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At least 19 records

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DOE OSTI2025

Kinetic and structural evidence for specific DMSO interference with reversible binding of uncharged bis-oximes to hAChE and their reactivation kinetics of OP-hAChE

The structural basis of inhibitory effect of organic solvent dimethyl sulfoxide (DMSO) on human acetylcholinesterase (EC 3.1.1.7; hAChE) was inferred from the effect of DMSO on kinetics of reversible inhibition of uncharged, heterocyclic bis-oximes to hAChE, from DMSO effect on rates of reactivation of inactive organophosphate (OP)-hAChE conjugates by bis-oximes and by X-ray structures of bis-oxime and DMSO binding to hAChE. Here, the reversible inhibition constant of DMSO for hAChE in 0.1 M phosphate buffer pH 7.4 at 22 °C, was K i = (0.32 ± 0.04) % (or 45 ± 5 mM). The K i of the bis-oxime LG-703 for hAChE was 3.2-fold larger in 1 % DMSO, consistent with direct competition between LG-703 and DMSO. The X-ray structure of the LG-703∗hAChE complex (PDB ID: 6U3P) shows DMSO and LG-703 bound to individual hAChE monomers, LG-703 in the chain A and DMSO in the chain B. In the co-crystallization both small molecules were present at a similar excess over their corresponding K i values for hAChE (7.8-fold for DMSO and 6.5-fold for LG-703) and formation of two different complexes (DMSO∗hAChE and LG-703∗hAChE), in the same crystal, appears consistent with inhibition kinetics. Furthermore, rates of reactivation of paraoxon-inhibited hAChE (POX-hAChE) and of VX-hAChE by LG-703 and by a novel heterocyclic bis-oxime LG-1922 were reduced 2 – 3-fold in DMSO, consistent with observation of the active-center-bound DMSO molecules in the newly solved structure of the LG-1922∗POX-hAChE complex presented here and in our POX-hAChE structure (PDB ID: 8DT2) showing obstruction of the reactivator access to the conjugated P atom.

Acetylcholinesterase inhibition↗

DOE OSTI2024

Reversible Binding Interfaces Made of Microstructured Polymer Brushes

The polymer brush architecture of the end-tethered polymer molecules is one of the most widely used efficient methods to regulate interfacial interactions in colloidal systems found in live matter and manufactured materials. Emerging applications of polymer brush structures require solutions to new tasks in the control of interfacial interactions. The rapid development of live cell manufacturing relies on scalable and efficient cell harvesting methods. Stimuli-responsive surfaces made of surface-grafted poly(N-isopropylacrylamide) (PNIPAM) can bind and detach the adherent cell upon changes in temperature and have been used for cell growth and harvesting. The applications are limited by the requirement to satisfy a range of PNIPAM coating characteristics that depend on the dimensions of the integrin complex in the cell membrane and the basal surface. The analysis of the microstructured surfaces, when adhesive and disjoining functions of the microdomains are decoupled, shows that many limitations of PNIPAM one-component coatings can be avoided by using a much broader range of structural characteristics of the microstructured interfaces composed of alternating disjoining PNIPAM domains and adhesive polymeric domains with cell-affinity functional groups. Temperature-controlled reversible adhesion to such microstructured interfaces is studied here experimentally with model systems of solid spherical particles and by employing simulations for solid and soft membranes interacting with the microstructured surfaces to mimic interactions with soft and solid disk-like particles.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Engineering and characterization of carbohydrate‐binding modules for imaging cellulose fibrils biosynthesis in plant protoplasts

