title: Crystal structure of pyruvate decarboxylase from Zymobacter palmae

authors: Buddrus, Lisa

subjects: Science & Technology

abstract: Pyruvate decarboxylase (PDC; EC 4.1.1.1) is a thiamine pyrophosphate- and Mg²⁺ ion-dependent enzyme that catalyses the non-oxidative decarboxylation of pyruvate to acetaldehyde and carbon dioxide. It is rare in bacteria, but is a key enzyme in homofermentative metabolism, where ethanol is the major product. Here, the previously unreported crystal structure of the bacterial pyruvate decarboxylase from Zymobacter palmae is presented. The crystals were shown to diffract to 2.15 Å resolution. They belonged to space group P21, with unit-cell parameters a = 204.56, b = 177.39, c = 244.55 Å and Rᵣ.ᵢ.ₘ. = 0.175 (0.714 in the highest resolution bin). The structure was solved by molecular replacement using PDB entry 2vbi as a model and the final R values were Rwₒᵣₖ = 0.186 (0.271 in the highest resolution bin) and Rfᵣₑₑ = 0.220 (0.300 in the highest resolution bin). Each of the six tetramers is a dimer of dimers, with each monomer sharing its thiamine pyrophosphate across the dimer interface, and some contain ethylene glycol mimicking the substrate pyruvate in the active site. Comparison with other bacterial PDCs shows a correlation of higher thermostability with greater tetramer interface area and number of interactions.

text: Crystal structure of pyruvate decarboxylase from Zymobacter palmae Pyruvate decarboxylase (PDC; EC 4.1.1.1) is a thiamine pyrophosphate- and Mg²⁺ ion-dependent enzyme that catalyses the non-oxidative decarboxylation of pyruvate to acetaldehyde and carbon dioxide. It is rare in bacteria, but is a key enzyme in homofermentative metabolism, where ethanol is the major product. Here, the previously unreported crystal structure of the bacterial pyruvate decarboxylase from Zymobacter palmae is presented. The crystals were shown to diffract to 2.15 Å resolution. They belonged to space group P21, with unit-cell parameters a = 204.56, b = 177.39, c = 244.55 Å and Rᵣ.ᵢ.ₘ. = 0.175 (0.714 in the highest resolution bin). The structure was solved by molecular replacement using PDB entry 2vbi as a model and the final R values were Rwₒᵣₖ = 0.186 (0.271 in the highest resolution bin) and Rfᵣₑₑ = 0.220 (0.300 in the highest resolution bin). Each of the six tetramers is a dimer of dimers, with each monomer sharing its thiamine pyrophosphate across the dimer interface, and some contain ethylene glycol mimicking the substrate pyruvate in the active site. Comparison with other bacterial PDCs shows a correlation of higher thermostability with greater tetramer interface area and number of interactions.

year: 2016

title: Timestamp representations for virtual sequences

authors: Cleary, John G.

subjects: computer science

abstract: The problem of executing sequential programs optimistically using the Time Warp algorithm is considered. It is shown how to do this, by first mapping the sequential execution to a control tree and then assigning timestamps to each node in the tree. For such timestamps to be effective they must be finite, this implies that they must be periodically rescaled to allow old timestamps to be reused. A number of timestamp representations are described and compared on the basis of: their complexity; the frequency and cost of rescaling; and the cost of performing basic operations, including comparison and creation of new timestamps.

text: Timestamp representations for virtual sequences The problem of executing sequential programs optimistically using the Time Warp algorithm is considered. It is shown how to do this, by first mapping the sequential execution to a control tree and then assigning timestamps to each node in the tree. For such timestamps to be effective they must be finite, this implies that they must be periodically rescaled to allow old timestamps to be reused. A number of timestamp representations are described and compared on the basis of: their complexity; the frequency and cost of rescaling; and the cost of performing basic operations, including comparison and creation of new timestamps.

year: 1996-11

title: Cooperation in Maori and European children

authors: Vercoe, Glynis Price

subjects: Maori children

abstract: The object of this study is to compare the cooperative behaviour of Maori and European children and to investigate and compare the effects, upon the performance of the two ethnic groups, of working under cooperative conditions and under competitive conditions. Certain differences are expected to exist between the two ethnic groups as a result of the different child rearing practices employed by the Maoris and by the Europeans.

text: Cooperation in Maori and European children The object of this study is to compare the cooperative behaviour of Maori and European children and to investigate and compare the effects, upon the performance of the two ethnic groups, of working under cooperative conditions and under competitive conditions. Certain differences are expected to exist between the two ethnic groups as a result of the different child rearing practices employed by the Maoris and by the Europeans.

year: 1971