EPR assessment of protein sites for incorporation of Gd(III) MRI contrast labels

Jens O. Lagerstedt, Jitka Petrlova, Silvia Hilt, Antonin Marek, Youngran Chung, Renuka Sriram, Madhu S. Budamagunta, Jean F. Desreux, David Thonon, Thomas Jue, Alex I. Smirnov, John C Voss

Research output: Contribution to journalArticle

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Abstract

We have engineered apolipoprotein A-I (apoA-I), a major protein constituent of high-density lipoprotein (HDL), to contain DOTA-chelated Gd(III) as an MRI contrast agent for the purpose of imaging reconstituted HDL (rHDL) biodistribution, metabolism and regulation in vivo. This protein contrast agent was obtained by attaching the thiol-reactive Gd[MTS-ADO3A] label at Cys residues replaced at four distinct positions (52, 55, 76 and 80) in apoA-I. MRI of infused mice previously showed that the Gd-labeled apoA-I migrates to both the liver and the kidney, the organs responsible for HDL catabolism; however, the contrast properties of apoA-I are superior when the ADO3A moiety is located at position 55, compared with the protein labeled at positions 52, 76 or 80. It is shown here that continuous wave X-band (9GHz) electron paramagnetic resonance (EPR) spectroscopy is capable of detecting differences in the Gd(III) signal when comparing the labeled protein in the lipid-free with the rHDL state. Furthermore, the values of NMR relaxivity obtained for labeled variants in both the lipid-free and rHDL states correlate to the product of the X-band Gd(III) spectral width and the collision frequency between a nitroxide spin label and a polar relaxation agent. Consistent with its superior relaxivity measured by NMR, the rHDL-associated apoA-I containing the Gd[MTS-ADO3A] probe attached to position 55 displays favorable dynamic and water accessibility properties as determined by X-band EPR. While room temperature EPR requires >1m m Gd(III)-labeled and only >10μ m nitroxide-labeled protein to resolve the spectrum, the volume requirement is exceptionally low (~5μl). Thus, X-band EPR provides a practical assessment for the suitability of imaging candidates containing the site-directed ADO3A contrast probe.

Original languageEnglish (US)
Pages (from-to)252-264
Number of pages13
JournalContrast Media and Molecular Imaging
Volume8
Issue number3
DOIs
StatePublished - May 2013

Fingerprint

Apolipoprotein A-I
Electron Spin Resonance Spectroscopy
HDL Lipoproteins
Proteins
Contrast Media
Lipids
Spin Labels
Sulfhydryl Compounds
Spectrum Analysis
Kidney
Temperature
Water
Liver

Keywords

  • Apolipoprotein A-I
  • Electron paramagnetic resonance (EPR) spectroscopy
  • High-density lipoprotein (HDL)
  • Magnetic resonance imaging (MRI)
  • Protein contrast agent
  • Site-directed MRI label

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

Cite this

EPR assessment of protein sites for incorporation of Gd(III) MRI contrast labels. / Lagerstedt, Jens O.; Petrlova, Jitka; Hilt, Silvia; Marek, Antonin; Chung, Youngran; Sriram, Renuka; Budamagunta, Madhu S.; Desreux, Jean F.; Thonon, David; Jue, Thomas; Smirnov, Alex I.; Voss, John C.

In: Contrast Media and Molecular Imaging, Vol. 8, No. 3, 05.2013, p. 252-264.

Research output: Contribution to journalArticle

Lagerstedt, JO, Petrlova, J, Hilt, S, Marek, A, Chung, Y, Sriram, R, Budamagunta, MS, Desreux, JF, Thonon, D, Jue, T, Smirnov, AI & Voss, JC 2013, 'EPR assessment of protein sites for incorporation of Gd(III) MRI contrast labels', Contrast Media and Molecular Imaging, vol. 8, no. 3, pp. 252-264. https://doi.org/10.1002/cmmi.1518
Lagerstedt, Jens O. ; Petrlova, Jitka ; Hilt, Silvia ; Marek, Antonin ; Chung, Youngran ; Sriram, Renuka ; Budamagunta, Madhu S. ; Desreux, Jean F. ; Thonon, David ; Jue, Thomas ; Smirnov, Alex I. ; Voss, John C. / EPR assessment of protein sites for incorporation of Gd(III) MRI contrast labels. In: Contrast Media and Molecular Imaging. 2013 ; Vol. 8, No. 3. pp. 252-264.
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