Abstract Carbohydrate binding modules (CBMs) are noncatalytic domains that assist tethered catalytic domains in substrate targeting. CBMs have therefore been used to visualize distinct polysaccharides present in the cell wall of plant cells and tissues. However, most previous studies provide a qualitative analysis of CBM‐polysaccharide interactions, with limited characterization of engineered tandem CBM designs for recognizing polysaccharides like cellulose and limited application of CBM‐based probes to visualize cellulose fibrils synthesis in model plant protoplasts with regenerating cell walls. Here, we examine the dynamic interactions of engineered type‐A CBMs from families 3a and 64 with crystalline cellulose‐I and phosphoric acid swollen cellulose. We generated tandem CBM designs to determine various characteristic properties including binding reversibility toward cellulose‐I using equilibrium binding assays. To compute the adsorption ( nk on ) and desorption ( k off ) rate constants of single versus tandem CBM designs toward nanocrystalline cellulose, we employed dynamic kinetic binding assays using quartz crystal microbalance with dissipation. Our results indicate that tandem CBM3a exhibited the highest adsorption rate to cellulose and displayed reversible binding to both crystalline/amorphous cellulose, unlike other CBM designs, making tandem CBM3a better suited for live plant cell wall biosynthesis imaging applications. We used several engineered CBMs to visualize Arabidopsis thaliana protoplasts with regenerated cell walls using confocal laser scanning microscopy and wide‐field fluorescence microscopy. Lastly, we also demonstrated how CBMs as probe reagents can enable in situ visualization of cellulose fibrils during cell wall regeneration in Arabidopsis protoplasts.

09 BIOMASS FUELS↗

NASA NTRS1983

Intracellular Calcium Receptors: Calmodulin and Related Proteins

Studies on intracellular calcium receptors, calmodulin and related proteins were carried out. Calcium binding proteins, like calmodulin fall into a class of proteins that are predominantly intracellular and reversibly bind calcium with dissociation constants in the micromolar to nanomolar range. Calcium regulation of these proteins appears to be due to localized increases in calcium concentrations in the cytoplasm. The main thrust of the research is concerned with purifying and characterizing the calcium receptors and trying to elucidate mechanistically how they are involved in cellular responses.

Watterson, D. M.↗

DOE OSTI2024

Engineering and evaluation of FXa bypassing agents that restore hemostasis following Apixaban associated bleeding

Direct oral anticoagulants (DOACs) targeting activated factor Xa (FXa) are used to prevent or treat thromboembolic disorders. DOACs reversibly bind to FXa and inhibit its enzymatic activity. However, DOAC treatment carries the risk of anticoagulant-associated bleeding. Currently, only one specific agent, andexanet alfa, is approved to reverse the anticoagulant effects of FXa-targeting DOACs (FXaDOACs) and control life-threatening bleeding. However, because of its mechanism of action, andexanet alfa requires a cumbersome dosing schedule, and its use is associated with the risk of thrombosis. Here, we present the computational design, engineering, and evaluation of FXa-variants that exhibit anticoagulation reversal activity in the presence of FXaDOACs. Our designs demonstrate low DOAC binding affinity, retain FXa-enzymatic activity and reduce the DOAC-associated bleeding by restoring hemostasis in mice treated with apixaban. Importantly, the FXaDOACs reversal agents we designed, unlike andexanet alfa, do not inhibit TFPI, and consequently, may have a safer thrombogenic profile.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1977

Ionene modified small polymeric beads

Linear ionene polyquaternary cationic polymeric segments are bonded by means of the Menshutkin reaction (quaternization) to biocompatible, extremely small, porous particles containing halide or tertiary amine sites which are centers for attachment of the segments. The modified beads in the form of emulsions or suspensions offer a large, positively-charged surface area capable of irreversibly binding polyanions such as heparin, DNA, RNA or bile acids to remove them from solution or of reversibly binding monoanions such as penicillin, pesticides, sex attractants and the like for slow release from the suspension.

Rembaum, Alan↗

DOE OSTI2024

High-temperature carbon dioxide capture in a porous material with terminal zinc hydride sites

Carbon capture can mitigate point-source carbon dioxide (CO 2 ) emissions, but hurdles remain that impede the widespread adoption of amine-based technologies. Capturing CO 2 at temperatures closer to those of many industrial exhaust streams (>200°C) is of interest, although metal oxide absorbents that operate at these temperatures typically exhibit sluggish CO 2 absorption kinetics and instability to cycling. Here, in this study, we report a porous metal–organic framework featuring terminal zinc hydride sites that reversibly bind CO 2 at temperatures above 200°C—conditions that are unprecedented for intrinsically porous materials. Gas adsorption, structural, spectroscopic, and computational analyses elucidate the rapid, reversible nature of this transformation. Extended cycling and breakthrough analyses reveal that the material is capable of deep carbon capture at low CO 2 concentrations and high temperatures relevant to postcombustion capture.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Functional stimuli-responsive polymers on micro- and nano-patterned interfaces

