【求助】28s和18s的比值

biolinkphilic wrote:
Because mammalian 28S and 18S rRNAs are approximately 5 kb and 2 kb in size, the theoretical 28S:18S ratio is approximately 2.7:1; but a 2:1 ratio has long been considered the benchmark for intact RNA. While crisp 28S and 18S rRNA bands are indicative of intact RNA, it is less clear how these long-lived and abundant molecules actually reflect the quality of the underlying mRNA population, which turns over much more rapidly.
Visual assessment of the 28S:18S rRNA ratio on agarose gels is somewhat subjective because appearance of rRNA bands is affected by electrophoresis conditions, amount of RNA loaded, and saturation of ethidium bromide fluorescence.

Although the 28S/18S rRNA ratio is a reasonable way to estimate RNA integrity, it is not ideal and in particular in the context of the Bioanalyzer, which does not run under denaturing conditions sometimes the ratios do not reflect the exact level of RNA degradation. Besides the ratio of the 18S to 28S ribosomal RNAs, Agilent has introduced a software algorithm that takes the entire electrophoretic trace into account to help scientists estimate the integrity of total RNA samples。

详见下面的链接

http://www.ambion.com/techlib/tn/111/8.html



http://www.biomedicalgenomics.org/The_RNA_Integrity_Number.html