Publications
171 results found
Varshitha G, Othman A, Colin B, et al., 2023, Determining the hydrophobicity index of protected amino acids and common protecting groups, Separations, Vol: 10, Pages: 1-11, ISSN: 2297-8739
Peptides are in great demand in the pharmaceutical arena and a majority of these peptides contain 20 or more amino acids. They are infrequently synthesised using the fragment condensation approach. A key limitation in adopting this approach more commonly is that protected peptide fragments with high purity are often required prior to the final condensation steps. It is hypothesized that understanding the hydrophobic nature of the protected amino acids will assist with designing optimal fragment purification processes when needed. Whilst a myriad of hydrophobicity indices are reported in the literature for unprotected amino acids, the literature lacks any data regarding the protected amino acids which form the key precursor for the fragment condensation task. In this current study, hydrophobicity indices for protected amino acids with common α-amino and sidechain protecting groups were experimentally determined. Different positions for each amino acid within the peptide chain were considered, namely at the C-terminal and N-terminal as well as internal positions. These data give deep insights on the hydrophobicity of each amino acid with respect to its position in the peptide chain. The data acquired in this research facilitated the prediction of the retention time of protected peptide fragments with an uncertainty of less than ±1.5%.
Saenz Cavazos P, Hunter-Sellars E, Iacomi P, et al., 2023, Evaluating solid sorbents for CO2 capture: linking material properties and process efficiency via adsorption performance, Frontiers in Energy Research, Vol: 11, Pages: 1-22, ISSN: 2296-598X
Expanding populations and growing economies result in higher energy needs. Meeting this increasing demand, while lowering carbon emissions, calls for a broad energy mix and commercial deployment of solutions like carbon capture and carbon removal technologies. The scale-up of these solutions is partially hindered by the lack of materials-related information, particularly in the case of solid adsorption-based carbon capture technologies. Furthermore, experimental measurement parameters used and how data is presented lack uniformity, which makes material comparisons extremely difficult. This review examines the current state of solid sorbent characterization for carbon capture, exploring physical and chemical properties, performance parameters, and process indicators. Adsorbent performance parameters demonstrate to be the crucial link between intrinsic material properties and the overall adsorption process effectiveness and therefore are the focus of this work. This paper outlines the relevant techniques used to measure Key Performance Indicators (KPIs) related to adsorption performance such as CO2 adsorption capacity, selectivity, kinetics, ease of regeneration, stability, adsorbent cost, and environmental impact. Additionally, this study highlights the relevant experimental conditions for diluted versus concentrated CO2 streams. Lastly, efforts in harmonizing experimental data sets are considered, and an outlook on solid sorbent characterization for carbon capture processes is presented. Overall, the aim of this work is to provide the reader a critical understanding of KPIs from atomic to process scale, highlighting the importance of experimental data throughout.
Kondor A, Burnett DJ, Bismarck A, et al., 2023, Correct specific retention volume determination in inverse gas chromatography, JOURNAL OF CHROMATOGRAPHY A, Vol: 1700, ISSN: 0021-9673
Almusaimi O, Williams D, 2023, Methods of Chemical Synthesis of Peptides - GB2309538.3, Patent
Mohamed NAN, Han Y, Harcourt-Vernon S, et al., 2023, Effects of surfactant head group modification on vertically oriented mesoporous silica produced by the electrochemically assisted surfactant assembly method, NANOSCALE ADVANCES, Vol: 5, Pages: 3316-3325, ISSN: 2516-0230
Hausmann A, Buck B, Shaw L, et al., 2023, The importance of humidity control in powder rheometer studies, POWDER TECHNOLOGY, Vol: 421, ISSN: 0032-5910
McIntyre SR, Hunter-Sellars E, Saenz-Cavazos PA, et al., 2023, Novel zero-length column analysis of desorption curves for single cylindrical pellets, POWDER TECHNOLOGY, Vol: 416, ISSN: 0032-5910
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Al Musaimi O, Morse SV, Lombardi L, et al., 2023, Successful synthesis of a glial-specific blood-brain barrier shuttle peptide following a fragment condensation approach on a solid-phase resin, Journal of Peptide Science, Vol: 29, Pages: 1-9, ISSN: 1075-2617
Successful manual synthesis of the TD2.2 peptide acting as a blood-brain barrier shuttle was achieved. TD2.2 was successfully synthesised by sequential condensation of four protected peptide fragments on solid-phase settings, after several unsuccessful attempts using the stepwise approach. These fragments were chosen to minimize the number of demanding amino acids (in terms of coupling, Fmoc removal) in each fragment that are expected to hamper the overall synthetic process. Thus, the hydrophobic amino acids as well as Fmoc-Arg (Pbf)-OH were strategically spread over multiple fragments rather than having them congested in one fragment. This study shows how a peptide that shows big challenges in the synthesis using the common stepwise elongation methodology can be synthesised with an acceptable purity. It also emphasises that choosing the right fragment with certain amino acid constituents is key for a successful synthesis. It is worth highlighting that lower amounts of reagents were required to synthesise the final peptide with an identical purity to that obtained by the automatic synthesiser.
