Grape pomace, generated during wine making, is one of the most abundant and underutilized fruit-derived wastes on the planet. The large amount of pomace waste may present a serious environmental problem if not being properly disposed of. In the meantime, grape pomace contains valuable components that can be recovered or used as intermediates for the production of other chemicals or materials. Although many studies have been working on grape pomace utilization, they were limited to the production of a single product leading to the generation of secondary waste. Therefore, to make comprehensive utilization of grape pomace, a biorefinery approach converting grape pomace to multiple value-added products including seed oil, polyphenols, biofuels, and biochars was developed. Grape pomace was dried and ground to fine powders followed by pressurized hexane extraction to get seed oil. The oil-free solid residue was then extracted by ethanol and water mixture under the pressurized condition to obtain polyphenols. After extractives removal, NaOH was used to pretreat oil- and polyphenol-free solid residue to dissolve lignin which was further purified by acid precipitation. The lignin-partial-removed solid was then hydrolyzed by enzyme to obtain structural carbohydrate hydrolyzed sugars, which were used as fermentation medium for acetone-butanol-ethanol (ABE) production by Clostridium beijerinckii P260. The residual solid left after hydrolysis was pyrolyzed to biochar for potential heavy metal (lead) removal in contaminated water. Under optimized conditions, from 1 kg dry grape pomace, 71.9 g crude seed oil, 322.8 g crude polyphenols (equivalent to 72.6 g gallic acid), 20.7 g ABE, 219.3 g lignin, and 132.0 g biochars could be obtained. The biochars showed the lead adsorption capacities upward of 134 mg/g and followed pseudo-second-order kinetics, with 66.5% adsorption capacity reached in 30 min. The designed process shows a novel way of grape pomace utilization and has the potential to reduce winery waste disposal and promote a sustainable bioeconomy.

Toward a winery waste biorefinery: converting grape pomace to seed oil, polyphenols, biofuels, and biochar

Glioblastoma is the most aggressive solid tumor of the brain. Prior studies from our lab found that carmofur, an acid ceramidase inhibitor has shown promising results in suppressing and killing tumor cell lines compared to the FDA-approved drug temozolomide. In addition to glioblastoma, carmofur has also gained attention as a potential lead compound in a variety of diseases such as colorectal cancer, acute lung injury, and SARS-CoV-2 (COVID-19). Therefore, a sensitive bio-analytical method is required in order to quantify the drug in biological matrices for further preclinical and clinical studies. To the best of our knowledge, there is no liquid chromatography-tandem mass spectrometric (LC-MS/MS) method available for carmofur analysis. Therefore, a rapid, sensitive, and accurate LC-MS/MS method was developed for quantitative bioanalysis of carmofur in rat plasma. The method was validated for specificity, linearity, carry-over, accuracy, precision, dilution integrity, and stability according to the FDA guideline for bioanalytical method validation. The analyte was extracted employing liquid-liquid extraction using ethyl acetate and 2-propanol at 85:15 (v:v) ratio. Carmofur and internal standard (5-chlorouracil) were separated on an XBridge BEH C18 XP column (100 mm × 3 mm, 2.5 µm) column with a runtime of eight minutes. The multiple reaction monitoring (MRM) transitions were m/z 256.25 to m/z 129.00 for carmofur and m/z 145.10 to m/z 42.00 for 5-chlorouracil in negative electrospray ionization. Carmofur showed good linearity over the range of 5-1,000 ng/mL. The three quality control samples low (5 ng/mL), medium (100 ng/mL), and high (1000 ng/mL) showed acceptable recovery, matrix effect, accuracy, precision, and stability. This validated method can be applied for pharmacokinetic studies in rat plasma. Application of this method to other types of matrices is currently underway.

Development and validation of LC-MS/MS method for quantitative bioanalysis of carmofur in rat plasma

