April 2011
Volume 52, Issue 14
Free
ARVO Annual Meeting Abstract  |   April 2011
The Effect of Metal Cations on Protein-Protein Interactions in Human and Rabbit Tears
Author Affiliations & Notes
  • Eric Xiaojia Wei
    Brien Holden Vision Institute, Sydney, Australia
    School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
  • Zhenjun Zhao
    Brien Holden Vision Institute, Sydney, Australia
    School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
  • Mark D. Willcox
    School of Optometry & Vision Science, University of New South Wales, Sydney, Australia
    Vision CRC, Sydney, Australia
  • Footnotes
    Commercial Relationships  Eric Xiaojia Wei, None; Zhenjun Zhao, None; Mark D. Willcox, None
  • Footnotes
    Support  Brien Holden Vision Institute; Australian Postgraduate Award; Cornea and Contact Lens Society of Australia
Investigative Ophthalmology & Visual Science April 2011, Vol.52, 3731. doi:
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      Eric Xiaojia Wei, Zhenjun Zhao, Mark D. Willcox; The Effect of Metal Cations on Protein-Protein Interactions in Human and Rabbit Tears. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3731.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: : Protein-protein interactions may play a role in tear film stability due to their effect on tear film viscosity. Metal cations in solution have an effect on protein-protein interactions and thus tear film stability. As rabbits have a more stable tear film than humans, we sought to examine the tears of rabbits and humans for protein-protein interactions, metal types and concentrations and how they affect protein-protein interactions.

Methods: : Tears were collected from normal adult humans (n=10) and rabbits (n=6) using microcapillary tubes and pooled for each study group. Tear metal cations were analyzed using inductively coupled plasma (ICP) mass spectrometry and ICP atomic emission spectroscopy. Protein-protein interactions were studied using blue native-polyacrylamide gel electrophoresis (BN-PAGE). The effect of cations on protein-protein interactions was studied by using modified BN-PAGE in which cations were added to sample buffer and running buffer at levels of 0, human tears or rabbit tears.

Results: : Major metals in tears did not differ between species, however, rabbit tears had a higher concentration of divalent cations: [Mg2+], Human=0.39mM, Rabbit=1.13mM; [Ca2+], Human=0.38mM, Rabbit=0.75mM. In the absence of cations, protein-protein interactions were identified in both human (DMBT1-lactoferrin-lysozyme and lactoferrin-lipocalin) and rabbit tears (interactions of lipophilin subclasses). Additional protein-protein interactions were found in rabbit tears (prolactin inducible protein-lipophilins), but not in human tears, in the presence of cations at either of concentrations tested.

Conclusions: : The presence of cations shows no effect on protein-protein interactions in human tears, but increases the protein-protein interactions in rabbit tears. However, the cation’s contribution to tear film stability needs further investigation.

Keywords: cornea: tears/tear film/dry eye • protein structure/function • proteomics 
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