This question has to do with developing blocking agents to block nonspecific binding during a FISH (fluorescent in situ hybridization) procedure.  The procedure labels the DNA of various organisms being studied, but nonspecific binding to other tissue components also occurs.  The developers of the procedure have produced a tRNA blocking agent that works, but they are interested in what other sorts of compounds might be used to do the same thing.  The blocking agent works by the positive and negative charges that are inherent to DNA and RNA,  and they wonder what other negatively charged molecules might be able to be used to block nonspecific binding.  If this sounds confusing, it is because my understanding of the whole thing is limited, but I think I have phrased the question so that you all get the gist of what we're trying to do here. So, ideas or explanations on this subject are welcome, reply to me directly or share answers with the group.
Thanks in advance, 
Joyce Kotzuk, Univ. of New Mexico pathology dept.