I'm reading document about Solid phase protein synthesis (SPPS) from Wikipedia, and according to the document:
SPPS is limited by yields, and typically peptides and proteins in the range of 70 amino acids are pushing the limits of synthetic accessibility. Synthetic difficulty also is sequence dependent; typically amyloid peptides and proteins are difficult to make. Longer lengths can be accessed by using native chemical ligation to couple two peptides together with quantitative yields.
I'm a bit not understanding why this synthesis method is limited to 70 amino acids in length. Anyone please help me to explain what is the issue?