A paper chromatographic procedure for separating 1-mono-, 1,3-di-, and triglycerides,cholesterol, and cholesteryl esters

Summary A reproducible paper chromatographic procedure has been developed for resolving a mixture consisting of 1-mono-, 1,3-di-, and triglycerides, cholesterol, and cholesteryl esters. The separation is accomplished, using silicic acid impregnated glass fiber filter paper as the chromatographic medium and various ethyl ether-isooctane mixtures as the solvent systems. A reagent consisting of 1:1 concentrated sulfuric acid: water has been introduced for visualizing the lipides on the chromatogram and for distinguishing between glycerides and cholesterol-containing lipides. Unsaturation in the fatty acid moiety of the mono-, di-, and triglycerides had no detectable effect on the R_f values of these substances. Fatty acid chain length did not affect the R_f of the cholesteryl esters with the solvent systems studied. Increasing the percentage ethyl ether in the solvent system caused an increase in the R_f values of each lipide not moving at the solvent front. This work was supported in part by grants from the National Science Foundation, and the Office of Naval Research.     

Identification of some marine oil constituents by chromatography

Summary and Conclusion A scheme for the separation and identification of some constituents of marine oils was developed. A preliminary separation on a silicic acid column with five solvent systems was followed by further separation and identification on silicic acid impregnated glass-fiber filter paper. This method can be used successfully for qualitative determinations, but the irregularities in the density of the glass paper prevent an accurate quantitative assay. Supported, in part, by grants from the Fish and Wildlife Service of the United States Department of the Interior, the Robert A. Welch Foundation, and the Office of Naval Research.     

On the stability of finite difference schemes in transient semiconductor problems

Nonlinear instabilities of explicit and half-implicit Crank-Nicholson schemes are analyzed by perturbation techniques. The time step is found to be inversely proportional to μN, a criterion which is in good agreement with experience. Based on this result, an optimal choice between the fast half-implicit method and the fully implicit Newton method is possible, favoring the former for Gunn-diodes and Schottky-barrier field-effect transistors, and the latter for insulated-gate field-effect transistors and some bipolar transistor problems.     

Revised amino acid sequence of Qbeta coat protein between positions 1 and 60

A reinvestigation of the primary structure of Qbeta coat protein between positions 1 and 60 was undertaken to resolve two discrepancies between the published amino acid seuqence (Maita, T., and Konigsberg, W. (1971) J. Biol. Chem. 246, 5003-5024) and the cognate nucleotide sequence recently determined in our laboratory (C. Escarmis and M. A. Billeter, unpublished results). The 22nd amino acid was asparagine rather than aspartic acid, and an additional amino acid, serine, was present between proline in position 55 and arginine in position 56. The revised structure agrees with the nucleotide sequence determined so far.     

The origin and metabolism of marine fatty acids: The effect of diet on the depot fats of mugil cephalus (The common mullet)

It appears that young mullet make excellent experimental fish for dietary studies. They are hardy, easily caught, resistant to disease, and take well to aquaria conditions. Of particular interest, they may be fed synthetic food and they resist changes in salinity well. These experiments indicate that, on a fatfree diet, the mullet does not synthesize the large amounts of polyunsaturated fatty acids normally found in its body fat. However the mullet, like land animals, can apparently convert dienoic acid from cottonseed oil into small amounts of tetraenoic, pentaenoic, and hexaenoic acids. Unlike land animals, the mullet appears to be capable of the conversion of linoleic acid to a trienoic acid. Finally, when fed a diet containing a typical marine fat such as menhaden oil, the mullet stores it almost unchanged.