Shape and size of red blood cells from the Pygoscelid penguins of Antarctica using atomic force microscopy

Antarctic biodiversity is evolutionarily complex, reflecting the extreme ambient conditions. Therefore, Antarctic organisms exhibit sophisticated adaptations in all organization levels, including organs, tissues, and cells. Since red blood cells (RBCs) travel through the vertebrates blood delivering O(2) to all tissues and organs and purging the unwanted CO(2), they represent an interesting model to investigate biological adaptations. We have used atomic force microscopy (AFM) to compare the shape and size of RBCs of the Pygoscelid penguins. A total of 18 landmarks were measured in AFM images. When analyzed individually, the parameters were not capable of discriminating the RBCs of each species. However, the simultaneous use of multiple parameters discriminated (74%) among the RBCs. In addition, the use of RBC measurements was sufficient to hierarchically cluster the species in accordance to other common and reliable phylogenetic strategies. In light of these results, the use of RBC characters could effectively benefit taxonomic inferences.

Electrostatic and Hydrophobic Interactions Involved in CNT Biofunctionalization with Short ss-DNA

This work is aimed at studying the adsorption mechanism of short chain 20-mer pyrimidinic homoss-DNA (oligodeoxyribonucleotide, ODN: polyC(20) and polyT(20)) onto CNT by reflectometry. To analyze the experimental data, the effective-medium theory using the Bruggemann approximation represents a Suitable optical model to account for the surface properties (roughness, thickness, and optical constants) and the size of the adsorbate. Systematic information about the involved interactions is obtained by changing the physicochemical properties of the system. Hydrophobic and electrostatic interactions are evaluated by comparing the adsorption oil hydrophobic CNT and oil hydrophilic silica and by Modulating the ionic Strength With and without Mg(2+). The ODN adsorption process oil CNT is driven by hydrophobic interactions only when the electrostatic repulsion is Suppressed. The adsorption mode results in ODN molecules in a side-on orientation with the bases (nonpolar region) toward the surface. This unfavorable orientation is partially reverse by adding Mg(2+). On the other hand, the adsorption oil silica is dominated by the strong repulsive electrostatic interaction that is screened at high ionic strength or mediated by Mg(2+). The cation-mediated process induces the interaction of the phosphate backbone (polar region) with the surface, leaving the bases free for hybridization. Although the general adsorption behavior of the pyrimidine bases is the same, polyC(20) presents higher affinity for the CNT Surface due to its acid-base properties.

Electrostatic layer-by-layer deposition and electrochemical characterization of thin films composed of MnO(2) nanoparticles in a room-temperature ionic liquid

Thin films of MnO(2) nanoparticles were grown using the layer-by-layer method with poly (diallyldimetylammonium) as the intercalated layer. The film growth was followed by UV-vis, electrochemical quartz crystal microbalance (EQCM), and atomic force microscopy. Linear growth due to electrostatic immobilization of layers was observed up to 30 bilayers, but electrical connectivity was maintained only for 12 MnO(2)/PPDA bilayers. The electrochemical characterization of this film in 1-butyl-2,3-dimethyl-imidazolium (BMMI) bis(trifluoromethanesulfonyl)imide (TFSI) (BMMITFSI) with and without addition of a lithium salt indicated a higher electrochemical response of the nanostructured electrode in the lithium-containing electrolyte. On the basis of EQCM experiments, it was possible to confirm that the charge compensation process is achieved mainly by the TFSI anion at short times (<2 s) and by BMMI and lithium cations at longer times. The fact that large ions like TFSI and BMMI participate in the electroneutrality is attributed to the redox reaction that occurs at the superficial sites and to the high concentration of these species compared to that of lithium cations.