Earlier studies from our lab identified acid ceramidase as a novel target for glioblastoma. While acid ceramidase inhibitors are able to kill the tumor cell lines in vitro, a little is known about their blood brain barrier (BBB) permeability which is the most important consideration for glioblastoma drug development. Parallel artificial membrane permeability assay (PAMPA) is a technique that mimics passive and transcellular transmission which is the principal mechanism of BBB permeability for small molecules. PAMPA kit is composed of two parts, the donor plate, and the acceptor plate, and estimates the permeability from donor to acceptor plate over an incubation period. An important consideration while doing PAMPA is to use multiple controls ranging from low to high BBB permeability in order to evaluate the membrane integrity and validation of study results. PAMPA samples from acceptor and donor wells are analyzed using either ultraviolet-visible (UV-Vis) spectrophotometry or liquid chromatography-tandem mass spectrometry (LC-MS/MS). Although, the UV-Vis spectrophotometry is an easier, cost effective and faster technique, it can falsely report a result if the test compounds are unstable and multiple compounds in the solution absorb light at the same wavelength. To overcome this limitation, we developed a reliable LC-MS/MS method for the quantification of controls (ranitidine, naproxen, verapamil) and acid ceramidase inhibitors (carmofur, N-oleoylethanolamine, ARN14988). The compounds are retained on an XBridge BEH C18 XP column (100 mm × 3 mm, 2.5 µm) column with a run time of nine minutes. The multiple reaction monitoring (MRM) transitions for the compounds were m/z 256.26 to m/z 129.00 for carmofur, m/z 264.10 to m/z 147.10 for ARN14988, m/z 326.35 to m/z 62.05 for N-oleoylethanolamine. The developed methods were evaluated in terms of selectivity, linearity, carryover, intra-day and inter-day accuracy, precision, and stability. The method shows adequate sensitivity with application to PAMPA and work as complement to UV-Vis spectrophotometry.

PAMPA-BBB permeability of acid ceramidase inhibitors using LC-MS/MS and UV-Vis spectrophotometry

Mexico is a diversity rich country in culture, food. It has been related since pre-Hispanic times by the fermented beverages production such as tepache and pulque, where its consumption has been related to the health care. The Mexican Vanilla (Vanilla planifolia, Jackson) is considered one of the most important worldwide flavorings. Once it has harvested, it must undergo a traditional curing process to develop its characteristic aroma and flavor (more than one hundred compounds). Once it has cured, vanilla bean produces a large amount of aromatic, phenolic, organic acids, fatty acids and essential oil compounds, which together give it a high antioxidant capacity. The commercialized gourmet beans are in specific sectors, while the smaller pods are used to produce an alcoholic extract corresponding to 2-3% of the vanilla production. The present work aims to evaluate the use of small cured vanilla beans, subjecting them to a fermentation process using microorganisms to obtain a drink whit low alcohol content (digestive drink) rich in phenolic and aromatic compounds with antioxidant capacity. According to the preliminary results of the proximal chemical analysis, the cured beans contain a high amount of carbohydrates (79.26%) of which approximately 60% corresponds to fiber, which is partially hydrolyzed during the curing process by the endophyte flora. In such way these storage sugars and those from the hydrolysis of structural polysaccharides remain available to be fermented and obtain a beverage with flavor, aroma, quality and biological properties.

Production of a fermented beverage from vanilla coproducts

For the purpose of ensuring the bioavailability of bioactive ingredients, a nano-delivery system was developed using metal organic framework. Two kinds of zeolitic imidazolate framework-8 loading with curcumin (CCM@ZIF-8) was synthesized by high-temperature one-pot method and room-temperature two-steps method respectively. The characteristic of CCM@ZIF-8 particle was also demonstrated by the analysis of morphology and crystalline structure. From the results of FTIR and BET, CCM@ZIF-8 by high-temperature one-pot method (CCM@ZIF-8-HT) had encapsulated CCM molecular into the framework structure of ZIF-8, and those by room-temperature two-steps method (CCM@ZIF-8-RT) had a few curcumins embedded into the surface of ZIF-8. This difference lead CCM@ZIF-8-HT with higher curcumin encapsulation efficiency than CCM@ZIF-8-RT. An in vitro release study showed that 96.57±0.79% curcumin released from CCM@ZIF-8-HT during simulated gastric fluid transportation because ZIF-8 had no resistance to low pH environment. Compared to this, CCM@ZIF-8-RT could retained a large part of curcumin and transported to simulated small intense and colon, which related to the curcumin embedded into ZIF-8 and reduced the erosion from acidic medium. Furthermore, with room-temperature two-steps method, a ZIF-8 nanoparticle loading with BSA was synthesized. Similarly, this nanoparticle also exhibited controlled releasing profile for protein delivery. This study will make a development of MOF as carrier material in functional food.

