Infrared lipids

Applications Food. Immunoassays, Techniques Enzyme Immunoassays. Infrared Spectroscopy Near-Infrared. Lipids Fatty Acids. Liquid Chromatography Food Applications. Microscopy Applications Food. Nitrogen. Nitrosamines. pH. Phosphorus. Proteins Foods. Sampling Theory Practice. Sulfur. Water Determination. X-Ray Absorption and Diffraction X-Ray Absorption. 

McClure, G.L., et. al. "Application of Computerized Quantitative Infrared Spectroscopy to the Determination of the Principal Lipids Found in Blood Serum", Computerized Quantitative Infrared Analysis, ASTM STP 934, G.L. McClure, Ed. American Society for Testing and Materials, Philadelphia, 1987, 131-154. 

Gordon, L.M., Lee, K.Y.C., Lipp, M.M., Zasadzinski, J.A., Walther, F.J., Sherman, M. A., and Waring, A.J. Conformational mapping of the N-terminal segment of surfactant protein B in lipid using C-13-enhanced Fourier transform infrared spectroscopy. J. Peptide Res. 

The availability of the purified transporter in large quantity has enabled investigation of its secondary structure by biophysical techniques. Comparison of the circular dichroism (CD) spectrum of the transporter in lipid vesicles with the CD spectra of water-soluble proteins of known structure indicated the presence of approximately 82% a-helix, 10% ) -turns and 8% other random coil structure [97]. No / -sheet structure was detected either in this study or in a study of the protein by the same group using polarized Fourier transform infrared (FTIR) spectroscopy [98]. In our laboratory FTIR spectroscopy of the transporter has similarly revealed that... 

In addition, data obtained from infrared, thermal, and fluorescence spectroscopic studies of the outermost layer of skin, stratum corneum (SC), and its components imply enhancer-improved permeation of solutes through the SC is associated with alterations involving the hydrocarbon chains of the SC lipid components. Data obtained from electron microscopy and x-ray diffraction reveals that the disordering of the lamellar packing is also an important mechanism for increased permeation of drugs induced by penetration enhancers (for a recent review, see Ref. 206). 

The analytical techniques proposed in the literature generally give reliable information on lipids present in the paint layer. However, the presence of lipid mixtures and of particular environmental conservation conditions may affect the lipid pattern to such an extent that their identification may be very difficult and sometimes erroneous. Thus, a multianalytical approach is recommended which integrates chromatographic data with techniques such as mapping based on Fourier transform infrared spectroscopy or SIM on cross-sections, in order to better understand the distribution of lipids in the various paint layers. 

The conventional approach to solvent extraction is the batch method. Early work with this method was hampered by the low concentration of the compounds present and the relative insensitivity of the methods of characterization. Thus lipids and hydrocarbons have been separated from seawater by extraction with petroleum ether and ethyl acetate. The fractionation techniques include column and thin-layer chromatography with final characterisation by thin-layer chromatography, infrared, and ultra-violet spectroscopy and gas chromatography. Of these techniques, only gas chromatography is really useful at levels of organic matter present in seawater. With techniques available today such as glass capillary gas chromatography and mass spectrometry, much more information could be extracted from such samples [20]. 

Infrared Absorption Analysis of Tissue Constituents, particularly Tissue Lipids (Schwarz), 3, 1 Iron, Plasma (Ramsay), 1, 2... 

In order to learn about the phase states adopted by LPS and lipid A, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and X-ray small-angle diffraction with CuXa or synchrotron radiation have been applied. In the following section, some recent results are summarized. 

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. 

Vandenbussche G, Clercx A, Clercx M, et al. Secondary structure and orientation of the surfactant protein SP-B in a lipid environment. A Fourier transform infrared spectroscopy study. Biochemistry 1992 31(38) 9169-9176. 

Infrared Absorption Analysis of Tissue Constituents, Particularly Tissue Lipids... 

Most of the above membrane-oriented studies were carried out for peptides in multilayer systems that were collapsed or transferred onto a sample cell surface. An alternative and very interesting way to study membrane systems is by IRRAS (infrared reflection absorption spectroscopy) at the air-water interface. In this way, unilamellar systems can be studied as a function of surface pressure and under the influence of various membrane proteins and peptides added. Mendelsohn et al.[136] have studied a model series of peptides, [K2(LA) ] (n = 6, 8, 10, 12), in nonaqueous (solution), multilamellar (lipid), and unilamellar (peptide-IRRAS) conditions. In the multilamellar vesicles these peptides are predominantly helical in conformation, but as peptide only monolayers on a D20 subphase the conformation is (1-sheet like, at least initially. For different lengths, the peptides show variable surface pressure sensitivity to development of some helical component. These authors further use their IR data to hypothesize the existence of the less-usual parallel (i-sheet conformation in these peptides. A critical comparison is available for different secondary structures as detected using the IRRAS data for peptides on H20 and D20 subphasesJ137 ... 

Although glycosphingolipids are the specific lipid components in the antigen-antibody complex, their activity is markedly enhanced by other (auxiliary) lipids such as lecithin and lecithin-cholesterol mixtures (15). The present study deals with the effect of lipid composition on the penetration of lactoside—cholesterol and lactoside—lecithin monolayers by rabbit y-globulin. We also investigated the lecithin-cholesterol system. Furthemore, since criteria for the existence of lipid-lipid complexes in monolayers are still few (8, 17), we have used infrared spectroscopy to examine lipid mixtures for the presence of complexes. 

Infrared Spectra. A Perkin-Elmer model 237 spectrometer was used. Solutions of 5 to 10 mg. per ml. of lipid in spectral grade chloroform were placed in a NaCl microcell of 1.0-mm. path length for study in the region from 2.5 to 6.0 microns. The film technique was used for observations between 5 and 15 microns, with a beam condenser and attenuator (Perkin-Elmer, Norwalk, Conn.). The lipid, 75 to 100 /i.grams in either chloroform or chloroform-methanol 85 to 15, was deposited on 1 sq. cm. of the NaCl plate, and the solvent was removed by evaporation under an infrared lamp for 10 minutes. 

Three criteria for lipid-lipid interactions in lipid mixtures are the mean area of the lipids in the mixed film, the surface potential of the mixed monolayer, and the infrared spectra of the lipid mixtures. 

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