Electrochemistry of unfolded cytochrome c in neutral and acidic urea solutions

The present investigation reports the first experimental measurements of the reorganization energy of unfolded metalloprotein in urea solution. Horse heart cytochrome c (cyt c) has been found to undergo reversible one-electron transfer reactions at pH 2 in the presence of 9 M urea. In contrast, the protein is electrochemically inactive at pH 2 under low-ionic strength conditions in the absence of urea. Urea is shown to induce ligation changes at the heme iron and lead to practically complete loss of the alpha-helical content of the protein. Despite being unfolded, the electron-transfer (ET) kinetics of cyt c on a 2-mercaptoethanol-modified Ag(111) electrode remain unusually fast and diffusion controlled. Acid titration of ferric cyt c in 9 M urea down to pH 2 is accompanied by protonation of one of the axial ligands, water binding to the heme iron (pK(a) = 5.2), and a sudden protein collapse (pH < 4). The formal redox potential of the urea-unfolded six-coordinate His18-Fe(III)-H(2)O/five-coordinate His18-Fe(II) couple at pH 2 is estimated to be -0.083 V vs NHE, about 130 mV more positive than seen for bis-His-ligated urea-denatured cyt c at pH 7. The unusually fast ET kinetics are assigned to low reorganization energy of acid/urea-unfolded cyt c at pH 2 (0.41 +/- 0.01 eV), which is actually lower than that of the native cyt c at pH 7 (0.6 +/- 0.02 eV), but closer to that of native bis-His-ligated cyt b(5) (0.44 +/- 0.02 eV). The roles of electronic coupling and heme-flattening on the rate of heterogeneous ET reactions are discussed.     

Electromechanical effects in ferroelectric liquid crystalline polymers

Electric fields can induce mechanical vibrations in planar aligned sandwich cells of ferroelectric liquid crystals. Measurements on a polysiloxane and a polyacrylate side chain polymer proved that the electromechanical effect also exists in ferroelectric liquid crystalline polymers. The main characteristics of the electromechanical responses of these polymers are described and compared to the response of low molecular weight ferroelectric liquid crystals. According to the proposed interpretation, the vibrations in the direction parallel to both the smectic layers and cell substrates are due to coupling between the director rotation and the flow, while the resonances in the vibrations normal to the plates are connected to layer deformations.     

Sulfito- und Thiosulfato-Komplexe des Kobalts(III) mitα-Benzildioxim Überα-Dioximinkomplexe der Übergangsmetalle, 52. Mitt.

Some new ligand exchange reactions of [Co(diph·H)₂Cl(H₂O)] and [Co(diph·H)₂(SO₃)(H₂O)]^– complexes with N₃ ^–, S₂O₃ ^2– and with aromatic and heterocyclic amines were carried out. A series of derivatives of the types [Co(diph·H)₂(SO₃)X] ^n– (X=N₃ ^–, S₂O₃ ^2– oramine) and [Co(diph·H)₂(S₂O₃)₂]^3– were described and characterized. Some structural problems are resolved and discussed on the basis of UV and IR spectral data.     

Preparation and electron spin resonance study of copper(II) complexes with sugar type ligands

A series of copper(II) complexes with sugar type ligands (polyalcohols, sugar acids, di- and trisaccharides) was prepared. The compositions of the complexes were determined by standard analytical methods. The results showed that carboxylato and deprotonated alcoholic hydroxy groups participate in the complex formation. The EPR spectra and magnetic susceptibility data reflected the formation of species containing isolated copper(II) centers indicating that in those molecules which contain two copper ions, these are separated by sugar ligands.     

