Effect of different glycation agents on Cu(II) binding to human serum albumin, studied by liquid chromatography, nitrogen microwave-plasma atomic-emission spectrometry, inductively-coupled-plasma mass spectrometry, and high-resolution molecular-mass spectrometry

Anal Bioanal Chem. 2015 Feb;407(4):1149-57. doi: 10.1007/s00216-014-8335-1. Epub 2014 Nov 27.

Abstract

The ability of human serum albumin to capture unbound copper under different clinical conditions is an important variable potentially affecting homeostasis of this element. Here, we propose a simple procedure based on size-exclusion chromatography with on-line UV and nitrogen microwave-plasma atomic-emission spectrometry (MP-AES) for quantitative evaluation of Cu(II) binding to HSA upon its glycation in vitro. The Cu-to-protein molar ratio for non-glycated albumin was 0.98 ± 0.09; for HSA modified with glyoxal (GO), methylglyoxal (MGO), oxoacetic acid (GA), and glucose (Glc), the ratios were 1.30 ± 0.22, 0.72 ± 0.14, 0.50 ± 0.06, and 0.95 ± 0.12, respectively. The results were confirmed by using ICP-MS as an alternative detection system. A reduced ability of glycated protein to coordinate Cu(II) was associated with alteration of the N-terminal metal-binding site during incubation with MGO and GA. In contrast, glycation with GO seemed to generate new binding sites as a result of tertiary structural changes in HSA. Capillary reversed-phase liquid chromatography with electrospray-ionization quadrupole-time-of-flight tandem mass spectrometry enabled detection and identification of Cu(II) coordinated to the N-terminal metal-binding site (Cu(II)-DAHK) in all tryptic digests analyzed. This is the first report confirming Cu(II)-DAHK species in HSA by means of high-resolution tandem mass spectrometry, and the first report on the use of MP-AES in combination with chromatographic separation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Chromatography, Gel
  • Chromatography, High Pressure Liquid
  • Chromatography, Reverse-Phase
  • Copper Sulfate / analysis*
  • Copper Sulfate / chemistry
  • Glucose / chemistry*
  • Glycosylation
  • Glyoxal / chemistry*
  • Glyoxylates / chemistry*
  • Humans
  • Protein Binding
  • Protein Structure, Tertiary
  • Pyruvaldehyde / chemistry
  • Serum Albumin / chemistry*
  • Spectrometry, Mass, Electrospray Ionization
  • Spectrophotometry, Atomic
  • Tandem Mass Spectrometry

Substances

  • Glyoxylates
  • Serum Albumin
  • Glyoxal
  • Pyruvaldehyde
  • Glucose
  • glyoxylic acid
  • Copper Sulfate