Maize proteins

Of these materials zein, the maize protein, has been used for plastics on a small scale. It can be cross-linked by formaldehyde but curing times are very long. Complicated bleaching processes have led to the production of almost colourless samples in the laboratory but the process cannot readily be extended to large-scale operation. The cured product has a greater water resistance than casein. Proteins from soya bean, castor bean and blood have also been converted into plastic masses but each have the attendant dark colour. 

Maize proteins do have the ability to develop in a similar way to wheat. The use of maize in Latin America is not too surprising as the plant is native of that region. 

Saz and Marina [148] published a comprehensive review on HPLC methods and their developments to characterize soybean proteins and to analyze soybean proteins in meals. In the case of soybean derived products, a number of papers dealing with cultivar identification [149,150], quantification of soybean proteins [151-154], detection of adulteration with bovine milk proteins [151,155-158], and characterization of commercial soybean products on the basis of their chromatographic protein profile [159,160] have been published in the last years. Other studies deal with the analysis of soybean proteins added to meat [161-165], dairy [151,165-167], and bakery products [156,163,168,169]. The same research group developed perfusion RP-HPLC methods for very rapid separation of maize proteins (3.4 min) and characterization of commercial maize products using multivariate analysis [170], and for the characterization of European and North American inbred and hybrid maize lines [171]. 

Bovine proalbumin Mouse antibody H chain Chicken lysozyme Bee promellitin Drosophila glue protein Zea maize protein 19 Yeast invertase Human influenza virus A... 

If these results can be relied on, it suggests that the different behavior of wheat and maize proteins may depend on differences in amino acid composition/structure of the functional proteins rather than differences in their relative proportions. How these differences might influence the Tg is an area that offers a challenge for future research. Of course. 

Regenerated protein fibers exist as random coils, e.g., peanut protein, zein (maize protein), casein, and egg albumin. They convert to pleated sheet structures on drawing. 

RP-HPLC also rapidly became important and widely used. Early studies showed resolution of wheat and maize proteins by RP-HPLC to be equal or superior to that of other methods [7]. For example, gliadin was resolved into more than 50 peaks and shoulders in 50min on a Cig column at 60 C [53]. RP-HPLC is also more rapid, sensitive, and reproducible than SE-HPLC it gives good quantitation and recovery and it is suitable for both preparative and analytical separations. Proteins resolve primarily on the basis of differences in surface hydrophobicity therefore, RP-HPLC complements techniques such as gel electrophoresis based on size or charge [7,93,94],... 

Pellagra is now recognized as a multifactorial disease and the vitamin status of nicotinic acid is questionable. The body is able to synthesize nicotinic acid from tryptophan so that nicotinic acid only becomes a dietary essential when the tryptophan content of the diet is low. The fact that maize proteins are relatively poor in tryptophan, and that the nicotinic acid it contains is in a form which is not readily available, would seem to explain the association of pellagra and the use of maize as a staple foodstuff. For nutritional purposes 60 mg tryptophan are believed to be equivalent to 1 mg of nicotinic acid and the recommended intake for an adult male is given as 18 mg of nicotinic acid or its equivalent. Primary nicotinic acid deficiency is unlikely to occur in this country where appreciable amounts of animal products are consumed and where flour must, by law, contain 1-6 mg nicotinamide per 100g. 

Maize protein has a higher biological value than was at one time thought, but the use of maize as a staple food is associated with pellagra (page 164). 

Leudne Leucine occurs in all common proteins, usually in amounts of 7-10% (average content is 7.5%). Cereals contain a variable amount of leucine, wheat proteins contain about 7% and maize proteins about 13%. Free leucine forms in larger amounts during cheese ripening due to bacterial activity. 

Aspartic add and aspart hic The average content of aspartic add in proteins is 5.5% the average content of asparagine is 4.4%. Aspartic add is the major amino acid of animal proteins known as globuhns and albumins (6-10%). Vegetable proteins contain 3-13% aspartic add, mainly in the form of asparagine (e.g. wheat proteins contain about 4% and maize proteins about 12%). 

The zein test developed by Gotte [6] is based on the solubilization by surfactants of a maize protein which is normally insoluble in aqueous solution, unless denaturated. The protein is incubated with the surfactant solution for 1 h, at a constant temperature and under slight shaking at the end of incubation, the soluble fraction is separated from the insoluble one by centrifugation and filtration. Solubilized zein is assayed. The more irritating the surfactant, the more zein will be denaturated and solubilized. 

This approach has been used to study the transfer of spin-labeled phosphatidylcholine mediated by maize protein (Kader, unpublished) or spin-labeled monogalactosyldiacylglycerol facilitated by spinach protein (Nishida and Yaraada, 1986). 

Isoelectric point - As indicated above, the lipid transfer proteins from plants are mainly basic. The determination of pHi values by chromatofocusing or isoelectric focusing gave values of 8.8 for maize protein, higher than 10.5 for castor bean protein and around 9 for spinach protein (Table 1). The isoelectric points of the various isoform of lipid transfer proteins have not been determined. However, very low values were found for acidic proteins from castor bean (from 5.4 to 6.6) or spinach leaf (around 4.5). 

The main problem for such a model is to demonstrate the binding of phospholipids on the transfer protein. Binding of phosphatidylcholine has been found with basic proteins from maize (Douady et al., 1982) and spinach (Kader et al., 1984) while Tanaka and Yamada (1982) observed a binding of phosphatidylcholine and phosphatidylserine on acidic proteins from castor bean. However, this binding, in the case of spinach and maize proteins, is very low. A possible explanation of this observation is that the binding of lipids on the basic protein is reversible and competes with the interaction of lipids with membranes. It is interesting to note that non-specific proteins from animal cells are also unable to bind phospholipids (Kader, 1985). In future experiments, the sites of binding of phospholipids and fatty acids to plant proteins will have to be studied. 

The maize protein of Mr 16,500 represents about 40% of the total membrane proteins (Figure 1). It was chosen for detailed studies (14). 

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