Isotope Ratio Encoding of Sequence-Defined Oligomers

A Workflow Enabling the Automated Synthesis, Chain-End Degradation, and Rapid Mass Spectrometry Analysis for Molecular Information Storage in Sequence-Defined Oligourethanes

The field of molecular information storage has recently expanded to include abiotic sequence-defined polymers. While robust methods have been developed, there is a current bottleneck in the throughput of this work as information density is increased. Herein, we introduce an automated workflow in which a commercial peptide synthesizer composed of a single XYZ liquid-handling robot was adapted to both synthesize and sequence sequence-defined oligourethanes. Our sequencing method was improved to cut down the number of samples required for each oligomer from 13 to one. Additionally, we introduce the use of desorption electrospray ionization mass spectrometry as our analysis method for sequencing, which allowed for simplified and increased speed of data acquisition. Finally, we created a Python script that is able to reconstruct the sequence information from the MS data in an automated fashion. We demonstrate this new workflow by encoding and decoding a quote from the late Maya Angelou: "When you learn, teach, when you get, give".

Shotgun Sequencing of 512-mer Copolyester Allows Random Access to Stored Information

Digital information encoded in polymers has been exclusively decoded by mass spectrometry. However, the size limit of analytes in mass spectrometry restricts the storage capacity per chain. In addition, sequential decoding hinders random access to the bits of interest without full-chain sequencing. Here we report the shotgun sequencing of a 512-mer sequence-defined polymer whose molecular weight (57.3 kDa) far exceeds the analytical limit of mass spectrometry. A 4-bit fragmentation code was implemented at aperiodic positions during the synthetic encoding of 512-bit information without affecting storage capacity per chain. Upon activating the fragmentation code, the polymer chain splits into 18 oligomers, which could be individually decoded by tandem-mass sequencing. These sequences were computationally reconstructed into a full sequence using an error-detection method. The proposed sequencing method eliminates the storage limit of a single polymer chain and allows random access to the bits of interest without full-chain sequencing.

High density information storage through isotope ratio encoding

The need for reliable information storage is on a steep rise. Sequence-defined polymers, particularly oligonucleotides, are already in use in several areas, while compound mixtures also offer a simple way for storing information. We investigated the use of a set of isotopologues in information storage by mixing, where the information is stored in the form of a mass spectrometric (MS) fingerprint of the mixture. A small molecule with 24 non-labile and replaceable hydrogen atoms was selected as a model, and a set of components covering the D0-D24 deuteration range were synthesized. Theoretical analysis predicted that by mixing up to 10 out of the prepared components, one can encode over 130 million different combinations and distinguish their MS fingerprints. As a proof of principle, several mixtures predicted to have similar fingerprints were prepared and their MS fingerprints were recorded. From each measured MS fingerprint, we were able to unambiguously identify the actual composition of the mixture. It was also demonstrated that one can make the MS fingerprints of a given mixture unique, thereby making counterfeiting of the stored information very difficult. Finally, the utility of isotope ratio encoding in covalent tagging was also demonstrated.

Platform for Multiple Isotope Labeling via Carbon-Sulfur Bond Exchange

In this work, we explore a nickel-catalyzed reversible carbon-sulfur (C-S) bond activation strategy to achieve selective sulfur isotope exchange. Isotopes are at the foundation of applications in life science, such as nuclear imaging, and are essential tools for the determination of pharmacokinetic and dynamic profiles of new pharmaceuticals. However, the insertion of an isotope into an organic molecule remains challenging, and current technologies are element-specific. Despite the ubiquitous presence of sulfur in many biologically active molecules, sulfur isotope labeling is an underexplored field, and sulfur isotope exchange has been overlooked. This approach enables us to move beyond standardized element-specific procedures and was applied to multiple isotopes, including deuterium, carbon-13, sulfur-34, and radioactive carbon-14. These results provide a unique platform for multiple isotope labeling and are compatible with a wide range of substrates, including pharmaceuticals. In addition, this technology proved its potential as an isotopic encryption device for organic molecules.