Successful synthesis of a glial-specific blood-brain barrier shuttle peptide following a fragment condensation approach on a solid-phase resin.

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 minimise 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 Arg(Pbf) 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.

Prediction of peptides retention behavior in reversed-phase liquid chromatography based on their hydrophobicity.

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.

Increasing the Diameter of Vertically Aligned, Hexagonally Ordered Pores in Mesoporous Silica Thin Films.

The variation in pore size in mesoporous films produced by electrochemically assisted self-assembly (EASA) with the surfactant chain length is described. EASA produces a hexagonal array of pores perpendicular to the substrate surface by using an applied potential to organize cationic surfactants and the resultant current to drive condensation in a silica sol. Here, we show that a range of pore sizes between 2 and 5 nm in diameter is available with surfactants of the form [Me3NCnH2n+1]Br, with alkyl chain lengths between C14 and C24. The film quality, pore order, pore size, and pore accessibility are probed with a range of techniques.

On the Origins of Some Spectroscopic Properties of "Purple Iron" (the Tetraoxoferrate(VI) Ion) and Its Pourbaix Safe-Space.

In this work, the authors attempt to interpret the visible, infrared and Raman spectra of ferrate(VI) by means of theoretical physical-inorganic chemistry and historical highlights in this field of interest. In addition, the sacrificial decomposition of ferrate(VI) during water treatment will also be discussed together with a brief mention of how Rayleigh scattering caused by the decomposition of FeVIO42- may render absorbance readings erroneous. This work is not a compendium of all the instrumental methods of analysis which have been deployed to identify ferrate(VI) or to study its plethora of reactions, but mention will be made of the relevant techniques (e.g., Mössbauer Spectroscopy amongst others) which support and advance this overall discourse at appropriate junctures, without undue elaboration on the foundational physics of these techniques.

A Robust and Biocompatible Bismuth Ellagate MOF Synthesized Under Green Ambient Conditions.

The first bioinspired microporous metal-organic framework (MOF) synthesized using ellagic acid, a common natural antioxidant and polyphenol building unit, is presented. Bi2O(H2O)2(C14H2O8)·nH2O (SU-101) was inspired by bismuth phenolate metallodrugs, and could be synthesized entirely from nonhazardous or edible reagents under ambient aqueous conditions, enabling simple scale-up. Reagent-grade and affordable dietary supplement-grade ellagic acid was sourced from tree bark and pomegranate hulls, respectively. Biocompatibility and colloidal stability were confirmed by in vitro assays. The material exhibits remarkable chemical stability for a bioinspired MOF (pH = 2-14, hydrothermal conditions, heated organic solvents, biological media, SO2 and H2S), attributed to the strongly chelating phenolates. A total H2S uptake of 15.95 mmol g-1 was recorded, representing one of the highest H2S capacities for a MOF, where polysulfides are formed inside the pores of the material. Phenolic phytochemicals remain largely unexplored as linkers for MOF synthesis, opening new avenues to design stable, eco-friendly, scalable, and low-cost MOFs for diverse applications, including drug delivery.

Mapping the mAb Aggregation Propensity Using Self-Interaction Chromatography as a Screening Tool.

The osmotic second virial coefficient ( B2), which describes protein-protein molecular interactions in solution, was determined using self-interaction chromatography (SIC) for an IgG1-type mAb across a wide range of solution conditions. These data were compared with its time dependent aggregation behavior, as determined using size-exclusion chromatography (SEC), and its temperature dependent aggregation behavior using dynamic light scattering (DLS) over a four-week period (SEC) or overnight (DLS). DLS and SEC gave consistent data on aggregation behavior, which correlated well with experimental B2 trends across the wide pH (4-9) and NaCl concentration (0-1.0 M) ranges studied. The IgG aggregated at pH 4 for 0.5-1.0 M NaCl concentrations and for 0 M NaCl concentrations at pH 8. Best stability against aggregation was exhibited for the pH range from 5 to 8 at 0.8-1.0 M NaCl. SIC data were able to be classified within the one-day solution conditions for aggregation, which were not identified for 2-3 weeks in the accelerated SEC stability study. The ability of SIC to provide such data rapidly reflects the fundamentally thermodynamic nature of this parameter and of the aggregation process itself. Proteins with attractive protein-protein interactions and negative B2 coefficients in the range -3 to -6 clearly exhibit aggregation behavior, while B2 values in the range 0 to 2 showed good stability toward aggregation. SIC allows the rapid screening of solution conditions for which mAbs will exhibit stability to aggregation while requiring 90% less time and material compared with that required for a conventional SEC aggregation study.

