Bioinspired, Non-Enzymatic, Aqueous Synthesis of Size-Tunable CdS Quantum Dots for Sustainable Optoelectronic Applications

The enzymatic production of hydrogen sulfide (H₂S) from cysteine in various metabolic processes has been exploited as an intrinsically "green" and sustainable mode for the aqueous biomineralization of functional metal sulfide quantum dots (QDs). Yet, the reliance on proteinaceous enzymes tends to limit the efficacy of the synthesis to physiological temperature and pH, with implications for QD functionality, stability, and tunability (i.e., particle size and composition). Inspired by a secondary non-enzymatic biochemical cycle that is responsible for basal H₂S production in mammalian systems, we establish how iron(III)- and vitamin B₆ (pyridoxal phosphate, PLP)-catalyzed decomposition of cysteine can be harnessed for the aqueous synthesis of size-tunable QDs, demonstrated here for CdS, within an expanded temperature, pH, and compositional space. Rates of H₂S production by this non-enzymatic biochemical process are sufficient for the nucleation and growth of CdS QDs within buffered solutions of cadmium acetate. Ultimately, the simplicity, demonstrated robustness, and tunability of the previously unexploited H₂S-producing biochemical cycle help establish its promise as a versatile platform for the benign, sustainable synthesis of an even wider range of functional metal sulfide nanomaterials for optoelectronic applications.

Sequential, low-temperature aqueous synthesis of Ag-In-S/Zn quantum dots via staged cation exchange under biomineralization conditions

The development of high quality, non-toxic (i.e., heavy-metal-free), and functional quantum dots (QDs) via 'green' and scalable synthesis routes is critical for realizing truly sustainable QD-based solutions to diverse technological challenges. Herein, we demonstrate the low-temperature all-aqueous-phase synthesis of silver indium sulfide/zinc (AIS/Zn) QDs with a process initiated by the biomineralization of highly crystalline indium sulfide nanocrystals, and followed by the sequential staging of Ag⁺ cation exchange and Zn²⁺ addition directly within the biomineralization media without any intermediate product purification. Therein, we exploit solution phase cation concentration, the duration of incubation in the presence of In₂S₃ precursor nanocrystals, and the subsequent addition of Zn²⁺ as facile handles under biomineralization conditions for controlling QD composition, tuning optical properties, and improving the photoluminescence quantum yield of the AIS/Zn product. We demonstrate how engineering biomineralization for the synthesis of intrinsically hydrophilic and thus readily functionalizable AIS/Zn QDs with a quantum yield of 18% offers a 'green' and non-toxic materials platform for targeted bioimaging in sensitive cellular systems. Ultimately, the decoupling of synthetic steps helps unravel the complexities of ion exchange-based synthesis within the biomineralization platform, enabling its adaptation for the sustainable synthesis of 'green', compositionally diverse QDs.

Probing IgG1 FC-Multimodal Nanoparticle Interactions: A Combined Nuclear Magnetic Resonance and Molecular Dynamics Simulations Approach

In this study, NMR and molecular dynamics simulations were employed to study IgG1 F_C binding to multimodal surfaces. Gold nanoparticles functionalized with two multimodal cation-exchange ligands (Capto and Nuvia) were synthesized and employed to carry out solution-phase NMR experiments with the F_C. Experiments with perdeuterated ¹⁵N-labeled F_C and the multimodal surfaces revealed micromolar residue-level binding affinities as compared to millimolar binding affinities with these ligands in free solution, likely due to cooperativity and avidity effects. The binding of F_C with the Capto ligand nanoparticles was concentrated near an aliphatic cluster in the C_H2/C_H3 interface, which corresponded to a focused hydrophobic region. In contrast, binding with the Nuvia ligand nanoparticles was more diffuse and corresponded to a large contiguous positive electrostatic potential region on the side face of the F_C. Results with lower-ligand-density nanoparticles indicated a decrease in binding affinity for both systems. For the Capto ligand system, several aliphatic residues on the F_C that were important for binding to the higher-density surface did not interact with the lower-density nanoparticles. In contrast, no significant difference was observed in the interacting residues on the F_C to the high- and low-ligand density Nuvia surfaces. The binding affinities of F_C to both multimodal-functionalized nanoparticles decreased in the presence of salt due to the screening of multiple weak interactions of polar and positively charged residues. For the Capto ligand nanoparticle system, this resulted in an even more focused hydrophobic binding region in the interface of the C_H2 and C_H3 domains. Interestingly, for the Nuvia ligand nanoparticles, the presence of salt resulted in a large transition from a diffuse binding region to the same focused binding region determined for Capto nanoparticles at 150 mM salt. Molecular dynamics simulations corroborated the NMR results and provided important insights into the molecular basis of F_C binding to these different multimodal systems containing clustered (observed at high-ligand densities) and nonclustered ligand surfaces. This combined biophysical and simulation approach provided significant insights into the interactions of F_C with multimodal surfaces and sets the stage for future analyses with even more complex biotherapeutics.

Evaluation of guanidine-based multimodal anion exchangers for protein selectivity and orthogonality

In this paper, we examined the chromatographic behavior of a new class of guanidine-based multimodal anion exchange resins. The selectivities and protein recoveries on these resins were first evaluated using linear gradient chromatography with a model acidic protein library at pH 5, 6 and 7. While a single-guanidine based resin exhibited significant recovery issues at high ligand density, a bis-guanidine based resin showed high recoveries of all but two of the proteins evaluated in the study. In addition, the bis-guanidine resin showed a more pH dependent selectivity pattern as compared to the low density single-guanidine resin. The salt elution range for the low density single-guanidine and bis-guanidine resins was also observed to vary from 0.250 to 0.621 M and 0.162 to 0.828 M NaCl, respectively. A QSAR model was then developed to predict the elution behavior of these proteins on the guanidine prototypes at multiple pH with overall training and test scores of 0.88 and 0.85, respectively. In addition, molecular dynamics simulations were performed with these ligands immobilized on a self-assembled monolayer (SAM) to characterize their conformational preferences and to gain insight into the molecular basis of their chromatographic behavior. Finally, a recently developed framework was employed to evaluate the separability of the bis-guanidine resin as well as its orthogonality to the multimodal cation exchanger, Nuvia cPrime. This evaluation was carried out using a second model protein library which included both acidic and basic proteins. The results of this analysis indicated that the bis-guanidine prototype exhibited both higher pair separability (0.73) and pair enhancement (0.42) as compared to the less hydrophobic commercial Nuvia aPrime 4A with pair separability and enhancement factors of 0.57 and 0.22, respectively. The enhanced selectivity and orthogonality of this new multimodal anion exchange ligand may offer potential opportunities for bioprocessing applications.

