Starch granule surface imaging using low-voltage scanning electron microscopy and atomic force microscopy.

High resolution imaging of wheat and potato starch granule surfaces has been performed using low-voltage scanning electron microscopy and atomic force microscopy. The complimentary images of uncoated granules demonstrate that the two starch types possess substantially different surface topologies; potato starch has many protrusions (100-300 nm in diameter), above a flatter surface containing 20-50 nm structures, whilst wheat starch possesses far fewer protrusions and generally has a smoother surface composed of approximately 20 nm structures. The protrusions are believed to be carbohydrate in nature and thus represent the ends of amylopectin side-chain clusters at the granule surface.

Análise electroforética da farinha de trigo sarraceno em comazaçao com a farinha de trigo suave / Electrophoretic analysis of meal of buckwheat in comparison with common wheat flour

A composiçao das proteínas alcool (prolaminas) obtidas das farinhas de trigo suave por dois procedimentos foram analizadas por el electroforense a pH 3,1 e, após disociaçao, na presença de dodecil sulfato de sódio a pH 8,0. Os perfis obtidos da fracâo prolamina do trigo sarraceno muito diferentes tanto qualitativamente como quantitativamente daqueles da prolamina, do trigo suave. Parece, portanto, provável que ofeitos adversos associados com alimentares contendo gliadina de trigo a pacientes celíacos seriam reduzidos e possivelmente evitados se a farinha de trigo fosse substituida pela farinha de trigo sarraceno

Available carbohydrates of cereal grains as affected by storage and insect infestation

Total soluble sugar, reducing sugar, non-reducing sugar and starch contents of wheat, maize and sorghum grains were affected adversely at 25, 50 and 75 percent insect infestation caused by Trogoderma granarium Everts and Rhizopertha dominica Fabricius, separately and mixed population. R. dominica caused significant (P < 0.05) reduction in available carbohydrates at 50 and 75 percent. Mixture of both insect species caused intermediate losses. Storage of cereal grains up to 4 months resulted in substantial increase in sugars and decrease in starch content, but storage for a shorter period of time did not cause any significant changes in levels of carbohydrates (Summary)

Influencia del solvente de extracción de proteínas de trigo para su detección por electroforesis en alimentos para celiacos / Influence of solvent extraction on wheat electrophoregram in order to control gluten free products

Se estudió la influencia de distintos solventes de extracción, sobre el perfil electroforético de proteínas de trigo, como etapa previa a su posible detección en alimentos para celiacos. Se utilizó electroforesis en placas de gel de poliacrimida en sistema discontinuo y disociante. Los solventes de extracción estudiados para gliadinas fueron: 1) etanol 70§, 2) dioxano 40§, 3) isopropanol 55§, 4) isopropanol 55§ + 2 mercaptoetanol, y para proteínas totales: 5) Buffer conteniendo dodecilsulfato de sodio y 2 Mercaptoetanol. Del análisis de los densitogramas, surge que los solventes 4) y 5), son los más adecuados, debido a la buena extracción y resolución proteica. Si bien con el resto de los solventes se obtienen pocas bandas proteicas, en principio es conveniente extraer también con el solvente 3 en caso de mezclas con otras proteinas que pudieran presentar perfiles proteicos complejos con los solventes 4 y 5. Los resultados se aplican al análisis de trigo sarraceno

Extreme variations in the ratios of non-synonymous to synonymous nucleotide substitution rates in signal peptide evolution.

Nucleotide sequences encoding signal peptides from the precursors of alpha-amylase/trypsin inhibitors from cereals are homologous to those corresponding to the precursors of thaumatin II and of plastocyanins. Non-synonymous (KA) and synonymous (KS) rates of nucleotide substitutions have been calculated for all possible binary combinations. Extreme variation in KA/KS ratios has been observed; from the 0.167 average found within the plastocyanin family to an average of 1.90 calculated for the inhibitors/thaumatin II transition. A similar calculation has been carried out for the signal peptide sequences of thionins, which are unrelated to those of the alpha-amylase/trypsin inhibitor family, and an average KA/KS of 0.12 has been obtained. This variation can be largely explained in terms of an empirical index of stability related to amino acid composition and seems to be independent of functional constraints.

Determination of diclofop-methyl and diclofop residues in soil and crops by gas chromatography.

A method is described for the determination of residues of the herbicide diclofop-methyl and its metabolite, diclofop, in soil and crops. The residues were extracted with acetone-light petroleum and extracts were concentrated (diclofop was derivatized to its pentafluorobenzyl derivative), and then the products were purified on a chromatographic column containing alumina, silver-alumina and Florisil. Finally, they were determined by gas chromatography using an electron-capture detector. The detection limits of diclofop-methyl and diclofop were between 0.01 and 0.05 mg/kg. The average recoveries were 76.4-97.2% and 72.8-105.2%, respectively, making the method suitable for statutory residue testing purposes.