Almusaimi O, Mercado-Valenzo OM, Williams DR, 2023, Factors influencing the prediction accuracy of model peptides in reversed-phase liquid chromatography, Separations, Vol: 10, Pages: 1-37, ISSN: 2297-8739
Hydrophobicity is an important physicochemical property of peptides in solution. As well as being strongly associated with peptide stability and aggregation, hydrophobicity governs the solution based chromatographic separation processes, specifically reversed-phase liquid chromatography (RPLC). In addition, hydrophobicity is a major physicochemical property of peptides in comparison to H-bonding, electrostatic, and aromatic properties in intermolecular interactions. However, a wide range of molecular factors can influence peptide hydrophobicity, with accurate predictions depending on specific peptide amino acid compositions, structure, and conformation. It is noticeable that peptide composition, the position of the amino acid, and its neighbouring groups play a crucial role in the elution process. In light of this, the same amino acid behaved differently depending on its position and neighbouring amino acid in the peptide chain. Extra attention should be paid to the denaturation process during the course of elution, as it has been shown to complicate and alter the elution pattern. This paper reports on the key peptide properties that can alter hydrophobicity and, consequently, the RPLC elution behaviour of the peptides, and it will conclude by proposing improved prediction algorithms for peptide elution in RPLC.
Al Musaimi O, Gavva V, Williams DR, 2023, Greener cleavage of protected peptide fragments from Sieber Amide Resin., ChemistryOpen, Vol: 11, Pages: 1-7, ISSN: 2191-1363
Following the successful introduction of two benign solvents for cleaving protected acid peptide fragments from 2-chlorotrityl chloride (2-CTC) resin, there is a need to green the cleavage process for obtaining protected peptide amide fragments. In this work, p-xylene and toluene are introduced as greener alternates to dichloromethane (DCM) for preparing protected peptide amide fragments from a Sieber amide resin. The N-dealkylation is a demanding chemical reaction, requiring that the cleavage protocol be optimised to ensure complete cleavage from the resin. After a 30 min reaction time, only 66 % of the final peptide product was retrieved even with the conventional dichloromethane solvent. Therefore, 120 min was considered sufficient to fully cleave the peptide from the Sieber amide resin. This work reaffirms the fact that greening strategies are far from detrimental, with green alternatives often outperforming their replaced counterparts.
McIntyre SR, Saenz-Cavazos PA, Hunter-Sellars E, et al., 2023, Product selectivity and mass transport in levulinic acid transfer hydrogenation by monolithic MIL-100, MIL-88B and ZIF-8@Pd MOFs, FRONTIERS IN CHEMISTRY, Vol: 10, ISSN: 2296-2646
Cheung PCW, Williams DR, Kirk DW, et al., 2023, Decolourisation of Metal-azo Dyes in Wastewaters by Sodium Peroxodi sulphate: A Template for Experimental Investigations, Open Environmental Research Journal, Vol: 16
Background: It has long been recognized that the presence of azo metal complex dyes and their non-complexed counterparts in wastewaters, which is due totheir manufacturing and use in the textile industries, renders natural waterways intensely coloured, and is therefore aesthetically unacceptable. Azodye moieties are also known to be precursors of human carcinogenicity. Objective:This work aimed at the decolourisation of metal-azo dyes present in wastewaters so that pollution of natural bodies of water can be prevented. Decolourisation is indicative of the destruction of the metal-ligand complex, allowing the retrieval of transition metal ions, which are also water contaminants. Fracturing of the azo bond itself minimizes the potential for the carcinogenicity of these dyes. Methods: Decolourisation is achieved by the oxidative action of free radicals furnished by Na2S2O8, the sodium salt of peroxodisulphuric acid (Marshall’s acid). Raman spectroscopy characterizes the dye (ligand) known as “Eriochrome Black T (EBT)” by a peak at 1425 cm-1. Dismantling of its molecular structure by peroxodisulphate will lead to decolourisation accompanied by the collapse of the peak. Concomitantly, as EBT ligands fracture and cease to chelate, metallic ions are released, oxidized to a higher oxidation state, and precipitated as insoluble compounds in alkaline media. Results: The concentration of metallic ions in the aqueous phase has been found to be substantially reduced. The successfully treated dye solutions aremostly clear and colourless; their Beer-Lambert absorbances are in the range of 0.02 ≤ absorbance ≤ 0.05. The treatment of Ni(II), Co(II) and Fe(II)-EBT solutions is straightforward; the Cu(II) and Cr(III)-EBT solutions require additional treatment to be included in the above absorbancerange. The Cr(III)-EBT is the least responsive to treatment. Fracturing of the azo bond is evinced by Raman Spectroscopy. Conclusion:A template to investigate the feasi
