Comparison on the interaction of Al3+/nano-Al13 with calf thymus DNA /salmon sperm DNA

On-Demand Aligned DNA Hydrogel Via Light Scanning

DNA is an anisotropic, water-attracting, and biocompatible material, an ideal building block for hydrogel. The alignment of the anisotropic DNA chains is essential to maximize hydrogel properties, which has been little explored. Here, we present a method to fabricate the anisotropic DNA hydrogel that allows precise control for the polymerization process of photoreactive cationic monomers. Scanning ultraviolet light enables the uniaxial alignment of DNA chains through the polymerization-induced diffusive mass flow using a concentration gradient. While studying anisotropic mechanical properties and orientation recovery according to the DNA chain alignment direction, we demonstrate the potential of directionally controlled DNA hydrogels as smart materials.

Mechanisms of ZnO Nanoparticles Enhancing Phototransformation of Biologically Derived Organic Phosphorus in Aquatic Environments

Zinc oxide nanoparticles (ZnO NPs), as the highly efficient photocatalysts, could enhance the transformation of biogenic organic phosphorus (OP) to orthophosphate (PO₄^3-) by photodegradation, accelerating eutrophication. Conversely, orthophosphate can also transform ZnO NPs and thus potentially alter their catalytic and chemical properties. Here, we investigated the transformation mechanisms of three biogenic OP compounds and ZnO NPs under ultraviolet light (UV) illumination: inositol phosphates (IHPs), nucleic acids (DNA), and aminoethylphosphonic acid (AEP). The physicochemical characteristics of the resulting products were systematically characterized. Results show that ZnO NPs accelerated the transformation of IHPs, DNA, and AEP to inorganic phosphorus with the direct photolysis efficiencies of 98.14, 87.68, and 51.76%, respectively. The main component of the precipitates remained ZnO NPs, and Zn₃(PO₄)₂ was identified. Zinc phytate was determined in the ZnO NP-IHP system. ³¹P NMR and FTIR further confirmed that the aquatic phase contained orthophosphate. Photoproduced hydroxyl (·OH) and superoxide (·O₂^-) were proved to play a dominant role in the OP photomineralization. Furthermore, ZnO NPs significantly enhanced the intensity of ·OH and ·O₂^- compared to the OP and Zn²⁺ solution alone. This work explored the light-induced mineralization processes of OP with ZnO NPs indicating that nanophotocatalysts may play a positive role in transformation of OP species in aquatic environments to further contribute to eutrophication.

Interactions between Extracellular DNA and Perfluoroalkyl Acids (PFAAs) Decrease the Bioavailability of PFAAs in Pakchoi (Brassica chinensis L.)

Perfluoroalkyl acids (PFAAs) are emerging ionic organic pollutants worldwide. Great amounts of extracellular DNA (∼mg/kg) coexist with PFAAs in the environment. However, PFAA-DNA interactions and effects of such interactions have not been well studied. Herein, we used isothermal titration calorimetry (ITC), spectroscopy, and computational simulations to investigate the PFAA-DNA interactions. ITC assays showed that specific binding affinities of PFHxA-DNA, PFOA-DNA, PFNA-DNA, and PFOS-DNA were 5.14 × 10⁵, 3.29 × 10⁵, 1.99 × 10⁵, and 2.18 × 10⁴ L/mol, respectively, which were about 1-2 orders of magnitude stronger than those of PFAAs with human serum albumin. Spectral analysis suggested interactions of PFAAs with adenine (A), cytosine (C), guanine (G), and thymine (T), among which grooves associated with thymine were the major binding sites. Molecular dynamics simulations and quantum chemical calculations suggested that hydrogen bonds and van der Waals forces were the main interaction forces. Such a PFAA-DNA binding decreased the bioavailability of PFAAs in plant seedlings. The findings will help to improve the current understanding of the interaction between PFAAs and biomacromolecules, as well as how such interactions affect the bioavailability of PFAAs.

