This application provides a bead with a covalently attached chemical compound and a covalently attached DNA barcode and methods for using such beads. The bead has many substantially identical copies of the chemical compound and many substantially identical copies of the DNA barcode. The compound consists of one or more chemical monomers, where the DNA barcode takes the form of barcode modules, where each module corresponds to and allows identification of a corresponding chemical monomer. The nucleic acid barcode can have a concatenated structure or an orthogonal structure. Provided are method for sequencing the bead-bound nucleic acid barcode, for cleaving the compound from the bead, and for assessing biological activity of the released compound.

The present invention provides a method of solid-phase synthesis of DNA-encoded compound library. The method includes following steps: a) reacting solid carrier G-1 with linker molecule L-1 to prepare L-G-1; b) reacting DNA with linker molecule L-0 to prepare L-2; c) reacting L-G-1 with L-2 to prepare L-G-2; d) removing protection group of the L-G-2 and obtaining L-G-2-1; e) reacting the L-G-2-1 with synthetic building block and performing DNA encoding; and f) removing the solid carrier and obtaining the DNA-encoded compound library. Compared with the prior art, the present invention can complete post-treatment purification of the reaction only by filtration and irrigation processes for several times. The present invention is simple to operate, can shorten the production cycle of DNA encoded compound library with more than 50%, significantly increases the production efficiency and the unicity as well as the purity of the final products.

The present invention provides a method of solid-phase synthesis of DNA-encoded compound library. The method includes following steps: a) reacting solid carrier G-1 with linker molecule L-1 to prepare L-G-1; b) reacting DNA with linker molecule L-0 to prepare L-2; c) reacting L-G-1 with L-2 to prepare L-G-2; d) removing protection group of the L-G-2 and obtaining L-G-2-1; e) reacting the L-G-2-1 with synthetic building block and performing DNA encoding; and f) removing the solid carrier and obtaining the DNA-encoded compound library. Compared with the prior art, the present invention can complete post-treatment purification of the reaction only by filtration and irrigation processes for several times. The present invention is simple to operate, can shorten the production cycle of DNA encoded compound library with more than 50%, significantly increases the production efficiency and the unicity as well as the purity of the final products.

Provided herein is a method of sequencing hydroxymethyated cell-free DNA. In some embodiments, the method comprises adding an affinity tag to only hydroxymethyated DNA molecules in a sample of cfDNA, enriching for the DNA molecules that are tagged with the affinity tag; and sequencing the enriched DNA molecules.

The present disclosure methods for identifying binding partners using cell surface display libraries, where the cells of the library display engineered peptides on their cell surfaces for identification of peptides that bind to targets of interest. The engineered peptides are preferably expressed in the cells under conditions that provide both secretion and display of the engineered peptides on the cell surfaces, thus providing access of the engineered peptides to identify potential binding pairs. The cell libraries cab be engineered using an automated editing system that provides for one or more targeted edits per cell.

Provided herein is a method of sequencing hydroxymethylated cell-free DNA. In some embodiments, the method comprises adding an affinity tag to only hydroxymethylated DNA molecules in a sample of cfDNA, enriching for the DNA molecules that are tagged with the affinity tag; and sequencing the enriched DNA molecules.

Provided herein is a method of sequencing hydroxymethyated cell-free DNA. In some embodiments, the method comprises adding an affinity tag to only hydroxymethyated DNA molecules in a sample of cfDNA, enriching for the DNA molecules that are tagged with the affinity tag; and sequencing the enriched DNA molecules.

Provided herein is a method of sequencing hydroxymethyated cell-free DNA. In some embodiments, the method comprises adding an affinity tag to only hydroxymethyated DNA molecules in a sample of cfDNA, enriching for the DNA molecules that are tagged with the affinity tag; and sequencing the enriched DNA molecules.

Embodiments of a method and/or system, such as for preparation of a normalized library for sequencing such as next-generation sequencing, can include one or more of: generating one or more normalized amplicon libraries; generating one or more normalized microbial community-associated libraries; and/or generating one or more normalized combined sequence libraries associated with amplicon-associated sequencing and microbial community-associated sequencing.

Provided herein is a method of sequencing hydroxymethyated cell-free DNA. In some embodiments, the method comprises adding an affinity tag to only hydroxymethyated DNA molecules in a sample of cfDNA, enriching for the DNA molecules that are tagged with the affinity tag; and sequencing the enriched DNA molecules.