Structural differences between mesophilic, moderately thermophilic and extremely thermophilic protein subunits: results of a comprehensive survey

AbstractBackground: Proteins from thermophilic organisms usually show high intrinsic thermal stability but have structures that are very similar to their mesophilic homologues. From prevous studies it is difficult to draw general conclusions about the structural features underlying the increased thermal stability of thermophilic proteins.Results: In order to reveal the general evolutionary strategy for changing the heat stability of proteins, a non-redundant data set was compiled comprising all high-quality structures of thermophilic proteins and their mesophilic homologues from the Protein Data Bank. The selection (quality) criteria were met by 64 mesophilic and 29 thermophilic protein subunits, representing 25 protein families. From the atomic coordinates, 13 structural parameters were calculated, compared and evaluated using statistical methods. This study is distinguished from earlier ones by the strict quality control of the structures used and the size of the data set.Conclusions: Different protein families adapt to higher temperatures by different sets of structural devices. Regarding the structural parameters, the only generally observed rule is an increase in the number of ion pairs with increasing growth temperature. Other parameters show just a trend, whereas the number of hydrogen bonds and the polarity of buried surfaces exhibit no clear-cut tendency to change with growth temperature. Proteins from extreme thermophiles are stabilized in different ways to moderately thermophilic ones. The preferences of these two groups are different with regards to the number of ion pairs, the number of cavities, the polarity of exposed surface and the secondary structural composition

Emerging fractal patterns in a real 3D cerebral aneurysm

The behaviour of biological fluid flows is often investigated in medical practice to draw conclusions on the physiological or pathological conditions of the considered organs. One area where such investigations are proven to be useful is the flow-related formation and growth of different pathologic malformations of the cerebro vascular system. In this work, a detailed study is presented on the effect of a cerebral aneurysm on blood transport inside a human brain artery segment. This malformation causes strong flow instabilities that drives the flow system towards chaotic behaviour. The emerging fractal structure and some of its measurable properties have been explored using a method that makes the measurement of these properties feasible even in complicated large three dimensional data sets. We find that, from the investigated chaos parameters, the information dimension turns out to be the most reliable parameter to characterize chaotic advection in the vicinity of the aneurysm sac. We propose that properties of chaotic mixing close to aneurysms might be relevant for the condition of this pathologic malformation

Pethő Sándor találkozása Görgei Artúrral

Sándor Pethő was one of the most important publicists of the period between the two World Wars. He is part of the national memory as the founder and editor in chief of the anti-Nazi newspaper Magyar Nemzet (Hungarian Nation). He received a thorough education in history as a student of Sándor Márki and the recipient of a state scholarship, his historical works drew a lot of attention in the 1920s and 30s. Pethő quickly developed sympathy for Artúr Görgei, the great figure of 1848-49, and he even visited him personally at Visegrád. From that point on he constantly studied the deeds and personality of the general of the War of Independence for more than 20 years in more and more accurate and deep works, until he wrote the– even to this day – only full biography of Artúr Görgei in 1930. While examining Pethő’s works on Görgei we can find connections to historiographic antecedents, as well as contemporary evaluations, and we can learn a lot about the changes in Görgei’s public image. As a supporter of independence, in the final years of dualism Pethő joined the moderate opposition based on the Austro-Hungarian compromise of 1867, the circle of Gyula Andrássy the Younger. After 1920 as a follower of Andrássy he was a legitimist, hoping for the restoration of the unity of the Danube basin. This is important to mention, because, sadly, the perception of Görgei has been influenced by the conflicts between political parties, and these changes and discrepancies can be seen in Pethő’s works as well