Examinando por Autor "Comer, Jeffrey"

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    Molecular determinants of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) binding to transient receptor potential V1 (TRPV1) channels
    (American Society for Biochemistry and Molecular Biology Inc., 2015-01) Poblete, Horacio; Oyarzún, Ingrid; Olivero, Pablo; Comer, Jeffrey; Zuñiga, Matías; Sepulveda, Romina V.; Báez-Nieto, David; Leon, Carlos González; González-Nilo, Fernando; Latorre, Ramón
    Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) has been recognized as an important activator of certain transient receptor potential (TRP) channels. More specifically, TRPV1 is a pain receptor activated by a wide range of stimuli. However, whether or not PI(4,5)P2 is a TRPV1 agonist remains open to debate. Utilizing a combined approach of mutagenesis and molecular modeling, we identified a PI(4,5)P2 binding site located between the TRP box and the S4-S5 linker. At this site, PI(4,5)P2 interacts with the amino acid residues Arg-575 and Arg-579 in the S4-S5 linker and with Lys-694 in the TRP box. We confirmed that PI(4,5)P2 behaves as a channel agonist and found that Arg-575, Arg-579, and Lys-694 mutations to alanine reduce PI(4,5)P2 binding affinity. Additionally, in silico mutations R575A, R579A, and K694A showed that the reduction in binding affinity results from the delocalization of PI(4,5)P2 in the binding pocket. Molecular dynamics simulations indicate that PI(4,5)P2 binding induces conformational rearrangements of the structure formed by S6 and the TRP domain, which cause an opening of the lower TRPV1 channel gate. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.
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    Ítem
    Self-Assembly of Amphiphilic Dendrimers: The Role of Generation and Alkyl Chain Length in siRNA Interaction
    (Nature Publishing Group, 2016-07) Márquez-Miranda, Valeria; Araya-Durán, Ingrid; Camarada, María Belén; Comer, Jeffrey; Valencia-Gallegos, Jesús A.; González-Nilo, Fernando Danilo
    An ideal nucleic-acid transfection system should combine the physical and chemical characteristics of cationic lipids and linear polymers to decrease cytotoxicity and uptake limitations. Previous research described new types of carriers termed amphiphilic dendrimers (ADs), which are based on polyamidoamine dendrimers (PAMAM). These ADs display the cell membrane affinity advantage of lipids and preserve the high affinity for DNA possessed by cationic dendrimers. These lipid/dendrimer hybrids consist of a low-generation, hydrophilic dendron (G2, G1, or G0) bonded to a hydrophobic tail. The G2-18C AD was reported to be an efficient siRNA vector with significant gene silencing. However, shorter tail ADs (G2-15C and G2-13C) and lower generation (G0 and G1) dendrimers failed as transfection carriers. To date, the self-assembly phenomenon of this class of amphiphilic dendrimers has not been molecularly explored using molecular simulation methods. To gain insight into these systems, the present study used coarse-grained molecular dynamics simulations to describe how ADs are able to self-assemble into an aggregate, and, specifically, how tail length and generation play a key role in this event. Finally, explanations are given for the better efficiency of G2/18-C as gene carrier in terms of binding of siRNA. This knowledge could be relevant for the design of novel, safer ADs with welloptimized affinity for siRNA.