angioplasty). Though they permeate through intercellular spaces in tissues effectively, unconjugated PMOs have limited distribution into the cytosol and nuclear spaces within healthy tissues following IV administration. Systemic delivery into many cells in adult organisms can be accomplished by using covalent conjugates of Morpholino oligos with cell-penetrating peptides, and, while toxicity has been associated with moderate doses of the peptide conjugates, they have been used in vivo for effective oligo delivery at doses below those causing observed toxicity. An octa-guanidinium dendrimer attached to the end of a Morpholino can deliver the modified oligo (called a Vivo-Morpholino) from the blood to the cytosol. Delivery-enabled Morpholinos, such as peptide conjugates and Vivo-Morpholinos, show promise as therapeutics for viral and genetic diseases. See also Oligonucleotide synthesis Nucleic acid analogue References Further reading Wiley-Liss, Inc. Special Issue: Morpholino Gene Knockdowns of genesis Volume 30, Issue 3 Pages 89-200 (July 2001). This is a special issue of Genesis that consists of a series of peer-reviewed short papers using Morpholino knock downs of gene function in various animal and tissue culture systems. "Peptide Nucleic Acids, Morpholinos and Related Antisense Biomolecules." eds. Janson & During (Springer, 2007) Genetics techniques Phosphoramidates Molecular genetics Nucleic acids Morpholines Gene expression Biotechnology