Used in bioconjugation to link molecules or surfaces while maintaining biocompatibility. The SH group reacts selectively with maleimides or gold surfaces, enabling immobilization of proteins, peptides, or nanoparticles. The PEG spacer reduces non-specific binding and increases solubility in aqueous environments. Commonly applied in drug delivery systems, biosensors, and surface modification of medical devices. The terminal OH group allows further chemical modification or coupling to activated matrices. Stable in physiological conditions, making it suitable for in vivo applications.