Chromatography of complex protein mixtures

Evaluation of pharmacological efficacy of 'insulin-surfoplex' encapsulated polymer vesicles

The present study has been designed to study whether formation of ion-pair complex or 'surfoplex' can enhance the pharmacological efficacy of protein-loaded PCL-PEG-based polymerosomes. Insulin was selected as the model protein and was complexed with sodium deoxycholate, a naturally occurring bile salt. The surfoplexes were characterized for extent and site of complexation, stability, mass and partition coefficient. The lipophilicity of insulin was enhanced 5-fold upon complexation resulting in an increase in entrapment efficiency by 10-50% for all formulations compared to free insulin. The release of insulin from the systems was also modulated with reduction in burst release by 30%. The surfoplex was found to be therapeutically active for 8h duration (C(max) serum insulin=64.15+/-13.28 mIU/mL) in diabetic rat model. However, pharmacological efficacy of the complex-loaded nanoparticles (Nps) did not show significant enhancement with respect to insulin-loaded systems. The study therefore suggests that while ion-pair complexes may improve the in vitro kinetics of protein-loaded carriers, their therapeutic potential is dependent on the intensity of interactions between the peptide chains and polymer matrix.

Extensive cell envelope modulation is associated with virulence in Brucella abortus

Brucella virulence is linked to components of the cell envelope and tightly connected to the function of the BvrR/BvrS sensory-regulatory system. To quantify the impact of BvrR/BvrS on cell envelope proteins, we performed a label-free mass spectrometry-based proteomic analysis of spontaneously released outer membrane fragments from four strains of Brucella abortus (wild type virulent, avirulent bvrR- and bvrS- mutants as well as reconstituted virulent bvrR+ (bvrR-/pbvrR+)). We identified 167 differentially expressed proteins, of which 25 were assigned to the outer membrane. Approximately half of the outer membrane proteins decreased in abundance, whereas half increased. Notably, expression of five Omp3 family proteins decreased whereas five lipoproteins increased in the mutant strains. In the periplasmic space, by contrast, approximately 80% of the 60 differentially expressed proteins were increased in at least one avirulent mutant. Periplasmic proteins are primarily involved in substrate uptake and transport, and a uniform increase in this class may indicate a nutritional stress response, possibly a consequence of defective outer membrane function. Virtually all proteins reverted to wild type levels in the reconstituted virulent bvrR+ strain. We propose that the wide changes in cell envelope protein expression relate to the markedly avirulent phenotype of bvrR- and bvrS- mutants and that Brucella virulence depends on regulatory networks involving cell envelope and metabolism rather than on discrete virulence factors. This model may be relevant to other alpha-Proteobacteria harboring BvrR/BvrS orthologous systems known to be essential for parasitism or endosymbiosis.

The yeast two-hybrid system and its pharmaceutical significance

The detected phenotypes in many diseases are caused from dysfunction in protein-protein, protein-DNA and receptor-ligand interactions. Therefore, determination of these molecular interactions followed by designing or screening the compounds to target these interactions provides a significant challenge in drug development. This review aims to highlight the yeast two-hybrid system in determination of protein-protein interactions and its possible outcomes in pharmaceutical research. The variations of the basic methodology as one- and three-hybrid systems are also discussed in relation to their potential pharmaceutical applications.

Hydrophobic interaction chromatography of human serum alpha1-antitrypsin and alpha1-acid glycoprotein

The relative hydrophobicity of human serum alpha1-antitrypsin (AAT) and alpha1-acid glycoprotein (AGP) in comparison to various reference proteins was determined by hydrophobic interaction chromatography (HIC). Apolar character of glycoproteins was generated using three different cosmotropic salts, ammonium sulfate, sodium sulfate, sodium citrate and isocratic, or reversed linear gradient elution techniques. Human serum AAT and AGP showed different apolar properties on Fractogel EMD phenyl and propyl columns modulated either by the type and concentration of cosmotropic salts, or by the pH of the mobile phase. According to its higher carbohydrate content AGP proved to be more polar than AAT. Human serum AAT and AGP were pre-separated by Cibacron Blue F3G-A dye ligand affinity chromatography and based on their different hydrophobicity were fractionated and purified by HIC.

Kinetic study of the mass transfer of bovine serum albumin in anion-exchange chromatography

A kinetic study was made on the mass transfer phenomena of bovine serum albumin (BSA) in two different anion-exchange columns (Resource-Q and TSK-GEL-DEAE-5PW). The analysis of the concentration dependence of the lumped mass transfer rate coefficient (km,L) provided the information about the kinetics of the several mass transfer processes in the columns and the anion exchangers, i.e., the axial dispersion, the fluid-to-particle mass transfer, the intraparticle diffusion, and the adsorption/desorption. In the Resource-Q column, the intraparticle diffusion had a dominant contribution to the band broadening compared with those of the other processes. The surface diffusion coefficient (Ds) of BSA showed a positive concentration dependence, by which the linear dependence of km,L on the BSA concentration seemed to be interpreted. On the other hand, in the TSK-GEL-DEAE-5PW column, the contribution of the adsorption/desorption was also important and almost same as that due to the intraparticle diffusion. There are some differences between the intrinsic properties of the mass transfer kinetics inside the two anion exchangers. It was likely that the positive concentration dependence of Ds was explained by the heterogeneous surface model.

