Natural Polysaccharides Tuning Ice Nucleation by Charges

In nature, organisms evolve various adaptive strategies to survive extreme cold, such as producing antifreeze proteins and polysaccharides. While antifreeze proteins have been extensively studied due to their prominent role, the specific functions of natural polysaccharides in biological adaptation to extreme environments, particularly their ability to influence ice formation processes (e.g., nucleation, growth, or recrystallization), and the underlying mechanisms remain poorly understood. Here, we systematically investigated a series of linearly charged polysaccharides to elucidate their regulatory effects on ice nucleation processes. Experimental results demonstrated that polysaccharides with elevated negative surface charge densities exhibit an enhanced suppression of heterogeneous ice nucleation (HIN). Kinetic analysis of ice nucleation behavior revealed a critical dependence on the energy barrier scaling factor (Γ), highlighting its pivotal role in modulating nucleation dynamics. Through sum-frequency generation (SFG) spectroscopy, we further discovered that highly negatively charged polysaccharides induce pronounced orientational ordering of interfacial water molecules. This study provides novel insights into the charge-specific effects of natural polysaccharides on interfacial water orientation, enhancing our understanding of how highly negatively charged polysaccharides can effectively inhibit ice nucleation.