Enzo Benedetti

Determination of the Relative Amount of Nucleic Acids and Proteins in Leukemic and Normal Lymphocytes by Means of Fourier Transform Infrared Microspectroscopy

Previous Fourier transform infrared (FT-IR) spectroscopic studies on neoplastic and normal cells have shown different band profiles and intensity associated with absorptions of proteins and nucleic acids. In the present study, an interpretation of such differences has been attempted by comparing the spectra of DNA/RNA/protein mixtures with the spectra, particularly, obtained for lymphocytes from B-chronic lymphatic leukemia (B-CLL) patients and normal donors. FT-IR microspectroscopy analysis showed a good agreement between the intensity and the band profile of the spectra of leukemic lymphocytes and those of the binary mixture made up of 75% human serum albumin and 25% DNA. The addition of small amounts of RNA (1–5%) modified the band shape, making it more similar to the spectrum of normal lymphocytes. An attempt was also made to estimate the relative amounts of DNA and RNA. The results demonstrated an increase in the DNA/RNA ratio value in neoplastic lymphocytes with respect to that reported in literature for normal ones.

Determination of the secondary structure of isomeric forms of human serum albumin by a particular frequency deconvolution procedure applied to fourier transform IR analysis

A new deconvolution procedure was applied to the analysis of Fourier transform ir spectra of human serum albumin secondary structure in the native state and in states denatured by heat and acid treatment. The deconvolution method is based on the use of the Conjugate Gradient Minimization Algorithm, with the addition of suitable constraints directly obtained by the application to the measured spectrum of the second derivative operator. This method computes central band frequency, bandwidth, and amplitude of the different spectral components of conformation-sensitive amide bands. In the specific case, it was applied to analysis of the amide I band, and the quantitative determination of the different secondary structures (alpha-helix, beta-sheet, beta-turns, and random) was attempted for all the samples examined. The precision of the quantitative determination depends on the amounts of these structures present in the protein. The coefficient of variation is < 10% for values of amide I component > 15%. The accuracy was tested by comparing, by means of linear regression, the results obtained for human serum albumin, hemoglobin, alpha-chymotrypsin, and cytochrome c, using our method, with those obtained by x-ray crystallography and CD; the results obtained by other vibrational spectroscopic approaches were also compared. The fit standard error between x-ray and ir secondary structure values estimated by our method is 2.5% for alpha-helix, 7.16% for beta structures, and 5.1% for other structures (turns and random coils). Quantitative results are given for the secondary structures (alpha-helix, turns, and beta-strands) present in the native state (turns and beta-strands up to now unknown in aqueous solution), together with the percentages of these structures and additional ones (random coils and beta-sheets) formed during denaturization.

Infrared spectra and reactivity of DI-μ-halobis(halotricarbonylruthenium)

The IR spectra of the di-μ-halobis(halotricarbonylruthenium) complexes of formula [Ru(CO)3X2]2 (X = Cl, Br) have been studied in different solvents and a tentative assignment of the bands observed made. The change with time of the IR spectra in chloroform solution observed by several authors is due to the interaction of the compounds with the ethanol present in the solvent as stabilizer. The reactions of [Ru(CO)3X2]2 (X = Cl, Br) with oxygenated solvents, nitrogen and phosphorous ligands are described. Some complexes of type RuX2(CO)3L and RuX2(CO)2L2 (L = nitriles, pyridine or triphenylphosphine) have been isolated and characterized.

A New Approach to the Study of Human Solid Tumor Cells by Means of FT-IR Microspectroscopy

Cells coming from normal and neoplastic human lung tissue were analyzed by means of FT-IR microspectroscopy. Among the various methods tested to isolate the cells, mechanical treatment alone was found to yield the best results. Monolayers of cells were homogeneously distributed by cytocentrifuge preparation on BaF2 windows, and several spectra were obtained for different circular micro-areas of the order of one hundred microns in diameter. This procedure made it possible to obtain reliable spectra and to reject those containing additional bands due to impurities arising from the isolation treatment. Spectral differences between normal and neoplastic cells reflect an increase in the intensity of the bands corresponding mainly to PO2− symmetrical and asymmetrical vibrations of DNA in pathological samples with respect to normal ones. The value of the ratio of the integrated areas of the bands at 1080 and 1540 cm−1 due to DNA and proteins, respectively, makes it possible to differentiate between normal and abnormal cells, thus suggesting the use of this parameter as an original approach in the recognition of early neoplastic transformation undetectable by means of traditional procedures.

