Paul A. Wabnitz

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.

An immunomodulator used to protect young in the pouch of the Tammar wallaby, Macropus eugenii

Eugenin [pGluGlnAspTyr(SO3)ValPheMetHisProPhe‐NH2] has been isolated from the pouches of female Tammar wallabies (Macropus eugenii) carrying young in the early lactation period. The sequence of eugenin has been determined using a combination of positive and negative ion electrospray mass spectrometry. This compound bears some structural resemblance to the mammalian neuropeptide cholecystokinin 8 [AspTyr(SO3)MetGlyTrpMetAspPhe‐NH2] and to the amphibian caerulein peptides [caerulein: pGluGlnAspTyr(SO3)ThrGlyTrpMetAspPhe‐NH2]. Eugenin has been synthesized by a route which causes only minor hydrolysis of the sulfate group when the peptide is removed from the resin support. Biological activity tests with eugenin indicate that it contracts smooth muscle at a concentration of 10−9 m, and enhances the proliferation of splenocytes at 10−7 m, probably via activation of CCK2 receptors. The activity of eugenin on splenocytes suggests that it is an immunomodulator peptide which plays a role in the protection of pouch young.

Peptides from the Skin Glands of the Australian Buzzing Tree Frog Litoria electrica. Comparison with the Skin Peptides of the Red Tree Frog Litoria rubella

Eleven peptides have been isolated from the skin glands of the ‘buzzing tree frog’ Litoria electrica. The two most abundant peptides are tryptophyllin L 3.1 [Phe Pro Trp Pro (NH2)] and electrin 1 [Phe Val Pro Ile Tyr Met (NH2)]. These peptides show neither significant antimicrobial nor smooth muscle activity. Tryptophyllin L 3.1 is thought to be a neuromodulator or neurotransmitter, and it is similar in structure to the human endomorphins [e.g. Tyr Pro Trp Phe (NH2)] which act on the γ-receptor. Both Litoria electrica and the ‘red tree frog’ Litoria rubella produce tryptophyllin peptides: it is considered that both species evolved from the same ancestor.

The Application of Mass Spectrometry to the Study of Evolutionary Trends in Amphibians

The glandular secretions of the skin of Litoria rubella specimens collected from five locations on the eastern seaboard of Queensland (Australia) contain the three tryptophyllin peptides Phe Pro Trp Leu (NH2), Phe Pro Trp Pro (NH2) and Phe Pro Phe Pro Trp Leu (NH2). The relative proportions of these peptides in the glandular secretion are associated with geographic location, i.e. Phe Pro Trp Pro (NH2) is a minor component of the peptide mixture in frogs from southern Queensland, but becomes significantly more abundant as the location becomes more northerly. This trend indicates an evolutionary change in the animal, but for what reason, and over what timescale is not known at this time.

The negative ion mass spectra of deprotonated 2,5-diketopiperazines

Abstract Deprotonation of 2,5-diketopiperazine (with HO − ) can occur either on N (position 1(4)) or on carbon (position 3(6)). The two depotonated forms are interconvertible on collisional activation. The major collision-induced fragmentations of (M  H) − ions of substituted 2,5-diketopiperazines are (i) characteristic side-chain losses (e.g. Me . for Ala, PhCH 2 . for Phe, and O  C 6 H 4  CH 2 for Tyr), which identify the particular 2,5-diketopiperazine, and (ii) an unusual loss of RCHO (R is the substituent, e.g. Me for Ala), which involves initial 1,2 migration of R . to the carbon of the adjacent carbonyl group.

New caerin 1 antibiotic peptides from the skin secretion of the Australian tree frog Litoria chloris. Part 2. Sequence determination using electrospray mass spectrometry

Electrospray mass spectrometry and automated Edman sequencing provides the structures of two new caerin 1 antimicrobial peptides from the skin glands of the Australian tree frog Litoria chloris. These are: caerin 1.8 Gly Leu Phe Lys Val Leu Gly Ser Val Ala Lys His Leu Leu Pro His Val Val Pro Val Ile Ala Glu Lys Leu (NH2), and caerin 1.9, Gly Leu Phe Gly Val Leu Gly Ser Ile Ala Lys His Val Leu Pro His Val Val Pro Val Ile Ala Glu Lys Leu (NH2).