Liquid Structure of Magnesium Aluminates.

Magnesium aluminates (MgO)(AlO) belong to a class of refractory materials with important applications in glass and glass-ceramic technologies. Typically, these materials are fabricated from high-temperature molten phases. However, due to the difficulties in making measurements at very high temperatures, information on liquid-state structure and properties is limited.

Molecular Basis of the Mechanisms Controlling MASTL.

The human MASTL (Microtubule-associated serine/threonine kinase-like) gene encodes an essential protein in the cell cycle. MASTL is a key factor preventing early dephosphorylation of M-phase targets of Cdk1/CycB. Little is known about the mechanism of MASTL activation and regulation.

Structure of Csx1-cOA complex reveals the basis of RNA decay in Type III-B CRISPR-Cas.

Type III CRISPR-Cas multisubunit complexes cleave ssRNA and ssDNA. These activities promote the generation of cyclic oligoadenylate (cOA), which activates associated CRISPR-Cas RNases from the Csm/Csx families, triggering a massive RNA decay to provide immunity from genetic invaders. Here we present the structure of Sulfolobus islandicus (Sis) Csx1-cOA complex revealing the allosteric activation of its RNase activity.

Molecular basis of Tousled-Like Kinase 2 activation.

Tousled-like kinases (TLKs) are required for genome stability and normal development in numerous organisms and have been implicated in breast cancer and intellectual disability. In humans, the similar TLK1 and TLK2 interact with each other and TLK activity enhances ASF1 histone binding and is inhibited by the DNA damage response, although the molecular mechanisms of TLK regulation remain unclear. Here we describe the crystal structure of the TLK2 kinase domain.

Large-Scale Biophysical Evaluation of Protein PEGylation Effects: In Vitro Properties of 61 Protein Entities.

PEGylation is the most widely used method to chemically modify protein biopharmaceuticals, but surprisingly limited public data is available on the biophysical effects of protein PEGylation. Here we report the first large-scale study, with site-specific mono-PEGylation of 15 different proteins and characterization of 61 entities in total using a common set of analytical methods. Predictions of molecular size were typically accurate in comparison with actual size determined by size-exclusion chromatography (SEC) or dynamic light scattering (DLS).

A PTIP-PA1 subcomplex promotes transcription for IgH class switching independently from the associated MLL3/MLL4 methyltransferase complex.

Class switch recombination (CSR) diversifies antibodies for productive immune responses while maintaining stability of the B-cell genome. Transcription at the immunoglobulin heavy chain (Igh) locus targets CSR-associated DNA damage and is promoted by the BRCT domain-containing PTIP (Pax transactivation domain-interacting protein). Although PTIP is a unique component of the mixed-lineage leukemia 3 (MLL3)/MLL4 chromatin-modifying complex, the mechanisms for how PTIP promotes transcription remain unclear.

Liquid demixing of intrinsically disordered proteins is seeded by poly(ADP-ribose).

Intrinsically disordered proteins can phase separate from the soluble intracellular space, and tend to aggregate under pathological conditions. The physiological functions and molecular triggers of liquid demixing by phase separation are not well understood. Here we show in vitro and in vivo that the nucleic acid-mimicking biopolymer poly(ADP-ribose) (PAR) nucleates intracellular liquid demixing.

The impact of structural integrity and route of administration on the antibody specificity against three cow's milk allergens - a study in Brown Norway rats.

Background: Characterisation of the specific antibody response, including the epitope binding pattern, is an essential task for understanding the molecular mechanisms of food allergy. Examination of antibody formation in a controlled environment requires animal models. The purpose of this study was to examine the amount and types of antibodies raised against three cow's milk allergens; β-lactoglobulin (BLG), α-lactalbumin (ALA) and β-casein upon oral or intraperitoneal (i.

Functional and structural properties of a novel protein and virulence factor (Protein sHIP) in Streptococcus pyogenes.

Streptococcus pyogenes is a significant bacterial pathogen in the human population. The importance of virulence factors for the survival and colonization of S. pyogenes is well established, and many of these factors are exposed to the extracellular environment, enabling bacterial interactions with the host.

Liquid-liquid phase transition in supercooled yttria-alumina.

The structure and thermal characteristics of aerodynamically levitated samples of yttria-alumina in the liquid, supercooled liquid and solid phases were explored in an extensive series of high energy x-ray diffraction, small angle neutron scattering, and pyrometric cooling measurements. Particular focus was placed on the compound (Y2O3)(x)(Al2O3)(1-x) with x = 0.2 for which a liquid-liquid phase transition at a temperature of 1788 K has recently been reported.

Non-linear effects of macromolecular crowding on enzymatic activity of multi-copper oxidase.

Enzymes catalyze biochemical reactions in highly crowded environments where the amount of macromolecules may occupy up to 40% of the volume. Here we report how cell-like conditions tune catalytic parameters for the monomeric multi-copper oxidase, Saccharomyces cerevisiae Fet3p, in vitro. At low amounts of crowding agent, we detect increases in both of K(M) (weaker substrate binding) and k(cat) (improved catalytic efficiency), whereas at higher crowding levels, both parameters were reduced.

Identification of differentially expressed proteins in ovarian cancer using high-density protein microarrays.

