Densitometric and Videodensitometric TLC Determination of Timolol and Betaxolol in Ophthalmic Solutions

JPC – Journal of Planar Chromatography – Modern TLC - A new, accurate, rapid TLC method has been established for determination of timolol maleate (Timohexal 0.1%, Timoptic 0.25%) and...     

Elastic and inelastic scattering of 1.03 GeV 12C projectiles

Elastic scattering cross sections of 86 MeV/N ¹²C ions on ¹²C, ^NATCa, ⁸⁹Y and ²⁰⁸Pb targets has been measured together with inelastic scattering to the 4.4 MeV state of ¹²C. There is some indication for giant (quadrupole) resonance excitation in ⁴⁰Ca. Optical model and DWBA analyses are reported. Nuclear transparency effect is discussed.     

Three particle reactions observed from 10Ne + 12C at 160 MeV

Coincidences between light particles (Z ? 4) and heavy ions (A ? 9) have been measured for the ²⁰Ne + ¹²C reaction at $\text{E}{}_{\mathrm{<mtext>lab</mtext>}}\text{(}{}^{20}\text{Ne}\text{) = 160}\text{MeV}$. α, ¹⁶O events from the ¹²C(²⁰Ne, α¹⁶O)¹²C reaction and α, ²⁰Ne events from ¹²C(²⁰Ne, α²⁰Ne)⁸Be have been found. Energy distributions and angular correlations of these events are consistent with α-decay from the intermediate nuclei ²⁰Ne and ²⁴Mg formed by inelastic scattering and α-transfer in a first reaction step.     

Ueber die Bestimmung der St?rke in Cerealien, Kartoffeln und in der Handelsst?rke

Ohne Zusammenfassung     

Ueber die L?slichkeit der Benzo?s?ure und der Salicyls?ure

Ohne Zusammenfassung     

Oxygen activation and electron transfer in flavocytochrome P450 BM3

In flavocytochrome P450 BM3, there is a conserved phenylalanine residue at position 393 (Phe393), close to Cys400, the thiolate ligand to the heme. Substitution of Phe393 by Ala, His, Tyr, and Trp has allowed us to modulate the reduction potential of the heme, while retaining the structural integrity of the enzyme's active site. Substrate binding triggers electron transfer in P450 BM3 by inducing a shift from a low- to high-spin ferric heme and a 140 mV increase in the heme reduction potential. Kinetic analysis of the mutants indicated that the spin-state shift alone accelerates the rate of heme reduction (the rate determining step for overall catalysis) by 200-fold and that the concomitant shift in reduction potential is only responsible for a modest 2-fold rate enhancement. The second step in the P450 catalytic cycle involves binding of dioxygen to the ferrous heme. The stabilities of the oxy-ferrous complexes in the mutant enzymes were also analyzed using stopped-flow kinetics. These were found to be surprisingly stable, decaying to superoxide and ferric heme at rates of 0.01-0.5 s(-)(1). The stability of the oxy-ferrous complexes was greater for mutants with higher reduction potentials, which had lower catalytic turnover rates but faster heme reduction rates. The catalytic rate-determining step of these enzymes can no longer be the initial heme reduction event but is likely to be either reduction of the stabilized oxy-ferrous complex, i.e., the second flavin to heme electron transfer or a subsequent protonation event. Modulating the reduction potential of P450 BM3 appears to tune the two steps in opposite directions; the potential of the wild-type enzyme appears to be optimized to maximize the overall rate of turnover. The dependence of the visible absorption spectrum of the oxy-ferrous complex on the heme reduction potential is also discussed.