Design of stapled DNA-minor-groove-binding molecules with a mutable atom simulated annealing method

We report the design of optimal linker geometries for the synthesis of stapledDNA-minor-groove-binding molecules. Netropsin, distamycin, and lexitropsinsbind side-by-side to mixed-sequence DNA and offer an opportunity for thedesign of sequence-reading molecules. Stapled molecules, with two moleculescovalently linked side-by-side, provide entropic gains and restrain theposition of one molecule relative to its neighbor. Using a free-atom simulatedannealing technique combined with a discrete mutable atom definition, optimallengths and atomic composition for covalent linkages are determined, and anovel hydrogen bond zipper is proposed to phase two molecules accuratelyside-by-side.     

Independent collections of translates of boxes and a conjecture due to Grünbaum

A collection ofn setsA ₁, ...,A _n is said to beindependent provided every set of the formX ₁ ... X _n is nonempty, where eachX _i is eitherA _i orA _i ^c . We give a simple characterization for when translates of a given box form an independent set inR ^d. We use this to show that the largest number of such boxes forming an independent set inR ^d is given by 3d/2 ford2. This settles in the negative a conjecture of Grünbaum (1975), which states that the maximum size of an independent collection of sets homothetic to a fixed convex setC inR ^d isd+1. It also shows that the bound of 2d of Rényiet al. (1951) for the maximum number of boxes (not necessarily translates of a given one) with sides parallel to the coordinate axes in an independent collection inR ^d can be improved for these special collections.Daniel Q. Naiman was supported by National Science Foundation Grant No. DMS-9103126. Henry P. Wynn was supported by the Science and Engineering Research Council, UK.     

Bonding in Halide and Interhalide Complexes with Ammonia: Studies by Microwave Spectroscopy and Density Functional Theory

Electron density redistribution and quadrupole coupling constants (QCC) in XY···NH₃ complexes were analyzed. Data on bond lengths and QCC calculated by the BHandHLYP/aug-cc-pVTZ were used to compare the results obtained with experimental data of rotational spectroscopy. Analysis of QCC values and of the results of approximation of the natural bonding orbitals reveals prevailing electrostatic nature of intermolecular interaction.     

Rhodium-105 complexes as potential radiotherapeutic agents

Rhodium-105 complexes have been investigated for their suitability as the basis of potential bifunctional chelating agents for therapeutic radiopharmaceuticals. Rhodium-105 is a reactor-produced therapeutic radionuclide that is available in high specific activity. The chemistry and biology of several six-coordinate Rh(III) complexes of the general form [RhCl2L]+, where L is a tetradentate ligand containing at least three thioethers donor atoms, is discussed. The backbone chain length of the acyclic or macrocyclic ligand determines the geometry about the Rh(III) centre (cis vs. trans), with the larger ligands preferentially forming trans-dichloro complexes. The stability of all of the 105Rh complexes is very high (>5 days) and the biological clearance properties of the complexes are consistent with their relative lipophilicities.     

Spectroscopic investigations of hydrogen bonding interactions in the gas phase: Part VI. A microwave spectroscopie determination of geometry for the heterodimer (CH2)3O⋯HF formed between oxetane and hydrogen fluoride: hydrogen bonding as a probe for lone pairs

The hydrogen-bonded heterodimer formed between oxetane and hydrogen fluoride is identified and characterised by means of its IR and microwave spectra. The following rotational constants (MHz) and centrifugal distortion constants (kHz) have been derived:

     

107.

D-nuclear quadrupole coupling in the rotational spectrum of ¹⁵N₂…DF and an interpretation of the hyperfine coupling constants χ _aa^D and D_aa^HF within a series of complexes B…HF     

A.C. Legon  L.C. Willoughby 《Chemical physics letters》1984,109(5):502-508

Hyperfine structure in the J = 1 ← 0 and J = 2 ← 1 transitions of ¹⁵N₂…DF, arising from D-nuclear quadrupole coupling and D, ¹⁹F nuclear-spin—nuclear-spin coupling, has been observed and measured by using pulsed-nozzle Fourier-transform microwave spectroscopy. The following rotational, centrifugal distortion and hyperfine coupling constants were determined: β_o = 3091.9004 MHz, D_J = 14.75 kHz, χ_aa^D = 278.6(38) kHz and D_aa^HF = ?38.5(38) kHz. An interpretation is presented for the variation of the coupling, constants χ_aa^D and D_aa^HF along the series B…DF and B…HF, where B = Ar, Kr, Xe, ¹⁵N₂, CO, PH₃, H₂S, HC¹⁵N and H₂O.     

108.

