Constructing energy maps of metabolic cycles

1998 ◽  
Vol 26 (3) ◽  
pp. 261
Keyword(s):  
1982 ◽  
Vol 17 (2) ◽  
pp. 397-405 ◽  
Author(s):  
J. K. Wells ◽  
P. W. R. Beaumont

2008 ◽  
Vol 73 (5) ◽  
pp. 591-607 ◽  
Author(s):  
Lucie Sihelniková ◽  
Stanislav Kozmon ◽  
Igor Tvaroška

Conformational behavior of the [(2S,3R,4R,5S)-3,4,5-trihydroxy-2-(phenylsulfanyl)tetrahydrofuran-2-yl]methyl sulfate anion (2), which is the potential transition state (TS) analogue of the inverting glycosyltransferases, was studied by means of two-dimensional potential-energy maps, using a density functional theory method at the B3LYP/6-31+G* level. The maps revealed the presence of eight low-energy domains which were refined at the B3LYP/6-311++G** level and led to six conformers in vacuum. In aqueous solution, two conformers dominate at equilibrium. The preferred conformers superimpose well with the transition state structure, as determined previously for glycosyltransferase GnT-I. The conformations of 2 in the active site of glycosyltransferase GnT-I were obtained by docking methods. It was found that one of the two best docking poses mimics the binding mode of TS. These results suggest that the proposed TS mimics 2 have the potential to be used as a scaffold for the design of TS analogue inhibitors.


Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 176-176
Author(s):  
R Watt ◽  
P Carlin

When a sample of natural images is taken and compared with a set of noise images, the two are obviously distinguishable. Even when the noise images are set to have the same power spectral characteristics as the natural images, there is no doubt which is a normal image and which is a noise image. In the study to be reported, we have examined the nature of the spatial characteristics of natural images that allow them to be so discriminated from noise images. The approach is to process large sets of images belonging to various categories through mechanisms that have some similarities to known operations in biological visual systems. Thus, the images are filtered at various spatial scales and at various orientations; the filter outputs are combined into local energy maps; and features are detected in such processed images. The result of these calculations is the distribution of values of some parameter which describes a particular image characteristics for each set of images. Parameters that could support adequate discrimination between two sets of images, for example natural images and noise images, will have largely non-overlapping distributions. In practice it is found that no simple parameters can distinguish obviously different sets of images, but parameters that encapsulate spatial patterns, especially those related to non-accidental image properties, can do so. It is concluded that filter outputs must be followed by nontrivial spatial operations. Suggestions are made as to what are the most plausible.


Author(s):  
Alberto Ortega ◽  
Rodrigo Escobar ◽  
Sergio Colle

The Chilean government’s energy policy and the power generation sector plans include wind, geothermal, hydro and biomass powerplants in order to introduce renewable energy systems to the country, but they do not mention solar energy to be a part of the plan. This apparent lack of interest in solar energy is partly due to the absence of a valid solar energy database, adequate for energy system planning activities. The only available solar radiation database is relatively old, with measurements taken in 89 stations from the 60’s onwards, obtained with high-uncertainty sensors such as Campbell-Stokes devices and pyranographs. Moreover, not all stations have measured incoming solar radiation for an adequate time span. Here, we compare the existing database of solar radiation in Chile with estimations made with satellite measurements, obtained from the GOES program through collaboration with the Brazilian space institution, INPE. Monthly mean solar energy maps are created from both data sources and compared, using Krigging methods for spatial interpolation. It is found that a maximum 30 percent deviation exist, with snow covers in the Andes Mountains adding additional uncertainty levels. The solar energy levels throughout the country can be considered as high, and it is thought that they are adequate for energy planning given proper diffusion and support by editing a Chilean Solar Atlas.


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