Zwitteriona

Zwitteriona denotes a zwitterionic molecule—one that contains both positively and negatively charged groups within a single structure, giving rise to an overall neutral charge under most physiological or aqueous conditions.

Structure and formation: Zwitterions arise when internal proton transfer occurs between acidic and basic groups, such as amino and carboxyl groups in amino acids; at a characteristic pH, the isoelectric point, the molecule exists predominantly as a zwitterion. For example, glycine carries NH3+ and COO− in water. This internal charge separation creates a high dipole moment and affects intermolecular interactions.

Properties and behavior: Zwitterions exhibit high polarity and strong hydration, typically resulting in good water solubility and limited solubility in nonpolar solvents. Their charge distribution influences conformation and binding, and many zwitterions can form internal salt bridges that influence stability in both solid and solution states. Their performance is often sensitive to pH, ionic strength, and solvent characteristics.

Occurrence and applications: In biochemistry, amino acids and peptides are commonly zwitterionic at physiological pH. In materials science, zwitterionic polymers and coatings show antifouling properties. In analytical chemistry, zwitterionic stationary phases improve the separation of ionic compounds. In medicine and pharmacology, zwitterionic drugs can exhibit improved solubility, stability, and bioavailability due to their balanced charge characteristics.

Detection and terminology: Techniques such as NMR, infrared spectroscopy, and mass spectrometry help identify zwitterionic character, while isoelectric focusing separates species by their isoelectric point. The term "zwitteriona" appears in some non-English texts as a direct noun for such species.