In this article, the capability of encoding information using a homologous series
of monodisperse monomethoxypolyethylene glycols (mPEG), with a number of ethylene
oxide units ranging from nEO = 5 to 8, and monodisperse linear aliphatic isocyanates
containing a number of CH2 units from 3 to 7, is demonstrated. The “click” reaction
of the two corresponding homologous series yielded 20 different isocyanate end-capped
polyethylene glycol derivatives (mPEG-OCONHR) whose sodiated adduct ion’s nominal
m/z values spanned from 360 to 548, providing an average ca. 8 m/z unit for the storage
of one-bit information. These mPEG-OCONHR oligomers were then used to encode information
in binary sequences using a 384-well MALDI sample plate and employing the common dried-droplet
sample preparation method capable of encoding 20 bit, i.e., 2.5 byte information in
one spot, was employed. The information stored in the spots was read by MALDI-TOF
MS using the m/z value of the corresponding mPEG-OCONHR oligomers. The capability
of the method to store data was demonstrated by writing and reading a text file, visualizing
a small picture and capturing a short audio file written in Musical Instrument Digital
Interface (MIDI) sequence. Due to the very large similarities in the chemical structures
of the encoding oligomers and their “easy to be ionized” property, as well as their
very similar ionization efficiencies, the MALDI-TOF MS signal intensities from each
compound was so strong and unambiguous that complete decoding could be performed in
each case. In addition, the set of the proposed encoding oligomers can be further
extended to attain higher bit “densities”.
