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Structural Modelling (structural + modelling)

Distribution by Scientific Domains

Medical Sciences	42%

Selected Abstracts

Aspergillus nidulans,-galactosidase of glycoside hydrolase family 36 catalyses the formation of ,-galacto-oligosaccharides by transglycosylation

FEBS JOURNAL, Issue 17 2010
Hiroyuki Nakai
The ,-galactosidase from Aspergillus nidulans (AglC) belongs to a phylogenetic cluster containing eukaryotic ,-galactosidases and ,-galacto-oligosaccharide synthases of glycoside hydrolase family 36 (GH36). The recombinant AglC, produced in high yield (0.65 g·L,1 culture) as His-tag fusion in Escherichia coli, catalysed efficient transglycosylation with ,-(1,6) regioselectivity from 40 mm 4-nitrophenol ,- d -galactopyranoside, melibiose or raffinose, resulting in a 37,74% yield of 4-nitrophenol ,- d -Galp -(1,6)- d -Galp, ,- d -Galp -(1,6)-,- d -Galp -(1,6)- d -Glcp and ,- d -Galp -(1,6)-,- d -Galp -(1,6)- d -Glcp -(,1,,2)- d -Fruf (stachyose), respectively. Furthermore, among 10 monosaccharide acceptor candidates (400 mm) and the donor 4-nitrophenol ,- d -galactopyranoside (40 mm), ,-(1,6) linked galactodisaccharides were also obtained with galactose, glucose and mannose in high yields of 39,58%. AglC did not transglycosylate monosaccharides without the 6-hydroxymethyl group, i.e. xylose, l -arabinose, l -fucose and l -rhamnose, or with axial 3-OH, i.e. gulose, allose, altrose and l -rhamnose. Structural modelling using Thermotoga maritima GH36 ,-galactosidase as the template and superimposition of melibiose from the complex with human GH27 ,-galactosidase supported that recognition at subsite +1 in AglC presumably requires a hydrogen bond between 3-OH and Trp358 and a hydrophobic environment around the C-6 hydroxymethyl group. In addition, successful transglycosylation of eight of 10 disaccharides (400 mm), except xylobiose and arabinobiose, indicated broad specificity for interaction with the +2 subsite. AglC thus transferred ,-galactosyl to 6-OH of the terminal residue in the ,-linked melibiose, maltose, trehalose, sucrose and turanose in 6,46% yield and the ,-linked lactose, lactulose and cellobiose in 28,38% yield. The product structures were identified using NMR and ESI-MS and five of the 13 identified products were novel, i.e. ,- d -Galp -(1,6)- d -Manp; ,- d -Galp -(1,6)-,- d -Glcp -(1,4)- d -Glcp; ,- d -Galp -(1,6)-,- d -Galp -(1,4)- d -Fruf; ,- d -Galp -(1,6)- d -Glcp -(,1,,1)- d -Glcp; and ,- d -Galp -(1,6)-,- d -Glcp -(1,3)- d -Fruf. [source]

Sense of coherence and adjustment to divorce among Muslim Arab citizens of Israel

EUROPEAN JOURNAL OF PERSONALITY, Issue 4 2003
Orna Cohen
This study examined the distinctiveness and causal relationships of Antonovsky's (1979) Sense of Coherence Scale and the Mental Health Index of Veit and Ware (1983) in a sample of 306 divorced Muslim Arab men and women in Israel. The findings, based on confirmatory factor analysis and latent-variable structural modelling, suggest that in the present sample sense of coherence (SOC) and mental health are two independent but correlated constructs. They also suggest that, consistent with Antonovsky's theory, SOC may be better viewed as a mediator between stress and mental health than as a concurrent outcome of stress, although the latter possibility is not ruled out. Finally, the findings indicate that the SOC of the sample was relatively low in comparison with other groups. Copyright © 2003 John Wiley & Sons, Ltd. [source]

The chitinolytic system of Lactococcus lactis ssp. lactis comprises a nonprocessive chitinase and a chitin-binding protein that promotes the degradation of ,- and ,-chitin

