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1.
The conventional Landry‐Moureaux method for selective extraction of maize proteins was modified by reducing the contact time of meal with extractants and by removing 55% 2‐propanol as extractant. The new procedure, coupled with a method for quantitating protein at microgram level, was used for assessing the nitrogen distribution of four soluble protein fractions present in 100‐mg samples of endosperm originating from six maize inbreds and opaque‐2 versions. Proteins extracted with 55% 2‐propanol plus reductant were made up of α‐, β‐, γ‐, and δ‐zeins. Proteins extracted subsequently with salt plus reductant were minor and poor in lysine (1 mol%).They were associated with zeins. Comparison of present data with those available in the literature showed a close similarity for a given genotype between the percentage of total α‐amino nitrogen extracted by 2‐propanol plus reductant than by salt plus reductant under conditions of the modified procedure and that of total Kjeldhal nitrogen extracted by 2‐propanol with and without reductant, and by salt plus reductant, using the conventional procedure. A simplified protocol was described and tested for isolating and quantitating α‐amino nitrogen as nonprotein, true protein, salt‐soluble proteins, zeins, and true glutelins in any sample of maize endosperm.  相似文献   

2.
Two high lysine maize endosperm mutations, opaque-5 (o5) and opaque-7 (o7), were biochemically characterized for endosperm protein synthesis and lysine metabolism in immature seeds. Albumins, globulins, and glutelins, which have a high content of lysine, were shown to be increased in the mutants, whereas zeins, which contain trace concentrations of lysine, were reduced in relation to the wild-type lines B77xB79+ and B37+. These alterations in the storage protein fraction distribution possibly explain the increased concentration of lysine in the two mutants. Using two-dimensional polyacrylamide gel electrophoresis of proteins of mature grains, variable amounts of zein polypeptides were detected and considerable differences were noted between the four lines studied. The analysis of the enzymes involved in lysine metabolism indicated that both mutants have reduced lysine catabolism when compared to their respective wild types, thus allowing more lysine to be available for storage protein synthesis.  相似文献   

3.
Samples of Argentine maize from 12 landraces were analyzed for starch and amylose content and were evaluated for hardness parameters. Amylose contents of these Argentine landraces were generally higher than for typical dent hybrids grown in the United States. Hardness, as estimated by near‐infrared reflectance; from wavelength shift of the near‐infrared transmittance spectrum absorbance maximum (λmax) in the 610–680 nm region; and by percentage of γ‐zein in zein‐2 (determined by reversed‐phase HPLC), correlated well with classical definitions of endosperm type and with amylose content. Starch content correlated negatively with hardness. Flint landraces varied substantially in amylose and starch content. The strong correlation between amylose content and maize endosperm hardness confirms and strengthens previous observations, and may provide a compositional basis for endosperm quality.  相似文献   

4.
To understand the influence of the sorghum and maize endosperm protein matrix honeycomb structure on starch hydrolysis in flours, three‐dimensional fluorescence microscopy was applied to floury and vitreous endosperm flours cooked under various conditions. Cooking caused the collapse and matting of the sorghum and maize vitreous endosperm matrices, with the effect being greater in sorghum. The effect of cooking was rather different in the floury endosperm in that the protein matrices expanded and broke up to some extent. These effects were a consequence of expansion of the starch granules through water uptake during gelatinization. Cooking in the presence of 2‐mercaptoethanol caused an expansion of the vitreous endosperm matrix mesh due to breakage of disulfide bonds in the protein matrix. Mercaptoethanol also caused an increase in the proportion of β‐sheet structure relative to α‐helical structure of the endosperm proteins. Increased energy of cooking caused collapse of the sorghum matrix. Disulfide bonding and an increase in β‐sheet structure occurred with cooking, with the increase in disulfide bonding being greatest in sorghum vitreous endosperm. The tendency for the sorghum protein matrix to collapse and mat more with cooking than the maize matrix appears to be due to greater disulfide bonding. This is responsible for the observed low starch digestibility of cooked sorghum flour as a result of the more disulfide‐bonded protein matrix limiting the expansion of the starch granules and hence amylase access.  相似文献   