Zeolitic imidazolate framework-8 applied in functional food for curcumin intestinal delivery

Aflatoxin B1 (AFB1) is a mycotoxin produced as a secondary metabolite by filamentous fungi such as Aspergillus flavus and Aspergillus parasiticus. Among other illness-related issues attributed to AFB1, according to the International Agency for Research on Cancer, there is evidence that it is carcinogenic. This mycotoxin proliferates mainly in nuts, spices, milk, and cereals, such as corn, rice, and amaranth. For that reason, many countries have set rules about the maximum AFB1 levels allowed in different food items (around the ppb range). The standard mycotoxin detection protocols rely on liquid or gas chromatography methods, in many cases coupled to mass spectrometry. These methods can detect AFB1 concentrations in the range of 1-20 ppt, but they are not very accessible, require tedious sample preparation, highly trained personnel, and expensive equipment. These requirements narrow their applicability in quality control by farmers and small to medium businesses, so novel sensors that overcome these drawbacks are needed. Herein, we present the development of a detection system based on gold nanotriangles (AuNTs) functionalized with mercaptopropionic acid (MPA) to induce the adsorption of the mycotoxin. Once the AFB1 is close to the AuNTs, these nanostructures' excellent optical properties make them act as nanoantennas capable of enhancing the mycotoxin's Raman signals in solution without the need of any additional reporter. A multivariate analysis method based on partial least squares (PLS) regression has also been implemented to process the surface-enhanced Raman scattering (SERS) spectra. Very promising results have been obtained, being able to selectively discriminate AFB1 content in amaranth extract solutions down to the ppb level.

SERS detection of aflatoxin B1 in amaranth using an optical nanosensor based on gold nanotriangles

The field of nuclear forensics and safeguards has seen increased importance in recent years. In particular, particle analysis has been an increasingly important component of these fields. In nuclear forensics, a specimen can be analyzed using a number of different techniques to narrow down its possible origin. The development of new, non-destructive analysis tools are an important part of refining this process to yield more accurate results. X-ray probes are a promising non-destructive method of providing additional information about specimens, particularly chemical speciation, which is not typically currently examined. To this end, prior work done using a Scanning Transmission X-ray Microscope (STXM) has shown that soft X-ray Absorption Spectroscopy (XAS) has demonstrated the ability to distinguish between many different uranium species, offering an opportunity to provide important information on a sample's origin. Current efforts are focused on improving a particle identification method by providing additional elemental and chemical information through x-ray fluorescence, as well as improving throughput to analyze particles more quickly.

Synchrotron X-ray techniques for nuclear forensics and safeguards particle analysis

Marine organisms, such as mussels and barnacles, are able to bond to surfaces under water using protein-based adhesives. Several physicochemical interactions contribute to the extraordinary adhesion and cohesive strength of these adhesive proteins, including oxidative crosslinking, hydrogen-bonding, metal coordination, hydrophilic interaction, π-π interaction and cation-π interaction. The cation-π interaction occurs between amino acids with an electron-rich π system (such as phenylalanine) and a cationic molecule (such as cationic ions Na+ and K+ or amino acids with a cationic charge such as lysine). Cation-π interaction involves highly hydrophilic/hydrated positively-charged functional groups as the cationic partner. Hydration shells, especially those surrounding cationic species, are known to be strongly bound to their cationic center, providing strongly repulsive forces and inhibiting any possible adhesive interactions. This observation raises the important question of the role of cation hydration shells in modulating cation-π interactions. We address this question by dissecting cation-π interactions between surfaces coated with peptides bearing π-donor and cationic residues. Without changing the composition of the peptides, we modulate their hydration shells by changing systematically their sequence, while monitoring the cation-π interaction by measuring the adhesion energyusing the surface forces apparatus. Engineered peptides with short sequences of phenylalanine (F) and lysine (K) amino acids were used and demonstrated the ability of forming the most efficient cation-π interactions reported for underwater adhesive systems in the literature to date. This outstanding cation-π binding efficiency was achieved only when an isolated K amino acid is flanked by F amino acids in the peptide sequence. The results provided in this study allow to rationalize the molecular determinants necessary for strong cation-π interactions and offer new avenues for the development of strong mussel-inspired underwater adhesive materials.

