A GC/MS method for determination of succinylacetone in Arabidopsis thaliana.

Succinylacetone was known to be a toxic metabolite of tyrosine in human and animals caused by blockage of the final step in tyrosine degradation pathway, but its existence in plant was unclear though the metabolic disturbance of tyrosine was also found in plant. A GC-MS method for determination of succinylacetone in Arabidopsis thaliana was developed for the first time. Both oximation and silylation were applied in the derivation procedure, and a low-temperature condition before completion of oximation was found to be necessary to obtain good linearity of the calibration curve due to the thermolability of succinylacetone. The specific chromatogram pattern formed by the four isomers of succinylacetone derivatives provided a helpful feature for its identification. The detection limit of the proposed method was 0.25 ppm in A. thaliana. The recoveries were between 95.4 and 109.3 % with the coefficient of variation ranging from 4.36 to 7.81 % for intra-day assays and 6.47 to 8.52 % for inter-day assays. Application to wild-type and the short-day sensitive cell death 1 mutant of A. thaliana represented an obvious correlation between the measured amount of succinylacetone and wilting symptom, suggesting the proposed method could be a powerful tool in further study on toxicology of succinylacetone and tyrosine catabolism in plants.

Dried blood spot analysis by digital microfluidics coupled to nanoelectrospray ionization mass spectrometry.

Dried blood spot (DBS) samples on filter paper are surging in popularity as a sampling and storage vehicle for a wide range of clinical and pharmaceutical applications. For example, a DBS sample is collected from every baby born in the province of Ontario, Canada, for quantification of approximately one hundred analytes that are used to screen for 28 conditions, including succinylacetone (SA), a marker for hepatorenal tyrosinemia. Unfortunately, the conventional methods used to evaluate DBS samples for newborn screening and other applications are tedious and slow, with limited options for automated analysis. In response to this challenge, we have developed a method to couple digital microfluidics (DMF) to nanoelectrospray ionization mass spectrometry (nESI-MS) for SA quantification in DBS samples. The new system is formed by sandwiching a pulled glass capillary emitter between the two DMF substrates such that the capillary emitter is immobilized without external seals or gaskets. Moreover, we introduce a new feedback control system that enables high-fidelity droplet manipulation across DBS samples without manual intervention. The system was validated by application to on-chip extraction, derivatization, and analysis of SA and other analytes from DBS samples, with comparable performance to gold-standard methods. We propose that the new methods described here can potentially contribute to a new generation of analytical techniques for quantifying analytes in DBS samples for a wide range of applications.

Improved tandem mass spectrometry (MS/MS) derivatized method for the detection of tyrosinemia type I, amino acids and acylcarnitine disorders using a single extraction process.

BACKGROUND: Succinylacetone (SUAC), a specific marker for tyrosinemia type I (Tyr I) cannot be detected by the routine LC-MS/MS screening of amino acids (AA) and acylcarnitines (AC) in newborns. The current derivatized methods require double extraction of newborn dried blood spots (DBS); one for AA and AC and the second for SUAC from the blood spot left after the first extraction. We have developed a method in which AA, AC and SUAC are extracted in a single extraction resulting in significant reduction in labor and assay time. METHODS: The 3.2 mm DBS were extracted by incubating at 45 °C for 45 min with 100 µl of acetonitrile (ACN)-water-formic acid mixture containing hydrazine and stable-isotope labeled internal standards of AA, AC and SUAC. The extract was derivatized with n-butanolic-HCl and analyzed by LC-MS/MS. RESULTS: The average inter-assay CVs for, AA, AC and SUAC were 10.1, 10.8 and 7.1% respectively. The extraction of analytes with ACN-water mixture showed no significant difference in their recovery compared to commonly used solvent MeOH. The concentration of hydrazine had considerable impact on SUAC extraction. CONCLUSION: We developed a new MS/MS derivatized method to detect AA/AC/SUAC in a single extraction process for screening Tyr I along with disorders of AA and AC.

Ethyl 4-methyl heptanoate: a male-produced pheromone of Nicrophorus vespilloides.

Sexually mature male beetles of the genus Nicrophorus (Coleoptera: Silphidae) exhibit a conspicuous behavior, recognized as pheromone-releasing activity. Laboratory and field studies demonstrated that females are attracted to males that exhibit this behavior, both on or off reproductive resources. Here, we report the results of a study in which volatile chemicals released by calling Nicrophorus vespilloides were collected by solid-phase microextraction and analyzed by using coupled gas chromatography-mass spectrometry. These analyses revealed that ethyl 4-methyl heptanoate and (E)-geranylacetone are emitted by males that engage in the behavior. In the field, traps baited with racemic ethyl 4-methyl heptanoate caught roughly equal numbers of male and female N. vespilloides. Some male and female Nicrophorus vespillo and male Nicrophorus humator were also caught in traps baited with this compound. Traps baited with (E)-geranylacetone did not catch significant numbers of beetles.

