Fused silica capillary deactivation with D4 in the presence of oxygen

A new, simple procedure to deactivate fused silica capillaries without hydrothermal treatment is proposed. Based on high temperature reactions of octamethylcyclotetrasiloxane (D₄) in the presence of oxygen, this procedure results, upon coating with dimethylsilicone (SE-30), in columns which give almost symmetric peaks for as little as 150 pg of critical compounds, such as decylamine, thereby demonstrating very high inertness. A mechanism of the deactivation procedure, which, in contrast to previously developed procedures, is based on thermal reactions under aerobic conditions, is proposed.     

Determination of cisplatin and related platinum complexes in plasma ultrafiltrate and urine by high-performance liquid chromatography with on-line radioactivity detection

A reversed-phase ion-pair chromatographic method with on-line radioactivity detection for the simultaneous determination of 195mPt-labelled cisplatin and related platinum complexes has been developed. With this system a good resolution of various radiolabelled platinum complexes can be achieved. The detection limit of the radioactivity detector is 10 ng of cisplatin (specific activity of 15 MBq/mg cisplatin) per millilitre of urine or plasma ultrafiltrate. The detector response is independent of both the chemical structure of the platinum complexes and the matrix composition of the samples. This method may serve as a reference system for other high-performance liquid chromatographic systems with less specific and sensitive detectors.     

InclusiveK *0(890) and\bar K*^0 (890) production on beryllium byK − and π− at 175 GeV

The reactions \(K^ - Be \to {}^(\bar K^) *^0 (890)X,\pi ^ - Be \to {}^(\bar K^) *^0 (890)X\) , have been studied in a 175 GeV unseparated hadron beam in the kinematic range 0<x _F <1.0 andp _T ² <5 GeV². Integrated cross-sections and the dependence of the cross-sections on the longitudinal and transverse momentum are presented, together with quark counting rules predictions. The nuclear dependence ofK ^? fragmentation intoK ^*0(890) with respect to Feynmanx is investigated from hydrogen to beryllium.     

A preliminary 3D model for cytochrome P450 2D6 constructed by homology model building

Summary A homology model building study of cytochrome P450 2D6 has been carried out based on the crystal structure of cytochrome P450 101. The primary sequences of P450 101 and P450 2D6 were aligned by making use of an automated alignment procedure. This alignment was adjusted manually by matching -helices (C, D, G, I, J, K and L) and -sheets (3/4) of P450 101 that are proposed to be conserved in membrane-bound P450s (Ouzounis and Melvin [Eur. J. Biochem., 198 (1991) 307]) to the corresponding regions in the primary amino acid sequence of P450 2D6. Furthermore, -helices B, B and F were found to be conserved in P450 2D6. No significant homology between the remaining regions of P450 101 and P450 2D6 could be found and these regions were therefore deleted. A 3D model of P450 2D6 was constructed by copying the coordinates of the residues from the crystal structure of P450 101 to the corresponding residues in P450 2D6. The regions without a significant homology with P450 101 were not incorporated into the model. After energy-minimization of the resulting 3D model of P450 2D6, possible active site residues were identified by fitting the substrates debrisoquine and dextrometorphan into the proposed active site. Both substrates could be positioned into a planar pocket near the heme region formed by residues Val³⁷⁰, Pro³⁷¹, Leu³⁷², Trp³¹⁶, and part of the oxygen binding site of P450 2D6. Furthermore, the carboxylate group of either Asp¹⁰⁰ or Asp³⁰¹ was identified as a possible candidate for the proposed interaction with basic nitrogen atom(s) of the substrates. These findings are in accordance with a recently published predictive model for substrates of P450 2D6 [Koymans et al., Chem. Res. Toxicol., 5 (1992) 211].