Method for the identification of a receptor

A method for the identification and investigation of a receptor in target tissue for which a selected vector has affinity, said method comprising:

• i) creating retroviral particles containing a library of mRNA from the targe tissue;
• ii) transfecting a non-adherent cell line which does not bind with the selected vector by infecting the cells with said retroviral particles;
• iii) adding to the transfected cell line a suspension of encapsulated gas microbubbles to which the selected vector is coupled and allowing the microbubbles and cells coupled thereto to float to the surface of the suspension;
• iv) isolating the microbubble-bound cells at the surface;
• and either
• v-a) lysing the isolated cells, amplifying the receptor-encoding cDNA therefrom and sequencing said cDNA;
• and optionally
• v-b) comparing the thus-obtained sequence data with gene bank sequence data;
• or
• vi-a) culturing the isolated cells;
• and
• vi-b) investigating affinities of vectors to the isolated cells.