The ab initio study and NBO interpretation of solvent effects on the structural stability and the chemical reactivity of penicillin-V conformations

Synthesis of samarium orthoferrite-based perovskite nanoparticles as a turn-on fluorescent probe for trace level detection of picric acid

Picric acid (2,4,6-trinitrophenol, PA) is a common constituent of many powerful explosives, thus, development of the chemical probes for trace level detection of PA is a crucial current challenge in both public security and environmental protection. In this work, the applicability of the new perovskite-type oxide SmFeO₃ nanoparticles as an inorganic fluorescence turn-on probe for the selective and sensitive recognition of PA in organic and aqueous media was investigated. The synthesis of nanoparticles SmFeO₃ was carried out using the surfactant-assisted templating approach which proceeds through the sol-gel process based on nonionic surfactant Triton X-100. The synthesized SmFeO₃ nanoparticles exhibited strong solvent-dependent emission at 330 nm wavelength with absorption maxima at 225 nm. Among the tested explosives, the probe showed the highest sensitivity and selectivity for detecting PA in water and water/acetonitrile mixture. The response time for detecting PA was less than 5 s. The limits of detection for PA in acetonitrile and water/acetonitrile mixture were 2.1 µM and 1.1 µM, respectively. Furthermore, to investigate the nature of the fluorescence turn-on sensing mechanism, the experimental data of the dynamic light scattering (DLS) technique and zeta-potential were used. Both techniques confirmed the aggregation-induced emission (AIE) mechanism for detection of PA with the synthesized turn-on probe. The results of the present work will have a considerable impact on the development and applications of a new class of inorganic fluorescence turn-on probes for the detection of PA.

Template-directed synthesis of Sm2Ti2O7 nanoparticles: a FRET-based fluorescent chemosensor for the fast and selective determination of picric acid

Fluorescence “turn off” detection of picric acid using a Sm₂Ti₂O₇ nanoprobe.

A Natural Deep Eutectic Solvent Formulated to Stabilize β-Lactam Antibiotics

β-lactam antibiotics, such as penicillin share a very unstable chemical structure. In water-based solutions, such as those used for clinical applications, the β-lactam ring is readily opened due to a nucleophilic or electrophilic attack, leading to the loss of antimicrobial activity. Since the achievement and maintenance of optimum therapeutic levels of β-lactam antibiotics is critical for the resolution of many infectious clinical situations, and to avoid antibiotic resistance generation, the design of new non-aqueous dosage forms is urgent. Recently, natural deep eutectic solvents (NADES) have emerged as alternative non-toxic and non-aqueous solvents for different biomedical applications. In this work, we formulated and characterized a NADES composed by betaine and urea (BU). Using this solvent, we evaluated the stability of clavulanic acid (CLV) and imipenem (IMP) and characterized their antimicrobial activities calculating the minimal inhibitory concentration. Characterization of BU solvent by infrared spectroscopy (IR) and nuclear magnetic resonance spectroscopy (NMR) indicated that the obtained solvent has a microstructure mainly based on hydrogen bonding interactions and water addition strongly affects its dynamic. The stability of β-lactam antibiotic IMP and CLV using this solvent was increased by 7 fold and 2.5 fold respectively compared to water when analysed seven days after being dissolved. Microbiological assays showed that antibacterial activity at day seven was significantly decreased for both CLV and IMP when dissolved in water, while no change in their antibacterial properties was observed when antibiotics were dissolved in BU. The increased stability of IMP and CLV in BU may be related to the inert behaviour of the solvent and the higher dynamic restriction that helps antibiotics to maintain a more stable conformation. These data suggest the potential use of BU as a solvent to prevent degradation of β-lactam antibiotics.

Theoretical investigation of NMR–NQR tensors of hallucinogenic harmine in monomeric and cluster states

In the present study, density functional theory was employed to analyze the structure and nuclear magnetic resonance (NMR) — nuclear quadrupole resonance (NQR) spectra of hallucinogenic harmine in monomeric, dimeric, trimeric, and tetrameric states in the gas phase. Furthermore, the effects of hydrogen and resonance interactions on the values of NMR and NQR parameters of nitrogen nuclei in the four states mentioned above were investigated. The computations at the B3LYP/6-311[Formula: see text]G** level of theory indicated that NQR — NMR parameters of nitrogen nuclei varied for each of the four states and were strongly affected by chemical environment, molecular cluster size and molecular interactions. Accordingly, by increasing the participation of lone pair electrons in resonance interactions and aromaticity development, the values of NMR chemical shielding around them increased, whereas their NQR parameters ([Formula: see text] and [Formula: see text] decreased. In contrast, it could be observed that resonance interaction was not the only effective factor influencing changes in values and trends of NMR — NQR parameters by passing from monomeric state to other ones. Moreover, the negative charge on nitrogen atoms and the possibility of hydrogen bond formation were other important factors influencing NMR — NQR parameters.