Structures and functions of carotenoids bound to reaction centers from purple photosynthetic bacteria

The photoprotective function of 15,15'-cis-carotenoids bound to the photosynthetic reaction centers (RCs) of purple bacteria has been studied using carotenoids reconstituted into carotenoidless RCs from Rhodobacter sphaeroides strain R26.1. The triplet-energy level of the carotenoid has been proposed to affect the quenching of the triplet state of special-pair bacteriochlorophyll (P). This was investigated using microsecond flash photolysis to detect the carotenoid triplets as a function of the number of conjugated double bonds, n. The carotenoid triplet signals were extracted by using singular-value decomposition (SVD) of the huge matrices data, and were confirmed for those having n = 8 to 11. This interpretation assumes that the reconstituted carotenoids occupy the same binding site in the RC. We have been able to confirm this assumption using X-ray crystallography to determine the structures of carotenoidless, wild-type carotenoid-containing, and 3,4-dihydro-spheroidene-reconstituted RCs. The X-ray study also emphasized the importance of the methoxy group of the carotenoids for binding to the RCs. Electroabsorption (Stark) spectroscopy was used to investigate the effect of the carotenoid on the electrostatic field around P. This electrostatic field changed by 10 % in the presence of the carotenoid

Novel Loci for Adiponectin Levels and Their Influence on Type 2 Diabetes and Metabolic Traits : A Multi-Ethnic Meta-Analysis of 45,891 Individuals

J. Kaprio, S. Ripatti ja M.-L. Lokki työryhmien jäseniä.Peer reviewe

Crystal structure of cis-dichloro-cis-bis(dimethylsulphoxide)-trans-di- methyltin(IV)

The crystal structure of cis-dichloro-cis-bis(dimethylsulphoxide)-trans- dimethyltin(VI), CHClOS Sn, has been determined by use of three-dimensional equi-inclination Weissenberg X-ray diffraction data with 947 visually estimated reflections. The orthorhombic unit cell, space group P222, has dimensions, a = 13·39(1), b = 15·58(1), c = 6·95(1) Å, with Z = 4. The structure was refined by least-squares methods to a conventional R of 0·12. The tin atom has an octahedral environment with cis-chlorine atoms and -(dimethyl sulphoxide) groups, bonded through the oxygen, and trans-methyl groups. [Sn-Cl, 2·48(1), 2·53(1); Sn-O, 2·32(3), 2·38(3); Sn-C, 2·07(6), 2·08(5) Å, C-Sn-C, 170(2)°]

Crystal structure of 3,6-anhydro-α-D-glucosyl-1,4:3,6-dianhydro-β-D-fructoside

The crystal structure of the title compound has been determined from three-dimensional data collected on a diffractometer. The structure was solved by direct methods, using phases refined by the tangent formula. The orthorhombic unit cell, space group P212121 has dimensions: a= 6·437(1), b= 11·298(1), c= 16·754(1)Å with Z= 4. The structure was refined by least squares to R 0·071 for 991 independent reflections. The dehydrated sucrose compound has three extra rings, two on the furanose moiety causing strain about atoms C(3′) and C(4′). The additional ring in the pyranose group causes a change in conformation from the sucrose structure to one with axial hydroxy-groups, and equatorial hydrogen atoms

X-Ray crystallographic determination of the structure of 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole

The S-C distance is 1·681(4) Å in the structure of 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole

A neutron diffraction study of potassium lead hexanitrocuprate(II), an example of a regular octahedral copper(II) complex

The crystal structure of potassium lead hexanitrocuprate(II), K Pb[Cu(NO)], has been redetermined using three-dimensional neutron diffraction data. The compound crystallises in the cubic system, space group Fm3 or F, with a = 10·66 ± 0·01 Å. The copper atom is surrounded by six nitro-groups to form a regular octahedron. The Cu-N bond distance of 2·11 Å is significantly longer than that usually observed

1.2 Å crystal structure of the <i>S. pneumoniae</i> PhtA histidine triad domain a novel zinc binding fold

The recently described pneumococcal histidine triad protein family has been shown to be highly conserved within the pneumococcus. As part of our structural genomics effort on proteins from &lt;i&gt;Streptococcus pneumoniae&lt;/i&gt;, we have expressed, crystallised and solved the structure of PhtA-166–220 at 1.2 Å using remote SAD with zinc. The structure of PhtA-166–220 shows no similarity to any protein structure. The overall fold contains 3β-strands and a single short α-helix. The structure appears to contain a novel zinc binding motif. The remaining 4 histidine triad repeats from PhtA have been modelled based on the crystal structure of the PhtA histidine triad repeat 2. From this modelling work, we speculate that only three of the five histidine triad repeats contain the residues in the correct geometry to allow the binding of a zinc ion

Structure of Bordetella pertussis virulence factor P.69 pertactin

A new generation of whooping-cough vaccines contain P.69 pertactin, a surface-exposed domain of an outer membrane protein expressed by the virulent bacterium Bordetella pertussis. This protein is a virulence factor that mediates adhesion to target mammalian cells, a reaction that is in part mediated by an RGD sequence. The X-ray crystal structure of P.69 pertactin has been determined to 2.5 A. The protein fold consists of a 16-stranded parallel beta-helix with a V-shaped cross-section, and is the largest beta-helix known to date. Several between-strand weakly conserved amino-acid repeats form internal and external ladders. The structure appears as a helix from which several loops protrude, which contain sequence motifs associated with the biological activity of the protein. One particular (GGXXP)5 sequence is located directly after the RGD motif, and may mediate interaction with epithelial cells. The carboxy-terminal region of P.69 pertactin incorporates a (PQP)5 motif loop containing the major immunoprotective epitop