Behavior of Water Near Multimodal Chromatography Ligands and Its Consequences for Modulating Protein-Ligand Interactions

Multimodal chromatography is a powerful approach for purifying proteins that uses ligands containing multiple modes of interaction. Recent studies have shown that selectivity in multimodal chromatographic separations is a function of the ligand structure and geometry. Here, we performed molecular dynamics simulations to explore how the ligand structure and geometry affect ligand-water interactions and how these differences in solution affect the nature of protein-ligand interactions. Our investigation focused on three chromatography ligands: Capto MMC, Nuvia cPrime, and Prototype 4, a structural variant of Nuvia cPrime. First, the solvation characteristics of each ligand were quantified via three metrics: average water density, fluctuations, and residence time. We then explored how solvation was perturbed when the ligand was bound to the protein surface and found that the probability of the phenyl ring dewetting followed the order: Capto MMC > Prototype 4 > Nuvia cPrime. To explore how these differences in dewetting affect protein-ligand interactions, we calculated the probability of each ligand binding to different types of residues on the protein surface and found that the probability of binding to a hydrophobic residue followed the same order as the dewetting behavior. This study illustrates the role that wetting and dewetting play in modulating protein-ligand interactions.

Identification of preferred multimodal ligand-binding regions on IgG1 FC using nuclear magnetic resonance and molecular dynamics simulations

In this study, the binding of multimodal chromatographic ligands to the IgG1 F_C domain were studied using nuclear magnetic resonance and molecular dynamics simulations. Nuclear magnetic resonance experiments carried out with chromatographic ligands and a perdeuterated ¹⁵ N-labeled F_C domain indicated that while single-mode ion exchange ligands interacted very weakly throughout the F_C surface, multimodal ligands containing negatively charged and aromatic moieties interacted with specific clusters of residues with relatively high affinity, forming distinct binding regions on the F_C . The multimodal ligand-binding sites on the F_C were concentrated in the hinge region and near the interface of the C_H 2 and C_H 3 domains. Furthermore, the multimodal binding sites were primarily composed of positively charged, polar, and aliphatic residues in these regions, with histidine residues exhibiting some of the strongest binding affinities with the multimodal ligand. Interestingly, comparison of protein surface property data with ligand interaction sites indicated that the patch analysis on F_C corroborated molecular-level binding information obtained from the nuclear magnetic resonance experiments. Finally, molecular dynamics simulation results were shown to be qualitatively consistent with the nuclear magnetic resonance results and to provide further insights into the binding mechanisms. An important contribution to multimodal ligand-F_C binding in these preferred regions was shown to be electrostatic interactions and π-π stacking of surface-exposed histidines with the ligands. This combined biophysical and simulation approach has provided a deeper molecular-level understanding of multimodal ligand-F_C interactions and sets the stage for future analyses of even more complex biotherapeutics.

Tailored Coupling of Biomineralized CdS Quantum Dots to rGO to Realize Ambient Aqueous Synthesis of a High-Performance Hydrogen Evolution Photocatalyst

Nanocomposite photocatalysts offer a promising route to efficient and clean hydrogen production. However, the multistep, high-temperature, solvent-based syntheses typically utilized to prepare these photocatalysts can limit their scalability and sustainability. Biosynthetic routes to produce functional nanomaterials occur at room temperature and in aqueous conditions, but typically do not produce high-performance materials. We have developed a method to produce a highly efficient hydrogen evolution photocatalyst consisting of CdS quantum dots (QDs) supported on reduced graphene oxide (rGO) via enzyme-based syntheses combined with tuned ligand exchange-mediated self-assembly. All preparation steps are carried out in an aqueous environment at ambient temperature. Size-controlled CdS QDs and rGO are prepared through enzyme-mediated turnover of l-cysteine to HS^- in aqueous solutions of Cd-acetate and graphene oxide, respectively. Exchange of cysteamine for the native l-cysteine ligand capping the CdS QDs drives self-assembly of the now positively charged cysteamine-capped CdS (CdS/CA) onto negatively charged rGO. The use of this short linker molecule additionally enables efficient charge transfer from CdS to rGO, increasing exciton lifetime and, subsequently, photocatalytic activity. The visible-light hydrogen evolution rate of the resulting CdS/CA/rGO photocatalyst is 3300 μmol h^-1 g^-1. This represents, to our knowledge, one of the highest reported rates for a CdS/rGO nanocomposite photocatalyst, irrespective of the synthesis method.

Integrated clinical pathways with watertight, multi-layer closure to improve patient outcomes in total hip and knee joint arthroplasty

The number of primary total hip and knee replacement surgeries is increasing primarily due to an aging population. There is also a concomitant increase in the number of complications which could be attributed to high variation in arthroplasty techniques, peri-operative methods and the absence of integrated clinical pathways (ICP) to mitigate risks such as surgical site infections (SSIs). The implementation of ICPs incorporating watertight, multi-layer closure could increase the preventative effectiveness against joint prosthetic adverse events. The objective of this review is to describe the ICPs implemented by one US facility to help address ten adverse events synergistically.

