Gas-Phase Folding of a Prototypical Protonated Pentapeptide: Spectroscopic Evidence for Formation of a Charge-Stabilized β-Hairpin

2016 ◽  
Vol 138 (8) ◽  
pp. 2849-2857 ◽  
Author(s):  
Nicole L. Burke ◽  
Andrew F. DeBlase ◽  
James G. Redwine ◽  
John R. Hopkins ◽  
Scott A. McLuckey ◽  
...  
Keyword(s):  
Gas Phase ◽  
Spectroscopic Evidence ◽  
A Charge

Gas-phase solvation of N+2 with Ar atoms: a charge switch in the reaction N+2 + Ar → Ar+ …N2

1992 ◽  
Vol 189 (1) ◽  
pp. 7-12 ◽  
Author(s):  
Kenzo Hiraoka ◽  
Toshiharu Mori ◽  
Shinichi Yamabe
Keyword(s):  
Gas Phase ◽  
A Charge

Spectroscopic evidence for a gas-phase librating G-quartet–Na+ complex

2014 ◽  
Vol 50 (94) ◽  
pp. 14767-14770 ◽  
Author(s):  
C. Fraschetti ◽  
M. Montagna ◽  
L. Guarcini ◽  
L. Guidoni ◽  
A. Filippi
Keyword(s):  
Gas Phase ◽  
Room Temperature ◽  
Spectroscopic Evidence

The Na+–G4 adduct exists as a mixture of two metastable populations, rapidly interconverting at room temperature.

Spectroscopic evidence of α-methylbenzyl radical in the gas phase

2008 ◽  
Vol 465 (4-6) ◽  
pp. 193-196 ◽  
Author(s):  
Gi Woo Lee ◽  
Hyeon Geun Ahn ◽  
Tae Kyu Kim ◽  
Sang Kuk Lee
Keyword(s):  
Gas Phase ◽  
Spectroscopic Evidence

The Excited Singlet State of Chloropentafluoroacetone; Quenching by Unsaturated Hydrocarbons

1971 ◽  
Vol 49 (12) ◽  
pp. 2053-2058 ◽  
Author(s):  
H. S. Samant ◽  
A. J. Yarwood
Keyword(s):  
Gas Phase ◽  
Singlet State ◽  
Excited Singlet State ◽  
Energy Relation ◽  
Excited Singlet ◽  
Quenching Rate ◽  
Unsaturated Hydrocarbons ◽  
Linear Free Energy ◽  
Free Energy Relation ◽  
A Charge

The fluorescence of chloropentafluoroacetone in the gas phase at 23 °C is quenched by the addition of certain olefins. The quenching rate constants of 17 unsaturated hydrocarbons for the first excited singlet state of chloropentafluoroacetone are reported. The molecules are divided into two classes on the basis of their quenching abilities, (a) olefins with only electron-withdrawing substituents and (b) olefins with electron-donating substituents. It is shown that the quenching by molecules in the latter group can be quantitatively correlated with the ionization potential (i.p.) of the quenching molecule. The relation is log k = 18.0 − 0.79 (i.p.), i.e. a type of linear free energy relation is obeyed. This implies that the quenching by molecules containing only electron-donating substituents involves a charge-transfer complex.

Gas-phase ion decomposition occurring remote to a charge site

1985 ◽  
Vol 107 (7) ◽  
pp. 1863-1868 ◽  
Author(s):  
Nancy J. Jensen ◽  
Kenneth B. Tomer ◽  
Michael L. Gross
Keyword(s):  
Gas Phase ◽  
Charge Site ◽  
A Charge ◽  
Gas Phase Ion

Quenching of the fluorescence of substituted benzenes by halomethanes

1983 ◽  
Vol 61 (9) ◽  
pp. 1952-1956 ◽  
Author(s):  
H. A. Khwaja ◽  
G. P. Semeluk ◽  
I. Unger
Keyword(s):  
Charge Transfer ◽  
Gas Phase ◽  
Singlet State ◽  
Charge Transfer Complex ◽  
Substituted Benzenes ◽  
Exciplex Formation ◽  
Benzene Toluene ◽  
A Charge ◽  
Klein’S Model ◽  
Protonated Molecules

