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Biochromatography- Proteins (2)
Conan Lecture 2:
Terms in this set (21)
Describe the different types of protein and folding
-Peptide: small # of amino acid residues linked with a defined sequence
-Polypeptide: long chain of amino acid residues with either sequence of length undefined
-Protein: 1 or more polypeptide chain of specific sequence and length which FOLDS into specific conformation
Describe the different levels of protein structure and which bonds are important:
-Primary- amino acid sequence
-Secondary - structurally ordered domains within protein i.e. a-helices or B-sheets/coils.
-Tertiary-3D arrangement of various domains
-quarternary- assembly of multiple peptide chains to form a functional protein
di-sulfide, hydrogen and hydrophobic forces
List 3 physiochemical properties for chromatography
1. size and shape
2.change in charge
what is amphipathic?
a molecule that has both polar and non-polar portions to its structure
what are the 2 types of 2ndary structure beta sheets?
parallel and anti-parallel
What are disulphide bonds used for?
stabalizing protein using inter and intrachain bridges.
forms cans be misfiled by scrambled disulfide bonds
What is at the centre of a tertiary structure 40helix bundle?
hydrophobic core, hydrophyllic outer.
What does protein stability depend on?
pH and temperature
Describe how unfolded proteins occur and how to remedy this
unstable intermediates lead to aggregates that form an amount of unfolded proteins.
unfolded proteins can be refiled using protein conc. use batch dilution in a STR. long process.
Give 2 types of protein variations/isoforms
Microheterogeneity- (PTM, enzymatic processing)
Polymorphism- (point mutations, gene families, deletions)
List 3 types of PTMs
Glycosylation, deamidation, phosphorylation
What does it mean when a PTM is "not directly determined by genetic code"?
more variable and affected by processing
what does demidation achieve?
converts polar groups to acidic groups. proteins become more negatively charged.
What is the difference between N-linkage and O-linkage?
N= asparagine residue
O= serine residue
What does glycosylation achieve?
carbohydrates linked to proteins often affect the bioactivity, pharmacokinetics nd sometimes toxicity.
What are biosimilars? what opportunities & problems are associated?
-can copy the drugs produced by others.
They seek to emulate existing products using a different process that yields similar safety and efficiency but lower cost.
-complex processes, products and raw materials, inaccurate analytical tools, uncertain relationship between product quality and process.
for the dissociation of ionizable R-groups when is a charge negative/positive?
negative charge at pH>>pKa
positive charge at pH<<pKa
which kind of proteins are often easier to purify?
basic protieins (pI>8) PI= isoelectric point.
from 4-6 are most common (antibodies, whey proteins) so are harder to separate
what affects the pH of a protein? how does the pH affect the solubility of the protein?
The heterogeinity of its surface charge
protein solubility at its minimum at pI/pH=5.2 but is dependent on ionic strength and salt type. adding salt increases the solubility up to a point, and then some proteins "salt out"- precipitate out
Describe the viscosity and "syringability" of protein solutions
Newtonian behaviour at low concs and shear thinning at high concs > high conc=difficult to put through column due to high viscosity
Describe the time scales for diffusion
Td=L^2/Do time to diffuse=distance squared/diffusivity
the time to diffuse influences the scale of the process
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