In Situ Biomineralization of CuxZnySnzS4 Nanocrystals within TiO2-Based Quantum Dot Sensitized Solar Cell Anodes

CuZnSnS (CZTS) quantum dots (QDs) have potential application in quantum dot sensitized solar cells (QDSSCs); however, traditional synthesis approaches typically require elevated temperatures, expensive precursors, and organic solvents that can hinder large-scale application. Herein we develop and utilize an enzymatic, aqueous-phase, ambient temperature route to prepare CZTS nanocrystals with good compositional control. Nanoparticle synthesis occurs in a minimal buffered solution containing only the enzyme, metal chloride and acetate salts, and l-cysteine as a capping agent and sulfur source. Beyond isolated nanocrystal synthesis, we further demonstrate biomineralization of these particles within a preformed mesoporous TiO₂ anode template where the formed nanocrystals bind to the TiO₂ surface. This in situ biomineralization approach facilitates enhanced distribution of the nanocrystals in the anode and, through this, enhanced QDSSC performance.

An Assembly and Interfacial Templating Route to Carbon Supercapacitors with Simultaneously Tailored Meso- and Microstructures

The development of facile strategies for simultaneously tailoring robust pore hierarchy and integrated microstructures in carbonaceous materials is critical for the efficient multiscale control of fluid, molecular/ionic, and charge transport in applications spanning separations, catalysis, and energy storage. Here, we synthesize three-dimensionally ordered hierarchically porous carbon powders by the assembly of glucose with silica nanoparticle building blocks of sacrificial NP-crystalline templates. Such template-replica coassembly offers an attractive alternative to conventional nanocasting by circumventing the need for sequential template preformation and infiltration-based replication. In addition, interfacial templating leads to hierarchically structured carbons with tunable mesopore volumes (as high as 5.8 cm³/g). Beyond mesostructuring, we identify the template-replica interface as a potentially versatile but generally unexploited handle for tailoring the sp² hybridized carbon content in the porous replicas under mild carbonization conditions and without specific chemical activation or catalytic graphitization. This multiscale (meso-micro) templating offered by a single template expands the potential versatility of nanocasting for the hierarchical structuring of replica materials. Application of the resulting carbons as electrochemical double layer capacitors demonstrates the combined benefit of simultaneously tailored pore hierarchy and tuned microstructures upon ion and charge transport, respectively, yielding supercapacitors achieving specific capacitance as high as 275 F/g in the aqueous electrolyte (H₂SO₄) and retention of 90% up to a current density of 10 A/g.

Greenhouse- and orbital-forced climate extremes during the early Eocene

The Palaeocene-Eocene Thermal Maximum (PETM) was a significant global warming event in Earth's deep past (56 Mya). The warming across the PETM boundary was driven by a rapid rise in greenhouse gases. The event also coincided with a time of maximum insolation in Northern Hemisphere summer. There is increased evidence that the mean warming was accompanied by enhanced seasonality and/or extremes in precipitation (and flooding) and drought. A high horizontal resolution (50 km) global climate model is used to explore changes in the seasonal cycle of surface temperature, precipitation, evaporation minus precipitation and river run-off for regions where proxy data are available. Comparison for the regions indicates the model accurately simulates the observed changes in these climatic characteristics with North American interior warming and drying, and warming and increased river run-off at other regions. The addition of maximum insolation in Northern Hemisphere summer leads to a drier North America, but wetter conditions at most other locations. Long-range transport of atmospheric moisture plays a critical role in explaining regional changes in the water cycle. Such high-frequency variations in precipitation might also help explain discrepancies or misinterpretation of some climate proxies from the same locations, especially where sampling is coarse, i.e. at or greater than the frequency of precession.This article is part of a discussion meeting issue 'Hyperthermals: rapid and extreme global warming in our geological past'.

Binary Superlattice Design by Controlling DNA-Mediated Interactions

Most binary superlattices created using DNA functionalization rely on particle size differences to achieve compositional order and structural diversity. Here we study two-dimensional (2D) assembly of DNA-functionalized micron-sized particles (DFPs), and employ a strategy that leverages the tunable disparity in interparticle interactions, and thus enthalpic driving forces, to open new avenues for design of binary superlattices that do not rely on the ability to tune particle size (i.e., entropic driving forces). Our strategy employs tailored blends of complementary strands of ssDNA to control interparticle interactions between micron-sized silica particles in a binary mixture to create compositionally diverse 2D lattices. We show that the particle arrangement can be further controlled by changing the stoichiometry of the binary mixture in certain cases. With this approach, we demonstrate the ability to program the particle assembly into square, pentagonal, and hexagonal lattices. In addition, different particle types can be compositionally ordered in square checkerboard and hexagonal-alternating string, honeycomb, and Kagome arrangements.

Template-Induced Structuring and Tunable Polymorphism of Three-Dimensionally Ordered Mesoporous (3DOm) Metal Oxides

Convectively assembled colloidal crystal templates, composed of size-tunable (ca. 15-50 nm) silica (SiO₂) nanoparticles, enable versatile sacrificial templating of three-dimensionally ordered mesoporous (3DOm) metal oxides (MO_x) at both mesoscopic and microscopic size scales. Specifically, we show for titania (TiO₂) and zirconia (ZrO₂) how this approach not only enables the engineering of the mesopore size, pore volume, and surface area but can also be leveraged to tune the crystallite polymorphism of the resulting 3DOm metal oxides. Template-mediated volumetric (i.e., interstitial) effects and interfacial factors are shown to preserve the metastable crystalline polymorphs of each corresponding 3DOm oxide (i.e., anatase TiO₂ (A-TiO₂) and tetragonal ZrO₂ (t-ZrO₂)) during high-temperature calcination. Mechanistic investigations suggest that this polymorph stabilization is derived from the combined effects of the template-replica (MO_x/SiO₂) interface and simultaneous interstitial confinement that limit the degree of coarsening during high-temperature calcination of the template-replica composite. The result is the identification of a facile yet versatile templating strategy for realizing 3DOm oxides with (i) surface areas that are more than an order of magnitude larger than untemplated control samples, (ii) pore diameters and volumes that can be tuned across a continuum of size scales, and (iii) selectable polymorphism.

