Polymorphism generation

Of interest in this work is that the polymorphs, generated via the tailor-made impurity, turned out to be photoreactive. It is clear that this approach, despite the uncertainties associated with obtaining a new photoreactive crystalline modification, is worthy of experimentation. 

Chyall LJ, Tower JM, Coates DA, Houston TL, and Childs SL. Polymorph Generation in Capillary Spaces The Preparation and Structural Analysis of a Metastable Polymorph of Nabumetone. Cryst Growth Des 2002 2 505-510. 

All parameters in Eq. (9) are polymorph dependent except for Ap at the transition temperature, where the Gibbs free energies of the polymorphs are identical. In addition to the AG term, the d and N parameters in Eq. (10) will also be polymorph dependent. The particular polymorph generated would... 

The key issues in the study of drug polymorphism are the identification of different polymorphs (from a regulatory and patent viewpoint as much as from a formulation one), the determination of polymorph stability, and the assessment of processing conditions on polymorph generation. Whereas DSC is widely used as a means of routine screening for polymorphs, it is by no means universally effective as a means of identification. For example, several studies have indicated that DSC shows very similar traces for the various polymorphs of cimetidine (e.g., 15) hence, the generation of apparently identical peaks is not a guarantee of the absence of different crystal modifications. In other cases, however, the differentiation between polymorphs may be more obvious. 

This occurs, for instance, when a molded manufact tends to have a transition between polymorphic forms in conditions of use. In fact solid-solid transitions can generate problems of dimensional instability of the manufacts. 

C, Charmley P, Kaiser R, Hood L. Identification of clusters of biallelic polymorphic sequence-tagged sites (pSTSs) that generate highly informative and... 

Once the proton Tx and Tcli values are determined for a polymorphic system, physical mixtures of the two polymorphs can be generated (calibration samples). Subsequent acquisition of the solid state NMR spectra under quantitative conditions yields signal intensities representative of the amount of each solid state phase... 

In forming the double-helix polymeric DNA structure, the two sugar-phosphate backbones twist around the central stack of base pairs, generating a major and minor groove. Several conformations, known as DNA polymorphs, are possible. 

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