Al Musaimi O, Valenzo OMM, Williams DR, 2023, Prediction of peptides retention behavior in reversed-phase liquid chromatography based on their hydrophobicity, Journal of Separation Science, Vol: 46, Pages: 1-17, ISSN: 1615-9306
Hydrophobicity is an important physicochemical property of peptides and proteins. It is responsible for their conformational changes, stability, as well as various chemical intramolecular and intermolecular interactions. Enormous efforts have been invested to study the extent of hydrophobicity and how it could influence various biological processes, in addition to its crucial role in the separation and purification endeavor as well.Here, we have reviewed various studies that were carried out to determine the hydrophobicity starting from (i) simple amino acids solubility behavior, (ii) experimental approach that was undertaken in the reversed-phase liquid chromatography mode, and ending with (iii) some examples of more advanced computational and machine learning models.
Holmes AS, Yang SKE, Kiziroglou ME, et al., 2022, Miniaturized wet-wet differential pressure sensor, IEEE Sensors Conference, Publisher: IEEE, ISSN: 1930-0395
We report a miniaturized wet-wet differential pressure sensor with applications in pressure and flow sensing in water networks and other harsh environments. The device is similar in concept to a conventional wet-wet differential pressure sensor in that the sensing element is protected from the external environment by oil-filled cavities closed off by corrugated diaphragms. However, with a package envelope of 11.0 x 4.8 x 3.4 mm 3 , corresponding to a volume of only 0.18 cm 3 , the device is considerably smaller than commercially available wet-wet differential pressure sensors. A high degree of miniaturization has been achieved by using micromachining to fabricate the corrugated diaphragms. Preliminary experimental results are presented showing operation of the device as a delta-pressure flow speed sensor in a water flow test rig.
Valsecchi M, Ramadani J, Williams D, et al., 2022, Influence of Tie-Molecules and Microstructure on the Fluid Solubility in Semicrystalline Polymers., J Phys Chem B - Special Issue in Honor of Doros N. Theodorou
Predicting the absorption of gases and liquids in semicrystalline polymers is of critical importance for numerous applications; the mechanical and transport properties of these materials are highly dependent on the amount of solutes dissolved in their bulk. For most semicrystalline polymers which are in contact with an external fluid, the observed uptake of the solute is found to be lower than that predicted by treating the amorphous domains of the polymer as subcooled polymer melts at the same thermodynamic state. This observation has recently led to the hypothesis that the amorphous domains effectively behave as polymer liquids subject to an additional "constraint pressure" which reduces the equilibrium solubility in the domains. We present a new statistical mechanical model of semicrystalline polymers. The constraint pressure emerges naturally from our treatment, as a property of the interlamellar amorphous domains caused by the stretching and localization in space of the tie-molecules (polymer chains linking different lamellae). By assuming that the interlamellar domains exchange monomers reversibly with the lamellae, the model allows one to simultaneously predict the increase of constraint pressure at low temperatures and the variation of the lamellar thickness as a function of temperature─a phenomenon known as premelting. The sorption isotherms of a range of fluids in different polyethylene and polypropylene samples are determined experimentally and the data is compared with calculations of the new model using the SAFT-VR Mie EoS. In order to accurately predict the absorption close to the vapor pressure of the penetrant, we find that it is essential to include the "free", unconstrained amorphous domains in the description, resulting in a multiscale model with two adjustable parameters (the fractions of tie-molecules and free amorphous domains) that characterize the morphology of a given semicrystalline polymer sample. The trends observed fo
Almusaimi O, Lombardi L, Williams D, et al., 2022, Strategies for improving peptide stability and delivery, Pharmaceuticals, Vol: 15, ISSN: 1424-8247
Peptides play an important role in many fields, including immunology, medical diagnostics, and drug discovery, due to their high specificity and positive safety profile. However, for their delivery as active pharmaceutical ingredients, delivery vectors, or diagnostic imaging molecules, they suffer from two serious shortcomings: their poor metabolic stability and short half-life. Major research efforts are being invested to tackle those drawbacks, where structural modifications and novel delivery tactics have been developed to boost their ability to reach their targets as fully functional species. The benefit of selected technologies for enhancing the resistance of peptides against enzymatic degradation pathways and maximizing their therapeutic impact are also reviewed. Special note of cell-penetrating peptides as delivery vectors, as well as stapled modified peptides, which have demonstrated superior stability from their parent peptides, are reported.