Bio-inspired superadhesive peptides with enhanced cation-π interactions

The mechanism of robust underwater adhesion of mussels has been the research highlight over the last two decades. Recently, it has been increasingly acknowledged that cation-π interaction plays an important role in underwater adhesion. In our previous study, we found that peptides with short sequences of phenylalanine (F) and lysine (K) amino acids capable of forming the efficient cation-π interactions when an isolated K amino acid is flanked by F amino acids. Surface force analysis and molecular dynamic simulation reveal that such sequence of amino acids minimizes repulsive hydration forces that prevent effective cation-π interactions. Recently, we furtherly study the impact of sequence on underwater adhesion of short peptides containing the motif of FKF, which is proved to be the smallest groups with underwater adhesion capacity based on our previous study. Using the surface force apparatus, we measured the adhesive force and cohesive force of peptide FKF and peptides with the sequence of XFKFX, where X can be glycine(G), serine(S) and glutamic acid(E). These peptides usually have the better capacity in cohesive mode. The most hydrophobic peptide GFKFG has the highest force in both mode which furtherly prove that removal of water molecule layer on peptides surfaces is very important for the cation-π interaction. We also found there is a relationship between the peptides film thickness and adhesive or cohesive force. Peptides can have strong interaction when there is monolayer on surfaces and when peptides self-assembly, the thickness increases, and the peptides lost most of adhesion capacity. The results provided in this study further explore the mechanism of cation-π interactions acting in underwater adhesion and provide useful insights into the design and development of high-performance underwater adhesives.

Impact of sequence on underwater adhesion of short peptides wtih cation-π synery

Using past and contemporary anecdotal experiences, the speaker will demonstrate how creativity can impact innovative solutions in STEM related industries. Several topics will include: where do ideas come from, what sparks creativity, what macro trends drive new ideas, the important differences between collaborative and personal creativity, and the importance of integrating your passions to ‘make it your own’. Finally, we’ll discuss the use of creativity in selling your idea both internally as well as externally to your customer with the eventual endgame being to monetize your creativity, put some of the profits back into your creativity process, and start again. Wear, wash, rinse, and repeat!

Creativity drives success in STEM innovation

One of the most well-known chemical processes is the synthesis of ammonia by the Haber-Bosch process. However, there are several drawbacks including the high pressure and high temperatures required and the dependence on hydrogen gas which comes from steam-methane reforming and leads to a large carbon footprint. Among the various alternative approaches being studied, electrolytic approaches that can be integrated with renewable sources such as solar and wind and operate near ambient conditions are the most attractive. Unfortunately, to date, these methods have suffered from low yields and selectivities associated with the catalyst and their high overpotentials and preference for the hydrogen evolution reaction. In this talk, I will present a new electrolytic approach to ammonia synthesis from nitrogen and water based on non-equilibrium, atmospheric-pressure plasmas in contact with water surfaces. Distinctly, nitrogen is reduced without a catalyst by the unique interactions of the plasma and water. Specifically, electrons in the plasma potentially excite or even dissociate the nitrogen molecule in the gas phase, and solvate to produce one of the strongest reducing agents known. Remarkably, we find that for certain configurations and certain processing conditions, ammonia is synthesized with 100% charge-transfer (faradaic) efficiency. To make the process continuous and potentially overcome mass transport issues, we have recently also developed a plasma-droplet reactor in which water droplets flow through a plasma. Studies to reveal key reaction intermediates and potential reaction mechanisms in support of results in both reactors will be discussed.

Catalyst-free, electrolytic synthesis of ammonia from nitrogen and water by atmospheric-pressure plasma processes

The photochemistry of polyoxovanadates has been studied using electrochemistry, X–ray crystallography, gas chromatography, IR and electron paramagnetic resonance (EPR) spectroscopy. These materials show potential as photoresponsive catalysts that can operate in an aqueous environment. The photoreduction reaction of V(V) to V(IV) in the respective tartrates is presented and discussed. Additionally, it is possible to use light to switch between different oxidation states through the presence of a mixed valence [V(V)/V(IV)] intermediate species. Irradiation at 365 nm (175 mW/cm2 LED source) causes solutions of V(V) tartrate to change from orange yellow through green to brownish purple, developing a characteristic three–band absorption spectrum with maxima corresponding to a V(IV) photoproduct. The crystal structures as characterized by X–ray crystallography reveals that the initial V(V) species is tetranuclear Na5 [V4O8(2R,3R)-tart) (2S,3S)-tart)] and the final photoproduct is dinuclear Na4 [(VO)2(2R,3R)-tart) (2S,3S)-tart)]. EPR spectroscopy confirms that reduction from diamagnetic V(V) to paramagnetic V(IV) takes place, with the growth of an 8-line V(IV) hyperfine pattern over time, with the corresponding color change. This suggests that the odd electron is located on a mixed valence intermediate. Gas chromatography and IR spectroscopy showed that CO2 is produced during photolysis of this system, indicating catalytic oxidation of the hydroxy acid. The process is reversible, suggesting that novel macroscopic photoresponsive effects in molecules and materials may emerge from this photochemistry. We now expect to develop interesting macroscopic effects with the light responsive properties of Vanadium at the molecular level in cellulose-agarose hydrogels.

