Figure 5. Probing loop V by using “sliding ruler” approach.

Series of 29 dodecapeptides corresponding to the loop V sequence were synthesized using the pin method (Experimental Procedures). Each peptide in the series differed from its predecessor by one amino acid. The “ruler” has been moved from the C- to the N-end, allowing for complete coverage of the loop sequence. Binding of the IgG fraction from the umbilical cord serum was performed as described in Fig. 3. The results represent the average of the nine most active umbilical cord sera.