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All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

A Critical Assessment of Protein Crystal Growth in Microgravity

Experiments to grow higher diffraction quality protein crystals in the microgravity environment of an orbiting spacecraft are one of the most frequently flown space experiments. Ground-based research has shown that convective flows occur even about protein crystals growing in the Earth's gravitational field. Further, this research has shown that the resultant flow velocities can cause growth cessation, and probably affect the measured X-ray data quality obtained. How flow deleteriously affects protein crystal growth (PCG) is still not known, and is the subject of ongoing research. Failing a rational method for ameliorating flow effects on Earth, one can, through NASA and other nations space agency sponsored programs, carry out protein crystal growth in the microgravity environment of an orbiting spacecraft. Early first generation PCG hardware was characterized by a very low success rate and a steep design learning curve. Subsequent hardware designs have improved upon their predecessors. Now the crystal grower has a wide variety of hardware configurations and crystal growth protocols to choose from, many of which implement "standard" laboratory protein crystal growth methods. While many of these are first or early second generation hardware the success rate, defined as growing crystals giving data better than has been obtained on Earth, is at least 20% overall and may be considerably higher if one only considers latter experiments. There are a large number of protein crystals grown every year, with hundreds of structures determined. Those crystallized in microgravity represent a small proportion of this total, and there is concern that the costs of the microgravity PCG program(s) do not justify such limited returns. Empirical evidence suggests that optimum crystal growth conditions in microgravity differ from those determined on Earth, further exacerbating the chances of success. Microgravity PCG is probably best suited for "mature" crystallizations, where one has considerable experience with the particular macromolecular system and has reached an apparent limit in diffraction resolution. Under such circumstances the cost of one or two successful flight experiments may more than offset the equivalent cost of several years effort to obtain the same improvement in data quality.

Pusey, Marc↗
NASA NTRSDate not supplied

Rational Design of Nanoplasmonic Array Geometries for Biosensing

Background: Molecular diagnostics provide early and accurate diagnosis, which is essential for the prevention and treatment of infectious as well as chronic diseases. These tests are designed to detect disease-specific bioanalytes such as nucleic acid (DNA or RNA) or protein (antigens, antibodies) biomarkers. In the context of infectious disease diagnosis, nucleic acid-based detection methods are known to provide more specific and sensitive results. Here, the presence of a unique sequence belonging to the pathogenic genomic material is targeted to identify species, organism, genera and/or antimicrobial resistant gene markers. The majority of the common nucleic acid based diagnostic techniques require amplification (polymerase chain reaction, isothermal amplification etc.) of the pathogenic genetic material prior to detection impacting diagnostic speed, complexity, and cost thereby limiting ease of use. Thus, the development of simplified nucleic acid-based diagnostics that can be even used in resource-poor settings may hugely benefit patients across the globe. Nanopath is a molecular diagnostics company utilizing a solid-state nanosensor to enable sequence-specific detection of target nucleic acids without the need of amplification. These nanostructures enable ultra-sensitive biomarker detection using geometric, feature-dependent properties highly dependent on the local dielectric environment, allowing them to be sensitive to low concentration binding events. This paper describes an application of this approach to provide highly relevant clinical information within a single doctor’s office visit. Intro: The Nanopath team is in collaboration with NASA (National Aeronautics and Space Administration) and NIST (National Institute of Standards and Technology) to push the bounds of the fundamental physics associated with their biosensing platform. The ability of metals to support electromagnetic surface waves gives rise to surface plasmons when optically illuminated. This property, and its strong sensitivity to changes in the local refractive index, allows for the use of metal nanoparticles as ultra-sensitive transducers. In prior work by members of this team, ensembles of randomly oriented nanoparticles (i.e., colloidal nanorods dispersed on chip) were employed for sequence-specific nucleic acid sensing (1-3). While these particle sensors have the advantage of rapid fabrication, they suffer from low sensitivity and quality factor due to the random particle dispersity. In contrast, in this study we employ ordered array nanoparticle ensembles which can be used to improve sensor sensitivity and figure-of-merit. Study Methods Overview: In this talk, we detail the results of sensing experiments and computational simulations to outline a rational design of the structure of these plasmonic nanoparticle arrays for biomolecular sensing. Through simulation and experiment, we iteratively tailor nanostructure dimension to provide high quality signal and large resonance shifts upon modeled nucleic acid binding. In particular, full-wave electromagnetic simulations were conducted using Lumerical photonic simulation software in which periodic boundary conditions were applied in the x- and y- dimensions for each of the nanoplasmonic sensor geometries. To simulate the resonance response to changes in the bulk solution in contact with the sensor surface, the refractive index of the surrounding media was changed appropriately. Nucleic acid hybridization events were modeled using either using spherical structures approximating the relevant radius of genomic material as estimated by polymer models, or as conformal layers with the known refractive indices for nucleic acids. On the basis of initial simulations, nanosensors were fabricated using traditional electron-beam lithography protocols at NIST. To evaluate consensus between simulations and experiments, bulk sensing experiments were carried out in which the resonance peaks were obtained by submerging the sensors in refractive index standards. Key nanosensor characteristics including resonance peak locations, resonance peak shifts as a function of refractive index, and figure of merit (FOM) of extinction curves were examined between the experimental and simulation results prior to proceeding with simulations on additional geometries and more complex solution conditions, and further device fabrication. This iterative process is repeated toward a rational design of nanoplasmonic array geometries for biosensing optimizing response for targeted disease detection. In summary, this study puts forth a methodology for rational design and characterization of regularly spaced nanoparticle arrays for optics-based biosensing. The results of this study will allow for more informed design of nanostructure geometries towards sequence-specific nucleic acid detection. These improved designs have the potential to improve clinical sensitivity and limit-of-detection across disease indication.

