Photosensitization of DNA damage by a new cationic pyropheophorbide derivative: sequence-specific formation of a frank scission

Pyropheophorbides are red-absorbing porphyrin-like photosensitizers that may interact with DNA either by intercalation or by external binding with self-stacking according to the value of the nucleotide to chromophore molar ratio (N/C). This article reports on the nature and sequence selectivity of the DNA damage photoinduced by a water-soluble chlorhydrate of aminopyropheophorbide. First, this pyropheophorbide is shown to induce on irradiation the cleavage of phiX174 DNA by both Type-I and -II mechanisms, suggested by scavengers and D2O effects. These conclusions are then improved by sequencing experiments performed on a 20-mer oligodeoxynucleotide (ODN) irradiated at wavelengths >345 nm in the presence of the dye, N/C varying from 2.5 to 0.5. Oxidation of all guanine residues to the same extent is observed after piperidine treatment on both single- and double-stranded ODN. Moreover, unexpectedly, a remarkable sequence-selective cleavage occurring at a 5'-CG-3' site is detected before alkali treatment. This frank break is clearly predominant for a low nucleotide to chromophore molar ratio, corresponding to a self-stacking of the dye along the DNA helix. The electrophoretic properties of the band suggest that this lesion results from a sugar oxidation, which leads via a base release to a ribonolactone residue. The proposal is supported by high-performance liquid chromatography-matrix-assisted laser desorption-ionization mass spectrometry experiments that also reveal other sequence-selective frank scissions of lower intensity at 5'-GC-3' or other 5'-CG-3' sites. This sequence selectivity is discussed with regard to the binding selectivity of cationic porphyrins.     

A surprising method for green extraction of essential oil from dry spices: Microwave dry-diffusion and gravity

Without adding any solvent or water, we proposed a novel and green approach for the extraction of secondary metabolites from dried plant materials. This "solvent, water and vapor free" approach based on a simple principle involves the application of microwave irradiation and earth gravity to extract the essential oil from dried caraway seeds. Microwave dry-diffusion and gravity (MDG) has been compared with a conventional technique, hydrodistillation (HD), for the extraction of essential oil from dried caraway seeds. Essential oils isolated by MDG were quantitatively (yield) and qualitatively (aromatic profile) similar to those obtained by HD, but MDG was better than HD in terms of rapidity (45min versus 300min), energy saving, and cleanliness. The present apparatus permits fast and efficient extraction, reduces waste, avoids water and solvent consumption, and allows substantial energy savings.     

Green ultrasound-assisted extraction of carotenoids based on the bio-refinery concept using sunflower oil as an alternative solvent

A green, inexpensive and easy-to-use method for carotenoids extraction from fresh carrots assisted by ultrasound was designed in this work. Sunflower oil was applied as a substitute to organic solvents in this green ultrasound-assisted extraction (UAE): a process which is in line with green extraction and bio-refinery concepts. The processing procedure of this original UAE was first compared with conventional solvent extraction (CSE) using hexane as solvent. Moreover, the UAE optimal conditions for the subsequent comparison were optimized using response surface methodology (RSM) and ultra performance liquid chromatography – diode array detector – mass spectroscopy (UPLC–DAD–MS). The results showed that the UAE using sunflower as solvent has obtained its highest β-carotene yield (334.75 mg/l) in 20 min only, while CSE using hexane as solvent obtained a similar yield (321.35 mg/l) in 60 min. The green UAE performed under optimal extraction conditions (carrot to oil ratio of 2:10, ultrasonic intensity of 22.5 W cm^?2, temperature of 40 °C and sonication time of 20 min) gave the best yield of β-carotene.     

Synthesis of a New Cationic Pyropheophorbide Derivative and Studies of its Aggregation Process in Aqueous Solution

Abstract— A new water-soluble cationic pyropheophorbide was prepared from pyropheophorbide a by a Curtius rearrangement. The self-aggregation process of this chlorhydrate of aminopyropheophorbide was investigated from the changes observed in its spectroscopic properties when passing from ethanol to aqueous solutions. The formation of aggregates was characterized in the absorption spectrum by a broadening of the Qy band, which is slightly shifted to the red, a significant increase in signals of circular dichroism and a drastic quenching of the fluorescence intensity at 674 nm. Analysis of the nonlinear variation of the fluorescence intensity with the dye concentration in Tris-buffered solutions shows that dimerization is the dominant aggregation process. The dimerization equilibrium constant(at 25_AoC, pH 7.5 in 5 m M Tris buffer, 10 m M NaCl) was determined to be 3.10₆ M _-l. NMR measurements performed in DMSO at various dye concentrations showed that only the chemical shifts of some atoms are affected by these changes, indicating the part of the ring involved in the overlap of the two molecules in the dimer.A molecular modeling study of the packing arrangement of the aminopyropheophorbide molecules in aggregates performed by both semi-empirical quantum chemical PM3 and force field MM2 methods provided a structure consistent with these spectroscopic data.     

