Backbone Structure of Diatom Silaffin Peptide R5 in Biosilica Determined by Combining Solid-State NMR with Theoretical Sum-Frequency Generation Spectra.

Silaffin peptide R5 is key for the biogenesis of silica cell walls of diatoms. Biosilification by the R5 peptide has potential in biotechnology, drug development, and materials science due to its ability to precipitate stable, high fidelity silica sheets and particles. A true barrier for the design of novel peptide-based architectures for wider applications has been the limited understanding of the interfacial structure of R5 when precipitating silica nanoparticles.

Binding of Dipeptides to Fatty Acid Membranes Explains Their Colocalization in Protocells but Does Not Select for Them Relative to Unjoined Amino Acids.

Dipeptides, which consist of two amino acids joined by a peptide bond, have been shown to have catalytic functions. This observation leads to fundamental questions relevant to the origin of life. How could peptides have become colocalized with the first protocells? Which structural features would have determined the association of amino acids and peptides with membranes? Could the association of dipeptides with protocell membranes have driven molecular evolution, favoring dipeptides over individual amino acids? Using pulsed-field gradient nuclear magnetic resonance, we find that several prebiotic amino acids and dipeptides bind to prebiotic membranes.

Serine-Lysine Peptides as Mediators for the Production of Titanium Dioxide: Investigating the Effects of Primary and Secondary Structures Using Solid-State NMR Spectroscopy and DFT Calculations.

A biomimetic approach to the formation of titania (TiO) nanostructures is desirable because of the mild conditions required in this form of production. We have identified a series of serine-lysine peptides as candidates for the biomimetic production of TiO nanostructures. We have assayed these peptides for TiO-precipitating activity upon exposure to titanium bis(ammonium lactato)dihydroxide and have characterized the resulting coprecipitates using scanning electron microscopy.

Comparative Study of Secondary Structure and Interactions of the R5 Peptide in Silicon Oxide and Titanium Oxide Coprecipitates Using Solid-State NMR Spectroscopy.

A biomimetic, peptide-mediated approach to inorganic nanostructure formation is of great interest as an alternative to industrial production methods. To investigate the role of peptide structure on silica (SiO) and titania (TiO) morphologies, we use the R5 peptide domain derived from the silaffin protein to produce uniform SiO and TiO nanostructures from the precursor silicic acid and titanium bis(ammonium lactato)dihydroxide, respectively. The resulting biosilica and biotitania nanostructures are characterized using scanning electron microscopy.

Steps for Shigella Gatekeeper Protein MxiC Function in Hierarchical Type III Secretion Regulation.

Type III secretion systems are complex nanomachines used for injection of proteins from Gram-negative bacteria into eukaryotic cells. Although they are assembled when the environmental conditions are appropriate, they only start secreting upon contact with a host cell. Secretion is hierarchical.

Left atrial appendage morphology is closely associated with specific echocardiographic flow pattern in patients with atrial fibrillation.

Aims: To assess the relation between left atrial appendage (LAA) morphology and echocardiographic flow pattern of the LAA by means of two- and three-dimensional transoesophageal echocardiography (3D-TEE).

Methods And Results: In a total of 131 patients with atrial fibrillation, LAA morphology was analyzed by 3D-TEE and classified into four types (Chicken Wing, Windsock, Cactus, Cauliflower). Left atrial appendage flow pattern as maximal LAA emptying flow velocity and spontaneous echo contrast (SEC) were retrieved from 2D-TEE imaging in all patients.

Three-dimensional electron microscopy reconstruction and cysteine-mediated crosslinking provide a model of the type III secretion system needle tip complex.

Type III secretion systems are found in many Gram-negative bacteria. They are activated by contact with eukaryotic cells and inject virulence proteins inside them. Host cell detection requires a protein complex located at the tip of the device's external injection needle.

Diatom mimics: directing the formation of biosilica nanoparticles by controlled folding of lysine-leucine peptides.

Silaffins, long chain polyamines, and other biomolecules found in diatoms are involved in the assembly of a large number of silica nanostructures under mild, ambient conditions. Nanofabrication researchers have sought to mimic the diatom's biosilica production capabilities by engineering proteins to resemble aspects of naturally occurring biomolecules. Such mimics can produce monodisperse biosilica nanospheres, but in vitro production of the variety of intricate biosilica nanostructures that compose the diatom frustule is not yet possible.

Silica morphogenesis by lysine-leucine peptides with hydrophobic periodicity.

The use of biomimetic approaches in the production of inorganic nanostructures is of great interest to the scientific and industrial community due to the relatively moderate physical conditions needed. In this vein, taking cues from silaffin proteins used by unicellular diatoms, several studies have identified peptide candidates for the production of silica nanostructures. In the current article, we study intensively one such silica-precipitating peptide, LKα14 (Ac-LKKLLKLLKKLLKL-c), an amphiphilic lysine/leucine repeat peptide that self-organizes into an α-helical secondary structure under appropriate concentration and buffer conditions.

Solid-state NMR studies of biomineralization peptides and proteins.

Nature has evolved sophisticated strategies for engineering hard tissues through the interaction of proteins, and ultimately cells, with inorganic mineral phases. This process, called biomineralization, is how living organisms transform inorganic materials such as hydroxyapatite, calcite, and silica into highly intricate and organized structures. The remarkable material properties of shell, bone, and teeth come from the activities of proteins that function at the organic-inorganic interface.

Shigella IpaD has a dual role: signal transduction from the type III secretion system needle tip and intracellular secretion regulation.

Type III secretion systems (T3SSs) are protein injection devices essential for the interaction of many Gram-negative bacteria with eukaryotic cells. While Shigella assembles its T3SS when the environmental conditions are appropriate for invasion, secretion is only activated after physical contact with a host cell. First, the translocators are secreted to form a pore in the host cell membrane, followed by effectors which manipulate the host cell.

Isolation of Salmonella mutants resistant to the inhibitory effect of Salicylidene acylhydrazides on flagella-mediated motility.

Salicylidene acylhydrazides identified as inhibitors of virulence-mediating type III secretion systems (T3SSs) potentially target their inner membrane export apparatus. They also lead to inhibition of flagellar T3SS-mediated swimming motility in Salmonella enterica serovar. Typhimurium.

Structural and functional studies on the N-terminal domain of the Shigella type III secretion protein MxiG.

MxiG is a single-pass membrane protein that oligomerizes within the inner membrane ring of the Shigella flexneri type III secretion system (T3SS). The MxiG N-terminal domain (MxiG-N) is the predominant cytoplasmic structure; however, its role in T3SS assembly and secretion is largely uncharacterized. We have determined the solution structure of MxiG-N residues 6-112 (MxiG-N(6-112)), representing the first published structure of this T3SS domain.

The extreme C terminus of Shigella flexneri IpaB is required for regulation of type III secretion, needle tip composition, and binding.

Type III secretion systems (T3SSs) are widely distributed virulence determinants of Gram-negative bacteria. They translocate bacterial proteins into host cells to manipulate them during infection. The Shigella T3SS consists of a cytoplasmic bulb, a transmembrane region, and a hollow needle protruding from the bacterial surface.

Low temperature 65Cu NMR spectroscopy of the Cu+ site in azurin.

(65)Cu central-transition NMR spectroscopy of the blue copper protein azurin in the reduced Cu(I) state, conducted at 18.8 T and 10 K, gave a strongly second order quadrupole perturbed spectrum, which yielded a (65)Cu quadrupole coupling constant of +/-71.2 +/- 1 MHz, corresponding to an electric field gradient of +/-1.