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41.
A detailed exposition of spin–spin operator matrix elements is presented in the context of the graphical unitary group approach (GUGA ) to atomic and molecular physics and quantum chemistry. A compendium of subgraph types and formulae is given. Aspects of computer implementation within the structure of the Columbus CI programs is discussed. 相似文献
42.
Petersen M Bondensgaard K Wengel J Jacobsen JP 《Journal of the American Chemical Society》2002,124(21):5974-5982
Locked nucleic acids (LNAs) containing one or more 2'-O,4'-C-methylene-linked bicyclic ribonucleoside monomers possess a number of the prerequisites of an effective antisense oligonucleotide, e.g. unprecedented helical thermostability when hybridized with cognate RNA and DNA. To acquire a detailed understanding of the structural features of LNA giving rise to its remarkable properties, we have conducted structural studies by use of NMR spectroscopy and now report high-resolution structures of two LNA:RNA hybrids, the LNA strands being d(5'-CTGAT(L)ATGC-3') and d(5'-CT(L)GAT(L)AT(L)GC-3'), respectively, T(L) denoting a modified LNA monomer with a thymine base, along with the unmodified DNA:RNA hybrid. In the structures, the LNA nucleotides are positioned as to partake in base stacking and Watson-Crick base pairing, and with the inclusion of LNA nucleotides, we observe a progressive change in duplex geometry toward an A-like duplex structure. As such, with the inclusion of three LNA nucleotides, the hybrid adopts an almost canonical A-type duplex geometry, and thus it appears that the number of modifications has reached a saturation level with respect to structural changes, and that further incorporations would furnish only minute changes in the duplex structure. We attempt to rationalize the conformational steering induced by the LNA nucleotides by suggesting that the change in electronic density at the brim of the minor groove, introduced by the LNA modification, is causing an alteration of the pseudorotational profile of the 3'-flanking nucleotide, thus shifting this sugar equilibrium toward N-type conformation. 相似文献
43.
Wang Zhong-Ming Lin Hua-Kuan Zhou Zhi-Fen Zhu Shou-Rong Chen Yun-Ti Murmann R. Kent 《Transition Metal Chemistry》2000,25(5):562-567
The kinetics of the reaction of CH2O with a quasi-aromatic metal complex (1,1,2,8,9,9-hexamethyl-4,6-dioxa-5-hydro-3,7,10,14-tetraazacyclotetradecane-2,7,10,12-tetraene)copper(II), [Cu(PnAO)-6H]0 (AH), have been studied spectrophotometrically under neutral conditions in 1/3(v/v) MeOH–H2O. The Cu, 2N, 3C quasi-aromatic heterocyclic ring in AH is highly reactive towards CH2O at the central-aromatic-carbon atom, C(12) and the following reaction mechanism is proposed.
The compounds AH, A—CH2OH and A—CH2—A were isolated and identified by i.r spectroscopy and by elemental analysis. The kinetic data supported the proposed reaction sequence. All reactions were second order overall. The rate constants and corresponding activation parameters for every step were obtained and are discussed. 相似文献
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Dr. Subhabrata Chaudhury Dr. Penchala Narasimharao Meka Dr. Monimoy Banerjee Caitlin N. Kent Prof. Dr. Brian S. J. Blagg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(59):14747-14764
The 90 kDa heat shock proteins (Hsp90) are molecular chaperones that are responsible for the folding and/or trafficking of ∼400 client proteins, many of which are directly associated with cancer progression. Consequently, inhibition of Hsp90 can exhibit similar activity as combination therapy as multiple signaling nodes can be targeted simultaneously. In fact, seventeen small-molecule inhibitors that bind the Hsp90 N-terminus entered clinical trials for the treatment of cancer, all of which exhibited pan-inhibitory activity against all four Hsp90 isoforms. Unfortunately, most demonstrated undesired effects alongside induction of the pro-survival heat shock response. As a result, isoform-selective inhibitors have been sought to overcome these detriments. Described herein is a structure-based approach to design Hsp90β-selective inhibitors along with preliminary SAR. In the end, compound 5 was shown to manifest ∼370-fold selectivity for Hsp90β versus Hsp90α, and induced the degradation of select Hsp90β-dependent clients. These data support the development of Hsp90β-selective inhibitors as a new paradigm to overcome the detriments associated with pan-inhibition of Hsp90. 相似文献
47.
Dr. Steffen Bähring Dr. Luis Martín‐Gomis Gunnar Olsen Prof. Dr. Kent A. Nielsen Dr. Dong Sub Kim Dr. Troels Duedal Prof. Dr. Ángela Sastre‐Santos Prof. Dr. Jan O. Jeppesen Prof. Dr. Jonathan L. Sessler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(6):1958-1967
Supramolecular polymers are a class of macromolecules stabilized by weak non‐covalent interactions. These self‐assembled aggregates typically undergo stimuli‐induced reversible assembly and disassembly. They thus hold great promise as so‐called functional materials. In this work, we present the design, synthesis, and responsive behavior of a short supramolecular oligomeric system based on two hetero‐complementary subunits. These “monomers” consist of a tetrathiafulvalene‐functionalized calix[4]pyrrole (TTF‐C[4]P) and a glycol diester‐linked bis‐2,5,7‐trinitrodicyanomethylenefluorene‐4‐carboxylate (TNDCF), respectively. We show that when mixed in organic solvents, such as CHCl3, CH2ClCH2Cl, and methylcyclohexane, supramolecular aggregation takes place to produce short oligomers stabilized by hydrogen bonding and donor–acceptor charge‐transfer (CT) interactions. The self‐associated materials were characterized by 1H NMR and UV/Vis/NIR absorption spectroscopy, as well as by concentration‐ and temperature‐dependent absorption spectroscopy and dynamic light scattering (DLS) analyses of both the monomeric and oligomerized species. The self‐associated system produced from TTF‐C[4]P and TNDCF exhibits a concentration‐dependent aggregation behavior typical of supramolecular polymers. Further support for the proposed self‐assembly came from theoretical calculations. The fluorescence emitting properties of TNDCF are quenched under conditions that promote the formation of supramolecular aggregates containing TTF‐C[4]P and TNDCF. This quenching effect has been utilized as a probe for the detection of substrates in the form of anions (i.e., chloride) and nitroaromatic explosives (i.e., 1,3,5‐trinitrobenzene). Specifically, the addition of these substrates to mixtures of TTF‐C[4]P and TNDCF produced a fluorescence “turn‐on” response. 相似文献
48.
Abstract A number of γ and δ ketonitriles have been synthesized and their reduction with bakers yeast carefully studied. Both 4-oxopentanenitrile and 5-oxohexanenitrile are reduced in moderate yields to the corresponding (S) alcohols of high ee while other substrates gave products of varying optical purities. These alcohols are useful intermediates for the preparation of chiral lactones, including the synthetically important (S)(?)-4-methylbutyrolactone and (S)-(?)-5-hexanolide. 相似文献
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