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121.
Summary Vibrational spectra of lanthanide oxines have been measured in the far-infrared region. In addition, the similar yttrium complex was investigated for further experimental evidence for the proposed band assignments. The most important metal-oxygen and metal-nitrogen bond vibrations have been attributed to absorptions between 390–350 cm–1 and 210–170 cm–1, respectively.
Ferne IR-Spektren von Lanthanidenkomplexen mit 8-Hydroxychinolin
Zusammenfassung Es wurden die Vibrationsspektren von Lanthanid-Oxinen im fernen IR-Bereich gemessen. Zusätzlich wurde der analoge Yttrium-Komplex untersucht, um die Bandenzuordnungen experimentell zu stützen. Die wichtigsten Metall-Sauerstoff- und Metall-Stickstoff-Bindungsschwingungen wurden den Absorptionen zwischen 390–350 cm–1 und 210–170 cm–1 zugeordnet.相似文献
122.
Wang F Wang Y Polavarapu PL Li T Drabowicz J Pietrusiewicz KM Zygo K 《The Journal of organic chemistry》2002,67(18):6539-6541
The enantiomers of tert-butyl-1-(2-methylnaphthyl)phosphine oxide 1 have been separated using a homemade HPLC column and an analytical gradient system. Vibrational absorption and circular dichroism spectra for both enantiomers have been measured in CD2Cl2 and CH2Cl2 solutions in the 2000-900 cm(-1) region. The fully relaxed potential energy surface of (S)-tert-butyl-1-(2-methylnaphthyl)phosphine oxide, obtained using the B3LYP functional with a 6-31G basis set, indicated two stable conformers with their populations in a approximately 2:1 ratio. The vibrational absorption and VCD spectra are predicted for these two conformers using the B3LYP functional with a 6-31G basis set. The comparison of predicted and experimental spectra indicated that (+)-tert-butyl-1-(2-methylnaphthyl)phosphine oxide is in the (S)-configuration. This assignment is supported by the ab initio prediction of positive optical rotation for the most stable conformer with an (S)-configuration and the nonequivalence sense of the tert-butyl group chemical shift observed in the 1H NMR spectrum of this enantiomer measured in the presence of (+)-(S)-mandelic acid as a chiral solvating agent. 相似文献
123.
Synthesis of Methylenebis(Phosphonate) Analogues of Nucleotide Coenzymes. A Novel Coupling Mechanism
Krzysztof W. Pankiewicz Krystyna B. Lesiak Kyoichi A. Watanabe 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):671-674
Synthesis of P1, P2-disubstituted methylenebis(phosphonate)s as inhibitors of inosine monophosphate dehydrogenase is presented. 相似文献
124.
Andrzej Zwierzak Krystyna Osowska-Pacewicka 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):569-572
Abstract: New organophosphorus equivalents of a2 type N-protected amine synthons are presented. 相似文献
125.
Jerzy T. Wróbel Agnieszka Iwanow Krystyna Wojtasiewicz Halszka Bielawska Barbara Bobeszko 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2)
Abstract Further studies on basic compounds from Nuphar luteum L. Sm. resulted in isolation of a new group of sulfoxides with thiohemiaminal type of structure. 相似文献
126.
Krystyna Wieczorek-Ciurowa K. Gamrat 《Journal of Thermal Analysis and Calorimetry》2007,88(1):213-217
Presented work describes
mechanical treatment as a non-conventional solid-state process for preparation
of some functional materials. Mechanochemical syntheses may be alternative
as waste-free and ecologically safer methods of preparing pigments, composites,
catalysts, biomaterials, which obey main principles of Green Chemistry. 相似文献
127.