sensor↗
NASA NTRS2004

Phosphate binding protein as the biorecognition element in a biosensor for phosphate

This work explores the potential use of a member of the periplasmic family of binding proteins, the phosphate binding protein (PBP), as the biorecognition element in a sensing scheme for the detection of inorganic phosphate (Pi). The selectivity of this protein originates from its natural role which, in Escherichia coli, is to serve as the initial receptor for the highly specific translocation of Pi to the cytoplasm. The single polypeptide chain of PBP is folded into two similar domains connected by three short peptide linkages that serve as a hinge. The Pi binding site is located deep within the cleft between the two domains. In the presence of the ligand, the two globular domains engulf the former in a hinge-like manner. The resultant conformational change constitutes the basis of the sensor development. A mutant of PBP (MPBP), where an alanine was replaced by a cysteine residue, was prepared by site-directed mutagenesis using the polymerase chain reaction (PCR). The mutant was expressed, from plasmid pSD501, in the periplasmic space of E. coli and purified in a single chromatographic step on a perfusion anion-exchange column. Site-specific labeling was achieved by attaching the fluorophore, N-[2-(1-maleimidyl)ethyl]-7-(diethylamino)coumarin-3-carboxamide (MDCC), to the protein through the sulfhydryl group of the cysteine moiety. Steady-state fluorescence studies of the MPBP-MDCC conjugate showed a change in the intensity of the signal upon addition of Pi. Calibration curves for Pi were constructed by relating the intensity of the fluorescence signal with the amount of analyte present in the sample. The sensing system was first developed and optimized on a spectrofluorometer using ml volumes of sample. It was then adapted to be used on a microtiter plate arrangement with microliter sample volumes. The system's versatility was finally proven by developing a fiber optic fluorescence-based sensor for monitoring Pi. In all three cases the detection limits for the analyte were in the sub-microMolar range. It was also demonstrated that the sensing system was selective for phosphate over other structurally-similar anions, paving the way for the design and development of a new family of biosensors utilizing the specific binding properties of periplasmic proteins. c2003 Elsevier B.V. All rights reserved.

