Diss. (sammanfattning)--Stockholm : Karol. inst., 2006. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [117]-125).

Thesis (Ph. D.)--Case Western Reserve University, 2005. / [School of Medicine] Department of Physiology and Biophysics. Includes bibliographical references. Available online via OhioLINK's ETD Center.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2010.

Thesis (Ph.D. in Molecular Biology) -- University of Colorado Denver, 2008. / Typescript. Includes bibliographical references (leaves 155-167). Free to UCD affiliates. Online version available via ProQuest Digital Dissertations;

Thesis (Ph. D.)--University of Missouri-Columbia, 2005. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Vita. Includes bibliographical references.

Thesis (Ph.D. in Pharmaceutical Sciences) -- University of Colorado, 2006. / Typescript. Includes bibliographical references (leaves 144-161). Free to UCDHSC affiliates. Online version available via ProQuest Digital Dissertations;

Accumulation and aggregation of the 42-residue amyloid-[beta] (A[beta]) protein fragment, which originates from the cleavage of amyloid precursor protein by beta and gamma secretase, correlates with the pathology of Alzheimer's disease (AD). Possible therapies for AD include peptides based on the A[beta] sequence, and recently identified small molecular weight compounds designed to mimic these, that interfere with the aggregation of A[beta] and prevent its toxic effects on neuronal cells in culture. Here, we use molecular dynamics simulations to compare the mode of interaction of an active (LPFFD) and inactive (LHFFD) [beta]-sheet breaker peptide with an A[beta] fibril structure from solid state NMR studies. We found that LHFFD had a weaker interaction with the fibril than the active peptide, LPFFD, from geometric and energetic considerations, as estimated by the MM/PBSA approach. Cluster analysis and computational alanine scanning identified important ligand-fibril contacts, including a possible difference in the effect of histidine on ligand-fibril [pi]-stacking interactions, and the role of the proline residue establishing contacts that compete with those essential for maintenance of the inter-monomer [beta]-sheet structure of the fibril. Our results show that molecular dynamics simulations can be a useful way to classify the stability of docking sites. These mechanistic insights into the ability of LPFFD to reverse aggregation of toxic A[beta] will guide the redesign of lead compounds, and aid in developing realistic therapies for AD and other diseases of protein aggregation. We have also performed long explicit solvent MD simulations of unliganded amyloid fibril in three putative protonation states, in order to better understand the energetic and mechanical features of the fibril receptor. Over 100 ns MD simulations, the trajectories where fibril has Glu11 and Glu22 side-chains protonated exhibit the least deviation from the initial solid state NMR structures. Free energy calculations on these rajectories suggest that the weakest fibril interface lies in the lateral rather than transverse direction and that there is little dependence on whether the lateral interface is situated at the edge or middle of the fibril. This agrees with recent reported steered molecular dynamics calculations. Secondly, in an effort to improve the ability of atomistic simulation techniques to directly resolve protein tertiary structure from primary amino acid sequence, we explore the use of a molecular dynamics technique based on swarm intelligence, called SWARM-MD, to identify the native states of two peptides, polyalanine and AEK17, as well as Trp-cage miniprotein. We find that the presence of cooperative swarm interactions significantly enhanced the efficiency of molecular dynamics simulations in predicting native conformation. However, it also is evident that the presence of outlying simulation replicas can adversely impact correctly folded replica structures. By slowly removing the swarm potential after folding simulations, the negative effect of the swarm potential can be alleviated and better agreement with experiment obtained.

Ca2+ is an important messenger that affects almost all cellular processes. Ca2+ signaling involves events that happen at various time-scales such as Ca2+ diffusion, trans-membrane Ca2+ transport and Ca2+-mediated protein-protein interactions. In this work, we utilized multi-scale computational methods to quantitatively characterize Ca2+ diffusion efficiency, Ca2+ binding thermodynamics and molecular bases of Ca2+-dependent protein-protein interaction. Specifically, we studied 1) the electrokinetic transport of Ca2+ in confined sub-µm geometry with complicated surfacial properties. We characterized the effective diffusion constant of Ca2+ in a cell-like environment, which helps to understand the spacial distribution of cytoplasmic Ca2+. 2) the association kinetics and activation mechanism of the protein phosphatase calcineurin (CaN) by its activator calmodulin (CaM) in the presence of Ca2+. We found that the association between CaM and CaN peptide is diffusion-limited and the rate could be tuned by charge density/distribution of CaN peptite. Moreover, we proposed an updated CaM/CaN interaction model in which a secondary interaction between CaN’s distal helix motif and CaM was highlighted. 3) the roles of Mg2+ and K+ in the active transport of Ca2+ by sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) pump. We found that Mg2+ most likely act as inhibitor while K+ as agonist in SERCA’s transport process of Ca2+. Results reported in this work shed insights into various aspects of Ca2+ signaling from molecular to cellular level.