Probing the non-covalent binding interaction of the Na+ channel inactivation gate peptide in a linker between domain III and IV with 5,5-diphenyhydantoin in electrospray ion trap tandem mass spectrometry

The Na(+) channel-subunit containing an Ile1488, Phe1489 and Met1490 (IFM) motif is critical for a fast inactivation process. BL-1, a model IFM-containing peptide with a sequence of acetyl-GGQDIFMTEEK-OH, was observed as a doubly charged potassium-adduct ion by electrospray ionization mass spectrometry (ESI-MS) and a singly charged ion by atmospheric-pressure matrix-assisted laser desorption/ionization mass spectrometry (AP-MALDI-MS). Two crown ethers were applied to demonstrate their desalting ability and then to confirm the potassium-adduct assignments. In order to probe the best binding condition for BL-1 with a local anesthetic drug, 5,5-diphenyhydantoin (DPH), a series of experiments were performed and the parameters affecting complexation were carefully investigated including molar ratios, reaction time and reaction temperature. The most effective conditions for the observation of the complex by ESI-MS were molar ratio of BL-1 and DPH of 1:28 after 18 h of incubation at 40 degrees C. In addition, collision-activated dissociation (CAD) was successfully applied to confirm the formation of the complex between BL-1 with DPH that is via a weak non-covalent bonding with a 1:1 stoichiometry.     

Enzymatic glucose biosensor based on bismuth nanoribbons electrochemically deposited on reduced graphene oxide

We describe the electrochemical preparation of bismuth nanoribbons (Bi-NRs) with an average length of 100 ± 50 nm and a width of 10 ± 5 μm by a potentiostatic method. The process occurs on the surface of a glassy carbon electrode (GCE) in the presence of disodium ethylene diamine tetraacetate that acts as a scaffold for the growth of the Bi-NRs and also renders them more stable. The method was applied to the preparation of Bi-NRs incorporated into reduced graphene oxide. This nanocomposite was loaded with the enzyme glucose oxidase onto a glassy carbon electrode. The resulting biosensor displays an enhanced redox peak for the enzyme with a peak-to-peak separation of about 28 mV, revealing a fast electron transfer at the modified electrode. The loading of the GCE with electroactive GOx was calculated to be 8.54 × 10⁻¹⁰ mol∙cm⁻², and the electron transfer rate constant is 4.40 s⁻¹. Glucose can be determined (in the presence of oxygen) at a relatively working potential of −0.46 V (vs. Ag|AgCl) in the 0.5 to 6 mM concentration range, with a 104 μM lower detection limit. The sensor also displays appreciable repeatability, reproducibility and remarkable stability. It was successfully applied to the determination of glucose in human serum samples.

A potentiostatic method was used to prepare reduced graphene oxide and bismuth nanoribbons nanocomposite on a glassy carbon electrode. This nanocomposite was loaded with enzyme glucose oxidase to fabricate a glucose biosensor.