Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Yield stability”

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.

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

At least 991 records · Page 55Linked to original sources
PubMed2004

Effects of the SO4 groups on the textural properties and local order deformation of SnO2 rutile structure.

Sulfated tin oxide was synthesized from a hydroxylated tin oxide obtained by the precipitation method, followed by ion exchange of OH groups by SO4 species with a sulfuric acid solution. The samples were characterized by X-ray diffraction, transmission electron microscopy, thermoanalysis, and nitrogen physisorption by the Brunauer-Emmett-Teller method. The rutile crystalline structure was refined by the Rietveld method. Thermal analysis suggests the following stoichiometric formulas: SnO2-x(OH)2x and SnO2-x(OH)x(HSO4)x with X = 0.35 and 0.17 for non-sulfated and sulfated samples, respectively. The SO4 species remained strongly bonded at the SnO2 surface stabilizing its crystallite size against sintering, inhibiting the crystallite aggregation, and it acts as a structure porogen director mediating nanoparticle growth and assembly yielding a mesostructure form of SnO2 with wormhole morphology and high thermal stability. The interaction between SO4(2-) and the SnO2 surface changes the symmetry of the representative tin-oxygen octahedron. It relaxes the four tin-oxygen bond lengths located at the basal plane of the octahedron while the two apical Sn-O bonds decrease, producing a strong deformed octahedron, which could be transformed into a higher asymmetry in the electronic distribution around the Sn4+ nuclei. The elimination of SO4 groups brings about the coalescence and crystallite growth, which collapse the mesostructure form of SnO2, decreasing the surface area and porosity.

Journal Article↗
PubMed2006

Meniscus-stabilizing function of the meniscofemoral ligament: experimental study of pig knee joints.

PURPOSE: To demonstrate experimentally, with the use of pig knee joints, that the posterior meniscofemoral ligament (PML) stabilizes the lateral meniscus (LM). METHODS: Amputated stumps of the knee joints of Yorkshire pigs, which are anatomically similar to human knee joints, were used. The PML was intact or was cut according to 1 of 6 different conditions: (1) intact PML with intact LM, (2) intact PML with a radial tear of the posterior horn of the LM, (3) intact PML with total lateral meniscectomy, (4) cut PML with intact LM, (5) cut PML with a radial tear of the posterior horn of the LM, and (6) cut PML with total lateral meniscectomy. Pressure-sensitive film was inserted beneath the lateral femoral condyle, an axial load of 150 kg was placed on the knee joint with a universal testing machine, and the pressed area and maximum and average pressures were measured with the Prescale Imaging Analysis System (Fujifilm Medical Systems, Stamford, CT). RESULTS: With an intact PML, no difference was seen between the intact meniscus and the radial tear of the posterior horn of the LM in pressed area and maximum and average pressures. With a cut PML, pressure concentration, detected as significantly reduced pressed area and increased maximum and average pressures, was observed, regardless of the condition of the LM. CONCLUSIONS: PML of the pig stabilized the LM under an axial load, and an intact PML yielded results similar to those observed in total lateral meniscectomy. Our findings suggest that posterior horn tears of the LM, which are rarely symptomatic, may be caused by stabilizing of the lateral meniscus by the PML against the load placed on the knee joint. CLINICAL RELEVANCE: Findings suggest that the PML, lateral side, stabilizes the LM when the ligament is intact. Even when a tear of the meniscus occurs, no increased localized pressure areas appear on the meniscus; this may explain why these tears are rarely symptomatic.

Animals↗
PubMed1998

Salter-Harris type III epiphyseal fractures of the proximal phalanx.

Of 823 pediatric hand fractures treated between 1981 through 1996, only 11 (1.3%) were Salter-Harris type III fractures of the proximal phalanx. We review the anatomic basis, etiology, age prevalence, treatment, and results of these epiphyseal injuries. The average age at injury was 14.9 years, with a narrow range from 14 years 2 months to 15 years 11 months. Nine of 11 fractures were displaced and treated with open reduction and internal fixation. At an average follow-up of 21 months, 9 of 11 had full joint motion. The other two had minimal loss of motion, and all had normal function and collateral ligament stability. The displacement and size of the epiphyseal fragment, avulsed and rotated by the collateral ligament, are often underestimated by radiographs. We found that anatomic reduction and fixation yielded good results in all displaced fractures. This restores both the stability of the collateral ligament and a smooth articular surface.