Mononuclear Co(II) polypyridyl complexes: synthesis, molecular structure, DNA binding/cleavage, radical scavenging, docking studies and anticancer activities

Mononuclear Co(II) complexes [CoII(L)Cl2]; 1, [CoII(L)(bpy)Cl]PF6; 2, [CoII(L)(phen)Cl]PF6; 3 and [CoII(L)(pic)Cl]; 4, (where L = N,N-bis(pyridin-2-ylmethyl)aniline, bpy = 2,2/-bipyridine, phen = 1,10-phenanthroline, pic = picolinic acid) were systematically synthesized and...

Amino and hydroxy substitution influences pyrene-DNA binding

Polycyclic aromatic hydrocarbon (PAH)-DNA binding is an essential step in PAH-induced carcinogenesis. A large number of PAHs contain substituents, it is unclear whether functional groups will influence the PAH-DNA binding. Here, we investigated amino (-NH₂) and hydroxy (-OH) substitution on pyrene-DNA binding. Because of the considerable effects of electrostatic surface potential (ESP), -NH₂ substitution significantly facilitated binding by increasing the binding constant (log K_A) from 4.14 L mol^-1 to 12.31 L mol^-1, while -OH substitution inhibited binding by reducing log K_A to 3.68 L mol^-1. Spectroscopy results revealed that pyrene and its derivatives were able to bind with thymine to induce DNA damage or double helix distortion. Quantum chemical calculations showed that -NH₂ substitution induces hydrogen bond formation, thereby enhancing the binding of pyrene with DNA; moreover, binding force changes due to -OH substitution may not be an essential factor. All structural descriptors were not correlated with the quenching constant (K_SV) or binding constant, indicating that changes in physicochemical properties shows no influence on pyrene-DNA binding. The results of this study will improve our understanding of the contribution of functional groups to PAH-DNA binding.

Enzymatic degradation of extracellular DNA exposed to chlorpyrifos and chlorpyrifos-methyl in an aqueous system

The persistence of extracellular DNA (eDNA) is crucial for ensuring species diversity and ecological function in aquatic systems. However, scarce information exists about the impact of pesticides on eDNA, although they often co-exist in the aquatic environment. Using a variety of spectroscopic analyses, eDNA degradation and the associated alterations in DNA secondary structure was investigated by exposing DNase I to tested DNA in the presence of chlorpyrifos, a commonly used organophosphate pesticide. Molecular dynamics simulation was used to explore the weak interactions between the tested DNA and chlorpyrifos. The results indicated that chlorpyrifos significantly enhanced DNA degradation without affecting the enzyme activity of DNase I in an aqueous system. Spectroscopic experiments confirmed that chlorpyrifos and the analog chlorpyrifos-methyl could bind with DNA to cause the bases noncovalent stacking interaction. Molecular simulations further demonstrated that pesticide binding with DNA molecules caused widening of the DNA grooves and destruction of the hydrated layer, which enhanced DNA degradation. The findings presented herein provide novel insight into the genotoxicity and ecotoxicity of chlorpyrifos and chlorpyrifos-methyl, as well as their impacts on DNA persistence in aquatic environments.

Organochlorinated pesticides expedite the enzymatic degradation of DNA

Extracellular DNA in the environment may play important roles in genetic diversity and biological evolution. However, the influence of environmental persistent organic contaminants such as organochlorinated pesticides (e.g., hexachlorocyclohexanes [HCHs]) on the enzymatic degradation of extracellular DNA has not been elucidated. In this study, we observed expedited enzymatic degradation of extracellular DNA in the presence of α-HCH, β-HCH and γ-HCH. The HCH-expedited DNA degradation was not due to increased deoxyribonuclease I (DNase I) activity. Our spectroscopic and computational results indicate that HCHs bound to DNA bases (most likely guanine) via Van der Waals forces and halogen bonds. This binding increased the helicity and accumulation of DNA base pairs, leading to a more compact DNA structure that exposed more sites susceptible to DNase I and thus expedited DNA degradation. This study provided insight into the genotoxicity and ecotoxicity of pesticides and improved our understanding of DNA persistence in contaminated environments.

Binding of aluminium/cacodylate complexes with DNA and RNA. Experimental and “in silico”study

Mechanism of the interaction of a dinuclear aluminium/cacodylate complex with nucleic acids.