Fingerprint libraries

In both cases, GC fingerprint libraries must be built before quantitative analysis can be routinely carried out. In analysis of QTLC by laser pyrolysis scanning (LPS), the TLC plates are placed in a chamber after development, and were irradiated with an IR laser to produce a high temperature at the location of the spot. The analyte is swept by a carrier gas to a GC, and detected with FID or ECD. The technique combines the separation power of TLC and the detection modes of GC [846]. 

Fig. 2. MS methods for rapid microorganism identification (a) fingerprint library matching of mass spectra and (b) bioinformatics-based strategies. While the former rely on previously collected experimental mass spectra, the latter rely on in silico prediction of biomarker protein sequences from the respective genome seqnences.

Fingerprints structural keys identify a molecule - code is highly compact represented in bits ambiguous not convertible to other representations dependent on the fragment library... 

Dowms G M and J M Barnard 1997. Techniques for Generating Descriptive Fingerprints in Combina torial Libraries. Journal of Chemical Information and Computer Science 37 59-61. 

Beno BR, Mason JS. The design of combinatorial libraries using properties and 3D pharmacophore fingerprints. Drug Discov Today 2001 6(5) 251-8. 

McGregor, M. J., Muskal, S. M. Pharmacophore fingerprinting. 2. Application to primary library design. 

Clearly, within the conceptual framework described above, there is extensive room for exploration in creating fingerprints and similarity measures to retrieve molecules based on varying conceptions of similarity [42—441. The simplest types of fingerprint consist simply of features indices that map the presence or absence of a small library of functional groups. The most well known and effective are the MACCS keys. These were initially chemical feature indices, that we later used successfully as a similarity metric. 

When considering libraries of spectra for identification purposes, the effect of sample preparation on spectral characteristics is also important. Two FUR sampling methods have been adopted for IR analysis of TLC eluates in the presence of a stationary phase, namely DRIFTS [741] and PAS [742], of comparable sensitivity. It is to be noted that in situ TLC-PA-FTIR and TLC-DRIFT spectra bear little resemblance to KBr disc or DR spectra [743,744]. This hinders spectral interpretation by fingerprinting. For unambiguous identification, the use of a reference library consisting of TLC-FTIR spectra of adsorbed species is necessary. 

As may be obvious from previous chapters, quantitative analysis requires more substantial advancements to be made than qualitative analysis (library-based fingerprinting, screening, identification, recognition). For many polymer/additive problems, the classical methods are usually sensitive enough, and sophisticated instrumental methods are available, allowing analytical chemists to probe samples for components at much lower concentration levels. 

Mass spectra of numerous single compounds are available in reference libraries. However these spectra have not always been obtained in the same conditions as those used in DE or DI EI-MS modes and the spectra of molecules of specific interest in the field of cultural heritage have not been systematically registered. It is thus of importance to achieve mass spectra on a set of standard molecular constituents in order to study their mass spectral fingerprint in detail before investigating the more complex mass spectra of multicomponent materials. 

On the other hand, there is considerable interest to quantify the similarities between different molecules, in particular, in pharmacology [7], For instance, the search for a new drug may include a comparative analysis of an active molecule with a large molecular library by using combinatorial chemistry. A computational comparison based on the similarity of empirical data (structural parameters, molecular surfaces, thermodynamical data, etc.) is often used as a prescreening. Because the DFT reactivity descriptors measure intrinsic properties of a molecular moiety, they are in fact chemical fingerprints of molecules. These descriptors establish a useful scale of similarity between the members of a large molecular family (see in particular Chapter 15) [18-21],... 

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