Engineering topics

Pusey, Marc L.

Publications and source records attributed to Pusey, Marc L..

84 records · Page 5

NASA NTRS1992

The effects of acid treatment and calcium ions on the solubility of concanavalin A

The effects of acid treatment (which removes Mn and Ca ions) and Ca(2+) ions on the solubility of jack-bean-meal concanavalin A were investigated using two techniques: the sitting drop technique and the microcolumn technique. It was found that the solubility of concanavalin A varied with the protein preparation procedures and with measurement techniques. Addition of Ca(2+) resulted in greatly lowered solubilities compared with the acid treated protein. The sitting drop solubilities for the recalcified protein agreed better with those reported by Mikol and Giege (1989) than with solubilities determined from column data.

Cacioppo, Elizabeth↗

NASA NTRS1992

Drop deployment system for crystal growth apparatus

This invention relates to a crystal growth apparatus (10) generally used for growing protein crystals wherein a vapor diffusion method is used for growing the crystals. In this apparatus, a precipitating solution and a solution containing dissolved crystalline material are stored in separate vials (12, 14), each having a resilient diaphragm (28) across one end and an opening (24) with a puncturable septum (26) thereacross at an opposite end. The vials are placed in receptacles (30) having a manifold (41) with a manifold diaphragm (42) in contact with the vial diaphragm at one end of the receptacle and a hollow needle (36) for puncturing the septum at the other end of the manifold. The needles of each vial communicate with a ball mixer (40) that mixes the precipitate and protein solutions and directs the mixed solution to a drop support (64) disposed in a crystal growth chamber (16), the drop support being a tube with an inner bevelled surface (66) that provides more support for the drop (68) than the tubes of the prior art. A sealable storage region (70) intermediate the drop support and mixer provides storage of the drop (68) and the grown crystals.

Rhodes, Percy H.↗

NASA NTRS1991

The solubility of the tetragonal form of hen egg white lysozyme from pH 4.0 to 5.4

Hen egg white lysozyme solubilities in the presence of the tetragonal crystal form have been determined. Conditions investigated cover the pH range 4.0 to 5.4, varying from 2.0 to 7.0 percent NaCl concentrations and from 4 to 25 C. In all instances, the solubilities were found to increase with temperature and decrease with increasing salt concentration. The effects of pH were more complex, showing a decreasing solubility with increasing pH at low salt concentration and an increasing solubility with increasing pH at high salt concentration.

Cacioppo, Elizabeth↗

NASA NTRS1991

Integrated Protein-Crystal-Growing Apparatus

Proposed apparatus for research on growth of protein crystals dispenses drops of protein and precipitating solutions, provides controlled environment for crystalization, and stores crystals. Intended for use in microgravity of outer space, concept of apparatus also useful in design of self-contained terrestrial experiments for remote and/or automatic execution.

Rhodes, Percy H.↗

NASA NTRS1991

Estimation of the initial equilibrium constants in the formation of tetragonal lysozyme nuclei

Results are presented from a study of the equilibria, kinetic rates, and the aggregation pathway which leads from a lysozyme monomer crystal to a tetragonal crystal, using dialyzed and recrystallized commercial hen eggwhite lysozyme. Relative light scattering intensity measurements were used to estimate the initial equilibrium constants for undersaturated lysozyme solutions in the tetragonal regime. The K1 value was estimated to be (1-3) x 10 exp 4 L/mol. Estimates of subsequent equilibrium constants depend on the crystal aggregation model chosen or determined. Experimental data suggest that tetragonal lysozyme crystal grows by addition of aggregates preformed in the bulk solution, rather than by monomer addition.

Pusey, Marc L.↗

NASA NTRS1991

Micro-apparatus for rapid determinations of protein solubilities

We have developed a column-based micro-technique for rapid determinations of protein solubilities. While retaining a large crystal surface area, the column dead volume has been reduced to equal to or less than 5 micro liters. The technique was tested with tetragonal lysozyme (pH 4.5, 0.1 M acetate, 3.0 percent NaCl, 5-25 C) and column volumes of about 60, 300, and 900 micro liters. Identical solubility data were obtained, indicating that equilibration was obtained even in the smallest columns. In addition, solubility data for Br- and I- salts of lysozyme (pH 4.5, 0.1 M acetate buffer, 0.5 M salt concentrations) were obtained. It appears that the technique can be further miniaturized. The limit in further reducing the crystalline column volume is determined by the minimum solution sample size needed to determine the protein concentration.

