Russell J. Waugh

The Maculatin peptides from the skin glands of the tree frog Litoria genimaculata: a comparison of the structures and antibacterial activities of Maculatin 1.1 and Caerin 1.1

Six peptides have been isolated and characterized from the dorsal glands of the tree frog Litoria genimaculata. One of these is the known hypotensive peptide caerulein; the others have been named maculatins. The amino acid sequences of the maculatin peptides have been determined using a combination of fast atom bombardment mass spectrometry and automated Edman sequencing. Four of the maculatin peptides show antibiotic activity, with maculatin 1.1 [GLFGVLAKVAAHVVPAIAEHF(NH2;)] showing the most pronounced activity, particularly against Gram‐positive organisms. Maculatin 1.1 resembles the known caerin 1 antibiotic peptides, except that four of the central amino acid residues (of the caerin 1 system) are missing in maculatin 1.1. A comparison of the antibiotic activity of maculatin 1.1 with those of caerin 1.1 is reported. ©1998 European Peptide Society and John Wiley & Sons, Ltd.

New caerin antibacterial peptides from the skin glands of the Australian tree frog Litoria xanthomera

The secretion of the skin glands of the ‘orange‐thighed frog’ Litoria xanthomera contains seven peptides. One of these is the known hypotensive peptide caerulein. Two new peptides, caerin 1.6 [GLFSVLGAVAKHVLPHVVPVIAEKL(NH2)], and caerin 1.7 [GLFKVLGSVAKHLLPHVAPVIAEKL(NH2)] show antibacterial properties. Two other peptides lack the first two amino acid residues of caerins 1.6 and 1.7 and show no antibacterial activity. The identification of the peptides in Litoria xanthomera confirms that this species is related to Litoria caerula, Litoria gilleni and Litoria splendida but not as closely as those three species are related to each other.

Collision induced dissociations of deprotonated peptides: Dipeptides containing phenylalanine, tyrosine, histidine and tryptophan

Abstract The presence and position of Phe, Tyr, His and Trp residues in dipeptides may be determined from a consideration of the collisional activation mass spectra of the (M  H) − ions, formed by fast atom bombardment. Product ion and deuterium labelling studies have been used in an attempt to elucidate fragmentation mechanisms some of which are complex.

Collision induced dissociations of deprotonated peptides: dipeptides containing serine or threonine

The collisional activation mass spectra of (M — H)− ions from dipeptides containing serine or threonine show respective losses of CH2O or MeCHO from the α chains, thus allowing ready identification of these amino acids. The C terminal amino acid may be identified by the general dipeptide fragmentation NH2CH(R′)CONHCH(R2)CO−2 → NH2C(R1)CONHCH(R2)CO2H → −NHCH(R2)CO2H + NH2C(R1)CO, except in certain cases when the C terminal amino acid is threonine.

Peptides from Australian frogs. Structures of the caerins and caeridin 1 from Litoria splendida

Seven peptides have been isolated from the parotoid and rostral glands of the Australian green tree frog Litoria splendida. These include caerulein (a known hypotensive toxin), and six new compounds named caerin 1.1 (M, 2582), 1.1.1 (2412), 1.1.2 (2299), 2.1 (2392), 3.1 (2382) and caeridin 1 (1139). The primary structures of the peptides have been determined by FAB mass spectrometric methods, and confirmed by automated sequencing. The major peptides have been synthesised using t-BOC (N-tert-butoxycarbonyl)N-protection and a p-methylbenzhydrylamine support.

New caerin antibacterial peptides from the skin glands of the Australian tree frog Litoria xanthomera. Part 2. Sequence determination using mass spectrometry and associated techniques

Mass spectrometric sequencing, enzymic digestion and Edman degradation provide the structures of the two antimicrobial peptides from the skin glands of the Australian tree frog Litoria xanthomera as:- Gly Leu Phe Ser Val Leu Gly Ala Val Ala Lys His Val Leu Pro His Val Val Pro Val Ile Ala Glu Lys Leu (NH2) (caerin 1.6), and Gly Leu Phe Lys Val Leu Gly Ser Val Ala Lys His Leu Leu Pro His Val Ala Pro Val Ile Ala Glu Lys Leu (NH2) (caerin 1.7).

Collision-induced dissociations of deprotonated dipeptide methyl esters containing H, alkyl or benzyl α side-chains

The mass spectra of (M - H)− ions derived from dipeptide methyl esters are not as useful from an analytical viewpoint as those of the underivatised peptides in that they lack the characteristic backbone cleavage which provides the primary sequencing data. Instead, major fragmentation occurs through the ester group, viz. competitive losses of MeOH and HCO2Me are noted. Specific fragmentations differentiate between dipeptide methyl esters containing C- and N-terminal Phe. Deuterium labelling and product ion studies have aided this investigation.

Collision induced dissociations of deprotonated peptides. Dipeptides and tripeptides containing proline

Abstract The presence and position of Pro in di- and tripeptides may be determined from a consideration of the collisional activation mass spectra of the (M — H) − ions, formed by fast atom bombardment. Product ion and deuterium labelling studies have been used to elucidate fragmentation mechanisms.

Peptides from Australian frogs. Structures of the caeridins from Litoria caerulea

The secretions of the parotoid glands of the Australian tree frog Litoria caerulea contain twenty-five peptides of which six, the caeridins, have molecular weights in the 1100–1550 dalton range. The paper describes the primary structures of the caeridins, and indicates how the exudates caeridin composition varies with the geographic location of the species.

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.