The interaction of native calf thymus DNA with clodinafop-propargyl (CP), in 10 mM HEPES aqueous solutions at neutral pH 7.2, has been investigated by spectrophotometric, circular dichroism (CD), spectrofluorometric, melting temperature (Tm), and viscosimetric techniques. It was found that CP molecules could intercalate between base pairs of DNA as evidenced by hyperchromism in UV absorption band of DNA, an increase in melting temperature, a sharp increase in specific viscosity of DNA, induced CD spectral changes, and increase in the fluorescence of methylene blue (MB)-DNA solutions in the presence of increasing amounts of CP, which indicates that it is able to release the intercalated MB completely. All results suggest that the CP interacts with calf thymus DNA by an intercalative mode of binding.
Oxyhydroxy cobalt CoO(OH) nanoparticles (Co-NPs) were prepared in horse spleen apoferritin (HsAFr) cavity. Transmission electron microscopy revealed the particle size was 5.5-6 nm. Mineralization effect on HsAFr was investigated by fluorescence and far-UV circular dichroism (far-UV CD) spectroscopies. The far-UV CD experiments indicated an increase in the α-helical content after mineralization. Intrinsic fluorescence data showed that mineralization acts as a quencher of HsAFr. For the first time, direct electron transfer between Co(NPs)-HsAFr and a glassy carbon electrode in the thin film of dihexadecylphosphate (DHP) was investigated by cyclic voltammetry (CV) to design a biosensor. The anionic surfactant DHP was used to achieve direct electron-transfer between Co(NPs)-HsAFr molecules and the GC electrode surface. CV result showed clearly a pair of well-defined and quasi-reversible redox peaks arise from Co(NPs)-HsAFr embedded in DHP film. This novel biosensor can be used in medical and industrial fields to detect different analytes.
The iron storage protein, ferritin, has a cavity of ∼7 nm in diameter in which iron is oxidised and stored as a hydrated oxide core. Electron transfer is known to be an important step in the sequestering of iron by cellular ferritin. The cavity was used as a nanocontainer to grow cobalt nanoparticles. The immobilisation of ferritin on the electrode surface is essential for various bioelectronic applications. A cobaltferritin-immobilised electrode based on self-assembled monolayer (SAM)-modified gold electrode was developed. The cobaltferritin-immobilised SAM-modified electrode was characterised by electrochemical and atomic force microscopy (AFM) techniques. The results indicated that cobaltferritin was selectively immobilised onto succinimidyl alkanedisulfide-modified Au electrode by the covalent interaction between cobaltferritin and the terminal functional groups of the SAMs. The cobaltferritin immobilised modified electrode showed a direct electron transfer reaction between cobaltferritin and the electrode. The electrochemically regulated uptake and release of cobalts for cobaltferritin immobilised on the SAMs were demonstrated. The results obtained in this study indicate that cobaltferritin has potential for a biomaterial in nanoscale synthesis for potential magnetic, catalytic and biomedical-sensing applications.
In this report, a highly sensitive electrochemical biosensor based on cobaltferritin immobilised on a self-assembled monolayer modified gold electrode for determination of hydrogen peroxide (H2O2) in phosphate buffer solution (pH 7.5) was investigated. The modified electrode showed excellent electrochemical activity for oxidation of H2O2. The response to H2O2 on the modified electrode was examined using linear sweep and differential pulse voltammetries. In phosphate buffer (pH 7.5, 0.1 M), the fabricated biosensor exhibited a linear dependence (R = 0.989) on the concentration of H2O2 from 2.49 × 10(-9) to 1.91 × 10(-8) M, a high sensitivity of -0.4099 µA/nM and detection limit of 2.48 × 10(-9) based on a signal-to-noise ratio of 3. Charge transfer coefficient (α) and the exchange current (i0) of oxidation for H2O2 were found to be 0.57 and 7.55 A, respectively. It has been shown that, this modified electrode is able to determine H2O2 with a high sensitivity, low detection limit and high selectivity.
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