Potential Of Tandem Mass Spectrometry Research Articles

A preliminary retrospective evaluation of screening and diagnosis of ornithine transcarbamylase deficiency in high-risk patients at a referral center in Vietnam

IntroductionTo date, newborn screening (NBS) for proximal urea cycle disorders, including Ornithine transcarbamylase deficiency (OTCD), was not recommended due to the lack of appropriate tests and insufficient evidence of the benefits. This study aimed to investigate the potential of tandem mass spectrometry (MS/MS) for OTCD screening and its value in guiding further investigation to obtain a final diagnosis in high-risk patients. MethodsThe study included patients with OTCD referred to the National Children's Hospital between April 2020 and November 2023. A retrospective evaluation of amino acid concentrations measured by MS/MS and their ratios in patients with early-onset and late-onset OTCD was conducted. ResultsWhile all ten early-onset cases had glutamine concentrations above the upper limit, only five of them had citrulline concentrations below the lower limit of the reference interval. Only two late-onset cases had elevated glutamine levels, while all had citrulline within reference intervals. The Cit/Phe ratio was decreased, and the Gln/Cit and Met/Cit ratios were increased in all early-onset OTCD cases, while they were abnormal in only one late-onset case. ConclusionsThe preliminary results suggest that hyperglutaminemia, in combination with low or normal citrulline concentrations and specific ratios (Gln/Cit, Met/Cit, and Cit/Phe), can serve as reliable markers for screening early-onset OTCD in high-risk patients. However, these markers proved less sensitive for detecting the late-onset form, even in symptomatic patients.

Versatility of tandem mass spectrometry for focused analysis of oxylipids

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the multiple reaction monitoring (MRM) scan mode has been the primary MS method applied for the target identification of specific and minor oxylipids in complex matrices, such as eicosanoids and docosanoids, which are potent lipid mediators derived from polyunsaturated fatty acid oxygenation. However, the high specificity of MRM can limit the detection of species with m/z MRM transitions not covered by the method. In addition to MRM, tandem-quadrupole mass analyzers enable other experiments to be conducted, by fragmenting ions via collision-induced dissociation process (CID). This paper presents the potential of tandem mass spectrometry for the focused analysis of oxylipids. We have successfully developed an LC-MS/MS method for the identification of precursor ions of m/z 115, a diagnostic product ion of 5-hydroxy- and 5-epoxy-fatty acids. As a proof of concept, the developed method was used to discover several oxylipids oxidized at C5 derived from arachidonic acid (C20 : 4) oxygenation in a hypothalamus rat extract that were not identified using the target MRM methodology. The proposed focused MS/MS-based approach in a tandem mass analyzer has proven to be a powerful strategy to accelerate the identification of oxylipids with structural similarities and assist the field of lipidomic research.

Early identification of type C2 Niemann–Pick disease by urinary bile acid profile determination in a newborn: Potential of tandem mass spectrometry for the differential diagnosis of neonatal cholestasis

Background: Neonatal cholestasis (NC) is a rare but potentially life-threatening condition. It can be determined by primary hepatobiliary diseases as well as by endocrinological, genetic, infectious and metabolic disorders. Early recognition of the underlying cause is essential to ensure rapid treatment and optimal prognosis. Even in specialized centers, however, a prompt diagnosis may be hampered by the wide overlap among diseases causing NC and by the complexity of many metabolic and genetic diagnostic tests.

Accurate mass measurement and tandem mass spectrometry of intact globin chains identify the low proportion variant hemoglobin Lepore–Boston–Washington from the blood of a heterozygote

