Morphological Diversity of Dps Complex with Genomic DNA.

In response to adverse environmental factors, Escherichia coli cells actively produce Dps proteins which form ordered complexes (biocrystals) with bacterial DNA to protect the genome. The effect of biocrystallization has been described extensively in the scientific literature; furthermore, to date, the structure of the Dps-DNA complex has been established in detail in vitro using plasmid DNA. In the present work, for the first time, Dps complexes with E. coli genomic DNA were studied in vitro using cryo-electron tomography. We demonstrate that genomic DNA forms one-dimensional crystals or filament-like assemblies which transform into weakly ordered complexes with triclinic unit cells, similar to what is observed for plasmid DNA. Changing such environmental factors as pH and KCl and MgCl2 concentrations leads to the formation of cylindrical structures.

Protective Dps-DNA co-crystallization in stressed cells: an in vitro structural study by small-angle X-ray scattering and cryo-electron tomography.

Under severe or prolonged stress, bacteria produce a nonspecific DNA-binding protein (Dps), which effectively protects DNA against damaging agents both in vitro and in vivo by forming intracellular biocrystals. The phenomenon of protective crystallization of DNA in living cells has been intensively investigated during the last two decades; however, the results of studies are somewhat contradictory, and up to now, there has been no direct determination of a Dps-DNA crystal structure. Here, we report the in vitro analysis of the vital process of Dps-DNA co-crystallization using two complementary structural methods: synchrotron small-angle X-ray scattering in solution and cryo-electron tomography. Importantly, for the first time, the DNA in the co-crystals was visualized, and the lattice parameters of the crystalline Dps-DNA complex were determined.

Polymorphic Protective Dps-DNA Co-Crystals by Cryo Electron Tomography and Small Angle X-Ray Scattering.

Rapid increase of intracellular synthesis of specific histone-like Dps protein that binds DNA to protect the genome against deleterious factors leads to in cellulo crystallization-one of the most curious processes in the area of life science at the moment. However, the actual structure of the Dps-DNA co-crystals remained uncertain in the details for more than two decades. Cryo-electron tomography and small-angle X-ray scattering revealed polymorphous modifications of the co-crystals depending on the buffer parameters. Two different types of the Dps-DNA co-crystals are formed in vitro: triclinic and cubic. Three-dimensional reconstruction revealed DNA and Dps molecules in cubic co-crystals, and the unit cell parameters of cubic lattice were determined consistently by both methods.

Functional connectivity between salience, default mode and frontoparietal networks in post-stroke depression.

BACKGROUND: Previous studies have demonstrated altered resting state functional connectivity (rsFC) in patients with post-stroke depression (PSD). It remains unclear whether rsFC is changed at the network level as was shown for major depressive disorder (MDD). To address this question, we investigated rsFC of resting sate networks (RSNs) in PSD. METHODS: Eleven subjects with PSD underwent fMRI scanning at rest before and after treatment. The severity of depression was assessed using the aphasic depression rating scale (ADRS). We performed functional network connectivity (FNC) analysis for RSNs, region of interest - FC analysis (ROI-FC) and calculation of brain matter volumes in ROIs overlapping with RSNs and in other brain regions associated with mood maintenance. RESULTS: We found positive correlation of FNC between anterior default mode network (aDMN) and salience network (SAL) with depression severity before treatment, the latter accompanied by the increase of white matter in the middle frontal and left angular gyri. FNC of aDMN and left frontoparietal network (LFP) decreased after treatment. ROI-FC and the brain matter volumes of several regions of DMN, LFP and SAL also showed a correlation with ADRS or significant change after treatment. LIMITATIONS: Limitations include small sample size and methodological issues concerning altered hemodynamics in stroke. However, we took complex preprocessing steps to overcome these issues. CONCLUSION: Present results of altered rsFC in PSD are consistent with previous findings in MDD. The convergence of results obtained in PSD and MDD supports the validity of rsFC approach for investigation of brain network dysfunctions underling these psychiatric symptoms.

Hexagonal ferrites: a unified model of the (TS)nT series in superspace.

Hexagonal ferrites represent an extensive family of mixed-layer magnetic materials with periods up to 1500 A along the stacking direction, probably constituting the largest unit cells in the inorganic realm. The (TS)(n)T subfamily includes P3m1 and R3m structures that can be derived from Y ferrite Ba(2)M(2)Fe(12)O(22) (M = Zn, Fe, Co, Mg, Mn) by introducing stacking faults. A unified (3 + 1)-dimensional superspace model is proposed for all members of the (TS)(n)T family. The model belongs to the superspace group X3m1(00gamma) with X = {(1/3, 2/3, 0, 1/3), (2/3, 1/3, 0, 2/3)}, has a unit cell of the basic structure with a = 5.88, c = 4.84 A and modulation vector q = 4n+3/9n+6 c*, where n is rational for periodic structures and irrational for the aperiodic ones. The model was tested on calculated data of one of the principal members of the (TS)(n)T family, the Y ferrite (n = infinity). The fit obtained with the superspace model was excellent. The model allowed a reduction of refinable parameters by 19% with respect to the ordinary refinement without a significant increase of the refinement R values.