Identification of pollutants in a municipal well using high resolution mass spectrometry

An elevated incidence of childhood cancer was observed near a contaminated site. Trace amounts of several isomeric compounds were detected by gas chromatography/mass spectrometry (GC/MS) in a concentrated extract of municipal well water. No matching library mass spectra were found and Fourier transform IR and NMR analyses were not feasible due to the low concentration of the compounds. Mass peak profiling from selected-ion-recording data (MPPSIRD) provided the sensitivity and scan speed necessary to acquire mass peak profiles at mass resolutions of 10,000 to 20,000 for the molecular ion (M+) and 10 fragment ions as capillary GC peaks eluted. Using a profile generation model (PGM), the elemental composition of the molecular ion was determined from the exact masses and abundances of the M, M + 1 and M + 2 profiles. Fragment ion compositions were determined from their exact masses based on the elements in the molecular ion. Exact mass differences between the molecular and fragment ions corresponded to unique combinations of atoms for the neutral losses. Consequent reduction of the number of possible structures for the fragment ions simplified mass spectral interpretation. After inspecting library mass spectra for smaller molecules, isomeric structures were hypothesized with cyano and alkylcyano groups attached to tetralin. A literature search found such isomers produced by an industrial polymer synthesis. Three isomers in a standard form polymerization of styrene and acrylonitrile provided the same mass spectra and GC retention times as isomers in the extract.     

Identification of viral mutants by mass spectrometry

A method to identify mutations of virus proteins by using protein mass mapping is described. Comparative mass mapping was applied to a structural protein of the human rhinovirus Cys1199 --> Tyr mutant and to genetically engineered mutants of tobacco mosaic virus. The information generated from this approach can rapidly identify the peptide or protein containing the mutation and, in cases when nucleic acid sequencing is required, significantly narrows the region of the genome that must be sequenced. High-resolution matrix-assisted laser desorption/ionization (MALDI) mass spectrometry and tandem mass spectrometry were used to identify amino acid substitutions. This method provides valuable information for those analyzing viral variants and, in some cases, offers a rapid and accurate alternative to nucleotide sequencing.     

Rapid assessment of early glycation products by mass spectrometry

In order to detect the early glycation products, we have reacted a model peptide (t-boc-lys-ala-ala) with L-threose (a degradation product of ascorbic acid) and analyzed the reaction products by a combination of HPLC and mass spectrometry. Amino group modification, as observed by a fluorescamine assay, indicated complete modification after 3 days of incubation with a 10-fold excess of threose. As much as 60% of the adducts were acid labile and only 4% of the adducts could be observed by amino acid analysis. However, Fast atom bombardment mass spectrometry (FABMS) of the samples incubated for 6 hr showed relative molecular masses consistent with the formation of adducts corresponding to the addition of one and two molecules of L-threose to the peptide. Likewise, samples incubated for 12 hr showed peptide adducts with two and three L-threoses. The number of threose molecules added to the peptide was also confirmed from the FABMS analysis by using [1-13C]-threose as the glycating agent.     

Identification of Glu-540 as the catalytic nucleophile of human beta-glucuronidase using electrospray mass spectrometry

Human beta-glucuronidase is a member of the Family 2 glycosylhydrolases that cleaves beta-D-glucuronic acid residues from the nonreducing termini of glycosaminoglycans. The enzyme is shown to catalyze glycoside bond hydrolysis with net retention of anomeric configuration, presumably via a mechanism involving a covalent glucuronyl-enzyme intermediate. Incubation of human beta-glucuronidase with 2-deoxy-2-fluoro-beta-D-glucuronyl fluoride resulted in time-dependent inactivation of the enzyme through the accumulation of a covalent 2-deoxy-2-fluoro-alpha-D-glucuronyl-enzyme, as observed by electrospray mass spectrometry. Regeneration of the free enzyme by hydrolysis or transglycosylation and removal of excess inactivator demonstrated that the covalent intermediate was kinetically competent. Peptic digestion of the 2-deoxy-2-fluoro-alpha-D-glucuronyl-enzyme intermediate and subsequent analysis by liquid chromatography coupled with electrospray ionization triple quadrupole mass spectrometry indicated the presence of a 2-deoxy-2-fluoro-alpha-D-glucuronyl peptide. Sequence determination of the labeled peptide by tandem mass spectrometry in the daughter ion scan mode permitted the identification of Glu-540 as the catalytic nucleophile within the sequence SEYGAET.     

