Lipid structure analysis

Christie, W.W., Lipids their structure and occurrence, in Lipid Analysis, Isolation, Separation, Identification and Structural Analysis of Lipids, Vol. 5, Christie, W.W., Ed., The Oily Press, England, 2003, pp. 3-33. 

Fig. 1 Solid-state NMR structure analysis relies on the 19F-labelled peptides being uniformly embedded in a macroscopically oriented membrane sample, (a) The angle (0) of the 19F-labelled group (e.g. a CF3-moiety) on the peptide backbone (shown here as a cylinder) relative to the static magnetic field is directly reflected in the NMR parameter measured (e.g. DD, see Fig. 2c). (b) The value of the experimental NMR parameter varies along the peptide sequence with a periodicity that is characteristic for distinct peptide conformations, (c) From such wave plot the alignment of the peptide with respect to the lipid bilayer normal (n) can then be evaluated in terms of its tilt angle (x) and azimuthal rotation (p). Whole-body wobbling can be described by an order parameter, S rtlo. (d) The combined data from several individual 19F-labelled peptide analogues thus yields a 3D structural model of the peptide and how it is oriented in the lipid bilayer...

For the orientation-based structure analysis of MAPs, uniformly oriented lipid bilayers are typically prepared on solid supports as illustrated in Fig. 2 [23, 47, 55]. These mechanically oriented membranes are advantageous for static ssNMR experiments, as they provide a robust way to orient a sample with any desired lipid composition, peptide concentration, and at any desired temperature. The lipids... 

Fig. 5 Membrane models for NMR structure analysis, (a) An isotropic detergent micelle (left) is compared to the dimensions of lipid bilayers (right), (b) Macroscopically oriented membrane samples can be prepared on solid support, as nanodiscs, or as magnetically oriented bicelles. (c) Nomenclature and variability of liposomes small (SUV, 20-40 nm), intermediate (IUV, 40-60 nm), large (LUV, 100-400 nm), and giant unilamellar vesicles (GUV, 1 pm) multi-lamellar (MLV), oligo-lamellar (OLV) and highly heterogeneous multi-oligo-lamellar vesicles (MOLV)...

Afonin S, Durr UHN, Wadhwani P, Salgado J, Ulrich AS (2008) Solid state NMR structure analysis of the antimicrobial peptide gramicidin S in lipid membranes concentration-depen-dent re-alignment and self-assembly as a beta-barrel. Top Curr Chem 273 139-154... 

Lipid A constitutes the covalently bound lipid component and the least variable component of LPS (25). It anchors LPS to the bacterial cell by hydrophobic and electrostatic forces and mediates or contributes to many of the functions and activities that LPS exerts in prokaryotic and eukaryotic organisms. In the following sections, the primary structure of lipid A of different Gram-negative bacteria is described, together with some of its characteristic biological properties. Furthermore, this article describes some of the principal methods that have been used for the structural analysis of lipid A and discusses their merits and limitations. 

Gas-liquid chromatography is a very useful technique in lipid analysis, particularly for the separation of very similar compounds within classes. Because of the wide variations in structure and properties between classes it is not usually possible to resolve members of different classes on the same column. GLC is useful for both quantitative and qualitative analysis and also in the investigation of lipid structure. 

However, full structural analysis of a lipid will often necessitate further analysis of the collected column effluent for a single GLC peak. Infrared and NMR spectroscopy and mass spectrometry are all useful techniques which will give information for identification purposes, including the position and configuration of any double bonds. 

Solid State NMR Structure Analysis of the Antimicrobial Peptide Gramicidin S in Lipid Membranes ... 

Mariani, R, Luzzati, V., and Delacroix, H. (1988). Cubic phases of lipid-containing systems structure analysis and biological implications. J. Mol. Biol, 204, 165-89. Marks-Tarlow, T., Robertson, R., and Combs, A. (2001). Varela and the Uroborus the psychological significance of reentry. Cybernetics Human Knowing, 9, 31. 

Christie, W.W. (1998) Gas chromatography-mass spectrometry methods for structural analysis of fatty acids. Lipids 33, 343-353. A detailed description of the methods used to obtain data such as those presented in Figure 10-24. 

