Search results for "Escher"
showing 10 items of 728 documents
Artificial chromosomes for antibiotic-producing actinomycetes.
2000
Bacteria belonging to the order Actinomycetales produce most microbial metabolites thus far described, several of which have found applications in medicine and agriculture. However, most strains were discovered by their ability to produce a given molecule and are, therefore, poorly characterized physiologically and genetically. Thus, methodologies for genetic manipulation of actinomycetes are not available and efficient tools have been developed for just a few strains. This constitutes a serious limitation to applying molecular genetics approaches to strain development and structural manipulation of microbial metabolites. To overcome this hurdle, we have developed bacterial artificial chrom…
Giant liposomes as model membranes for immunological studies: spontaneous insertion of purified K1-antigen (poly-alpha-2,8-NeuAc) of Escherichia coli.
1990
A flow chamber has been constructed to use giant liposomes (diameter 5-50 microns) as model membranes for immunological studies and other experiments involving the interaction with water-soluble compounds. As an example of immunological importance, the insertion of purified K-antigen from Escherichia coli K1 has been studied. Despite its large hydrophilic part (poly-alpha-2,8-NeuAc), which is capped at its potential reducing end with phosphatidic acid acting as a lipid anchor group, this water-soluble material is readily incorporated into liposomal membranes of dimyristoylphosphatidylcholine (DMPC). The incorporation has been proven by immunofluorescence using a FITC-labeled monoclonal anti…
Double-spanning Plant Viral Movement Protein Integration into the Endoplasmic Reticulum Membrane Is Signal Recognition Particle-dependent, Translocon…
2005
The current model for cell-to-cell movement of plant viruses holds that transport requires virus-encoded movement proteins that intimately associate with endoplasmic reticulum membranes. We have examined the early stages of the integration into endoplasmic reticulum membranes of a double-spanning viral movement protein using photocross-linking. We have discovered that this process is cotranslational and proceeds in a signal recognition particle-dependent manner. In addition, nascent chain photocross-linking to Sec61alpha and translocating chain-associated membrane protein reveal that viral membrane protein insertion takes place via the translocon, as with most eukaryotic membrane proteins, …
Variable presence of 5-methylcytosine in commercial RNA and DNA
2015
Nucleoside methylations and other nucleic acid modifications have recently encountered a surge in interest, prompted, among other things, by the detection of methylation and active demethylation of DNA and mRNA by similar mechanisms. In DNA, deoxycytidine methylation by Dnmt enzymes generates 5-methyldeoxycytidine,1 an important epigenetic mark that typically causes inactivation of transcription of the methylated promoter region. Recent exciting developments have shown that these marks are not concrete-cast, but can be actively removed by the oxidative action of TET enzymes,2 which generate, through a series of 2-electron oxidations, first hydroxymethylcytidine (hm5C), then formyldeoxycytid…
Halloysite nanotubes loaded with peppermint essential oil as filler for functional biopolymer film
2016
Abstract The purpose of this paper is to show how a functional bionanocomposite film with both antioxidant and antimicrobial activities was successfully prepared by the filling of a pectin matrix with modified Halloysite nanotubes (HNT) containing the essential peppermint oil (PO). Firstly, HNT surfaces were functionalized with cucurbit[6]uril (CB[6]) molecules with the aim to enhance the affinity of the nanofiller towards PO, which was estimated by means of HPLC experiments. The HNT/CB[6] hybrid was characterized by several methods (thermogravimetry, FT-IR spectroscopy and scanning electron microscopy) highlighting the influence of the supramolecular interactions on the composition, therma…
Apoptosis in marine sponges: a biomarker for environmental stress (cadmium and bacteria)
1998
The marine demosponge Suberites domuncula is abundantly present on muddy sand bottoms, both in the open sea and in harbors. In the present study it is shown that exposure of S. domuncula to cadmium (CdCl2) in concentrations ranging from 0.01 to 5.0 g ml−1 for up to 5 d results in apoptotic fragmentation of DNA. Kinetics experiments revealed that after 24 h a significant increase of DNA fragmentation already occurred. Besides cadmium a second stimulus was identified to also cause apoptosis in this species, namely exposure to heat-treated Escherichia coli. In order to support the finding that both cadmium and E. coli induce apoptosis in the sponge, expression of the apoptotic gene MA-3 was st…
Induction of carbonic anhydrase in SaOS-2 cells, exposed to bicarbonate and consequences for calcium phosphate crystal formation.
2013
Ca-phosphate/hydroxyapatite crystals constitute the mineralic matrix of vertebrate bones, while Ca-carbonate dominates the inorganic matrix of otoliths. In addition, Ca-carbonate has been identified in lower percentage in apatite crystals. By using the human osteogenic SaOS-2 cells it could be shown that after exposure of the cells to Ca-bicarbonate in vitro, at concentrations between 1 and 10 mm, a significant increase of Ca-deposit formation results. The crystallite nodules formed on the surfaces of SaOS-2 cells become denser and larger in the presence of bicarbonate if simultaneously added together with the mineralization activation cocktail (β-glycerophosphate/ascorbic acid/dexamethason…
A new assay for O6-alkylguanine-DNA-alkyltransferase to determine DNA repair capacities using lambda-phage DNA as substrate.
1990
One O6-methylguanine (O6-meG) was introduced into each BamHI site of lambda-phage DNA as a substrate for the determination of the DNA repair protein O6-alkylguanine-DNA-alkyltransferase. A new assay using as the detection group 32P-labeled phosphate introduced at the 3' position of the modified nucleoside by incorporation of 32P-labeled TTP in the 3'-neighboring position proved highly sensitive: 10(-16) mol of the DNA lesion was still easily detectable. This DNA, which has greater than 1000 bp represents a good model for cellular DNA and was used as a substrate to measure the individual repair capacities for O6-meG in human lymphocytes of 20 healthy male and female donors. There were great …
Transplantation of prodrug-converting neural progenitor cells for brain tumor therapy
2003
Since neural progenitor cells can engraft stably into brain tumors and differentiate along the neuronal and glial line, we tested the hypothesis that transplanted cytosine deaminase (CD)-expressing ST14A cells (an immortalized neural progenitor cell line) can convert locally 5-fluorocytosine (5-FC) into 5-fluorouracil (5-FU) and produce a regression of glioma tumors. ST14A, retrovirally transduced with the E. coli CD gene, showed a strong bystander effect on glioma cells as assessed by in vitro assay. Intracerebral injection of C6 glioma cells generated a rapidly growing tumoral mass. DiI prelabeled ST14A, coinjected into the rat brain with C6 glioma cells, survived in the tumoral mass up t…
Subcellular localization of bacteriophage PRD1 proteins in Escherichia coli
2014
Bacteria possess an intricate internal organization resembling that of the eukaryotes. The complexity is especially prominent at the bacterial cell poles, which are also known to be the preferable sites for some bacteriophages to infect. Bacteriophage PRD1 is a well-known model serving as an ideal system to study structures and functions of icosahedral internal membrane-containing viruses. Our aim was to analyze the localization and interactions of individual PRD1 proteins in its native host Escherichia coli. This was accomplished by constructing a vector library for production of fluorescent fusion proteins. Analysis of solubility and multimericity of the fusion proteins, as well as their …