Diverse Molecular Weights Research Articles

Bringing comfort to the masses: A novel evaluation of comfort agent solution properties

Ocular comfort agents are molecules that relieve ocular discomfort by augmenting characteristics of the tear film to stabilize and retain tear volume and lubricate the ocular surface. While a number of clinical comparisons between ocular comfort agent solutions are available, very little work has been done correlating the properties of specific comfort agents (species, molecular weight, and water retention) and solution properties (concentration, viscosity, zero shear viscosity, and surface tension) to the performance and effectiveness of comfort agent solutions. In this work, comfort-promoting properties related strongly to comfort agent concentration and molecular weight, the first objective demonstration of this relationship across diverse comfort agent species and molecular weights. The comfort agents with the greatest comfort property contributions (independent of specific molecular weight and concentration considerations) were hyaluronic acid (HA), hydroxypropyl methylcellulose (HPMC), and carboxymethylcellulose (CMC), respectively. The observed, empirical relationships between comfort property contribution and comfort agent species, solution properties, comfort agent molecular weight, and solution concentration was used to develop novel comfort agent index values. The comfort agent index values provided much insight and understanding into the results of experimental studies and/or clinical trials and offer potential resolution to numerous conflicting reports within the literature by accounting for the difference in comfort agent performance due to molecular weight and concentration of comfort agents. The index values provide the first objective, experimental validation and explanation of numerous general trends suggested by clinical data.

Bacterial exopolysaccharides: functionality and prospects.

Diverse structural, functional and valuable polysaccharides are synthesized by bacteria of all taxa and secreted into the external environment. These polysaccharides are referred to as exopolysaccharides and they may either be homopolymeric or heteropolymeric in composition and of diverse high molecular weights (10 to 1000 kDa). The material properties of exopolysaccharides have revolutionized the industrial and medical sectors due to their retinue of functional applications and prospects. These applications have been extensive in areas such as pharmacological, nutraceutical, functional food, cosmeceutical, herbicides and insecticides among others, while prospects includes uses as anticoagulant, antithrombotic, immunomodulation, anticancer and as bioflocculants. Due to the extensive applications of bacterial exopolysaccharides, this overview provides basic information on their physiologic and morphologic functions as well as their applications and prospects in the medical and industrial sectors.

Study of Protein Partitioning in Polymer-Salt Aqueous Two-Phase Systems Using Electrolyte-SAFT (E-SAFT) Equation of State

The statistical associating fluid theory (SAFT) has been applied to correlate partition coefficients of proteins in polymer-salt aqueous two-phase systems. Accordingly, interactions among the association on the partition coefficients of proteins have been thoroughly studied by the SAFT equation of state. The parameters of the SAFT equation of state (EoS) for pure water were obtained from our previous work. Additionally, the parameters of SAFT for poly (ethylene glycol) with diverse molecular weights were estimated using densities of aqueous polymer solutions. Finally, partition coefficients of proteins in aqueous two-phase systems were investigated. The restrictive primitive mean spherical approximation (RP-MSA) has been used for long-range interactions whereas the parameters of SAFT for proteins were obtained, primarily by utilizing the electrolyte-SAFT (E-SAFT). The results showed that the E-SAFT is capable of accurately correlate partition coefficients of proteins in aqueous two-phase systems.

Cross-linked membranes based on acrylated cyclodextrins and polyethylene glycol dimethacrylates for aromatic/aliphatic separation