A new method to determine dispersive surface energy site distributions by inverse gas chromatography.

A computational model to predict the relative energy site contributions of a heterogeneous material from data collected by finite dilution-inverse gas chromatography (FD-IGC) is presented in this work. The methodology employed a multisolvent system site filling model utilizing Boltzmann statistics, expanding on previous efforts to calculate "experienced energies" at varying coverage, yielding a retention volume distribution allowing calculation of a surface free energy distribution. Surface free energy distributions were experimentally measured for racemic ibuprofen and ß-mannitol powders, the energies of each were found in the ranges 43-52 and 40-55 mJ/m(2), respectively, over a surface coverage range of 0-8%. The computed contributions to surface energy values were found to match closely with data collected on macroscopic crystals by alternative techniques (±<1.5 mJ/m(2)).

Correct specific retention volume determination in inverse gas chromatography.

Inverse Gas Chromatography (IGC) is an important technique for characterization of solids. Determining the specific retention volume of the injected probe molecule is the basis of the analysis for all the physico-chemical properties that the technique can determine, most importantly in Heat of Sorption, Glass Transition Temperature, Gibbs Adsorption Free Energy. Two equations have been used in the literature to calculate the specific retention volume; one normalizes the retention volume to 0 °C (standard temperature), which was previously proven to be thermodynamically incorrect, while the other calculates the retention volume at the measurement temperature. Here, we compare the heat of sorption for a series of alkanes on two substrates, micro crystalline cellulose and natural graphite, calculated using these two equations. This study shows that the specific retention volume is strongly dependent on the column temperature. Using the retention volume values normalised to 0 °C consistently overestimates the heats of sorption by up to 10%. Most importantly, correcting the retention volume to standard temperature will misrepresent the effect of temperature on the retention volume and the thermodynamic parameters derived from it.

Effects of surfactant head group modification on vertically oriented mesoporous silica produced by the electrochemically assisted surfactant assembly method.

Production of mesoporous silica films with vertically oriented pores has been a challenge since interest in such systems developed in the 1990s. Vertical orientation can be achieved by the electrochemically assisted surfactant assembly (EASA) method using cationic surfactants such as cetyltrimethylammonium bromide (C16TAB). The synthesis of porous silicas using a series of surfactants with increasing head sizes is described, from octadecyltrimethylammonium bromide (C18TAB) to octadecyltriethylammonium bromide (C18TEAB). These increase pore size, but the degree of hexagonal order in the vertically aligned pores reduces as the number of ethyl groups increases. Pore accessibility is also reduced with the larger head groups.

Functional differentiation of myoglobin isoforms in hypoxia-tolerant carp indicates tissue-specific protective roles.

Because of a recent whole genome duplication, the hypoxia-tolerant common carp and goldfish are the only vertebrates known to possess two myoglobin (Mb) paralogs. One of these, Mb1, occurs in oxidative muscle but also in several other tissues, including capillary endothelial cells, whereas the other, Mb2, is a unique isoform specific to brain neurons. To help understand the functional roles of these diverged isoforms in the tolerance to severe hypoxia in the carp, we have compared their O(2) equilibria, carbon monoxide (CO) and O(2) binding kinetics, thiol S-nitrosation, nitrite reductase activities, and peroxidase activities. Mb1 has O(2) affinity and nitrite reductase activity comparable to most vertebrate muscle Mbs, consistent with established roles for Mbs in O(2) storage/delivery and in maintaining nitric oxide (NO) homeostasis during hypoxia. Both Mb1 and Mb2 can be S-nitrosated to similar extent, but without oxygenation-linked allosteric control. When compared with Mb1, Mb2 displays faster O(2) and CO kinetics, a lower O(2) affinity, and is slower at converting nitrite into NO. Mb2 is therefore unlikely to be primarily involved in either O(2) supply to mitochondria or the generation of NO from nitrite during hypoxia. However, Mb2 proved to be significantly faster at eliminating H(2)O(2,) a major in vivo reactive oxygen species (ROS), suggesting that this diverged Mb isoform may have a specific protective role against H(2)O(2) in the carp brain. This property might be of particular significance during reoxygenation following extended periods of hypoxia, when production of H(2)O(2) and other ROS is highest.

Effect of milling on particle shape and surface energy heterogeneity of needle-shaped crystals.