Nanostructured europium oxide thin films deposited by pulsed laser ablation of a metallic target in a He buffer atmosphere

Nanostrucured europium oxide and hydroxide films were obtained by pulsed Nd:YAG (532 nm) laser ablation of a europium metallic target, in the presence of a 1 mbar helium buffer atmosphere. Both the produced film and the ambient plasma were characterized. The plasma was monitored by an electrostatic probe, for plume expansion in vacuum or in the presence of the buffer atmosphere. The time evolution of the ion saturation current was obtained for several probe to substrate distances. The results show the splitting of the plume into two velocity groups, being the lower velocity profile associated with metal cluster formation within the plume. The films were obtained in the presence of helium atmosphere, for several target-to-substrate distances. They were analyzed by Rutherford backscattering spectrometry, x-ray diffraction, and atomic force microscopy, for as-deposited and 600 degrees C treated-in-air samples. The results show that the as-deposited samples are amorphous and have chemical composition compatible with europium hydroxide. The thermally treated samples show x-ray diffraction peaks of Eu(2)O(3), with chemical composition showing excess oxygen. Film nanostructuring was shown to be strongly correlated with cluster formation, as shown by velocity splitting in probe current versus time plots. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3457784]

Cholesterol Mediates Chitosan Activity on Phospholipid Monolayers and Langmuir-Blodgett Films

The polysaccharide chitosan has been largely used in many biological applications as a fat and cholesterol reducer, bactericide agent, and wound healing material. While the efficacy for some of such uses is proven, little is known about the molecular-level interactions involved in these applications. In this study, we employ mixed Langmuir and Langmuir-Blodgett (LB) films of negatively charged dimyristoyl phosphatidic acid (DMPA) anti cholesterol as cell membrane models to investigate the role of cholesterol in the molecular-level action of chitosan. Chitosan does not remove cholesterol froth the monolayer. The interaction with chitosan tends to expand the DMPA monolayer due to its interpenetration within the film. On the other hand, cholesterol induces condensation of the DMPA monolayer. The competing effects cause the surface pressure isotherms of mixed DMPA-cholesterol films on a chitosan subphase to be unaffected by the cholesterol mole fraction, due to distinct degrees of chitosan penetration into the film in the presence of cholesterol. By combining polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) and sum-frequency generation spectroscopy (SFG), we showed that chitosan induces order into negatively charged phospholipid layers, whereas the opposite occurs for cholesterol. In conclusion, chitosan has its penetration in the film modulated by cholesterol, and electrostatic interactions with negatively charged phospholipids, such as DMPA, are crucial for the action of chitosan.

Adsorption of anionic amphiphilic polyelectrolytes onto amino-terminated solid surfaces

The adsorption behavior of several amphiphilic polyelectrolytes of poly(maleic anhydride-alt-styrene) functionalized with naphthyl and phenyl groups, onto amino-terminated silicon wafer has been studied by means of null- ellipsometry, atomic force microscopy (AFM) and contact angle measurements. The maximum of adsorption, Gamma(plateau), varies with the ionic strength, the polyelectrolyte structure and the chain length. Values of Gamma(plateau) obtained at low and high ionic strengths indicate that the adsorption follows the ""screening-reduced adsorption"" regime. Large aggregates were detected in solution by means of dynamic light scattering and fluorescence measurements. However. AFM indicated the formation of smooth layers and the absence of aggregates. A model based on a two-step adsorption behavior was proposed. In the first one, isolated chains in equilibrium with the aggregates in solution adsorbed onto amino-terminated surface. The adsorption is driven by electrostatic interaction between protonated surface and carboxylate groups. This first layer exposes naphtyl or phenyl groups to the solution. The second layer adsorption is now driven by hydrophobic interaction between surface and chains and exposes carboxylate groups to the medium, which repel the forthcoming chain by electrostatic repulsion. Upon drying some hydrophobic naphtyl or phenyl groups might be oriented to the air, as revealed by contact angle measurements. Such amphiphilic polyelectrolyte layers worked well for the building-up of multilayers with chitosan. (C) 2010 Elsevier Ltd. All rights reserved.