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How the bacteriochlorophyll (BChl) c molecules are assembled in the aggregate of an isomeric mixture from Chlorobium limicola in the solid state, as determined by intermolecular [sup.13.C]-[sup.13.C] dipolar correlations, and how the assembly of BChl c in a large aggregate in the solid state compares to, or contrasts to, those in the smaller aggregates in suspension are considered. Results reveal that the structure of the solid-state aggregate of BChl c contains both types of stackings, the dimer-based stacking and the (pseudo) monomer-based stacking.

Magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) is a powerful method for structure determination of insoluble biomolecules. However, structure determination by MAS solid-state NMR remains challenging because it is difficult to obtain a sufficient amount of distance restraints owing to spectral complexity. Collection of distance restraints from paramagnetic relaxation enhancement (PRE) is a promising approach to alleviate this barrier. However, the precision of distance restraints provided by PRE is limited in solid-state NMR because of incomplete averaged interactions and intermolecular PREs. In this report, the backbone structure of the B1 domain of streptococcal protein G (GB1) has been successfully determined by combining the CS-Rosetta protocol and qualitative PRE restraints. The derived structure has a Cα RMSD of 1.49 Å relative to the X-ray structure. It is noteworthy that our protocol can determine the correct structure from only three cysteine-EDTA-Mn mutants because this number of PRE sites is insufficient when using a conventional structure calculation method based on restrained molecular dynamics and simulated annealing. This study shows that qualitative PRE restraints can be employed effectively for protein structure determination from a limited conformational sampling space using a protein fragment library. [ABSTRACT FROM AUTHOR]

Magic-angle-spinning solid-state C NMR spectroscopy is useful for structural analysis of non-crystalline proteins. However, the signal assignments and structural analysis are often hampered by the signal overlaps primarily due to minor structural heterogeneities, especially for uniformly-C,N labeled samples. To overcome this problem, we present a method for assigning C chemical shifts and secondary structures from unresolved two-dimensional C-C MAS NMR spectra by spectral fitting, named reconstruction of spectra using protein local structures (RESPLS). The spectral fitting was conducted using databases of protein fragmented structures related to C, C, and C′ chemical shifts and cross-peak intensities. The experimental C-C inter- and intra-residue correlation spectra of uniformly isotope-labeled ubiquitin in the lyophilized state had a few broad peaks. The fitting analysis for these spectra provided sequence-specific C, C, and C′ chemical shifts with an accuracy of about 1.5 ppm, which enabled the assignment of the secondary structures with an accuracy of 79 %. The structural heterogeneity of the lyophilized ubiquitin is revealed from the results. Test of RESPLS analysis for simulated spectra of five different types of proteins indicated that the method allowed the secondary structure determination with accuracy of about 80 % for the 50-200 residue proteins. These results demonstrate that the RESPLS approach expands the applicability of the NMR to non-crystalline proteins exhibiting unresolved C NMR spectra, such as lyophilized proteins, amyloids, membrane proteins and proteins in living cells. [ABSTRACT FROM AUTHOR]

• Curcumin and polyglycerol fatty acid ester have abbreviated as CUR and PGFE. • A novel amorphous CUR formulation with PGFE has stably enhanced water solubility. • The amorphous CUR has greatly improved absorbability. • The amorphous CUR has significantly reduced blood triglyceride concentrations. • As the mechanism, PGFE has suppressed CUR-CUR interaction and diffusion rate of CUR. Curcumin (CUR), a polyphenol, is an attractive component of functional foods, owing to various physiological activities. However, CUR is highly hydrophobic, insoluble in water, and difficult to absorb in the body. Here, we report an amorphous CUR formulation containing the dispersant polyglycerol fatty acid ester (PGFE), demonstrating high and stable water solubility. Improved water solubility enhanced the absorbability of CUR in our amorphous formulation along with enhanced triglyceride inhibition, compared to that in a commercial formulation. Nuclear Overhauser effect spectroscopy (NOESY) analysis revealed that PGFE reduced CUR-CUR interaction, resulting in higher dispersion and improved solubility of CUR. Taylor dispersion analysis showed a lower diffusion coefficient of CUR in the highly water-soluble formulation (with PGFE) than that in the low water-soluble formulation (without PGFE), which prevents recontact and recrystallization of CUR, which is trapped by PGFE. Overall, the amorphous CUR with high solubility could be used as a promising functional food. [ABSTRACT FROM AUTHOR]

A mixture of bacteriochlorophyll (BChl) c isomers was extracted from the cells of Chlorobium limicola that were grown in the media of 13C-enriched and natural-abundance isotopic compositions. The magic-angle spinning 13C NMR proton-driven spin-diffusion spectra were recorded with mixing times of 50, 100, and 250 ms for two different kinds of in vitro aggregates, one consisting of pure [13C]BChl c and the other consisting of a 1:1 mixture of [13C]BChl c and [12C]BChl c; those peaks whose intensities were reduced to approximately 1/4 by this dilution were assigned to intermolecular 13C-13C dipolar correlation peaks. On the other hand, the nearest-neighbor intermolecular carbon-carbon close contacts with distances of 4-6 A were simulated, to predict observed correlation peaks, for six different models of BChl c assembly. They include weakly overlapped monomers forming structure 1 and structure 2, strongly overlapped dimers forming straight and inclined columns, and weakly overlapped dimers forming aligned and displaced layers. Comparison between the observed correlation peaks and the predicted carbon-carbon close contacts, for both the macrocycles and the side chains, led us to a conclusion that the weakly overlapped dimers forming displaced layers are most likely the assembly of the BChl c molecules in the aggregate.