NASA Program Fundamental Space Biology↗
NASA NTRS1998

Advanced High Brilliance X-Ray Source

The possibility to dramatically increase the efficiency of laboratory based protein structure measurements through the use of polycapillary X-ray optics was investigated. This project initiated April 1, 1993 and concluded December 31, 1996 (including a no cost extension from June 31, 1996). This is a final report of the project. The basis for the project is the ability to collect X-rays from divergent electron bombardment laboratory X-ray sources and redirect them into quasiparallel or convergent (focused) beams. For example, a 0.1 radian (approx. 6 deg) portion of a divergent beam collected by a polycapillary collimator and transformed into a quasiparallel beam of 3 millradian (0.2 deg) could give a gain of 6(exp 2)/0.2(exp 2) x T for the intensity of a diffracted beam from a crystal with a 0.2 deg diffraction width. T is the transmission efficiency of the polycapillary diffraction optic, and for T=0.5, the gain would be 36/0.04 x O.5=45. In practice, the effective collection angle will depend on the source spot size, the input focal length of the optic (usually limited by the source spot-to-window distance on the x-ray tube) and the size of the crystal relative to the output diameter of the optic. The transmission efficiency, T, depends on the characteristics (fractional open area, surface roughness, shape and channel diameter) of the polycapillary optic and is typically in the range 0.2-0.4. These effects could substantially reduce the expected efficiency gain. During the course of this study, the possibility to use a weakly focused beam (0.5 deg convergence) was suggested which could give an additional 10-20 X efficiency gain for small samples . Weakly focused beams from double focusing mirrors are frequently used for macromolecular crystallography studies. Furthermore the crystals are typically oscillated by as much as 2 deg during each X-ray exposure in order to increase the reciprocal space (number of crystal planes) sampled and use of a slightly convergent beam could, in principle, provide a similar sampling benefit without oscillation. Although more problematic, because of complications in analyzing the diffraction patterns, it was also suggested that even more extreme beam convergence might be used to give another order of magnitude intensity gain and even smaller focused spot size which could make it possible to study smaller protein crystals than can be studied using standard laboratory based X-ray diffraction systems. This project represents the first systematic investigation of these possibilities. As initially proposed, the contract included requirements for design, purchase, evaluation and delivery of three polycapillary lenses to the Laboratory for Structural Biology at MSFC and demonstration of such optics at MSFC for selected protein crystal diffraction applications.

Gibson, Walter M.↗
NASA NTRS1986

Plan for CELSS test bed project

The Closed Ecological Life Support Systems (CELSS) testbed project will achieve two major goals: It will develop the knowledge and technology needed to build and test biological or combined biological physiochemical regenerative life support systems. It will fabricate, test, and operate ground based facilities to accomplish proof-of-concent testing and evaluation leading to flight experimentation. The project will combine basic research and applied research/engineering to achieve a phased, integrated development of hardware, systems, and techniques for food and oxygen production, food processing, and waste processing in closed systems. The project will design, fabricate, and operate within three years a botanical production system scaled to a sufficient size to verify oxygen and nutrient load production (carbohydrates, fats, proteins) at a useable level. It will develop within five years a waste management system compatible with the botanical production system and a food processing system that converts available biomass into edible products. It will design, construct, and operate within ten years a ground based candidate CELSS that includes man as an active participant in the system. It will design a flight CELSS module within twelve years and construct and conduct initial flight tests within fifteen years.

Knott, W. M.↗
NASA NTRS1994

Universal Test Facility

A universal test facility (UTF) for Space Station Freedom is developed. In this context, universal means that the experimental rack design must be: automated, highly marketable, and able to perform diverse microgravity experiments according to NASA space station requirements. In order to fulfill these broad objectives, the facility's customers, and their respective requirements, are first defined. From these definitions, specific design goals and the scope of the first phase of this project are determined. An examination is first made into what types of research are most likely to make the UTF marketable. Based on our findings, the experiments for which the UTF would most likely be used included: protein crystal growth, hydroponics food growth, gas combustion, gallium arsenide crystal growth, microorganism development, and cell encapsulation. Therefore, the UTF is designed to fulfill all of the major requirements for the experiments listed above. The versatility of the design is achieved by taking advantage of the many overlapping requirements presented by these experiments.

Laughery, Mike↗
NASA NTRS2001

A novel reagentless sensing system for measuring glucose based on the galactose/glucose-binding protein

