The highly-cross absorbed DSB-X™ biotin goat anti—mouse IgG is prepared from antibodies that have been adsorbed against bovine, goat, human, rabbit and rat IgG and human serum to minimize crossreactivity. DSB-X™ biotin is a derivative of desthiobiotin, a stable biotin percursuor. DSB-X™ biotin utilizes a seven-atom spacer to increase the available of the DSB-X™ biotin conjugate to bind in the deep biotin-binding pocket of streptpavidin or avidin. Whereas harsh chaotropic agents and low pH are required to dissociate a biotin complex from avidin or steptavidin, binding can be reversed by adding excess D-desthiobiotin or natural D-biotin at neutral pH and at room temperature.