Efficacy in Deep Vein Thrombosis Prevention With Extended Mechanical Compression Device Therapy and Prophylactic Aspirin Following Total Knee Arthroplasty: A Randomized Control Trial

BACKGROUND

Aspirin at 325 mg twice daily is now included as a nationally approved venous thromboembolism (VTE) prophylaxis protocol for low-risk total knee arthroplasty (TKA) patients. The purpose of this study is to examine whether there is a difference in deep vein thrombosis (DVT) occurrence after a limited tourniquet TKA using aspirin-based prophylaxis with or without extended use of mechanical compression device (MCD) therapy.

METHODS

One hundred limited tourniquet TKA patients, whose DVT risk was managed with aspirin 325 mg twice daily for 3 weeks, were randomized to either using an MCD during hospitalization only or extended use at home up to 6 weeks postoperatively. Lower extremity duplex venous ultrasonography (LEDVU) was completed on the second postoperative day, 14 days postoperatively, and at 3 months postoperatively to confirm the absence of DVT after treatment.

RESULTS

The DVT rate for the postdischarge MCD therapy group was 0% and 23.1% for the inpatient MCD group (P < .001). All DVTs resolved by 3 months postoperatively. Patient satisfaction was 9.56 (±0.82) for postdischarge MCD patients vs 8.50 (±1.46) for inpatient MCD patients (P < .001).

CONCLUSION

Limited tourniquet TKA patients who were mobilized early, managed with aspirin for 3 weeks postoperatively, and on MCD therapy for up to 6 weeks postoperatively experienced superior DVT prophylaxis than patients receiving MCD therapy only as an inpatient (P < .05). The 0% incidence of nonsymptomatic DVTs prevented by aspirin and extended-use MCD further validates this type of prophylaxis in low DVT risk TKA patients.

A Review of Biorefinery Separations for Bioproduct Production via Thermocatalytic Processing

With technological advancement of thermocatalytic processes for valorizing renewable biomass carbon, development of effective separation technologies for selective recovery of bioproducts from complex reaction media and their purification becomes essential. The high thermal sensitivity of biomass intermediates and their low volatility and high reactivity, along with the use of dilute solutions, make the bioproducts separations energy intensive and expensive. Novel separation techniques, including solvent extraction in biphasic systems and reactive adsorption using zeolite and carbon sorbents, membranes, and chromatography, have been developed. In parallel with experimental efforts, multiscale simulations have been reported for predicting solvent selection and adsorption separation. We discuss various separations that are potentially valuable to future biorefineries and the factors controlling separation performance. Particular emphasis is given to current gaps and opportunities for future development.

A Randomized, Multicenter, Double-Blind Study of Local Infiltration Analgesia with Liposomal Bupivacaine for Postsurgical Pain Following Total Knee Arthroplasty: Rationale and Design of the Pillar Trial

INTRODUCTION

Liposomal bupivacaine, a prolonged-release formulation of bupivacaine hydrochloride, is indicated for infiltration into the surgical site for postsurgical analgesia. Results from previous total knee arthroplasty (TKA) studies suggest that analgesic efficacy associated with liposomal bupivacaine may be impacted by variability in infiltration technique. The PILLAR study is designed to assess liposomal bupivacaine efficacy in TKA using a standardized infiltration protocol. Materials and Methods/Design: This phase 4, multicenter, randomized, double-blind, controlled, parallel-group study will compare the safety and efficacy of infiltration with liposomal bupivacaine versus standard bupivacaine for postsurgical pain control in adults undergoing primary unilateral TKA. All subjects will receive a standardized pre-surgical analgesic regimen, and will be randomized to receive either liposomal bupivacaine 266 mg/20 mL (admixed with standard bupivacaine 0.5% 20 mL and expanded to a total volume of 120 mL) or bupivacaine 0.5% 20 mL (expanded to a total volume of 120 mL). The study drug will be infiltrated using six syringes (prefilled with 20 mL of study drug solution) to deliver 1-1.5 mL infusions into prespecified periarticular tissues. All subjects will receive standardized postsurgical analgesia and access to rescue medication. The co-primary efficacy endpoints are area under the curve of visual analog scale pain intensity scores from 12-48 hours postsurgery and total postsurgical opioid consumption from 0-48 hours. Secondary efficacy endpoints include other pain assessments, time to first use of rescue medication, discharge readiness, use of skilled nursing facilities, and hospital length of stay. Safety will be evaluated based on adverse events.

DISCUSSION/CONCLUSION

The use of a standardized protocol comparing infiltration of equal volumes of the study drug, designed by experienced investigators to ensure complete coverage of all areas innervating the surgical site while minimizing leakage of study drug, will help define the role of liposomal bupivacaine in the setting of TKA.

Effect of Nonionic Surfactant on Association/Dissociation Transition of DNA-Functionalized Colloids

We report the effect of nonionic surfactants (Pluronics F127 and F88) on the melting transition of micron-sized colloids confined in two dimensions, mediated by complementary single-stranded DNA as a function of the surfactant concentration. Micron-sized silica particles were functionalized with single-stranded DNA using cyanuric chloride chemistry. The existence of covalently linked DNA on particles was confirmed by fluorescence spectroscopy. The nonionic surfactant not only plays a significant role in stabilization of particles, with minimization of nonspecific binding, but also impacts the melting temperature, which increases as a function of the nonionic surfactant concentration. These results suggest that the melting transition for DNA-mediated assembly is sensitive to commonly used additives in laboratory buffers, and that these common solution components may be exploited as a facile and independent handle for tuning the melting temperature and, thus, the assembly and possibly crystallization within these systems.

