Chemical and biomolecular insights into the Staphylococcus aureus agr quorum sensing system: Current progress and ongoing challenges.

Staphylococcus aureus is a ubiquitous bacterium that has become a major threat to human health due to its extensive toxin production and tremendous capacity for antibiotic resistance (e.g., MRSA "superbug" infections). Amid a worsening antibiotic resistance crisis, new strategies to combat this deadly microbe that remove the selective pressure of traditional approaches are in high demand. S. aureus utilizes an accessory gene regulator (agr) quorum sensing network to monitor its local cellular population and trigger a devastating communal attack, like an invading horde, once a threshold cell density has been reached. The role of the agr system in a range of disease types is still being unraveled. Herein, we discuss the present-day biochemical understanding of agr along with unresolved details, describe its connection to the progression of infection, and review how chemical strategies have been implemented to study and intercept this signaling pathway. This research is illuminating the potential of agr as an anti-virulence target in S. aureus and should inform the study of similar, yet less studied, agr systems in related bacterial pathogens.

Molecular Encryption and Steganography Using Mixtures of Simultaneously Sequenced, Sequence-Defined Oligourethanes.

Molecular encoding in abiotic sequence-defined polymers (SDPs) has recently emerged as a versatile platform for information and data storage. However, the storage capacity of these sequence-defined polymers remains underwhelming compared to that of the information storing biopolymer DNA. In an effort to increase their information storage capacity, herein we describe the synthesis and simultaneous sequencing of eight sequence-defined 10-mer oligourethanes. Importantly, we demonstrate the use of different isotope labels, such as halogen tags, as a tool to deconvolute the complex sequence information found within a heterogeneous mixture of at least 96 unique molecules, with as little as four micromoles of total material. In doing so, relatively high-capacity data storage was achieved: 256 bits in this example, the most information stored in a single sample of abiotic SDPs without the use of long strands. Within the sequence information, a 256-bit cipher key was stored and retrieved. The key was used to encrypt and decrypt a plain text document containing The Wonderful Wizard of Oz. To validate this platform as a medium of molecular steganography and cryptography, the cipher key was hidden in the ink of a personal letter, mailed to a third party, extracted, sequenced, and deciphered successfully in the first try, thereby revealing the encrypted document.

Efficient molecular encoding in multifunctional self-immolative urethanes.

Molecular encoding in sequence-defined polymers shows promise as a new paradigm for data storage. Here, we report what is, to our knowledge, the first use of self-immolative oligourethanes for storing and reading encoded information. As a proof of principle, we describe how a text passage from Jane Austen's Mansfield Park was encoded in sequence-defined oligourethanes and reconstructed via self-immolative sequencing. We develop Mol.E-coder, a software tool that uses a Huffman encoding scheme to convert the character table to hexadecimal. The oligourethanes are then generated by a high-throughput parallel synthesis. Sequencing of the oligourethanes by self-immolation is done concurrently in a parallel fashion, and the liquid chromatography-mass spectrometry (LC-MS) information decoded by our Mol.E-decoder software. The passage is capable of being reproduced wholly intact by a third-party, without any purifications or the use of tandem MS (MS/MS), despite multiple rounds of compression, encoding, and synthesis.

Sequencing of Sequence-Defined Oligourethanes via Controlled Self-Immolation.

Sequence-defined polymers show promise for biomimetics, self-assembly, catalysis, and information storage, wherein the primary structure begets complex chemical processes. Here we report the solution-phase and the high-yielding solid-phase syntheses of discrete oligourethanes and methods for their self-immolative sequencing, resulting in rapid and robust characterization of this class of oligomers and polymers, without the use of MS/MS. Crucial to the sequencing is the inherent reactivity of the terminal alcohol to "unzip" the oligomers, in a controlled and iterative fashion, releasing each monomer as a 2-oxazolidinone. By monitoring the self-immolation reaction via LC/MS, an applied algorithm rapidly produces the sequence of the oligourethane. Not only does this process provide characterization of structurally complex molecules, it works as a reader of molecular information.