Identification of pesticides by liquid chromatography--particle beam mass spectrometry using electron ionization and chemical ionization

Liquid chromatography-mass spectrometry (LC-MS) with a particle beam (PB) interface is used to separate and identify a group of pesticides. The mass spectra obtained under the different ionization modes, electron ionization (EI) and positive and negative chemical ionization (PCI and NCI) are compared. The operating conditions under each mode, determined by studying the influence on the ion abundance of the ion source temperature of the EI mode, and the gas pressure and ion source temperature in the methane CI were optimized. EI was more sensitive than PCI and NCI and of the latter two modes, NCI gave higher responses, especially for organophosphorus compounds. When on-line solid-phase extraction-LC-PB-MS was applied to real samples, limits of detection in full scan mode were in the range of 0.5 and 10 micrograms l-1 for EI. The analysis of real samples by on-line solid-phase extraction-LC-PB-MS enabled EI detection of one of the pesticides studied and confirmation by PCI and NCI. The combined EI/CI information also enabled the detection of some non-target compounds.     

Rapid typing and elucidation of new secondary metabolites of intact cyanobacteria using MALDI-TOF mass spectrometry

Cervical leakage, occurring on average in 20-50% of the patients, is one of the major causes of morbidity following oesophagectomy for cancer. We report on a new technique of gastroplasty, namely fundus rotation gastroplasty which was used in 53 patients. There were 49 patients with oesophageal cancer and 4 with benign lesions. Hospital mortality was 5.7% (3/53) and the leakage rate 7.5% (4/53). The advantages of fundus rotation gastroplasty over conventional gastroplasty are the better blood supply and the greater length of the gastric tube. Controlled clinical trials will be necessary to confirm the advantages of fundus rotation gastroplasty versus conventional gastroplasty.     

Determination of four anabolic steroid metabolites by gas chromatography/mass spectrometry with negative ion chemical ionization and tandem mass spectrometry

A gas chromatography/mass spectrometry method is described which uses negative ion chemical ionization and tandem mass spectrometry for the determination of anabolic steroid metabolites. Four anabolic steroid metabolites to be derivatized by Pentafluoropropionic anhydride (PFPA) were determined using gas chromatography/mass spectrometry (GC/MS) with negative chemical ionization (NCI) and NCI/MS/MS. The repeatability and reproducibility of this procedure were in the range of 5.3-9.7% and 6.1-10.2%, respectively. This method of derivatization with PFPA for NCI and NCI/MS/MS was useful to determine four metabolites of nandrolone, dromostanolone, methenolone and boldenone. The derivatized metabolites of boldenone could be detected to 2 ppb and the other three steroids could be detected to 25 ppb in urine at a signal-to-noise ratio of S/N = 3.     

Heterogeneity in Bacillus cereus PCR products detected by ESI-FTICR mass spectrometry

PCR amplification of a segment of the 16/23S rDNA interspace region (ISR) from Bacillus cereus 6464 produced a mixture of products. An 89-bp product was predicted on the basis of the reported sequence. The ESI-FTICR analysis revealed three double-stranded products, differing in size by a single nucleotide corresponding to two homoduplexes of 89 and 88 base pairs and a heteroduplex of 89 and 88 nucleotide strands. These were produced from a single preparation of genomic DNA and a single primer pair. ESI-FTICR analysis of the single strands identified a deletion of a T in the coding strand and a corresponding loss of an A in the noncoding strand of this product. The ESI-FTICR analysis indicated the presence of an unreported sequence variation between rRNA operons in this organism. This report illustrates that PCR products amplified from templates differing by a single nucleotide can be resolved and identified using ESI-FTICR at the 89-bp level. Furthermore, the ESI-FTICR mass measurements provided the identity of the deletion, which is indicative of interoperon variability.     

Sequencing DNA using mass spectrometry for ladder detection

Sequencing of DNA fragments of 130 and 200 bp using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for DNA ladder detection was demonstrated. With further improvement in mass resolution and detection sensitivity, mass spectrometry shows great promise for routine DNA sequencing in the future.     

