Diacetylene fatty acids

LB films of CO-tricosenoic acid, CH2=CH—(CH2)2qCOOH, have been studied as electron photoresists (26—28). A resolution better than 50 nm could be achieved. Diacetylenic fatty acids have been polymerized to yield the corresponding poly (diacetylene) derivatives that have interesting third-order nonlinear optical properties (29). 

First, a mixture of synthetic or natural phospholipids, polymerizable lipids, and proteins can be converted to liposomes and then be polymerized. Second, polymerizable lipids are introduced into e.g. erythrocyte ghost cells by controlled hemolysis and subsequent polymerization as described by Zimmermann et al.61). This hemolysis technique is based on a reversible dielectric breakdown of the cell membrane. Dielectric breakdown provides a third possible path to the production of bi omembrane models. Zimmermann et al. could show that under certain conditions cells can be fused with other cells or liposomes61). Thus, lipids from artificial liposomes could be incorporated into a cell membrane. A fourth approach has been published by Chapman et al.20). Bacterial cells incorporate polymerizable diacetylene fatty acids into their membrane lipids. The diacetylene units can be photopolymerized in vivo. The investigations discussed in more detail below are based on approaches 1. and 3. 

Figure 5.2. Tricosa-m, n-diynoic acid (a diacetylene fatty acid). This is a schematic diagram to illustrate the definition of m and n. n = m + 2.

While increasing chain length, often with dicationic aqueous substrates, can help promote a condensed state that facilitates polymerization, similar effects can be achieved by lowering the temperature. It is, however, very important to define the temperature ranges where expanded or condensed or both states may exist. In addition, consideration of film stability, in so far as it is significant in achieving a polymerized state, should be taken into account. In this paper, we present temperature dependent studies of the physical states of films of two simple diacetylenic fatty acids, tricosanoyl and pentacosanoyl-10 12-diynoic acids. We also report the results of spectral studies of polymerized films under carefully defined conditions of the shorter chain acid, both at the air/water interface and on glass substrates. 

Diacetylene fatty acids were purchased from GFS. N-(2-Hydroxyethyl)-10,12-pentacosadiynamide (10) was synthesized by literatnre methods (77). 1-Amino-10,12-pentacosadiyne (11) was synthesized in fom steps from 10,12-pentacosadiynoic acid the acid in anhydrous tetrahydrofuran (THF) at 0 °C was reduced to the alcohol through treatment with hthinm alnminnm hydride (LAH, 2.5 equivalents) in diethyl ether for two hours, the alcohol was then converted to the mesylate by treatment with mesyl chloride (6 eqnivalents) in methylene chloride with diisopropyl ethyl amine over 30 minntes, the mesylate was displaced by sodium azide (1.5 equivalents) in dimethyl formamide (DMF) at 70 °C over one hour and the azide, in THF, was reduced to the amine with LAH (2 equivalents) in diethyl ether at 0 °C over one hour. N-(10,12-pentacosadiynyl)-glutamic acid (12) was prepared from 11 as follows 11 was reacted with glutaric anhydride (2 equivalents) in DMF, in the presence of diisopropylethylamine (3 equivalents), at 70 °C for 1 hour and the crade product recrystallized from a mixture of chloroform and hexanes. The identity of products were confirmed by H and C NMR. 

We also explored using the attached hposomes for detection of BG spores. Early experiments suggested that attached liposomes composed of diacetylene fatty acids (1) were more responsive to the spores than ones based on diacetylene ethanol amides (2). The liposomes were prepared with 20% of 11 incorporated so antibodies could be conjugated via the BS3 linker. We compared the performance of attached fatty acid hposomes in three different buffer... 

Fig. 11. Structure model of monomeric and polymerized multilayers of cadmium salts of diacetylene fatty acids. Polymer chains grow within the layer plane, the aliphatic chains are tilted with regard to...

An additional method to model biomembranes was recently described by Leaver et al. Polymerizable diacetylene fatty acids were biosynthetically incorporated into Acholeplasma laidlawii cells and their polymerization via UV-irradiation could be realized. In order to determine the effect of polymerization on the properties of the membrane, the activity of intrinsic and extrinsic membrane-bound enzymes, NADH oxidase and ribonuclease were studied. The NADH oxidase activity decreased rapidly upon polymerization of the lipid environment whereas the ribonuclease activity was unaffected. 

Phospholipids, phosphatidylcholines, have been synthesized which contain the diacetylene group in their acyl chains. These lipids may be dispersed in water or deposited in Langmuir-Blodgett multilayers and their polymerisation initiated with ultraviolet light. The polymers are optically active and thermochromic. A similar polymerisation can be initiated in the membranes of microorganisms which have been grown in the presence of diacetylenic fatty acids. 

There are two ways in which membranes of diacetylenic lipids containing intrinsic membrane proteins can be obtained either proteins extracted from natural membranes with detergent can be reconstituted into synthetic diacetylenic phosphatidylcholines or the growth medium of micro-organisms incapable of synthesizing their own fatty acids can be enriched with diacetylenic fatty acid. In this laboratory, Ca2+-ATPase from sarcoplasmic reticulum and bacteriorhodopsin from the purple membrane of Halobacterium halobium have been reconstituted into diacetylenic phosphatidylcholines. Provided the more reactive mixed-chain lipids are used polymerisation can be achieved before the protein is denatured by the UV irradiation. Both proteins remain active within polymeric bilayers. 

Incorporation of diacetylenic fatty acids into biomembrane phospho- and glycolipids has been accomplished with the bacterium. 

Alonso, A., J. Leaver, D. Johnston, S. Sanghera, C. Villaverde and D. Chapman. Polymerisation of Diacetylenic Fatty Acids in Cultures of Bacillus cereus. Biochim. Biophys. Acta. 712 (1982) 292-298. 

Johnston, D.S., S. Sanghera, A. Manjon-Rubio and D. Chapman The Formation of Polymeric Model Membranes From Diacetylenic Fatty Acids and Phospholipids. Biochim. Biophys. Acta 602 (1980) 213-216. 

Leaver, J., A. Alonso, A.A. Durrani and D. Chapman. The Biosynthetic Incorporation of Diacetylenic Fatty Acids into the Biomembranes of Acholeplasma laidlawii A Cells and Polymerisation of the Biomembranes by Irradiation with Ultraviolet Light. Biochim. Biophys. Acta. 727 (1983) 327-335. 

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