Direct labelling of octreotide with 99mTc: effect of different concentration of reducing agents and amount of sodium pertechnetate on radiolabelling efficiency.

Octreotide, a synthetic analog of natural hormone somatostatin, was labelled with 99mTc. Labelling was accomplished by reduction of the cysteine bridge, which provided sulfhydryl groups for chelating with 99mTc. Sodium ascorbate and sodium dithionite in different concentrations were used as reducing agents. Different amounts of sodium pertechnetate were used for labelling of peptide. When the mass ratio of peptide and sodium ascorbate was 1:100 and the final concentration of dithionite in the labelling vial was 0.2-0.4 microg/microl with 0.18-1.48 GBq sodium pertechnetate more than 80% radiolabelling efficiency was confirmed by RP-HPLC, ITLC-SG and C18 Cartridge analysis. The stability of the 99mTc-peptide bond was evaluated by human serum challenge and that showed the stability was 90% after 4h.

Increased stability and lifetime of the complex formed between DNA and meta-phenyl-substituted Hoechst dyes as studied by fluorescence titrations and stopped-flow kinetics.

The large increase in fluorescence upon binding of five para- and meta-phenyl substituted hydroxy and methoxy derivatives of the Hoechst dye with poly[d(A-T)], d(CGCGAATTCGCG)2, and its corresponding T4-looped 28-mer hairpin was used to monitor the binding by equilibrium titrations and by stopped-flow kinetics. The affinity increases in the same order for the three DNAs: p-OH