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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

ATCUN-like Copper Site in βB2-Crystallin Plays a Protective Role in Cataract-Associated Aggregation

Cataract is the leading cause of blindness worldwide, and it is caused by crystallin damage and aggregation. Senile cataractous lenses have relatively high levels of metals, while some metal ions can directly induce the aggregation of human γ-crystallins. Here, for this work, we evaluated the impact of divalent metal ions in the aggregation of human βB2-crystallin, one of the most abundant crystallins in the lens. Turbidity assays showed that Pb 2+ , Hg 2+ , Cu 2+ , and Zn 2+ ions induce the aggregation of βB2-crystallin. Metal-induced aggregation is partially reverted by a chelating agent, indicating the formation of metal-bridged species. Our study focused on the mechanism of copper-induced aggregation of βB2-crystallin, finding that it involves metal-bridging, disulfide-bridging, and loss of protein stability. Circular dichroism and electron paramagnetic resonance (EPR) revealed the presence of at least three Cu 2+ binding sites in βB2-crystallin, one of them with spectroscopic features typical for Cu 2+ bound to an amino-terminal copper and nickel (ATCUN) binding motif, which is found in Cu transport proteins. The ATCUN-like Cu binding site is located at the unstructured N-terminus of βB2-crystallin, and it could be modeled by a peptide with the first six residues in the protein sequence (NH 2 -ASDHQF-). Isothermal titration calorimetry indicates a nanomolar Cu 2+ binding affinity for the ATCUN-like site. An N-truncated form of βB2-crystallin is more susceptible to Cu-induced aggregation and is less thermally stable, indicating a protective role for the ATCUN-like site. EPR and X-ray absorption spectroscopy studies reveal the presence of a copper redox active site in βB2-crystallin that is associated with metal-induced aggregation and formation of disulfide-bridged oligomers. Our study demonstrates metal-induced aggregation of βB2-crystallin and the presence of putative copper binding sites in the protein. Whether the copper-transport ATCUN-like site in βB2-crystallin plays a functional/protective role or constitutes a vestige from its evolution as a lens structural protein remains to be elucidated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Anomalous Anisotropic Nanoparticle Aggregation in Cu 2 (OH) 3 Br Gels

Aerogels are of interest for their ability to uniformly incorporate nanoscale features into macroscopic assemblies, which enabled applications that require low density, high surface area, and/or bicontinuous networks. The structure of the nanoporous network is intrinsically linked to the macroscopic properties of aerogels. Hence, control of this structure is of paramount importance. Small-angle X-ray scattering (SAXS) is used here to monitor nanoparticle aggregation in situ in Cu 2 (OH) 3 Br aerogels formed via epoxide-assisted gelation. Anomalous anisotropic aggregation is observed in the absence of templating agents and is attributed to the molecular structure of the inorganic nanoparticles themselves. This is a fundamental departure from the models currently used to describe traditional inorganic sol–gel chemistry where nanoparticles are believed to undergo isotropic diffusion- and/or kinetically limited aggregation. Time-resolved SAXS indicates that Cu 2 (OH) 3 Br nanoparticles nucleate rapidly from solution to form unbranched chain-like aggregates rather than branched mass-fractal aggregates. Sizes of primary particles (~1.5 nm) and the chain-like structure of their aggregates are independent of particle concentration (gel density), while rates of particle aggregation, gelation time, and aggregate size are strongly dependent upon particle concentration, which implies that the chemistry of particle formation and the physics of particle aggregation are independent processes. Because the conditions necessary for creating anisotropic structures are not unique to Cu 2 (OH) 3 Br, these results could provide insight into the structure and gelation mechanisms of other inorganic aerogels.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

What Role Do Aggregators Play in Power System Security and Resilience?

Barriers to the participation of distributed energy resources (DERs) in wholesale electricity markets have limited the use of DERs for power system security and resilience. In September 2020, the Federal Energy Regulatory Commission (FERC) approved an order to reduce these barriers. FERC Order No. 2222 enables the participation of DER aggregators in wholesale electricity markets. DERs include renewable generation and technologies that support the integration of renewable generation by increasing grid flexibility and resilience. Requiring wholesale energy markets to allow DER aggregator participation provides a path for DERs to become competitive in these markets. As the contribution from aggregated DERs continues to increase, the aggregator's role in supporting grid security and resilience will become more critical. This paper reviews work that demonstrates how DER aggregators can provide resilience support through technical capabilities, operational strategies, and secure communication architectures. Socioeconomic influences and impacts of aggregators, including implications for social resilience, are presented. In surveying the current state-of-the-art across different but interconnected topics, we illustrate how aggregators can be power system participants that enhance grid security. There is no one-size-fits-all approach to enhancing resilience in a power grid that includes a growing cohort of DER aggregators, but there are many options for aggregators to contribute to a more resilient and secure power grid.

