New antibiotic caerin 1 peptides from the skin secretion of the Australian tree frog Litoria chloris. Comparison of the activities of the caerin 1 peptides from the genus Litoria

The skin glands of the tree frog Litoria chloris contain a variety of peptides including four antibacterial peptides of the caerin 1 family. Two of these, caerins 1.6 and 1.7, are also present in the related species Litoria xanthomera. The other two peptides, caerins 1.8 and 1.9, are new. Their sequences are: GLFKVLGSVAKHLLPHVVPVIAEKL-NH2 [Caerin 1.8] and GLFGVLGSIAKHVLPHVVPVIAEKL-NH2 [Caerin 1.9]. Comparison of the skin peptide profiles of L. chloris and L. xanthomera confirms that these species are more closely related to each other than to any other species of the genus Litoria that we have studied. A comparison is made of the antibiotic activities of nine members of the caerin 1 family of peptides isolated from tree frogs of the genus Litoria.

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).

Structure of the N-linked oligosaccharides from tridacnin, a lectin found in the haemolymph of the giant clam Hippopus hippopus

Tridacnin, a glycoprotein lectin, was isolated from the symbiotic marine clam Hippopus hippopus and the structure of its major N-glycan chains determined. Tridacnin contains only N-linked glycans which were quantitatively cleaved by peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F. Following purification by anion-exchange HPLC, the structures of the oligosaccharides were established using a combination of electrospray ionisation mass spectrometry, 1H-NMR spectroscopy and linkage analysis. The N-glycans are primarily of the oligomannose type but, in addition, some contain a novel 6-O-Me group on the terminal mannose residue of the chain. The N-glycan chains had the following structures. [formula: see text]

A simplified liquid chromatography assay for the quantitation of halofantrine and desbutylhalofantrine in plasma and identification of a degradation product of desbutylhalofantrine formed under alkaline conditions

The development of a new and simplified, validated LC assay for the quantitation of halofantrine and desbutylhalofantrine in plasma is described. The methodology employs an inexpensive, rapid and simple liquid-liquid extraction procedure in combination with previously reported chromatographic conditions. The method has been employed to study aspects of the pharmacokinetics of orally administered halofantrine in beagle dogs and some preliminary data are presented. During development of the extraction procedure, degradation of desbutylhalofantrine was observed under non-acidic conditions in the extraction solvent (tert-butyl methyl ether) and we also report the structural elucidation of the breakdown product and the conditions required to avoid this degradation.

Analysis of oligodeoxynucleotides by negative-ion matrix-assisted laser desorption mass spectrometry

Thirty compounds were tested in combination with ammonium acetate for the ability to desorb and ionize oligodeoxynucleotides by ultraviolet matrix-assisted laser desorption mass spectrometry. Negative ion yields using matrices such as 2,5-dihydroxybenzoic acid and 3-hydroxy-4-methoxybenzaldehyde are enhanced by the addition of ammonium salts at a molar ratio of 1:1, pH 7. 3-Hydroxy-4-methoxybenzaldehyde was tested with 12 different ammonium, alkylammonium, and pyridinium salts for the ability to cocrystallize with oligodeoxynucleotides and to improve desorption and ionization. Ions of oligodeoxynucleotides 9, 10, and 11 nucleotides in length were observed with a matrix of 3-hydroxy-4-methoxybenzaldehyde and ammonium acetate, pH 7, at a mass resolution of 100-150 (fwhm). A small oligodeoxynucleotide (11-mer) was observed at the femtomole level with a combination of 2,5-dihydroxybenzoic acid and ammonium acetate as the matrix. Ions from single stranded DNA (60 nucleotides in length) were also observed using this same matrix combination. The results of these studies have shown that both sensitivity and desorption conditions need to be further improved before complex mixtures of large pieces of DNA can be effectively analyzed.

