Unexpected side products in the conjugation of an amine-derivatized morpholino oligomer with p-isothiocyanate benzyl DTPA and their removal
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Authors
Liu, GuozhengDou, Shuping
Liu, Yuxia
Liang, Min Min
Chen, Ling
Cheng, Dengfeng
Greiner, Dale L.
Rusckowski, Mary
Hnatowich, Donald J.
Document Type
Journal ArticlePublication Date
2011-02-01Keywords
AminesAnimals
Base Sequence
Chemical Fractionation
DNA
Isothiocyanates
Isotope Labeling
Mice
Morpholines
Pentetic Acid
Phosphorus Compounds
Polymers
Chelator
Conjugation
Radiolabeling
DNA analogues
Radiochemistry
Radiology
Metadata
Show full item recordAbstract
In connection with pretargeting, an amine-derivatized morpholino phosphorodiamidate oligomer (NH(2)-cMORF) was conjugated conventionally with p-isothiocyanate benzyl-DTPA (p-SCN-Bn-DTPA). However, after (111)In radiolabeling, unexpected label instability was observed. To understand this instability, the NH(2)-cMORF and, as control, the native cMORF without the amine were conjugated in the conventional manner. Surprisingly, the (111)In labeling of the native cMORF conjugate was equally effective as that of the NH(2)-cMORF conjugate (>95%) despite the absence of the amine group. Furthermore, heating the radiolabeled NH(2)-cMORF and native cMORF conjugates resulted in a 35% loss and a complete loss of the label, respectively. Since the (111)In labeled DTPA is known to be stable, the instability in both cases must be due to some unstable association of DTPA to the cMORF, presumably unstable association to some endogenous sites in cMORF. Based on this assumption, a postconjugation-prepurification heating step was introduced, and labeling efficiency and stability were again investigated. By introducing the heating step, the side products were dissociated, and after purification and labeling, the NH(2)-cMORF conjugate provided a stable label and high labeling efficiency with no need for postlabeling purification. The biodistribution of this radiolabeled conjugate in normal mice showed significantly lower backgrounds compared with the labeled unstable native cMORF conjugate. In conclusion, the conventional conjugation procedure to attach the p-SCN-Bn-DTPA to NH(2)-cMORF resulted in side product(s) that were responsible for the (111)In label instability. Adding a postconjugation-prepurification heating step dissociated the side products, improved the label stability and lowered tissue backgrounds in mice.Source
Nucl Med Biol. 2011 Feb;38(2):159-63. doi: 10.1016/j.nucmedbio.2010.08.008. Link to article on publisher's siteDOI
10.1016/j.nucmedbio.2010.08.008Permanent Link to this Item
http://hdl.handle.net/20.500.14038/48390PubMed ID
21315270Related Resources
Link to Article in PubMedae974a485f413a2113503eed53cd6c53
10.1016/j.nucmedbio.2010.08.008