Dialysis

Dialysis is a process where substances in solution are separated by their differences in molecular weight. The dialysis tubings are semipermeable, made of regenerated cellulose or cellulose ester having a gel-like structure. The driving force is the concentration difference between 2 solutions on opposite sides of the membrane. Since the porous membrane selectively allows smaller solutes to pass while retaining larger species, dialysis can effectively be used as a separation process based on size rejection.

Since the dialysis membrane consists of a spongy matrix of crosslinked polymers, the pore rating referred to as Molecular Weight Cut Off (MWCO), is an indirect measure of the retention performance. The membrane MWCO is determined as the solute size that is retained by at least 90 %. However, since a solute’s permeability is also dependent upon molecular shape, degree of hydration, ionic charge and polarity, it is recommended to select a MWCO that is half the size of the MW of the species to be retained and/or twice the size of the MW of the species intended to pass through.

For many years, dialysis has been successfully used as a routine method for desalting and concentration of complex biomolecules in solution. In addition, macromolecules, differing substantially in molecular weight can be separated.

Applications

  • Desalting of protein solutions, e.g. for further purification by ion exchange chromatography
  • Concentration of protein solutions by embedding the filled tubing in dry PEG 20000 (cat. no. 33138) e.g. before further separation by gel permeation chromatography
  • Separation of high molecular weight proteins from low molecular weight peptides and other substances
  • Buffer exchange with solutions of proteins or other macromolecules
  • Desalting of metallo colloids


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SERVA Catalog
2018

Product of the Month January 2018:

SERVAColor
Blot Solutions

Western Blotting -
New Brochure!

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New !

SERVA Catalog
2018

In summary here is a short description of products made available for the research community in 2018:
• Protein extraction kits for rapid isolation of membrane, cytoplasmic and nuclear proteins from mammalian tissues and cells
• Cell-based assays for apoptosis and cell profliferation/viability like XTT or Sulforhodamine B
• Enzymes like recombinant PNGase F or Lysyl Endopeptidase • Ultrapure reagents for UHPLC-MS analysis like acetonitrile and water
• Biochemicals for nucleic acid purification like recombinant Proteinase K or BlueZol for RNA isolation
• Electrophoresis gel and blot documentation: SERVA Musketeer is an all-in-one solution for UV/VIS, fluorescence and chemiluminescence applications

Download our new catalog here:

 

SERVA Catalog 2018 (pdf)
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Product of the Month January 2018:

SERVAColor
Blot Solutions

For detection of alkaline phosphatase or horseradish peroxidase on Western Blot membranes.

This way to the Special Offer

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Western Blotting -
New Brochure!
  • • Molecular Weight Standards
  • • SDS PAGE for Western Blotting
  • • Transfer Membranes and Buffers
  • • Blocking Reagents
  • • Detection Systems
  • • Instruments for Western Blotting
SERVA Brochures: Western Blotting (pdf)
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