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 NH 2 terminus, with the thiol-selective reagent (18)F-labeling agent N-[4-[(4-[(18)F]fluorobenzylidene)aminooxy]butyl]maleimide ([(18)F]FBABM). We also examined the cell binding affinity of the (18)F-labeled annexin V-128 ([(18)F]FAN-128). [(18)F]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 [(18)F]FBABM was 23 +/- 4% (n = 4, decay-corrected) and the specific activity was approximately 6000 Ci/mmol. The total synthesis time was approximately 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 [(18)F]FBABM with the thiol-containing annexin V-128 gave [(18)F]FAN-128 in 37 +/- 9% yield (n = 4, decay corrected). Erythrocyte binding assay of [(18)F]FAN-128 showed that this modification of annexin V-128 did not compromise its membrane binding affinity. Thus, an in vivo investigation of [ (18)F]FAN-128 as an apoptosis imaging agent is warranted.
Li
Xuehe
X
Department of Radiology, University of Washington Medical Center, Seattle, Washington 98195, USA.
Link
Jeanne M
JM
Stekhova
Svetlana
S
Yagle
Kevin J
KJ
Smith
Christina
C
Krohn
Kenneth A
KA
Tait
Jonathan F
JF
D017304:Annexin A5 / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D017209:Apoptosis; D001665:Binding Sites; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism; D005462:Fluorine Radioisotopes; D008301:Maleimides / Q000737:chemistry / Q000378:metabolism; D049268:Positron-Emission Tomography; D012680:Sensitivity and Specificity; D013194:Staining and Labeling / Q000379:methods*; D013438:Sulfhydryl Compounds / Q000737:chemistry
D017304:Annexin A5; D005462:Fluorine Radioisotopes; D008301:Maleimides; D013438:Sulfhydryl Compounds; C043592:maleimide