The adsorption of endothelin 1 to phospholipids is governed by electrostatic interactions: A monolayer and fluorescence study

In order to elucidate the influence on the lipidic environment on the recognition process of its membrane associated receptor, the interactions of the vasoconstrictor peptide endothelin 1 with various phospholipids have been investigated using different lipidic model membranes: monolayers at constant surface pressure, vesicles and micelles. A monolayer study of ET1 adsorbed onto the water surface has shown that the C-terminus of the peptide points towards the aqueous phase. Penetration measurements into lipidic monolayers indicate that ET1 adsorbs to phospholipids with an orientation similar to that of the air–water interface and fluorescence measurements are in agreement with such an orientation of the peptide. This adsorption is selective for neutral phospholipids and indicates that the nature of the phospholipid headgroups is of major importance for the approach of the membrane associated receptor.     

Quantum yields of the mercury photosensitized cis-trans isomerization of 1,3-pentadiene

The quantum yields of thecis trans andtrans cis Hg 6(³P₁) photosensitized isomerizations of 1,3-pentadiene at 100 Torr and 22°C are 0.54±0.02 and 0.42±0.02, respectively. The steady state ratio ([trans]/[cis])_ss is 1.27±0.05 which is almost identical with the ratio of the quantum yields, (ct)/(tc)=1.29±0.10. Thecistrans isomerization is suggested as a useful actinometer for mercury sensitized reactions.

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Hg 6(³P₁) 1,3- 100 22°C 0,54±0,02 0,42±0,02, . ([]/[]) 1,27±0,05, ( )/( )=1,29±0,10. , .

     

alpha and piDL helical states of alternating poly(gamma-benzyl D-L-glutamate) in solution.

As in solid state, strictly alternating poly(gamma-benzyl D-L-glutamate) in solution can adopt two different helical conformations. Besides the alpha helix, a second helical conformation is found at higher temperatures in dioxane and chloroform, the properties of which correspond to that of the piDL4 helix. As the molecules have a finite length a screw sense is favored for both helical forms thus giving rise to optical activity allowing the study of the transconformation by optical rotatory dispersion and circular dichroism besides infrared and dielectric measurements. Thus, as the temperature is raised the equilibria right-left handed alpha helices and alpha-piDL helical forms can be followed. The favored screw senses are determined by the number of interacting side chains for the alpha helix and by the number of hydrogen bonds which are formed in the piDL helical conformation. The side chain-side chain interactions in the alpha helix are experimentally shown to be attractive.     

Gel Chromatography

Gel chromatography can be regarded as a network-limited partitioning of substances. The theory of this method and the preparation and properties of various gel systems are reviewed. Optimization of the method is illustrated for the separation of oligomers.     

Preparation of (AB)n-type block copolymers by use of polyazoesters

Polyesters of the formula, [(OR)_n? O? CO? C(CH₃)₂? N?N? C(CH₃)₂? CO]_m, where (OR)_n are poly(ethylene oxide), Poly(propylene oxide), or PTHF units, were used to prepare block copolymers with styrene. Ester and ether groups were cleaved with HI, NaOCH₃, and diisobutylaluminum hydride. The resulting polystyrene is telechelic with two COOH and OH groups, respectively. The number of styrene blocks per polymer molecule is 3–4.     

Cu(I)/bis(azaferrocene)-catalyzed enantioselective synthesis of beta-lactams via couplings of alkynes with nitrones

As a consequence of the wide-ranging significance of beta-lactams (e.g., use as drugs and as chiral building blocks), a great deal of effort has been dedicated to the development of methods for their stereoselective synthesis. Although considerable progress has been achieved, nearly all of the approaches that have been described are based on the use of chiral precursors; direct catalytic enantioselective routes to beta-lactams are rare as well as limited in scope. In this communication, we establish that, using a new C2-symmetric planar-chiral bis(azaferrocene) ligand, we can generate beta-lactams with very good enantiomeric excess and cis diastereoselection via catalytic enantioselective Kinugasa reactions (couplings of alkynes with nitrones). Appealing attributes of this process include the ready availability of the starting materials, the functional-group tolerance of the reaction, and the convergency of the approach.     

Measurements of branching fractions for B --> K pi and B --> pi pi decays

We report measurements of branching fractions for B --> K pi and B --> pi pi decays based on a data sample of 449 x 10(6) BB[over] pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We also measure the ratios of partial widths for B-->Kpi decays, namely R(c) identical with 2Gamma(B(+) --> K(+) pi(0))/Gamma(B(+) --> K(0) pi(+)) = 1.08+/-0.06+/-0.08 and R(n) identical with Gamma(B(0) --> K(+) pi(-))/2 Gamma(B(0) --> K(0) pi(0)) = 1.08+/-0.08+/-0.08, where the first and the second errors are statistical and systematic, respectively. These ratios are sensitive to enhanced electroweak penguin contributions from new physics; the new measurements are, however, consistent with standard model expectations.