SEARCH · Search PubMed

Results for “Assembly process”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,225 records · Page 68Linked to original sources

PubMed2001

Potential health and environmental issues of mercury-contaminated amalgamators.

BACKGROUND: Dental amalgamators may become contaminated internally with metallic mercury. This contamination may result from mercury leakage from capsules during trituration or from the long-term accrual from microscopic exterior contaminants that result from the industrial assembly process. The potential health risk to dental personnel from this contamination is unknown. METHODS: The authors assessed used amalgamators from the federal service inventory for the amounts of mercury vapor levels, as well as the visual presence of mercury contamination. They evaluated these amalgamators for potential mercury vapor health risk, using established National Institute for Occupational Safety and Health methods and American Conference of Governmental Industrial Hygienists standards. RESULTS: Ten of the 11 amalgamators assessed had measurable mercury vapor levels. Four amalgamators were found to have internal static mercury vapor levels above Occupational Safety and Health Administration ceiling limit thresholds. During a simulated worst-case clinical use protocol, the authors found that no amalgamators produced mercury vapor in the breathing space of dental personnel that exceeded established time-weighted federal mercury vapor limits. CONCLUSIONS: Amalgamators may be contaminated internally with metallic mercury. Although the authors detected mercury vapor from these units during aggressive, simulated clinical use, dilution factors combined with room air exchange were found to keep health risks below established federal safety thresholds. CLINICAL IMPLICATIONS: Dental personnel should be aware that amalgamators may be contaminated with mercury and produce minute amounts of mercury vapor. These contaminated amalgamators may require disposal as environmentally hazardous waste.

Air Pollution, Indoor↗

PubMed1999

Site-specific fluorescence labelling of recombinant polyomavirus-like particles.

For the development of gene therapy protocols based on polyomavirus-like particles, we describe a method for fluorescence labelling of virions in order to study virus-cell interactions preceding gene delivery. Site-specific fluorescence labelling of polyomavirus-like particles is achieved via a single cysteine residue and maleimide conjugates of fluorescence dyes (fluorescein, Texas Red). Polyomavirus-like particles can be assembled in vitro from recombinant capsomers produced in E. coli. Since the assembly process is independent of disulfide bond formation, all cysteine residues of the wild-type protein were replaced by serines, and a new unique cysteine residue was introduced for the attachment of the fluorescence marker.

Animals↗

PubMed2005

Initial conformational changes of human transthyretin under partially denaturing conditions.

Human transthyretin (TTR) is an amyloidogenic protein. The pathway of TTR amyloid formation has been proposed based on lines of evidence: TTR tetramer first dissociates into native monomers, which is shown to be a rate-limiting step in the formation of fibrils. Subsequently, the monomeric species partially unfold to form the aggregation intermediates. Once such intermediates are formed, the following self-assembly process is a downhill polymerization. Hence, tertiary structural changes within the monomers after the dissociation are essential for the amyloid formation. These tertiary structural changes can be facilitated by partial denaturation. To probe the conformational changes under the partially denaturing conditions, five independent trajectories were collected for the wild-type (WT) and its pathogenic variants at 300 and 350 K, resulting in simulations that totaled 59 ns. Under these conditions, L55P variant is more labile than the wild-type and V30M variant. We have observed that the D strand of WT-TTR is trapped in two local minima: the native conformation and the amyloidogenic fold that resembles the surface loop of residues 54-55 of L55P variant. In the tetrameric state, the F strand is bent with large separations at the F-F' interface. This strand becomes flatter in the monomeric state, which may facilitate the formation of new F-F' interface with possible prolonged hydrogen bonds and/or shift in beta-strand register in the fibril state. During the unfolding process, the anticorrelated motion between the strands H and G as well as the strands H and A pulls the H strand out of the inner sheet plane, leading to a more twisted inner sheet. Our simulation has provided important detailed structural information about the partially unfolded state of TTR that may be related to the amyloidogenic intermediates.

Amyloid↗

PubMed2005

Substrate-supported phospholipid membranes studied by surface plasmon resonance and surface plasmon fluorescence spectroscopy.

Substrate-supported planar lipid bilayer membranes are attractive model cellular membranes for biotechnological applications such as biochips and sensors. However, reliable fabrication of the lipid membranes on solid surfaces still poses significant technological challenges. In this study, simultaneous surface plasmon resonance (SPR) and surface plasmon fluorescence spectroscopy (SPFS) measurements were applied to the monitoring of adsorption and subsequent reorganization of phospholipid vesicles on solid substrates. The fluorescence intensity of SPFS depends very sensitively on the distance between the gold substrate and the fluorophore because of the excitation energy transfer to gold. By utilizing this distance dependency, we could obtain information about the topography of the adsorbed membranes: Adsorbed vesicles could be clearly distinguished from planar bilayers due to the high fluorescence intensity. SPSF can also incorporate various analytical techniques to evaluate the physicochemical properties of the adsorbed membranes. As an example, we demonstrated that the lateral mobility of lipid molecules could be estimated by observing the recovery of fluorescence after photobleaching. Combined with the film thickness information obtained by SPR, SPR-SPFS proved to be a highly informative technique to monitor the lipid membrane assembly processes on solid substrates.

