Hyperentangled mixed phased Dicke states: optical design and detection.

A recently introduced family of multipartite entangled states, the 4-qubit phased Dicke states, has been created by 2-photon hyperentanglement. Our experimental method allows high state fidelity and generation rate. By introducing quantum noise in the multipartite system in a controlled way, we have tested the robustness of these states. To this purpose the entanglement of the resulting multipartite entangled mixed states has been verified by using a new kind of structural witness.

Distributed quantum dense coding.

We introduce the notion of distributed quantum dense coding, i.e., the generalization of quantum dense coding to more than one sender and more than one receiver. We show that global operations (as compared to local operations) of the senders do not increase the information transfer capacity, in the case of a single receiver. For the case of two receivers, using local operations and classical communication, a nontrivial upper bound for the capacity is derived. We propose a general classification scheme of quantum states according to their usefulness for dense coding. In the bipartite case (for any dimensions), bound entanglement is not useful for this task.

Optimal eavesdropping in cryptography with three-dimensional quantum states.

We study optimal eavesdropping in quantum cryptography with three-dimensional systems, and show that this scheme is more secure against symmetric attacks than protocols using two-dimensional states. We generalize the according eavesdropping transformation to arbitrary dimensions, and discuss the connection with optimal quantum cloning.

Classification of mixed three-qubit states.

We introduce a classification of mixed three-qubit states, in which we define the classes of separable, biseparable, W, and Greenberger-Horne-Zeilinger states. These classes are successively embedded into each other. We show that contrary to pure W-type states, the mixed W class is not of measure zero. We construct witness operators that detect the class of a mixed state. We discuss the conjecture that all entangled states with positive partial transpose (PPTES) belong to the W class. Finally, we present a new family of PPTES "edge" states with maximal ranks.

The aqueous conformation of cyclo(1,6)Ac-Cys-Arg-Gly-Asp-Phe-Pen-NH2.

RGD peptides are known as important ligands for integrin receptors in the cell adhesion process. The selectivity of RGD peptides for a certain integrin receptor is partly dependent on the RGD conformation and the residues surrounding the RGD sequence. This paper investigates the effect of the addition of a phenylalanine residue on the RGD conformation in cyclo(1,6)Ac-Cys-Arg-Gly-Asp-Phe-Pen-NH2 (1) as compared to the previously studied cyclo(1,5)Ac-Pen-Arg-Gly-Asp-Cys-NH2 (2). The conformational study of peptide 1 was done in aqueous solution using nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics simulations. This work will increase the understanding of the flanking residue's effect in RGD peptides.

Ochrindoles A-D: new bis-indolyl benzenoids from the sclerotia of Aspergillus ochraceus NRRL 3519.

Four new prenylated bis-indolyl benzenoid metabolites (ochrindoles A-D; 1-4) were isolated from antiinsectan organic extracts of the sclerotia of Aspergillus ochraceus (NRRL 3519). The structures of these compounds were determined primarily through HMBC, selective INEPT, and NOESY experiments. These compounds displayed moderate activity in feeding assays against the corn earworm Helicoverpa zea and the driedfruit beetle Carpophilus hemipterus. Compounds 1-4 also exhibited activity against Gram-positive bacteria.