The galactose/glucose-binding protein (GBP) is synthesized in the cytoplasm of Escherichia coli in a precursor form and exported into the periplasmic space upon cleavage of a 23-amino-acid leader sequence. GBP binds galactose and glucose in a highly specific manner. The ligand induces a hinge motion in GBP and the resultant protein conformational change constitutes the basis of the sensing system. The mglB gene, which codes for GBP, was isolated from the chromosome of E. coli using the polymerase chain reaction (PCR). Since wild-type GBP lacks cysteines in its structure, introducing this amino acid by site-directed mutagenesis ensures single-label attachment at specific sites with a sulfhydro-specific fluorescent probe. Site-directed mutagenesis by overlap extension PCR was performed to prepare three different mutants to introduce a single cysteine residue at positions 148, 152, and 182. Since these residues are not involved in ligand binding and since they are located at the edge of the binding cleft, they experience a significant change in environment upon binding of galactose or glucose. The sensing system strategy is based on the fluorescence changes of the probe as the protein undergoes a structural change on binding. In this work a reagentless sensing system has been rationally designed that can detect submicromolar concentrations of glucose. The calibration plots have a linear working range of three orders of magnitude. Although the system can sense galactose as well, this epimer is not a potential interfering substance since its concentration in blood is negligible. Copyright 2001 Academic Press.

Non-NASA Center↗
NASA NTRS2019

De novo design of symmetric ferredoxins that shuttle electrons in vivo

A symmetric origin for bacterial ferredoxins was first proposed over 50 y ago, yet, to date, no functional symmetric molecule has been constructed. It is hypothesized that extant proteins have drifted from their symmetric roots via gene duplication followed by mutations. Phylogenetic analyses of extant ferredoxins support the independent evolution of N- and C-terminal sequences, thereby allowing consensus-based design of symmetric 4Fe-4S molecules. All designs bind two [4Fe-4S] clusters and exhibit strongly reducing midpoint potentials ranging from −405 to −515 mV. One of these constructs efficiently shuttles electrons through a designed metabolic pathway in Escherichia coli. These finding establish that ferredoxins consisting of a symmetric core can be used as a platform to design novel electron transfer carriers for in vivo applications. Outer-shell asymmetry increases sequence space without compromising electron transfer functionality.

Andrew C. Mutter↗
NASA NTRS1987

Food production and gas exchange system using blue-green alga (spirulina) for CELSS

In order to reduce the cultivation area required for the growth of higher plants in space adoption of algae, which have a higher photosynthetic ability, seems very suitable for obtaining oxygen and food as a useful source of high quality protein. The preliminary cultivation experiment for determining optimum cultivation conditions and for obtaining the critical design parameters of the cultivator itself was conducted. Spirulina was cultivated in the 6 liter medium containing a sodium hydrogen carbonate solution and a cultivation temperature controlled using a thermostat. Generated oxygen gas was separated using a polypropyrene porous hollow fiber membrane module. Through this experiment, oxygen gas (at a concentration of more than 46 percent) at a rate of 100 to approx. 150 ml per minute could be obtained.

Oguchi, Mitsuo↗
NASA NTRS2000

Evolutionary Cell Computing: From Protocells to Self-Organized Computing

On the path from inanimate to animate matter, a key step was the self-organization of molecules into protocells - the earliest ancestors of contemporary cells. Studies of the properties of protocells and the mechanisms by which they maintained themselves and reproduced are an important part of astrobiology. These studies also have the potential to greatly impact research in nanotechnology and computer science. Previous studies of protocells have focussed on self-replication. In these systems, Darwinian evolution occurs through a series of small alterations to functional molecules whose identities are stored. Protocells, however, may have been incapable of such storage. We hypothesize that under such conditions, the replication of functions and their interrelationships, rather than the precise identities of the functional molecules, is sufficient for survival and evolution. This process is called non-genomic evolution. Recent breakthroughs in experimental protein chemistry have opened the gates for experimental tests of non-genomic evolution. On the basis of these achievements, we have developed a stochastic model for examining the evolutionary potential of non-genomic systems. In this model, the formation and destruction (hydrolysis) of bonds joining amino acids in proteins occur through catalyzed, albeit possibly inefficient, pathways. Each protein can act as a substrate for polymerization or hydrolysis, or as a catalyst of these chemical reactions. When a protein is hydrolyzed to form two new proteins, or two proteins are joined into a single protein, the catalytic abilities of the product proteins are related to the catalytic abilities of the reactants. We will demonstrate that the catalytic capabilities of such a system can increase. Its evolutionary potential is dependent upon the competition between the formation of bond-forming and bond-cutting catalysts. The degree to which hydrolysis preferentially affects bonds in less efficient, and therefore less well-ordered, peptides is also critical to evolution of a non-genomic system. Based on these results, a new computational object called a "molnet" is defined. Like a neural network, it is formed of interconnected units that send "signals" to each other. Like molecules, neural networks have a specific function once their structure is defined. The difference between a molnet and traditional neural networks, is that input to molnets is not simply passed along and processed from input to output units, but rather it is utilized to form and break connections(bonds), and thus to form new structures. Molnets represent a powerful tool that can be used to understand the conditions under which chemical systems can form large molecules, such as proteins, and display ever more complex functions. This has direct applications, for example to the design of smart,synthetic fabrics. Additional information is contained in the original.