Improving total knee arthroplasty perioperative pain management using a periarticular injection with bupivacaine liposomal suspension

Patients undergoing total knee arthroplasty (TKA) report low satisfaction with postoperative pain control. The purpose of this study is to examine if there is a difference in post-operative pain for TKA patients without femoral nerve block receiving an intra-operative pericapsular injection of bupivacaine liposome suspension (EXPAREL; Pacira Pharmaceuticals, Inc., San Diego, California) versus a concentrated multi drug cocktail. Seventy TKA patients were randomly assigned to either the bupivacaine liposome or the multi-drug cocktail. Post-operative pain scores, morphine sulfate equivalence consumption values, adverse events, and overall pain control satisfaction scores were collected. Patients reported significantly higher pain level for the cocktail group on post-op day 1 (p < .05) and post-op day 2 (p < .01) versus the bupivacaine liposome group. This same trend was found for morphine sulfate equivalence consumption in the PACU (p < .01) and post-op day 2 (p < .01). Higher satisfaction in pain control (p < .001) and overall experience (p < .01) was also found in the bupivacaine liposome group. Finally, significantly more adverse events were found in the multi-drug group versus the bupivacaine liposome group (p < .05). The study findings demonstrated a non-inferior difference, albeit not a clinically significant difference, in patient-perceived pain scores, morphine sulfate equivalence consumption, adverse events, and overall satisfaction.

Flow-induced alignment of (100) fcc thin film colloidal crystals

The realization of structural diversity in colloidal crystals obtained by self-assembly techniques remains constrained by thermodynamic considerations and current limits on our ability to alter structure over large scales using imposed fields and confinement. In this work, a convective-based procedure to fabricate multi-layer colloidal crystal films with extensive square-like symmetry is enabled by periodic substrate motion imposed during the continuous assembly. The formation of film-spanning domains of (100) fcc symmetry as a result of added vibration is robust across a range of micron-scale monosized spherical colloidal suspensions (e.g., polystyrene, silica) as well as substrate surface chemistries (e.g., hydrophobic, hydrophilic). The generation of extensive single crystalline (100) fcc domains as large as 15 mm(2) and covering nearly 40% of the colloidal crystalline film is possible by simply tuning coating conditions and multi-layer film thickness. Preferential orientation of the square-packed domains with respect to the direction of deposition is attributed to domain generation based upon a shear-related mechanism. Visualization during assembly gives clues toward the mechanism of this flow-driven self-assembly method.

Nanocasting of carbon films with interdigitated bimodal three-dimensionally ordered mesopores by template-replica coassembly

Carbon films with interdigitated bimodal three-dimensionally ordered mesoporosity (ib3DOm) are realized by a scalable nanoreplication process that removes the common need plaguing hard-templating strategies for multistep prefabrication of porous sacrificial templates. Specifically, evaporation-induced convective codeposition of size-tunable (ca. 20-50 nm) silica nanoparticles with a surrogate molecular carbon precursor (glucose), followed by carbonization and template etching, leads to remarkably ordered, crack-free mesoporous carbon films of tunable thickness (ca. 100-1000 nm) and pore size. Association of the molecular carbon precursor with the assembling pore forming particles is found to transition the system among three distinct film morphologies (collapsed, ib3DOm C, disordered), thereby establishing a pseudophase behavior controlled by silica solids content and incipient glucose concentration. Namely, a parametric window wherein ib3DOm C films can be realized is identified, with a diffuse lower phase boundary associated with collapsing carbon films, and a more distinct order-to-disorder transition encountered at higher glucose concentrations. Mechanistic insight suggests that glucose association with the lysine-silica nanoparticle surface modulates the lattice spacing, d, of the periodically ordered mesopores in the coassembled films, with the onset of the order-to-disorder transition occurring at a critical normalized lattice spacing, dc/D ∼ 1.16. This appears to apply across the phase space associated with D = 50 nm silica particles and to translate among other phase spaces associated with smaller particles (e.g., 30 nm). We briefly demonstrate the robustness of the codeposition process for realizing ib3DOm C films on rough FTO glass substrates and show that, in this form, these materials hold potential as low-cost alternatives to costly platinum electrodes for dye-sensitized solar cells.

Template-free ordered mesoporous silicas by binary nanoparticle assembly

Evaporation-induced convective binary assembly of large (A) and small (B) silica nanoparticles is demonstrated as a template-free route to three-dimensionally ordered mesoporous silicas (OMSs), the pore topology of which derives from the interconnected interstices of the resulting ordered nanoparticulate structures. Even without explicit solvent index matching or stabilization (e.g., charge or steric) beyond intrinsic properties of the amino acid nanoparticle synthesis solution, assembly of binary mixtures of silica nanoparticles of ca. 10-50 nm in diameter primarily obeys hard-sphere phase behavior despite differences in electrostatic character of the particles. Specifically, the particle size ratio, γ, governs symmetry of the assemblies among AB2 and AB13 phases and enables access of the AB phase. Small-angle X-ray scattering (SAXS) reveals the high yield of ordered binary assemblies and confirms, in combination with transmission electron microscopy, the AlB2, NaZn13, and NaCl crystalline isostructures. Interstitial solid solutions result for the smallest γ considered (γ ≤ 0.3), wherein cubic crystallization of the large particles is templated by interstitially mobile small particles. New mechanistic insight into factors influencing the yield of ordered binary structures includes the degree to which the smaller particles (ca. 15-24 nm) within the mixture undergo unary crystallization, as influenced by lysine or other basic amino acids used in the nanoparticle synthesis, as well as matching of the time scales for convective nanoparticle assembly and crystallization. Ultimately, the demonstrated robustness of the binary nanoparticle assembly and the control over silica particle size translate to a facile, template-free approach to OMSs with independently tunable pore topology and pore size.