Evaluación de un método in vivo para determinar la fibra dietética / Assessment of an in vivo method for determination of dietary fiber

Se presentan los resultados obtenidos al evaluar un método in vivo para determinar la fibra dietética, propuesto por los autores en un trabajo anterior, en dietas que contienen diferentes niveles de salvado de trigo fino como principal portador de fibra. Se estudia la influencia que tiene el período de adaptación sobre los valores de fibra dietética obtenidos, la linealidad de los mismos en el intervalo de trabajo (de 0 a 30 %de salvado), así como las correlación que presentan estos valores de los resultados obtenidos por un método in vivo y con los porcentajes de salvado de trigo al evaluar dietas con distintos niveles de salvado. Se concluye que los valores de porcentaje de fibra dietética total y fibra dietética del portador obtenidos por el método estudiado, aceptable como método de análisis

[Detection and analysis of IgG antibodies in sera of patient with atopic dermatitis (AD) to individual wheat polypeptides by immunoblotting techniques].

To detect IgG antibodies in sera of patients with atopic dermatitis (AD) to individual wheat polypeptides, wheat flour proteins were extracted with tris-citrate buffered saline containing urea and 2-mercaptoethanol (UTC solvent), and fractionated as polypeptides of molecular weights between 12 and 100 KDa. By means of the immunoblotting techniques, specific IgG antibodies to fractionated proteins could be detected in sera from healthy individuals and AD patients. Twenty AD patients' sera with high titers of wheat specific RAST (scores of more than 3) reacted not only to five major wheat components (33-38, 40-45, 55-60, 80, 90-98 KDa), which stained intensively with Coomassie brilliant blue G-250, but also to polypeptides of 14, 16, 22, 29, 70 KDa. Twelve control sera reacted to a limited number of the five major wheat components, and levels of specific IgG antibodies increased with age. The sera of AD patients in the present study contained increased level of IgG antibodies to the five major components, and additionally to several minor components, 70 KDa, 29 KDa and much smaller proteins.

A rapid (less than 10 minute) electrophoresis method for identification of wheat varieties.

Conventional procedures for electrophoretic identification of grain samples according to variety are too slow to permit checking at the time of delivery. The method described permits electrophoretic identification within an hour. It involves extraction of gliadin proteins from crushed grain with 6% urea solution or ethylene glycol, cathodic electrophoresis for 9 min at 300 V in a Micrograd gel (MG 315 from Gradipore Ltd, Sydney, Australia) using sodium lactate buffer (pH 3.1), and staining in Gradipore (at about 50 degrees C). Distinction between a set of Australian varieties was similar to that obtainable with the Australian Standard Procedure.

The three-dimensional structure of the bifunctional proteinase K/alpha-amylase inhibitor from wheat (PK13) at 2.5 A resolution.

Wheat germ contains an inhibitor for proteinase K, called PK13 (Mr approximately 19,600) which simultaneously inhibits alpha-amylase. PK13 was crystallized, space group P21, a = 43.02 (5) A, b = 65.18 (7) A, c = 32.33 (4) A, beta = 112.79 degrees (9), X-ray data were collected to 2.5 A resolution, the structure solved by molecular replacement on the basis of the atomic coordinates of the homologous Erythrina caffra DE-3 inhibitor, and refined with simulated annealing techniques with a current R-factor of 21%. The three-dimensional structure of PK13 is stabilised by two disulfide bridges and has a central beta-barrel with distorted beta-structure. In analogy to related inhibitors, the binding site for proteinase K is assumed to be located on the surface of the protein (amino acid residues 66-67), although the 75-76 peptide bond is cleaved upon binding.

gamma-Purothionins: amino acid sequence of two polypeptides of a new family of thionins from wheat endosperm.

Two homologous sulfur-rich basic polypeptides form wheat endosperm, so-called gamma 1-purothionin and gamma 2-purothionin, are described. Purification involves extraction with volatile solvents and ammonium bicarbonate fractionation followed by reversed-phase high-performance liquid chromatography. The complete primary structure of these two polypeptides has been determined by automatic degradation of the intact, S-carboxymethylated gamma-purothionins and peptides obtained by enzymatic cleavage. gamma 1-Purothionin and gamma 2-purothionnin consist of 47 amino acids with an molecular weight of 5239 and 5151 Da, respectively and 8 cysteines organized in 4 disulfide bridges. They present a high degree of homology among themselves (89% of identity) and are the first two thionin-like polypeptides, so-called gamma-thionins, described from wheat endosperm.

Multielement determination in rice, wheat, and barley by instrumental neutron activation analysis.

