28.02.2013 Views

Handbook of Size Exclusion Chromatography and Related ...

Handbook of Size Exclusion Chromatography and Related ...

Handbook of Size Exclusion Chromatography and Related ...

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Figure 2 Separation <strong>of</strong> total E. coli RNAs containing 4S tRNA <strong>and</strong> 5S, 16S, <strong>and</strong> 23S<br />

rRNAs obtained on a TSKgel G4000SW two-column system (each column<br />

60 cm 7.5 mm ID) in 0.1 M phosphate buffer (pH 7.0) containing 0.1 M sodium<br />

chloride <strong>and</strong> 1 mM EDTA at a flow rate <strong>of</strong> 1 mL/min. (From Ref. 8.)<br />

about 40 minutes. Although the separation between 16S <strong>and</strong> 23S rRNAs seems<br />

insufficient, this is a result <strong>of</strong> other components eluting at the same position as the<br />

rRNAs. A pure mixture <strong>of</strong> 16S <strong>and</strong> 23S rRNAs was separated almost completely.<br />

The 5S <strong>and</strong> 5.8S rRNAs with approximate chain lengths <strong>of</strong> 120 <strong>and</strong> 158 were also<br />

separated well on a TSKgel G3000SW column (60 cm 7.5 mm ID) in about 20<br />

minutes (2).<br />

Samples <strong>of</strong> mRNA usually contain many components whose molecular<br />

weights differ continuously in a rather wide range. Consequently, single broad<br />

peaks are usually obtained in the SEC <strong>of</strong> mRNA mixtures. However, it has been<br />

confirmed by an in vitro translation test <strong>of</strong> the fractionated mRNA samples that<br />

the separation <strong>of</strong> mRNA is roughly based on molecular size (3,6). mRNA easily<br />

aggregates in nondenaturing buffers, which results in inferior resolution.<br />

Therefore, it is recommended to separate mRNA under denaturing conditions<br />

in the presence <strong>of</strong> 6 M urea. Under denaturing conditions, aggregation<br />

formation is avoided <strong>and</strong> the resolution is considerably improved (3,6). SEC<br />

under denaturing conditions has a resolution equivalent to or even better than<br />

that <strong>of</strong> sucrose gradient centrifugation, which has been the most common<br />

method to separate mRNA.<br />

Satisfactory separation has also been obtained for small nuclear RNAs on<br />

UltroPac TSK SW type columns (4).<br />

© 2004 by Marcel Dekker, Inc.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!