144 Sculpting light with DNA origami

We used the DNA origami method (Rothemund, 2006) for the fabrication of self-assembled nanoscopic materials (Seeman, 2010). In DNA origami, a virus-based 8?kilobase-long DNA single-strand is folded into shape with the help of ～ 200 synthetic oligonucleotides. The resulting DNA nanostructures can be designed to adopt any three-dimensional shape and can be addressed through DNA hybridization or chemical modification with nanometer precision. We have realized that complex assemblies of nanoparticles, including magnetic, fluorescent, and plasmonic nanoparticles. Such nanoconstructs may exhibit striking optical properties such as strong optical activity in the visible range (Kuzyk et al., 2012). To this end, plasmonic particles were assembled in solution to form helices of controlled handedness. We achieved spatial control over particle placement better than 2?nm and attachment yields of 97% and above. As a collective optical response emerging from our dispersed nanostructures, we detected pronounced circular dichroism (CD) originating from the plasmon–plasmon interactions in the particle helices. In recent experiments, we were able to show that the optical response of chiral biomolecules can be transferred from the UV into the visible region in plasmonic hotspots. Thus, sensitive detection of chiral biomolecules may become feasible in the near future. We also found that the orientation of the helices in respect to the incoming light beam critically influences the resulting CD spectra. Our results can be explained with theoretical models based on plasmonic dipole interaction and demonstrate the potential of DNA origami for the assembly of metafluids with designed optical properties.     

Design and synthesis of paclitaxel conjugated with an ErbB2-recognizing peptide, EC-1

The selective delivery of therapeutic agents to receptors overexpressed in cancer cells without harming the rest of the body is a major challenge in clinical oncology today. In this study, we report the design and synthesis of paclitaxel (PTX) conjugated with an erbB2-recognizing peptide (EC-1). The cyclic peptide EC-1 specifically binds to the extracellular domain of ErbB2 and selectively inhibits proliferation of breast cancer cells overexpressing ErbB2. PTX is a potent antitumor agent commonly used in the treatment of advanced metastatic breast cancer, yet patients have to suffer some side effects caused by its systemic toxicity. The aim of our conjugate is to specifically deliver antitumor agent PTX to breast cancer cells that overexpress oncogenic ErbB2 with the purpose to reduce toxicity and enhance selective killing of cancer cells. In this study, a concise and efficient synthetic route for the preparation of the PTX-EC-1 conjugate has been developed in 6% overall yield. This synthetic approach provides a general method for conjugating a highly functionalized and disulfide-bridge containing cyclopeptide to Taxol or other antitumor agents.     

U(L)31 and U(L)34 proteins of herpes simplex virus type 1 form a complex that accumulates at the nuclear rim and is required for envelopment of nucleocapsids

The herpes simplex virus type 1 (HSV-1) U(L)34 protein is likely a type II membrane protein that localizes within the nuclear membrane and is required for efficient envelopment of progeny virions at the nuclear envelope, whereas the U(L)31 gene product of HSV-1 is a nuclear matrix-associated phosphoprotein previously shown to interact with U(L)34 protein in HSV-1-infected cell lysates. For these studies, polyclonal antisera directed against purified fusion proteins containing U(L)31 protein fused to glutathione-S-transferase (U(L)31-GST) and U(L)34 protein fused to GST (U(L)34-GST) were demonstrated to specifically recognize the U(L)31 and U(L)34 proteins of approximately 34,000 and 30,000 Da, respectively. The U(L)31 and U(L)34 gene products colocalized in a smooth pattern throughout the nuclear rim of infected cells by 10 h postinfection. U(L)34 protein also accumulated in pleiomorphic cytoplasmic structures at early times and associated with an altered nuclear envelope late in infection. Localization of U(L)31 protein at the nuclear rim required the presence of U(L)34 protein, inasmuch as cells infected with a U(L)34 null mutant virus contained U(L)31 protein primarily in central intranuclear domains separate from the nuclear rim, and to a lesser extent in the cytoplasm. Conversely, localization of U(L)34 protein exclusively at the nuclear rim required the presence of the U(L)31 gene product, inasmuch as U(L)34 protein was detectable at the nuclear rim, in replication compartments, and in the cytoplasm of cells infected with a U(L)31 null virus. When transiently expressed in the absence of other viral factors, U(L)31 protein localized diffusely in the nucleoplasm, whereas U(L)34 protein localized primarily in the cytoplasm and at the nuclear rim. In contrast, coexpression of the U(L)31 and U(L)34 proteins was sufficient to target both proteins exclusively to the nuclear rim. The proteins were also shown to directly interact in vitro in the absence of other viral proteins. In cells infected with a virus lacking the U(S)3-encoded protein kinase, previously shown to phosphorylate the U(L)34 gene product, U(L)31 and U(L)34 proteins colocalized in small punctate areas that accumulated on the nuclear rim. Thus, U(S)3 kinase is required for even distribution of U(L)31 and U(L)34 proteins throughout the nuclear rim. Taken together with the similar phenotypes of the U(L)31 and U(L)34 deletion mutants, these data strongly suggest that the U(L)31 and U(L)34 proteins form a complex that accumulates at the nuclear membrane and plays an important role in nucleocapsid envelopment at the inner nuclear membrane.     

