Large molecule broad spectrum

Though a large number of small molecule inhibitors against a variety of tyrosine kinases are being developed, the most advanced drugs can be roughly classified as (i) Bcr-Abl/Src family kinase inhibitors, (ii) ErbB inhibitors and (iii) broad spectrum TfCIs with an anti-angiogenic component. 

A large number of a, 3-didehydro-a-amino acids have been identified as constituents of relatively low molecular weight cyclic compounds from microbial sources. However, the presence of a,p-didehydroalanine in bacterial as well as in mammalian histidine ammonia lyase and in phenylalanine ammonia lyase shows that the occurrence of a,p-didehydro-a-amino acids is not limited to small molecules alone 8 These residues are incorporated in natural sequences by posttranslation modification. a,p-Didehydro-a-amino acids have also been postulated to be precursors in the biosynthesis of several heterocyclic metabolites including penicillin and cephalosporin 9 Other well-known compounds containing ,( -di-dehydro-a-amino acids are nisin 10,11 (a food preservative112 ), subtilin (a broad spectrum antibiotic) 13 and some of the metabolites isolated from Streptomyces strains such as gri-seoviridin 14 ... 

Many pulse sequence suppression schemes exist and these can be loosely classified into three broad classes (i) saturation based, (ii) magnetization destruction based, and (iii) methods avoiding solvent saturation. An ideal method would suppress the solvent only with no other effect on the spectrum. In reality this is never the case. For example, some suppression sequences which involve frequency-selective excitation result in frequency-dependent artifacts such as phase shifts and amplitude responses. Sometimes the applicability of a suppression method depends on the sample. For example, in addition to creating artifacts, caution must be taken when using suppression methods that involve saturation since cross-relaxation can result in significant signal loss, especially with large molecules. 

Very roughly, one might think of the highly structured spectrum as a signature of a small molecule and of the broad spectrum as the signature of a large molecule. The latter may be further elucidated by considering Eq. (6) in the limit where the states /c> are so closely spaced that there is no... 

Intermediate-sized systems are systems that are larger than the molecules we have considered sofar but not so large that they can be considered as approximately infinite. This class of materials covers a broad spectrum of different types of systems, each with its special chemical and physical properties as well as problems when treating them theoretically. 

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