Changes in cell morphology due to plasma membrane wounding by acoustic cavitation.

Acoustic cavitation-mediated wounding (i.e., sonoporation) has great potential to improve medical and laboratory applications requiring intracellular uptake of exogenous molecules; however, the field lacks detailed understanding of cavitation-induced morphologic changes in cells and their relative importance.

Outer membrane-associated serine protease involved in adhesion of Shewanella oneidensis to Fe(III) oxides.

The facultative anaerobe Shewanella oneidensis MR-1 respires a variety of anaerobic electron acceptors, including insoluble Fe(III) oxides. S. oneidensis employs a number of novel strategies for respiration of insoluble Fe(III) oxides, including localization of respiratory proteins to the cell outer membrane (OM).

Fibrillogenesis in continuously spun synthetic collagen fiber.

The universal structural role of collagen fiber networks has motivated the development of collagen gels, films, coatings, injectables, and other formulations. However, reported synthetic collagen fiber fabrication schemes have either culminated in short, discontinuous fiber segments at unsuitably low production rates, or have incompletely replicated the internal fibrillar structure that dictates fiber mechanical and biological properties. We report a continuous extrusion system with an off-line phosphate buffer incubation step for the manufacture of synthetic collagen fiber.

A permanent change in protein mechanical responses can be produced by thermally-induced microdomain mixing.

Electrospinning was employed to fabricate 3-D fiber networks from a recombinant amphiphilic elastin-mimetic tri-block protein polymer and the effects of moderate thermal conditioning (60 degrees C, 4 h) on network mechanical responses investigated. Significantly, while cryo-high resolution scanning electron microscopy (cryo-HRSEM) revealed that the macroscopic and microscopic morphology of the network structure was unchanged, solid-state (1)H-NMR spectroscopy demonstrated enhanced interphase mixing of hydrophobic and hydrophilic blocks. Significantly, thermal annealing triggered permanent changes in network swelling behavior (28.

D-periodic collagen-mimetic microfibers.

Self-assembling peptides have been previously designed that assemble into macroscopic membranes, nanotapes, and filaments through electrostatic interactions. However, the formation of highly ordered collagen-like fibrils, which display D-periodic features, has yet to be achieved. In this report, we describe for the first time a synthetic peptide system that self-assembles into a fibrous structure with well-defined periodicity that can be visualized by transmission electron microscopy (TEM).

Cerebral aneurysm formation in nitric oxide synthase-3 knockout mice.

We sought to evaluate the influence of specific vasoactive gene knockouts on the process of intracranial aneurysm formation in mice. Thirty wild type, 7 nitric oxide synthase (NOS)-2 knockout, 6 NOS-3 knockout, and 8 plasminogen activator inhibitor (PAI)-1 knockout female mice underwent left common carotid artery ligation at 2 to 6 months of age. After a survival period (average 20.

Basic residues in the Mason-Pfizer monkey virus gag matrix domain regulate intracellular trafficking and capsid-membrane interactions.

Mason-Pfizer monkey virus (M-PMV) capsids that have assembled in the cytoplasm must be transported to and associate with the plasma membrane prior to being enveloped by a lipid bilayer during viral release. Structural studies have identified a positive-charge density on the membrane-proximal surface of the matrix (MA) protein component of the Gag polyprotein. To investigate if basic amino acids in MA play a role in intracellular transport and capsid-membrane interactions, mutants were constructed in which lysine and arginine residues (R10, K16, K20, R22, K25, K27, K33, and K39) potentially exposed on the capsid surface were replaced singly and in pairs by alanine.

Macroscale assembly of peptide nanotubes.

Simple oligopeptides that self-assemble into homogeneous nanotubes can be directed to further assemble into macroscale parallel arrays through protein "salting out" strategies.

Semagenesis and the parasitic angiosperm Striga asiatica.

Over the last several years, intermediates in the reduction of dioxygen have been attributed diverse functional roles ranging from protection against pathogen attack to the regulation of cellular development. Evidence now suggests that parasitic angiosperms, which naturally commit to virulence through the growth of new organs, depend on reduced oxygen intermediates, or reactive oxygen species (ROS), for signal generation. Clearly, the role of ROS in both plant defense and other physiological responses complicates any models that employ these intermediates in host plant recognition.

Scanning electron microscopic analysis of defects in polymer coatings of three commercially available stents: comparison of BiodivYsio, Taxus and Cypher stents.

Background: Although the use of polymer-based drug-eluting stents appears to markedly reduce the risk of in-stent restenosis, there are concerns about their safety including polymer layer integrity.

