The denaturation temperature of collagen has been determined using several methods, such as circular dichroism, fourier transform infrared spectroscopy, and differential scanning calorimetry, etc. Such methods need specific equipment or mass samples (more than 75 mg samples), which means higher inspection costs. In this study, Sirius red was employed to determine the Tds of collagen from calf tendon, silver carp skin, frog and salmon skins (38.2 °C, 32.6 °C, 33.8 °C, and 15.6 °C, respectively) to explore a new method that does not require special equipment and only needs 2–3 mg sample for one measurement. This method was suitable for the determination of the denaturation temperature of collagen from terrestrial, aquatic and amphibian animals. Analysis of variance and t -test revealed that no significant difference was found between Sirius Red and viscosity methods. However, the Sirius Red method needs simpler equipment and less sample than viscosity and other methods. So it could be used as a convenient approach to determine the denaturation temperature of collagen instead of the viscosity method.
Indole-2-carboxylic acid copper complex (ICA-Cu) was successfully prepared and characterized through elemental analysis, IR, UV-Vis,1H-NMR, TG analysis, and molar conductance, and its molecular formula was [Cu2(C9H6O2N)4(H2O)2]·2H2O. The binding ability of ICA-Cu to calf thymus DNA (CT-DNA) was examined by fluorescence spectrometry and the viscosity method. The results indicated that, upon the addition of increasing amounts of CT-DNA, the excitation and emission intensity of ICA-Cu decreased obviously and the excitation spectra shifted towards a long wavelength. ICA-Cu could displace ethidium bromide (EB) from the EB-DNA system, making the fluorescence intensity of the EB-DNA system decrease sharply; the quenching constantKSVvalue was 3.99 × 104M−1. The emission intensity of the ICA-Cu-DNA system was nearly constant, along with the addition of Na+in a series of concentrations. The fluorescence of the complex could be protected after the complex interacted with DNA. A viscosity measurement further supported the result that the ICA-Cu complex may interact with DNA in an intercalative binding mode. The antioxidant activities of ICA-Cu were evaluated by a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, a hydroxyl radical (OH) scavenging assay, and a 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assay. The ICA-Cu exhibited the highest inhibitory effects on the ABTS radical (94% inhibition at 60 µM), followed by OH and DPPH radicals (the degrees of inhibition being 71% and 56%, respectively). The in vitro cytotoxicity activity of ICA-Cu against two human breast cancer cell lines, MDA-MB-231 and MCF-7, was investigated by 3-[4,5-dimethyltiazol2-yl]-2.5-diphenyl-tetrazolium bromide (MTT) assay and cellular morphological analysis. The results showed that, upon increasing the concentration of ICA-Cu, an increase was observed in growth-inhibitory activity and the inhibition percentage were greater than 90% at 20 µM in both cell lines. Also, cellular morphological changes in the two cell lines agreed with the cytotoxicity results.Keywords:DNA-binding;antioxidant;anticancer;indole-2-carboxylicacid;copper(II) complexes
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