Anna Maria Villa

Plasma-induced graft-polymerization of polyethylene glycol acrylate on polypropylene films: Chemical characterization and evaluation of the protein adsorption

This work deals with the optimization of argon plasma-induced graft-polymerization of polyethylene glycol acrylate (PEGA) on polypropylene (PP) films in order to obtain surfaces with a reduced protein adsorption for possible biomedical applications. To this end, we examined the protein adsorption on the treated and untreated surfaces. The graft-polymerization process consisted of four steps: (a) plasma pre-activation of the PP substrates; (b) immersion in a PEGA solution; (c) argon plasma-induced graft-polymerization; (d) washing and drying of the samples. The efficiency of these processes was evaluated in terms of the amount of grafted polymer, coverage uniformity and substrates wettability. The process was monitored by contact angle measurements, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS) and atomic force microscopy (AFM) analyses. The stability of the obtained thin films was evaluated in water and in Phosphate Buffer Saline (PBS) at 37 degrees C. The adsorption of fibrinogen and green fluorescent protein (GFP)--taken as model proteins--on the differently prepared surfaces was evaluated through a fluorescence approach using laser scanning confocal microscopy with photon counting detection. After plasma treatments of short duration, the protein adsorption decreases by about 60-70% with respect to that of the untreated film, while long plasma exposure resulted in a higher protein adsorption, due to damaging of the grafted polymer.

Mitochondria in tumor cells studied by laser scanning confocal microscopy

We present here a confocal fluorescence microscopy study of mitochondria in sensitive and resistant carcinoma cells by using two potentiometric probes of mitochondria, rhodamine 123 (R123) and dimethylaminostyryl-methylpyridiniumiodine. We have found that active mitochondria in sensitive MCF-7 and multidrug resistant MCF-7/DX carcinoma cells are very different in localization and morphology. In sensitive cells active mitochondria are found in the perinuclear region, whereas in the multidrug resistance (MDR) subline they are confined to the cell periphery. Interestingly, the MDR revertant verapamil has been found to restore in MCF-7/DX cells the same pattern of active mitochondria seen in sensitive cells. We have also studied R123 in human lung carcinoma A549 cells, which display a low responsivity to doxorubicin, and overexpress the lung resistance-related protein. In addition to perinuclear mitochondria, peripheral mitochondria with weaker fluorescence can be seen in this cell line. Interestingly, in the two examined carcinoma lines we have been able to recognize by image analysis a common new star-lobed morphology. Our results indicate that in resistant carcinoma cells two populations of mitochondria coexist with different localization, morphology, and activity.

Three-Dimensional Imaging of Monogenoidean Sclerites by Laser Scanning Confocal Fluorescence Microscopy

A nondestructive protocol for preparing specimens of Monogenoidea for both α-taxonomic studies and reconstruction of 3-dimensional structure is presented. Gomoris trichrome, a stain commonly used to prepare whole-mount specimens of monogenoids for taxonomic purposes, is used to provide fluorescence of genital spines, the copulatory organ, accessory piece, squamodisc, anchors, hooks, bars, and clamps under laser scanning confocal microscopy.

Conformational behaviour of the antineoplastic peptide dolastatin-10 and of two mutated derivatives

SummaryThe three-dimensional structure of dolastatin-10, an extremely potent cytostatic and antineoplastic peptide extracted from the mollusc Dolabella auricularia, has not yet been fully characterized in an experimental way. By means of a systematic conformational search of the natural peptide and of two mutated analogs, carried out both in vacuo and in aqueous solution, the present work allows to obtain insights into the conformational preferences of this remarkable compound. In addition, the ability to form intra- and intermolecular H-bonds as a function both of the sequence and of the conformation is discussed. The search for the best molecular conformations has been carried out using a molecular mechanics approach, based on the CVFF potential. Dolastatin-10 contains some unusual amino acids for which no experimental structural data are available. In order to check the reliability of the CVFF potential in predicting structures of such nonconventional amino acids, geometry optimizations have been carried out using the ab initio Hartree-Fock procedure. The CVFF parameterization is found to be adequate also for nonconventional amino acids.