Martinez-Ahumada E, Kim DW, Wahiduzzaman M, et al., 2022, Capture and detection of SO<sub>2</sub> using a chemically stable Mg(ii)-MOF, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 10, Pages: 18636-18643, ISSN: 2050-7488
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- Citations: 3
Chadha D, Williams D, Lukham P, et al., 2022, Doing design differently: hybrid teaching in the age of Covid-19, American Society for Engineering Education Annual Meeting
McIntyre SR, Hunter-Sellars E, Haycock PR, et al., 2022, Considerations when determining Counter-diffusion constants in liquid phase catalytic reactions using the Zero Length column (ZLC) method, Chemical Engineering Science, Vol: 258, ISSN: 0009-2509
A Zero Length Column (ZLC) method was developed using a liquid chromatographic system to calculate reactant counter-diffusion coefficients in porous, solvent swollen catalytic pellets and gate-opening support materials. Reactant diffusivities within these porous materials were determined at the reaction conditions of 80 °C and 0.3–0.75 mL min−1. For all materials, molecules of a similar size to the pore apertures, or molecules with strong interactions with the material surfaces, catalysts, were observable by the ZLC method, with both micro and macropore diffusion observed. Differences between Pd(II) and Pd(0) forms of the EnCat30 catalyst were examined to determine the effects of catalytic deactivation. The deactivated catalyst showed iodobenzene macroporous diffusion constants similar to the relatively inert toluene molecules. Finally, pulse field gradient NMR was utilised to compare and validate ZLC diffusion measurements for solvent swollen reaction systems. This study presents much needed novel findings on diffusivity data for liquid phase catalytic systems.
Holmes AS, Kiziroglou ME, Yang SKE, et al., 2022, Minimally invasive online water monitor, IEEE Internet of Things Journal, Vol: 9, Pages: 14325-14335, ISSN: 2327-4662
Sensor installation on water infrastructure is challenging due to requirements for service interruption, specialised personnel, regulations and reliability as well as the resultant high costs. Here, a minimally invasive installation method is introduced based on hot-tapping and immersion of a sensor probe. A modular architecture is developed that enables the use of interchangeable multi-sensor probes, non-specialist installation and servicing, low-power operation and configurable sensing and connectivity. A prototype implementation with a temperature, pressure, conductivity and flow multi-sensor probe is presented and tested on an evaluation rig. This paper demonstrates simple installation, reliable and accurate sensing capability as well as remote data acquisition. The demonstrated minimally invasive multi-sensor probes provide an opportunity for the deployment of water quality sensors that typically require immersion such as pH and spectroscopic composition analysis. This design allows dynamic deployment on existing water infrastructure with expandable sensing capability and minimal interruption, which can be key to addressing important sensing parameters such as optimal sensor network density and topology.
Lopez-Olvera A, Pioquinto-Garcia S, Zarate JA, et al., 2022, SO<sub>2</sub> capture in a chemical stable Al(III) MOF: DUT-4 as an effective adsorbent to clean CH<sub>4</sub>, FUEL, Vol: 322, ISSN: 0016-2361
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- Citations: 9
Ye C, Wang A, Breakwell C, et al., 2022, Development of efficient aqueous organic redox flow batteries using ion-sieving sulfonated polymer membranes, Nature Communications, Vol: 13, ISSN: 2041-1723
Redox flow batteries using aqueous organic-based electrolytes are promising candidates for developing cost-effective grid-scale energy storage devices. However, a significant drawback of these batteries is the cross-mixing of active species through the membrane, which causes battery performance degradation. To overcome this issue, here we report size-selective ion-exchange membranes prepared by sulfonation of a spirobifluorene-based microporous polymer and demonstrate their efficient ion sieving functions in flow batteries. The spirobifluorene unit allows control over the degree of sulfonation to optimize the transport of cations, whilst the microporous structure inhibits the crossover of organic molecules via molecular sieving. Furthermore, the enhanced membrane selectivity mitigates the crossover-induced capacity decay whilst maintaining good ionic conductivity for aqueous electrolyte solution at pH 9, where the redox-active organic molecules show long-term stability. We also prove the boosting effect of the membranes on the energy efficiency and peak power density of the aqueous redox flow battery, which shows stable operation for about 120 h (i.e., 2100 charge-discharge cycles at 100 mA cm−2) in a laboratory-scale cell.
