Quantitative analysis of protein adsorption via atomic force microscopy and surface plasmon resonance

Surface properties have a significant influence on the performance of biomedical devices. The influence of surface chemistry on the amount and distribution of adsorbed proteins has been evaluated by a combination of atomic force microscopy (AFM) and surface plasmon resonance (SPR). Adsorption of albumin, fibrinogen, and fibronectin was analyzed under static and dynamic conditions, employing self-assembled monolayers (SAMs) as model surfaces. AFM was performed in tapping mode with antibody-modified tips. Phase-contrast images showed protein distribution on SAMs and phase-shift entity provided information on protein conformation. SPR analysis revealed substrate-specific dynamics in each system investigated. When multi-protein solutions and diluted human plasma interacted with SAMs, SPR data suggested that surface chemistry governs the equilibrium composition of the protein layer.     

The use of plasmatic acceptors as specific ligands in affinity chromatography cleanup of veterinary drugs from biological matrices

Bovine α₁-acid glycoprotein (bAAG) and bovine serum albumin (BSA) are plasmatic acceptors working as carriers by the specific and reversible binding of several drugs in vivo. We synthesized affinity columns by coupling bAAG and BSA to an activated chromatographic support through their carbohydrate moieties, to preserve protein tertiary structure and, consequently, to improve the biological activity in vitro. The bAAG and BSA affinity columns were used to study the binding of acidic and basic drugs. Moreover, a purification strategy was developed for the cleanup of drug residues from biological matrices and foods, prior to screening and/or confirmatory analysis, on the basis of the specific molecular recognition between the protein and the drug. The aim of this work was to test the potency of bAAG- and BSA-based affinity chromatography to bind some veterinary drugs and purify them in the context of the official control of animal products. The efficiency of these homemade affinity columns in minimising matrix interference and in selective cleanup of different classes of substances was reported and discussed. Figure “Coupling strategies in synthesizing plasmatic acceptor affinity columns: the covalent coupling of bAAG and BSA through their carbohydrate moiety allows one to preserve the gross tertiary structure of the protein and thus its biological activity, whereas coupling through the ε-amine group of lysine residues can reduce the interactions with the binding sites of the plasmatic acceptor.”     

CuO based catalysts on modified acidic silica supports tested in the de-NOx reduction

A series of dispersed CuO catalysts supported on modified silica supports with Al2O3 (SA), TiO2 (ST), and ZrO2 (SZ) were prepared optimising the adsorption method of copper deposition assisted by ultrasound treatment, already reported in a previous paper (S. Bennici, A. Gervasini, V. Ragaini, Ultrason. Sonochem. 10 (2003) 61). The obtained catalysts were characterized in their bulk (atomic absorption, X-ray diffraction, temperature programmed reduction) and surface (N2 adsorption, X-ray photoelectron spectroscopy, scanning electron microscopy) properties. The morphology of the finished materials was not deeply modified compared with that of the relevant supports. The employed complemented techniques evidenced a well dispersed CuO phase with a copper-support interaction on the most acidic supports (SA and SZ). The catalyst performances were studied in the reaction of selective catalytic reduction of NOx with ethene in oxidizing atmosphere in a flow apparatus under variable times (0.360-0.072 s) and temperatures (200-450 degrees C). The catalysts prepared on the most acidic supports (SA and SZ) were the most active and selective towards N2 formation. They showed a particular interesting activity in the reaction of NO2 reduction besides that of NO reduction.     

Noise adjusted principal component reconstruction to optimize infrared microspectroscopy of individual live cells

We have optimized an imaging methodology capable of monitoring individual live HeLa cells using non-synchrotron FTIR in an aqueous environment. This methodology, in combination with MATLAB based pre-processing techniques, allows fast and efficient collection of data with high signal-to-noise ratio in comparison with previous methods using point mode data collection, which required manual operation and more collection time. Also, presented are early results that illustrate interpretable spectral differences from live cells treated with chemotherapeutic drugs, demonstrating the potential of this methodology to develop more desirable modes of treatment for patients in their diagnoses and treatments for disease.     