Reversible photoresponse in vanadium(V) tartrate clusters containing a mixed-valent intermediate

Bioenergy and bioproducts have traditionally been developed as separate biomass processing technologies such as pyrolysis, combustion, gasification etc. However, there are several obstacles to the full commercialisation of bioenergy and bioproducts via these technologies, which include the resourcing of biomass, inadequate biomass refinery technologies, a lack of cost-competitive bioproducts and a limited and/or unstable supply of biofuels and bioproducts. The biomass processing technologies of the future needs a whole life cycle approach to processing to ensure its economic sustainability by maximising the potential of the feedstock valorisation. In this study, the potentials of different biomass feedstocks (Rapeseed, Whitewood and Seaweed) in integrated hydrothermal processing technologies (gasification, liquefaction, and carbonisation) were investigated for bioproducts and bioenergy applications. Hydrothermal treatments of these biomass feedstocks were investigated in a continuous hydrothermal process rig under the following conditions: 100°C (4-180bar) for low-temperature extraction, 200°C (55-240bar) for carbonisation, 300°C (140-240bar) for liquefaction and 375°C (240bar) for gasification at 1.5-2.0 h. The extracted liquefied bioproducts were identified using high-performance liquid chromatography (HPLC). The hydrochars (or residues) were investigated in energy and water treatment applications as the potential integrated processes applications. The energy applications of hydrochars were identified with intrinsic reactivity in the thermogravimetric analysis (TGA); approximately 15-25 mg of hydrochar (or residue) was heated from ambient temperature to 900 °C with a heating rate of 5 °C/min under an airflow rate of 100 ml/min. The combustion kinetics of the hydrochars and raw biomasses were identified using the distributed activation energy model. The water treatment applications were carried out in dye (methylene blue) adsorption; 20 mg of hydrochar with 10 mL of 300 mg/L methylene blue solution at 30 °C using an incubator at 160 rpm and the dye solutions were then analysed by UV–Vis spectrophotometry. The water treatment and energy applications were assessed as the integrated process to hydrothermal processing technology for different biomasses feedstocks and the optimal routes were identified for each kind of biomasses with a life cycle analysis model to establish the environmental impact of the integrated process.

Optimisation of hydrothermal processing technologies for different kind of biomass feedstocks: Integration of water treatment technology

Metal catalyzed cross coupling and olefin isomerization are synthetically useful and versatile tools in the synthesis of key building blocks. The most crucial challenge is the control of selectivity. Site-selective and sequential cross-couplings of poly(pseudo)halogenated arenes leads to densely functionalized arenes, whereas regio- and stereo-control of an olefin is key for its properties as well as follow up transformations. Metal catalyzed olefin isomerisation often requires dry and inert conditions. In this report, we present a new air-stable PdI dimer, [Pd(µ-I)(PCy2tBu)]2, which enables efficient E-selective olefin migration to enamides and styrene derivatives in air. The presented dimer also triggers rapid and chemoselective C-C functionalization (alkylation and arylation), allowing us to achieve a triply selective sequence of poly(pseudo)halogenated arenes.

Olefin transposition and modular functionalization of arenes in a triply selective sequence enabled by a next generation air-stable palladium(I) dimer in air

In order to gain a better understanding the gas-surface reactions on heat shields during hypersonic flight through air, we have used molecular beam-surface scattering experiments to study reactions of O and N atoms on high-temperature carbon surfaces. The experiments were performed with both pulsed and continuous molecular beams of O or N atoms and, in some cases, mixed beams containing O and N atoms. The reactive scattering dynamics of O on various carbon surfaces suggest that the oxidation mechanisms on all sp2 types of carbon are similar but that surface morphology influences the relative importance of the individual mechanisms. All products exhibited the dynamical characteristics of thermal desorption. The efficiencies of the gas-surface interactions, both reactive and non-reactive, were quantified as a function of surface temperature. In addition to reacting with carbon to produce CO2 (minor product) and CO (major product), oxygen atoms may recombine on the surface to produce O2 with an efficiency that is somewhat lower than that to produce CO. Nitrogen atoms may recombine on the surface to produce N2 or react to produce CN. The recombination efficiency of N atoms is generally more than an order of magnitude higher than the reaction efficiency to produce CN. Even a small percentage of N atoms in the presence of O atoms can increase the reactivity of O atoms on a carbon surface by more than 50%. The data from these studies have been used in the formulation of oxygen-carbon ablation models.

