RSC Advances

Zhu, Xue-Lin; Wen, Chao; Ye, Qing-Mei; Xu, Wei; Zou, Deng-Lang; Liang, Guang-Ping; Zhang, Fan; Chen, Wan-Na; Jiang, Ren-Wang

doi: 10.1039/c7ra11979hpmid: 35542447

The glycosyltransferase OleD variant as a catalyst for the glycosylation of four pairs of epimers of cardiotonic steroids (CTS) are assessed. The results of this study demonstrated that the OleD-catalyze glycosylation of CTS is significantly influenced by the configuration at C-3 and the A/B fusion mode. 3β-OH and A/B ring cis fusion are favoured by OleD (ASP). An epoxide ring at C-14 and C-15 further increases the bioconversion rate; while an acetyl group at C-16 and lactone ring type at C-17 did not influence the biotransformation. A high conversion rate corresponded to a low Km value. A molecular docking simulation showed that filling of hydrophobic pocket II and interaction with residue Tyr115 may play an important role in the glycosylation reactions catalyzed by OleD glycosyltransferases. Furthermore, the glycosylation products showed a stronger inhibitory activity for Na+, K+-ATPase than the corresponding aglycones. This study provides the first stereoselective properties for OleD (ASP) catalyzed glycosylation.

Zhao, Guo; Wang, Hui; Liu, Gang

doi: 10.1039/c7ra12767gpmid: 35542410

In this study, a simple but effective electrochemical method was developed to minimize the interference from real soil samples and increase the sensitivity of Pb(ii) and Cd(ii) detection by square-wave anodic stripping voltammetry (SWASV) using a novel electrochemical measurement system, which can be used for the on-site determination of trace Cd(ii) and Pb(ii) in real soil samples. The method involved performing SWASV following double deposition and stripping steps at two in situ plated bismuth-film electrodes with drastically different surface properties. Pb(ii) and Cd(ii) were first deposited on an in situ plated bismuth-film graphite carbon paste electrode (Bi/GCPE). When the first deposition was finished, the GCPE was moved to a micro-electrolytic cell to perform the first stripping step. The following measurements were performed with the other deposition and stripping steps using a highly sensitive in situ plated bismuth-film multiwalled carbon nanotube–Nafion composite modified glassy carbon electrode (Bi/MWCNT–Nafion/GCE) as the working electrode. Pb(ii), Cd(ii) and Bi(iii) stripped from the GCPE in the micro-electrolytic cell were partially deposited on the MWCNT–Nafion/GCE, and the stripping current signals were obtained from their oxidation during the second stripping step. Considering the small volume of the micro-electrolytic cell, the concentrations of Cd(ii) and Pb(ii) were drastically higher than those in the bulk solution, and therefore, the detection limits were reduced. Under the optimized conditions, the concentrations in the linear range spanned from 1.0 to 45.0 μg L−1 for both Pb(ii) and Cd(ii), with a detection limit of 0.03 μg L−1 for Pb(ii) and 0.02 μg L−1 for Cd(ii) (S/N = 3). Finally, analyses of real samples were performed to detect trace levels of Pb(ii) and Cd(ii) in soil with satisfactory results.

Misichronis, Konstantinos; Wang, Weiyu; Cheng, Shiwang; Wang, Yangyang; Shrestha, Umesh; Dadmun, Mark; Mays, Jimmy W.; Saito, Tomonori

doi: 10.1039/c7ra08641epmid: 35542424

Multigraft copolymer superelastomers consisting of a poly(n-butyl acrylate) backbone and polystyrene side chains were synthesized and the viscoelastic properties of the non-sulfonated and sulfonated final materials were investigated using extensional rheology (SER3). The non-linear viscoelastic experiments revealed significantly increased true stresses (up to 10 times higher) after sulfonating only 2–3% of the copolymer while the materials maintained high elongation (<700%). The linear viscoelastic experiments showed that the storage and loss modulus are increased by sulfonation and that the copolymers can be readily tuned and further improved by increasing the number of branching points and the molecular weight of the backbone. In this way, we show that by tuning not only the molecular characteristics of the multigraft copolymers but also their architecture and chemical interaction, we can acquire thermoplastic superelastomer materials with desired viscoelastic properties.

Boersch, M.; Rudrawar, S.; Grant, G.; Zunk, M.

doi: 10.1039/c7ra12950epmid: 35542397

Menaquinone is essential in electron transport and ATP generation in all Gram-positive, and anaerobically respiring Gram-negative bacteria. By inhibiting menaquinone production in target organisms, bactericidal action can be achieved irrespective of the organisms' growth phase. This pathway is absent in human cells, as menaquinone is obtained only through the diet. This paper provides a succinct review of major advancements, where present, at all enzymatic steps of the biosynthetic pathway of menaquinone. Structure–activity relationships are evaluated, as well as results translating these relationships to growth inhibition studies.

