Two new types of xenon-carbon species: the zwitterion, 1-(Xe+)C6F4-4-(BF3-), and the dication, [1,4-(Xe)2C6F4]2+.

In the 1:1 reaction of XeF(2) with 1,4-(F(2)B)(2)C(6)F(4) in 1,1,1,3,3-pentafluoropropane the insoluble zwitterion 2,3,5,6-tetrafluorophenylene-1-xenonium-4-trifluoroborate, 1-(Xe(+))C(6)F(4)-4-(BF(3)(-)), was formed as the main product (77%) along with the zwitterion, 1-(Xe(+))-cyclo-1,4-C(6)F(6)-4-(BF(3)(-)), the [BF(4)](-) salts of the dication, [1,4-(Xe)(2)C(6)F(4)](2+), and the cation, [1-Xe-cyclo-1,4-C(6)F(6)-4-H](+). The isolation of pure 1-(Xe(+))C(6)F(4)-4-(BF(3)(-)) was feasible after extraction of the byproduct with 27% aq HF. The zwitterion, 1-(Xe(+))C(6)F(4)-4-(BF(3)(-)), was characterized by multi-NMR and Raman spectroscopy and by DSC.

Reactions of dizincocene with sterically demanding bis(iminodi(phenyl)phosphorano)methanes.

Reactions of Cp*(2)Zn(2) with sterically demanding bis(iminodi(phenyl)phosphorano)methanes LH (LH = CH(2)(Ph(2)P=NR)(2) (R = Ph L(1)H, SiMe(3)L(2)H, 2,6-i-Pr(2)C(6)H(3) (Dipp) L(3)H) at ambient temperature occurred with elimination of Cp*H and subsequent formation of the homoleptic complex L(1)(2)Zn(2)1 and the heteroleptic complexes LZnZnCp* (L = L(2)2, L(3)3, L(1)4). 3 is the first structurally characterized heteroleptic organozinc complex with the zinc atoms in the formal oxidation state +1.

Reactions of a β-diketiminate zinc hydride complex with heterocumulenes.

The β-diketiminate zinc hydride MesnacnacZnH (1) reacts with CO(2), C(Ni-Pr)(2) and t-BuNCO at ambient temperature with insertion into the Zn-H bond and subsequent formation of the corresponding formato (2), formamido (3) and formamidinato (4) complexes.

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).

Superelectrophilic tetrakis(carbonyl)palladium(II)- and -platinum(II) undecafluorodiantimonate(V), [Pd(CO)4][Sb(2)F(11)]2 and [Pt(CO)4][Sb(2)F(11)]2: syntheses, physical and spectroscopic properties, their crystal, molecular, and extended structures, and density functional calculations: an experimental, computational, and comparative study .

The salts [M(CO)(4)][Sb(2)F(11)](2), M = Pd, Pt, are prepared by reductive carbonylation of Pd[Pd(SO(3)F)(6)], Pt(SO(3)F)(4) or PtF(6) in liquid SbF(5), or HF-SbF(5). The resulting moisture-sensitive, colorless solids are thermally stable up to 140 degrees C (M = Pd) or 200 degrees C (M = Pt). Their thermal decompositions are studied by differential scanning calorimetry (DSC).

Chromophore-protein interaction controls the complexity of the phytochrome photocycle.

A new protocol for the preparation of recombinant phytochromes results in significantly higher yields which, for the first time, have made kinetic studies possible. Flash photolysis with nanosecond laser excitation reveals that, in recombinant and native phytochromes, the decay kinetics of the primary photoproducts I700i and the kinetics of the formation of the Pfr form are similar. Phycocyanobilin-containing recombinant phytochrome, however, shows only a monoexponential decay of the I700 intermediate with a time constant of approximately 90 microseconds, and a biexponential formation of the Pfr form, albeit with time constants (approximately 13 and 100 ms) somewhat shorter than those from native phytochrome.

[Retino-hypothalamic pathways in vertebrates].

Forty years ago Hollwich (1948) introduced the conception of an "energetic portion of the visual pathway". Contributions to this conception of a direct connection of the retina with the hypothalamus accumulated since then and summarized here in tabular form give rise to the following conclusions: In fish the main hypothalamic termination of retinofugal axons is the nucleus hypothalamicus opticus. It may pass for the suprachiasmatic nucleus of fishes.

Steroid-protein interaction: from past to present.

