Three-dimensional exchange spectroscopy

Native monellin consists of two polypeptide chains, a 45-residue A-chain and a 50-residue B-chain, linked by non-covalent interactions. At neutral pH, it is fairly resistant to heat denaturation with a higher than 80 °C. The crystal structure of native monellin shows a tertiary structure comprising an anti-parallel /1-sheet with five strands and an a-helix. H NMR spectroscopy and hydrogen exchange methods have been used to characterize the alcohol-denaturated state of monellin in order to understand how its secondary structure depends on environmental conditions. " Structural and dynamic studies by NMR have been carried out in order to compare native monellin and a non-sweet analogue in which Asp was replaced by Abu . The three-dimensional structures of the two proteins are found to be very... 

Other apphcations of covariance NMR include natural abundance deuterium NMR spectroscopy in chiral polypeptide liquid crystals [78] and three-dimensional experiments of combined homonuclear spin-exchange and separated-local-field spectroscopies [79]. These works also presented new sampling schemes and will be introduced in the next section. 

Even more information may be obtained by the. separate determination of A// and AS from differential scanning calorimetry, from the binding of 8-anilino-l-naphthalenesul-fonic acid, a fluorescent dye which preferentially binds to the molten globule state, and from proton exchange rates determined by NMR spectroscopy. Ultimately, all of these methods are required for a complete characterization of the protein. The final test remains the determination of the three-dimensional structure by X-ray crystallography or NMR. For a soluble, stable, folded protein, this should generally be possible. 

AAS = atomic absorption spectroscopy ATOF-MS = aerosol time-of-flight mass spectrometry 2,6-ndc = 2,6-naphthalenedicarboxylate bdc = 1,4-benzenedicar-boxylate bpdc = 1,3,5-benzenetricarboxylate bpydc = 2,2 -bipyridine-5,5 -dicarboxylate btb = 4,4, 4"-benzene-1,3,5-triylbenzoate btc = 1,3,5-benzenetricarboxylate 3D = three-dimensional dabco = l,4-diaza[2.2.2]bicyclo-octane EDX = energy-dispersive X-ray spectroscopy EXAFS = extended X-ray fine structure Fc = ferrocenyl ICP-AES = inductively coupled plasma atomic emission spectroscopy MOF = metal-organic framework PSD = postsynthetic deprotection PSM = Postsynthetic modification PXRD = Powder X-ray diffraction 1,4-ndc = 1,4-naphthalenedicarboxylate SALE = solvent-assisted linker exchange SBU = secondary building unit ... 

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