Peptide solid phase synthesis.

-related topics
peptide
synthetic
peptide synthesis
is a process of repeatedly adding
amino acids
in a solid-phase synthesis sequence that typically synthesizes from the C end (the base end) to the N end (the amino end). Solid-phase synthesis greatly reduces the difficulty of purifying each step of the product. In order to prevent the occurrence of side reactions, the side chains of the amino acids participating in the reaction are protected. The base end is free and must be active before reaction. There are two methods of solid-phase synthesis, namely Fmoc and tBoc. Since Fmoc has many advantages over tBoc, it is now mostly synthesized using Fmoc.
(1) the specific composition consists of the following loops:
. 1. De-protection: Fmoc-protected columns and monobodies must be removed from the amino protection group with an alkaline solvent (piperidine).
2. Activation and crosslinking: the nirch base of the next amino acid is activated by an activator. The active monosome is interlinked with the free amino reaction to form a peptide bond. In this step, a large number of
reagents are used
drive the reaction to complete. Loop: These two-step reactions are repeated until the composition is complete.
3. Escape and de-protection: Peptides are removed from the column and their protective groups are de-protected by a de-protective agent (TFA).
(2) resin selection and amino acid fixation . The most important feature of the separation of solid phase synthesis from other technologies is solid phase carriers, which must meet the following requirements: reaction points (or reaction groups) must be included so that the peptide chain is connected to these points and removed later; And chemical conditions are stable; the carrier must allow for rapid, unhindered contact between the growing peptide chain and reagents; and the carrier must allow sufficient connection points to give useful yield peptides per unit volume carrier, and the interaction between the vector-bound peptide chains must be minimized.
There are three main types of polymer carriers used for solid phase synthesis of polypeptides: polystyrene-styrene crosslinking resins, polyacrylamides, polyethylene-glycol resins and derivatives, which can only be directly connected to (first) amino acids if they are imported into the reaction group.
according to the imported reaction group, these resins and resin derivatives are divided into chloramethylene resin, carboxyl resin, amino resin or argon resin. BOC synthesis usually chooses chlorpymethyl resins, such as Merrifield resins, and FMOC synthesis usually chooses pyridine-based resins such as Wang's resins.the fixation of
amino acids is mainly achieved by protecting the co-price bonds formed between the amino acid's carboxyl and the resin's reaction group, and there are many ways to form co-price bonds: chlorpymethyl resins, which are usually pre-made to protect the amino acids of tetraammonium salts or sodium salts, potassium salts, cesium salts, and then, at appropriate temperatures, react directly with the resin or in the appropriate
organic
solvents such as dioxychloride. , DMF or DMSO reaction; carboxyl resin, usually added with appropriate shrink agents such as DCC or diazine, so that the protected amino acids and resins form a common ester to complete the amino acid fixation;
(3) Amino, carboxyl, side chain protection and removal
to successfully synthesize peptides with a specific amino acid sequence, it is necessary to temporarily participate in the formation of amino and niacin, while the amino acid side chain activity
gene
should also be protected, after the reaction will be removed from the protection gene. As with liquid phase synthesis, the type of alkyladrophexyl is used as the protective base of α amino in solid phase synthesis, because it is not easy to occur. The earliest is the use of pyrethroids, because it requires strong acid release conditions to remove, so later changed to statins (BOC) protection, with TFA (tefluoroacetic acid) de-protection, but not applicable to the synthesis of acid-unstable peptides such as tryptophan. Chang Meienlofer and Atherton et al. used the Carpino-reported Fmoc (9- methyl) as a α amino protection base, Fmoc-based acid is stable, but can be taken off with pyridine-CH2CL2 or pyridine-DMF, in recent years, Fmoc synthesis method has been widely used. The nirboxyl is usually protected by forming an ester base.
methyl and ethyl esters are commonly used methods for the protection of argon in progressive synthesis and can be removed or converted by saponification for use in piece combinations; For the synthesis of peptides containing cysteine, histamines, arginine and other amino acids with side-chain functional basis, in order to avoid side-reaction due to side-chain functional groups, it is generally necessary to use appropriate protective base to temporarily protect the side-chain group.
the choice of protective base should ensure that the side chain group does not participate in the reaction to the formation of alamide, but also ensures that the peptide synthesis process is not destroyed, and at the same time ensure that the final peptide chain can be removed when it is cracked. Such as the use of triamcinolone to protect the S-cysteine, acid or silver salt, mercury salt removed, histamine methane ring with 2,2,2,2-teflon-1-pyrethroid and 2,2,2-teflon-1-statin-statin ethyl protection, can be catalytic hydrogenation or cold trifluoroacetic acid removal. Arginine is protected with acetaminophen (Adoc) and dislodged with cold tropluoroacetic acid.
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