Polyamide resin swells to 10 times its volume in polar solvents such as DMF, and it is higher in water. In nonpolar DCM, the expansion is much lower. In this sense, their properties are opposite to those of resins.
Sparrow JT et al. used some functional monomers when preparing polyamide resin: N-(2- (methylsulfonyl) acetylcarbonyl)-allylamine (MSC- allylamine), N- acryloyl-1, 6- diaminohexane hydrochloride [8], or N- methacryloyl-1. The resin loading is 0. 15- 1.4 mmol/g, which is very suitable for Fmoc chemical synthesis. Pure peptides can account for 80-95% of the crude product, including those amino acid sequences that failed to be synthesized by traditional PS resin. HaynieSL et al. prepared ethylenediamine modified polyamide resin (Pepsn K), and synthesized amphiphilic polypeptide on it, and reported that this polypeptide has bactericidal activity [10]. 3. Polyethylene glycol resin
3. 1 polyethylene glycol grafted polystyrene (PEG-PS)
It consists of insoluble PS matrix, to which polyethylene glycol (PEG) chains are attached. Like the polyamide resin discussed above, it tries to improve the solvation of peptide chains in solid-phase carriers. Pegs with different chain lengths have been studied, but the most successful application is that the molecular weight is between 2000 and 3000 da.
In recent years, the application of machines in peptide synthesis has developed rapidly. Mechanical synthesis includes semi-automatic (intermittent) and automatic (continuous flow). Compared with artificial synthesis, it has the advantages of rapidity, completeness and convenience. PEG-PS resin has been developed because of its good physical and chemical properties, such as swelling, physical stability, wear resistance and mechanical pressure resistance in flowing system. For example, Kate SA, McGuinners BF and others recently reported the advantages of "low load" (substitution value 0. 15-0.25mmol/g) and high load (0.3-0.5mmol/g)PEG-PS resin studied in our laboratory [1 1]. 3.2 New applications of PEGA resin and PEG resin
PEGA resin is a hydrophilic resin developed by Morten Melder, which is formed by crosslinking PEG with amide groups [4]. Generally used for intermittent and continuous flow polypeptide synthesis. Their properties are similar to those of PEG-PS resins, such as NovaSyn? The average bead size of TG resin (3- 1) is 90μm, and there are 2.86x106 beads per gram of resin. Because it is particularly suitable for continuous flow polypeptide synthesis. Novartis? TGA resin (3-2) is a branched PEG based on PS carrier, which can resist high flow rate and is an ideal choice for rapid synthesis of long-chain peptides. Others like Novartis? TGA resin (3-3) is functionalized by excellent Rink linker. Thus, polypeptide amide can be easily obtained by treating peptide-resin with TFA. In addition, it is noted that the resin has free amino groups, which will increase the stability of the product during storage; It also means that the first amino acid can be directly linked without pre-protection cycle. Their substitution values are usually 0.2-0.3 mmol/g. The Rink amide PEGA resin is also functionalized by the Rink linker, which is similar to the above (3-3): however, it has a higher substitution value (0.3-0.4mmol/g).
In recent years, some new applications of polyethylene glycol resins (such as PEGA) have attracted more and more interest. These applications include immunology, enzyme synthesis and enzyme analysis on resin, and the synthesis of polypeptide library, which is a powerful tool for discovering new drugs. The above (3- 1) is especially suitable for this kind of work.
Auzanneau FI et al. [12] studied three kinds of PEGA with high PEG content. The resin swells well in different solvents from water to DCM, and the loading capacity is 0.35 mmol/g. They synthesized several high-purity peptides on this resin, and the research shows that they have enough lethal activity as corresponding bactericidal peptides.
Renil M, Ferreras M and others [13] synthesized two types of PEGA. Poly (bis/monoacrylamide -PEG) and acrylamide PEG*** were used to obtain a resin with low crosslinking degree. In addition, a resin with more crosslinking was obtained by poly (acryloyl-sarcosine ethyl ester) and bisacrylamide PEG*** (type II). The carrier showed high expansibility in various solvents, including H2O, DCM, acetonitrile, TFA and toluene. Type I can be used in solid-phase enzyme library because of different monomer composition, and its capacity is between 0.07- 1.0mmol/g; After treating type II with ethylenediamine, it can be used to synthesize continuous polypeptide, and it can give quite good yield and purity.