene polymerization at 110 °C, has been investigated. As a rule, the styrene radical polymerization is controlled, and the mechanism is one of the classical nitroxide‐mediated polymerization. Only one type of nitroxide (low‐molecular‐mass nitroxide) is formed whatever the prereaction conditions at 85 °C, and the equilibrium constant (K) between active and dormant species is 8.7 × 10^?10 mol L^?1 at 110 °C. At this temperature, the dissociation rate constant (k_d) is 3.7 × 10^?3 s^?1, the recombination rate constant (k_c) is 4.3 × 10⁶ L mol^?1 s^?1, whereas the activation energy (E_a,diss.), for the dissociation of the alkoxyamine at the chain‐end is ～125 kJ mol^?1. Importantly, the propagation rate at 110 °C, which does not change significantly with the prereaction time and the PBN/AIBN molar ratio at 85 °C, is higher than that for the thermal polymerization at 110 °C. This propagation rate directly depends on the equilibrium constant K and on the alkoxyamine and nitroxide concentrations, as well. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1219–1235, 2007     

Fine Tuning of β‐Peptide Foldamers: a Single Atom Replacement Holds Back the Switch from an 8‐Helix to a 12‐Helix

Cyclic homologated amino acids are important building blocks for the construction of helical foldamers. N‐aminoazetidine‐2‐carboxylic acid (AAzC), an aza analogue of trans‐2‐aminocyclobutanecarboxylic acid (tACBC), displays a strong hydrazino turn conformational feature, which is proposed to act as an 8‐helix primer. tACBC oligomers bearing a single N‐terminal AAzC residue were studied to evaluate the ability of AAzC to induce and support an 8‐helix along the oligopeptide length. While tACBC homooligomers assume a dominant 12‐helix conformation, the aza‐primed oligomers preferentially adopt a stabilized 8‐helix conformation for an oligomer length up to 6 residues. The (formal) single‐atom exchange at the N terminus of a tACBC oligomer thus contributes to the sustainability of the 8‐helix, which resists the switch to a 12‐helix. This effect illustrates atomic‐level programmable design for fine tuning of peptide foldamer architectures.     

Structure and Dynamics of Oligonucleotides in the Gas Phase

By combining ion‐mobility mass spectrometry experiments with sub‐millisecond classical and ab initio molecular dynamics we fully characterized, for the first time, the dynamic ensemble of a model nucleic acid in the gas phase under electrospray ionization conditions. The studied oligonucleotide unfolds upon vaporization, loses memory of the solution structure, and explores true gas‐phase conformational space. Contrary to our original expectations, the oligonucleotide shows very rich dynamics in three different timescales (multi‐picosecond, nanosecond, and sub‐millisecond). The shorter timescale dynamics has a quantum mechanical nature and leads to changes in the covalent structure, whereas the other two are of classical origin. Overall, this study suggests that a re‐evaluation on our view of the physics of nucleic acids upon vaporization is needed.     

Diketopyrrolopyrrole‐Porphyrin Conjugates with High Two‐Photon Absorption and Singlet Oxygen Generation for Two‐Photon Photodynamic Therapy

Two‐photon photodynamic therapy is a promising therapeutic method which requires the development of sensitizers with efficient two‐photon absorption and singlet‐oxygen generation. Reported here are two new diketopyrrolopyrrole‐porphyrin conjugates as robust two‐photon absorbing dyes with high two‐photon absorption cross‐sections within the therapeutic window. Furthermore, for the first time the singlet‐oxygen generation efficiency of diketopyrrolopyrrole‐containing systems is investigated. A preliminary study on cell culture showed efficient two‐photon induced phototoxicity.     

Lipoxygenase inhibitory activity of Cuspidaria pulchra and isolated compounds

This work evaluated the in vitro inhibitory activity of the crude ethanolic extract from the aerial parts of Cuspidaria pulchra (Cham.) L.G. Lohmann against 15-lipoxygenase (15-LOX). The bioassay-guided fractionation of the n-butanol fraction, which displayed the highest activity, led to the isolation of three compounds: caffeoylcalleryanin (1), verbascoside (2) and 6-hydroxyluteolin-7-O-β-glucoside (3). Assessment of the ability of the isolated compounds to inhibit 15-LOX revealed that compounds 1, 2 and 3 exerted strong 15-LOX inhibitory activity; IC₅₀ values were 1.59, 1.76 and 2.35 μM respectively. The XTT assay showed that none of the isolated compounds seemed to be significantly toxic.