Protein-polymer hybrids consisting of protein and natural polymers or synthetic polymers exhibit superior properties to un- modified proteins, generating a high demand for these materials in the fields of medicine, biotechnology, and nanotechnology. Herein, protein-polysaccharide hybrids were fabricated via the formation of an amide bond between bovine serum albumin （BSA） and chitosan （CS） using N-ethyl-N-（3-dimethylaminopropyl） carbodiimide hydrochloride （EDC） as the couple reagent. FTIR spectrum reveals that the carboxyl group of BSA conjugated with the amino group of chitosan backbone. The molecular weight of BSA-CS hybrids was identified by matrix-associated laser desorption ionization time of flight mass spectra （MALDI-TOF MS） and sodium dodecyl sulfate polyacrylamide gel electrophoresis （SDS-PAGE）. The maximum number of chitosan chains binding to each BSA molecule was estimated as 6, and the optimal number was estimated as 2. In addition, the secondary structure and surface property of BSA were dependent upon the number of polymer conjugating on protein. The secondary structure of BSA was not significantly changed, if a few chitosans were coupled with BSA. By further increasing the molar ratio of chitosan to BSA, the secondary structure of BSA was markedly damaged. The surface＇s negative charges of modified BSA also decreased. The result of native polyaerylamide gel electrophoresis （native-PAGE） also demonstrated the changes in surface charges and molecular weight of BSA-CS hybrids.
