Foliar transfer into the biosphere: review of translocation factors to cereal grains

A review of the published literature about foliar transfer radionuclides to cereal grains was carried out with a special interest for translocation factors. Translocation describes the distribution of radionuclides within the plant after foliar deposition and radionuclide absorption onto the surface of leaves. It mainly depends on elements and the plant growth stage. The collected data were derived from both in-field and greenhouse experiments. They were analysed in order to select those coming from a contamination simulating a sprinkling irrigation or a rain. The data set contains 307 values. For each radionuclide the translocation factor values were sorted according to 5 characteristic stages of the cereal vegetative cycle: leaf development-tillering, stem elongation, earing-flowering, grain growth and ripening. Wheat, barley and rye have been treated together, independently of rice. For mobile elements such as cesium, the translocation factor is maximum when the contamination occurred at the earing-flowering stage. For less mobile elements such as strontium this maximum occurred for a foliar contamination at the grain growth stage. This review enabled us to propose the most probable value as well as the range of variation of translocation factors for some radionuclides according to the cereal vegetative cycle. Moreover, from these results, a radionuclide classification is proposed according to three mobility groups.

In situ micropatterning technique by cell crushing for co-cultures inside microfluidic biochips

To perform dynamic cell co-culture on micropatterned areas, we have developed a new type of "on chip and in situ" micropatterning technique. The microchip is composed of a 200 microm thick PDMS (polydimethylsiloxane) chamber at the top of which are located 100 mum thick microstamps. The PDMS chamber is bonded to a glass slide. After sterilization and cell adhesion processes, a controlled force is applied on the top of the PDMS chamber. Mechanically, the microstamps come into contact of the cells. Due to the applied force, the cells located under the microstamps are crushed. Then, a microfluidic perfusion is applied to rinse the microchip and remove the detached cells. To demonstrate the potential of this technique, it was applied successfully to mouse fibroblasts (Swiss 3T3) and liver hepatocarcinoma (HepG2/C3a) cell lines. Micropatterned areas were arrays of octagons of 150, 300 and 500 microm mean diameter. The force was applied during 30 to 60s depending on the cell types. After cell crushing, when perfusion was applied, the cells could successfully grow over the patterned areas. Cultures were successfully performed during 72 h of perfusion. In addition, monolayers of HepG2/C3a were micropatterned and then co cultured with mouse fibroblasts. Numerical simulations have demonstrated that the presence of the microstamps at the top of the PDMS chamber create non uniform flow and shear stress applied on the cells. Once fabricated, the main advantage of this technique is the possibility to use the same microchip several times for cell micropatterning and microfluidic co-cultures. This protocol avoids complex and numerous microfabrication steps that are usually required for micropatterning and microfluidic cell culture in the same time.

Development of a renal microchip for in vitro distal tubule models

Current developments in tissue engineering and microtechnology fields have allowed the proposal of pertinent tools, microchips, to investigate in vitro toxicity. In the framework of the proposed REACH European directive and the 3R recommendations, the purpose of these microtools is to mimic organs in vitro to refine in vitro culture models and to ultimately reduce animal testing. The microchip consists of functional living cell microchambers interconnected by a microfluidic network that allows continuous cell feeding and waste removal controls by fluid microflow. To validate this approach, Madin Darby Canine Kidney (MDCK) cells were cultivated inside a polydimethylsiloxane microchip. To assess the cell proliferation and feeding, the number of inoculated cells varied from 5 to 10 x 10(5) cells/microchip (corresponding roughly to 2.5 to 5 x 10(5) cells/cm2) and from four flow rates 0, 10, 25, and 50 microL/min were tested. Morphological observations have shown successful cell attachment and proliferation inside the microchips. The best flow rate appears to be 10 microL/min with which the cell population was multiplied by about 2.2 +/- 0.1 after 4 days of culture, including 3 days of perfusion (in comparison to 1.7 +/- 0.2 at 25 microL/min). At 10 microL/min flow rate, maximal cell population reached about 2.1 +/- 0.2 x 10(6) (corresponding to 7 +/- 0.7 x 10(7) cells/cm(3)). The viability, assessed by trypan blue and lactate deshydrogenase measurements, was found to be above 90% in all experiments. At 10 microL/min, glucose monitoring indicated a cell consumption of 16 +/- 2 microg/h/10(6) cells, whereas the glutamine metabolism was demonstrated with the production of NH3 by the cells about 0.8 +/- 0.4 micromol/day/10(6) cells. Augmentation of the flow rate appeared to increase the glucose consumption and the NH3 production by about 1.5- to 2-fold, in agreement with the tendencies reported in the literature. As a basic chronic toxicity assessment in the microchips, 5 mM and 10 mM ammonium chloride loadings, supplemented in the culture media, at 0, 10, and 25 micaroL/min flow rates were performed. At 10 microL/min, a reduction of 35% of the growth ratio with 5 mM and of 50% at 10 mM was found, whereas at 25 microL/min, a reduction of 10% with 5 mM and of 30% at 10 mM was obtained. Ammonium chloride contributed to increase the glucose consumption and to reduce the NH3 production. The microchip advantages, high surface/volume ratio, and dynamic loadings, coupled with the concordance between the present and literature results dealing with ammonia/ammonium effects on MDCK illustrate the potential of our microchip for wider in vitro chronic toxicity investigations.

