*2.6. Isothermal Titration Calorimetry*

Titration experiments are performed by using a Nano ITC Low Volume calorimeter from TA Instruments (New Castle, DE, USA) in accordance with our previously adopted protocol [44]. The sample cell (700 µL) and the syringe (50 µL) are filled with aqueous solutions of HA (from 0.1 to 0.7%*w*/*v*) and Gd-DTPA (1.5 mM) respectively. Injection volumes and intervals are fixed at 1 µL and 500 s, respectively. Measurements are performed at 25 ◦C with a stirring rate of 200 rpm. Analysis and modeling of the raw data is carried out using the NanoAnalyze (TA instruments, New Castle, DE, USA). The function adopted to analyze the ITC data is the sum of two models: independent sites model plus a constant used for the blank (i.e., Gd-DTPA in water). The first point is excluded from the analysis. Statistics of the thermodynamic parameters are calculated on 1000 trials with a confidence level equal to 95%.