Improving selectivity in gas chromatography by using chemically modified multi-walled carbon nanotubes as stationary phase

Amino-terminated alkyl MWCNTs (MWCNTs-R-NH₂), synthesized by chemical modification of the nanotube skeleton by nucleophilic substitution with 2,2′-(ethylenedioxy)diethylamine, were successfully used as stationary phases for gas chromatographic separation of esters and chloroaromatics. The presence of alkyl chains with polar embedded groups made the functionalized MWCNTs (f-MWCNTs) a mixed-mode GC separation material able to interact in different ways with the analytes. Compared with non-functionalized MWCNTs (nf-MWCNTs), MWCNTs-R-NH₂ had higher selectivity, enhanced resolution, and optimum retention behaviour, and they were proved to perform better than the commercial stationary phase Porapak QS (PQS), claimed to be suitable for similar applications. The so-prepared stationary phase was used for analysis of a synthetic mixture containing different classes of analytes, viz. esters, ketones, alcohols, alkanes, and aromatic hydrocarbons, and finally used for investigation of similar real matrices. In particular, the constituents of a commercial paint thinner were determined by direct injection of the sample, with good reproducibility (inter-day precision RSDs from 5 to 19%). Two unknown samples of commercial white spirit were also analysed for determination of the aromatic hydrocarbon content, and their composition was profiled on the basis of the different compounds identified.     

A 2DE approach for high-throughput antigen separation applicable to mAb production

A constantly increasing number of mABs are required for the validation of a large proportion of proteomic and protein-protein interaction data. The development of new robotic platforms has greatly enhanced the throughput of monoclonal antibody production; however, the availability of highly purified proteins to use as antigens currently represents the major bottleneck of the process. In this article, we describe a new 2DE approach to purify hundreds of proteins from cellular extracts in a very cost-effective and time-efficient way. The accuracy of the new purification method is shown to be comparable to high-resolution analytical 2DE. The effectiveness and the throughput of the method to purify proteins suitable for the development of mAbs are then assessed. Using this methodology, we were able to separate 447 proteins starting from 50 mg of proteins extracted from HT29 cells. Fractions containing more than 30 μg of protein constantly induced immunization in mice. Using a high-throughput process for monoclonal antibody production, we obtained an average of 3.5 mAbs for each protein. According to pilot experiments, we can predict that starting from an unfractionated cellular extract it is possible to obtain approximately 200 proteins usable for monoclonal antibody development. Our results indicate that the number of antigens available for monoclonal antibody production can be further increased by running parallel separations. The proposed methodology will then facilitate the high-throughput monoclonal antibody process providing a vast array of high quality antigens at very low cost.     

High-speed gas chromatography in doping control: fast-GC and fast-GC/MS determination of beta-adrenoceptor ligands and diuretics

In official doping controls, about 300 drugs and metabolites have to be screened for each sample. Moreover, the number of determinations to be routinely processed increases continuously as the number of both samples and potential illicit drugs keeps growing. As a consequence, increasingly specific, sensitive, and, above all, fast methods for doping controls are needed. The present study presents an efficient fast-GC/MS approach to the routine screening of two different classes of doping agents, namely beta-adrenoceptor ligands and diuretics (belonging to the S3, P2, and S5 groups of the WADA list of prohibited substances). Narrow bore columns (100 mm id) of different lengths and coated with apolar stationary phases were successfully used to separate the derivatized analytes; preliminary experiments (results not shown) showed better performances with OV-1701 for the separation of beta-adrenoceptor ligands. On the same stationary phase some diuretics required too high a temperature or a long isothermal time for elution, in which case a DB1-MS column was preferred. Two methods of sample preparation, derivatization, and analysis were used on aqueous standard mixtures of, respectively, (i) eight beta-adrenoceptor ligands, including five beta-antagonists (acebutolol, alprenolol, atenolol, metoprolol, pindolol) and three beta2-agonists (salbutamol, clenbuterol, terbutaline) and (ii) seventeen diuretic drugs (acetazolamide, althiazide, bendroflumethiazide, bumethanide, canrenone, chlorothiazide, chlortalidone, clopamide, ethacrinic acid, furosemide, hydrochlorothiazide, hydroflumethiazide, indapamide, indomethacine, spironolactone, triamterene, trichloromethiazide) and one masking agent (probenecid). The mixture of beta-adrenoceptor ligand derivatives was efficiently separated in about 5.6 min, while the one of 18 diuretics and masking agents required less than 5 min for analysis. Limits of detection were from 1 microg/L for pindolol, ethacrinic acid, furosemide, indomethacine, and trichloromethiazide, to 20 microg/L for terbutaline, salbutamol, and metoprolol, and 50 microg/L for clopamide; the instrumental repeatability proved to be excellent (area RSD% <2 for almost all analytes). For this work a quadrupole MS with inert ion source has been used, demonstrating that the quadrupole technology is perfectly adequate to provide precise integration of 400 ms-wide GC peaks.     

