Rapid and quantitative blood amino acid analysis by chemical ionization mass spectrometry

Peptidal Sex Hormones Inducing Conjugation Tube Formation in Compatible Mating-Type Cells of Tremella mesenterica

The pair of peptidal sex hormones (tremerogen A-10 and tremerogen a-13) that induce conjugation tube formation in compatible type cells (A and a types) of Tremella mesenterica were isolated. Tremerogen A-10 is a dodecapeptide and tremerogen a-13, a tridecapeptide. In both peptides, the sulfiydryl group of the cysteines at the carboxyl terminus was blocked by farnesyl moieties.

Disulfooxy fatty acids from the American bird grasshopper Schistocerca americana, elicitors of plant volatiles

A previously unidentified class of compounds has been isolated from the regurgitant of the grasshopper species Schistocerca americana. These compounds (named here "caeliferins") are composed of saturated and monounsaturated sulfated alpha-hydroxy fatty acids in which the omega-carbon is functionalized with either a sulfated hydroxyl or a carboxyl conjugated to glycine via an amide bond. The regurgitant contains a series of these compounds with fatty acid chains of 15-20 carbons and in varying proportions. Of these, the 16-carbon analogs are predominant and are also most active in inducing release of volatile organic compounds when applied to damaged leaves of corn seedlings. Caeliferins are nonlepidopteran elicitors identified in insect herbivores. This adds a category of insect herbivore-produced elicitors of plant responses, providing further evidence of the ability of plants to detect and respond to a broad range of insect herbivore-produced compounds.

Absolute configuration of volicitin from the regurgitant of lepidopteran caterpillars and biological activity of volicitin-related compounds

Volicitin [N-(17-hydroxylinolenoyl)-L-glutamine] and N-linolenoyl-L-glutamine are known as insect-produced plant volatile elicitors. The absolute configuration of the hydroxylinolenoyl moiety of volicitin from three noctuid species, Helicoverpa armigera, Mythimna separata and Spodoptera litura, was determined to be all 17S in high enantiomeric excess. When treated with 30 pmol of (17S)- and (17R)-volicitin, corn seedlings were induced to release volatiles, there being no significant difference in the amount released between the two isomers. On the other hand, N-linolenoyl-L-glutamine was only about 30% as active as volicitin. Among several synthesized N-linolenoylamino acid conjugates, only the L-glutamine conjugate induced the emission of volatile organic compounds. These results show that the L-glutamine moiety of volicitin played a more critical role than the hydroxyl moiety, although both moieties affected the elicitor activity inducing the release of volatiles.

Differential activity and degradation of plant volatile elicitors in regurgitant of tobacco hornworm (Manduca sexta) larvae

Plants respond to insect herbivory by emitting volatile compounds that attract natural enemies of the herbivores. Biosynthesis of many of these volatiles in plants is induced by herbivore-produced compounds. Components of tobacco hornworm (THW) regurgitant were investigated for their efficacy as elicitors of corn seedling volatiles. Two components that elicited the strongest release of volatiles were isolated and identified as N-linolenoyl-L-glutamine (18:3-GLN) and N-linolenoyl-L-glutamic acid (18:3-GLU). The approximately 10 times more active 18:3-GLN, which also is found in the regurgitant of several other Lepidopteran larvae, was rapidly degraded when THW regurgitant was left at room temperature, while 18:3-GLU degraded at a much slower rate. Different dietary sources of THW and tobacco bud worm larvae, including both host and nonhost plants, did not affect the amino acid composition of the fatty acid-amino acid conjugates in the regurgitant.

Enzymatic decomposition of elicitors of plant volatiles in Heliothis virescens and Helicoverpa zea

Feeding by larvae of Heliothis virescens induces cotton, corn and tobacco plants to release blends of volatile organic compounds that differ in constituent proportions from blends released when Helicoverpa zea larvae feed on the same plant species. The same elicitors (and analogs) of plant biosynthesis and release of volatiles, originally identified in oral secretions of Spodoptera exigua larvae, were also found in oral secretions of H. virescens and H. zea. However, relative amounts of these compounds, particularly N-(17-hydroxylinolenoyl)-L-glutamine (volicitin), 17-hydroxylinolenic acid, and N-linolenoyl-L-glutamine, varied among batches of oral secretions, more so in H. virescens than in H. zea. This variation was due to cleavage of the amide bond of the fatty acid-amino acid conjugates by an enzyme, or enzymes, originating in the midgut. The enzymatic activity in guts of H. virescens was significantly greater than that found in guts of H. zea. Furthermore, H. zea frass contains N-linolenoyl-L-glutamine in more than 0.1% wet weight, while this conjugate comprises only 0.003% wet weight in H. virescens frass. These results indicated that physiological differences between these two species affect the proportions of volicitin and its analogs in the caterpillars. Whether this causes different proportions of volatiles to be released by plants damaged by each caterpillar species is yet to be determined.

Concerted biosynthesis of an insect elicitor of plant volatiles

A variety of agricultural plant species, including corn, respond to insect herbivore damage by releasing large quantities of volatile compounds and, as a result, become highly attractive to parasitic wasps that attack the herbivores. An elicitor of plant volatiles, N-(17-hydroxylinolenoyl)-L-glutamine, named volicitin and isolated from beet armyworm caterpillars, is a key component in plant recognition of damage from insect herbivory. Chemical analysis of the oral secretion from beet armyworms that have fed on 13C-labeled corn seedlings established that the fatty acid portion of volicitin is plant derived whereas the 17-hydroxylation reaction and the conjugation with glutamine are carried out by the caterpillar by using glutamine of insect origin. Ironically, these insect-catalyzed chemical modifications to linolenic acid are critical for the biological activity that triggers the release of plant volatiles, which in turn attract natural enemies of the caterpillar.

