Rapid method for the determination of lysine in cereal grains without hydrolysis.

A rapid spectrophotometric method for lysine determination in cereal grains is reported. The reagent is sodium dinitrobenzene sulfonate (DNBS). The absorbance of the acid solution of the DNBS derivative is read at 385 nm. Under prescribed conditions, the reagent is sensitive and specific for free or protein-bound lysine. The conditions: For rice, the reaction medium is a urea-phosphate-HgCl₂ solution (pH 10.5); reaction at 60°C for 1 hr. For other grains, the reaction medium is a urea-phosphate-phenylmercuric chloride (PMC) solution (pH 12.3); reaction at 40°C for 1 hr. Interferences are eliminated by ether extraction after color development and acidification and addition of formic acid and the sulfhydryl masking agents, HgCl₂ or phenylmercuric chloride (PMC). NaOH extracts of cereal proteins are used for analysis. Values are in agreement with those of the ion-exchange amino acid analyzer.     

A simple colorimetric method for the determination of tryptophan

A simple, sensitive, and reproducible colorimetric method for the determination of tryptophan in amounts as low as 2 μg is described. It is based on the oxidation of tryptophan by sodium nitrite and the coupling of the oxidized product to the leucodye N-1-(naphthyl)ethylenediamine dihydrochloride. The purple-pink product has an absorption maximum at 550 nm. There is no interference by carbohydrates, other amino acids, neutral salts, or a number of other compounds likely to be found in tissue hydrolysates. A number of indole derivatives including indole-3-acetic acid also react to give a colored product. Dipeptides containing tryptophan are much less reactive than free tryptophan; hence proteins must be hydrolyzed completely for the method to be useful. The assay is carried out at room temperature and can be modified easily to increase or decrease its sensitivity. It has been employed to determine the tryptophan content of a number of proteins following alkaline hydrolysis. Generally, values obtained were in close agreement with values reported in the literature.     

Rapid micro Kjeldahl digestion of cereal grains and other biological materials

To accomplish the micro Kjeldahl digestion of cereal grains and other biological materials in approximately 10 minutes, two techniques were developed: (1) digestion in the presence of hydrogen peroxide, K₂SO₄HgOH₂SO₄ mixture, with lauric acid as anti-foaming agent, and (2) precarbonization of sample in K₂SO₄HgOH₂SO₄ mixture to produce foam-forming materials which are immediately destroyed by H₂O₂. Oxidation of the sample is enhanced by H₂O₂ and high digestion temperature resulting from increased salt-acid ratio.     

A specific method for determination of free tryptophan and endogenous tryptophan in Escherichia coli.

A sensitive, simple spectrofluorometric technique for determination of tryptophan inamounts as small as 10 pmol is described. It is based on tryptophanase hydrolysis of tryptophan and spectrofluorometric analysis of the resulting indole. The relationship between released indole and fluorescence is linear over three orders of magnitude. The method is free from interference by other amino acids, polar indole derivatives, and a number of other compounds found in cell extracts or used in bacterial growth media. The method is rapid, reproducible, and accurate. A simple method for extraction and measurement of endogenous free tryptophan from bacterial cells is also described.     

Rapid and simple method for the determination of zolpidem in human plasma by high-performance liquid chromatography

A simple and reproducible method for the determination of zolpidem in human plasma is presented. This method involves protein precipitation with methanol (2 ml of methanol are added to 0.5 ml of plasma) and reversed-phase chromatography with fluorescence detection (excitation wavelength 244 nm, emission wavelength 388 nm). The mobile phase consists of methanol–30 mM dihydrogen potassium phosphate–triethylamine (30:69:1). pH of the aqueous part of the mobile phase is 6.8. No internal standard is required. Limit of quantitation is 1.5 ng/ml and the calibration curve is linear up to 400 ng/ml. Within-day and between-day precision expressed by relative standard deviation is less than 5% and inaccuracy also does not exceed 9%. The assay is useful for pharmacokinetic studies.     

Rapid and simple method for the most-probable-number estimation of arsenic-reducing bacteria.

A rapid and simple most-probable-number (MPN) procedure for the enumeration of dissimilatory arsenic-reducing bacteria (DARB) is presented. The method is based on the specific detection of arsenite, the end product of anaerobic arsenate respiration, by a precipitation reaction with sulfide. After 4 weeks of incubation, the medium for the MPN method is acidified to pH 6 and sulfide is added to a final concentration of about 1 mM. The brightly yellow arsenic trisulfide precipitates immediately and can easily be scored at arsenite concentrations as low as 0.05 mM. Abiotic reduction of arsenate upon sulfide addition, which could yield false positives, apparently produces a soluble As-S intermediate, which does not precipitate until about 1 h after sulfide addition. Using the new MPN method, population estimates of pure cultures of DARB were similar to direct cell counts. MPNs of environmental water and sediment samples yielded DARB numbers between 10(1) and 10(5) cells per ml or gram (dry weight), respectively. Poisoned and sterilized controls showed that potential abiotic reductants in environmental samples did not interfere with the MPN estimates. A major advantage is that the assay can be easily scaled to a microtiter plate format, enabling analysis of large numbers of samples by use of multichannel pipettors. Overall, the MPN method provides a rapid and simple means for estimating population sizes of DARB, a diverse group of organisms for which no comprehensive molecular markers have been developed yet.     

分光光度法测定豆类及其粗蛋白质中的色氨酸

建立一种快速、准确测定各种豆类试样及粗蛋白质中的色氨酸含量的分光光度法讨论最佳试验条件及试剂用量,反应物在410nm处具有最大吸收波长ε=1.103×104L·mol-1·cm-1,回收率93.50-110.20%,相对标准偏差RSD＜2.61.     