aggregator↗
DOE OSTI2023

Aggregation of Leslie matrix models with application to ten diverse animal species

Some grouping is necessary when constructing a Leslie matrix model because it involves discretizing a continuous process of births and deaths. Here, the level of grouping is determined by the number of age classes and frequency of sampling. It is largely unknown what is lost or gained by using fewer age classes, and I address this question using aggregation theory. I derive an aggregator for a Leslie matrix model using weighted least squares, determine what properties an aggregated matrix inherits from the original matrix, evaluate aggregation error, and measure the influence of aggregation on asymptotic and transient behaviors. To gauge transient dynamics, I employ reactivity of the standardized Leslie matrix. I apply the aggregator to 10 Leslie models developed for animal populations drawn from a diverse set of species. Several properties are inherited by the aggregated matrix: (a) it is a Leslie matrix; (b) it is irreducible whenever the original matrix is irreducible; (c) it is primitive whenever the original matrix is primitive; and (d) its stable population growth rate and stable age distribution are consistent with those of the original matrix if the least squares weights are equal to the original stable age distribution. In the application, depending on the population modeled, when the least squares weights do not follow the stable age distribution, the stable population growth rate of the aggregated matrix may or may not be approximately consistent with that of the original matrix. Transient behavior is lost with high aggregation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Chaperone protein HYPK interacts with the first 17 amino acid region of Huntingtin and modulates mutant HTT-mediated aggregation and cytotoxicity

Highlights: • HYPK reduces mutant HTT-mediated aggregate formation and cytotoxicity. • Interaction of HYPK with HTT requires N-terminal 17 amino acid of HTT (HTT-N17). • Deletion of HTT-N17 leads to SDS-soluble, smaller, nuclear aggregates. • These smaller aggregates do not associate with HYPK and are more cytotoxic. • Maybe, interaction of HYPK with amphipathic HTT-N17 block HTT aggregate formation. - Abstract: Huntington’s disease is a polyglutamine expansion disorder, characterized by mutant HTT-mediated aggregate formation and cytotoxicity. Many reports suggests roles of N-terminal 17 amino acid domain of HTT (HTT-N17) towards subcellular localization, aggregate formation and subsequent pathogenicity induced by N-terminal HTT harboring polyQ stretch in pathogenic range. HYPK is a HTT-interacting chaperone which can reduce N-terminal mutant HTT-mediated aggregate formation and cytotoxicity in neuronal cell lines. However, how HYPK interacts with N-terminal fragment of HTT remained unknown. Here we report that specific interaction of HYPK with HTT-N17 is crucial for the chaperone activity of HYPK. Deletion of HTT-N17 leads to formation of tinier, SDS-soluble nuclear aggregates formed by N-terminal mutant HTT. The increased cytotoxicity imparted by these tiny aggregates might be contributed due to loss of interaction with HYPK.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2011

The effect of recycled concrete aggregate properties on the bond strength between RCA concrete and steel reinforcement

The purpose of this study was to investigate the influence that replacing natural coarse aggregate with recycled concrete aggregate (RCA) has on concrete bond strength with reinforcing steel. Two sources of RCA were used along with one natural aggregate source. Numerous aggregate properties were measured for all aggregate sources. Two types of concrete mixture proportions were developed replacing 100% of the natural aggregate with RCA. The first type maintained the same water-cement ratios while the second type was designed to achieve the same compressive strengths. Beam-end specimens were tested to determine the relative bond strength of RCA and natural aggregate concrete. On average, natural aggregate concrete specimens had bond strengths that were 9 to 19% higher than the equivalent RCA specimens. Bond strength and the aggregate crushing value seemed to correlate well for all concrete types.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Understanding Solution State Conformation and Aggregate Structure of Conjugated Polymers via Small Angle X-ray Scattering

