Inhibition of HeLa cell messenger RNA translation by 7-methylguanosine 5'-monophosphate

Translation of HeLa cell RNA containing poly(A) in a wheat germ cell-free system is markedly but incompletely inhibited by 7-methylguanosine 5'-monophosphate (m7G5'p). We have analyzed the translation products synthesized in the presence of different concentrations of m7G5'p and find that translation of all mRNAs is equally inhibited. To demonstrate the specificity of the inhibitor for RNAs with 5'-terminal m7G5' ppp... we show that specific translation products of satellite tobacco necrosis virus RNA, which does not have this 5' terminus, are synthesized in the presence of m7G5' p. Protein synthesis programmed by endogenous mRNA in a HeLa cell-free system is inhibited after a 10-min lag by m7G5' p. Other guanosine nucleotides without the 7-methyl group or with the phosphate in a different position are not inhibitor. We show that translation of all mRNAs is inhibited to a similar extent by m7G5'p in the HeLa cell-free system, by synthesizing 35S-labeled proteins in the presence of different inhibitory concentrations of this nucleotide and analyzing the translation products by electrophoresis and autoradiography. Translation of encephalomyocarditis virus RNA added to the HeLa cell-free system is not inhibited by m7"g5p; this viral RNA does not have this nucleotide at the 5' terminus. This indicates that m7G5'p specifically inhibits translation of mRNAs with the 5' terminus m7G5'ppp... and suggests that initiation of translation of picornavirus RNA may proceed via a mechanism different from that of cellular mRNAs.     

Comparison of the phenylalanine determination by ion exchange column chromatography and the guthrietest in treated phenylketonuric children (author''s transl)]

Simultaneous measurements of phenylalanine by ion exchange column chromatography and microbiologal inhibition test according to Guthrie were performed on 22 treated children with phenylketonuria within two years. The results coincide in 40,3% (229 of 569 estimations), in 15,8% the real phenylalanine concentration by the method of Guthrie were overestimated, in 43,9% underestimated. Bacterial inhibition assay is successful in routine screening of phenylketonuria in the newborn, but not suitable for dietary control of phenylketonuria.     

Effect of Processing on the Detectability of Pecan Proteins Assessed by Immunological and Proteomic Tools

The present study evaluates the effect of food processing on the antigenicity of pecan proteins as measured by enzyme-linked immunosorbent assay (ELISA). In addition, proteomic tools were used to identify potential pecan markers suitable for confirming the presence of pecan proteins in food and validating new methods developed to detect traces of the commodity. To assess the effects of processing on protein stability and antigenicity, pecan nuts were submitted to heat treatments and extracts were analysed by ELISA, sodium dodecyl sulphate polyacrylamide gel electrophoresis and Western blot. The ELISA method was able to detect pecan traces even after submitting the commodity to rigorous treatments, though these treatments affected the detectability to varying degrees. Proteomic assessment showed that the majority of pecan proteins were matched by homology to walnut proteins, which are more abundantly populated in the protein sequence databases. However, there were a few important exceptions: 7S vicilin, 11S legumin and putative allergen I1, unambiguously identified as pecan in origin. Interestingly, putative allergen I1 offered unique analytical advantages to be used as a pecan marker for validation and confirmation purposes.     

Product-oriented flavor research: learnings from the past, visions for the future

In the past flavor research and the development of new flavorings were constantly driven by the interaction of flavor analysis, structure elucidation, and chemical synthesis accompanied by sensory. Highly potent flavor compounds were identified in numerous food products and helped to establish a powerful toolbox for flavorists. Nowadays we experience the merging of various scientific disciplines, for example medicine, biology, chemistry, and various technologies in the field of flavor research, which shows direct impact on our understanding of flavors. At the same time modern life has profoundly changed our eating habits. This situation generates new challenges for product development teams, which represent all facets of technologies. This paper will illustrate different examples for the evolution of product-oriented flavor research and future trends.     

Commercial soybean lecithins: a source of hidden allergens?

