Calcium complexes conformation

C. Pigault, A. Follenius-Wund, B. Lux, and D. Gerard, A fluorescence spectroscopy study of the calpactin I complex and its subunits pit and p36 Calcium-dependent conformational changes, Biochim. Biophys. Acta 1037, 106-114 (1990). 

Nieuwenhuizen, M.S., Kieboom, A.P.G., and van Bekkum, H., Preparation of calcium complexation properties of a series of oxidized polysaccharides structural and conformational effects, Starch/Starke, 37, 192-200, 1985. 

The fact that the two signals observed in the free ligand for the t-butyl groups and the aromatic protons (Fig. 3a) approach each other in the calcium complex (Fig. 3b) indicates that the conformation of the calixarene macrocycle is less flattened in the complex and tends to become closer to the cone structure shown by the tetracid (1). 

Bou-Assaf GM, Chamoun JE, Emmett MR, Fajer PG, Marshall AG. Complexation and calcium-induced conformational changes in the cardiac troponin complex monitored by hydrogen/deuterium exchange and FT-ICR mass spectrometry. Int J Mass Spectrom. 

Curiously, the calcium-catalyzed epimerization does not occur with galactose. It was found to require a threo configuration of 0-3 and 0-4. To explain this, it was postulated [52] that calcium complexes with four oxygen atoms, namely 0-1,0-2,0-3 and 0-4. Structure 7 was therefore suggested for the complex. If the configuration of C-4 were reversed, such a complex would have a very unfavorable conformation. Cations usually complex with only three hydroxyl groups on a carbon chain however, an ionic form of the sugar would have a... 

Calcium is the trigger behind the muscle contraction process (24,25). Neural stimulation activates the release of stored Ca(Il) resulting in a dramatic increase in free calcium ion levels. The subsequent binding of Ca(Il) resulting in a dramatic increase in free calcium ion levels. The subsequent binding of Ca(Il) to the muscle protein troponin C provides the impetus for a conformational change in the troponin complex and sets off successive events resulting in muscle contraction. 

Figure 6.21 Schematic diagram of the conformational changes of calmodulin upon peptide binding, (a) In the free form the calmodulin molecule is dumhhell-shaped comprising two domains (red and green), each having two EF hands with bound calcium (yellow), (b) In the form with bound peptides (blue) the a helix linker has been broken, the two ends of the molecule are close together and they form a compact globular complex. The internal structure of each domain is essentially unchanged. The hound peptide binds as an a helix.

Calcium(II) complexes maleic acid conformation, 2, 475 mandelic acid, 2, 474... 

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