Claudio Pratesi - Academia.edu (original) (raw)

Papers by Claudio Pratesi

Rivista Italiana Delle Sostanze Grasse, 2001

A very efficient reductive derivatization was applied to linear alkylbenzene sulfonic acids or sa... more A very efficient reductive derivatization was applied to linear alkylbenzene sulfonic acids or salts (LAS) and to alkyl sulfonates (SAS) to make volatile derivatives that can be analysed by GC-MS. The sulfonic acid or salt groups are reduced to thiotrifluoroacetate derivatives by using iodide-trifluoroacetic anhydride in dimethylformamide in a one-step reaction. By this method, the LAS derivatives show gas-chromatogram profiles that are comparable with those of the parent LABs, so that alkyl chain distribution, phenyl isomers and even minor components such as tetralins or diphenylalkanes can be easily identified and quantified. When the method is applied to alkyl sulphates (AS) and to alkyl ethoxysulphates (AES) the alkyl-thiotrifluoroacetate derivatives that form are not stable, and react with iodide ions to give the corresponding alkyl iodides.

Biochemical analysis of the soluble hydrogenase from the thermophilic organism Acetomicrobium fla... more Biochemical analysis of the soluble hydrogenase from the thermophilic organism Acetomicrobium flavidum revealed that the enzyme is an ad2 tetramer, with the a and /l subunits having a molecular mass of 50 kDa and 25 kDa, respectively. The most important biochemical properties of the enzyme are a specific activity of 77 pmol min-I (mg protein)-l, a Km for methylviologen of 02 mM, a pH optimum of 7-5 and a T5,, of about 70 "C. In addition, the enzyme is remarkably stable to oxygen inactivation, retaining full activity after 24 h exposure to air. By using oligodeoxynucleotides designed on the basis of the N-terminal sequences of the two subunits, the corresponding genes have been isolated and sequenced. When compared to the other hydrogenases so far characterized, the A. flawidurn hydrogenase appears to be a typical [Ni-Fe] enzyme. The hydrogenase was expressed in Escherichia coli at high levels in a soluble form but it was not active. The analysis of the recombinant large subunit...

Eniricerche SPA, Via F. Maritano 26,20097 San Donato Milanese, Milan, Italy D-Amino acids, import... more Eniricerche SPA, Via F. Maritano 26,20097 San Donato Milanese, Milan, Italy D-Amino acids, important intermediates in the production of semisynthetic penicillins and cephalosporins, are currently prepared from the corresponding hydantoins using bacterial biomass containing two enzymes, hydantoinase and carbamylase. These enzymes convert the hydantoins first into carbamyl derivatives and then into the corresponding D-amino acids. In an attempt to select more efficient biocatalysts, the hydantoinase and carbamylase genes from Agrobacterium tumefaciens (formerly A. radiobacter) were cloned in Escherichia coli. The genes were assembled to give two operon-type structures, one having the carbamylase gene preceding the hydantoinase gene and the other with the carbamylase gene following the hydantoinase gene. The recombinant strains stably and constitutively produced the two enzymes and efficiently converted the corresponding hydantoins into p-hydroxyphenylglycine and phenylglycine. The ord...

The hydBGDA genes, which encode the four subunits /?, y, S and a of the [Ni-Fe] hydrogenase from ... more The hydBGDA genes, which encode the four subunits /?, y, S and a of the [Ni-Fe] hydrogenase from the archaeon Pymcoccus furiosus, have been isolated and sequenced using a PCWIPCR-based strategy. From the sequence analysis it appears that the four structural genes are tightly linked and organized in a single transcription unit. The hydD and hydA gene products are related to the small and the large subunits of several archaeal and eubacterial [Ni-Fe] hydrogenases with an overall degree of sequence relatedness ranging from 35 YO to 50% (identity +similarity). In particular, the amino acid sequence motifs involved in the accommodation of nickel and iron-sulfur clusters are conserved. In addition, the database search revealed that the hydB and hydG gene products are homologous to the asrA-and asrB-encoded subunits of the sulf ite reductase enzyme from Salmonella typhimurium. This is particularly interesting in view of the recent finding that the P. furiosus hydrogenase appears t o be a bifunctional enzyme endowed with both proton-and sulfurreducing activities.

Author Institution: Department of Chemistry, Syracuse University; Instituto di Biofisica, Syracus... more Author Institution: Department of Chemistry, Syracuse University; Instituto di Biofisica, Syracuse University

Journal of Surfactants and Detergents

Derivatization of a C12Φ-methyl ester sulfonic acid by using iodide-trifluoroacetic anhydride in ... more Derivatization of a C12Φ-methyl ester sulfonic acid by using iodide-trifluoroacetic anhydride in dimethylformamide in a one-step reaction yielded derivatized sulfonic thiotrifluoroacetates. The latter have been analyzed by gas chromatography-mass spectrometry (MS) and liquid chromatography-MS techniques so that, for the first time, the acid composition and the mono sulfonic acid isomer distribution are shown.

