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The interaction between silver nanoparticle and calf thymus DNA was studied by UV−visible, fluorescence, and far UV circular dichroism (CD) spectroscopies at a physiologic temperature of 37 °C. By the analysis of UV−visible titration and thermal denaturation studies of DNA, it was found that silver nanoparticle can form a new complex with double-helical DNA and increase the T m value of DNA. This kind of binding may cause a slight change of the conformation of DNA. The fluorescence emission spectra of intercalated ethidium bromide (EB) with increasing concentration of silver nanoparticle at 37 °C represented a significant reduction of the ethidium intensity and quenching of EB fluorescence. Also, CD results suggested that silver nanoparticle can significantly change the helicity conformation of DNA and then induce the alteration of nonplanar and tilted orientations of DNA bases, resulting in the changes of DNA base stacking, and act as an intercalator. Spectroscopic results represented that binding of silver nanoparticle to DNA resulted in significant changes in the structure and conformation of DNA in a concentration dependent manner and act as an intercalator via increasing stability of DNA by increasing T m, quenching of EB fluorescence intensity, and alteration of CD spectra. Also, the antitumor property of silver nanoparticle was studied by testing it on human tumor cell line K562. The 50% cytotoxic concentration (Cc50) of silver nanoparticle was determined using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay after a 24 h incubation time. Results of the present study may provide useful information to design better anticancer compounds using metal nanoparticles with lower side effects in the future.

The aim of this study was to investigate the effects of enzymatic hydrolysis with digestive enzymes of camel whole casein and beta-casein (β-CN) on their antioxidant and Angiotensin Converting Enzyme (ACE)-inhibitory properties. Peptides in each hydrolysate were fractionated with ultra-filtration membranes. The antioxidant activity was determined using a Trolox equivalent antioxidant capacity (TEAC) scale. After enzymatic hydrolysis, both antioxidant and ACE-inhibitory activities of camel whole casein and camel β-CN were enhanced. Camel whole casein and β-CN showed significant ACE-inhibitory activities after hydrolysis with pepsin alone and after pepsinolysis followed by trypsinolysis and chymotrypsinolysis. Camel β-CN showed high antioxidant activity after hydrolysis with chymotrypsin. The results of this study suggest that when camel milk is consumed and digested, the produced peptides start to act as natural antioxidants and ACE-inhibitors.

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