No abstract

A sulfur-containing compound found in acid hydrolysates of proteins was identified 30 years ago as a trisulfide: bis-(2-amino-2-carboxyethyl) trisulfide (cysteine2S3). At that time, studies concerning the chemistry of sulfur-transferring enzyme systems suggested that cysteine2S3 also existed in biological systems. Two decades later, a cystine trisulfide structure was postulated in the regulator protein molecule for the activation of delta-aminolevulinate synthetase. Recently, a trisulfide bond was reported to occur in the minor loop disulfide at Cys182-Cys189 in human growth hormone. We have detected a trisulfide structure in methionyl human growth hormone in the major loop disulfide Cys53-Cys165. The development of mass spectral analyses of high molecular weight molecules, such as proteins, led to the eventual identification of the modification. A tandem mass spectral analysis on a Sciex electrospray instrument localized an addition of 32 Da to the Cys53-Cys165 fragment. Elemental composition was determined by accurate mass measurement obtained by peak matching to a synthetic peptide and established that an extra sulfur atom was involved.

A synthetic DNA fragment of 19 residues was enlarged by the enzymatic addition of deoxyadenylate residues to its 3'-end with calf thymus terminal deoxynucleotidyl transferase. The 3'-terminus of this elongated DNA strand was blocked with 2',3'-dideoxyadenylate to prevent hydrolysis by the 3'-exonuclease function of E. coli DNA polymerase I. This elongated and 3'-blocked fragment was annealed to an oligomeric primer and used as a template for the synthesis of a complementary copy of the synthetic 19-mer. The product of such a repair synthesis was separated by gel filtration and analyzed by nearest neighbor techniques.All template strands were copied with complgte repair in over 90% of the chains. Facile recovery of the elongated template by virtue of its size permitted repetition of the copy process, thus allowing accumulation of the desired strand.

No abstract

An artificial DNA duplex, each strand consisting of 45 monomers, is constructed from chemically synthesized deoxyriboöligonucleotides. The resulting bihelical polymer may code for a modified S-peptide of Ribonuclease A. This is the first synthetic duplex designed to code for a eukaryotic message.