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Zwitterioniccarboxybetaine and sulfobetaine materials have shownan excellent ability to resist nonspecific protein adsorption. Itis desirable to obtain a better understanding of zwitterionicmaterials based on their molecular structures. This work aims to understandthe roles of charged groups in zwitterionic moieties and todesign new protein-resistant zwitterionic moieties beyond carboxybetaineand sulfobetaine. We conducted molecular simulations to studythe hydration, self-association, and protein interactions of 12 zwitterionicmoieties derived from three anionic groups (carboxylic, sulfonate,and sulfate) and four cationic groups (quaternary ammonium, tertiaryammonium, secondary ammonium, and primary ammonium). The partial chargesof atoms in these moieties were obtained from quantum chemical calculations.Hydration was studied by evaluating the hydration free energy of moietiesand the hydration structure and dynamics of the charged groups. Allzwitterionic moieties have strong hydration, but their structuraland dynamic properties depend on the types of cationic and anionicgroups involved. The self-association and protein interactions ofzwitterionic moieties also show relationships with the chargedgroups. Our simulation results indicate good protein-resistant abilityof several zwitterionic moieties, one of which has also beenshown by recent experiments. [ABSTRACT FROM AUTHOR]

Zwitterionic materials have showntheir excellent performance inmany biological and chemical applications. Zwitterionic materialspossess moieties that own both cationic and anionic groups. The associationsamong zwitterionic moieties through electrostatic interactions playan important role in properties of zwitterionic materials. However,the relationship between the molecular structures and associationsof zwitterionic moieties are still not well understood. This workcompared thermal- and salt-responsive behaviors of sulfobetaine andcarboxybetaine polymers by examining their rheological propertiesas a function of temperature and their hydrodynamic sizes as a functionof salt concentration. Results showed that carboxybetaine polymersdo not exhibit stimuli responses as expected from the antipolyelectrolytebehavior of zwitterionic polymers as observed in sulfobetaine polymers.We studied and compared the associations among zwitterionic moietiesin these two zwitterionic polymers using molecular dynamic simulations.Simulation results show that the charge-density difference betweencationic and anionic groups determines the associations among zwitterionicmoieties, which are responsible for different stimuli responses ofcarboxybetaine and sulfobetaine polymers. [ABSTRACT FROM AUTHOR]