Zein of maize grain. Preparation and characterization]

A laboratory procedure for isolation and purification of zein from grains of 4 varieties of Maize was described. The preparations were characterized by their physicochemical properties. Upon polyacrylamide gel electrophoresis in sodium dodecyl sulphate (SDS), native zein (from INRA 260 hybrid) was resolved into 2 major classes with average molecular weights of 45,000 and 22,000. After reduction with mercaptoethanol zein contained only two subunits of 22,000 and 24,000 daltons. Upon starch gel electrophoresis in 6 M urea at pH 3.5, native zein exhibited five major or medium intensity bands and several minor ones. The latter, under reducing conditions, disappeared to reinforce the major bands or to yield some new minor bands. Amino acid analysis revealed a very low content of lysine. The NH2-terminal amino acids were determined to be threonine and phenylalanine with a preponderance of the former. Zeins isolated from the varieties studied appeared tohave the same NH2-terminal residues and similar amino acid compositions with an arginine/histidine ratio ranging from 1.1 to 1.2. They differed in relative importance of components, detected by electrophoresis in the presence of SDS or urea. Changes in zein characteristics with the grain genotype allow one to conclude that the components of molecular weights of 22,000 and 24,000 consist of several subunits differing in charge and amino acid content.     

Purification and characterization of an iron-binding protein from the blue crab (Callinectes sapidus)

The presence of an iron-binding protein in the hemolymph of the blue crab (Callinectes sapidus) was detected by gel filtration of 59Fe-labeled hemolymph. The iron-binding protein was purified to homogeneity by ion exchange chromatography. 2. This protein has a mol. wt of 155,000 and consists of a single polypeptide chain with an isoelectric point of 5.0. 3. Analysis of the iron-loaded protein indicates that it has a high affinity for iron and the capacity to bind approximately 10 atoms iron/molecule protein. 4. The isolation of a specific iron-binding protein from the blue crab (Callinectes sapidus) provides additional support for the proposal that such proteins are an ancient evolutionary development not necessarily linked to the appearance of iron proteins (hemoglobin and hemerythrin) as a means for oxygen transport.     

High-performance liquid chromatography and ultraviolet spectrophotometry for quantitation of tryptophan in barytic hydrolysates

A procedure for quantitation of tryptophan in feedstuffs is described. It is based on barytic hydrolysis of material at 125 degrees C for 16 h, acidification of hydrolysate to pH 3 with HCl, high-performance liquid chromatography on Nova Pak C18 (Waters Assoc.), and spectrophotometric determination of tryptophan at 280 nm. The recovery of tryptophan from lysozyme added to samples ranges from 98.7 to 100%.     

Conservative N cycling despite high atmospheric deposition in early successional African tropical lowland forests

Plant and Soil - Many applied disciplines have recognized problems related to the practice of data analysis within their own communities. Some of them have even declared the existence of a...