High-performance liquid chromatography analysis of peanut phospholipids. II. Effect of postharvest stress on phospholipid composition

Peanuts are harvested in late September, and sometimes the harvest season can extend through most of October. When weather patterns delay harvest, the result may cause an immature crop, curing problems, rain damage, and freeze damage. All of the above stress situations can affect oil quality and flavor of the peanuts by altering phospholipid composition. Such changes are related to refining problems as well as flavor problems. A new high-performance liquid chromatography (HPLC) method was used for the analysis of phospholipids from postharvest stressed peanuts. The concentrations of phosphatidic acid (PA), phosphatidylethanolamine (PE), and phosphatidylcholine (PC) were higher in immature seed when compared to mature seed. A slight increase in concentration was observed for phosphatidylglycerol (PG), and a decrease in phosphatidylinositol occurred in immature peanuts. All phospholipids increased in concentration except PG when peanuts were cured at a high temperature (40°C). When peanut seeds were frozen at −16°C (before curing), a significant increase in concentration was observed for PA and PG, whereas the concentrations of PC and PE decreased to very low levels when compared to the control. Where concentration permitted, molecular species were separated on a reverse-phase column by HPLC.     

A transketolase assembly defect in a Wernicke-Korsakoff syndrome patient

Thiamine deficiency, a frequent complication of alcoholism, contributes significantly to the development of damage in various organ systems, including the brain. The molecular mechanisms that underlie the differential vulnerabilities to thiamine deficiency of tissue and cell types and among individuals are not understood. Investigations into these mechanisms have examined potential variations in thiamine utilizing enzymes. Transketolase is a homodimeric enzyme containing two molecules of noncovalently bound thiamine pyrophosphate. In the present study, we examined a his-tagged human transketolase that was produced in and purified from Escherichia coli cells. Previous findings demonstrated that purified his-transketolase had a Km app for cofactor and a thiamine pyrophosphate-dependent lag period for attaining steady-state kinetics that was similar to transketolase purified from human tissues. Interestingly, the time of the lag period, which is normally independent of enzyme concentration, was found herein to be dependent on the concentration of the recombinant protein. This atypical behavior was due to production in E. coli. Generation of the normal, enzyme concentration-independent state required a cytosolic factor(s) derived from human cells. Importantly, the required factor(s) was found to be defective in a Wernicke-Korsakoff patient whose cells in culture show an enhanced sensitivity to thiamine deficiency.     

Spectral properties of the nonspherically decaying radiation generated by a rotating superluminal source

The focusing of the radiation generated by a polarization current with a superluminally rotating distribution pattern is of a higher order in the plane of rotation than in other directions. Consequently, our previously published [J. Opt. Soc. Am. A24, 2443 (2007)] asymptotic approximation to the value of this field outside the equatorial plane breaks down as the line of sight approaches a direction normal to the rotation axis, i.e., is nonuniform with respect to the polar angle. Here we employ an alternative asymptotic expansion to show that, though having a rate of decay with frequency (mu) that is by a factor of order mu(2/3) slower, the equatorial radiation field has the same dependence on distance as the nonspherically decaying component of the generated field in other directions: It, too, diminishes as the inverse square root of the distance from its source. We also briefly discuss the relevance of these results to the giant pulses received from pulsars: The focused, nonspherically decaying pulses that arise from a superluminal polarization current in a highly magnetized plasma have a power-law spectrum (i.e., a flux density S infinity mu(alpha)) whose index (alpha) is given by one of the values -2/3, -2, -8/3, or -4.     

A preconcentration and subsequent gas liquid chromatographic analysis method for trace volatiles

A glass column containing a porous polymer was used to concen-trate headspace volatiles from enzymatically mediated reactions and inserted directly into the injection port of a gas liquid chromatog-raphy (GLC) for elution and separation of adsorbed volatiles. The polymer column was placed in an entrainment system attached to a water aspirator at 30 psi to collect volatiles produced by the en-zymatic reaction. A useful chromatogram was obtained from 1 g of raw material by this method. Volatiles collected in this manner could be stored on the polymer matrix at ambient temperatures without deleterious effects for subsequent GLC analysis. Multiple columns of the same or different trapping material could also be used in the entrainment system. Paper Number 5523 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27650.     

The determination of specific free fatty acids in peanut oil by gas chromatography

Peanut oil is dissolved in 2,2,4-trimethylpentane standard. The free acids are extracted into N,N-dimethylformamide as their sodium salts and treated with methyl iodide. The resulting methyl esters are analyzed by gas chromatography. A typical result for oleic acid is about 200 ppm with a relative standard deviation of 6%. An average recovery of 95% is obtained from a sample spiked with an additional 200 ppm of oleic acid. Evidence is presented that the procedure does not give high values as a result of sample hydrolysis.     

Irreversibility Line Measurement and Vortex Dynamics in High Magnetic Fields in Ni- and Co-Doped Iron Pnictide Bulk Superconductors

The de-pinning or irreversibility lines were determined by ac susceptibility, magnetization, radio-frequency proximity detector oscillator (PDO), and resistivity methods in Ba(Fe_0.92Co_0.08)₂As₂ ( T _c = 23.2 K), Ba(Fe_0.95Ni_0.05)₂As₂ ( T _c = 20.4 K), and Ba(Fe_0.94Ni_0.06)₂As₂ ( T _c = 18.5 K) bulk superconductors in ac, dc, and pulsed magnetic fields up to 65 T. A new method of extracting the irreversibility fields from the radio-frequency proximity detector oscillator induction technique is described. Wide temperature broadening of the irreversibility lines, for any given combination of ac and dc fields, is dependent on the time frame of measurement. Increasing the magnetic field sweep rate (dH/dt) shifts the irreversibility lines to higher temperatures up to about dH/d t = 40,000 Oe/s; for higher dH/dt, there is little impact on the irreversibility line. There is an excellent data match between the irreversibility fields obtained from magnetization hysteresis loops, PDO, and ac susceptibility measurements, but not from resistivity measurements in these materials. Lower critical field vs. temperature phase diagrams are measured. Their very low values near 0 T indicate that these materials are in mixed state in nonzero magnetic fields, and yet the strength of the vortex pinning enables very high irreversibility fields, as high as 51 T at 1.5 K for the Ba(Fe_0.92Co_0.08)₂As₂ polycrystalline sample, showing a promise for liquid helium temperature applications.