Non-Enzymatic Phospholipid Synthesis in Water

Cell membranes are dynamic structures found in all living organisms. There have been numerous constructs that model phospholipid membranes. However, unlike natural membranes, these biomimetic systems cannot sustain growth owing to an inability to replenish phospholipid-synthesizing catalysts. Here we report on the design and synthesis of artificial membranes embedded with synthetic, self-reproducing catalysts capable of perpetuating phospholipid bilayer formation. Replacing the complex biochemical pathways used in nature with an autocatalyst that also drives lipid synthesis leads to the continual formation of triazole phospholipids and membrane-bound oligotriazole catalysts from simpler starting materials. In addition to continual phospholipid synthesis and vesicle growth, the synthetic membranes are capable of remodeling their physical composition in response to changes in the environment by preferentially incorporating specific precursors. These results demonstrate that complex membranes capable of indefinite self-synthesis can emerge when supplied with simpler chemical building blocks.

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Phospholipid synthesis and exchange between rat liver microsomes and mitochondria in the presence of benzo(a)pyrene.

The Journal of Lipid Research ◽

10.1016/s0022-2275(20)39814-x ◽

1980 ◽

Vol 21 (3) ◽

pp. 347-353

Author(s):

J Baraud ◽

A Maurice

Keyword(s):

Rat Liver ◽

Liver Microsomes ◽

Rat Liver Microsomes ◽

Phospholipid Synthesis

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Influence of mitochondria on phospholipid synthesis in preparations from rat liver

Biochemical Journal ◽

10.1042/bj1360467 ◽

1973 ◽

Vol 136 (3) ◽

pp. 467-475 ◽

Cited By ~ 7

Author(s):

J. B. Roberts ◽

F. L. Bygrave

Keyword(s):

Rat Liver ◽

Inhibitory Effect ◽

Total Radioactivity ◽

Phospholipid Synthesis ◽

Low Concentrations ◽

Absolute Requirement ◽

Reconstituted System ◽

Protein Incorporation ◽

Very High ◽

Cellular Phospholipid

1. The addition of mitochondria to an incubation system containing the soluble and microsomal fractions of rat liver enhances severalfold the incorporation of each of ethanolamine, phosphorylethanolamine and CDP-ethanolamine into phosphatidylethanolamine. 2. In the presence of microsomal, mitochondrial and soluble fractions, CDP-ethanolamine exhibits the greatest initial rate of incorporation (approx. 6nmol/h per mg of protein), being slightly faster than that of phosphorylethanolamine (approx. 5nmol/h per mg of protein). Incorporation of ethanolamine proceeds very slowly for the first 20min and only after 30min gives rates approaching those of the other two precursors. 3. By using a substrate ‘dilution’ technique it was shown that in the reconstituted system the affinity of each of the enzymes for their respective substrates is very high: 10μm for ethanolamine, 25μm for phosphorylethanolamine and 5μm for CDP-ethanolamine. 4. Isolation of the mitochondrial and microsomal fractions from the medium after incubation together with phosphorylethanolamine showed that about 70% of the total radioactivity was present in the microsomal fraction and about 30% in the mitochondria after only 20min. Similar experiments with ethanolamine as precursor revealed that after 20min only about 15% of the total radioactivity was present in the mitochondria but that after 40min about 30% was present in this fraction. 5. Heating and phospholipase treatment of mitochondria, but not freeze-thawing, eliminated the stimulatory effect of mitochondria on phospholipid synthesis. 6. The reconstituted system exhibits an absolute requirement for Mg2+(2mm gave maximal rates) and is inhibited by very low concentrations of Ca2+(100μm-Ca2+produced half-maximal inhibition with 3mm-Mg2+). Further addition of Mg2+overcame the Ca2+inhibition, suggesting that the inhibitory effect is readily reversible. 7. The concept that modification of the Mg2+/Ca2+ratio is a means of controlling the rate of cellular phospholipid synthesis is introduced.

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