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Solid-phase oligonucleotide synthesis - ATDBio

Atherton E andSheppard RC(1989)Solid Phase Peptide Synthesis: A Practical ApproachOxford: IRL Press.

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Solid-Phase Peptide Synthesis | SpringerLink

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A fluorine-19 NMR approach for studying Merrifield solid phase peptide synthesis.

Currently, two protective groups (Fmoc, Boc) are commonly used in solid-phase peptide synthesis. Their lability is caused by the carbamate group which readily releases CO2 for an irreversible decoupling step.

solid-phase peptide synthesis is the most common method ..

How is solid phase synthesis of DNA and peptide done? - …

Currently,“peptide synthesis” includes a large range of techniques and procedures that enable the preparation of materials ranging from small peptides to large proteins. The pioneering work of Bruce Merrifield, which introduced solid phase peptide synthesis (SPPS), dramatically changed the strategy of peptide synthesis and simplified the tedious and demanding steps of purification associated with solution phase synthesis. Moreover, Merrifield’s SPPS also permitted the development of automation and the extensive range of robotic instrumentation now available. After defining a synthesis strategy and programming the amino acid sequence of peptides, machines can automatically perform all the synthesis steps required to prepare multiple peptide samples. SPPS has now become the method of choice to produce peptides, although solution phase synthesis can still be useful for large-scale production of a given peptide.

DCC activation has been used from the first days of the solid phase technique [19] and is still popular today. DIC [20] is also frequently used and presents the advantage that the corresponding urea is more soluble than the one obtained from DCC.

of solid-phase peptide synthesis ..

solid-phase peptide synthesis proceeds in a C-terminal to N-terminal fashion.

Manual peptide synthesis can be accomplished in a fritted-filter reaction vessel with a three-way valve fitted onto a 1 L side arm vacuum flask by way of a 1-hole stopper. One valve is used to bubble nitrogen, which is first passed through a small column of Drierite, and then into the reaction mixture to agitate the solution and mix reagents. The other valve is used to evacuate excess reaction solutions and wash solvent using a vacuum flask. All glass pieces to be used in Solid-phase synthesis should be treated with a silanizing agent (such as 1-5% dimethyldichlorosilane in DCM) prior to use, to avoid accumulation of static charge, which makes the resin very difficult to handle.

Certain groups of chemical functionality have exceptional affinities for selective reaction, particularly in the formation of small rings. Recent developments have led to the synthesis of large peptide fragments by solid-phase synthesis, removal from the polymeric support and of most, if not all, side-chain protecting groups, and then selective coupling of the unprotected fragments based on chemical ligation. The most developed strategy for this approach is the use of an N-terminal cysteine residue with a special reactive C-terminal group on the other peptide. This approach was initially conceived by Kemp in his thiol capture strategy (7) and was reduced to a practically successful general approach by the groups of Kent (8-10) and Tam (11-13). For illustrative purposes, the native chemical ligation procedure of Dawson et al. (9) is described (Fig. 4), because it seems to have had the most practical impact. In this case, solid-phase synthesis is used to prepare two unprotected peptide segments that are combined in aqueous solution. The C-terminal fragment contains an N-terminal cysteine residue, and the C-terminal peptide fragment is prepared as the thioester. The thioester is displaced by the thiolate anion of a Cys residue. If the Cys is N-terminal, an acyl migration through formation of a five-membered ring occurs to generate the desired stable amide bond. If the sulfur atom of a Cys residue within the peptide chain is involved, then the thioether formed is capable of being displaced by other thiols, until the fragment migrates to the N-terminal Cys, when the stable rearrangement can occur. An alternative strategy, using an N-terminal b-bromoalanine of fragment two and the C-terminal thioester of fragment one to give the same covalent thioester intermediate by thioesterification, has been explored by Tam et al. (12)

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History of solid phase peptide synthesis ..

Automation of the solid-phase reaction was initiated almost immediately once a viable synthetic scheme for peptides was evolved, and the first automated synthesizer was announced by Merrifield and Stewart in 1965 (4). Continuous development of synthesizers and the associated chemistry allows the automated addition of 75 residues per day to a growing peptide chain (5). In many cases, the repetitive yields are sufficiently high that useful products can be isolated from the synthetic mixture by HPLC when small proteins are prepared. If one desires to be more confident that the observed properties are uniquely determined by the targeted sequence, then a more conservative approach utilizing fragment condensation is still required.

Merrifield Solid-Phase Peptide Synthesis (SPPS) R

The solid-phase approach utilizes a polymeric protecting group that allows the use of excess reagents to force reactions to near completion by the mass action law and trivial isolation of polymeric product by filtration and washing. Intermediates are not isolated, and purity of the final product depends on complete reaction at each synthetic step and minimization of side reactions during the buildup of the oligomeric peptide and subsequent removal from the polymer with deprotection, to give the desired product. The advent of high-performance liquid chromatography (HPLC) with more sophisticated techniques such as nuclear magnetic resonance (NMR), capillary electrophoresis, and mass spectrometry for purification and characterization of the intermediates and final products allows routine synthesis of peptides in the 50- to 100-residue range. Because of the difficulties in purification of larger peptides and small proteins with only minor differences in structure from byproducts, the unambiguous synthesis of larger peptides and small proteins is best accomplished by assembly of fragments that have been purified and fully characterized. This prevents accumulation of side products with only minor structural differences that can be difficult to remove in the final mixture. Initially, chain assembly was relatively easy to optimize, and the majority of undesirable side products in the final cleavage were due to incomplete deprotection of side chains. Considerable effort over two decades was devoted to understanding the sequence-dependent problems leading to truncated sequences or those missing a residue, but these efforts were hampered by the polymeric support itself, which limited application of the normal methods for characterizing intermediates. This effort has led to the current state of the technology, in which average reaction yields are estimated to be greater than 99.5%. Such yields are essential if multiple sequential chemical reactions are performed without isolation and purification of intermediate products.

Solid‐phase Peptide Synthesis: Fmoc

Illustrative are the solid-phase protocols for the two strategies (Boc and Fmoc) commonly used for the synthesis of peptides. The Boc strategy (Fig. 1) is often combined with a 1% to 2% cross-linked polystyrene support and a benzyl ester linkage to the polymer, requiring strong acid such as hydrogen fluoride for deprotection. The procedure favored by most synthetic laboratories uses an acid-labile linkage similar to the p-methoxybenzyl ester linkage of the Wang resin and a base-labile amino protecting group, the fluorenylmethyloxycarbonyl (Fmoc), on the added amino acids (Fig. 2). One can use side-chain protection with similar acid lability to the Wang linkage to give free peptide upon cleavage, or use more stable side-chain protection to give the protected peptide for fragment condensation after purification and characterization. In the latter case, a final deprotection with strong acid such as HF is required.

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