Addition of Difluoromethyl Radicals to Glycals: A New Route to α-CF2-d-Glycosides

The synthesis of synthetically useful alpha-CF2-glycosides by radical addition of ethyl bromodifluoroacetate onto 2-benzyloxyglycals is described. The methodology provides an access to alpha-O-glycoside mimics and, potentially, to valuable alpha-O-glycoconjugate analogues.

Selective control of liver and kidney cells migration during organotypic cocultures inside fibronectin-coated rectangular silicone microchannels

In this work, the behaviors of embryonic liver and kidney explants were studied inside rectangular polydimethylsiloxane (PDMS) microchannels. The organs were cultured under monoculture and coculture conditions on PDMS coated with or without fibronectin. The results demonstrated that the migration of cells from both organs is dependent on culture conditions and thus can be selectively controlled. In liver monocultures without fibronectin, cell migration in the microchannels resulted in the formation of a dense 3D tissue. Fibronectin reduced liver cell migration and enhanced the emergence of cells demonstrating typical hepatocyte phenotypes at the vicinity of the explant. The migration rate in liver-liver cocultures, with and without fibronectin, was roughly twice the rate of cells under monoculture conditions. In cocultures, both livers merged to form a large tissue in which the two initial organs could not be identified. In kidney monocultures, with and without fibronectin, we did not observe any migration inside the microchannels. Contrary to liver cells, kidney cell migration was triggered when both fibronectin coating and coculture with liver or another kidney explant were used. The migration was more largely observed in coculture with liver when compared to kidney-kidney cocultures. In the case of liver-kidney coculture with fibronectin, the progression of the kidney cells inside the microchannels appears as a displacement of the entire kidney explant in the direction of the liver. The liver cells did not move in those cases. After contact, we observed a complete merging of both liver and kidney explants. In contrast, for liver-kidney cocultures without fibronectin, only the liver moved toward the kidney.

Variation of the distribution coefficient (Kd) of selenium in soils under various microbial states

This study aimed to (i) evaluate whether the K(d) value of selenium is dependent upon the soil microbial activity and (ii) define the limitation of the use of the K(d) concept to describe selenium behaviour in soils when assessing the long-term radiological waste disposal risk. K(d) coefficients, as well as information on selenite speciation in the soil-solution, were derived from short- and long-term batch experiments with a calcareous silty clay soil in various microbial states. Soil microbial activity induced (i) an increase of the K(d) value from 16 l kg(-1) in sterile conditions to 130 l kg(-1) when the soil was amended with glucose and nitrate, and (ii) changes in selenium speciation both in the solution (presence of seleno-species other than free Se(IV)) and in the solid phase (Se linked to microorganisms). Although the K(d) coefficient adequately reflects the initial fractionation between soil-solid and soil-solution, it does not allow for speciation and microbial processes, which could affect reversibility, mobility and the long-term accumulation and uptake into crops.

