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The application of liquid chromatography/mass spectrometry (LC/MS) and LC/MS/MS with electrospray ionization to drug metabolism studies was investigated using S 9788 and various synthesized metabolic products as model compounds to assess the response characteristics with regard to compound lipophilicity and the influence of biological matrix components. The results obtained demonstrate the versatility of the electrospray ionization technique to analyse compounds of widely varying polarity and the power of MS/MS to identify unequivocally metabolic products. These techniques offer a very rapid screening procedure that can be used to identify metabolic products and thus provide important early metabolic information that can be used in the candidate drug selection programme. These procedures were then applied to an in vivo study sample and, using neutral loss MS/MS, it was possible to detect metabolites of S 9788 directly from a crude biological matrix (bile) without prior extraction or chromatography to confirm positively the identity of five important metabolites of S 9788 in the rat.

The near ultraviolet (UV) and visible photodissociation dynamics of BrCl have been explored using the technique of photofragment ion imaging at 26 wavelengths in the range 235 to 540 nm. Ion images of the Cl(2P3/2), Cl(2P1/2), Br(2P3/2) and Br(2P1/2) photofragments reveal both the angular distributions of photofragment velocities (characterized by anisotropy parameters, β) and which of the four possible photofragment pathways are active at different wavelengths. The anisotropy parameters show extensive variation both with wavelength and for the different fragmentation channels, and these variations are interpreted largely in terms of excitations to the A 3Π(1), B 3Π(0+), C 1Π(1) and D(0+) states as the wavelength is reduced. At wavelengths between 235 and 262 nm, the Br(2P1/2)+Cl(2P3/2) channel is dominant and β=2.0±0.1 at 235 nm, characteristic of a parallel parent transition (ΔΩ=0) and supporting previous assignments of the absorption in this wavelength range being due to the D(0+)–X 1Σ+(0+) transition. A minor channel forms Cl(2P1/2)+Br(2P3/2) with an anisotropy indicative of the involvement of an underlying perpendicular absorption (ΔΩ=±1) to a state with Ω=1. Br(2P3/2)+Cl(2P3/2) and Br(2P1/2)+Cl(2P1/2) fragmentation channels are not observed. Excitation in the wavelength range 320 nm to 410 nm results in Cl(2P3/2)+Br(2P3/2) products with an anisotropy parameter of β=−1.0±0.1, consistent with assignment of the strong parent absorption to the C 1Π(1)–X 1Σ+(0+) transition. For photolysis wavelengths longer than 400 nm, the Cl(2P1/2)/Cl(2P3/2) branching ratio increases [with β∼1.0 to 1.4 for the Cl(2P1/2)], β for Cl(2P3/2) becomes less negative (and for λ⩾450 nm, values lie in the range 0 to −0.2) and Br(2P3/2) β-parameters also increase. No formation of Br(2P1/2) is observed. These observations are, in part, consistent with absorption via the B 3Π(0+)–X 1Σ+(0+) transition, although the nonlimiting β-parameter values imply a significant perpendicular contribution to the absorption spectrum. The measured anisotropy parameters for λ⩾410 nm are interpreted in terms of excitation both to an Ω=0 state [B 3Π(0+)] and an Ω=1 state [A 3Π(1) or C 1Π(1)], together with transfer of dissociating flux between states during the dissociation.

1. Rubredoxin isolated from the green photosynthetic bacterium Chloropseudomonas ethylica was similar in composition to those from anaerobic fermentative bacteria. Amino acid analysis indicated a minimum molecular weight of 6352 with one iron atom per molecule. 2. The circular-dichroism and electron-paramagnetic-resonance spectra of Ch. ethylica rubredoxin showed many similarities to those of Clostridium pasteurianum, but suggested that there may be subtle differences in the protein conformation about the iron atom. 3. Mössbauer-effect measurements on rubredoxin from Cl. pasteurianum and Ch. ethylica showed that in the oxidized state the iron (high-spin Fe(3+)) has a hyperfine field of 370+/-3kG, whereas in the reduced state (high-spin Fe(2+)) the hyperfine field tensor is anisotropic with a component perpendicular to the symmetry axis of the ion of about -200kG. For the reduced protein the sign of the electric-field gradient is negative, i.e. the ground state of the Fe(2+) is a [unk] orbital. There is a large non-cubic ligand-field splitting (Delta/k=900 degrees K), and a small spin-orbit splitting (D~+4.4cm(-1)) of the Fe(2+) levels. 4. The contributions of core polarization to the hyperfine field in the Fe(3+) and Fe(2+) ions are estimated to be -370 and -300kG respectively. 5. The significance of these results in interpretation of the Mössbauer spectra of other iron-sulphur proteins is discussed.

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