Memory Effects Explain the Fractional Viscosity Dependence of Rates Associated with Internal Friction: Simple Models and Applications to Butane Dihedral Rotation.

Barrier-crossing rates of biophysical processes, ranging from simple conformational changes to protein folding, often deviate from the Kramers prediction of an inverse viscosity dependence. In many recent studies, this has been attributed to the presence of internal friction within the system. Previously, we showed that memory-dependent friction arising from the nonequilibrium solvation of a single particle crossing a smooth one-dimensional barrier can also cause such a deviation and be misinterpreted as internal friction.

Comparative Evaluation of Cotton PTFE Tape and Foam Pellets as Endodontic Spacer in Primary Teeth: An Study.

Aim And Objective: This study was conducted to microbiologically evaluate cotton, PTFE tape, and foam pellets as endodontic spacer in primary teeth.

Materials And Methods: Thirty primary second molars indicated for pulpectomy were included in this study. Followed by the completion of pulpectomy in each teeth cotton, PTFE tape, and foam pellets were placed as endodontic spacers randomly in 10 teeth each.

Dynamical Recrossing in the Intercalation Process of the Anticancer Agent Proflavine into DNA.

Intercalation into DNA is the interaction mode of some anthracycline antibiotics. Recently, the molecular mechanism of this process was explored using the static free energy landscape. Here we explore the dynamical effects in the intercalation of proflavine into DNA by calculating the transmission coefficient κ-providing a measure of the departure from transition state theory for the reaction rate constant-by examination of the recrossing events at the transition state.

Probing the Viscosity Dependence of Rate: Internal Friction or the Lack of Friction?

Deviation from the Kramers' inverse viscosity dependence of rate, k ∝ 1/η, is often attributed to the presence of internal friction in proteins after Ansari et al. in 1992 showed that the folding rate could fit k ∝ 1/(η + σ) where σ is considered the internal friction. Several experimental and computational studies thereafter used fits to Ansari's equation or extrapolated the rate to η = 0 to estimate the internal friction in proteins and attributed its origin to various internal interactions such as ruggedness, dihedral rotation, and salt bridges.

Design of Bivalent Nucleic Acid Ligands for Recognition of RNA-Repeated Expansion Associated with Huntington's Disease.

We report the development of a new class of nucleic acid ligands that is comprised of Janus bases and the MPγPNA backbone and is capable of binding rCAG repeats in a sequence-specific and selective manner via, inference, bivalent H-bonding interactions. Individually, the interactions between ligands and RNA are weak and transient. However, upon the installation of a C-terminal thioester and an N-terminal cystine and the reduction of disulfide bond, they undergo template-directed native chemical ligation to form concatenated oligomeric products that bind tightly to the RNA template.