Antigenic properties of a synthetic protein complex with glycolipids and related substances

Erythro-sphingosine was obtained from sphingomyelin by alkaline hydrolysis. N-p-nitrobenzoyl-sphingosine, N-p-aminobenzoyl-dihydrosphingosine and dihydrosphingosine-protein were synthesized. It was found that dihydrosphingosine-protein can produce a specific antibody which can be detected by the complement fixation test and by Ouchterlony's double diffusion method in agar. The determining factor of dihydrosphingosine may be due to the hydroxy groups at C₁ and C₃. In the course of experimental allergic encephalomyelitis, the cross-reactivity of rabbit antisera against spinal cord, and with psychosine-protein in particular, was observed by the complement fixation test and by the Arthus reaction. Presented at the Prof. Ernst Klenk Symposium on Glycolipids and the Nervous System, AOCS Meeting, Houston, April 1965.     

Analysis of residual solvents in natural flavorings by headspace GC using the standard addition method

Headspace GC using the standard addition method has been developed for the simultaneous determination of organic solvents in natural flavorings. The procedure can be outlined as follows: an aliquot of the sample is transferred to a 10 mL vial. To each vial, a DMSO solution containing solvents at different concentrations is added as the standard solution. The vials are kept at 50 degrees C (for automatic injection) or 40 degrees C (for hand-operated injection) for 40 minutes. One mL of the vapor phase in each vial is injected into a gas chromatograph equipped with an Aquatic-2 column (0.25 mm i.d. x 60 m). To evaluate this method, we conducted a performance study in collaboration with 10 laboratories, using ginger oleoresin. We analyzed 6 solvents (methanol, 2-propanol, acetone, dichloromethane, hexane, and 1,1,2-trichloroethene) for which the maximum residue limits are established in Japan's Specifications and Standards for Food Additives. Methanol and acetone existed in the ginger oleoresin, so only the other that four kinds of solvents were added to it. Eight of the laboratories used automatic injection, while the remaining two used hand-operated injection. Statistical analyses were conducted on the data obtained from the 8 laboratories. Repeatability standard deviations (RSDr) ranged from 4.3 to 11.4%, and reproducibility standard deviations (RSDR) ranged from 8.4 to 19.0%.     

Nonresonant Microwave Absorption in Bi2212 Single Crystal: Second Peak and Microwave Power Dependence

Nonresonant microwave absorption (NMA) measurements were carried out at liquid-nitrogen temperature on a high quality Bi2212 single crystal, as a function of microwave power in three mutual orientations of crystal ab plane, dc field (H_dc), and microwave magnetic field (H_w). NMA line shapes in Bi2212 crystal are complicated with a narrow peak (P₁ peak) located near zero field, followed by a much broader second peak (P₂ peak) in the particular orientations. More excitingly, we show that the P₂ peak qualitatively evolves as a function of microwave power in the orientation of H_dc ab plane, plane, and H_dc H_w. In this configuration, as the microwave power is progressively increased, the broad P₂ peak first gets smeared off and then a multiple peak structure appears, which develops into another narrower second peak (P_s-peak) at high enough microwave powers. In the orientation of plane, H_w ab plane, and H_dc H_w, we report for the first time the appearance and disappearance of a new second peak (P₂-like peak) as a function of microwave power.     

Positioning in Releasing Manipulation by Iterative Learning Control

In order to improve the positioning precision of the stop posture (position and orientation) of an object and decrease the trial numbers in our proposed releasing manipulation, two iterative learning control (ILC) schemes, learning control based on convergent condition (LCBCC), and learning control based on optimal principle (LCBOP) are designed in experimental-oriented way. These two methods are all based on a linearized system model. The experimental results show that these methods are effective. Having discussed the characteristics of these control methods, we conclude that in the case there is no enough system knowledge, LCBCC is the only choice to be used to learn the system knowledge; after the enough experience has been acquired, LCBOP is better than LCBCC, in the view of both of the convergent rate and the precision.     

Determination of acrylamide in foods by GC/MS using 13C-labeled acrylamide as an internal standard

A method was developed for the determination of trace amounts of acrylamide (AA) in foods. The method includes the addition of 13C-labeled acrylamide-1-13C (AA-1-13C) as an internal standard, extraction with water, bromination, clean-up with a Florisil cartridge column, dehydrobromination and GC/MS analysis in the selected ion monitoring (SIM) mode. Bromination of AA to 2,3-dibromopropionamide (2,3-DBPA) was done using potassium bromide and potassium bromate under an acidic condition. 2,3-DBPA was converted to 2-bromopropenamide (2-BPA) by dehydrobromination with triethylamine before GC/MS analysis. The recoveries of AA from spiked potato chips, corn snack, pretzel and roasted tea were 97-105%, and their relative standard deviations were 0.8-3.9%. The detection limit of AA in foods was 9 ng/g. The method was applied to thirty-one foods purchased from retail markets. AA was found in potato chips at the level of 466-3,340 ng/g, and in other foods at the level of ND-520 ng/g.     

