Dataset Information

Liquid water is a dynamic polydisperse branched polymer.

ABSTRACT: We developed the RexPoN force field for water based entirely on quantum mechanics. It predicts the properties of water extremely accurately, with T melt = 273.3 K (273.15 K) and properties at 298 K: ?Hvap = 10.36 kcal/mol (10.52), density = 0.9965 g/cm3 (0.9965), entropy = 68.4 J/mol/K (69.9), and dielectric constant = 76.1 (78.4), where experimental values are in parentheses. Upon heating from 0.0 K (ice) to 273.0 K (still ice), the average number of strong hydrogen bonds (SHBs, rOO ? 2.93 Å) decreases from 4.0 to 3.3, but upon melting at 273.5 K, the number of SHBs drops suddenly to 2.3, decreasing slowly to 2.1 at 298 K and 1.6 at 400 K. The lifetime of the SHBs is 90.3 fs at 298 K, increasing monotonically for lower temperature. These SHBs connect to form multibranched polymer chains (151 H2O per chain at 298 K), where branch points have 3 SHBs and termination points have 1 SHB. This dynamic fluctuating branched polymer view of water provides a dramatically modified paradigm for understanding the properties of water. It may explain the 20-nm angular correlation lengths at 298 K and the critical point at 227 K in supercooled water. Indeed, the 15% jump in the SHB lifetime at 227 K suggests that the supercooled critical point may correspond to a phase transition temperature of the dynamic polymer structure. This paradigm for water could have a significant impact on the properties for protein, DNA, and other materials in aqueous media.

SUBMITTER: Naserifar S

PROVIDER: S-EPMC6369747 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Liquid water is a dynamic polydisperse branched polymer.

Naserifar Saber S Goddard William A WA

Proceedings of the National Academy of Sciences of the United States of America 20190124 6

We developed the RexPoN force field for water based entirely on quantum mechanics. It predicts the properties of water extremely accurately, with Tmelt = 273.3 K (273.15 K) and properties at 298 K: ΔHvap = 10.36 kcal/mol (10.52), density = 0.9965 g/cm3 (0.9965), entropy = 68.4 J/mol/K (69.9), and dielectric constant = 76.1 (78.4), where experimental values are in parentheses. Upon heating from 0.0 K (ice) to 273.0 K (still ice), the average number o ...[more]

PMID: 30679278

Similar Datasets

Project description:BackgroundWe previously determined that polyplexes formed by linear H2K peptides were more effective in transfecting tumors in vivo than polyplexes formed by branched H2K4b-20 peptides. Based on trypsin digest and salt displacement studies, the linear H2K polyplexes were less stable than the branched H2K4b-20 polyplexes. Because binding and release of the polymer and DNA from the H2K4b-20 polyplex may account for the ineffectiveness, we investigated whether four-branched histidine-lysine (HK) peptides with varying numbers of amino acids in their branches would be more effective in their ability to increase gene expression in tumors in vivo.MethodsLinear and branched peptides with multiple -KHHK- motifs were synthesized by solid-phase synthesis. The branched H2K4b-20, -18, -14 and 12 peptides had 20, 18, 14 and 12 amino acids in their branches, respectively. These peptides were examined for their ability to carry luciferase-expressing plasmids to human breast cancer xenografts in a mouse model. With gel retardation and in vivo transfection, the incorporation of a targeting ligand and an endosomal lysis peptide into these polyplexes was also examined. A blocking antibody was pre-injected prior to the polyplexes to determine the role of neuropilin 1 in the uptake of these polyplexes by the tumor. The size of the polyplexes was measured by dynamic light scattering.ResultsOf the four negative surface-charge polyplexes formed by the branched carriers, the H2K4b-14 polyplex was determined to be the most effective plasmid delivery platform to tumors. The incorporation of a targeting ligand and an endosomal lysis peptide into H2K4b-14 polyplexes further enhanced their ability to transfect tumors in vivo. Furthermore, after pre-injecting tumor-bearing mice with a blocking antibody to the neuropilin-1 receptor (NRP-1), there was a marked reduction of tumor gene expression with the modified H2K4b-14 polyplexes, suggesting that NRP-1 mediated their transport into the tumor.ConclusionsThe present study established that branched peptides intermediate in length were very efficient in delivering plasmids to tumors in vivo.

Dataset Information

Liquid water is a dynamic polydisperse branched polymer.

Publications

Liquid water is a dynamic polydisperse branched polymer.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets