I've been trying to measure the total proteins in my colostrum samples but I haven't been able to get a right reading
In the same sample I can not get the same value in two experiments
So I've wondering if the viscocity in my samples affect the reading of the concetrations
Samples are typically diluted substantially in the Bradford method (e.g. 10 ul of sample + 200 ul of Bradford reagent) so the viscosity should not be a problem as long as the sample is well-mixed.
Before reading protein concentration in milk with the bradford method you should consider that:
Milk (and colostrum) contain CASEINS, that precipitate at pH below 4.6 and the bradford reagent is very acidic so caseins will cause turbidity and bad readings;
Milk is rich in fat (and colostrum is richer) and high fat concentrations can react with the bradford reagent too;
Caseins are not soluble molecules but they are organised in micelles, so the dye might not diffuse evenly through these protein particles, specially at low pH.
Bovine milk contains >30 mg/ml of protein, Human milk contains >10 mg/ml... colostrum may contain more than twice these concentrations, so you should dilute your sample before analysis about the middle of your standard curve (between 0.1 and 1.5 mg/ml, I think)
What protein do you use for your standard curve? Usually BSA is used and it is good if you want to compare relative values between samples. If you want to obtain more absolute values, then you should probably use the same protein for your standard curve (pure casein from Sigma, for instance)
Long story short,
I would suggest that you dilute your sample in a buffer compatible with the bradford reaction (check the product instructions) and that you dilute your standard with the same buffer. If it does not work, try to repeat your readings after skimming your (diluted) samples (centrifuge 20 minutes, 4°C, 1500 xg)...
Good luck
Hi, I agree totally with leonardo answer! When I worked on this subject, I always proceeded to milk./colostrum defatting and used not a BSA curve that is not adequate for colostrum but an IgG ou IgA (depending of species). You can work in the same way by a classical folin reaction that could be miniaturized in microplate
good luck
Hi. Midwife with 35 years of birthing experience. I have seen drops of colostrum, tried many times to extract colostrum, and never got more than a few drops. I am super curious to know how you get 10 cc of colostrum. If one manages to extract 10 cc or more, then in my experience, it isnt colostrum. It is mothers milk. looking forward to your answer