Quaternary macromolecular

Quaternary structures are formed between nonidentical subunits to give irregular macromolecular complexes or between identical subunits to give geometrically regular structures. 

In principle, protein structure can be described by the same structural parameters used for other macromolecular compounds, that is, constitution, configuration, microconformation, macroconformation, association and superstructure. But for convenience and for historical reasons, a different classification is used primary, secondary, tertiary, and quaternary structure. 

Although the applications described here have concerned diverse macromolecular samples, pyrolysis is also of utility in the analysis of smaller molecules, particularly quaternary ammonium compounds, which undergo quantitative thermal fragmentation to volatile products. For example, the specificity and sensitivity afforded by Py-GC/MS with mass fragmentography renders the technique suitable for the analysis of endogenous neurotransmitters such as acetylcholine at the l-2pmol level. However, in all cases, analytical throughput is limited by the retention times of the pyrolysis products, a condition that is particularly severe in taxonomic applications. Automation allows extended use, but direct Py-MS... 

The neuropharmacology of the ionenes is presumably not restricted to interactions with AcChR. Choline re-uptake, release of transmitter, and esterase activity may also be affected by this class of polymers, since in all cases recognition sites for quaternary nitrogen functions are involved. Thus the present paper is no more than a beginning in the application of ionenes to the pharmacological and biochemical study of the various macromolecular structures functioning in cholinergic transmission. 

Benesch, j. L. R Aquhjna, J. A. Ruotolo, B. T. SoBOTT, F. Robinson, C. V. Tandem mass spectrometry reveals the quaternary oiganization of macromolecular assemblies. Chem. Biol 2006, 13, 597-605. 

Quaternary structure Arrangement of polypeptides in macromolecular assembly. 

Although a substantial number of proteins function as monomers there are many others that exist as multimers. The arrangement of protein subunits in a macromolecular assembly is referred to as its quaternary structure. This aspect of protein structure plays an important role in the stability and regulation of a large number of enzymes, virus assembly, cellular regulation, and motility. Indeed, quaternary structure underlies all aspects of protein-protein interaction. 

This limitation in depth of labeling under TA conditions has been exploited in the study of proteins and protein assemblages, where the method is sometimes called tritium planigraphy. Such macromolecular systems, when treated under TA conditions are tritiated only in parts of molecules located at or very near the surface, leaving interior parts unlabeled. Subsequent dissection of the substrate, for example by separation of protein subunits or tryptic hydrolysis of protein followed by radioanalysis, can form the basis for inferences about the structure of the substrate. Applications of the TA method in this area include studies of the organization of the coat proteins of potato virus conformational dynamics of ribonuclease A spatial localization of coenzyme FAD in the quaternary structure of yeast alcohol dehydrogenase and subunit organization of the bacterial ribosome " . ... 

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