Biomedical subjects

C Giovannoli

Publications and source records attributed to C Giovannoli.

8 recordsLinked to original sources

PubMed2004

Multivariate analysis of the selectivity for a pentachlorophenol-imprinted polymer.

A pentachlorophenol (PCP)-imprinted polymer (MIP) was obtained by thermal polymerization of a mixture of template, 4-vinylpyridine and ethylene glycol dimethacrylate with molar ratio 1 +3 + 27, using as porogenic solvent methanol-water ( 3 + 1(v/v)). The polymer was packed in an HPLC column and selectivity towards 52 PCP-related phenols (22-chloro-, 21-alkyl-, 4-aryl-, 3-methoxy- and 6-polyphenols) was measured using acetonitrile-acetic acid (99 + 1(v/v)) as mobile phase. The same was made for a reference polymer obtained without pentachlorophenol (NIP). The molecular recognition properties of the imprinted polymer were expressed in terms of selectivity index (SI), calculated for each phenol as k(NIP)/k(MIP). Sixteen molecular descriptors were calculated for each molecule: qO, the partial charge of the phenolic oxygen atom; qH, the partial charge of the phenolic hydrogen atom; Deltaq, the absolute value of the difference qO - qH; HOMO, the highest occupied molecular orbital; LUMO, the lowest unoccupied molecular orbital; Deltaorb, absolute value of the difference HOMO - LUMO; micro(2), the square of total dipole moment; MW, the molecular weight; SAS, the solvent-accessible molecular surface area; hSAS, the hydrophobic solvent-accessible molecular surface area; Svdw, the van der Waals molecular surface area; hSvdw, the hydrophobic part of Svdw; MOv, the molecular ovality; RG, the radius of gyration; logP, the logarithm of n-octanol-water partition coefficient; pK, the phenolic dissociation constant. Correlations between selectivity index and these descriptors were searched utilizing multivariate principal component analysis (PCA). The multivariate model obtained by regression on the principal components correlate collectively several of the calculated descriptors with the polymer selectivity. The magnitude of the model's parameters shows that selectivity is strongly influenced by molecular descriptors having structural character, such as MW, hSvdw and logP, while the effect of molecular descriptors having electronic character, such as qO and pK, is much less marked.

Multivariate Analysis↗

PubMed2002

Catalytic and spectroscopic characterisation of a copper-substituted alcohol dehydrogenase from yeast.

Yeast alcohol dehydrogenase (Y-ADH) is widely studied for its biotechnological importance and various attempts to improve its catalytic properties have been made. In this paper, a catalytically active metal-substituted Y-ADH was prepared in vitro by substituting one zinc atom with copper. EPR and Raman spectroscopy suggest that copper maintains the same co-ordination geometry as zinc in native Y-ADH. The active Cu-ADH shows lower substrate affinity and lower specific activity (SA) than native ADH, but greater than a previously obtained Co-ADH. Furthermore, Cu-ADH maintains its catalytic efficiency in a wider pH range than native enzyme.

Alcohol Dehydrogenase↗

PubMed2001

Molecularly imprinted solid-phase extraction sorbent for the clean-up of chlorinated phenoxyacids from aqueous samples.

A molecularly imprinted polymer (MIP) was synthesized using the herbicide 2,4,5-trichlorophenoxyacetic acid as a template, 4-vinylpyridine as an interacting monomer, ethylendimethacrylate as a cross-linker and a methanol-water mixture as a porogen. The binding properties and the selectivity of the polymer towards the template were investigated by frontal and zonal liquid chromatography. The polymer was used as a solid-phase extraction material for the clean-up of the template molecule and some related herbicides (2,4-dichlorophenoxyacetic acid, fenoprop, dichlorprop) from river water samples at a concentration level of ng/ml with quantitative recoveries comparable with those obtained with a traditional C18 reversed-phase column when analyzed by capillary electrophoresis. The results obtained show that the MIP-based approach to the solid-phase extraction is comparable with the more traditional solid-phase extraction with C18 reversed-phase columns in terms of recovery, but it is superior in terms of sample clean-up.

2,4,5-Trichlorophenoxyacetic Acid↗

PubMed2000

Chromatographic characterization of molecularly imprinted polymers binding the herbicide 2,4,5-trichlorophenoxyacetic acid.

