A novel class of metal-directed supramolecular DNA-delivery systems

The bis-complexes [Cu(L(dt))(2)](OTf)(2) (1) and [Cu(L(ot))(2)](OTf)(2) (2), where L(dt) = 1-dodecyl-1,4,7-triazacyclononane, L(ot) = 1-octadecyl-1,4,7-triazacyclononane and OTf = trifluoromethanesulfonate, formed a novel class of metallo-liposomes in water that transfect pEGFP-N1 plasmids into HEK 293-T cells at 38% and 4% efficiency, respectively.     

Electrospray ionization mass spectrometry of a novel family of complexes in which various nitroso compounds are stabilized via coordination to [IrCl5]2-

Electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) data of a unique family of complexes of nitroso compounds coordinated to pentachloroiridate(III), [Cl5IrN(O)XR]2- (X=NH, S, CH and R=alkyl, aryl) are presented. These novel complexes are obtained by nucleophilic attack of primary amines, thiols. and alkenes to the coordinated nitrosyl. Despite their lability and low volatility, MS analysis of complexes of the type MN(O)X was done for the first time, complementing other spectroscopic techniques. The intrinsic dissociation chemistry of the gaseous diagnostic ions was studied via ESI-MS/MS and found to be very useful to confirm the proposed connectivities of the parent complexes. In particular, ESI-MS of their solutions allows the detection of series of diagnostic ions, mainly, [M-Cl]-, [M+K]-, [M-NO]-*, and [M-Cl+AcN]- (AcN=acetonitrile), which confirmed the identity of the analyzed complexes to be M=[Cl5IrN(O)XR]2-. Major fragments were formed by losses of NO or N(O)XR. ESI-MS and ESI-MS/MS measurements are therefore shown to be the proper techniques to complement the spectroscopic characterization of this important class of nitroso complexes. An interesting rearrangement that does not take place in solution was observed in the gaseous phase, and a plausible mechanism is discussed.     

A new synthesis of lysophosphatidylcholines and related derivatives. Use of p-toluenesulfonate for hydroxyl group protection

A new stereoselective synthesis of lysophosphatidylcholines is reported. The synthesis is based upon (1) the use of 3-p-toluenesulfonyl-sn-glycerol to provide the stereocenter for construction of the optically active lysophospholipid molecule, (2) tetrahydropyranylation of the secondary alcohol function to achieve orthogonal protection of the sn-2- and sn-3-glycerol positions, and (3) elaboration of the phosphodiester headgroup using a 2-chloro-1,3,2-dioxaphospholane/trimethylamine sequence. In the course of developing the synthesis it has been discovered that methoxyacetate displacement of the sn-3-p-toluenesulfonate yields a reactive methoxyacetyl ester, which in turn can be selectively cleaved with methanol/tert-butylamine, while the ester group at the sn-1-position remains unaffected. The sequence has been shown to be suitable for preparation of spectroscopically labeled lysophosphatidylcholines. One of these compounds was readily converted to a double-labeled mixed-chain phosphatidylcholine applicable for real-time fluorescence resonance energy transfer (FRET) assay of lipolytic enzymes. In addition, the work led to new synthetic strategies based on chemoselective manipulation of the tosyl group in the presence of other base-labile groups such as FMOC derivatives that are often used for the protection of amino and hydroxyl groups in syntheses.     

Reverse-micelle formation in the partitioning of trivalent F-element cations by biphasic systems containing a tetraalkyldiglycolamide

The conditions for reverse-micelle formation were studied for solutions of tetra-n-octyldiglycolamide (TODGA) in alkane diluents equilibrated with aqueous solutions of nitric or hydrochloric acids in the presence and absence of Nd3+. Small-angle neutron scattering, vapor-pressure osmometry, and tensiometry are all consistent with the partial formation of TODGA dimers at the lowest acidities, transitioning to a polydisperse mixture containing TODGA monomers, dimers, and small reverse-micelles of TODGA tetramers at aqueous nitric acid acidities of 0.7 M or higher in the absence of Nd. Application of the Baxter model to the samples containing 0.005-0.015 M Nd reveals the persistence of tetrameric TODGA reverse-micelles with significant interparticle attraction between the polar cores of the micelles that increases with increasing organic phase concentrations of acid or Nd. Our experimental findings suggest that the peculiar behavior of TODGA with respect to the extraction of trivalent lanthanide and actinide cations arises from the affinity of these metal cations for the preformed TODGA reverse-micelle tetramers.     

One-and-a-Half Quantum de Finetti Theorems

When n − k systems of an n-partite permutation-invariant state are traced out, the resulting state can be approximated by a convex combination of tensor product states. This is the quantum de Finetti theorem. In this paper, we show that an upper bound on the trace distance of this approximation is given by , where d is the dimension of the individual system, thereby improving previously known bounds. Our result follows from a more general approximation theorem for representations of the unitary group. Consider a pure state that lies in the irreducible representation of the unitary group U(d), for highest weights μ, ν and μ + ν. Let ξ_μ be the state obtained by tracing out U _ν. Then ξ_μ is close to a convex combination of the coherent states , where and is the highest weight vector in U _μ. For the class of symmetric Werner states, which are invariant under both the permutation and unitary groups, we give a second de Finetti-style theorem (our “half” theorem). It arises from a combinatorial formula for the distance of certain special symmetric Werner states to states of fixed spectrum, making a connection to the recently defined shifted Schur functions [1]. This formula also provides us with useful examples that allow us to conclude that finite quantum de Finetti theorems (unlike their classical counterparts) must depend on the dimension d. The last part of this paper analyses the structure of the set of symmetric Werner states and shows that the product states in this set do not form a polytope in general.     

Solvent Trapping during Large Volume Injection with an Early Vapor Exit,Part 2: Chromatographic Results and Conclusions

Solvent trapping reconcentrates volatile components after injection or on-line transfer of large volumes. When an early vapor exit is used, typically after a 5–10 m × 0.53 mm i.d. uncoated precolumn, the solvent trapping process differs from that described previously. The visual experiments and the conclusions drawn therefrom, as described in a previous paper, are supplemented with chromatographic results. They show that even hexane can be quantitatively analyzed in 250 μl of a pentane solution. Injection of a volume of 250 μl by vaporizer/precolumn solvent splitting was used in the analysis of gasoline in drinking water. Conditions for the transfer of a 1000 μl volume can easily be adjusted through detection of the front end of the flooded zone by a thermocouple mounted on the outer wall of the precolumn.     

Synthesis of Aristotelia‐Type Alkaloids,Part XVI

Two independent total syntheses of the Aristotelia alkaloid (−)‐serratenone ((−)‐ 1 ) are disclosed, one starting with (−)‐α‐pinene, the other one with (S)‐α‐terpineol. These correlations led to a revision of the originally proposed absolute configuration of the natural product. In the course of systematic investigations of the behavior of the indole alkaloids (+)‐makomakine ((+)‐ 18 ) and (−)‐hobartine ((−)‐ 22 ) towards oxidizing reagents, it was found that treatment with I₂ leads to no less than five different products. Depending on the exact reaction conditions, each of them can be obtained as the major component in yields between 40 and 60%. One of these compounds was shown to be identical with the natural product (+)‐11,12‐didehydromakonin‐10‐one ((+)‐ 28 ).