The Synergistic Lubrication Effects of h-BN and g-C3N4 Nanoparticles as Oil-Based Additives for Steel/Steel Contact.

The synergistic effect of different types of solid particles in liquid lubricants is of great interest. In this work, g-C3N4 nanosheets were initially prepared using a calcination method and then as-prepared, and h-BN were used as lubricating additives to the white oil. A comparison between the mixed additives and the single g-C3N4 or h-BN additives revealed that the base oil with the addition of g-C3N4 and h-BN showed the best lubricating properties. The results show a 12.3% reduction in friction coefficient, resulting in a 68.6% reduction in wear rate compared to the white oil when filled with 0.5 wt% g-C3N4 and h-BN (1:1 by weight). Moreover, the addition of g-C3N4 and h-BN improves the high-temperature lubrication properties of the white oil. However, the friction coefficient and wear rate increase with increasing oil temperature. The large contact area between g-C3N4 and its sliding counterpart and the strong adhesive force between h-BN and its sliding counterpart improve the film formation efficiency, leading to enhanced tribological properties under oil lubrication conditions.

A Widespread Glycosidase Confers Lobophorin Resistance and Host-Dependent Structural Diversity.

Identifying new environmental resistance determinants is significant to combat rising antibiotic resistance. Herein we report the unexpected correlation of a lobophorin (LOB) resistance-related glycosidase KijX with the host-dependent chemical diversity of LOBs, by a process of glycosylation, deglycosylation and reglycosylation. KijX homologues are widespread among bacteria, archaea and fungi, and encode the same glycohydrolytic activity on LOBs. The crystal structure of AcvX (a KijX homologue) shows a similar fold to that of the glycoside hydrolase family 113 and a special negatively charged groove to accommodate and deglycosylate LOBs. Antagonistic assays indicate kijX as a defense weapon of actinomycetes to combat LOB producers in environment, reflecting an elegant coevolution relationship. Our study provides insight into the KijX-related glycosidases as preexisting resistance determinants and represents an example of resistance genes accidentally integrated into natural product assembly.

Palindrome-Embedded Hairpin Structure and Its Target-Catalyzed Padlock Cyclization for Label-Free MicroRNA-Initiated Rolling Circle Amplification.

Highly sensitive detection of microRNAs (miRNAs) is of great significance in early diagnosis of cancers. Here, we develop a palindrome-embedded hairpin structure and its target-catalyzed padlock cyclization for rolling circle amplification, named PHP-RCA for simplicity, which can be applied in label-free ultrasensitive detection of miRNA. PHP-RCA is a facile system that consists of only an oligonucleotide probe with a palindrome-embedded hairpin structure (PHP). The two ends of PHP were extended as overhangs and designed with the complementary sequences of the target. Hence, the phosphorylated PHP can be cyclized by T4 DNA ligase in the presence of the target that serves as the ligation template. This ligation has formed a palindrome-embedded dumbbell-shaped probe (PDP) that allows phi29 polymerase to perform a typical target-primed RCA on PDP by taking miRNA as a primer, resulting in the production of a lengthy tandem repeat. Benefits from the palindromic sequences and hairpin-shaped structure in padlock double-stranded structures can be infinitely produced during the RCA reaction and provide numerous binding sites for SYBR Green I, a double-stranded dye, achieving a sharp response signal for label-free target detection. We have demonstrated that the proposed system exhibits a good linear range from 0.1 fM to 5 nM with a low detection limit of 0.1 fM, and the non-target miRNA can be clearly distinguished. The advantages of high efficiency, label-free signaling, and the use of only one oligonucleotide component make the PHP-RCA suitable for ultrasensitive, economic, and convenient detection of target miRNAs. This simple and powerful system is expected to provide a promising platform for tumor diagnosis, prognosis, and therapy.

Tribological Properties of Carbon Fabric/Epoxy Composites Filled with FGr@MoS2 Hybrids under Dry Sliding Conditions.

Hybrids of fluorinated graphite/MoS2 (FGr@MoS2) were prepared via a hydrothermal method and used as lubricating additives to take full advantage of the synergy between FGr and MoS2 in carbon-fiber-reinforced polymer (CFRP). The results show a 21.6% reduction in the friction coefficient compared to the neat sample when the CFRP was filled with 1.2 wt.% FGr@MoS2 hybrids. The addition of 1.5 wt.% FGr@MoS2 resulted in a 60.9% reduction in the wear rate compared to neat CFRP. For the 1.2 wt.% FGr@MoS2-reinforced CFRP, the friction coefficient maintained a relatively steady value of approximately 0.46 at various temperatures, indicating frictional stability. However, the wear rate increased by 13.95% at 60 °C compared to that at room temperature. The interfacial bonding force between the FGr@MoS2 hybrid and the matrix, as well as the adhesive force with the surface of the counterpart ball, is improved, caused by the heterostructure of FGr@MoS2, resulting in enhanced mechanical properties and formation efficiency as well as the transfer film on the surface of the counterpart ball. The results suggest that an FGr@MoS2 micro-nano structure is a promising additive to be applied in polymer tribology.

