Site-Specific Labeling of Annexin V with F-18 for Apoptosis Imaging

Annexin V is useful in detecting apoptotic cells by binding to phosphatidylserine (PS) that is exposed on the outer surface of the cell membrane during apoptosis. In this study, we examined the labeling of annexin V-128, a mutated form of annexin V that has a single cysteine residue at the NH2 termi...

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Bibliographic Details
Published in:Bioconjugate chemistry 2008-08, Vol.19 (8), p.1684-1688
Main Authors: Li, Xuehe, Link, Jeanne M, Stekhova, Svetlana, Yagle, Kevin J, Smith, Christina, Krohn, Kenneth A, Tait, Jonathan F
Format: Article
Language:English
Subjects:
Annexin A5 - analysis
Annexin A5 - chemistry
Annexin A5 - isolation & purification
Annexin A5 - metabolism
Apoptosis
Binding Sites
Cells
Erythrocytes - cytology
Erythrocytes - metabolism
Fluorine Radioisotopes
Maleimides - chemistry
Maleimides - metabolism
Mutation
Positron-Emission Tomography
Protein synthesis
Proteins
Sensitivity and Specificity
Staining and Labeling - methods
Studies
Sulfhydryl Compounds - chemistry
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Summary:Annexin V is useful in detecting apoptotic cells by binding to phosphatidylserine (PS) that is exposed on the outer surface of the cell membrane during apoptosis. In this study, we examined the labeling of annexin V-128, a mutated form of annexin V that has a single cysteine residue at the NH2 terminus, with the thiol-selective reagent 18F-labeling agent N-[4-[(4-[18F]fluorobenzylidene)aminooxy]butyl]maleimide ([18F]FBABM). We also examined the cell binding affinity of the 18F-labeled annexin V-128 ([18F]FAN-128). [18F]FBABM was synthesized in two-step, one-pot method modified from literature procedure. (Toyokuni et al., Bioconjugate Chem. 2003, 14, 1253−1259). The average yield of [18F]FBABM was 23 ± 4% (n = 4, decay-corrected) and the specific activity was ∼6000 Ci/mmol. The total synthesis time was ∼92 min. The critical improvement of this study was identifying and then developing a purification method to remove an impurity N-[4-[(4-dimethylaminobenzylidene)aminooxy]butyl]maleimide 4, whose presence dramatically decreased the yield of protein labeling. Conjugation of [18F]FBABM with the thiol-containing annexin V-128 gave [18F]FAN-128 in 37 ± 9% yield (n = 4, decay corrected). Erythrocyte binding assay of [18F]FAN-128 showed that this modification of annexin V-128 did not compromise its membrane binding affinity. Thus, an in vivo investigation of [18F]FAN-128 as an apoptosis imaging agent is warranted.
ISSN:1043-1802
1520-4812
DOI:10.1021/bc800164d