In vitro transfection mediated by dendrigraft poly(L-lysines): the effect of structure and molecule size.

Dendritic poly(L-lysines) (DGL) constitute promising nanomaterials applicable as a nonviral gene-delivery vector. In this study, we evaluate the transfection abilities of four DGL generations with special emphasis on the systematic description of the relationship of how generation (i.e., molecule size) affects the transfection efficacy. Using Hep2 cells, we demonstrated that the capability of unmodified DGL to deliver plasmid is of a magnitude lower than that of jetPEI. On the other hand, employing the Hep2 cell line stably transduced with eGFP, we observed that DGL G5 delivers the siRNA oligonucleotide with the same efficiency as Lipofectamine 2000. In further experiments, it was shown that DGL affords excellent ability to bind DNA, protect it against DNase I attack, and internalize it into cells.

Profiling and characterization of volatile secretions from the European stink bug Graphosoma lineatum (Heteroptera: Pentatomidae) by two-dimensional gas chromatography/time-of-flight mass spectrometry.

An efficient method combining the headspace solid-phase microextraction (HS-SPME) sampling procedure and comprehensive two-dimensional gas-chromatography/time-of-flight mass spectrometry (GC×GC/TOF-MS) was established to study the volatile secretion components of stink bugs (Heteroptera: Pentatomidae). The combined power of this approach is illustrated by the identification of fifty-seven compounds in the secretion of a European stink-bug representative, Graphosoma lineatum. (E)-4-oxohex-2-enal and (E)-dec-2-enal were found to be the major components in the adult bug secretions followed by lower amounts of n-alkenal (C5-C12), n-alkenyl acetate (C5-C11), n-alkane (C11-C17) homologs, dienals and other compounds. More than thirty known compounds have been identified that had not been described before in G. lineatum adults. Of these compounds, (E)-4-oxohex-2-enal is of particular interest, since its isolation and identification, while calling some previous reports into question, clearly demonstrates a potential ability of our approach to yield artifact-free secretion profiles.

(R)-2-{2-[(S)-(2'-Benzo-yloxy-1,1'-binaphthyl-2-yl)oxycarbonyl-amino]-3-phenylpropanamido-meth-yl}pyridinium picrate acetone solvate.

In the crystal structure of the title compound, C(43)H(34)N(3)O(5) (+)·C(6)H(2)N(3)O(7) (-)·C(3)H(6)O, the large dimension and shape of the cation are responsible for the elongation of the ortho-rhom-bic unit cell. The ions and acetone mol-ecules are linked together by a system of hydrogen bonds involving an inter-molecular hydrogen bond between one N atom of the cation and the O atom of acetone and two inter-molecular hydrogen bonds between the cation N atoms and the O atoms of the picrate anion. No intra-molecular hydrogen bonds exist in the structure. The dihedral angle between the two naphthalene ring systems is 76.16 (13)°. The chiral C atom has a known R configuration, but this cannot be confirmed from this X-ray analysis.

Determining the vapour pressures of plant volatiles from gas chromatographic retention data.

The frequently used vapour pressure versus Kováts retention index relationship has been evaluated in terms of its universal applicability, highlighting the problems associated with predicting the vapour pressures of structurally divergent organic compounds from experimentally measured isothermal Kováts retention indices. Two models differing in approximations adopted to express the activity coefficient ratio have been evaluated using 32 plant volatiles of different structural types as a test set. The validity of these models was established by checking their ability to reproduce 22 vapour pressures known from independent measurements. Results of the comparison demonstrated that (i) the original model, based on the assumption of equal activity coefficients for the test and reference substances, led, as expected, to a poor correlation (r2 = 89.1% only), with significantly deviating polar compounds and (ii) the model showed significant improvement after incorporating a new empirical term related to vaporization entropy and boiling point. The addition of this term allowed more than 99% of the vapour pressure variance to be accounted for. The proposed model compares favourably with existing correlations, while having an added advantage of providing a convenient tool for vapour pressure determination of chemically divergent chemicals.

Synthesis of (R)- and (S)-3,3,3-trifluoro-2-phenylpropanoyl isocyanates and their use as reactive analogues of Mosher's acid.

The title compounds have been prepared from the respective 3,3,3-trifluoro-2-methoxy-2-phenylpropanoic acids (MTPA) by a three-step synthesis with MTPA chloride and MTPA amide as reaction intermediates. The requested compounds were obtained in high chemical yields without any change in optical purity during the preparation. To ascertain the usefulness of this auxiliary agent in the chiral analysis, isomeric 3,3,3-trifluoro-2-phenylpropanoyl isocyanates were subjected in NMR tubes to noncatalyzed reactions with 16 different commercially available chiral alcohols. The steric arrangement of all diastereomers prepared correlated well with their NMR spectral nonequivalence data (Deltadelta), thus demonstrating the regular sign distribution of Deltadelta of particular groups according to the devised molecular model. The usefulness of the novel derivatization is discussed.

Alkynyltrifluoroborates as versatile tools in organic synthesis: a new route to spiroketals.

[reaction: see text] A simple and efficient two-step approach to spiroketals is described. Key steps include the preparation of functionalized hydroxyl alpha-alkynones by ring-opening reactions of lactones with lithium alkynyltrifluoroborates followed by a palladium-catalyzed hydrogenation/spirocyclization of the prespiroketal intermediate.

Chiral derivatives of 2-(1-naphthyl)-2-phenylacetic acid.

The spectral properties of diastereomeric esters and amides (1b-20b), derived from optically pure 2-(1-naphthyl)-2-phenylacetic acids (1-NPA), were systematically investigated. It was found that all compounds prepared exhibit the NMR spectral nonequivalence (Deltadelta) with regular sign distribution of particular groups according to the predicted model. Further, the analysis of data revealed that the phenyl ring is responsible for a shielding effect (upfield shift) instead of a naphthyl one. This conclusion is supported by the crystallographic analysis showing the almost ap-arrangement of the acid methine hydrogen atom and carbonyl group. In this arrangement, the phenyl ring faces toward the ester part of the molecule while the naphthyl one is orthogonal to the phenyl plane. Therefore, the mutual position of phenyl and alkyl groups with respect to the central molecule co-planarity thus determines the chemical shifts of the alcohol/amine substituents. The relative magnitude of the Deltadelta corresponds to those of Mosher's derivatives.

(S)-2-chloro-2-fluoroethanoyl isocyanate, a chiral derivative of trichloroacetyl isocyanate.

Carbamate diastereomers 3b-18b were prepared from easily accessible (S)-2-chloro-2-fluoroethanoyl isocyanate (1) and various secondary chiral alcohols. Compound 1 as a chiral analog of trichloroacetyl isocyanate undergoes the reaction with alcohols very fast, thus blocking the hydroxyl group for the purposes of NMR investigation. Moreover, the correlation of stereochemistry of 3b-18b with their (1)H NMR spectra revealed that the constitution as well as configuration influences regularly the values of chemical shift difference (deltadelta = delta(R) - delta(S)) except for those diastereomers bearing simple alkyl groups in the molecule. Spectral as well as crystallographic data manifest the predominant planar conformation of the central part of the molecule. Due to the good accessibility and high reactivity in particular, the acylisocyanate 1 might be considered, to some extent, an alternative for TAI giving additional information on a compound's spatial structure.