Asymmetric synthesis by chiral ruthenium complexes : II. Enantioselective hydrogenation of α,β-unsaturated carboxylic acids catalyzed by ruthenium complexes containing the ligand ()-diop

Abstract Cluster rutheniumcarbonyl hydrides complexes containing ()-DIOP as asymmetric ligand are efficient catalysts for asymmetric reduction of α,β-unsaturated acids at 90–120°C under hydrogen pressure. Optical yields up to 68% have been achieved. The course of the reaction has been investigated by IR spectroscopy using a high pressure cell.

FT-IR investigation of the structural changes of Sulcis and South Africa coals under progressive heating in vacuum

Two samples of coals coming from South Africa and Sulcis (Sardinia, Italy) were subjected to progressive heating up to 800°C in vacuum. The infrared (IR) spectra of the residuals obtained at 100°C intervals from room temperature to 800°C show spectral changes ascribed to transformations at the level of the organic and inorganic components. Comparing these results with those previously obtained by heating the same coals in the presence of air and examining their pyridinic extracts, it appears that the Sulcis coal with respect to the other coals contains a lower amount of clay-minerals. Furthermore, the IR analysis shows that this coal is nearer to being a lignite than a hard-coal.

New possibilities of research in chronic lymphatic leukemia by means of fourier transform-infrared spectroscopy-II

Ten samples of lymphocytes coming from patients affected by chronic lymphatic leukemia and ten samples from normal subjects were studied by FT-IR spectroscopy. Spectral differences observed between the two kinds of cells correspond to an increase of the intensities, in the leukemic samples with respect to the normal ones, of the bands corresponding mainly to PO2- symmetrical and asymmetrical stretching vibrations of DNA. The ratios of the integrated areas of the band at 1080 cm-1 mainly involving the symmetrical stretching vibration of the O-P-O linkages of DNA, and of the band at 1540 cm-1, due to the proteic components of the lymphocytes, assume different values for the two kinds of cells. These ratios can constitute an additional marker to diagnose chronic lymphatic leukemia and may be usefully employed to evidence the early phases of the disease.

Analytical infrared spectral differences between human normal and leukaemic cells (CLL) — I

Two series of normal and leukaemic lymphocytes were examined by infrared spectroscopy in order to try to find spectral differences connected with chemical and biological modifications. The bands at 965 and 530 cm-1 present only in the spectra of leukaemic lymphocytes, assume particular significance. The C-H stretching region furnishes useful indications about the different ratios of the methyl groups compared with the methylene ones in the two cases. The infrared bands characteristic of the leukaemic lymphocytes seem to be due to chemical modifications not involving the DNA chain.

Asymmetric synthesis by chiral ruthenium complexes : III. Regioselectivity and asymmetric induction in catalytic hydrogenation of α,β-unsaturated dicarboxylic acids

Abstract The homogeneous catalytic hydrogenation of citraconic and mesaconic acids in the presence of H4Ru4(CO)8[(—)-DIOP]2 gives, in addition to (—)(S)-methylsuccinic acid, a mixture of λ-lactones in ratios which depend on the substrate and the reaction temperature. An exceptionally high regioselectivity is obtained in the hydrogenation at 120°C of the more hindered carboxyl group of mesaconic acid.

LOW-TEMPERATURE AIR OXIDATION OF COAL AND ITS PYRIDINE EXTRACTION PRODUCTS - FOURIER-TRANSFORM INFRARED STUDIES

Abstract Fourier transform infrared spectroscopy has been used to study the evolution of the structure of a bituminous coal and its pyridine extraction products during oxidation. Different methods of analysis of the spectra have been used, such as curve-resolving routines, coupled to second derivative methods and area integration. The pyridine extract has been found to maintain the characteristic absorption bands of the original coal and to present marked susceptibility towards oxidation, to a greater extent than its parent coal. The analysis of the coal, extract and residue spectra and their comparison as oxidation proceeds, give an insight into the complex phenomena occurring. Pyridine extract spectra present a better separation of contributions of the bands involved, by the low temperature oxidation of low rank coals, particularly in the zones 3500-2800 and 1800-1500 cm −1 .