The Cryo-EM Structure of a Complete 30S Translation Initiation Complex from Escherichia coli

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Dispersion of carbon nanotubes: Mixing, sonication, stabilization, and composite properties

Advances in functionality and reliability of carbon nanotube (CNT) composite materials require careful formulation of processing methods to ultimately realize the desired properties. To date, controlled dispersion of CNTs in a solution or a composite matrix remains a challenge, due to the strong van der Waals binding energies associated with the CNT aggregates. There is also insufficiently defined correlation between the microstructure and the physical properties of the composite. Here, we offer a review of the dispersion processes of pristine (non-covalently functionalized) CNTs in a solvent or a polymer solution. We summarize and adapt relevant theoretical analysis to guide the dispersion design and selection, from the processes of mixing/sonication, to the application of surfactants for stabilization, to the final testing of composite properties. The same approaches are expected to be also applicable to the fabrication of other composite materials involving homogeneously dispersed nanoparticles. © 2012 by the authors; licensee MDPI, Basel, Switzerland.

Hydrazines probe of interaction of horseradish peroxidase with cryo-hydrogel

The interaction between horseradish peroxidase (HRP) and the cryo-hydrogel was probed by using hydrazines which show high specificity of the reaction of the edge in the prosthetic heme of horseradish peroxidase. For comparison, the interaction of hydrazine with the horseradish peroxidase adsorbed on graphite electrode was also carried out by using steady-state response of the enzyme electrode and cyclic voltammetry. In order to obtain a proper explanation of the kinetic parameters for the enzymatic reaction, the theoretical expressions of I-max and K-M' in the Michaelis-Menten equation for the experimental system were provided. (C) 1997 Elsevier Science B.V.

The direct electrochemistry of cryo-hydrogel immobilized myoglobin at a glassy carbon electrode

A cryo-hydrogel membrane (CHM) immobilized at a glassy carbon (GC) electrode is reported for the direct electron transfer of redox proteins. The most attractive characteristics of this CHM were its hydrophilic micro-environment for incorporated proteins to retain their activities, its high ability for protection against interference of denatured and adsorbed proteins at the electrode, its potential applications for various proteins or enzymes, as well as its high mechanical strength and thermal stability. A clear well developed and stable redox wave was obtained for commercially available horse heart myoglobin without further purification, giving a peak to peak separation Delta E(p) = 93 mV at 5 mV s(-1) and the formal electrode potential E(0)' = -0.158 V (vs. Ag/AgCl). The formal heterogeneous electron transfer rate constant was calculated as k(0)' = 5.7 X 10(-4) cm s(-1) at pH 6.5, showing rapid electron transfer was achieved. The pH controlled conformational equilibria, acid state --> natural state --> basic I state --> basic II state, of myoglobin at the CHM GC electrode in the pH range 0-13.8 were also observed and are discussed in detail.

A cryo-hydrogel immobilized protein electrode for direct electron transfer of myoglobin

The direct electron transfer process of horse heart myoglobin, which was immobilized into a new type of cryo-hydrogel membrane on a glassy carbon electrode surface, was studied and the characteristics of this cryo-hydrogel immobilized protein electrode were discussed.

Microbiologic Diagnosis of Prosthetic Shoulder Infection by Use of Implant Sonication

We recently described a sonication technique for the diagnosis of prosthetic knee and hip infections. We compared periprosthetic tissue culture to implant sonication followed by sonicate fluid culture for the diagnosis of prosthetic shoulder infection. One hundred thirty-six patients undergoing arthroplasty revision or resection were studied; 33 had definite prosthetic shoulder infections and 2 had probable prosthetic shoulder infections. Sonicate fluid culture was more sensitive than periprosthetic tissue culture for the detection of definite prosthetic shoulder infection (66.7 and 54.5%, respectively; P = 0.046). The specificities were similar (98.0% and 95.1%, respectively; P = 0.26). Propionibacterium acnes was the commonest species detected among culture-positive definite prosthetic shoulder infection cases by periprosthetic tissue culture (38.9%) and sonicate fluid culture (40.9%). All subjects from whom P. acnes was isolated from sonicate fluid were male. We conclude that sonicate fluid culture is useful for the diagnosis of prosthetic shoulder infection.

Sonication of removed breast implants for improved detection of subclinical infection.

BACKGROUND: Capsular fibrosis is a severe complication after breast implantation with an uncertain etiology. Microbial colonization of the prosthesis is hypothesized as a possible reason for the low-grade infection and subsequent capsular fibrosis. Current diagnostic tests consist of intraoperative swabs and tissue biopsies. Sonication of removed implants may improve the diagnosis of implant infection by detachment of biofilms from the implant surface. METHODS: Breast implants removed from patients with Baker grades 3 and 4 capsular contracture were analyzed by sonication, and the resulting sonication fluid was quantitatively cultured. RESULTS: This study investigated 22 breast implants (6 implants with Baker 3 and 16 implants with Baker 4 capsular fibrosis) from 13 patients. The mean age of the patients was 49 years (range, 31-76 years). The mean implant indwelling time was 10.4 years (range, 3 months to 30 years). Of the 22 implants, 12 were used for breast reconstruction and 10 for aesthetic procedures. The implants were located subglandularly (n = 12), submuscularly (n = 6), and subcutaneously (n = 4). Coagulase-negative staphylococci, Propionibacterium acnes, or both were detected in the sonication fluid cultures of nine implants (41%), eight of which grew significant numbers of microorganisms (>100 colonies/ml of sonication fluid). CONCLUSIONS: Sonication detected bacteria in 41% of removed breast implants. The identified bacteria belonged to normal skin flora. Further investigation is needed to determine any causal relation between biofilms and capsular fibrosis.