Molecular beam studies of O and N reactions on carbon at high temperatures

Biofilms form at the interface of condensed matters by bacterial activities. They affect our daily lives as well as industrial processes in various ways. Solving biofilm problems need intensive investigations. For this purpose, we need biofilm reactors and also some proper evaluation processes. In our experiment, we invented a new type of biofilm reactor used in laboratories to form biofilms on materials' surfaces. This apparatus makes us possible to form biofilms by using environmental biota. Usually, for most biofilm laboratory biofilm reactors, single bacterial species are used. However, this apparatus uses unknown bacterial species. In this presentation, we will show the appearance of the apparatus, the principle, the unique characteristics compared with other conventional ones. Biofilms generally form, so that bacteria in oligotrophic environments would survive. Therefore, bacteria seeking nutrition must exist in the system. This apparatus always makes it possible for us to utilize bacteria having a high potential capability of biofilm formation since the system would always contain plural bacteria. Some of the bacteria in the system could form biofilms well. Some concrete results using some metallic, polymeric, and ceramics materials will be shown as examples.

New laboratory biofilm reactor using environmental biota and its characteristics

The generation of industrious waste and the burning of fossil fuels has created an existential crisis for modern society, whereby solutions to these problems will require the innovation of waste-to-energy technologies that simultaneously meet renewable energy demands without further contributing to the problem. Microbial fuel cells (MFCs) are a promising technology which utilize microbe-substrate interactions as a vehicle for green energy production. Therefore, expanding the utility of waste-to-energy technologies will require the development of tunable biopolymer composites to address the major charge transfer limitations in current MFC designs. This work aims to design a conductive polysaccharide network (i.e., agarose and alginate) using thermal and photochemical radical initiated polymerization of polyaniline at the decarboxylated regions of the polymer backbone. Initial results indicate that the addition of photochemically polymerized polyaniline established uniform distributions of conducting polymer throughout the polymer matrix. Current voltage (I-V) sweeps of photopolymerized polyaniline composites show enhanced current flow and reduced internal resistance compared to current carbon cloth technologies, as well as thermally polymerized (no UV light) and non-functionalized polysaccharide systems. Additionally, I-V performance is highly dependent on the type of photoinitator (i.e., Fe3+, Cu2+, camphor) incorporated into the polymer network, highlighting the importance of coordinated complexation between the photoinitator and the carboxylate groups along the polysaccharide backbone. These enhanced current-voltage properties have been realized in a mediator-less E. coli MFC system over a period of 48 hours, with the mediator-less system exhibiting increased open circuit potentials comparable to similar mediated carbon cloth MFC systems. In addition to I-V performance, the application of conductive bioscaffold polymer electrodes in MFCs indicate the vast capacity of these tunable composites to be used as a conduit for various mediator-less electron transfer applications.

Development of polymer nanocomposite electrode for enhanced mediator-less electron transfer in microbial fuel cells

A few compounds with polar crystal structures existing in the Ag/Cu-Ge-Q (Q = S, Se, Te) phase diagrams have been reported as promising thermoelectric materials with low thermal conductivities. Ag2GeS3 was identified as another promising thermoelectric compound based on its polar crystal structure (space group Cmc21) and relationship with previously reported thermoelectric materials. Polycrystalline Ag2GeS3 sample was synthesized through a simple one-step solid-state method at high temperature and consolidated into a dense pellet via spark plasma sintering (SPS). The high-temperature thermoelectric properties measurements reveal a very low thermal conductivity of the dense pellet. A possible structural conversion from Ag2GeS3 to Ag10Ge3S11 and GeS2 was observed during the SPS process. The thermal stability of Ag2GeS3 is currently under further investigation with in-situ synchrotron powder X-ray diffraction technique in addition to the thermogravimetric analysis and differential scanning calorimetry measurements. Density functional theory calculations will be preformed to understand the origin of the low thermal conductivity and compare it with the experimental result.

Thermal stability and low thermal conductivity of Ag2GeS3 and Ag10Ge3S11

Reactive-atom scattering (RAS) has recently been demonstrated to be an interesting addition to the armoury of tools available to analyse the composition of liquid surfaces. The method relies on the selective chemical reaction of a chosen gas-phase probe atom with particular functional groups exposed at the surface of a liquid. Because reactions that take place at the extreme outer layers of the liquid can be distinguished by their dynamical characteristics, RAS has inherently high surface sensitivity combined with chemical specificity. Its application is illustrated in liquids of practical interest, consisting of mixtures of a common family of ionic liquids containing alkyl and fluoroalkyl chains of different lengths. These materials have interesting potential applications as solvents in multiphase catalysis, where the properties of the stationary phase can be tuned controllably through the variation in mole fraction of the base materials. The composition of the outer surface is not known trivially, because of the balance between competing intermolecular forces in these chemically heterogeneous materials. We present experimental results combining O(3P) atoms as the RAS probe with detection of the OH product of selective reaction with exposed alkyl chains by laser-induced fluorescence. We compare the OH yields with molecular dynamics (MD) simulations of the structures of the liquid surfaces, and discuss how improved understanding of dynamical factors would further enhance the analytical information that can be extracted from the measurements. We will also consider briefly how the methodology might be generalised to detect a wider range of exposed functional groups.