Trends in the development of microfluidic cell biochips for in vitro hepatotoxicity

Current developments in the technological fields of liver tissue engineering, bioengineering, biomechanics, microfabrication and microfluidics have lead to highly complex and pertinent new tools called "cell biochips" for in vitro toxicology. The purpose of "cell biochips" is to mimic organ tissues in vitro in order to partially reduce the amount of in vivo testing. These "cell biochips" consist of microchambers containing engineered tissue and living cell cultures interconnected by a microfluidic network, which allows the control of microfluidic flows for dynamic cultures, by continuous feeding of nutrients to cultured cells and waste removal. Cell biochips also allow the control of physiological contact times of diluted molecules with the tissues and cells, for rapid testing of sample preparations or specific addressing. Cell biochips can be situated between in vitro and in vivo testing. These types of systems can enhance functionality of cells by mimicking the tissue architecture complexities when compared to in vitro analysis but at the same time present a more rapid and simple process when compared to in vivo testing procedures. In this paper, we first introduce the concepts of microfluidic and biochip systems based on recent progress in microfabrication techniques used to mimic liver tissue in vitro. This includes progress and understanding in biomaterials science (cell culture substrate), biomechanics (dynamic cultures conditions) and biology (tissue engineering). The development of new "cell biochips" for chronic toxicology analysis of engineered tissues can be achieved through the combination of these research domains. Combining these advanced research domains, we then present "cell biochips" that allow liver chronic toxicity analysis in vitro on engineered tissues. An extension of the "cell biochip" idea has also allowed "organ interactions on chip", which can be considered as a first step towards the replacement of animal testing using a combined liver/lung organ model.

Guidance of liver and kidney organotypic cultures inside rectangular silicone microchannels

We have studied the effect of rectangular polydimethylsiloxane (PDMS) microchannels on the behavior of embryonic liver and kidney explants maintained in contact with these microchannels. The microchannel widths were varied from 35 to 300 microm and depth from 45 to 135 microm. The growth of these tissue types were compared to the development on flat silicone and plastic control material. At seeding, due to the viscoelastic properties of both organs, "capillary-like filling" was observed inside the narrowest microchannels. In those cases, the tissues grew to a confluent layer joining the microchannels with no cell migration and proliferation inside the microchannels. In the largest microchannels, only a weak migration was observed and the cellular behavior appears quite similar to that of PDMS flat culture conditions. In intermediate geometries, we observed different tissue growth progressed inside those microchannels with an average growth properties inside the microchannels when compared to other sizes. The liver tissues velocity of up to 72 microm/day resulting to form a dense three-dimensional multicellular 'liver-like tissue'. Scanning electron microscopy (SEM) observations demonstrated that the tissue was organized like an epithelial layer with round cells embedded in an extracellular matrix. Liver cell mobility may result primarily from the activity of the marginal cells, whereas the sub-marginal cells appeared passively dragged. Parenchymal organization demonstrating differentiated states was also observed. Kidney grew mainly on the microchannel walls and the tissues never appeared dense and organized as the liver ones.

Copper induces conformational changes in the N-terminal part of cell-surface PrPC

Prion diseases are caused by misfolding of the cellular prion protein, PrPC. In vitro studies have shown that PrP binds copper via the octarepeat region lying within the unstructured N-terminal segment of the protein, but the significance of copper in PrP metabolism remains unclear. Here, six specific antibodies recognizing different epitope regions of PrP were used to measure the effect of copper on the conformation of the molecule at the cell surface. Binding of an antibody, E149, to an epitope within the octarepeat domain of PrP is halved in the presence of copper, whereas binding of antibodies recognizing epitope motifs C-terminal to residue 90 of PrP remain relatively unaltered under equivalent conditions. These experiments strongly suggest that copper induces localized conformational change within the N-terminal portion of cell-surface PrPC.

