The shape and magnitude of the UV spectra depends on the composition of amino acid in each protein.
800 WordsApr 23, 20194 Pages
The shape and magnitude of the UV spectra depends on the composition of amino acid in each protein. Due to the aromatic amino acid residues in the protein, the observed UV absorbance was mainly in the 240 nm to 340 nm region. In Figure 1 to 3, the maximal absorbance of each protein was approximately at 280 nm. The difference in magnitudes of the peak observed was linked to the differences in the amino acid contents in each of the proteins. The peak of lysozyme was greater than those of BSA and gelatin, because lysozyme has a greater number of tryptophan residues. Lysozyme has six tryptophan residues, whereas BSA and gelatin has two and zero, respectively (Department of Chemistry, 2014). Lysozyme has three times more tryptophan residues…show more content…
In order to examine the variation in sensitivity of lysozyme, gelatin, and BSA, the absorbance reading was obtained using the Bradford and BCA assay
Gelatin is observed to have a lower absorbance reading than lysozyme in only the Bradford assay, while in the BCA assay gelatin was observed to have about the same absorbance as lysozyme. In Bradford assay, the color yield for proteins with higher content of tryptophan, tyrosine, or cysteine residue, will be higher. The observed protein sensitivities did not correlates with the amino acid content in the Bradford assay. As presented in Table I, the mole fractions of lysine and arginine in BSA were 10 mole percent and 4 mole percent, respectively. The sensitivity should have been higher in BSA than in the Bradford assy. However, the observed sensitivities did correlates with the amino acid contents in the BCA assay. Bradford assay would be ideal if an accurate estimation of a newly isolated protein using BSA as a standard. With the data obtain from the Bradford assay, it shows that it was more sensitive and quicker, also it had less interference from substance that were possibly present in the protein solution, expect for the interfering substance SDS.
The interference of RNA and ME in the Bradford assay was compensated by using the blank, because the difference between the addition of the protein and the non-protein blank