Zur Kenntnis der Benzylpenicilloinsäure

The molar penamaldate value of benzylpenicilloic acid and the influence of large amounts of benzylpenicillin on the estimation of penamaldate values and penamaldate stabilities of benzylpenicilloic acid and ε-(benzylpenicilloyl-α-amido)-caproic acid have been determined. The molar penamaldate values of purified benzylpenicilloate and of benzylpenicillin hydrolyzed in alkali were equal, indicating that benzylpenicillin upon alkaline hydrolysis is converted to penicilloic acid exclusively, with no side reactions occurring to any considerable degree. Benzylpenicilloate mutarotates in neutral solution as well as in alkali, the reaction being unaffected by metal ion complexing with ethylene diamine tetraacetate. ε-(Benzylpenicilloyl-α-amido)-caproate also mutarotates in alkali; no mutarotation occurs however in neutral solution. Different mechanisms of epimerisation have therefore to be considered for the mutarotations of penicilloates and of α-amides of penicilloic acid respectively.     

Role of bound water in biological membrane structure: fluorescence and infrared studies.

Bound water is a major component of biological membranes and is required for the structural stability of the lipid bilayer. It has also been postulated that it is involved in water transport, membrane fusion, and mobility of membrane proteins and lipids. We have measured the fluorescence emission of membrane-bound 1-anilino-8-naphthalenesulfonate (ANS) and the infrared spectra of membranes, both as a function of hydration. ANS fluorescence is sensitive to polarity and fluidity of the membrane-aqueous interface, while infrared absorption is sensitive to the hydrogen bonding and vibrational motion of water and membrane proteins and lipids. The fluorescence results provide evidence of increasing rigidity and/or decreasing polarity of the membrane-aqueous interface with removal of water. The membrane infrared spectra show prominent hydration-dependent changes in a number of bands with possible assignments to cholesterol (vinyl CH bend, OH stretch), protein (amide A, II, V), and bound water (OH stretch). Further characterization of the bound water should allow its incorporation into current models of membrane structure and give insight into the role of membrane hydration in cell surface function.     

Quantitative behandlung kinetischer racematspaltungen bei der umsetzung optisch aktiver 1,1-diphenyl-alkan-2-ole mit racemischem 2-phenylbuttersäureanhydrid

The absolute configurations have been determined of a series of 1,1-diphenyl-alkane-2-ols by kinetic resolution in the reaction with 2-phenylbutyric anhydride (Horeau's method). There is an agreement with the results obtained in a quantitative interpretation of this reaction by the stereochemical analogy model of Ruch and Ugi. The (?)-carbinols have S-configuration. In this special reaction, the effective bulk of the isopropyl substituent must be more important than of the diphenylmethyl group.     

Polymeric amphiphiles with hydrophilic main chain spacers: Studies in monolayers and Langmuir-Blodgett multilayers

A methacrylic lipid was polymerized to form an amphiphilic homopolymer and random copolymers with various levels of acrylic acid comonomers. The behavior of these polymeric lipids was investigated in monolayers at the air-water interface and in Langmuir-Blodgett multilayers on polymer foil supports. The acrylic acid acts as a hydrophilic spacer along the polymer backbone, and improves the ability of the polymer to self-organize into highly ordered monolayers and ultimately LB multilayers. It is shown that the quality and stability of the multilayers increase substantially with the increase in comonomer content.     

Efficient synthesis of gamma-alkylidenetetronic esters by sequential Lewis acid catalyzed

A new approach for the synthesis of gamma-alkylidenetetronic acids and esters is reported which involves Me3SiOTf-catalyzed, regio- and stereoselective cyclization of 4-alkoxy-1,3-bis(trimethylsilyloxy)-1,3-butadienes with oxalyl chloride. The alpha-hydroxy group of the butenolides is efficiently functionalized by palladium-catalyzed cross-coupling reactions via the corresponding enol triflates.     

Recent studies of phase equilibria at high pressures

In its first part the present review considers the dependence of phase transition temperatures of some selected liquid crystals on pressure up to 300 MPa with differential thermal analysis (DTA) and diamond anvil techniques; here also pressure-induced phases as well as tricritical and reentrant phenomena will be discussed. In the second part the most important types of high-pressure phase diagrams of fluid mixtures are shortly reviewed. Here recent results on binary systems (containing trifluoromethane, tetrafluoromethane, nitrogen etc) will be presented and compared with data that are calculated from an equation of state. The results will be discussed in relation to some applications e.g. in fluid extraction and supercritical fluid chromatography (SFC).     

Determination of the spectroscopic quadrupole moments of 33 75 As and 29 63 Cu

The HFS-splitting of the 2s-2p and 3d-2p transitions of muonic arsenic and 3d-2p transitions of copper have been measured with high resolution Ge-semiconductor detectors to determine the nuclear quadrupole moments. A coincidence measurement was performed to separate the 2s-2p transition from the background. The nuclear spectroscopic quadrupole moments were found to be:Q _spec=0.314(6) b for ₃₃ ⁷⁵ AsQ _spec=0.220(15) b for ₂₉ ⁶³ Cu. In addition, generalized Barrett moments were determined in a model-independent analysis of muonic transition energies.     

Structure of high-spin states in 143Pm

High-spin states of ¹⁴³Pm have been studied in the reactions ¹⁴¹Pr(α, 2n)¹⁴³Pm and ¹⁴³Nd(d, 2n)¹⁴³Pm by means of in-beam spectroscopy. The level scheme, spin and parity assignments are based on results obtained from singles γ-ray spectra, conversion electron spectra, prompt and delayed γ-γ coincidences, γ-ray angular distribution and linear polarization measurements. Positive- and negative-parity states with energies up to 4580 keV and spins up to $\text{25}\text{2}$ have been established including 22 new levels. For two nanosecond isomeric states the nuclear spin precession in an external magnetic field was observed providing the following g-factors:

$\text{g(}\text{11?}\text{2}\text{, 959.7 keV)=1.14(9), g(}\text{15+}\text{2}\text{, 1898.3 keV)=1.00(7).}$

The experimental results are well understood by calculations which have been performed in the framework of the shell model (for positive-parity states of 11 valence protons above a Z = 50, N = 82 core) and of the cluster-vibration model (for 3 holes in a Z = 64, N = 82 core). In the case of positive-parity states no evidence for particle-core coupling could be found, while the negative-parity states could qualitatively be understood within the particle-core coupling picture.