57 Questions
At which wavelength does the protein-bound dye absorb orange light strongly?
595 nm
What does the UV-visible spectrophotometer measure?
Absorbance or transmittance of light in ultraviolet and visible ranges
What is the Beer-Lambert law related to?
Concentration and absorbance
What should be done if the absorbance of a sample is higher than the absorbance of the standard solution with the highest concentration?
Both a and b
What causes interference with dye-protein complex formation in the protein solution?
Presence of surfactants/detergents
What should be the molecular weight of proteins to be detected by the Bradford assay?
$3 kDa$
For how long should absorbance be measured after mixing the dye with the protein sample?
Less than 1 hour
What is used to convert a given absorbance back to transmittance?
$Antilog [Absorbance]$
Up to what concentration is the absorbance measured with Bradford assay linear?
$2000 ug/mL$
What does the sensitivity of CBB G-250 vary with?
$Protein type$
How many micrograms per microliter (ug/uL) are equivalent to 2 milligrams per milliliter (mg/mL)?
2000 ug/uL
What is the equivalent concentration of 2 milligrams per milliliter (mg/mL) when expressed in micrograms per milliliter (ug/mL)?
2000 ug/mL
What volume of BSA stock solution would be needed to prepare 500 microliters of a 2 micrograms per microliter (ug/uL) BSA solution, if the BSA stock solution has a concentration of 10 micrograms per microliter?
250 uL
What is the formula used to prepare a dilute solution given the target concentration and final volume for the new solution?
C1V1=C2V2
If you have a BSA stock solution with a concentration of 10 micrograms per microliter, and you want to prepare a 500 microliter solution with a concentration of 2 micrograms per microliter, what would be the final volume after dilution?
500 uL
What is the equivalent concentration of 5 milligrams per milliliter when expressed in micrograms per microliter?
5000 ug/uL
If you have a solution with a concentration of 3 milligrams per milliliter, what would be the concentration in micrograms per microliter?
3000 ug/uL
For preparing a dilute solution using the formula C1V1=C2V2, what does 'C1' represent?
Concentration of the stock solution
What does 'V1' represent in the formula C1V1=C2V2 used for preparing dilute solutions?
Volume of the stock solution
If a stock solution has a concentration of 8 milligrams per milliliter and you want to prepare a 4 milligram per milliliter solution, what would be the final volume after dilution?
Equal to the stock solution volume
What is the equation for the line of best fit in the Bradford assay?
y = 0.2869x - 0.0007
If the absorbance (y) is 0.2772, what is the concentration (x) of the protein standard (BSA)?
0.9160 ug/uL
What is the absorbance value for a protein sample with a concentration of 0.5 ug/uL?
0.1401
What is the value of x when y = 0?
-0.0012
If the absorbance (y) is 0.25, what is the concentration (x) of the protein standard (BSA)?
-1.2434 ug/uL
What is the concentration of the protein sample with an absorbance of 0.2902?
-1 ug/uL
What is the relationship between absorbance (y) and concentration (x) in the Bradford assay?
y = -0.0012x + 0.2869
A dilution factor of 1:150 means that the solute is diluted 150 times in the final solution.
True
A 750 uL solution of a 1:150 dilution can be prepared by adding 5 uL of the stock solution to 745 uL of buffer or dH20.
True
If you know the concentration of the original solution, you can determine the concentration of the new dilute solution by multiplying the initial concentration by the dilution factor.
False
The dilution factor equation Final volume / Solute volume is represented as DF = Final volume + Solute volume.
False
The formula C1V1 = C2V2 can be used to prepare a dilute solution given the target concentration and final volume for the new solution.
True
A dilution factor of 1:12 means that the solute is diluted 12 times in the final solution.
True
If a stock solution has a concentration of 8 milligrams per milliliter and you want to prepare a 4 milligram per milliliter solution, the final volume after dilution would be double the initial volume.
False
Dilute solutions can only be prepared using a desired final concentration, not a desired dilution factor.
