A note on polydegree (n, 1) rational inner functions,slice matrices,and singularities

Archiv der Mathematik - We analyze certain compositions of rational inner functions in the unit polydisk $$\mathbb {D}^{d}$$ with polydegree (n, 1), $$n\in \mathbb {N}^{d-1}$$ , and...     

The redox chemistry of the covalently immobilized native and low-pH forms of yeast iso-1-cytochrome c

Cyclic voltammetry experiments were carried out on native Saccharomyces cerevisiae iso-1-cytochrome c and its C102T/N62C variant immobilized on bare polycrystalline gold electrode through the S-Au bond formed by a surface cysteine. Experiments were carried out at different temperatures (5-65 degrees C) and pH values (1.5-7). The E degrees ' value at pH 7 (+370 mV vs SHE) is approximately 100 mV higher than that for the protein in solution. This difference is enthalpic in origin and is proposed to be the result of the electrostatic repulsion among the densely packed molecules onto the electrode surface. Two additional electrochemical waves are observed upon lowering the pH below 5 (E degrees ' = +182 mV) and 3 (E degrees ' = +71 mV), which are attributed to two conformers (referred to as "intermediate" and "acidic", respectively) featuring an altered heme axial ligation. This is the first determination of the reduction potential for low-pH conformers of cytochrome c in the absence of denaturants. Since the native form of cytochrome c can be restored, bringing back the pH to neutrality, the possibility offered by this transition to reversibly modulate the redox potential of cytochrome c is appealing for bioelectronic applications. The immobilized C102T/N62C variant, which differs from the native protein in the orientation of the heme group with respect to the electrode, shows very similar reduction thermodynamics. For both species, the rate constant for electron transfer between the heme and the electrode increases for the acidic conformer, which is also found to act as a biocatalytic interface for dioxygen reduction.     

Preparation of phosphinoferrocene carboxamides from isocyanates. Synthesis and structural characterisation of palladium(II) and platinum(II) complexes with 1′-(diphenylphosphino)-1-(N-phenylcarbamoyl)ferrocene

The reaction of in situ generated 1′-(diphenylphosphino)-1-lithioferrocene with isocyanates RNCO affords the respective phosphino-carboxamides Ph₂PfcCONHR (fc = ferrocene-1,1′-diyl, R = cyclohexyl (2), and Ph (3)) in moderate yields. The coordination behaviour of 3 chosen as a representative was studied in palladium(II) and platinum(II) complexes. Depending on the metal precursor and the reaction conditions, the following compounds featuring this ligand as a P-monodentate or an O,P-chelating donor were isolated and characterised by spectroscopic methods (IR, multinuclear NMR and electrospray ionisation MS): trans-[PdCl₂(3-κP)₂] (5), trans-[PtCl₂(3-κP)₂] (6), cis-[PtCl₂(3-κP)₂] (7), [SP-4-4]-[(L^NC)PdCl(3-κP)] (8; L^NC = 2-[(dimethylamino-κN)methyl]phenyl-κC¹), and [SP-4-3]-[(L^NC)PdCl(3-κ²O,P)]SbF₆ (9). Besides, the crystal structures of a phosphine oxide resulting by oxidation of 2, viz Ph₂P(O)fcCONHCy (4), and of complexes 5·2Et₂O and 9 have been determined by single-crystal X-ray diffraction analysis.     

Highly enantioselective addition of diethylzinc to diphenylphosphinoyl imines under dual amino Alcohol/Halosilane mediation

Arylethylene-derived, enantiomerically pure amino alcohols have been evaluated as ligands for the dual-catalyzed (amino alcohol/halosilane) enantioselective addition of diethylzinc to diphenylphosphinoyl imines. Among them, the conformationally restricted 9-fluorenone-derived ligand 4c provides the highest enantioselectivities so far reported over a range of substrate imines.     

Squeezing the ground vibrational state of diatomic molecules

We study the squeezing of minimal width vibrational wave packets of diatomic molecules, like Na₂, by using several laser schemes that couple the ground and excited electronic configurations of the molecule. The different schemes imply diabatic and adiabatic laser transformations, or a combination of both, whose efficiency and required physical resources are compared and analyzed.     

