Fragment similarity

Unsubstituted polynuclear aromatic hydrocarbons show intense molecular ions. The aklylated polynuclear aromatics and the alkylated benzenes fragment similarly ... 

The corresponding A4-oxide (132, C22H26N205, [a]D +86.6°) isolated from T. heyneana (Ervatamia heyneana) shows loss of 16 amu from M+ and subsequent fragmentation similar to that of other 3,6-oxidovoacangines (128). Skeletal... 

Quite generally the fragment similarity measure for a fragment / between two molecules A and B is then computed as... 

Different studies have appeared on fragment similarity using all the three partitioning schemes mentioned above, although in the case of the Hirshfeld method, the stockholder partitioning has also been applied directly to the similarity index [46,66,67]. 

Cioslowski et al. used fragment similarity indices to compute the degree of similarity between atoms of the same element in different molecules, where the atoms were those derived from Bader s atoms in molecules theory [68,69]. They introduced a novel atomic similarity index for atom A in molecule X and atom B in molecule Y defined as [70]... 

Studies on borohydride complexes of post-transition metals are as follows. Theoretical calculations on M(BH4) (M = Cu, Ag, Au) at the ab initio level indicate that Cu(i) and Ag(i) congeners have tetrahydridoborate structures, while the gold complex adopts a hydridoborane structure HAu(BH3).37 MeZn 2 /-BH4) 30 is prepared by addition of B2H6 to ZnMe2 or MeZnCl and Li[BH4]. The X-ray structure shows a polymeric helical arrangement of ZnMe + and [BH4]- fragments—similar to Be(BH4) or H2Ga(BH4) 50.38... 

As to the stoichiometry of the H3-H4-DNA particle, two complexes were identified an H3-H4 tetramer and an H3-H4 octamer, each associated with about 140 base pairs of DNA. The complexing of 140 base pairs of DNA with H3 and H4 resulted in the formation of nucleosome-like particles, as observed by the EM, and reported to have an s20base pairs (Bina-Stein and Simpson, 1977 Bina-Stein, 1978). These results differ from those of Simon et al. (1978) who report that at least two complexes of H3 H4-DNA can be obtained upon reconstitution of H3, H4, and 150 bp DNA. In this experiment both an octamer and a tetramer of H3-H4 were found bound to 150 base pairs of DNA, having sM,w equal to 10.4 and 7.5 for the octamer and tetramer, respectively. The stoichiometry of the complexes obtained is dependent on the histone-to-DNA ratio. At low ratios of histone to DNA the predominant species contains an H3-H4 tetramer per 150 base pairs of DNA. At a histone-to-DNA ratio of 1 1 the octamer prevails. The nuclease and protease digestion experiments (Camerini-Otero et al., 1976 Sollner-Webb et al., 1976) were performed at a histone-to-DNA ratio of 0.5, conditions which for 140-base-pair DNA would lead primarily to a tetrameric complex. Therefore, it seems that a tetramer of H3 H4 is sufficient for the generation of nuclease-resistant fragments similar to those of complete nucleosomes. Upon addition of H2A and H2B to the tetrameric complex, nucleosomes are formed. Addition of H3-H4 to the tetrameric complex resulted in an octameric complex which is similar in compaction to nucleosomes. H3-H4 tetramers and octamers were similarly found complexed with about 140 base pairs of DNA upon reconstitution of H3-H4 with SV40 DNA. Both complexes were reported to be able to fold 140 base pairs of DNA (Thomas and Oudet, 1979). 

Thiadiazoles often undergo photochemical fragmentation similar to the fragmentation observed in a mass spectrometer (see Section 4.10.3.4). An ethanolic solution of thia-... 

The RDA cleavage of (129) consists of expulsion of neutral methylacetylene with the formation of the acetylketene radical cation at m/e 84 loss of a methyl radical gives the abundant ketene ion (18b). The isomeric pyran-4-one (130) fragments similarly. In this case, however, RDA cleavage of the pyranone ring is followed by loss of CO, producing methylketene ions, m/e 56. Carbon monoxide loss from the molecular ion also occurs but to a lesser extent than for (129). 

The recorded fragmentation peaks for 3H-pyrrolizin-3-one (94a)66121 are due to loss of CO and then of HCN. A series of 2-substituted pyrrolizin-3-ones (95a-d) shows fragmentations similar to those of the acylpyrrolizines with loss... 

The benzyl p-dimethylaminobenzyl alcohol (25) is fragmented similarly with formation of p-(iV,JV-dimethylamino)benzaldehyde and toluence. Once again, the benzyl alcohol function is oxidized, the second benzyl function is reduced, and the acceptor remains unchanged it is involved only as a sensitizer. 

Let us first consider the catalyst/polyolefin particle in the early stage of its evolution. The particle consists of the solid catalyst carrier with catalyst sites immobilized on its surface, polymer phase, and pores. The first-principle-based meso-scopic model of particle evolution has to be capable of describing the formation of polymer at catalyst sites, transport of monomer(s) and other re-actants/diluents through the polymer and pore space, and deformation of the polymer and catalyst carrier (including its fragmentation). Similar discrete element modeling techniques have been applied previously to different problems (Heyes et al., 2004 Mikami et al., 1998 Tsuji et al., 1993). 

C N.m.r. chemical shifts and spin-relaxation times have been reported for /3-cyclocitral.246 Mass spectral data have been recorded for a -pyronene (147), which fragments similarly to allo-ocimene through common ions.247 Brief acid-catalysed treatment of a-pyronene (147) gives predominantly the diene... 

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