Gregory Lars Olsen

Bullvalene is a fluxional molecule that rapidly rearranges via low-barrier [3,3] sigmatropic rearrangements, allowing each of its 10 carbon atoms to exchange rapidly at room temperature, accessing all possible configurational permutations with submillisecond half-lives. We previously demonstrated that the incorporation of this fluxional core into polymeric systems imbues materials with force-responsive properties, as bullvalene’s fluxionality can reversibly “respond” to applied mechanical stress. However, direct observation of such rearrangements within the bullvalene core in response to applied force has remained elusive in soft materials because of the complexity of the resulting isomer distributions and the rapid thermal reversion of perturbed isomers. In this work, we utilize a polymer-chain-centered fluorinated bullvalene core to provide direct spectroscopic evidence of changes to the bullvalene isomer distribution in response to mechanical force. These findings position bullvalene as the first example in a unique class of mechanophores capable of undergoing multiple mechanochemical reactions without requiring an external stimulus for subsequent mechanochemical activity. We anticipate these results to provide key insights into the development of force-responsive materials with enhanced mechanical properties and macromolecular sensing capabilities.

We present the structure of the HIV-1 transactivation response (TAR) element bound to the kinase inhibitor palbociclib, a single-digit nM ligand and low nM inhibitor of assembly of the super elongation complex. The small molecule rearranges the RNA to create a deep binding pocket within a new structure of TAR. It displaces A22 to form an “intermolecular pair” with U40, generating a continuously stacked 11 base-pair helix, which includes three new base triples involving A22 itself and the UCU bulge nucleotides. Mutation of nucleotides within the binding pocket or small modifications of the small molecule that abrogate high-affinity binding also disrupt direct intermolecular contacts or interactions that stabilize the RNA structure required for binding. It is highly unlikely that such an extensive combination of sequence and structural requirements is duplicated anywhere else in the transcriptome and in a functional context. This structure demonstrates that RNA refolding in response to small molecule binding is key both to providing potent and specific interactions and to eliciting a biochemical response.

We report that the kinase inhibitor Palbociclib is a very low nanomolar ligand for the HIV-1 TAR, a paradigmatic ‘difficult-to-drug’ RNA. Binding is exquisitely specific, since simple chemical modifications of the small molecule, single nucleotide substitutions, or base pair inversions abolish high affinity binding, and is independent from kinase inhibition. Palbociclib also inhibits recruitment of the super elongation complex (SEC) at low nM concentration, the long-standing aim of Tat-TAR targeting efforts. Thus, we demonstrate that low nM affinity, specificity, and potent biochemical activity against ‘undruggable’ RNAs can be readily found within the chemical space of drugs. The structural basis for binding and biochemical activity is demonstrated in the accompanying manuscript.

We report the discovery of drug-like small molecules that bind specifically to the precursor of the oncogenic and pro-inflammatory microRNA-21 with mid-nanomolar affinity. The small molecules target a local structure at the Dicer cleavage site and induce distinctive structural changes in the RNA, which correlate with specific inhibition of miRNA processing. Structurally conservative single nucleotide substitutions eliminate the conformational change induced by the small molecules, which is also not observed in other miRNA precursors. The most potent of these compounds reduces cellular proliferation and miR-21 levels in cancer cell lines without inhibiting kinases or classical receptors, while closely related compounds without this specific binding activity are inactive in cells. These molecules are highly ligand-efficient (MW < 330) and display specific biochemical and cellular activity by suppressing the maturation of miR-21, thereby providing an avenue toward therapeutic development in multiple diseases where miR-21 is abnormally expressed.

We present a system for facilitated sample vitrification, melting, and transfer in dissolution dynamic nuclear polarization (DDNP) experiments. In DDNP, a sample is typically hyperpolarized at cryogenic temperatures before dissolution with hot solvent and transfer to a nuclear magnetic resonance (NMR) spectrometer for detection in the liquid state. The resulting signal enhancements can exceed 4 orders of magnitude. However, the sudden temperature jump from cryogenic temperatures close to 1 K to ambient conditions imposes a particular challenge. It is necessary to rapidly melt the sample to avoid a prohibitively fast decay of hyperpolarization. Here, we demonstrate a sample dissolution method that facilitates the temperature jump by eliminating the need to open the cryostat used to cool the sample. This is achieved by inserting the sample through an airlock in combination with a dedicated dissolution system that is inserted through the same airlock shortly before the melting event. The advantages are threefold: (1) the cryostat can be operated continuously at low temperatures. (2) The melting process is rapid as no pressurization steps of the cryostat are required. (3) Blockages of the dissolution system due to freezing of solvents during melting and transfer are minimized.

