BSA Concentration Determination Quiz
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Questions and Answers

What is the formula to calculate dilution factor (DF)?

  • Dilution factor = Final volume / Initial volume
  • Dilution factor = Initial concentration / Final concentration (correct)
  • Dilution factor = Initial volume / Final volume
  • Dilution factor = Final concentration / Initial concentration

    • What is the wavelength of maximum absorption of the Coomassie Brilliant Blue G-250 dye when it is not yet bound to protein?

  • 1 < pH < 2 (correct)
  • Information is not given in the text
  • pH < 1
  • pH > 2

    • How is the Coomassie Brilliant Blue G-250 dye affected by different pH levels?

  • At pH > 2, the dye has + charge and turns red/brown
  • At pH > 2, the dye has – charge and turns blue (correct)
  • At pH < 1, the dye has – charge and turns blue
  • At pH < 1, the dye has no net charge and turns green

    • What happens to the protein's conformation upon initial contact with CBB G-250 dye?

    <p>The protein's hydrophobic regions are exposed</p> Signup and view all the answers

    How is the Bradford reagent prepared?

    <p>With methanol (or ethanol) and glacial acetic acid</p> Signup and view all the answers

    What does the UV-visible spectrophotometer measure?

    <p>Absorbance or transmittance of light in the ultraviolet and visible range</p> Signup and view all the answers

    At which wavelength does the protein-bound dye absorb orange light strongly?

    <p>595 nm</p> Signup and view all the answers

    What is the Beer-Lambert law's relationship between absorbance and concentration?

    <p>Absorbance is directly proportional to concentration</p> Signup and view all the answers

    What happens if the absorbance of a sample is higher than the absorbance of the standard solution with the highest concentration?

    <p>Another standard solution with a higher concentration should be prepared</p> Signup and view all the answers

    Why should absorbance be measured immediately after mixing the dye with the protein sample?

    <p>To prevent the formation of unwanted precipitates</p> Signup and view all the answers

    What does the correlation coefficient (R or r) measure?

    <p>The strength and direction of the linear relationship between two variables</p> Signup and view all the answers

    What does the coefficient of determination (R2 or r2) quantify?

    <p>The proportion of variance in the dependent variable explained by the independent variable</p> Signup and view all the answers

    What color does the reaction produce in the Biuret Assay?

    <p>Faint blue to purple</p> Signup and view all the answers

    In which wavelength is the absorbance measured in Colorimetric copper-based assays?

    <p>280 nm</p> Signup and view all the answers

    What does the Lowry Assay primarily measure in protein samples?

    <p>The protein concentration in a sample</p> Signup and view all the answers

    What is the color produced by the Lowry Assay?

    <p>Intense blue color measured at 750 nm</p> Signup and view all the answers

    Which protein quantitation technique can detect lower protein concentrations than the Biuret assay?

    <p>BCA Assay</p> Signup and view all the answers

    What does the Folin-phenol reagent do in the Lowry Assay?

    <p>Binds to the peptide-copper complex, producing an intense blue color</p> Signup and view all the answers

    How is homology modeling related to the Lowry Assay?

    <p>It predicts the unknown three-dimensional structure of a protein</p> Signup and view all the answers

    What is the function of the Lowry Assay?

    <p>To measure protein concentration based on color intensity</p> Signup and view all the answers

    What is the best protein to use as a standard in a protein assay?

    <p>Purified preparation of the protein being assayed</p> Signup and view all the answers

    Why are the standard curves made using the same concentrations of 2 different proteins not the same?

    <p>Because BSA and BGG have different color sources</p> Signup and view all the answers

    Where should the Bradford reagent be stored?

    <p>In a cool, dark place</p> Signup and view all the answers

    Why should the incubation of protein solutions after mixing with the Bradford reagent be done away from light?

    <p>To ensure accurate color development</p> Signup and view all the answers

    In the absence of an absolute reference protein, what should be used as a relative standard in a protein assay?

    <p>The protein being assayed</p> Signup and view all the answers

    What is the purpose of using a protein standard like Bovine serum albumin (BSA) in the Lowry assay?

    <p>To compare the absorbance of the protein sample with a known standard</p> Signup and view all the answers

    In the given data, what is the relationship between the protein standard's concentration (ug/uL) and its absorbance?

    <p>The absorbance increases as the concentration increases</p> Signup and view all the answers

    What is the formula used to calculate the concentration (x) of a protein sample based on its absorbance (y) in the Lowry assay?

    <p>$x = \frac{y + 0.0007}{0.2869}$</p> Signup and view all the answers

    Why are protein samples concentrations unknown in the Lowry assay?

    <p>To allow for comparison with a known protein standard</p> Signup and view all the answers

    What is the significance of the equation y = 0.2869x – 0.0007 in the context of the Lowry assay?

    <p>It represents the relationship between absorbance and concentration for a specific protein standard</p> Signup and view all the answers

    What is the result of converting 2 mg/mL to ug/uL?

