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Now showing items 145 - 160 of 71389

  • Alice G. Brandfonbrener, MD—A Personal Remembrance

    Lederman, Richard  

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  • Identification of an RNase that preferentially cleaves A/G nucleotides

    Xie, Jumin   Chen, Zhen   Zhang, Xueyan   Chen, Honghe   Guan, Wuxiang  

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  • A G Protein-Coupled Receptor Dimerization Interface in Human Cone Opsins

    Jastrzebska, Beata   Comar, William D.   Kaliszewski, Megan J.   Skinner, Kevin C.   Torcasio, Morgan H.   Esway, Anthony S.   Jin, Hui   Palczewski, Krzysztof   Smith, Adam W.  

    G protein-coupled receptors (GPCRs) detect a wide variety of physical and chemical signals and transmit that information across the cellular plasma membrane. Dimerization is a proposed modulator of GPCR signaling, but the structure and stability of class A GPCR dimerization have been difficult to establish. Here we investigated the dimerization affinity and binding interface of human cone opsins, which initiate and sustain daytime color vision. Using a time-resolved fluorescence approach, we found that human red cone opsin exhibits a strong propensity for dimerization, whereas the green and blue cone opsins do not. Through mutagenesis experiments, we identified a dimerization interface in the fifth transmembrane helix of human red cone opsin involving amino acids 1230, A233, and M236. Insights into this interface of red cone opsin should aid ongoing investigations of the structure and function of GPCR quaternary interactions in cell signaling. Finally, we demonstrated that the same residues needed for dimerization are also partially responsible for the spectral tuning of red cone opsin. This last observation has the potential to open up new lines of inquiry regarding the functional role of dimerization for red cone opsin.
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  • Method to determine the anisotropy parameter g of a turbid medium

    Gupta Kalpak   Shenoy M. R.  

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  • Light control of G protein signaling pathways by a novel photopigment.

    Osorno, Tomas   Arenas, Oscar   Ramirez-Suarez, Nelson J   Echeverry, Fabio A   Gomez, Maria Del Pilar   Nasi, Enrico  

    Channelopsins and photo-regulated ion channels make it possible to use light to control electrical activity of cells. This powerful approach has lead to a veritable explosion of applications, though it is limited to changing membrane voltage of the target cells. An enormous potential could be tapped if similar opto-genetic techniques could be extended to the control of chemical signaling pathways. Photopigments from invertebrate photoreceptors are an obvious choice-as they do not bleach upon illumination -however, their functional expression has been problematic. We exploited an unusual opsin, pScop2, recently identified in ciliary photoreceptors of scallop. Phylogenetically, it is closer to vertebrate opsins, and offers the advantage of being a bi-stable photopigment. We inserted its coding sequence and a fluorescent protein reporter into plasmid vectors and demonstrated heterologous expression in various mammalian cell lines. HEK 293 cells were selected as a heterologous system for functional analysis, because wild type cells displayed the largest currents in response to the G-protein activator, GTP-gamma-S. A line of HEK cells stably transfected with pScop2 was generated; after reconstitution of the photopigment with retinal, light responses were obtained in some cells, albeit of modest amplitude. In native photoreceptors pScop2 couples to Go; HEK cells express poorly this G-protein, but have a prominent Gq/PLC pathway linked to internal Ca mobilization. To enhance pScop2 competence to tap into this pathway, we swapped its third intracellular loop-important to confer specificity of interaction between 7TMDRs and G-proteins-with that of a Gq-linked opsin which we cloned from microvillar photoreceptors present in the same retina. The chimeric construct was evaluated by a Ca fluorescence assay, and was shown to mediate a robust mobilization of internal calcium in response to illumination. The results project pScop2 as a potentially powerful optogenetic tool to control signaling pathways.=20
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  • A new RHD variant allele is caused by a RHD 662C>G mutation

    Jing Feng   Li Tian   Jian Chen  

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  • The on-going legacy of February: A response to Steven G. Marks

    Orlovsky, Daniel  

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  • The Mormon Jesus: A Biography, by John G. Turner

    Gullotta, Daniel N.  

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  • A new RHD variant allele is caused by a RHD 662C>G mutation

    Feng, Jing   Tian, Li   Chen, Jian  

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  • A&G Volume 57 Issue 3, Full Issue

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  • Light control of G protein signaling pathways by a novel photopigment

    Osorno, Tomás; Arenas, Oscar; Ramírez-Suarez, Nelson J.; Echeverry, Fabio A.; Gomez, María del Pilar; Nasi, Enrico; Barnes, Steven  

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  • A&G Volume 57 Issue 3, Full Issue

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  • A&G Volume 57 Issue 2, Full Issue

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  • A hybrid model of ordinal ranking-based clustering using G+Rank K-Means

    Suhailan, S; Abdul Samad, S; Burhanuddin, M A; Makhtar, M  

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  • G(a)-ACTIONS ON AFFINE CONES

    Kishimoto, Takashi   Prokhorov, Yuri   Zaidenberg, Mikhail  

    An affine algebraic variety X is called cylindrical if it contains a principal Zariski dense open cylinder U similar or equal to Z x A(1). A polarized projective variety (Y, H) is called cylindrical if it contains a cylinder U =3D Y \ suppD, where D is an effective Q-divisor on Y such that [D] is an element of Q(+) [H] in Pic(Q) (Y). We show that cylindricity of a polarized projective variety is equivalent to that of a certain Veronese affine cone over this variety. This gives a criterion of the existence of a unipotent group action on an affine cone.
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  • A&G Volume 57 Issue 6, Full Issue

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