Dynamical factors in reactive-atom scattering used to probe ionic-liquid surfaces

Quantitative analysis has been well studied and frequently used in chemistry and biology in recent years. Although many a concept and strategy of quantitative analysis has been presented in current analytical chemistry curriculums such as the linear relationship between the absorption and concentration of analytes based on Beer's law in spectroscopy and peak area/height quantification in chromatography. However, these quantitative approaches are currently dispersed among different analytical methods, such as spectroscopy, chromatography and so on. So far, there has not been a section specifically devoted to quantitative analysis in chemistry or even biology classes. Therefore, most students still have vague and unclear ideas about quantitative analysis, sometimes lacking of awareness of quantity when faced with practical problems. PCR presents an alternative for demonstration of quantitative analysis because various PCR techniques are designed for different analytical purposes. Therefore, in this article, we take conventional, real-time and digital PCR as examples to introduce semi-, relative and absolute quantification to students in a section of the bioanalytical chemistry curriculum. The basic principle and theories of three PCR techniques for quantification are demonstrated and derived in detail. This will help students obtain comprehensive knowledge of quantitative analysis by studying the theoretical principles of different PCR techniques and will help them further understand the applications by comparing the characteristics of semi-, relative and absolute quantification. This tutorial report is a creative attempt to combine the teaching of chemistry with biology and present the theoretical principles in a new way, which we believe will be a helpful complement to teaching theoretical concepts in analytical chemistry and biochemistry courses.

Introducing theoretical principles of semi-, relative and absolute quantification via conventional, real-time and digital PCR to graduate and senior undergraduate students of chemistry

In aqueous solutions proteins can undergo a variety of different phase behaviours, inlcuding liquid-liquid phase separation and reentrant condensation. The latter process has been observed in solutions containing charged globular proteins in the presence of oppositely charged multivalent ions. Reentrant condensation is characterised by the formation of a condensed protein regime between two critical ion concentrations. Formation of the condensed regime is thought to be driven by neutralization and inversion of the protein charge by the ion. Similarly, decondensation at the upper boundary is caused by overcharging of the protein by the ion, resulting in long-range electrostatic repulsion between protein molecules. Recently, reentrant condensation of the cationic globular protein lysozyme by the polyvalent anions pyrophosphate and tripolyphosphate, but not by cirtrate was observed. Despite the fact that citrate has similar charge and size to pyrophosphate. Therefore, besides electrostatic interactions, other specific interactions between the polyphosphate ions and the protein, contribute. Here, we show that additional attractive interactions between arginine residues and tripolyphosphate determine the reentrant condensation and decondensation boundaries of the cationic, intrinsically disordered saliva protein, Histatin 5. Furthermore, we show by SAXS that polyvalent anions cause compaction of Histatin 5, above what is expected based solely on electrostatic interactions. Hence, we conclude that arginine-phosphate specific interactions not only regulate solution properties but also influence the conformational ensemble, which, is shown to vary with the number of arginine residues. Together the results presented here provide further insight into a organizational mechanism that can be used to tune protein interactions in solution of both naturally occurring and synthetic proteins.

The impact of arginine-phosphate interactions on the reentrant condensation of the intrinsically disordered histatin 5 protein