Glucose-based amphiphilic telomers designed to keep membrane proteins soluble in aqueous solutions: synthesis and physicochemical characterization

A novel class of nonionic amphipols (NAPols) designed to handle membrane proteins in aqueous solutions has been synthesized, and its solution properties have been examined. These were synthesized through free radical cotelomerization of glucose-based hydrophilic and amphiphilic monomers derived from tris(hydroxymethyl)acrylamidomethane using azobisisobutyronitrile as the initiator and thiol as the transfer agent. The molecular weight and the hydrophilic/lipophilic balance of the cotelomers were modulated by varying the thiol/monomers and the hydrophilic monomer/amphiphilic monomer ratios, respectively, and were characterized by 'H NMR, UV, gel permeation chromatography, and Fourier transform infrared spectroscopy. Their physicochemical properties in aqueous solution were studied by dynamic light scattering, aqueous size-exclusion chromatography, analytical ultracentrifugation, and surface-tension measurements. NAPols are highly soluble in water and form, within a large concentration range, well-defined supramolecular assemblies with a diameter of approximately 6-7 nm, a narrow particle size distribution, and an average molecular weight close to 50 x 10(3) g x mol(-1). Varying the hydrophilic/amphiphilic monomer ratio of NAPols in the range of 3.0-4.9, the degree of polymerization in the range of 51-78, and the resulting average molar mass in the range of 20-29 x 10(3) g x mol(-1) has little incidence on their solution properties. Glucose-based NAPols efficiently kept soluble in aqueous solutions two test membrane proteins: bacteriorhodopsin and the transmembrane domain of Escherichia coli's outer membrane protein A.     

Lactobionamide surfactants with hydrogenated, perfluorinated or hemifluorinated tails: physical-chemical and biochemical characterization

Detergents are customarily used to solubilize cell membranes and keep membrane proteins soluble in aqueous buffers, but they often lead to irreversible protein inactivation. Hemifluorinated amphiphiles with hybrid hydrophobic chains have been specifically designed to minimize the denaturating propensity of surfactants toward membrane proteins. We have studied the physical-chemical and biochemical properties of lactobionamide surfactants bearing either a hydrogenated, a fluorinated or a hemifluorinated chain (respectively H-, F-, and HF-Lac). We show that the dual composition of the hydrophobic chain of HF-Lac endows it with unusual physical-chemical properties as regards its critical micellar concentration, interfacial area per molecule, and behavior upon reverse phase chromatography. Analytical ultracentrifugation shows that, whereas H-Lac assembles into well-defined micelles, F-Lac and HF-Lac form large and heterogeneous assemblies, whose size increases with surfactant concentration. Molecular dynamics calculations suggest that F-Lac forms cylindrical micelles. The ability of HF-Lac to keep membrane proteins soluble was examined using the cytochrome b(6) f complex from Chlamydomonas reinhardtii's chloroplast as a model protein. HF-Lac/b(6) f complexes form particles relatively homogeneous in size, in which the b(6) f complex is as stable or markedly more stable, depending on the surfactant concentration, than it is in equivalent concentrations of hydrogenated surfactants, including H-Lac.     

Parameter optimization in microwave-assisted distillation of frankincense essential oil

The essential oil of Boswellia species is extracted by the conventional method of hydrodistillation (HD). In this study, we aimed to compare this reference to microwave-assisted distillation (MAD) at different power densities. The results showed that microwave extraction can result in a substantial reduction (48 min against 180 min for reference) of the batch time when the power density of 2 W/g is applied. Also, the energy consumed by the new process is 2.7 times less than HD. The essential oil produced by MAD has a chemical composition different from that of reference treatment. Although microwave treatment increased the proportions of the main components (α-thujene and α-pinene), the opposite tendency was observed for o-cymene, estragole, methyl eugenol, and δ-guaiene. A 26.5% decrease in oil extracted by MAD at 1 W/g is required to achieve 50% inhibition of the DPPH radical compared to HD. In conclusion, MAD is a promising technology for producing olibanum oil with new qualitative attributes.