Robust Self-assembly Properties of Glyceryl Decanoates Synthesized Under Wetting and Drying Cycles†

doi:10.7503/cjcu20170857

Abstract

Abstract:

Nonenzymatic dehydration reactions of decanoic acid with glycerol has been reported to occur under mimicked prebiotic conditions at near neutral pH, yielding more evolved membrane precursor compound glyceryl decanoates. Two isomers of glyceryl monodecanoate were the main products after the condensation reactions, and the yield of glyceryl monodecanoates could be increased to 4.7% with temperature rising to 90 ℃. Vesicles were observed when the mixture after reactions was rehydrated. Experiments demonstrate that trace glyceryl decanoates produced in the mixture play a great role in robust self-assembly process, it is the existence of such lipid products that makes a lower critical vesicle concentration. Meanwhile, organic compounds have been encapsulated during the self-assembly of vesicles, so membranous structures provid a place for organic compounds to exist stably. The dehydration reactions at near neutral pH, followed by rehydration, are suitable for increasing protocell membrane stability to environment. It implies that the condensation reaction is plausible for yielding more complex amphiphiles and the appearance of membrane structures on the early earth.

Key words: Condensation, Wetting and drying cycle, Glyceryl decanoate, Protocell membrane, Origin of life

TrendMD:

GAO Jing,HUANG Keke,ZHANG Xianlong,SUN Yu,FENG Shouhua. Robust Self-assembly Properties of Glyceryl Decanoates Synthesized Under Wetting and Drying Cycles^†[J]. Chem. J. Chinese Universities, 2018, 39(5): 849.

Figures/Tables 9

Fig.1 Mass spectrum for the extracts of the dehydration/ condensation reaction at 90 ℃

Fig.2 Schematic diagram of the condensation reaction of decanoic acid with glycerol

Table 1 HRMS data of target compounds

m/z	Molecular formula	Adduct	Mass accuracy(ppm)	Assignment
269.1724	C₁₃H₂₆O₄	[M+Na]⁺	0.37	Glyceryl monodecanoate
423.3083	C₂₃H₄₄O₅	[M+Na]⁺	0.47	Glyceryl didecanoate

Fig.3 Mass spectral signals of standard GMD(A) and sample GMD(B)

Fig.4 Relationship between signal intensity and concentration of GMD ranging from 0.01—0.7 mg/L

Fig.5 Influence of temperature on the yield of GMD

Fig.6 Samples of DA under condensation reactions(A1—A6) and corresponding micrographs with DA concentrations from 40 mmol/L to 60 mmol/L(B1—B6)

Fig.7 Images of DA alone in a solution of 300 mmol/L NaCl at pH=7.0(A) and DA+glyceryl decanoates in a solution of 400 mmol/L NaCl at pH=7.0(B)

Fig.8 Light micrographs of the structures of amphiphiles (A) Vesicles produced from micelles at pH=7.0 were disturbed once dehydrated; (B) no vesicle was formed when rehydrated the sample of 30 mmol/L DA with equivalent glycerol; (C) vesicles were formed again after a second condensation reaction of DA with glycerol; (D) vesicles were not formed after a second dehylration cycle with only DA; (E) Rhodamine 6G molecules were encapsulated within decanoate vesicles. Concentration of DA for (A) and (C)—(E): 60 mmol/L.

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