The fragmentation of positively charged gas-phase samples of peptides is used to infer the primary structure of such molecules. In electron capture dissociation (ECD) experiments, very low-energy electrons attach to the sample and rupture bonds to effect the fragmentation. It turns out that ECD fragmentation tends to produce cleavage of very specific types of bonds. In earlier works by this gro...

A protocol is presented for the quantitative conversion of cysteine and cystine residues in proteins to residues of Scyanocysteine, using the reagent 2-nitro-S-thiocyanobenzoic acid (DEGANI, Y., AND PATCHORNIK, A. (1971) J. Org. Chem. 36, 2727). Cleavage of the amino peptide bond of the Scyanocysteine residue is obtained upon exposure to 6 M guanidinium chloride-O.1 M sodium borate, pH 9.0, at ...

Adeninylethylcobalamin (AdeEtCbl) underwent cleavage of the C-Co bond by interaction with apoprotein of diol dehydrase from Klebsiella pneumoniae ATCC 8724, although this analog was quite inactive as coenzyme. Spectroscopic observation indicates that AdeEtCbl was converted to the enzyme-bound hydroxocobalamin without intermediates. The conversion was stoichiometric (1:1) and obeyed the second-o...

In addition to the standard halogen bond formed when NH3 approaches XCN (X = F, Cl, Br, I) along its molecular axis, a perpendicular approach is also possible, toward a π-hole that is present above the X-C bond. MP2/aug-cc-pVDZ calculations indicate the latter geometry is favored for X = F, and the σ-hole structure is preferred for the heavier halogens. The π-hole structure is stabilized by cha...

Concatemer DNA duplexes which contain at the EcoRII restriction endonuclease cleavage sites (formula; see text) phosphodiester, phosphoamide or pyrophosphate internucleotide bonds have been synthesized. It has been shown that this enzyme did not cleave the substrate at phosphoamide bond. EcoRII endonuclease catalyzes single-strand cleavages both in dA- and dT-containing strands of the recogniti...

The peptides produced by the tryptic digestion of S-aminoethylated bovine pancreatic ribonuclease support the generally accepted amino acid sequence for this enzyme and also demonstrate the usefulness as well as some special limitations of the aminoethylation procedure. The relative extents of hydrolysis at different peptide bonds were estimated from the yields of purified peptides. Under the c...