N-Fmoc-N'-(azido-PEG4)-L-Lysine

N-Fmoc-N'-(azido-PEG4)-L-Lysine is a protected lysine building block featuring an azide functional handle and a PEG4 spacer, supplied as an Fmoc-compatible reagent for solid-phase workflows. As an azide-bearing click chemistry partner, it is commonly used to introduce bioorthogonal attachment points onto peptides, linkers, and molecular imaging scaffolds via copper-free or copper-catalyzed azide–alkyne cycloaddition. The PEG4 segment provides spacing and solubility benefits that help preserve accessibility of the reactive group in aqueous and biomolecular environments, making it valuable for downstream conjugation and surface or material functionalization.

1. Peptide Conjugation Handles

N-Fmoc-N'-(azido-PEG4)-L-Lysine is widely used during solid-phase peptide synthesis to incorporate a PEG-spaced azide functionality at a defined lysine position. Researchers and probe developers rely on this handle to enable modular late-stage conjugation of peptides with fluorescent dyes, affinity tags, or other reporter moieties using click chemistry. The PEG4 spacer helps reduce steric congestion around the azide, supporting efficient coupling to alkynyl partners while maintaining the peptide’s overall solubility and handling characteristics for labeling workflows.

2. Molecular Imaging Probes

N-Fmoc-N'-(azido-PEG4)-L-Lysine supports the preparation of imaging and detection reagents where a peptide or peptide-like scaffold must be equipped with a robust, orthogonal attachment point. By embedding the azide through Fmoc-based synthesis, imaging teams can subsequently attach alkynyl imaging reporters such as fluorophores or other signal-generating groups through click conjugation, facilitating rapid exchange of labels across probe libraries. The PEG4 linker is particularly useful when probe performance depends on maintaining accessibility of the labeling site in complex biological assay media and conjugate mixtures.

3. Biomaterials Surface Functionalization

N-Fmoc-N'-(azido-PEG4)-L-Lysine is used to introduce azide groups into polymeric or peptide-based biomaterials that require subsequent click-based coupling to functional surfaces. Material scientists incorporate this lysine-PEG-azide motif into hydrogel precursors, peptide-functional coatings, or crosslinking components so that alkynyl reagents can be attached post-fabrication under conditions compatible with sensitive functional groups. The PEG4 spacer improves the presentation of reactive sites at the material interface, which can be critical for consistent surface density and for reproducible attachment of ligands used in biosensing and research-grade surface engineering.

4. Affinity Reagent and Linker Libraries

N-Fmoc-N'-(azido-PEG4)-L-Lysine is a common choice for generating affinity reagent and linker libraries where modular assembly is needed across many constructs. By providing an Fmoc-protected azide-bearing lysine unit, it enables systematic variation of conjugation geometry and spacing when building peptide or peptidomimetic linkers that later undergo click attachment to alkynyl components such as capture ligands, biotin analogs, or detection handles. The PEG4 spacer supports flexible presentation of the conjugated group, helping maintain reactivity and accessibility across a range of downstream reagent formats used in biochemical research and assay development.