The present disclosure describes pan-SUMO trapping proteins and fusion proteins comprising the pan-SUMO trapping proteins that are stable and bind SUMO-modified proteins with high avidity. The proteins described herein can be used to detect the localization of SUMO-modified proteins cells. The proteins described herein can be used to identify biomarkers for diseases associated with oxidative stress. They can also be used to diagnose and monitor diseases associated with genotoxic and/or proteotoxic stress conditions.

The disclosure provides a peptide library with increased peptide diversity. The increase in peptide diversity can occur via cleavage of particular amino acids within a peptide. The disclosure further provides a method for promoting folding of a peptide into an active conformation.

The present disclosure describes pan-SUMO trapping proteins and fusion proteins comprising the pan-SUMO trapping proteins that are stable and bind SUMO-modified proteins with high avidity. The proteins described herein can be used to detect the localization of SUMO-modified proteins cells. The proteins described herein can be used to identify biomarkers for diseases associated with oxidative stress. They can also be used to diagnose and monitor diseases associated with genotoxic and/or proteotoxic stress conditions.

The preparation method for a polypeptide includes the steps of constructing an engineering strain for fusion-expressing a polypeptide gene with a Sumo tag, and inducing the engineering strain for the soluble expression of a polypeptide, obtaining a crude protein containing a polypeptide precursor from the engineering strain by purification, cleaving the crude protein containing the polypeptide precursor by a Ulp1 protease to remove the Sumo tag, and purifying a cleavage product of the Ulp1 protease by a method of acetonitrile combined with heating precipitation or a method of precipitation with hexafluoro isopropanol to obtain the polypeptide.

The present disclosure provides methods and compositions for determining the antigen specificity of T cells and in a scalable, high-throughput approach. The disclosure provides methods for producing RNA-barcoded pMHC multimers that can be decoded using single-cell RNA sequencing methods. Among these, disclosed herein are multivalent virus-like-particles bound with pMHC in E. coli cells that encapsulate an RNA barcode encoding the peptide identity.