Peracetylated 1,6-dibromo-D-glucitol as efficient precursor of 1,6-diiodo and some mono-, disubstituted and heterocyclic D-glucitol derivatives

2,3,4,5-Tetra-O-acetyl-1,6-dibromo-1,6-dideoxy-D-glucitol (1a) obtained from D-glucitol was easily transformed into the 1,6-diiodo derivative in excellent yield (97%) by reaction with an excess of sodium iodide in refluxing butanone in 2 h. When the reaction time was prolonged to 24 h and the crude product was acetylated, 1,2,3,4,5-penta-O-acetyl-6-deoxy-6-iodo-D-glucitol and D-glucitol hexaacetate were isolated in 50 and 26% yields, respectively. The monodehalogenation then took place regioselectively at C-1. This regioselectivity allowed the synthesis of some mono- and disubstituted derivatives of D-glucitol. Thus, the peracetylated derivatives of D-glucitol, 6-bromo, 6-bromo-1-S-butyl, 6-bromo-1-S-octyl, 6-S-butyl, 6-S-butyl-1-S-octyl, 1-S-butyl, 1,6-di-S-octyl and 6-S-phenyl were synthesised in good to excellent yields. With S= as binucleophilic reagent, 1a gave mainly the thiepane derivative (75%) plus the 1-S-acetyl-2,6-anhydro-D-glucitol derivative as a by-product (10%).     

Chemical synthesis of methyl 6'-alpha-maltosyl-alpha-maltotrioside and its use for investigation of the action of starch synthase II

The branched pentasaccharide methyl 6'-alpha-maltosyl-alpha-maltotrioside was chemically synthesised and investigated as a primer for particulate starch synthase II (SSII) using starch granules prepared from the low-amylose pea mutant lam as the enzyme source. For chemical synthesis, the trichloroacetimidate activation method was used to synthesise methyl O-(2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl)-(1-->4)-O-(2,3,6-tri-O-benzyl-alpha-D-glucopyranosyl)-(1-->6)-O-[(2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl-(1-->4)]-O-(2,3-di-O-benzyl-alpha-D-glucopyranosyl)-(1-->4)-2,3,6-tri-O-benzyl-alpha-D-glucopyranoside, which was then debenzylated to provide the desired branched pentasaccharide methyl 6'-alpha-maltosyl-alpha-maltotrioside as documented by 1H and 13C NMR spectroscopy. Using a large excess of the maltoside, the pentasaccharide was tested as a substrate for starch synthase II (SSII). Both of the non-reducing ends of methyl 6'-alpha-maltosyl-alpha-maltotrioside were extended equally resulting in two hexasaccharide products in nearly equal amounts. Thus, SSII catalyses an equimolar and non-processive elongation reaction of this substrate. Accordingly, the presence of the alpha-1,6 linkages does not dictate a specific structure of the pentasaccharide in which only one of the two non-reducing ends are available for extension.     

Monkeys and toads define areas of endemism on Sulawesi

Abstract.— Ecological or geological phenomena can impose limits on geographic diversification that cause biogeographical patterns of distantly related but sympatrically occurring taxa to be similar. Concordant patterns of diversity facilitate conservation management because strategic designation of protected areas can capture complementary rather than redundant components of variation. Here we demonstrate that on the biodiverse Indonesian island of Sulawesi, seemingly idiosyncratic distributions of diversity in endemic monkeys (Macaca species) and toads (Bufo celebensis) are actually virtually identical on a fine geographic scale. It appears that range fragmentation has generated seven multi-taxon areas of genetic endemism, each of which should be targeted for conservation. Joint consideration of molecular phylogeography, morphology, and demography helps resolve apparent contradictions in paraphyletic macaque mitochondrial DNA and in undifferentiated toad morphology, and facilitates an understanding of biogeography and conservation genetics of Sulawesi fauna.     

Amino acid availability regulates S6K1 and protein synthesis in avian insulin-insensitive QM7 myoblasts

The regulation of S6K1 by nutritional status and insulin has been recently reported in vivo in chicken muscle despite the relative insulin resistance of this tissue as estimated by phosphatidylinositol 3-kinase (PI3-kinase) activity. The present work aimed to study the impact of amino acids on S6K1 activity in quail muscle (QM7) myoblasts. Firstly, we characterized S6K1 in QM7 cells and demonstrated the absence of insulin receptors in these cells. Secondly, we showed that amino acids in the absence of insulin induced S6K1 phosphorylation on Thr389 and concomitantly increased its enzymatic activity. Amino acid-induced S6K1 activation was inhibited by LY294002 (PI3-kinase inhibitor) and rapamycin (inhibitor of the mammalian target of rapamycin, mTOR), suggesting the involvement of an avian homolog of mTOR. The availability of individual amino acids (methionine or leucine) regulated S6K1 phosphorylation on Thr389 and QM7 protein synthesis. In conclusion, amino acids regulate S6K1 phosphorylation and activity in QM7 cells through the mTOR/PI3-kinase pathway in an insulin-independent manner.     