PURPOSE: Milling and micronization of particles are routinely employed in the pharmaceutical industry to obtain small particles with desired particle size characteristics. The aim of this study is to demonstrate that particle shape is an important factor affecting the fracture mechanism in milling. METHODS: Needle-shaped crystals of the ß polymorph of D-mannitol were prepared from recrystallization in water. A portion of the recrystallized materials was ball-milled. Unmilled and milled sieved fractions of recrystallized D-mannitol were analyzed by dynamic image analysis (DIA) and inverse gas chromatography (IGC) at finite concentration to explain the breakage/fracture behavior. RESULTS: In the process of ball-milling, D-mannitol preferentially fractured along their shortest axis, exposing (011) plane with increased hydrophilicity and increased bounding rectangular aspect ratio. This is in contrary to attachment energy modeling which predicts a fracture mechanism across the (010) plane with increased hydrophobicity, and small change in particle shape. CONCLUSIONS: Crystal size, and more importantly, crystal shape and facet-specific mechanical properties, can dictate the fracture/cleavage behavior of organic crystalline materials. Thorough understanding of the crystal slip systems, combining attachment energy prediction with particle shape and surface characterization using DIA and IGC, are important in understanding fracture behavior of organic crystalline solids in milling and micronization.

Greener Cleavage of Protected Peptide Fragments from Sieber Amide Resin.

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.

Strategies for Improving Peptide Stability and Delivery.

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.

Product selectivity and mass transport in levulinic acid transfer hydrogenation by monolithic MIL-100, MIL-88B and ZIF-8@Pd MOFs.

The diffusion processes between adsorbent and adsorbate naturally play a significant role in the efficiency and selectivity of the heterogenous catalytic process. This paper considers the importance of diffusion processes in the transfer hydrogenation reaction of levulinic acid to γ-valerolactone by MIL-88B, MIL-100, and ZIF8@Pd monolithic catalysts. Over a period of five catalytic cycles, it was shown that the Fe-based catalysts can achieve similar conversions to the ZIF-8 supported Pd, with the only current limitation being the lower aqueous stability of these MOFs. Diffusion constants were calculated using the ZLC method, with micropore diffusion limitation found for ZIF-8 and MIL-100 monolithic frameworks at 2.7 x 10-8 and 4.6 x 10-8 cm2 s-1 respectively. This diffusion limitation was also confirmed by IR spectroscopy with an increasing concentration of C-H bands on the MOF substrate post-reaction. Mass transfer coefficients, also calculated by ZLC, revealed increased mass transport for the hydrophobic ZIF-8 framework, which perhaps aids in the γ-valerolactone selectivity over side products that are produced in the absence of catalytic material, as seen for MIL-88B and MIL-100 after multiple uses.

Development of efficient aqueous organic redox flow batteries using ion-sieving sulfonated polymer membranes.

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.

Polymer-assisted modification of metal-organic framework MIL-96 (Al): influence of HPAM concentration on particle size, crystal morphology and removal of harmful environmental pollutant PFOA.

A new synthesis method was developed to prepare an aluminum-based metal organic framework (MIL-96) with a larger particle size and different crystal habits. A low cost and water-soluble polymer, hydrolyzed polyacrylamide (HPAM), was added in varying quantities into the synthesis reaction to achieve >200% particle size enlargement with controlled crystal morphology. The modified adsorbent, MIL-96-RHPAM2, was systematically characterized by SEM, XRD, FTIR, BET and TGA-MS. Using activated carbon (AC) as a reference adsorbent, the effectiveness of MIL-96-RHPAM2 for perfluorooctanoic acid (PFOA) removal from water was examined. The study confirms stable morphology of hydrated MIL-96-RHPAM2 particles as well as a superior PFOA adsorption capacity (340 mg/g) despite its lower surface area, relative to standard MIL-96. MIL-96-RHPAM2 suffers from slow adsorption kinetics as the modification significantly blocks pore access. The strong adsorption of PFOA by MIL-96-RHPAM2 was associated with the formation of electrostatic bonds between the anionic carboxylate of PFOA and the amine functionality present in the HPAM backbone. Thus, the strongly held PFOA molecules in the pores of MIL-96-RHPAM2 were not easily desorbed even after eluted with a high ionic strength solvent (500 mM NaCl). Nevertheless, this simple HPAM addition strategy can still chart promising pathways to impart judicious control over adsorbent particle size and crystal shapes while the introduction of amine functionality onto the surface chemistry is simultaneously useful for enhanced PFOA removal from contaminated aqueous systems.