D Holme and H Peck, Analytical Biochemtstiy, 3rd ed (1998), Addison Wi li Longman (New York), pp 406-442 Structure, function, and analysis of lipids C Matthews, K van Holde, and K Ahern, Biochemistry, 3rd ed (2000), Benjamin/ Cummings (San Francisco), pp 315-357 Lipid structure and function G Patton, S Cann, H Brunengraber, and J. Lowenstein, in Methods in Enzymology, Vol 72, J Lowenstein, Editor (1981), Academic Press (New York), pp 8-20 Separation of fatty acid methyl esters by gas chromatography on capillary columns N Radin, in Methods in Enzymology, Vol 72, J M Lowenstein, Editor (1981), Academic Press (New York), pp 5-7 Extraction of lipids with hexane-isopropanol L Stryer, Biochemistry, 4th ed (1995), W H Freeman (New York), pp 263-270, 603-606 Lipid structure and function... 

WW Christie. Lipid Analysis Isolation, Separation, Identification and Structural Analysis of Lipids. 2nd ed. Oxford Pergamon Press, 1982. 

Observations were made of lipid-protein phases in which the structure is determined mainly by the protein. Raman spectroscopy is a useful method for structure analysis of such phases. The structures described above were analyzed successfully by an x-ray diffraction technique. Lipid-protein complexes, however, are often amorphous, and alternative methods to study their structures are therefore needed. It was demonstrated that Raman spectroscopy can be used to obtain structural information about lipid-protein interaction (16, 17). It is thus possible to determine the conformation as well as the type of environment of the lipid molecules. With the protein, interpretation is more complicated. It is usually possible to determine whether the complex has the same protein conformation as the component used in the preparation, or, if a change occurs, it may be possible to correlate it with denaturation of the pure protein. For complexes formed by long-chain alkyl phosphates and insu-... 

The Lipid A Backbone An important step for the isolation and structural analysis of the hydrophilic region of lipid A was the... 

While these compounds may be useful as reference compounds for structural analysis of endotoxins and helpful for orienting investigations aiming at the establishment of the chemical structure/biological activity relationship of these substances, they are still far from representing any Lipid A fragment and even less the hydrophobic region of an endotoxin. From... 

The exact structural and spatial characterization of the lipids is still very limited, particularly in routine determination of lipids. As an example, routine determination of snl/sn2 acyl positions in PLs is not possible, nor is the determination of positions of double bonds or acyl chain branching. Such information would be important to understand the data in the biochemical context (e.g., affinity for specific lipid enzymes). While promising efforts are under way, it may still take time before the emerging tools for lipid structural elucidation are introduced in routine lipidomic analyses. Big advances have also been made over the past years in the developments of methods for surface analysis of lipids. These approaches will be crucial for in-depth elucidation of the spatial complexity of cellular and subcellular lipidomes. 

Diols have been rarely observed in insect cuticular lipids (Buckner, 1993). Odd-carbon-number diols (C23-C29) were the major lipid class (55%) of the larval cuticular lipids from the flour beetle, Tenebrio molitor (Bursell and Clements, 1967). The major diol constituent was 8, 9-pentacosanediol. For the cuticular lipids of M. sexta larvae, very small amounts (<1%) of 7,8- and 8,9-C27 diols and 8,9- and 9,10-C29 diols were identified (Espelie and Bernays, 1989). Hydroxy n-alkanols are diols with a hydroxyl functional group on the C, position (terminal) of the alkyl chain, but are technically not alcohol derivatives of hydrocarbons. There are a few reports of the occurrence of insect hydroxy -alkanols (Buckner, 1993 Nelson and Blomquist, 1995 Buckner et al., 1996). In a structure analysis study of beeswax, the major alcohol moieties of the diester fraction were identified as 1,23-tetracosanediol (42.2%), 1,27-octacosanediol (26.0%) and 1,25-hexacosanediol (20.2%) (Tulloch, 1971). The hydroxy n-alkanols comprised 16% of the cuticular lipids of FI. zea pupae and were identified as C30-C36 even-chain n-alcohols with hydroxyl groups on carbon numbers 11, 12, 13, 14, or 15 (Buckner et al., 1996). Mass spectral analysis indicated the presence of unsaturation in the alkyl chain of the major diol components. 

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