ABSTRACT
A simple and reliable strategy was proposed to engineer the glutathione grafted graphene oxide/ZnO nanocomposite(glutathione-GO/ZnO)as electrode material for the high-performance piroxicam sensor.The prepared glutathione-GO/ZnO nanocomposite was well characterized by X-ray diffraction(XRD),Fourier transform infrared spectrum(FTIR),X-ray photoelectron spectroscopy(XPS),field emission scanning electron microscopy(FE-SEM),cyclic voltammetry(CV),electrochemical impedance spectros-copy(EIS)and differential pulse voltammetry(DPV).The novel nanocomposite modified electrode showed the highest electrocatalytic activity towards piroxicam(oxidation potential is 0.52 V).Under controlled experimental parameters,the proposed sensor exhibited good linear responses to piroxicam concentrations ranging from 0.1 to 500 μM.The detection limit and sensitivity were calculated as 1.8 nM and 0.2 μA/μM·cm2,respectively.Moreover,it offered excellent selectivity,reproducibility,and long-term stability and can effectively ignore the interfering candidates commonly existing in the pharmaceutical tablets and human fluids even at a higher concentration.Finally,the reported sensor was successfully employed to the direct determination of piroxicam in practical samples.
ABSTRACT
The amino terminal 1-18 domain of dermaseptin s is an important determinant of its structure as well as the antibacterial activity. A thorough investigation on the structure of the 18-residue peptide (D18) and its binding to model membranes in presence of salt and denaturant guanidinium chloride has been carried out. In presence of salt, there is an increase in the fraction of peptide molecules in helical conformation. In presence of the denaturant, D18 is unordered, but addition of the structure-promoting solvent trifluoroethanol results in a transition to the helical conformation. In presence of denaturant, the peptide is unordered, but binding to lipid vesicles is not abolished. Investigation of model membrane permeabilizing ability of the peptide in solutions containing various proportions of sodium chloride and guanidinium chloride indicates that vesicle permeabilization parallels extent of binding. The peptide thus binds to lipid vesicles in an unfolded state. Since the peptide has propensity to fold into a helical conformation, lipid induced transition to a helical structure occurs, followed by membrane permeabilization as a result of pore formation.