Interactions of proteins with uniform colloidal hematite and chromium hydroxide particles. I. Adsorption

The adsorption of ovalbumin, mg src="/content/vg346089n13m2880/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-globulin, and lysozyme on uniform spherical hematite and chromium hydroxide particles in aqueous media has been studied as a function of the pH at a constant ionic strength. The uptake of ovalbumin and mg src="/content/vg346089n13m2880/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-globulin was greatest at their isoelectric points and differed little at 10^{–2} and 10^{–3} mol dm^{–3} NaNO₃. The adsorption of lysozyme was strongly influenced by the ionic strength.The deposition of ovalbumin on hematite in the presence of Mg (NO₃)₂ was significantly greater than that with NaNO₃ under otherwise comparable conditions. Dialysis experiments with ovalbumin against magnesium nitrate solutions showed Mg²⁺ to be specifically bound to the protein.The shapes of isotherms indicated monolayer coverage for ovalbumin and multilayer coating for lysozyme for both adsorbents. The shapes of isotherms of mg src="/content/vg346089n13m2880/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-globulin on hematite point to a rearrangement of the protein on the particle surface, while a monolayer was found on chromium hydroxide particles.Supported by the NSF Grant CHE-9108420Part of a Ph.D. thesis     

Kraftfeldrechnungen an linearen Oligopyrrolen: 2,2′-Bipyrrol, 2,2′-Furylpyrrol und Prodigiosen

Using a specific force field model, relative stabilities of 2,2mg src="/content/m7823x1g4t80pn6r/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-bipyrrole and 2,2mg src="/content/m7823x1g4t80pn6r/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-furylpyrrole conformers as well as of prodigiosene tautomers, configurations, and conformations, are studied. 2,2mg src="/content/m7823x1g4t80pn6r/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-Bipyrrole adopts anantiperiplanar conformation in accord with other theoretical calculations and experimental findings. Its rotational barrier calculated by this method compares favourably to the one derived by other means. For the parent prodigiosene the (Z)sp,sp arrangement is found to be the most stable one. The two possible tautomers within its dipyrrin fragment do not show a significant energy difference.

     

Tetramethyldisilan-1,2-diyl-verbrückte Dicyclopentadienyl-und Diindenylmetalldichloride der 4. Gruppe – Kristallstruktur von

Tetramethyldisilane-1,2-diyl bridged Dicyclopentadienyl and Diindenyl Metal Dichlorides of the Group 4 Metals – Crystal Structure of mg loading="lazy" alt="equation image" class="section_image" src="/cms/asset/000d98ef-6e39-4521-8098-54751dfe05bb/nueq001.gif"> Dicyclopentadienyl and diindenyl metal dichlorides of the type Cp′? SiMe₂SiMe₂? Cp′MCl₂ (Cp′ = C₅H₄, M = Ti ( 1 ), Zr ( 2 ), Hf ( 3 ); Cp′ = C₉H₇, M = Zr ( 4 ), Hf ( 5 )) were synthesized and characterized by means of their ¹H, ¹³C, ²⁹Si-n.m.r., MS, and IR spectra. The crystal structure of 2 was determined.     

Additions- und SubstitutionsReaktionen an Tetrafluor- und Tetrachlordiboran(4)

Addition and Substitution Reactions at Tetrafluoro- and Tetrachlorodiborane(4) From equimolar mixtures of B₂F₄ and Me_nN(SiMe₃)_3-n (n = 0–3) the mono-addition products 1–4 are formed at low temperatures. By elimination of Me₃SiF the adduct 2 gives the dimeric monosubstituted diborane 8 , which slowly decomposes at room temperature to the aminoborane 6 and (BF)_n. The course of the reactions was studied by means of ¹¹B and ¹⁹F NMR spectroscopy and by measuring the vapor pressures. According to the ¹¹B and ³¹P NMR spectra the reaction of B₂Cl₄ with PCl₅ or [Me₄N]Cl in liquid hydrogen chloride at 0°C does not yield [PCl₄]₂⁺[B₂Cl₆]^2? or [Me₄N]₂⁺[B₂Cl₆]^2? but gives [PCl₄]⁺[BCl₄]^?, PCl₃ and BCl₃ or [Me₄N]⁺[BCl₄]^? and BCl₃ besides (BCl)_n.     

Molekulares S=GeCl2 Matrix-IR-Untersuchungen und ab initio SCF-Rechnungen

The Molecule S?GeCl₂. Matrix IR Investigation and Ab initio SCF Calculation Molecular S?GeCl₂ is found in a matrix reaction between the high-temperature molecule Ge?S and Cl₂. A structure analog to that of phosgene can be derived from the isotopical shifts (⁷⁰Ge/⁷²Ge/⁷³Ge/⁷⁴Ge/⁷⁶Ge and ³⁵Cl/³⁷Cl) within the IR spectra. The normal coordinate analysis results for the Ge?S force constant a value of 4.21 mdyn/Å. The spectroscopic results are confirmed by ab initio SCF calculations.     

