STRUCTURE-ACTIVITY-RELATIONSHIPS OF CYCLIC AND LINEAR PEPTIDE-T ANALOGS

Using the potent cyclic peptide T analog Thr-Thr-Asn-Tyr-Thr-Asp- as p arent compound, a series of analogues were synthesized and their poten cies in a monocyte chemotaxis assay were compared with those of corres pondingly modified linear peptides. Structure-activity relationships o bserved with cyclic compounds did not always parallel those determined with linear analogues. -Thr-Hse-Asn-Tyr-Thr-Asp- showed the highest a ffinity to CD4 receptor of monocytes of any peptide thus far studied. It also proved to be highly resistant to degradation by plasma or brai n enzymes.