5. Refer to the titration curve of human serum albumin (HSA) in Figure 3.19 of y

Question

5. Refer to the titration curve of human serum albumin (HSA) in Figure 3.19 of your text. At what pH value would you estimate HSA to have no electrophoretic mobility? Explain your answer in a concise manner. Given the pH at which the zwitterionic form exists and using the data in the Figures 3.19 & 3.20, would you expect HSA to have proportionately more acidic side chains, or more basic side chains. Explain concisely. Based on Figure 3.20, does fibrinogen have a greater or lesser electrophoretic mobility at pH 8.6 than HSA? Explain. Given the pl values (Table 3.6) for these proteins how might their relative amino acid composition differ from cytochrome c? Again, explain concisely your reasoning. How might you experimentally establish your inferences about relative proportions of types of amino acid side chains? TABLE 3.6 pl Values for Some 5.9 5.5 5.8 Human serum albumin Zwitterion Fibrinogen Hemoglobin A 7.8 10.0 10.6 Cytochrome c Figure 3.19 CRP Pre A gM lgG Figure 3.20

Explanation / Answer

Any protein has the least mobility on its PI value. As on PI value the protein is present as zwitterion its net charge is zero. So, mobility is also not possible. Same with HSA it will have zero mobility at 5.9 pH.

According to the graph and the pI value i think that HSA has uncharged and non ploar side chains. As acidic side chains has its pI near to 2.5-3.2. And basic side chains has 7.5-10.7, and titration graph also shows us that there are only two ionizable group and have no side chains ionizable groups.

According to the figure 3.20 as we know that all proteins after there pI have NEGATIVE charge. So, according to this fact albumin has higher mobility than fibronogen.

According to the pI cytochrome c has more amount of basic amino acids like arginine and lysine whereas others like pepsin has a lot of basic amino acids. Most of these ezymes shows pI near 5-6 it shows they have uncharged side chains. Wheras pI near 7 shows the presence of histidine.

We can use mass spectroscopy for sequencing the proteins and analysing the proportion of various amino acids.

Related Questions

Navigate

• Browse (All)
• Browse 5
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.