1. How much protein is really in my… -milk? -soy “milk”?
Bradford Assay
How much protein is really in my…
-milk?
-soy “milk”?

2. Protein Qualitative v. Quantitative
Qualitative: Which of the following chemicals turns purple in the presence of protein?
Lugols iodine
Benedicts solution
Biuret Solution

3. Protein Qualitative v. Quantitative
But what if you want to know the concentration of protein in a solution?...how can this be quantified

4. Where do these numbers come from?
Both Soy “milk” and Cow milk have the same serving size: 1 cup…AKA 240ml

5. Protein Quantitation p220-221
Bradford Assay-developed 1976
Coomassie Brilliant Blue G-250 (AKA Bradford reagent) interacts w/ specific amino acids (especially the R-group on the amino acid arginine)
Protein Absent: redish-Brown
Protein present: blue (peak absorbance between 470nm & 595nm)
Amount of blue is proportional to protein concentration
The greater the protein concentration the more intense the blue color is!
Semi Micro Cuvettes

6. Which tube has a greater protein concentration… 3 or 7? 1 or 8?

7. How do we measure color? Smart Spec Plus by BioRad Spectrophotometer
Measures a specific wavelength of light absorbed by material.
Narrow beam of light at set wavelength shines through cuvette and sample…how much light makes through to the other side to be detected by the “detector”

8. How do we measure protein concentration. Activity 7
How do we measure protein concentration? Activity Youtube: Bradford Assay by BioRadLifeScience
Spectrophotometer
Smart Spec Plus by BioRad
Before determining unknown protein concentration (Unit read out will be in mg/ml)
Generate a standard curve of known protein concentrations!
SmartSec can save a standard curve…modify Activity 7.1 accordingly
you will only need to make unknown samples
Also, Ms. McKay will make a blank that everyone can share

9. Protein Concentration
Use Milk nutritional information to determine expected protein.
In a 1cup serving size (240ml) there are 8g protein
Give answer in 𝑚𝑔 𝑝𝑟𝑜𝑡𝑒𝑖𝑛 𝑚𝑙
Wait! Don’t we dilute the milk before we measure the protein concentration in the SmartSpec?
By what factor will the milk be diluted?
1/50
So in an ideal world, with an ideal cow, and “perfect” lab technique, how many mg or protein do you expect to measure per ml of 1/50th diluted milk?

10. Prelab Review p220-221 Activity 7.1
Read over Overview, tips and notes…etc
Can you answer Prelab Focus Questions?
In lab notebook
Purpose:….
Procedure: note that steps 6-8 are predone! Skip step 10! Note step 11 predone also!!! Stop after step 13!