LC-MS analysis

As the masses of all potential library members can be predicted from the nature of the building blocks, it should be possible to automate the procedure of comparing mass chromatograms for all potential library members between templated and untemplated libraries. This may then lead to a computer-generated shortlist of amplifications, which can then be verified, within a reasonable time, by hand and by some selected additional experiments using only the building blocks incorporated into the amplified compounds. 

LC-MS has been used by Gagne et al. in an elegant study showcasing some clever analytical chemistry for investigating chiral recognition in DCLs [11, 12]. The 

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Fig. 6. Particle beam lc/ms analysis of a complex ha2ardous waste sample (a) TIC showing peak at 23.23 min (b) mass spectmm of 23.23 min peak of...

Figure 3.13 (a) UV and (b) HC traces obtained from the LC-MS analysis of a pesticide mixture. From applications literatnre pnblished by Micromass UK Ltd, Manchester, UK,... 

The fundamental piece of information on which the subsequent spectral analysis is based is the total-ion-current (TIC) trace. Such a trace, obtained from the LC-MS analysis of a pesticide mixture, is shown in Figure 3.13, together with the UV trace recorded simultaneously. For the purposes of this discussion, the HPLC and MS conditions used to generate the data, other than the fact that electrospray ionization was used, are irrelevant. 

Figure 3.30 TIC trace obtained from the LC-MS analysis of atrazine and its degradation products. Reprinted from J. Chromatogr., A, 915, Steen, R. 1. C. A., Bobeldijk, I. and Brinkman, U. A. Th., Screening for transformation products of pesticides using tandem mass spectrometric scan modes , 129-137, Copyright (2001), with permission from Elsevier Science.

The TIC trace from the LC-MS analysis of an extracted river water sample, spiked with 3 p.g dm of atrazine and three of its degradation products, is shown in Figure 3.30. The presence of significant levels of background makes confirmation of the presence of any materials related to atrazine very difficult. The TIC traces from the constant-neutral-loss scan for 42 Da and the precursor-ion scan for m/z 68 are shown in Figure 3.31 and allow the signals from the target compounds to be located readily. 

Figure 4.18 Electrospray spectrum from a single chromatographic response in the LC-MS analysis of a tryptic digest. From applications literature published by SCIEX, Concord, Ontario, Canada, and reproduced by permission of MDS SCIEX, a division of MDS Inc.

Figure 5.6 Positive-ion electrospray spectrum obtained from the major component in the LC-MS analysis of a purified recombinant 62 kDa protein using a Cig microbore 50 X 1 mm column and a flow rate of 50 p.lmin . The starting buffer (buffer A ) was 0.1% TEA in water, while the gradient buffer (buffer B ) consisted of 0.1% TEA in acetonitrile-water (9 1 vol/vol). The running conditions consisted of 0% B for 5 min, followed by a linear gradient of 100% B for 55 min. Reprinted from J. Chromatogr., B, 685, McAtee, C. P., Zhang, Y., Yarbough, P. O., Fuerst, T. R., Stone, K. L., Samander, S. and Williams, K. R., Purification and characterization of a recombinant hepatitis E protein vaccine candidate by liquid chromatography-mass spectrometry , 91-104, Copyright (1996), with permission from Elsevier Science.

Figure 5.8 Electrospray and transformed electrospray spectra of the light- and heavy-chain antibody fragments of recombinant ritnximab obtained by LC-MS analysis. Reprinted from 7. Chromatogr., A, 913, Wan, H. Z., Kaneshiro, S., Frenz, J. and Cacia, J., Rapid method for monitoring galactosylation levels dnring recombinant antibody production by electrospray mass spectrometry with selective-ion monitoring , 437-446, Copyright (2001), with permission from Elsevier Science.

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