Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026837 (muscle rigidity)
 1,077 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Binding of neurotoxin II Naja naja oxiana derivatives containing one spin label at various positions (Leu 1, Glu 2, Lys 15, Lys 25, Lys 26, His 31, Lys 44 and Lys 46) to purified solubilized acetylcholine receptor protein (AchR) from Torpedo marmorata was studied by EPR techniques. AchR interaction with several dansylated neurotoxin II derivatives was followed by difference fluorescence spectroscopy. A series of neurotoxin II p-azidobenzoyl derivatives were prepared and in three of them modified lysine residues were identified. In combination, spectroscopic data and photolabeling implicate a considerable area of the neurotoxin in association with AchR. Rigidity of the neurotoxin II conformation allowed to regard its binding surface as a mould of the AchR corresponding site and to estimate the minimal size of the latter. Conformation of the long-chain neurotoxins and their binding to AchR are briefly discussed basing on the 1H and 19F NMR studies of neurotoxin I Naja naja oxiana, toxin 3 Naja naja siamensis and its acetylated or trifluoroacetylated derivatives, as well as on Achr interaction with the derivatives spin labeled at Lys 27 and His 71.
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PMID:Interaction surfaces of neurotoxins and acetylcholine receptor. 708 49

Key atoms at specific positions along the ring govern the shape, or "topology" of a group of [13]-macrodiolides. Here we report the synthesis of these macrocycles and their characterization by functional and structural methods. The [13]-macrodiolides are organized by three four-atom planar units that help to rigidify them and one hinge atom that enables the planar units to orient themselves. The driving force for the organization of the structures is the minimization of steric strain on groups attached to the key atoms. When the key atom is a stereocenter, a macrocycle with planar chirality is observed. An alternative cup-like topology arises when the key atom bears two alkyl groups. Additionally, the key atoms can work in a coordinated fashion to guide one topology over another. The synthesis relied on an acylation-ring closing metathesis sequence. Rigidity was demonstrated by variable-temperature NMR experiments and diastereoselective epoxidation reactions. X-ray crystal structures of representative [13]-macrodiolides served as the basis of the structural observations made. The results provide a framework for the design of new macrocycles with well-defined structures as well as for understanding some general principles that influence the topology of natural product macrocycles.
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PMID:Positioning and configuration of key atoms influence the topology of [13]-macrodiolides. 2380