Sequence-Specific and Stereospecific Assignment of Methyl Groups Using Paramagnetic Lanthanides

2007 ◽  
Vol 129 (44) ◽  
pp. 13749-13757 ◽  
Author(s):  
Michael John ◽  
Christophe Schmitz ◽  
Ah Young Park ◽  
Nicholas E. Dixon ◽  
Thomas Huber ◽  
...  
Keyword(s):  
Methyl Groups ◽  
Stereospecific Assignment

Reduction of carbon impurities in aluminium nitride from time-resolved chemical vapour deposition using trimethylaluminum

2020 ◽  
Author(s):  
Polla Rouf ◽  
Pitsiri Sukkaew ◽  
Lars Ojamäe ◽  
Henrik Pedersen
Keyword(s):  
Chemical Vapour Deposition ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
Aluminium Nitride ◽  
Methyl Groups ◽  
Time Resolved ◽  
Thermally Induced ◽  
Light Emitting ◽  
Carbon Impurities ◽  
Wide Range

<p>Aluminium nitride (AlN) is a semiconductor with a wide range of applications from light emitting diodes to high frequency transistors. Electronic grade AlN is routinely deposited at 1000 °C by chemical vapour deposition (CVD) using trimethylaluminium (TMA) and NH<sub>3</sub> while low temperature CVD routes to high quality AlN are scarce and suffer from high levels of carbon impurities in the film. We report on an ALD-like CVD approach with time-resolved precursor supply where thermally induced desorption of methyl groups from the AlN surface is enhanced by the addition of an extra pulse, H<sub>2</sub>, N<sub>2</sub> or Ar between the TMA and NH<sub>3</sub> pulses. The enhanced desorption allowed deposition of AlN films with carbon content of 1 at. % at 480 °C. Kinetic- and quantum chemical modelling suggest that the extra pulse between TMA and NH<sub>3</sub> prevents re-adsorption of desorbing methyl groups terminating the AlN surface after the TMA pulse. </p>

Detection of Chemical Exchange in Methyl Groups of Macromolecules

2019 ◽  
Author(s):  
Michelle Gill ◽  
Andrew Hsu ◽  
Arthur G. Palmer, III
Keyword(s):  
Relaxation Rate ◽  
Chemical Exchange ◽  
Double Quantum ◽  
Methyl Groups ◽  
Multiple Quantum ◽  
Relaxation Data ◽  
E Coli ◽  
Methyl Trosy ◽  
Dynamics Simulations ◽  
Exchange Broadening

<div> <div> <div> <p>The zero- and double-quantum methyl TROSY Hahn-echo and the methyl <sup>1</sup>H-<sup>1</sup>H dipole- dipole cross-correlation nuclear magnetic resonance experiments enable estimation of multiple quantum chemical exchange broadening in methyl groups in proteins. The two relaxation rate constants are established to be linearly dependent using molecular dynamics simulations and empirical analysis of experimental data. This relationship allows chemical exchange broadening to be recognized as an increase in the Hahn-echo relaxation rate constant. The approach is illustrated by analyzing relaxation data collected at three temperatures for <i>E. coli </i>ribonuclease HI and by analyzing relaxation data collected for different cofactor and substrate complexes of <i>E. coli </i>AlkB. </p> </div> </div> </div>

The synthesis and stereochemistry of the ternary cobalt(III) complex with a stereospecific ligand derived from (S)-leucine

1986 ◽  
Vol 51 (2) ◽  
pp. 318-326 ◽  
Author(s):  
Milan Strašák ◽  
Pavol Novomeský
Keyword(s):  
Ir Spectroscopy ◽  
Aqueous Medium ◽  
Absorption Spectroscopy ◽  
Absolute Configuration ◽  
Nmr Spectra ◽  
Methyl Groups ◽  
Electron Absorption Spectroscopy ◽  
Electron Absorption ◽  
C Nmr

A new stereospecific ligand, ethylenediamine-N,N'-di(S)-α-isocapronic acid, was synthesized by condensation of (S)-leucine with 1,2-dibromoethane in alkaline aqueous medium. It follows from the 1H and 13C NMR spectra that the terminal methyl groups are chemically and magnetically nonequivalent. Of the four theoretically possible isomers of the ternary cobalt (III) complex with ethylenediamine, separation on catex yielded only one, whose absolute configuration was determined by a combination of 1H and 13C NMR, electron absorption spectroscopy and CD and IR spectroscopy.

scholarly journals Effects of Alkyl-Substituted Polybenzoxazines on Tribological Properties of Non-Asbestos Composite Friction Materials

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 567
Author(s):  
Anun Wongpayakyotin ◽  
Chanchira Jubsilp ◽  
Sunan Tiptipakorn ◽  
Phattarin Mora ◽  
Christopher W. Bielawski ◽  
...  
Keyword(s):  
Wear Resistance ◽  
Composite Materials ◽  
Coefficient Of Friction ◽  
Aromatic Amines ◽  
Underlying Structure ◽  
Methyl Groups ◽  
Friction Materials ◽  
Wear Rates ◽  
Structure Properties ◽  
Crosslink Densities

A series of substituted polybenzoxazines was synthesized and studied as binders in non-asbestos friction composite materials. The structures of the polybenzoxazines were varied in a systemic fashion by increasing the number and position of pendant alkyl (methyl) groups and was accomplished using the respective aromatic amines during the polymer synthesis step. By investigating the key thermomechanical and tribological characteristics displayed by the composite materials, the underlying structure-properties relationships were deconvoluted. Composite friction materials with higher thermomechanical and wear resistance properties were obtained from polybenzoxazines with relatively high crosslink densities. In contrast, polybenzoxazines with relatively low crosslink densities afforded composite friction materials with an improved coefficient of friction values and specific wear rates.

scholarly journals Microwave-assisted Efficient Synthesis of Alliodorin and (±)-Curcuhydroquinone

1999 ◽  
Vol 23 (2) ◽  
pp. 164-165
Author(s):  
Goverdhan L. Kad ◽  
Anupam Khurana ◽  
Vasundhara Singh ◽  
Jasvinder Singh
Keyword(s):  
Grignard Reagents ◽  
Methyl Groups ◽  
Efficient Synthesis ◽  
Alkyl Aryl ◽  
Microwave Assisted ◽  
Aryl Bromides ◽  
Key Steps

Terpenoids 1 and 2 have been synthesized from readily available starting materials using Li2CuCI4-catalysed coupling of Grignard reagents with alkyl/aryl bromides and microwave-assisted oxidation of allylic methyl groups, using SeO2/ButOOH adsorbed over SiO2 as key steps.

scholarly journals COMPOUNDS RELATED TO DIMETHYLTHETIN AS SOURCES OF LABILE METHYL GROUPS

1948 ◽  
Vol 176 (3) ◽  
pp. 1037-1045 ◽  
Author(s):  
George A. Maw ◽  
Vincent. du Vigneaud
Keyword(s):  
Methyl Groups
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