The lowercase "r" in rRNA stands for this adjective
[DOC] [TLE] Instructions to Authors - ScienceSocieties.org [PAR] lowercase, unless it is a proper noun; key words are separated by commas ... 
stand-alone DISCUSSION should not refer to any ta- bles or figures, nor should it
... [DOC] [TLE] symbols for nucleic - iupac [PAR] I, T, U, P, Xfor the known nucleosides; R and Y for unspecified purine and ... 
ribosomal RNA rRNA ... connect a noun-adjective; (il) the attached aminoacyl 
residue [in (b)] has the ... Specification of source may be made in parentheses 
before or after the abbreviation, e.g.