The cost and energy efficient separation of aromatic/aliphatic and isomeric mixtures using membranes is a great challenge for the petrochemical industry. However since these mixtures are causing strong swelling effects with most of the polymeric membrane materials, especially at elevated temperatures, cross-linking is necessary in many cases. Furthermore highly selective membranes can be reached, if the well-known ability of cyclodextrins to form host–guest interactions with specific substrates is used. Therefore in this work, cross-linked polymers based on PEG-DMA (polyethylene glycol dimethacrylate) and acrylated cyclodextrins have been prepared and investigated in pervaporation experiments using toluene/cyclohexane mixtures at 60 °C. Thereby membranes with different ratios of PEG-DMA having diverse molecular weights as well as membranes with acrylated α-cyclodextrin and acrylated β-cyclodextrin, respectively have been investigated. Also membranes without any acrylated cyclodextrins have been prepared as a reference. In this case, an aliphatic triacrylate with a similar molecular weight as the cyclodextrin acrylate has been used as a multifunctional cross-linker. The separation experiments using a toluene/cyclohexane mixture showed that especially the membranes based on PEG-DMA and acrylated β-cyclodextrins obtained high selectivities already at low aromatic concentrations in the feed, e.g. with a toluene content of 10 wt.% in the feed a selectivity of α = 14 and a permeability of 0.3 kg μm m −2 h −1 was found at 60 °C feed temperature.

Identification and quantification of polyethylene glycol types in polyethylene glycol methyl ether and polyethylene glycol vinyl ether

Quantitative determination of polyethylene glycol (PEG) impurities in two monofunctional polyglycol types, PEG methyl ether (M-PEG) and PEG vinyl ether (V-PEG), has been carried out by reversed-phase liquid chromatography with evaporative light scattering detection (ELSD). In addition to optimizing the resolution between PEG and monofunctional PEG peaks, the major focus has been to determine the molecular weights of PEG impurities in M-PEG and V-PEG of diverse molecular weights. The latter is achieved by examining liquid chromatography–mass spectrometry (LC–MS) mass spectra of both monofunctional PEG and PEG in several cases, and matching peak retention times with those of available PEG standards for all M-PEG and V-PEG sample types. This information is helpful in selecting the appropriate PEG standard to determine PEG content in each sample type. ELSD response factors for various PEG standards have also been compared. It has been found that PEG standards with molecular weights from 1000 Da to 8000 Da show responses that are within 10% of each other. However, a low molecular weight PEG such as PEG 400, provides approximately 30% less response compared to its higher molecular weight counterparts.

Proteomics Identification of Proteins in Human Cortex Using Multidimensional Separations and MALDI Tandem Mass Spectrometer

It is essential to characterize the proteome of various regions of human brain because most, if not all, neurodegenerative diseases are region-specific. Here we report an in-depth proteomics identification of proteins extracted from the frontal cortex, a region playing a critical role in cognitive function. The integrated proteomics analytical flow consisted of biochemical fractionation, strong cation exchange chromatography, reverse phase liquid chromatography, and MALDI-TOF/TOF mass spectrometric analysis. In total, 812 proteins were confidently identified with two or more peptides. These proteins demonstrated diverse isoelectric points and molecular weights and are involved in several molecular functions, including protein binding, catalytic activity, transport, structure, and signal transduction. A number of proteins known to be associated with neurodegenerative diseases were also identified. Detailed characterization of these proteins will supply the necessary information to appropriately interpret proteins associated with aging and/or age-related neurodegenerative diseases. Finally 140 proteins found in the cortical proteome were present in the proteome of cerebrospinal fluid, providing tissue-specific candidates for biomarker discovery in body fluid.

Electrosynthesis of Linear and Branched Methylene-Bridged Oligo- and Polycarbosilanes

