Lipoprotein lipase is active as a monomer

Lipoprotein lipase (LPL), the enzyme that hydrolyzes triglycerides in plasma lipoproteins, is assumed to be active only as a homodimer. In support of this idea, several groups have reported that the size of LPL, as measured by density gradient ultracentrifugation, is ∼110 kDa, twice the size of LPL monomers (∼55 kDa). Of note, however, in those studies the LPL had been incubated with heparin, a polyanionic substance that binds and stabilizes LPL. Here we revisited the assumption that LPL is active only as a homodimer. When freshly secreted human LPL (or purified preparations of LPL) was subjected to density gradient ultracentrifugation (in the absence of heparin), LPL mass and activity peaks exhibited the size expected of monomers (near the 66-kDa albumin standard). GPIHBP1-bound LPL also exhibited the size expected for a monomer. In the presence of heparin, LPL size increased, overlapping with a 97.2-kDa standard. We also used density gradient ultracentrifugation to characterize the LPL within the high-salt and low-salt peaks from a heparin-Sepharose column. The catalytically active LPL within the high-salt peak exhibited the size of monomers, whereas most of the inactive LPL in the low-salt peak was at the bottom of the tube (in aggregates). Consistent with those findings, the LPL in the low-salt peak, but not that in the high-salt peak, was easily detectable with single mAb sandwich ELISAs, in which LPL is captured and detected with the same antibody. We conclude that catalytically active LPL can exist in a monomeric state

Analytic Markovian Rates for Generalized Protein Structure Evolution

A general understanding of the complex phenomenon of protein evolution requires the accurate description of the constraints that define the sub-space of proteins with mutations that do not appreciably reduce the fitness of the organism. Such constraints can have multiple origins, in this work we present a model for constrained evolutionary trajectories represented by a Markovian process throughout a set of protein-like structures artificially constructed to be topological intermediates between the structure of two natural occurring proteins. The number and type of intermediate steps defines how constrained the total evolutionary process is. By using a coarse-grained representation for the protein structures, we derive an analytic formulation of the transition rates between each of the intermediate structures. The results indicate that compact structures with a high number of hydrogen bonds are more probable and have a higher likelihood to arise during evolution. Knowledge of the transition rates allows for the study of complex evolutionary pathways represented by trajectories through a set of intermediate structures

Los 'fueguinos', Robert Lehmann-Nitsche y el estudio de los onas en la Exposición Nacional de Buenos Aires (1898)

Entre los primeros trabajos del antropólogo alemán Robert Lehmann-Nitsche como jefe del Departamento de Antropología del Museo de La Plata, Argentina, se cuentan las investigaciones sobre los habitantes de Tierra del Fuego, considerados como un 'relicto' evolutivo de la humanidad. Se repasa la importancia de las ferias y exposiciones como espacios de popularización científica y de 'trabajo de campo' para los estudiosos de fines del siglo XIX y principios del XX. Se examina la presentación de los 'fueguinos' en los espacios de las ferias y exposiciones europeas, los debates, los estudios realizados en Europa y el trabajo de Robert Lehmann-Nitsche en la Exposición Nacional de la Industria Argentina (Buenos Aires, 1898).Among the first projects of German anthropologist Robert Lehmann-Nitsche as head of the Museum de La Plata's Department of Anthropology in Argentina was his research on the inhabitants of Tierra del Fuego, deemed evolutionary 'relics' of humanity. The article explores the role of shows and exhibits as spaces where science was popularized and where late nineteenth- and early twentieth-century scholars could do field work. The focus is on the presentation of 'fueguinos' at European shows and exhibits, debates, and studies, especially the work of Robert Lehmann-Nitsche at the National Exhibit of Argentinean Industry, held in Buenos Aires, 1898

Nine Nevada Depressions, Dissipate #8

general view, photograph taken 365 days after environmental installatio

Compression Line

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Untitled

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Nine Nevada Depressions, Isolated Mass/Circumflex 1

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Complex One, Central Eastern Nevada

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Double Negative

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