Étude structurale conformationnelle des toxines de l’anthrax par cryo-microscopie et dynamique moléculaire

Les toxines de l’anthrax font partie de la famille des toxines A-B dans laquelle la moitié B se fixe à la membrane de la cellule permettant par la suite la translocation de la moitié A. Dans le cas de l’anthrax, la moitié B est représentée par le Protective Antigen (PA) et la moitié A par les deux protéines Edema Factor (EF) et Lethal Factor (LF). Après le recrutement par les récepteurs cellulaires (CMG2 et TEM8), PA s’organise en heptamère. Il peut fixer jusqu'à 3 ligands (EF et LF) avant d'être endocyté. Les modèles actuels de PA suggèrent que la baisse de pH à l’intérieur des endosomes permet un changement de conformation de la forme pré-pore vers la forme pore et que les ligands EF et LF passeraient au travers le pore pour entrer dans le cytoplasme. Cependant, le diamètre du pore est environ dix fois inférieur à celui des ligands (10 Å contre 100 Å). Un processus de folding/unfolding a été proposé mais demeure controversé. Afin d'identifier le processus de passage des facteurs EF et LF dans le cytoplasme, nous avons déterminé par cryo-microscopie électronique combinée avec l’analyse d’image les structures tridimensionnelles des complexes formés par PA et LF aux étapes prépore et pore. Par la suite, une étude complémentaire par dynamique moléculaire nous a permis de modéliser à haute résolution les différentes interactions qui ont lieu au sein du complexe. La structure 3D du complexe prépore combiné à 3 LF a été déterminée à une résolution de 14 Å. Nous avons aussi calculé une structure préliminaire du complexe pore également combiné à 3 LF Celles-ci n’ont jamais été résolues auparavant et leur connaissance permet d’envisager l’étude en profondeur du mécanisme infectieux de l’Anthrax in vivo.

Purification of coronavirus virions for Cryo-EM and proteomic analysis

Purification of intact enveloped virus particles can be useful as a first step in understanding the structure and function of both viral and host proteins that are incorporated into the virion. Purified preparations of virions can be used to address these questions using techniques such as mass spectrometry proteomics. Recent studies on the proteome of coronavirus virions have shown that in addition to the structural proteins, accessory and non-structural virus proteins and a wide variety of host cell proteins associate with virus particles. To further study the presence of virion proteins, high quality sample preparation is crucial to ensure reproducible analysis by the wide variety of methods available for proteomic analysis.

Effect of sonication on the particle size of montmorillonite clays

This paper reports on the effect of sonication on SAz-1 and SWy-1 montmorillonite suspensions. Changes in the size of the particles of these materials and modifications of their properties have been investigated. The variation of the particle size has been analyzed by DLS (dynamic light scattering). In all cases the clay particles show a bimodal distribution. Sonication resulted in a decrease of the larger modal diameter, as well as a reduction of its volume percentage. Simultaneously, the proportion of the smallest particles increases. After 60 min of sonication, SAz-1 presented a very broad particle size distribution with a modal diameter of 283 nm. On the other hand, the SWy-1 sonicated for 60 min presents a bimodal distribution of particles at 140 and 454 nm. Changes in the properties of the clay suspensions due to sonication were evaluated spectroscopically from dye-clay interactions, using Methylene Blue. The acidic sites present in the interlamellar region, which are responsible for dye protonation, disappeared after sonication of the clay. The changes in the size of the scattering particles and the lack of acidic sites after sonication suggest that sonication induces delamination of the clay particles. (c) 2008 Elsevier Inc. All rights reserved.

Effect of Sonication on the Thermotropic Behavior of DODAB Vesicles Studied by Fluorescence Probe Solubilization

The effect of sonication on fluorescence probe solubilization in cationic vesicles of dioctadecyldimethylammonium bromide (DODAB) was investigated by steady-state fluorescence of pyrene (Py), trans-diphenylpolyenes-diphenylbutadiene (DPB), diphenylhexatriene (DPH), and their corresponding 4,4'-dialkyl derivatives 4B4A and 4H4A fluorescence probes. The data indicate that sonication affects the bilayer polarity, the melting temperature (T (m)), and the cooperativity of the melting process due to changes in vesicle morphology. The effect of temperature on the fluorescence intensity and yielding I broken vertical bar(f) and anisotropy < r > shows that the ionizable probes 4B4A and 4H4A are solubilized close to the vesicle interfaces, whereas the non-ionizable DPH and DPB are deeper in the bilayers. Py solubilization indicates that sonicated vesicles exhibit less densely packed bilayers.