RSC Advances

Chen, Taoyi; Manz, Thomas A.

doi: 10.1039/c9ra07327bpmid: 35539031

A host of important performance properties for metal–organic frameworks (MOFs) and other complex materials can be calculated by modeling statistical ensembles. The principle challenge is to develop accurate and computationally efficient interaction models for these simulations. Two major approaches are (i) ab initio molecular dynamics in which the interaction model is provided by an exchange–correlation theory (e.g., DFT + dispersion functional) and (ii) molecular mechanics in which the interaction model is a parameterized classical force field. The first approach requires further development to improve computational speed. The second approach requires further development to automate accurate forcefield parameterization. Because of the extreme chemical diversity across thousands of MOF structures, this problem is still mostly unsolved today. For example, here we show structures in the 2014 CoRE MOF database contain more than 8 thousand different atom types based on first and second neighbors. Our results showed that atom types based on both first and second neighbors adequately capture the chemical environment, but atom types based on only first neighbors do not. For 3056 MOFs, we used density functional theory (DFT) followed by DDEC6 atomic population analysis to extract a host of important forcefield precursors: partial atomic charges; atom-in-material (AIM) C6, C8, and C10 dispersion coefficients; AIM dipole and quadrupole moments; various AIM polarizabilities; quantum Drude oscillator parameters; AIM electron cloud parameters; etc. Electrostatic parameters were validated through comparisons to the DFT-computed electrostatic potential. These forcefield precursors should find widespread applications to developing MOF force fields.

Badar, Asim; Arif, Zarina; Islam, Shireen Naaz; Alam, Khursheed

doi: 10.1039/c9ra05875cpmid: 35539070

Carbamylation is an ubiquitous process in which cyanate (OCN−) reacts with the N-terminal amino or ε-amino moiety and generates α-carbamyl amino acids and ε-carbamyl-lysine (homocitrulline). The process leads to irreversible changes in protein charge, structure and function. In this study, we have investigated the effect of carbamyl (generated from potassium cyanate) on human serum albumin (HSA) structure and function. The carbamylated-HSA (c-HSA) showed various modifications when examined by UV, fluorescence, FT-IR and far-UV CD spectroscopies. c-HSA exhibited hypochromicity, loss in α-helical content, changes in the amide I and amide II band, etc. Native-PAGE showed increase in the mobility of c-HSA compared to native-HSA. Aggregate(s) formation in c-HSA was detected by thioflavin T dye. The biochemical investigations carried out on c-HSA suggested increase in carbonyl content and decreased binding of TNBS (trinitrobenzenesulphonic acid) and Sakaguchi reagent. The attachment of the carbamyl moiety to HSA was confirmed from MALDI-TOF results. The functional defects in c-HSA were confirmed from the low binding of bilirubin. Taken together, carbamylation of albumin caused changes in the structural and functional properties of HSA. To the best of our knowledge, this is the first report on detailed biophysical characterization of carbamylated-HSA.

Zhang, Hao; Liu, Weihua; Tian, Feng; Tang, Zhongfeng; Lin, Haitao

doi: 10.1039/c9ra06656jpmid: 35539060

Treating water that has been polluted with chemical dyes is an important task related to water resources. Advanced oxidation processes are highly efficient for the destruction of organic contaminants. In this study, a Co3O4/graphene oxide (GO)/polyacrylonitrile (PAN) filter membrane was prepared through hydrothermal synthesis followed by vacuum filtration. The samples were characterised using different methods. The results showed that the Co3O4/GO sheets securely entered the voids of the PAN nanofibres. The Co3O4/GO/PAN filter membrane demonstrated the effective degradation of the organic dye Orange II, with a degradation rate of 93.5949%. The degradation rate remained at a high level after five cycles. The Co3O4/GO/PAN filter membrane has huge potential for application in industrial dye wastewater treatment.