Colombano, Silvano↗
NASA NTRS1971

The effect of variable calcium and very low calcium diets on human calcium metabolism

The effects of a very low calcium diet, with variable high and low protein intake, on the dynamics of calcium metabolism and the mechanism of calciuretics, are examined. The experiment, using male subjects, was designed to study the role of intestinal calcium absorption on urinary calcium excretion, and the rate of production of endogeneously secreted calcium in the gastrointestinal tract. The study showed an average of 70% fractional absorption rate during very low calcium intake, and that a decrease in renal tubular reabsorption of calcium is responsible for calciuretic effects of high protein intake. The study also indicates that there is a tendency to develop osteoporosis after long periods of low calcium intake, especially with a concurrent high protein intake.

Chu, J.↗
NASA NTRS1993

Stiffening of deployable space booms: Automated Protein Crystal Growth Facility

Part of the curriculum for the seniors at Vanderbilt University in the Mechanical Engineering Program is to take a design class. The purpose of the class is to expose the students to the open ended problems which working engineers are involved with every day. In the past, the students have been asked to work in a variety of projects developed by the professor. This year Vanderbilt was admitted into the Advanced Design Program (ADP) sponsored by the Universities Space Research Association (USRA) and the National Aeronautics and Space Association (NASA). The grant sponsored undergraduate design and research into new and innovative areas in which NASA is involved. The grant sponsors the Teaching Assistant as well as provides monies for travel and other expenses. The design and research of the seniors of the 1992-1993 school year in association with NASA and USRA is documented.

Cruse, Thomas↗
NASA NTRS1999

First Results from a Microfocus X-Ray System for Macromolecular Crystallography

The design and performance of a 40 Watt laboratory crystallography system optimized for the structure determination of small protein crystals are described. This system combines a microfocus x-ray generator (40 microns FWHM spot size at a power level of 40 Watts) and a short focal length (F = 2.6 mm) polycapillary collimating optic, and produces a small diameter quasi-parallel x-ray beam. Measurements of x-ray flux, divergence and spectral purity of the resulting x-ray beam are presented. The x-ray flux in a 250 microns diameter aperture produced by the microfocus system is 14.7 times higher .than that from a 3.15 kW rotating anode generator equipped with graphite monochromator. Crystallography data taken with the microfocus system are presented, and indicate that the divergence and spectral purity of the x-ray are sufficient to refine the diffraction data using a standard crystallographic software. Significant additional improvements in flux and beam divergence are possible, and plans for achieving these coals are discussed.

Gubarev, Mikhail↗
NASA NTRS2014

Biomaterials Out of Thin Air: In Situ, On-Demand Printing of Advanced Biocomposites: A New Materials Design and Production Technique Using 3D-Printed Arrays of Bioengineered Cells