5.
Nonzein proteins were analyzed using SDS-PAGE to study their relationship to lysine level in mature endosperm of three isogenic lines and 29 inbred lines. The majority of nonzein proteins are glutelins that contain a relatively high lysine content. Trinitrobenzene-sulfonic acid was used to visualize high-lysine proteins on nitrocellulose membrane. Seven intense yellow bands (high-lysine proteins) were found in the glutelin fraction: 35, 43, 48, 52, 84, 92, and 100 kDa. These seven glutelin proteins were also significantly correlated to each other. Lysine content of the triads correlated with three glutelin proteins (35, 43, and 52 kDa), while lysine content of 29 inbred lines correlated with six glutelin proteins (all except 52-kDa protein). Immunoassays based on these higher lysine glutelin proteins provide an effective screening method in the presence of variable zein levels. Retention or improvement of lysine content is possible using this information in a maize improvement program.  相似文献   

6.
The protein distribution in five gluten samples isolated during and after wet-milling of maize grains (slurry before and after filtration, total industrial gluten meal, and coarse and fine fractions obtained after sieving) was investigated by sequential extraction. Six fractions (FI-FVI), including residue, were isolated. Heating filtered slurry to draw water away did not alter protein distribution. Compared with values reported in the literature for endosperm protein, we found a decrease in FI and FIV, respectively, extracted with salt alone and with reductant, due to proteolysis and partial elimination of nonprotein nitrogen during slurry filtration, and an increase in FII and decrease in FIII, alcohol-soluble proteins extracted without and with reductant, respectively, due to the presence of SO2 in the steeping liquor. Gluten, with respect to the endosperm from which it originated, was richer in zeins (FII + FIII) and glutelins (FV + FVI) due to partial removal of salt-soluble proteins (FI + FIV) during the isolation process.  相似文献   

7.
Development of high‐protein digestibility (HPD)/high‐lysine (hl) sorghum mutant germplasm with good grain quality (i.e., hard endosperm texture) has been a major research objective at Purdue University. Progress toward achieving this objective, however, has been slow due to challenges posed by a combination of genetic and environmental factors. In this article, we report on the identification of a sorghum grain phenotype with a unique modified endosperm texture that has near‐normal hardness and possesses superior nutritional quality traits of high digestibility and enhanced lysine content. These modified endosperm lines were identified among F6 families developed from crosses between hard endosperm, normal nutritional quality sorghum lines, and improved HPD/hl sorghum mutant P721Q‐derived lines. A novel vitreous endosperm formation originated in the central portion of the kernel endosperm with opaque portions appearing both centrally and peripherally surrounding the vitreous portion. Kernels exhibiting modification showed a range of vitreous content from a slight interior section to one that filled out to the kernel periphery. Microstructure of the vitreous endosperm fraction was dramatically different from that of vitreous normal kernels in sorghum and in other cereals, in that polygonal starch granules were densely packed but without the typically associated continuous protein matrix. We speculate that, due to the lack of protein matrix, such vitreous endosperm may have more available starch for animal nutrition, and possibly have improved wet‐milling and dry‐grind ethanol processing properties. The new modified endosperm selections produce a range that approaches the density of the vitreous parent, and have lysine content and protein digestibility comparable to the HPD/hl opaque mutant parent.  相似文献   

8.
Corn distillers' grains with solubles (CDGS), the major coproduct of fermentation of corn to produce ethanol, were extracted with 0.1M NaOH, 0.1% dithiothreitol (DTT), and 0.5% SDS yielding 35% of the total nitrogen and ≈25% of the protein nitrogen. Gel electrophoresis revealed that the extractable proteins contained zein plus other proteins similar to the extractable proteins from corn flour. Although difficult to extract, the proteins isolated from the fermentation coproducts appeared undegraded and apparently survived gelatinization, fermentation, distillation, and drying during the production of ethanol. Extraction of CDGS with 60% ethanol at 60°C yielded 1.5–3.9% of crude zein. When the ethanol contained DTT, yields of crude zein were increased to 3.2–6.6%. Protein contents of the crude zeins were only 37–57%, indicating that lipids and pigments were coextracted with the ethanol. Gel electrophoresis showed that the protein fractions extracted by ethanol contained primarily α-zein whereas the proteins extracted by ethanol + DTT contained α- + β-zein. Further confirmation of the presence of zein in the crude prolamin preparations was obtained by amino acid analyses. The amino acid compositions of the crude zeins paralleled those of commercial zein and α-zein.  相似文献   