You, Nan; Liu, Tian-Hong; Fan, Hong-Tao; Shen, Hua

doi: 10.1039/c7ra13074kpmid: 35542403

This work reported on the application of mercapto-functionalized silica-supported organic–inorganic hybrid sorbent as a solid phase extraction (SPE) extractant for effective separation and preconcentration of Sb(iii) species in real water samples. The influences of pH, sorbent amounts, flow rates and the concentration of eluent on the adsorption and desorption of Sb(iii) species had been evaluated. The recovery of Sb(iii) species at pH 5 with 100 mg mercapto-functionalized hybrid sorbent at the flow rate of 5.0 mL min−1 was greater than 95% without interference from all of metal ions tested. The trapped Sb(iii) species by extractant was then eluted with 5% HCl solution at the flow rate of 5.0 mL min−1. The proposed procedure permitted large enrichment factors of about 200 and higher for 10 μg L−1 of Sb(iii) species. The merits of analytical figures for the determination of Sb(iii) species were as follows: detection limit (3σ, n = 11), 2 ng L−1; precision, 1.6% (n = 11) for 10 μg L−1 of Sb(iii) species; the linear calibration curve presented in the concentration range of 1.0–200.0 μg L−1. The validity of the proposed procedure was checked by the analysis of standard reference materials. Excellent agreement between the analytical results and the certified values (t-test at 95% confidence level) was found. The mercapto-functionalized hybrid sorbent as a SPE extractant was applied to the determination of Sb(iii) species in various water samples with satisfactory results.

Zheng, Yang; Yu, Xinling; Lv, Songyang; Mykhailiuk, Pavel K.; Ma, Qiang; Hai, Li; Wu, Yong

doi: 10.1039/c7ra13141kpmid: 35558341

A practical synthesis of CHF2-substituted 3-azabicyclo[3.1.0]hexanes was developed for the first time. The key step was photochemical decomposition of CHF2-substituted pyrazolines. This protocol has the advantages of simple operation, and mild conditions, as well as excellent functional group tolerance, giving the desired products in moderate to excellent yields.

Li, Liansheng; Xiao, Rui; Wang, Qi; Rong, Zhen; Zhang, Xueqing; Zhou, Pingkun; Fu, Hanjiang; Wang, Shengqi; Wang, Zhidong

doi: 10.1039/c7ra12238apmid: 35542392

In a large-scale radiological catastrophe, it is expected that hundreds and thousands of people could be exposed to radiation. A rapid method is required for triage of casualties to determine proper medical treatment. In this article, mice were exposed to different radiation doses and sera of mice were investigated by surface-enhanced Raman spectroscopy (SERS) and orthogonal projections to latent structure discriminant analysis (OPLS-DA) after total body irradiation (TBI). The results of the present study indicated that differences have widened over time. The different radiation groups showed a slight overlap at 24 h and 72 h but were completely distinct at the 10th day after TBI. The SERS spectrum between the normal group and the irradiated group showed a significant difference at 24 hours. The same trend was depicted in scatting score plots. Significant differences in Raman peaks were found, such as 744 and 1495 cm−1 corresponding to riboflavin and 593 and 1204 cm−1 corresponding to l-tryptophan. The lack of riboflavin and l-tryptophan will influence metabolism levels. Above all, these results bear potential in the development of label-free and rapid tools for on-site detection and screening of irradiation injuries.

Si, Zhihao; Hu, Song; Cai, Di; Qin, Peiyong; Xu, Qinghong

doi: 10.1039/c7ra11043jpmid: 35542416

In the current work, MCM-41/polydimethylsiloxane (PDMS) mixed matrix membrane (MMM) was prepared for effective n-butanol pervaporation from a model aqueous solution. In order to improve the compatibility between MCM-41 and PDMS, different types of silane coupling agents including n-propyltrimethoxysilane (PTMS), n-octyltrimethoxysilane (OTMS), n-dodecyltrimethoxysilane (DTMS) and n-hexadecyltrimethoxysilane (HDTMS) were used to modify the MCM-41. The results showed that the highest n-butanol separation performance was achieved by bonding 20 wt% of PTMS-modified MCM-41 with PDMS. Under these conditions, total flux of 1476 g m−2 h−1 was obtained when separating a 1.5 wt% n-butanol aqueous solution at 55 °C. The total flux increased by nearly 40% compared to the pure PDMS membrane with no obvious changes of the n-butanol separation factor at the same time. The curing process of the casting solution was also significantly improved after MCM-41 modification.

Goel, Saurav; Stukowski, Alexander

doi: 10.1039/c7ra12219epmid: 35542430

A recent molecular dynamics simulation study on nanoindentation of diamond carried out by Xu et al. 1 has reported observation of the presence of a controversial hexagonal lonsdaleite phase of carbon in the indentation area. In this comment, we question the reported observation and attribute this anomaly to shortcomings of the long range bond order potential (LCBOP) employed in the nanoindentation study.

Chen, Ming-Hua; Chang, Shan-Shan; Dong, Biao; Yu, Li-Yan; Wu, Ye-Xiang; Wang, Ren-Zhong; Jiang, Wei; Gao, Zeng-Ping; Si, Shu-Yi

doi: 10.1039/c7ra13241gpmid: 35542440

Ahmpatinin iBu (1) and statinin iBu (2), two new linear peptides, a novel pyrrolidine derivative, (−)-(S)-2-[3-(6-methylheptanamido)-2-oxopyrrolidin-1-yl] acetic acid (3), and three known pepstatin derivatives (4–6) along with their corresponding methanolysis artifacts (7–9) were isolated from Streptomyces sp. CPCC 202950. Their structures were elucidated on the basis of extensive spectroscopic data using Marfey's analysis, chiral-phase HPLC, and ECD and OR calculation to determine the absolute configurations. Compound 1 contains an unusual amino acid, 4-amino-3-hydroxy-5-(4-methoxyphenyl)pentanoic acid (Ahmppa), and 3 is the first natural product with a 2-(3-amino-2-oxopyrrolidin-1-yl)acetic acid system. Compounds 1, 2, and 4–9 are HIV-1 protease inhibitors. In particular, ahmpatinin iBu (1) exhibits significant inhibitory activity against HIV-1 protease with an IC50 value of 1.79 nM. A preliminary structure–activity relationship is discussed.