Di-, Tri-, Tetra-, and Pentacationic Alkylammonium Salts. Ligands Designed To Prevent the Nonspecific Electrostatic Precipitation of Polyanionic, Functionalized Cyclopentadienyltitanium-Substituted Heteropolytungstate Electron Microscopy Labels with Cationic Biomolecules.

Article abstract of DOI:10.1021/jo00388a041

This work relates to the use of organic functionalized heteropolytungstates (HPTs) as protein-specific electron microscopy labels.The objective is the development of a polycationic ligand that prevents the nonspecific precipitation reaction observed between certain polycationic biomolecules and polianionic heteropolytungstates.Simple tetra- and pentaammonium salts between Keggin HPT 1b or Dawson HPT 2b and amines 3-6 or quaternary ammonium compounds 8 and 9 were all of low aqueous solubility as were salts derived from the oxygenated partners 7, 11, 12, and 15-18.However, tetrakis quaternary salt 23a, which is made up of several highly oxygenated alkyl groups, effectively prevents precipitation between Dawson HPT 2b and the exemplary basic proteins lysozyme and poly-L-lysine as well as the lectin concanavalin A.