    <p>1000 ug/uL</p> Signup and view all the answers

    What is the result of converting 2 mg/mL to ug/mL?

    <p>2000 ug/mL</p> Signup and view all the answers

    What volume of BSA stock solution is needed to prepare 500 uL of 2 ug/uL BSA solution, if the BSA stock solution has a concentration of 10 ug/uL?

    <p>50 uL</p> Signup and view all the answers

    What does the formula C1V1=C2V2 represent?

    <p>Dilution formula</p> Signup and view all the answers

    What is the final volume for a new BSA concentration if 2 ug/uL BSA solution is prepared using 100 uL of BSA stock solution with a concentration of 20 ug/uL?

    <p>200 uL</p> Signup and view all the answers

    What happens to the protein's conformation upon initial contact with Coomassie Brilliant Blue G-250 dye?

    <p>It undergoes partial unfolding</p> Signup and view all the answers

    What is the wavelength of maximum absorption of Coomassie Brilliant Blue G-250 dye when it is not yet bound to protein?

    <p>$300-400$ nm</p> Signup and view all the answers

    "Coomassie Blue" stains proteins by binding to which amino acid residues?

    <p>[Arginine and lysine]</p> Signup and view all the answers

    What is the formula to calculate dilution factor (DF)?

    <p>DF = Vf / Vi</p> Signup and view all the answers

    Study Notes

    Protein Quantitation and Assays

    • The formula to calculate dilution factor (DF) is not specified in the text.
    • The wavelength of maximum absorption of the Coomassie Brilliant Blue G-250 dye when it is not yet bound to protein is 465 nm.
    • The Coomassie Brilliant Blue G-250 dye is affected by different pH levels, with varying absorption spectra.
    • Upon initial contact with CBB G-250 dye, the protein's conformation changes, allowing the dye to bind.
    • The Bradford reagent is prepared by mixing the Coomassie Brilliant Blue G-250 dye with other reagents.
    • The UV-visible spectrophotometer measures the absorbance of a sample at a specific wavelength.
    • The protein-bound dye absorbs orange light strongly at a wavelength of 595 nm.
    • The Beer-Lambert law states that there is a linear relationship between absorbance and concentration.
    • If the absorbance of a sample is higher than the absorbance of the standard solution with the highest concentration, the sample may be too concentrated.
    • Absorbance should be measured immediately after mixing the dye with the protein sample to avoid errors.
    • The correlation coefficient (R or r) measures the strength of the linear relationship between variables.
    • The coefficient of determination (R2 or r2) quantifies the proportion of the variance in the dependent variable that is predictable from the independent variable.
    • The Biuret Assay produces a purple color.
    • In Colorimetric copper-based assays, the absorbance is measured at a wavelength of 540 nm.
    • The Lowry Assay primarily measures the protein content in protein samples.
    • The Lowry Assay produces a blue color.
    • The Lowry Assay can detect lower protein concentrations than the Biuret assay.
    • The Folin-phenol reagent reacts with the copper ions in the Lowry Assay to form a chromophore.
    • Homology modeling is not directly related to the Lowry Assay.
    • The function of the Lowry Assay is to quantify protein concentrations in a sample.
    • The best protein to use as a standard in a protein assay is a protein with a known concentration.
    • Standard curves made using the same concentrations of 2 different proteins are not the same due to differences in protein structure and composition.
    • The Bradford reagent should be stored in a dark place to avoid degradation.
    • The incubation of protein solutions after mixing with the Bradford reagent should be done away from light to prevent photobleaching.
    • In the absence of an absolute reference protein, a relative standard should be used in a protein assay.
    • The purpose of using a protein standard like Bovine serum albumin (BSA) in the Lowry assay is to create a standard curve.
    • The formula used to calculate the concentration (x) of a protein sample based on its absorbance (y) in the Lowry assay is y = 0.2869x – 0.0007.
    • Protein samples concentrations are unknown in the Lowry assay because the assay is used to quantify protein concentrations.
    • The equation y = 0.2869x – 0.0007 represents the linear relationship between absorbance and concentration in the Lowry assay.
    • 2 mg/mL is equivalent to 2 ug/uL.
    • 2 mg/mL is equivalent to 2000 ug/mL.
    • To prepare 500 uL of 2 ug/uL BSA solution, 100 uL of BSA stock solution with a concentration of 10 ug/uL is needed.
    • The formula C1V1=C2V2 represents the law of conservation of mass, used in dilution calculations.
    • The final volume for a new BSA concentration is 500 uL if 2 ug/uL BSA solution is prepared using 100 uL of BSA stock solution with a concentration of 20 ug/uL.
    • The protein's conformation changes upon initial contact with Coomassie Brilliant Blue G-250 dye.
    • Coomassie Blue stains proteins by binding to basic amino acid residues.
    • The formula to calculate dilution factor (DF) is not specified in the text.

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