Tandem mass spectrometric determination of succinylacetone in dried blood spots enables presymptomatic detection in a case of hepatorenal tyrosinaemia.

Tyrosinaemia type I, or fumarylacetoacetase deficiency, causes hepatorenal damage by accumulation of fumarylacetoacetate. Patients are generally in good condition at birth, but are at risk of developing serious metabolic crises with liver failure and hepatic coma. An early start of treatment with NTBC and a tyrosine-balanced diet can prevent harm to the patients. The application of tandem mass spectrometry to newborn screening allows for easy determination of tyrosine to detect the presence of hypertyrosinaemia in the neonate, but most patients with tyrosinaemia type I do not present with high tyrosine levels at the time of newborn screening. We report on a 7-week-old girl presenting with acute hepatopathy and severe coagulopathy due to tyrosinaemia type I. The metabolic screening, which was performed by tandem mass spectrometry at the age of 48 h, had revealed normal values for tyrosine and methionine that were well within ranges observed in the general population and equally normal ratios of methionine/tyrosine and tyrosine/serine. In this patient even lowering the cut-off levels for tyrosine and methionine would not have provided better sensitivity. Residual blood spots from the newborn screening filter paper were retrospectively analysed using a specific mass-spectrometric method for the detection of succinylacetone and revealed a 5-fold elevated succinylacetone concentration. This indicates that identification of all newborns with hepatorenal tyrosinaemia is only possible by determination of succinylacetone as part of the newborn screening process.

A GC/MS validated method for the nanomolar range determination of succinylacetone in amniotic fluid and plasma: an analytical tool for tyrosinemia type I.

A sensitive and accurate stable isotope dilution GC/MS assay was developed and validated for the quantification of succinylacetone (SA) in plasma and amniotic fluid (AF). SA is pathognonomic for tyrosinemia type I, a genetic disorder caused by a reduced activity of fumarylacetoacetate hydrolase (FAH). In untreated patients, SA can easily be measured in plasma and urine because the expected concentrations are in the micromol/L range. Due to a founder effect, the province of Quebec has an unusually high prevalence of tyrosinemia type I, hence, the quantification of SA in AF or plasma of treated patients in the nmol/L range becomes very useful. The method utilizes 13C5-SA as an internal standard and a three-step sample treatment consisting of oximation, solvent extraction and TMCS derivatization. The assay was validated by recording the ion intensities of m/z 620 for SA and m/z 625 for ISTD in order to demonstrate the precision of measurements, the linearity of the method, limit of quantification and detection (LOQ and LOD), specificity, accuracy, as well as metabolite stability. Values for the intra-day assays ranged from 0.2 to 3.2% while values for the inter-day assays ranged from 1.9 to 5.6% confirming that the method has good precision. A calibration plot using SA detected by GC/MS gave excellent linearity with a correlation coefficient of 0.999 over the injected concentration range of 5-2000 nmol/L. LOQ and LOD were 3 and 1 nmol/L, respectively. The usefulness of this method was demonstrated by SA quantification in an AF sample of an affected fetus and in plasma of patients treated with NTBC. The results demonstrate that this novel GC/MS method may be a valuable tool for metabolic evaluation and clinical use.

Monitoring seasonal variation in apple fruit volatile emissions in situ using solid-phase microextraction.

Emissions of volatiles from apple fruits (Malus domestica Borkh.) were monitored in situ over the course of a growing season (from early June to mid September) for two apple varieties, Golden Delicious and Maigold. Results indicate a characteristic time-course of volatile emissions as the sampling date was a statistically significant factor for nine of the 13 compounds considered. The amounts of volatiles collected were greatest early and late in the season. The temporal effect on emissions was generally much larger than the effect of variety, which was significant for only four of the 13 compounds considered. The possible sources of variation which are not explained by the statistical models are discussed, and it is considered that they are most likely related to differences in the emissions from individual fruits.

Genotyping of a case of tyrosinaemia type I with normal level of succinylacetone in amniotic fluid.

Tyrosinaemia type I is caused by a deficiency of fumarylacetoacetate hydrolase and mainly affects the liver. This disease is characterized by the presence of a high level of succinylacetone. This metabolite has been used for prenatal diagnosis from amniotic fluid samples. One case with a normal level of succinylacetone in amniotic fluid has recently been described (Grenier et al., 1996). Here, we report that this patient is a compound heterozygote for two known mutations: E364X and IVS6-1g-->t. The low level of succinylacetone cannot be explained by these mutations.

A case of tyrosinaemia type I with normal level of succinylacetone in the amniotic fluid.

Prenatal diagnosis of tyrosinaemia type I can be achieved in cultured amniotic cells and in chorionic villus material by testing the activity of fumarylacetoacetate hydrolase and by DNA analysis, and in amniotic fluid by succinylacetone measurement. This specific metabolite can be measured either by gas chromatography-mass spectrometry or by delta-aminolevulinate dehydratase inhibition assay. In a series of 65 at-risk cases tested with the enzyme inhibition assay, one case out of the 18 with the disease had a normal level of succinylacetone. This case is presented.

