			Home About us Contact

Phase Chromatography (phase + chromatography)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

Simulation and Experiment of Temperature and Cosolvent Effects in Reversed Phase Chromatography of Peptides

BIOTECHNOLOGY PROGRESS, Issue 3 2005
Kosta Makrodimitris
Experiments and simulations have been carried out for several polar protected peptides in reversed phase chromatography in order to demonstrate how simulation can describe the effects of varying temperature and cosolvent fraction. Comparisons of adsorption chemical potentials from mesoscopic simulations and experimental chromatographic retention data show very good agreement with only one temperature-independent solvent parameter from a single peptide. Such simulations should help guide the design of chromatography experiments with biomolecules and predict retention, including conditions for which empirical correlations such as hydrophobicity scales and molecular descriptors have not been developed. [source]

BJ46a, a snake venom metalloproteinase inhibitor

FEBS JOURNAL, Issue 10 2001
Isolation, characterization, cloning, insights into its mechanism of action
Fractionation of the serum of the venomous snake Bothrops jararaca with (NH4)2SO4, followed by phenyl-Sepharose and C4 -reversed phase chromatographies, resulted in the isolation of the anti-hemorrhagic factor BJ46a. BJ46a is a potent inhibitor of the SVMPs atrolysin C (class P-I) and jararhagin (P-III) proteolytic activities and B. jararaca venom hemorrhagic activity. The single-chain, acidic (pI 4.55) glycoprotein has a molecular mass of 46 101 atomic mass units determined by MALDI-TOF MS and 79 kDa by gel filtration and dynamic laser light scattering, suggesting a homodimeric structure. mRNA was isolated from the liver of one specimen and transcribed into cDNA. The cDNA pool was amplified by PCR, cloned into a specific vector and used to transform competent cells. Clones containing the complete coding sequence for BJ46a were isolated. The deduced protein sequence was in complete agreement with peptide sequences obtained by Edman degradation. BJ46a is a 322-amino-acid protein containing four putative N-glycosylation sites. It is homologous to the proteinase inhibitor HSF (member of the fetuin family, cystatin superfamily) isolated from the serum of the snake Trimeresurus flavoviridis, having 85% sequence identity. This is the first report of a complete cDNA sequence for an endogenous inhibitor of snake venom metalloproteinases (SVMPs). The sequence reveals that the only proteolytic processing required to obtain the mature protein is the cleavage of the signal peptide. Gel filtration analyses of the inhibitory complexes indicate that inhibition occurs by formation of a noncovalent complex between BJ46a and the proteinases at their metalloproteinase domains. Furthermore, the data shows that the stoichiometry involved in this interaction is of one inhibitor monomer to two enzyme molecules, suggesting an interesting mechanism of metalloproteinase inhibition. [source]

Physicochemical properties of low-fat and full-fat Cheddar cheeses

INTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 3 2006
E KÜÇÜKÖNER
Low-fat (6% fat) and full-fat (32% fat) Cheddar cheese was manufactured and aged up to 6,9 months at 5°C. The objective was to study the impact of fat on the physicochemical properties of Cheddar cheese. Total soluble nitrogen (TSN) and protein nitrogen (TPSN) in aqueous extracts were determined by the Kjeldahl method. The peptide content of each cheese was determined with reverse phase chromatography (RPC). Low-fat Cheddar (LFC) had a markedly higher peptide content than full-fat Cheddar (FFC). The overall peptide quantity increased with age with a marked increase in hydrophobic peptide content. Rheological properties were determined using an Instron Universal Testing Machine. LFC had significantly higher stress values, indicating hard and rubbery texture, than FFC. Furthermore, LFC had lower strain values, indicating crumbliness. [source]

Kinetic study of carbon nanotubes synthesis by fluidized bed chemical vapor deposition

AICHE JOURNAL, Issue 2 2009
R. Philippe
Abstract Multi-walled carbon nanotubes (MWCNTs) have been produced with high selectivity by fluidized bed catalytic chemical vapor deposition from ethylene on Fe/Al2O3 catalysts. The influence of operating parameters such as deposition duration, temperature, ethylene and hydrogen partial pressures, and iron loading on MWCNT productivity, process selectivity, characteristics of final powders, and chemical composition of the outlet gases has been analyzed. Using gas phase chromatography, methane and ethane have been detected, whatever are the conditions used. Between 650 and 750°C, no catalyst deactivation occurs because nucleation remains active all along the synthesis, thanks to the explosion of the catalyst grains. Above 650°C, ethane itself produces MWCNTs, whereas methane does not react in the temperature range, 550,750°C. The formation of MWCNTs induces marked bed expansions and sharp decreases of grain density. Apparent kinetic laws have been deduced from the collected data. The apparent partial orders of reaction for ethylene, hydrogen, and iron were found to be 0.75, 0, and 0.28, respectively. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source]

Profiling of polar metabolites in biological extracts using diamond hydride-based aqueous normal phase chromatography

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2009
Damien L. Callahan
Abstract Highly polar metabolites, such as sugars and most amino acids are not retained by conventional RP LC columns. Without sufficient retention low concentration compounds are not detected due ion suppression and structural isomers are not resolved. In contrast, hydrophilic interaction chromatography (HILIC) and aqueous normal phase chromatography (ANP) retain compounds based on their hydrophilicity and therefore provides a means of separating highly polar compounds. Here, an ANP method based on the diamond hydride stationary phase is presented for profiling biological small molecules by LC. A rapid separation system based upon a fast gradient that delivers reproducible chromatography is presented. Approximately 1000 compounds were reproducibly detected in human urine samples and clear differences between these samples were identified. This chromatography was also applied to xylem fluid from soyabean (Glycine max) plants to which 400 compounds were detected. This method greatly increases the metabolite coverage over RP-only metabolite profiling in biological samples. We show that both forms of chromatography are necessary for untargeted comprehensive metabolite profiling and that the diamond hydride stationary phase provides a good option for polar metabolite analysis. [source]

A review of the background, operating parameters and applications of microemulsion liquid chromatography (MELC)

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 15 2005
A. Marsh
Abstract Microemulsions are dispersions of nanometre-sized droplets of an immiscible liquid within another liquid. Droplet formation is facilitated by the addition of surfactants and often also cosurfactants. Microemulsions are classified as either oil-in-water (O/W) (oil droplets such as octane dispersed throughout aqueous buffer) or water-in-oil (W/O) (aqueous droplets in oil such as hexane). Both microemulsion types have been used as mobile phases for separation in microemulsion HPLC (MELC). There has been a recent increase of interest in this area with new applications and developments such as gradient elution and optimisation of methods using experimental design. O/W microemulsions have been employed as eluents for RP-HPLC while W/O microemulsions have been used for normal phase chromatography. Separations can have superior speed and efficiency to conventional HPLC modes while offering a unique selectivity with excellent resolution. The capability for quantitative and stability-indicating analysis has also been demonstrated. Specific advantages include the ability to operate at low UV wavelengths and elimination of the need for an equilibration rinse between gradients. Operational issues associated with the use of MELC have been identified including the need to add salt to the gradient eluent, relatively high back-pressures and increased need for equipment cleaning compared to conventional RP eluent. This report details the different microemulsion types and compositions used and their reported applications. The use of gradient and isocratic elution is described. The effects on separations of varying operating parameters such as temperature, oil type and concentration, surfactant type and concentration, sample solvent, column type, and organic solvent addition will be discussed and illustrated. [source]