Effect of Copper Segregation at Low-Angle Grain Boundaries on the Mechanisms of Plastic Relaxation in Nanocrystalline Aluminum: An Atomistic Study.

The paper studies the mechanisms of plastic relaxation and mechanical response depending on the concentration of Cu atoms at grain boundaries (GBs) in nanocrystalline aluminum with molecular dynamics simulations. A nonmonotonic dependence of the critical resolved shear stress on the Cu content at GBs is shown. This nonmonotonic dependence is related to the change in plastic relaxation mechanisms at GBs.

Molecular versus Excitonic Disorder in Individual Artificial Light-Harvesting Systems.

Natural light-harvesting antennae employ a dense array of chromophores to optimize energy transport via the formation of delocalized excited states (excitons), which are critically sensitive to spatio-energetic variations of the molecular structure. Identifying the origin and impact of such variations is highly desirable for understanding and predicting functional properties yet hard to achieve due to averaging of many overlapping responses from individual systems. Here, we overcome this problem by measuring the heterogeneity of synthetic analogues of natural antennae-self-assembled molecular nanotubes-by two complementary approaches: single-nanotube photoluminescence spectroscopy and ultrafast 2D correlation.

Self-Assembly Can Direct Dynamic Covalent Bond Formation toward Diversity or Specificity.

With the advent of reversible covalent chemistry the study of the interplay between covalent bond formation and noncovalent interactions has become increasingly relevant. Here we report that the interplay between reversible disulfide chemistry and self-assembly can give rise either to molecular diversity, i.e.

Assessing the level of matrix metal proteinases 1,8,9, their tissue inhibitor, type I, in cases of odontogenic phlegmons.

The article considers the measured values of the level of MMP-1, MMP-8 and MMP-9, and of their tissue inhibitor Type I (TIMP-1) in the blood serum and mixed saliva samples of 78 patients (31 women - 36.2 %, 47 men - 63.8 %) suffering from odontogenic phlegmons in the oral and maxillofacial region.

Impact of osmotic stress on protein diffusion in Lactococcus lactis.

We measured translational diffusion of proteins in the cytoplasm and plasma membrane of the Gram-positive bacterium Lactococcus lactis and probed the effect of osmotic upshift. For cells in standard growth medium the diffusion coefficients for cytosolic proteins (27 and 582 kDa) and 12-transmembrane helix membrane proteins are similar to those in Escherichia coli. The translational diffusion of GFP in L.

[The influence of carbon dioxide baths differing in the total mineralization levels on the functional state of the cardiovascular system of the patients presenting with hypertensive disease associated with coronary heart disease].

The results of the study on the influence of carbon dioxide baths differing in the total mineralization levels on the clinical course of hypertensive disease associated with coronary heart disease and on various functional systems of the body. The data obtained provide an insight into the role of salt concentrations (10 and 20 g/l) in carbon dioxide bath water (1.2 g/l) applied for the traditional treatment of the patients with hypertensive disease associated with concomitant coronary heart disease and musculoskeletal pathology.

Evaluation of pulsed-FRAP and conventional-FRAP for determination of protein mobility in prokaryotic cells.

Background: Macromolecule mobility is often quantified with Fluorescence Recovery After Photobleaching (FRAP). Throughout literature a wide range of diffusion coefficients for GFP in the cytoplasm of Escherichia coli (3 to 14 µm²/s) is reported using FRAP-based approaches. In this study, we have evaluated two of these methods: pulsed-FRAP and "conventional"-FRAP.

A single copy of SecYEG is sufficient for preprotein translocation.

The heterotrimeric SecYEG complex comprises a protein-conducting channel in the bacterial cytoplasmic membrane. SecYEG functions together with the motor protein SecA in preprotein translocation. Here, we have addressed the functional oligomeric state of SecYEG when actively engaged in preprotein translocation.

Quaternary structure of SecA in solution and bound to SecYEG probed at the single molecule level.

Dual-color fluorescence-burst analysis (DCFBA) was applied to measure the quaternary structure and high-affinity binding of the bacterial motor protein SecA to the protein-conducting channel SecYEG reconstituted into lipid vesicles. DCFBA is an equilibrium technique that enables the direct observation and quantification of protein-protein interactions at the single molecule level. SecA binds to SecYEG as a dimer with a nucleotide- and preprotein-dependent dissociation constant.

Lateral diffusion of membrane proteins: consequences of hydrophobic mismatch and lipid composition.

Biological membranes are composed of a large number lipid species differing in hydrophobic length, degree of saturation, and charge and size of the headgroup. We now present data on the effect of hydrocarbon chain length of the lipids and headgroup composition on the lateral mobility of the proteins in model membranes. The trimeric glutamate transporter (GltT) and the monomeric lactose transporter (LacY) were reconstituted in giant unilamellar vesicles composed of unsaturated phosphocholine lipids of varying acyl chain length (14-22 carbon atoms) and various ratios of DOPE/DOPG/DOPC lipids.

Influence of hydrophobic mismatch and amino acid composition on the lateral diffusion of transmembrane peptides.

