Biomedical subjects

A Ljunglöf

Publications and source records attributed to A Ljunglöf.

7 recordsLinked to original sources

PubMed2006

An exclusion mechanism in ion exchange chromatography.

Protein dynamic binding capacities on ion exchange resins are typically expected to decrease with increasing conductivity and decreasing protein charge. There are, however, conditions where capacity increases with increasing conductivity and decreasing protein charge. Capacity measurements on two different commercial ion exchange resins with three different monoclonal antibodies at various pH and conductivities exhibited two domains. In the first domain, the capacity unexpectedly increased with increasing conductivity and decreasing protein charge. The second domain exhibited traditional behavior. A mechanism to explain the first domain is postulated; proteins initially bind to the outer pore regions and electrostatically hinder subsequent protein transport. Such a mechanism is supported by protein capacity and confocal microscopy studies whose results suggest how knowledge of the two types of IEX behavior can be leveraged in optimizing resins and processes.

Antibodies, Monoclonal↗

PubMed2000

Measurement of ligand distribution in individual adsorbent particles using confocal scanning laser microscopy and confocal micro-Raman spectroscopy.

Two methods, confocal scanning laser microscopy and confocal micro-Raman spectroscopy were used to analyse the distribution of IgG antibodies immobilized on CNBr-activated agarose beads. In the first method the internal distribution profile of fluorescent labelled Protein A was used as an indirect measure of the distribution of IgG, while the second method detects vibrations originating from aromatic amino acids present in the immobilized antibodies. Both these methods indicate an homogeneous ligand distribution within IgG Sepharose 4 Fast Flow and IgG Sepharose 6 Fast Flow.

Adsorption↗

PubMed1999

Visualizing two-component protein diffusion in porous adsorbents by confocal scanning laser microscopy.

The use of confocal scanning laser microscopy (CSLM) has recently been described for the visualization of intraparticle protein profiles during single-protein finite bath uptake experiments. By coupling of fluorescent molecules to proteins the penetration of porous media by labeled macromolecules could be detected by scanning single adsorbent particles for fluorescence emission after laser excitation. Thus the internal protein distribution profile, which is a central element in modeling of protein transport in porous adsorbents, became experimentally accessible. Results from the simultaneous visualization of two proteins by this technology are shown here. The use of two different fluorescent dyes for protein labeling and two independent detectors in the CSLM allowed for the first time ever the direct observation of a two-component diffusion process within a porous stationary phase. The finite bath uptake of human immunoglobulin G (hIgG) and bovine serum albumin (BSA) to two different ion exchange adsorbents (SP Sepharose Fast Flow and Source 30S) and to an affinity adsorbent (Protein A Sepharose) was measured using Cy5 and Oregon Green as labels. Single adsorbent particles were scanned for intensity distribution of fluorescence emission from the two fluorophors. The intraparticle profiles obtained from the confocal images were translated into a relative protein concentration thus allowing the calculation of protein uptake kinetics from direct measurement in the stationary phase. The confocal technique may prove to be a very powerful means of data generation for modeling of multi-component mass transfer phenomena in protein adsorption.

Adsorption↗

PubMed1999

Confocal Microscopy Studies of Trypsin Immobilization on Porous Glycidyl Methacrylate Beads.

The immobilization of trypsin on porous glycidyl methacrylate (GMA-GDMA) beads has been investigated. In particular, the distribution within the beads of trypsin and of dextran used for hydrophilizing the bead surface prior to protein immobilization was investigated with confocal microscopy. For the system investigated, the fluorescence intensity profiles obtained when using borate buffer as an ambient solution displayed a distinct minimum at the center of the beads, irrespective of the observation depth. However, by reduction of the refractive index difference between the solution and the beads through the addition of glucose to the aqueous solution, artifacts relating to optical length differences could be reduced. For both low molecular weight fluorescein isothiocyanate (FITC), FITC-labeled trypsin, and FITC-labeled dextran, an essentially homogeneous distribution throughout the beads was observed. This simple "contrast matching" method seems therefore to be an interesting tool when investigating the distribution of immobilized protein in porous chromatography media. Copyright 1999 Academic Press.

Journal Article↗

PubMed1999

Direct visualisation of plasmid DNA in individual chromatography adsorbent particles by confocal scanning laser microscopy.

Confocal microscopy was used for the measurement of plasmid DNA adsorbed to individual adsorbent particles intended for anion-exchange and triple helix affinity chromatography. Plasmid DNA was visualized with the fluorescent dye YOYO-1, that forms a highly fluorescent complex with double stranded DNA. Confocal images were translated into fluorescence intensity profiles and the distribution of plasmid DNA in the particles was measured. The results that adsorption of plasmid DNA mainly takes place in an outer layer of the particles. The described procedure can also be advantageously used to demonstrate triple helix formation between plasmid DNA and immobilized oligonucleotides.

Adsorption↗

PubMed1998

Visualising intraparticle protein transport in porous adsorbents by confocal microscopy.

Confocal scanning microscopy was used to study protein uptake to porous adsorbents during batch experiments in a finite bath. By coupling of a fluorescent dye to the protein molecules the penetration of single adsorbent particles at different times during batch uptake could be observed visually. Intensity profiles of the protein distribution within a single particle were obtained by horizontal scanning. After integration of the profiles the overall fluorescence within a bead could be calculated. Relating the overall fluorescence at different incubation times to the value at equilibrium allowed the construction of the fractional approach to equilibrium versus time. These data were compared to uptake curves, which had been obtained by measurements of the protein concentration in the supernatant and an excellent agreement of the curves was detected. The procedure was performed for two different proteins (lysozyme and human IgG) on two different media for protein adsorption (SP Sepharose Fast Flow and SP Sepharose XL; Pharmacia Biotech) and in all cases it could be shown, that the results from the direct measurements by confocal microscopy correspond very well to the data obtained from the indirect measurements in the fluid phase.

Adsorption↗

PubMed1988

One-step purification of monoclonal IgG antibodies from mouse ascites. An evaluation of different adsorption techniques using high performance liquid chromatography.

Monoclonal antibodies were purified in one step from mouse ascites by four different high performance liquid chromatography (HPLC) adsorption techniques. The antibodies were of the IgG1, IgG2a, IgG2b and IgG3 subtypes, with isoelectric points between 6.4 and 7.6. Similarly pretreated samples were applied to columns for anion exchange (Mono Q), cation exchange (Mono S), chromatofocusing (Mono P) and hydrophobic interaction chromatography (Alkyl Superose), respectively. Highly purified IgG fractions, as judged by electrophoresis, were obtained in all these techniques. The yields of immunoreactive material were above 80%. A strategy for single step HPLC purification of monoclonal IgG antibodies from mouse ascites by adsorption techniques is proposed, as a complement to the well-established technique of affinity chromatography on immobilized protein A. The strategy involves (i) cation exchange chromatography as a first choice for antibodies with high isoelectric points (greater than 7.2), and (ii) hydrophobic interaction chromatography as a first choice when the isoelectric point is below 7.2.

Animals↗