Adsorption↗

PubMed2006

Ile-phe dipeptide self-assembly: clues to amyloid formation.

Peptidic self-assembled nanostructures are said to have a wide range of applications in nanotechnology, yet the mechanistic details of hierarchical self-assembly are still poorly understood. The Phe-Phe recognition motif of the Alzheimer's Abeta peptide is the smallest peptide able to assemble into higher-order structures. Here, we show that the Ile-Phe dipeptide analog is also able to self-associate in aqueous solution as a transparent, thermoreversible gel formed by a network of fibrillar nanostructures that exhibit strong birefringence upon Congo red binding. Besides, a second dipeptide Val-Phe, differing only in a methyl group from the former, is unable to self-assemble. The detailed analysis of the differential polymeric behavior of these closely related molecules provides insight into the forces triggering the first steps in self-assembly processes such as amyloid formation.

Amyloid↗

PubMed1989

Severed nerve stumps around a laser-irradiated locus in the deep muscular plexus of the guinea-pig small intestine.

Small foci of photocoagulation necrosis (diameter about 0.5 mm) were produced in the wall of the guinea-pig small intestine by argon laser irradiation applied to the serosal surface. Features of the nerve elements around the necrotic masses were examined by immunocytochemistry, scanning electron microscopy, and transmission electron microscopy. The severed ends of nerve strands were examined at various intervals from 10 to 60 h after the laser irradiation, and the acute cytological responses of the nerve terminals, glial cells and connective tissue cells were studied. The laser irradiated foci in the deep muscular plexus (plexus muscularis profundus: CAJAL, 1911) had concentric configuration: 1) central necrotic area, 2) inner transitional zone, 3) outer transitional zone, and 4) normal area. In the necrotic area, there were inflammatory cells such as neutrophile leukocytes and macrophages. Contours of the smooth muscle cells and nerve strands were well preserved in spite of the damage to their subcellular structures. In the inner transitional area, individual nerve fibers gathered to form bundles. Some of these nerve bundles were devoid of a glial cell framework. In the outer transitional zone, there were swollen nerve terminals with a strong immunoreactivity for methionine-enkephalin-Arg6-Gly7-Leu6. In transmission electron microscopy, some of these swollen nerve fibers contained many large cored vesicles. Glial cells in the outer transitional zone exhibited an S-100b protein-like immunoreactivity. Scanning electron microscopy revealed gatherings of fibroblast-like (FBL) cells in the outer transitional zone. Two subtypes of these were distinguished: the first subtype (FBL I) was characterized by short, blunt cytoplasmic processes; the second subtype (FBL II), possessing long, slender dendritic processes, assembled to form a dense network which intermeshed with that of the nerve strands. The enteric nerve plexuses severed by laser-irradiation affords a unique experimental model in the cytological investigation of the plasticity of the peripheral autonomic nervous system.

Animals↗

PubMed2003

Sensing phenothiazine drugs at a gold electrode co-modified with DNA and gold nanoparticles.

DNA and gold nanoparticles are co-immobilized at a gold electrode through elaborate self-assembly processes. This configuration has proven to be useful as a sensor for phenothiazine drugs, taking advantage of the well-known, relatively large surface area of gold nanoparticles and the strong intercalation between dsDNA and phenothiazine drugs. This modified electrode has demonstrated good sensitivity and stability towards the oxidation of two model phenothiazine drugs: promethazine and chlorpromazine. A linear dependence between the concentration of phenothiazine drugs and the peak current is observed, with a concentration range of 2.0 x 10(-5)-1.6 x 10(-4) M and 1.0 x 10(-5)-1.2 x 10(-4) M, and a detection limit of 1.0 x 10(-5) M and 7.0 x 10(-6) M, for promethazine and chlorpromazine, respectively.

Animals↗

PubMed2006

High pressure modulates amyloid formation.

A common mechanism of conformational changes and pathological aggregation of proteins associated with amyloid diseases remains to be proven. High pressure is emerging as a new strategy for studying aspects of amyloid formation. Pressure provides a convenient means to populate and characterize partially folded states, which are thought to have a key role in assembly processes of proteins into amyloid fibrils. High pressure can also be used to dissociate aggregates and amyloid fibrils or on the opposite to generate such species.

