RESUMEN

Accumulation of brown products in long-lived proteins might be an important factor in determining long-term diabetic complications. Fluorescent chromophore 2-(2-furoyl)-4-(5)-(2-furanyl)-1H-imidazole (FFI), isolated from hydrolyzed brown products synthesized in vitro, was proposed as a specific brown product responsible for functional and structural changes in long-lived proteins. In this study, an attempt was made to demonstrate by means of collision spectroscopy the presence of FFI in collagen samples taken from diabetic rats. Diabetic rat collagen samples showed mean values of absorbance per milligram of 4-hydroxy-L-proline significantly higher than those observed in nondiabetic rats, suggesting higher FFI levels. Surprisingly, all collagen samples from diabetic and nondiabetic rats gave collision spectra in which no peak diagnostic of FFI presence was observed. These data suggest that the absorbance level observed in diabetic rats is not due to the presence of FFI but to structurally related compounds, which are being investigated by means of mass spectrometry.

Asunto(s)

RESUMEN

Melanins are naturally occurring macromolecules whose structural complexity appeared evident from the first researches of Quilico. Their structural characterization remains a difficult problem, mainly due to the physico-chemical properties of such compounds. Melanins are insoluble in organic solvents as well as aqueous solutions and are infusible. Consequently the traditional chemical degradation and physicochemical methods such as ultraviolet, infrared, 1H and 13C nuclear magnetic resonance, ESR (electron spin resonance), XPS (X-rays photoelectron spectroscopy) and X-ray diffraction have led, until now, to limited information on melanin chemical structure.

Asunto(s)

RESUMEN

The build-up of brown products on long-lived proteins could be an important factor in determining long-term diabetic complications. A brown product 2-(2-furoyl)-4(5)-(2-furanyl)-1H-imidazole (FFI), present in the acid hydrolysate mixtures of beta-polylysine and beta-albumin has been identified by collisional spectroscopy, using a commercial double-focusing, reverse-geometry mass spectrometer. Using this approach the analyses were carried out without any sample derivatization or need for chromatographic separation procedures.

Asunto(s)

RESUMEN

The direct determination of 2-(2-furoyl)-4(5)-(2-furanyl)-1H-imidazole (FFI), present in the acid hydrolysis products of B-poly(L-lysine) and B-albumin and which appears to be a key intermediate in the physicochemical changes occurring during the incubation of protein with glucose, has been carried out by collisional spectroscopy, using a commercial double-focusing, reverse-geometry mass spectrometer and without any sample derivatization and chromatographic separation procedures.

Asunto(s)

RESUMEN

The mass spectral behaviour of pentachlorophenyl beta-carbonylenolate phosphino nickel(II) square planar complexes has been investigated under electron impact (EI) and field desorption (FD) conditions. The fragmentation has been interpreted on the basis of the B/E linked scans and mass-analysed ion kinetic energy (MIKE) techniques. The acetylacetonate diphenylphosphino complex was found to undergo a solid state reaction in the probe, which led to the generation in situ of a nickel(III) chloro complex. Careful control of instrumental conditions and computer-assisted EI measurements made it possible to characterize the addition products as [NiCl(C(6)Cl(5))(AcAc)PPh(2)Me] and to propose a mechanism for its solid state generation.

RESUMEN

A new analytical procedure for the identification of morphine in the hair of heroin addicts has been developed using collisional spectroscopy, on a commercially available, reverse geometry, double focusing instrument. Either collision-induced dissociation (B/E = const) linked scans or mass analysed ion kinetic energy spectra lead to an unequivocal and rapid determination of morphine in hydrolysed hair extract which may be compared with the data obtained by different and more traditional analytical methods.

Asunto(s)

RESUMEN

The structural investigation of four bio- and synthetic melanins, obtained by the action of polyphenol oxidase from potatoes and Psalliota campestris mushrooms and of tyrosinase from Sepia officinalis on tryptophan, or by means of performic oxidation, has been carried out by thermal decomposition performed in the ion source of a mass spectrometer. The structural characterization of the ionic species [C8H7ON](+.), common and abundant for all the examined compounds, has been obtained by accurate mass measurements and collisional spectroscopy. These mass spectrometric techniques have shown unequivocally for ionic species [C8H7ON](+.) the structure of 2-indolinone.

Asunto(s)

RESUMEN

A rapid and sensitive method for the selective detection and quantification of oxytetracycline residues at the ppb level in crude extracts of bovine milk and meat is described. The technique employed is a tandem mass spectrometric method: CAD MIKE spectrometry (collisionally activated decomposition mass-analysed ion kinetic energy spectrometry). Quantification is performed by single ion monitoring of CAD species of oxytetracycline and of its internal standard.

Asunto(s)