Hyaluronan (HA) is an anionic, highly hydrated bio-polyelectrolyte found in the extracellular environment, like the synovial fluid between joints. We explore the extended hydration shell structure of HA in water using femtosecond elastic second-harmonic scattering (fs-ESHS). HA enhances orientational water-water correlations. Angle-resolved fs-ESHS measurements and nonlinear optical modeling show that HA behaves like a flexible chain surrounded by extended shells of orientationally correlated water. We describe several ways to determine the concentration-dependent size and shape of a polyelectrolyte in water, using the amount of water oriented by the polyelectrolyte charges as a contrast agent. The spatial extent of the hydration shell is determined via temperature-dependent measurements and can reach up to 475 nm, corresponding to a length of 1600 water molecules. A strong isotope effect, stemming from nuclear quantum effects, is observed when light water (H₂O) is replaced by heavy water (D₂O), amounting to a factor of 4.3 in the scattered SH intensity.

透明质酸 (HA) 是一种阴离子、高度水合的生物聚电解质，存在于细胞外环境中，例如关节之间的滑液。我们利用飞秒弹性二次谐波散射 (fs-ESHS) 探索了水中 HA 的扩展水合壳结构。 HA 增强水-水的定向相关性。角分辨 fs-ESHS 测量和非线性光学模型表明，HA 的行为就像一条被定向相关水的延伸壳包围的柔性链。我们描述了几种方法来确定水中聚电解质的浓度依赖性尺寸和形状，使用聚电解质电荷定向的水量作为造影剂。水化壳的空间范围通过与温度相关的测量来确定，最高可达 475 nm，相当于 1600 个水分子的长度。当轻水 (H ₂ O) 被重水 (D ₂ O) 取代时，会观察到源自核量子效应的强同位素效应，相当于散射 SH 强度的 4.3 倍。