Electrosynthesis methods have been employed as a mild and facile alternative for the syntheses of polycarbosilanes. Electropolymerization was conducted on chloromethylchlorosilanes, [ClCH2Si(CH3)3-mClm (m = 1, 2)], taking advantage of the fact that these compounds contain two types of functional groups, CH2−Cl and Si−Cl, both of which are electrochemically active with different reduction potentials. Under a constant current, −CH2Cl is preferentially reduced to a carbanion, −SiCH2:-, that can nucleophilically attack a Si−Cl bond to form a CH2−Si linkage; branching should occur when more than one Cl atom resides on the silicon atom since each group is capable of reacting with the nucleophilic carbanion. Thus, the condition for polymerization of highly branched polycarbosilanes is m > 1. Detailed spectroscopic characterizations of the oligomers and polymers with GPC, NMR, IR, and GC-MS are given. The formation of diverse structures, molecular weights, and reaction yields is strongly dependent on the electrosynthesis conditions, such as electrode composition and supporting electrolyte (SE). Thus, high molecular weight (Mn ≈ 57 000) of highly branched but soluble poly[methylsilylenemethylene] is obtained by electropolymerization of ClCH2Si(CH3)Cl2 with the Al/nickel (anode/cathode) pair and Bu4N+BF4 (SE). GC-MS analysis confirms that a number of oligomeric structures can be produced by electrosynthesis, and diverse structural irregularities (i.e., cross-linking, loop, and fused rings) can be incorporated into the branched skeleton of polycarbosilanes. Cyclic voltammetric analysis suggests that electroreduction of chlorocarbosilanes undergoes an ECE mechanism to initiate polymerization, as well as a myriad of side reactions.

Enhancer of Polycomb1, a Novel Homeodomain Only Protein-binding Partner, Induces Skeletal Muscle Differentiation

Homeodomain only protein, Hop, is an unusual small protein that modulates target gene transcription without direct binding to DNA. Here we show that Hop interacts with Enhancer of Polycomb1 (Epc1), a homolog of a Drosophila polycomb group gene product that regulates transcription, to induce the skeletal muscle differentiation. Yeast two-hybrid assay with the human adult heart cDNA library revealed that Hop can associate with Epc1. The amino-terminal domain of Epc1 as well as full Epc1 physically interacted with Hop in mammalian cells and in yeast. Epc1 is highly expressed in the embryonic heart and adult skeletal muscles. Serum deprivation induced differentiation of H9c2, a myoblast cell line, into skeletal myocytes, and Epc1 was up-regulated. Differentiation of H9c2 was induced by Epc1 overexpression, although it was severely impaired in Epc1-knockdown cells. Co-transfection of Hop potentiated Epc1-induced transactivation of myogenin and myotube formation. Hop knock-out mice elicited a decrease in myosin heavy chain and myogenin expressions in skeletal muscle and showed delay in hamstring muscle healing after injury. Differentiation was impaired in skeletal myoblasts from Hop knock-out mice. These results suggest that Epc1 plays a role in the initiation of skeletal muscle differentiation, and its interaction with Hop is required for the full activity.

QSPR-modeling of oligophenylene melting points

QSPR-modeling of melting temperatures has been performed for oligophenylenes of diverse structures and different molecular weights. It has been shown that optimization of correlation weights of graph local invariants can be used for prediction of melting points of oligomers. The best statistical quality of the model is observed for correlation weights calculated using third-order Morgan degrees.

Pruritus precipitated by hydroxyethyl starch: a review

Hydroxyethyl starch (HES) is widely used for fluid management in broad populations of patients, particularly in the surgery and intensive care settings. Pruritus, often manifested as pruritic crises, is increasingly being recognized as a common major adverse effect of HES administration. This iatrogenic form of pruritus is frequently severe and protracted with a serious negative impact on patient quality of life, including sleep disturbance, disruption of daily routine and mental distress. Such pruritus is generally refractory to available therapies and can persist for up to 12-24 months. All currently clinically available HES solutions entail the risk of pruritus, including those of diverse molecular weights and substitutions. Although dose dependent, HES-induced pruritus nevertheless can often be provoked by relatively low routine doses. The pathophysiological basis for pruritus is the widespread tissue deposition of HES, prominently in macrophages. HES tissue deposits are long lasting and sometimes massive. Usually several weeks elapse between HES exposure and the onset of pruritus. Consequently, it is important to inquire about prior HES exposure in the diagnostic evaluation of pruritus sine materia. Awareness about the scope of the pruritus problem needs to increase among physicians administering HES. Well-designed clinical outcome studies are needed to assess more fully the incidence, dose dependency and mechanisms of pruritus with particular HES solutions.

