( ucts because the rRNA ratio ...)Determinants of RNA Integrity and Purity

Figure 3. Low Baseline Fluorescence Indicates Good RNA Quality.(A) Partially degraded total RNA. The 28:18S rRNA ratio is 0.9 and the baseline fluorescence is elevated both between the 28S and 18S and below the 18S, making the rRNA peaks appear to be riding on top of the baseline. (B) Human intestinal RNA containing abundant small RNAs. This sample can be distinguished from partially degraded RNA by the relatively high 28S:18S rRNA ratio, and the relatively low baseline both between the 28S and 18S peaks, and immediately below the 18S peak.

Our data suggest that, aside from integrity, trace contaminants may be the largest contributor to poor performance in sensitive enzymatic applications such as amplification for microarray analysis. Most often impurities interfere with cDNA synthesis steps, resulting in reduced size and yield of aRNA following in vitro transcription. In fact, a recent study on the impact of moderate RNA degradation on microarray analysis suggests that while the loss of the 5' end of transcripts results in higher ratios of hybridization to 3' end probes than 5' end probes, the number of genes detected or differentially expressed is not significantly reduced (4). Stated simply, RNA quality can be defined as the sum of RNA integrity and RNA purity. Many researchers are finding that their application may be tolerant of some loss in
'"/>

Source: