Use of tin-117m to study the role of tin in the direct labeling of proteins with rhenium-188

Journal Article · Wed May 01 04:00:00 EDT 1996 · Journal of Nuclear Medicine

OSTI ID:447778

Dadachova, E ^[1]; Mirzadeh, S; Knapp, Jr, F F ^[2]

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1. Australian Nuclear Science and Technology Organisation, Sydney (Australia)
2. Oak Ridge National Lab., TN (United States); and others

Sn-117m provided an opportunity to study the effect of [Sn(II)] on the complexation of carrier-free Re-188, radiolabeling efficiency and incorporation of Sn into reduced IgG. Endogenous thiols of the IgG were exposed using dithiothreitol. Reduction of Re-188 was achieved with SnCl{sub 2} [spiked with Sn-117m(II)] in either gluconate(Glu) or citrate(Cit) buffer at pH=4.2. Concentration of Sn(II) varied from 5x10{sup -4} to 1 mg per mg protein. Complexation of reduced Re-188 was monitored by ITLC-SG, and protein was monitored by HPLC. Complexation of Re-188 at [Sn(II)]=5x10{sup -4} mg was higher in Cit (20%) than in Glu (10%); at 5x10{sup -2} mg - 50% in both buffers; and at 1 mg - higher in Glu (95%) than in Cit (60%). The efficiency of protein labeling was considerably higher in Glu than in Cit for the entire range of [Sn(II)]. Experiments with Sn-117m demonstrated that the absolute amount of Sn(II) associated with protein increased with increasing [Sn(II)], and distinct saturation levels were found for both Glu and Cit. Saturation levels were 6.4 and 33 {mu}g of Sn/mg of protein for Flu and Cit, respectively (19 and 48% incorporation). For all [Sn(II)] studied, the amount of Sn bound to the protein was 5-10 times higher in Cit than in Glu. In summary, Glu seems to release Re for transchelation to the protein more readily than Cit. Simultaneously, it complexes Sn(II) more efficiently than Cit thus preventing competition between Re and Sn for thiol groups. These data provide additional insights into the mechanism of direct labeling of proteins with carrier-free Re-188 as well as into the choice of supporting ligand for direct labeling.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 447778
• Report Number(s): CONF-960659--
• Journal Information: Journal of Nuclear Medicine, Journal Name: Journal of Nuclear Medicine Journal Issue: Suppl.5 Vol. 37; ISSN JNMEAQ; ISSN 0161-5505
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
CITRATES
COMPLEXES
CONCENTRATION RATIO
GLUCONIC ACID
LABELLING
PROTEINS
RHENIUM 188
THIOLS
TIN