Molecular interaction and partitioning in α-keratin using 1H NMR spin-lattice (T1) relaxation times.

The interactions between small molecules and keratins are poorly understood. In this paper, a nuclear magnetic resonance 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 fibre. 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 with bulk solvent were shown to be related to the molecular weight (MW) and the partition coefficient, LogP, of the solvent investigated. Compounds with low MWs and high hydrophilicities had greater reductions in their T1 relaxation times and therefore experienced increased interactions with the hair fibre. The relative population sizes were also calculated. This is a significant step towards modelling the behaviour of small molecules in keratinous materials and other large insoluble fibrous proteins.

Fluorinated MIL-101 for carbon capture utilisation and storage: uptake and diffusion studies under relevant industrial conditions.

Carbon capture utilisation and storage (CCUS) using solid sorbents such as zeolites, activated carbon and Metal-Organic Frameworks (MOFs) could facilitate the reduction of anthropogenic CO2 concentration. Developing efficient and stable adsorbents for CO2 capture as well as understanding their transport diffusion limitations for CO2 utilisation plays a crucial role in CCUS technology development. However, experimental data available on CO2 capture and diffusion under relevant industrial conditions is very limited, particularly for MOFs. In this study we explore the use of a gravimetric Dynamic Vapour Sorption (DVS) instrument to measure low concentration CO2 uptake and adsorption kinetics on a novel partially fluorinated MIL-101(Cr) saturated with different water vapour concentrations, at ambient pressure and temperature. Results show that up to water P/P 0 = 0.15 the total CO2 uptake of the modified material improves and that the introduction of small amounts of water enhances the diffusion of CO2. MIL-101(Cr)-4F(1%) proved to be a stable material under moist conditions compared to other industrial MOFs, allowing facile regeneration under relevant industrial conditions.

SO2 Capture by Two Aluminum-Based MOFs: Rigid-like MIL-53(Al)-TDC versus Breathing MIL-53(Al)-BDC.

Metal-organic frameworks MIL-53(Al)-TDC and MIL-53(Al)-BDC were explored in the SO2 adsorption process. MIL-53(Al)-TDC was shown to behave as a rigid-like material upon SO2 adsorption. On the other hand, MIL-53(Al)-BDC exhibits guest-induced flexibility of the framework with the presence of multiple steps in the SO2 adsorption isotherm that was related through molecular simulations to the existence of three different pore opening phases narrow pore, intermediate pore, and large pore. Both materials proved to be exceptional candidates for SO2 capture, even under wet conditions, with excellent SO2 adsorption, good cycling, chemical stability, and easy regeneration. Further, we propose MIL-53(Al)-TDC and MIL-53(A)-BDC of potential interest for SO2 sensing and SO2 storage/transportation, respectively.

The Influence of Moisture Content and Temperature on the Long-Term Storage Stability of Freeze-Dried High Concentration Immunoglobulin G (IgG).

High protein concentration products for targeted therapeutic use are often freeze-dried to enhance stability. The long-term storage stability of freeze-dried (FD) plasma-derived Immunoglobulin G (IgG) from moderate to high concentrations (10-200 mg/mL) was assessed. Monomer content, binding activity and reconstitution times were evaluated over a 12-month period under accelerated and real-term storage conditions. In the first case study it was shown that FD IgG from 10 to 200 mg/mL had minimal monomer/activity losses at up to ambient temperature after 12 months of storage. However, at 45 °C the sucrose-to-protein ratio played a significant impact on IgG stability above 50 mg/mL. All IgG concentrations witnessed moisture ingress over a 12-month period. The impact of moisture ingress from environmental exposure (between 0.1% and 5% w/w moisture) for IgG 50 mg/mL was assessed, being generated by exposing low moisture batches to an atmospheric environment for fixed time periods. Results showed that at -20 °C and 20 °C there was no significant difference in terms of monomer or antigen-binding activity losses over 6 months. However, at 45 °C, there were losses in monomer content, seemingly worse for higher moisture content samples although model binding activity indicated no losses. Finally, the difference between a low moisture product (0.1-1% w/w) and a moderately high moisture (3% w/w) product generated by alternative freeze-drying cycles, both stoppered under low oxygen headspace conditions, was evaluated. Results showed that at -20 °C and 20 °C there was no difference in terms of binding activity or monomer content. However, at 45 °C, the low moisture samples had greater monomer and binding activity losses than samples from the highest moisture cycle batch, indicating that over-drying can be an issue.