An old workhorse for new applications: Fe(dpm)3 as a precursor for low-temperature PECVD of iron(III) oxide.

An iron(III) ß-diketonate complex, Fe(dpm)3 (Hdpm = 2,2,6,6-tetramethyl-3,5-heptanedione), has been investigated as a potential precursor for plasma enhanced chemical vapor deposition (PECVD) of iron(III) oxide nanomaterials. Thanks to the combined experimental-theoretical approach, spectroscopic properties, spin state, thermal behavior and fragmentation pathways of Fe(dpm)3 have been carefully analysed, obtaining an excellent agreement between simulation and experiment. Preliminary PECVD tests evidenced the possibility of obtaining pure and homogeneous Fe2O3 deposits with controlled nano-organization at temperatures as low as 100 °C, even on flexible plastic substrates. The present results open up intriguing perspectives for the exploitation of Fe(dpm)3 as an efficient molecular source for the preparation of nanostructured iron(III) oxides to be used in energetics and gas sensing applications.

High-density lipoprotein oxidation in type 2 diabetic patients and young patients with premature myocardial infarction.

BACKGROUND AND AIMS: ApoA-I can undergo oxidative changes that reduce anti-atherogenic role of HDL. The aim of this study was to seek any significant differences in methionine sulfoxide (MetO) content in the ApoA-I of HDL isolated from young patients with coronary heart disease (CHD), type 2 diabetics and healthy subjects. METHODS AND RESULTS: We evaluated the lipid profile of 21 type 2 diabetic patients, 23 young patients with premature MI and 21 healthy volunteers; we determined in all patients the MetO content of ApoA-I in by MALDI/TOF/TOF technique. The typical MALDI spectra of the tryptic digest obtained from HDL plasma fractions all patients showed a relative abundance of peptides containing Met(112)O in ApoA-I in type 2 diabetic and CHD patients. This relative abundance is given as percentages of oxidized ApoA-I (OxApoA-I). OxApoA-I showed no significant correlations with lipoproteins in all patients studied, while a strong correlation emerged between the duration of diabetic disease and OxApoA-I levels in type 2 diabetic patients. CONCLUSIONS: The most remarkable finding of our study lies in the evidence it produced of an increased HDL oxidation in patients highly susceptible to CHD. Levels of MetO residues in plasma ApoA-I, measured using an accurate, specific method, should be investigated and considered in prospective future studies to assess their role in CHD.

The chemical characterization of melanin contained in substantia nigra of human brain.

The pigment of substantia nigra human brain has been extracted by a mild procedure consisting of washes with phosphate buffer, methanol and incubation with SDS-proteinase. Pyrolysis gas chromatography mass spectrometry, infrared spectrometry, termogravimetric analysis and elemental analysis were the techniques used for the chemical characterization. An indole moiety bound to a sulfur containing amino acid and to palmitic acid were the main aspects found in the structure. The presence of a 7% inorganic component was observed. This probably contains Fe, Cu, Zn and Cr which are also relevant, for the formation and the role of melanin in substantia nigra neurons. The fatty acid moiety is chemically bound to the indole structure as it was not eliminated by repeated methanol washing. The same situation occurs for the sulfur containing group. Considering these data and the most abundant molecules present in substantia nigra the precursor of neuromelanin seems to be a cysteinyl-catechol, to which is then bound a palmityl group.

A study on in vitro glycation processes by matrix-assisted laser desorption ionization mass spectrometry.

The number of glucose molecules condensed on glycated bovine serum albumin have been easily determined by means of matrix-assisted laser desorption/ionization mass spectrometry. Measurements were carried out on samples from incubation of the protein with glucose at different concentrations (0.02 M, 0.2 M, 2 M and 5 M). A clear increase in molecular mass of BSA with respect to incubation time is detected. In contrast to what is observed with fluorescence, the plots of molecular mass increase vs. incubation time show the occurrence of a steady state, corresponding to the complete saturation of all the protein sites reactive against glucose. Comparison of fluorescence and molecular mass data reveals that some further reactions, different from condensation, must take place, which could be in principle either intramolecular or originated by reactivity of modified condensed glucose moieties vs. free glucose.

Identification of furoyl-containing advanced glycation products in collagen samples from diabetic and healthy rats.