Pusey, Marc L.↗

NASA NTRS1990

Drop deployment system for crystal growth apparatus

A crystal growth apparatus is presented. It utilizes a vapor diffusion method for growing protein crystals, and particularly such an apparatus wherein a ball mixer is used to mix the fluids that form a drop within which crystals are grown. Particular novelty of this invention lies in utilizing a ball mixer to completely mix the precipitate and protein solutions prior to forming the drop. Additional novelty lies in details of construction of the vials, the fluid deployment system, and the fluid storage system of the preferred embodiment.

Rhodes, Percy↗

NASA NTRS1990

X ray sensitive area detection device

A radiation sensitive area detection device is disclosed which comprises a phosphor-containing film capable of receiving and storing an image formed by a pattern of incoming x rays, UV, or other radiation falling on the film. The device is capable of fluorescing in response to stimulation by a light source in a manner directly proportional to the stored radiation pattern. The device includes: (1) a light source capable of projecting light or other appropriate electromagnetic wave on the film so as to cause it to fluoresce; (2) a means to focus the fluoresced light coming from the phosphor-containing film after light stimulation; and (3) at least one charged coupled detector or other detecting element capable of receiving and digitizing the pattern of fluoresced light coming from the phosphor-containing film. The device will be able to generate superior x ray images of high resolution from a crystal or other sample and will be particularly advantageous in that instantaneous near-real-time images of rapidly deteriorating samples can be obtained. Furthermore, the device can be made compact and sturdy, thus capable of carrying out x ray or other radiation imaging under a variety of conditions, including those experienced in space.

Carter, Daniel C.↗

NASA NTRS1989

Apparatus Makes Precisely Saturated Solutions

Simple laboratory apparatus establishes equilibrium conditions of temperature and concentration in solutions for use in precise measurements of saturation conditions. With equipment typical measurement of saturation concentration of protein in solution established and measured within about 24 hours. Precisely saturated solution made by passing solvent or solution slowly along column packed with solute at precisely controlled temperature. If necessary, flow stopped for experimentally determined interval to allow equilibrium to be established in column.

Pusey, Marc L.↗

NASA NTRS1988

A method for rapid liquid-solid phase solubility measurements using the protein lysozyme

Using hen's egg white lysozyme crystals as the test material, a simple system was developed for rapidly and unambiguously determining solubilities in (aqueous) solutions. The system is based upon a maximization of the solid surface area available for solute transfer to or from the solution, and a minimization of both the solution volume which must be equilibrated and the distance over which diffusive solute exchange occurs. This technique is further enhanced by using duplicate test systems which differ only in that one approaches equilibrium from an oversaturated solution, while the other from an undersaturated solution. Thus, the resulting data pair brackets the solubility value. In practical terms, the data points are found to usually be within 3 percent of each other, and individual solubility data points may usually be made at this resolution within 8-24 h depending upon the temperature change made since the previous determination.

Pusey, Marc L.↗

NASA NTRS1988

High-Resolution Detector For X-Ray Diffraction

Proposed x-ray-sensitive imaging detector offers superior spatial resolution, counting-rate capacity, and dynamic range. Instrument based on laser-stimulated luminescence and reusable x-ray-sensitive film. Detector scans x-ray film line by line. Extracts latent image in film and simultaneously erases film for reuse. Used primarily for protein crystallography. Principle adapted to imaging detectors for electron microscopy and fluorescence spectroscopy and general use in astronomy, engineering, and medicine.

Carter, Daniel C.↗

NASA NTRS1986

An apparatus for protein crystal growth studies

An apparatus is described for observing protein crystals growing under varying growth conditions, and for changing or manipulating crystal orientation for viewing selected faces or growth modes. This flexibility permits a wide variety of protein crystal growth experiments to be performed using the same crystal(s).

Pusey, Marc L.↗