Aggregation Of DNA Molecules Research Articles

Multi-target antibacterial mechanism of eugenol and its combined inactivation with pulsed electric fields in a hurdle strategy on Escherichia coli

Eugenol (2-Methoxy-4-(2-Propenyl) Phenol; EUG) is a natural antibacterial ingredient of the essential oil from many aromatic plants. The antimicrobial mechanism of EUG and its combined inactivation effect with pulsed electric fields (PEF) treatment in a hurdle strategy on E. coli ATCC 8739 were investigated. Results showed that membrane integrity and the morphology of E. coli cell were damaged and the membrane permeability was increased when E. coli was exposed to higher levels of EUG. Analysis of fluorescence spectra, molecular docking and atomic force microscope indicated that EUG bound to the AT-rich region of DNA through groove binding mode, leading to morphological alterations and the aggregation of DNA molecules. The combinations of EUG and PEF demonstrated strong synergistic effects for sterilization and it was proven to be an effective method to achieve a higher level of E. coli inactivation.

Antimicrobial activities of lauric arginate and cinnamon oil combination against foodborne pathogens: Improvement by ethylenediaminetetraacetate and possible mechanisms

The objective of this work was to study if ethylenediaminetetraacetate (EDTA) could enhance the antimicrobial activity of lauric arginate (LAE) and cinnamon oil (CO) combination, and the possible mechanisms. With 500 mg/L of EDTA, 5 mg/L of LAE and 200 mg/L of CO showed an increased log reduction of Escherichia coli O157: H7, Salmonella Enteritidis, and Listeria monocytogenes by ca. 4, 5, and 1 log CFU/mL, respectively. EDTA at 500 mg/L significantly increased the permeability of outer membrane of E. coli O157: H7 based on a crystal violet assay. Scanning electron microscopy (SEM) showed that 600 mg/L CO damaged the cell membrane of S. Enteritidis, while 40 mg/L LAE did not. Atomic force microscopy demonstrated that LAE caused the aggregation of DNA molecules. It was hypothesized that EDTA increased the permeability of the outer membrane of Gram-negative bacteria to facilitate the penetration of LAE and CO enabling enhanced antimicrobial activity. Compared to the treatment with LAE or CO alone, severe damage of L. monocytogenes membrane occurred with LAE and CO in combination based on SEM, increase in loss of intracellular nucleic acids, and increase of extracellular ATP level, suggesting LAE and CO acted synergistically on L. monocytogenes cell membranes.

Molecular Voids Formed from Effective Attraction in Submonolayer DNA Deposited on Au(111)

The development of DNA-based biosensors requires a deep understanding of how DNA molecules adsorb and organize on solid state surfaces as well as the electronic properties of individual and aggregates of DNA molecules. Using scanning tunneling microscopy (STM) and atomic force microscopy (AFM), we have successfully characterized an attractive force driven molecular void formation for DNA chemically adsorbed on Au(111) as a function of strand length and deposition conditions. Here we report the observation of these void structures formed on the Au(111) surface by adsorption of both 45 and 90 base pair long, thiolated double-stranded DNA. We found that the average void diameter decreases when increasing the number of base pairs exposed to the surface. The critical determinant in the molecular void formation is the total charge delivered to the surface via the adsorption of the DNA strands and the related counterions, which can ultimately be quantified by the number of base pairs in each adsorbed DNA molecule. Complementary measurements involving STM and AFM suggest that an intact Au(111) surface area is preserved inside the void and is surrounded by a submonolayer of DNA molecules adsorbed on the surface. The discussion of the possible mechanisms for the void formation implies an effective attraction between the DNA molecules.

Formation of macromolecular complexes and other effects of DNA treatment with diethyl and dimethyl sulfate: physico-chemical and electron microscopic studies

In vitro exposures of isolated DNA to one of the two carcinogenic and mutagenic chemicals, diethylsulfate or dimethylsulfate, induces several kinds of physicochemical and morphological alterations. These changes are detectable by a variety of independent techniques. A fraction of DNA treated briefly with either of these two chemicals moves during velocity centrifugation experiments less rapidly than the bulk of control DNA and more rapidly through gels during electrophoresis. This apparent decrease in size is paralleled by the formation of large DNA aggregates with mobilities indicating molecular weights several times that of the untreated, control DNA. The presence of a basic protein in the incubation mixture increases the rate of formation of such complexes. the tendency of the alkylated DNA to bind to both biological and non-biological materials is reflected in the increased attachment of DNA to columns built with methyl-esterified serum albumin and in its quantitative retention on nitrocellulose filters. DNA exposed to dimethylsulfate decreases its density in CsCl gradients. A mixture of two or more DNAs of different densities exposed to this chemical produces an u.v.-absorbing band which is found in such gradients at an intermediate density. If the alkylation reaction is carried out in the presence of a protein, a portion of DNA bands at a density intermediate between the density of DNA and that of the protein, even in the presence of an ionic detergent in the gradient. Under the electron microscope the alkylated DNA shows multiple single-strand breaks and peeling-off whiskers of denatured DNA. Aggregates of DNA molecules become visible upon further incubation of DNA with the alkylating agent. We suggest that the DNA-DNA and DNA- protein complexes play an important role in the process of carcinogenesis and mutagenesis.