Glycoform Differentiation by a Targeted, Self-Assembled, Pattern-Generating Protein Surface Sensor

A method for generating targeted, pattern-generating, protein surface sensors via the self-assembly of modified oligodeoxynucleotides (ODNs) is described. The simplicity by which these systems can be created enabled the development of a sensor that can straightforwardly discriminate between distinct glycoform populations. By using this sensor to identify glycosylation states of a therapeutic protein, we demonstrate the diagnostic potential of this approach as well as the feasibility of integrating a wealth of supramolecular receptors and sensors into higher-order molecular analytical devices with advanced properties. For example, the facile device integration was used to attach the well-known anthracene-boronic acid (An-BA) probe to a biomimetic DNA scaffold and consequently, to use the unique photophysical properties of An-BA to improve glycoform differentiation. In addition, the noncovalent assembly enabled us to modify the sensor with a trinitrilotriacetic acid (tri-NTA)-Ni²⁺ complex, which endows it with selectivity toward a hexa-histidine tag (His-tag). The selective responses of the system to diverse His-tag-labeled proteins further demonstrate the potential applicability of such sensors and validate the mechanism underlying their function.

Molecular Logic as a Means to Assess Therapeutic Antidotes

An emerging direction in the area of molecular logic and computation is developing molecular-scale devices that can operate in complex biological environments, such as within living cells, which are beyond the reach of conventional electronic devices. Herein we demonstrate, at the proof-of-principle level, how concepts applied in the field of molecular logic gates can be used to convert a simple fluorescent switch (YES gate), which lights up in the presence of glutathione s-transferase (GST), into a medicinally relevant INHIBIT gate that responds to both GST and beta-cyclodextrin (β-CD) as input signals. We show that the optical responses generated by this device indicate the ability to use it as an enzyme inhibitor, and more importantly, the ability to use β-CD as an "antidote" that prevents GST inhibition. The relevance of this system to biomedical applications is demonstrated by using the INHIBIT gate and β-CD to regulate the growth of breast cancer cells, highlighting the possibility of applying supramolecular inputs, commonly used to control the fluorescence of molecular logic gates, as antidotes that reverse the toxic effect of chemotherapy agents. We also show that the effect of β-CD can be prevented by introducing 1-adamantanecarboxylic acid (Ad-COOH) as an additional input signal, indicating the potential of obtaining precise, temporal control over enzyme activity and anticancer drug function.

Mimicking the Function of Signaling Proteins: Toward Artificial Signal Transduction Therapy

Signal transduction pathways, which control the response of cells to various environmental signals, are mediated by the function of signaling proteins that interact with each other and activate one other with high specificity. Synthetic agents that mimic the function of these proteins might therefore be used to generate unnatural signal transduction steps and consequently, alter the cell's function. We present guidelines for designing 'chemical transducers' that can induce artificial communication between native proteins. In addition, we present detailed protocols for synthesizing and testing a specific 'transducer', which can induce communication between two unrelated proteins: platelet-derived growth-factor (PDGF) and glutathione-S-transferase (GST). The way by which this unnatural PDGF-GST communication could be used to control the cleavage of an anticancer prodrug is also presented, indicating the potential for using such systems in 'artificial signal transduction therapy'. This work is intended to facilitate developing additional 'transducers' of this class, which may be used to mediate intracellular protein-protein communication and consequently, to induce artificial cell signaling pathways.