Fragment relationships

Musharraf SG, Ali A, Ali RA, Yousuf S, Atta-ur-Rahman, Choudhary MI (2011) Analysis and development of structure-fragmentation relationship in withanolides using an electrospray ionization quadrapole time of flight tandem mass spectrometry hybrid instrument. Rapid Commun Mass Spectrom 25 104—114... 

Structure-activity relationship (SAR), 1205, 1667, 3351, 3479 Structure-based design, 1247 Structure-fragmentation relationship (SFR), 3474... 

The advantages of SIMS are its high sensitivity (ppm detection limit for certain elements), its ability to detect hydrogen and the emission of molecular fragments which often bear tractable relationships with the parent... 

Several relationships aid in deducing the empirical formula of the parent ion (and also molecular fragments). From the empirical formula hypothetical molecular structures can be proposed, using the entries in the formula indices of Beilstein and Chemical Abstracts. 

Exact Mass Differences. If the exact mass of the parent or fragment ions are ascertained with a high-resolution mass spectrometer, this relationship is often useful for combinations of C, H, N, and O (Table 1.15b) ... 

Linker-Scanning Mutagenesis. Using linker-scanning mutagenesis (24) small sequences of DNA are removed and replaced with a synthetic restriction fragment or linker. This technique is commonly used in analysis of promoters and other control sequences in DNA, while preserving the spatial relationship between the sequences. 

The simplest relationship for calculating fragment range neglects drag and lift forces. Vertical and horizontal range, and z, then depend upon initial velocity and initial trajectory angle Oj ... 

Demethylvasconine (85) (9-methoxy-5-methyl-phenanthridin-8-olate) presented in Scheme 31 was found in Crinum kirkii (95P1291) (Amaryllidaceae). Although published as cation, no information about the anion of this alkaloid is given. Its relationship to other alkaloids of this class, however, makes a betainic structure more than likely and this is confirmed by a comparison of the NMR data of 85 with the cationic and betainic alkaloids presented in Table III. This betaine is isoconjugate with the 2-methylphenanthrene anion and thus defined the alkaloid as a member of class 1 (odd alternant hydrocarbon anions). Whereas substitution of the isoconjugate phenanthridinium moiety at the 1-position with an anionic fragment results in zwitterions (cf. Section III.D), the phenanthridinium-2-olate is a mesomeric betaine. 

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