Study of osteoblastic cells in a microfluidic environment

Bone tissue engineering consists of culturing osteoblastic cells onto synthetic three-dimensional (3D) porous scaffolds. The organization of bone cells into 3D scaffolds is crucial for ex vivo tissue formation. Diffusional rates of nutrients could be greatly improved by perfusing media through the 3D microporous scaffolds. However, bone cells cultured in vitro are responsive to a variety of different mechanical signals including fluid flow and shear stresses. In this work, we attempt to study osteoblastic cells behaviour cultured within microdevices allowing continuous and homogenous feeding of cells. We have fabricated polydimethylsiloxane PDMS microdevices with a 3D microstructured channel network. Mouse calvarial osteoblastic cells MC3T3-E1 were seeded at 2x10(6)cells/ml and cultured into the microdevices under flow rates of 0, 5, 35 microl/min. Cells attached and proliferated well in the designed microdevices. Cell viability was found around 85% up to 1 to 2 weeks for shear stress value under 5 mPa. The alkaline phosphatase (ALP) activity was enhanced 3- and 7.5-fold inside the microdevices under static and dynamic flow of 5 microl/min as compared to flat static cultures in PDMS coated Petri dishes. Therefore, osteoblastic cells could be successfully cultured inside the microdevices under dynamic conditions and their ALP activity was enhanced. These results are promising for bone cell growth and differentiation as well as future tissue regeneration using larger 3D microfluidic microdevices.

Gas-phase reactivity of the O=P(OCH3)2 + phosphonium ion towards alpha,beta-unsaturated esters in a quadrupole ion trap

Ion-molecule reactions between the O=P(OCH3)2 + phosphonium ions and eight alpha,beta-unsaturated esters (methyl acrylate, ethyl acrylate, methyl crotonate, ethyl crotonate, methyl 3,3-dimethylacrylate, ethyl 3,3-dimethylacrylate, methyl methacrylate and ethyl methacrylate) were performed in a quadrupole ion trap mass spectrometer. The O=P(OCH3)2 + phosphonium ions, formed by electron ionization from neutral trimethyl phosphite, were found to react with alpha,beta-unsaturated esters to give an adduct [RR'C=CR''COOR''', O=P(OCH3)2]+, which lose spontaneously a molecule of trimethyl phosphate (R'''=CH3) or dimethyl ethyl phosphate (R'''=C2H5). An ion corresponding to a protonated trialkyl phosphate is also observed when substituent R''=H. To confirm the experimental results, and to elucidate the mechanism for the formation of the ionic species, a theoretical study using the density functional theory (DFT) approach was carried out. The potential energy surface obtained from B3LYP/6-31G(d,p) calculations for the reaction between O=P(OCH3)2 + and methyl acrylate is described.

Fabrication of microstructures in photosensitive biodegradable polymers for tissue engineering applications

Combining the MEMS technology and biology requirements for tissue engineering, the fabrication processes of microstructured chambers and microchannels made in biodegradable photosensitive polymers are presented. The fabrication processes, based on softlithography are very fast and flexible. Various single and multistepwise microstructures could be achieved using the biodegradable polymers. Microstructures down to 50microm, which are suitable for liver reconstructs, could be fabricated. As the pCLLA acrylate photosensitive polymer has interesting property for implantable bioreactors, that is, its softness, we examined the ability of various mammalian cells to grow and spread on it. With Hep G2 cells, human umbilical blood vessel endothelial cells (HUVEC), 3T3-L1 mouse fibroblasts, static cultures could be successfully performed on single stepwise microstructures. Then, by using this photosensitive biodegradable polymer, a microstructure with simple fluidic channels is fabricated and a perfusion experiment could be carried out. Both cell cultures and perfusion experiments suggested the possibility to use the present photosensitive polymer as microfluidic supports for biodegradable bioreactors for implantation applications.

Microfluidic PDMS (Polydimethylsiloxane) Bioreactor for Large-Scale Culture of Hepatocytes