Cherukupally P, Sun W, Williams DR, et al., 2022, Reclamation of Oily Wastewater at High Temperatures Using Thermosetting Polyurethane-Nanosilicon Sponges, ACS APPLIED POLYMER MATERIALS, Vol: 4, Pages: 1544-1550, ISSN: 2637-6105
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- Citations: 4
Mohamed NAN, Han Y, Hector AL, et al., 2022, Increasing the Diameter of Vertically Aligned, Hexagonally Ordered Pores in Mesoporous Silica Thin Films, LANGMUIR, Vol: 38, Pages: 2257-2266, ISSN: 0743-7463
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- Citations: 7
Azmi LHM, Cherukupally P, Hunter-Sellars E, et al., 2022, Fabrication of MIL-101-polydimethylsiloxane composites for environmental toluene abatement from humid air, CHEMICAL ENGINEERING JOURNAL, Vol: 429, ISSN: 1385-8947
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- Citations: 9
Velasquez-Hernandez MDJ, Lopez-Cervantes VB, Martinez-Ahumada E, et al., 2022, CCIQS-1: A Dynamic Metal-Organic Framework with Selective Guest-Triggered Porosity Switching, CHEMISTRY OF MATERIALS, Vol: 34, Pages: 669-677, ISSN: 0897-4756
Molisso S, Williams DR, Ces O, et al., 2021, Molecular interaction and partitioning in α-Keratin using 1H NMR Spin-Lattice (T1) relaxation times, Journal of the Royal Society Interface, Vol: 18, Pages: 1-8, ISSN: 1742-5662
The interactions between small molecules and keratins are poorly understood. In this paper an NMR method is presented to measure changes in the 1H T1 relaxation times of small molecules in human hair keratin to quantify their interaction with the fiber. Two populations of small molecule compounds were identified with distinct relaxation times, demonstrating the partitioning of the compounds into different keratin environments. The changes in relaxation time for solvent in hair compared to bulk solvent were shown to be related to the molecular weight, MW, and the partition coefficient, LogP, of the solvent investigated. Compounds with low molecular weights and high hydrophilicities had greater reductions in their T1 relaxation times and therefore experienced increased interactions with the hair fiber. The relative population sizes were also calculated. This is a significant step toward modelling the behavior of small molecules in keratinous materials and other large insoluble fibrous proteins.
Kondor A, Santmarti A, Mautner A, et al., 2021, On the BET surface area of nanocellulose determined using volumetric, gravimetric and chromatographic adsorption methods, Frontiers in Chemical Engineering, Vol: 3, Pages: 1-12, ISSN: 2673-2718
Volumetric N2 adsorption at –196 °C is generally accepted as “gold standard” for estimating the Brunauer-Emmet-Teller (BET) surface area of nanocellulose. It is unclear however, whether the BET surface area of nanocellulose obtained at such low temperatures and pressures is meaningful at an absolute sense, as nanocellulose is used at ambient temperature and pressure. In this work, a systematic evaluation of the BET surface area of nanocellulose using a highly crystalline bacterial cellulose (BC) as model nanocellulose was undertaken to achieve a comprehensive understanding of the limitations of BET method for nanocellulose. BET surface area obtained using volumetric N2 adsorption at –196 °C was compared with the BET surface area acquired from gravimetric experiments using n-octane adsorption measured using dynamic vapour sorption (DVS) and n-octane adsorption determined by inverse gas chromatography (iGC), both at 25 °C. It was found that the BET surface area calculated from volumetric N2 adsorption data was 25% lower than that of n-octane adsorption at 25 °C obtained using DVS and iGC adsorption methods. These results supported the hypothesis that the BET surface area of nanocellulose is both a molecular scale (N2 vs n-octane, molecular cross section of 0.162 nm2 vs 0.646 nm2) and temperature (–196 °C vs 25 °C) dependent property. This study also demonstrates the importance of selecting appropriate BET pressure range based on established criteria and would suggest that the room temperature gravimetric measurement is more relevant for many nanocellulose applications.
del Gaudio I, Hunter-Sellars E, Parkin IP, et al., 2021, Water sorption and diffusion in cellulose acetate: The effect of plasticisers, CARBOHYDRATE POLYMERS, Vol: 267, ISSN: 0144-8617
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- Citations: 11
Cheung PCW, Williams DR, Barrett J, et al., 2021, On the Origins of Some Spectroscopic Properties of "Purple Iron" (the Tetraoxoferrate(VI) Ion) and Its Pourbaix Safe-Space, MOLECULES, Vol: 26
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- Citations: 6
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