Triacylglycerols of human milk: rapid analysis by ammonia negative ion tandem mass spectrometry

Human milk triacylglycerols (TAG) were analyzed by ammonia negative ion chemical ionization tandem mass spectrometry. The deprotonated molecular ions of triacylglycerols were fractionated at the first mass spectrometry (MS) stage. Twenty-nine of the deprotonated TAG ions were further analyzed based on their collisionally activated (CA) spectra. The tandem MS analysis covered eleven major acyl carbon number fractions, two of which contained odd carbon number fatty acids. Fatty acids of 28 different molecular weights were recorded from the daughter spectra. Hexadecanoic acid was present in all CA spectra, octadecenoic acid in the CA spectra of all mono- and higher unsaturated TAG, and octadecadienoic acid in the CA spectra of all di- and higher unsaturated TAG. The major fatty acid combinations in triacylglycerols were: with 0 double bonds (DB), 12:0/12:0/16:0; with 1 DB, 12:0/16:0/18:1; with 2 DB, 16:0/18:1/18:1; with 3 DB, 16:0/18:2/18:1; with 4 DB, 18:2/18:1/18:1; and with 5 DB, 18:2/18:2/18:1; hexadecanoic acid typically occupied the sn-2 position. The most abundant TAG was shown to be sn-18:1-16:0-18:1, comprising about 10% of all triacylglycerols.

Collision-Induced Dissociations of Negative-Ions Formed by Reaction of HO- With Alkyl and Aryl Silanes. The Formation of Multiple Bonds to Silicon

Collisional activation of alkyl and aryl siloxide ions produces a variety of ions and neutrals containing double bonds to silicon. Sila enolate ions and sila acyl ions RSi =O are common features of the spectra of alkylsiloxide ions; ab initio calculations suggest these ions to have considerable multiple bond character. It is proposed that most reactions proceed through ion complex intermediates. Specific proton transfer reactions often occur for ions Me3SiCHR (R = C3H5, C3H3 or Ph), i.e. Me3SiCHR → -CH2(Me)2SiCH2R. In the particular case of the formation of PhCH2- from Me3SiCHPh, i.e. Me3SiCHPh → -CH2(Me)2SiCH2Ph → PhCH2- +Me2Si=CH2, the proton transfer competes with scrambling of all hydrogens in the decomposing ion.

Collision-Induced Carbanion Rearrangements. The Elimination of Ethene From the 3,3-Dimethylheptan-4-one Enolate Ion

The mechanisms of formation of the major product ions produced by collision activation of the enolate negative ion of 3,3-dimethylheptan-4-one have been studied by deuterium labelling. H2 loss involves 1,2-elimination from the 6- and 7-positions. Methane elimination is complex involving three competitive rearrangement processes. Ethene loss produces the most abundant fragment ion and occurs by elimination of the C1-C2 ethyl group with concomitant proton transfer from the 1-position. In the case of the enolate ion from CD3CH2CMe2COPr, the expected elimination of C2H2D2 competes with loss of C2H4 from positions 6 and 7. Other decompositions are as follows: loss of C3H8 involves the methyl and ethyl substituents at positions 7, 1 and 2 respectively; loss of C4H8 occurs by two processes, ( i ) successive losses of two C2H4 units (from the 1, 2 then 6, 7 positions), and (ii) loss of CH2=CMe2 (from the 2 and 3 positions); and loss of C5H12 produces Et-C=C-0-. .

The Mechanism(S) of the Addition of Alcohols to Protonated Acetone in the Gas-Phase

The gas phase reactions of the systems Me2C=+OH/ROH (R = Me and Pri ) have been investigated by using a combination of experimental [ion cyclotron resonance ( i.c.r .) and flowing afterglow ( f.a .)] and ab initio (4-31G, GAUSSIAN 82) methods. A stabilized adduct, thought to correspond to Me2C=+OH...O(H)R, is observed when R = Pri but not for Me. Decomposing forms of adducts eliminate water; 18O labelling shows the major (overall) reaction to be Me2C=+OH+R18OH → Me2C=+(18O)R+H2OAb initio calculations indicate ( i ) that the product ion in this reaction is produced by two channels, both proceeding through Me2(HO)C-+O(H)R; one directly, the other indirectly through Me2C=+OH...O(H)R, and (ii) that the transition state for the key proton transfer reaction Me2(HO)C-+O(H)Me → Me2( MeO )C-+OH2 is of higher energy than reactants. The latter result suggests that precursor ion Me2C=+O needs to be vibrationally hot for the elimination of water to occur: a comparison of i.c.r . and f.a . experiments confirms this to be the case.