Search results for "DEP"

Isotopes Trace Biogeochemistry and Sources of Cu and Zn in an intertidal soil

2013

River floodplain soils are sinks and potential sources for toxic trace metals like Cu and Zn. We hypothesize that stable Cu and Zn isotope ratios reflect both the mobilization and the sources of metals. We determined the soil properties, the concentrations and partitioning of Cu and Zn, and variations in δ65Cu and δ66Zn values in a core obtained from an Aquic Udifluvent developed on a freshwater intertidal mudflat of the River Elbe, Germany. The core was sampled at 2 cm intervals to a depth of 34 cm, which corresponds to approximately 9 yr of sedimentation. Elevated concentrations of Cu (up to 320 μg g−1) and Zn (up to 2080 μg g−1) indicated anthropogenic pollution. At the time of sampling …

Solvation chemistry of water-soluble thiol-protected gold nanocluster Au102 from DOSY NMR spectroscopy and DFT calculations

2014

The hydrodynamic diameter of Aum(pMBA)n [(m, n) = (102, 44) and (144, 60)] clusters in aqueous media was determined via DOSY NMR spectroscopy. The apparent size of the same (n, m) cluster depends on the counter ion of the deprotonated pMBA− ligand as explained by the competing ion-pair strength and hydrogen bonding interactions studied in DFT calculations. The choice of the counter ion affects the surface chemistry and molecular structure at the organic/water interface, which is relevant for biological applications.

Synthesis of γ-Amino Acid Esters by 1,4-Addition of Deprotonated α-Aminonitriles and α-(Alkylideneamino)nitriles to α,β-Unsaturated Esters.

2007

α-Aminonitriles and α-(alkylideneamino)nitriles can serve as readily available α-aminocarbanion equivalents. Their conjugate addition to α,β-unsaturated esters followed by reduction furnishes polysubstituted γ-amino acid esters in moderate to high yield.

Stereoselektive synthese von D-α-hydroxycarbonsäuren bzw. D-α-hydroxycarbonsäuren enthaltenden depsipeptiden aus L-aminosäuren

1985

Abstract Depsipeptides containing D-α-hydroxy carboxylic acids are efficiently synthesized by the reactions of L-α-halo-carboxylic acid esters (obtained from L-amino acids) with caesium salts of N-protected amino acids.

Synthese sterisch gehinderter Peptide und Depsipeptide nach einem Säurechlorid-Verfahren mit 2-Phosphonioethoxycarbonyl-(Peoc-)Aminosäuren und -Hydro…

1982

2-(Triphenylphosphonio)ethoxycarbonyl-(Peoc-)aminosauren 1 und -hydroxysauren 5 werden mit Oxalylchlorid in bei Raumtemp. stabile Saurechloride 2 bzw. 6 ubergefuhrt. Mit diesen aktivierten Verbindungen werden sterisch gehinderte Amidbindungen — z. B. in den geschutzten Valin-Peptiden 3a—g und in Hydroxyacyl-Dipeptiden 7 — hergestellt. Nach Schutzgruppenabspaltung aus der voll geschutzten Form 7a entsteht so die Sporidesmolsaure B (9a), die in ihren Eigenschaften mit dem Abbauprodukt aus dem Sporidesmolid I ubereinstimmt. Trotz zweimaliger Anwendung der Saurechlorid-Kondensation ist keine Racemisierung eingetreten. Syntheses of Sterically Hindered Peptides and Depsipeptides by Means of an Ac…

1992

A structural investigation is described of poly(L-lactic acid) by best fitting of powder X-ray diffraction patterns. The examined sample shows the already known pseudo-orthorhombic α-form, and it was possible to determine the location of the two 103 polymeric helices in the unit cell and the size distribution of the crystallites. Furthermore, a study is reported of the crystallization kinetics of the above cited polymer by light depolarization measurements in an optical microscope. The crystallization kinetic constants in bulk were evaluated in a temperature range (70–165°C) wider than that previously resulting from measurements of radial growth of spherulites.

Spectroscopic behavior of metal–drug complexes. Infrared spectra of Cu(II) dimer complexes with acetazolamide (H2acm) and an analogue sulfonamide (B-…

1999

Abstract The infrared spectra of the drugs H2acm and B-H2ats, and their copper(II) dimer complexes with stoichiometries [Cu(acm)(NH3)2(OH2)]2·H2O and [Cu(B-ats)(NH3)2]2 are reported and discussed. The Raman spectra of H2acm and B-H2ats are also reported. An assignment of H2acm and B-H2ats modes in the complexes is proposed in comparison with the modes of the free ligands. The spectral modifications due to the deprotonation and coordination effects are analyzed. The ν(N–H) modes of the sulfonamido, carbonamido and Nring–H of the imine tautomer have been accurately assigned. Important information about the S–O and S–N vibrations has been obtained.

Complexes of tryptophan dipeptides with the R2Sn(IV)2+ ion (R=Me, Ph): Spectroscopic studies, solution properties and structural implications

1995

Tryptophan dipeptides such as L-tryptophyl-L-alanine (H 2 TrpAla), L-tryptophyl-L-tyrosine (H 2 TrpTyr), L-tryptophyl-L-tryptophan (H 2 TrpTrp), along with L-histidyl-L-tyrosine (H 2 HisTyr), were reacted with R 2 SnO (R=Me, Ph) yielding the corresponding complexes. The complexes have been characterized by IR and 119 Sn Mossbauer spectroscopy in the solid state and by 1 H and 13 C NMR in CD 3 OD solutions. Monomeric species were detected, with the tin atom arranged in a pentacoordinated trigonal-bipyramidal structure. The dipeptides are coordinated via the terminal amino group, deprotonated peptide nitrogen and terminal carboxylate group. No side-chain appears to be involved in bonding. Det…

Blockcopolymere aus 2-Isopropenylnaphthalin und Hexamethylcyclotrisiloxan, 7

1985

Anionic polymerization of 2-isopropenylnaphthalene (2-IPN), with butyllithium in THF at −78°C was terminated with ethylene oxide and the resulting terminal alkoxide was used to initiate the polymerization of hexamethylcyclotrisiloxane (D3) at +40°C. This led to the formation of AB-block copolymers which were coupled to ABBA-block copolymers by addition of dichlorodimethylsilane. ABBA-blockcopolymers were obtained with contents of polymethylsiloxane (poly(DMS)) between 77 and 84% of weight and block molecular weights between 1 700 and 27 000 (poly(2-IPN)) and 13 000 and 240 000 (poly(DMS)). Phase separation in polymer films casted from different solvents was studied by electron microscopy an…

Quantitative study of the capture of silver nanoparticles by several kinds of soils

2018

The capacity of different soils to capture silver nanoparticles (AgNPs) by measuring changes of an AgNP intrinsic property such as the plasmon for the first time, was studied. In-tube solid-phase microextraction (IT-SPME) coupled on-line to capillary liquid chromatography (CapLC) with diode array detection (DAD) was employed for measuring the interactions between soil and in-contact AgNP dispersions. Its achieved LOD 9 pM assures quantitative retention measurements and selectivity for soil lixiviation was suitable. Electronic microscopy was employed for corroborating the entrapped Ag into the soils. Capture % of AgNPs was calculated in compost (>99%), mountain (>99%), orchard (15±1%) and ur…