Rate constants, kq, for the quenching of the singlet state of benzene, toluene, p-xylene, fluorobenzene, trifluoromethyl benzene, p-bis(trifluoromethyl)benzene, and aniline by CCl4, CH3CCl3, CHCl3, and CFCl3, in the gas phase have been determined. In each instance the quenching is via a charge-transfer complex with the aromatic acting as donor. There is a linear dependence between ln kq and IP (ionization potential) of the aromatics which supports Klein's model for exciplex formation. The most effective quencher is CCl4 while the least effective is CFCl3. The most effective donor was aniline while the least effective one was p-bis(trifluoromethyl)benzene. In general, fluorinated aromatics are less effective donors than the corresponding protonated molecules.

Vacuum-ultraviolet (147.0 nm and 123.6 nm) photolysis of 1,1-dimethylcyclopropane

1981 ◽  
Vol 59 (3) ◽  
pp. 537-542
Author(s):  
Joseph B. Binkewicz ◽  
Michael Kaplan ◽  
Richard D. Doepker
Keyword(s):  
Gas Phase ◽  
Vacuum Ultraviolet ◽  
Molecular Processes ◽  
Radical Scavengers ◽  
Primary Reaction ◽  
Radical Species ◽  
Molecule Reaction ◽  
Reaction Channels ◽  
A Charge ◽  
Photo Decomposition

The gas-phase photolysis of 1,1-dimethylcyclopropane has been investigated using xenon (147.0 nm) and krypton (123.6 nm) resonance radiation. Major products observed in order of decreasing importance were isobutene, ethylene, hydrogen, 1,3-butadiene 2-methyl-1,3-butadiene, propylene, allene, methylacetylene, and acetylene. Radical scavengers, NO and O2, and radical interceptors, H2S/D2S and HI, were used to determine the relative importance of radical and molecular processes. CH3, C2H3, C3H5, and C4H7 radical species were identified and quantified. Ten primary reaction channels were postulated, of which the elimination of methylene was the most predominant, accounting for 34% of the photo-decomposition at 147.0 nm and 39% at 123.6 nm. Although ionization was established at 123.6 nm (η = 0.10) the nature of a charge transfer or other ion-molecule reaction channel leading to the formation of 2-methyl-1-butene and 2-methyl-2-butene could not be determined.

Computational and ultraviolet photoelectron spectroscopic evidence that (Z)-2-methyl-1,3-pentadiene prefers twisted s-cis conformers in the gas phase

1992 ◽  
Vol 70 (7) ◽  
pp. 1971-1977 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
George Timmins ◽  
Jiangong Ma ◽  
Timothy A. Wildman
Keyword(s):  
Potential Energy ◽  
Gas Phase ◽  
Computational Methods ◽  
Potential Energy Surfaces ◽  
Spectroscopic Evidence ◽  
Orbital Energies ◽  
Trans Conformer ◽  
Energy Surfaces ◽  
Good Agreement

A redetermination of the ultraviolet photoelectron (pe) spectrum of (Z)-2-methyl-1,3-pentadiene has led to a correction of the published spectrum. By studying (Z)-2-methyl-1,3,-pentadiene (1a) and (E)-2-methyl-1,3-pentadiene (1b) with MMX, MNDO, AM1, and abinitio MO computational methods and pe spectroscopy, we have shown that a combination of these methods provides useful insights on the conformational behaviour of methyl-substituted 1,3-dienes in the gas phase. Synthetic pe spectra, derived from the computed potential energy surfaces and angle-dependent orbital energies, are in good agreement with experiment. Thus, the E isomer prefers the s-trans conformer but the Z isomer prefers twisted s-cis conformations in the gas phase.

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