We have completed the proof of concept described in our Phase I proposal, a two-material array of nonstructural proteins. We created an implementation of each step in our technology concept and demonstrated its critical functionality. The biological chassis and printing hardware we created as part of this work can be re-used for future work by inserting a material coding region upstream of the fluorescent tag. Overall, we showed that our technology concept is sound. The mission benefit analyses, as described in our Phase I proposal, are complete and contained in this report. These calculations show that our technology can save hundreds of kilograms of upmass for a potential planetary human habit construction mission: the mass per habitat module can be reduced by approximately one third if the biomaterials are manufactured on Earth and included in the mission upmass, and the full 240 kg per module can be saved if the materials are derived entirely from in situ resources. Mass savings between these two extremes is expected for an actual mission, depending on the level of in situ resource extraction technology. We have shown that continued advancement of this technology concept for use in a space mission environment is justified. Our survey of future development pathways proved extremely informative in light of the lessons learned from our proof of concept work and mission scenario analyses. For example, we were able for the first time to distinguish between the levels of functionality provided by production of structural proteins, other polymers such as polysaccharides, and true organic-inorganic composites such as bone and mineralized shell. This new information represents a significant advance in formulating specific applications, and key enabling technologies, for our proposed concept. We surveyed potential collaborations with other projects and synergies with enabling technologies that are developing. We have received requests for collaboration from other institutions, including labs at Stanford University and Drexel University. We have also received visits from industry, including Organovo, a tissue engineering company, and Autodesk, a major 3D and materials design software company. Finally, we have been in touch with the team behind the 2013 NIAC Phase ll 'Super Ball Bot-Structures for Planetary Landing and Exploration' and are planning to develop our biomaterial printing technology with the goal of enabling tensegrity-based rovers such as theirs to use lighter, more robust materials. A smooth transition from TRL 2 to TRL 3 assumes that the implementations of the technology concept which demonstrate critical functionality are also pathways for future development; while this is the case for most hardware or software projects, the multidisciplinary nature of our project, particularly the biological aspect of it, means that this is not always true. For example, as part of this work we showed that although there are large number of known genetic parts that correspond to non-structural materials, this is not true for sequences for structural organic proteins, let alone biominerals. These realizations allowed us to further subdivide our concept into more detailed development areas, some of which are clearly established at TRL 3, others of which were newly identified sub-technologies moved from TRL 1 to TRL 2. Similarly, although a single feasibility /benefit analysis is sufficient for advancement from TRL 2 to TRL 3, not all potential benefits to a technology concept as broad in scope as ours are apparent at TRL 2. Both our future pathways survey and our proof of concept work highlighted that the true mass savings potential of our technology concept cannot be quantified without modification of existing materials modelling tools to take into account the possibility of positional materials properties customization. Therefore, we have simultaneously both advanced one potential set of applications of our technology concept from TRL 2 to TRL 3 and also identified a previously unknown set of applications and advanced it from TRL 1 to TRL 2. Overall, we have moved the original formulation of our concept forward from TRL 2 to TRL 3, and the expanded formulation of it presented in this document has been advanced from a combination of TRL 1 and early 1RL 2 to an overall late TRL 2. We have also identified the key areas necessary for both short-term and long-term advancement, and made recommendations for specific future work in the most promising directions. With future work on a 1-2 year timeframe to continue advancement to overall TRL 3, we will be well positioned to begin work on a specific space mission technology insertion path.

Biology↗
NASA NTRS1977

Simulation and display of macromolecular complexes

In association with an investigation of the interaction of proteins with DNA and RNA, an interactive computer program for building, manipulating, and displaying macromolecular complexes has been designed. The system provides perspective, planar, and stereoscopic views on the computer terminal display, as well as views for standard and nonstandard observer locations. The molecule or its parts may be rotated and/or translated in any direction; bond connections may be added or removed by the viewer. Molecular fragments may be juxtaposed in such a way that given bonds are aligned, and given planes and points coincide. Another subroutine provides for the duplication of a given unit such as a DNA or amino-acid base.

Nir, S.↗
NASA NTRS2003

The Effect of Simulated Microgravity Environment of RWV Bioreactors on Surface Reactions and Adsorption of Serum Proteins on Bone-bioactive Microcarriers

Biomimetically modified bioactive materials with bone-like surface properties are attractive candidates for use as microcarriers for 3-D bone-like tissue engineering under simulated microgravity conditions of NASA designed rotating wall vessel (RWV) bioreactors. The simulated microgravity environment is attainable under suitable parametric conditions of the RWV bioreactors. Ca-P containing bioactive glass (BG), whose stimulatory effect on bone cell function had been previously demonstrated, was used in the present study. BG surface modification via reactions in solution, resulting formation of bone-like minerals at the surface and adsorption of serum proteins is critical for obtaining the stimulatory effect. In this paper, we report on the major effects of simulated microgravity conditions of the RWV on the BG reactions surface reactions and protein adsorption in physiological solutions. Control tests at normal gravity were conducted at static and dynamic conditions. The study revealed that simulated microgravity remarkably enhanced reactions involved in the BG surface modification, including BG dissolution, formation of bone-like minerals at the surface and adsorption of serum proteins. Simultaneously, numerical models were developed to simulate the mass transport of chemical species to and from the BG surface under normal gravity and simulated microgravity conditions. The numerical results showed an excellent agreement with the experimental data at both testing conditions.