Chiral polymers containing a carbohydrate moiety: synthesis.

This paper reports the preparation of poly(acetal-ethers) by two alternative synthetic pathways (alkaline and acid-catalyzed conditions). Polycondensations of methyl 2,3:4,6-di-O-salicylidene-alpha-D-mannopyranoside (3) (mixtures of endo-H and exo-H dioxolan-2-yl-diastereomers) with 1,4-dibromobutane (4) (method I a and I b) were performed in solvents (DMF, butyl acetate/DMF, DMSO) and were catalyzed by K2CO3/KI or KOH. A similar polymer (6) was formed by the reaction of methyl alpha-D-mannopyranoside (1) and 1,4-bis(2-formylphenoxy)butane (7), catalyzed by p-toluenesulfonic acid (method II). Regardless of conversion or initial comonomer feed ratios, the composition of the polycondensates depended on the reaction conditions, leading to the formation of macrocyclic [1 + 1] (5) and [2 + 2] compounds, which were macromolecules with diverse molecular weights and optical properties. The regioselective polycondensation was examined by 1H NMR spectroscopy of selected polymers. In the case of 5-membered cyclic acetal units, mixtures of the endo-H and exo-H dioxolan-2-yl system, diastereomers were formed in the polymer chain. The macrocycles and linear oligomers were identified by NMR and electrospray mass spectrometry (ESI-MS). Thermodynamically controlled reactions for making macrocycles as well as oligomers in the absence of templates are also discussed.

Condensation and Polycondensation of Terephthaldehyde with MethylD-Hexopyranosides

The condensation and polycondensations of terephthaldehyde (1) and methyl D-hexopyranosides (gluco-, galacto- and mannopyranoside) are described. Methyl α-D-glucopyranoside and methyl α-D-galactopyranoside react with 1 to give mono-5 a and 6 a and diacetals 5 b and 6 b. Their structures were confirmed by NMR and IR spectroscopy. The polycondensation of methyl α-D-mannopyranoside (4) with 1 was studied in various solvents within the temperature range of 80–140°C. Regardless of the conversion or the initial comonomer feed ratios the composition of polycondensates depended on the reaction conditions leading to the formation of materials with diverse solubilities, molecular weights and optical properties. The regioselective polycondensation of 1 and 4 was examined by the 1H NMR spectroscopy of polymer 7. In the case of five-membered cyclic acetal units, mixtures of the endo-H and exo-H dioxolan-2-yl system diastereomers are formed. Experimental examples of functionalization via ester units in polymer molecules 8 are described and the efficiency of the reaction routes and procedures are evaluated. The molecular weight was estimated by size-exclusion chromatography (SEC) measurements before and after the functionalization.

Condensation and Polycondensation of Terephthaldehyde with Methyl D-Hexopyranosides

The condensation and polycondensations of terephthaldehyde (1) and methyl D-hexopyranosides (gluco-, galacto- and mannopyranoside) are described. Methyl α-D-glucopyranoside and methyl α-D-galactopyranoside react with 1 to give mono-5 a and 6 a and diacetals 5 b and 6 b. Their structures were confirmed by NMR and IR spectroscopy. The polycondensation of methyl α-D-mannopyranoside (4) with 1 was studied in various solvents within the temperature range of 80–140°C. Regardless of the conversion or the initial comonomer feed ratios the composition of polycondensates depended on the reaction conditions leading to the formation of materials with diverse solubilities, molecular weights and optical properties. The regioselective polycondensation of 1 and 4 was examined by the 1H NMR spectroscopy of polymer 7. In the case of five-membered cyclic acetal units, mixtures of the endo-H and exo-H dioxolan-2-yl system diastereomers are formed. Experimental examples of functionalization via ester units in polymer molecules 8 are described and the efficiency of the reaction routes and procedures are evaluated. The molecular weight was estimated by size-exclusion chromatography (SEC) measurements before and after the functionalization.