Microfluidics could provide suitable environments for cell culture because of the larger surface-to-volume ratio and fluidic behavior similar to the environments in vivo. Such microfluidic environments are now used to investigate cell-to-cell interactions and behaviors in vitro, emulating situations observed in vivo, for example, microscale blood vessels modeled by microfluidic channels. These emulated situations cannot be realized by conventional technologies. In our previous works, microfluidic channels composed of two PDMS (poly(dimethylsiloxane)) layers were successfully used for Hep G2 cell culture. To achieve physiologically meaningful functions in vitro, a culture with a larger number of cells and higher density must be performed. This will require bioreactors with larger surface areas for cell attachment and sufficient amounts of oxygen and nutrition supply. For those purposes, we fabricated a bioreactor by stacking 10 PDMS layers together, i.e., four cell culture chambers, and a chamber dedicated to the oxygen supply inserted in the middle of the 10-stacked layers. The oxygen supply chamber is separated from the microfluidic channels for the culture medium perfusion by thin 300-microm PDMS walls. The high gas permeability of PDMS allows oxygen supply to the microfluidic channels through the thin walls. On the basis of the measurement of glucose consumption and albumin production, it is shown that cellular activity exhibits a gradual increase and saturation throughout the culture. We clearly observed that in the case of the microfluidic bioreactor for large-scale cultures, the oxygen chamber is indispensable to achieve longer and healthy cultures. In the present bioreactor, the cell density was found to be about 3-4 x 10(7) cells/cm(3), which is in the same order of magnitude as the conventional macroscale bioreactors. Consequently, by stacking single culture chambers and oxygen chambers in between, we could have a scalable method to realize the microfluidic bioreactor for large-scale cultures.

The Palladium(II)-Catalyzed Nazarov Reaction

The PdCl(2)-catalyzed cyclization of alpha-alkoxy dienones leads to 2-hydroxycyclopentenones, whereas the Pd(OAc)(2)-catalyzed reaction leads to cross-conjugated cyclopentenones through an oxidative process. [reaction: see text]

The first example of Nazarov reactions of vinyl cumulenyl ketones

[reaction: see text] alpha-Lithio cumulenyl ethers can be prepared in situ and converted to alpha-allenyl cyclopentenones. Isomerization of the product of one such reaction has led to a furanyl cyclopentenone, the core structure of nakadomarin A.

Diastereoselective aldolization of alpha-aminonitriles. Diastereoselective synthesis of beta-amino alcohols and beta,gamma-diamino alcohols

Aldolization performed by addition of lithiated N-benzyl-N-tert-butylaminoacetonitrile to aldehydes provides diastereomerically pure anti-beta-hydroxy-alpha-aminonitriles. They are transformed into syn,anti-protected beta,gamma-diamino alcohols by a two-step procedure, involving addition of a Grignard reagent and reduction. The cleavage of the N-tert-butyl group is achieved by a simple acidic treatment. The application of this methodology to chiral, nonracemic aldehydes is studied. Starting from D-isopropylideneglyceraldehyde, an anti, anti, syn, anti-(2R,3S,4S,5R,6R)-diaminotriol is prepared in acceptable yield and with a good level of diastereoselectivity.

Unusual property of prion protein unfolding in neutral salt solution

The unfolding of cellular prion protein and its refolding to the scrapie isoform are related to prion diseases. Studies in the literature have shown that structures of proteins, either acidic or basic, are stabilized against denaturation by certain neutral salts, for example, sulfate and fluoride. Contrary to these observations, the full-length recombinant prion protein (amino acid residues 23-231) is denatured by these protein structure stabilizing salts. Under identical concentrations of salts, the structure of the sheep prion protein, which contains a greater number of glycine groups in the N-terminal unstructured segment than the mouse protein, becomes more destabilized. In contrast to the full-length protein, the C-terminal 121-231 prion protein fragment, consisting of all the structural elements of the protein, viz., three alpha-helices and two short beta-strands, is stabilized against denaturation by these salts. We suggest that an increase in the concentration of the anions on the surface of the prion protein molecule due to their preferential interaction with the glycine residues in the N-terminal segment destabilizes the structure of the prion protein by perturbing the prion helix 1 which is the most soluble of all the protein alpha-helices reported so far in the literature. The present results could be relevant to explain the observed structural conversion of the prion protein by anionic nucleic acids and sulfated glycosaminoglycans.

DNA-induced partial unfolding of prion protein leads to its polymerisation to amyloid

The full-length mouse recombinant prion protein (23-231 amino acid residues) contains all of its structural elements viz. three alpha-helices and a short two-stranded antiparallel beta-sheet in its C-terminal fragment comprising 121-231 amino acid residues. The incubated mixture of this prion protein fragment and nucleic acid results in the formation of amyloid fibres evidenced from electron microscopy, birefringence and fluorescence of the fibre bound Congo Red and Thioflavin T dyes, respectively. The secondary structure of the amyloid formed in nucleic acid solution is similar to the in vivo isolated prion protein 27-30 amyloid but unlike in it, a hydrophobic milieu is absent in the 121-231 amyloid. Thermal denaturation study demonstrates a partial unfolding of the protein fragment in nucleic acid solution. We propose that nucleic acid catalyses unfolding of prion protein helix 1 followed by a nucleation-dependent polymerisation of the protein to amyloid.