Adolescent↗
PubMed1980

Stabilization of biological photosystems : immobilization of thylakoids and chromatophores for hydrogen production and ATP regeneration.

Lettuce thylakoïds were immobilized by the action of glutaraldehyde at subzero temperature in the presence of albumin. Foam structures with good mechanical properties were obtained. The activity yields for photosystem II and photosystems I + II were found equal to 71 per cent and 35 per cent respectively. The yield for ATP regeneration from ADP and Pi was 26 per cent. Increases of stability after immobilization were observed for all the functions of thylakoïds when stored and when continuously working. Spheroplasts and chromatophores from Rhodopseudomonas capsulata were immobilized with the same method; yields for ATP regeneration were found equal to 40 per cent and 70 per cent, respectively. An important increase of stability after immobilization was observed in both cases.

Adenosine Triphosphate↗
PubMed2006

Expression and purification of dalcochinase, a beta-glucosidase from Dalbergia cochinchinensis Pierre, in yeast and bacterial hosts.

The coding sequence of the mature dalcochinase, a beta-glucosidase from Dalbergia cochinchinensis Pierre, was cloned and expressed in various systems. Expression in Escherichia coli resulted in an insoluble protein, which could be made soluble by co-expression with bacterial chaperonin GroESL. However, the enzyme had no activity. Recombinant expression in Pichia pastoris and Saccharomyces cerevisiae yielded an active enzyme. Dalcochinase was expressed under methanol induction in P. pastoris, since this was much more efficient than constitutive expression in P. pastoris or in S. cerevisiae. Addition of 0.5% casamino acids to the culture medium stabilized the pH of the culture and increased the protein yield by 3- to 5-folds. Insertion of a polyhistidine-tag either after the N-terminal alpha factor signal sequence or at the C-terminus failed to assist in purification by immobilized metal-ion affinity chromatography (IMAC) due to post-translational processing at both termini. A new construct of dalcochinase with an N-terminal truncation following the propeptide and eight histidine residues enabled its purification by IMAC, following hydrophobic interaction chromatography. The purified recombinant dalcochinase was apparently composed of differently post-translationally modified forms, but had kinetic properties and pH and temperature optima comparable to natural dalcochinase. The procedures reported here overcome the limitation in enzyme supply from natural sources, and allow further studies on structure-function relationships in this enzyme.

Animals↗
PubMed1995

Informational suppression to investigate structural functional and evolutionary aspects of the Erwinia chrysanthemi cellulase EGZ.

The cellulase EGZ produced by the plant pathogen Erwinia chrysanthemi belongs to family 5 of the beta-glycohydrolases (also referred to as cellulase family A), which contains over 40 members from Gram-negative and Gram-positive bacteria and fungi. Amber mutations were introduced into 16 codons of the celZ gene encoding EGZ. Targeted residues included: (1) two Glu, two His and one Arg residue, strictly conserved throughout family 5; (2) one Arg and one His residue conserved in sub-family 5-2; and (3) one His and six Arg residues not conserved at all. Each amber allele was introduced into 13 Escherichia coli strains each carrying a different suppressor tRNA that inserts an amino acid at the mutated position. In vivo stability of the mutated forms of EGZ and their cellulase activity were analysed as well as suppression efficiency. For some positions of particular interest, missense mutations were introduced into the celZ gene either to confirm the effect of the suppressor-mediated amino acid substitution or to broaden the spectrum of mutations available. The substitution patterns of the two Glu positions were interpretable in the light of the stereospecificity of the reaction catalysed by EGZ: Glu133 and Glu220 are proposed to act as a proton donor and as a nucleophile, respectively, forming the glycosyl-enzyme intermediate. Substitution at His-occupied positions, including two non-conserved positions, yielded proteins affected in their catalytic activity but not their in vivo stability. In particular, evidence was obtained for His at position 98 to be involved in interactions with the substrate. The view that Arg residues are important in stabilizing proteins was supported by the identification of three Arg residues, whose substitution yielded thermosensitive forms of EGZ. In addition, Pro substitutions of any of the six Arg residues altered protein stability in vivo but the substitutions scored almost neutral for activity. Five positions, predicted to be within alpha-helices, were found to be susceptible to Pro substitutions (but not to Ala) with respect to stability in vivo. Overall, the systematic alteration of all His and Arg residues coupled with the simultaneous analysis of activity and in vivo stability allowed us to demonstrate that substitution matrices vary at each position and for each biological property considered. Ideally, therefore, substitution matrices used in sequence alignment procedures should be reconsidered as position-specific and as property-specific.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed2001

Topological diversity of artificial beta-barrels in water.