Modeling of nanofiltration - assisted organic synthesis

The molecular weight of target compounds in many organic syntheses in the pharmaceutical industry is in the range of 300–1000 Da. Separation processes based on organic solvent-resistant nanofiltration membranes are being explored to separate these valuable products from the smaller molecular weight products and residual reactants present in the reaction mixture. Through numerical modeling and use of realistic values for the parameters in organic syntheses involving compounds of diverse molecular weights and hence, diverse sizes, this study shows that the production of the target compound can be enhanced significantly using nanofiltration. Enhancement is examined from the perspectives of conversion (yield), reduction of reaction time, selectivity and potential elimination of subsequent downstream separation steps.

Hole transport in polysilanes with diverse side-chain substituents

Abstract The hole drift mobilities in polysilanes with diverse substituents and different molecular weights have been measured by the conventional time-of-flight technique. Depending on the kind of substituents, hole drift mobilities varied by more than one order of magnitude; poly(?henyltrimethyldisilane) gave the highest room temperature hole drift mobility, 6·0 × 10−4cm2V−1s−1 at a field of 2 × 105 V cm−1, of all the polysilanes reported so far. The electric field and temperature dependences of the hole drift mobilities in polysilanes were analysed in the framework of Gill's expression and Bassler's consideration. Polysilanes with an aromatic side group exhibited a zero-field activation energy E 0 of ca. 0·35 eV compared to E 0 = 0·22-0·26 eV obtained for polysilanes with non-aromatic groups, while poly(phenyltrimethyldisilane), with one aromatic side group at every two Si atoms, manifested E 0 = 0·26 eV, a value which may be categorized in the latter group with non-aromatic substituents. The effects o...

Molecular epidemiology of plasmid patterns inShigella flexneritypes 1–6

A total of 123 drug-resistant and drug-sensitive Shigella flexneri types 1-6, and their Escherichia coli K12 transconjugants were used for plasmid profile analysis by agarose gel electrophoresis. Resistance factors (R-factors) were further characterized by incompatibility testing. The overall distribution of small plasmids in S. flexneri showed that a cryptic plasmid of about 4.6 Kb was found in all serotypes, and a plasmid of about 4.2 Kb was found in serotypes 1-4. Shigella flexneri types 2, 4 and 6 showed a 6.5 Kb plasmid which correlated with SSu-resistance. All S. flexneri serotypes harboured large plasmids of about 217 Kb. Plasmid profile analysis of S. flexneri in Ethiopia showed a high degree of uniformity within individual serotypes. However, there was a limited variability which, at times, could be useful for epidemiological investigation. Shigella flexneri serotypes 1-6 harboured resistance plasmids with diverse molecular weights but mostly belonging to incompatibility groups N and X.

Identification of a cell surface glycoprotein family of olfactory receptor neurons with a monoclonal antibody

