Stability of plasmid pBR322 within Escherichia coli cells

nsertion of plasmids into the bacterial cells is of great significance especially in course of the transfer of drug resistance, virulence and other traits. Retention of plasmids within the host bacteria is therefore an important factor for bacterial homeostasis. Current study inferred the pBR322 plasmid stability within the Escherichia coli competent cells. The calcium chloride heat shock method was used for the transformation purpose. The plasmid retention phenomenon was assessed through the replica plating. The results positively showed the plasmid retention within E. coli.

DNA Cleavage Properties, Antimicrobial and Cytotoxic Activity and 4D-QSAR Analysis of Some Pyrazole Derivatives

Background:An extensive study of 19 pyrazole derivatives were carried out based on the evaluation of DNA cleavage properties, antimicrobial and cytotoxic activities and 4D-QSAR analysis including pharmacophore modelling and bioactivity prediction by the Electron Conformational-Genetic Algorithm (EC-GA) method.Methods:The pyrazole derivatives were tested for their antimicrobial activity against certain human pathogenic organisms using the agar diffusion procedure. Binding of compounds with DNA was studied by gel electrophoresis using plasmid pBR322 DNA. The compounds were investigated for their properties as cytotoxic agents by brine shrimp lethality bioassay. To identify the pharmacophoric elements and find out the most important molecular properties which govern cytotoxic activity, multiple conformations of the compounds were used.Results:The urea derivatives of pyrazole had higher antibacterial activities against Gram-negative bacteria than against Gram-positive bacteria. Many of the compounds were found to cleave plasmid pBR322 DNA from the supercoiled form to the nicked circular. The cytotoxicity values of the compounds ranged from 13.87 to 84.1 µg/mL. The generated QSAR model was evaluated through the use of the Leave-One-Out Cross Validation (LOO-CV) method. A statistically significant and considerably predictive QSAR model was obtained with 4- descriptors resulting in R2 training =0.8223, R2 test =0.9346, q2=0.6201, q2 ext1=0.8672, q2 ext2= 0.8662 and q2 ext3=0.9511.Discussion:The generated model demonstrates that geometrical parameters are more correlated with cytotoxic activity. The resulting EC-GA model would provide benefits to design novel bioactive pyrazole derivatives which are more potent and have less side effects.Conclusion:It is believed that the generated QSAR model gives insight into developing new more potent pyrazole derivative drugs.

Plasmid pBR322 and Nonlinear Conformational Distortions (Kinks)

Plasmid pBR322 containing two coding regions in the matrix chain is a convenient object to study the DNA nonlinear dynamics that is known to play an important role in the processes of transcription, replication, denaturation and transmission of structural changes and information along the DNA molecule. The aim of the present work is to study by the methods of mathematical modeling the dynamics of local conformational distortions – kinks, in the plasmid pBR322. To calculate the dynamic characteristics of the kinks, we applied the method of McLaughlin-Scott, complemented by the block method. This permitted us to model kinks as quasi-particles moving in the potential field of the plasmid. We calculated the time dependences of the kink energy, velocity and coordinate. Calculations were made for three different values of the initial kink velocity: 150 m/s, 1650 m/s and 1879 m/s. The results obtained presented in the form of 3D trajectories and their projections, showed that the necessary condition for kink passing the entire plasmid is the enough large value of the initial kink velocity υ not less than 1656.66 m/c which is, however, less than sound velocity (1904.60 m/c).

Interactions of the anti-tumor sesquiterpene hydroquinone avarol with DNA in vitro

Changes in electrophoresis pattern after interaction of supercoiled plasmid pBR322 DNA with avarol was studied at a micromolar concentration of reactants under mild reaction conditions. Interactions of avarol with linear high-molecular CT-DNA at millimolar concentrations were analyzed by electrophoresis and UV spectrophotometry. It was observed that avarol is capable of quenching ethidium bromide fluorescence in DNA bands. An increase in the absorbance of DNA was detected. The results indicate the binding of avarol to DNA and/or modification of nucleotide bases.