Characterization of the elusive disulfide bridge forming human Hb variant: Hb Ta-Li β83 (EF7)Gly → Cys by electrospray mass spectrometry

An electrospray mass spectrometric approach to the identification of a human hemoglobin (Hb) variant involving a Cys residue incorporation is presented. In Hb Ta-Li (beta83Gly --> Cys), Cys83 forms inter-molecular disulfide bridges. Routine analysis of the denatured Hb showed the presence of a minor beta chain variant whose mass apparently was 1 Da less than the expected mass difference of 46 Da for a Gly --> Cys substitution. Reduction of the globin chains with dithiothreitol gave an intense monomer with the expected mass difference for the Gly --> Cys substitution. After reprocessing the original raw data from the denatured Hb and taking into account the possibility of dimer formation, a component was revealed whose mass was consistent with a disulfide linked dimer of Ta-Li beta globins. The mutation was localized to peptide betaT10 by analysis of a tryptic digest. Tandem mass spectrometry and DNA sequencing confirmed the Gly --> Cys substitution occurred at residue 83 of the beta chain. Problems encountered in identifying the components in mixtures of monomers and dimers are discussed.     

About Tracing Problems in Dynamic Geometry

Dynamic Geometry is the field of interactively performing geometric construction on a computer. In addition to simulating ruler-and-compass constructions we allow a drag mode. This drag mode allows to move geometric objects that have at least one degree of freedom. The remaining part of the construction should adjust automatically. Thus, during the motion, we have to trace the resulting paths of all geometric objects. This path tracking problem is known as the Tracing Problem from Dynamic Geometry. It combines the step-by-step procedure of doing geometric constructions with the continuous concept of motions. This study is based on the model for Dynamic Geometry used in the interactive geometry software Cinderella. We give a numerical solution to the Tracing Problem based on continuation methods and a reliable algorithm based on real and complex interval arithmetic. Degenerate situations like the intersection of two identical lines lead to critical points in the configuration space and are treated separately.     

Synthese des Makrolid-Antibiotikums (−)-A26771B mit Photolactonisierung als Schlüsselreaktion und Computersimulation als effektive Optimierungshilfe

Synthesis of the Macrolide Antibiotic (?)-A2677IB Using Photolactonization as a Key Reaction and Computer Simulation as an Effective Aid in Optimization The title compound has been synthesized in a sequence of 21 steps starting from phenol. The cyclic skeleton has been built up in the earlier part of the synthesis by photolactonization. This reaction supplies C(6), with a functionality, not present in the target structure, but useful for oxygenation at C(4) and generation of the stereogenic center C(5). The Barton/McCombie reaction provides a product deoxygenated at C(6), but only after an adjacent oxirane ring has been opened at the cost of an increase in the number of overall steps. X-Ray structural information and computational modelling of appropriate molecules proved to be essential to selection of optimal conditions for various transformations.     

Zur Oxydation von Nickel(0)-Komplexen mit Halogenverbindungen des Kobalt(II), Kupfer(II) und Zink(II)

Oxidation of Nickel(0) Complexes by Halogen Compounds of Cobalt(II), Copper(II), and Zine(II) In aceton as a solvent Ni(PPh₃)₄ is oxidized by; cobalt(II) complexes of the type (Ph₃P)₂CoX₂ to nickel(I) compounds. In the case of X = Cl (Ph₃P)₃NiCl and (Ph₃P)₃CoCl separately crystallize, while for X = Br the lattice compound CoNi(PPh₃)₆Br₂ and for X = I CoNi(PPh₃)₅I₂ are formed. CuBr₂ and Ni(PPh₃)₄ react to (Ph₃P)₂NiBr and (Ph₃P)_nCuBr. With (Ph₃P)₂ZnCl₂ also (Ph₃P)₃NiCl is formed But in this case the oxidant is hydrogen chloride originating from hydrolysis. The magnetic moments of the new compounds were measured and their vis and fir spectra compared with those of the simple compounds (Ph₃P)_nNiX (n = 2, 3) and (Ph₃P)₃CoX. The M–X stretching frequencies are assigned. The cobalt (I) complexes (Ph₃P)₃CoCl have identical (distorted tetrahedral) structures, but most probably the nickel (I) complexes have not.     

Stereochemistry of the Conversion of 2‐Phenoxyethanol into Phenol and Acetaldehyde by Acetobacterium sp.

The conversion of 2‐phenoxyethanol to phenol and acetate by the anaerobic bacterium Acetobacterium sp. strain LuPhet1 proceeds through acetaldehyde with concomitant migration of a H‐atom from C(1) to C(2) of the glycolic moiety. Separate feeding experiments with (R)‐ and (S)‐2‐phenoxy(1‐²H)ethanol, prepared via chemoenzymatic syntheses, indicate that the H‐atom involved in the 1,2‐shift is the pro‐S one of the enantiotopic couple of the alcohol function.     

Homoleptic, sigma-bonded octahedral [M(CO)(6)](2+) cations of iron(II), ruthenium(II), and osmium(II). Part 1: Syntheses, thermochemical and vibrational characterizations, and molecular structures as [Sb(2)F(11)](-) and [SbF(6)](-) salts. A comprehensive, comparative study

Homoleptic octahedral, superelectrophilic sigma-bonded metal carbonyl cations of the type [M(CO)(6)](2+) (M = Ru, Os) are generated in the Bronsted-Lewis conjugate superacid HF/SbF(5) by reductive carbonylation of M(SO(3)F)(3) (M = Ru, Os) or OsF(6). Thermally stable salts form with either [Sb(2)F(11)](-) or [SbF(6)](-) as anion, just as for the previously reported [Fe(CO)(6)](2+) cation. The latter salts are generated by oxidative (XeF(2)) carbonylation of Fe(CO)(5) in HF/SbF(5). A rationale for the two diverging synthetic approaches is provided. The thermal stabilities of [M(CO)(6)][SbF(6)](2) salts, studied by DSC, range from 180 degrees C for M = Fe to 350 degrees C for M = Os before decarbonylation occurs. The two triads [M(CO)(6)][SbF(6)](2) and [M(CO)(6)][Sb(2)F(11)](2) (M = Fe, Ru, Os) are extensively characterized by single-crystal X-ray diffraction and vibrational and (13)C NMR spectroscopy, aided by computational studies of the cations. The three [M(CO)(6)][SbF(6)](2) salts (M = Fe, Ru, Os) crystallize in the tetragonal space group P4/mnc (No. 128), whereas the corresponding [Sb(2)F(11)](-) salts are monoclinic, crystallizing in space group P2(1)/n (No. 14). In both triads, the unit cell parameters are nearly invariant of the metal. Bond parameters for the anions [SbF(6)](-) and [Sb(2)F(11)](-) and their vibrational properties in the two triads are completely identical. In all six salts, the structural and vibrational properties of the [M(CO)(6)](2+) cations (M = Fe, Ru, Os) are independent of the counteranion and for the most part independent of M and nearly identical. Interionic C...F contacts are similarly weak in all six salts. Metal dependency is noted only in the (13)C NMR spectra, in the skeletal M-C vibrations, and to a much smaller extent in some of the C-O stretching fundamentals (A(1g) and T(1u)). The findings reported here are unprecedented among metal carbonyl cations and their salts.