Donor-acceptor (D-A) conjugated polymers are high-performance organic electronic materials that exhibit complex aggregation behavior. Understanding the solution state conformation and aggregation of conjugated polymers is crucial for controlling morphology during thin-film deposition and the subsequent electronic performance. However, a precise multiscale structure of solution state aggregates is lacking. Here, we present an in-depth small-angle X-ray scattering (SAXS) analysis of the solution state structure of an isoindigo-bithiophene-based D-A polymer (PII-2T) in chlorobenzene and decane as our primary system. Modeling the system as a combination of hierarchical fibrillar aggregates mixed with dispersed polymers, we extract information about conformation and multiscale aggregation and also clarify the physical origin of features often observed but unaddressed or misinterpreted in small-angle scattering patterns of conjugated polymers. The persistence length of the D-A polymer extracted from SAXS agrees well with a theoretical model based on the dihedral potentials. Additionally, we show that the broad high q structure factor peak seen in scattering profiles can be attributed to lamellar stacking occurring within the fibril aggregates and that the low q aggregate scattering is strongly influenced by the polymer molecular weight. Overall, the SAXS profiles of D-A polymers in general exhibit a sensitive dependence on the co-existence of fibrillar aggregate and dispersed polymer chain populations. We corroborate our findings from SAXS with electron microscopy of freeze-dried samples for direct imaging of fibrillar aggregates. Finally, we demonstrate the generality of our approach by fitting the scattering profiles of a variety of D-A polymers based on thieno-isoindigo (PTII-2T), diketopyrrolopyrrole (DPP2T-TT, DPP-BTZ, PDPP2FT-C- 16 ), naphthalenediimide (P(NDI2OD-T2)), and a conjugated block copolymer P3HT-b-DPPT-T. The results presented here establish a picture of the D-A polymer solution state structure and provide a general method of interpreting and analyzing their scattering profiles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Structure and aggregation in model tetramethylurea solutions

The structure of model aqueous tetramethylurea (TMU) solutions is investigated employing large-scale (32 000, 64 000 particles) molecular dynamics simulations. Results are reported for TMU mole fractions, X{sub t}, ranging from infinite dilution up to 0.07, and for two temperatures, 300 and 330 K. Two existing force fields for TMU-water solutions are considered. These are the GROMOS 53A6 united-atom TMU model combined with SPC/E water [TMU(GROMOS-UA)/W(SPC/E)], and the more frequently employed AMBER03 all-atom force field for TMU combined with the TIP3P water model [TMU(AMBER-AA)/W(TIP3P)]. It is shown that TMU has a tendency towards aggregation for both models considered, but the tendency is significantly stronger for the [TMU(AMBER-AA)/W(TIP3P)] force field. For this model signs of aggregation are detected at X{sub t} = 0.005, aggregation is a well established feature of the solution at X{sub t} = 0.02, and the aggregates increase further in size with increasing concentration. This is in agreement with at least some experimental studies, which report signals of aggregation in the low concentration regime. The TMU aggregates exhibit little structure and are simply loosely ordered, TMU-rich regions of solution. The [TMU(GROMOS-UA)/W(SPC/E)] model shows strong signs of aggregation only at higher concentrations (X{sub t} ≳ 0.04), and the aggregates appear more loosely ordered, and less well-defined than those occurring in the [TMU(AMBER-AA)/W(TIP3P)] system. For both models, TMU aggregation increases when the temperature is increased from 300 to 330 K, consistent with an underlying entropy driven, hydrophobic interaction mechanism. At X{sub t} = 0.07, the extra-molecular correlation length expected for microheterogeneous solutions has become comparable with the size of the simulation cell for both models considered, indicating that even the systems simulated here are sufficiently large only at low concentrations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

SIZE AND SURFACE AREA OF ICY DUST AGGREGATES AFTER A HEATING EVENT AT A PROTOPLANETARY NEBULA

The activity of a young star rises abruptly during an FU Orionis outburst. This event causes a temporary temperature increase in the protoplanetary nebula. H{sub 2}O icy grains are sublimated by this event, and silicate cores embedded inside the ice are ejected. During the high-temperature phase, the silicate grains coagulate to form silicate core aggregates. After the heating event, the temperature drops, and the ice recondenses onto the aggregates. I determined numerically the size distribution of the ice-covered aggregates. The size of the aggregates exceeds 10 {mu}m around the snow line. Because of the migration of the ice to large aggregates, only a small fraction of the silicate core aggregate is covered with H{sub 2}O ice. After the heating event, the surface of an ice-covered aggregate is totally covered by silicate core aggregates. This might reduce the fragmentation velocity of aggregates when they collide. It is possible that the covering silicate cores shield the UV radiation field which induces photodissociation of H{sub 2}O ice. This effect may cause the shortage of cold H{sub 2}O vapor observed by Herschel.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