Within a mixture of proteins, minor polymorphic components are difficult to identify using a conventional proteomic approach. Their identification generally requires multi-dimensional separation steps, before or after proteolytic cleavage, followed by sequence analysis of the proteolytic products. In this study, we investigated the potential of tandem mass spectrometry for protein characterization by identifying the delta-beta hybrid human hemoglobin variant Lepore-Boston-Washington using electrospray ionization tandem mass spectrometry. Hemoglobin Lepore-Boston-Washington occurs mainly in heterozygotes, where it comprises approximately 10% of the total non-alpha-chains, the dominant non-alpha-chain being the normal beta (approximately 90%). Furthermore, Hemoglobin Lepore-Boston-Washington has an average molecular mass (15,865.23 Da) that is only 2 Da lower than that of the normal beta-chain (15,867.24 Da). Consequently, it cannot be resolved from the normal beta-chain by mass spectrometry. Here we show how Hemoglobin Lepore-Boston-Washington was identified directly from the diluted blood of a heterozygote by analyzing the product ions from the Lepore-Boston-Washington and normal beta-chain ions without prior separation of the individual chains. This study shows the potential of the tandem mass spectrometry for identifying a minor component in an unseparated mixture of proteins.

Identification of non-peptide species in selenized yeast by MALDI mass spectrometry using post-source decay and orthogonal Q-TOF detection.

The potential of tandem mass spectrometry following matrix-assisted laser desorption ionization (MALDI) was studied for speciation of selenium. Non-peptide selenium-containing compounds were isolated from a selenized yeast aqueous extract by size-exclusion chromatography. Post-source decay (PSD) was compared with orthogonal quadrupole collision cell dissociation for the purpose of obtaining fragmentation and structural information. In the PSD mode, the use of ion gate covering the whole isotopic cluster of the parent compound allowed the immediate recognition of fragments containing Se and those in which this element was absent. The tandem mass spectra obtained by orthogonal MALDI Q-TOF were equally informative in terms of the number of fragments but suffered from a poorer sensitivity. The mass accuracy was ca. 20 times better in the oMALDI configuration than in the PSD mode. An unknown selenium compound with an m/z 388 was detected with a mass accuracy of 3 ppm according to the proposed empiric formula.

Mass spectral analyses of microcystins from toxic cyanobacteria using on-line chromatographic and electrophoretic separations

The application of capillary electrophoresis and of reversed-phase liquid chromatography coupled to electrospray mass spectrometry is presented for the analysis of microcystins isolated from toxic strains of Microcystis aeruginosa. The separation performance of these two techniques is compared in terms of both sensitivity and of resolution of closely related microcystins. Quantitation of microcystin-LR present at low μg/ml concentrations in cell extracts is demonstrated using both techniques. A marked advantage of capillary electrophoresis over liquid chromatography was its ability to resolve different desmethyl microcystin-LR analogues. Identification of these positional isomers was facilitated using capillary electrophoresis combined with tandem mass spectrometry (MS-MS). Rationalization of fragment ions observed in MS-MS spectra of microcystins was made possible through comparison with 15N labelled microcystins obtained from stable isotope feeding experiments. The potential of tandem mass spectrometry in providing selective detection of microcystins in cell extracts, and in structural characterization of novel microcystins, was also investigated.

Analysis of microcystins from cyanobacteria by liquid chromatography with mass spectrometry using atmospheric‐pressure ionization

AbstractA combined liquid chromatographic mass spectrometric method was developed for the analysis of microcystins (hepatotoxic cyclic heptapeptides) produced by cyanobacteria (blue‐green algae). The method was used to confirm the identity of microcystins, tentatively identified by high‐performance liquid chromatography using diode‐array detection, in extracts from natural‐bloom material and a sample of river water where hepatotoxic cyanobacteria were present. The potential of tandem mass spectrometry for obtaining structural information and providing a selective screen for these compounds was also investigated.

Quantitative determination of N-acetyl(-L-)cysteine derivatives in human urine by tandem mass spectrometry.

