Gas chromatography method for the characterization of ethanol steam reforming products.

Ethanol steam reforming is a promising reaction for producing fuel cell hydrogen. Depending on catalyst and reaction conditions, mixtures of condensable hydrocarbons and organic and inorganic gases are produced. This paper proposes an economic and effective solution for separating and detecting these compounds employing a gas chromatograph equipped with two columns, two 6-way valves, and two detectors.

Primary and secondary structure dependence of peptide flexibility assessed by fluorescence-based measurement of end-to-end collision rates.

The intrachain fluorescence quenching of the fluorophore 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) is measured in short peptide fragments, namely the two strands and the turn of the N-terminal beta-hairpin of ubiquitin.

Identification of a novel non-carbohydrate molecule that binds to the ribosomal A-site RNA.

We report the identification of a novel compound that binds to the Escherichia coli 16S ribosomal A-site. Binding by the compound was observed using nuclear magnetic resonance and mass spectrometry techniques. We show that the compound binds in the same position in the A-site RNA as occupied by the aminoglycoside class of antibiotics.

Direct probing of zwitterion formation in unsolvated peptides.

Molecular beam electric deflection measurements have been used to determine electric susceptibilities for small unsolvated alanine-based peptides. The electric susceptibility provides information about the charge distribution within the peptide and can be used to distinguish between zwitterionic and canonical forms. Measured electric susceptibilities for WAn peptides (n = 1-5) are similar to those for capped Ac-WAn-NH2 peptides (which cannot form zwitterions).

Mechanism of host-guest complexation by cucurbituril.

The factors affecting host-guest complexation between the molecular container compound cucurbit[6]uril (CB6) and various guests in aqueous solution are studied, and a detailed complexation mechanism in the presence of cations is derived. The formation of the supramolecular complex is studied in detail for cyclohexylmethylammonium ion as guest. The kinetics and thermodynamics of complexation is monitored by NMR as a function of temperature, salt concentration, and cation size.

An antibiotic linked to peptides and proteins is released by electron capture dissociation fourier transform ion cyclotron resonance mass spectrometry.

Desfuroylceftiofur (DFC) is a bioactive beta-lactam antibiotic metabolite that has a free thiol group. Previous experiments have shown release of DFC from plasma extracts after addition of a disulfide reducing agent, suggesting that DFC may be bound to plasma and tissue proteins through disulfide bonds. We have reacted DFC with [Arg(8)]-vasopressin (which has one disulfide bond) and bovine insulin (which has three disulfide bonds) and analyzed the reaction products by use of electron capture dissociation Fourier transform ion cyclotron resonance mass spectrometry (ECD FT-ICR MS), which has previously shown preferential cleavage of disulfide bonds.

Electron capture dissociation and infrared multiphoton dissociation of oligodeoxynucleotide dications.

We report electron capture dissociation (ECD) and infrared multiphoton dissociation (IRMPD) of doubly protonated and protonated/alkali metal ionized oligodeoxynucleotides. Mass spectra following ECD of the homodeoxynucleotides polydC, polydG, and polydA contain w or d "sequence" ions. For polydC and polydA, the observed fragments are even-electron ions, whereas radical w/d ions are observed for polydG.

Electric susceptibility of unsolvated glycine-based peptides.

The DC electric susceptibilities of unsolvated glycine-based peptides, WGn (W = tryptophan and G = glycine) with n = 1-5, have been measured by deflection of a molecular beam in an electric field. These are the first electric deflection measurements performed on peptides. At 300 K the susceptibilities are in the range of 200-400 A(3).

Characterization of amino acid side chain losses in electron capture dissociation.

We have used electrospray ionization (ESI) Fourier-transform ion cyclotron resonance (FTICR) mass spectrometry to characterize amino acid side chain losses observed during electron capture dissociation (ECD) of ten 7- to 14-mer peptides. Side-chain cleavages were observed for arginine, histidine, asparagine or glutamine, methionine, and lysine residues. All peptides containing an arginine, histidine, asparagine or glutamine showed the losses associated with that residue.

A fluorescence-based method for direct measurement of submicrosecond intramolecular contact formation in biopolymers: an exploratory study with polypeptides.

A fluorescent amino acid derivative (Fmoc-DBO) has been synthesized, which contains 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) as a small, hydrophilic fluorophore with an extremely long fluorescence lifetime (325 ns in H2O and 505 ns in D2O under air).