Objectives: The objective of this study was to investigate the morphology of the polymer layer of 3 commercially available polymercoated stents, including the effects of balloon catheter expansion, by scanning electron microscopy (SEM).

Methods: We assessed discontinuities and other irregularities in the polymer layer of BiodivYsio, Taxus and Cypher stents by SEM after balloon expansion in saline solution at 37 degrees C.

Polymeric sulfated amino acid surfactants: a class of versatile chiral selectors for micellar electrokinetic chromatography (MEKC) and MEKC-MS.

In this work, three amino acid-derived (l-leucinol, l-isoleucinol, l-valinol) sulfated chiral surfactants are synthesized and polymerized. These chiral sulfated surfactants are thoroughly characterized to determine critical micelle concentration, aggregation number, polarity, optical rotation, and partial specific volume. For the first time the morphological behavior of polymeric sulfated surfactants is revealed using cryogenic high-resolution electron microscopy.

Terminal electron acceptors influence the quantity and chemical composition of capsular exopolymers produced by anaerobically growing Shewanella spp.

Bacterial exopolymers perform various roles, including acting as a carbon sink, a protective layer against desiccation or antimicrobial agents, or a structural matrix in biofilms. Despite such varied roles, little is known about the heterogeneity of bacterial exopolymer production under varying growth conditions. Here we describe experiments designed to characterize the quantity and quality of exopolymers produced by two commonly studied members of the widely distributed genus Shewanella.

The effect of a recombinant elastin-mimetic coating of an ePTFE prosthesis on acute thrombogenicity in a baboon arteriovenous shunt.

A recombinant elastin-mimetic triblock protein polymer with an inverse transition temperature (approximately 20 degrees C) was used to impregnate small-diameter (4 mm i.d.) expanded polytetrafluoroethylene (ePTFE) vascular grafts.

Mechanism of intracellular delivery by acoustic cavitation.

Using conditions different from conventional medical imaging or laboratory cell lysis, ultrasound has recently been shown to reversibly increase plasma membrane permeability to drugs, proteins and DNA in living cells and animals independently of cell or drug type, suggesting a ubiquitous mechanism of action. To determine the mechanism of these effects, we examined cells exposed to ultrasound by flow cytometry coupled with electron and fluorescence microscopies. The results show that cavitation generated by ultrasound facilitates cellular incorporation of macromolecules up to 28 nm in radius through repairable micron-scale disruptions in the plasma membrane with lifetimes >1 min, which is a period similar to the kinetics of membrane repair after mechanical wounding.

Rational design of a reversible pH-responsive switch for peptide self-assembly.

Peptide TZ1H, based on the heptad sequence of a coiled-coil trimer, undergoes fully reversible, pH-dependent self-assembly into long-aspect-ratio helical fibers. Substitution of isoleucine residues with histidine at the core d-positions of alternate heptads introduces a mechanism by which self-assembly is coupled to the protonation state of the imidazole side chain. Circular dichroism spectroscopy, transmission electron microscopy, and microrheology techniques revealed that the self-assembly of TZ1H coincides with a distinct coil-helix conformational transition that occurs within a narrow pH range near the pKa of the imidazole side chains of the core histidine residues.

Geobacter lovleyi sp. nov. strain SZ, a novel metal-reducing and tetrachloroethene-dechlorinating bacterium.

A bacterial isolate, designated strain SZ, was obtained from noncontaminated creek sediment microcosms based on its ability to derive energy from acetate oxidation coupled to tetrachloroethene (PCE)-to-cis-1,2-dichloroethene (cis-DCE) dechlorination (i.e., chlororespiration).

Quantitative PCR confirms purity of strain GT, a novel trichloroethene-to-ethene-respiring Dehalococcoides isolate.

A novel Dehalococcoides isolate capable of metabolic trichloroethene (TCE)-to-ethene reductive dechlorination was obtained from contaminated aquifer material. Growth studies and 16S rRNA gene-targeted analyses suggested culture purity; however, the careful quantitative analysis of Dehalococcoides 16S rRNA gene and chloroethene reductive dehalogenase gene (i.e.

Fabrication of a phospholipid membrane-mimetic film on the luminal surface of an ePTFE vascular graft.

A stabilized, membrane-mimetic film was produced on the luminal surface of an ePTFE vascular graft by in situ photopolymerization of an acrylate functonalized phospholipid using a fiber optic diffusing probe. The phospholipid monomer was synthesized, prepared as unilamellar vesicles, and fused onto close-packed octadecyl chains that were components of an amphiphilic terpolymer anchored onto the polyelectrolyte multilayer (PEM) by electrostatic interactions. Scanning electron microscopy (SEM) confirmed that gelatin impregnation of the graft followed by the subsequent biomimetic film coating filled in the fibril and node structure of the luminal surface of the ePTFE graft and was smooth.

