siRNAs have been chemically modified to enhance their therapeutic properties, Short interfering RNA (siRNA) must be delivered to the site of action in the cells of target tissues in order for RNAi to fulfill its therapeutic promise. A detailed database of all such chemical modifications is manually curated as [http://crdd.osdd.net/servers/sirnamod siRNAmod] in scientific literature. Chemical modification of siRNA can also inadvertently result in loss of single-nucleotide specificity.