Final answer:
The molecular mass discrepancy of cyclin B in SDS-PAGE likely arises from its high fraction of hydrophobic amino acids that affect its interaction with SDS and consequent migration through the gel. The most likely reason for the discrepancy is option 1: Because it contains a high fraction of hydrophobic amino acids.
Step-by-step explanation:
SDS-PAGE Molecular Mass Discrepancy for Cyclin B
The molecular mass of cyclin B as estimated by SDS-PAGE can be significantly different from its predicted value due to the unique composition of its amino acids. SDS-PAGE is a technique that separates proteins based on size, under the denaturing conditions imposed by the detergent sodium dodecyl sulfate (SDS). Proteins are coated with SDS, which denatures them and masks the native charges. Thus, they carry a uniform negative charge and are separated solely based on their molecular size when an electric current is applied.
The question seems to suggest that the presence of certain types of amino acids within cyclin B could account for the discrepancy in molecular mass measurement. Hydrophobic amino acids, for instance, may cause abnormal migration patterns on the SDS-PAGE gel due to their tendency to interact differently with the SDS, which could lead to a higher or lower apparent molecular weight compared to the protein's actual size. This alteration is commonly attributed to the differential binding of SDS to the protein, affecting its conformation and resulting in anomalous mobility during the electrophoretic process.
Therefore, the most likely reason for the discrepancy is option 1: Because it contains a high fraction of hydrophobic amino acids. Hydrophobic residues could be less compatible with the SDS detergent, altering the protein’s conformation and causing it to migrate differently than predicted through the gel matrix.