Properties of Protein and Polymer Systems

Fredrik Carlsson

Research output: ThesisDoctoral Thesis (compilation)


Interactions of proteins with other proteins, with polymers and with surfaces are of great practical importance within for instance protein purification, drug delivery, and food technology. The aim of this work is to increase the understanding of protein-protein, protein-polyelectrolyte, and protein-surface interactions, particularly concerning the role of electrostatic interactions in these systems. Properties that have been studied include the role of discrete charges of the protein in protein self-association, complexation with a polyelectrolyte, and adsorption to a surface.

The main method used in the present investigation has been Monte Carlo simulation. Lysozyme was chosen as a model protein because of its high degree of structural stability under a variety of conditions and because of the large amount of experimental data available for comparison with the simulation results. The protein model consists of a hard sphere with positive and negative charges beneath the surface. The positions of the charges have been taken from the lysozyme crystal structure and projected on a sphere.

In the first study the interaction between one protein and one polymer was investigated. It was found that the polymer was distributed unevenly over the surface of the protein because of the discrete charges. Furthermore, it was found that the discrete-charge protein model gave a higher level of adsorbed polyelectrolyte than a model with uniformly distributed charge. In the second study, a solution with many proteins was investigated, and the short-range interaction between the proteins was adjusted according to experimental light scattering data. Simulation results on protein self-association agreed with previously reported results in the literature. In the third study, different ways to represent the charges of the protein and different ways to include the small ions were compared. There was a small difference between the different charge representations. The difference between the ion models was minute at low ionic strength and slightly larger at higher ionic strength. In a fourth study, the system was extended to many proteins and many polymers. We were able to simulate the precipitation and redissolution, which is observed experimentally when a charged polymer is added to a protein solution. In a final study, the protein model was investigated at a surface. Simulated adsorption isotherms as well as lateral radial distribution functions for adsorbed proteins agreed well with experimental data.
Original languageEnglish
Awarding Institution
  • Physical Chemistry
  • [unknown], [unknown], Supervisor, External person
Award date2002 Oct 31
ISBN (Print)91-628-5372-4
Publication statusPublished - 2002

Bibliographical note

Defence details

Date: 2002-10-31
Time: 10:15
Place: Lund

External reviewer(s)

Name: Dickinson, Eric
Title: [unknown]
Affiliation: [unknown]


Article: Paper I. Monte Carlo Simulations of Polyelectrolyte-Protein ComplexationFredrik Carlsson, Per Linse, and Martin MalmstenJournal of Physical Chemistry B vol. 105, pp. 9040-9049 (2001)

Article: Paper II. Monte Carlo Simulations of Lysozyme Self-Association in Aqueous SolutionFredrik Carlsson, Martin Malmsten, and Per LinseJournal of Physical Chemistry B vol. 105, pp. 12189-12195 (2001)

Article: Paper III. A Comparison of Charge Representations and Ion Models for an Aqueous Solution of LysozymeFredrik Carlsson, Martin Malmsten, and Per LinseJournal of Chemical Physics submitted (2002)

Article: Paper IV. Protein-Polyelectrolyte Cluster Formation and Redissolution. A Monte Carlo StudyFredrik Carlsson, Martin Malmsten, and Per LinseJournal of the American Chemical Society submitted (2002)

Article: Paper V. Lysozyme Adsorption to a Charged Surface. A Monte Carlo StudyFredrik Carlsson, Elin Hyltner, Thomas Arnebrant, Martin Malmsten, and Per LinseManuscript to be submitted (2002)

Article: Paper VI. Interactions between Local Anaesthetic Agents and Poly (N-isopropyl acrylamide) through Phase Behavior, Surface Tension, and Adsorption MeasurementFredrik Carlsson, Ulla Elofsson, Thomas Arnebrant, and Martin MalmstenJournal of Colloid and Interface Science vol. 233, pp. 320-328 (2001)

Subject classification (UKÄ)

  • Physical Chemistry

Free keywords

  • Fysikalisk kemi
  • Physical chemistry
  • lysozyme
  • mica
  • surface
  • dimerization
  • precipitation
  • aggregate
  • cluster
  • complex
  • polyelectrolyte
  • protein
  • polymer


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