title: [Preparation of a novel targeted MR contrast agent Gd-DTPA-streptavidin and exploration of its reaction conditions].
abstract: OBJECTIVE
  To explore the optimal reaction condition of DTPA-coupled streptavidin labeled with gadolinium ion.
  
  
  METHODS
  The number streptavidin-coupled of gadolinium ions and maximum biotin-binding capacity of Gd-DTPA-SA complex were analyzed at different DTPA-to-SA molar ratios (1000, 500, 200, 100) and in buffer solutions of different pH values (pH 5, 6, 7, and 8, respectively).
  
  
  RESULTS
  The number of streptavidin-coupled gadolinium ions increased with the pH value of the reaction system. When the DTPA-to-SA molar ratio was below 500, the number of gadolinium ions that SA-DTPA coupled increased with the DTPA-to-SA molar ratio, but tended to decrease when the ratio was 1,000. No significant difference in the maximum biotin-binding capacity of Gd-DTPA-SA complex was noted between the groups.
  
  
  CONCLUSIONS
  The number of gadolinium ions that streptavidin coupled depends on the pH value of the reaction system and DTPA-to-SA molar ratio, but the maximum biotin-binding capacity of Gd-DTPA-SA complex is not affected by the reaction conditions.
authors.affiliation: Medical Imaging Center, Nanfang Hospital, First Military Medical University, Guangzhou 510515, China. liuxian@fimmu.com
authors.forename: Xian
authors.initials: X
authors.lastname: Liu
authors.forename: Yi-kai
authors.initials: YK
authors.lastname: Xu
authors.forename: Qi-liu
authors.initials: QL
authors.lastname: Huang
mesh_terms: D003287:Contrast Media / Q000737:chemistry*; D019786:Gadolinium DTPA / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008279:Magnetic Resonance Imaging; D004369:Pentetic Acid / Q000737:chemistry*; D019809:Streptavidin / Q000737:chemistry*
chemical_list: D003287:Contrast Media; D004369:Pentetic Acid; D019809:Streptavidin; D019786:Gadolinium DTPA