Gas-phase reactivity of the O=P(OCH3)2+ phosphonium ion with aliphatic esters in a quadrupole ion trap. Spontaneous elimination of ketenes

Ion-molecule reactions between the O=P(OCH(3))(2) (+) phosphonium ions and five aliphatic esters (methyl acetate, methyl propionate, methyl 2-methylpropionate, methyl butyrate and ethyl acetate) were performed in a quadrupole ion trap mass spectrometer. The O=P(OCH(3))(2) (+) phosphonium ions, formed by electron ionization from neutral trimethyl phosphite, were found to react with aliphatic esters to give an adduct ion [RR'CHCOOR", O=P(OCH(3))(2)](+), which loses spontaneously a molecule of ketene CH(2)=CO or substituted ketenes RR'C=CO. Isotope-labeled methyl acetate was used to elucidate fragmentation mechanisms. The potential energy surface obtained from B3LYP/6-31G(d,p) calculations for the reaction between O=P(OCH(3))(2) (+) and methyl acetate is described.

Gas-phase ion/molecule reactions between dimethoxyphosphonium ions and aromatic hydrocarbons

Ion/molecule reactions between O=P(OCH(3))(2)(+) phosphonium ions and six aromatic hydrocarbons (benzene, toluene, 1,2,4-trimethylbenzene, naphthalene, acenaphthylene and fluorene) were performed in a quadrupole ion trap mass spectrometer. The O=P(OCH(3))(2)(+) phosphonium ions, formed by electron impact from neutral trimethyl phosphite, were found to react with aromatic hydrocarbons (ArHs) to give (i) an adduct [ArH, O=P(OCH(3))(2)](+) and (ii) for ArHs which have an ionization energy below or equal to 8.14 eV, a radical cation ArH(+ *) by charge transfer reaction. Collision-induced dissociation experiments, which produce fragment ions other than the O=P(OCH(3))(2)(+) ions, indicate that the adduct ions are covalent species. Isotope-labeled ArHs were used to elucidate fragmentation mechanisms. The charge transfer reactions were investigated using density functional theory at the B3LYP/6-311 + G(3df,2p)//B3LYP/6-31G(d,p) level of theory. The potential energy surface obtained from B3LYP/6-31G(d,p) calculations for the reaction between O=P(OCH(3))(2)(+) and benzene is described.

Selection and characterization of single chain Fv fragments against murine recombinant prion protein from a synthetic human antibody phage display library

We describe the selection of single chain Fv fragments (scFv) against recombinant murine prion protein (mPrP) from a synthetic human antibody phage display library. Six different antibodies were isolated after three rounds of panning against full-length mPrP. All antibodies recognized a truncated form of mPrP containing residues (121-231). The amino acid sequence of the CDR3 of the scFv fragments has been determined. Five of the antibodies have been over-expressed, purified and their affinity for full-length mPrP determined by ELISA. The observed binding affinities vary from 30 nM to 2.7 microM.

Antibodies inhibit prion propagation and clear cell cultures of prion infectivity

Prions are the transmissible pathogenic agents responsible for diseases such as scrapie and bovine spongiform encephalopathy. In the favoured model of prion replication, direct interaction between the pathogenic prion protein (PrPSc) template and endogenous cellular prion protein (PrPC) is proposed to drive the formation of nascent infectious prions. Reagents specifically binding either prion-protein conformer may interrupt prion production by inhibiting this interaction. We examined the ability of several recombinant antibody antigen-binding fragments (Fabs) to inhibit prion propagation in cultured mouse neuroblastoma cells (ScN2a) infected with PrPSc. Here we show that antibodies binding cell-surface PrPC inhibit PrPSc formation in a dose-dependent manner. In cells treated with the most potent antibody, Fab D18, prion replication is abolished and pre-existing PrPSc is rapidly cleared, suggesting that this antibody may cure established infection. The potent activity of Fab D18 is associated with its ability to better recognize the total population of PrPC molecules on the cell surface, and with the location of its epitope on PrPC. Our observations support the use of antibodies in the prevention and treatment of prion diseases and identify a region of PrPC for drug targeting.