The compounds resulting from the reaction of glucose with proteins (advanced glycation products) can be important markers of chronic diabetic complications. To test the possible diagnostic value of advanced glycation products containing the furoyl moiety, collagen samples from diabetic and healthy rats were analyzed by parent ion spectroscopy. In our study, we compared normal collagen, diabetic collagen and normal collagen incubated with different glucose concentrations and we employed different hydrolysis procedures (HCl and proteinase). Mass spectroscopic measurements performed on hydrolyzed samples showed that either different samples or different hydrolysis procedures produce a similar set of furoyl-containing compounds. 2-(2-Furoyl)-4(5)-(2-furanyl)-1H-imidazole (FFI) which has been reported to be one of the advanced glycation products, was never found in any of the samples examined. Hence neither FFI nor furoyl-containing molecules can be considered markers of advanced glycation processes.

Advanced glycation end products/peptides: an in vivo investigation.

Advanced glycation end products/peptides (AGE/peptides) originate by in vivo enzymatic digestion of nonenzymatically glycated proteins, which are produced by reaction of glucose with primary amino groups present in the protein chain following the Maillard pattern. AGE/peptides are highly reactive species and can interact with tissue and circulating proteins, leading to tissue modification and impaired protein functionality. Serum levels of AGE/peptides are reported to be particularly high in diabetes (in terms of higher production) or in end-stage renal disease (in terms of accumulation). For these reasons, their structural identification is of high interest, giving information on their relationship with the pathological state and allowing the design of possible therapeutic interventions. We report here some preliminary results obtained by liquid chromatography/electrospray ionization/mass spectrometry (LC/ESI/MS) and matrix-assisted laser desorption ionization MS (MALDI-MS) investigations carried out on the low-molecular-weight serum peptide fraction from 10 healthy subjects, 10 patients with poorly controlled diabetes, and 10 patients with end-stage nephropathy.

Evaluation of glyoxal and methylglyoxal levels in uremic patients under peritoneal dialysis.

Advanced glycation end products (AGEs) accumulate in serum and tissues of patients with chronic renal failure, even in the absence of diabetes, and a different clearance of these species has been observed by hemodialysis and peritoneal dialysis (CAPD). Furthermore, it has been shown that not only AGE but also 1,2-dicarbonyl compounds are formed during heat sterilization of glucose-based peritoneal dialysis fluids. Therefore, we investigated the level of some AGEs (pentosidine and free pentosidine) and dicarbonyl compounds (glyoxal and methylglyoxal) in end-stage renal disease patients subjected to peritoneal dialysis. Samples (20 from healthy subjects, 16 from uremic patients before and after 12 h of peritoneal dialysis) were analyzed, and the plasma and dialysate levels of glyoxal, methylglyoxal, pentosidine, and free pentosidine were determined. In plasma of uremic patients, mean values of pentosidine showed a small decrease after dialysis and were always higher than those of healthy control subjects. An analogous trend was observed for free pentosidine. In the case of peritoneal dialysate, no pentosidine and free pentosidine were found at time zero, whereas both compounds were detected after 12 h of dialysis. Glyoxal and methylglyoxal mean levels showed a decrease in plasma after dialysis even if their values were always higher than those of healthy control subjects. Surprisingly, an analogous trend was observed also in dialysate. These results might indicate that glyoxal and methylglyoxal already present in the dialysis fluid react with the peritoneal matrix proteins, accounting for the gradual loss of peritoneal membrane function that is often observed in patients subjected to CAPD for a long time.

Surfactant self-assembling in gas phase: electrospray ionization- and matrix-assisted laser desorption/ionization-mass spectrometry of singly charged AOT clusters.

The self-assembling of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) in gas phase has been investigated by electrospray ionization- and matrix-assisted laser desorption/ionization mass spectrometry. Large surfactant clusters with an aggregation number close to that found in apolar media have been observed either as positive or negative ions. Moreover, the marked predominance of singly charged species as well as preliminary theoretical calculations strongly suggest an aggregate structure characterized by an internal hydrophilic core hosting the extra charge surrounded by an apolar shell constituted by the surfactant alkyl chains. This structure is similar to that of the more familiar reversed micelles formed when an appropriate surfactant is solubilized in apolar solvents. Finally, similar trends are observed independently either on the ionization technique or the polarity of the solvent used. This, together with the large dependence of the aggregation number on the flow rates, strongly indicates that self-assembling of the surfactant molecules occurs during the evaporation step.

Analysis of plasma cholesterol oxidation products using gas- and high-performance liquid chromatography/mass spectrometry.

