From organic molecules to protocells The question "How do simple organic molecules form a protocell?" is largely unanswered but there are many hypotheses. Some of these postulate the early appearance of nucleic acids ("genes-first") whereas others postulate the evolution of biochemical reactions and pathways first ("metabolism-first"). Recently, trends are emerging to create hybrid models that combine aspects of both
Protocells by Dr Rachel Armstrong – Self assembling chemical systems without DNA, which is generally thought of as the molecule that programs all aspects of the behaviours of natural cells.These simple ‘protocells’ are made up of a very small number of chemicals yet they are able to sense their environment, modify it, and exhibit complex life-like behaviour such as shedding skins.
Traditional schemes for the origin of cellular life on earth generally suppose that the chance assembly of polymer synthesis systems was the initial event, followed by incorporation into a membrane-enclosed volume to form the earliest cells. Here we discuss an alternative system consisting of replicating membrane vesicles, which we define as minimum protocells. These consist of vesicular bilayer membranes that self-assemble from relatively rare organic amphiphiles present in the prebiotic environment. If some of the amphiphiles are primitive pigment molecules asymmetrically oriented in the bilayer, light energy can be captured in the form of electrochemical ion gradients. This energy could then be used to convert relatively common precursor molecules into membrane amphiphiles, thereby providing an initial photosynthetic growth process, as well as an appropriate microenvironment for incorporation and evolution of polymer synthesis systems.
We show that model protocells can proceed through multiple cycles of reproduction. Encapsulated RNA molecules, representing a primitive genome, are distributed to the daughter vesicles. Our observations bring us closer to the laboratory synthesis of a complete protocell consisting of a self-replicating genome and a self-replicating membrane compartment. In addition, the robustness and simplicity of this pathway suggests that similar processes might have occurred under the prebiotic conditions of the early Earth
other names CFSE; Carboxyfluorescein N-succinimidyl ester Identifiers CAS number 92557-81-8, 117548-22-8 (5/6 mixture)
O=C(C5=C4C=C(C(ON6C(CCC6=O)=O)=O)C=C5)OC24C3=C(C=C(O)C=C3)OC1=CC(O)=CC=C12 Properties Molecular formula C25H15NO9 Molar mass 473.39 g mol−1 Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Carboxyfluorescein succinimidyl ester (CFSE) is a fluorescent cell staining dye. CFSE is commonly confused with carboxyfluorescein diacetate succinimidyl ester (CFDA-SE), although they are not strictly the same molecule; CFDA-SE, due to its acetate groups, is highly cell permeable, while CFSE is much less so. As CFDA-SE, which is non-fluorescent, enters the cytoplasm of cells, intracellular esterases remove the acetate groups and convert the molecule to the fluorescent ester, CFSE, which is retained within cells and covalently couples, via its succinimidyl group, to intracellular molecules. Due to this covalent coupling reaction fluorescent CFSE can be retained within cells for extremely long periods. Also, due to this stable linkage, once incorporated within cells the dye is not transferred to adjacent cells.
CFSE was originally developed as a fluorescent dye that could be used to stably label lymphocytes and track their migration within animals for many months. Subsequent studies revealed that the dye can be used to monitor lymphocyte proliferation, both in vitro and in vivo, due to the progressive halving of CFSE fluorescence within daughter cells following each cell division. The only limitation is that CFSE at high concentrations can be toxic for cells.
Division of Medical Biotechnology, Paul-Ehrlich-Institut, 63225 Langen, Germany.
Membrane fusion plays a key role in many biological processes including vesicle trafficking, synaptic transmission, fertilization or cell entry of enveloped viruses. As a common feature the fusion process is mediated by distinct membrane proteins. We describe here 'Fusoselect', a universal procedure allowing the identification and engineering of molecular determinants for cell-cell fusion-activity by directed evolution. The system couples cell-cell fusion with the release of retroviral particles, but can principally be applied to membrane proteins of non-viral origin as well. As a model system, we chose a gamma-retroviral envelope protein, which naturally becomes fusion-active through proteolytic processing by the viral protease. The selection process evolved variants that, in contrast to the parental protein, mediated cell-cell fusion in absence of the viral protease. Detailed analysis of the variants revealed molecular determinants for fusion competence in the cytoplasmic tail (CT) of retroviral Env proteins and demonstrated the power of Fusoselect.
tash: Hi skizit, I have watched all your videos on youtube and cant thank you enough for all you have educated me on. I cry for you alot and a bit for me. I was wanting to send you photos of what is raining down everyday here in Australia in hope you can tell me
Dec 11, 2019 23:28:22 GMT -5
tash: not sure where to send them as hush mail and rocket mail bounced back
Dec 11, 2019 23:30:03 GMT -5