One of the solutions adopted to palliate water scarcity, especially in hyper-arids area is the recycling of wastewater as a water source for irrigation for crops and other vegetables. However, wastewater, treated or not, is a source of emerging contaminants (ECs). Plants have a tendency to uptake chemicals present in soil. This presentation summarized, three examples of the uptake, metabolism and translocation of ECs into crops, following uptake via the roots and subsequent distribution to other plant tissues. Two of them are based on laboratory studies carried out under controlled conditions to study the fate of three emerging contaminants ibuprofen (IBU), carbamazepine (CBZ) and tris(chloroisopropyl)-phosphate (TClPP) in beans (Vigna ungiculata) or spinach (Spinacea oleracea). In the third example, water, sediment/soil, natural vegetation and crops intended for human consumption were taken from several stations in Riyadh (Saudi Arabia). The area was under the influence of the south wastewater treatment plant and includes the artificial pond that receives the effluent (through a channel) also used to irrigate surrounding crops. Samples were extracted by solvent extraction and cleaned up using solid-phase extraction (SPE). The identification of ECs and some of their metabolites was carried out using an UHPLC in tandem with a high resolution mass spectrometry (HRMS) TripleTOF™ 5600 LC/MS/MS System manufactured by AB SCIEX. IBU and CBZ are able to form also a number of metabolites and/or degradation products. Contrarily, at the moment no metabolites of TClPP were identified. The concentrations of CBZ and TClPP in Spinach were higher in leaves than in roots. Presence of IBU was also detected in V. Unguiculata with a higher number of metabolites. The study performed in IBU showed concentration in roots far above those in leaves, in agreement with other studies. In the field experiments, pharmaceuticals carbamazepine, 10,11-epoxycarbamazepine, caffeine, atenolol, gemfibrozil, naproxen and ibuprofen hexoside were identified in few vegetables at concentrations ranging from 35 to 125 ng g−1. Diazinon, atrazine deethyl, malathion, azoxystrobin, bupirimate, acetamiprid, imidacloprid and pirimicarb were found in these vegetables. These examples showed the irreplaceable role that HRMS can play in the identification of complex mixtures of ECs as well as metabolites and/or degradation products

Profiling the uptake, metabolism and translocation of emerging contaminants from water and soil to plants by liquid chromatography-high resolution mass spectrometry

Layered intermetallic kagomés have served as an ideal platform to study the exotic phenomenon associated with flat bands and Dirac-type dispersions. It is essential to explore the electronic properties of these structures for the experimental realization of 2D kagomé lattice in bulk materials. We explore a specific type of MT6X6 compound where M = Mg, T = Co and X = Ge. Single crystals of MgCo6Ge6 were grown by laser Bridgman technique. X-ray precession images and electron diffraction measurements collected at T = 293(2) K show that the compound crystallizes in space group P6/mmm, with a = 5.06094(15) Å, c = 7.7271(2) Å. Residual electron maps provide evidence of columnar disorder along c axis. Further investigation of the crystal structure reveals spontaneous twisting of the Co kagomé layers. We look into crystal orbital hamiltonian population analysis to understand the cooperative twisting between layers within the Co-kagomé network and the interlayer tetragonal bonding. Despite the appearance of static tilting, no evidence for a phase transition was found in magnetization, resistivity, or specific heat measurements, implying that the twisting exists at all temperatures, but is thermally fluctuating at room temperature. This behavior is further supported by looking into related materials to understand the pairwise twisting and bonding in layered structures.

Laser Bridgman growth, columnar disorder and low temperature twisting of kagomé layers in intermetallics

Tumor-derived exosomes are considered as potential biomarkers for early non-invasive cancer diagnosis. Although quite a few methods have been reported for quantitative detection of exosomes, the nanoparticle tracking analysis (NTA) and BCA protein assay are most commonly employed. However, NTA instrument is expensive and requires a large volume of sample, preventing its widespread application. Whereas BCA assay will lead to inaccurate results due to heteroproteins obtained during isolation process. Therefore, it is still necessary to develop more practical and accurate methods for quantification of exosomes derived from various samples. Here, we designed a PDMS microfluidic chip with a simple cross channel (figure1). The depth of both channels is 600 um and all channels and wells are open to the air for convenient manipulation. First, 3% of agarose was injected into the gel channel and the other channel was filled with TAE buffer only. After that, 10 μL of exosomes (from A375 cell line) pre-stained with PKH67 dye was injected into the sample well. Fluorescence intensity was recorded by a home-made detection system.When a voltage of 100V was applied at the both end wells of electrophoresis channel, the PKH67 stained exosomes migrated to the anode which were found not able to enter 3% agarose gel in short time, thus enriched at the interface of the gel/buffer. Accordingly, the fluorescence intensity of exosomes was accumulated as well. Under optimized conditions, a linear range of 2×107-1×1011 particles/mL is obtained and 1×107 particles/mL of detection of limit (LOD) was achieved. In summary, we proposed a simple and practical method as a universal tool for quantitative detection of exosomes. The process of electrophoresis and detection was within 10 minutes and the performance is equal to NTA. But only 10 μL of exosome sample was required.

Rapid enrichment and sensitive detection of exosomes by electrophoresis in a microchip

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.