Rigid urea and self-healing thiourea ethanolamine monolayers

A series of long-tail alkyl ethanolamine analogs containing amide-, urea-, and thiourea moieties was synthesized and the behavior of the corresponding monolayers was assessed on the Langmuir–Pockels trough combined with grazing incidence X-ray diffraction experiments and complemented by computer simulations. All compounds form stable monolayers at the soft air/water interface. The phase behavior is dominated by strong intermolecular headgroup hydrogen bond networks. While the amide analog forms well-defined monolayer structures, the stronger hydrogen bonds in the urea analogs lead to the formation of small three-dimensional crystallites already during spreading due to concentration fluctuations. The hydrogen bonds in the thiourea case form a two-dimensional network, which ruptures temporarily during compression and is recovered in a self-healing process, while in the urea clusters the hydrogen bonds form a more planar framework with gliding planes keeping the structure intact during compression. Because the thiourea analogs are able to self-heal after rupture, such compounds could have interesting properties as tight, ordered, and self-healing monolayers

Against the rules: pressure induced transition from high to reduced order

Envisioning the next generation of drug delivery nanocontainers requires more in- depth information on the fundamental physical forces at play in bilayer membranes. In order to achieve this, we combine chemical synthesis with physical–chemical analytical methods and probe the relationship between a molecular structure and its biophysical properties. With the aim of increasing the number of hydrogen bond donors compared to natural phospholipids, a phospholipid compound bearing urea moieties has been synthesized. The new molecules form interdigitated bilayers in aqueous dispersions and self-assemble at soft interfaces in thin layers with distinctive structural order. At lower temperatures, endothermic and exothermic transitions are observed during compression. The LC1 phase is dominated by an intermolecular hydrogen bond network of the urea moieties leading to a very high chain tilt of 52°. During compression and at higher temperatures, presumably this hydrogen bond network is broken allowing a much lower chain tilt of 35°. The extremely different monolayer thicknesses violate the two-dimensional Clausius–Clapeyron equation

Lipids with artificial backbones

Phospholipids constitute the major components of a cell membrane and are subdivised in two major classes: glycerophospholipids and sphingophospholipids. While a great variety of phospholipids exists due to the particularity of their hydrophobic chain (saturation, chain length, number of chains) and their hydrophilic headgroup (phosphate, phosphocholine, phosphoethanolamine), the region between the two parts remain quite common. It is always a glycerol or a 2-amino-1,3-propanediol backbone. This thesis was mainly focused on the synthesis and characterization of lipids with nitrogen-bearing interfaces in order to create new materials for biomedical applications. In the first part of the thesis, the introduction of diamino groups at the interface allowed us to prepare the first phospholipids polymerizable at the interface thank to amine groups. “Clickable” phospholipids with natural interfaces were also made. In the second part of the thesis, the possibility to create and to characterize hydrogen bonds on the backbone was explored thank to fluorescent phospholipids, N-acylethanolamine (NAEs) and double-tail surfactants

BODP - A Versatile Reagent for Phospholipid Synthesis

Benzyloxydichlorophosphine (BODP) has been found to be a convenient reagent for the synthesis of phospholipids. A series of artificial ether and ester phospholipids have been prepared in good to high yields

Study of surfactant alcohols with various chemical moieties at the hydrophilic–hydrophobic interface

The melting behavior, the solubility, and the influence of hydrogen bonds were analyzed for a series of single- and double-tailed surfactant alcohols. Various effects such as the presence of free amides or the intermolecular spacing were found to be important factors for increasing or decreasing the melting temperature of a surfactant. Furthermore, we present a model for the packing of diamido-lipids and study the temperature-dependence of the IR signals

The synthesis of an amine-bearing polymerizable phospholipid

Exchange of the natural glycerol phospholipid backbone with an artificial 1,3-diaminopropanol backbone led to the first synthetic 1,3-diaminophospholipid. The amines in the polar head group region were reacted to acrylamides giving a UV polymerizable phospholipid. Preliminary experiments demonstrate that formulated vesicles can be polymerized into large aggregates of vesicles

Putting the 'P' into Phospholipids

Despite almost hundred years of dedicated research, the synthesis of phospholipids remains a challenge. Here, we briefly review important trends and point out possible future directions that might lead to interesting new probes for the membrane environment. An improved liposome purification and concentration protocol rounds up the article

Clickosomes—using triazole-linked phospholipid connectors to fuse vesicles

Two complementary artificial diether phospholipids were synthesized that can undergo a Cu(I)-catalyzed Huisgen–Sharpless click reaction. The resulting lipid can bridge the membranes of large unilamellar vesicles and cause their aggregation and ultimately their fusion

Conference report of the 43rd Chemistry CUSO Summer School Villars 2012: Inorganic and Metallosupramolecular Polymers: Conference Report

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