Hard templating of symmetric and asymmetric carbon thin films with three-dimensionally ordered mesoporosity

Sacrificial colloidal crystal templating of porous carbon films of tunable thickness is demonstrated using a facile thin-film assembly and hard-template-based nanoreplication process. Convectively assembled, colloidal crystal films composed of size-tunable silica nanoparticles (ca. 10-50 nm) serve as scalable sacrificial scaffolds for the formation of thickness-tunable, structurally robust, and flexible porous carbon films. Both precursor vapor infiltration (PVI) and precursor immersion/spin-off (PIS) techniques, suitable for replication by various carbon sources (e.g., furfural/oxalic acid, phenol-formaldehyde, resorcinol-formaldehyde, sucrose), result in continuous, crack-free porous replica films. Systematic PVI-based underfilling of the template film or PIS-based complete spin-off of excess carbon replica precursor results in porous carbon films endowed with a symmetric three-dimensionally ordered mesopore (3DOm) topology uniformly distributed across the film thickness. Alternatively, by tuning the nanoparticle crystal film thickness and the degree of overfilling (PVI) or rate of spin-off of the carbon replica precursor (PIS), films bearing an asymmetric structure composed of 3DOm-supported ultrathin carbon layers can be realized. The stability of the silica templates under polymerization and carbonization conditions helps bolster mesopore robustness within the replica films, eliminating uniaxial pore shrinkage upon template sacrifice. The decoupling of the template assembly and its replication enables film formation from a wide range of carbon sources and possibly a further expanded materials palette. Realization of porous carbon films on various substrates without degradation of the mesostructure is enabled by robustness of the coating/replication process to characteristic surface roughness at scales several-fold larger than the template particle size as well as to polymer-mediated film transfer. Among various possible applications, we demonstrate how properties of the symmetric 3DOm films in particular (e.g., high surface area, large pore volume) enable their exploitation as potential low-cost alternatives to costly Pt-based electrodes for dye-sensitized solar cell (DSSC) technologies.

Monoclonal antibody purification by ceramic hydroxyapatite chromatography

Hydroxyapatite chromatography is shown to be an excellent method for chromatographically purifying monoclonal antibodies (Mab). Mab contained in eluates from Protein A columns was partially purified on ceramic hydroxyapatite (CHT™) Type I, 40 μm ceramic hydroxyapatite using two scouting methods which provide milligram amounts of Mab typical at laboratory scale. The result from one of the scouting methods was optimized to obtain a high concentration of purified Mab with acceptable clearance of cell culture impurities. Several techniques (linear phosphate screening, linear alkaline salt screening, and two alkaline salt step gradients) are described for obtaining high concentrations of purified Mab in a lab-scale CHT chromatography column.

Multivariate discrimination of host use by dwarf mistletoeArceuthobium vaginatum subsp.cryptopodum: Inter- and intraspecific comparisons

The parasitic dwarf mistletoeArceuthobium vaginatum attacksPinus ponderosa as its primary host andP. contorta as an occasional host. Within ponderosa pine stands there is also differential parasitism among individual trees. We compared biochemical features of phloem and xylem oleoresin between infected individuals of the two pine species (N=15 for each species) and also between infected (N=30) and nearby uninfected (N=30) ponderosa pine conspecifics. There were significant differences in chemical features, both at the interspecific (P. ponderosa vs.P. contorta) and intraspecific (P. ponderosa) levels. Discriminant function analysis based on chemical features of phloem correctly classified all trees used in the analysis as eitherP. ponderosa orP. contorta, and 95% of all ponderosa pine trees as either parasitized or nonparasitized. Monoterpene composition of oleoresin was distinct between species, and differences between parasitized and nonparasitizedP. ponderosa were also significant. Many of the observed chemical differences are probably constitutive, although levels of nonstructural carbohydrates and α-pinene may change in response to dwarf mistletoe infection. Biochemical differences at the intraspecific level were distinct from interspecific differences. Patterns of differential attack can have genetic consequences upon both the parasite and its hosts, and, in the process, may contribute to the evolution of host races of the parasite and to the evolution of host resistance within ponderosa pine.

Purification of β-lactoglobulin with a high-capacity anion exchanger: high-throughput process development and scale-up considerations

BACKGROUND

β-Lactoglobulin is the most abundant protein in bovine whey. It is a valuable nutriceutical with multiple physiological functions. There are many ongoing efforts to improve approaches by which this whey protein can be conveniently and economically purified in significant quantities. High-capacity resins for protein fractionation are currently available in the biotech industry. One such resin is evaluated in the present investigation.

RESULTS

This work describes a high-capacity ion exchange chromatography method for one-column fractionation of β-lactoglobulin from whey. It was obtained with a >90% purity. The dynamic binding capacity was measured in packed columns. Comparable value predicted on the basis of Langmuir isotherm analysis from batch adsorption data in a high-throughput 96-well format is shown. Scale-up considerations are discussed with respect to feed concentration and binding capacity.

CONCLUSIONS

The feasibility of preparing purified β-lactoglobulin with a single high-capacity anion exchanger step was demonstrated. A capacity of >200 mg mL(-1) was obtained. A significant improvement in productivity can be realized by a simultaneous increase of binding capacity and feed concentration.

Water Transport through Nanotubes with Varying Interaction Strength between Tube Wall and Water

We present the results from extensive molecular dynamics simulations to study the effect of varying interaction strength, ε_NT-OW, between the nanotube atoms and water's oxygen atom. We find the existence of a narrow transition region (ε_NT-OW ≈ 0.05 - 0.075 kcal/mol) in which water occupancy within a nanotube and flux through it increases dramatically with increasing ε_NT-OW, with the exact location defined by nanotube diameter and length. This transition region narrows with increasing nanotube diameter to nearly a step-change in water transport from no flow to high water flux between ε_NT-OW= 0.05 kcal/mol to 0.055 kcal/mol for tube diameter 1.6 nm. Interestingly, this transition region (ε_NT-OW= 0.05 - 0.075 kcal/mol) also coincides with water contact angles close to 90° on an unrolled nanotube surface hinting at a fundamental link between nanotube wetting characteristics and water transport through it. Finally, we find that the observed water flux is proportional to the average water occupancy divided by the average residence time within the nanotube, with a proportionality constant found to be 0.36, independent of the nanotube diameter and length.

Re-shuffling of species with climate disruption: a no-analog future for California birds?