Titanocen-cyandithioformiat-Komplexe

The reaction of titanocene dichloride,Cp ₂TiCl₂ (Cp=mg src="/content/q8m723l3lgjn7307/xxlarge951.gif" alt="eegr" align="MIDDLE" BORDER="0">⁵-C₅H₅), with one or two equivalents of sodium cyanodithioformate affords the new mono- or bis(dithiocarboxylato) derivativesCp ₂TiCl(S₂CCN) (1) andCp ₂Ti(S₂CCN)₂ (2). Elimination of sulfur converts2 into the metallacyclicCp ₂TiS₂C₂(CN)₂ (3), which does not react with the diene isoprene, but can be reconverted into the appropriate titanocene dihalides by chlorine or bromine.

     

Linear silver clusters in aqueous solution (clusterites): radiation-induced chemical synthesis and properties

The formation and properties of the products of the radiation-induced chemical reduction of silver ions in aqueous solutions containing sodium polyacrylate were investigated. The absorption spectra of these species exhibit a band at 290 mn and a band in the visible region. The latter shifts from 470 nm to -800 nm with time or after the addition of silver ions. The species obtained (clusterites) arc linear silver clusters bound to the carboxyl groups of the ion exchanger. The red shift of the visible band is due to the increase in their size. The mechanism of the formation and the structure of the clusterites are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1429–1435, June, 1996.     

Strukturelle Abwandlungen anN-Acetylneuraminsäure, 3

From methyl-5-acetylamino-7,8-anhydro-4,9-O-bis-(t-butyldimethylsilyl)-3,5-dideoxy-mg src="/content/m4575158vn7q22n0/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-D-glycero-D-galacto-2-nonulopyranosidonic acid methylester (1) the derivatives1 a and1 b were obtained by removing the 9-O-(t-butyldimethylsilyl)group withBu ₄NF, followed by acetylation. Treatment of1 b with 80% acetic acid and acetanhydride/pyridine yields the 8-epi-N-acetylneuraminic acid derivative2 a and the 7-epi-N-acetylneuraminic acid derivative3 a in a ratio of 3:1 (Scheme 1). The structure elucidation of2 b was achieved by converting2 b via the 4,9-bis-O-(tBDMSi)-8-O-tosyl-derivative2 d into the epoxide1 (Scheme 2). Using the same sequence the epoxides4 and5 were transformed into theN-acetylneuraminic acid derivative6 a and the 7,8-bis-epi-N-acetylneuraminic acid derivative7 a (Scheme 3). After treatment with sodium hydroxide and 0.025m HCl and Dowex 50 H⁺ the 8-epi-, 7-epi- and 7,8-bis-epi-N-acetylneuraminic acids2,3, and7 were obtained. These three compounds were tested withCMP-N-acetylneuraminic acid synthetase.

Herrn KollegenK. Schlögl mit den besten Wünschen zum 60. Geburtstag.     

Molecule-Responsive Fluorescent Sensors of α-Helix Peptides Bearing α-Cyclodextrin, Pyrene and Nitrobenzene Units in Their Side Chains

mg src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-Helix peptides bearing one unit of mg src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-cyclodextrin (mg src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-CD), one unit of pyrene and one unit of nitrobenzene (NB) in their side chains have been designed and synthesized as novel molecule-responsive devices.In both the CD-peptides, mg src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> -PR17 and mg src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> -PL17, the NB unit is separated from the CD unit by two turns of the helix. Two reference peptides (PL17, and -P17,) have also been synthesized. The circular dichroism studies in the peptide absorption region (200–250 nm)of mg src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> -PR17 and mg src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> -PL17 suggestthat the CD-peptides form stablemg src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-helixstructures (83–77%), which was destabilized by accommodating guest molecules (e.g., n-pentanol) into the CD cavity. It suggests that formation of intramolecular host–guest(CD–NB) complex stabilized thehelical structure and exogenous guest molecule excluded the appending NB moiety from inside to outside of the CD cavity, thereby causing destabilization of the helical structure and increasing the random coil content. The ICD spectra of the peptides in the pyrene and nitrobenzene absorption region (250–40 nm) suggest that NB forms inclusion complex with CD. The fluorescence studies revealed that the fluorescence of the pyrene unit is quenched by the NB unit in mg src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> -PR17 and mg src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> -PL17. The fluorescence intensity increases with increasing guest concentration for the CD-peptides.This guest-responsiveenhancement in the fluorescence intensity can be explained in terms of increased distance between the pyrene and NB moieties, which is caused by exclusion of the NB moiety from the CD cavity by guest accommodation. Using the guest-responsive fluorescence quenching properties of the CD-peptides, we have obtained binding constants for various short chain alkanols.mg src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> -PL17 has higher binding affinity to the guest molecules than its isomer, mg src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> -PR17, indicating that the location of functional groups on the peptide scaffold is important in molecule detection.     

Preparation and characterization of theβ-cyclodextrin inclusion complex with sulfafurazole

The 1 : 1 inclusion complex involving sulfafurazole (SF) andmg src="/content/l3m2m67387h07724/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin (mg src="/content/l3m2m67387h07724/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-CD) is prepared by the freeze-drying method and characterized on the basis of its chemical analysis, thermal behavior, infrared spectrum, X-ray powder pattern and¹³C NMR spectrum in DMSO-d₆ solution. The stability constant of the inclusion complex was determined by the solubility method. The effect of cyclodextrin on the UV absorption spectrum of sulfafurazole was also observed.