Plasma desorption characteristics

The purified peptide has been used for additional studies of its physical properties. The peptide has certain unusual characteristics (such as its solvent solubility) that render it difficult to sequence. We found that the peptide has a free N-terminus. However, we have only been able to sequence through the first four amino acids (Phe-Leu-Cys-Ala...). After these residues the analysis stopped, probably due either to peptide substitutions or to the hydrophobic nature of this peptide. Current studies in our laboratory, therefore, are centered on using plasma desorption MS and microbore HPLC/dynamic FAB-MS to obtain physical data on this peptide. Such studies have shown that this peptide has a molecular mass of 3627.4 based on the singly charged molecular ion. 

Principles and Characteristics As well known, transformation of atoms and high mass organic molecules from a surface-adsorbed state into the gas phase (for mass spectrometric detection) may be achieved by various methods, including field desorption, plasma desorption, laser desorption, fast atom bombardment (FAB) and ion sputtering. These techniques address different analytical problem areas. For example, the development of the laser desorption (LD) technique has been prompted by the desire to study thermally labile and high mass compounds by mass spectrometry. 

Surface Ionization Sources. In this system, a low ionization potential atom (e.g. caesium) is adsorbed on a high work function metal (e.g. iridium). The temperature is raised so that the rate of desorption exceeds the rate of arrival of the atoms at the surface, and the Cs is then desorped as ions with very small energy spread (< 1 eY). The spot size - current characteristics of these sources lie between liquid metal and plasma discharge sources. 

In this study, breakthrough and desorption experiments were performed in activated carbon and zeolite SA beds to study the adsorption characteristics of binary and ternary hydrogen mixture gas (H2/CH4 43/57 and H2/CO/CO2 39.3/35.4/25.3 vol.%). The ternary mixture is the pseudo composition of effluent gas from incinerator for pyrolysis gasification while the binary mixture is the converted mixture gas from LNG by the cold plasma reaction. The ultimate purpose of this study is to find out the optimum condition for obtaining high purity hydrogen from H2 mixtures by using PSA process. 

It is obvious from works devoted to the investigation of adsorption-desorption dynamics of chains on attractive surfaces that chains attached to the surface, even by strong specific bonding, are able to detach completely due to thei-mally activated processes [62-65]. Thus, the chain once attached to the surface can leave the surface aftei- a period correlated to the time characteristic of cooperative multiple adsorption-desorption steps. For instance, Grauick and co-workers [62,64] have shown that the time needed for complete desorption of PS chains from the oxygen-plasma treated silicon surface in cyclohexane solution may reach the value 1(1 s and higher (in dependence on molecular-weight). 

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