Effect of Stalling after Mismatches on the Error Catastrophe in Nonenzymatic Nucleic Acid Replication

The frequency of errors during genome replication limits the amount of functionally important information that can be passed on from generation to generation. During the origin of life, mutation rates are thought to have been quite high, raising a classic chicken-and-egg paradox: could nonenzymatic replication propagate sequences accurately enough to allow for the emergence of heritable function? Here we show that the theoretical limit on genomic information content may increase substantially as a consequence of dramatically slowed polymerization after mismatches. As a result of postmismatch stalling, accurate copies of a template tend to be completed more rapidly than mutant copies and the accurate copies can therefore begin a second round of replication more quickly. To quantify this effect, we characterized an experimental model of nonenzymatic, template-directed nucleic acid polymerization. We found that most mismatches decrease the rate of primer extension by more than 2 orders of magnitude relative to a matched (Watson-Crick) control. A chemical replication system with this property would be able to propagate sequences long enough to have function. Our study suggests that the emergence of functional sequences during the origin of life would be possible even in the face of the high intrinsic error rates of chemical replication

Effect of deposition temperature on the microstructure, ferroelectric and mechanical properties of lead free BCZT ceramic thin films

Thin films of 0.5[Ba0.7Ca0.3TiO3] – 0.5[Ba(Zr0.2Ti0.8)O3] (BCZT) ceramics were grown on platinized Si-substrates by pulsed laser deposition using a BCZT ceramic target. The crystal structure, morphology, ferroelectric and mechanical properties of the BCZT films were studied as a function of different deposition temperatures: 600, 650 and 700 °C. The XRD studies confirmed the crystallization of tetragonal structure for all the BCZT films and the crystallinity of these films tend to increase with increase of deposition temperature. The FESEM analysis revealed homogeneous microstructure with columnar grains, particularly at higher deposition temperature. The presence of both dark and bright ferroelectric domains with oppositely polarized states and switching behaviour is evident in the PFM images. The estimated ferroelectric polarization values and mechanical properties such as hardness and elastic modulus showed an increasing trend against deposition temperature