Tetramethylammonium-calcium-triazid. Darstellung und Kristallstruktur

[N(CH₃)₄]Ca(N₃)₃,M=240.29, was prepared from aqueous solutions of tetramethylammoniumazide with calciumazide at 298 K. The crystals are tetragonala=936.6(7) pm,c=694.7(5)pm, space group P4/nmm,Z=2, (x)=1.31Mgm^–3. The crystal structure was determined by single crystal x-ray diffraction (234 Mo-K-reflections, =0.469 mm^–1,R=0.064). Calcium is octahedrally coordinated to six azide groups. The octahedra are connected via azide groups to a threedimensional array with the complex ammonium ions between. The terminal nitrogen atoms of the azide groups and the methyl groups are considerably disordered.

     

Die Gasmolekeln Pd2Al2Cl10 und PdAlCl5 als Begleiter von PdAl2Cl8

Gas Molecules Pd₂Al₂Cl₁₀ and PdAlCl₅ as Accompanists of PdAl₂Cl₈ Mass spectrometric observations using a double cell showed that the reaction of gaseous Al₂Cl₆ with solid PdCl₂ besides the known gaseous complex PdAl₂Cl₈ gives PdAlCl₅ and the unexpected complex Pd₂Al₂Cl₁₀. For the equilibrium (with ΔCp? ?1 cal/K) ΔH°(298) = 7.5 kcal/Mol and ΔS°(298) = 5.3 ± 2 cl have been obtained.     

Calorimeters for biotechnology

The isothermal and temperature scanning calorimeters manufactured by Calorimetry Sciences Corporation are briefly described. Applications of calorimetry to determine thermodynamics and kinetics of reactions of interest in biotechnology are described with illustrative examples.     

Analytical procedures for quantification of peptides in pharmaceutical research by liquid chromatography–mass spectrometry

Peptide quantification by liquid chromatography–mass spectrometry (LC–MS) combines the high resolving power of reversed-phase (RP) chromatography with the excellent selectivity and sensitivity of mass spectrometric detection. On the basis of comprehensive practical experience in the analysis of small molecules, pharmaceutical research is developing technologies for analysis of a growing number of peptidic drug candidates. This article is a detailed review of procedures based on LC–MS techniques for quantitative determination of peptides. With the focus on pharmaceutical applications several technologies for sample preparation, various aspects of peptide chromatography, important characteristics of ESI–MS, selectivity of MS-detection modes, the large variability of internal standards, and modern instrumentation are discussed. The demand for reliable, robust, sensitive, and accurate methods is discussed using numerous examples from the literature, complemented by experiments and results from our laboratory.     

Thiol- and disulfide-modified oligonucleotide monolayer structures on polycrystalline and single-crystal Au(111) surfaces

We provide a comprehensive study of single- (ss) and double-strand (ds) oligonucleotides with either 25 or 10 bases or base pairs (bp) immobilized on polycrystalline and single-crystal Au(111) surfaces. The study is based on X-ray photoelectron spectroscopy, cyclic and differential pulse voltammetry, interfacial capacitance data, and electrochemical scanning tunnelling microscopy (in situ STM). The sequences used were the 25-bp sequence from the BRCA1 gene (25-mer), while the 10-bp oligonucleotides contained solely linear adenine and thymine sequences. The oligonucleotides were modified by the dimethoxytrityl group (DMT) via a disulfide group [DMT-S-S-ss25-mer and DMT-S-S-ds(AT)₁₀], a pure disulfide group (A₁₀-S-S-T₁₀), or a thiol group [HS-ss25-mer and HS-ds-(AT)₁₀], all via a hexamethylene linker. The overall pattern suggests strategies for controlled adsorption of DNA-based molecules and recognition of complementary strands or other molecules.     

The fluorescence of biliverdin dimethyl ester

Freshly prepared solutions of biliverdin dimethyl ester ( 2 ) in ethanol showed fluorescence maxima at 710 and 770 nm [Φ_F = 1.1. 10^?4 (room temperature) and 5.0 10^?4 (77 K)]. The maxima of monoprotonated 2 at 77 K were shifted to 725 and 806 nm and the quantum yield was increased to 2.6. 10^?2. This acid effect was reversible by neutralization with base. When a neutral solution was kept standing in the dark at room temperature, or when an acidic solution was neutralized by base, an additional fluorescence maximum at 500 nm with a mirror image excitation spectrum with λ_max = 470 nm developed, which disappeared on addition of acid and which is attributed to a chemical change of 2 .     

