Volume 93, Issue 10

To commemorate the centenary of the birth of modern polymer science, a review of the life and accomplishments of Hermann Staudinger is given within the framework of the first half of the twentieth century. Staudinger is remembered for his discovery of ketenes and the Staudinger reaction, but his greatest contribution to chemistry was in developing the concept of macromolecules, for which he received the Nobel Prize in 1953.

This contribution attempts to describe the path towards determination of cellulose crystal structure down to atomic coordinates, towards the determination of its molecular conformation, as well as towards the details of the intricate pattern of hydrogen bonds and their dynamics. This path started at the beginning of the 20 th century with X-ray diffraction, continued with electron diffraction, infrared and Raman spectroscopy, and significant knowledge was gained by methods of NMR spectroscopy. Towards the end of the 20 th century and at the beginning of the 21 st century, X-ray diffraction in conjunction with neutron diffraction provided the position of hydrogens, which led to detailed description of the geometry of hydrogen bonding network in cellulose. Quantum chemical and molecular dynamics calculations, polarized infrared spectroscopy and sum frequency generation vibrational spectroscopy were used to identify the origins of the vibrational modes in cellulose and to describe their extensive coupling mediated by hydrogen bonds. The role of amphiphilic character of cellulose macromolecule (and consequent hydrophobic interactions) in cellulose properties and behavior has been gaining more recognition in the 21 st century.

Dynamic studies of several processed cheeses were carried out for evaluation of their dielectric properties and their relaxation behavior. Impedance spectroscopy has been used to study the systems under discussion in low-frequency domain. A substantial number of impedance spectra will be given and discussed that relate the dielectric properties to food nutrients. Also influence of moisture on food quality might be evaluated.

The development of self-cleaning biomimetic surfaces has the potential to be of great benefit to human health, in addition to reducing the economic burden on industries worldwide. Consequently, this study developed a biomimetic wax surface using a moulding technique which emulated the topography of the self-cleaning Gladiolus hybridus (Gladioli) leaf. A comparison of topographies was performed for unmodified wax surfaces (control), biomimetic wax surfaces, and Gladioli leaves using optical profilometry and scanning electron microscopy. The results demonstrated that the biomimetic wax surface and Gladioli leaf had extremely similar surface roughness parameters, but the water contact angle of the Gladioli leaf was significantly higher than the replicated biomimetic surface. The self-cleaning properties of the biomimetic and control surfaces were compared by measuring their propensity to repel Escherichia coli and Listeria monocytogenes attachment, adhesion, and retention in mono- and co-culture conditions. When the bacterial assays were carried out in monoculture, the biomimetic surfaces retained fewer bacteria than the control surfaces. However, when using co-cultures of the bacterial species, only following the retention assays were the bacterial numbers reduced on the biomimetic surfaces. The results demonstrate that such surfaces may be effective in reducing biofouling if used in the appropriate medical, marine, and industrial scenarios. This study provides valuable insight into the anti-fouling physical and chemical control mechanisms found in plants, which are particularly appealing for engineering purposes.

Solution-processable conductive polymers are advantageous materials for making inexpensive, electrical junctions to crystalline semiconductors. We have investigated methods to improve the device performance of hybrid solar cells made from n-type silicon and a conductive polymer glue based on a blend of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and D -sorbitol. The PEDOT:PSS blend behaves like a high work function metal creating a Schottky-type junction. The addition of D -sorbitol increases PEDOT:PSS conductivity and provides adhesive properties, allowing the top contact of the solar cell to be laminated onto the silicon substrate. Unfortunately, the addition of the D -sorbitol to the PEDOT:PSS significantly alters the shape of the measured current-voltage performance curve of a crystalline silicon (n-Si)/PEDOT:PSS junction. Under illumination, this results in a decline in the fill factor ( FF ) and a drop in photocurrent density ( J sc ) compared to PEDOT:PSS-only devices. We have discovered that the decline in device performance is likely due to surface trap states caused by D -sorbitol/silicon interaction and/or silicon oxidation. X-ray photoelectron spectroscopic (XPS) analysis shows that surface oxidation quickens, and possible silicon surface functionalization with D -sorbitol occurs while processing the D -sorbitol/PEDOT:PSS contact on H-terminated surfaces. To overcome these interface issues, the silicon surface was chemically modified using surface methylation, making it insensitive to D -sorbitol/silicon interactions and surface oxidation during the processing of the PEDOT:PSS polymer blend contact. This also enabled the crystalline silicon (n-Si)/s-PEDOT:PSS device performance to be maintained for longer periods. Using a silicon surface methylation strategy, good device performance could be achieved without changing the adhesive properties of D -sorbitol/PEDOT:PSS polymer blend.