Phosphorylation of serine residues affects the conformation of the calmodulin binding domain of human protein 4.1

We have previously characterized the calcium-dependent calmodulin (CaM)-binding domain (Ser76-Ser92) of the 135-kDa human protein 4.1 isoform using fluorescence spectroscopy and chemically synthesized nonphosphorylated or serine phosphorylated peptides [Leclerc, E. & Vetter, S. (1998) Eur. J. Biochem. 258, 567-671]. Here we demonstrate that phosphorylation of two serine residues within the 17-residue peptide alters their ability to adopt alpha helical conformation in a position-dependent manner. The helical content of the peptides was determined by CD-spectroscopy and found to increase from 36 to 45% for the Ser80 phosphorylated peptide and reduce to 28% for the Ser84 phosphorylated peptide; the di-phosphorylated peptide showed 32% helical content. Based on secondary structure prediction methods we propose that initial helix formation involves the central residues Leu82-Phe86. The ability of the peptides to adopt alpha helical conformations did not correlate with the observed binding affinities to CaM. We suggest that the reduced CaM-binding affinities observed for the phosphorylated peptides are more likely to be the result of unfavorable sterical and electrostatic interactions introduced into the CaM peptide-binding interface by the phosphate groups, rather than being due to the effect of phosphorylation on the secondary structure of the peptides.

Anti-DNA antibodies are a major component of the intrathecal B cell response in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of unknown cause that afflicts the central nervous system. MS is typified by a highly clonally restricted antigen-driven antibody response that is confined largely to the central nervous system. The major antigenic targets of this response and the role of antibody in disease pathogenesis remain unclear. To help resolve these issues, we cloned the IgG repertoire directly from active plaque and periplaque regions in MS brain and from B cells recovered from the cerebrospinal fluid of a patient with MS with subacute disease. We found that high-affinity anti-DNA antibodies are a major component of the intrathecal IgG response in the patients with MS that we studied. Furthermore, we show DNA-specific monoclonal antibodies rescued from two subjects with MS as well as a DNA-specific antibody rescued from an individual suffering from systemic lupus erythematosus bound efficiently to the surface of neuronal cells and oligodendrocytes. For two of these antibodies, cell-surface recognition was DNA dependent. Our findings indicate that anti-DNA antibodies may promote important neuropathologic mechanisms in chronic inflammatory disorders, such as MS and systemic lupus erythematosus.

Serine/threonine phosphorylation of calmodulin modulates its interaction with the binding domains of target enzymes

The interaction of serine/threonine-phosphorylated calmodulin with synthetic peptides corresponding to the calmodulin-binding domains of six enzymes has been studied by fluorescence spectroscopy. For five peptides, the dissociation constant of the calmodulin-peptide complex (K(d)) increased when calmodulin was phosphorylated. An increase of more than one order of magnitude was observed with peptides derived from smooth-muscle myosin light-chain kinase and cAMP phosphodiesterase. In contrast, only a slight increase in K(d) was noted with two peptides derived from the plasma membrane Ca(2+)-ATPase and for the peptide derived from nitric oxide synthase. No significant change in affinity was detected with the peptide derived from calcineurin. In contrast, a decrease in the dissociation constant was observed with the peptide derived from the Ca(2+)-calmodulin dependent kinase II. Phosphorylation also affected the peptide-calmodulin binding stoichiometry: a decrease from two to one binding sites was observed with the peptides derived from myosin light-chain kinase and phosphodiesterase.