Fungal metabolic model for human type I hereditary tyrosinaemia.

Type I hereditary tyrosinaemia (HT1) is a severe human inborn disease resulting from loss of fumaryl-acetoacetate hydrolase (Fah). Homozygous disruption of the gene encoding Fah in mice causes neonatal lethality, seriously limiting use of this animal as a model. We report here that fahA, the gene encoding Fah in the fungus Aspergillus nidulans, encodes a polypeptide showing 47.1% identity to its human homologue, fahA disruption results in secretion of succinylacetone (a diagnostic compound for human type I tyrosinaemia) and phenylalanine toxicity. We have isolated spontaneous suppressor mutations preventing this toxicity, presumably representing loss-of-function mutations in genes acting upstream of fahA in the phenylalanine catabolic pathway. Analysis of a class of these mutations demonstrates that loss of homogentisate dioxygenase (leading to alkaptonuria in humans) prevents the effects of a Fah deficiency. Our results strongly suggest human homogentisate dioxygenase as a target for HT1 therapy and illustrate the usefulness of this fungus as an alternative to animal models for certain aspects of human metabolic diseases.

Determination of succinylacetone and succinylacetoacetate in physiological samples as the common product 5(3)-methyl-3(5)-isoxazole propionic acid using an isotope dilution method and mass spectrometry.

A stable isotope dilution method was developed for the determination of succinylacetone and succinylacetoacetate in physiological samples. Succinylacetone and succinylacetoacetate were both converted to 5(3)-methyl-3(5)-isoxazole propionic acid by treating them with a solution of hydroxylamine-HCl at a pH less than 3 and at 80 degrees C. After extraction with diethyl ether tertiary butyldimethyl silyl derivatives were prepared using N-methyl-N-t. butyldimethyl silyl-trifluoro acetamide and analyzed by gas chromatography mass spectrometry. Selective ion monitoring was carried out at m/z 138.1 (M-131) and m/z 212.1 (M-57) for the natural, and at m/z 139.1 and 213.1 for the labelled compound. (15N)-5(3)-methyl-3(5)-isoxazole propionic acid was synthesized and used as internal standard for the isotope dilution analysis. Concentrations in physiological samples as low as 10 nmol/l could be accurately measured.

Stable isotope dilution analysis of succinylacetone using electron capture negative ion mass fragmentography: an accurate approach to the pre- and neonatal diagnosis of hereditary tyrosinemia type I.

A sensitive and accurate isotope dilution assay using electron capture negative ion mass fragmentography was developed for succinylacetone in amniotic fluid, plasma and urine. The method utilizes (D4)-5(3)-methyl-3(5)-isoxasole propionic acid as internal standard. Sample pretreatment consisted of oximation at pH less than 2 to 5(3)-methyl-3(5)-isoxasole propionic acid, clean up using liquid partition chromatography and further derivatization to the pentafluorobenzyl ester. Control values in plasma revealed a mean means = 0.044 mumol/l, range = 0.005-0.163 mumol/l, in urine means = 0.15 mumol/l, range 0.01-0.40 mumol/l corresponding to means = 0.03 mumol/mmol creat., range 0.01-0.14 mumol/mmol creat., and in amniotic fluid means = 0.016 mumol/l, range = 0.001-0.030 mumol/l. The utility of the method was demonstrated by quantification of succinylacetone in urine from patients with hereditary tyrosinemia type I (n = 8, excretion range 2.60-493.3 mumol/l corresponding to 0.67-197.3 mumol/mmol creat.) and in two amniotic fluid samples from fetuses affected with this disorder (concentration of succinylacetone 0.085 and 1.50 mumol/l, respectively). Maternal urine from a woman carrying an affected fetus did not show elevated urinary succinylacetone excretion.

Chemical analysis of succinylacetone and 4-hydroxyphenyllactate in amniotic fluid using selective ion monitoring.

A method for the measurement of the concentration of succinylacetone and 4-hydroxyphenyllactic acid in amniotic fluid was developed for the prenatal diagnosis of hereditary tyrosinemia. Succinylacetone was converted to 5-methyl-3-isoxazolepropionic acid and isolated with 4-hydroxyphenyllactic acid by liquid partition chromatography and the trimethylsilyl derivatives quantified by ammonia chemical ionization selected ion monitoring gas chromatography-mass spectrometry with 2-hydroxy-n-caproic acid as the internal standard. The concentration of 4-hydroxyphenyllactic acid in normal amniotic fluid was 1.97 +/- 0.75 (S.D.) mumol/l while succinylacetone was undetectable. A pregnancy at risk for tyrosinemia type II was monitored. The concentration of 4-hydroxyphenyllactic acid was within the normal range and a healthy child was born.