336 research outputs found
Carbonic Anhydrase in Certain Species of Plants
Author Institution: Charles F. Kettering Foundation, Yellow Springs, Ohi
The Photosynthetic Function of Manganese and Chloride
Author Institution: Charles F. Kettering Foundation, Yellow Springs, Ohi
The Vibrational Energy Levels and Specific Heat of Ethylene
In a recent review of the experimental infra-red and Raman spectra of ethylene and tetradeuteroethylene [1], Conn and Sutherland have succeeded in giving very reasonable estimates of the positions of the four fundamental lelvels associated with the "rocking frequencies" of the methylene groups in C2H4. They have at the same time revised the previous estimate of the position of the "torisional" lelvel [2] to 700 cm^-1, for reasons which are in our opinion inadequate, and with results which prove to be unsatisfactory. In particular, as they themselves remark, the calculated heat capacities then become too large. We wish to point out that a return to the Bonner assignment of this level not only yields a more reasonable explanation of the weak combination and harmonic lines in the Raman spectra, but also leads to a theoretical heat capacity which is in good agreement with the existing measured values [3] and with new experimental values recently obtained in these Laboratories
Mathematical Manipulative Models: In Defense of Beanbag Biology
Mathematical manipulative models have had a long history of influence in biological research and in secondary school education, but they are frequently neglected in undergraduate biology education. By linking mathematical manipulative models in a four-step process-1) use of physical manipulatives, 2) interactive exploration of computer simulations, 3) derivation of mathematical relationships from core principles, and 4) analysis of real data sets-we demonstrate a process that we have shared in biological faculty development workshops led by staff from the BioQUEST Curriculum Consortium over the past 24 yr. We built this approach based upon a broad survey of literature in mathematical educational research that has convincingly demonstrated the utility of multiple models that involve physical, kinesthetic learning to actual data and interactive simulations. Two projects that use this approach are introduced: The Biological Excel Simulations and Tools in Exploratory, Experiential Mathematics (ESTEEM) Project (http://bioquest.org/esteem) and Numerical Undergraduate Mathematical Biology Education (NUMB3R5 COUNT; http://bioquest.org/numberscount). Examples here emphasize genetics, ecology, population biology, photosynthesis, cancer, and epidemiology. Mathematical manipulative models help learners break through prior fears to develop an appreciation for how mathematical reasoning informs problem solving, inference, and precise communication in biology and enhance the diversity of quantitative biology education
Membrane-Associated RING-CH Proteins Associate with Bap31 and Target CD81 and CD44 to Lysosomes
Membrane-associated RING-CH (MARCH) proteins represent a family of transmembrane ubiquitin ligases modulating intracellular trafficking and turnover of transmembrane protein targets. While homologous proteins encoded by gamma-2 herpesviruses and leporipoxviruses have been studied extensively, limited information is available regarding the physiological targets of cellular MARCH proteins. To identify host cell proteins targeted by the human MARCH-VIII ubiquitin ligase we used stable isotope labeling of amino-acids in cell culture (SILAC) to monitor MARCH-dependent changes in the membrane proteomes of human fibroblasts. Unexpectedly, we observed that MARCH-VIII reduced the surface expression of Bap31, a chaperone that predominantly resides in the endoplasmic reticulum (ER). We demonstrate that Bap31 associates with the transmembrane domains of several MARCH proteins and controls intracellular transport of MARCH proteins. In addition, we observed that MARCH-VIII reduced the surface expression of the hyaluronic acid-receptor CD44 and both MARCH-VIII and MARCH-IV sequestered the tetraspanin CD81 in endo-lysosomal vesicles. Moreover, gene knockdown of MARCH-IV increased surface levels of endogenous CD81 suggesting a constitutive involvement of this family of ubiquitin ligases in the turnover of tetraspanins. Our data thus suggest a role of MARCH-VIII and MARCH-IV in the regulated turnover of CD81 and CD44, two ubiquitously expressed, multifunctional proteins
Basigin-mediated redistribution of CD98 promotes cell spreading and tumorigenicity in hepatocellular carcinoma
Arp2/3- and Cofilin-coordinated Actin Dynamics Is Required for Insulin-mediated GLUT4 Translocation to the Surface of Muscle Cells
Insulin increases GLUT4 at the muscle cell surface, and this process requires actin remodeling. We show that a dynamic cycle of actin polymerization and severing is induced by insulin, governed by Arp2/3 and dephosphorylation of cofilin, respectively. The cycle is self-perpetuating and is essential for GLUT4 translocation
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