| The essential biological materials, such as nucleic acid and protein, have played vital roles in all kinds of biological phenomenan. They participate in many reactions. And the reactions and the function of nucleic acid and protein have high specificity. Medicines pass through several processes: absorption, distribution, metabolism and excretion from entering the organisms to leaving them. Nucleic acid and protein are the main targets of all drugs in organisms. The forms and binding sites of the interactions between the drugs and biomacromolecules influence the physiological, physical and chemical characters of biomacromolecules. Therefore, the researches on the functions between medicines and the nucleic acids or the proteins have the special value to design new medicines and study the pharmacology and toxicity of anticancer medicines. In this paper, the interactions of some drugs with DNA and serum albumin were studied by fluorescence and ultraviolet-visible absorption spectrometry.The structure and nature of DNA cannot be directly studied by fluorescence technique because the fluorescence of DNA is very weak, and the fluorescent probes can be brought in to solve this problem. Ethidium bromide is used as the earliest and broadest fluorescent probe. It can be used in the selecting of anticancer treatment medicine and the sensitive probe of binding mechanism between medicine and DNA. Chrysophanol, physcion and 1, 8-dihydroxy anthraquinone are the effective components in traditional herbal in China for treating various diseases. They possess antibacterial, laxative, and antitumor functions. In this work, the binding mechanism on the reaction of fish sperm deoxyribonucleic acid (DNA) with anthraquinones, such as chrysophanol, physcion and 1,8-dihydroxy anthraquinone, were investigated using ethidium bromide (EB) as fluorescence probe by fluorescence quenching technique and UV–vis spectrophotometry. The fluorescence intensities of DNA-EB were measured at different concentrations of anthraquinone compounds. According to the relationship of the fluorescence intensity and quenching reagent concentration, the binding constants of anthraquinones with DNA-EB complex at 25°C were figured out. The binding constants of chrysophanol, physcion and 1,8-dihydroxy anthraquinone with DNA-EB were 1.64×104,3.04×104,2.88×105 L·mol-1, respectively. In the experiment, the effects of the temperatures and ionic strength were further obtained. And the effects of DNA melting were also investigated, after three anthraquinones was added into the solution containing the DNA-EB. These studies suggest that the binding mode of chrysophanol, physcion and 1, 8-dihydroxy anthraquinone with DNA were evaluated to be groove binding.Ethidium bromide (EB) is a typical intercalative reagent of DNA. Its binding to DNA makes the fluorescence intensity of the system greatly enhanced. The interaction mechanisms of flavonoids, such as rutin, hyperoside and quercitrin, and DNA were studied using EB as fluorescence probes by fluorescence and ultraviolet-visible absorption spectrometry. Flavonoid is a secondary metabolite plant of widespread distribution. They widely exist in vegetables, fruits and medicinal plants. Their poisonous effect is small, and is one of the main active constituents in the medicinal plant. Here, the interactions of rutin, hyperoside and quercitrin with fish sperm deoxyribonucleic acid (DNA) by using EB as fluorescence probe were first reported. The character of fluorescence quenching process was investigated by spectrometric methods. The binding constants of flavonoids-double stranded DNA (dsDNA) or flavonoids-single stranded DNA (ssDNA) were obtained by the fluorescence quenching technique. Further, the effects of ionic strength and temperature on the fluorescence property of the system have also been investigated. The melting temperature (Tm) and viscosity of DNA was carried out to investigate binding mechanism of these flavonoids with DNA. The results of the assay indicate that the binding mode of rutin, hyperoside and quercitrin with DNA was evaluated to be intercalative binding. The binding constants of rutin, hyperoside and quercitrin with dsDNA (or ssDNA)-EB complex are 3.72×104 (or 7.65×103), 1.13×105 (or 5.73×104) and 5.59×104 (or 3. 63×104) L·mol?1, respectively.Doxycycline Hyclate is a semi-synthetic tetracycline antibiotic. It is frequently used to treat chronic prostatitis, sinusitis, syphilis, chlamydia, pelvic inflammatory disease, acne and rosacea. There are several advantages, such as relatively cheap, minor side-effects, and a slim risk of liver damage during prolonged use of the drug. Distribution and metabolism of many pharmaceutical molecules in the body are correlated with their affinities toward serum albumin. In this paper, the interactions of doxycycline with human serum albumin (HSA) and bovine serum albumin (BSA) were studied by fluorescence and ultraviolet-visible absorption spectrometry. The results showed that the fluorescence of serum albumins was strongly quenched by doxycycline. The quenching mechanism was static quenching procedure proved by the quenching rate constant (Kq). The main acting forces between doxycycline and serum albumins were hydrophobic force according to the thermodynamic parameters. The binding constants of doxycycline with human serum albumin and bovine serum albumin at different temperatures were obtained. The effects of metal ions, such as Ca2+, Mg2+, Zn2+, Fe3+ and Cu2+, on binding constants were also evaluated.
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