High-Temperature Tribological Behavior of HDPE Composites Reinforced by Short Carbon Fiber under Water-Lubricated Conditions.

The polymer water-lubricated bearing is widely used in marine transmission systems, and the tribological properties can be improved by addition of inorganic nano-fillers. The aim of this study is to investigate the effect of SCFs and temperature on the water-lubricating properties of high-density polyethylene (HDPE) composites. HDPE composites reinforced by varying content of short carbon fibers (SCFs) were fabricated via twin-screw extrusion and injection molding techniques to study the hardness and surface wettability of those composites. The tribological properties under water-lubricated conditions were investigated through a pin-on-disk reciprocating tribometer under different temperatures. The results showed that the increase in hardness of HDPE composites reached maximum to 42.9% after adding 25 wt % SCFs. The contact angle also increased with the increase in SCFs content and reached a maximum of 95.2° as the amount of SCFs increased to 20 wt %. The incorporation of SCFs increased the wear resistance and lubricating property of HDPE composites at different temperatures. The HDPE composite containing 20 wt % SCFs showed the lowest friction coefficient of 0.076 at 40 °C, and the wear track depth reached a maximum of 36.3 mm at 60 °C. Based on the surface wetting property and wear analysis, potential effect mechanisms of fillers and temperature were discussed. The knowledge from this study is useful for designing the anti-wear water-lubricated polymer bearing.

Natural products from mangrove sediments-derived microbes: Structural diversity, bioactivities, biosynthesis, and total synthesis.

The mangrove forests are a complex ecosystem, and the microbial communities in mangrove sediments play a critical role in the biogeochemical cycles of mangrove ecosystems. Mangrove sediments-derived microbes (MSM), as a rich reservoir of natural product diversity, could be utilized in the exploration of new antibiotics or drugs. To understand the structural diversity and bioactivities of the metabolites of MSM, this review for the first time provides a comprehensive overview of 519 natural products isolated from MSM with their bioactivities, up to 2021. Most of the structural types of these compounds are alkaloids, lactones, xanthones, quinones, terpenoids, and steroids. Among them, 210 compounds are obtained from bacteria, most of which are from Streptomyces, while 309 compounds are from fungus, especially genus Aspergillus and Penicillium. The pharmacological mechanisms of some representative lead compounds are well studied, revealing that they have important medicinal potentials, such as piericidins with anti-renal cell cancer effects, azalomycins with anti-MRSA activities, and ophiobolins as antineoplastic agents. The biosynthetic pathways of representative natural products from MSM have also been summarized, especially ikarugamycin, piericidins, divergolides, and azalomycins. In addition, the total synthetic strategies of representative secondary metabolites from MSM are also reviewed, such as piericidin A and borrelidin. This review provides an important reference for the research status of natural products isolated from MSM and the lead compounds worthy of further development, and reveals that MSM have important medicinal values and are worthy of further development.

A new xanthostatin analogue from the marine sponge-associated actinomycete Streptomyces sp. SCSIO 40064.

A new cyclo-heptadepsipeptide xanthostatin B (1), together with isobutyryl hexapeptide (2), xanthostatin (3), TXS-1 (4) and TXS-2 (5), were isolated from the marine sponge derived Streptomyces sp. SCSIO 40064. The structures were elucidated by comprehensive spectroscopic data analyses and comparison with the literatures. The D-Val unit in 1 was assigned by Marfey's method. The absolute configuration of 4 was determined by X-ray crystallographic analysis. Compounds 1‒5 were evaluated for the inhibitory activities against four pharmaceutical targets and six antibacterial indicator strains. Compound 5 displayed α-glucosidase inhibitory activity with IC50 value of 18.67 ± 1.27 µM.

Dassonmycins A and B, Polycyclic Thioalkaloids from a Marine Sponge-Derived Nocardiopsis dassonvillei SCSIO 40065.

