The nomenclature of Morpholinos is messy.

Jim Summerton (inventor of Morpholino oligos) calls them Morpholinos and that’s how Gene Tools markets them.

After Summerton’s departure from AVI, Pat Iversen (who took over R&D at AVI Biopharma when Summerton left) called them PMO (phosphorodiamidate Morpholino oligomer).

Prior to that, AVI was already calling them Neugenes.

Gene Tools customers sometimes use their own acronyms, such as MORF (from the Hnatowich lab) or MO (in fairly common use, standing for Morpholino oligo).

Morpholino = Neugene = PMO = MORF = MO

Then we have the peptide-linked Morpholino oligos, PPMO, which were developed at AVI Biopharma. These were the oligos used for the paper just published by Ryszard Kole’s group in collaboration with AVI:
Jearawiriyapaisarn N, Moulton HM, Buckley B, Roberts J, Sazani P, Fucharoen S, Iversen PL, Kole R. Sustained Dystrophin Expression Induced by Peptide-conjugated Morpholino Oligomers in the Muscles of mdx Mice. Mol Ther. 2008 Jun 10. [Epub ahead of print]
The PPMO-B used in this paper is a Morpholino with a particular delivery peptide attached. AVI has built and assayed many, many different peptide conjugates seeking (and finding!) good delivery efficacy with minimal toxicity.

My friend and colleague Yongfu Li considered the papers by Paul Wender, who published his group’s work with arginine-rich peptides. Wender also reported some experiments with the guanidinium groups on alternative (non-peptide) support structures. Realizing that it is the guanidinium head groups of the arginine amino acids that give the peptide moieties of the PPMOs their efficacy, Yongfu set out to find a commercially useful method for synthesizing eight-tipped scaffolds, called dendrimers, that can be built on Morpholinos and then decorated with a guanidinium at each tip. This presents the guanidiniums in a hemispherical shape. Yongfu predicted that this hemispherical presentation would distort the endosomal membrane very effectively and lead to good delivery. So far, the data is looking good. Morpholinos with these guanidinium-tipped dendrimers are called Vivo-Morpholinos. Yongfu’s paper describing the synthesis and initial biological assays of Vivo-Morpholinos is:
Li YF, Morcos PA. Design and Synthesis of Dendritic Molecular Transporter that Achieves Efficient in Vivo Delivery of Morpholino Antisense Oligo. Bioconjug Chem. 2008 Jun 20. [Epub ahead of print]

So, we have two general kinds of Morpholino oligos with delivery groups enhancing in-vivo delivery:
PPMO (including PPMO-B) from AVI;
Vivo-Morpholinos from Gene Tools.

I was blessed with a biochem professor who would drop memorable pearls of wisdom like this: “There is no field so simple that we cannot muck it up by introducing more complex nomenclature”. Sigh.