Identification of a new all-trans-retinol metabolite produced through a new retinol metabolic pathway

In vitro incubation of all-trans-retinol (atROL) with kidney homogenate from vitamin A-deficient and retinoic acid-supplemented (VAD-RAS) female rats produces a new retinol metabolite. Reverse-phase (RP) and normal-phase (NP) high-performance liquid chromatography (HPLC) analysis showed that this metabolite coelutes with the unknown all-trans-retinol (atROL) metabolite previously found in the day 10 conceptus and kidneys of vitamin A-deficient rats maintained on all-trans-retinoic acid (VAD-RA) and given 2 microg of [3H]atROL. Normal-phase (NP) HPLC purification of the metabolite collected from a RP HPLC column further separated the radiolabeled material into two components. The two isolated compounds have identical or very similar spectroscopic properties. Their nuclear magnetic resonance (1H NMR) and mass spectra (MS) indicated that they are isomers. Spectroscopic studies of the metabolites and their derivatives showed that they are nine-carbon fragments resulting from an oxidative cleavage of the side chain of atROL. The cleavage occurs at C-9, and the product is then oxidized to a keto group. The primary hydroxy group from atROL is preserved in the metabolite. A sulfide bridge is formed between C-11 and C-14, which interrupts the conjugation. The formation of the new metabolites, possessing a 2,5-dihydrothiophene ring, is catalyzed by an enzyme(s) located in the cytosolic fraction of kidneys. The process represents a new retinol metabolic pathway; however, its biological significance is unknown.     

Identification of hydroxyhalobiphenyls as their methyl ethers by gas chromatography mass spectrometry

The mass spectra and gas chromatographic properties of 17 synthetic fluoro-, chloro- and bromomethoxy-biphenyls and 12 dichlorodimethoxybiphenyls have been examined. From this representative series it appears that the position of the methoxy group (ortho, meta and para to the biphenyl bond) in all monomethoxy compounds examined, and the positions of the two methoxy groups in most of the dimethoxy compounds, can be assigned unambiguously by their difference in fragmentation pattern. The value of this method was shown by metabolism experiments in which 4,4'-difluoro- and 4,4'-dibromobiphenyl were fed to rats and 4,4'-dichlorobiphenyl was administered to plants. All hydroxylated metabolites found were identified by gas chromatography mass spectrometry. Relationships between structure and gas chromatographic retention time of these compounds are discussed.     

Identification of urinary oligosaccharides by matrix-assisted laser desorption ionization time-of-flight mass spectrometry

A new method of urinary oligosaccharides identification by matrix-assisted laser desorption time-of-flight mass spectrometry is presented. The method involves three steps: coupling of the urinary oligosaccharides with 8-aminonaphthalene-1,3,6-trisulfonic acid; fast purification over a porous graphite carbon extraction column; and mass spectrometric analysis. Identification of urinary oligosaccharides is based on the patterns and values of the pseudomolecular ions observed. We report here the patterns in urines from patients with Pompe disease, alpha and beta mannosidoses, galacto-sialidosis, and GM1 gangliosidosis. The protocols described here allowed facile and sensitive identification of the pathognomonic oligosacchariduria present in lysosomal diseases and can be extended to any pathological oligosacchariduria.     

Identification of eicosanoids in the red algae, Gracilaria asiatica, using high-performance liquid chromatography and electrospray ionization mass spectrometry

The "gold standard" inflow cytometric DNA analysis of breast cancer uses fresh tumor cells simultaneously labeled for cytokeratin (CK) and DNA. We developed a 2-parameter CK-DNA flow assay suitable for archival, paraffin-embedded tissue (PT). Six anti-CK monoclonal antibodies were tested by immunocytochemistry and our assay for staining of nuclei extracted from PT breast cancers by combination pepsin-trypsin digestion. Clone CAM 5.2 was inadequate for PT nuclear suspensions, but a cocktail of 2 anti-CK clones (AE1/AE3 and KL-1) distinguished epithelial from nonepithelial nuclei in 2-parameter flow dot plots. We studied 82 routine PT breast tumors by our assay and used a univariate flow DNA histogram based on fresh biopsy tissue for comparison. Three histogram data quality indicators were improved. A trend toward higher S-phase fractions was found for DNA diploid PT tumors, although when inflammation was evident histologically, the increment in S-phase fraction with gating was often marked. CK gating identified PT tumors containing concurrent CK-positive DNA diploid and nondiploid populations (27 of 56 DNA nondiploid histograms). By excluding nonepithelial nuclei, 2-color CK-DNA flow methods may increase the accuracy of ploidy and S-phase fraction measurements. Our method appears superior to previous techniques using clone CAM 5.2 for labeling of archival breast cancers.     