Ma, Tianyu; Xu, Lihua; Wang, Xinming; Li, Jia; Guo, Lanping; Wang, Xiao

doi: 10.1039/c9ra06969kpmid: 35539068

Phenolic acids represented by caffeoylquinic acids in Xanthii Fructus have various pharmacological activities such as anti-inflammatory, anti-nociceptive, anti-oxidative and anti-allergic effects. In this study, pH-zone-refining counter-current chromatography was successfully applied in the segmentation of crude samples and further separation of phenolic acids from Xanthii Fructus. We initially segmented 1.6 g of the crude sample to yield three sample fractions using a two-phase solvent system composed of EtOAc–ACN–H2O (4 : 1 : 5, v/v/v) with 10 mM TFA added to the organic phase as the stationary phase and 10 mM NH3·H2O added to the aqueous phase as the mobile phase. The first fraction was separated using EtOAc–H2O (1 : 1, v/v) (10 mM TFA was added in the upper phase and 20 mM NH3·H2O was added in the lower phase) solvent system, the second fraction containing low-content compounds was separated using semi-preparative high performance liquid chromatography, and the third fraction contained one pure compound. As a result, seven phenolic acids including six caffeoylquinic acid isomers (3-caffeoylquinic acid, 4-caffeoylquinic acid, 5-caffeoylquinic acid, 1,5-O-dicaffeoylquinic acid, 3,5-O-dicaffeoylquinic acid, and 4,5-O-dicaffeoylquinic acid) and caffeic acid were successfully isolated from Xanthii Fructus with purities above 90%. This study demonstrated that pH-ZRCCC is an efficient preparative separation method for phenolic acids, especially isomeric caffeoylquinic acids, from natural products.

Kaur, Sarabjeet; Sharma, Purshotam

doi: 10.1039/c9ra08001epmid: 35539032

Due to the inability of canonical nucleobases (adenine, uracil, guanine and cytosine) to spontaneously form ribonucleosides and base pairs in free form in solution, RNA is believed to be preceded by a primitive information polymer (preRNA). The preRNA is proposed to contain non-canonical, heterocyclic bases that possess the above-mentioned capabilities. An extensive search for such candidate heterocycles has recently revealed that barbituric acid (BA), melamine (MM) and 2,4,6-triaminopyrimidine (TAP) have the capability to spontaneously form ribonucleosides and supramolecular assemblies that are held by Watson–Crick type hydrogen-bonded base pairs involving BA, MM, TAP and cyanuric acid (CA) heterocycles. However, despite this evidence, the prebiotic formation pathways of these heterocycles have not been fully explored. Further, for these heterocycles to interact and assemble into informational polymers under prebiotic conditions, it is expected that they should have formed in the proximity of each other. In this context, the present work employs density functional theory to propose the associated radical based formation pathways starting from cyanamide. Our pathways suggest that cyanamide, its derivatives (malonic acid and urea) and malononitrile can form BA, MM, CA and TAP in the presence of ammonia and hydroxyl radicals. In addition to originating from a common precursor, similarities in the highest reaction barriers (13 to 20 kcal mol−1) obtained for these pathways suggest that these heterocycles may likely form under similar conditions. Specifically, these pathways are relevant to high energy events such as meteoritic impact during the late heavy bombardment period on the early earth, which would have created conditions where radicals might have formed in reasonable concentrations. Overall, the present study emphasizes the importance of cyanamide in prebiotic heterocycle formation.

Du, Chi-Xin; Huang, Zhu

doi: 10.1039/c9ra05956cpmid: 35539085

Amino acids in human tears play certain physiological roles and their determination is challenging due to complicated chemical properties. This study described a fast and sensitive method for the simultaneous determination of 15 amino acids (AAs) in tears by hydrophilic interaction liquid chromatography and quadrupole orbitrap mass spectrometry (HILIC-Q-Orbitrap-MS). Amino acids in tears were extracted by methanol, and then cleaned up with a solid phase extraction (SPE) cartridge. Chromatographic separation was performed on a 1.7 μm BEH Amide column within 8 min. Tear samples spiked with free AAs were tested in terms of linearity, sensitivity, repeatability, and recovery. Two stable isotope-labeled amino acids were used as internal standards to improve the method performance. Recoveries for all analytes ranged from 89 to 107%. Intra-day and inter-day precision, expressed as relative standard deviations, were all below 10%, and the method detection limits ranged from 0.02 μmol L−1 to 0.11 μmol L−1. The developed method with high throughput and high analyte specificity shows good promise for consistent analysis of free amino acids in tears.

