Spot-Synthesis on Membranes

The amount of each peptide in the array is easy to control by the size of each spot. For instance, synthesis on Whatman 540 paper (capacity 0.4-0.6 pmol cm-2) with the volume of reagents used for the coupling step 0.5-0.7 pL yields 25 nmol of a peptide on a spot, which is 7 mm in diameter [55], These parameters are used in a standard format, an 8 x 12 array with 9-mm distance between the centers of the synthesis sites. Larger 40 x 50 arrays can be prepared on Whatman 50 paper with the help of automation. Drops 0.03-0.05 pL in volume form spots that are 1 mm in diameter, producing an array containing 2000 peptides, each of 1.0 nmol [55], 

The spot-synthesis technique is simple and easily accessible for practical use. There are some limitations to the scope of chemistries that can be used with cellulose as a solid support. To eliminate some shortcomings of cellulose, Gao and Esnouf [58,59 proposed using a different membrane, Immobilon AV-1, for the spot synthesis. Before synthesis of peptide arrays can be carried out, this polyvinylidene fluoride-based material is derivatized with ethylene diamine, followed by coupling of Fmoc-p-alanine as a spacer. In most other aspects, the peptide array synthesis is very similar to the spot synthesis proposed by Frank. 

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