Galactomannans as a sieving matrix in capillary electrophoresis

Purification of galactomannans including guaran, tara gum, and locust bean gum is described as well as their use as a sieving matrix in DNA sequencing by capillary electrophoresis (CE). Three methods of galactomannan purifica tion were developed and tested using guaran. The first method is based on h ydrolysis of proteins using alkali treatment and precipitation of guaran wi th acetone. The second method uses ion-exchange resins QAE Sephadex A-25 an d SP Sephadex C-25 together with acetone precipitation. The third method is similar to the second one, except that it uses ion-exchange resins based o n polystyrene, Source 30Q and Source 30S. Capillary zone electrophoresis of acetonitrile extracts from guaran revealed 4-5 characteristic major peaks and several minor peaks. Guar gum from different suppliers differed in the content of proteins. In purified guaran, protein peaks were detectable only using a 300-fold concentrate of extract. The content of proteins in the gu aran purified using the third method was 0.001% m/m as determined by CE. Th e weight average molecular mass of purified guaran can be as large as 2.2 x 10(6). The purified galactomannans were used as a sieving matrix in DNA se quencing by CE. M13 DNA was sequenced to read lengths of about 600 bases in less than 90 min. Separation efficiencies exceeded 1 million theoretical p lates for DNA fragments shorter than about 600 bases.