Functional interplay between NTP leaving group and base pair recognition during RNA polymerase II nucleotide incorporation revealed by methylene substitution.

RNA polymerase II (pol II) utilizes a complex interaction network to select and incorporate correct nucleoside triphosphate (NTP) substrates with high efficiency and fidelity. Our previous 'synthetic nucleic acid substitution' strategy has been successfully applied in dissecting the function of nucleic acid moieties in pol II transcription. However, how the triphosphate moiety of substrate influences the rate of P-O bond cleavage and formation during nucleotide incorporation is still unclear. Here, by employing β,γ-bridging atom-'substituted' NTPs, we elucidate how the methylene substitution in the pyrophosphate leaving group affects cognate and non-cognate nucleotide incorporation. Intriguingly, the effect of the β,γ-methylene substitution on the non-cognate UTP/dT scaffold (∼3-fold decrease in kpol) is significantly different from that of the cognate ATP/dT scaffold (∼130-fold decrease in kpol). Removal of the wobble hydrogen bonds in U:dT recovers a strong response to methylene substitution of UTP. Our kinetic and modeling studies are consistent with a unique altered transition state for bond formation and cleavage for UTP/dT incorporation compared with ATP/dT incorporation. Collectively, our data reveals the functional interplay between NTP triphosphate moiety and base pair hydrogen bonding recognition during nucleotide incorporation

Impact of template backbone heterogeneity on RNA polymerase II transcription.

Variations in the sugar component (ribose or deoxyribose) and the nature of the phosphodiester linkage (3'-5' or 2'-5' orientation) have been a challenge for genetic information transfer from the very beginning of evolution. RNA polymerase II (pol II) governs the transcription of DNA into precursor mRNA in all eukaryotic cells. How pol II recognizes DNA template backbone (phosphodiester linkage and sugar) and whether it tolerates the backbone heterogeneity remain elusive. Such knowledge is not only important for elucidating the chemical basis of transcriptional fidelity but also provides new insights into molecular evolution. In this study, we systematically and quantitatively investigated pol II transcriptional behaviors through different template backbone variants. We revealed that pol II can well tolerate and bypass sugar heterogeneity sites at the template but stalls at phosphodiester linkage heterogeneity sites. The distinct impacts of these two backbone components on pol II transcription reveal the molecular basis of template recognition during pol II transcription and provide the evolutionary insight from the RNA world to the contemporary 'imperfect' DNA world. In addition, our results also reveal the transcriptional consequences from ribose-containing genomic DNA

Two essential light chains regulate the MyoA lever arm to promote Toxoplasma gliding motility

Key to the virulence of apicomplexan parasites is their ability to move through tissue and to invade and egress from host cells. Apicomplexan motility requires the activity of the glideosome, a multicomponent molecular motor composed of a type XIV myosin, MyoA. Here we identify a novel glideosome component, essential light chain 2 (ELC2), and functionally characterize the two essential light chains (ELC1 and ELC2) of MyoA in Toxoplasma. We show that these proteins are functionally redundant but are important for invasion, egress, and motility. Molecular simulations of the MyoA lever arm identify a role for Ca2+ in promoting intermolecular contacts between the ELCs and the adjacent MLC1 light chain to stabilize this domain. Using point mutations predicted to ablate either the interaction with Ca2+ or the interface between the two light chains, we demonstrate their contribution to the quality, displacement, and speed of gliding Toxoplasma parasites. Our work therefore delineates the importance of the MyoA lever arm and highlights a mechanism by which this domain could be stabilized in order to promote invasion, egress, and gliding motility in apicomplexan parasites

Representation of Color Space Transformations for Effective Calibration and Control

We propose the minvar algorithm for computing continuous, continuously invertible, piecewise linear (PL) approximations of color space transformations that can serve as functional replacements wherever look-up tables are presently used. After motivating the importance of invertible approximants in color space management applications, we review the parameterization and computational implementation of PL functions as representing one useful instance of this notion. Finally, we describe the present version of the minvar algorithm and compare the approximations it yields with standard industrial practice — interpolation of look-up table data

Modeling the archetype cysteine protease reaction using dispersion corrected density functional methods in ONIOM-type hybrid QM/MM calculations: the proteolytic reaction of papain

K

Manufacturing French-Canadian Tradition: tabac canadien and the Construction of French-Canadian Identity, 1880-1950

From the late nineteenth century to the end of the Second World War, several tobacco companies in Quebec produced and marketed domestic pipe tobacco specifically for the French-Canadian market. While these tabac canadien brands were rooted in pre-industrial French-Canadian economic and cultural life, by the time this traditional tobacco was being commercially manufactured, smoking rituals had already been transformed by the separation of production and consumption and by the increasing restriction of smoking to only a male activity. The urbanization of the francophone population and the appearance of industrially produced foreign tobacco gave the French-Canadian brands a new, nationalist symbolism. Companies producing tabac canadien sought in various ways to present their tobacco as authentically French Canadian while distancing themselves from the pre-industrial, supposedly inferior, product. The decline of these brands was linked to businesspromoted changes in tariff policy and broader changes in Quebec culture following the Second World War.De la fin du XIXe siècle à la fin de la Seconde Guerre mondiale, plusieurs compagnies de tabac du Québec ont produit et mis en marché du tabac à pipe d’ici à l’intention expresse du marché canadien français. Bien que ces marques de tabac canadien étaient enracinées dans la vie économique et culturelle préindustrielle des Canadiens français, au moment où l’on a commencé à commercialiser ce tabac traditionnel, la séparation de la production et de la consommation avait déjà modifié les rituels d’usage du tabac, cantonnant de plus en plus le tabagisme au seul camp masculin. L’urbanisation de la population francophone et l’apparition de tabacs industriels d’origine étrangère ont conféré aux marques canadiennes françaises une valeur de symbole national. Les fabricants de tabac canadien ont cherché par divers moyens à présenter leur tabac comme un produit authentiquement canadien français tout en se distançant du produit prétendument inférieur d’avant l’industrialisation. Les changements aux politiques tarifaires souhaités par l’entreprise et l’évolution générale du Québec sur le plan culturel après la Seconde Guerre mondiale ont sonné le glas de ces marques

Digital Color Imaging

This paper surveys current technology and research in the area of digital color imaging. In order to establish the background and lay down terminology, fundamental concepts of color perception and measurement are first presented us-ing vector-space notation and terminology. Present-day color recording and reproduction systems are reviewed along with the common mathematical models used for representing these devices. Algorithms for processing color images for display and communication are surveyed, and a forecast of research trends is attempted. An extensive bibliography is provided