inosine in oligonucleotides

[Robert H. Proctor]

Hello:

Does anyone out there know how to calculate the concentration of an 
oligonucleotide using Absorbtion at 260 nm?   Normally, I use an equation 
that takes into account the effect of base composition on extiction 
coefficient of the oligo.  So, for a 1:100 dilution of an oligo prep the 
equation is: 
conc. ( in pmole/uL) 
= (100 x Abs at 260nm) / (1.54Na + 0.75Nc + 1.17Ng + 0.92 Nt) 

where Na, Nc, Ng, and Nt  = number of adenosines, cytosines, guanosine, 
and thymidine, respectively.  I think the 1.54, 0.75, 1.17, and 0.92 are 
the extinction coefficients (divided by 10,000)  of the various 
nucleotides at 260 nm.

Does anyone know how to incorporate inosine and its extinction 
coefficient into such an equation?  Thanks in advance for any help you 
can provide.

Bob Proctor
Bob proctorh at ncaur1.ncaur.gov
USDA ARS NCAUR 
1815 N. University St.
Peoria IL  61604