Academic literature on the topic 'Lipide circulant'

The promise of algae to address the renewable energy and green-product production demands of the globe has yet to be realized. Over the past ten years, however, there has been a substantial investment and interest in realizing the potential of algae to meet these needs. Tremendous progress has been achieved. Ten years ago, the price of gasoline produced from algal biomass was 20-fold greater than it is today. Technoeconomic models indicate that algal biocrude produced in an optimized cultivation, harvesting, and biomass conversion facility can achieve economic parity with petroleum while reducing carbon-energy indices substantially relative to petroleum-based fuels. There is also an emerging recognition that algal carbon capture and sequestration as lipids may offer a viable alternative to direct atmospheric CO2 capture and sequestration. We review recent advances in basic and applied algal biomass production from the perspectives of algal biology, cultivation, harvesting, energy conversion, and sustainability. The prognosis is encouraging but will require substantial integration and field testing of a variety of technology platforms to down select the most economical and sustainable systems to address the needs of the circular economy and atmospheric carbon mitigation.

The basic structures of a bacterial and a eukaryotic cell are shown in Fig. 8.1. The differences whose origins call for an explanation are as follows: • The bacterial cell has a rigid outer cell wall, usually made of the peptidoglycan, murein. In eukaryotes, the rigid cell wall is not universal, and cell shape is maintained primarily by an internal cytoskeleton of filaments and microtubules. • Eukaryotic cells have a complex system of internal membranes, including the nuclear envelope, endoplasmic reticulum and lysosomes. • Bacteria have a single circular chromosome, attached to the rigid outer cell wall. In eukaryotes, linear chromosomes are contained within a nuclear envelope, which separates transcription from translation: communication between nucleus and cytoplasm is via pores in the nuclear envelope. • Eukaryotes have a complex cytoskeleton. The actomyosin system powers cell division, phagocytosis, amoeboid motion and the overall contractility to resist osmotic swelling. Microtubules and the associated motor proteins (kinesin, dynein and dynamin) ensure the accurate segregation of chromosomes in mitosis, ciliary motility and the movement of transport vesicles. Intermediate filaments form the structural basis for the association of the endomembranes and nuclear-pore complexes with the chromatin to form the nuclear envelope, while other intermediate filaments help to anchor the nucleus in the cytoplasm. One crucial difference between prokaryotes and most eukaryotes has been omitted from Fig. 8.1: this is the presence of mitochondria, and, in plants and algae, of chloroplasts. The reason for the omission is that, on the scenario for eukaryote origins that seems to us most plausible, these intracellular organelles originated later in time than the structures shown in the figure. The differences between these cell types justifies the recognition of two empires of life (above the kingdom level): Bacteria and Eukaryota (Cavalier-Smith, 199la; Table 8.1). (It is interesting that this taxonomic rank was recognized by Linnaeus.) Within each of the empires, there are two major categories: Bacteria consist of the kingdoms Eubacteria and Archaebacteria, and Eukaryota are divided into the superkingdoms Archaezoa and Metakaryota. The justification for these divisions is as follows. The Archaebacteria, in contrast to the Eubacteria, never have murein cell walls, and their single cell membrane contains isoprenoidal ether rather than acyl ester lipids.

The many proteins and nucleic acids encoded in the genome predominantly perform their functions as macromolecular assemblies. In fact, modern biomedical research often targets the interactions of individual molecules of these assemblies, usually by disrupting or enhancing specific contacts, to provide treatment for many different diseases. Therefore, efficient pharmaceutical design requires knowledge of how macromolecular assemblies are built and function. To achieve this goal, sensitive and quantitative tools are essential. This chapter will discuss the use of flow cytometry as a general platform for sensitive measurement and quantification of molecular assemblies. First, this chapter will introduce general methods for analysis of molecular interactions along with a comparison of flow cytometry with these methods. Second, an overview of current flow cytometry instrumentation, assay technologies, and applications in molecular assembly analysis will be given. Third, the implementation of the above approaches in molecular assembly will be discussed. Finally, potential future directions of flow cytometry in molecular assembly analysis will be explored. At present, the analysis of macromolecular assemblies is performed by a wide variety of techniques that are chosen for the target molecules under study (proteins, DNA, lipids, etc.), the type of measurement required (kinetic or equilibrium), and whether the assembly of interest needs to be studied in vivo or in vitro. This continuum of techniques can be divided into the heterogeneous assays, which require a separation step to resolve products from reactants, and homogeneous assays, which can measure interactions without a separation step. Heterogeneous assays, in general, use radioisotopes, which are not perturbing; offer excellent sensitivity; and provide accurate quantification. The products are quantified after a separation step such as gel filtration, gel electrophoresis, or centrifugation. Rapid quench methods can provide subsecond kinetic resolution; however, the added separation steps are tedious and make collection of kinetic time courses difficult, as each time point must be separated and measured individually. Furthermore, in the time it takes the separation to occur, the interaction of interest can dissociate, which is a problem specific to low-affinity assemblies. Nonetheless, by using rapid chemical quench techniques, reaction times as short as a few milliseconds can be observed. Homogenous assays can be separated into solution- or surface-based assays. Solutionbased assays measure an optical signal generated by the assembly to quantify an interaction. High component concentrations (micromolar) allow changes in intrinsic molecular properties, such as protein fluorescence or circular dichroism, to be used to study molecular assemblies. For greater sensitivity (nanomole component concentrations), resonance energy transfer or polarization assays using exogenous fluorescent labels can be used. In combination with stopped-flow spectroscopy methodologies, solution-based assays allow reactions to monitored in a continuous fashion with submillisecond dead times.