This bifunctional compound, Mal-C2-cyclohexylcarboxyl-hydrazide (TFA salt), is used in bioconjugation and protein labeling. The maleimide group enables selective and efficient conjugation to free sulfhydryl (-SH) groups on cysteine residues under mild physiological conditions. The hydrazide group allows selective reaction with aldehydes or ketones (e.g., from periodate-oxidized glycans or modified biomolecules). The C2 spacer provides flexibility, while the cyclohexyl group enhances hydrophobicity and stability in biological environments. Applications include attaching peptides, proteins, or drugs to biomolecules or surfaces; targeted drug delivery; diagnostic assays; antibody-drug conjugates (ADCs) for cancer therapy; and research on protein interactions/modifications.