Availability of Arg,but Not tRNA,Is a Rate-Limiting Factor for Intracellular Arginylation

Protein arginylation, mediated by arginyltransferase ATE1, is a posttranslational modification of emerging biological importance that consists of transfer of the amino acid Arg from tRNA to protein and peptide targets. ATE1 can bind tRNA and exhibits specificity toward particular tRNA types, but its dependence on the availability of the major components of the arginylation reaction has never been explored. Here we investigated key intracellular factors that can potentially regulate arginylation in vivo, including several tRNA types that show strong binding to ATE1, as well as availability of free Arg, in an attempt to identify intracellular rate limiting steps for this enzyme. Our results demonstrate that, while modulation of tRNA levels in cells does not lead to any changes in intracellular arginylation efficiency, availability of free Arg is a potentially rate-limiting factor that facilitates arginylation if added to the cultured cells. Our results broadly outline global pathways that may be involved in the regulation of arginylation in vivo.     

A Modified Microcomputer-Controlled Proportioning Valve Instrument for Programmable Dilution of Gases

Abstract

A commercial VG-400 gas dilution apparatus from Microsensor Systems, Inc. was modified with an updated microcomputer, revised software, electronic mass flow controllers, and a needle valve pressure restrictor in order to enhance its performance. The instrument's maximum linear dilution factor has been extended to 330,000 from the previous practical limit of 100,000 while its dilution accuracy, precision, resolution, and stability have been increased. The modification also decreased the fluctuations in the instrument's output concentrations to ≤ 1.5%.     

Radix-2 FFT butterfly processor using distributed arithmetic

A parallel-data VLSI architecture for computation of the fast Fourier transform (FFT) is described. The processor is based on a computationally efficient vector rotate algorithm. Use of a 2-dimensional pipeline configuration allows a radix-2 butterfly operation to be performed once every system clock cycle (250 ns) to generate real or imaginary transform components. The architecture is considered to be a computationally efficient VLSI approach for high-bandwidth computation of the FFT. The design and performance of an 8-bit FFT butterfly processor are described.