The influence of thermal treatment on the thermal stability, thermal properties, dielectric properties and intermolecular interaction of binary epoxidized natural rubber (ENR)-salt systems, which may be a candidate for solid polymer electrolytes (SPEs) was investigated. Solubility of salt in ENR enhances, which may be due to the disruption of the lightly-crosslinked microgel under heat treatment. The increase in the ionic conductivities of the thermally treated ENR SPEs at constant salt content is correlated to the higher glass transition temperatures, development of percolation network and higher extent of intermolecular interactions between ENR and charged entities in this study.

Diversity, equity, inclusion and belonging (DEIB) will be key to unlocking and accelerating sustainable polymer-based solutions to meet the needs of our rapidly growing world. To achieve faster innovation, we must increase team performance by embracing diversity, ensuring systems and processes within polymer science are equitable and through increased emotional intelligence (EQ), fostering inclusion and belonging. In examining the participation of women and other historically marginalized groups in publishing, intellectual property filings and society leadership, this paper highlights the gaps and the extent of the work needed to close those gaps. Additionally, we provide an opportunity for members of the polymer science community to provide their perspective on DEIB. Polymer science is for everyone and it is imperative for all to be able to make full and meaningful contributions to advance the field. To this end, we provide recommendations for cultivating a more inclusive culture in all facets of the polymer sciences.

Cancer is the second leading cause of death worldwide. Peptidases participate in tumor development and growth. Mammalian neutral aminopeptidase (APN, EC 3.4.11.2, M1 family) catalyzes the cleavage of neutral and basic amino acids from the N-terminus of substrates. APN expression is dysregulated in several types of cancer, being a target for the development of new anticancer agents. Recently, we identified three new non-competitive inhibitors of soluble porcine APN (pAPN) by virtual screening (BTB11079, JFD00064, BTB07018, from Maybridge). In the present contribution we assayed their effect on the activity of APN in a microsomal preparation of porcine kidney cortex, a model of the physicochemical environment of the enzyme. These classical inhibitors had an IC 50 value of 3–5 µM. Additionally, using a kinetic approach and a specific substrate, we quantified APN activity on the cell surface of human and murine lung, colon, prostate, and skin tumor cells. APN inhibitors reduced tumor cells viability, more efficiently in the higher APN activity tumor cell lines, but not in non-tumoral cells. BTB11079, JFD00064, BTB07018 effects on cell viability were stronger than that of bestatin, a positive control. Thus, these non-competitive APN inhibitors may be useful tools for cancer treatment.

Herein, we report on the performance of graphene oxide (GOx) and zinc oxide nanoparticles (ZnONPs) on a platinum (Pt) electrode, immobilized with the human T1R2 sweet taste receptor subunit for the detection of rebaudioside A (Reb-A). The characterization studies performed in this work confirmed the thin-layered structure of GOx and the polydispersed nature of ZnONPs. The elucidation of the mass loss observed by TGA demonstrates the stability of GOx. The cyclic voltammetry results for Pt/GOx revealed good catalytic activity over Pt/ZnONPs for adsorption of the T1R2-Reb-A complex. In addition, a series of computational modelling studies were carried out to better understand the surface adsorption phenomena of GOx and ZnONPs to mimic the layer-by-layer electrode modification strategies independently. The strongest interaction energy observed (−573 kcal mol −1 ) for the direct interaction of ZnONPs onto the Pt electrode surface, demonstrates a stronger adsorption in contrast to the GOx modified Pt electrode (−23 kcal mol −1 ). However, the overall results for the layered-nanocomposite revealed that the GOx (−256 kcal mol −1 ) were more strongly adsorbed in contrast to ZnONPs (−231 kcal mol −1 ) for the detection of the T1R2-ReB-A complex, demonstrating the reliability of our GOx electrode functionalization strategy. The results of this study can potentially be used to improve the design of rapid Reb-A sensors for the food and beverage industry.

