Preparation of indium-115-labeled diethylenetriaminetetraacetic acid monoacetamide peptides purified by 8-hydroxyquinoline.
In this communication we describe a novel procedure for the preparation and purification of diethylenetriaminepentaacetic (DTPA)-acylated and (115)In(3+)-labeled oligopeptides using 8-hydroxyquinoline for the removal and quantification of nonbound indium ions. First the N(alpha)- or N(alpha),N(epsilon)-DTPA oligopeptides containing C-terminal KDEL signal motif were produced by solid-phase synthesis. For this the free carboxyl group of DTPA dianhydride was activated in situ for a short period of time yielding a major product. Reversed-phase HPLC-purified DTPA oligopeptides were labeled with (115)In(3+) in aqueous buffer solution at pH 3.8. For the removal as well as for the detection of uncoordinated (115)In(3+) ions we have utilized the (115)In(3+) complex-forming ability of 8-hydroxyquinoline in chloroform. Following an optimized extraction procedure the free indium ion content was measured by spectrophotometry in the organic phase. Data obtained by this method and verified by total-reflection X-ray fluorescence spectroscopy and thin-layer chromatography demonstrated that free (115)In(3+) could be efficiently removed and sensitively detected in the presence of DTPA oligopeptide chelator. No release of (115)In(3+) from its DTPA complex was observed. This method could be useful for the preparation of indium complexes of peptides and perhaps proteins containing a DTPA moiety and nonradioactive isotope ligand.
Nagy
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IB
Research Group for Peptide Chemistry, Hungarian Academy of Sciences, Eötvös L. University, Budapest 112, H-1518, Hungary.
Varga
I
I
Hudecz
F
F
D002021:Buffers; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D007204:Indium; D007553:Isotope Labeling / Q000379:methods*; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000302:isolation & purification; D015125:Oxyquinoline / Q000737:chemistry*; D004369:Pentetic Acid / Q000138:chemical synthesis* / Q000302:isolation & purification; D011786:Quality Control; D012680:Sensitivity and Specificity; D013052:Spectrometry, X-Ray Emission; D013997:Time Factors
D002021:Buffers; D009842:Oligopeptides; D007204:Indium; D015125:Oxyquinoline; D004369:Pentetic Acid