Wang, Bin; Du, Min; Zhang, Jing; Li, Chengjie; Liu, Jie; Liu, Huanxia; Li, Rongrong; Li, Zhuoran

doi: 10.1039/c9ra05322kpmid: 35539064

The synthesized imidazoline phosphate quaternary ammonium salt has low stability, which is spontaneously and rapidly hydrolyzed to the long-chain fatty acid amide (LFA). The hydrolysate (LFA) has been found to be an efficient inhibitor for Q235 steel against CO2 corrosion, which yields a maximum value above 90% at a concentration of 1000 mg L−1. The LFA inhibitor acts as an anodic type inhibitor and its inhibition mechanism is a “negative catalysis effect”. The heteroatoms in the acyl, amine and phosphate groups in the LFA molecule are the active centers to bond with Fe atoms to form a chemisorbed film on the steel surface.

Leng, Faning; Liu, Yali; Li, Guobing; Lai, Wenjing; Zhang, Qian; Liu, Wuyi; Hu, Changpeng; Li, Pantong; Sheng, Fangfang; Huang, Jingbin; Zhang, Rong

doi: 10.1039/c9ra06245apmid: 35539053

Cu2−xSe nanoparticles (Cu2−xSe NPs) are widely used for optical diagnostic imaging and photothermal therapy due to their strong near-infrared (NIR) optical absorption. With the continuous expansion of applications using Cu2−xSe NPs, their biosafety has received increasing attention in recent years. Cu2−xSe NPs can enter the brain by crossing the blood–brain barrier, but the neurotoxicity of NPs remains unclear. The present investigation provides direct evidence that the toxicity of Cu2−xSe NPs can be specifically exploited to kill rat pheochromocytoma PC-12 cells (a cell line used as an in vitro model for brain neuron research) in dose- and time-dependent manners. These cytotoxicity events were accompanied by mitochondrial damage, adenosine triphosphate (ATP) depletion, production of oxidizing species (including reactive oxygen species (ROS), malondialdehyde (MDA) and hydrogen peroxide (H2O2)), as well as reductions in antioxidant defense systems (glutathione (GSH) and superoxide dismutase (SOD)). Moreover, our in vivo study also confirmed that Cu2−xSe NPs markedly induced neurotoxicity and oxidative stress damage in the striatum and hippocampal tissues of BALB/c mice. These findings suggest that Cu2−xSe NPs induce neurotoxicity in PC-12 cells and BALB/c mice via oxidative stress damage, which provides useful information for understanding the neurotoxicity of Cu2−xSe NPs.

Xu, Zili; Zhang, Fangfang; Lin, Weiran; Zhang, Haining

doi: 10.1039/c9ra07619kpmid: 35539037

Rational design and simple synthesis of carbon-based materials with high electrocatalytic activity are essential for their practical applications in electrochemical energy conversion and storage devices. Herein, we report the synthesis of nitrogen, sulfur co-doped three-dimensional interconnected hierarchically porous carbon (NSHPC) by zinc acetate assisted pyrolysis of polymer networks. The thus-synthesized NSHPC has a specific surface area of 1057 cm2 g−1 with the coexistence of micro- and meso-pores. As metal-free electrocatalyst, the NSHPC exhibits a promising activity towards oxygen reduction reactions as evidenced by the slightly negative shift of half-wave potential compared with commercial Pt/C catalyst. The assembled lithium ion battery using NSHPC as anode delivers the reversible capacity of 740 and 470 mA h g−1 at current densities of 2 and 5 A g−1 without performance decay after 1000 charge–discharge cycles. Moreover, the assembled supercapacitor using NSHPC as electrode has the capacitance of 203 F g−1 at 1 A g−1.

Wang, Xue; Chen, Shujun; Tang, Xiaomin; Lin, Daiqin; Qiu, Ping

doi: 10.1039/c9ra06481hpmid: 35539041

A ultrasensitive assay for the determination of uric acid (UA) based on Pt@Ag nanoflowers (Pt@Ag NFs) was constructed. H2O2 was formed by the reaction of uricase and UA and produced the hydroxyl radical (˙OH). The system was catalyzed by Pt@Ag NFs to change the color of 3,3′,5,5′-tetramethylbenzidine (TMB) from colorless to blue, and the morphology and chemical properties of Pt@Ag NFs were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. Under the optimized conditions, a linear relationship between the absorbance and UA concentration was in the range of 0.5–150 μM (R2 = 0.995) with a limit of detection of 0.3 μM (S/N = 3). The method can be applied to detection of UA in actual samples with satisfactory results. The proposed assay was successfully applied to the detection of UA in human serum with recoveries over 96.8%. Thus, these results imply that the UA assay provides an effective tool in fast clinical analysis of gout.