As society becomes more technologically complex, post-secondary institutions have responded by incorporating science-based courses in the non-science curriculum. As chemist, we are often called upon to teach these courses and explain complex concepts to learners with limited science background. An effective method to engage students with the material is using demonstrations. In this study, we examine the use of science-based demonstration in our third-year science course for non-science students.

In this study, the dimension or dimensionality paradox is defined and discussed in a dedicated context. This paradox appears when discrete vector representations of the elements of a molecular set are constructed employing several descriptor parameters, adopting specific values for each molecule. The dimension paradox consists in that when constructing discrete N -dimensional molecular vectors, the primal structure of the attached molecular set, chosen as a collection of different objects, cannot be well-defined if the number of descriptors N and the number of molecules M do not bear a convenient relation like: N ≥ M $N\ge M$ . This has implications for the linear independence of the vectors connected with each molecule.

In order to understand the atmospheric implication of the chlorinated hydrofluoroolefin (HFO), the geometrical structures and the IR absorption cross sections of the stereoisomers 1-chloro-3,3-difluoropropene were studied using the B3LYP/6-31G(3df) and M06-2X/6-31G(3df) methods in the gas phase. The cis-trans isomerization was assessed using the M06-2X/6-311++G(3df,p)//6-31+G(3df,p) method. The latter method was also employed for thermochemistry and the rate coefficients of the reactions of • OH with the cis - and trans -isomers in the temperature ranging from 200 to 400 K. The computational method CCSD/cc-pVTZ//M06-2X/6-31+G(3df,p) was used to benchmark the rate coefficients. It turns out that, the trans -isomer is more stable than cis -isomer and the trans - to cis -isomerization is thermodynamically unfavorable. The rate coefficient follows the Gaussian law with respect to the inverse of temperature. At the global temperature of stratosphere, the calculated rate coefficients served to estimate the atmospheric lifetime along with the photochemical ozone creation potential (POCP). This yielded lifetimes of 4.31 and 7.31 days and POCPs of 3.80 and 2.23 for the cis - and trans -isomer, respectively. The radiative forcing efficiencies gave 0.0082 and 0.0152 W m −2  ppb −1 for the cis - and trans -isomer, respectively. The global warming potential approached zero for both stereoisomers at 20, 100, and 500 years time horizons.

Combination therapies that include treatment of cancerous cells with histone deacetylase (HDACs) inhibitors prior to treatment with topoisomerase inhibitors have shown synergistic anti-tumor effects. The promising results of such combination therapies have led to the development of a novel class of multitarget hybrid inhibitors that are designed by merging the scaffolds of topoisomerase and HDAC inhibitors, which consequently inhibit both classes of cancer-inducing targets simultaneously. These multitarget hybrids also have pharmacokinetic advantages over the traditional combinatorial approach, which struggles with disadvantages like maintaining optimum concentrations of multiple toxic drugs, which in turn leads to enhanced toxicity and other side-effects associated with the multiple drugs administered. Binding modes of some Top-HDAC hybrids have been predicted with the help of molecular docking in order to understand the binding of such hybrids with their target receptors and to identify the structural determinants responsible for their synergistic anti-tumor effect. Extra precision docking of Top1-HDAC and Top2-HDAC hybrid inhibitors has been carried out with Top1-DNA, Top2-DNA, HDAC1 and HDAC6 receptor structures. A detailed analysis of the molecular interactions of the hybrids with the target receptor binding sites has been undertaken and their predicted binding modes have been compared with the crystal binding modes of their component drugs. An explanation for the apparent selectivity of the hybrids towards HDAC6 has also been provided.

Hybrid density functional theory has been used to study the phase stability and formation of native point defects in Cu 4 O 3 . This intermediate copper oxide compound, also known as paramelaconite, was observed to be difficult to synthesize due to stabilization issues between mixed-valence Cu 1+ and Cu 2+ ions. The stability range of Cu 4 O 3 was investigated and shown to be realized in an extremely narrow region of phase space, with Cu 2 O and CuO forming readily as competing impurity phases. The origin of p -type conductivity is confirmed to arise from specific intrinsic copper vacancies occurring on the 1+ site. Away from the outlined stability region, the dominant charge carriers become oxygen interstitials, impairing the conductivity by creating deep acceptor states in the electronic band gap region and driving the formation of alternative phases. This study further demonstrates the inadequacy of native defects as a source of n -type conductivity and complements existing experimental findings.