In 2010, a Van 't Hoff analysis was used to determine whether water preferentially forms a hydrogen bond with the "C"-terminus or the "N"-terminus of the amino acid proline. The equilibrium constant for each reaction was found at a variety of temperatures, and a Van 't Hoff plot was created. This analysis showed that enthalpically, the water preferred to hydrogen bond to the "C"-terminus, but entropically it was more favorable to hydrogen bond with the "N"-terminus. Specifically, they found that "C"-terminus hydrogen bonding was favored by 4.2–6.4 kJ/mol. The "N"-terminus hydrogen bonding was favored by 31–43 J/(K mol).