Dr John Merrick is characterizing a protein from a gene that

Dr John Merrick is characterizing a protein from a gene that he cloned from a frozen mammoth tissue. Since this protein has the ability to bind oxygen, Merrick called the protein OBP (oxygen binding protein). To characterize OBP, he decided to compare its O2 binding ability with that of elephant hemoglobin. He did the experiment at normal pH = 7.2 and at high pH = 6.9. Note that O_2 being a gas, its concentration\" is not measured in molarity, it is measured as a pressure and the units are \"mmHg\" (referring to old barometer usage). You can use this unit Your discussion, just treat it like a concentration. Dr Merrick concludes that mammoth OBP has a lower affinity for oxygen than elephant hemoglobin at normal pH. Is he correct? Justify your response. Dr Merrick repeats the experiment at high pH (pH = 6.9 and pH = 7.2 determine which protein is affected the most by the pH change? Describe concisely. Before this experiment, Dr Merrick didn\'t know whether the OBP that he cloned was a type of myoglobin or hemoglobin form mammoth. Now he is quite sure of what CAP is, what is it? and how can be know? Dr Merrick now measures the rates of complex formation (ka) at pH = 6.9. He found that the following values: For OBP: kA = 2 times 10^6 M^-1 s^-2

Solution

I am assuming that the question has some misprinted informtion. I am taking 6.9 as 9.0 as the authoor siad that the second pH was higher than 7.2.

Answers

a) No, Dr. Merrick\'s conclusion is wrong here. OBP has higher affinity to oxygen than the elephant haemoglobin. Careful observation of the plot at 7.2 pH reveals that % oxygen saturation (Y axis) of the two proteins was equal with a value of about 87% while, the corresponding oxygen partial pressure (X axis) were different with values about 22 and 34 for OBP and elephant haemoglobin, respectively. OBP showed higher oxygen staturation at lower oxygen partial pressure as compared to elephant haemoglobin. Hence, OBP had highe affinity to oxygne than elephant haemoglobin.

b) At a higher pH of 9.0, the dotted line plot shows that both OBP and elephant haemoglobin have become closely similar in terms of their oxyen affinity. Now by compaing the curves at pH 7.2 and 9.0 we can conclude that OBP has suffered the highest change due to pH change as compared to elephant haemoglobin.

c) Now, with the experiment it is clear that OBP is actually a type of myoglobin, not haemoglobin. It is based on the fact that myoglobin has higher oxygen affinity than haemoglobin.

d) The values mentioned in the picture are not clearly visible, therefore I can not answer it.