Tenside Surfactants Detergents, 2010

ABSTRACT Φ-Sulfo Fatty Methyl Esters sulfonates (Φ-MES) were obtained via sulfoxidation of fatty ... more ABSTRACT Φ-Sulfo Fatty Methyl Esters sulfonates (Φ-MES) were obtained via sulfoxidation of fatty acid methyl esters (FAME) with SO2, O2, and ultraviolet light of appropriate wavelength. Expectedly, these products may be used as linear alkylbenzene sulfonate (LAS) and alkyl ether sulfate (AES) partners, either in heavy-duty or in hand dishwashing liquids. Φ-MES are new anionic surfactants that can be regarded as potential components for detergent formulations and body care products as well. In this work we summarize the most relevant results of our research started fifteen years ago, on the synthesis, separation and analysis of Φ-sulfo fatty methyl ester sulfonates known as Φ-MES, and we update our last findings. We have to point out that we are for the time being, the only research group in the world to have published our research on Φ-MES. This paper describes the optimum batch conditions for the sulfoxidation of FAME and a reaction mechanism is proposed. The paper depicts an improved workup for the separation of reaction products from non reacted methyl ester and the GC-MS analysis of Φ-sulfo fatty methyl ester sulfonate is shown. Finally, an interpretation of conversion and selectivity of sulfoxydation reaction is given. Read More: http://www.hanser-elibrary.com/doi/abs/10.3139/113.110048

International Journal of Peptide and Protein Research, 2009

The dehydropeptide Ac-delta Phe-L-Val-delta Phe-NH-Me, containing two dehydrophenylalanine (delta... more The dehydropeptide Ac-delta Phe-L-Val-delta Phe-NH-Me, containing two dehydrophenylalanine (delta Phe) residues, crystallizes from methanol/water in space group P212121, with a = 12.622 (1), b = 12.979 (1), and c = 15.733 (1) A. In the solid state, the molecular structure is characterized by the presence of two intramolecular hydrogen bonds which form two consecutive beta-bends. The (phi, psi) torsion angles of the three residues are very similar and close to the standard values of type III beta-bends, so the molecular conformation corresponds to an incipient right-handed 3(10)-helix, only slightly distorted. In the crystal, the molecules are linked by head-to-tail hydrogen bonds, thus forming continuous helical columns packed in antiparallel mode. There are no lateral hydrogen bonds; the only interactions are hydrophobic contacts between the apolar side chains of neighboring helical columns.

Rivista Italiana Delle Sostanze Grasse

The characterization of alcohol ethoxylates (AE) has been approached in our laboratory for many y... more The characterization of alcohol ethoxylates (AE) has been approached in our laboratory for many years. Both Atmospheric Pressure Chemical Ionization (APCI) and Electro Spray Ionization (ESI) Mass Spectrometry techniques have been used with pure and derivatized AE. The APCI techni-que revealed the problem of low sensitivity for lower ethoxymers and showed some thermal degradation with some types of derivatized AE. Better results were obtained with LC-MS in ESI mode with non-derivatized AE but free alcohol and low ethoxymers were again lost because of low sensitivity. The outcome of all our approaches to have reliable and accurate EO distributions, was to convert alcohol ethoxylates into alcohol ethoxy sulfates (AES) followed by LC-MS analysis in ESI negative ion mode. The mass spectra of AS and AES present only R-OSO 3 – ions and all ethoxymers have almost the same molar response, indicating that their responses do not depend on the number of ethoxy units as in the case of underivati...

Φ-Sulfo Fatty Methyl Esters sulfonates (- MES) are new anionic surfactants obtained via sulfoxid... more Φ-Sulfo Fatty Methyl Esters sulfonates (- MES) are new anionic surfactants obtained via sulfoxidation of fatty acid methyl esters (FAME) with SO2, O2, and ultraviolet light of appropriate wavelength. The designation of Φ refers to the random positioning of SO3 in the alkyl chain. In this work we summarize the most relevant results of our research started fifteen years ago, on the synthesis, separation, analysis and performance of -sulfo fatty methyl ester sulfonates known as -MES, and we update our last findings . We have to point out that we are for the time being, the only research group in the world to have published our research on -MES. This work describes the optimum batch conditions for the sulfoxidation of FAME and a reaction mechanism is proposed. The paper depicts an improved workup for the separation of reaction products from non reacted methyl ester and the GC-MS analysis of - sulfo fatty methyl ester sulfonate is shown. Besides, an interpretation of conversion and ...

Φ-Sulfo Fatty Methyl Esters sulfonates (Φ- MES) are new anionic surfactants obtained via sulfoxid... more Φ-Sulfo Fatty Methyl Esters sulfonates (Φ- MES) are new anionic surfactants obtained via sulfoxidation of fatty acid methyl esters (FAME) with SO2, O2, and ultraviolet light of appropriate wavelength. The designation of Φ refers to the random positioning of SO3 in the alkyl chain. In this work we summarize the most relevant results of our research started fifteen years ago, on the synthesis, separation, and analysis of Φ-sulfo fatty methyl ester sulfonates known as Φ-MES, and we update our last findings . This work describes the optimum batch conditions for the sulfoxidation of FAME and a reaction mechanism is proposed. The paper depicts an improved workup for the separation of reaction products from non reacted methyl ester and the GC-MS analysis of Φ- sulfo fatty methyl ester sulfonate is shown. Besides, an interpretation of conversion and selectivity of sulfoxydation reaction is given. Even if this paper doesn’t describe performance, we can advance that the experimental results o...

Tenside Surfactants Detergents, 2008

Sulfonation with SO3 of an oleic methyl ester has led to a mixture of sulfonates with potential p... more Sulfonation with SO3 of an oleic methyl ester has led to a mixture of sulfonates with potential properties as a surfactant, an emulsifier or even a wetting agent that can be used in detergent formulations. For the first time, the products from the sulfonation reaction with SO3 are identified.

Journal of Molecular Graphics, 1991

Journal of Surfactants and Detergents, 2004

The characterization of alcohol ethoxylates (AE) to determine ethylene oxide (EO) adduct distribu... more The characterization of alcohol ethoxylates (AE) to determine ethylene oxide (EO) adduct distribution has been studied in our laboratory for many years by using high-performance liquid chromatography-mass spectrometry (LC-MS). This paper describes the LC-MS approach being used to analyze both nonderivatized and derivatized AE. We conclude that the best way to determine EO adduct distribution is by first converting the