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Metastable Prepores in Tension-Free Lipid Bilayers

Physical Review Letters

Ting, Christina T.; Awasthi, Neha; Müller, Marcus; Hub, Jochen S.

The formation and closure of aqueous pores in lipid bilayers is a key step in various biophysical processes. Large pores are well described by classical nucleation theory, but the free-energy landscape of small, biologically relevant pores has remained largely unexplored. The existence of small and metastable "prepores" was hypothesized decades ago from electroporation experiments, but resolving metastable prepores from theoretical models remained challenging. Using two complementary methods - atomistic simulations and self-consistent field theory of a minimal lipid model - we determine the parameters for which metastable prepores occur in lipid membranes. Both methods consistently suggest that pore metastability depends on the relative volume ratio between the lipid head group and lipid tails: lipids with a larger head-group volume fraction (or shorter saturated tails) form metastable prepores, whereas lipids with a smaller head-group volume fraction (or longer unsaturated tails) form unstable prepores.

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TYPE Journal Article YEAR 2018
ScopusOSTIDOI

Collaborative analytics for biological facility characterization

Proceedings of SPIE - The International Society for Optical Engineering

Caswell, Jacob C.; Cairns, Kelsey L.; Ting, Christina T.; Hansberger, Mark W.; Stoebner, Matthew A.; Brounstein, Tom R.; Cueller, Christopher R.; Jurrus, Elizabeth R.

Thousands of facilities worldwide are engaged in biological research activities. One of DTRA's missions is to fully understand the types of facilities involved in collecting, investigating, and storing biological materials. This characterization enables DTRA to increase situational awareness and identify potential partners focused on biodefense and biosecurity. As a result of this mission, DTRA created a database to identify biological facilities from publicly available, open-source information. This paper describes an on-going effort to automate data collection and entry of facilities into this database. To frame our analysis more concretely, we consider the following motivating question: How would a decision maker respond to a pathogen outbreak during the 2018 Winter Olympics in South Korea? To address this question, we aim to further characterize the existing South Korean facilities in DTRA's database, and to identify new candidate facilities for entry, so that decision makers can identify local facilities properly equipped to assist and respond to an event. We employ text and social analytics on bibliometric data from South Korean facilities and a list of select pathogen agents to identify patterns and relationships within scientific publication graphs.

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TYPE Conference Poster YEAR 2018
ScopusOSTIDOI

Footprint of Sandia's August 15 2016 Informal Idea Exploration Session on "Towards an Engineering and Applied Science of Research"

Tsao, Jeffrey Y.; Fleming Lindsley, Elizabeth S.; Heffelfinger, Grant S.; Narayanamurti, Venkatesh N.; Schneider, Rick S.; Starkweather, Lynne M.; Ting, Christina T.; Yajima, Rieko Y.; Bauer, Travis L.; Coltrin, Michael E.; Guy, Donald W.; Jones, Wendell J.; Mareda, John F.; Nenoff, T.M.; Turnley, Jessica G.

On August 15, 2016, Sandia hosted a visit by Professor Venkatesh Narayanamurti. Prof Narayanamurti (Benjamin Peirce Research Professor of Technology and Public Policy at Harvard, Board Member of the Belfer Center for Science and International Affairs, former Dean of the School of Engineering and Applied Science at Harvard, former Dean of Engineering at UC Santa Barbara, and former Vice President of Division 1000 at Sandia). During the visit, a small, informal, all-day idea exploration session on "Towards an Engineering and Applied Science of Research" was conducted. This document is a brief synopsis or "footprint" of the presentations and discussions at this Idea Exploration Session. The intent of this document is to stimulate further discussion about pathways Sandia can take to improve its Research practices.

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TYPE SAND Report YEAR 2017
OSTIDOI

Nonequilibrium simulations of model ionomers in an oscillating electric field

Journal of Chemical Physics

Ting, Christina T.; Sorensen-Unruh, Karen E.; Stevens, Mark J.; Frischknecht, Amalie F.

We perform molecular dynamics simulations of a coarse-grained model of ionomer melts in an applied oscillating electric field. The frequency-dependent conductivity and susceptibility are calculated directly from the current density and polarization density, respectively. At high frequencies, we find a peak in the real part of the conductivity due to plasma oscillations of the ions. At lower frequencies, the dynamic response of the ionomers depends on the ionic aggregate morphology in the system, which consists of either percolated or isolated aggregates. We show that the dynamic response of the model ionomers to the applied oscillating field can be understood by comparison with relevant time scales in the systems, obtained from independent calculations.

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TYPE Journal Article YEAR 2016
ScopusOSTIDOI
Results 26–50 of 52
Results 26–50 of 52