9.
In this study, the structure and selected properties of zeins extracted from corn gluten meal (CGM) pretreated by extrusion and removal of starch were investigated. The structure and properties of the zeins from pretreated CGM changed significantly. Pretreatments can decrease the extraction yields of zeins and change the granule shape and size of zein aggregates. The studies indicated that extrusion and removal of starch can significantly decrease the thermal enthalpy (ΔH1 and ΔH2) of zein from 1.94 ± 0.20 to 0.19 ± 0.10 and from 107.20 ± 0.80 to 78.62 ± 2.30 and J/g, respectively. The SDS‐PAGE results confirmed that the molecular weight of zeins from CGM was 24,000 and 27,000, and the molecular weight of zeins did not change with the pretreatment. On the other hand, the circular dichroism spectroscopy results showed that the processing of extrusion and removal of starch can change the secondary structure content of β‐sheets and β‐turns; these results indicated that extrusion and removal of starch can significantly break the secondary structure of zeins. Furthermore, extrusion and removal of starch can change the sulfhydryl content of zeins. The obtained results provided some fundamental information that is useful for further modification of CGM to improve its functional properties and industrial applications.  相似文献   

10.
Protein distribution in endosperm of maize grains differing by their texture, flint or dent, and by their genotype, wild or waxy or amylose-extender, was examined by the successive use of 0.5 M NaCl, 0.5 M NaCl plus 0.6% 2-mercaptoethanol (2ME) at neutral and then alkaline pH, and 55% 2-propanol plus 0.6% 2ME as extractants. Proteins extracted in the presence of 2ME were characterized by their size polymorphism and amino acid composition. Proteins isolated with NaCl plus 2ME at neutral pH corresponded with a mixture of gamma-zein (27 kDa) and glutelin-like proteins. Proteins isolated with NaCl plus 2ME at pH 10 were a mixture of gamma-zeins (27 and 16 kDa) and beta-zeins (14 kDa). Alcohol-soluble proteins consisted of alpha-, beta-, and delta-zeins, alpha subunits being predominant. Zein quantitation was improved by weighing the nitrogen percentage of extracts by their zein content, as estimated from the data on amino acid composition. The data reported by Wolf et al. (Cereal Chem. 1975, 52, 765) were integrated to the results of this work to suggest the occurrence of an inverse correlation between amylose in starch and zeins in proteins.  相似文献   

11.
Seed protein and starch composition determine the efficiency of the fermentation process in the production of grain‐based ethanol. Sorghum, a highly water‐ and nutrient‐efficient plant, provides an alternative to fuel crops with greater irrigation and fertilizer requirements, such as maize. However, sorghum grain is generally less digestible because of extensive disulfide cross‐linking among sulfur‐rich storage proteins in the protein– starch matrix. Thus, the fine structure and composition of the seed endosperm directly impact grain end use, including fermentation performance. To test the hypothesis that kafirin (prolamin) seed storage proteins specifically influence the efficiency of ethanol production from sorghum, 10 diverse genetic lines with allelic variation in the β‐, γ‐, and (δ‐kafirins, including three β‐kafirin null mutants, were tested for ethanol yield and fermentation efficiency. Our selected lines showed wide variation in grain biochemical features, including total protein (9.96–16.47%), starch (65.52–74.29%), and free amino nitrogen (FAN) (32.84–73.51 mg/L). Total ethanol yield (ranging from 384 to 426 L/metric ton), was positively correlated to starch content (R2 = 0.74), and there was a slight positive correlation between protein digestibility and ethanol yield (R2 = 0.52). Increases in FAN content enhanced fermentation efficiency (R2 = 0.65). The highest ethanol producer was elite staygreen breeding line B923296, and the line with the highest fermentation efficiency at the 72 h time point was inbred BT×623. A large‐seeded genotype, KS115, carrying a novel γ‐kafirin allele, was rich in FAN and exhibited excellent short‐term fermentation efficiency at 85.68% at the 20 h time point. However, the overall ethanol yield from this line was comparatively low at 384 L/metric ton, because of insufficient starch, low digestibility, and high crude protein. Multivariate analysis indicated an association between the β‐kafirin allele and variation in grain digestibility (P = 0.042) and FAN (P = 0.036), with subsequent effects on ethanol yield. Reversed‐phase HPLC profiling of the alcohol‐soluble kafirin protein fraction revealed diversity in protein content and composition across the lines, with similarities in peak distribution profiles among β‐kafirin null mutants compared with normal lines.  相似文献   

