Biophysical characterization of human protamine-1 as a responsive CEST MR contrast agent

Nikita Oskolkov, Amnon Bar-Shir, Kannie W Y Chan, Xiaolei Song, Peter C Van Zijl, Jeff W Bulte, Assaf A. Gilad, Michael T Mcmahon

Research output: Contribution to journalArticle

Abstract

The protamines are a low-molecular-weight, arginine-rich family of nuclear proteins that protect chromosomal DNA in germ cells by packing it densely using electrostatic interactions. Human protamine-1 (hPRM1) has been developed as a magnetic resonance imaging (MRI) chemical exchange saturation transfer (CEST) reporter gene, based on a sequence that is approximately 50% arginine, which has a side chain with rapidly exchanging protons. In this study, we have synthesized hPRM1 and determined how its CEST MRI contrast varies as a function of pH, phosphorylation state, and upon noncovalent interaction with nucleic acids and heparin (as antagonist). CEST contrast was found to be highly sensitive to phosphorylation on serine residues, intra- and intermolecular disulfide bridge formation, and the binding of negatively charged nucleotides and heparin. In addition, the nucleotide binding constants (Keq) for the protamines were determined through plotting the molar concentration of heparin versus CEST contrast and compared between hPRM1 and salmon protamine. Taken together, these findings are important for explaining the CEST contrast of existing arginine-rich probes as well as serving as a guideline for designing new genetic or synthetic probes. (Chemical Equation Presented)

Original languageEnglish (US)
Pages (from-to)34-38
Number of pages5
JournalACS Macro Letters
Volume4
Issue number1
DOIs
StatePublished - 2015

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Protamines
Contrast Media
Arginine
Phosphorylation
Heparin
Magnetic resonance
Nucleotides
Gene transfer
Imaging techniques
Nucleic acids
Coulomb interactions
Nuclear Proteins
Protons
DNA
Disulfides
Serine
Nucleic Acids
Molecular weight
Cells

ASJC Scopus subject areas

  • Organic Chemistry
  • Materials Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry

Cite this

Biophysical characterization of human protamine-1 as a responsive CEST MR contrast agent. / Oskolkov, Nikita; Bar-Shir, Amnon; Chan, Kannie W Y; Song, Xiaolei; Van Zijl, Peter C; Bulte, Jeff W; Gilad, Assaf A.; Mcmahon, Michael T.

In: ACS Macro Letters, Vol. 4, No. 1, 2015, p. 34-38.

Research output: Contribution to journalArticle

Oskolkov, Nikita ; Bar-Shir, Amnon ; Chan, Kannie W Y ; Song, Xiaolei ; Van Zijl, Peter C ; Bulte, Jeff W ; Gilad, Assaf A. ; Mcmahon, Michael T. / Biophysical characterization of human protamine-1 as a responsive CEST MR contrast agent. In: ACS Macro Letters. 2015 ; Vol. 4, No. 1. pp. 34-38.
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