A simple method for determination of gait events.

Simple and effective methods for determining the timing of gait events are necessary for the proper normalization and statistical analysis of gait data when a variety of gait measurements are available. The approach presented was developed for cases in which overall center of pressure under the body and marker trajectories are being measured over multiple steps. The new method presented uses the relative positioning of the overall center of pressure and an ankle marker in the direction of forward progression for the determination of "heel-contact" and "toe-off" events. The difference between the locations of the overall center of pressure and the ankle in the direction of progression readily delineates the timing of these events. The new method was tested against force records from individual force platforms and was found to detect "heel-contact" events an average of 1 sample (at a sampling frequency of 120Hz, 0.00833s) before the event found using the individual force platforms. "Toe-off" events were found an average of 2 samples (0.0167s) prior to the events found using individual force plates. The method appears new and is attractive because of its simplicity in determining gait events when the appropriate gait measurements are available.     

Loading and bioavailability of iron in cereal grains

Cereal plants take up iron from the soil via a phytosiderophore-mediated chelation system. Following root absorption, iron is transported through the xylem and phloem of the plant with the help of a variety of efflux and influx transporters belonging to the Zrt Irt-like protein (ZIP) and yellow stripe-like (YSL) protein families. Iron-regulated transporter1, a member of the ZIP family, mobilises ferrous [Fe(II)] ions, while several YSL family members such as YSL2, YSL15 and YSL18 can transport both ferric [Fe(II)] and ferrous [F`III)] ions into developing grains via chelation with mugineic acid or its derivatives. The iron is accumulated largely in the outer aleurone layer and embryo of the grains, which are removed during milling, leaving behind consumable endosperm that contains a very low amount of iron. This review highlights the uptake, transport and loading mechanisms for iron in cereal grains and provides an overview of strategies adopted for developing highly iron-enriched grains.     

A HPTLC method for the determination of the mycotoxin zearalenone in cereal products

An HPTLC method for the quantification of zearalenone (ZEA) in cereals and cereal products (wheat flour and malt) has been developed. ZEA was extracted with 50 ml of acetonitrile-purified water (9+1) with addition of 2 g NaCl. The extracts were further purified on VICAM ZearalaTest^(tm) immunoaffinity columns, then analysed by instrumental high-performance thin-layer chromatography (HPTLC) on silica gel plates with fluorescence detection. Ethyl acetate - n-hexane (1+1) was used as the mobile phase. The chromatogram was scanned in fluorescence mode after excitation at λ=254 nm with λ=400 nm measuring filter: SENS and SPAN parameters were 195 and 20, respectively. TheR _F of ZEA under these conditions was 0.43. The recovery was 95% in the range 15–65 μg/kg cereal products; the mean relative standard deviation of repeatability (RSDr) was 7.6%. The limit of quantification (LoQ) of ZEA was 10 μg/kg. Validation of the method was performed according to the principles of the ICH for pharmaceutical analysis. Presented at the 25^th Mykotoxin Workshop in Giessen, Germany, May 19–21, 2003     

A fluorimetric method for the determination of tryptophan in animal tissues

Tryptophan, tryptamine and peptides containing N-terminal tryptophan give two highly fluorescent products on treatment with dithiothreitol and acid ninhydrin reagent 1 or 2. The first fluorescent product (product A) gives an emission at 500nm on activation at 390–400nm and is stable for 20min. The second product (product B), which gives an emission at 530nm on activation at 470nm, is detectable within 1h after the reaction. It gives almost maximum intensity in 4h and is stable for at least 48h. Except lysine, which in equimolar amounts gives less than 1% of a product similar to product B, no other naturally occurring amino compounds give fluorescent products. A procedure is given for the determination of 0.05–34nmol of tryptophan in tissue extracts. By using this procedure rat brain was found to contain 17.56±0.76 (s.e.m.) nmol/g wet wt.     

Regulation of aleurone development in cereal grains

The aleurone layer of cereal grains is important biologically as well as nutritionally and economically. Here, current knowledge on the regulation of aleurone development is reviewed. Recent reports suggest that the control of aleurone development is more complex than earlier models portrayed. Multiple levels of genetic regulation control aleurone cell fate, differentiation, and organization. The hormones auxin and cytokinin can also influence aleurone development. New technical advances promise to facilitate future progress.     

A simple method for the determination of heparin content in heparin--sepharose.

A potentiometric titration method for the determination of heparin content in heparin-Sepharose is suggested. The procedure is simple and rapid.     

A simple method for the isolation of intact mesophyll protoplasts from cereal plants

Intact mesophyll protoplasts from cereal plants were easilyprepared by incubating leaves with the abaxial epidermis peeledoff at 20–25?C for 2–3 hr in 0.6 M mannitol containing1% cellulase at pH 5.6. From one gram (fresh weight) of leaves1.5–6?10⁶ protoplasts, more than 90% of which were morphologicallyintact, could be obtained. Protoplasts isolated from wheat,oat, corn and barley were efficiently infected with brome mosaicvirus (BMV), and supported viral multiplication. (Received June 21, 1977; )     

A new simple method for determination of erythrocyte filtrability.

A new simple filtration technique designed for measuring red cell filtrability in the routine laboratory use was developed. The suspension of the whole blood in saline (1:20,000 dilution) was processed on the Sartorius filter membranes, pore size 8 micron. The percentage of passed erythrocytes indicating red cell filtrability was determined. The suitability and perspective applicability of this method for studying various hematological disorders is proposed.