12.
Thermal properties are among the most important end‐use characteristics of starch from maize (Zea mays L.). Knowledge of the contribution of genotype and environment to the total variance for starch thermal properties is needed to aid in defining a testing strategy for selecting maize with desirable thermal starch properties. Thus, the objectives of this study were 1) to characterize the thermal properties of starches from a group of recently developed Argentine maize inbred lines, and 2) to assess the variability in starch properties attributable to genetic and crop year effects. Twelve inbred lines developed by the National Institute of Agricultural Technology (INTA) in Argentina derived from a wide array of germplasm sources were evaluated. Gelatinization and retrogradation properties were measured by differential scanning calorimetry. Enthalpy means for gelatinization were below means reported in the literature, suggesting possible energy savings when using these starches. The ratio between change in enthalpy for retrogradation and gelatinization was above the mean reported in the literature, suggesting a starch that may be useful as a dietary fiber. Significant environmental effects caused by crop year were detected. Some inbred lines, with smaller observed ranges and standard deviations across environments, may be more stable for some properties.  相似文献   

13.
《Cereal Chemistry》2017,94(6):942-949
Since the discovery of the o2 mutation in maize, many studies have reported the characterization of the protein quality of opaque‐2 genotypes. However, few have reported the properties of their starch. The objective of this study was to characterize flour starch properties of 12 half‐sib families of opaque‐2 maize from Argentina. Chemical composition and thermal and pasting properties of whole grain flour were determined. Nonopaque genotypes were used as a control. Starch content of opaque‐2 genotypes did not show significant differences compared with nonopaque genotypes, yet amylose content was significantly lower. A high variability in pasting and thermal properties was observed in genotypes. Opaque samples showed a significantly higher peak viscosity and a lower pasting temperature compared with nonopaque samples, probably owing to larger and less compact starch granules in the floury endosperm. The higher the gelatinization enthalpy of opaque‐2 genotypes was, the lower the amylose content in relation to nonopaque varieties. Two retrogradation endotherms were observed in DSC analysis: one corresponding to amylopectin crystallization and the other to melting of amylose‐lipid complex. Both enthalpies were considered total starch retrogradation (ΔH RT). A wide range of variation was obtained in ΔH RT in opaque‐2 genotypes, but no significant differences between opaque and nonopaque genotypes were observed. The differences in starch properties found in this study would make it possible to identify opaque‐2 families with particular characteristics for the development of starchy food items adapted to specific processing traits.  相似文献   

14.
The mechanical, physical, and biochemical characteristics of mealy and vitreous endosperm were investigated. Endosperm were obtained from four durum wheat cultivars grown under different nitrogen fertilization designs. The textural properties and the density of the endosperm were measured on hand‐shaped parallelepiped endosperm samples. Endosperm protein content and composition and also gliadin composition were investigated by HPLC. Mechanical tests showed that mealy and vitreous endosperm differed in hardness and vitreousness. Vitreousness increased with nitrogen fertilization supply whereas there was no variation among the different cultivars. Hardness seemed to be linked to genotype and insensitive to nitrogen supply. From this result, we concluded that hardness and vitreousness are not related. Endosperm protein content and gliadin‐to‐glutenin ratio were related to nitrogen supply and increased especially when nitrogen supply was applied at flowering. At the same time, endosperm vitreousness increased. Further biochemical analyses were performed on 270 kernels, mealy or vitreous, hand‐picked from 148 different crops. Results showed that protein content of vitreous endosperm exceeded 9.7% in >90% of the cases. The glia/glu ratio was a less accurate predictor of kernel vitreousness, indicating that, by itself, it cannot account for the change in kernel vitreousness. Endosperm vitreous texture would rise above a threshold content of 9.7% protein within the endosperm.  相似文献   

