John H. Bowie

Host-defence peptides of Australian anurans: structure, mechanism of action and evolutionary significance.

Host-defence peptides secreted from the skin glands of Australian frogs and toads, are, with a few notable exceptions, different from those produced by anurans elsewhere. This review summarizes the current knowledge of the following classes of peptide isolated and characterized from Australian anurans: neuropeptides (including smooth muscle active peptides, and peptides that inhibit the production of nitric oxide from neuronal nitric oxide synthase), antimicrobial and anticancer active peptides, antifungal peptides and antimalarial peptides. Other topics covered include sex pheromones of anurans, and the application of peptide profiling to (i). recognize particular populations of anurans of the same species and to differentiate between species, and (ii). investigate evolutionary aspects of peptide formation.

Aquatic sex pheromone from a male tree frog.

Many creatures use chemical signals (pheromones) as sources of information about the world around them. For example, a sex pheromone produced by one sex (usually the female) of a particular species induces an immediate behavioural response in the opposite sex of the same species. However, very little is known about amphibian pheromones. We have now discovered and characterized an aquatic, female-attracting pheromone from the parotoid and rostral glands of a male frog, the magnificent tree frog, Litoria splendida. To our knowledge, this pheromone, which we have named splendipherin, is the first pheromone from an anuran (frog or toad) to be identified.

Gas phase acidities of the α amino acids

Abstract The gas phase acidities of 19 α amino acids have been determined using the kinetic method of Cooks and co-workers [R.G. Cooks and T.L. Kruger, J. Am. Chem. Soc., 99 (1977) 1279; S.A. McLuckey, D. Cameron and R.G. Cooks, J. Am. Chem. Soc., 103 (1981) 1313]. The range of gas phase acidities for this class of biomolecules spans from glycine, the least acidic (ΔG°acid = 1402.0 kJ mol−1), to histidine, the most acidic (ΔG°acid = 1356.0 kJ mol−1). For a few, simple amino acids (glycine, alanine, serine, and cysteine), ab initio theory at the HF/6-31 + G*//HF/3-21 (+)G* level was used to calculate gas phase acidities. There is good agreement between the theoretical and experimental acidities with the average deviation being ±8.5 kJ mol−1. Fully optimized structures are reported for these amino acids and their corresponding carboxylates.

Antimicrobial Peptides from Amphibian Skin Potently Inhibit Human Immunodeficiency Virus Infection and Transfer of Virus from Dendritic Cells to T Cells

ABSTRACT Topical antimicrobicides hold great promise in reducing human immunodeficiency virus (HIV) transmission. Amphibian skin provides a rich source of broad-spectrum antimicrobial peptides including some that have antiviral activity. We tested 14 peptides derived from diverse amphibian species for the capacity to inhibit HIV infection. Three peptides (caerin 1.1, caerin 1.9, and maculatin 1.1) completely inhibited HIV infection of T cells within minutes of exposure to virus at concentrations that were not toxic to target cells. These peptides also suppressed infection by murine leukemia virus but not by reovirus, a structurally unrelated nonenveloped virus. Preincubation with peptides prevented viral fusion to target cells and disrupted the HIV envelope. Remarkably, these amphibian peptides also were highly effective in inhibiting the transfer of HIV by dendritic cells (DCs) to T cells, even when DCs were transiently exposed to peptides 8 h after virus capture. These data suggest that amphibian-derived peptides can access DC-sequestered HIV and destroy the virus before it can be transferred to T cells. Thus, amphibian-derived antimicrobial peptides show promise as topical inhibitors of mucosal HIV transmission and provide novel tools to understand the complex biology of HIV capture by DCs.

Interaction of antimicrobial peptides from Australian amphibians with lipid membranes

Solid-state NMR and CD spectroscopy were used to study the effect of antimicrobial peptides (aurein 1.2, citropin 1.1, maculatin 1.1 and caerin 1.1) from Australian tree frogs on phospholipid membranes. 31P NMR results revealed some effect on the phospholipid headgroups when the peptides interact with DMPC/DHPC (dimyristoylphosphatidylcholine/dihexanoylphosphatidylcholine) bicelles and aligned DMPC multilayers. 2H NMR showed a small effect of the peptides on the acyl chains of DMPC in bicelles or aligned multilayers, suggesting interaction with the membrane surface for the shorter peptides and partial insertion for the longer peptides. 15N NMR of selectively labelled peptides in aligned membranes and oriented CD spectra indicated an alpha-helical conformation with helix long axis approximately 50 degrees to the bilayer surface at high peptide concentrations. The peptides did not appear to insert deeply into PC membranes, which may explain why these positively charged peptides preferentially lyse bacterial rather than eucaryotic cells.