FEBS JOURNAL, Issue 8 2009
Gustav Vaaje-Kolstad
It has recently been shown that the Gram-negative bacterium Serratia marcescens produces an accessory nonhydrolytic chitin-binding protein that acts in synergy with chitinases. This provided the first example of the production of dedicated helper proteins for the turnover of recalcitrant polysaccharides. Chitin-binding proteins belong to family 33 of the carbohydrate-binding modules, and genes putatively encoding these proteins occur in many microorganisms. To obtain an impression of the functional conservation of these proteins, we studied the chitinolytic system of the Gram-positive Lactococcus lactis ssp. lactis IL1403. The genome of this lactic acid bacterium harbours a simple chitinolytic machinery, consisting of one family 18 chitinase (named LlChi18A), one family 33 chitin-binding protein (named LlCBP33A) and one family 20 N -acetylhexosaminidase. We cloned, overexpressed and characterized LlChi18A and LlCBP33A. Sequence alignments and structural modelling indicated that LlChi18A has a shallow substrate-binding groove characteristic of nonprocessive endochitinases. Enzymology showed that LlChi18A was able to hydrolyse both chitin oligomers and artificial substrates, with no sign of processivity. Although the chitin-binding protein from S. marcescens only bound to ,-chitin, LlCBP33A was found to bind to both ,- and ,-chitin. LlCBP33A increased the hydrolytic efficiency of LlChi18A to both ,- and ,-chitin. These results show the general importance of chitin-binding proteins in chitin turnover, and provide the first example of a family 33 chitin-binding protein that increases chitinase efficiency towards ,-chitin. [source]

Structural analysis of lithium lanthanum titanate with perovskite structure

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2009
Koji Ohara
Abstract Neutron and high-energy X-ray diffraction analysis of polycrystalline La4/3-xLi3xTi2O6 have been performed to clarify the extent of disorder of the distribution of La and Li ions and to understand the relation of these distributions to ionic conduction. The distributions of the La and Li ions in a 10 × 10 × 20 cubic box (i.e., 10 × 10 × 10 unit cell) super-structure, in which Ti and O atoms are fixed onto their regular sites, were obtained by the reverse Monte Carlo (RMC) structural modelling of both diffraction data sets. When the occupancy of La ions in the planes perpendicular to the c-axis is analysed, one can find a La-rich and La-poor layers alternating, which is consistent with the results of earlier Rietveld analysis (Stramare et al., Chem. Mater. 15, 3974 (2003) [1]). Of particular interest, the Li ions are found mainly on the interstitial sites between the O-3 triangle plane of the TiO6 octahedron and a La ion, which is different from the earlier work (Yashima et al., J. Am. Chem. Soc. 127, 3491 (2005) [2]). (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Loss of the JAK2 intramolecular auto-inhibition mechanism is predicted by structural modelling of a novel exon 12 insertion mutation in a case of idiopathic erythrocytosis

BRITISH JOURNAL OF HAEMATOLOGY, Issue 6 2008
Elena Albiero
Summary We report a novel gain-of-function JAK2 exon 12 insertion mutation in a patient with idiopathic erythrocytosis and low serum erythropoietin level. To date, only rare cases of such mutations have been reported in the JAK2 exon 12. Using computer-based structural modelling we propose that this mutation causes the loss of the JAK2 auto-inhibition step, leading to the constitutive activation of JAK2 tyrosine kinase-dependent activity. Our model-based hypothesis provides a useful approach for the investigation of the phenotype-genotype relationship in myeloproliferative disorders involving JAK2. [source]

Psychological factors, immune function and recovery from major surgery

ACTA NEUROPSYCHIATRICA, Issue 4 2009
Ute Vollmer-Conna
Objective: This study used a prospective design and the technique of structural modelling to examine the complex interrelations between psychological factors, immune status and complications after major surgery. Methods: Twenty-nine women scheduled for elective cholecystectomy were studied prospectively. Information regarding medical history, health practices, life stressors, and coping strategies was obtained two weeks prior to admission. At this initial meeting, as well as three days after surgery, and at one month follow-up immunological tests were performed and the level of psychological distress was assessed. The study additionally included measures of post-operative complications, and infections and negative effect during follow-up. Results: Pre-operative immune status emerged as a key variable exerting strong effects on subsequent immune function and, thereby producing significant, indirect effects on every recovery variable. Pre-operative distress was directly linked to increased mood disturbance at follow-up. Moreover, distress significantly influenced immune function both before and after surgery, which mediated a significant impact on most recovery variables. Active coping behaviour directly increased the risk of a complicated recovery. Conclusions: The study demonstrated that distress-induced changes in immune functioning have clinical relevance. Overall, the present findings suggest that recovery from surgery is facilitated in patients with a well-functioning immune system, a low-level of pre-operative distress and a passive coping disposition. [source]