Applications of chromic acid-celite columns to lipid analysis. Location of double bond position in submicro- and microgram amounts of methyl octadecenoates.

A procedure for locating the double bond position in a series of methyl octadecenoates is detailed. Submicrogram or microgram amounts of substrate dissolved in CS₂ are brought in contact with a very small column of chromic acid on Celite, and the oxidation products (car?ylic acids) are eluted, converted to methyl esters, and resolved by gas-liquid chromatography. Beside the acids resulting from scission of the double bond, acids containing one less carbon atom arise from oxidation of the allylic carbons on both sides of the double bond so that pairs of peaks appear on the chromatogram. All positions from Δ3 to Δ17 were located successfully. The Δ2 position failed to oxidize.     

Mass spectrometry of fatty aldehydes

Fatty aldehydes are important components of the cellular lipidome. Significant interest has been developed towards the analysis of the short chain α,β-unsaturated and hydroxylated aldehydes formed as a result of oxidation of polyunsaturated fatty acids. Multiple gas chromatography-mass spectrometry (GC/MS) and subsequently liquid chromatography-mass spectrometry (LC/MS) approaches have been developed to identify and quantify short-chain as well as long-chain fatty aldehydes. Due to the ability to non-enzymaticaly form Schiff bases with amino groups of proteins, lipids, and with DNA guanidine, free aldehydes are viewed as a marker or metric of fatty acid oxidation and not the part of intracellular signaling pathways which has significantly limited the overall attention this group of molecules have received. This review provides an overview of current GC/MS and LC/MS approaches of fatty aldehyde analysis as well as discusses technical challenges standing in the way of free fatty aldehyde quantitation.     

Plasmalogen degradation by oxidative stress: production and disappearance of specific fatty aldehydes and fatty alpha-hydroxyaldehydes.

Plasmalogens are often considered as antioxidant molecules that protect cells from oxidative stress. Their vinyl ether bond could indeed be among the first targets for newly formed radicals. However, the long chain aldehydes released from plasmalogens were seldom studied and possible injurious or harmless effects were poorly examined. Thus, the sensitivity of the vinyl ether bond of plasmalogens was investigated in a cerebral cortex homogenate under UV irradiation- or Fe2+/ascorbate-induced peroxidation. Kinetics of aldehyde production was followed by gas chromatography/mass spectrometry. This confirmed that plasmalogens were highly sensitive to oxidative stress (70% cleavage after 90 min UV irradiation and 30% after 30 min of Fe2+/ascorbate). The aldehydes corresponding to sn-1 position 16:0, 18:0, or 18:1 were poorly detected. Conversely, oxidation of plasmalogens yielded preferentially 15:0, 17:0, and 17:1 aldehydes under UV and the alpha-hydroxyaldehydes 16:0-OH and 18:0-OH following a Fe2+/ascorbate oxidation. Kinetics showed that free aldehydes and above all free alpha-hydroxyaldehydes disappeared from the medium as soon as produced. Consequently, the behavior of these released aldehydes in the tissues has to be investigated in order to ascertain the protective effect of plasmalogens against oxidation.     

Application of the Rosenmund reaction to the synthesis of saturated fatty aldehydes

A method is described for the simple and rapid formation of saturated fatty aldehydes from the corresponding acid chlorides. It is not suitable for the preparation of unsaturated aldehydes because of the partial reduction and positional and geometrical isomerization of the double bond in the chain.     

Reductive and oxidative synthesis of saturated and unsaturated fatty aldehydes

Saturated and unsaturated fatty aldehydes were synthesized 99+% pure with yields of up to 80% by the reduction of 1-acylaziridines with lithium aluminium hydride, and in yields of up to 87% by oxidation of the corresponding alcohol with 1-chlorobenzotriazole. It was found for the reduction that optimum aldehyde yield was obtained with a mole ratio of reactants, consisting of acid chloride-ethylenimine-triethylamine-LiAlH(4), equal to 1:2:2:2. Optimum conditions for alcohol oxidation were found to be a mole ratio of oxidant to alcohol of 1:1.3 with refluxing for 45 min in methylene chloride containing 25% pyridine. Methods for the purification of the final product are also described. Purity criteria were thin-layer and gas-liquid chromatography and infrared and nuclear magnetic resonance spectroscopy.     

Gas chromatography-mass spectrometry of fatty aldehydes and their oxime derivatives

Gas chromatography-mass spectrometry (GC-MS) investigation of long chain several aldehydes and their O-methyl and O-t-butyldimethylsilyl oximes has established that chemical ionization of the unmodified aldehydes is the most satisfactory procedure for both qualitative and quantitative analysis of these compounds.     

Unsaturated fatty acids and aldehydes during treatment of oak wood

The use of considerable amounts of ground oak to accelerate maturation of strong drinks was accompanied by the appearance of an undesirable taste due to the presence of unsaturated aldehydes (2-nonenal and 2,4-nonadienal). The greater the degree of wood grinding, the higher was the content of C₁₈-unsaturated acids and C₉-aldehydes. Wood heating was accompanied by a decrease in the content of C₁₈-acids, but had no effect on the amount of aldehydes. An undesirable taste decreased during the maintenance of alcoholic tinctures in 70% ethyl alcohol for 6 months. It was related to the formation of acetals and ethoxy and hydroxy derivatives of unsaturated aldehydes.     

The heptadecanoic fatty aldehyde--one of the main aldehydes of the far-eastern Bryozoa.