Rapid and improved determination of furan in baby foods and infant formulas by headspace GC/MS

Furan is a 5-membered ring compound with high volatility. The U.S. Food and Drug Administration (FDA) has recently published a report on the occurrence of furan in a large number of thermally processed foods. However, the FDA's analytical method, using standard curve addition, is not suitable for high-throughput routine laboratory operations. We developed a rapid and improved method for determination of furan in foods by headspace GC/MS. Quantification was achieved by using an internal standard of d4-furan and an external calibration curve of furan normalized against the internal standard. The incubation temperature for equilibration was set at 60 degrees C to avoid the formation of furan during analysis. The levels of furan in baby foods and infant formulas were determined with this method. Validation data showed good precision and accuracy. The LOD and LOQ were 0.2-0.5 ng/g and 0.5-2 ng/g for various food matrixes, respectively. The level of furan detected was in the range of 1.4 to 90 ng/g in baby foods and in the range of non-detectable to 36 ng/g in infant formulas.     

Laboratory-performance study of the notified methods to detect genetically modified maize (CBH351) and potato (NewLeaf Plus and NewLeaf Y)

To investigate the key factors affecting the reliability of the analytical results, a laboratory-performance study was attempted for the notified methods to detect genetically modified (GM) maize (CBH351) and GM potato (NewLeaf Plus and NewLeaf Y). The test samples were designed as three pairs of blind duplicates, which included 0%, 0.1% and 1.0% GM maize (CBH351) or GM potato (NewLeaf Plus or NewLeaf Y). Fourteen laboratories participated in the study. The test samples were sent to the participating laboratories along with the protocol. The data were collected from all laboratories and statistically analyzed. For the 0% sample of the CBH351 maize, one laboratory reported a false-positive result. It was considered that contamination could have occurred via the common use of equipment or tools for the test. For the 0.1% samples of the NewLeaf Plus potato or NewLeaf Y potato, on the other hand, three laboratories reported false-negative results. It was presumed that these results were due to changes of the conditions of the electrophoresis and agarose-gel staining. The other laboratories reported appropriate results. It was considered that the method employed in this study was suitable for the assessment of laboratory performance.     

Cleanup of food samples with pre-packed multi-layer silica gel column for the analysis of PCDDs,PCDFs and dioxin-like PCBs

The cleanup procedure for the determination of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (PCBs) in food samples using a disposable pre-packed multi-layer silica gel column (multi-layer dioxin tube; D-tube) was evaluated. The blank test showed the need for conditioning of the column with n-hexane. To compare the method with the D-tube and the conventional method for the analyses of actual food samples, seven food samples (spinach, komatsuna, rice, salmon, beef, egg and butter) were extracted by shaking with acetone-n-hexane or n-hexane after alkaline treatment, and then the extracts were cleaned up by use of the D-tube or the prepared conventional column, followed by several column chromatographic steps. Both cleanup procedures gave similar values at each isomeric concentration level and showed similar efficiency with favorable recoveries. The results suggest that the D-tube is applicable to cleanup for the analysis of PCDD/Fs and dioxin-like PCBs in foods.     

Development and evaluation of qualitative detection methods for unapproved genetically modified rice (LLRice)

We developed a specific method to extract DNA from rice grain samples and modified the qualitative real-time PCR method provided by Bayer Co., Ltd. for reliable detection of the genetically modified (GM) rice variety, LLRice601, which has not undergone safety assessment for regulatory approval in Japan. Moreover, we conducted a data analysis to confirm the results obtained with real-time PCR. The yields of DNA extracted from powdered samples of rice grains were almost equal among 5 different varieties of rice, and there was no significant difference in the yield over three days. Reliable results were obtained using 50 ng of the extracted DNA as the template for real-time PCR. To examine the adequacy of the methods, we organized an interlaboratory study with the participation of 2 laboratories, in which 80 test samples were analyzed in a blinded manner. The statistical analysis revealed no significant difference in the Ct value for the endogenous gene of the DNA samples and for the targeted DNA sequence of 0.1% samples. The limit of detection of the method was approximately 0.1%. Analysis of the fluorescence intensity of the PCR-amplified product of the construct-specific DNA sequence suggested that it may be reasonable to judge a sample as positive when a Ct value of less than 40 is obtained.