ACS Publications最新文献

N-Acetylneuraminic acid (NeuAc) performs a variety of biological activities where it is used as a nutraceutical and pharmaceutical intermediate. N-Acetylglucosamine-2-epimerase (AGE) and N-acetylneuraminic lyase (NAL) are the most widely used key enzymes in the industrial production of NeuAc through whole-cell catalytic synthesis. However, both AGE and NAL catalyze reversible reactions, and the equilibrium of these two reactions lies between substrates and products, resulting in a lower conversion rate of NeuAc. In this study, affinity analysis based on the dynamic docking (ADD) strategy was used to rationally design the AGE and NAL to improve enzymes properties. The variant AGE^A172S/C118A showed a 2.19-fold improvement in the catalytic rate. Then, we combinatorially expressed the variant of AGE and NAL in two plasmids for whole cell catalytic synthesis. NeuAc production was 35% higher with the combination of AGE^A172S/C118A and NAL^F252M compared with the wild type. When substrate GlcNAc/Pyruvate was 3:8 and AGE^A172S/C118A and NAL^F252M expressed strains were 1:0.6, the molar conversion rate was 62%. Thus, our modification of AGE and NAL, the key enzymes in producing NeuAc, gave a better AGE variant AGE^A172S/C118A, which could produce 128 g/L NeuAc when using low substrate concentration (0.6 M GlcNAc).

The escalating prevalence of multidrug-resistant Gram-negative pathogens, coupled with dwindling antibiotic development, has created a critical void in the clinical pipeline. This alarming issue is exacerbated by the formation of biofilms by these superbugs and their frequent coexistence in mixed-species biofilms, conferring extreme antibiotic tolerance. Herein, we present an amphiphilic cationic macromolecule, ACM-A_Hex, as an innovative antibiotic adjuvant to rejuvenate and repurpose resistant antibiotics, for instance, rifampicin, fusidic acid, erythromycin, and chloramphenicol. ACM-A_Hex mildly perturbs the bacterial membrane, enhancing antibiotic permeability, hampers efflux machinery, and produces reactive oxygen species, resulting in a remarkable 64-1024-fold potentiation in antibacterial activity. The macromolecule reduces bacterial virulence and macromolecule-drug cocktail significantly eradicate both mono- and multispecies bacterial biofilms, achieving >99.9% bacterial reduction in the murine biofilm infection model. Demonstrating potent biocompatibility across multiple administration routes, ACM-A_Hex offers a promising strategy to restore obsolete antibiotics and combat recalcitrant Gram-negative biofilm-associated infections, advocating for further clinical evaluation as a next-generation macromolecular antibiotic adjuvant.

The microspecies-specific physicochemical properties of eutectic solids of sparingly water-soluble micronutrient, Vitamin B₂ (Riboflavin), with a few representative BCS drugs, viz., Theophylline, Theobromine, Mesalamine, and Barbituric acid are established. The interplay of solubility and drug permeation behavior is experimentally determined for the eutectic solids, and properties are corroborated with the concomitant relative concentrations of pH-dependent microspecies of Riboflavin and the drugs. Partner drug candidates are selected from different quadrants of BCS classification to apprehend the influence of their solubility on the overall efficacy of the eutectic solids. The coexistence and inseparable ionic, neutral, and/or zwitterionic microspecies are spotted, and the pH-reliant isomer-specific inflection of physicochemical and pharmacokinetic properties in such multicomponent solid formulations is demonstrated.

Parkinson's disease is a neurodegenerative proteinopathy that primarily affects mesencephalic dopaminergic neurons. This dopaminergic depletion can be phenotypically reproduced in various experimental models through the administration of two neurotoxins: N-methyl-4-phenylpyridinium (MPP⁺) and 6-hydroxydopamine (6-OHDA). The mechanisms underlying the cell death processes induced by these toxins remain a subject of debate. In this context, studies suggest that oxidative-stress-related processes may contribute to the dysfunction and death of dopaminergic neurons. Therefore, investigating pharmacological compounds that can counteract these processes remains crucial for developing therapeutic strategies targeting these neuropathological mechanisms. Withania somnifera (L.) Dunal, commonly known as ashwagandha, is a plant whose roots are used in Ayurvedic medicine to treat various ailments, including those affecting the central nervous system. The active compound Withaferin-A (WFA), a steroid lactone from the withanolide group, is reported to possess antioxidant properties. In this study, we explored the potential neuroprotective effects of WFA and two of its molecular derivatives, cr-591 and cr-777, which contain, respectively, an additional cysteine or glutathione chemical group, known for their antiradical properties. We demonstrated that WFA and its two derivatives, cr-591 and cr-777, protect the integrity and function of dopaminergic neurons exposed to the neurotoxins MPP⁺ and 6-OHDA both in vitro, using primary mesencephalic neuron cultures from rodents, and in vivo, using the nematode Caenorhabditis elegans.