Rigid-rod beta-barrels are composed of interdigitating, short, amphiphilic peptide strands flanked by stabilizing rigid-rod "staves". We here report studies on the topological diversity of these recently devised artificial beta-barrels with regard to their length. For this purpose, homologous p-octiphenyl, p-sexiphenyl, and p-quarterphenyl rods were equipped with complementary tripeptide strands based on the sequences Lys-Leu-Lys and Glu-Leu-Glu. The stability of rigid-rod beta-barrels of different length was determined by denaturation with guanidinium chloride. Free energies of delta GH2O = -5.2 kcalmol-1, delta GH2O = -2.9 kcalmol-1, and delta GH2O < -0.3 kcalmol-1 found for homologous p-octiphenyl, p-sexiphenyl, and p-quarterphenyl beta-barrels demonstrated strong dependence of beta-barrel stability on beta-barrel length. These results revealed a very qualitative minimal (approximately 23 A) and an "ideal" beta-barrel length (approximately 34 A), synergistic formation (alpha = 1.4) and remarkable stability for "ideal" p-octiphenyl beta-barrels exceeding that of several proteins and most synthetic models. Rigid-rod beta-barrels with p-oligophenyl "staves" longer than approximately 34 A will be very difficult to make and study because of rapidly decreasing rod solubilities. However, a strategy to bypass this apparent upper limitation of beta-barrel length is introduced: supramolecular matching of mismatched rods yielded elongated beta-barrels (61 A) of acceptable stability (delta GH2O = 2.2 - 3.1 kcalmol-1).

Protein Conformation↗
PubMed1992

Specific sequences and a hairpin structure in the template strand are required for N4 virion RNA polymerase promoter recognition.

Coliphage N4 virion-encapsidated, DNA-dependent RNA polymerase (vRNAP) is inactive on double-stranded N4 DNA; however, denatured promoter-containing templates are accurately transcribed. We report that all determinants of vRNAP promoter recognition exist in the template strand, indicating that this enzyme is a site-specific, single-stranded DNA-binding protein. We show that conserved sequences and the integrity of inverted repeats present at the promoters are essential for activity, suggesting the necessity for specific secondary structure. Evidence for such a structure is presented. We propose a model for in vivo utilization of vRNAP promoters in which template negative supercoiling yields single-strandedness at the promoter to reveal the determinants of vRNAP binding. This structure is stabilized by the binding of E. coli single-stranded DNA-binding protein to yield an "activated promoter."

Affinity Labels↗
PubMedDate not supplied

An in vitro biomechanical investigation of an MP35N intramedullary interlocking nail system for repair of third metacarpal fractures in adult horses.

OBJECTIVE: To compare monotonic mechanical properties of gap-ostectomized third metacarpal bones (MC3) stabilized with an MP35N interlocking nail system with contralateral intact bones. ANIMALS OR SAMPLE POPULATION: Twenty-four pairs of cadaveric equine MC3s. METHODS: Third metacarpal bones were divided into 4 mechanical testing groups (6 pairs per group): compression, palmarodorsal (PD) and mediolateral (ML) 4-point bending, and torsion. One MC3 from each pair was randomly selected as an intact specimen, and the contralateral gap ostectomized bone was stabilized with a 4-hole, 14-mm-diameter, 250-mm-long, MP35N intramedullary nail, and four, 7-mm-diameter, 60-mm-long MP35N interlocking screws (constructs). Mechanical testing properties were compared between intact specimens and constructs with a paired t test (significance set at P <.05). RESULTS: Intact specimens were significantly stronger and stiffer than constructs in all testing modes except PD bending. Constructs achieved mean yield strengths that were 57% (compression), 81% (PD bending), 68% (ML bending), and 78% (torque) of intact specimens. Constructs achieved mean stiffnesses that were 53% (compression), 58% (PD bending), 41% (ML bending), and 47% (torque) of intact specimens. CONCLUSION: Monotonic yield mechanical properties of MP35N intramedullary interlocking nail-stabilized, gap-ostectomized MC3 were lower than those of paired intact bones but exceeded reported in vivo loads for dorsopalmar bending and compression and estimated in vivo torsional loads. CLINICAL RELEVANCE: Considering the benefits associated with intramedullary interlocking nail fixation of fractures, this system should be considered for use for repair of MC3 fractures with applicable fracture configurations.