15.
Phosphorus (P) fertilizers are essential for achieving high crop productivity, but declining soil P reserves and cost of fertilizers suggest that improving crop varieties for improved use efficiency of P be important for sustainability. To explore the possibility of selecting crops suitable for low P conditions, two maize (Zea mays L.) inbred lines, i.e., W22 and W23 were compared for growth, root morphology, and electrophysiological parameters, under hydroponic conditions with either insoluble P source (LP) or soluble P source (HP) in a factorial completely randomized design. Relative shoot biomass of W23 was significantly (38%) greater than that of W22 with LP, while relative root biomass of the two inbred lines did not differ. With LP, the P stress factor was the lowest (25%) and P dissolution in hydroponic solution was the greatest for W23. Root electrophysiological analysis revealed that W23 had 89% greater H+ efflux and 225% greater Ca2+ influx than W22 with LP. The distant elongation zone (DEZ) of W23 root was significantly longer and more shoot‐ward than W22 with LP. Thus, W23, having significantly greater relative shoot biomass, lower P stress factor, greater P dissolution, greater H+ efflux and Ca2+ influx, longer and more shoot‐ward DEZ, was better adapted to low‐P condition compared to W22. In the future, the W23 inbred line can be used for developing low‐P stress resistant varieties to utilize native insoluble soil P efficiently or to produce commercially acceptable yields using lower rates of soluble P fertilizers.  相似文献   

16.
Abstract

Recovery of residual nitrogen (N) from the subsoil by maize (Zea mays L.) was studied by injecting 15N‐labeled nitrate at 110 cm for treatments with and without N fertilizer in a calcareous soil on the North China Plain. The results show that the recovery of 15N‐labeled nitrate diffusing in the 90‐ to 130‐cm soil horizon was 11.9% with N fertilizer application and 6.7% without N application in maize. Nitrogen fertilizer applied to topsoil stimulated growth of maize roots in the subsoil, thus increasing the recovery of 15N‐labeled nitrate. In the relatively dry growing season in this experiment, the 15N‐labeled nitrate did not move downward because there was no downward water flow at 110 cm. Hence, under dry weather conditions, the maize crop can re‐utilize a small part of the residual soil nitrate in deep soil layers. Most of the nitrogen uptake was in the 0‐ to 80‐cm layer during the experiment.  相似文献   

17.
Corn (Zea mays L.) is an important source of protein for humans and animals. Because dent corn is highly responsive to nitrogen (N) fertilization, substantial amounts of N are used for corn production. Application of N fertilizer may reduce protein quality of corn kernels through an increase in zein content. The objective of this study was to determine if corn endosperm characteristics influence the effect of N fertilization on protein quality. In 1988, six corn hybrids differing for endosperm characteristics were grown at two locations in Ohio and with two N rates, 34 and 200 kg/ha. The waxy hybrid had a greater concentration of fraction I protein than the non‐wary hybrid. These two hybrids did not differ for other fractions except fraction III at Columbus. The soft endosperm hybrid had a higher concentration of fraction I protein than the hard endosperms hybrids. Soft and hard endosperm hybrids differed for fraction II protein for the 34 kg N/ha fertilizer rate but not the 200 kg N/ha fertilizer rate. These two classes of hybrids did not differ for fraction III protein. Increasing N fertilizer increased fraction II concentration for all hybrids. Concentrations of the other two protein fractions did not respond to fertilizer rate. The increase in fraction II concentration with N fertilization may result in a decrease of protem quality and feed value. Although all hybrids responded to N fertilizer, some hybrids had bigger increases in fraction II proteins than other hybrids.  相似文献   

