We’ve talked a lot in both lab and lecture about the importance of considering environmental effects in an experiment. I was thinking recently about two of the major obstacles we have discussed: pH levels and the presence of ions/salts. The water at Wellesley is horrifyingly hard, as my hair can demonstrate. if you leave some tap water out in an open container, it will evaporate away and leave a thin white film. This white film is calcium carbonate, which is the primary source of water hardness and has a pKa of 9.0, making it basic. One of the reasons we are so concerned about environmental conditions in our lab experiments is because pH levels and excess ions in solution can interfere with noncovalent bonds between proteins. Case in point: Human hair is composed of long, fibrous strands of proteins called keratin. These proteins undergo a variety of noncovalent bonds, notably disulfide bonds, which keep hair appearing happy and healthy. The ions and basicity of hard water can contribute to breaking disulfide bonds, which leads to damaged hair, ,split ends, and one unhappy Lynn. In summary, I think I need a better conditioner…