Elements of the granular gland peptidome and transcriptome persist in air-dried skin of the South American orange-legged leaf frog, Phyllomedusa hypocondrialis.

The defensive strategy of amphibians against predator attack relies heavily on the secretion of noxious/toxic chemical cocktails from specialized skin granular glands. Bioactive peptides constitute a major component of secretions in many species and the most complex are produced by neotropical leaf frogs of the sub-family Phyllomedusinae. We recently reported that these skin secretions contain elements of both the granular gland peptidome and transcriptome and that polyadenylated mRNAs constituting the latter are protected from degradation by interactions with endogenous amphipathic peptides. This thus permits parallel amino acid sequencing of peptides and nucleic acid sequencing of cloned precursor transcripts from single lyophilized samples of secretion. Here we report that the protection afforded is sufficiently robust to permit transcriptome studies by cloning of full-length polyadenylated peptide precursor encoding mRNAs from libraries constructed using ambient temperature air-dried skin from recently deceased specimens as source material. The technique was sufficiently sensitive to permit the identification of cDNAs encoding antimicrobial peptides constituted by six different isoforms of phylloseptin and two dermaseptins. Also, for the first time, establishment of the nucleic acid and amino acid sequence of the precursor encoding the phyllomedusine frog skin bradykinin-related peptide, phyllokinin, from cloned cDNA, was achieved. These data unequivocally demonstrate that the granular gland transcriptome persists in air-dried amphibian skin—a finding that may have fundamental implications in the study of archived materials but also in the wider field of molecular biology.

Contribution of the UV component of natural sunlight to photoinhibition of photosynthesis in six species of subtidal brown and red seaweeds.

Field-collected specimens of three species of Laminaria and three species of subtidal red algae (Delesseria sanguinea, Plocamium cartilagineum and Phyllophora pseudoceranoides) were exposed to natural summer sunlight on Helgoland (southern North Sea) for up to 4 h at 15 °C. Dark-adapted variable fluorescence (Fv : Fm) was measured immediately after these treatments, and following 6, 24 and 48 h of recovery in moderate irradiances of white light. The response of plants to the full spectrum of natural sunlight was compared with that to PAR alone, UV-A + visible, UV-A + UV-B, or UV-A alone. The Fv : Fm values of all species were reduced to minimal values after 4 h in all of these treatments, but those of the more resistant species (Laminaria spp. and P. pseudoceranoides) were higher after shorter exposures to UV radiation alone than to PAR with or without UV. The recovery of Fv : Fm in all species was also more rapid in the two treatments that contained UV radiation alone than in those that included PAR. These results suggest that it is the high irradiances of PAR in natural sunlight which are responsible for the photoinhibition of photosynthesis of subtidal seaweeds and that the current ambient irradiances of UV radiation (either UV-B or UV-A) in northern temperate latitudes would not contribute significantly to this photoinhibition.

Ruthenium complexes of the 1,4-bis(diphenylphosphino)-1,3-butadiene-bridged diphosphine 1,2,3,4-Me-4-NUPHOS: Solvent-dependent interconversion of four- and six-electron donor coordination and transfer hydrogenation activity

In chloroform, [RuCl2(nbd)(py)(2)] (1) (nbd = norbornadiene; py = pyridine) reacts with 1,4-bis(diphenylphosphino)-1,2,3,4-tetramethyl-1,3-butadiene (1,2,3,4-Me-4-NUPHOS) to give the dimer [Ru2Cl3(eta(4)-1,2,3,4-Me-4-NUPHOS)(2)]Cl (2a), whereas, in THF [RuCl2(1,2,3,4-Me-4-NUPHOS)(PY)(2)] (3) is isolated as the sole product of reaction. Compound 2 exists as a 4:1 mixture of two noninterconverting isomers, the major with C, symmetry and the minor with either C, or C-2 symmetry. A single-crystal X-ray analysis of [Ru2Cl3 (eta(4)-1,2,3,4-Me-4-NUPHOS)(2)] [SbF6] (2b), the hexafluoroantimonate salt of 2a, revealed that the diphosphine coordinates in an unusual manner, as a eta(4)-six-electron donor, bonded through both P atoms and one of the double bonds of the butadiene tether. Compounds 2a and 3 react with 1,2-ethylenediamine (en) in THF to afford [RuCl2(1,2,3,4-Me-4-NUPHOS)(en)] (4), which rapidly dissociates a chloride ligand in chloroform to give [RuCl(eta(4)-1,2,3,4-Me-4-NUPHOS)(en)] [Cl] (5a). Complexes 4 and 5a cleanly and quantitatively interconvert in a solvent-dependent equilibrium, and in THF 5a readily adds chloride to displace the eta(2)-interaction and re-form 4. A single-crystal X-ray structure determination of [RuCl(eta(4)-1,2,3,4-Me-4-NUPHOS)(en)][ClO4] (5b) confirmed that the diphosphine coordinates in an eta(4)-manner as a facial six-electron donor with the eta(2)-coordinated double bond occupying the site trans to chloride. The eta(4)-bonding mode can be readily identified by the unusually high-field chemical shift associated with the phosphorus atom adjacent to the eta(2)-coordinated double bond. Complexes 2a, 2b, 4, and 5a form catalysts that are active for transfer hydrogenation of a range of ketones. In all cases, catalysts formed from precursors 2a and 2b are markedly more active than those formed from 4 and 5a.