ABSTRACT
Three silver(I) complexes containing N-methylbenzothiazole-2-thione (mbtt) have been prepared and structurally characterized by X-ray single-crystal analysis. Silver(I) nitrate, and silver(I) triflate react with mbtt to give homoleptic complexes of formula [(mbtt)2Ag(µ-mbtt)2Ag(mbtt)2](NO3)2 (1) and [Ag(mbtt)3](CF3SO3) (2) respectively, while silver(I) chloride gives the binuclear halide-bridged [(mbtt)2Ag(µ2-Cl)2Ag(mbtt)2] (3). In the binuclear complex 1 the two metal ions, separated by 3.73 Å from each other, are doubly bridged by the exocyclic S-atoms of two mbtt ligands, with the tetrahedral environment around each silver ion being completed by the S-atoms of two terminally bonded mbtt units. Compound 2 is mononuclear with the metal ion surrounded by the exocyclic S-atoms of three mbtt ligands in a nearly ideal trigonal planar arrangement. The new complexes showed significant in vitro antibacterial activity against certain Gram-positive and Gram-negative bacterial strains.
Subject(s)
Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/pharmacology , Benzothiazoles/chemical synthesis , Benzothiazoles/pharmacology , Coordination Complexes/chemical synthesis , Coordination Complexes/pharmacology , Silver/pharmacology , Anti-Bacterial Agents/chemistry , Benzothiazoles/chemistry , Coordination Complexes/chemistry , Crystallography, X-Ray , Escherichia coli/drug effects , Microbial Sensitivity Tests , Molecular Conformation , Superoxides/metabolismABSTRACT
We present molecular-level simulations of dendrimer/DNA complexes in the presence of a model cell membrane. We determine the required conditions for the complex to arrive intact at the membrane, and the lifetime of the complex as it resides attached to the membrane. Our simulations directly pertain to critical issues arising in emerging gene delivery therapeutic applications, where a molecular carrier is required to deliver DNA segments to the interior of living cells.
Subject(s)
Cell Membrane/chemistry , Dendrimers/chemistry , Genetic Vectors/chemical synthesis , Computer Simulation , DNA/chemistry , Genetic Vectors/chemistry , Models, Molecular , ProbabilityABSTRACT
A study of the micromechanical unzipping of DNA in the framework of the Peyrard-Bishop-Dauxois model is presented. We introduce a Monte Carlo technique that allows accurate determination of the dependence of the unzipping forces on unzipping speed and temperature. Our findings agree quantitatively with experimental results for homogeneous DNA, and for lamda-phage DNA we reproduce the recently obtained experimental force-temperature phase diagram. Finally, we argue that there may be fundamental differences between in vivo and in vitro DNA unzipping.
Subject(s)
Base Pairing , DNA, Viral/chemistry , DNA/chemistry , Models, Chemical , Nucleic Acid Conformation , Bacteriophage lambda/chemistry , Nucleic Acid DenaturationABSTRACT
Using a well established model, we systematically analyze fundamental limitations on the viability of using mechanical unzipping of DNA as a fast and inexpensive sequencing method. Standard unzipping techniques, where double-stranded DNA is unzipped through the application of a force at one end of the molecule, are shown to be inadequate. Emerging techniques that unzip DNA by local force application are more promising, and we establish the necessary experimental requirements that must be met for these techniques to succeed as single molecule sequencing tools.
Subject(s)
Sequence Analysis, DNA , Microscopy, Atomic Force , Models, Chemical , Sequence Analysis, DNA/instrumentation , Sequence Analysis, DNA/methodsABSTRACT
The onset of intermediate states (denaturation bubbles) and their role during the melting transition of DNA are studied using the Peyrard-Bishop-Dauxois model by Monte Carlo simulations with no adjustable parameters. Comparison is made with previously published experimental results finding excellent agreement. Melting curves, critical DNA segment length for stability of bubbles, and the possibility of a two-state transition are studied.