1. The relative content of 16:0, 17:0 and 18:0 fatty aldehydes in the lipids of eight species of the far-eastern Bryozoa was studied. 2. Heptadecanoic aldehyde is one of the main aldehydes in the seven species investigated comprising about 30% of the sum of these main bryozoan aldehydes. 3. We suggest the unusually high relative heptadecanoic aldehyde content in the lipids of Bryozoa may be helpful in settling some problems concerning their system.     

Unsaturated fatty acids and aldehydes during treatment of oak wood

The use of considerable amounts of ground oak to accelerate maturation of strong drinks was accompanied by the appearance of an undesirable taste due to the presence of unsaturated aldehydes (2-nonenal and 2,4-nonadienal). The greater the degree of wood grinding, the higher was the content of C18-unsaturated acids and C9-aldehydes. Wood heating was accompanied by a decrease in the content of C18-acids, but had no effect on the amount of aldehydes. An undesirable taste decreased during the maintenance of alcoholic tinctures in 70% ethyl alcohol for 6 months. It was related to the formation of acetals and ethoxy and hydroxy derivatives of unsaturated aldehydes.     

Oxidation of fatty aldehydes to fatty acids by Escherichia coli cells expressing the Vibrio harveyi fatty aldehyde dehydrogenase (FALDH)

Fatty acids represent an important renewable feedstock for the chemical industry. To enable biotechnological one carbon truncations of fatty acids, the enzymes α-dioxygenase and fatty aldehyde dehydrogenase (FALDH) have to be combined in a two-step process. We expressed an FALDH from V. harveyi in E. coli and characterized its substrate spectrum with a focus on the number and position of double bonds in the fatty aldehyde molecules. Synthesis of the expected fatty acid products was proven by analysis of whole cell biotransformation products. Coexpression of a H₂O-forming NADPH oxidase (NOX) from Lactobacillus sanfranciscensis led to the implementation of a cofactor regeneration cycle in in vitro oxidation experiments. The presence of NOX in whole cell biotransformations improved reaction velocity but did not result in higher product yields. We could further demonstrate that at least part of the endogenous NAD(P)⁺ regeneration capacity in the resting cells results from the respiratory chain. The whole cell catalyst with the high broad range FALDH activity described here is an important biotechnological module for lipid biotransformation processes, especially the shortening of fatty acids.     

Phospholipids and phospholipid-bound fatty acids and aldehydes of spermatozoa and seminal plasma of rhesus monkeys.

The major components of the phospholipids of rhesus monkey spermatozoa are phosphatidyl choline (33%), phosphatidyl ethanolamine (25%), ethanolamine plasmalogen (16-1%), sphingomyelin (8-1%), choline plasmalogen (6-9%) and cardiolipin (4-5%). The major phospholipid-bound fatty acids are 16:0, 18:0, 18:1 and 22:6; the major fatty aldehydes are 15:0, 16:0 and 18:2. The same phospholipids are also present in the seminal plasma.     

Variability in fatty acids and fatty aldehydes in different organs of two prosobranch gastropod mollusks

The distribution of fatty acids and fatty aldehydes of total lipids in mantle, foot and digestive gland of two prosobranch gastropod mollusks, Bellamya bengalensis and Pila globosa, from India were studied. The individual volatile compounds, e.g., acids and aldehydes, were separated by serially coupled capillary columns with different polarity stationary phase and identified by gas chromatography-mass spectrometry. Saturated fatty acids were the main components and vary from 48–60%, monoenic are 18–30%, while polyunsaturates vary between 21–33%. The digestive glands of both the snail species contained cyclopropane fatty acids, not previously reported in gastropods.     

Biohydrogenation of unsaturated fatty acids. Hydrogenation by cell-free preparations of Butyrivibrio fibrisolvens.

Hydrogenation of cis-9,trans-11-octadecadienoic acid to yield trans-11-octadecenoic acid by cell-free preparations of Butyrivibrio fibrisolvens has been obtained under strictly anaerobic conditions. Reduced methyl viologen, NADH, and an endogenous electron donor each can serve as a reductant. Inhibition studies and gel filtration patterns reveal the presence of at least two hydrogenation systems, one of which is coupled through a flavin, possibly FMN. Although the enzymes comprising the biohydrogenation pathway, the fatty acid reductases and linoleic acid isomerase, are part of the bacterial membrane, they do not appear to be constituted as a multienzyme complex.     

Applications of monolithic silica capillary columns in proteomics

The use and applicability of silica based capillary monolithic reversed-phase columns in proteomic analysis has been evaluated by liquid chromatography-mass spectrometry (LC-MS). Chromatographic performance of the monolithic capillaries was evaluated with a tryptic digest of cytochrome C showing very good resolution and reproducibility in addition to the known advantages of a low pressure drop over a time period of 6 months. Monoliths were subsequently tested for their suitability to separate proteins and peptides from samples typically encountered in proteomic research such as in-gel digested tryptic peptide mixtures or fractions of proteolytically digested human serum. The monolithic capillaries also proved useful in the analysis of phospholipid species in bronchoalveolar lavage fluid. Compared to particle-filled conventional capillary columns, rapid and highly efficient separation of peptides and proteins was achieved using these bimodal pore size distribution columns, and good quality collision induced dissociation (CID) mass spectra were obtained on an ion trap mass spectrometer. These novel monolithic separation media are thus a promising addition to the methodological toolbox of proteomics research.