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2-chloroethanol solution was performed to clarify

Time:2015/12/18 5:55:19

A 13C nuclear magnetic resonance study of histone H1 in 2-chloroethanol and aqueous solutions. Identification of peaks characteristic of secondary folding

A 13C NMR study of calf thymus histone H1 in both aqueous solution and 2-chloroethanol solution was performed to clarify the folding behavior in these systems. To ascertain the general trend of displacements of 13C shifts upon folding in an enhanced manner, the latter solvent was employed since it is known to increase the amount of α-helix content in histone to about 50%. Generally, upfield displacements of Cβ signals (up to 1.4 ppm) were clearly identified as helix-induced peaks, although displacements of Cα signals, which might be much larger, were not easily distinguished because of overlap of several broadened signals with reduced peak intensities. In particular, we found that the upfield displacement of Ala Cβ, by 1.1 ppm, is an excellent probe to monitor the presence of α-helix conformation in both 2-chloroethanol and aqueous solutions. This upfield displacement of the Cβ signal in α-helix segment is consistent with our previous findings for a number of model polypeptides by ordinary and solid-state high resolution 13C NMR spectroscopy. Further, we observed that 13C peaks of several residues (Tyr, Ser, Leu, Ile, and Val) were suppressed as a result of specific folding of H1 in the presence of NaCl in aqueous solution. Thus, it appears that several tightly-folded segments whose 13C signals were considerably broadened are located in the central core portion.

Properties of Opsin-Lipid Complex in Aqueous 2-Chloroethanol

ABSTRACT Cattle and squid opsins were found to be associated with phospholipids after extensive dialysis of the salt-free digitonin extract of rhodopsin against 30% aqueous 2-chloroethanol (v/v) at pH 2.5. The approximate sizes of opsin-lipid complexes were estimated by sedimentation studies to be around 110,000 and 150,000 daltons, respectively, for the cattle and the squid opsin. Phospholipids did not dissociate from opsin even in 80% 2-chloroethanol. The complexes were purified by passage through a Sephadex G-200 gel column equilibrated with 30% 2-chloroethanol. The optical properties of the complex suggested the presence of 尾-conformation and a small amount of 伪-helix in solubilized cattle opsin.