Lance James Twyman

Inhibiting unwanted protein–protein interactions (PPIs) by targeting extensive protein binding surfaces presents a significant challenge. Macro-ligands offer a promising approach, but traditional covalent functionalization strategies often suffer from synthetic complexity, particularly in controlling the spatial arrangement of binding moieties. This study introduces a new method for macro-ligand design based on the noncovalent, modular self-assembly of functional units within an inert dendrimer scaffold. Although these units are embedded within the dendrimer in a random arrangement, they are mobile and free to move. As such, when a target protein is introduced, these binding units can undergo a self-organization process to optimize their spatial distribution and maximize cooperative interactions with the protein’s binding surface. This dynamic process is controlled by the protein, as it guides and controls the formation of its own optimized macromolecular ligand. When sensor units are combined and included in the assembly process, real-time monitoring and quantification of binding can be detected and quantified. This study details the synthetic methodology employed for the preparation of the component parts and their self-assembly into dendrimer complexes. Subsequent binding assays using cytochrome-c as the target protein, and associated dendrimer complexes, exhibited binding affinities in the nanomolar (nM) range.

Being able to bind, select, and transport species is central to a number of fields, including medicine, materials, and environmental science. In particular, recognizing a specific species from one phase and transporting it across, or into another phase, has obvious applications in environ-mental science, for example, removal of unwanted or toxic materials from an aqueous or organic phase. In this paper, we describe an approach that uses a functionalized dendritic polymer to bind and transport a small anionic molecule across an organic phase (and between two aqueous phases). The design was based on encapsulation principles borrowed from nature, where anions are bound and transported by proteins that have specific sites within their globular ordered structures. For the work reported here, a globular dendritic polymer functionalized with an isophthalamide-based receptor was used to replace the protein structure and anion-binding site. Along with control experiments, the binding and transport properties of two functionalized HBPs were assessed using a Pressman U tube experiment. Both HBPs demonstrated an enhanced ability to bind and transport anions (when compared to the anion-binding site used in isolation). Furthermore, optimum binding and transport occurred when the smaller of the two HBPs were used. This supports our previous observations regarding the existence of a dense packed limit for HBPs.

In the presence of Celite mono and disubstituted alkenes could be alkylated with benzylic halides at room temperature. In order to form the C-C bond, it was necessary to use activated aromatics with alkenes or propargylic esters.Resumen. En presencia de celita, alquenos mono- y di-sistituidos pueden ser alquilados con halogenuros de bencilo a temperatura ambiente. Para formar el enlace C-C, fue necesario usar compuestosaromáticos activados con alquenos o ésteres propargílicos.

Graphene oxide (GO) is a versatile, monomolecular layered nanomaterial that possess various oxygen containing functionality on its large surface. These characteristics allow GO to interact with a variety of materials, for application to a number of areas. The strength and selectivity of these interactions can be improved significantly through further functionalization. In this paper we describe the functionalization of GO and its application as a protein ligand and an enzyme inhibitor. The work reported in this paper details how chymotrypsin inhibition can be improved using GO functionalized with a monomeric and oligomer layer of tyrosine. The results indicated that the mono and oligo functionalized systems performed extremely well, with Ki values nearly four times better than GO alone. Our original premise was that the oligomeric system would bind better, due to the length of the oligomeric arms and potential for a high degree of flexibility. However, the results clearly showed that the shorter monomeric system was the better ligand/inhibitor. This was due to weaker intramolecular interactions between the aromatic side chains of tyrosine and the aromatic surface of GO. Although these are possible for both systems, they are cooperative and therefore stronger, for the oligomeric functionalized GO. As such, the protein must compete and overcome these cooperative intramolecular interactions before it can bind to the functionalized GO. Whereas, the tyrosines on the surface of the monomeric system interact with the surface of GO through a significantly weaker mono-valent interaction, but interact cooperatively with the protein surface.

