Y-ions

Neodymium and YAG Lasers. The principle of neodymium and YAG lasers is very similar to that of the ruby laser. Neodymium ions (Nd +) are used in place of Cr + and are often distributed in glass rather than in alumina. The light from the neodymium laser has a wavelength of 1060 nm (1.06 xm) it emits in the infrared region of the electromagnetic spectrum. Yttrium (Y) ions in alumina (A) compose a form of the naturally occurring garnet (G), hence the name, YAG laser. Like the ruby laser, the Nd and YAG lasers operate from three- and four-level excited-state processes. 

The PTCR effect is complex and not fully understood in terms of the grain boundary states and stmcture. Both the PTCR effect and room temperature resistivities are also highly dependent on dopant type and ionic radius. Figure 11 (32) illustrates this dependence where comparison of the PTCR behavior and resistivity are made for near optimum concentrations of La ", Nd ", and ions separately substituted into BaTiO. As seen, lowest dopant concentration and room temperature resistivity are obtained for the larger radius cation (La " ), but thePTCR effect was sharpest for the smallest radius cation (Y " ), reflecting dual site occupancy of the Y " ion. 

If the solution were removed from Tank 1 and added to Tank 2, which also contained 1 eq of resin in the X ion form, the solution and resin phase would both contain 0.25 eq of Y ion and 0,75 eq of X ion. Repeating the procedure in a third and fourth tank would reduce the solution content of Y ions to 0.125 and 0.0625 eq. respectively. Despite an unfavorable resin preference. using a sufficient number of stages could reduce the concentration of Y ions in solution to any level desired. This analysis simplifies the column technique, but it does provide insights into the process dynamics. Separations are possible despite poor selectivity for the ion being removed. Most industrial applications of ion exchange use fixed-bed column... 

Protonation of the enolate ion is chiefly at the oxygen, which is more negative than the carbon, but this produces the enol, which tautomerizes. So, although the net result of the reaction is addition to a carbon-carbon double bond, the mechanism is 1,4 nucleophilic addition to the C=C—C=0 (or similar) system and is thus very similar to the mechanism of addition to carbon-oxygen double and similar bonds (see Chapter 16). When Z is CN or a C=0 group, it is also possible for Y to attack at this carbon, and this reaction sometimes competes. When it happens, it is called 1,2 addition. 1,4 Addition to these substrates is also known as conjugate addition. The Y ion almost never attacks at the 3 position, since the resulting carbanion would have no resonance stabilization " ... 

Imaoka, S. and Funae, Y., Ion-exchange high-performance liquid chromatography of membrane-bound protein cytochrome P-450,. Chromatogr., 375,83,1986. 

Xiang, X., Ko, C. Y., and Guh, H. Y., Ion-exchange chromatography/ electrospray mass spectrometry for the identification of organic and inorganic species in topiramate tablets, Anal. Chem., 68, 3726, 1996. 

Marcus, Y., Ion Solvation, John Wiley Sons, Chichester, 1986. 

Figure 2.5. Tandem mass spectrometry. A. A peptide mixture is electrosprayed into the mass spectrometer. Individual peptides from the mixture are isolated (circled peptide) and fragmented. B. The fragments from the peptide are mass analyzed to obtain sequence information. The fragments obtained are derived from the N or C terminus of the peptide and are designated "b" or "y" ions, respectively. The spectrum shown indicates peptides that differ in size by the amino acids shown.

Two major product ions were observed from the CID of protonated glycylglycine (Gly-Gly)H+ at low kinetic energies 10 eV (CM). These were the immonium ion NH2CH a, and the protonated glycine (Gly)H+ which is the y, ion. The a, ion is... 

YjAlsOn)—YAG Most garnets are silicates, whereas yttrium aluminum garnet (YAG) is an aluminate. In YAG, both the tetrahedral and the octahedral holes of the garnet structure are occupied by Al-ions and the quasi-cubic holes are occupied by Y-ions. 

Figure 6.4. Fragmentation spectrum of a tryptic peptide obtained from bovine serum albumin. Peptide sequence LGEYGFQNALIVR, monoisotopic [M + H]+ = 1479.796, monoisotopic [M+2H]2+ =740.402. Upper panel full scan MS spectrum. Lower panel MS/MS spectrum of a doubly-charged ion at 740.7 m/z with a ladder of y ions, the distances between which correspond to amino acid residues (upper row of letters). A shorter series of b ions is also seen (lower row of letters). See Fig. 6.5 for description of nomenclature. Note the often observed phenomenon where multiply-charged ions lose the charge during fragmentation process and, therefore, have higher m/z values than the original parent ion.

As we cannot obtain any further information from the N-terminal fragments, we should try to supplement our sequence coverage with the information obtained from C-terminal fragments. First the N-terminal amino acid can be identified through a mass difference between the mass of the precursor ion and the heaviest of the y-ion... 

The third idea is focused on finding the reverse ion series that might cover some additional amino acids. Masses of b-ions and y-ions emerging from the cleavage of the same bond add to the mass of the whole precursor increased by 1 Da. If the peptide is 10 AA long, the sum of masses of, for example, b8 and y2 ions is equal to the mass of the singly charged precursor +1 Da. This additional dalton is because... 

Complete sequencing of this peptide requires acquisition of additional tandem mass spectra, preferably MS3 fragmentation, of one of the low-mass y-ions. Because the peptide of interest is derived from a biological source, yet another possibility might be the use of sequence databases, similarly to the previous example. Actually, this approach works very well in this case, allowing identification of the peptide of interest as H-LGEYGFQNALIVR-OH, the 421-433 fragment of bovine serum albumin. 

The second example contained two basic amino acids in the middle of the sequence, but closer to the C-terminus. The fragmentation spectrum contained a huge number of both C- and N-terminal peaks, with a high number of doubly charged ions, including both basic amino acids. The presence of basic residues caused a more balanced number of b- and y-ions but also made it very difficult to obtain fragments with bond cleavage near basic residues. 

First of all, the shortest fragments in both b- and y-ion series should be available. Such ions can be used to assign the sequence strings to either N- or C-terminal ion... 

Most of the research performed in this field is based on tryptic peptides. As discussed earlier, such peptides contain basic amino acid residues on their C-terminus, which causes formation of the high intensity C-terminal ion series, mostly y-ions. In such peptides the N-terminal ions have lower intensity and do not provide important sequence information. Introduction of a highly basic group, such as dimethylalkyl-ammonium acetyl (DMAA) or tra(2,4,6-trimcthoxyphcnyl)phosphonium acetate into... 

A similar situation applies to stoichiometric LijN, which shows fast y -ion conduction within U2N planes (Von Alpen, Rabenau and Talat, 1977 Schulz and Thiemann, 1978 Schulz, 1982 Goodenough, 1984). 

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