Biodrugs Flashcards
peptide drug
-max 50 amino acids
solution phase peptide synthesis
1)star with 1 equiv of amino acid
2) COUPLING: with 1 equiv of DIC with a protecting group
3) purification
4) deprotection
5) purification
6) repeat as needed
solution phase peptide synthesis: yield
80-90%
solution phase peptide synthesis: purification
crystallization or column chromatography
solution phase peptide synthesis: protecting groups
-Boc
-Fmoc
-Cbz
how to remove Boc
acid
how to remove Fmoc
base
how to remove Cbz
Pd/C, H2
What happens if amino acids are not protected in solution peptide synthesis?
-infinite amount of products
Solid phase peptide synthesis
1)attachment of two products
2) deprotection
3)Coupling
4) repeat 2 and 3
5) deprotection and cleavage from resin
6)purification by column chromatography
Solid phase peptide synthesis: yeild
over 99%
Solid phase peptide synthesis: solid phase purification
-filter and wash
Advantages of Solid phase peptide synthesis
-easy purification after each chemical step
-drive rxs to completion by using huge excess of reagents
-many different resins
Disadvantages of Solid phase peptide synthesis
-uses a lot of resources
-resins in expensive
-not great at making peptides>50 amino acids
What do you use native chemical ligation(Kent ligation) for?
-making large peptides or proteins
native chemical ligation(Kent ligation)
1) Transthioesterification: chemo selective reaction
2) Acyl transfer: spontaneous rearrangement
Limitations of native chemical ligation(Kent ligation)
-presence of cysteine in the product id REQUIRED
Why use native chemical ligation(Kent ligation) over standard peptide synthesis?
-large peptides can be coupled
-does not require side chain protection
-can be done in water pH-7
Why use native chemical ligation(Kent ligation) over biological protein production?
-free of biologic contaminants
-easier to scale up
-can easily introduce unnatural aa into protein
-circular proteins
-D-amino acids
Modified native chemical ligation for non cysteine containing peptides
1)normal native chemical ligation
2) selective desulfrization: at an alanine residue
presence of cysteine is ok if its protected
Desulfurization
-palladium catalyst and H2
-radical reduction
Modified native chemical ligation at valine
1) transthioesterfiication
2) acyl transfer
3)desulfurization
Racemization
-mixture of D and L isomers (1:1)
-affects all amino acids except Gly
-most of the time, partially racemized
-Avoid pH>8
Hydrolysis
-adition of OH
-imide intermediate
-Affects Asn and Gln
Avoid strong acids and bases: catalyze process