Glutamine and glutamate: automated quantification and isotopic enrichments by gas chromatography/mass spectrometry

A method is described for simultaneous quantification of glutamine and glutamate plasma levels and isotopic enrichments in these compounds. Glutamine and glutamate are analyzed intact as their tertiary-butyldimethylsilyl derivatives. Deuterated glutamine and glutamate are used as internal standards for quantification by reverse isotope dilution. Preparation of plasma samples is accomplished by adding ammonium formate as an ion-pairing agent followed by extraction of the amino acids into 4.3:1 methanol:water. Negligible amounts of glutamine to glutamate conversion are observed during the sample preparation and GC/MS analysis. Since glutamine is analyzed intact, both single and double [15N]glutamine labels can be quantified. [15N]Glutamine at 0.2 to 11 mol% excess was measured in plasma with an average relative standard error of 3.8%, and [15N]glutamate over a range of 0.4 to 9 mol% excess was measured with a mean relative standard error of 12%. At glutamate levels above 1 mol% excess 15N, the mean relative standard error was 6%. Finally, automated sample injection into the GC/MS and automated data reduction are used for the analysis of samples by GC/MS.

Mass spectographic analysis of stimulated release of endogenous amino acids from rat hippocampal slices

Amino acids released from in vitro rat hippocampal slices following stimulation of the Schaffer's collateral pathway, were collected by micro-perfusion and analysed by chemical ionization mass spectrometry, with isotope ratiodetermination as the quantitative technique, through the use of stable, isotopically labeled internal standards. Stimulation at 10 pulses/sec resulted in a doubling of the release of aspartic acid over the resting level and about a 60% increase in glutamate release, which is in essential agreement with studies utilizing K+ depolarization-evoked release from slices.

Effects of liver disease on urinary excretion of methadone and metabolites in maintenance patients: quantitation by direct probe chemical ionization mass spectrometry

This study was performed to define the amounts of methadone and metabolites excreted in urine in otherwise healthy maintenance patients, and to determine whether the metabolism and elimination of methadone, as assessed by analyses of urines, is altered in patients with liver disease. A method was developed for the simultaneous quantitation of methadone and six of its major and minor metabolites using chemical ionization mass spectrometry with direct probe introduction to increase sensitivity for analyses of the minor metabolites. Analyses of urine from unmedicated volunteers showed that the interferences at the mass range of interest (264-326) were usually small and therefore would not introduce significant error into analysis. Nineteen patients well-stabilized in chronic long-term methadone treatment were studied, five otherwise healthy males and fourteen patients with chronic liver disease (nine males and four females). Twenty-four hour urine collections were made and analyzed following extraction procedures. The concentrations of methadone and the major pyrrolidine metabolite exceeded 1 microgram ml-1 in all cases; the concentration (listed in descending order) of pyrrolidone, pyrroline, hydroxymethadone, hydroxypyrroline, methadol and hydroxypyrrolidine were all less than 1 microgram ml-1. The total 24 hour urinary excretion of methadone and its metabolites was 48.3% (+/- 1.71 SEM) in otherwise healthy patients but was significantly lower, 32.6% (+/- 3.19 SEM) in patients with liver disease (p less than 0.05). The total 24 hour excretion of the pyrrolidone metabolite, the end product of two pathways of methadone metabolism, was also significantly reduced in patients with liver disease (p less than 0.05). Females with liver disease had significantly higher ratios of pyrrolidine to methadone than did males with liver disease (p less than 0.05).

Protein amino acid analysis by an isotope ratio gas chromatography mass spectrometry computer technique

A method for quantitative analysis of protein amino acids by a gas chromatography mass spectrometry computer system is described. Amino acids were analysed as their N-trifluoroacetyl n-butyl ester derivatives. Isotope ratio determination was used as the quantitating technique via multiple internal standards. The exact composition of a deuterated amino acid mixture was determined against a standard amino acid calibration mixture and in turn the protein amino acid composition was determined against the deuterated amino acid mixture. The amount of protein taken for analysis was 100 micrograms and the procedure, excluding hydrolysis, could be performed with 2 1/2 hours. The introduction of the internal standards prior to protein hydrolysis provides a method with good precision (mean coefficient of variation less than 5%). The method, tested on insulin, gave results which agreed well with the known composition of the protein and with simultaneous analysis on ion exchangers.

Plasma amino acid quantitation using gas chromatography chemical ionization mass spectrometry and 13C amino acids as internal standards

A specific and sensitive method for the quantitation of 16 alpha amino acids has been developed. The technique employed uses methane chemical ionization gas chromatography mass spectrometry of the carboxy-n-butyl, N-trifluoroacetyl amino acid derivatives. A commercial 13C amino acid mixture provided individual internal standards for 14 alpha amino acids. A computer controlled quadrupole mass spectrometer was used for selected ion monitoring of those ions characteristic of each N-trifluoroacetyl amino acid/13C amino acid pair. A BASIC computer program located peak maxima and background intensities in each selected ion recording. Standard curves for each amino acid/13C amino acid pair were utilized by the program to calculate the plasma concentration of each detected amino acid. The total instrumental analysis occupied 30 min with sample preparation and derivatization accounting for an additional 2 h. Based on the detection of known amounts of standard amino acids the method will quantitate at the 1-5 nanogram level of detection.