Temperature‐accelerated sliced sampling (TASS) is an enhanced sampling method for achieving accelerated and controlled exploration of high‐dimensional free energy landscapes in molecular dynamics simulations. With the aid of umbrella bias potentials, the TASS method realizes a controlled exploration and divide‐and‐conquer strategy for computing high‐dimensional free energy surfaces. In TASS, diffusion of the system in the collective variable (CV) space is enhanced with the help of metadynamics bias and elevated‐temperature of the auxiliary degrees of freedom (DOF) that are coupled to the CVs. Usually, a low‐dimensional metadynamics bias is applied in TASS. In order to further improve the performance of TASS, we propose here to use a highdimensional metadynamics bias, in the same form as in a parallel bias metadynamics scheme. Here, a modified reweighting scheme, in combination with artificial neural network is used for computing unbiased probability distribution of CVs and projections of high‐dimensional free energy surfaces. We first validate the accuracy and efficiency of our method in computing the four‐dimensional free energy landscape for alanine tripeptide in vacuo. Subsequently, we employ the approach to calculate the eight‐dimensional free energy landscape of alanine pentapeptide in vacuo. Finally, the method is applied to a more realistic problem wherein we compute the broad four‐dimensional free energy surface corresponding to the deacylation of a drug molecule which is covalently complexed with a β‐lactamase enzyme. We demonstrate that using parallel bias in TASS improves the efficiency of exploration of high‐dimensional free energy landscapes.
The relations and correlation between the physicochemical characteristics of a chemical compounds and the molecular structure connectivity of the same compound are used in quantitative structure activity and property relationship studies (QSAR/QSPR) by using the appropriate graph‐theoretical techniques. Szeged index has been extensively studied for modeling physicochemical properties of organic compounds acting as drugs or possess pharmacological activity. In this paper, we consider the two‐dimensional lattices of titanium oxide nanotubes TiO2. We compute several Szeged‐type indices such as vertex Szeged, edge Szeged, edge‐vertex Szeged, total Szeged, Padmaker–Ivan, revised Szeged and revised‐edge Szeged indices of these graphs. We define new types of cuts that are different from orthogonal cuts and can be used to obtain Szeged‐type results of titania nanotubes.
The relations between the physico‐chemical properties of a chemical compounds its molecular structure properties are used in quantitative structure activity and property relationship studies by using graph‐theoretical techniques. The Wiener polarity index is the number of unordered pairs of vertices lying at distance 3 in a graph. This index is correlated to the cluster coefficient of chemical networks. The Wiener polarity index has been used to exhibit quantitative structure–property relationships in a series of acyclic and cycle‐containing hydrocarbons. In this paper, we consider three variants of the graph of titanium oxide TiO2, that is, two‐dimensional lattice, nanotubes and nanotorus. For all these graphs, we compute the number of pairs of vertices lying at distance one, two and three. Using this information, we compute the Wiener polarity index and leap Zagreb indices of these graphs.
Genetic characterization of maize genotypes is of great importance in maize breeding program to identify diverse populations and divergent genotypes. Divergence and genetic diversity were assessed in a set of 20 maize genotypes representing popcorn, white corn, sweet corn and yellow corn, through morphological characteristics and Random Amplified Polymorphic DNA (RAPD) markers. Field experiment was conducted in randomized complete block design with three replications. Morphological data revealed that sweet corn genotype SCLY-1 was earlier in days to 50% pollen shedding than other genotypes while white corn genotype WL-3 was earlier in days to 50% silking. Maximum plant height was recorded for PCLY-5 (133.3 cm) while lowest for WL-4 (92.8 cm), whereas highest ears height was recorded for popcorn PCLY-1 (64.4 cm) and lowest (29.4 cm) for SCLY-5. The yellow corn had maximum (4.5 kg) grain yield at harvest as compared to sweet and popcorn (3.0 kg). Negative but weak correlation was recorded between ear height and grain yield. Cluster analysis based on yield related parameters grouped all the studied genotypes in to five sub clusters. Molecular genotyping based on four primers amplified 37 loci which were (100%) polymorphic. Maximum elven loci were identified by primer GLA-04, while minimum was reported for primer GLA-03. The loci GLD-18B1000, GLA-04B300 recorded highest gene diversity (0.500) followed by loci GLE05B750, GLE-05B650 and GLE-05B550. The loci of primer GLD-18 (GLD-18B1000) detected highest alleles evenness and Simpson’s diversity index of 1.00 and 0.526, respectively. Maximum gene diversity (0.354) among populations were recorded for yellow corn, while the minimum was detected for white corn (0.254), while genotypic diversity was same for all maize types. Cluster analysis based on molecular genotypic data grouped the maize genotypes into four distinct groups. Lack of concordance was observed while comparing the clustering based on phenotypic and molecular data. The overall diversity among the studied maize genotypes could be used in future maize breeding program.
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