18.
A high-throughput method has been developed to allow rapid analysis of maize seed storage proteins by matrix-assisted laser desorption time-of-flight mass spectrometry. The extraction solution containing an organic solvent, a reducing agent, and a volatile base has been optimized to enable extraction of all classes of zein proteins (alpha-, beta-, gamma-, and delta-). A near-saturating concentration of matrix, 2-(4-hydroxyphenylazo)benzoic acid, was necessary to obtain strong peaks for the most lipophilic zeins, the alpha-zeins. Zein proteins with small mass differences, difficult to separate by sodium dodecyl sulfate polyacrylamide gel electrophoresis, were resolved through this analysis. Mass signals corresponding to the 10-kDa delta-, 15-kDa beta-, 16-kDa gamma-, 27-kDa gamma-, and several 19 and 22-kDa alpha-zeins were detected. The zein identities were further confirmed by the association of the number of cysteine residues in each zein MS peak, as determined by iodoacetamide derivatization, with the number predicted from its coding sequence. The relative zein abundance in the zein MS peaks was also correlated with the relative zein EST abundance among endosperm EST libraries. This method was utilized to examine the zein composition of a number of corn inbred lines and opaque mutants.  相似文献   

19.
Kjeldahl analysis is commonly used to measure zein proteins in corn maize (N × 5.7) with no attempt to eliminate contribution from other nitrogen sources. In this study, dry milled corn was extracted with 70% ethanol or 0.1N NaOH and the zein content of the extract measured using capillary electrophoresis in the presence of sodium dodecyl sulfate. The amount of zein protein in alcohol extracts, using this method, was in good agreement with that determined by Kjeldahl nitrogen analysis. However, less than half of the Kjeldahl nitrogen in the alkaline extracts could be attributed to corn zein. Reproducibility expressed as relative standard deviation for migration time and peak area was 0.10 and 1.05, respectively. The technique permits rapid analysis of a large number of samples without interference from other compounds present in the extracts.  相似文献   

20.
For better understanding of mechanisms responsible for genotypic differences in uptake and translocation of cadmium (Cd) in different plant species, two maize (Zea mays L.) inbred lines (B37 and F2) and a bean (Phaseolus vulgaris L.) cultivar (Saxa) were grown in a complete nutrient solution with additional 0.5 μM Cd and 250 μM buthionine sulfoximine (BSO), an inhibitor of PC synthesis, alone or in combination. The maize line B37 had a much higher Cd content in shoots (116.2 mg Cd kg?1 dry wt.) than F2 (32.7 mg Cd kg?1 dry wt.) and bean (1.83 in leaves, and 2.85 mg Cd kg?1 dry wt. in stems), whereas in roots the Cd content was much higher in bean (602.6 mg Cd kg?1 dry wt.) than in maize (427.1 mg Cd kg?1 dry wt. in B37, and 428.2 mg Cd kg?1 dry wt. in F2). Application of BSO markedly decreased Cd contents in roots of bean and maize lines, and also Cd contents in shoots and stem basis of both maize lines, while Cd contents in leaves, stems and stem basis of bean were not reduced by BSO. In root extracts (Tris-HCl buffer, pH 8.0) the proportion of Cd in the soluble fraction was much lower in bean (29.6%) than in the maize lines B37 (58.6%) and F2 (60.1%). Compared with the whole root tissue, Cd contents in the stele of the roots were much lower, especially in bean, and decreased by BSO in both maize lines, but not in bean. Gel-chromatography of root extracts strongly suggested that in the soluble fraction about 80% of the Cd was present as Cd-phytochelatin (PC) complexes in B37, whereas in F2 this Cd fraction accounted for about 50%, and in bean only for a few percent in the soluble fraction, Our results suggest that Cd-PC complexes constitute a mobile form in plants. The lower proportion of Cd in the soluble fraction as well as lower PC production in roots of bean compared to maize lines may be the main reasons for the very low Cd translocation from roots to shoots in bean plants.  相似文献   

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