On the role of the colloidal stability of mesoporous silica nanoparticles as gene delivery vectors

Mesoporous silica nanoparticles have been synthesized and functionalized with four different types of molecules containing amino groups, i.e., with primary amines only, with quaternary amines, with quaternized cyclic amines, or with polyethylenimine (PEI), which is formed by primary, secondary, and tertiary amines. These nanoparticles were then incubated with reporter plasmids and the ability of the resulting complexes to transfect human cells was studied. Only nanoparticles functionalized with PEI were efficient for transfection. The agglomeration behavior and the electrokinetic potential of the nanoparticle–plasmid complexes have been studied, as well as their cell internalization behavior using a fluorescent-labeled plasmid that allows its monitorization by confocal microscopy. The results indicate that the efficiency of PEI-functionalized nanoparticles for transfection resides to some extent in the different characteristics imparted to the nanoparticles regarding agglomeration and surface charge behavior.     

Crystallizability of ethylene homopolymers by crystallization analysis fractionation

The effect of molecular weight and long‐chain branching on the crystallization analysis fractionation (CRYSTAF) of ethylene homopolymers was investigated. Several ethylene homopolymers were prepared with different molecular weights and levels of long‐chain branching to isolate these effects from the dominant effect of comonomer content on crystallizability measured by CRYSTAF. Molecular weight effects might be significant for samples with number‐average molecular weights below 5000, but this effect can be corrected if terminal methyl groups are taken into account. Long‐chain branching has only a very small effect on the CRYSTAF profile of the samples investigated in this study. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1616–1628, 2001     

Characterization of three saponins from a fraction using 1D DOSY as a solvent signal suppression tool. Agabrittonosides E–F. Furostane Saponins from Agave brittoniana Trel. spp. Brachypus

A careful NMR analysis, especially by 1D TOCSY and 1D ROESY, of a refined saponin fraction allowed us to determine the structure of three saponins from a polar extract of Agave brittoniana Trel. spp. Brachypus leaves. The use of 1D DOSY for the suppression of the solvent signal was useful to obtain the chemical shifts of anomeric signals. A full assignment of the ¹H and ¹³C spectral data for the new saponins, agabrittonosides E–F (1–2) and the well‐known Karatavioside C (3) and their methoxyl derivatives, is reported. The structures were established using a combination of 1D and 2D (¹H, ¹H‐COSY, TOCSY, ROESY, g‐HSQC, g‐HMBC and g‐HSQC‐TOCSY) NMR techniques and ESI–MS. In addition, the methoxylation of these furostane saponins in the presence of MeOH was studied. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of polymers containing regularly distributed tetrathia‐[7]‐elicene units along the backbone

A tetrathia‐[7]‐helicene bearing in the 2 and 13 positions cyanovinyl groups was used as comonomer in the Michael‐type polyaddition reaction with N,N′‐bis(β‐mercaptoethyl)piperazine. This led to a new polymer bearing tetrathia‐[7]‐helicene units regularly distributed along the polymer backbone, which may be regarded as the first example of a new family of potentially useful nonlinear optical materials. All products were structurally characterized by ¹H and ¹³C NMR spectroscopy. Differential scanning calorimetry characterizations revealed the presence, in both monomeric and polymeric helicenes, of glass‐transition like temperatures, associated to some conformational variation of the helicene units. The optical properties, the film formation and the morphology of the polymer‐containing tetratia‐[7]‐helicenes were also investigated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

First description of B chromosomes in the family Auchenipteridae,Parauchenipterus galeatus (Siluriformes) of the São Francisco River basin (MG,Brazil)

B chromosomes are considered additional and non-essential; they likely originate from A chromosomes and follow a distinct evolution. In fish, approximately half of the Neotropical species with B chromosomes are Characiformes and 35% are Siluriformes. There has been no report of B chromosomes in Auchenipteridae until this moment. B chromosomes found in a population of Parauchenipterus galeatus from the São Francisco River basin in the state of Minas Gerais (Brazil) were small, metacentric, totally heterochromatic and exhibited intra-individual and inter-individual variation. The diploid number was 58 chromosomes (22 metacentric, 16 submetacentric, 12 subtelocentric and 8 acrocentric). The nucleolar organizing regions were simple and the heterochromatin intercalated in the ribosomal sites, characterized by CMA₃ and DAPI fluorochromes, was of a GC-rich constitution. The 5S rDNA genes were located in an intercalary position in only one chromosome pair. An hypothesis about the origin of the B chromosomes in P. galeatus and a review on B chromosomes in catfish are also presented in this study.     

Measure homology and singular homology are isometrically isomorphic

Measure homology is a variation of singular homology designed by Thurston in his discussion of simplicial volume. Zastrow and Hansen showed independently that singular homology (with real coefficients) and measure homology coincide algebraically on the category of CW-complexes. It is the aim of this paper to prove that this isomorphism is isometric with respect to the ℓ¹-seminorm on singular homology and the seminorm on measure homology induced by the total variation. This, in particular, implies that one can calculate the simplicial volume via measure homology – as already claimed by Thurston. For example, measure homology can be used to prove Gromov's proportionality principle of simplicial volume.     

Semiempirical calculations of the hydrolysis of penicillin G

A theoretical study of the gas-phase alkaline hydrolysis of penicillin G on the assumption of a B_AC2 mechanism is reported. Various semiempirical methods were used to determine the influence of different parameterizations on the process. Among the most salient results obtained, the standard AM1 method predicted opening of the thiazolidine ring to yield the corresponding imine and enamine structures.     

Literatur

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