Shamrock surfactants with terminal carboxylate headgroups and a central phosphorodithioate or quaternary ammonium headgroup.

Surfactants 3 (tripotassium O,O'-di-[11-(carboxylato)undecyl]phosphorodithioate) and 4 (sodium 12-[dimethyl-(11-carboxylatoundecyl)ammonio]dodecanoate), which are new shamrock surfactants, were prepared and characterized. Shamrock surfactants represent a novel class of surfactants that contain a central headgroup connected to two flanking headgroups by hydrocarbon chains; they do not contain long-chain alkyl groups. Surfactants 3 and 4 were characterized in water by measurement of their Krafft temperatures and critical aggregation concentrations, and their aggregates were studied by 1H and 31P NMR spectroscopy, dynamic laser light scattering, and phase-contrast optical microscopy.

Surfactant quaternary ammonium hydrotris(1-pyrazolyl)borates.

Quaternary ammonium surfactants with the hydrotris(1-pyrazolyl)borate anion as an unusual counterion were prepared and characterized. Dodecyl- (1a), tetradecyl- (1b), and hexadecyltrimethylammonium hydrotris(1-pyrazolyl)borate (1c), as well as didodecyldimethylammonium hydrotris(1-pyrazolyl)borate (2), were prepared by metathesis reactions with the corresponding quaternary ammonium bromides and potassium hydrotris(1-pyrazolyl)borate (4). Although the surfactants have limited stabilities in water at 23 degrees C, they were characterized by measurement of their Krafft temperatures and critical aggregation concentrations.

Imaging amyloid beta peptide oligomeric particles in solution.

While all protein misfolding diseases are characterized by fibrous amyloid deposits, the favorable free energy and strongly cooperative nature of the self-assembly have complicated the development of therapeutic strategies aimed at preventing their formation. As structural models for the amyloid fibrils approach atomic resolution, increasing evidence suggests that early folding intermediates, rather than the final structure, are more strongly associated with the loss of neuronal function. For that reason we now demonstrate the use of cryo-etch high-resolution scanning electron microscopy (cryo-HRSEM) for the direct observation of pathway intermediates in amyloid assembly.

Design and synthesis of asymmetric acyclic phospholipid bolaamphiphiles.

[structure: see text] A synthetic route was devised for the generation of asymmetric lipid bolaamphiphiles through the sequential esterification of an alkyldioic acid, bearing distinct terminal protecting groups, with propanylamine and lyso-phosphatidylcholine headgroups. Bolaamphiphile self-assembly was investigated in solvent mixes of varying polarity by nuclear magnetic resonance (NMR) and Fourier transform-infrared (FT-IR) spectroscopy, as well as in water by cryo-high-resolution scanning electron microscopy (cryo-HRSEM). We anticipate that asymmetric lipid bolaamphiphiles will provide facile building blocks for engineering a variety of unique membrane-mimetic structures.

Shamrock surfactants: synthesis and characterization.

Two types of a new class of surfactants with three headgroups, which possess the general structure 1, have been prepared. Within structure 1, a central headgroup is connected to two flanking headgroups by hydrocarbon chains. The term "shamrock" is used to describe surfactants of structure 1, denoting their triple-headed character and reflecting the fact that shamrocks have leaflets in groups of three.

Ultrastructure in frozen/etched saline solutions: on the internal cleansing of ice.

Seawater, with its 3.5% salt content, freezes into hexagonal ice (Ih) that encloses concentrated brine within its matrix. When unsubmerged sea ice reaches a certain height and temperature, the brine drains downward through narrow channels.

Synthesis and characterization of glycopolymer-polypeptide triblock copolymers.

Glycopolymer-polypeptide triblock copolymers of the structure, poly(l-alanine)-b-poly(2-acryloyloxyethyl-lactoside)-b-poly(l-alanine) (AGA), have been synthesized by sequential atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP). Controlled free radical polymerization of 2-O-acryloyl-oxyethoxyl-(2,3,4,6-tetra-O-acetyl-beta-d-galactopyranosyl)-(1-4)-2,3,6-tri-O-acetyl-beta-d-glucopyranoside (AEL) by ATRP with a dibromoxylene (DBX)/CuBr/bipy complex system was used to generate a central glycopolymer block. Telechelic glycopolymers with diamino end groups were obtained by end group transformation and subsequently used as macroinitiators for ROP of l-alanine N-carboxyanhydride monomers (Ala-NCA).