title: Design and solid phase synthesis of new DOTA conjugated (+)-biotin dimers planned to develop molecular weight-tuned avidin oligomers.
abstract: Chemical modifications of the biotin carrier in pretargeted avidin–biotin radionuclide therapy may be of paramount importance for tuning the amount of the radioactivity delivered to cancer cells by labelled biotins. We report here the synthesis of a collection of new synthetic DOTA-constructs bearing two (+)-biotin molecules (bis-biotins), designed for the creation of multimeric Av units (tetramers) bonded to the antibody. All the syntheses were carried out following the solid phase strategy and growing the molecules on a Rink Amide resin. The biotin heads are connected through spacers containing PEG or non-PEG residues. Molecular modelling calculations suggested that the Av cross-linking ability of the bis-biotins depends mainly on the spacers length, with the best results being expected for arms affording distances in the range of 10–25 Å between the biotin carboxylate atoms, in the fully extended conformation. SEC-HPLC MALLS analysis of the products of our Av/bis-biotin reaction mixtures have confirmed this hypothesis. The bis-biotin 16, where the non-PEG linker ensured a distance of 26.7 Å between the biotin moieties, gave about 50% of Av oligomers while the shorter analogue 18 (19.5 Å) afforded 100% of an Av polymer containing about 21 protein units. Remarkably, the solubility of both the bis-biotins, i.e.16 and 18, in aqueous solutions was good and they showed excellent stability against the action of peptidases.
authors.affiliation: Interdepartmental Laboratory of Peptide & Protein Chemistry & Biology, University of Florence, 50019 Sesto Fiorentino, Firenze, Italy. annamaria.papini@unifi.it.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Pratesi
authors.forename: Mauro
authors.initials: M
authors.lastname: Ginanneschi
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Melani
authors.forename: Marco
authors.initials: M
authors.lastname: Chinol
authors.forename: Angela
authors.initials: A
authors.lastname: Carollo
authors.forename: Giovanni
authors.initials: G
authors.lastname: Paganelli
authors.forename: Marco
authors.initials: M
authors.lastname: Lumini
authors.forename: Mattia
authors.initials: M
authors.lastname: Bartoli
authors.forename: Marco
authors.initials: M
authors.lastname: Frediani
authors.forename: Luca
authors.initials: L
authors.lastname: Rosi
authors.forename: Giorgio
authors.initials: G
authors.lastname: Petrucci
authors.forename: Luigi
authors.initials: L
authors.lastname: Messori
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Papini
mesh_terms: D001360:Avidin / Q000737:chemistry*; D001710:Biotin / Q000138:chemical synthesis* / Q000737:chemistry*; D019281:Dimerization; D015195:Drug Design; D004355:Drug Stability; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry*; D007553:Isotope Labeling; D008958:Models, Molecular; D008970:Molecular Weight; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D060327:Solid-Phase Synthesis Techniques
chemical_list: D006573:Heterocyclic Compounds, 1-Ring; D001360:Avidin; C071349:1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid; D001710:Biotin