Synthesis of Globular Precursors

o‐Carborane (C₂B₁₀H₁₂) was adapted to perform as the core of globular macromolecules, dendrons or dendrimers. To meet this objective, precisely defined substitution patterns of terminal olefin groups on the carborane framework were subjected to Heck cross‐coupling reactions or hydroboration leading to hydroxyl terminated arms. These led to new terminal groups (chloro, bromo, and tosyl leaving groups, organic acid, and azide) that permitted ester production, click chemistry, and oxonium ring opening to be performed as examples of reactions that demonstrate the wide possibilities of the globular icosahedral carboranes to produce new dendritic or dendrimer‐like structures. Polyanionic species were obtained in high yield through the ring‐opening reaction of cyclic oxonium compound [3,3′‐Co(8‐C₄H₈O₂‐1,2‐C₂B₉H₁₀)(1′,2′‐C₂B₉H₁₁)] by using terminal hydroxyl groups as nucleophiles. These new polyanionic compounds that contain multiple metallacarborane clusters at their periphery may prove useful as new classes of compounds for boron neutron capture therapy with enhanced water solubility and as cores to make a new class of high‐boron globular macromolecules.     

Voltammetric Behaviour of 7‐Methylguanine Using Screen‐printed Graphite Electrodes: towards a Guanine Methylation Electrochemical Sensor

The determination of 7‐methylguanine (7mG) is an interesting analytical target since its quantification can be correlated with the methylation of cytosine which is one of the most relevant epigenetic modification of DNA. In this work, screen‐printed graphite electrodes were used to study the electrochemical characterization of 7mG by cyclic and square wave voltammetry. 7mG concentration and pH were examined, as well as the repeatability of the measurements. The electrochemical response of 7mG in the presence of guanine and adenine was also investigated. Results aim to the future development of an electrochemical sensor for the methylation degree in DNA.     

HERAS: A helium jet to prevent damage on works of art in Raman experiments

Raman spectroscopy is often used for non‐destructive analysis of works of art, polymers and biological materials, but in some cases, the laser beam can cause damages on the surface being studied due to the deposited beam energy. When possible, such damage can be prevented by minimizing laser intensity or acquisition time, but this is usually available only on high sensitivity bench‐top spectrometers. Portable Raman spectrometers are commonly not so flexible and an alternative is needed to ensure the safe study of sensitive works of art and other fragile materials. A helium jet aimed directly at the laser spot may prevent this damage from occurring and, in some cases, helps improving the Raman spectra. We designed a simple system (HERAS, Helium Raman System) consisting of a pinhole collimator, coupled to a helium line and a gas mass flux control and tested it on pyroxylin, vermilion and ochre paint references and pigment samples, using a 785 nm portable Raman spectrometer at various laser powers. Experimental conditions slightly differ for each sample, but small burns on the surface were avoided in all cases and only some ablation was observed on the most sensitive materials. The use of this coupled system allows the non‐destructive application of Raman to a wider variety of materials, while the technique remains portable. This setup may be used in bench‐top apparatus as well. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of sialic acid content on glycoprotein pI analyzed by two‐dimensional electrophoresis

2‐DE is broadly used for quantitative analysis of differential protein expression in complex mixtures such as serum samples or cell lysates. PTMs directly influence the 2‐DE pattern, and knowledge of the rules of protein separation is required in order to understand the protein distribution in a 2‐DE gel. Glycosylation is the most common PTM and can modify both the molecular weight and the pI of a protein. In particular, the effect of charged monosaccharides (mainly sialic acids, SAs) on the 2‐DE pattern of a protein is of major interest since changes in sialylation are regularly observed in comparative studies. Little is known about the pI shift of a glycoprotein induced by the presence of SAs, or whether this shift is the same for all glycoproteins. To address this issue, this study examined the influence of SA on the 2‐DE pattern of three serum glycoproteins (haptoglobin, α1‐antitrypsin and ribonuclease 1), which N‐glycan chains had been previously characterised, and reviewed existing bibliographic data. The SA content of the different glycoforms of a glycoprotein showed a negative linear correlation with the pI, although the slope varied among the studied glycoproteins. We also described a positive correlation between the protein pI and the pI decrease per SA molecule.     

