Small computer, magnetic tape oriented, rapid search system applied to mass spectrometry

Wangen, L.E.; Woodward, W. S.; Isenhour, T. L.

doi:10.1021/ac60306a042

Cited by 58 publications

(21 citation statements)

References 15 publications

(6 reference statements)

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“…Many systems for computer matching of mass spectra have been proposed; most are described in the comprehensive review by Ridley.2 Recent methods include the Biemann-MIT system which utilizes the two largest peaks in each 14 mass unit i n t e r~a l ,~ the Heller-NIH conversational retrieval system4 and condensed systems for rapid searches5 utilizing small laboratory computers. 6 As recognized in an early machine retrieval system,' the most abundant mass spectral peaks are not necessarily the most characteristic; thus a quantitative comparison of the m/e and abundance values ('degree of match',2 'similarity index'3) of the unknown and reference spectrum is not a direct indication of the certainty of the molecular recognition. For example, a trained mass spectrometrist would be much more confident that an unknown and reference spectrum were due to the same compound if these showed the same abundances for the mass 141, 243 and 357 peaks, than if this were true for the 41, 43 and 57 peaks.…”

mentioning

confidence: 99%

Probability based matching of mass spectra. Rapid identification of specific compounds in mixtures

McLafferty

Hertel²,

Villwock³

1974

Org. Mass Spectrom.

167

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An automated system is described for computer examination of the mass spectrum of an unknown mixture for the presence of a specific compound. The probability that the compound is present is indicated as a 'confidence index' K ; 2= should signify the average number of compounds, selected at random, whose mass spectra would have to be examined to find data which match the target spectrum to the same degree as does the unknown. The value of Kis determined by the uniqueness U of the nz/e value, the abundance A , and the criterion of abundance agreement W of the matching peaks, and of the compound concentration D in the sample. Application to spectra from a variety of compounds, including illicit drugs, indicates that the system has high sensitivity and selectivity, and that the value of Kis a useful index of the reliability of the identification. Initial testing of this system has utilized an automated quadrupole mass spectrometer under control of a dedicated microcomputer with sample introduction through a flash evaporator and membrane separator,

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mentioning

confidence: 99%

Probability based matching of mass spectra. Rapid identification of specific compounds in mixtures

McLafferty

Hertel²,

Villwock³

1974

Org. Mass Spectrom.

167

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“…nificantly higher rate than did the Euclidean distance search. The average rate for the search of modulo 14 spectra is comparable to that for a propagation with the Euclidean distance search which includes seven nearest matches.…”

Section: Search Evaluation By a Propagation Methodsmentioning

confidence: 99%

The Evaluation of Mass Spectral Search Algorithms

Rasmussen¹,

Isenhour²

1979

J. Chem. Inf. Comput. Sci.

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“…Thiamine pyrophosphate (diphosphate) or cocarboxylase, ThPP, is the metabolically active coenzyme form of thiamine in a large number of enzymes catalyzing acyl group transfer reactions, for example, decarboxylation of a-keto acids and the formation of a-hydroxy carbonyl linkages (1,2). In blood, thiamine pyrophosphate is found mostly in the erythrocytes and, to a lesser extent, in the plasma (3).…”

Section: Purneshwar Seegopaul and Garry A Rechnitz*mentioning

confidence: 99%

Quantitative evaluation of library searching performance

Delaney¹,

Warren²,

Hallowell³

1983

Anal. Chem.

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A procedure Is descrlbed for the quantltatlve evaluatlon of the performance of a llbrary searchlng system employed for molecular structure elucldatlon. The technlque allows the evaluatlon of any form of spectral representation or any spectral comparison metrlc. The approach Is applicable to any type of spectrometry used for llbrary searchlng (LS) or to comblnatlons of different types of spectra. All comparisons are made relative to a chosen standard of quallty for library searching performance. I t Is assumed that the results of searchlng a llbrary of full-Intensity, full-resolution spectra by a least-squares metrlc will provlde an acceptable standard for comparlson. Results are presented to demonstrate the utlllty of thls procedure for the examlnatlon of alternatlves for llbrary searching of vapor-phase Infrared spectra.Library searching (LS) has been used effectively for both the identification and interpretation of spectra. The continued interest in instruments such as the gas chormatography/ Fourier transform infrarled spectrometer (GC/FTIR) underscores the need for an objective approach to the development of versatile and efficient LS systems. The tremendous quantity of data which can be generated in a single GC/FTIR experiment necessitates computer-assisted data processing.Consequently, 1,s systems are included in most commercial GC/FTIR instruments.Two important choices must be made in the design of a library searching system: (1) the manner in which the spectra are to be processed prior to storage in the reference library, and (2) the comparison >metric to be used during the search. A diversity of options for each of these has appeared in the literature (1-9) but it is not clear what combination of options would provide the best L S system for a given application. As a result, the development of LS systems is typically approached empirically. Various possibilities are tried until "satisfactory" porformance is obtained. Commercial FTIR search systems reflect this problem, in that they generally offer a number of options for spectral processing and choice of search metric, with little guidance as to how to design an optimal searching system.The need for a quantitative evaluation of library searching systems has received some attention in the literature. LS systems designed for th,e identification of spectra are most easily treated. Here the goal is unambiguous. The search system succeeds if it gets the right answer. Quality for LS systems of this sort has been expressed as the percentage of correctly identified spectra (10).For interpretive LS systems, the problem is more complex. These systems are designed to give useful information for spectal interpretation even when the unknown spectrum is not present in the refer~ence library. The entire "hit-list" of closest matches thus becomes important in determining quality. The most cominon approach to assessing quality in such systems has been by subjective visual inspection of hit-lists (11). Such "evaluation by acclamation" is too qualitative to provide a soun...

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Small computer, magnetic tape oriented, rapid search system applied to mass spectrometry

Cited by 58 publications

References 15 publications

Probability based matching of mass spectra. Rapid identification of specific compounds in mixtures

Probability based matching of mass spectra. Rapid identification of specific compounds in mixtures

The Evaluation of Mass Spectral Search Algorithms

Quantitative evaluation of library searching performance

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