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1. Measuring Absorbance with a spectrophotometer provides aunitless value. Why?

2. Name the reagent that will be used to measure theconcentration of BSA.

What does BSA stand for?

2b. Describe why BSA can be used as a protein standard

can u please help me with this question?

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Tod Thiel
Tod ThielLv2
28 Sep 2019

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Related questions

1. Look up the tyr and trp content and molecular masses ofbovine serum albumin and chicken

lysozyme in the ExPASy Protein Knowledgebase

  1. ExPASy Protein knowledgebase: http://www.uniprot.org

Search the Protein Knowledgebase (UniProtKB) for �bovine serumalbumin�. Select ALBU_BOVIN by clicking on accession P02769. Thensearch for �chick egg lysozyme� and select LYSC_CHICK by clickingon accession P00698. Scroll down each of these pages and you willcome to a section entitled "Sequence". This section gives thelength of the protein in amino acid residues, its molecular mass indaltons, and its sequence using one-letter abbreviations. Thesequence and molecular mass given for both BSA and chicken lysozymeare derived from the DNA sequence and therefore are of theunprocessed protein. This includes an N-terminal extension for bothproteins. To get the information about the processed protein,select �ProtParam� from the Tools function at the upper right ofthe protein sequence. Then click �GO�. This will take you to a newwindow with a list of regions of the protein that can be analyzed.Click on the numbers to the right of �CHAIN� (these numbers denotethe amino acid residues of the main chain. A new window will openthat shows only the amino acid sequence of the processed protein.Below the sequence you will find the molecular mass of theprocessed protein, listed as �molecular weight�, and a tableshowing the amino acid composition of the protein. You will findthe number of tyrosine and tryptophan resides listed on thistable.

2. Calculate ?mol tyr + trp / mg protein

for BSA and lysozyme.

3. Answer the following questions:

  1. Should a standard curve for a Lowry protein assay using a BSAstandard look identical to

    a standard curve based on lysozyme? Why or why not? A comparisonof the amino acid composition of these two proteins that you justcalculated will help you answer this question. If you believe thatthe curves will look different, be specific about how they will bedifferent.

  2. Why would it be poor lab procedure to use a standard curve froma previous assay and run an assay only on the new unknown sampleswith fresh reagents? Name specific sources of error that this wouldcreate.

BIOCHEM LAB HELP:

here are our data :

concentration absorbance
0.02mL 0.071A
0.04mL 0.090A
0.06mL 0.115A
0.1mL 0.156A
0.2mL 0.282A
0.3mL 0.357A
0.4mL 0.423A
0.6mL 0.626A
0.8mL 0.811A
1.0mL 1.040A
UMKNOWN 0.546


please answer all questions

Spectrophotometric Analysis of Protein

1. Provide the standard curve for your experiment and the calculation of the unknown concentration from absorbance.

2. Is the concentration of the unknown you calculated from your standard curve the same as the concentration of the unknown stock solution? Why or why not?

3. Explain the process through which the Biuret reagent complexes with proteins to produce the characteristic color.

4. Why is it important to condition your cuvette prior to each reading?

5. Why is it important to blank your spectrophotometer, prior to use?

6. The lab manual discusses how proteins have characteristic absorption at 275-280 nm due to the presence of tyrosine and tryptophan (to some extent phenylalanine as well) in addition to the absorbance that occurs at 190 nm. Why not simply measure the absorbance of our protein sample at this wavelength and forego the Biuret reagent entirely? Discuss this question in light of the information provided in your lab manual, your knowledge of protein structure, and limitations inherent to a teaching laboratory.

7. According to Beer’s law, the relationship between concentration and absorbance should be perfectly linear, as would be indicated by a linear regression (R^2) value of 1. However, often the regression value is less than one, indicating an imperfect correlation. Considering the possible limitations of the Beer-Lambert law, and give a detailed explanation as to why this result may have been observed.

The gene (R) inserted into the GMO varieties can be passed onto future generations, and exhibits an autosomal dominant inheritance pattern. A farmer cross-pollinates his non-GMO corn (rr) with the GMO variety (RR). What are the expected genotypic and phenotypic ratios of the offspring? [2 pt; L2; I.A.3]

25% RR, 50% Rr, 25% rr; three fourths are resistant and one fourth are susceptible to ECB infestation

50% rr, 50% RR; half are resistant and half are susceptible to ECB infestation

100% Rr; all are susceptible to ECB infestation

100% Rr; all are resistant to ECB infestation

2 points

Question 17

To create the GMO derivatives, the CRY gene from Bacillus thuringensis was cloned, and the cloned gene was introduced into the corn plant. How was this most likely accomplished? [2 pt; L1; II.C]

by infecting the corn plants with Bacillus thuringensis

using a recombinant plasmid containing the CRY gene

by co-culturing Bacillus thuringensis with the corn plants

growing the corn plants under UV light to introduce random mutations

2 points

Question 18

To determine the amount of CRY protein produced by the GMO derivatives, which assay would be used? [1 pt; L2; II.C]

measure the intensity of the orange color produced by the precipitation of the CRY protein with Benedict’s reagent using a spectrophotometer set to 520 nm

measure the intensity of the violet color produced by the reaction of the CRY protein with the biuret reagent using a spectrophotometer set to 540 nm

measure the intensity of the red color produced by the reaction of the CRY protein with the Allura Red reagent using a spectrophotometer set to 480 nm

measure the intensity of the blue color produced by the reaction of the CRY protein with the iodine reagent using a spectrophotometer set to 620 nm

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