Synthesis and HIV-1 integrase inhibitory activity of dimeric and tetrameric analogs of indolicidin

We found that indolicidin, a natural antimicrobial peptide, has HIV-1 integrase inhibitory activity. Subsequently, we also discovered analogs of indolicidin with substantially higher inhibitory potency. The dimers and tetramers of the most active sequence (ILPWKWPWWPWPP) were prepared by connection of the monomers' C-terminal ends, using lysine as a linker. The inhibitory potency of the dimeric peptide is higher than the monomeric peptide. The tetrameric peptide, prepared by connection of two dimers at C-ends using again lysine as the linker, is the most potent integrase inhibitor with IC(50) value of 0.6 microM for both 3'-end processing and strand transfer.     

Halogenated acetic and acrylic acids from the red alga Asparagopsis taxiformis

Nine halogenated acetic acids and nine halogenated acrylic acids have been identified in the aqueous extract of Hawaiian Asparagopsis taxiformis.     

Potentiating effect of distant sites in non-phosphorylated cyclic peptide antagonists of the Grb2-SH2 domain

Without the presence of a phosphotyrosyl group, a phage library derived non-phosphorylated cyclic peptide ligand of Grb2-SH2 domain attributed its high affinity and specificity to well-defined and highly favored interactions of its structural elements with the binding pocket of the protein. We have disclosed a significant compensatory role of the Glu(2-) sidechain for the absence of the phosphate functionality on Tyr(0) in the peptide ligand, cyclo(CH(2)CO-Glu(2-)-Leu-Tyr(0)-Glu-Asn-Val-Gly-Met(5+)-Tyr-Cys)-amide (termed G1TE). In this study, we report the importance of hydrophobic residue at the Tyr+5 site in G1TE. Both acidic and basic amino acid substitutes are disfavored at this position, and replacement of Met with beta-tert-butyl-Ala was found to improve the antagonist properties. Besides, the polarity of the cyclization linkage was implicated as important in stabilizing the favored binding conformation. Oxidation of the thioether linkage into sulfoxide facilitated the binding to Grb2-SH2 markedly. Simultaneous modification of the three distant sites within G1TE provided the best agent with an IC(50) of 220 nM, which is among the most potent non-phosphorous- and non-phosphotyrosine-mimic containing Grb2-SH2 domain inhibitors yet reported. This potent peptidomimetic provides a novel template for the development of chemotherapeutic agents for the treatment of erbB2-related cancer. Biological assays on G1TE(Gla(2-)) in which the original residue of Glu(2-) was substituted by gamma-carboxyglutamic acid (Gla) indicated that it could inhibit the interaction between activated GF receptor and Grb2 protein in cell homogenates of MDA-MB-453 breast cancer cells at the 2 microM level. More significantly, both G1TE(Gla(2-)) alone and the conjugate of G1TE(Gla(2-)) with a peptide carrier can effectively inhibit intracellular association of erbB2 and Grb2 in the same cell lines with IC(50) of 50 and 2 microM, respectively.     

Corazonin reduces the spinning rate in the silkworm,Bombyx mori

The insect neuropeptide, [Arg⁷]-corazonin was injected into larvae of the silkworm, Bombyx mori to investigate its influence on development and behavior. A single injection of 50 pmol of corazonin into the fourth and fifth instar larvae induced prolongation of the spinning period in all experimental groups except for those injected on day 10 of the fifth instar. The injection also caused a prolongation of the pupal period in some experimental groups, while it had no effect on the timing of larval ecdysis and the length of feeding period of the fifth instar. The spinning period was significantly prolonged even at a low dose of 1 pmol. Both the spinning rate and the rate of increase in hemolymph ecdysteroid level during the spinning stage were reduced by injection of corazonin. However, corazonin injection during days 5-7 of the fifth instar reduced the spinning rate without influencing the ecdysteroid level until the end of day 8, thereafter the rate of increase in hemolymph ecdysteroid level was slower in the corazonin-injected larvae than in the control larvae. Therefore, the suppressed ecdysteroid level observed in the corazonin-injected larvae appears to be a result rather than a cause of the reduced spinning rate. This study is the first published report for the corazonin effect on the behavior in insects.     

Vasodilatory activity in horsefly and deerfly salivary glands

Salivary gland extract (SGE) of four horsefly species (Hybomitra bimaculata Macquart, Hybomitra ciureai Séguy, Tabanus bromius L., Tabanus glaucopis Meigen) and one deerfly species (Chrysops relictus Meigen) (Diptera: Tabanidae) were shown to contain vasodilatory activity. Aliquots equivalent to 1, 5 and 10 pairs of salivary glands (SG) relaxed rat femoral artery (with intact endothelium) pre-constricted with phenylephrine. Vasodilatory activity was dose-dependent. SGE of one horsefly species (Haematopota pluvialis L.) did not induce relaxation. The kinetics of vasodilation induced by SGE of four horsefly species differed from the deerfly. These results indicate that tabanid species may produce more than one type of vasodilator to aid blood feeding.     

The physiology and ecological implications of efficient growth

The natural habitats of microbes are typically spatially structured with limited resources, so opportunities for unconstrained, balanced growth are rare. In these habitats, selection should favor microbes that are able to use resources most efficiently, that is, microbes that produce the most progeny per unit of resource consumed. On the basis of this assertion, we propose that selection for efficiency is a primary driver of the composition of microbial communities. In this article, we review how the quality and quantity of resources influence the efficiency of heterotrophic growth. A conceptual model proposing innate differences in growth efficiency between oligotrophic and copiotrophic microbes is also provided. We conclude that elucidation of the mechanisms underlying efficient growth will enhance our understanding of the selective pressures shaping microbes and will improve our capacity to manage microbial communities effectively.