Combining Phage Display and Next-Generation Sequencing for Materials Sciences: A Case Study on Probing Polypropylene Surfaces.

Phage display biopanning with Illumina next-generation sequencing (NGS) is applied to reveal insights into peptide-based adhesion domains for polypropylene (PP). One biopanning round followed by NGS selects robust PP-binding peptides that are not evident by Sanger sequencing. NGS provides a significant statistical base that enables motif analysis, statistics on positional residue depletion/enrichment, and data analysis to suppress false-positive sequences from amplification bias. The selected sequences are employed as water-based primers for PP-metal adhesion to condition PP surfaces and increase adhesive strength by 100% relative to nonprimed PP.

Features of Auxiliaries That Enable Native Chemical Ligation beyond Glycine and Cleavage via Radical Fragmentation.

Native chemical ligation (NCL) is an invaluable tool in the total chemical synthesis of proteins. Ligation auxiliaries overcome the requirement for cysteine. However, the reported auxiliaries remained limited to glycine-containing ligation sites and the acidic conditions applied for cleavage of the typically applied N-benzyl-type linkages promote side reactions. With the aim to improve upon both ligation and cleavage, we systematically investigated alternative ligation scaffolds that challenge the N-benzyl dogma. The study revealed that auxiliary-mediated peptide couplings are fastest when the ligation proceeds via 5-membered rather than 6-membered rings. Substituents in α-position of the amine shall be avoided. We observed, perhaps surprisingly, that additional ß-substituents accelerated the ligation conferred by the ß-mercaptoethyl scaffold. We also describe a potentially general means to remove ligation auxiliaries by treatment with an aqueous solution of triscarboxyethylphosphine (TCEP) and morpholine at pH 8.5. NMR analysis of a 13 C-labeled auxiliary showed that cleavage most likely proceeds through a radical-triggered oxidative fragmentation. High ligation rates provided by ß-substituted 2-mercaptoethyl scaffolds, their facile introduction as well as the mildness of the cleavage reaction are attractive features for protein synthesis beyond cysteine and glycine ligation sites.