Animals↗
PubMed1993

Evaluation of sterically stabilized liposomes as a vehicle for targeting technetium-99m labelled radiopharmaceuticals.

Sterically stabilized neutral liposomes (multilamellar vesicles) were prepared by sonicating phosphatidylcholine and cholesterol (molar ratio 4:1) film in phosphate buffered saline (50 mM, pH 7.4) containing 4% Tween 20. Tc-99m-GHA was incorporated in these liposomes by treating 0.5 ml of the suspension with lyophilized GHA kit (5 mg GHA and 250 micrograms SnCl2 x 2 H2O) followed by addition of 1 ml 99mTcO4- (1-3 mCi). The labelling yield was 60-70%. Tween 20 has provided significant stability of the radiolabel as compared to that without its addition, when radiolabelled liposomes were incubated in serum up to 24 h. With respect to Tc-99m-GHA alone, radiolabelled liposomes exhibited 4- to 6-fold greater radioactivity in the blood of rabbits (15 min-24 h). Comparison of biodistribution data of radiolabelled liposomes and Tc-99m-GHA in mice demonstrated a 10- to 12-fold greater hepatic accumulation of radiolabelled liposomes with respect to that of Tc-99m-GHA throughout the period of study (15 min-24 h), though their concentration in the kidneys was comparable.

Animals↗
PubMed1997

Crystal structures of A-DNA duplexes.

All crystal structures of A-DNA duplexes exhibit a typical crystal packing, with the termini of one molecule abutting the shallow grooves of symmetry related neighbors, while all other forms (B, Z, and RNA) tend to form infinitely stacked helices. The A-DNA arrangement leads to the formation of shallow groove base multiples that have implications for the structure of DNA in compacted states. The characteristic packing leaves big solvent channels, which can be sometimes occupied by B-DNA duplexes. Comparisons of the structures of the same oligomer crystallizing in two different space groups and of different sequences crystallizing in the same space group show that the lattice forces dominate the A-DNA conformation in the crystals, complicating the effort to elucidate the influence of the base sequence on the structures. Nevertheless, in both alternating and nonalternating fragments some sequence effects can still be uncovered. Furthermore, several studies have started to define the minimal sequence changes or chemical modifications that can interconvert the oligomers between different double-helical conformers (A-, B-, and Z-form). Overall, it is seen that the rigid nucleotide principle applies to the oligomeric fragments. Besides the structures of the naked DNAs, their interactions with water, polyamines, and metal ions have attracted considerable attention. There are conserved patterns in the hydration, involving both the grooves and the backbone, which are different from those of B-DNA or Z-DNA. Overall, A-DNA seems to be more economically hydrated than B-DNA, particularly around the sugar-phosphate backbone. Spermine was found to be able to bind exclusively to either of the grooves or to the phosphate groups of the backbone, or exhibit a mixed binding mode. The located metal cations prefer binding to guanine bases and phosphate groups. The only mispairs investigated in A-DNA are the wobble pairs, yielding structural insight into their effects on helix stabilities and hydration. G.T wobble pairs have been determined in various sequence contexts, where they differentially affect the conformations and stableness of the duplexes. The structure of a G.m5C base pair, which surprisingly also adopted the wobble conformation, suggests that a similar geometry may transiently exist for G.C pairs. These results from the crystalline state will be compared to the solution state and discussed in relation to their relevance in biology.

Base Sequence↗
PubMed2000

Observations on the shear damage to different animal cells in a concentric cylinder viscometer.

