Why is less cationic lipid required to prepare lipoplexes from plasmid DNA than linear DNA in gene therapy?

The most important objective of the present study was to explain why cationic lipid (CL)-mediated delivery of plasmid DNA (pDNA) is better than that of linear DNA in gene therapy, a question that, until now, has remained unanswered. Herein for the first time we experimentally show that for different types of CLs, pDNA, in contrast to linear DNA, is compacted with a large amount of its counterions, yielding a lower effective negative charge. This feature has been confirmed through a number of physicochemical and biochemical investigations. This is significant for both in vitro and in vivo transfection studies. For an effective DNA transfection, the lower the amount of the CL, the lower is the cytotoxicity. The study also points out that it is absolutely necessary to consider both effective charge ratios between CL and pDNA and effective pDNA charges, which can be determined from physicochemical experiments.     

On the Use of Metal Purine Derivatives (M=Ir,Rh) for the Selective Labeling of Nucleosides and Nucleotides

The reactions of neutral or cationic Ir^III and Rh^III derivatives of phenyl purine nucleobases with unsymmetrical alkynes produce new metallacycles in a predictable manner, which allows for the incorporation of either photoactive (anthracene or pyrene) or electroactive (ferrocene) labels in the nucleotide or nucleoside moiety. The reported methodology (metalation of the purine derivative and subsequent marker insertion) could be used for the postfunctionalization and unambiguous labeling of oligonucleotides.     

Preparation, structural analysis and dielectric properties of Bi x La1−x FeO3 perovskite

Rare earth element substituted bismuth ferrites (BiFeO₃) are of enormous importance as magnetoelectric materials. The polycrystalline samples of Bi _x La_1−x FeO₃ (x=0, 0.2, 0.4, 0.6, 0.8) were prepared by solid-state reaction using standard ceramic method. The single-phase formation of these compounds was confirmed by X-ray diffraction (XRD) studies. The samples with x=0, 0.2, 0.4, 0.6 are found to be orthorhombic while the sample with x=0.8 is triclinic. The dielectric constant (ε′) and dissipation factor (tan δ) were measured in the frequency range 100 Hz to 1 MHz at room temperature and as a function of temperature at certain fixed frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz). All the samples showed dielectric dispersion. The dielectric constant with temperature shows a broad peak; the peak temperature shifts with frequency which reflects the relaxor-type behavior. The peak above 600 K in the measured temperature range corresponds to antiferromagnetic ordering temperature (Néel temperature). The broadness of the peak changes with composition. The ac conductivity as well as ε′ are found to be maximum for the sample x=0.2 at room temperature.     

Duality and quantum groups

We show that the duality properties of Rational Conformal Field Theories follow from the defining relations and the representation theory of quantum groups. The fusion and braiding matrices are q-analogues of the 6j-symbols and the modular transformation matrices are obtained from the properties of the co-multiplication. We study in detail the Wess-Zumino-Witten models and the rational gaussian models as examples, but carry out the arguments in general. We point out the connections with the Chern-Simons approach. We give general arguments of why the general solution to the polynomial equations of Moore and Seiberg describing the duality properties of Rational Conformal Field Theories defines a Quantum Group acting on the space of conformal blocks. A direct connection between Rational Theories and knot invariants is also presented along the lines of Jones' original work.     

Magnetoelectric effect in cobalt ferrite-barium titanate composites and their electrical properties

CoFe₂O₄-BaTiO₃ composites were prepared using conventional ceramic double sintering process with various compositions. Presence of two phases in the composites was confirmed using X-ray diffraction. The dc resistivity and thermoemf as a function of temperature in the temperature range 300 K to 600 K were measured. Variation of dielectric constant (ɛ′) with frequency in the range 100 Hz to 1 MHz and also with temperature at a fixed frequency of 1 kHz was studied. The ac conductivity was derived from dielectric constant (ɛ′) and loss tangent (tan δ). The nature of conduction is discussed on the basis of small polaron hopping model. The static value of magnetoelectric conversion factor has been studied as a function of magnetic field.     