Amyloid↗

PubMed2002

Molecular biology of Borna disease virus and persistence.

Borna disease virus (BDV) causes central nervous system (CNS) disease that is frequently manifested by behavioral abnormalities. Recent evidence indicates that the natural host range and geographic distribution of BDV is wider than originally thought BDV has been molecularly characterized as a non-segmented, negative single-stranded (NNS) RNA virus. Its genome (ca 8.9 kb), the smallest among known NNS RNA viruses, has an organization similar to that of other members of the order Mononegavirales. BDV has the property, unique among known animal NNS RNA viruses, of a nuclear site for the replication and transcription of its genome. The nucleocytoplasmic transport of BDV macromolecules is an essential component of the life cycle of BDV. An overlap of transcription units and transcriptive signals, overlap of ORFs, transcriptional readthrough and RNA splicing regulate expression of the BDV compact genome. The concurrent use of such diversity of strategies for the regulation of virus gene expression is unique among known NNS RNA viruses. Moreover, BDV appears to have also an unusual assembly process. Based on its unique genetic and biological features, BDV is considered to be the prototypic member of a new virus family, Bornaviridae, within the order Mononegavirales. Therefore, the investigation of the molecular biology of BDV may provide new insights about the biology of mononegaviruses, which include important human pathogens.

Animals↗

PubMed1995

A review of the aggregation properties of a recombinant amelogenin.

The present paper reviews some recent data on the aggregation properties of a recombinant amelogenin using dynamic light scattering, transmission electron microscopy, atomic force microscopy, and size exclusion chromatography. It was found that the recombinant amelogenin M179 molecules in solution form spherical monodisperse aggregates (15-20 nm) which are predominantly stabilized by intermolecular hydrophobic interactions while their surfaces are charged, carrying the hydrophilic carboxy-terminal sequence. We concluded that the spherical aggregates represent the "stippled materials" secreted by the ameloblasts at the mineralization front. We further speculate that the self-assembly process in the formation of amelogenin aggregates may play a primary role in the structural organization of mineralizing enamel.

Agglutination↗

PubMed2006

Cytoplasmic bacteria and the autophagic pathway.

Cytoplasmic bacteria may assist in our study of the autophagic pathway. This review highlights the use of Listeria monocytogenes for examining the assembly of autophagic vacuoles in mammalian cells. Inhibiting protein synthesis of cytoplasmic L. monocytogenes results in their being sequestered into the autophagic pathway. Autophagic vacuoles form around the easily identified bacterial particles making the assembly process easy to study using morphological and biochemical methods. L. monocytogenes, which appears to be ideally adapted to life in the cell cytoplasm, does not normally become a target of autophagy. In model systems the bacteria thrive within host cell cytoplasm, indicating the importance of de novo protein synthesis in avoiding the autophagic pathway. This observation indicates an interesting opportunity for identifying the bacterial mechanisms that are mobilized to avoid the autophagic pathway.

Animals↗

PubMed1999

Stability and secretion of acetylcholinesterase forms in skeletal muscle cells.

Muscle cells express a distinct splice variant of acetylcholinesterase (AChE(T)), but the specific mechanisms governing this restricted expression remain unclear. In these cells, a fraction of AChE subunits is associated with a triple helical collagen, ColQ, each strand of which can recruit a tetramer of AChE(T). In the present study, we examined the expression of the various splice variants of AChE by transfection in the mouse C2C12 myogenic cells in vitro, as well as in vivo by injecting plasmid DNA directly into tibialis anterior muscles of mice and rats. Surprisingly, we found that transfection with an ACHE(H) cDNA, generating a glycophosphatidylinositol-anchored enzyme species, produced much more activity than transfection with AChE(T) cDNA in both C2C12 cells and in vivo. This indicates that the exclusive expression of AChE(T) in mature muscle is governed by specific splicing. Interaction of AChE(T) subunits with the complete collagen tail ColQ increased enzyme activity in cultured cells, as well as in muscle fibers in vivo. Truncated ColQ subunits, presenting more or less extensive C-terminal deletions, also increased AChE activity and secretion in C2C12 cells, although the triple helix could not form in the case of the larger deletion. This suggests that heteromeric associations are stabilized compared with isolated AChE(T) subunits. Coinjections of AChE(T) and ColQ resulted in the production and secretion of asymmetric forms, indicating that assembly, processing, and externalization of these molecules can occur outside the junctional region of muscle fibers and hence does not require the specialized junctional Golgi apparatus.

5' Untranslated Regions↗

PubMed1999

The crystal structure of triosephosphate isomerase (TIM) from Thermotoga maritima: a comparative thermostability structural analysis of ten different TIM structures.