Macromolecules are potentially useful delivery systems for cancer drugs as their size allows them to utilize the enhanced permeability and retention effect (EPR), which facilitates selective delivery to (and retention within) tumors. In addition, macromolecular delivery systems can prolong circulation times as well as protecting and solubilizing toxic and hydrophobic drug moieties. Overall these properties and abilities can result in an enhanced therapeutic effect. Photodynamic therapy (PDT) combines the use of oxygen and a photosensitizer (PS), that become toxic upon light-irradiation. We proposed that a PS encapsulated within a water-soluble macromolecule could exploit the EPR effect and safely and selectively deliver the PS to a tumor. In this paper, we describe the synthesis of a porphyrin cored hyperbranched polymer that aggregated into larger micellar structures. DLS and TEM indicated that these aggregated structures had diameters of 45 nm and 20 nm for the solvated and non-solvated species respectively. The porphyrin cored HBP (PC-HBP), along with the non-encapsulated porphyrin (THPP), were screened against EJ bladder carcinoma cells in the dark and light. Both THPP and PC-HBP displayed good toxicity in the light, with LD50 concentrations of 0.5 μM and 1.7 μM respectively. However, in the dark, the non-incorporated porphyrin (THPP) displayed significant toxicity, generating an LD50 of 4 μM. On the other hand, no dark toxicity was observed for the polymer system (PC-HBP) at concentrations of 100 μM or less. As such, incorporation within the large polymer aggregate serves to eliminate dark toxicity, whilst maintaining excellent toxicity when irradiated.

One of the most important functions of blood is to solubilize and distribute oxygen within the body. As such, it is vital that this property is replicated (safely) by any artificial blood product. In this paper, we describe the facile synthesis of a series of simple diblock polymers capable of self-assembling into micellar structures at concentrations around 3×10-3 mg/mL. Using a dissolved oxygen meter, we were able to demonstrate that aqueous solutions of these aggregated structures could retain oxygen and release it (into the aqueous bulk phase). The increased oxygen retention was quantified by measuring the rate of oxygen release and its half-life. These experiments indicated that oxygen retention/binding was dependent on the fluorine concentration. 19F NMR experiments on a micellar solution saturated with oxygen showed small upfield shifts in the fluorine peaks, which provided qualitative evidence that indicated oxygen binding occurred within the fluorine region of the polymer aggregates. Using a modified enzyme/glucose oxidation assay, we were able to establish that the aqueous oxygen concentrations were 33% higher in a solution of polymer.

It is known that dendrimers can bind proteins with good selectively. This selectivity comes about from an optimization based on matching the size of the dendrimer with the size of the protein’s interfacial binding area. In this paper, we report how this selectivity can be moderated by the functionality on the surface of the dendrimer. Specifically, we describe the synthesis of amino acid functionalized dendrimers and the effect of functionality on the dendrimer’s ability to bind and inhibit the enzymatic protein, chymotrypsin. The results show how dendrimer binding can be increased or decreased depending on the terminal functionality. These results will allow new ligands to be designed and synthesized, possessing increased and selective protein-binding abilities.

Despite the technological advancement in the biomedical science, cancer remains a life-threatening disease. In this study, we designed an anticancer nanodelivery system using graphene oxide (GO) as nanocarrier for an active anticancer agent gallic acid (GA). The successful formation nanocomposite (GOGA) was characterized using XRD, FTIR, HRTEM, Raman, and UV/Vis spectroscopy. The release study shows that the release of GA from the designed anticancer nanocomposite (GOGA) occurs in a sustained manner in phosphate-buffered saline (PBS) solution at pH 7.4. In in vitro biological studies, normal fibroblast (3T3) and liver cancer cells (HepG2) were treated with different concentrations of GO, GOGA, and GA for 72 h. The GOGA nanocomposite showed the inhibitory effect to cancer cell growth without affecting normal cell growth. The results of this research are highly encouraging to go further for in vivo studies.