An important component of protein–nucleic acid interactions is the formation of salt bridges between cationic amino acid
side chains and the anionic phosphate groups of the nucleic acid. We have used molecular mechanics to study the energetic
and conformational impact of such interactions. Firstly, crystallographic protein–nucleic acid complexes from the Protein
Data Bank were analysed in terms of DNA curvature and the presence of salt bridges. For complexes where the DNA is significantly
bent, the contribution of salt bridges to this curvature was modelled by studying the effect of neutralising the appropriate
phosphate groups. The number and the distribution of salt bridges vary widely for different DNA binding motifs and appear
to have very different effects on DNA. In the case of homeodomain, bZIP and helix–loop–helix proteins, salt bridges induce
DNA bending, whereas for prokaryotic helix–turn–helix proteins the number of salt bridges is much smaller and little bending
is found. By analysing the components of the DNA deformation energy involved in protein binding we show that salt bridges
consistently increase the flexibility of the DNA backbone.
Received: 1 September 2000 / Accepted: 5 January 2001 / Published online: 3 May 2001 相似文献
128.
We present a novel two-step chemical synthesis route to produce of disodium ethylenediaminetetraacetic acid (EDTA) capped and europium doped CdS nanoparticles. First EDTA was applied to chelate with cadmium on the surface of cadmium-rich CdS nanoparticles and act as a capping agent. Further, the purified EDTA-capped particles were used to bind with Eu3+. The purified and redispersed particles were characterized by UV/vis absorption, photoluminescence, TEM and SEM. It was observed that Eu3+ on the nanoparticle surface significantly increased the band gap emission intensity of the CdS nanoparticles. 相似文献
129.
Krystyna Stępień Anna Dzierżęga-Lęcznar Slawomir Kurkiewicz Irena Tam 《Journal of the American Society for Mass Spectrometry》2009,20(3):464-468
Pigmentation of human skin is determined by the presence of melanin, the polymeric pigment that is produced in melanocytes
and transferred to adjacent keratinocytes. Epidermal melanocytes produce two distinct types of melanin pigments: eumelanin,
composed mainly of indole-type monomers, and pheomelanin that contains benzothiazine-type backbone. Eumelanin protects skin
against UV-induced damages, whereas pheomelanin is believed to act as a potent UV photosensitizer and promote carcinogenesis.
In this study, pyrolysis in combination with gas chromatography and mass spectrometry (Py-GC/MS) was applied for structural
studies of the epidermal pigment isolated from the cultured human melanocytes. The analysis was preceded by investigations
of DOPA-originated synthetic eumelanin and pheomelanin standards. This allowed determination of pyrolytic markers for both
types of melanin pigments. To obtain additional information on the natural pigment structure, the samples were thermally degraded
in the presence of tetramethylammonium hydroxide as the derivatizing agent. It was shown that the analyzed pigment from normal
human epidermal melanocytes derived from moderately pigmented skin is of eumelanin type with little incorporation of a pheomelanin
component. The results indicate that Py-GC/MS is a rapid and efficient technique for the differentiation of epidermal melanin
types and may be an alternative to commonly used methods based on chemical degradation. 相似文献
130.
Datta B Schuster GB McCook A Harvey SC Zakrzewska K 《Journal of the American Chemical Society》2006,128(45):14428-14429
A series of polyaniline (PANI) oligomers was constructed from monomer units covalently linked to duplex DNA through N-(2-aminoethyl) groups bonded through cytosines. DNA oligomers containing the aniline monomers were treated with horseradish peroxidase (HRP) and H2O2 under conditions known to cause polymerization of aniline. No change in the absorption spectrum of the DNA was observed for samples containing fewer than four contiguous aniline groups. However, for oligomers containing four, five, or six aniline units, treatment with HRP and H2O2 led to the appearance of absorption features characteristic of the conducting "proton doped" emeraldine oxidation state of PANI. Molecular modeling shows that the DNA is distorted in the region of the PANI, but flanking regions of the DNA maintain their B-form structure. These findings provide a method to exploit the self-recognition, self-assembly, and sequence programmability of DNA for the formation of conducting polymers. 相似文献