DETERMINATION OF DIFFUSION COEFFICIENTS AND MOLECULAR WEIGHTS OF RIBONUCLEIC ACIDS AND VIRUSES

Nanoparticle Enhanced Interfacial Solar Photothermal Water Disinfection Demonstrated in 3-D Printed Flow-Through Reactors

Heat treatment, i.e., boiling or pasteurization, is the most widely recognized and practiced form of household water treatment. Considering recent advances in the development of light harvesting nanoparticles for solar-to-heat conversion, we envision that a nanomaterial enhanced water heating treatment system could obviate the need to use fuels or electricity to heat water by replacing the energy source with sunlight. In this study, we demonstrate that functional disinfection temperatures can be easily achieved with unconcentrated sunlight using a single layer interfacial photothermal film in direct contact with a tortuous flowing water channel. Photothermal films were fabricated by dispersing high concentrations of light harvesting nanoparticles, carbon black and Au nanorods, into a highly transparent curable polymer. Bench-scale 3-D printed reactors were employed to determine the effect of different parameters on reactor performance, such as channel height, retention time, flow rate, initial water temperature, and light intensity. Simulations demonstrate the scalability of the treatment system, predicting that a reactor footprint of 45 × 45 cm would be required for a photothermal treatment system that could produce 8 L of water per day with 8 h of sunlight at 1 Sun intensity.

Free Diffusivity of Icosahedral and Tailed Bacteriophages: Experiments, Modeling, and Implications for Virus Behavior in Media Filtration and Flocculation

The aqueous bulk diffusivities of several near-spherical (icosahedral) and nonspherical (tailed) bacterial viruses were experimentally determined by measuring their flux across large pore membranes and using dynamic light scattering, with excellent agreement between values measured using the two techniques. For the icosahedral viruses, good agreement was also found between measured diffusivity values and values predicted with the Stokes-Einstein equation. However, when the tailed viruses were approximated as spheres, poor agreement was found between measured values and Stokes-Einstein predictions. The shape of the tailed organisms was incorporated into two modeling approaches used to predict diffusivity. Model predictions were found to be in good agreement with measured values, demonstrating the importance of the tail in the diffusive transport of these viruses. Our calculations also show that inaccurate estimates of virus diffusion can lead to significant errors when predicting diffusive contributions to flocculation and to single collector efficiency in media filtration.

A novel application of small-angle scattering techniques: Quality assurance testing of virus quantification technology

Small-angle scattering (SAS) techniques, like small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS), were used to measure and thus to validate the accuracy of a novel technology for virus sizing and concentration determination. These studies demonstrate the utility of SAS techniques for use in quality assurance measurements and as novel technology for the physical characterization of viruses.

Bacteriophage MS2: molecular weight and spatial distribution of the protein and RNA components by small-angle neutron scattering and virus counting

Small-angle neutron scattering (SANS) has been used to extend the structural characterization of the MS2 phage by examining its physical characteristics in solution. Specifically, the contrast variation technique was employed to determine the molecular weight of the individual components of the MS2 virion (protein shell and genomic RNA) and the spatial relationship of the genomic RNA to its protein shell. A consequence of this work was to evaluate a novel particle counting instrument, the integrated virus detection system (IVDS) that, in combination with SANS, has the potential to provide rapid quantitative physical characterization of unidentified viruses and phage.

Phosphorylase b covalently bound to glycogen: properties of the complex

Rabbit skeletal muscle glycogen phosphorylase b was covalently bound to oyster glycogen by means of cyanogen bromide. Removal of the unbound enzyme was achieved, using DEAE-Sephadex A-50 chromatography. Glycogen-bound phosphorylase b showed a higher affinity toward glucose 1-phosphate but a lower homotropic cooperativity, with respect to AMP activation, than the native enzyme. However, at low AMP concentrations conjugated phosphorylase b was as efficient as the free enzyme. It is of interest that glycogen-bound phosphorylase b exhibited catalytic activity upon its polysaccharide carrier. Kinetics of heat and cold inactivation indicated that the bound enzyme was considerably more resistant toward heat inactivation but less stable upon exposure to cold. It was shown also that both conjugated and native enzymes had identical pH optima, similar activity/temperature dependencies and the same resistance against trypsin inactivation.

Flow field-flow fractionation: new method for separating, purifying, and characterizing the diffusivity of viruses

The nature and theory of flow field-flow fractionation is described, and its potential applicability to virus-like particles is discussed. Different virus types are shown to be retained at different levels. Retention can be controlled by variation of the experimental parameters, in good agreement with theory. However, a mild adsorption effect is indicated and requires the development of alternate strategies for measuring diffusion coefficients. For Qbeta, our value agrees well within 10% of literature values; the values obtained for other viruses, using Abeta as an internal standard, are untested. Finally, it is demonstrated that flow field-flow fractionation can cleanly fractionate two viruses from one another and from an albumin impurity, that samples as large as several milligrams in size can be analyzed, and that the method has potential utility in the quantitative and qualitative analysis of virus systems.

