Identification of Cuticular and Web Lipids of the Spider Argiope bruennichi

Emerging evidence shows that the cuticular and silk lipids of spiders are structurally more diverse than those of insects, although only a relatively low number of species have been investigated so far. As in insects, such lipids might play a role as signals in various contexts. The wasp spider Argiope bruennichi has probably the best investigated chemical communication system within spiders, including the known structure of the female sex pheromone. Recently we showed that kin-recognition in A. bruennichi could be mediated through the cuticular compounds consisting of hydrocarbons and, to a much larger proportion, of wax esters. By use of mass spectrometry and various derivatization methods, these were identified as esters of 2,4-dimethylalkanoic acids and 1-alkanols of varying chain lengths, such as tetradecyl 2,4-dimethylheptadecanoate. A representative enantioselective synthesis of this compound was performed which proved the identifications and allowed us to postulate that the natural enantiomer likely has the (2R,4R)-configuration. Chemical profiles of the silk and cuticular lipids of females were similar, while male cuticular profiles differed from those of females. Major components of the male cuticular lipids were tridecyl 2,4-dimethyl-C17-19 alkanoates, whereas those of females were slightly longer, comprising tridecyl 2,4-dimethyl-C19-21 alkanoates. In addition, minor female-specific 4-methylalkyl esters were detected.

Identification of Cuticular And Web Lipids of The Spider Argiope Bruennichi

Emerging evidence shows that the cuticular and silk lipids of spiders are structurally more diverse than those of insects, although only a relatively low number of species have been investigated so far. As in insects, such lipids might play a role as signals in various context. The wasp spider Argiope bruennichi has probably the best investigated chemical communication system within spiders, including the known structure of the female sex pheromone. Recently we showed that kin-recognition in A. bruennichi is mediated through the cuticular compounds consisting of hydrocarbons and to a much larger proportion of wax esters. By use of MS and various derivatization methods these esters were identified here to be esters of 2,4-di­methyl­alkanoates with varying chain length and 1-alkanols, such as tetradecyl 2,4‑di­methyl­hepta­decanoate. A representative enantioselectively synthesis to this compound was performed which proved the identifications and allowed to postulate the natural enantiomer to have (2R,4R)-configuration. Cuticular profiles of the silk and cuticula of females were similar, while male cuticular profiles differed quantitatively from those of females. In addition, minor female specific 4-methylalkyl esters were detected.

Ultrahigh-resolution centrosymmetric crystal structure of Z-DNA reveals the massive presence of alternate conformations

The self-complementary d(CGCGCG) hexanucleotide was synthesized with both D-2′-deoxyribose (the natural enantiomer) and L-2′-deoxyribose, and the two enantiomers were mixed in racemic (1:1) proportions and crystallized, producing a new crystal form withC2/csymmetry that diffracted X-rays to 0.78 Å resolution. The structure was solved by direct, dual-space and molecular-replacement methods and was refined to anRfactor of 13.86%. The asymmetric unit of the crystal contains one Z-DNA duplex and three Mg2+sites. The crystal structure is comprised of both left-handed (D-form) and right-handed (L-form) Z-DNA duplexes and shows an unexpectedly high degree of structural disorder, which is manifested by the presence of alternate conformations along the DNA backbone chains as well as at four nucleobases (including one base pair) modelled in double conformations. The crystal packing of the presented D/L-DNA–Mg2+structure exhibits novel DNA hydration patterns and an unusual arrangement of the DNA helices in the unit cell. The paper describes the structure in detail, concentrating on the mode of disorder, and compares the crystal packing of the racemic d(CGCGCG)2duplex with those of other homochiral and heterochiral Z-DNA structures.

The Enantiocontrolled Synthesis of a Highly Functionalized Cyclohexenone Related to the A-Ring of the Furanosteroid Viridin

A seven-step reaction sequence has been used to convert the enantiomerically pure cis-1,2-dihydrocatechol 10 into the cyclohexenone 17a. A near equivalent sequence involving the same starting material has allowed for the synthesis of the regioisomeric system 17b. Compound 17a is related to the A-ring of ent-viridin (ent-1), the non-natural enantiomer of the furanosteroid viridin (1).

barS1, a Gene for Biosynthesis of a γ-Butyrolactone Autoregulator, a Microbial Signaling Molecule Eliciting Antibiotic Production in Streptomyces Species

ABSTRACT From Streptomyces virginiae, in which production of streptogramin antibiotic virginiamycin M1 and S is tightly regulated by a low-molecular-weight Streptomyces hormone called virginiae butanolide (VB), which is a member of the γ-butyrolactone autoregulators, the hormone biosynthetic gene (barS1) was cloned and characterized by heterologous expression in Escherichia coli and by gene disruption in S. virginiae. The barS1 gene (a 774-bp open reading frame encoding a 257-amino-acid protein [M r, 27,095]) is situated in the 10-kb regulator island surrounding the VB-specific receptor gene, barA. The deduced BarS1 protein is weakly homologous to β-ketoacyl-acyl carrier protein/coenzyme A reductase and belongs to the superfamily of short-chain alcohol dehydrogenase. The function of the BarS1 protein in VB biosynthesis was confirmed by BarS1-dependent in vitro conversion of 6-dehydro-VB-A to VB-A, the last catalytic step in VB biosynthesis. Of the four possible enantiomeric products from racemic 6-dehydro-VB-A as a substrate, only the natural enantiomer of (2R,3R,6S)-VB-A was produced by the purified recombinant BarS1 (rBarS1), indicating that rBarS1 is the stereospecific reductase recognizing (3R)-isomer as a substrate and reducing it stereospecifically to the (6S) product. In the ΔbarS1 mutant created by homologous recombination, the production of VB as well as the production of virginiamycin was lost. The production of virginiamycin by the ΔbarS1 mutant was fully recovered by the external addition of VB to the culture, which indicates that the barS1 gene is essential in the biosynthesis of the autoregulator VBs in S. virginiae and that the failure of virginiamycin production was a result of the loss of VB production.