INAA has been used for the determination of Na, Mg, Al, Cl, K, Sc, Cr, Mn, Fe, Co, Cu, Zn, As, Se, Br, Rb, Sr, Mo, and W in grains of rice, wheat, and barley, which were collected from different plant fields in Iraq. Samples and standards were irradiated in the IRT-5000 reactor, at neutron fluxes of 2 x 10(13) cm-2.s-1 and 3.2 x 10(11) cm-2.s-1. Interferences of photopeaks with each other were considered, and reaction interferences were calculated and determined experimentally. Accuracy of our method was assessed by the analysis of IAEA standards Wheat Flour and Bovine liver. A good agreement has been achieved between the present results and recommended values. The precision and detection limit were determined for all elements in all types of grain.

A survey of the occurrence of deoxynivalenol in wheat from 1986-1988 harvests in the USSR.

The occurrence of deoxynivalenol (DON; vomitoxin) in wheat from 1986-1988 harvests in the USSR was surveyed. A significant frequency of DON contamination (81.3% of samples analyzed) was observed. A correlation between levels of DON contamination and percentage of Fusarium-damaged kernels was demonstrated. It was shown that DON contamination did not exceed the maximum tolerated level (MTL) established in the USSR (1.0 mg/kg) if samples contained no more than 0.6% of Fusarium-damaged kernels.

Preparative isoelectric focusing of reduced wheat gluten proteins.

Proteins extracted from gluten of the bread wheat cultivar Fiorello 2 in the presence of 2-mercaptoethanol or dithiothreitol were separated by isoelectric focusing in a free solution in a pH 3-10 gradient containing 50% v/v 1-propanol or urea. The collected fractions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis in 10% gels (high and medium molecular weight glutenin subunits) and 16% gels (low molecular weight gliadins). The isoelectric focusing pattern of gluten polypeptides in 50% v/v 1-propanol was comparable to that obtained on two-dimensional gel electrophoresis, based on isoelectric focusing and polyacrylamide gel electrophoresis or nonequilibrium pH gradient electrophoresis and polyacrylamide gel electrophoresis. A similar isoelectric focusing pattern was also observed when 3M urea was used as solvent. New gluten polypeptides, similar in mobility to the high molecular weight subunits of glutenin were detected at acidic pH.

The isolation of high molecular weight DNA from wheat, barley and rye for analysis by pulse-field gel electrophoresis.

A method is presented for the preparation of large DNA molecules from protoplasts embedded in agarose blocks of three different cereals--hexaploid bread wheat (Triticum aestivum), barley (Hordeum vulgare) and rye (Secale cereale). Pulse-field gel electrophoresis (PFGE) analysis of these DNA preparations using a contour-clamped homogeneous field (CHEF) apparatus indicated that the size of the DNA molecules was greater than 6 Mb. DNA samples prepared by this method were shown to be useful for restriction analysis using both frequent and rare cutting enzymes.

Liquid chromatographic determination of total niacin in beef, semolina, and cottage cheese.

A sensitive and precise liquid chromatographic method has been developed for the determination of total niacin in beef, semolina, and cottage cheese. The samples are extracted with Ca(OH)2, cleaned up using C18 Sep-Pak cartridges, and chromatographed on a C18 column using a mobile phase consisting of 23% acetonitrile, 0.10% H3PO4, and 0.10% sodium dodecyl sulfate in water. Niacin is detected using an absorbance detector operating at 254 nm. This chromatographic system produces an unusually sharp peak for niacin, enabling a detection limit of approximately 0.05 mg/100 g. The mean recovery was 99.5% and the coefficients of variation for beef, semolina, and cottage cheese were 3.58, 1.02, and 10.0%, respectively.

[The nutritive value of wheat germ floc]. / Pishchevaia tsennost' khlop'ev pshenichnykh zarodyshei.

The experimental investigation of the food value of wheat germ floc included the study of their chemical composition, biological value, and assimilability of the protein. Basing on the results obtained the authors have made a conclusion on the high food value of wheat germ floc and on their promising use as enriching additives to varying foodstuffs.

Separation of durum wheat proteins by ultrathin-layer isoelectric focusing: a new tool for the characterization and quantification of low molecular weight glutenins.

An isoelectric focusing method capable of resolving all groups of storage protein of the wheat seed, including the most basic low molecular weight glutenin (LMWG), was developed. Ultrathin polyacrylamide gels were used after drying and rehydration with 8 M urea, 50 mM DTE and 2.4% carrier ampholytes (pH 4-9). Densitometric scanning of the isoelectric focusing gels permitted a more accurate and specific quantitation of LMWG components among various cultivars than patterns based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The two main genetic types (i.e. 'gamma-42' and 'gamma-45') of durum wheats were separated on the basis of the proportion in LMWG in storage proteins, but no significant difference was found within these groups. Advantages of the system as regards reliability, high resolution, ability to abolish protein oxidation and preventing reaggregation of LMWG were also discussed.