Tuftsin analogs for probing its specific receptor site on phagocytic cells.

Six new analogs of the phagocytosis-stimulating peptide tuftsin were synthesized with the eventual aim of characterizing and isolating the tuftsin receptor. These analogs can be classified as follows: (a) photoaffinity labelling analogs for the specific covalent attachment to the tuftsin receptor: (b) fluorescent analogs containing either rhodamine or dansyl fluorescent probes for microscopic visualization of the tuftsin receptor; (c) biotin analog for separation and purification of the receptor by affinity methods. In this paper we describe the various synthetic pathways employed to introduce sensitive prosthetic groups into the tuftsin molecule while preserving its biological activity. Activities of the various analogs synthesized as compared to tuftsin in biological and receptor-binding assays are described. All analogs are able to stimulate phagocytosis of the macrophage cell as well as complete specifically for tuftsin binding sites on these cells.