Enantiomeric separation of glycidyl tosylate by CE: Application to the study of catalytic asymmetric epoxidation of allyl alcohol

A CE method using CDs as chiral selectors was developed and validated to achieve the separation of glycidyl tosylate enantiomers originated by in situ derivatization of glycidol enantiomers obtained in asymmetric epoxidation of allyl alcohol with chiral titanium‐tartrate complexes as catalysts. The effects of the nature, pH and concentration of the buffer, the nature and concentration of chiral selector, the addition of SDS, methanol, ethanol or 2‐propanol, the capillary temperature, the effective capillary length and the applied voltage on the chiral resolution of glycidyl tosylate enantiomers were investigated. The best separation conditions were achieved using a Tris‐borate buffer mixture (50 and 25 mM, respectively) at pH=9.3 with a dual CD system consisting of 2.5% succinyl‐β‐CD and 1.0% β‐CD w/v at 15°C. A baseline separation (resolution～2.0) of the glycidyl tosylate enantiomers was obtained in a relatively short time (less than 12 min). Satisfactory results were obtained in terms of linearity (r>0.99) and intermediate precision (RSD below 8.5%). The LOD and LOQ were 3.0 and 10.0 mg/L, respectively, and the recoveries ranged from 99.8 to 108.8%. Finally, the method was applied to the determination of the enantiomeric excess and the yield obtained in the asymmetric epoxidation of allyl alcohol employing chiral titanium‐tartrate complexes as catalysts after an in situ derivatization of glycidol enantiomers to glycidyl tosylate.     

Identification of sites within a monomeric red fluorescent protein that tolerate peptide insertion and testing of corresponding circular permutations

In recent years the class of known fluorescent proteins (FPs) has dramatically expanded as an ever-increasing numbers of variants and homologs of the green fluorescent protein (GFP) from Aequorea jellyfish have been either engineered in the lab or discovered in other marine organisms. The red fluorescent protein (RFP) from Discosoma coral (also known as dsFP583 and DsRed) has proven to be a particularly fruitful progenitor of variants with biochemical and spectroscopic properties conducive to applications in live cell imaging. We have investigated the tolerance of an engineered monomeric descendent of Discosoma RFP, known as mCherry, towards peptide insertion and circular permutation. Starting from a random library of insertion variants, we identified six genetically distinct sites localized in three different loops where a sequence of five residues could be inserted without abolishing the ability of the protein to form its intrinsic red fluorescent chromophore. For each of these insertion variants, a corresponding circular permutation variant was created in which the original N- and C-termini were connected by a six-residue linker and new termini were introduced at the site of the insertion. All six circular permutation variants had significantly diminished brightness relative to the analogous insertion variants. The most promising circular permutation variant has termini at the position corresponding to residue 184 of mCherry and retains 37% of the intrinsic fluorescent brightness of mCherry. These circularly permuted variants may serve as the foundation for construction of genetically encoded Ca2+ sensors analogous to the previously reported camgaroo, pericam and G-CaMP sensors based on variants of Aequorea GFP.     

In vivo detection of DNA adducts induced by cisplatin using capillary HPLC–ICP-MS and their correlation with genotoxic damage in Drosophila melanogaster

The antitumoral effect of cisplatin [cis-diamminodichloroplatinum(II)] in mammals is related to its binding to DNA components. However, there is a lack of specific chemical methods to selectively detect those adducts formed in vivo at low concentrations. In this work, a new sensitive and selective method of determining cisplatin–DNA adducts based on the use of element-selective mass spectrometry is proposed, and the method is then applied to detect cisplatin adducts induced in vivo in somatic cells of Drosophila melanogaster. The bioanalytical strategy proposed here allows the determination of the most important DNA adduct formed between adjacent guanine units of the same DNA strand with cisplatin, and it is based on the coupling of capillary liquid chromatography (cap-LC) to inductively coupled plasma mass spectrometry (ICP-MS). This set-up allows the simultaneous monitoring of the Pt (from the drug) and P (from the DNA components) present in these adducts, once they have been cleaved by enzymatic hydrolysis of the DNA samples. Using this instrumental set-up, the adducts of cisplatin formed in vivo when D. melanogaster flies are exposed to different cisplatin concentrations can be detected and their concentration determined. The results obtained show a direct correlation between the concentration of cisplatin adducts, the induced genotoxic damage (measured as DNA strand breaks using the Comet assay) and the cisplatin concentration. Figure The work illustrates the complementary use of bioanalytical and biological information to study cisplatin interactions with DNA is vivo at biologically relevant concentrations of the drug     

Antimicrobial activity of three baccharis species used in the traditional medicine of Northern Chile

The antimicrobial activities of aqueous ethanol and chloroform extracts of three Baccharis species currently used in Northern Chile folk medicine for the treatment of several infectious and inflammatory disorders were tested against Gram-positive and negative bacteria and fungal spp. using the agar-disc diffusion assay. The results indicated that the activity was more pronounced against Gram-positive than against Gram-negative bacteria and yeast. No significant differences on the antibacterial activity were observed in the aqueous ethanol versus chloroform extracts. None of the plant extracts evaluated exhibited any activity against ten fungi tested.