Radin, Shula↗
NASA NTRS2007

NASA Tech Briefs, December 2007

Topics include: Ka-Band TWT High-Efficiency Power Combiner for High-Rate Data Transmission; Reusable, Extensible High-Level Data-Distribution Concept; Processing Satellite Imagery To Detect Waste Tire Piles; Monitoring by Use of Clusters of Sensor-Data Vectors; Circuit and Method for Communication Over DC Power Line; Switched Band-Pass Filters for Adaptive Transceivers; Noncoherent DTTLs for Symbol Synchronization; High-Voltage Power Supply With Fast Rise and Fall Times; Waveguide Calibrator for Multi-Element Probe Calibration; Four-Way Ka-Band Power Combiner; Loss-of-Control-Inhibitor Systems for Aircraft; Improved Underwater Excitation-Emission Matrix Fluorometer; Metrology Camera System Using Two-Color Interferometry; Design and Fabrication of High-Efficiency CMOS/CCD Imagers; Foam Core Shielding for Spacecraft CHEM-Based Self-Deploying Planetary Storage Tanks Sequestration of Single-Walled Carbon Nanotubes in a Polymer PPC750 Performance Monitor Application-Program-Installer Builder Using Visual Odometry to Estimate Position and Attitude Design and Data Management System Simple, Script-Based Science Processing Archive Automated Rocket Propulsion Test Management Online Remote Sensing Interface Fusing Image Data for Calculating Position of an Object Implementation of a Point Algorithm for Real-Time Convex Optimization Handling Input and Output for COAMPS Modeling and Grid Generation of Iced Airfoils Automated Identification of Nucleotide Sequences Balloon Design Software Rocket Science 101 Interactive Educational Program Creep Forming of Carbon-Reinforced Ceramic-Matrix Composites Dog-Bone Horns for Piezoelectric Ultrasonic/Sonic Actuators Benchtop Detection of Proteins Recombinant Collagenlike Proteins Remote Sensing of Parasitic Nematodes in Plants Direct Coupling From WGM Resonator Disks to Photodetectors Using Digital Radiography To Image Liquid Nitrogen in Voids Multiple-Parameter, Low-False-Alarm Fire-Detection Systems Mosaic-Detector-Based Fluorescence Spectral Imager Plasmoid Thruster for High Specific-Impulse Propulsion Analysis Method for Quantifying Vehicle Design Goals Improved Tracking of Targets by Cameras on a Mars Rover Sample Caching Subsystem Multistage Passive Cooler for Spaceborne Instruments GVIPS Models and Software Stowable Energy-Absorbing Rocker-Bogie Suspensions

Source record↗
NASA NTRS1997

Computer-aided design of a proton pump

The use of transmembrane proton gradients in energy transduction is an almost universal feature of life on earth. These proton gradients are established and maintained by specialized assemblies of proteins which actively pump protons across membranes. One broad class of proton pumps uses captured light energy to drive the proton pumping. Our goal is to elucidate the minimum structural requirements of a light-driven proton-pump. There are two basic components to a simple light-driven proton pump: a source of photo-generated protons and a "gate-keeper" which prevents these protons from reattaching themselves to their source. A wide variety of molecules in the membrane, even as simple as polycyclic aromatic hydrocarbons, are capable of releasing protons when illuminated. Our work is therefore focused on the design of the "gate-keeper." Our initial model involves a pair of proton acceptors, coupled to each other by a transient water bridge, and supported in the membrane by a small bundle of peptide helices. Upon illumination, the proton source transfers its proton to the:- first acceptor of the gate-keeper. While the reverse reaction is highly probable, all that is needed to ensure irreversibility is a nonvanishing probability that the proton will be transferred to the second acceptor across a transient water bridge. Back transfer of the proton to the first acceptor, and thence to the proton source, is impeded by the free energy required to move the proton uphill towards the. proton source and by the disruption of the transient water bridge. As a prototypical water-bridged proton transfer system, we are studying the transfer of a proton across a water bridge from a formic acid to a formate anion. With a pK(sub alpha), of 3.7. formic acid is a good model for the acidic amino acids glutamate and aspartate which are good candidates for gate-keeper proton acceptors. Simulations of proton transfer reactions in a membrane are complicated by the quantum mechanical nature of the process breaking and forming chemical bonds.

New, Michael H.↗