can adversely influence localization when these molecules are used.F. Chang, Ph.D.METHODS. As
RESULTS.In both the infection and tumor mouse models, increased localization of radiolabel was achieved in animals receiving both injectates compared with control animals receiving only the radiolabeled PNA. In the infection model, the infected to normal thigh radioactivity ratio was 3.5 for the study animals compared with 1.7 for control animals (P Å 0.0001). In the tumor model, these values were 1.7 versus 1.2 (P Å 0.003).
CONCLUSIONS.We conclude that PNA may be considered an alternative to (strept)avidin and biotin for pretargeting studies.
Early Results in the Irrational Design of New Bifunctional Chelators BACKGROUND. The development of a simple route for the synthesis of the N-F. Chang, Ph.D. hydroxysuccinimide (NHS) ester of S-acetyl-protected mercaptoacetyltriglycine M. Rusckowski, Ph.D. (MAG 3 ) has opened the possibility of preparing novel bifunctional N 3 S chelators Timothy Qu, Ph.D.for technetium-99m ( 99m Tc) and other radionuclides. In particular, the synthesis Donald J. Hnatowich, Ph.D.may be applied to a vast number of tripeptides in place of triglycine, to provide a ''library'' of bifunctional N 3 S chelators, each with unique properties related to Department of Nuclear Medicine, University of the particular amino acid residues within each tripeptide.
METHODS. The authors have synthesized by this simple route the NHS esters of
Massachusetts.four N 3 S chelators by reacting NHS-S-acetylthioglycolic acid with ala-gly-gly, phegly-gly, pro-gly-gly, and ser-ser-ser, in addition to gly-gly-gly. Each bifunctional chelator was conjugated to biocytin as a model primary amine and radiolabeled with 99m Tc. The properties of the four chelators were compared with MAG 3 with respect to the stability of the label in saline and serum, the extent of serum protein binding, and the instability to cysteine challenge.
RESULTS.A range of values was observed. Labeled mercaptoacetyltriserine showed stability towards transchelation to cysteine similar to that of MAG 3 as well as lower serum protein binding; labeled mercaptoacetylalanyldiglycine showed slightly higher serum protein binding than labeled MAG 3 but greater stability to cysteine challenge.
CONCLUSIONS.The authors concluded that this simple synthesis and evaluation scheme may be used to prepare and screen a large library of bifunctional chelators for those with useful properties.
The authors concluded that this simple synthesis and evaluation scheme may be used to prepare and screen a large library of bifunctional chelators for those with useful properties.
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