Novel nontoxic mitochondrial probe for confocal fluorescence microscopy

We propose a 2,5-Bis[1-(4-N-methylpyridinium)ethen-2-yl)]-N-methylpyrrole ditriflate (PEPEP) as a novel nontoxic, nonpotentiometric mitochondrial probe for confocal fluorescence microscopy. PEPEP is a representative chromophore of a large family of heterocyclic fluorescent dyes that show fluorescence emission in aqueous media and great DNA affinity. We check its cytotoxicity and intracellular localization in mammalian and yeast cell cultures. We demonstrate that PEPEP is a very efficient dye for fluorescence confocal microscopy and a valuable alternative to the most frequently used mitochondrial stains.

Laboratory Craters: Modeling Experiments for Meteorite Impact Craters?

In this paper, we reveal the feasibility of obtaining laboratory craters to investigate planetary events such as meteorite craters. Experiments were performed by using 0.44-mum laser beam with energy of les15 J in 350 ps (full-width at half-maximum) on aluminum targets. We obtain simple and complex craters similar in contour that are formed due to large meteorite impacts on the terrestrial surface. Simulations performed with the 2-D radiation hydrodynamic code MULTI help in understanding the origin of the experimentally observed central uplift of complex craters.

Conformational behaviour and molecular similarity of some beta 1 -adrenergic ligands.

SummaryThe conformational behaviour of a series of aryloxypropanolamines was investigated by means of a new procedure which allows the sampling of the molecular torsional surface in a very efficient way. The combination of such a procedure with the standard molecular mechanics algorithms for the geometry optimization gives, as a result, the definition of a powerful computational scheme for the detailed analysis of the potential energy surface of complex molecules. The compounds studied show a remarkable tendency to form intramolecular hydrogen bonds, which seem to play a key role in determining the lowest energy structures. The indices of molecular similarity proposed by Carbó, computed for the most stable conformers, do not account for differences between diastereoisomers, and, as a consequence, can hardly be used to attempt a structure-activity correlation.

The NIR absorption spectrum of water in FeCl2·4H2O single crystals

Abstract The polarized near i.r. absorption spectrum of water in FeCl 2 ·4H 2 O single crystals has been measured at 10 K in the 3600–7200cm −1 region. The observed bands can be assigned to overtones and combinations of the fundamental and librational modes of the crystal water molecules. Polarization helps in attributing the contribution of the two different types of water present in the crystal and in understanding which fundamental vibrations combine. This analysis gives support to the assignment of the fundamental spectrum bands which are not experimentally accessible on single crystals and are of difficult interpretation, particularly in the stretching and librational regions.

Influence of consecutive picosecond pulses at 532 nm wavelength on laser ablation of human teeth

The interaction of 40 ps pulse duration laser emitting at 532 nm wavelength with human dental tissue (enamel, dentin, and dentin–enamel junction) has been investigated. The crater profile and the surface morphology have been studied by using a confocal auto-fluorescence microscope (working in reflection mode) and a scanning electron microscope. Crater profile and crater morphology were studied after applying consecutive laser pulses and it was found that the ablation depth increases with the number of consecutive pulses, leaving the crater diameter unchanged. We found that the thermal damage is reduced by using short duration laser pulses, which implies an increased retention of restorative material. We observe carbonization of the irradiated samples, which does not imply changes in the chemical composition. Finally, the use of 40 ps pulse duration laser may become a state of art in conservative dentistry.

Analogy of meteorite impacts in laboratory conditions

In this work, we report on the possibility of using laser-generated craters to investigate planetary events such as meteorite impact craters. Experiments using a 0.44 μm/350 ps wavelength laser beam on aluminum foil targets are performed. We obtain simple and complex craters similar in contour to those formed due to meteorite impacts on the terrestrial surface. Our preliminary results show that the central peak of complex craters seems to be higher because of the turbulence beneath the crater floor. Results obtained using a two-dimensional radiation hydrodynamic code, MULTI, show that the laser ablation surface modifies and rises. This could be one of several factors explaining the central peak existence.