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Quantum dots (QDs) have many potential clinical and biological applications because of their advantages over traditional fluorescent dyes. However, the genotoxicity potential of QDs still remains unclear. In this paper, a plasmid-based system was designed to explore the genotoxic mechanism of QDs by detecting changes in DNA configuration and biological activities. The direct chemicobiological interactions between DNA and mercaptoacetic acid-coated CdSecore QDs (MAA-QDs) were investigated. After incubation with different concentrations of MAA-QDs (0.043, 0.13, 0.4, 1.2, and 3.6 µmol/L) in the dark, the DNA conversion of the covalently closed circular (CCC) DNA to the open circular (OC) DNA was significantly enhanced (from 13.9% ± 2.2% to 59.9% ± 12.8%) while the residual transformation activity of plasmid DNA was greatly decreased (from 80.7% ± 12.8% to 13.6% ± 0.8%), which indicated that the damages to the DNA structure and biological activities induced by MAA-QDs were concentration-dependent. The electrospray ionization mass spectrometry data suggested that the observed genotoxicity might be correlated with the cadmium-mercaptoacetic acid complex (Cd-MAA) that is formed in the solution of MAA-QDs. Circular dichroism spectroscopy and transformation assay results indicated that the Cd-MAA complex might interact with DNA through the groove-binding mode and prefer binding to DNA fragments with high adenine and thymine content. Furthermore, the plasmid transformation assay could be used as an effective method to evaluate the genotoxicities of nanoparticles.

The solid−liquid equilibrium solubility and solvent effects of Nbenzyloxycarbonyl-L-serine in 12 monosolvent systems (water, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, n-pentanol, acetonitrile, 2butanone, acetone, methyl acetate, and ethyl acetate) were reported in this work. All of the solubility data were measured at 283.15−323.15 K (5 K interval) by the static gravimetric method at a pressure of 101.2 kPa. Among the 12 monosolvents, the solubility increased with the increase of absolute temperature; the order is acetone > isopropanol > n-propanol > sec-butanol > n-butanol > 2butanone > isobutanol ≈ n-pentanol > methyl acetate > ethyl acetate > acetonitrile > water. The solubility is the largest in acetone (0.2055 mol•mol −1 at 323.15 K) and the smallest in water (9.737 × 10 −4 mol•mol −1 at 283.15 K). According to the solubility data analysis results, the solubility of Nbenzyloxycarbonyl-L-serine is positively correlated with the polarity of the solvent. However, its solubility could be affected by other factors, such as propensity for hydrogen bonding acceptor for isopropanol, structural similarity for acetone, cohesive energy density for water, acetonitrile, and sec-butanol, which lead to different dissolution behavior. In addition, the Hansen solubility parameters (HSPs) were used to further analyze its solubility behavior. The Yaws model and the modified Apelblat model were employed to correlate the experimental solubility, and the fitting results of the two models were both well. In addition, through the comparison of the AIC values and Akaike weights of the two models, the modified Apelblat model yielded a more satisfactory correlation result. The results may provide a theoretical basis for the preparation and application of N-benzyloxycarbonyl-L-serine.

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