Micro- and nano-patterned surfaces offer precise control over morphology and chemical composition, enhancing the stability, durability, and functionality of coating materials. When combined with stimuli-responsive polymers, these surfaces gain dynamic adaptability, enabling reversible binding, reusable sensing, and selective molecular capture. Furthermore, while recent review articles have explored various aspects of stimuli-responsive materials, from hydrogel patterns for bioanalytical applications to shape-morphing hydrogels for soft robotics and sensors, a comprehensive review focused on the integration of smart polymers with micro- or nano-patterned interfaces remains absent. This review addresses key surface patterning techniques, including soft lithography, colloidal lithography, and polymer brush photolithography, as well as advances in surface-initiated polymerization methods, such as surface-initiated controlled radical polymerization (SI-CRP). In addition, we discuss recent progress in integrating stimuli-responsive polymers with patterned surfaces to create advanced, functional materials.

Colloidal lithography↗

DOE OSTI2024

Hexagonal Lattices of HIV Capsid Proteins Explored by Simulations Based on a Thermodynamically Consistent Model

HIV capsid proteins (CAs) may self-assemble into a variety of shapes under in vivo and in vitro conditions. Here, we employed simulations based on a residue-level coarse-grained (CG) model with full conformational flexibility to investigate hexagonal lattices, which are the underlying structural pattern for CA aggregations. Facilitated by enhanced sampling simulations to rigorously calculate CA dimerization and polymerization affinities, we calibrated our model to reproduce the experimentally measured affinities. Here using the calibrated model, we performed unbiased simulations on several large systems consisting of 1512 CA subunits, allowing reversible binding and unbinding of the CAs in a thermodynamically consistent manner. In one simulation, a preassembled hexagonal CA sheet developed spontaneous curvatures reminiscent of those observed in experiments, and the edges of the sheet exhibited local curvatures larger than those of the interior. In other simulations starting with randomly distributed CAs at different concentrations, existing CA assemblies grew by binding free capsomeres to the edges and by merging with other assemblies. At high CA concentrations, rapid establishment of predominant aggregates was followed by much slower adjustments toward more regular hexagonal lattices, with increasing numbers of intact CA hexamers and pentamers being formed. Our approach of adapting a general CG model to specific systems by using experimental binding data represents a practical and effective strategy for simulating and elucidating intricate protein aggregations.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2026

Protein Adhesion on Semi-Fluorinated Polystyrene Surfaces in Static and Dynamic Measurements

Reducing protein adhesion is a critical strategy in fouling-resistant material innovation, with broad applications spanning biomedical and healthcare devices, biosensors, industrial and environmental systems, and other important technological domains. Here, in this study, we elucidated protein adhesion behavior on polystyrene-based thin films by neutron reflectometry (NR) and quartz crystal microbalance with dissipation (QCM-D), using both lysozyme and bovine serum albumin (BSA) as model proteins. To this end, semifluorinated polystyrene thin films with gradient wettability and surface energy were fabricated through dry processing using plasma oxidation and gas-phase deposition. Although it is believed that a fully fluorinated alkyl chain offers extremely low surface energy, thus rejecting foulants, and has been used in many fouling-resistant surface designs, enhanced protein–surface interactions were observed consistently in NR and QCM-D results, due to the combined effects of surface morphology and chemistry. On the contrary, depositing shorter fluorinated silane onto a hydrophilic PS surface contributed to a more homogeneous nanoscale fluorine coating, resulting in less initial protein adsorption and improved surface recovery. Comparative analysis of proteins with different sizes on the nanopatterned semifluorinated surface revealed the influence of molecular characteristics on surface interactions. Lysozyme, being smaller and more compact, showed faster adsorption kinetics and higher surface coverage but largely reversible binding, whereas BSA, with its larger and more flexible structure, formed broader and more stable interfacial layers. This study fills the gap in understanding protein adhesion within the range of hydrophobicity (water contact angle ∼90°), as current strategies often associate with extreme hydrophilic and superhydrophobic surfaces due to hydration or low-surface-energy rejection mechanisms, respectively. It also provides in-depth insights into current combinatorial fouling-resistant surface design.