Two polycyclic thioalkaloides dassonmycins A (1) and B (2) were isolated from Nocardiopsis dassonvillei SCSIO 40065 associated with marine sponge Petrosia sp. Structures of 1 and 2 were elucidated by comprehensive spectroscopic analysis and confirmed by single-crystal X-ray diffraction experiments, to have a 6/6/6/6-fused tetracyclic ring featuring a naphthoquinone[2,3-e]piperazine[1,2-c]thiomorpholine scaffold. Compound 2 formed a caged core through an additional ether bridge. Both compounds exhibited moderate antibacterial and cytotoxic activities.

Inactivation of Flavoenzyme-Encoding Gene flsO1 in Fluostatin Biosynthesis Leads to Diversified Angucyclinone Derivatives.

Inactivation of the flavoenzyme-encoding gene flsO1 in fluostatin biosynthesis led to the isolation of four new angucyclinone derivatives (11, 12, 14, and 15), among which fluostarenes A (14) and B (15) featured the unprecedented 6/6/5/6/6 pentacyclic skeleton with fusion of a benzo[b]fluorene and a six-membered lactone ring. Both 14 and 15 were putatively generated via quinone methide-mediated nonenzymatic reactions. Fluostarene B (15) exhibited cytotoxicity against several cancer cell lines with IC50 values ranging from 7 to 10 µM. Fluostarenes A (14), B (15), and PK1 (16) showed α-glucosidase inhibition activity with IC50 of 0.89, 1.58, and 0.13 µM, respectively. Successful complementation of the ΔflsO1 mutant with alpK from kinamycin biosynthesis suggests that FlsO1 should function equivalently to AlpK as a putative C-5 hydroxylase.

A new uridine derivative and a new indole derivative from the coral-associated actinomycete Pseudonocardia sp. SCSIO 11457.

A new uridine derivative 11457 A (1), and a new indole derivative 11457B (2), together with a known compound 1H-indole-2-carbaldehyde (3), were characterized from the fermentation broth of the actinomycete Pseudonocardia sp. SCSIO 11457, an isolate associated with the scleractinian coral Galaxea fascicularis. Upon detailed spectroscopic analysis, 11457 A (1) was identified as a uridine analog, and 11457B (2) was elucidated as an indole derivative 2-hydroxy-1-(1H-indol-2-yl)pentane-1,4-dione. Biological evaluation indicated that none of compounds 1-3 showed antibacterial activities against pathogenic bacteria and cytotoxic activities against human cancer cell lines.

Association Between Selenium Level in Blood and Glycolipid Metabolism in Residents of Enshi Prefecture, China.

The present study aimed to detect selenium (Se) levels in the blood of Enshi Prefecture residents in China and investigate the relationship between blood Se levels and glucose or lipid metabolism disorder. A cross-sectional study was conducted, and 1876 subjects were selected through cluster random sampling from Enshi Prefecture using a questionnaire survey, physical examinations, and biochemical blood tests. The mean blood Se level in the overall population was 0.128 ± 0.178 µg/mL. Se exhibits a "U"-shaped curve on the serum fasting plasma glucose (FPG) of the total samples, that is, when the blood Se is more than 0.131 µg/mL or less than 0.062 µg/mL, the FPG increases significantly. A significant negative correlation was demonstrated between the FPG levels of the 4-17-year-old age group and different blood Se levels (P < 0.001). No significant correlation was demonstrated between the serum triglyceride (TG) and blood Se levels. However, a positive correlation was demonstrated between blood Se and serum total cholesterol (TC) levels and the incidence of high cholesterol in the total population (P < 0.001). The odds ratio and related 95% confidence interval for the incidence of high cholesterol between the highest (≥ 0.133 µg/mL) and lowest blood Se (< 0.064 µg/mL) levels was 2.64 and 1.48-4.79, respectively. The results of this study are very important for the safety scope and risk-benefit assessment of Se in the human; however, further investigation with a larger sample size is required.

Deciphering Biosynthetic Enzymes Leading to 4-Chloro-6-Methyl-5,7-Dihydroxyphenylglycine, a Non-Proteinogenic Amino Acid in Totopotensamides.

