CAPPED METAL CLUSTERS IN THE GAS PHASE

2005 ◽  
Vol 04 (05n06) ◽  
pp. 935-944 ◽  
Author(s):  
JOBIN CYRIAC ◽  
V. R. RAJEEV KUMAR ◽  
T. PRADEEP
Keyword(s):  
Gas Phase ◽  
Chain Length ◽  
Column Chromatography ◽  
Mass Spectra ◽  
Metal Clusters ◽  
Laser Desorption ◽  
Gold Clusters

Alkanethiol protected gold clusters of 29 kDa were prepared and separated by column chromatography. Laser desorption mass spectra of these clusters have been investigated. In the gas phase, monolayer–monolayer interaction leads to clustering of the protected clusters. Role of different matrices and effect of alkanethiol chain length on this process have been investigated.

Role of the support material on laser desorption/ionization mass spectra

2008 ◽  
Vol 22 (7) ◽  
pp. 925-929 ◽  
Author(s):  
A. Gruszecka ◽  
M. Szymanska-Chargot ◽  
A. Smolira ◽  
J. Cytawa ◽  
L. Michalak
Keyword(s):  
Mass Spectra ◽  
Laser Desorption ◽  
Ionization Mass ◽  
Support Material ◽  
Laser Desorption Ionization ◽  
Desorption Ionization

scholarly journals Phenylcopper(I) clusters in the gas phase obtained by laser desorption/ionization from bis(dibenzoylmethane)copper(II)

2010 ◽  
Vol 8 (3) ◽  
pp. 508-512 ◽  
Author(s):  
Rafał Frański ◽  
Tomasz Kozik ◽  
Bartosz Staniszewski ◽  
Włodzimierz Urbaniak
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Mass Spectra ◽  
Laser Desorption ◽  
Tandem Mass ◽  
Laser Desorption Ionization ◽  
Organometallic Clusters ◽  
Desorption Ionization ◽  
Straightforward Method ◽  
Wide Range

AbstractIt has been demonstrated that phenylcopper(I)-containing clusters are generated in the gas phase from bis(dibenzoylmethane) copper(II) (Cu(dbm)2) by laser desorption/ ionization (LDI) method. For example, the [Cu5dbm2(C6H5)2]+ ion can be considered as consisting of two Cudbm molecules, two CuC6H5 molecules and a Cu+ cation. The [Cu5(C6H5)4]+ ion can be considered as phenylcopper(I) cluster (consisting of four phenylcopper molecules) ionized by additional Cu+ cation. Results from MS/MS (tandem mass spectrometry) experiments have confirmed the presence of phenylcopper molecules in the analyzed clusters. Ease of preparation of dibenzoylmethane-metal complexes and straightforward method to obtain LDI mass spectra offer a wide range of possibilities to study similar organometallic clusters in the gas phase.

Updating Evidence for Cationization of Polymers in the Gas Phase during Matrix-Assisted Laser Desorption/Ionization

2005 ◽  
Vol 11 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Scott D. Hanton ◽  
Kevin G. Owens ◽  
Cynthia Chavez-Eng ◽  
Anne-Mette Hoberg ◽  
Peter J. Derrick
Keyword(s):  
Gas Phase ◽  
Mass Spectra ◽  
Secondary Ion Mass Spectrometry ◽  
Laser Desorption ◽  
Bottom Layer ◽  
Laser Desorption Ionization ◽  
Desorption Ionization ◽  
Delayed Extraction ◽  
Matrix Assisted Laser ◽  
Matrix Assisted Laser Desorption

Matrix-assisted laser desorption/ionization (MALDI) techniques have been developed to determine the chemical structure of a variety of industrial polymers. Despite the enormous popularity and power of MALDI, the details of the cationization mechanisms of the process are currently rather poorly understood. The MALDI cationization of polymer analytes was investigated previously by Hoberg and co-workers.1 They used layered samples to explore the role of gas-phase cationization in MALDI of polymers. This paper seeks to extend the work initiated by Hoberg and co-workers and update the results of the earlier work. The new experiments take advantage of a MALDI instrument with delayed extraction and show that separation in the initial acceleration region of the mass spectrometer is not a key component of cationization. Investigations of tri-layer samples by time-of-flight secondary ion mass spectrometry (ToF-SIMS) also show that there is considerable interaction among the layers. These interactions, specifically the solubility of the salts in the solvents, account for the presence of the bottom layer cation in the mass spectra. The absence of the top layer cation in the mass spectra is due to the inability of the polymer oligomers to penetrate that layer during desorption.

scholarly journals Analysis of Gas Phase Clusters Made from Laser-Vaporized Icosahedral Al-Pd-Mn

2000 ◽  
Vol 643 ◽  
Author(s):  
J.A. Barrow ◽  
E.F. Rexer ◽  
D.J. Sordelet ◽  
M.F. Besser ◽  
C.J. Jenks ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Mass Spectra ◽  
Metal Clusters ◽  
Time Of Flight ◽  
Laser Vaporization ◽  
Gas Phase Clusters ◽  
Flight Mass Spectrometry ◽  
Photon Ionization

AbstractLaser vaporization of an icosahedral Al-Pd-Mn sample with detection by time-of-flight mass spectrometry is used to probe metal clusters made from the alloy. After sample vaporization, clusters form by gas aggregation and may contain several to hundreds of atoms. Multi-photon ionization/fragmentation of these clusters yields mass spectra showing many cluster sizes with enhanced intensity. Clusters are identified at masses near those of pseudo- Mackay and Bergman clusters; however, these clusters do not appear special relative to neighboring clusters. Results of this study and its relationship to the proposed cluster structures in quasicrystalline materials are discussed.

