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91.
92.
93.
Conformational Analysis of a 20‐Membered Cyclic Peptide Disulfide from Conus virgo with a WPW Segment: Evidence for an Aromatic–Proline Sandwich 下载免费PDF全文
Rajesh Sonti K. N. Shashanka Rao Sudarshan Chidanand Dr. Konkallu Hanumae Gowd Dr. Srinivasarao Raghothama Prof. Padmanabhan Balaram 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(17):5075-5086
A novel peptide containing a single disulfide bond, CIWPWC (Vi804), has been isolated and characterised from the venom of the marine cone snail, Conus virgo. A precursor polypeptide sequence derived from complementary DNA, corresponding to the M‐superfamily conotoxins, has been identified. The identity of the synthetic and natural peptide sequence has been established. A detailed analysis of the conformation in solution is reported for Vi804 and a synthetic analogue, CIDWPWC (DW3‐Vi804), in order to establish the structure of the novel WPW motif, which occurs in the context of a 20‐membered macrocyclic disulfide. Vi804 exists exclusively in the cis W3?P4 conformer in water and methanol, whereas DW3‐Vi804 occurs exclusively as the trans conformer. NMR spectra revealed a W3?P4 type VI β turn in Vi804 and a type II′ β turn in the analogue peptide, DW3‐Vi804. The extremely high‐field chemical shifts of the proline ring protons, together with specific nuclear Overhauser effects, are used to establish a conformation in which the proline ring is sandwiched between the flanking Trp residues, which emphasises a stabilising role for the aromatic–proline interactions, mediated predominantly by dispersion forces. 相似文献
94.
R. Acharya A. G. C. Nair K. Sudarshan A. Goswami A. V. R. Reddy 《Journal of Radioanalytical and Nuclear Chemistry》2008,278(3):617-620
A summary of k
0-based R&D work on neutron activation analysis (NAA), internal mono standard NAA (IM-NAA) and prompt gamma-ray NAA (PGNAA)
is presented. The k
0-based NAA was standardized by characterizing irradiation sites of research reactors, validated using reference materials
and applied to samples of different origin. Recently IM-NAA method was developed, validated for small and large size samples
and applied for the analysis of large size as well as non-standard geometry samples. Studies on PGNAA included characterization
of neutron beam, determinations of detection efficiency and prompt k
0-factors, and analytical applications. 相似文献
95.
In this note, we show that a quasi-free Hilbert module R defined over the polydisk algebra with kernel function k(z,w) admits a unique minimal dilation (actually an isometric co-extension) to the Hardy module over the polydisk if and only if S ?1(z, w)k(z, w) is a positive kernel function, where S(z,w) is the Szegö kernel for the polydisk. Moreover, we establish the equivalence of such a factorization of the kernel function and a positivity condition, defined using the hereditary functional calculus, which was introduced earlier by Athavale [8] and Ambrozie, Englis and Müller [2]. An explicit realization of the dilation space is given along with the isometric embedding of the module R in it. The proof works for a wider class of Hilbert modules in which the Hardy module is replaced by more general quasi-free Hilbert modules such as the classical spaces on the polydisk or the unit ball in ? m . Some consequences of this more general result are then explored in the case of several natural function algebras. 相似文献
96.
This paper describes the details of surface reactions producing >100-nm-thick conjugated polymer films. When 2,5-diiodothiophene films deposited on copper are irradiated with UV at room temperature in Ar environments, oligothiophene films are synthesized. The average conjugation length of the produced film varies from approximately 7 to 3-4 as the film thickness increases from approximately 100 to approximately 500 nm. The X-ray photoelectron spectroscopy analysis of the produced films reveals evidence for the formation of organo-copper intermediate species at the copper-monomer film interface and their diffusion from the copper surface into the monomer film during the photochemical process. A one-dimensional diffusion-reaction model is presented to explain the formation, diffusion, and reaction of organo-copper intermediates in the multilayer film during the photochemical reaction. The model simulation results qualitatively explain the decrease of the Ullmann coupling contribution in the photochemical reaction with the film thickness. 相似文献
97.
98.
In contrast to the traditional thermally-activated Ullmann coupling, a photo-activated Ullmann coupling for facile synthesis of oligothiophene and polythiophene films and micropatterns is reported. 相似文献
99.
D. Chandra Shekhar Santosh K. Gupta K. Sudarshan R. M. Kadam T. P. Chaturvedi 《Journal of Radioanalytical and Nuclear Chemistry》2017,313(3):547-553
Nanocrystalline ThO2:Sm3+ was synthesized using wet-chemical route and characterized using X-ray diffraction (XRD), photoacoustic (PA) and photoluminescence (PL) spectroscopy. PA absorptions of Sm3+ doped samples are found to be quite weak as compared to Nd3+, while PL of Sm3+ was intense. As the energy gap between lowest luminescent levels and highest non-luminescent level in samarium ion is around 7000 cm?1; it is highly fluorescing compared to Nd3+ which has close by levels. Through photoacoustic data it was pointed out that large covalent character exists in ThO2:Nd3+ compared to ThO2:Sm3+. 相似文献
100.
We prove a conjecture of Zassenhaus that every normalized torsion unit of the integral group ring ZG of a finite group G is rationally conjugate to a group element for some metabelian groups including metacyclic groups G containing a normal cyclic group A such that G/A is cyclic of prime power order. The relative prime case was done in [11].
Received: 21 April 2005 相似文献