Control of cytochrome C redox potential: axial ligation and protein environment effects

Axial iron ligation and protein encapsulation of the heme cofactor have been investigated as effectors of the reduction potential (E degrees ') of cytochrome c through direct electrochemistry experiments. Our approach was that of partitioning the E degrees ' changes resulting from binding of imidazole, 2-methyl-imidazole, ammonia, and azide to both cytochrome c and microperoxidase-11 (MP11), into the enthalpic and entropic contributions. N-Acetylmethionine binding to MP11 was also investigated. These ligands replace Met80 and a water molecule axially coordinated to the heme iron in cytochrome c and MP11, respectively. This factorization was achieved through variable temperature E degrees ' measurements. In this way, we have found that (i) the decrease in E degrees ' of cytochrome c due to Met80 substitution by a nitrogen-donor ligand is almost totally enthalpic in origin, as a result of the stronger electron donor properties of the exogenous ligand which selectively stabilize the ferric state; (ii) on the contrary, the binding of the same ligands and N-acetylmethionine to MP11 results in an enthalpic stabilization of the reduced state, whereas the entropic effect invariably decreases E degrees ' (the former effect prevails for the methionine ligand and the latter for the nitrogenous ligands). A comparison of the reduction thermodynamics of cytochrome c and the MP11 adducts offers insight on the effect of changing axial heme ligation and heme insertion into the folded polypeptide chain. Principally, we have found that the overall E degrees ' increase of approximately 400 mV, comparing MP11 and native cytochrome c, consists of two opposite enthalpic and entropic terms of approximately +680 and -280 mV, respectively. The enthalpic term includes contributions from both axial methionine binding (+300 mV) and protein encapsulation of the heme (+380 mV), whereas the entropic term is almost entirely manifest at the stage of axial ligand binding. Both terms are dominated by the effects of water exclusion from the heme environment.     

Pump-dump iterative squeezing of vibrational wave packets

The free motion of a nonstationary vibrational wave packet in an electronic potential is a source of interesting quantum properties. In this work we propose an iterative scheme that allows continuous stretching and squeezing of a wave packet in the ground or in an excited electronic state, by switching the wave function between both potentials with pi pulses at certain times. Using a simple model of displaced harmonic oscillators and delta pulses, we derive the analytical solution and the conditions for its possible implementation and optimization in different molecules and electronic states. We show that the main constraining parameter is the pulse bandwidth. Although in principle the degree of squeezing (or stretching) is not bounded, the physical resources increase quadratically with the number of iterations, while the achieved squeezing only increases linearly.     

Binuclear Oxidative Addition of Hydrogen in Diamidonaphthalene-Bridged Diiridium Complexes

Binuclear iridium(ii) complexes readily activate H ₂ , in contrast to the behavior of related diiridium(I ) species. The reaction occurs at the pocket of the binuclear complex to produce dihydridoiridium(III ) complexes containing a bridging and a terminal hydride. Due to their Brønsted acidity, these dihydrido complexes can react with a second molecule of H₂ to form trihydrido complexes. This process implies the heterolytic activation of hydrogen.     

Sub-half-cycle polarization gates in ultra-short laser pulses induced by non-linear propagation effects

We demonstrate the possibility of imprinting a controlled ultra-fast time-varying ellipticity on few-cycle laser pulses through the non-linear propagation in a thin anisotropic crystal. The method is based on the self- and cross-phase modulation induced by the third-order (Kerr) non-linearity when the pulse propagates through the crystal. The feasibility of this technique is demonstrated through the numerical integration of the Maxwell equations, showing the possibility of producing a sub-half-cycle temporal gate of linear polarization. In comparison with alternative approaches, our method results in a polarization gate with higher efficiency, and also it can be controlled by changing the polarization axis of the laser pulse at the entrance of the crystal. We finally demonstrate the efficiency of this scheme in the generation of single attosecond pulses. PACS 42.81.Gs; 42.65.Re; 32.80.Wr