 Soybeans are known to be allergenic for adults as well as for infants. Processed products derived from soybeans are used in a wide spectrum of foods, drugs and other industrial products. In particular, soybean lecithins are used as stabilizers and emulsifiers and may not be suspected as possible source of allergens. To test this hypothesis, six commercial soy lecithins were investigated for residual allergenicity and compared with extracts from raw and heat-treated soybeans. They were characterized, the protein content was determined by enzyme-linked immunosorbent assay (ELISA) and allergens were analyzed with specific IgE from patients' sera using the enzyme allergosorbent test (EAST), EAST inhibition and protein blotting followed by immunodetection. For further characterization a polyclonal antiserum directed against soybean extract and a monoclonal antibody (mAb 025) directed against the acidic subunit of the soybean storage protein glycinin were used. The EAST studies revealed that three of six sera from patients with allergy to soybeans contained IgE to four soy lecithins (Topcithin 50, Topcithin 300, Emulfluid FD 12, Epikuron 100 P), the same lecithins which were found to contain residual proteins. Two lecithins with a protein content of less than 20 ppb did not bind IgE. EAST inhibition showed that the allergens from soy lecithin were immunologically more closely related to allergens from heat-treated soybeans than to those from raw soybeans. Protein blotting and immunodetection of the protein extract from the lecithins resulted in various allergen bands between 14 kDa and 94 kDa. A heat-stable allergen of 39 kDa was recognized by the monoclonal antibody and thus identified as a subunit of glycinin. The results obtained were confirmed by a mediator release assay based on a rat basophil leukemia cell line. Lecithins that contained residual proteins caused a specific mediator release, suggesting that these products may induce allergic symptoms. Our results show that soybean lecithins are capable of introducing hidden allergens to processed foods and that the IgE binding potential corresponds to the total protein determined by ELISA. Furthermore, it appears to be possible that by monitoring the protein content soy lecithins can be applied which may be safe for the allergic consumer. Received: 22 January 1998     

Spatial and seasonal trends in biogenic secondary organic aerosol tracers and water-soluble organic carbon in the southeastern United States

Twenty-four hour integrated filter samples of fine particulate matter (PM2.5) were collected from May 2004 to April 2005 at one rural site and three urban sites located in the southeastern United States. Filters were extracted and analyzed for both biogenic secondary organic aerosol (SOA) tracers via gas chromatography-mass spectrometry (GC-MS), and water-soluble organic carbon (WSOC) concentrations. The tracers reported in this study include isoprene-derived 2-methylthreitol and 2-methylerythritol, as well as pinene-derived cis-pinonic acid. The mean ambient concentrations ranged from 21.7 to 94.3 ng/m3, 5.31 to 17.9 ng/m3, and 1.87 to 3.18 microgC/m3 for 2-methyltetrols (sum of 2-methylerythritol and 2-methylthreitol), cispinonic acid and WSOC, respectively. Distinct spatial distributions were observed for all tracers with the highest concentration at the rural site and the lowest level at a coastal site. Although 2-methyltetrols were small fractions of WSOC, varying from 0.35% at an urban site to highest fractions of 1.09% at the rural site, WSOC exhibited significant correlation with 2-methyltetrols during summer, suggesting isoprene SOA makes an important contribution to WSOC. 2-Methyltetrols had the highest concentrations during the summer,when high temperature, intense solar radiation, and high ozone level occurred. However, no obvious seasonal variation was found for cispinonic acid. Between inland sites WSOC was more spatially homogeneous than the 2-methyltetrols, suggesting that WSOC was produced from a variety of mechanisms.     

Predesolventizing of soybean meal

Predesolventizing of meal provides opportunities for potential savings in the extraction operation. The reduction of the moisture level in meal can save considerable energy during the meal drying operation. Ways to reduce the hexane content before drying include: (a) changing seed preparation; (b) increasing drainage time; (c) mechanical pressing; (d) evaporating by indirect heating; (e) circulating metallic heat transferring units; and (f) using new technology. These options are evaluated in terms of economics and operating efficiencies.     

Determination of 5-methoxypsoralen in suntan cosmetics

A method for the determination of 5-methoxypsoralene in suntan-cosmetics is described. After liquid chromatographic clean-up, the final extract is screened by twodimensional thin layer chromatography. For positive extracts 5-methoxypsoralene is analysed quantitatively by capillary gas chromatography, using 5-alpha-cholestane as an internal standard and flame ionization detection (FID). The results were confirmed by gas chromatography-mass spectrometry (GC-MS). The recoveries for suntan-cosmetics of emulsion type were 70% and for tanning oils 90%. Detection limits of the method were 0,1 to 0,5 mg/kg, depending on the sample type. By application of this method 5-methoxypsoralene was detected in 6 of the 21 cosmetic products at levels up to 28 mg/kg.