Purification and properties of formaldehyde dehydrogenase and formate dehydrogenase from Candida boidinii

Formaldehyde hydrogenase and formate dehydrogenase were purified 130-fold and 19-fold respectively from Candida boidinii grown on methanol. The final enzyme preparations were homogenous as judged by acrylamide gel electrophoresis and by sedimentation in an ultracentrifuge. The molecular weights of the enzymes were determined by sedimentation equilibrium studies and calculated as 80000 and 74000 respectively. Dissociation into subunits was observed by treatment with sodium dodecylsulfate. The molecular weights of the polypeptide chains were estimated to be 40000 and 36000 respectively. The NAD-linked formaldehyde dehydrogenase specifically requires reduced glutathione for activity. Besides formaldehyde only methylglyoxal served as a substrate but no other aldehyde tested. The Km values were found to be 0.25 mM for formaldehyde, 1.2 mM for methylglyoxal, 0.09 mM for NAD and 0.13 mM for glutathione. Evidence is presented which demonstrates that the reaction product of the formaldehyde-dehydrogenase-catalyzed oxidation of formaldehyde is S-formylglutathione rather than formate. The NAD-linked formate dehydrogenase catalyzes specifically the oxidation of formate to carbon dioxide. The Km values were found to be 13 mM for formate and 0.09 mM for NAD.

Semi-micro quantitative gel precipitin reaction

Quantitative gel precipitin reactions were made on a semi-micro-scale. This required overall reduction of the dimensions of the necessary apparatus. Resulting from this was the ability to use agarose gel at low concentration not possible with the conventional macro quantitative gel precipitin technique. Further advantages were the reduction of time for the completion of the experiments and also that of the volume of the reactants. Diffusion coefficients of antigens determined by the semi-micro technique agreed with those obtained with the more accurate optical methods.

Physical properties of moloney murine leukemia virus high-molecular-weight RNA: a two subunit structure

The high-molecular-weight RNA of Moloney murine leukemia virus (MuLV) was analyzed by sedimentation equilibrium ultracentrifugation. Molecular weights of 7.2 x 10(6) and 3.4 x 10(6) were found for the native and subunit forms, respectively, indicating that the native structure is a dimer. S20,w and frictional coefficients were determined for MuLV RNA by analytical velocity centrifugation as a function of ionic strength. The apparent S20,w of native MuLV RNA was 47.3, 57.4, and 66.5 in 0.01, 0.1, and 0.20 M Na+, respectively; the corresponding frictional coefficients were 5.44, 4.48, and 3.87. Native RNA was estimated by circular dichroism to be 85% helical, whereas denatured RNA was 54% helical. Thermal denaturation profiles were obtained from uv absorbance scans. Melting temperatures of 57 and 68 C were obtained for high-molecular-weight RNA in 0.01 M Na+ and 0.122 M Na+, 1mM Mg2+, respectively. van't Hoff plots of the thermal denaturation data gave enthalpies for the helix-coil transition of 21,600 cal (ca. 90,500 J) per mol of cooperatively melting unit in high salt and 19,600 cal (ca. 82,100 J) per mol in low salt, consistent with both base stacking and pairing. The melting of Mu LV RNA occurred over a broad temprange and van't Hoff plots were linear over most of the melting range, indicating a noncooperative process of helix stabilization.

The nature of polydisperse ribonucleic acid in plants

The aggregation of ribosomal RNA species during chromatography on methylated albumin on kieselguhr was decreased from 50 to 15% by the lower salt concentrations made possible by the use of higher pH values. The polydisperse RNA was resolved into two fractions. About 50% was eluted with the rRNA whereas the remainder was bound to the column, and was recovered only by solubilization of the methylated albumin. Both fractions of polydisperse RNA were similar in size range, but the bound fraction was considerably richer in AMP. No D-RNA (DNA-like RNA) peak was resolved under these conditions of column fractionation. However, the properties of the bound RNA were consistent with it containing both D-RNA and TB-RNA (tenaciously bound RNA). The relationship between these two fractions of AMP-rich RNA was considered. The bound RNA and ribosomal RNA responded differently to various treatments. The salt concentration required to elute ribosomal RNA was halved by increasing the pH of the fractionation, but the amount of bound RNA was in fact increased. Denaturation by hot urea decreased the binding of ribosomal RNA to the methylated albumin, but did not facilitate elution of bound RNA. The high affinity between the AMP-rich polydisperse RNA and the methylated albumin does not therefore appear to arise for the secondary structure conferred by the high AMP content.