Ovarian cancer is a leading cause of deaths, yet many aspects of the biology of the disease and a routine means of its detection are lacking. We have used protein microarrays and autoantibodies from cancer patients to identify proteins that are aberrantly expressed in ovarian tissue. Sera from 30 cancer patients and 30 healthy individuals were used to probe microarrays containing 5,005 human proteins.

Magnetic critical scattering in solid CoPd.

Using small-angle neutron scattering combined with a containerless aerodynamic levitation technique for high temperatures, we have measured the temperature dependence of the correlation length ξ of near-critical magnetic fluctuations in the solid phase of the completely miscible fcc alloy CoPd. A fit to our data yields a critical exponent ν = 0.76 ± 0.

Structure of molten yttrium aluminates: a neutron diffraction study.

We used the aerodynamic levitation technique combined with CO laser heating to study the structure of liquid yttrium aluminates above their melting point with neutron diffraction. For various yttria contents, we determined the structure factors and corresponding pair correlation functions describing the short-range order in the liquids. In particular, we derived Al-O and Y-O bond distances and coordination numbers.

Fragile X mental retardation syndrome: structure of the KH1-KH2 domains of fragile X mental retardation protein.

Fragile X syndrome is the most common form of inherited mental retardation in humans, with an estimated prevalence of about 1 in 4000 males. Although several observations indicate that the absence of functional Fragile X Mental Retardation Protein (FMRP) is the underlying basis of Fragile X syndrome, the structure and function of FMRP are currently unknown. Here, we present an X-ray crystal structure of the tandem KH domains of human FMRP, which reveals the relative orientation of the KH1 and KH2 domains and the location of residue Ile304, whose mutation to Asn is associated with a particularly severe incidence of Fragile X syndrome.

Longitudinal excitations in Mg-Al-O refractory oxide melts studied by inelastic x-ray scattering.

The dynamic structure factor S(Q,omega) of the refractory oxide melts MgAl2O4 and MgAl4O7 is studied by inelastic x-ray scattering with aerodynamic levitation and laser heating. This technique allows the authors to measure simultaneously the elastic response and transport properties of melts under extreme temperatures. Over the wave vector Q range of 1-8 nm-1 the data can be fitted with a generalized hydrodynamic model that incorporates a slow component described by a single relaxation time and an effectively instantaneous fast component.

Development of structural order during supercooling of a fragile oxide melt.

The authors have studied the structural evolution of the fragile glass-forming liquid CaAl2O4 during supercooling from the stable liquid phase to the cold glass below Tg. The evolution is characterized by a sharpening of the first diffraction peak and a shortening of the average nearest-neighbor bond length around 1.25Tg, indicating an increase in the degree of both intermediate-range and short-range orders occurring close to the dynamical crossover temperature.

Structural properties of molten dilute aluminium-transition metal alloys.

The short-range order in liquid binary Al-rich alloys (Al-Fe, Al-Ti) was studied by x-ray diffraction. The measurements were performed using a novel containerless technique which combines aerodynamic levitation with inductive heating. The average structure factors, S(Q), have been determined for various temperatures and compositions in the stable liquid state.

New insights into Fragile X syndrome. Relating genotype to phenotype at the molecular level.

Lack of functional Fragile X mental retardation protein (FMRP) is the primary cause of the Fragile-mental retardation syndrome in humans. In most cases, the disease results from transcriptional silencing of fragile mental retardation gene 1, fmr1, which encodes FMRP. However, a single missense mutation (I304N) in the second KH domain of FMRP gives rise to a particularly severe case of Fragile X syndrome.

Methionine-121 coordination determines metal specificity in unfolded Pseudomonas aeruginosa azurin.

Pseudomonas aeruginosa azurin binds copper so tightly that it remains bound even upon polypeptide unfolding. Copper can be substituted with zinc without change in protein structure, and also in this complex the metal remains bound upon protein unfolding. Previous work has shown that native-state copper ligands Cys112 and His117 are two of at least three metal ligands in the unfolded state.

Approaching the speed limit for Greek Key beta-barrel formation: transition-state movement tunes folding rate of zinc-substituted azurin.

Azurin is a blue-copper protein with a beta-barrel structure of Greek Key topology. In vitro, copper can be substituted with zinc without change in protein structure. We here analyze the kinetic folding behavior of zinc-substituted Pseudomonas aeruginosa azurin.

If space is provided, bulky modification on the rim of azurin's beta-barrel results in folded protein.

Pseudomonas aeruginosa azurin is a blue-copper protein with a beta-barrel fold. Here we report that, at conditions where thermal unfolding of apo-azurin is reversible, the reaction occurs in a single step with a transition midpoint (T(m)) of 69 degrees C (pH 7). The active-site mutation His117Gly creates a cavity in the beta-barrel near the surface but does not perturb the overall fold (T(m) of 64 degrees C, pH 7).

Studies of Pseudomonas aeruginosa azurin mutants: cavities in beta-barrel do not affect refolding speed.

Pseudomonas aeruginosa azurin is a blue-copper protein with a Greek-key fold. Removal of copper produces an apoprotein with the same structure as holoazurin. To address the effects on thermodynamic stability and folding dynamics caused by small cavities in a beta-barrel, we have studied the behavior of the apo-forms of wild-type and two mutant (His-46-Gly and His-117-Gly) azurins.