The application of gas chromatography and high-pressure liquid chromatography/mass spectrometry techniques for analysis of plasma cholesterol oxidation products is described. Cholesterol oxides that are widely identified in biological samples were subjected to gas (GC) and high-pressure liquid chromatographic (HPLC) separations, and their detection and characterization by mass spectrometry (MS) were compared. Analysis of cholesterol oxides from plasma samples revealed distinct advantages for each method according to the specific cholesterol oxide in question. Whereas HPLC/MS analysis of cholesterol oxides provided less resolution and lower sensitivity as compared to GC/MS, a distinct advantage was evident for direct measurements of cholesterol-7-hydroperoxides and 7-ketocholesterol. These two cholesterol oxides are particularly sensitive to storage in solvents, derivatization procedures, and analytical conditions used for GC analysis, which are minimized or avoided using the HPLC/MS conditions described. Analysis of human and rabbit plasma samples identified cholest-5-ene-3 beta, 7 beta-diol (7 beta-hydroxycholesterol); 5,6 alpha-epoxy-5 alpha-cholestan-3 beta-ol (cholesterol-5 alpha, 6 alpha-epoxide); 5 alpha-cholestane-3 beta, 5,6 beta-triol (cholestanetriol); 3 beta-hydroxycholest-5-ene-7-one (7-ketocholesterol); and 5,6 beta-epoxy-5 beta-cholestan-3 beta-ol (cholesterol-5 beta,6 beta-epoxide) as commonly occurring components (trivial names indicated in parentheses). The latter two compounds were dramatically increased in hypercholesterolemic samples and were found in approximately equal amounts in the free cholesterol and cholesteryl ester fractions. Although most of the plasma cholesterol oxides are found in the dietary cholesterol, others are not, particularly cholesterol-5 beta,6 beta-epoxide, suggesting that at least some of these compounds are formed by in vivo oxidation of cholesterol. Despite the readily measurable levels of the above cholesterol oxides, as well as other less prominent oxides, there was no evidence of cholesterol-7-hydroperoxides associated with plasma free cholesterol. Although several of the plasma cholesterol oxides may derive from cholesterol-7-hydroperoxides, it appears that the latter are either unstable and decompose in plasma, are metabolized to other cholesterol oxidation products, or break down during their isolation.

Matrix-assisted laser desorption/ionization mass spectrometry, enzymatic digestion, and molecular modeling in the study of nonenzymatic glycation of IgG.

The glycation-induced functional change of immunoglobulins is of particular interest. The glycation levels of IgG in 10 healthy subjects and 20 diabetic patients with different degrees of metabolic control were studied by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. It reveals the number of glucose molecules that have condensed on the protein, which range from 1 to 5 for healthy subjects, from 5 to 9 for well controlled diabetic patients, and from 10 to 25 for poorly controlled ones. The identification of the most favored glycation sites has been obtained by MALDI analysis of standard and in vitro glycated IgG and plasma protein fraction of a healthy subject after digestion with papain, releasing Fab and Fc fragments of the molecule. Both experiments, as well as molecular modeling of the whole protein, confirm that the most of glucose molecules have condensed on the Fab fragment of IgG, suggesting that the immune deficiency observed in diabetic patients may be explained at the molecular level by a more effective glycation of the Fab fragment, thus inhibiting the process of molecular recognition between antibody and antigen.

The potential of matrix-assisted laser desorption/ionization mass spectrometry in the quality control of water buffalo mozzarella cheese.

Adulteration by addition of bovine milk to water buffalo milk employed for mozzarella cheese production is often observed. Water buffalo milk and mozzarella cheese were analysed by matrix-assisted laser desorption/ionization mass spectrometry in order to achieve their rapid and accurate characterization and to evaluate possible fraudulence in mozzarella cheese production.

Matrix-assisted laser desorption/ionization, fast atom bombardment and plasma desorption mass spectrometry of polyethylene glycol esters of (2-benzothiazolon-3-yl)acetic acid.

Fast atom bombardment (FAB), matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and plasma desorption (PD) mass spectra of newly synthesized polyethylene glycols (PEGs), (M(w) 600-4000 Da) chemically modified with biologically active (2-benzothiazolon-3-yl)acetyl end-groups are described (products 1-6). The spectra were also used for the determination of the molecular mass characteristics (number average (M(n)) and weight average (M(w)) molecular masses) of the initial and modified PEGs. As expected, M(n) and M(w) of the modified samples are higher than those of the non-modified samples. However, it is shown that molecular mass dispersity (determined by the comparison of the polydispersity indices (PDI = M(w)/M(n)) of both types of PEGs) essentially do not change during this modification. The FAB mass spectra, together with molecular species, show the presence of abundant [M + Na](+) ions of product 1 and [M + Na + H](+) species of 2 and 3, and [M + Na + 2H](+) of product 4. Two main series of fragment ions, derived from the cleavage of the ether bonds, are observed. The number fractions of the molecular adduct ions and fragment adduct ions, determined from the FAB and PD mass spectra of the modified PEGs, are compared. The MALDI-TOF mass spectra of compounds 1-6 show the presence of two series of polymers. The most abundant peaks are due to [M + Na](+) and [M + K](+) ions originating from the polymers, in which the two terminal hydroxyl groups of PEGs are esterified with (2-benzothiazolon-3-yl)acetic acid. The less abundant peaks are due to the monosubstituted polymers.