Collision-induced dissociation (CID) methods are described for the quantification of nanogram per millilitre (ppb) concentrations of 2-acetamido-3-(3'-hydroxypropylthio)-propanoic acid (I) and 2-acetamido-3-phenylthiopropanoic acid (II) in human urine extracts. I and II are potential detoxification products of acrolein and benzene in conjugation with N-acetyl(-L-)cysteine derived from glutathione. We have studied the potential of tandem mass spectrometry (MS/MS) under electron impact (EI) and chemical ionization (CI) conditions as a confirmatory screening technique for these compounds. Our main goals were high selectivity and low detection limits along with little or no sample clean-up. The effects of the mode of ionization and of collision conditions on the CID spectra have been investigated. Direct insertion probe without any derivatization or short-column gas chromatographic separation techniques are used. Total instrument and data analysis time is about 15 min for direct insertion probe MS/MS and about 30 min for short-column gas chromatography (GC)/MS/MS. Detection limits are: direct insertion probe MS/MS (EI mode), 50 ppb (100 pg) for compound I; short-column GC/MS/MS (EI mode), 1.5 ppb (5 pg) for compound II; and short-column GC/MS/MS (CI mode), 0.6 ppb (2 pg) for the methyl ester of compound II. Results are compared with non-mass spectrometric methods. The MS/MS methods were applied for the determination of I (EI mode) and II (CI mode) in urinary samples of a smoker and eight non-smokers. After smoking, the urinary levels of I and II were elevated, whereas no increase was observed after experimental passive smoking.

Tandem mass spectrometry in the structural analysis of an oviposition-deterring pheromone

The potential of tandem mass Spectrometry (MS/MS) as a stand-alone technique in the structural analyses of an oviposition-deterring pheromone (ODP, 1) is reviewed. Two facets of the salt-like glycolipid structure of 1 were of major interest in this context: the substitution pattern of the lipid backbone (15-glucosyioxy-8-hydroxypalmitate) and, more specifically, the configurational identity of the sugar portion (glucopyra nose). Throughout this study, trideuterioacetyl derivatives of ODP (1 → pentakis(trideuterioacetyl)-ODP la) and the reference substrates were used. Probing of the sugar moiety by fast atom bombardment (FAB) and both low- and high-energy collision-induced dissociation (CID) of B2-type sugar ions surprisingly failed as a single exception within a larger number of glycosidic substrates subjected to this approach. However, electrospray ionization (ESI) of la with the formation of the sugar ions in the gas phase by ‘first-stage’ CID before mass selection circumvented this difficulty and provided an unambiguous and sensitive probe for sugar stereochemistry. When studying the ODP molecule as a whole, FAB-generated M-like ions such as [M − H]−, [M + Na]+ and [M − H + 2Na]+ were subjected to high-energy CID using a four-sector tandem mass spectrometer. Analyses of simple model substrates such as the 12-trideuterioacetoxystearate anion facilitated the interpretation of the distinct charge-remote fragmentation (CRF) behaviour of la. Whereas all M-like species provided complete records of the lipid portion of la and its oxygenation pattern, only the sodiated cations allowed reliable location of the individual substituents. In these latter species complementary series of ‘sequence ions’ were observed that incorporated either the taurine or the sugar terminus and thus reflected CRF for both alternatives of terminal charge fixation.

MS/MS in structural analysis of an oviposition-deterring pheromone

A recently characterized oviposition-deterring pheromone (ODP, structure 1) of the European cherry fruit fly was used as a test case for probing the potential of tandem mass spectrometry (MS/MS) in structure elucidation as a stand-alone technique. The glycolipid-taurinate 1 was subjected to MS/MS analyses under a variety of conditions with and without preceding chemical degradation. Acidic methanolysis of 1 and subsequent in-batch derivatization (trideuterioacetylation) yielded methyl 2,3,4,6-tetrakis-O-trideuterioacetyl-glucopyranoside (2), methyl 8,15-bis-trideuterioacetoxy-palmitate (3), and taurine (4) as suitable target compounds for direct mixture analysis.Low energy collision induced dissociation (CID) on selected precursor ions (MS/MS on [M + H − CH3OH]+ and [M + H]+ produced by fast atom bombardment (FAB)) allowed direct identification of 2 and 4, respectively, by comparison with appropriate reference ions. In the case of 3, low energy CID (desorption chemical ionization (DCI) instead of FAB, MS/MS on [M + H]+) permitted deduction of gross molecular structure, but failed to provide positional detail. In sharp contrast,high energy CID of trideuterioacetylated intact 1 (FAB-MS/MS on [M − H]− ions of la) clearly revealed a linear 8,15-hydroxylated palmitic acid backbone. Less certain was assignment of 15-O-glucosylation by this approach.