Analytical techniques Flashcards
1
Q
Convert Nitrogen content to protein content, what it is used?
A
The nitrogen to protein conversion factor N-prot factor, g of protein/ g od nitrogen, but often a value of 6.25 is used.
2
Q
Molecular weight distribution:
A
- SDS-PAGE, for protein composition: which and how much of each, individual proteins are present in the sample. SDS surfactant that causes folded proteins to unfold and gives all the proteins a simlilar charge-to-mass ratio. Only individual polypetide chains are shown in the gel. Electric field, larger proteins move more slowely. E.g : caseins higher Mw thatn lactoglobulins.
- Size- exclusion chromatography: injected into a column. Will be separated on their hydrodynamic volume ( related to the molecular weight). `NATIVE´ conditions, no surfactants or reducing agents only buffer. Any aggregates or complex NOT dissociated.
3
Q
Measure solubility:
A
- Measured and disolve under solubility.
- pH adjusted with buffers.
- Centrifuged (to precipitate proteins that became insoluble).
- Determine the concentration od the supernatant with a colorimetric assay (Biuret).
4
Q
Free amino group content- Degree of hydrolysis.
A
Hydrolysis of the petide bonds–> liberation of free amino acids (colorimetric assays , OPA) and free carboxylic groups.