Identification of N-nitrosodimethylamine in ambient air by capillary gas-liquid chromatography mass spectrometry computer

Organic vapors in ambient air, at or near an industrial site in Baltimore, Maryland, were collected by adsorption on a sorbent of porous polymer (Tenax GC, 35/60). The pollutants were recovered by thermal desorption and analyzed by gas-liquid chromatography mass spectrometry computer using capillary glass SCOT columns. N-Nitrosodimethylamine was identified from its mass spectrum as a constituent of the atmosphere in the areas sampled. The identification of this compound was confirmed by comparison of its mass spectrum with that of authentic N-nitrosodimethylamine; identical retention times of unknown and authentic compound on three different capillary columns were observed.     

Structural assignment of permethylated oligosaccharide subunits using sequential tandem mass spectrometry

The sequential tandem mass spectrometry (MSn) capabilities offered by quadrupole ion trap instruments have been explored in a systematic study of permethylated oligosaccharides. Under collision-induced dissociation, protonated molecular species generated in the electrospray ionization mode yield simple and predictable mass spectra. Information on sequence, branching, and, to some extent, interglycosidic linkages can be deduced from fragments resulting from the cleavage of glycosidic bonds. Simple rules for the structural assignment of carbohydrates have been established for the fragmentation of protonated species and subunits thereof and corroborated by 18O-labeling experiments. Moreover, sequential tandem mass spectrometry was demonstrated to allow the straightforward structural characterization of unknown carbohydrate moieties by comparing their CID spectra with those of a set of references. As the collision-induced dissociation patterns are not dependent on the number of prior tandem mass spectrometric steps, structures can be unambiguously assigned by match of the spectra. These findings establish the basis of MSn performed on a quadrupole ion trap instrument for elucidating structures of large carbohydrates, which can be virtually degraded in the mass spectrometer into smaller entities in one or several steps. This powerful technique has been applied, used in conjunction with specific CD3 labeling, to the characterization of series of subunits generated from fucosylated and sialylated oligosaccharides, which are among the most important structures as far as biological activities are concerned.     

Measuring the metal-containing mass of pulp products using the electromagnetic method

Two ways of solving the problem of precisely measuring the metal-containing mass of pulp are considered. The first method involves continuously measuring the magnetic permeability of the pulp and automatically correcting the calculation of a dry mass of a metal-containing product. The second method involves applying the specific electromagnetic flowmeters insensitive to the variation in the magnetic properties of a measured medium. Technical solutions which allow one to obtain an additional electric signal characterizing the magnetic permeability of the pulp are analyzed. Its presence makes it possible not only to eliminate the error in measuring the volume flow rate due to the effect of the magnetic component of the pulp, but also to measure the mass of the metal-containing product. Applying the electromagnetic flowmeters is the most promising way to solve this problem.     

Characterization of labeled oligonucleotides using enzymatic digestion and tandem mass spectrometry

A simple and powerful method for the determination of labeling sites on oligodeoxynucleotides (ODN) has been developed. The method is based on the finding that nuclease P1 (NP1) digestions of label-containing ODNs produce site-specific products: 5'-labeled ODNs produce label-nucleotide (L-N); 3'-labeled ODN produces phosphorylated label (pL); and a label in between the ODN termini produces pL-N. Mass spectrometry spectra of these products from the digestion mixture can be easily utilized for structural verification of labeled ODNs such as DNA probes. We also developed a method for the determination of the labeling sites of ODNs with unknown label structures. In this method, NP1 digestion products generate site-specific fragmentation patterns upon collision-induced dissociation. These patterns can be easily recognized and used for the identification of labeling sites of ODNs with unknown label structures. When an ODN is internally labeled, phosphodiesterase digestion may be used to determine the exact labeling site (sequence location). It was demonstrated that these methods can be applied for ODNs with single or multiple labels, and for ODNs with the same or different labels within an ODN.