By facilitating independent shifts in species' distributions, climate disruption may result in the rapid development of novel species assemblages that challenge the capacity of species to co-exist and adapt. We used a multivariate approach borrowed from paleoecology to quantify the potential change in California terrestrial breeding bird communities based on current and future species-distribution models for 60 focal species. Projections of future no-analog communities based on two climate models and two species-distribution-model algorithms indicate that by 2070 over half of California could be occupied by novel assemblages of bird species, implying the potential for dramatic community reshuffling and altered patterns of species interactions. The expected percentage of no-analog bird communities was dependent on the community scale examined, but consistent geographic patterns indicated several locations that are particularly likely to host novel bird communities in the future. These no-analog areas did not always coincide with areas of greatest projected species turnover. Efforts to conserve and manage biodiversity could be substantially improved by considering not just future changes in the distribution of individual species, but including the potential for unprecedented changes in community composition and unanticipated consequences of novel species assemblages.

Grain Boundary Defect Elimination in a Zeolite Membrane by Rapid Thermal Processing

Microporous molecular sieve catalysts and adsorbents discriminate molecules on the basis of size and shape. Interest in molecular sieve films stems from their potential for energy-efficient membrane separations. However, grain boundary defects, formed in response to stresses induced by heat treatment, compromise their selectivity by creating nonselective transport pathways for permeating molecules. We show that rapid thermal processing can improve the separation performance of thick columnar films of a certain zeolite (silicalite-1) by eliminating grain boundary defects, possibly by strengthening grain bonding at the grain boundaries. This methodology enables the preparation of silicalite-1 membranes with high separation performance for aromatic and linear versus branched hydrocarbon isomers and holds promise for realizing high-throughput and scalable production of these zeolite membranes with improved energy efficiency.

Hierarchical nanofabrication of microporous crystals with ordered mesoporosity

Shaped zeolite nanocrystals and larger zeolite particles with three-dimensionally ordered mesoporous (3DOm) features hold exciting technological implications for manufacturing thin, oriented molecular sieve films and realizing new selective, molecularly accessible and robust catalysts. A recognized means for controlled synthesis of such nanoparticulate and imprinted materials revolves around templating approaches, yet identification of an appropriately versatile template has remained elusive. Because of their highly interconnected pore space, ordered mesoporous carbon replicas serve as conceptually attractive materials for carrying out confined synthesis of zeolite crystals. Here, we demonstrate how a wide range of crystal morphologies can be realized through such confined growth within 3DOm carbon, synthesized by replication of colloidal crystals composed of size-tunable (about 10-40 nm) silica nanoparticles. Confined crystal growth within these templates leads to size-tunable, uniformly shaped silicalite-1 nanocrystals as well as 3DOm-imprinted single-crystal zeolite particles. In addition, novel crystal morphologies, consisting of faceted crystal outgrowths from primary crystalline particles have been discovered, providing new insight into constricted crystal growth mechanisms underlying confined synthesis.

Germania nanoparticles and nanocrystals at room temperature in water and aqueous lysine sols

Facile synthesis of nanometer-sized germania crystals and amorphous germania nanoparticles (ca. 1 nm) is investigated through hydrolysis of germanium tetraethoxide and subsequent condensation of germania in both pure water and aqueous lysine solutions. Germanium tetraethoxide rapidly hydrolyzes in pure water, leading to solvated germanate species at lower germania concentrations and the onset of nanometer-sized germania crystals at room temperature with increasing germania content. In the presence of the basic amino acid L-lysine, amorphous germania nanoparticles (ca. 1 nm) spontaneously form with increasing germania content and coexist with nanometer-sized germania crystals at higher germania concentrations. Lysine and germania concentration both influence crystallite size and morphology (i.e., polyhedral, cubic). The facile, room-temperature crystallization of germania in the presence and absence of lysine is striking. The fact that the crystal morphology shows no signs of nanoparticle aggregative assembly, as has been observed in the formation of other oxide crystals, suggests that crystal growth takes place by addition of dissolved species rather than nanoparticles, and could have implications for other oxide systems.

Hierarchical Nanomanufacturing: From Shaped Zeolite Nanoparticles to High-Performance Separation Membranes

Despite more than a decade of intense research on the high-resolution selectivity of thin zeolite films as alternatives to energy-intensive industrial separations, membranes consisting of intergrown, oriented zeolite crystals have fallen short of gaining wide commercial application. Factors including poor performance, high cost, and difficulties in scale up have contributed to this, and have also stunted their application in other niche markets. Until recently, rational design of these materials was limited because of the elusive mechanism of zeolite growth, and forced more empirical approaches. New understanding of zeolite growth along with recent advances in the molecular engineering of crystal microstructure and morphology, assembly of crystal monolayers, and synthesis of ordered films constitute a strong foundation for meeting stringent industrial demands in the future. Together with new processing capabilities, such a foundation should make it possible to synthesize commercially viable zeolite membranes through hierarchical approaches. Such advances open exciting prospects beyond the realm of separations for assembly of novel and complex functional materials including molecular sensors, mechanically stable dielectrics, and novel reaction-diffusion devices.

Silica nanoparticle crystals and ordered coatings using lys-sil and a novel coating device

Silica nanoparticles with a narrow particle size distribution and controlled diameters of 10-20 nm are synthesized via hydrolysis and hydrothermal aging of tetraethylorthosilicate in an aqueous L-lysine solution. Cryo-transmission electron microscopy (cryo-TEM) reveals that the silica nanoparticles assemble to form close-packed nanoparticle crystals over short length scales on carbon-coated grids. Evaporative drying of the same sols results in nanoparticle stability and remarkable long-range facile ordering of the silica nanoparticles over scales greater than 10 microm. Whereas small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) discount the possibility of a core (silica)-shell (lysine) structure, the possibility remains for lysine occlusion within the silica nanoparticles and concomitant hydrogen bonding effects driving self-assembly. Facile ordering of the silica nanoparticles into multilayer and monolayer coatings over square-centimeter areas by evaporation-induced self-assembly is demonstrated using a novel dip-coating device.

New trends and early clinical outcomes with a modern knee revision system

The incidence of revision total knee arthroplasty (TKA) has grown tremendously the past decade, and all projections suggest that it will continue to increase during the next 25 years. Although primary TKA remains one of the most successful orthopedic procedures, revision TKA has not as well. Failure rates for revision TKA remain significantly higher than those for primary TKA. New revision systems should be developed with new implants and instrumentation to address the difficulties frequently experienced with revision TKA. In this article, design surgeons report on the development of a new system and the early clinical experience with its use. The researchers believe that this new system is easy to use and facilitates accurate implantation, which could improve revision TKA outcomes.

