Bacterial melanin interacts with double-stranded DNA with high affinity and may inhibit cell metabolism in vivo.

Melanin has been found to interact with a number of molecules including metal ions, antibiotics and proteins. In this study, we showed how melanin from bacteria can interact with double-stranded DNA. Investigation using capillary electrophoresis, various spectroscopic techniques and circular dichroism found that melanin interacts with DNA by intercalating between the base pairs of DNA.

Protective action of bacterial melanin against DNA damage in full UV spectrums by a sensitive plasmid-based noncellular system.

The purpose of this study was to introduce a simple and sensitive plasmid-based noncellular system to evaluate the photoprotection of bacterial melanin on DNA damage against ultraviolet (UV) radiation. Plasmid DNA was used to assess the role of melanin in different ranges of UV using a series of in vitro assays. Fluorometric measurements suggested that melanin could efficiently scavenge reactive oxygen species (ROS) generated by UVA irradiation in solution, and the scavenging capability was proportional to the pigment concentration.

Analysis of plasmid DNA damage induced by melanin with capillary electrophoresis.

Dilute linear poly(N-isopropylacrylamide) (PNIPAM) in Tris-Mes-EDTA (TME) buffer was used as sieving matrix for capillary electrophoresis (CE) of plasmid DNA and plasmid topological isomers induced by melanin in uncoated capillary. At the optimized condition of 0.1% (w/v) PNIPAM in TME buffer, base line separation of the plasmid DNA ladder (2-12 kbp) was achieved within 15 min.

pH effect on dynamic coating for capillary electrophoresis of DNA.

A buffer consisting of tris(hydroxymethyl)aminomethane, 2-(N-moropholino)ethanesulfonic acid (Mes) and EDTA with constant ion strength was used to investigate the effect of buffer pH on the dynamic coating behavior of poly(N-isopropylacrylamide) (PNIPAM) for DNA separation. The atomic force microscopy (AFM) image illustrated that PNIPAM in lower-pH buffer was much more efficient in covering a silica wafer than that in higher-pH buffer. The coating performance of PNIPAM was also quantitatively analyzed by Fourier transform IR attenuated total reflectance spectroscopy and by measuring the electroosmotic flow (EOF).