Polymerization of murine recombinant prion protein in nucleic acid solution

Recombinant prion protein has been used earlier to understand the structural properties of cellular prion protein PrP(C) and to understand conformational change of PrP(C) to its isoform, PrP(Sc) which is believed to be responsible for the prion disease. Here we report that murine recombinant prion protein, MoPrP(C) polymerizes in the presence of nucleic acid. The aggregation process and the properties of the aggregates have been monitored by physical, biochemical and ultrastructural studies. An increase in the turbidity at 0,90 degrees light scattering is observed when the protein is added to nucleic acid. An increase in the fluorescence of anilino naphthalene sulfonic acid dye (ANS) accompanying a blue shift in its emission maxima is observed when the aggregate obtained from prion protein and DNA reaction is added to it. The kinetics of the increase of the ANS fluorescence during aggregation process show lag periods which depend linearly on the nucleic acid concentration but show a biphasic dependence on the protein concentration. The change in the fluorescence properties of the dye in the presence of the aggregates obtained in the present study and in the presence of the protein PrP 27-30 amyloid isolated in vivo reported in literature are similar. The dye Congo Red binds to the aggregates resulting from the aggregation reaction.The ultrastructural analysis revealed polymeric structures with amyloid like morphologies and smaller oligomeric structures. In addition, condensed nucleic acid structures are also observed which are morphologically different from histone induced condensed nucleic acid structures but are similar to Human Immunodeficiency Virus-1 nucleocapsid protein, NCp7, induced nucleic acid structures. The aggregates show resistance to degradation by proteinase K treatment. Charge neutralization resulting from the MoPrP(C)-DNA interaction and accompanying structural changes in the molecules may explain the observed effects.

Asymmetric Multiblock Copolymers at the Gas-Liquid Interface: Phase Diagram and Surface Pressure

A theoretical model of copolymers made of N blocks is studied at the air-water interface. Each block is made of a sequence A of ZA hydrophobic and of a sequence B of ZB hydrophilic monomers. The A and B sequences cannot cross the interface. The conformation of an adsorbed polymer is determined as a random walk of N elements whose size is the Flory radius of a single sequence. The structure of the interfacial layer is determined as a function of alpha = ZA/ZB and of the surface concentration using scaling law arguments. Only three different regions are found in the phase diagram to describe the change of surface regime as a function of the total surface concentration. The energy of flower-like micelles of polymers is calculated and compared with the energy of adsorbed macromolecules in order to determine the surface concentration at saturation. The surface pressure is also calculated as a function of the surface concentration in the three different regions of the phase diagram. It is found that these surface pressure isotherms are not affected by the solvent quality except when the properties of the interfacial layer are dominated by a purely two-dimensional behavior (semidiluted regime of the whole polymer or of the A sequences on the air side of the interface). Finally the properties of this model are compared with experimental data obtained with protein adsorbed layers and encouraging agreement is found although proteins are much more complicated polymers than this crude model. Copyright 1999 Academic Press.

Characterization of a calcium-dependent calmodulin-binding domain in the 135-kD human protein 4.1 isoform

The putative calmodulin binding domain of non-erythroid protein 4.1, previously suggested by Kelly et al. [Kelly, G. M., Zelus, B. D. & Moon, R. T. (1991) J. Biol. Chem. 266, 12469-12473] has been synthesized, and its binding to calmodulin has been studied by fluorescence spectroscopy. For this purpose, the peptide has been N-terminally dansylated. The 4.1 peptide Dns-Abu-S76RGLSRLFSSFLKRPKS92, binds calmodulin in a calcium-dependent way with high affinity (Kd = 23 +/- 6 nM). The peptide inhibits bovine-heart phosphodiesterase with an IC50 of 50 nM. Since the sequence of the peptide shows two putative consensus sites of phosphorylation by cAMP-dependent protein kinase or Ca2+-calmodulin protein-kinase II, the interaction of the two mono-phosphorylated peptides (P4.1 Ser(80-P) and P4.1 Ser(84-P)) and the di-phosphorylated peptide (P4.1 Ser(80-P)/Ser(84-P)) with calmodulin has been investigated. A decrease of affinity by a factor 1.5-8 has been observed for the phosphorylated peptides. CD measurements have shown an increase of the content of alpha helices in the peptides when bound to calmodulin.

[A computerized nursing care and services management tool]

The Quebec government has initiated a project to review the funding of health care establishments by determining the average cost of a hospital stay. A committee of nursing directors studied existing nursing care measurement tools and decided to develop a new tool better suited to computerized care plans. The new tool is called MESSII, after the French acronym "Mesure des soins et des services infirmiers informatisée," meaning computerized measurement of nursing care and services. This article presents the development and validation stages of MESSII.