Antibody-drug conjugates (ADCs) represent promising therapeutic constructs to enhance the selective delivery of drugs to target cells; however, attaining precise control over the timing and location of payload release remains challenging due to the complex intracellular processes that define ADC internalization, trafficking, and linker cleavage. In this study, we present novel real-time fluorogenic probes to monitor both subcellular dynamics of ADC trafficking and payload release. We optimized a tandem molecular design of sequential pH- and enzyme-activatable naphthalimide fluorophores to (1) track their subcellular localization along the endolysosomal pathway and (2) monitor linker cleavage with OFF-to-ON fluorescence switches. Live-cell imaging microscopy revealed that fluorogenic ADCs can traffic to the lysosomes and yet require residence time in these subcellular compartments for efficient linker cleavage. Notably, the compact size of fluorogenic naphthalimides did not impair the recognition of target cell surface reporters or the kinetics of payload release. This modular platform is applicable to many ADCs and holds promise to inform their rational design for optimal release profiles and therapeutic efficacy.

Endowing polyethylenes with photodegradability via incorporation of low densities of in-chain keto units could reduce the problematic environmental persistency of littered polymer waste. A breakthrough enabling such materials is the recent finding of nickel catalyzed nonalternating copolymerization of ethylene-carbon monoxide. We reveal irreversible catalyst deactivation pathways operative in this reaction. Reductive elimination of the common phosphinephenolate Ni(II) motif occurs with the acyl intermediates formed upon incorporation of carbon monoxide into the growing chain, as observed by low temperature NMR spectroscopy and single crystal X-ray crystallography of the isolated product. Further, we show that such decomposition pathways are generally relevant during ethylene-carbon monoxide copolymerizations under pressure reactor conditions. These findings guide the development of more stable and productive polymerization catalysts to enable the production of environmentally benign polyethylenes.

Triplet-triplet annihilation (TTA) enables photon upconversion by combining two lower-energy triplet excitons to produce a higher-energy singlet exciton. This mechanism enhances light-harvesting efficiency for solar energy conversion and enables the use of lower-energy photons in bioimaging and photoredox catalysis applications. The magnetic modulation of such high-energy excitons presents an exciting opportunity to develop molecular quantum information technologies. While the spin dynamics of triplet exciton pairs are sensitive to external magnetic fields, the magnetic field effects (MFEs) associated with these pairs are generally limited by spin statistics to at most 10% at low fields (<1 T), making them challenging to apply in technological advancements. In contrast, MFEs on spin-correlated radical pairs (SCRPs) can be significantly greater, surpassing those on triplet pairs. By using SCRPs-based molecular qubits as triplet sensitizers in the sensitized TTA scheme, we can magnetically modulate TTA and consequently, the delayed fluorescence of annihilators. In our current system, we have achieved more than 70% magnetic modulation of delayed fluorescence, effectively harnessing and even amplifying magnetic modulation within SCRPs to influence high-energy excitons. This work opens new opportunities for advancing spin-controlled chemical reactions and molecular quantum information technologies.

A theoretical study on the mechanism, regioselectivity, and enantioselectivity of NHC-catalyzed dearomatizing annulation of benzoxazoles with enals has been conducted using density functional theory calculations. Our calculated results indicate that the favored mechanism occurs through eight reaction steps: initial binding of the NHC to enals, followed by formation of the Breslow intermediate via proton transfer. Subsequent oxidation generates the α,β-unsaturated acylazolium intermediate, which can undergo Michael addition with benzoxazoles. Sequential protonation/deprotonation/cyclization produces the six-membered cyclic intermediate that undergoes catalyst elimination, leading to the final product. DABCO·H⁺ was found to play important roles in proton transfer and cyclization. Without DABCO·H⁺, the energy barrier up to 44.2 kcal/mol for step 2 is too high to be accessible. With DABCO·H⁺, the corresponding value is lowered to 18.6 kcal/mol. The energy barrier for cyclization can be lowered by 7.4 kcal/mol by using DABCO·H⁺. The Michael addition step determines both the enantioselectivity and the regioselectivity. According to NCI analysis, the enantioselectivity is controlled by the strong interactions (such as C-H···O, C-H···N, and π···π) between the α,β-unsaturated acylazolium intermediate and benzoxazoles. We also discuss the solvent and substituent effects on the enantioselectivity and the role of the NHC. The mechanistic insights obtained in the present study would help improving current reaction systems or designing new synthetic routes.