In this review, the association between biologically active compounds and proteins is seen in the light of axioms expressed by Paracelsus and Paul Ehrlich long ago, and the physiological significance of the interactions is pointed out. Of the various types of proteins that form noncovalent complexes with steroid hormones, only the serum proteins will be discussed. Recent results, obtained in several laboratories, on the physicochemical properties of the human corticosteroid-binding globulin (CBG, transcortin) makes this glycoprotein perhaps the best known one among the steroid-binding serum proteins.

Corticosteroid-binding globulin. A review of some recent aspects.

Among the numerous corticosteroid-binding proteins that have been demonstrated to exist throughout the vertebrates, the corticosteroid-binding globulins (CBG or transcortin) of man and guinea pig have been most thoroughly investigated. Both are glycoproteins that contain one binding site for corticosteroid hormones and other steroids. The binding forces are predominantly of a hydrophilic nature, in addition to hydrophobic interaction.

Steroid-protein interactions. Human corticosteroid-binding globulin: characterization of dimer and electrophoretic variants.

Human corticosteroid-binding globulin (CBG) forms a dimer that was isolated by gel filtration, has full binding affinity and capacity, and can be dissociated to the monomer. Monomeric CBG consists of two distinct molecular variants, which were detected by polyacrylamide gel electrophoresis in the presence and absence of sodium dodecyl sulfate. The two monomeric CBG species were separated by preparative gel electrophoresis and were found to bind cortisol, as well as progesterone, with equal affinity.

Specificity and stability of guinea pig anti-progesterone antibodies.

Antibodies against progesterone were induced in guinea pigs of both sexes by injection of progesterone-y beta-hemisuccinate conjugated to bovine serum albumin (BSA) in a ratio of 16 moles of steroid per mole of protein. The concentration of antibody binding sites for progesterone of the animals studied ranged from 5 to 20 microM. The expected heterogeneity of binding affinity for progesterone was observed with two major populations apparently predominating.

Steroid-protein interactions. Human corticosteroid binding globulin: some physicochemical properties and binding specificity.

Reducing agents (dithiothreitol and beta-mercaptoethanol) significantly decrease the affinity constants of the human corticosteroid-binding globulin (CBG)-cortisol complex in proportion to their concentration; the resulting Ka values are more consistent than those obtained in the absence of the reductants. The effect is reversible. The equilibrium association constants of the CBG complexes with cortisol and progesterone show a relatively broad pH maximum between pH 8 and 11.

Purification and characterization of the corticosteroid-binding globulin of pregnant guinea pig serum.

The corticosteroid-binding globulin from guinea pig pregnancy serum was purified by the sequential use of affinity chromatography, hydroxylapatite chromatography, and gel filtration chromatography at a cumulative yield of 80%. The protein was found to be homogeneous by analytical gel electrophoresis, equilibrium sedimentation ultracentrifugation, immunoelectrophoresis, and stoichiometry (1:1) of steroid binding. Guinea pig corticosteroid-binding globulin has a molecular weight of 43 300 and contains 29% carbohydrate.

Steroid-protein interactions. 40. The effect of fatty acids on progesterone binding to human serum albumin.

Human serum albumin was delipidated by solvent extraction or by treatment with charcoal. Progesterone complexes formed with these albumin preparations had higher association constants than those formed with the untreated samples. The charcoal method of delipidation resulted in somewhat higher affinity constants than extraction with chloroform/methanol.

Alterations in the ultraviolet absorption spectra of steroids upon binding to serum proteins.

Difference spectra of progesterone-binding globulin (PBG) complexes with progesterone and testosterone were measured. The contributions of steroid and protein to the difference spectra were resolved by use of 5alpha-pregane-3,20-dione and dihydrotestosterone to compensate for the perturbation of PBG. The absorption spectra of seven bound steroids all showed increased extinction coefficients, sharpened absorption bands, a small blue shift, and an increased area implying an enhanced transition moment.

Mechanism of steroid binding to serum proteins.

Association and dissociation rate constants of steroid complexes with progesterone-binding globulin (PBG) and with corticosteroid-binding globulin have been determined, utilizing the fluorescence quenching phenomenon observed on steroid binding to protein. Stopped-flow techniques were used in most cases. The dissociation rates of the complexes with steroid-binding proteins of serum are much greater than those of steroid-receptor complexes, in accordance with the biological functions of these two types of proteins.