Unquenchable Surface Potential Dramatically Enhances Cu2+ Binding to Phosphatidylserine Lipids

Xiao Cong, Matthew F. Poyton, Alexis J. Baxter, Saranya Pullanchery, Paul S. Cremer

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

Herein, the apparent equilibrium dissociation constant, KDapp, between Cu2+ and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (POPS), a negatively charged phospholipid, was measured as a function of PS concentrations in supported lipid bilayers (SLBs). The results indicated that KDapp for Cu2+ binding to PS-containing SLBs was enhanced by a factor of 17 000 from 110 nM to 6.4 pM as the PS density in the membrane was increased from 1.0 to 20 mol %. Although Cu2+ bound bivalently to POPS at higher PS concentrations, this was not the dominant factor in increasing the binding affinity. Rather, the higher concentration of Cu2+ within the double layer above the membrane was largely responsible for the tightening. Unlike the binding of other divalent metal ions such as Ca2+ and Mg2+ to PS, Cu2+ binding does not alter the net negative charge on the membrane as the Cu(PS)2 complex forms. As such, the Cu2+ concentration within the double layer region was greatly amplified relative to its concentration in bulk solution as the PS density was increased. This created a far larger enhancement to the apparent binding affinity than is observed by standard multivalent effects. These findings should help provide an understanding on the extent of Cu2+-PS binding in cell membranes, which may be relevant to biological processes such as amyloid-β peptide toxicity and lipid oxidation. (Chemical Equation Presented).

Original languageEnglish (US)
Pages (from-to)7785-7792
Number of pages8
JournalJournal of the American Chemical Society
Volume137
Issue number24
DOIs
StatePublished - Jun 24 2015

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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