Separation of closely related intrinsic membrane polypeptides of the photosystem II light-harvesting complex (LHC II) by reversed-phase high-performance liquid chromatography on a poly(styrene-divinylbenzene) column

The three closely related intrinsic membrane polypeptides of the photosystem II light-harvesting complex (LHC II) were successfully resolved on a PRP-1 poly(styrene-divinylbenzene) column using a three-stage linear water-acetonitrile gradient containing 0.1% trifluoroacetic acid. The hydrophobic proteins of photosystem I (PS I-200) and photosystem II core particles were also separated by this method, showing that membrane proteins of different sizes and hydrophobicities can be resolved in this system.

Recent advances in capillary electrophoresis of proteins, peptides and amino acids

The current status of high-performance capillary electrophoresis as an analytical separation method for proteins, peptides and amino acids is assessed. Recent advances in suppressing the effects of electroosmotic flow and irreversible adsorption of proteins at the capillary wall are reviewed, together with procedures for optimal separations of peptides and amino acids. The detection aspects emphasize the role of laser-induced fluorescence and capillary electrophoresis/mass spectrometry in high-sensitivity measurements.

Food analysis on silica-bound HPLC phases

HPLC analysis of food on various silica bonded phases has been described. Technical and theoretical aspects of the materials such as normal-, reverse-, ion-exchange-, affinity-, chiral-, size-exclusion-, and ion-phases have been discussed. Special problems such as mobile phase or solvent-selection, selectivity and mechanisms of resolution on these bonded phases have been mentioned. Application of various bonded materials such as amino, cyano, diol, amino-cyano, C-18, C-8, anion-exchangers, strong and weak-cation exchangers, chiral and enzyme bound affinity phases to analyze and determine food components such as carbohydrates, food colors and pigments, flavors, proteins, vitamins and toxins has been described.

A rapid method for isolation of human hemoglobin benzo[a]pyrene diol epoxide derived adducts using high performance liquid chromatography

A method is described to isolate rapidly human hemoglobin-benzo[a]pyrene diol epoxide adducts. A combination of 300 A pore size C4 reversed phase HPLC to effect separation of adducted protein from native protein, and mu-bore C18 reversed phase HPLC to isolate and partially characterize proteolytic peptide adducts (by UV), was used.

Applications of preparative high-performance liquid chromatography to the separation and purification of peptides and proteins

The basic differences between the problems encountered in the development of the analytical and preparative applications of high-performance liquid chromatography are analyzed and the principles of optimization of a preparative separation outlined. The application of these principles to the purification of peptides and proteins are discussed with emphasis on the specific problems raised by the separation of high-molecular-mass compounds. The relative advantages and inconveniences of displacement and overloaded elution are presented. The applications of the various retention modes of liquid chromatography (ion exchange, reversed-phase adsorption, hydrophobic interactions, size exclusion and bioaffinity) to the separation of various peptide and protein mixtures and/or to the extraction and purification of some of these compounds are reviewed. Separation performance reported in the literature are summarized in table form.

Reversed-phase liquid chromatography of proteins with strong acids

Small organic acids are generally used as pairing agents at less than 1% concentration in reversed-phase chromatography (RPC) of proteins. When the protein is very hydrophobic and insoluble, as in the case of membrane proteins, up to 60% aq. formic acid has been used. This paper reports a study of the influence of acid concentration on both chromatographic retention and protein structure in RPC. Chromatographic retention increases in proportion to the concentration of organic acid in the mobile phase up to some intermediate concentration. Use of still higher concentrations of acid results in a sharp drop in chromatographic retention with a change in selectivity. The data indicate that the structure of proteins in strong acids are different from that in weak acids. This work examines the reason for this decrease in chromatographic retention at formic and trifluoroacetic acid concentrations above 30% (v/v). Spectroscopic studies show that protein conformation continuously changes with the addition of acid.

Synthesis of a non-porous, polystyrene-based strong anion-exchange packing material and its application to fast high-performance liquid chromatography of proteins

Adsorbed coating technology has been used to produce a strong anion-exchange stationary phase on 3-micron non-porous poly(styrene-divinylbenzene) particles. In order to take full advantage of the excellent kinetic properties of the resultant packing material, small columns of 5 mm X 6 mm I.D. were used. These columns were pressure- and pH-stable and allowed protein separations to be made in less than 1 min at ambient temperature.

Separation of proteins by reversed-phase high-performance liquid chromatography. I. Optimizing the column

In the process of developing a new analytical technology (the chromatophoresis process) which couples reversed-phase high-performance liquid chromatography (HPLC) to sodium dodecyl sulfate polyacrylamide gel electrophoresis in a real-time automated system, it was apparent that improvements in resolving power for the first-dimension (HPLC) separation were necessary. The present paper describes the optimization of the column for our initial work on reversed-phase HPLC separations. Polymeric (polystyrene) packings having particle diameters of 5 micron and pore diameters of 300 A were generally superior in terms of resolution, sample recovery and minimization of "ghosting". Optimum column dimensions were 50 x 1.0 mm I.D. for the flow-rates required in our system (10-100 microliter/min).