Interfacial adsorption of insulin. Conformational changes and reversibility of adsorption

S.H. Mollmann, J.T. Bukrinsky, U. Elofsson, W. Norde, S. Frokjaer

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

The adsorption of human insulin to Teflon particles was studied with respect to conformational changes and the reversibility of adsorption was examined by total internal reflection fluorescence (TIRF). Adsorption isotherms for the adsorption of human insulin indicated high affinity adsorption, even at electrostatic repulsive conditions. The plateau value for adsorption was in accordance with a protein layer consisting primarily of insulin monomers. Conformational changes of the insulin upon adsorption, was investigated by circular dicroism (CD) and fluorescence spectroscopy. The results suggested unfolding of adsorbed insulin, as observed by a decrease in ¿-helix and increase in random coil conformation. The changes in protein structure was not only related to the adsorbed species being monomeric, since CD and fluorescence results were different for adsorbed insulin compared to a monomeric analog of human insulin. Furthermore, the thermal stability in the adsorbed state was changed compared to insulin in solution. On the basis of the TIRF studies with FITC-labelled insulin it was not possible to firmly conclude whether exchange between human insulin in the adsorbed state and in solution takes place, due to the limited time range investigated. However, the desorption mechanism appeared to be different with unlabelled insulin in the bulk solution compared to phosphate buffer
Original languageEnglish
Pages (from-to)194-204
JournalEuropean Journal of Pharmaceutical Sciences
Volume27
Issue number2-3
DOIs
Publication statusPublished - 2006

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Adsorption
Insulin
Fluorescence
Fluorescence Spectrometry
Polytetrafluoroethylene
Static Electricity
Buffers
Proteins
Hot Temperature
Phosphates

Keywords

  • internal-reflection fluorescence
  • homomolecular exchange
  • circular-dichroism
  • structural-changes
  • aqueous-solutions
  • fibril formation
  • solid-surfaces
  • in-situ
  • protein
  • aggregation

Cite this

Mollmann, S.H. ; Bukrinsky, J.T. ; Elofsson, U. ; Norde, W. ; Frokjaer, S. / Interfacial adsorption of insulin. Conformational changes and reversibility of adsorption. In: European Journal of Pharmaceutical Sciences. 2006 ; Vol. 27, No. 2-3. pp. 194-204.
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abstract = "The adsorption of human insulin to Teflon particles was studied with respect to conformational changes and the reversibility of adsorption was examined by total internal reflection fluorescence (TIRF). Adsorption isotherms for the adsorption of human insulin indicated high affinity adsorption, even at electrostatic repulsive conditions. The plateau value for adsorption was in accordance with a protein layer consisting primarily of insulin monomers. Conformational changes of the insulin upon adsorption, was investigated by circular dicroism (CD) and fluorescence spectroscopy. The results suggested unfolding of adsorbed insulin, as observed by a decrease in ¿-helix and increase in random coil conformation. The changes in protein structure was not only related to the adsorbed species being monomeric, since CD and fluorescence results were different for adsorbed insulin compared to a monomeric analog of human insulin. Furthermore, the thermal stability in the adsorbed state was changed compared to insulin in solution. On the basis of the TIRF studies with FITC-labelled insulin it was not possible to firmly conclude whether exchange between human insulin in the adsorbed state and in solution takes place, due to the limited time range investigated. However, the desorption mechanism appeared to be different with unlabelled insulin in the bulk solution compared to phosphate buffer",
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Interfacial adsorption of insulin. Conformational changes and reversibility of adsorption. / Mollmann, S.H.; Bukrinsky, J.T.; Elofsson, U.; Norde, W.; Frokjaer, S.

In: European Journal of Pharmaceutical Sciences, Vol. 27, No. 2-3, 2006, p. 194-204.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Interfacial adsorption of insulin. Conformational changes and reversibility of adsorption

AU - Mollmann, S.H.

AU - Bukrinsky, J.T.

AU - Elofsson, U.

AU - Norde, W.

AU - Frokjaer, S.

PY - 2006

Y1 - 2006

N2 - The adsorption of human insulin to Teflon particles was studied with respect to conformational changes and the reversibility of adsorption was examined by total internal reflection fluorescence (TIRF). Adsorption isotherms for the adsorption of human insulin indicated high affinity adsorption, even at electrostatic repulsive conditions. The plateau value for adsorption was in accordance with a protein layer consisting primarily of insulin monomers. Conformational changes of the insulin upon adsorption, was investigated by circular dicroism (CD) and fluorescence spectroscopy. The results suggested unfolding of adsorbed insulin, as observed by a decrease in ¿-helix and increase in random coil conformation. The changes in protein structure was not only related to the adsorbed species being monomeric, since CD and fluorescence results were different for adsorbed insulin compared to a monomeric analog of human insulin. Furthermore, the thermal stability in the adsorbed state was changed compared to insulin in solution. On the basis of the TIRF studies with FITC-labelled insulin it was not possible to firmly conclude whether exchange between human insulin in the adsorbed state and in solution takes place, due to the limited time range investigated. However, the desorption mechanism appeared to be different with unlabelled insulin in the bulk solution compared to phosphate buffer

AB - The adsorption of human insulin to Teflon particles was studied with respect to conformational changes and the reversibility of adsorption was examined by total internal reflection fluorescence (TIRF). Adsorption isotherms for the adsorption of human insulin indicated high affinity adsorption, even at electrostatic repulsive conditions. The plateau value for adsorption was in accordance with a protein layer consisting primarily of insulin monomers. Conformational changes of the insulin upon adsorption, was investigated by circular dicroism (CD) and fluorescence spectroscopy. The results suggested unfolding of adsorbed insulin, as observed by a decrease in ¿-helix and increase in random coil conformation. The changes in protein structure was not only related to the adsorbed species being monomeric, since CD and fluorescence results were different for adsorbed insulin compared to a monomeric analog of human insulin. Furthermore, the thermal stability in the adsorbed state was changed compared to insulin in solution. On the basis of the TIRF studies with FITC-labelled insulin it was not possible to firmly conclude whether exchange between human insulin in the adsorbed state and in solution takes place, due to the limited time range investigated. However, the desorption mechanism appeared to be different with unlabelled insulin in the bulk solution compared to phosphate buffer

KW - internal-reflection fluorescence

KW - homomolecular exchange

KW - circular-dichroism

KW - structural-changes

KW - aqueous-solutions

KW - fibril formation

KW - solid-surfaces

KW - in-situ

KW - protein

KW - aggregation

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VL - 27

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JO - European Journal of Pharmaceutical Sciences

JF - European Journal of Pharmaceutical Sciences

SN - 0928-0987

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ER -