Advanced glycation end products: a highly complex set of biologically relevant compounds detected by mass spectrometry.

Structural information on 'AGE-peptides,' a class of substances belonging to advanced glycation end products (AGE) and originating by proteolysis of glycated proteins, was gained through various analytical approaches on the mixture produced by proteinase K digestion of in vitro glycated bovine serum albumin. Both matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and high-performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS) were employed, and the results were compared with those from conventional spectroscopic methods (UV, fluorescence, gel permeation). The data acquired by the various techniques all depict the digestion mixtures as highly complex, with components exhibiting molecular mass in the range 300-3500 Da. In the analysis of HPLC/ESI-MS data, identification of AGE-peptides was facilitated by 3D mapping. Structural information was gained by means of multiple mass spectrometric experiments.

Characterization studies and cytotoxicity assays of Pt(II) and Pd(II) dithiocarbamate complexes by means of FT-IR, NMR spectroscopy and mass spectrometry.

The precursors [M(ESDTM)Cl(2)] (M=Pt(II), Pd(II); ESDTM=EtO(2)CCH(2)(CH(3))NCS(2)Me, S-methyl(ethylsarcosinedithiocarbamate)) were synthesized as previously reported [J. Inorg. Biochem. 83 (2001) 31] and used to obtain [M(ESDT)Cl](n) (ESDT=ethylsarcosinedithiocarbamate anion) species. The complexes formed through reaction between [M(ESDT)Cl](n) and the two chiral amino-alcohols synephryne (Syn) and norphenylephrine (Nor) have been synthesized, with the ultimate goal of preparing mixed dithiocarbamate/amino metal complexes of the type [M(ESDT)(Am)Cl] (Am=Syn, Nor). These compounds have been isolated, purified and characterized by means of FT-IR, mono- and bidimensional NMR spectroscopy and mass spectrometry ESI/MS (electronspray mass spectra). The experimental data suggest that in all cases coordination of the dithiocarbamate ligand (ESDT) takes a place through the two sulfur atoms, the -NCSS moiety acting as a symmetrical bidentate chelating group, in a square-planar geometry around the M(II) ion, while the other two coordination positions are occupied by the chlorine atom and the amino-alcohol ligand, respectively. In particular, synephrine and norphenylephrine appear to be bound to the metal atom through the amino nitrogen atom by means of a dative bond. Finally, the biological activity of the new complexes has been studied by MTT (tetrazolio salt reduction) test and by detecting the inhibition of DNA synthesis and of clonal growth in various cancer cell lines. All Pd(II) derivatives showed a noticeable activity very close to that of cisplatin, used as reference drug. Moreover, they showed significantly reduced cross-resistance to cisplatin in a pair of cell lines (2008/C13*) with known acquired cisplatin resistance mechanisms.

Mass spectrometric approaches in structural identification of the reaction products arising from the interaction between glucose and lysine.

The products arising from the reaction of alpha-protected lysine with glucose have been studied by different techniques, viz. high-performance liquid chromatography (HPLC) with UV detection, fast atom bombardment (FAB) mass spectrometry (MS), and HPLC/MS. Most of the analytical data were obtained by the last approach and allowed identification of many molecular species for a thorough knowledge of possible reaction pathways or structural data already available in the literature.

A comparison between MALDI-MS and CE-MS data for biomarker assessment in chronic kidney diseases.

Non-invasive detection of diseases, based on urinary proteomics, is becoming an increasingly important area of research, especially in the area of chronic kidney disease (CKD). Different platforms have been used in independent studies, mostly capillary-electrophoresis coupled ESI-MS (CE-MS), liquid chromatography coupled mass spectrometry, and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). We have compared the performance of CE-MS with MALDI-MS in detecting CKD, based on a cohort of 137 urine samples (62 cases and 75 controls). Data cross-talk between the two platforms was established for the comparison of detected biomarkers. The results demonstrate superior performance of the CE-MS approach in terms of peptide resolution and obtained disease prediction accuracy rates. However, the data also demonstrate the ability of the MALDI-MS approach to separate CKD patients from controls, at slightly reduced accuracy, but expected reduced cost and time. As a consequence, a practical approach can be foreseen where MALDI-MS is employed as an inexpensive, fast, and robust screening tool to detect probable CKD. In a second step, high resolution CE-MS could be used in those patients only that scored negative for CKD in the MALDI-MS analysis, reducing costs and time of such a program.