Directive Effect of Chain Length in Modulating Peptide Nano-assemblies

2020 ◽  
Vol 27 (9) ◽  
pp. 923-929
Author(s):  
Gaurav Pandey ◽  
Prem Prakash Das ◽  
Vibin Ramakrishnan
Keyword(s):  
Electron Microscopy ◽  
Amino Acids ◽  
Light Scattering ◽  
Chain Length ◽  
Self Assembly ◽  
The Self ◽  
Ionic Charge ◽  
Self Assembling ◽  
Biophysical Techniques

Background: RADA-4 (Ac-RADARADARADARADA-NH2) is the most extensively studied and marketed self-assembling peptide, forming hydrogel, used to create defined threedimensional microenvironments for cell culture applications. Objectives: In this work, we use various biophysical techniques to investigate the length dependency of RADA aggregation and assembly. Methods: We synthesized a series of RADA-N peptides, N ranging from 1 to 4, resulting in four peptides having 4, 8, 12, and 16 amino acids in their sequence. Through a combination of various biophysical methods including thioflavin T fluorescence assay, static right angle light scattering assay, Dynamic Light Scattering (DLS), electron microscopy, CD, and IR spectroscopy, we have examined the role of chain-length on the self-assembly of RADA peptide. Results: Our observations show that the aggregation of ionic, charge-complementary RADA motifcontaining peptides is length-dependent, with N less than 3 are not forming spontaneous selfassemblies. Conclusion: The six biophysical experiments discussed in this paper validate the significance of chain-length on the epitaxial growth of RADA peptide self-assembly.

scholarly journals Transcriptome Changes in Pseudomonas putida KT2440 during Medium-Chain-Length Polyhydroxyalkanoate Synthesis Induced by Nitrogen Limitation

2020 ◽  
Vol 22 (1) ◽  
pp. 152
Author(s):  
Dorota Dabrowska ◽  
Justyna Mozejko-Ciesielska ◽  
Tomasz Pokój ◽  
Slawomir Ciesielski
Keyword(s):  
Chain Length ◽  
Nitrogen Limitation ◽  
Stringent Response ◽  
Wild Type ◽  
Pseudomonas Putida Kt2440 ◽  
Medium Chain ◽  
Environmental Stimuli ◽  
Medium Chain Length ◽  
In The Wild

Pseudomonas putida’s versatility and metabolic flexibility make it an ideal biotechnological platform for producing valuable chemicals, such as medium-chain-length polyhydroxyalkanoates (mcl-PHAs), which are considered the next generation bioplastics. This bacterium responds to environmental stimuli by rearranging its metabolism to improve its fitness and increase its chances of survival in harsh environments. Mcl-PHAs play an important role in central metabolism, serving as a reservoir of carbon and energy. Due to the complexity of mcl-PHAs’ metabolism, the manner in which P. putida changes its transcriptome to favor mcl-PHA synthesis in response to environmental stimuli remains unclear. Therefore, our objective was to investigate how the P. putida KT2440 wild type and mutants adjust their transcriptomes to synthesize mcl-PHAs in response to nitrogen limitation when supplied with sodium gluconate as an external carbon source. We found that, under nitrogen limitation, mcl-PHA accumulation is significantly lower in the mutant deficient in the stringent response than in the wild type or the rpoN mutant. Transcriptome analysis revealed that, under N-limiting conditions, 24 genes were downregulated and 21 were upregulated that were common to all three strains. Additionally, potential regulators of these genes were identified: the global anaerobic regulator (Anr, consisting of FnrA, Fnrb, and FnrC), NorR, NasT, the sigma54-dependent transcriptional regulator, and the dual component NtrB/NtrC regulator all appear to play important roles in transcriptome rearrangement under N-limiting conditions. The role of these regulators in mcl-PHA synthesis is discussed.

scholarly journals The role of radiolysis in the modelling of C2H4O2 isomers and dimethyl ether in cold dark clouds

2020 ◽  
Vol 500 (3) ◽  
pp. 3414-3424
Author(s):  
Alec Paulive ◽  
Christopher N Shingledecker ◽  
Eric Herbst
Keyword(s):  
Gas Phase ◽  
Dimethyl Ether ◽  
Recent Observation ◽  
Cosmic Ray ◽  
Thermal Method ◽  
Dark Clouds ◽  
Ice Surface ◽  
Dust Grain ◽  
Complex Organic

ABSTRACT Complex organic molecules (COMs) have been detected in a variety of interstellar sources. The abundances of these COMs in warming sources can be explained by syntheses linked to increasing temperatures and densities, allowing quasi-thermal chemical reactions to occur rapidly enough to produce observable amounts of COMs, both in the gas phase, and upon dust grain ice mantles. The COMs produced on grains then become gaseous as the temperature increases sufficiently to allow their thermal desorption. The recent observation of gaseous COMs in cold sources has not been fully explained by these gas-phase and dust grain production routes. Radiolysis chemistry is a possible non-thermal method of producing COMs in cold dark clouds. This new method greatly increases the modelled abundance of selected COMs upon the ice surface and within the ice mantle due to excitation and ionization events from cosmic ray bombardment. We examine the effect of radiolysis on three C2H4O2 isomers – methyl formate (HCOOCH3), glycolaldehyde (HCOCH2OH), and acetic acid (CH3COOH) – and a chemically similar molecule, dimethyl ether (CH3OCH3), in cold dark clouds. We then compare our modelled gaseous abundances with observed abundances in TMC-1, L1689B, and B1-b.

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