Escape of a Uniform Random Walk from an Interval

We study the first-passage properties of a random walk in the unit interval in which the length of a single step is uniformly distributed over the finite range [−a,a]. For a of the order of one, the exit probabilities to each edge of the interval and the exit time from the interval exhibit anomalous properties stemming from the change in the minimum number of steps to escape the interval as a function of the starting point. As a decreases, first-passage properties approach those of continuum diffusion, but non-diffusive effects remain because of residual discreteness effects. PACS: 02.50.C2, 05.40.Fb     

Separation of amino acids with simulated moving bed chromatography*

Authors have constructed an automatized four-column large laboratory scale (I.D. = 50 mm, L = 500 mm) simulated moving bed (SMB) equipment. The applied model system for separation of biomolecules is glycine, L-phenylalanine, water and Sepabeads SP825 adsorbent. The authors determined the adsorption equilibrium data and the packing characteristics. The operating conditions of SMB equipment were calculated with the help of the Morbidelli variables. During the SMB experiments, glycine and L-phenylalanine were separated in water on Sepabeads SP825 with an average particle size 0.3 mm at temperatures 20 degrees C and 60 degrees C. The measurement series were carried out on a four-column three-zone open loop SMB. Both L-phenylalanine and glycine were produced with more than 99.9% (m/m) purity and 99% yield at productivity 1.7-3.7, with productivity 3.7-8.1 mg/(g adsorbent h) in case of 2-1-1-0 column configuration. The measured and the calculated data agreed well.     

Zur Bestimmung von Mikrogrammengen Thorium in Silicatgesteinen, Sedimenten und anderen Materialien nach vorangehender Anreicherung des Thoriums mittels Ionenaustausches

Zusammenfassung Die vorliegende Methode erlaubt es, Mikrogrammengen von Thorium in verschiedenartigen Mineralen nach dessen Anreicherung an dem stark sauren Kationenaustauscher Dowex 50 (H⁺-Form) aus ascorbinhaltiger 1 n Salzsäure und nachfolgendem Auswaschen störender Ionen (Titan und Zirkonium) mit 0,1 m Citronensäure zu isolieren, so daß eine einfache und genaue spektrophotometrische Bestimmung des Thoriums nach der Thorinmethode möglich wird. Von gegebenenfalls anwesenden größeren Chrommengen wird durch Extraktion mittels TTA-Benzollösung getrennt. Auf Grund einer Reihe von Mineralanalysen konnte die Verwendbarkeit dieser Methode bestätigt werden.Herrn Prof. Gustaf Arrhenius, University of California, Scripps Institution of Oceanography, La Jolla, Calif., gewidmet.     

Amino Acid Functionalized Superparamagnetic Nanoparticles Inhibit Lysozyme Amyloid Fibrillization

Nanoparticles have great potential to be used in various biomedical applications, including therapy or diagnosis of amyloid-related diseases. The physical and chemical properties of iron oxide superparamagnetic nanoparticles (MNPs) functionalized with different amino acids (AAs), namely, with lysine (Lys), glycine (Gly), or tryptophan (Trp), have been characterized. The cytotoxicity of nanoparticles and their effect on amyloid fibrillization of lysozymes in vitro was also verified. The AA-MNPs under study are nontoxic to human SHSY5Y neuroblastoma cells. Moreover, the AA-MNPs were able to significantly inhibit lysozyme amyloid fibrillization and destroy amyloid fibrils. Kinetic studies revealed that the presence of AA-MNPs affected lysozyme fibrillization, namely, the lag phase and steady-state phase of the growth curves. The most effective activities were observed for Trp-MNPs, which revealed the importance of aromatic rings in the structure of AAs used as coating agents. The obtained results indicate the possible application of these AA-MNPs in the treatment of amyloid diseases associated with lysozyme or other amyloidogenic proteins.     

Ring transformations of β-lactam-condensed 1,3-benzothiazines to isoquinoline and thiazole derivatives by sulfur extrusion and addition sequences

The ring transformations of dichloro-β-lactam-fused 2-aryl-1,3-benzothiazines with sodium methoxide were investigated. With 2 equiv of base, the dichloro-β-lactam derivatives underwent rearrangement and dihydro-1,4-benzothiazepines, 3,4-substituted isoquinolines and substituted thiazole disulfides were isolated. A possible reaction mechanism is proposed for the simultaneous formation of the novel products. The formation of isoquinoline and thiazole derivatives can be explained by sulfur extrusion and addition sequences.