A clear distinction is made between damage to the population of cells and damage to individual cells on exposure to shear stress. Work on mechanical damage to animal cells in suspension is reported for six different cell lines. Precisely controlled shears of 1 Pa, 10 Pa, and 100 Pa were generated in a viscometer and distortions in morphology of the cells-for instance, the formation of transient pores, cytoplasmic extrusions, and ghost-cell membranes-are presented with photographic evidence. Low shears are shown to be just as damaging as the higher shears, although the type of damage is different. It follows that bioreactors should be operated at intermediate shear levels for optimal yield. A mechanism to account for the unexpected stability of animal cells at intermediate levels of shear is presented.

Animals↗
PubMed2006

Reversible chain transfer between organoyttrium cations and aluminum: synthesis of aluminum-terminated polyethylene with extremely narrow molecular-weight distribution.

Aminopyridinato-ligand-stabilized organoyttrium cations are accessible in very good yield through alkane elimination from trialkyl yttrium complexes with sterically demanding aminopyridines, followed by abstraction of one of the two alkyl functions using ammonium borates. At 80 degrees C and in the presence of small amounts of aluminum alkyl compounds, very high ethylene polymerization activities are observed if very bulky aminopyridinato ligands are used. During these polymerizations a reversible polyethylene chain transfer is observed between the organoyttrium cations and aluminum alkyls. The chain-transfer catalyst system described here is able to produce relatively long-chain (up to 4000 g mol-1) Al-terminated polyethylene with a molecular-weight distribution<1.1. In the synthesis of higher molecular PE a slight increase in polydispersity with increasing chain length (15,600 g mol-1, approximately 1.4) is observed owing to reduced reversibility caused by higher viscosity and precipitation of polymer chains (temperature of 80-100 degrees C).

Journal Article↗
PubMed1987

Methodology and safety considerations in the production of an intravenous immunoglobulin preparation.

Intravenous immunoglobulins are biologic substances and differ in many respects from chemical pharmaceuticals. To produce a safe and efficacious preparation, special points must be considered. Careful screening procedures and excluding high-risk donor populations reduce the risk of transmitting viral disease from the starting material. With plasma fractionation the immunoglobulins are purified, and safety is further improved by eliminating potentially remaining viruses. Cold ethanol-fractionation methods have proved to be safe and economical. Anticomplementary aggregates, responsible for anaphylactoid reactions in agammaglobulinemic patients, are removed to achieve intravenous tolerance. Enzymatic digestion or chemical modifications impair the efficacy of the preparation. Ion-exchange adsorption removes immunoglobulin subpopulations. Mild acid treatment at pH 4 yields a safe product with intact potency. Optimal stability is ensured by freeze-drying. A fine net of quality controls virtually guarantees a safe preparation.

Humans↗
PubMed2005

Synthesis of fullerene-like tantalum disulfide nanoparticles by a gas-phase reaction and laser ablation.

Motivated by the discovery of the C(60) molecule (buckminsterfullerene), the search for inorganic counterparts of this closed-cage nanostructure started in 1992 with the discovery of nested fullerene-like nanoparticles of WS(2). Inorganic fullerene-like (IF) materials have since been found in numerous two-dimensional compounds and are available in a variety of shapes that offer major applications such as in lubricants and nanocomposites. Various synthetic methodologies have been employed to achieve the right conditions for the constricted or templated growth needed for the occurrence of this new phase. In this study, IF-TaS(2) is produced from a volatile chloride precursor in the gas phase and in small yield by room temperature laser ablation both in argon and in liquid CS(2). For the gas-phase reaction, a high yield of IF nanoparticles was obtained between 400 and 600 degrees C with a low concentration of the precursor gas. The average size and the yield of the IF-TaS(2) nanoparticles decrease with temperature. Above 600 degrees C, IF nanoparticles were found in low yields and at sizes below 20 nm. The stability of the IF nanoparticles produced by the gas-phase reaction is discussed in the light of two existing theoretical models. Laser ablation in argon leads to IF nanoparticles filled with clusters of TaS(2). Agglomeration of the nanoparticles can be avoided by laser ablation in liquid CS(2).

Argon↗
PubMed1999

Bioaffinity based immobilization of enzymes.

