Surface roughness and oxide contents of gas-phase and solution-phase polysulfide passivation of III–V surfaces

1999 ◽  
Vol 17 (1) ◽  
pp. 93-96
Author(s):  
W. H. Choy ◽  
R. W. M. Kwok ◽  
B. K. L. So ◽  
G. K. C. Hui ◽  
Y. J. Chen ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Gas Phase ◽  
Solution Phase

scholarly journals Bridging the Gap between the Gas Phase and Solution Phase: Solvent Specific Photochemistry in 4-tert-Butylcatechol

2015 ◽  
Vol 119 (50) ◽  
pp. 11989-11996 ◽  
Author(s):  
Michael D. Horbury ◽  
Lewis A. Baker ◽  
Wen-Dong Quan ◽  
Jamie D. Young ◽  
Michael Staniforth ◽  
...  
Keyword(s):  
Gas Phase ◽  
Solution Phase

scholarly journals Photoproducts of the Photodynamic Therapy Agent Verteporfin Identified via Laser Interfaced Mass Spectrometry

Molecules ◽  
2020 ◽  
Vol 25 (22) ◽  
pp. 5280
Author(s):  
Chris Furlan ◽  
Jacob A. Berenbeim ◽  
Caroline E. H. Dessent
Keyword(s):  
Mass Spectrometry ◽  
Photodynamic Therapy ◽  
Macular Degeneration ◽  
Gas Phase ◽  
Mass Spectrometer ◽  
Red Light ◽  
Solution Phase ◽  
Collision Induced Dissociation ◽  
Free Base ◽  
New Information

Verteporfin, a free base benzoporphyrin derivative monoacid ring A, is a photosensitizing drug for photodynamic therapy (PDT) used in the treatment of the wet form of macular degeneration and activated by red light of 689 nm. Here, we present the first direct study of its photofragmentation channels in the gas phase, conducted using a laser interfaced mass spectrometer across a broad photoexcitation range from 250 to 790 nm. The photofragmentation channels are compared with the collision-induced dissociation (CID) products revealing similar dissociation pathways characterized by the loss of the carboxyl and ester groups. Complementary solution-phase photolysis experiments indicate that photobleaching occurs in verteporfin in acetonitrile; a notable conclusion, as photoinduced activity in Verteporfin was not thought to occur in homogenous solvent conditions. These results provide unique new information on the thermal break-down products and photoproducts of this light-triggered drug.

Do electrospray mass spectra reflect the ligand binding state of proteins in solution?

2005 ◽  
Vol 83 (11) ◽  
pp. 1953-1960 ◽  
Author(s):  
Belal M Hossain ◽  
Douglas A Simmons ◽  
Lars Konermann
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Protein Interactions ◽  
Noncovalent Complex ◽  
Deuterium Exchange ◽  
Solution Phase ◽  
Hydrogen Deuterium Exchange ◽  
Esi Ms ◽  
Protein Ions ◽  
Hydrogen Deuterium

Electrospray ionization (ESI) mass spectrometry (MS) has become a popular tool for monitoring ligand–protein and protein–protein interactions. Due to the "gentle" nature of the ionization process, it is often possible to transfer weakly bound complexes into the gas phase, thus making them amenable to MS detection. One problem with this technique is the potential occurrence of fragmentation events during ESI. Also, some analytes tend to cluster together during ionization, thus forming nonspecific gas-phase assemblies that do not represent solution-phase complexes. In this work, we implemented a hydrogen–deuterium exchange (HDX) approach that can reveal whether or not the free and (or) bound constituents of a complex observed in ESI-MS reflect the binding situation in solution. Proteins are subjected to ESI immediately following an isotopic labeling pulse; only ligand-free and ligand-bound protein ions that were formed directly from the corresponding solution-phase species showed different HDX levels. Using myoglobin as a model system, it is demonstrated that this approach can readily distinguish scenarios where the heme–protein interactions were disrupted in solution from those where dissociation of the complex occurred in the gas phase. Experiments on cytochrome c strongly suggest that dimeric protein ions observed in ESI-MS reflect aggregates that were formed in solution.Key words: electrospray mass spectrometry, ligand–protein interaction, noncovalent complex, hydrogen–deuterium exchange, protein folding.

