Articles publicats (D-Q)

PLA/PMMA Reactive Blending in the Presence of MgO as an Exchange Reaction Catalyst

2025-04-11T11:08:11Z

PLA/PMMA Reactive Blending in the Presence of MgO as an Exchange Reaction Catalyst Komeijani, Masoud; Bahri-Laleh, Naeimeh; Mirjafary, Zohreh; D’Alterio, Massimo Christian; Rouhani, Morteza; Sakhaeinia, Hossein; Moghaddam, Amin Hedayati; Poater Teixidor, Albert To address the limitations of poly (lactic acid) (PLA), it was blended with poly (methyl methacrylate) (PMMA) as a toughening component, using MgO nanoparticles (NPs, 0.075–0.15 wt%) as a catalyst. SEM pictures confirmed the good miscibility of the blends. Mechanical tests showed a slight decrease in elastic modulus and tensile strength for the PLA/PMMA125 sample containing 0.125% MgO. Yet, elongation at break rose by over 60% and impact strength increased by over 400% compared to pure PLA. Also, MgO facilitated the shifting of the glass transition temperature (Tg) of both polymers in DSC curves. Additionally, the absence of cold crystallization in PLA, coupled with reductions in its melting temperature (Tm) and crystallinity, were identified as critical factors contributing to improved miscibility within the reactive blend. Melt flow index (MFI) evaluation indicated a decrease in viscosity, while water contact angle measurements revealed an increase in polar groups on the surfaces of the MgO-containing samples. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses confirmed the effective distribution and dispersion of NPs throughout the blend, along with a significant decrease in crystallinity. Moreover, DFT calculations were performed to better understand the role of MgO in the reaction. The findings offered key insights into the reaction mechanism, confirming that MgO plays a crucial role in facilitating the transesterification between PLA and PMMA. These findings underscore the enhanced performance of exchange reactions between the active groups of both polymers in the presence of MgO, leading to the formation of PLA-PMMA copolymers with superior miscibility and mechanical properties. Finally, a cell culture assay confirmed the blend’s non-toxicity, showing its versatile potential

Atomic radii derived from the expectation value

2025-04-07T12:05:24Z

Atomic radii derived from the expectation value Linker, Gerrit-Jan; Swart, Marcel; Duijnen, Petrus Theodorus van The atomic radius as a fundamental chemical descriptor for the size of a chemical element is often used in physical chemistry. Many reference sets are available, based either on experiment or calculations. For example, Alvarez compiled a set of consistent van der Waals radii (Dalton Trans. 2013, 42, 8617) based on millions of measured interatomic non-bonded distances. In quantum mechanics, there are many ways in which the atom size can be defined and obtained because the atomic radius is not an observable. Here, we show that a theoretical measure can be based on expectation values such as and . These are easily obtained from atomic electric moments, routinely generated by popular quantum chemistry codes, with full control over electronic structure, charge, spin state, etc. As such we obtain a measure for the size of free atoms H to Xe and demonstrate linear scaling of atomic size in the series as outermost s, p or d subshells are filled according to the Madelung rule. Radii derived from compare best to Alvarez's empirical reference set of van der Waals radii, and atomic radii from theoretical sources. Known periodic trends of atomic radii are well reproduced by our data. Furthermore, we demonstrate the dependence of atomic size on the electronic structure and spin state for d-block elements

Fatty acid synthase (FASN) inhibition cooperates with BH3 mimetic drugs to overcome resistance to mitochondrial apoptosis in pancreatic cancer

2025-04-07T10:52:08Z

Fatty acid synthase (FASN) inhibition cooperates with BH3 mimetic drugs to overcome resistance to mitochondrial apoptosis in pancreatic cancer Vander Steen, Travis; Espinoza, Ingrid; Duran i Rebenaque, Cristina; Casadevall Franco, Guillem; Serrano Hervás, Eila; Cuyàs, Elisabet; Verdura, Sara; Kemble, George; Kaufmann, Scott H.; McWilliams, Robert; Osuna Oliveras, Sílvia; Billadeau, Daniel D.; Menéndez Menéndez, Javier Abel; Lupu, Ruth Resistance to mitochondrial apoptosis is a major driver of chemoresistance in pancreatic ductal adenocarcinoma (PDAC). However, pharmacological manipulation of the mitochondrial apoptosis threshold in PDAC cells remains an unmet therapeutic goal. We hypothesized that fatty acid synthase inhibitors (FASNis), a family of targeted metabolic therapeutics recently entering the clinic, could lower the apoptotic threshold in chemoresistant PDAC cells and be synergistic with BH3 mimetics that neutralize anti-apoptotic proteins. Computational studies with TVB-3166 and TVB-3664, two analogues of the clinical-grade FASNi TVB-2640 (denifanstat), confirmed their uncompetitive behavior towards NADPH when bound to the FASN ketoacyl reductase domain. The extent of NADPH accumulation, a consequence of FASN inhibition, paralleled the sensitivity of PDAC cells to the apoptotic effects of TVB FASNis in conventional PDAC cell lines that naturally express varying levels of FASN. FASN inhibition dramatically increased the sensitivity of "FASN-high" expressing PDAC cells to the BCL2/BCL-XL/BCL-W inhibitor ABT-263/navitoclax and the BCL2-selective inhibitor ABT-199/venetoclax, both in vitro and in in vivo xenografted tumors. The ability of TVB FASNis to shift the balance of pro- and anti-apoptotic proteins and thereby push PDAC cells closer to the apoptotic threshold was also observed in cell lines developed from patient-derived xenografts (PDXs) representative of the classical (pancreatic) transcriptomic subtype of PDAC. Experiments in PDAC PDXs in vivo confirmed the synergistic antitumor activity of TVB-3664 with navitoclax and venetoclax, independent of the nature of the replication stress signature of patient-derived PDAC cells. The discovery that targeted inhibition of FASN is a metabolic perturbation that sensitizes PDAC cells to BH3 mimetics warrants further investigation to overcome resistance to mitochondrial apoptosis in PDAC patients

A tale of two topological isomers: Uptuning [FeIV(O)(Me4cyclam)]2+ for olefin epoxidation

2025-03-21T11:44:45Z

A tale of two topological isomers: Uptuning [FeIV(O)(Me4cyclam)]2+ for olefin epoxidation Chandra, Bittu; Ahsan, Faiza; Sheng, Yuan; Swart, Marcel; Que, Lawrence The distinct oxidative reactivities reported here for the TMC-anti and TMC-syn isomers are surprising and require the examination of what factors can give rise to such differences for this class of iron complexes. In particular, our observation that the oxygen atom transfer reactivity of a nonheme FeIV=O unit can be so significantly enhanced by a simple flip in its orientation relative to its macrocyclic tetraamine host is truly remarkable and suggests that there is much more that can be learned for catalyst design by paying attention to the effect of ligand topology on the iron active site