Assessing analytical variability of measurement of vitamin A in corn-soy blend.

Two multilaboratory investigations were conducted by SUSTAIN to assess variability in the measurement of vitamin A, the marker used to verify levels of vitamin premix addition to enriched/fortified food aid products, including the widely distributed corn-soy blend (CSB). CSB specifications identify AACC Approved Method 86-06 or equivalent methods for vitamin A analysis, however there is no requirement to demonstrate equivalency. CSB samples with known and blinded levels of vitamin A and a reference standard were analyzed by 16 laboratories using their respective methods.

Dissimilarity in protein chain elongation factor requirements between yeast and rat liver ribosomes.

Factor requirements for yeast and rat liver ribosomes were determined in several different reactions using either yeast or liver factors. In polymerization assays yeast ribosomes required a factor in addition to elongation factor 1 (EF-1) and elongation factor 2 (EP-2). The third factor (EF-3) requirement was observed with EFs from either yeast or liver for both poly(U)-directed polyphenylalanine synthesis and elongation of endogenous peptidyl-tRNA.

A cycloheximide sensitivity factor from yeast required for N-acetylphenylalanylpuromycin formation.

A protein (factor P) has been isolated from yeast, which was required for sensitivity to cycloheximide of a partially purified polyphenylalanine synthesis system. In the absence of factor P, 10(-3) M cycloheximide was required for 50% inhibition of polyphenylalanine synthesis, while in its presence, 10(-6) M gave 50% inhibition. Coincident with cycloheximide sensitivity was an activity required for EF-2 dependent N-acetylphenylalanylpuromycin (N-AcPhePuro) formation.