Additive Tuning of Redox Potential in Metallacarboranes by Sequential Halogen Substitution

The first artificially made set of electron acceptors is presented that are derived from a unique platform Cs[3,3′‐Co(C₂B₉H₁₁)₂], for which the redox potential of each differs from its predecessor by a fixed amount. The sequence of electron acceptors is made by substituting one, two, or more hydrogen atoms by chlorine atoms, yielding Cs[3,3′‐Co(C₂B₉H_11?yCl_y)(C₂B₉H_11?zCl_z)]. The higher the number of chlorine substituents, the more prone the platform is to be reduced. The effect is completely additive, so if a single substitution implies a reduction of 0.1 V of the redox potential of the parent complex, then ten substitutions imply a reduction of 1 V.     

Entanglement measures of a new type pseudo-pure state in accelerated frames

In this work we analyze the characteristics of quantum entanglement of the Dirac field in noninertial reference frames in the context of a new type pseudo-pure state, which is composed of the Bell states. This will help us to understand the relationship between the relativity and quantum information theory. Some states will be changed from entangled states into separable ones around the critical value F = 1/4, but there is no such a critical value for the variable y related to acceleration a. We find that the negativity N_ABI (ρ^TA_ABI) increases with F but decreases with the variable y, while the variation of the negativity N_BIBII(ρ^TA_ABI) is opposite to that of the negativity N_ABI (ρ^TA_ABI). We also study the von Neumann entropies S(ρ_ABI) and S(ρ_BIBII). We find that the S(ρ_ABI) increases with variable y but S(ρ_BIBII) is independent of it. However, both S(ρ_ABI) and S(ρ_BIBII) first decreases with F and then increases with it. The concurrences C(ρ_ABI) and C(ρ_BIBII) are also discussed. We find that the former decreases with y while the latter increases with y but both of them first increase with F and then decrease with it.     

Radial position-momentum uncertainties for the infinite circular well and Fisher entropy

We show how the product of the radial position and momentum uncertainties can be obtained analytically for the infinite circular well potential. Some interesting features are found. First, the uncertainty Δr increases with the radius R and the quantum number n, the n-th root of the Bessel function. The variation of the Δr is almost independent of the quantum number n for $n>4$ and it will arrive to a constant for a large n, say $n>4$. Second, we find that the relative dispersion $\mathrm{\Delta }r/〈r〉$ is independent of the radius R. Moreover, the relative dispersion increases with the quantum number n but decreases with the azimuthal quantum number m. Third, the momentum uncertainty Δp decreases with the radius R and increases with the quantum numbers $m>1$ and n. Fourth, the product $\mathrm{\Delta }r\mathrm{\Delta }{p}_r$ of the position-momentum uncertainty relations is independent of the radius R and increases with the quantum numbers m and n. Finally, we present the analytical expression for the Fisher entropy. Notice that the Fisher entropy decreases with the radius R and it increases with the quantum numbers $m>0$ and n. Also, we find that the Cramer–Rao uncertainty relation is satisfied and it increases with the quantum numbers $m>0$ and n, too.     

Syntheses,Characterization, and DNA Binding Studies of a Series of Copper(II), Nickel(II), Platinum(II) and Zinc(II) Complexes Derived from Schiff Base Ligands

Three series of metal salophen complexes derived from Zn²⁺, Cu²⁺, Pt²⁺ and Ni²⁺ have been synthesized and their interaction with quadruplex DNA has been evaluated. The compounds differ on the number of ethyl piperidine substituents. They have been characterized by ¹H NMR, IR and UV-visible spectroscopies and by HR-mass spectrometry. Their luminescent properties have been also evaluated and we can observe that, as expected, Zn²⁺ and Pt²⁺ complexes are those displaying more interesting luminescence with an emission band red-shifted with respect to the corresponding uncoordinated ligand. DNA interactions with G4 and duplex DNA were evaluated by FRET melting assays (for the Zn²⁺, Cu²⁺ and Ni²⁺ complexes) and by emission titrations (for one Pt²⁺ complex) which indicated that the disubstituted compounds 2-Ni and 2-Pt are the only ones that display good affinity for G4 DNA structures.