Do electrospray mass spectra of surfactants mirror their aggregation state in solution?

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The interaction of native calf thymus DNA with FeIII-dipyrido[3,2-a:2\u2019,3\u2019-c]phenazine

The mono and bis dipyrido[3,2-a:20,30-c]phenazine (dppz) adducts of iron(III) chloride, i.e. [Fe(dppz)]Cl3 and [Fe(dppz)2]Cl3, have been synthesized and characterized. The interaction of the FeIIIdppz hydrolyzed aquo complex with native calf thymus DNA has been monitored as a function of the metal complex\u2013DNA molar ratio, by variable temperature UV absorption spectrophotometry, circular dichroism (CD) and fluorescence spectroscopy. The results obtained in solution at various ionic strength values give support for a tight intercalative binding of the FeIIIdppz cation with DNA. In particular, the appearance of induced CD bands, caused by the addition of FeIIIdppz, indicate the existence of a rigid metal complex\u2013DNA-binding leading to dominating chiral organization of FeIIIdppz species within the DNA double helix. The trend of selected CD bands with the molar concentration of FeIIIdppz emphasizes that the presence of high amounts of metal complex induces also the formation of DNA\u2013FeIIIdppz supramolecular aggregates in solution. The analysis of fluorescence measurements allowed us to calculate a value of the intercalative binding constant comparable to that obtained by UV spectrophotometric titration. Finally, the temperature dependence of the absorbance at 258 nm shows that the metal complex strongly increases the DNA melting temperature already at metal complex\u2013DNA molar ratio equal to 0.25 suggesting that metal complex intercalation effectively hinders DNA denaturation. Overall, the results of the present study point out that the FeIIIdppz aquo complex has DNA-binding properties analogous to those previously reported for the tris-chelate FeII(phen)2dppz complex (phen = 1,10-phenantroline)

Sodium bis-(2-ethylhexyl) sulfosuccinate sepf-aggregation in vacuo: Molecular Dynamics simulation

Molecular dynamics (MD) simulations were conducted for systems in vacuo consisting of n AOT anions (bis(2-ethylhexyl)sulfosuccinate ions) and n 1 or n Na+ ions up to n = 20. For n = 15, positively charged systems with Li+, K+, and Cs+ cations were also considered. All systems were observed to form reverse micelle-like aggregates whose centre is occupied by cations and polar heads in a very compact solid-like way, while globally the aggregate has the form of an elongated and rather flat ellipsoid. Various types of statistical analyses were carried out on the systems to enlighten structural and dynamical properties including gyration radius, atomic pair correlation functions, atomic B-factor and moment of inertia tensor. For completeness and comparison the stability of reverse micelle is tested in the case of neutral n = 20 system in CCl4 solution

COUPLING ELECTROCHEMISTRY TO ELECTROSPRAY: A NOVEL PREPARATION OF GOLD NANOSTRUCTURES

nanoparticles on ITO (Indium tin oxide) coated glass using the electrospray (ESI) method Method:The starting point of this study is that the ESI/MS spectrum (Figure 1) of an ethanolic solution of HAuCl 4 shows a reduction process of Au (III) strongly dependent on the Cone Voltage (CV) values (20, 80, 150 V), affording to the ion at m/z 197 (Au+). Further, the decrease of the abundance of this ion at the highest cone voltage suggests the subsequent its reduction with the formation of Au 0 . Figure 1: ESI/MS spectra of an ethanolic solution of HAuCl4 at various cone voltages: Conclusion: Such experimental evidence leads us to use electrospray technique as a preparative tool to obtain the formation and deposition of gold nanoparticles in a single step. In fact, using a home-made electrospray apparatus, we sprayed an ethanolic solution of HAuCl4, forming a very thin aerosol that has been uniformly deposited on ITO coated glass. Then, the deposit by SEM, UV-Vis, Optical-Microscopy and XPS has been characterized4,5. In particular, SEM micrographs show rod-like structures, while XPS spectra show that the deposited nanoparticles contain about 23% of Au0

Self-assembly in surfactant-based liquid mixtures: Bis(2-ethylhexyl)phosphoric acid/bis(2- ethylhexyl)amine systems

Surfactant-based liquid mixtures constitute an interesting class of nanostructured materials with promising potential in specialized applications. Here, structural and conductometric properties of liquid mixtures composed of bis(2-ethylhexyl)amine (BEEA) and bis(2-ethylhexyl)phosphoric acid (HDEHP) have been thoroughly investigated with the aim to correlate structural features with system charge transport capability. The evolution of self-assembled local nanostructures with system composition has been investigated by FT-IR and XRD while the conductometric properties were probed by conventional AC complex impedance. Both pure components exhibit nano-segregation due to their amphiphilic nature but with only very low proton conductivities. However their mixtures, characterized by local organization of polar and apolar domains driven by acid–base interactions between HDEHP PO4H and BEEA NH groups, show enhanced structural order and proton conductivity