LZ can try contact to below paper De Lay N, Gottesman S. (2011) Role of polynucleotide phosphorylase in sRNA function in Escherichia coli. RNA. 17: 1172-89. //www.ncbi.nlm.nih.gov/pubmed/21527671 last/corresponding author mail address within below link: //ccr.cancer.gov/staff/staff.asp?profileid=5786