Biologicals 1 Flashcards
What interactions affect protein folding and stabiliation?
Hydrophobic interactions Electrostatic H-bonding VDW forces Steric effects Hydration Disulphide bridges
Deamidation of proteins is favoured at what pH?
pH 5 and above
What AAs are potential sites for oxidation?
His, Met, Cys, Trp and Tyr
Which peptide bonds are not stable?
X-Asp-Y
What is Tm?
Temperature at which 50% of molecules are unfolded, usually 40-80degC
Melting of proteins can lead to what?
Deaggregation
Chemical reactions are more rapid at elevated or lowered temperatures?
Elevated
What physical conditions affect proteins?
Temperature pH Adsorption Salts and metal ions Concentration Interfaces
What are the possible consequences of aggregation/denaturation?
Altered solubility Hypo-potency Hyper-potency Off target binding Patient may generate neutralising antibodies No effect
What steps in making proteins can go wrong?
Manufacture Formulation Sterilisation Storage Administration Release Adsorption Circulation
What is stability of proteins influenced by?
Choice of excipients
Storage conditions-liquid, forzen, lyophilised
Delivery route and vehicle
Stability and PK of proteins can be altered by what?
Chemical modifications
What gets added to most proteins when formulating?
Solubility enhancers Antiabsorption and antiaggregation agents Buffering agents Preservatives and anti-oxidants Lyoprotectants/cake formers Osmotic agents
sugars and some amino acids cause what?
Increased surface tension of water
What do cyclodextrins do?
Suppress aggregation of proteins
What are polysorbates thought to do?
Stabilise proteins, preventing denaturation and aggregation.
What mechanisms do polysorbates use?
Preferential exclusion of solutes.
Acting as a chemical chaperone aiding protein refolding.
Binding to hydrophobic patches of proteins.
Why do polysorbates form a detergent film in aqueous systems?
To limit protein exposure to air/water interface
Polysorbates compete with proteins to what?
Adsorb to surfaces-glass, IV bags, tubing materials etc.
Polyorbates can lead to what?
Protein aggregation and denaturation
what residues are susceptible to reactive peroxides?
W and M
What can help prevent reactive peroxides from polysorbates?
Antioxidants
Which residues are susceptible to aldehydes?
K and N
Formaldehyde an acetaldehyde cause contact allergies and are potential what?
Carcinogens
