Protein Instabilities + Formulation Flashcards
What are proteins stabilised by?
Non-covalent interactions
Disulfide bridges
What may changes in non-covalent interactions result in?
Misfolding/unfolding = aggregation = mutations
What are the formulation challenges?
Conformational stability during manufacturing process
High viscosity = high doses
Storage stability
Container + closure systems
What are the physical protein instabilities?
Aggregation
What are the chemical protein instabilities?
Deamidation
Oxidation
Disulfide bridge formation/breakage
Hydrolysis
Isomerisation
Deglycosylation
What factors affect protein stability?
Temperature
pH
Ionic strengths
Metal ions + chelating agents
Protein concentration
Surface
Describe chemical instabilities
Certain amino acids are more prone to degradation than others
Location is crucial in determining how prone to degradation
Describe deamidation
Most common
Glutamine + asparagine prone
Fast BUT dependent on pH
Describe oxidation
Takes place in presence of transition metal ions/exposure to UV light
Describe hydrolysis
Reverse reaction to peptide formation
Describe isomerisation
Rate influenced by location + mobility of amino acid side chain
How does buffers stabilise proteins?
Proteins often stable over narrow pH
What does it depend on whether a salt stabilises or destabilises protein structure?
Type + conc of salt
Nature of ionic interactions
How does amino acids stabilise proteins?
By preferential hydration
= decreases rate of chemical degradation
How does sugars + polyols stabilise proteins?
By preferential hydration effect
Effective against chemical degradation
How does surfactants stabilise proteins?
Stop protein adsorption on surfaces
What are multiple stabilisers?
Mixture of three or more amino acids
How does multiple stabilisers stabilise proteins?
Stabilise recombinant factor during lyophilization + storage
How does chemical conjugation stabilise proteins?
Enhance protein stability due to steric hindrance + changes in surface properties
What is the most widely used conjugation agent?
PEGs
What do PEGs do?
Stabilise proteins against different stresses