Studies in mass spectrometry—XV : Mass spectra of sulphoxides and sulphones. The formation of CC and CO bonds upon electron impact☆

Abstract Although dialkyl sulphoxides and sulphones behave relatively simply upon electron impact, aromatic sulphoxides and sulphones show a pronounced tendency to undergo CO bond formation, as evidence by a number of decomposition pathways which involve the elimination of carbon monoxide. For example, dibenzothiophene dioxide (XV) decomposes from its molecular ion by successive eliminations of carbon monoxide.

Ethylenedione: An intrinsically short-lived molecule

Ethylenedione C2O2 is one of the elusive small molecules which have remained undetected even after numerous attempts with different experimental techniques, This is surprising, since theoretical studies predicted the triplet state of C2O2 to be stable towards spin-allowed dissociation and hence long-lived. Here we report a comprehensive study of charged and neutral ethylenedione by means of charge reversal and neutralization -reionization mass spectrometry. These experimental results, in conjunction with theoretical calculations, suggest that neutral ethylenedione is intrinsically short-lived rather than being elusive, Both the singlet and triplet states of C2O2 are predicted to dissociate rapidly into two ground-state CO molecules, and for the triplet species, this dissociation involves facile curve-crossing to the singlet surface within a few nanoseconds.

Solvent effects in NMR Spectroscopy : Solvent shifts of methoxyl resonances in flavones induced by benzene; an aid to structure elucidation

Abstract The position and relative orientation of OMe groups in methoxyflavones can be inferred from benzene-induced solvent shifts of the OMe resonances. OMe groups at C-5, C-7, C-10 and C-12 exhibit large positive Δ values (Δ = δCDC13 - δC6H6 ⋍ 0·5 to 0·8 ppm) in the absence of substituents ortho to these groups. In contrast, OMe groups at C-3, or those flanked by two ortho-OMe functions (or one ortho-OH and one orthoOMe function) show small positive or negative Δ values. An OMe at C-5 suffers a drastic algebraic decrease in solvent shift upon the introduction of an OMe group at C-6. Electronic and conformational factors which may account for these differences are considered.

Fragmentations of (M–H)− anions of underivatised peptides. Part 2: Characteristic cleavages of Ser and Cys and of disulfides and other post-translational modifications, together with some unusual internal processes

In a previous review (Bowie, Brinkworth, & Dua (2002); Mass Spectrom Rev 21:87-107) we described the characteristic backbone cleavages and side chain fragmentations which occur from (M-H)(-) parent anions of underivatized peptides. This work is briefly summarized in the present review. Cys was not described in the previous review: here we describe the Cys characteristic side chain loss of H(2)S, together with its gamma backbone cleavage. These processes are compared with those of the related Ser. All experimental observations are backed up with theoretical studies at the HF/6-31G(d)//AM1 level of theory, a level of theory which we have shown gives good geometries and acceptable relative energies. The negative ion cleavages of a number of post-translational modifications are described. Negative ion mass spectrometry is the method of choice for identification of disulfides in both peptides and proteins. Intramolecular disulfides are identified by the presence of the fragment anion [(M-H)(-)-H(2)S(2)], and CID MS2 of this fragment normally identifies the positions of the two Cys residues and often the full sequence of the peptide. An unsymmetrically substituted intermolecular disulfide can give up to eight characteristic fragment anions, and CID MS2 of some, or all of these often provides the full sequence of those peptides which form the initial intermolecular disulfide linkage. Negative ion cleavages of disulfides are the most energetically favored of all peptide negative cleavages studied to date. Negative ion mass spectrometry is also valuable for the identification of pyroglutamates, sulfates and phosphates. Finally, some unusual fragmentations are described which involve cyclization/elimination reactions which require the decomposing (M-H)(-) parent anions to adopt the same helical conformation that these peptides have in solution.

Electron impact studies—XXIX : The C13H9 skeletal-rearrangement fragment in the mass spectra of heterocyclic systems containing diphenyl substituents. A Deuterium labelling study

Abstract The m/e 165 ion (C 13 H 9 ) has been noted in the mass spectra of a variety of heterocyclic systems containing two (or more) phenyl substituents. This skeletal-rearrangement fragment is most prominent in the spectra of particularly subsituted oxazoles, imidazoles, and thiazoles. Deuterium-labelling studies have allowed probable mechanistic formulations in the case of the 4,5-diphenylimidazoles, and the detection of two alternate rearrangement pathways in the spectrum of 2,4,5-triphenyloxazole. A comparison is made between the formation of m/e 165 in the spectrum of stilbene and 9,10-dihydrophenanthrene.