False
For a dilution factor of 1:150, the solute volume required for preparing a 750 uL solution would be 75 uL.
False
A dilution factor of 1:150 means that for every 1 part solute, there are 150 parts solvent in the final solution.
True
The dilution factor refers to how many times less concentrated the dilute solution is compared to the original solution.
True
The dilution factor is calculated by dividing the volume of solute plus the volume of diluent by the volume of solute.
False
In the example given in Q3, the dilution factor for the solution is 1:5.
True
The dilution factor for a solution prepared by adding 50 uL of unknown protein sample to 550 uL of grinding buffer would be 1:10.
False
If a stock solution has a concentration of 5 milligrams per milliliter and you want to prepare a 1 milligram per milliliter solution, the final volume after dilution should be 6 milliliters.
False
The formula V1=C2V2/C1 can be used to calculate the volume of diluent needed to prepare a dilute solution.
True
The dilution factor and the volume of solute are inversely proportional.
False
A dilution factor of 1:20 means that the dilute solution is 20 times more concentrated than the original solution.
False
If a solution is diluted 1:8, it means that 8 parts of solute are mixed with 1 part of diluent.
False
The final volume after dilution can be calculated using the formula C1V1=C2V2.
True
Secondary structures in polypeptides are formed by hydrogen bonding between side chains (R groups).
False
The diameter of a pi-helix is greater than that of an alpha-helix.
True
Tertiary structure of a polypeptide is held together by hydrogen bonding between the side chains.
False
The quaternary structure of a protein is only formed by the assembly of identical polypeptides.
False
X-ray crystallography is considered as the gold standard for determining the primary structure of proteins.
False
The Ramachandran plot shows the allowable phi and psi angles for amino acids so that the protein can form certain tertiary structures.
False
In the Ramachandran plot, each dot represents one amino acid in the polypeptide chain.
True
The PB Φ angle in the Ramachandran plot refers to the angle between the central carbon and carboxyl group of an amino acid.
False
The quaternary structure of a protein can never be formed by different subunits or polypeptide chains.
False
Protein crystals are used to determine the secondary structure of proteins.
False
Study Notes
Bradford Assay
- The protein-bound dye absorbs orange light strongly at a wavelength of 595 nm.
- A UV-visible spectrophotometer measures the absorbance of a sample.
- The Beer-Lambert law relates to the absorbance of a sample being directly proportional to the concentration of the sample.
- If the absorbance of a sample is higher than the absorbance of the standard solution with the highest concentration, the sample should be diluted and re-measured.
Protein Concentration
- The Bradford assay can detect proteins with a molecular weight of 3,000-200,000 Da.
- The assay is linear up to a concentration of 1,400 μg/mL.
- The sensitivity of CBB G-250 varies with the molecular weight of the protein.
- 1 μg/μL is equivalent to 1 mg/mL.
Solution Preparation
- The formula C1V1=C2V2 is used to prepare a dilute solution given the target concentration and final volume for the new solution.
- The dilution factor refers to how many times less concentrated the dilute solution is compared to the original solution.
- A dilution factor of 1:150 means that the solute is diluted 150 times in the final solution.
Protein Structure
- Secondary structures in polypeptides are not formed by hydrogen bonding between side chains (R groups).
- The diameter of a pi-helix is not greater than that of an alpha-helix.
- Tertiary structure of a polypeptide is not held together by hydrogen bonding between the side chains.
- Quaternary structure of a protein can be formed by the assembly of identical or different polypeptides.
- X-ray crystallography is not considered the gold standard for determining the primary structure of proteins.
- The Ramachandran plot shows the allowable phi and psi angles for amino acids so that the protein can form certain tertiary structures.
- The quaternary structure of a protein can be formed by different subunits or polypeptide chains.
- Protein crystals are not used to determine the secondary structure of proteins.
Test your understanding of converting concentrations between different units with these practice questions. Explore how to convert milligrams per milliliter to micrograms per microliter and micrograms per milliliter using the provided solutions. Practice using the formula C1V1=C2V2 as part of the quiz questions.
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