muramidase and 4-cyano-4--pentylbiphenyl

Topics: Biphenyl Compounds; Liquid Crystals; Muramidase; Phospholipids

Aqueous-liquid crystal (LC) interfaces offer promise as responsive interfaces at which biomolecular recognition events can be amplified into macroscopic signals. However, the design of LC interfaces that distinguish between specific and non-specific protein interactions remains an unresolved challenge. Herein, we report the synthesis of amphiphilic monomers, dimers, and trimers conjugated to sulfonamide ligands via triazole rings, their assembly at aqueous-LC interfaces, and the orientational response of LCs to the interactions of carbonic anhydrase II (CAII) and serum albumin with the oligomer-decorated LC interfaces. Of six oligomers synthesized, only dimers without amide methylation were found to assemble at aqueous interfaces of nematic 4-cyano-4'-pentylbiphenyl (5CB) to induce perpendicular LC orientations. At dimer-decorated LC interfaces, we found that concentrations of CAII less than 4 μM did not measurably perturb the LC but prevented non-specific adsorption and penetration of serum albumin into the dimer-decorated interface that otherwise triggered bright, globular LC optical domains. These experiments and others (including competitive adsorption of CAII, BSA, and lysozyme) support our hypothesis that specific binding of CAII to the dimer prevents LC anchoring transitions triggered by non-specific adsorption of serum albumin. We illustrate the utility of the approach by reporting (i) the relative activity of two small-molecule inhibitors (6-ethoxy-2-benzothiazolesulfonamide and benzenesulfonamide) of CAII to sulfonamide and (ii) proteolytic digestion of a protein (CAII) by thermolysin. Overall, the results in this paper provide new insight into the interactions of proteins at aqueous-LC interfaces and fresh ideas for either blocking non-specific interactions of proteins at surfaces or reporting specific binding events at LC interfaces in the presence of non-specific proteins.

Topics: Adsorption; Benzenesulfonamides; Biphenyl Compounds; Carbonic Anhydrase II; Ethyl Ethers; Ligands; Liquid Crystals; Microscopy; Molecular Structure; Muramidase; Nitriles; Polymers; Protein Binding; Proteins; Serum Albumin; Sulfonamides; Surface Properties; Thermolysin; Triazoles; Water

The interface between nematic liquid crystal, 4-cyano-4'-pentylbiphenyl (5CB), and water in a transmission electron microscopy (TEM) grid cell coated with QP4VP-b-LCP (quaternized poly(4-vinylpyridine) (QP4VP) and poly(4-cyanobiphenyl-4'-oxyundecylacrylate) (LCP)) was examined for protein and DNA detection. QP4VP-b-LCP was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Quaternization of P4VP with iodomethane (CH3I) made it a strong cationic polyelectrolyte and allowed QP4VP-b-LCP to form complexes with oppositely charged biological species. Several proteins, such as bovine serum albumin (BSA), hemoglobin (Hb), α chymotrypsinogen-A (ChTg), and lysozyme (LYZ), were tested for nonspecific protein detection. By injecting the protein solutions into the TEM grid cell, the initial homeotropic orientation of the TEM grid cell changed to a planar orientation above their isoelectric points (PIs) due to electrostatic interactions between QP4VP (+charge) and proteins (-charge), which did not occur below the PIs of the tested proteins. Their minimum concentrations at which the homeotropic to planar configurational change (H-P change) occurred were 0.01, 0.02, 0.03, and 0.04 wt.% for BSA, ChTg, Hb, and LYZ, respectively. One of the strong anionic polyelectrolytes, deoxyribonucleic acid (DNA) (due to the phosphate deoxyribose backbone) was also tested. A H-P change was observed with as little as 0.0013 wt.% salmon sperm DNA regardless of the pH of the cell. A H-P change occurred in 5CB and was observed by polarized optical microscopy. This simple and inexpensive setup for nonspecific biomaterial detection provides the basic idea for developing effective selective biosensors by introducing specific binding groups, such as the aptamer and antibody.

Topics: Animals; Biosensing Techniques; Biphenyl Compounds; Chymotrypsin; DNA; Electrolytes; Hemoglobins; Hydrocarbons, Iodinated; Isoelectric Point; Liquid Crystals; Magnetic Resonance Spectroscopy; Microscopy, Electron, Transmission; Muramidase; Nitriles; Optics and Photonics; Polymers; Polyvinyls; Salmon; Serum Albumin, Bovine; Spectroscopy, Fourier Transform Infrared; Static Electricity

4-cyano-4'-pentylbiphenyl (5CB) microdroplets coated with PAA-b-LCP were successfully made via microfluidics. Their functionalized interfaces were examined for lysozyme and bovine serum albumin detection, which could be easily visualized with an optical microscope under crossed polarizers by the radial-to-bipolar configurational change of the 5CB. This transition was strongly dependent on the electrostatic states of the proteins and PAA chains, which were controlled by the pH of the water. This study demonstrated a simple approach for the development of a liquid crystal-based sensor for label-free detection of proteins, which may have diverse applications in various biomedical fields.

Topics: Acrylic Resins; Adsorption; Animals; Biphenyl Compounds; Cattle; Hydrogen-Ion Concentration; Liquid Crystals; Microfluidic Analytical Techniques; Muramidase; Nitriles; Particle Size; Serum Albumin, Bovine; Surface Properties; Water