Two polymers binding the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were prepared by utilising the technique of the non-covalent molecular imprinting polymerisation in an aqueous medium. The polymers obtained were packed in HPLC columns and the effects of the mobile phase composition on the retention of the imprinting molecule and the selectivity of the stationary phases towards several analogous structures were studied by liquid chromatography. The columns showed a good level of selectivity towards the template and strictly related molecules. It was found that the molecular recognition mechanism acting on the columns was dependent on a combination of ion pair and hydrophobic interactions.

2,4,5-Trichlorophenoxyacetic Acid↗

PubMed2000

Optimization of the cyclodextrin-assisted capillary electrophoresis separation of the enantiomers of phenoxyacid herbicides.

An ethylcarbonate derivative of beta-cyclodextrin (beta-CD) with three substituents per molecule, hydroxypropyl-beta-CD and native alpha-CD have been tested as resolving agents in the capillary zone electrophoresis (CZE) separation of the four enantiomers of the herbicides mecoprop and dichlorprop. The performances of the three compounds have been quantified by means of two-levels full factorial design and the inclusion constants were calculated from CZE migration time data. Possible structure of inclusion complexes have been proposed, on the basis of molecular mechanics simulations.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1999

A general method to perform a noncompetitive immunoassay for small molecules.

A new general method to perform a noncompetitive immunoassay for low-molecular-mass analytes (less than 6000 Da) is described and checked using cortisol as a model system. The method is based on the use of a "polydentate ligand" (cortisol-poly(L-lysine) conjugate) able to block the antibody sites unoccupied by the analyte, followed by the replacement of an antibody-bound analyte by an enzyme-labeled analyte (cortisol-horseradish peroxidase), and permits the direct measurement of the analyte bound sites. The observed signal shows a near-linear correlation with the analyte concentration. The characteristics of interactions between the analyte and polydentate ligand with the specific antibody were studied to perform a preliminary evaluation of the noncompetitive immunoassay for cortisol. The noncompetitive assay was compared with a competitive immunoassay obtained under the same conditions and using the same reagents. The results of the experiments showed a lower detection limit for the noncompetitive model (0.15 ng mL-1 rather than 0.72 ng mL-1), emphasizing that the model is successful. Moreover, as the polydentate ligand is prepared from the same hapten used for the immunogen synthesis, this type of noncompetitive immunoassay appears generally applicable to all small molecules for which antibodies have been obtained.

Animals↗

PubMedDate not supplied

Functionalized biopolymers as soluble macromolecular chelating agents.

Two different conjugates of bovine serum albumin (BSA) with lysine and a derivative of imidazole have been synthesized to obtain watersoluble macromolecules with binding properties against bivalent transition metal ions. Syntheses have been carried out using the 60 aminogroups or the 99 carboxylic groups on BSA for the coupling reactions, with such molar ratios able to produce highly substituted BSA. The skill of each conjugate to bind metal ions in aqueous medium was studied through the use of titration curves with some metal ions, characterized by a good affinity for the free ligand. Both the conjugates allow us to recover a high number of metal ions per protein molecule, close to the number of ligand molecules on the BSA surface in the case of the lysine conjugate, whereas in the case of the imidazole conjugate M3L complexes are performed.

Biopolymers↗

PubMedDate not supplied

The complexation of mercury (II) and organomercurial compounds by 8-hydroxyquinoline-bovine serum albumin conjugates.

The complexing properties of conjugates between 8-hydroxyquinoline and bovine serum albumin (Ox-BSA) towards inorganic and organic mercury were studied. Two Ox-BSA conjugates (different substitution ratio) were prepared and their complexing properties were studied. Through the use of titration curves with mercury (II), methylmercury and ethylmercury an evaluation of the complex stoichiometry and stability was obtained, showing that Ox-BSA has good affinity for all investigated mercuric compounds and that the stability increases in the order: Hg (II) < CH3Hg+ < C2H5Hg+, whatever conjugate is considered. Complexes show a stoichiometry of 1:1 between mercury and 8-hydroxyquinoline residues, except with the high substituted conjugate and Hg2+ ion. The skill of the high substituted conjugate to bind inorganic and organic mercury in the presence of NaCl was also studied. Organic mercuric complexes do not show significant modification due to NaCl. Nevertheless, considering inorganic mercury, the number of retained metal ions per protein molecule increases if the NaCl concentration becomes higher than 0.1 M, probably because at high NaCl concentrations 1:1 complexes between mercury and 8-hydroxyquinoline are preferred to 1:2 complexes.

Animals↗