Simultaneous analysis of cocaine,benzoylecgonine, methylecgonine,and ecgonine in plasma using an exchange resin and gas chromatography-mass spectrometry     

C. C. Okeke  J. E. Wynn  K. S. Patrick 《Chromatographia》1994,38(1-2):52-56

Summary A gas chromatographic-mass spectrometric method is described for the simultaneous analysis of cocaine and the hydrolytic products benzoylecgonine, methylecgonine and ecgonine from plasma (0.25–2 g/ml). Isopropylecgonine was incorporated as an internal standard. Samples were extracted using a sulfonate cation exchange resin, then derivatized with pentafluoropropionic anhydride and pentafluoropropanol. Analytical separations were on a dimethylsilicone capillary column using a temperature program, and detection was by selected ion monitoring of the electron impact generated fragments m/z 94, 182, 210, and 300.Presented at the poster session of American Association of Pharmaceutical Scientists 1991 Southeast Regional Meeting, Charleston, South Carolina, USA, April 4–5     

109.

Beneficial Effect of ortho‐Methoxy Groups in the Asymmetric Ring Opening of meso Epoxides with Silicon Tetrachloride Catalyzed by Chiral ortho‐Methoxyphenyldiazaphosphonamide Lewis Bases Response to the Communication by G. Buono et al.     

Scott E. Denmark  Thomas Wynn  Bradley G. Jellerichs 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2001,113(12):2315-2316

     

110.

Prereactive Complexes of Dihalogens XY with Lewis Bases B in the Gas Phase: A Systematic Case for the Halogen Analogue B⋅⋅⋅XY of the Hydrogen Bond B⋅⋅⋅HX     

Anthony C. Legon 《Angewandte Chemie (International ed. in English)》1999,38(18):2686-2714

Similar and yet also notably different are the B⋅⋅⋅XY and B⋅⋅⋅HX complexes in the gas phase, where B is a simple Lewis base, XY is a homo- or heterodihalogen molecule, and HX is a hydrogen halide. This is demonstrated, for example, by the structures of oxirane⋅⋅⋅ClF and oxirane⋅⋅⋅HCl (see picture). Both bonds are dominated by simple electrostatic interactions, but differ in terms of their propensity for nonlinearity.     

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A	B	C	ΔJ	ΔJK
(CH2)O3?HF	9217	2575.1	2350.6	11.3	?57.0
(CH2)3O?DF	9157(ass)	2544.7	2329.3	9.9	?56

D-nuclear quadrupole coupling in the rotational spectrum of 15N2…DF and an interpretation of the hyperfine coupling constants χ aaD and DaaHF within a series of complexes B…HF

Hyperfine structure in the J = 1 ← 0 and J = 2 ← 1 transitions of ¹⁵N₂…DF, arising from D-nuclear quadrupole coupling and D, ¹⁹F nuclear-spin—nuclear-spin coupling, has been observed and measured by using pulsed-nozzle Fourier-transform microwave spectroscopy. The following rotational, centrifugal distortion and hyperfine coupling constants were determined: β_o = 3091.9004 MHz, D_J = 14.75 kHz, χ_aa^D = 278.6(38) kHz and D_aa^HF = ?38.5(38) kHz. An interpretation is presented for the variation of the coupling, constants χ_aa^D and D_aa^HF along the series B…DF and B…HF, where B = Ar, Kr, Xe, ¹⁵N₂, CO, PH₃, H₂S, HC¹⁵N and H₂O.     

Simultaneous analysis of cocaine,benzoylecgonine, methylecgonine,and ecgonine in plasma using an exchange resin and gas chromatography-mass spectrometry

Summary A gas chromatographic-mass spectrometric method is described for the simultaneous analysis of cocaine and the hydrolytic products benzoylecgonine, methylecgonine and ecgonine from plasma (0.25–2 g/ml). Isopropylecgonine was incorporated as an internal standard. Samples were extracted using a sulfonate cation exchange resin, then derivatized with pentafluoropropionic anhydride and pentafluoropropanol. Analytical separations were on a dimethylsilicone capillary column using a temperature program, and detection was by selected ion monitoring of the electron impact generated fragments m/z 94, 182, 210, and 300.Presented at the poster session of American Association of Pharmaceutical Scientists 1991 Southeast Regional Meeting, Charleston, South Carolina, USA, April 4–5     

Prereactive Complexes of Dihalogens XY with Lewis Bases B in the Gas Phase: A Systematic Case for the Halogen Analogue B⋅⋅⋅XY of the Hydrogen Bond B⋅⋅⋅HX

Similar and yet also notably different are the B⋅⋅⋅XY and B⋅⋅⋅HX complexes in the gas phase, where B is a simple Lewis base, XY is a homo- or heterodihalogen molecule, and HX is a hydrogen halide. This is demonstrated, for example, by the structures of oxirane⋅⋅⋅ClF and oxirane⋅⋅⋅HCl (see picture). Both bonds are dominated by simple electrostatic interactions, but differ in terms of their propensity for nonlinearity.