Yuan, Yue [Oak Ridge National Laboratory (ORNL), O↗

DOE OSTI2026

A High-Fidelity Molecular Model of the Cu(111) Repeating Unit

Dynamic processes at surfaces are central to heterogeneous catalysis, but their atomistic mechanism(s) can prove difficult to elucidate due to variations in material structure and the corresponding impact on reactivity. Moreover, disparities between reaction conditions and those employed for spectroscopic characterization at surfaces can inhibit detailed understanding of catalysis-relevant chemistries. Herein, we substantiate the so-called “cluster-surface” analogy by leveraging a low-valent tricopper architecture ( 1 ) as a model system for small molecule activation at Cu(111). Two reaction classes are explored: the adsorption of carbon monoxide (CO) and the dissociative adsorption of dihydrogen (H 2 ). These processes serve as an ideal testbed to compare the reactivity of a molecular cluster ( 1 ) to that of a heterogeneous surface, as both reactions have empirical data from measurements performed on crystalline Cu(111). Cluster 1 reversibly binds CO. Variable temperature NMR analysis with 13 CO reveals a favorable enthalpy but large negative entropy (−5.1 kcal × mol –1 and −22.9 cal × mol –1 × K –1 , respectively) for CO binding, affording a process that is marginally endergonic at room temperature (ΔG ads (298.15 K) = 1.7 ± 0.5 kcal × mol –1 ). Similarly, analogous to a Cu(111) surface, 1 is shown to oxidatively add (chemisorb) H 2 . Kinetic parameters were determined for this process and the activation enthalpy (8.4 ± 0.5 kcal × mol –1 ) closely mirrors that established for H 2 binding at the Cu(111) facet (6.0 to 12.4 kcal × mol –1 ). Together, these results showcase that a trinuclear cluster can reproduce the small molecule binding and activation energetics of a bulk crystalline surface, setting the stage for studying less-defined surface processes in an atomically precise molecular setting.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2026

Primary biomolecular adsorption energetics of core–shell nanocomplexes: Implications for biological interactions

Molecular organization at the nano-bio interface governing the colloidal stability, reactivity, immune recognition, and drug delivery performance of nanoparticles remains difficult to predict. Quantifying the primary hydration energetics of biomolecule-coated nanomaterials can determine those interactions and provide a basis for engineered nanocarriers with tailored behavior in biological systems. Here, we measured the thermodynamics of water adsorption on patchy dry magnetite (Fe 3 O 4 ) nanoparticles coated with three model biomolecules, bovine serum albumin, potato starch, and lauric acid and compared these properties to the hydration energetics of the corresponding free dry biomolecules. The results demonstrate how the surface functionalization alters the hydrophilicity, the accessible hydrophilic surface, and the interaction potential of the nanocomplex surface with biological media. The protein coating increases the interaction potential of the surface of the nanocomplex. The weaker interaction potential of the polysaccharide coating and the relatively large hydrophilic surface area allow dynamic and reversible binding, while the fatty acid rearranges into a partial bilayer with very strong hydrophilicity. The findings establish the hydration enthalpy as a quantitative basis to determine and interpret nanoparticle interactions with proteins, membranes, and biological fluids, and provide a thermodynamic foundation for designing nanocarriers with predictable biological reactivity.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1994

Surface acoustic wave oxygen pressure sensor

A transducer for the measurement of absolute gas-state oxygen pressure from pressures of less than 100 Pa to atmospheric pressure (1.01 x 10(exp 5) Pa) is based on a standard surface acoustic wave (SAW) device. The piezoelectric material of the SAW device is coated with a compound which will selectively and reversibly bind oxygen. When oxygen is bound by the coating, the mass of the coating increases by an amount equal to the mass of the bound oxygen. Such an increase in the mass of the coating causes a corresponding decrease in the resonant frequency of the SAW device.

