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PNAs: from birth to adulthood
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Resin Loading
Deprotection
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Coupling
Capping
Cleavage
Figure 1-6 Schematic representation of the synthesis of PNAs by Solid Phase Peptide Synthesis
(SPSS)
Different strategies can be used, depending on the group used to temporarily protect the
amino terminal moiety. In a perfect analogy with standard peptides, the first strategy used for
PNA synthesis was the Boc strategy 31 , but later also the Fmoc approach has been extensively
used 32 ; nowadays, these two are the most used strategies for PNA synthesis and also the most
affordable, since Boc and Fmoc protected PNA monomers (Figure 1-7) are today
commercially available. The synthesis of PNAs always starts with the loading of the resin
used with the first monomer of the sequence. The loading of the resin is important, because it
sets the amount of molecules growing for each solid support: the high resin loading usually
adopted in standard peptide synthesis (0.5-1 mmol/g in active sites) may cause problems
during the synthesis, due to the steric hindrance among the growing PNA chains; thus usually
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