The molecular mechanisms that evolution has been employing to adapt to environmental temperatures are poorly understood. To gain some further insight into this subject we solved the crystal structure of triosephosphate isomerase (TIM) from the hyperthermophilic bacterium Thermotoga maritima (TmTIM). The enzyme is a tetramer, assembled as a dimer of dimers, suggesting that the tetrameric wild-type phosphoglycerate kinase PGK-TIM fusion protein consists of a core of two TIM dimers covalently linked to 4 PGK units. The crystal structure of TmTIM represents the most thermostable TIM presently known in its 3D-structure. It adds to a series of nine known TIM structures from a wide variety of organisms, spanning the range from psychrophiles to hyperthermophiles. Several properties believed to be involved in the adaptation to different temperatures were calculated and compared for all ten structures. No sequence preferences, correlated with thermal stability, were apparent from the amino acid composition or from the analysis of the loops and secondary structure elements of the ten TIMs. A common feature for both psychrophilic and T. maritima TIM is the large number of salt bridges compared with the number found in mesophilic TIMs. In the two thermophilic TIMs, the highest amount of accessible hydrophobic surface is buried during the folding and assembly process.

Amino Acid Sequence↗

PubMed1999

Self- and Directed Assembly of Hexaruthenium Macrocycles.

Rigid terpyridine-based building blocks allow easy access to large polymetallomacrocycles (see picture) through a self-assembly process. Such routes are envisioned to provide one-step methods to higher order motifs and facilitate the creation of precisely organized, metal-based networks for new energy storage devices.

Journal Article↗

PubMed1997

The change of productive skills and human work systems--function of work concept.

The techniques and skills of the age are changing, but the work situation is not corresponding to these changes. Furthermore, this causes problems in human resources development. We have investigated the contents of productive skills, vocational abilities, and work conditions, and as a result, productive skills were divided into two patterns: intellectual-management skills and sensory-motor skills. The contents of intellectual-management skills are divided into measurement, examination, design and arrangement, analysis and judgment, and understanding of technical knowledge. The contents of sensory-motor skills are divided into vision, audition and touch, visual judgment, motion of limbs, judgment by hands, and quality of the product. A sensory-motor skill is defined as one that mainly depends on judgment and memory capabilities. The former includes skills related to traditional handicrafts, processing assembling, and machine operation. The latter includes skills related to programming, designing, and controlling. A connection deeply related to the human being's essence can be found in both skills. When we examine human work systems, it is important to consider this essence.

Efficiency, Organizational↗

PubMed2000

Biogenesis and assembly of photosystem I.

Photosystem I (PS I) is a multisubunit membrane protein complex consisting of 11 to 14 different subunits. In addition, several cofactors, such as chlorophylls, phylloquinones, carotenoids and iron-sulfur clusters are bound by this complex. We now have a detailed understanding of the structural basics, yet we know very little about the molecular details of the assembly process that finally yields functional PS I. Moreover, not much is known about the molecular dynamics of PS I in the thylakoid membrane or its regulated degradation. These areas have become the focus of recent work and first results have emerged. In this minireview we describe the latest findings in this fascinating and rapidly evolving field.

Photosynthetic Reaction Center Complex Proteins↗

PubMedDate not supplied

[Self-assembly of extracellular tubular structures of non-protein nature produced by an actinomycete].

When grown on the solid synthetic medium with glucose as the only carbon source the dedifferentiated "fructose" mutant of Actinomyces roseoflavus var. roseofungini accumulated aggregates of tubular-like structures. The individual tubules had the internal diametre of 80 A and external diametre of approximately 200-220 A. These structures were isolated as a distinct fraction and their non-protein nature was demonstrated. They were easily soluble in acetone and reconstitutable in vitro. The possible significance of production of self-assembling structures by a mutant with impaired differentiation is discussed. The possibility of involvement of self-assembly processes in the formation of surface sheath of aerial mycelium in normally differentiating actinomycetes is mentioned.

Actinomyces↗

PubMed1998

[A novel gene delivery system targeting to epidermal growth factor receptor overexpressing cancer cells].

A polypeptide with 33 amino acid residues was designed and synthesized. Its C terminal was composed of multiple lysine residues, which played as a DNA condensing agent, whereas the N terminal was the receptor binding domain of Epidermal Growth Factor(N32-K48). Through a spontaneous self-assembly process with electrostatic interaction, the synthetic peptide combined with a luciferase expression vector, pEBluc, to form an EGF receptor targeting nucleic acid complex. Significant luciferase activity was detected 48 hours after adding this complex directly to the culture medium of the A431 cells. This synthetic peptide could be used to construct a gene transfer system mediated by the endocytosis via EGF receptor. It promoted a very possibility of the gene therapy for the cancers such as glioma, melanoma and squamous carcinoma which are known of epidermal growth factor receptor overexpression.

Carcinoma↗