Experimental study of accelerating field distribution optimization in the H-structure with comb holders

We have suggested to perform the tuning the structure accelerating field distribution at the wave similar to H, by changing the inductivity of the holder of a single drift tube. Changing the angle of bend of the adjacent drift tube holders along different sides relatively to the comb holder plane allows one to increase and decrease the field amplitude in the gap between them. The value Rch ≈90 MОhm/m has been obtained for the structure under consideration that is higher than that obtained by known methods of tuning.Пропонується проводити настройку розподілу прискорюючого поля структури на хвилі, аналогічній Н, зміною індуктивності утримувача одиночної трубки дрейфу. Зміна кута повороту утримувачів сусідніх трубок дрейфу в різні боки щодо площини гребінчастого утримувача дає можливість як збільшувати, так і зменшувати амплітуду поля в зазорі між ними. Для структур, що розглядаються, отримано значення Rш ≈ 90 МОм⋅м⁻¹, що більш, ніж при відомих методах настройки.Предлагается проводить настройку распределения ускоряющего поля структуры на волне, аналогичной Н, изменением индуктивности держателя одиночной трубки дрейфа. Изменение угла поворота держателей соседних трубок дрейфа в разные стороны относительно плоскости гребенчатого держателя дает возможность как увеличивать, так и уменьшать амплитуду поля в зазоре между ними. Для рассматриваемых структур получено значение Rш ≈90 МОм⋅м⁻¹, что больше, чем при известных методах настройки

Differential Expression of Iron Acquisition Genes by Brucella melitensis and Brucella canis during Macrophage Infection

Brucella spp. cause chronic zoonotic disease often affecting individuals and animals in impoverished economic or public health conditions; however, these bacteria do not have obvious virulence factors. Restriction of iron availability to pathogens is an effective strategy of host defense. For brucellae, virulence depends on the ability to survive and replicate within the host cell where iron is an essential nutrient for the growth and survival of both mammalian and bacterial cells. Iron is a particularly scarce nutrient for bacteria with an intracellular lifestyle. Brucella melitensis and Brucella canis share ∼99% of their genomes but differ in intracellular lifestyles. To identify differences, gene transcription of these two pathogens was examined during infection of murine macrophages and compared to broth grown bacteria. Transcriptome analysis of B. melitensis and B. canis revealed differences of genes involved in iron transport. Gene transcription of the TonB, enterobactin, and ferric anguibactin transport systems was increased in B. canis but not B. melitensis during infection of macrophages. The data suggest differences in iron requirements that may contribute to differences observed in the lifestyles of these closely related pathogens. The initial importance of iron for B. canis but not for B. melitensis helps elucidate differing intracellular survival strategies for two closely related bacteria and provides insight for controlling these pathogens

NADPH-sulfite reductase from Escherichia coli. A flavin reductase participating in the generation of the free radical of ribonucleotide reductase.

International audienceProtein R2, the small subunit of ribonucleotide reductase of Escherichia coli, contains an essential free radical localized to tyrosine 122 of its polypeptide chain. When this radical is scavenged by hydroxyurea, the enzyme is transformed into an inactive form, metR2. E. coli contains a NAD(P)H:flavin oxidoreductase, named Fre, absolutely required for the regeneration of the radical and the activation of metR2 into R2. Consequently, an E. coli mutant strain lacking an active fre gene is more sensitive to hydroxyurea during growth, demonstrating the physiological protective function of Fre from the loss of the radical. However, this gene is not essential, and we found that E. coli contains a second tyrosyl radical generating activity, also residing in a flavin reductase. The enzyme has been purified 200-fold to homogeneity and found to be identical to sulfite reductase. Pure sulfite reductase has the ability to catalyze the reduction of free riboflavin, FMN, or FAD by NADPH and thus, as Fre, to transfer electrons to the iron center of metR2, a key step during the activation reaction