The Influences of Neutron Irradiation on Aggregate Induced Degradation of Concrete

Reactor cavity concrete, the primary support structure for the reactor pressure vessel (RPV), is exposed to chronic neutron/gamma radiation during normal operation. During long term operation, the interaction of neutron irradiation with the concrete’s constituents may cause premature degradation of the concrete structure, as highlighted by a review of concrete properties in nuclear power plant environments. At high fluence levels, as in biological shielding, neutron irradiation may cause amorphization of the crystalline components of concrete, i.e., mineral aggregates, and volume changes, which are typically expansive in nature. Volume expansion can generate tensile stresses within concrete which can induce microcracking and/or result in debonding of aggregate with the matrix. On the other hand, structural disordering can result in changes in the stability of the phase in aqueous environments. This report presents the findings of investigations performed over 3 years through the collaboration of researchers from University of California, Los Angeles, Arizona State University, and Oak Ridge National Laboratory. The first part of the study addresses the effect of neutron irradiation on the durability of aggregates. Comparisons of aqueous dissolution rates, as a function of pH and temperature, were performed for aggregates that are either pristine (i.e., non-irradiated) or exposed to Ar+ ion irradiation at specified doses. These experimental results were coupled with molecular dynamics simulations of atomic scale changes in the crystallographic structure of the mineral and any resulting changes in physical properties (e.g., density) that result. The second section focuses on macroscopic effects of such changes in aggregate behavior in concrete degradation, primarily through changes in the concrete’s microstructure. Particularly, the effects akin to those originating from alkali-silica reaction (ASR) were evaluated. The project is structured to encompass 6 main tasks, as follows: Task 1: Selection of aggregates in relation to their abundance and mineralogy, and their irradiation Task 2: Molecular dynamics (MD): The effects of irradiation on the atomic disordering of aggregates Task 3: The influences of irradiation on aggregate reactivity Task 4: Reactive-transport simulation of expansive product formation in concrete microstructures Task 5: X-FEM-based modeling of damage evolution due to irradiation-induced aggregates reactions Task 6: Benchmarking, verification and validation of the simulation modules Thus, a rigorous understanding of irradiation-assisted mineral alterations was used to develop a mechanistic degradation model for concrete exposed to neutrons, while considering aspects of: chemical reaction (dissolution and precipitation), mass and ion transport, and damage evolutions. The models developed were embedded in a multi-physics aging code for nuclear components and structures called Grizzly, which allows for benchmarking, verification, and validation against expansion data acquired on concrete undergoing alkali-silica reaction, a physically/chemically equivalent form of degradation that develops in the absence of radiation. These findings provide insight into the sensitivities of minerals to irradiation, by highlighting characteristics of concretes and power plants subject to such risks. The research will aid the nuclear power industry to anticipate and mitigate such risks in light of second license renewals.

36 MATERIALS SCIENCE↗
DOE OSTI2016

LIGHT SCATTERING BY FRACTAL DUST AGGREGATES. I. ANGULAR DEPENDENCE OF SCATTERING

In protoplanetary disks, micron-sized dust grains coagulate to form highly porous dust aggregates. Because the optical properties of these aggregates are not completely understood, it is important to investigate how porous dust aggregates scatter light. In this study, the light scattering properties of porous dust aggregates were calculated using a rigorous method, the T -matrix method, and the results were then compared with those obtained using the Rayleigh–Gans–Debye (RGD) theory and Mie theory with the effective medium approximation (EMT). The RGD theory is applicable to moderately large aggregates made of nearly transparent monomers. This study considered two types of porous dust aggregates—ballistic cluster–cluster agglomerates (BCCAs) and ballistic particle–cluster agglomerates. First, the angular dependence of the scattered intensity was shown to reflect the hierarchical structure of dust aggregates; the large-scale structure of the aggregates is responsible for the intensity at small scattering angles, and their small-scale structure determines the intensity at large scattering angles. Second, it was determined that the EMT underestimates the backward scattering intensity by multiple orders of magnitude, especially in BCCAs, because the EMT averages the structure within the size of the aggregates. It was concluded that the RGD theory is a very useful method for calculating the optical properties of BCCAs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Plasmon Dynamics Driven by Aggregation of Tris(2,2′-bipyridine)ruthenium(II)-Functionalized Gold Nanoparticles Probed by XANES and Transient Absorption Spectroscopy

