Detection and quantitation of beta-2-microglobulin glycosylated end products in human serum by matrix-assisted laser desorption/ionization mass spectrometry.

beta-2-Microglobulin (beta 2M) is a major protein component found in the amyloid deposits of dialysis-related amyloidosis (DRA) patients. Evidence has been shown that the advanced glycosylated end-products (AGEs) of beta 2M present in sera were related to DRA. We demonstrated that matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a useful tool to investigate the nature of glycosylation of beta 2M and detection of beta 2M or beta 2M-AGEs in human serum. The high-mass end of beta 2M-AGE distribution was found to extend to the neighborhood of 12,868 Da, corresponding to condensations with seven glucose molecules. We also have shown that both beta 2M and beta 2M-AGEs can be detected at low picomole levels directly in bovine serum. Based on these findings, the sera of DRA patients were studied to determine whether beta 2M-AGEs can be detected by MALDI-MS. In an attempt to investigate the possibility of quantitation with MALDI, human sera samples with different concentrations of beta 2M-AGE were examined. We were able to correlate the concentration of beta 2M-AGE with the number of detected AGE products, pointing to the feasibility of MALDI as a quantitative tool.

Computer utilization in the Food and Drug Administration's bureau of foods mass spectrometry laboratory.

A network of computers is being used to support the Food and Drug Administration's Bureau of Foods mass spectrometry facility. Five mass spectrometers are each interfaced to at least 2 of the 6 dedicated minicomputers in the laboratory. This multiple interfacing provides data acquisition and processing backup, reducing the overall down-time. Selected data from all of the minicomputers can be sent to FDA's main computers via a digital cartridge tape recorder or paper tape. The digital cartridge tape recorder records data that are output from a minicomputer terminal and then plays it back on a terminal which is on-line with the main computer. This main computer stores and edits data; plots spectra for reports, data banks, and publications; and carries out some data processing. Multiple interfacing also serves to supplement the capabilities of the 8-year-old Finnigan MAT (formerly Varian MAT) SS-100 data system (Sperry-Univac/V-76) with the newer and more powerful Finnigan MAT INCOS (Data General/Nova 3) data system. The SS-100 data system is also enhanced by the substitution of the 110 baud paper tape with a 9600 baud cartridge tape recorder for I/O of system bootstraps, BASIC programs, and raw data.

Field desorption mass spectrometry of cyanogenic glycosides.

The field desorption mass spectra of several underivatized cyanogenic glycosides exhibit molecular ions or ions derived from the parent compound by protonation and alkali metal cationization. Abundant fragment ions are present and can be readily related to structure. Significant deviations from established fragmentation pathways are observed due to the nature of the aglycone. The ability to successfully determine the presence of cyanogenic glycosides by field desorption is demonstrated in crude extracts isolated from Vicia sativa, a food-contaminating plant material.

Isolation and identification of xanthomegnin, viomellein, rubrosulphin, and viopurpurin as metabolites of penicillium viridicatum.

Four of the metabolites of Penicillium viridicatum 66-68-2 grown on rice cultures were isolated and identified as xanthomegnin, viomellein, rubrosulphin, and viopurpurin. Melting points, elemental analysis, and infrared, ultraviolet, and field desorption and electron impact mass spectra of the isolated compounds were consistent with values reported in the literature for these compounds. In addition, diacetate and triacetate derivatives were prepared, and the chemical and physical analyses of the derivatives were also consistent with literature data. Proton magnetic resonance spectroscopy and thin-layer chromatography were also used for the additional identification of selected compounds.

Field desorption mass spectrometry of mycotoxins and mycotoxin mixtures, and its application as a screening technique for foodstuffs.

The field desorption mass spectra of a variety of mycotoxins have been studied. These include the 4 aflatoxins B1, B2, G1, and G2, rubratoxin B, T-2 toxin, and zearalenone, as well as mixtures of these mycotoxins. The spectra of all of the mycotoxins exhibited molecular ions [M]+. Under the conditions employed, only rubratoxin B exhibited major fragmentation. The field desorption technique has been applied to the analysis of both spiked and naturally contaminated extracts of foodstuffs. The potential of the method as an analytical screening technique for the presence of mycotoxins has been evaluated.

Determination of hexachloro-1,3-butadiene in spinach, eggs, fish, and milk by electron capture gas-liquid chromatography.

Hexachloro-1,3-butadiene (HCBD), a waste product formed in the manufacture of perchloroethylene and trichloroethylene, has been found in fish from the lower Mississippi River basin. The AOAC official method for organochlorine pesticide residues in fatty and nonfatty foods has been modified for the determination of HCBD residues in selected food commodities. Acetonitrile extracts of nonfatty foods, or the combined acetonitrile extracts obtained in acetonitrile-petroleum ether partitioning of fat isolated from fatty foods, are diluted with water and extracted with petroleum ether. The petroleum ether extracts are chromatographed on Florisil and HCBD is eluted with petroleum ether. The elute is analyzed by gas-liquid chromatography with an electron capture detector. Average recoveries of HCBD from fortified samples of fatty and nonfatty foods were greater than 90% in the interlaboratory trials of the method.