Synthesis and characterization of silver(I) coordination networks bearing flexible thioethers: anion versus ligand dominated structures

This report describes the synthesis and X-ray characterization of a series of L(n)AgX complexes wherein Ln = PhS(CH2)nSPh (n = 2, 4, 6, 10) and X = CF3SO3-, CF3COO-, CF3CF2COO-, CF3CF2CF2COO-, NO3-, and ClO4-. This study was undertaken in order to rationalize the structure of the coordination networks formed as a function of the anion coordinating strength and the ligand structure. The following complexes were examined: with L(2), CF3SO3- (1), CF3COO- (2), ClO4- (3); L4, CF3SO3- (4), CF3COO- (5), CF3CF2COO- (6), CF3CF2CF2COO- (7); L6, CF3COO-.H2O (8), CF3CF2COO- (9), CF3CF2CF2COO- (10); and L10, NO3- (11). The anions selected are classified in three groups of increasing coordinating strength: perchlorates, fluorosulfonates, and perfluorocarboxylates. Except in two cases, all complexes form 2D-coordination networks. The 2D-network in 1 (L2, CF3SO3-) is made up of Ag(I) and L2, while the anion is only a terminal co-ligand that completes the trigonal coordination around Ag(I). In 4 (L4, CF3SO3-), a 1D-coordination polymer, [Ag-L4-]infinity, is observed where the anions are coordinated to Ag(I) in a trigonal fashion. The perfluorocarboxylates form tetrameric units in a zigzag shape, but only with the L4 ligand. In these (6 and 7), the silver-silver distances are very short, especially those of the central bond, indicating the presence of weak Ag-Ag interactions. Dimers, with short silver-silver distances, are observed with ligands L2 and L6 and perfluorocarboxylates. In 8 (L6, CF3COO-.H2O), a 3D channel-like structure is built through water molecules that connect adjacent layers. An unusual stoichiometry is noted in 3 (L2, ClO4-, acetone); Ag:L is 4:2.5. In 11 (L10 and NO3-), the nitrate acts as a bidentate ligand and an [Ag-NO3-]infinity chain is formed. Adjacent chains are linked by the L10 ligands into a 2D-coordination network.     

Optimization of a comprehensive two-dimensional normal-phase and reversed-phase liquid chromatography system

The present investigation is based on the evaluation of the performance of a comprehensive two-dimensional liquid chromatography (LCxLC) system during method optimization. The LCxLC set-up, operated in normal phase (NP) mode (adsorption) in the first dimension (1D) and reversed-phase (RP) mode in the second dimension (2D), is equipped with a 1D microbore silica column and a 2D monolithic C(18) column with a 10-port two position valve as the interface. A photodiode array detector is used after the 2D separation. A possible cause of peak distorsion because of the immiscibility of the mobile phases employed in the two dimensions is resolved. The optimization of the analytical run time and flow rate for both dimensions and the initial gradient in the 2D is carried out with various standard compounds. The potential and versatility of this LCxLC approach is demonstrated through the separation of 11 standard components, most of them allergens. The latter, which are characterized by a scattered distribution on the 2D space plane, underwent separation on both a hydrophobicity and polarity basis.