Energy conversion dynamics is critical for advancing next-generation photovoltaics, optoelectronics, and light-harvesting technologies. Noble metal plasmonic nanoparticles play a pivotal role as nanoscale electromagnetic confinement structures, driving photon-induced chemical reactions. In this study, we explore the effects of [Ru(bpy) 3 ] 2+ functionalization and aggregation on citrate-capped gold nanoparticles (AuNPs) of 40 and 100 nm diameters, focusing on molecule-plasmon interactions and their influence on electronic and energy dissipation properties. X-ray absorption near-edge spectroscopy (XANES) revealed that [Ru(bpy) 3 ] 2+ functionalization induces controlled aggregation without altering the oxidation state of gold. A more pronounced white-line intensity is observed in 40 nm AuNPs, consistent with greater s–p–d hybridization and a higher density of surface states, likely influenced by both nanoparticle size and aggregation. Transient absorption (TA) spectroscopy highlights faster electron–phonon relaxation dynamics in aggregated 40 nm nanoparticles, which is attributed to increased electron delocalization and more efficient coupling to the phonon bath. In contrast, 100 nm nanoparticles exhibit minimal changes due to a lower degree of aggregation. Interestingly, we observe that enhanced electron–phonon coupling in aggregated nanoparticles coincides with a slowing of electron–electron scattering. These observations suggest a competitive interplay between the two relaxation pathways, where enhanced energy transfer to the lattice in aggregated systems can suppress electronic thermalization. In conclusion, these findings underscore the critical role of nanoparticle size, aggregation, and molecule–surface interactions in modulating plasmonic dynamics and excited-state lifetimes and further provide valuable insights into designing tailored plasmonic systems with transformative potential for sensing, catalysis, and energy conversion.

36 MATERIALS SCIENCE↗
DOE OSTI2012

The Properties of Mortar Mixtures Blended with Natural, Crushed, and Recycled Fine Aggregates for Building Construction Materials

In this research, the possible applicability of fine aggregates blended with natural, crushed, and recycled fine aggregate are discussed. The fresh and hardened properties of mortar using blended fine aggregates are monitored depending on various blending ratio of fine aggregates. Newly developed ternary diagram was also utilized for better interpretation of the data. It was found that air content increased and unit weight decreased as recycled fine aggregate content increased. With moisture type processing of recycled fine aggregate, the mortar flow was not negatively affected by increase in the recycled fine aggregate content. The ternary diagram is found to be an effective graphical presentation tool that can be used for the quality evaluation of mortar using blended fine aggregate.

36 MATERIALS SCIENCE↗
DOE OSTI2023

What Role Do Aggregators Play in Power System Security and Resilience? Preprint

Barriers to the participation of distributed energy resources (DERs) in wholesale electricity markets have limited the use of DERs for power system security and resilience. In September 2020, the Federal Energy Regulatory Commission (FERC) approved an order to reduce these barriers. FERC Order No. 2222 enables the participation of DER aggregators in wholesale electricity markets. DERs include renewable generation and technologies that support the integration of renewable generation by increasing grid flexibility and resilience. Requiring wholesale energy markets to allow DER aggregator participation provides a path for DERs to become competitive in these markets. As the contribution from aggregated DERs continues to increase, the aggregator's role in supporting grid security and resilience will become more critical. This paper reviews work that demonstrates how DER aggregators can provide resilience support through technical capabilities, operational strategies, and secure communication architectures. Socioeconomic influences and impacts of aggregators, including implications for social resilience, are presented. There is no one-size-fits-all approach to enhancing resilience in a power grid that includes a growing cohort of DER aggregators, but there are many options for aggregators to contribute to a more resilient and secure power grid.

aggregator↗
DOE OSTI2024

Tackling P3HT:Y‐Series Miscibility Through Advanced Processing for Tunable Aggregation

Abstract Polymer and small molecule blend thin films are of strong interest for organic electronics and particularly organic solar cells. The high miscibility in blends of ordinary P3HT and state‐of‐the‐art Y‐series non‐fullerene acceptors (NFAs) suppresses phase separation and aggregation challenging successful charge separation and transport. In a recent work, current‐induced doping (CID) is introduced, a method to precisely control the aggregation of Poly(3‐hexylthiophene) (P3HT) in solution. The highly ordered pre‐aggregation in solution is used here to control the P3HT aggregation in neat films and blends with Y12 (BTP‐4F‐12). This results in a 25‐fold increase in hole mobility in P3HT organic field‐effect transistor (OFET) devices and tunability of the P3HT aggregate quality in the presence of Y12 over large ranges. At the same time, particularly the Y12 long‐range ordering is heavily suppressed by increasing P3HT aggregation. However, solvent vapor annealing (SVA) leads to an extraordinarily high Y12 ordering, changes in the crystal orientation of Y12, and a further improvement of P3HT aggregation. A broad range of different degrees of aggregation of both materials can therefore be obtained in the final thin films solely by changing processing parameters without changing the composition of the material system.

