Prolamins solubility

Prolamines—soluble in 70% ethyl alcohol, insoluble in water... 

Cereal proteins when classified by the Osborne sequential extraction method yield four different classes albumins, which are water soluble, globulins, which are soluble in salt solutions, prolamins, which are soluble in alcohol-water mixtures, and glutelins, which are soluble in dilute acid or alkali. Chen and Bushuk added a fifth fraction by dividing the glutelin into two fractions, one soluble in dilute (0.05 m) acetic acid and the other insoluble in this reagent.5... 

Proteins historically have been classified on the basis of their solubility in water (albumins) salt solution (globulins) alcohol (prolamines) and alkali (glutelins) (20). 

Only proteins that contain proline bind polyphenols. Asano et al. (1982) demonstrated that the haze-forming activity of a protein is roughly proportional to the mole percentage of proline it contains (see Fig. 2.3). DNA has codes for exactly 20 amino acids. If each of these were equally present in a protein, there would be 5 mol% of each one. In fact, most proteins have much less proline than this. There are a few exceptions. Casein has about 8 mol% proline and the grain prolamins (proline-rich, alcohol-soluble proteins) are even higher. Hordein, the barley prolamin, contains about 20 mol% proline. As a result, it readily forms haze with polyphenols and is the main beer haze-active (HA) protein. Hordein contains even more glutamine (Q) than proline (P), and often these amino acids are adjacent in the protein (see Fig. 2.4). In fact, the sequence P-Q-Q-P occurs... 

A significantly higher amoimt of protein is found in beans from South Africa compared to beans from Botswana. The amount of protein in beans from Namibia is between the contents from the two other countries (Holse et al., 2010). The variation in protein content might be due to different concentration of nitrogen in the soils. Bower et al. (1988) found that globulins are the most abimdant (53%) protein constituents in morama beans. The beans furthermore consist of albumins (23.3%), prolamins (15.5%), alkali soluble glutelins (7.7%), and acid-soluble glutelins (0.5%). 

Identification of oat (Avena) cultivars by HPLC was first reported by Lookhart and coworkers (153-155) in combined electrophoresis/HPLC experiments. The HPLC technique used was a modification of the procedure described by Bietz (137) for wheat. Generally, the prolamin fraction, i.e., the alcohol-soluble fraction, of oat species generates complex polyacrylamide gel-electrophoresis (PAGE) and RP-HPLC patterns, with increasing complexity as ploidy of the selections increased. Readily (visible) identification of the cultivars was possible only when PAGE and RP-HPLC results were combined. An HPLC procedure for the characterization of the major oat protein fractions was developed by Lapvetelainen et al. (156). Salt-soluble, alcohol-soluble, and alkali-soluble protein fractions were extracted with 0.1 M NaCl, 52% ethanol, and 1% SDS in 0.05 M borate (pH 10), respectively. For the five cultivars examined, RP-HPLC separations of salt- and alkali-soluble proteins were very similar, whereas the prolamin fraction enabled culti-var differentiation, except for very closely related cultivars. 

Nonwater (gluten) and alcohol-soluble (prolamin) fractions from cereal proteins... 

Prolamins are insoluble in water but soluble in 70-80% aqueous alcohol. Upon hydrolysis they yield much proline and amide nitrogen. They are deficient in lysine. Example - Gliadin of wheat and Zein of com. 

Prolamins, a group of storage proteins occurring in cereals. They are soluble in 50-90% ethanol and can be so separated from the alcohol-insoluble glutelins. Prolamins are globular proteins (M, ... 

Zeins, the major storage proteins of maize belonging to the prolamins. In maize, the ethanol-soluble or protamine fraction consists of the zeins (Mr 10-22 kDa) that constitutes as much as half of the total protein of the endosperm. They are characterized by a high content of Glu (23%) and Leu (19%). The amino acid sequence of a representative of the zeins has been derived from the nucleotide sequence of a zein cDNA clone [D. Geraghty et al.. Nucleic Acids Res. 1981, 9, 5163]. 

The various solubility classes of proteins have been mimicked. Thus, one may prepare proteinoids that behave like albumins, globulins, protamines and histones, gliadins, glutelins, or prolamines, etc. 

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