Totopotensamide A (TPM A, 1) is a polyketide-peptide glycoside featuring a nonproteinogenic amino acid 4-chloro-6-methyl-5,7-dihydroxyphenylglycine (ClMeDPG). The biosynthetic gene cluster (BGC) of totopotensamides (tot) was previously activated by manipulating transcription regulators in marine-derived Streptomyces pactum SCSIO 02999. Herein, we report the heterologous expression of the tot BGC in Streptomyces lividans TK64, and the production improvement of TPM A via in-frame deletion of two negative regulators totR5 and totR3. The formation of ClMeDPG was proposed to require six enzymes, including four enzymes TotC1C2C3C4 for 3,5-dihydroxyphenylglycine (DPG) biosynthesis and two modifying enzymes TotH (halogenase) and TotM (methyltransferase). Heterologous expression of the four-gene cassette totC1C2C3C4 led to production of 3,5-dihydroxyphenylglyoxylate (DPGX). The aminotransferase TotC4 was biochemically characterized to convert DPGX to S-DPG. Inactivation of totH led to a mutant accumulated a deschloro derivative TPM H1, and the ΔtotHi/ΔtotMi double mutant afforded two deschloro-desmethyl products TPMs HM1 and HM2. A hydrolysis experiment demonstrated that the DPG moiety in TPM HM2 was S-DPG, consistent with that of the TotC4 enzymatic product. These results confirmed that TotH and TotM were responsible for ClMeDPG biosynthesis. Bioinformatics analysis indicated that both TotH and TotM might act on thiolation domain-tethered substrates. This study provided evidence for deciphering enzymes leading to ClMeDPG in TPM A, and unambiguously determined its absolute configuration as S.

Heterologous Expression Leads to Discovery of Diversified Lobophorin Analogues and a Flexible Glycosyltransferase.

The heterologous expression of the lobophorin biosynthetic gene cluster from marine-derived Streptomyces pactum SCSIO 02999 has led to the discovery of new analogues that carry d-kijanose (or its variants with a 3-amino or hydroxyl group) at C-9. The identification of intermediates resulting from the inactivation of lobG1 (encoding C-17 kijanosyltransferase) and lobG3 (encoding C-9 digitoxosyltransferase) demonstrates the substrate flexibility of LobG3 to also accept d-kijanose and its variants. Notably, two lobophorins with d-kijanose at C-9 show improved bioactivities.

Sodium butyrate induces autophagy in colorectal cancer cells through LKB1/AMPK signaling.

Butyrate is produced by the fermentation of undigested dietary fibers and acts as the promising candidate for cancer treatment. However, the mechanism underlying sodium butyrate (NaB)-induced autophagy in colorectal cancer is not yet completely understood. The expressions of LC3-II protein and mRNA were detected by western blot and quantitative RT-PCR in colorectal cancer (CRC) cell lines HCT-116 and HT-29, respectively. Autolysosome formation was observed by transmission electron microscope. AMPK and LKB1 were inhibited by chemical inhibitor or siRNAs and confirmed by western blot. NaB elevated the protein and mRNA expressions of LC3 in a dose-dependent manner. NaB treatment increased the formation of autolysosome and expression of phosphorylated liver kinase B1 (LKB1), AMP-activated protein kinase (AMPK), and acetyl-CoA carboxylase (ACC). Treatment with compound C (an inhibitor of AMPK) and siRNA-mediated knockdown of AMPK and LKB1 significantly attenuated NaB-induced autophagy in CRC cells. Collectively, these findings indicated that LKB1 and AMPK are critical for NaB-mediated autophagy and may act as the novel targets for colorectal cancer therapy in the future.

Direct interaction between selenoprotein R and Aß42.

Amyloid-ß (Aß) peptides have taken a central role in AD research, the aggregation of Aß peptide is involved in the progression of Alzheimer's disease (AD). The 35th amino acid was methionine (Met) in Aß peptides and it's redox state is critical in determining the biological activity of Aß. It has been suggested that oxidation of Met35 (Met35O) plays a key role in the formation of paranuclei and in the control of oligomerization pathway choice. As an antioxidative selenoenzyme, Selenoprotein R (SelR) plays important roles in reducing the R-form of MetO to Met to maintain intracellular redox balance. However, the relationship between SelR and Aß was little investigated. Here, we found that SelR can directly interact with Aß42, and the interaction between SelR and Aß42 was verified by fluorescence resonance energy transfer (FRET), co-immunoprecipitation (co-IP), and pull-down assays. SelR is closely related to AD, its biological functions in human brain become a research focus. This work implies that SelR makes it capable of modulating Aß42 aggregation and provides a novel avenue for further study on the mechanism of SelR in AD prevention.

Sodium Butyrate Induces Endoplasmic Reticulum Stress and Autophagy in Colorectal Cells: Implications for Apoptosis.

