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Further Structure Attributes

Below you will find some commands providing a higher output of results for a closed structure search as well as a reduction of results during a substructure search. [Pg.172]

The CONNECT command enables inclusion of non-hydrogen atoms at certain positions. This command is suited for a Closed Substructure Search (Sect. 7.2.1). [Pg.173]

During a search for an exact closed substructure, substitutions are not allowed and thus automatically all atoms are saturated by hydrogen. In a substructure search this is somewhat different. The command HCOUNT (HCO) permits enter the number of H atoms which attach at particular atoms of the structure (Sect. 7.2.7). If HCOUNT is undefined, an arbitrary number of H atoms for each node is allowed, including zero. During a CSS search HCOUNTS may be changed in order to place substitutions at certain positions. [Pg.173]

It is wise to restrict the search by means of the hydrogen augmented (HA) screens (Sect. 7.2.6). These screens describe the number of H atoms at one atom. For instance, HA screen 1186 describes a C atom with exactly two hydrogen atoms. [Pg.173]

The command CHARGE (CHA) relates charge to a molecule or an atom. [Pg.174]


TLC-Raman laser microscopy (X = 514 nm) in conjunction with other techniques (IR microscopy, XRF and HPLC-DAD-ESI-MS) has been used in the analysis of a yellow impurity in styrene attributed to reaction of the polymerisation inhibitor r-butylcatechol (TBC) and ammonia (from a washing step) [795]. Although TLC-FT-Raman did not allow full structural characterisation, several structural elements were identified. Exact mass measurement indicated a C20H25O3N compound which was further structurally characterised by 1H and 13C NMR. [Pg.537]

Some further work on the tryptoquivaline-related metabolites of Aspergillus fumigatus has been reported, but some features of their chemistry still remain to be elucidated.25 On the basis of its n.m.r. spectrum, tryptoquivaline D (FTD) is now regarded as a secondary acetate, and is formulated as (25), i.e. the structure attributed to nortryptoquivaline direct comparison of specimens subsequently confirmed this conclusion. Similar arguments led to the conclusion that tryptoquivaline C (FTC) is also a secondary acetate, rather than an O-acetyl-hydroxylamine derivative, and should be identical with Buchi s tryptoquivaline (26) however, direct comparison of specimens failed to support this conclusion, and the relationship between these two compounds is still not clear. [Pg.151]

It is important to note in this context that electroreflectance measurements on silver electrodes (in the absence of pyridine) have found structures attributed to surface states, which were unusually and strongly dependent on the electric potential. Normally, we would expect the energies of species in the interface to change not more than the change in the electric potential. When these findings are further verified, they may turn out to be very important for understanding SERS and interface problems in general. [Pg.316]

If, on the other hand, all elements of E (or FJ%) are isolated then the attributes should be checked for the degree of anti-correlation (Spearman rank correlation). It depends on the scientific question, whether such a trade-off among attributes (a decreasing sequence of values of one attribute is always accompanied by an increasing sequence of another attribute) should be maintained in the study. There are methods to deal with such cases, see the chapter by Simon et al., p. 221 and by Sorensen et al., p. 259. However, this shall not be further discussed here. The subsets d, e as well as a, b, c form nontrivial hierarchies. Hence, we have three order relations b < a, c < a, and e < d. The fact that the set E can thus be partitioned into three disjoint subsets is always of great interest with respect to the data structures. Further structural elements, which are of interest in the analysis of Hasse diagrams, are subsequently discussed ... [Pg.79]

These topological indexes, based on the molecular connectivity approach, include three types the ""Xr molecular connectivity chi indexes that characterize the structural attributes of molecules, the ""k kappa indexes of molecular shape, and the topological equivalence state T values that individually characterize atoms and groups in the molecular skeleton and are used primarily to determine chemically equivalent atoms within a molecule. A further development of this approach has led to the electrotopological state atom indexes, which will not be discussed here but will be presented elsewhere. Molecular connectivity chi indexes are discussed in the first part of this paper along with illustrative applications. Then kappa shape indexes are discussed. The topological state index is discussed in the final section. [Pg.368]

Thus we found that our purpose of further structural confirmation of 5 by total synthesis was completed, although the absolute value of the optical rotation of synthetic triacetate (6) was smaller than that of natural specimen of 6. The optical purity of the synthetic compound was examined by means of chiral HPLC analysis after conversion of the corresponding alcohol derived from 21 into tetraacetate (7), which had been obtained by ozonolysis of 5 [7], to reveal that the synthetic tetraacetate (7) obtained in this study was 60% ee. The optical purity of synthetic 6 was estimated to be parallel to this result. This result may be attributable to partial racemization during oxidation-reduction process to obtain the erythro-z coho (18). In our previous study [7], chiral HPLC had showed tihat no crucial racemization occurred since the erythro-zXcohoX (18) and its threo-Xsomtr were separated after conversion into monopivaloyl esters (10 and its isomer) by 4-times repeated silica gel chromatographies. [Pg.192]

L538-541J, and later reemphasized by Klotz in an examination of protein folding [542]. In these cases the pK, s hrst increase with temperature, then level off and later decrease as the temperature is raised still further. Klotz attributed these observed dome-shaped temperature variations to inherent changes in the water solvent structure, which result, for example, in a dome-shaped density variation that reaches a maximum near 4°C. [Pg.123]


See other pages where Further Structure Attributes is mentioned: [Pg.358]    [Pg.172]    [Pg.358]    [Pg.172]    [Pg.363]    [Pg.80]    [Pg.210]    [Pg.196]    [Pg.234]    [Pg.109]    [Pg.291]    [Pg.298]    [Pg.298]    [Pg.14]    [Pg.341]    [Pg.26]    [Pg.71]    [Pg.87]    [Pg.7]    [Pg.3]    [Pg.174]    [Pg.251]    [Pg.416]    [Pg.278]    [Pg.9]    [Pg.150]    [Pg.1133]    [Pg.126]    [Pg.16]    [Pg.237]    [Pg.436]    [Pg.66]    [Pg.179]    [Pg.447]    [Pg.224]    [Pg.49]    [Pg.14]    [Pg.405]    [Pg.179]    [Pg.300]    [Pg.330]    [Pg.1318]    [Pg.13]    [Pg.100]    [Pg.484]   


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