Studies on the structure and conformational flexibility of secondary structures in amyloid beta — A quantum chemical study

2020 ◽  
Vol 19 (06) ◽  
pp. 2050014
Author(s):  
Mahendiraprabu Ganesan ◽  
Selvarengan Paranthaman
Keyword(s):  
Gas Phase ◽  
Amyloid Beta ◽  
Density Functional ◽  
Conformational Transition ◽  
Intermolecular Hydrogen Bond ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Secondary Structures ◽  
Conformational Flexibility ◽  
Solution Phase

Density functional theory (DFT) calculations are performed to study the conformational flexibility of secondary structures in amyloid beta (A[Formula: see text]) polypeptide. In DFT, M06-2X/6-31[Formula: see text]G(d, p) method is used to optimize the secondary structures of 2LFM and 2BEG in gas phase and in solution phase. Our calculations show that the secondary structures are energetically more stable in solution phase than in gas phase. This is due to the presence of strong solvent interaction with the secondary structures considered in this study. Among the backbone [Formula: see text] and [Formula: see text] dihedral angles, [Formula: see text] varies significantly in sheet structure. This is due to the absence of intermolecular hydrogen bond (H-bond) interactions in sheets considered in this study. Our calculations show that the conformational transition of helix/coil to sheet or vice-versa is due to the floppiness of the amino acid residues. This is observed from the Ramachandran map of the studied secondary structures. Further, it is noted that the intramolecular H-bond interactions play a significant role in the conformational transition of secondary structures of A[Formula: see text].

Bond-dissociation enthalpies in the gas phase and in organic solvents: Making ends meet

2007 ◽  
Vol 79 (8) ◽  
pp. 1369-1382 ◽  
Author(s):  
Rui M. Borges dos Santos ◽  
Benedito J. Costa Cabral ◽  
José A. Martinho Simões
Keyword(s):  
Gas Phase ◽  
Organic Solvents ◽  
Solvent Effects ◽  
Solution Phase ◽  
Parent Molecule ◽  
Solvent Interaction ◽  
Solvation Effects ◽  
Bond Dissociation ◽  
The Difference

Solvent effects are responsible for the difference between gas- and solution-phase bond-dissociation enthalpies (BDEs), and are thus crucial for understanding reactivity in solution. While solvation effects can be negligible (e.g., in reactions involving carbon-centered radicals), they may be rather significant (e.g., when oxygen-centered radicals are formed). This paper reviews a number of models which have been proposed to deal with the difference between the solvation energetics of a radical and its parent molecule. It is concluded that the radical-solvent interaction may be larger than previously anticipated.

Desilylation of β-Silyl Pyridinium Ions: Gas-Phase and Solution-Phase Studies in Conjunction with DFT Calculations

2009 ◽  
Vol 28 (15) ◽  
pp. 4276-4282 ◽  
Author(s):  
Asimo Karnezis ◽  
Richard A. J. O’Hair ◽  
Jonathan M. White
Keyword(s):  
Dft Calculations ◽  
Gas Phase ◽  
Solution Phase ◽  
Pyridinium Ions

Gas-Phase and Solution-Phase Polymerization of Epoxides by Cr(salen) Complexes:  Evidence for a Dinuclear Cationic Mechanism

2004 ◽  
Vol 43 (23) ◽  
pp. 7278-7280 ◽  
Author(s):  
Eva Schön ◽  
Xiangyang Zhang ◽  
Zhiping Zhou ◽  
Malcolm H. Chisholm ◽  
Peter Chen
Keyword(s):  
Gas Phase ◽  
Solution Phase ◽  
Salen Complexes

Correlation between gas-phase and solution-phase reactivities of hydroxyl radicals towards saturated organic compounds

1988 ◽  
Vol 92 (17) ◽  
pp. 5024-5028 ◽  
Author(s):  
Timothy J. Wallington ◽  
Philippe Dagaut ◽  
Michael J. Kurylo
Keyword(s):  
Gas Phase ◽  
Organic Compounds ◽  
Hydroxyl Radicals ◽  
Solution Phase
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