PURPOSE: Butyrate, a short-chain fatty acid derived from dietary fiber, inhibits proliferation and induces cell death in colorectal cancer cells. However, clinical trials have shown mixed results regarding the anti-tumor activities of butyrate. We have previously shown that sodium butyrate increases endoplasmic reticulum stress by altering intracellular calcium levels, a well-known autophagy trigger. Here, we investigated whether sodium butyrate-induced endoplasmic reticulum stress mediated autophagy, and whether there was crosstalk between autophagy and the sodium butyrate-induced apoptotic response in human colorectal cancer cells. METHODS: Human colorectal cancer cell lines (HCT-116 and HT-29) were treated with sodium butyrate at concentrations ranging from 0.5-5mM. Cell proliferation was assessed using MTT tetrazolium salt formation. Autophagy induction was confirmed through a combination of Western blotting for associated proteins, acridine orange staining for acidic vesicles, detection of autolysosomes (MDC staining), and electron microscopy. Apoptosis was quantified by flow cytometry using standard annexinV/propidium iodide staining and by assessing PARP-1 cleavage by Western blot. RESULTS: Sodium butyrate suppressed colorectal cancer cell proliferation, induced autophagy, and resulted in apoptotic cell death. The induction of autophagy was supported by the accumulation of acidic vesicular organelles and autolysosomes, and the expression of autophagy-associated proteins, including microtubule-associated protein II light chain 3 (LC3-II), beclin-1, and autophagocytosis-associated protein (Atg)3. The autophagy inhibitors 3-methyladenine (3-MA) and chloroquine inhibited sodium butyrate induced autophagy. Furthermore, sodium butyrate treatment markedly enhanced the expression of endoplasmic reticulum stress-associated proteins, including BIP, CHOP, PDI, and IRE-1a. When endoplasmic reticulum stress was inhibited by pharmacological (cycloheximide and mithramycin) and genetic (siRNA targeting BIP and CHOP) methods, the induction of BIP, PDI, IRE1a, and LC3-II was blocked, but PARP cleavage was markedly enhanced. DISCUSSION: Taken together, these results suggested that sodium butyrate-induced autophagy was mediated by endoplasmic reticulum stress, and that preventing autophagy by blocking the endoplasmic reticulum stress response enhanced sodium butyrate-induced apoptosis. These results provide novel insights into the anti-tumor mechanisms of butyric acid.

[Effect of sodium butyrate on apoptosis and stromal interaction molecule and Orai1 activity in human colon cancer HCT-116 cells in vitro].

OBJECTIVE: To investigate the mechanism underlying sodium butyrate (NaB)-induced apoptosis of a human colon cancer cell line HCT-116. METHODS: The apoptosis of HCT-116 cells induced by NaB was confirmed by hoechst33342 staining and AnnexinV+ PI assay. The changes in the intracellular localization of stromal interaction molecule (STIM1) and Orai1 following NaB treatment were detected by immunofluorescence technique. Western blotting was used to investigate the protein expression levels of STIM1 and Orai1. RESULTS: NaB induced apoptosis and caused translocation and colocalization of STIM1 and Orai1 in HCT-116 cells. CONCLUSION: The apoptosis of human colon cancer cells induced by NaB is correlated to the redistribution of STIM1 and Orai1.

[Research on quality specification of Herba Justiciae].

OBJECTIVE: To provide scientific basis for the utilization and development of Herba Justiciae by setting up the quality control specification of Herba Justiciae. METHOD: Moisture and ash were determined by aquametry and method of ash determination. And the bioactive constituents were analyzed by HPLC. RESULT: The contents of total ash, acid-insoluble ash, and moisture of 28 samples from different origins were determined. The quantitative analysis of chinensinaphthol methyl ether by HPLC were preformed, respectively. CONCLUSION: The established method can be used for the quality control of Herba Justiciae.

[The cloning of human augmentor of liver regeneration-interacting proteins].

AIM: To screen human augmentor of liver regeneration(hALR)-interacting proteins and to explore the mechanisms of hALR in liver regeneration. METHODS: The open reading frame of hALR was used to construct the "bait" plasmid and the genes encoding hALR-interacting proteins were screened from the human liver cDNA library that was pretransformed into yeast Y187 by yeast two-hybrid system. Bioinformatic analysis of the sequences of the positive clones were performed. RESULTS: The positive clones encoding metallothionein, albumin, selenoprotein P,Na/K-ATPase, and 2 unknown proteins were screened out. CONCLUSION: The successful cloning of the genes encoding proteins interacting with hALR may pave the way for studying the interaction between the above proteins and hALR, and the molecular mechanisms of biological effect of hALR.