Oglesby, Donald M.↗

NASA NTRS1999

Engineering of Novel Biocolloid Suspensions

Colloidal suspensions are materials with a variety of uses from cleaners and lubricants to food, cosmetics, and coatings. In addition, they can be used as a tool for testing the fundamental tenets of statistical physics. Colloidal suspensions can be synthesized from a wide variety of materials, and in the form of monodisperse particles, which can self-assemble into highly ordered colloidal crystal structures. As such they can also be used as templates for the construction of highly ordered materials. Materials design of colloids has, to date, relied on entropic self-assembly, where crystals form as result of lower free energy due to a transition to order. Here, our goal is to develop a completely new method for materials fabrication using colloidal precursors, in which the self-assembly of the ordered colloidal structures is driven by a highly controllable, attractive interaction. This will greatly increase the range of potential structures that can be fabricated with colloidal particles. In this work, we demonstrate that colloidal suspensions can be crosslinked through highly specific biological crosslinking reactions. In particular, the molecules we use are protein-carbohydrate interactions derived from the immune system. This different driving force for self-assembly will yield different and novel suspensions structures. Because the biological interactions are heterotypic (A binding to B), this chemical system can be used to make binary alloys in which the two colloid subpopulations vary in some property - size, density, volume fraction, magnetic susceptibility, etc. An additional feature of these molecules which is unique - even within the realm of biological recognition - is that the molecules bind reversibly on reasonable time-scales, which will enable the suspension to sample different configurations, and allow us to manipulate and measure the size of the suspension dynamically. Because of the wide variety of structures that can be made from these novel colloids, and because the suspension structure can be altered dynamically, we believe this biocolloid system will yield a novel set of materials with many technological applications, including sensors (both biological and non-biological), optical filters and separation media.

Hammer, D. A.↗

NASA NTRS1985

Oxygen sorbent

The present invention discloses a novel and unique family of agents which reversibly binds molecular oxygen at room temperature.

Sievers, Robert E.↗

NASA NTRS1987

Oxygen sorbent

The present invention discloses a novel and unique family of agents which reversibly binds molecular oxygen at room temperature.

Sievers, Robert E.↗

NASA NTRS2008

Optical Detection of Formaldehyde

The potential for buildup .of formaldehyde in closed space environments poses a direct health hazard to personnel. The National Aeronautic Space Agency (NASA) has established a maximum permitted concentration of 0.04 ppm for 7 to 180 days for all space craft. Early detection is critical to ensure that formaldehyde levels do not accumulate. above these limits. New sensor technologies are needed to enable real time,in situ detection in a compact and reusable form factor. Addressing this need,research into the use of reactive fluorescent dyes which reversibly bind to formaldehyde (liquid or gas) has been conducted to support the development of a formaldehyde.sensor. In the presence of formaldehyde the dyes' characteristic fluorescence peaks shift providing the basis for an optical detection. Dye responses to formaldehyde exposure were characterized; demonstrating the optical detection of formaldehyde in under 10 seconds and down to concentrations of 0.5 ppm. To .incorporate the dye .in.an optical sensor device requires. a means of containing and manipulating the dye. Multiple form factors using two dissimilar s~bstrates were considered to determine a suitable configuration. A prototype sensor was demonstrated and considerations for a field able sensor were presented. This research provides a necessary first step toward the development of a compact, reusable; real time optical formaldehyde sensor suitable for use in the U.S. space program,

Patty, Kira D.↗

DOE OSTI2023

Examining Interactions of Uranyl(VI) Ions with Amino Acids in the Gas Phase

Gas-phase experiments, using electrospray ionization quadrupole ion trap mass spectrometry (ESI-QIT/MS), were conducted to probe basic interactions of the uranyl(VI) ion, UO 2 2+ , with selected natural amino acids, namely, L-cysteine (Cys), L-histidine (His), and L-aspartic acid (Asp), which strongly bind to metal ions. The simplest amino acid, glycine (Gly), was also studied for comparison. Cys, His, and Asp have additional potentially coordinating groups beyond the amino and carboxylic acid functional groups, specifically thiol in Cys, imidazole in His, and a second carboxylate in Asp. Gas-phase experiments comprised collision-induced dissociation (CID) of uranyl–amino acid complexes and competitive CID to assess the relative binding strength of different amino acids in the same uranyl complex. Reactivity of selected uranyl–amino acid complexes with water provided further insights into relative stabilities. In positive ion mode, CID and ensuing reactions with water suggested that uranyl–neutral AA binding strength decreased in the order His > Asp > Cys > Gly, which is similar to amino acid proton affinities. In negative ion mode, CID revealed a decreasing dissociation tendency in the order Gly >> His ≈ Cys > Asp, presumably reflecting a reverse enhanced binding to uranyl of the doubly deprotonated amino acids formed in CID.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