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 language | English (US) |
|---|---|
| Pages (from-to) | 252-264 |
| Number of pages | 13 |
| Journal | Contrast Media and Molecular Imaging |
| Volume | 8 |
| Issue number | 3 |
| DOIs | |
| State | Published - May 2013 |
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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 journal › Article
}
TY - JOUR
T1 - EPR assessment of protein sites for incorporation of Gd(III) MRI contrast labels
AU - Lagerstedt, Jens O.
AU - Petrlova, Jitka
AU - Hilt, Silvia
AU - Marek, Antonin
AU - Chung, Youngran
AU - Sriram, Renuka
AU - Budamagunta, Madhu S.
AU - Desreux, Jean F.
AU - Thonon, David
AU - Jue, Thomas
AU - Smirnov, Alex I.
AU - Voss, John C
PY - 2013/5
Y1 - 2013/5
N2 - 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.
AB - 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.
KW - Apolipoprotein A-I
KW - Electron paramagnetic resonance (EPR) spectroscopy
KW - High-density lipoprotein (HDL)
KW - Magnetic resonance imaging (MRI)
KW - Protein contrast agent
KW - Site-directed MRI label
UR - http://www.scopus.com/inward/record.url?scp=84876786430&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84876786430&partnerID=8YFLogxK
U2 - 10.1002/cmmi.1518
DO - 10.1002/cmmi.1518
M3 - Article
C2 - 23606429
AN - SCOPUS:84876786430
VL - 8
SP - 252
EP - 264
JO - Contrast Media and Molecular Imaging
JF - Contrast Media and Molecular Imaging
SN - 1555-4309
IS - 3
ER -