Procedures that utilize the affinities of biomolecules and ligands for the immobilization of enzymes are gaining increasing acceptance in the construction of sensitive enzyme-based analytical devices as well as for other applications. The strong affinity of polyclonal/monoclonal antibodies for specific enzymes and those of lectins for glycoenzymes bearing appropriate oligosaccharides have been generally employed for the purpose. Potential of affinity pairs like cellulose-cellulose binding domain bearing enzymes and immobilized metal ionsurface histidine bearing enzymes has also been recognised. The bioaffinity based immobilization procedures usually yield preparations exhibiting high catalytic activity and improved stability against denaturation. Bioaffinity based immobilizations are usually reversible facilitating the reuse of support matrix, orient the enzymes favourably and offer the possibility of enzyme immobilization directly from partially pure enzyme preparations or even cell lysates. Enzyme lacking innate ability to bind to various affinity supports can be made to bind to them by chemically or genetically linking the enzymes with appropriate polypeptides/domains like the cellulose binding domain, protein A, histidine-rich peptides, single chain antibodies, etc.

Antibodies↗
PubMed1992

Properties of hypotonized, crosslinked and crosslinked- permeabilized rat erythrocytes as potential carrier systems.

The osmotic fragility curves of isotonic rat RBCs, studied at pH 8 to avoid the Hb insolubility, are similar to those in humans at pH 7.4. Hypotonized rat RBCs, either directly or dialysed (0-24 h), are more hemolysis-resistant than isotonic rat RBCs. The discocyte-stomatocyte-spherocyte transformation can be observed with scanning electron microscopy. Protein crosslinking with dimethyl suberimidate can stabilize RBCs. The crosslinking level (60%), the cellular yield (80%), the mechanical and hemolytic resistance and the protective effect of enzyme activities, were studied in crosslinked or crosslinked- permeabilized RBCs after digitonin treatment. The normal discocytic shape of RBCs under scanning electron microscopy becomes stomatocytic in crosslinked and crosslinked- permeabilized RBCs with an erosioned surface.

Animals↗
PubMed1999

Synthesis, formation, and occurrence of contaminants in biotechnologically manufactured L-tryptophan.

The pattern of contaminants in pharmaceutical and feed grade L-tryptophan (Trp) was investigated in a market survey of 22 lots of 6 different manufacturers. To date, 5 case associated contaminants in Showa Denko tryptophan (SD-Trp) known to cause the autoimmune disease eosinophilia-myalgia syndrome (EMS) have been structurally elucidated: 3a-hydroxy-1,2,3,3a,8,8a-hexahydropyrroloindole-2-carboxylic acid (PIC), an indoline compound, is one of the most abundant degradation compounds of unbound Trp during oxidative treatment. 2-(3-indolylmethyl)-L-tryptophan (IMT) and 2-(2-hydroxyindoline)-tryptophan (HIT) are both 2-substituted Trp-derivatives. IMT was synthesized by the reaction of Trp and indole-3-methanol or indole-3-acetaldehyde, respectively. From this finding it is proposed that Trp-metabolites can decompose under formation of transitional, mesomerism-stabilized cations that react with excess Trp to yield 2-substituted Trp derivatives. The decomposition of Trp-metabolites could be induced by elevated or low pH-values that occur during the downstream processing of the Trp fermentation broth. IMT was detected in pharmaceutical-grade and feed-grade Trp in amounts of < 20-1,400 mg/kg. 1,1'-Ethylidenebis-(L-tryptophan) (EBT) is formed from acetaldehyde and Trp under acidic conditions and serves as a marker for EMS-suspicious Trp. 3-(Phenylamino)alanine (PAA) is the only not Trp derived case associated contaminant. Low amounts of PAA (20 mg/kg) could be detected in feed-grade Trp of one manufacturer. Non-EMS correlated 1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acids of Trp and formaldehyde, acetaldehyde and indole-3-acetaldehyde could be detected in the examined Trp raw materials (< 10-13,500 mg/kg). In order to guarantee the safety of Trp containing drugs the amount of EBT (< 10 mg/kg Trp) and the sum of UV220 nm detectable contaminants (< 400 mg/kg Trp) are limited by the European authorities.

Animal Feed↗