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Complete Structure (complete + structure)

Distribution by Scientific Domains

Chemistry	71%

Selected Abstracts

Antecedents of flow in online shopping: a test of alternative models

INFORMATION SYSTEMS JOURNAL, Issue 4 2009
Yi Maggie Guo
Abstract Flow is an optimal state of experience that has been studied in various situations, including online environments. In such environments, it has been found to be positively related to exploratory behaviour, revisit and purchase intention, and positive attitude towards web sites. Based on flow theory, this study tests the complete structure of the flow model as it was originally formulated in an online shopping context. The role of the preconditions of flow is elaborated and the effect of web site complexity, an important interface design variable, on flow is examined. Results show that web site complexity affects flow through the mediating effects of the three preconditions of flow. Theoretical and practical implications of this finding are discussed. [source]

Application of HPLC-NMR for the Rapid Chemical Profiling of a Southern Australian Sponge, Dactylospongia sp.

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 4 2009
Daniel Anthony Dias
Abstract Rapid chemical profiling of the antitumour active crude dichloromethane extract of the marine sponge, Dactylospongia sp. was undertaken. A combination of both offline (HPLC followed by NMR and MS) and on-line (on-flow and stop-flow HPLC-NMR) chemical profiling approaches was adopted to establish the exact nature of the major constituents present in the dichloromethane extract of this sponge. On-flow HPLC-NMR analysis was employed to initially identify components present in the dichloromethane extract, while stop-flow HPLC-NMR experiments were then conducted on the major component present, resulting in the partial identification of pentaprenylated p -quinol (5). Subsequent off-line RP semi-preparative HPLC isolation of 5 followed by detailed spectroscopic analysis using NMR and MS permitted the complete structure to be established. This included the first complete carbon NMR chemical shift assignment of 5 based on the heteronuclear 2-D NMR experiments, together with the first report of its antitumour activity. This study represents one of the few reports describing the application of HPLC-NMR to chemically profile secondary metabolites from a marine organism. [source]

Performance of phased rotation, conformation and translation function: accurate protein model building with tripeptidic and tetrapeptidic fragments

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2010
Franti, ek Pavel
The automatic building of protein structures with tripeptidic and tetrapeptidic fragments was investigated. The oligopeptidic conformers were positioned in the electron-density map by a phased rotation, conformation and translation function and refined by a real-space refinement. The number of successfully located fragments lay within the interval 75,95% depending on the resolution and phase quality. The overlaps of partially located fragments were analyzed. The correctly positioned fragments were connected into chains. Chains formed in this way were extended directly into the electron density and a sequence was assigned. In the initial stage of the model building the number of located fragments was between 60% and 95%, but this number could be increased by several cycles of reciprocal-space refinement and automatic model rebuilding. A nearly complete structure can be obtained on the condition that the resolution is reasonable. Computer graphics will only be needed for a final check and small corrections. [source]

Crystallization and preliminary X-ray crystallographic analysis of a full-length active form of the Cry4Ba toxin from Bacillus thuringiensis

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2010
Niramon Thamwiriyasati
To obtain a complete structure of the Bacillus thuringiensis Cry4Ba mosquito-larvicidal protein, a 65,kDa functional form of the Cry4Ba-R203Q mutant toxin was generated for crystallization by eliminating the tryptic cleavage site at Arg203. The 65,kDa trypsin-resistant fragment was purified and crystallized using the sitting-drop vapour-diffusion method. The crystals belonged to the rhombohedral space group R32, with unit-cell parameters a = b = 184.62, c = 187.36,Å. Diffraction data were collected to at least 2.07,Å resolution using synchrotron radiation and gave a data set with an overall Rmerge of 9.1% and a completeness of 99.9%. Preliminary analysis indicated that the asymmetric unit contained one molecule of the active full-length mutant, with a VM coefficient and solvent content of 4.33,Å3,Da,1 and 71%, respectively. [source]

Descent with modification: the unity underlying homology and homoplasy as seen through an analysis of development and evolution

BIOLOGICAL REVIEWS, Issue 3 2003
BRIAN K. HALL
ABSTRACT Homology is at the foundation of comparative studies in biology at all levels from genes to phenotypes. Homology similarity because of common descent and ancestry, homoplasy is similarity arrived at via independent evolution However, given that there is but one tree of life, all organisms, and therefore all features of organisms, share degree of relationship and similarity one to another. That sharing may be similarity or even identity of structure the sharing of a most recent common ancestor,as in the homology of the arms of humans and apes,or it reflect some (often small) degree of similarity, such as that between the wings of insects and the wings of groups whose shared ancestor lies deep within the evolutionary history of the Metazoa. It may reflect sharing entire developmental pathways, partial sharing, or divergent pathways. This review compares features classified homologous with the classes of features normally grouped as homoplastic, the latter being convergence, parallelism, reversals, rudiments, vestiges, and atavisms. On the one hand, developmental mechanisms may be conserved, when a complete structure does not form (rudiments, vestiges), or when a structure appears only in some individuals (atavisms). On the other hand, different developmental mechanisms can produce similar (homologous) features Joint examination of nearness of relationship and degree of shared development reveals a continuum within expanded category of homology, extending from homology , reversals , rudiments , vestiges , atavisms , parallelism, with convergence as the only class of homoplasy, an idea that turns out to be surprisingly old. realignment provides a glimmer of a way to bridge phylogenetic and developmental approaches to homology homoplasy, a bridge that should provide a key pillar for evolutionary developmental biology (evo-devo). It will and in a practical sense cannot, alter how homoplastic features are identified in phylogenetic analyses. But rudiments, reversals, vestiges, atavisms and parallelism as closer to homology than to homoplasy should guide toward searching for the common elements underlying the formation of the phenotype (what some have called deep homology of genetic and/or cellular mechanisms), rather than discussing features in terms of shared independent evolution. [source]

Generalized X-ray and neutron crystallographic analysis: more accurate and complete structures for biological macromolecules

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2009
Paul D. Adams
X-ray and neutron crystallographic techniques provide complementary information on the structure and function of biological macromolecules. X-ray and neutron (XN) crystallographic data have been combined in a joint structure-refinement procedure that has been developed using recent advances in modern computational methodologies, including cross-validated maximum-likelihood target functions with gradient-based optimization and simulated annealing. The XN approach for complete (including hydrogen) macromolecular structure analysis provides more accurate and complete structures, as demonstrated for diisopropyl fluorophosphatase, photoactive yellow protein and human aldose reductase. Furthermore, this method has several practical advantages, including the easier determination of the orientation of water molecules, hydroxyl groups and some amino-acid side chains. [source]