Light-dependent pH gradients are generated in liposomes containing ferrocyanide

Deamer, David W.; Harang, E.

doi:10.1016/0303-2647(90)90023-t

Cited by 24 publications

(14 citation statements)

References 7 publications

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“…There are several mechanisms by which ApH can be produced in simulated protocells under prebiotic conditions. For example, encapsulation of ferrocyanide within liposomes results in the generation of ApH (basic inside) upon illumination (Deamer and Harang 1990). Also, polyaromatic hydrocarbon (PAH) derivatives can generate proton gradients (acidic inside) in vesicles under certain conditions (Deamer 1992a).…”

Section: Protocells Generation Of Prebiotic Ph Gradients and Early mentioning

confidence: 99%

Permeation of membranes by the neutral form of amino acids and peptides: Relevance to the origin of peptide translocation

Chakrabarti

Deamer

1994

J Mol Evol

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The flux of amino acids and other nutrient solutes such as phosphate across lipid bilayers (liposomes) is 10(5) slower than facilitated inward transport across biological membranes. This suggest that primitive cells lacking highly evolved transport systems would have difficulty transporting sufficient nutrients for cell growth to occur. There are two possible ways by which early life may have overcome this difficulty: (1) The membranes of the earliest cellular life-forms may have been intrinsically more permeable to solutes; or (2) some transport mechanism may have been available to facilitate transbilayer movement of solutes essential for cell survival and growth prior to the evolution of membrane transport proteins. Translocation of neutral species represents one such mechanism. The neutral forms of amino acids modified by methylation (creating protonated weak bases) permeate membranes up to 10(10) times faster than charged forms. This increased permeability when coupled to a transmembrane pH gradient can result in significantly increased rates of net unidirectional transport. Such pH gradients can be generated in vesicles used to model protocells that preceded and were presumably ancestral to early forms of life. This transport mechanism may still play a role in some protein translocation processes (e.g. for certain signal sequences, toxins and thylakoid proteins) in vivo.

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Section: Protocells Generation Of Prebiotic Ph Gradients and Early mentioning

confidence: 99%

Permeation of membranes by the neutral form of amino acids and peptides: Relevance to the origin of peptide translocation

Chakrabarti

Deamer

1994

J Mol Evol

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“…Several models have been proposed to trap the released proton in the form of a chemiosmotic gradient (Deamer 1997). While substantial amounts of iron compounds were presumably present on the early Earth and PAHs have been found to make up 90% of the kerogen-like organic material of carbonaceous chondrites (Deamer 1997;Cronin et al 1988), studies to date have been conducted with phospholipid bilayers (Deamer 1997(Deamer , 1992Deamer and Harang 1990), not fatty acid vesicles. Because these reactions involve a proton gradient, they do not seem to be relevant to energy acquisition by cells bounded by fatty acid membranes due to the proton permeability of these systems.…”

Section: Energy Acquisitionmentioning

confidence: 98%

“…This assumes some type of pigment system was available to the cell ). Iron compounds have been shown to cause a shift in pH of up to 3 units when irradiated with near-UV light (Deamer 1997;Deamer and Harang 1990). If the iron compounds are encapsulated, this change produces a pH gradient that could be converted to usable energy.…”

Section: Energy Acquisitionmentioning

confidence: 98%

The Influence of Environmental Conditions, Lipid Composition, and Phase Behavior on the Origin of Cell Membranes

Thomas

Rana²

2007

Orig Life Evol Biosph

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At some point in life's development, membranes formed, providing barriers between the environment and the interior of the 'cell.' This paper evaluates the research to date on the prebiotic origin of cell membranes and highlights possible areas of continuing study. A careful review of the literature uncovered unexpected factors that influence membrane evolution. The major stages in primitive membrane formation and the transition to contemporary cell membranes appear to require an exacting relationship between environmental conditions and amphiphile composition and phase behavior. Also, environmental and compositional requirements for individual stages are in some instances incompatible with one another, potentially stultifying the pathway to contemporary membranes. Previous studies in membrane evolution have noted the effects composition and environment have on membrane formation but the crucial dependence and interdependence on these two factors has not been emphasized. This review makes clear the need to focus future investigations away from proof-of-principle studies towards developing a better understanding of the roles that environmental factors and lipid composition and polymorphic phase behavior played in the origin and evolution of cell membranes.

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“…It has been postulated that vesicle structures developed the ability to capture and transduce light, providing energy for reactions (Koch 1985;Morowitz et al 1988;King 1990). For example, pH gradients can be photochemically created across membrane surfaces (Deamer and Harang 1990;Deamer et al 1994;Sun and Mauzerall 1996), though linking this to driving chemical reactions has been problematic. Attempts have been made to take modern biological photochemical systems and work backward in order to "reverse-engineer" the simplest possible working model of photosynthesis.…”

Section: Introductionmentioning

confidence: 99%

Energy Transduction Inside of Amphiphilic Vesicles: Encapsulation of Photochemically Active Semiconducting Particles

Summers

Noveron

Basa

2009

Orig Life Evol Biosph

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Amphiphilic bilayer membrane structures (vesicles) have been postulated to have been abiotically formed and spontaneously assemble on the prebiotic Earth, providing compartmentalization for the origin of life. These vesicles are similar to modern cellular membranes and can serve to contain water-soluble species, concentrate species, and have the potential to catalyze reactions. The origin of the use of photochemical energy in metabolism (i.e. energy transduction) is one of the central issues in the origin of life. This includes such questions as how energy transduction may have occurred before complex enzymatic systems, such as required by contemporary photosynthesis, had developed and how simple a photochemical system is possible. It has been postulated that vesicle structures developed the ability to capture and transduce light, providing energy for reactions. It has also been shown that pH gradients across the membrane surface can be photochemically created, but coupling these to drive chemical reactions has been difficult. Colloidal semiconducting mineral particles are known to photochemically drive redox chemistry. We propose that encapsulation of these particles has the potential to provide a source of energy transduction inside vesicles, and thereby drive protocellular chemistry, and represents a model system for early photosynthesis. In our experiments we show that TiO2 particles, in the approximately 20 nm size range, can be incorporated into vesicles and retain their photoactivity through the dehydration/rehydration cycles that have been shown to concentrate species inside a vesicle.

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Light-dependent pH gradients are generated in liposomes containing ferrocyanide

Cited by 24 publications

References 7 publications

Permeation of membranes by the neutral form of amino acids and peptides: Relevance to the origin of peptide translocation

Permeation of membranes by the neutral form of amino acids and peptides: Relevance to the origin of peptide translocation

The Influence of Environmental Conditions, Lipid Composition, and Phase Behavior on the Origin of Cell Membranes

Energy Transduction Inside of Amphiphilic Vesicles: Encapsulation of Photochemically Active Semiconducting Particles

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