UV/Vis-spektroskopische Untersuchungen an Cyclosilanderivaten

UV/Vis-spectra of Cyclosilanes (SiX ₂) _n withX=Cl, Br, I, OMe andn=4, 5, 6 are recorded and interpreted qualitatively. The spectra exhibit increasing influence of the substituents on the Si-Si-bond system within the rings in the order Cl OMe Br I. At the low energy side of the spectra weak absorption bands, possibly due to intramolecular charge transfer transitions, appear. The strong inductive effect of the electronegative substituents is documented by a marked increase of the first IP's compared to permethylcyclosilanes.

     

Zur Stereochemie der Vitamin D3-Epoxide Röntgenstrukturanalyse einer 5,6-7,8-Diepoxidverbindung

Epoxidation of vitamin D₃ with benzonitrile ¦H₂O₂¦ KHCO₃ (Payne's reagent) yields exclusively the 5,6-mono-oxirane2. Further epoxidation with the same reagent gives the 5,6-7,8-bisepoxide3 a. Its stereochemistry and therefore the stereochemistry of2 was established by single crystal X-ray analysis of thep-Brbenzoate3b. Thereby for the first time a directive effect of a homoallylic hydroxyl group during thePayne-epoxidation was established.

Herrn Prof.Mihailovic (Universität Belgrad) mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Susceptibility to Effects of UVB Irradiation on Induction of Contact Sensitivity, Relevance of Number and Function of Langerhans Cells and Epidermal Macrophages

Sensitization on skin exposed to acute low-dose UVB irradiation separates normal humans into two phenotypically distinct groups: One group, following sensitization on UVB-irradiated skin, develops contact sensitivity, designated UVB resistant (UVB-R) and the second group, following sensitization on UVB-irradiated skin, fails to develop contact sensitivity, designated UVB susceptible (UVB-S). To investigate whether UVB susceptibility in humans is related to antigen-presenting activity in the skin we studied the effect of UVB irradiation on the number and function of the epidermal antigen-presenting cells in volunteers identified as UVB-R and UVB-S. Single cell suspensions of epidermal cells from control skin and skin exposed to 3 minimal erythema doses (MED) of UVB 3 days previously were stained for Langerhans cells (CD1a+HLA-DR+) and epidermal macrophages (CD1a-HLA-DR+). The UVB exposure of the skin significantly decreased the percentage of Langerhans cells (UVB-R: n = 7, P < 0.02, UVB-S: n = 6, P < 0.03) and increased the percentage of epidermal macrophages (UVB-R: n = 7, P < 0.03, UVB-S: n = 6, P < 0.03) however to the same degree in both the UVBR and the UVB-S group. To study the effect on Langerhans cell alloreactivity, epidermal cells were harvested immediately after UVB irradiation. However, in both UVB-R and UVB-S subjects the Langerhans cell alloreactivity was blocked to the same degree immediately after UVB irradiation compared to nonirradiated epidermal cells. To determine the effect of UVB irradiation on epidermal macrophages, epidermal cells were harvested 3 days after UVB irradiation. Irradiated epidermal cells from both UVB-R and UVB-S subjects demonstrated a strong antigen-presenting capacity compared to epidermal cells from control skin leading to activation of T cells that mainly secrete interferon (1FN)-γ and not interleukin (IL)-4. In conclusion we found that UVB susceptibility was not correlated with the number of Langerhans cells or epidermal macrophages in the skin at the same time of sensitization. Neither was it correlated with the capacity of Langerhans cells nor UVB-induced epidermal macrophages to activate T cells in vitro.     

Flow injection analysis : Part VI. The determination of phosphate and chloride in blood serum by dialysis and sample dilution

The rapid determination of chloride and inorganic phosphate in blood serum based on continuous flow spectrophotometry was adapted to Flow Injection Analysis by applying dialysis as well as differential dilution of the injected samples. In addition to the manual injection procedure, an automated microsampling unit was developed and used. By continuous dialysis, chloride could be determined reproducibly at a sampling rate of 125 samples per hour at sample volumes of 60 μl or less. A similar sampling rate and high precision were obtained for the determination of inorganic phosphate by using differential dilution.