Tea-bag synthesis

Figure 3-4 Various approaches lo immobilizing and separating chemical compounds during combinatorial synthesis have been Ctevised. a. Tea bag synthesis, b. Pins and "lollypops." c. Dots on cellulose, d. Spatial arrays on microchips...

C Pinilla, JR Appel, RA Houghten. Tea bag synthesis of positional scanning synthetic combinatorial libraries and their use for mapping antigenic determinants. Methods Molec Biol 66 171-179, 1996. 

However, other polymer composite materials also popular in solid-phase synthesis, such as polyethylene or polypropylene tea bags , lanterns, crowns, or plugs, are generally less suitable for high-temperature reactions (>160 °C). Therefore, micro-wave irradiation is typically not a very suitable tool to speed up reactions that utilize these materials as either a solid support or as containment for the solid support. 

In 1985 Houghton introduced his tea bag method for the rapid solid phase multiple peptide synthesis. In this technique the beads are contained within a porous polypropylene bag. All the reactions, including deprotections, are... 

In a similar approach, a pretuned glass encased microchip set to emit a unique binary code is placed in a polypropylene tea bag loaded with polystyrene beads. Using a modified split synthesis approach, a 125-membered tripeptide library N-capped as the /r-carboxy-cinnamic acid amide was prepared on Rink resin. Each porous reactor contained a radio frequency transporter which successfully defined the structure of two inhibitors of protein tyrosine phosphatase [37],... 

Parallel synthesis in tea-bags would not be as valuable if there was no method for the parallel cleavage of products from the solid support. For this reason, a 24-vessel parallel hydrofluoric acid (HF) cleavage apparatus was developed (23). Later it was found that the application of gaseous HF works well for the parallel cleavage of peptides synthesized in both tea-bags and microtiter plates (24,25). Chambers for the cleavage of 1728 products from resin in 18 microtiter plates were constructed (26). 

Pokorny, V., Mudra, P., Jehnicka, J., et al. (1994) Compas 242. New type of multiple peptide synthesizer utilizing cotton and tea bag technology. In Innovation and Perspectives in Solid Phase Synthesis (Epton, R., ed.), Mayflower Worldwide Limited, Birmingham, UK, pp. 643-648. 

The reagent BOP and the more recent reagents PyBOP, AOP, and PyAOP are widely used in solutionP P l and in sohd-phase synthesis with rnanual,P l automated, tea bag,t l or pint methods. One-pot or preactivation conditions as well... 

The tea bag method is very practical. It does not require any special tools, except a sealing device. A number of mesh materials of different porosity are available from Spectrum Medical Industries, Inc. Almost all commercially available resins can be used as long as the size of the beads is larger than the mesh size. The scale of the synthesis is easy to control by the size of the packet chosen to contain the desired amount of a polymer support. The multiple synthesis can be carried out manually or on a synthesizer. 

Similarly to the tea bag approach, pieces of any solid-phase support suitable for solid-phase synthesis can be used for parallel peptide preparation. One of the first materials used in this manner was paper. Frank used paper disks l (Whatman 3MM, 1.5-cm diameter) packed into the columns of a multicolumn continuous-flow synthesizer. Prior to the synthesis, the paper was derivatized with 4-alkoxybenzyl (Pab) linkage to allow for the cleavage with trifluoroacetic acid. The disks can be easily labeled with a pencil, sorted, and combined depending on the common amino acid to be coupled at the next step. 

In the so-called tea-bag method, originated in 1984 by Houghten et al. [14] for multiple peptide synthesis, the split-pool protocol occurs batchwise on 15 x 22 mm polypropylene mesh packets with pm-sized pores known as tea bags, sealed with resin beads for solid-phase synthesis. This method offers the advantage that a greater quantity of each compound of the library is available at once (up to 500 pmol), which is sufficient for a complete biological and structural characterization. Furthermore, the structural identity of... 

In 1985, Houghten [11] used this method in his tea bag approach described in section 3.4.4.2 of this chapter. As an elemental synthesis unit, instead of individual resin beads, he used small batches of resin packed into a polypropylene mesh. Furka [12,13] described the split/pool methodology for the synthesis of peptides. The peptides were cleaved and analyzed as mixtures and separated by HPLC as a rapid method for multiple peptide synthesis. In his work, Furka did not suggest explicitly to cleave individual compounds from individual beads. This seemingly obvious idea was recognized by Lam [14,15]. Split/pool synthesis was further developed and widely used by many others working in-the field of combinatorial chemistry [16]. The new Journal of Combinatorial Chemistry published a very interesting historical perspective on the major events in this field [17],... 

In 1985, R. Houghten reported on peptide synthesis carried on a resin sealed in porous polypropylene packets [11], The pore size of the polypropylene mesh (74 pm) allows for free access of chemicals to and from the contained resin. Each packet or tea bag can be individually labeled to identify the peptide synthesized on the entrapped polymer. Many tea bags can be combined in the same reaction to carry out common synthetic steps, such as washing and deprotection. The packets are sorted in separate reaction vessels according to the specific amino acid that will be coupled next. Cleavage, depending on the amount of used resin, can be carried out in separate vessels or in a 96-well microtiter plate with 2-mL well volume. In the original paper [11], 248 different tridecapeptides were synthesized in 10- to 20-mg quantities and characterized in less than four weeks. 

Houghten et al. described the tea-bag method for multiple peptide synthesis (Proc. Natl. Acad. Sci. USA, 1985, 82, 5131)... 

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