We present a system for facilitated sample vitrification, melting, and transfer in dissolution dynamic nuclear polarization (DDNP) experiments. For DDNP, a sample is typically hyperpolarized at cryogenic temperatures before dissolution with hot solvent and transfer to a nuclear magnetic resonance (NMR) spectrometer for detection in the liquid state. The resulting signal enhancements can exceed four orders of magnitude. However, the sudden temperature jump from cryogenic temperatures close to 1 K to ambient conditions imposes a particular challenge. It is necessary to rapidly melt the sample to avoid a prohibitively fast decay of hyperpolarization. Here, we demonstrate a sample dissolution method that facilitates the temperature jump by eliminating the need to open the cryostat used to cool the sample. This is achieved by inserting the sample through an airlock in combination with a dedicated dissolution system that is inserted through the same airlock shortly before the melting event. The advantages are threefold: 1. The cryostat can be operated continuously at low temperatures. 2. The melting process is rapid as no pressurization steps of the cryostat are required. 3. Blockages of the dissolution system due to freezing of solvents during melting and transfer are minimized.

We present a system for facilitated sample vitrification, melting, and transfer in dissolution dynamic nuclear polarization (DDNP) experiments. For DDNP, a sample is typically hyperpolarized at cryogenic temperatures before dissolution with hot solvent and transfer to a nuclear magnetic resonance (NMR) spectrometer for detection in the liquid state. The resulting signal enhancements can exceed four orders of magnitude. However, the sudden temperature jump from cryogenic temperatures close to 1 K to ambient conditions imposes a particular challenge. It is necessary to rapidly melt the sample to avoid a prohibitively fast decay of hyperpolarization. Here, we demonstrate a sample dissolution method that facilitates the temperature jump by eliminating the need to open the cryostat used to cool the sample. This is achieved by inserting the sample through an airlock in combination with a dedicated dissolution system that is inserted through the same airlock shortly before the melting event. The advantages are threefold: 1. The cryostat can be operated continuously at low temperatures. 2. The melting process is rapid as no pressurization steps of the cryostat are required. 3. Blockages of the dissolution system due to freezing of solvents during melting and transfer are minimized.

We present a system for facilitated sample vitrification, melting, and transfer in dissolution dynamic nuclear polarization (DDNP) experiments. For DDNP, a sample is typically hyperpolarized at cryogenic temperatures before dissolution with hot solvent and transfer to a nuclear magnetic resonance (NMR) spectrometer for detection in the liquid state. The resulting signal enhancements can exceed four orders of magnitude. However, the sudden temperature jump from cryogenic temperatures close to 1 K to ambient conditions imposes a particular challenge. It is necessary to rapidly melt the sample to avoid a prohibitively fast decay of hyperpolarization. Here, we demonstrate a sample dissolution method that facilitates the temperature jump by eliminating the need to open the cryostat used to cool the sample. This is achieved by inserting the sample through an airlock in combination with a dedicated dissolution system that is inserted through the same airlock shortly before the melting event. The advantages are threefold: 1. The cryostat can be operated continuously at low temperatures. 2. The melting process is rapid as no pressurization steps of the cryostat are required. 3. Blockages of the dissolution system due to freezing of solvents during melting and transfer are minimized.

We present a system for facilitated sample vitrification, melting, and transfer in dissolution dynamic nuclear polarization (DDNP) experiments. For DDNP, a sample is typically hyperpolarized at cryogenic temperatures before dissolution with hot solvent and transfer to a nuclear magnetic resonance (NMR) spectrometer for detection in the liquid state. The resulting signal enhancements can exceed four orders of magnitude. However, the sudden temperature jump from cryogenic temperatures close to 1 K to ambient conditions imposes a particular challenge. It is necessary to rapidly melt the sample to avoid a prohibitively fast decay of hyperpolarization. Here, we demonstrate a sample dissolution method that facilitates the temperature jump by eliminating the need to open the cryostat used to cool the sample. This is achieved by inserting the sample through an airlock in combination with a dedicated dissolution system that is inserted through the same airlock shortly before the melting event. The advantages are threefold: 1. The cryostat can be operated continuously at low temperatures. 2. The melting process is rapid as no pressurization steps of the cryostat are required. 3. Blockages of the dissolution system due to freezing of solvents during melting and transfer are minimized.

We present a system for facilitated sample vitrification, melting, and transfer in dissolution dynamic nuclear polarization (DDNP) experiments. For DDNP, a sample is typically hyperpolarized at cryogenic temperatures before dissolution with hot solvent and transfer to a nuclear magnetic resonance (NMR) spectrometer for detection in the liquid state. The resulting signal enhancements can exceed four orders of magnitude. However, the sudden temperature jump from cryogenic temperatures close to 1 K to ambient conditions imposes a particular challenge. It is necessary to rapidly melt the sample to avoid a prohibitively fast decay of hyperpolarization. Here, we demonstrate a sample dissolution method that facilitates the temperature jump by eliminating the need to open the cryostat used to cool the sample. This is achieved by inserting the sample through an airlock in combination with a dedicated dissolution system that is inserted through the same airlock shortly before the melting event. The advantages are threefold: 1. The cryostat can be operated continuously at low temperatures. 2. The melting process is rapid as no pressurization steps of the cryostat are required. 3. Blockages of the dissolution system due to freezing of solvents during melting and transfer are minimized.