A monoclonal antibody (Mab) has been developed which recognizes a family of cell surface glycoproteins found in high levels of rat olfactory receptor neurons. This Mab, designated 2B8, was produced by the fusion of X63-Ag8.653 myeloma cells and spleen cells of a mouse immunized with PC12 rat pheochromocytoma cells. Immunofluorescence analyses of cryostat sections of neonatal olfactory epithelium show prominent 2B8 binding to receptor neurons. Within the olfactory bulb only the glomerular and olfactory nerve layers show 2B8 binding. All other neural structures in the main olfactory bulb have background levels of reactivity. Analyses of 2B8 binding to particulate protein preparations from several central and peripheral nervous system components demonstrated highest 2B8 antigen specific activity in olfactory bulb and epithelium and detectable levels in dorsal root ganglia (DRG), whole cerebrum, cerebellum, and brainstem. However, 2B8 antigen could not be detected in non-olfactory structures by immunofluorescence. Some non-neural tissues also had the ability to bind 2B8 Mab in the particulate protein radioimmunoassay. In order to compare the 2B8-reactive molecules found in each tissue, Mab was applied to polyacrylamide gels of unlabeled membrane proteins. A family of molecules with diverse molecular weights was found. Some were unique to individual tissues whereas others were shared among tissues. Olfactory bulb and epithelium had a unique band with Mr = 215,000 and another band with Mr = 142,000. The 142,000-dalton band was also found with PC12 cells. PC12 cells also had several bands of lesser molecular weight, including 51,000 and 43,000. Testes membranes had immunoreactive bands only at Mr = 46,000 and 43,000. Bone marrow, perinatal liver, and DRG each expressed a single 2B8-reactive band with Mr = approximately 114,000. Salivary gland had four reactive bands, two common to it and only PC12 cells, the 114,000-dalton band which is similar to that found in adult rat bone marrow and DRG, and a unique band at Mr = 152,000. 2B8 immunoprecipitates of olfactory bulb and epithelium were analyzed for glycosyl groups by lectin reactivity. Wheat germ agglutinin and Ricinus communus agglutinin I bound the 2B8 antigens using two distinct assay methods. This suggests that the 2B8 antigens recognized in the olfactory system are glycoproteins having sialic acid and D-galactosyl components.(ABSTRACT TRUNCATED AT 400 WORDS)

Conjugation of ubiquitin to denatured hemoglobin is proportional to the rate of hemoglobin degradation in HeLa cells.

Ubiquitin was radioiodinated and introduced into HeLa cells by the erythrocyte-mediated fusion procedure. Fractionation of injected HeLa cells and subsequent NaDodSO4/polyacrylamide gel electrophoresis showed that HeLa nuclei contained two major labeled proteins: ubiquitin and the histone H2A-ubiquitin conjugate, protein A24. HeLa cytosol contained ubiquitin and a series of ubiquitin-protein conjugates of diverse molecular weights. When injected HeLa cells were treated with phenylhydrazine to denature the cotransferred hemoglobin, a series of prominent ubiquitin-globin conjugates appeared. The identity of these conjugates was established by microinjection experiments in which both proteins were labeled. At low doses of phenylhydrazine, the intracellular concentration of globin-ubiquitin conjugates was proportional to the rate of hemoglobin degradation. This result, together with the observation that ubiquitin conjugation to globin is markedly enhanced by phenylhydrazine-induced denaturation of hemoglobin, provides support for the hypothesis that the covalent attachment of ubiquitin to proteins signals proteolysis.

Protein Bodies from the Endosperm of Castor Bean

Protein bodies from the storage endosperm of dry castor bean (Ricinus communis L.) were isolated by successive nonaqueous linear density gradient centrifugation. The isolated protein bodies were lysed by the addition of water, and the various structural components of the organelles were separated by sucrose gradient centrifugation. The matrix protein remained at the top of the gradient while the membrane, the crystalloids, and the globoids migrated to densities 1.15 g/cm(3), 1.30 g/cm(3), and > 1.46 g/cm(3), respectively. The protein of the protein bodies was distributed evenly between the crystalloids and the matrix, and little protein was present in the globoids or the membrane.The proteins of the protein bodies were resolved into protein components of diverse molecular weights in sodium dodecyl sulfate-acrylamide gel electrophoresis. The protein components of the organelle matrix were distinct from those of the crystalloids. Whereas the matrix proteins had very diverse molecular weights, the crystalloid proteins were mainly composed of several proteins with molecular weights between 50,000 and 60,000 daltons. Also, the matrix proteins were soluble in water while the crystalloid proteins were insoluble in water but soluble in salt solution, thus representing albumins and globulins, respectively. Two of the matrix proteins with molecular weights approximately 120,000 and 65,000 daltons were identified as the phytohemagglutimin and the toxic protein ricin, respectively.During germination, the crystalloid proteins served as the storage protein and went through rapid degradation with smaller polypeptides formed as intermediates. In contrast, the proteins of the matrix under-went a much slower degradation during the same period and did not appear to be storage protein.