We investigated the effect of amino acid composition and hydrophobic length of alpha-helical transmembrane peptides and the role of electrostatic interactions on the lateral diffusion of the peptides in lipid membranes. Model peptides of varying length and composition, and either tryptophans or lysines as flanking residues, were synthesized. The peptides were labeled with the fluorescent label Alexa Fluor 488 and incorporated into phospholipid bilayers of different hydrophobic thickness and composition.

Molecular sieving properties of the cytoplasm of Escherichia coli and consequences of osmotic stress.

We determined the diffusion coefficients (D) of (macro)molecules of different sizes (from approximately 0.5 to 600 kDa) in the cytoplasm of live Escherichia coli cells under normal osmotic conditions and osmotic upshift. D values decreased with increasing molecular weight of the molecules.

Purification and functional reconstitution of the bacterial protein translocation pore, the SecYEG complex.

In bacteria, proteins are secreted across the cytoplasmic membrane by a protein complex termed translocase. The ability to study the activity of the translocase in vitro using purified proteins has been instrumental for our understanding of the mechanisms underlying this process. Here, we describe the protocols for the purification and reconstitution of the SecYEG complex in an active state into liposomes.

Lateral diffusion of membrane proteins.

We measured the lateral mobility of integral membrane proteins reconstituted in giant unilamellar vesicles (GUVs), using fluorescence correlation spectroscopy. Receptor, channel, and transporter proteins with 1-36 transmembrane segments (lateral radii ranging from 0.5 to 4 nm) and a alpha-helical peptide (radius of 0.

Nuclear transport factor directs localization of protein synthesis during mitosis.

Export of messenger RNA from the transcription site in the nucleus and mRNA targeting to the translation site in the cytoplasm are key regulatory processes in protein synthesis. In yeast, the mRNA-binding proteins Nab2p and Nab4p/Hrp1p accompany transcripts to their translation site, where the karyopherin Kap104p mediates both their dissociation from the mRNA and their transport back into the nucleus. We found that Kap104p localized to the distal bud tip and the bud neck during cell division, resulting in a localized release of translation-competent mRNA and increased protein synthesis in the emerging daughter cell.

Dual-color fluorescence-burst analysis to study pore formation and protein-protein interactions.

Dual-color fluorescence-burst analysis (DCBFA) enables to study leakage of fluorescently labeled (macro) molecules from liposomes that are labeled with a second, spectrally non-overlapping fluorophore. The fluorescent bursts that reside from the liposomes diffusing through the focal volume of a confocal microscope will coincide with those from the encapsulated size-marker molecules. The internal concentration of size-marker molecules can be quantitatively calculated from the fluorescence bursts at a single liposome level.

Probing receptor-translocator interactions in the oligopeptide ABC transporter by fluorescence correlation spectroscopy.

The oligopeptide transporter Opp is a five-component ABC uptake system. The extracytoplasmic lipid-anchored substrate-binding protein (or receptor) OppA delivers peptides to an integral membrane complex OppBCDF (or translocator), where, on ATP binding and hydrolysis, translocation across the membrane takes place. OppA and OppBCDF were labeled with fluorescent probes, reconstituted into giant unilamellar vesicles, and the receptor-translocator interactions were investigated by fluorescence correlation spectroscopy.

Protein mobility and diffusive barriers in Escherichia coli: consequences of osmotic stress.

The effect of osmotic stress on the intracellular diffusion of proteins in Escherichia coli was studied, using a pulsed version of fluorescence recovery after photo-bleaching, pulsed-FRAP. This method employs sequences of laser pulses which only partly bleach the fluorophores in a cell. Because the cell size and geometry are taken into account, pulsed-FRAP enables to measure diffusion in very small cells of different shapes.

The lipid dependence of melittin action investigated by dual-color fluorescence burst analysis.

Dual-color fluorescence-burst analysis was used to study melittin-induced leakage of macromolecules from liposomes of various lipid compositions. To perform dual-color fluorescence-burst analysis, fluorescently labeled size-marker molecules were encapsulated into liposomes, labeled with a second lipid-attached fluorophore. By correlating the fluorescence bursts, resulting from the liposomes diffusing through the detection volume of a dual-color confocal microscope, the distribution of size-marker molecules over the liposomes was determined.

Dual-color fluorescence-burst analysis to probe protein efflux through the mechanosensitive channel MscL.

The mechanosensitive channel protein of large conductance, MscL, from Escherichia coli has been implicated in protein efflux, but the passage of proteins through the channel has never been demonstrated. We used dual-color fluorescence-burst analysis to evaluate the efflux of fluorescent labeled compounds through MscL. The method correlates the fluctuations in intensity of fluorescent labeled membranes and encapsulated (macro)molecules (labeled with second fluorophore) for each liposome diffusing through the observation volume.

On the decrease in lateral mobility of phospholipids by sugars.

Upon cold and drought stress, sucrose and trehalose protect membrane structures from fusion and leakage. Similarly, these sugars protect membrane proteins from inactivation during dehydration. We studied the interactions between sugars and phospholipid membranes in giant unilamellar vesicles with the fluorescent lipid analog 3,3'-dioctadecyloxacarbocyanine perchlorate incorporated.