The role of molecular interactions and interfaces in diffusion: Permeation through single-crystal and polycrystalline microporous membranes

In this second paper of a two part series, we investigate the implications of the interfacial phenomenon, caused by adsorbate-adsorbate interactions coupled with the difference in adsorbate density between the zeolite and the gas phase, upon benzene permeation through single-crystal and polycrystalline microporous NaX membranes. The high flux predicted for thin single-crystal membranes reveals that substantially enhanced flux should be expected in submicron films. Simulations also indicate that the standard local equilibrium assumption made for larger scale membranes is inapplicable at the submicron scale associated with nanometer size grains of thin and/or polycrystalline membranes. Apparent activation energies predicted for benzene permeation through NaX membranes via kinetic Monte Carlo (KMC) simulations are in good agreement with laboratory experiments. The simulations also uncover temperature-dependent flux pathways leading to non-Arrhenius behavior observed experimentally. The failure of the Darken approximation, especially in the presence of the interfacial phenomenon, leads to a substantial overprediction of the flux. Simulations of polycrystalline membranes suggest that this same interfacial phenomenon leads to resistance that can reduce flux by an order of a magnitude with only moderate polycrystallinity.

The role of molecular interactions and interfaces in diffusion: Transport diffusivity and evaluation of the Darken approximation

Kinetic Monte Carlo (KMC) simulations are carried out to directly study diffusion of benzene through thin (37-100 nm) NaX zeolite membranes under a gradient in chemical potential. Nonlinearities in adsorbate loading near the membrane boundaries are shown to arise from the difference in adsorbate density between the zeolite and adjacent fluid phase. Direct extraction of the transport diffusivity from gradient KMC simulations enables testing of the Darken approximation. This rigorous approach reveals limitations of the Darken approximation and, for the first time, the potentially complex nonunique functionality and multiplicity of the transport diffusivity for strongly interacting adsorbates. In the companion paper we explore these nonlinear interfacial effects in the context of permeation through both single-crystal and polycrystalline membranes.

Modeled regional climate change and California endemic oak ranges

In the coming century, anthropogenic climate change will threaten the persistence of restricted endemic species, complicating conservation planning. Although most efforts to quantify potential shifts in species' ranges use global climate model (GCM) output, regional climate model (RCM) output may be better suited to predicting shifts by restricted species, particularly in regions with complex topography or other regionally important climate-forcing factors. Using a RCM-based future climate scenario, we found that potential ranges of two California endemic oaks, Quercus douglasii and Quercus lobata, shrink considerably (to 59% and 54% of modern potential range sizes, respectively) and shift northward. This result is markedly different from that obtained by using a comparable GCM-based scenario, under which these species retain 81% and 73% of their modern potential range sizes, respectively. The difference between RCM- and GCM-based scenarios is due to greater warming and larger precipitation decreases during the growing season predicted by the RCM in these species' potential ranges. Based on the modeled regional climate change, <50% of protected land area currently containing these species is expected to contain them under a future midrange "business-as-usual" path of greenhouse gas emissions.

Molecular valves actuated by intermolecular forces

Phase behavior in nanostructured thin films under a gradient in chemical potential is studied via kinetic Monte Carlo simulation. Switching between saturated, partially saturated, and unsaturated states drives precipitous changes in permeation. This phenomenon could render nanostructured thin films as molecular valves, where adsorbate-adsorbate forces actuate the flow of molecules.

Molecular sieve valves driven by adsorbate-adsorbate interactions: hysteresis in permeation of microporous membranes

A recently derived mesoscopic framework describing activated micropore diffusion is employed to explore system criticality in microporous membranes under nonequilibrium conditions. Rapid exploration of parameter space, possible with this continuum framework, elucidates a novel temperature-induced ignition and extinction of the molecular flux under a macroscopic gradient in pressure (chemical potential). Deviation from equilibrium like phase behavior (i.e., shifting and narrowing of phase envelopes and double hysteresis) derives from asymmetry of the coupled boundaries of the nonequilibrium membrane. We confirm this new phase behavior, akin to "opening" and "closing" of a molecular valve, via gradient kinetic Monte Carlo simulations of thin one-dimensional and three-dimensional systems. The heat of adsorption, strength of adsorbate-adsorbate intermolecular forces, and chemical potential gradient are all shown to control 'valve' actuation, suggesting potential implications in chemical sensing and novel diffusion control.

Could CO(2)-induced land-cover feedbacks alter near-shore upwelling regimes?

The response of marine and terrestrial environments to global changes in atmospheric carbon dioxide (CO(2)) concentrations will likely be governed by both responses to direct environmental forcing and responses to Earth-system feedbacks induced by that forcing. It has been proposed that anthropogenic greenhouse forcing will intensify coastal upwelling in eastern boundary current regions [Bakun, A. (1990) Science 247, 198-201]. Focusing on the California Current, we show that biophysical land-cover-atmosphere feedbacks induced by CO(2) radiative forcing enhance the radiative effects of CO(2) on land-sea thermal contrast, resulting in changes in eastern boundary current total seasonal upwelling and upwelling seasonality. Specifically, relative to CO(2) radiative forcing, land-cover-atmosphere feedbacks lead to a stronger increase in peak- and late-season near-shore upwelling in the northern limb of the California Current and a stronger decrease in peak- and late-season near-shore upwelling in the southern limb. Such changes will impact both marine and terrestrial communities [Bakun, A. (1990) Science 247, 198-201; Soto, C. G. (2001) Rev. Fish Biol. Fish. 11, 181-195; and Agostini, V. N. & Bakun, A. (2002) Fish. Oceanogr. 11, 129-142], and these and other Earth-system feedbacks should be expected to play a substantial role in shaping the response of eastern boundary current regions to CO(2) radiative forcing.