The extended multidomain solution structures of the complement protein Crry and its chimeric conjugate Crry-Ig by scattering,analytical ultracentrifugation and constrained modelling: implications for function and therapy

Complement receptor-related gene/protein y (Crry) is a cell membrane-bound regulator of complement activation found in mouse and rat. Crry contains only short complement/consensus repeat (SCR) domains. X-ray and neutron scattering was performed on recombinant rat Crry containing the first five SCR domains (rCrry) and mouse Crry with five SCR domains conjugated to the Fc fragment of mouse IgG1 (mCrry-Ig) in order to determine their solution structures at medium resolution. The radius of gyration R(G) of rCrry was determined to be 4.9-5.0 nm, and the R(G) of the cross-section was 1.2-1.5 nm as determined by X-ray and neutron scattering. The R(G) of mCrry-Ig was 6.6-6.7 nm, and the R(G) of the cross-section were 2.3-2.4 nm and 1.3 nm. The maximum dimension of rCrry was 18 nm and that for mCrry-Ig was 26 nm. The neutron data indicated that rCrry and mCrry-Ig have molecular mass values of 45,000 Da and 140,000 Da, respectively, in agreement with their sequences, and sedimentation equilibrium data supported these determinations. Time-derivative velocity experiments gave sedimentation coefficients of 2.4S for rCrry and 5.4S for mCrry-Ig. A medium-resolution model of rCrry was determined using homology models that were constructed for the first five SCR domains of Crry from known crystal and NMR structures, and linked by randomly generated linker peptide conformations. These trial-and-error calculations revealed a small family of extended rCrry structures that best accounted for the scattering and ultracentrifugation data. These were shorter than the most extended rCrry models as the result of minor bends in the inter-SCR orientations. The mCrry-Ig solution data were modelled starting from a fixed structure for rCrry and the crystal structure of mouse IgG1, and was based on conformational searches of the hinge peptide joining the mCrry and Fc fragments. The best-fit models showed that the two mCrry antennae in mCrry-Ig were extended from the Fc fragment. No preferred orientation of the antennae was identified, and this indicated that the accessibility of the antennae for the molecular targets C4b and C3b was not affected by the covalent link to Fc. A structural comparison between Crry and complement receptor type 1 indicated that the domain arrangement of Crry SCR 1-3 is as extended as that of the CR1 SCR 15-17 NMR structure.     

Efficient repair of cyclobutane pyrimidine dimers at mutational hot spots is restored in complemented Xeroderma pigmentosum group C and trichothiodystrophy/xeroderma pigmentosum group D cells

Xeroderma pigmentosum (XP) and trichothiodystrophy (TTD) are rare heritable diseases. Patients suffering from XP and 50% of TTD afflicted individuals are photosensitive and have a high susceptibility to develop skin tumors. One solution to alleviating symptoms of these diseases is to express the deficient cDNAs in patient cells as a form of gene therapy. XPC and TTD/XPD cell lines were complemented using retroviral transfer. Expressed wild-type XPC or XPD cDNAs in these cells restored the survival to UVC radiation to wild-type levels in the respective complementation groups. Although complemented XP cell lines have been studied for years, data on cyclobutane pyrimidine dimer (CPD) repair in these cells at different levels are sparse. We demonstrate that CPD repair is faster in the complemented lines at the global, gene, strand specific, and nucleotide specific levels than in the original lines. In both XPC and TTD/XPD complemented lines, CPD repair on the non-transcribed strand is faster than that for the MRC5SV line. However, global repair in the complemented cell lines and MRC5SV is still slower than in normal human fibroblasts. Despite the slower global repair rate, in the complemented XPC and TTD/XPD cells, almost all of the CPDs at "hotspots" for mutation in the P53 tumor database are repaired as rapidly as in normal human fibroblasts. Such evaluation of repair at nucleotide resolution in complemented nucleotide excision repair deficient cells presents a crucial way to determine the efficient re-establishment of function needed for successful gene therapy, even when full repair capacity is not restored.     

Cultivation of primmorphs from the marine sponge Suberites domuncula: morphogenetic potential of silicon and iron

Marine demosponges (phylum Porifera) are rich sources for potent bioactive compounds. With the establishment of the primmorph system from sponges, especially from Suberites domuncula, the technology to cultivate sponge cells in vitro improved considerably. This progress was possible after the elucidation that sponges are provided with characteristic metazoan cell adhesion receptors and extracellular matrix molecules which allow their cells a positioning in a complex organization pattern. This review summarizes recent data on the cultivation of sponges in aquaria and--with main emphasis--of primmorphs in vitro. It is outlined that silicon and Fe(+++) contribute substantially to the formation of larger primmorphs (size of 10 mm) as well as of a canal system in primmorphs; canals are probably required for an improved oxygen and food supply. We conclude that the primmorph system will facilitate a sustainable use of sponges in the production of bioactive compounds; it may furthermore allow new and hitherto not feasible insights into basic questions on the origin of Metazoa.     

Influence of ethylene-oxy spacer group on the activity of linezolid: synthesis of potent antibacterials possessing a thiocarbonyl group

The influence of an ethylene-oxy spacer element between the heterocycle and the aromatic ring in linezolid is reported. The introduction of such spacer group generated compounds with inferior antibacterial activity. However, the conversion of the acetamide group present in the linezolid analogues to either thiocarbamate or thioacetamide functionality restored the activity. The synthesis of linezolid analogues possessing the ethylene-oxy spacer group along with SAR studies with different heterocycles and preparation of some thiocarbonyl compounds possessing potent antibacterial property are presented.