Chemistry↗
DOE OSTI2016

A novel nuclear DnaJ protein, DNAJC8, can suppress the formation of spinocerebellar ataxia 3 polyglutamine aggregation in a J-domain independent manner

Polyglutamine (polyQ) diseases comprise neurodegenerative disorders caused by expression of expanded polyQ-containing proteins. The cytotoxicity of the expanded polyQ-containing proteins is closely associated with aggregate formation. In this study, we report that a novel J-protein, DNAJ (HSP40) Homolog, Subfamily C, Member 8 (DNAJC8), suppresses the aggregation of polyQ-containing protein in a cellular model of spinocerebellar ataxia type 3 (SCA3), which is also known as Machado-Joseph disease. Overexpression of DNAJC8 in SH-SY5Y neuroblastoma cells significantly reduced the polyQ aggregation and apoptosis, and DNAJC8 was co-localized with the polyQ aggregation in the cell nucleus. Deletion mutants of DNAJC8 revealed that the C-terminal domain of DNAJC8 was essential for the suppression of polyQ aggregation, whereas the J-domain was dispensable. Furthermore, 22-mer oligopeptide derived from C-termilal domain could suppress the polyQ aggregation. These results indicate that DNAJC8 can suppress the polyQ aggregation via a distinct mechanism independent of HSP70-based chaperone machinery and have a unique protective role against the aggregation of expanded polyQ-containing proteins such as pathogenic ataxin-3 proteins.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Kinetic regime of aggregation of UV-irradiated glyceraldehyde-3-phosphate dehydrogenase from rabbit skeletal muscle

Highlights: • Kinetic regime of aggregation of UV-irradiated glyceraldehyde-3-phosphate dehydrogenase at 37°C has been established. • The rate of stage of aggregate growth is limited by monomolecular structural reorganization of the irradiated protein. • 2-Hydroxypropyl-b-cyclodextrin decelerates stage of structural reorganization of irradiated enzyme and nucleation stage. The study of the kinetics of aggregation of UV-irradiated proteins has attracted considerable interest, since test systems based on aggregation of proteins denatured by UV radiation can be used for screening of the natural and artificial agents possessing chaperone-like activity (anti-aggregation activity). To provide the proper interpretation of the effects caused by the agents under study, the kinetic mechanism of the aggregation process should be established. In the present work the kinetic data on aggregation of UV-irradiated glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from rabbit skeletal muscle at 37 °C (O.I. Maloletkina et al. Biophys. Chem. 163–164 (2012) 11–20) have been analyzed. It has been shown that the stage of aggregate growth follows the first-order kinetics and the experimentally measured rate constant of the first order corresponds to heat-induced structural reorganization of UV-irradiated GAPDH containing concealed damage.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Efficient Long-range, Directional Energy Transfer through DNA-Templated Dye Aggregates

The benzothiazole cyanine dye, K21, forms dye aggregates on double stranded DNA (dsDNA) templates. These aggregates exhibit a red-shifted absorption band, enhanced fluorescence emission and an increased fluorescence lifetime, all indicating strong excitonic coupling among the dye molecules. K21 aggregate formation on dsDNA is only weakly sequence dependent, providing a flexible approach that is adaptable to many different DNA nanostructures. Donor (D) – bridge (B) – Acceptor (A) complexes consisting of Alexa Fluor 350 as the donor, a 30 bp (9.7 nm) DNA templated K21 aggregate as the bridge and Alexa Fluor 555 as the acceptor show an overall donor to acceptor energy transfer efficiency of ~60%, with the loss of excitation energy being almost exclusively at the donor-bridge junction (63%). There was almost no excitation energy loss due to transfer through the aggregate bridge and the transfer efficiency from the aggregate to the acceptor was about 96%. By comparing the energy transfer in templated aggregates at several lengths up to 32 nm, the loss of energy per nanometer through the K21 aggregate bridge was determined to be <1%, suggesting that it should be possible to construct structures that use much longer energy transfer “wires” for light-harvesting applications in photonic systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