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In pig production, early and abrupt weaning frequently causes weaning stress, which manifests as oxidative damage, barrier disruption, and digestion and absorption capacity decline. Lycopene exhibits beneficial antioxidant capacity in both humans and other animal models.The present study aimed to investigate the effects of lycopene supplementation on early weaning stress in piglets and the underlying mechanisms by examining the oxidative stress state, gut intestinal barrier function, and the gut microbiota.Twenty-four 21-day-old weaned piglets (Duroc × [Landrace × Yorkshire], castrated males, 5.48 ± 0.10 kg initial body weight) were randomly assigned to two treatments. The piglets were fed a basal diet (control treatment) or a basal diet supplemented with 50 mg/kg lycopene (lycopene treatment) for 28 days. Serum lipid levels, serum and jejunum enzyme activities, jejunum morphology, mRNA and protein expression, and gut microbiota were determined.Compared with the control treatment, lycopene supplementation increased serum CAT activity (P = 0.042, 62.0%); serum TC concentration (P = 0.020, 14.1%); and jejunum SOD (P = 0.032, 21.4%) activity, whereas it decreased serum (P = 0.039, 23.0%) and jejunum (P = 0.047, 20.9%) H2O2 concentrations. Additionally, lycopene increased the mRNA and protein expression of NRF2 (214.0%; 102.4%) and CD36 (100.8%; 145.2%) in the jejunum, whereas it decreased those of KEAP1 (55.6%; 39.8%). Lycopene also improved jejunal morphology, increasing the villus height (P = 0.018, 27.5%) and villus/crypt ratio (P 0.001, 57.9%). Furthermore, it increased the abundance of potentially beneficial bacterial groups, including Phascolarctobacterium and Parasutterella, and decreased that of potentially pathogenic bacterial groups, including Treponema_2 and Prevotellaceae_unclassified.Lycopene supplementation strengthens intestinal barrier function and improves the gut microbiota in weaned piglets by regulating intestinal antioxidant signaling.

The advanced cessation of lactation elevates the risk of programmed obesity and obesity-related metabolic disorders in adulthood. The study used multi-omics analysis to investigate the mechanism behind this phenomenon and the effects of leucine supplementation on ameliorating programmed obesity development. Wistar/SD rat offspring were subjected to early weaning (EW) at d 17 (EWWIS and EWSD groups) or normal weaning at d 21 (CWIS and CSD groups). Half rats from the EWSD group were selected to create a new group with two-month leucine supplementation at d 150. The results showed that EW impaired lipid metabolic gene expressions and increased insulin, neuropeptide Y, and feed intake, inducing obesity in adulthood. Six lipid metabolism-related genes (Acot1, Acot2, Acot4, Scd, Abcg8, and Cyp8b1) were influenced by EW during the whole experimental period. Additionally, adult early-weaned rats exhibited cholesterol and fatty acid β-oxidation disorders, liver taurine reduction, cholestasis, and insulin and leptin resistance. Leucine supplementation partly alleviated these metabolic disorders and increased liver L-carnitine, retarding programmed obesity development. This study provides new insights into the mechanism of programmed obesity development and the potential benefits of leucine supplementation, which may offer suggestions for life planning and programmed obesity prevention.

Obesity is the main factor involved in the onset of many diseases. Threonine supplementation has been demonstrated to reduce fat mass and serum triglycerides in already obese mice. However, it is unclear whether threonine could inhibit the development of obesity in mice without previous high-fat diet induction. In the present study, mice were fed a chow diet (CD) or a high-fat diet (HFD), supplemented or not with threonine (3.0% in drinking water) for 15 weeks. Results showed that mice subjected to chronic threonine supplementation showed decreased body weight, epididymal white adipose tissue weight, serum low-density lipoprotein cholesterol, and total cholesterol in comparison with HFD-fed mice. In the epididymal adipose tissue, gene expressions of sterol regulatory element-binding protein 1c and fatty acid synthase were up-regulated, while hormone sensitive lipase, adiponectin and fibroblast growth factor 21 were down-regulated. In the liver tissue, gene expressions of sirtuin1, adenosine monophosphate-activated protein kinase and peroxisome proliferator activated receptor γ co-activator 1α were up-regulated by threonine supplementation in HFD-fed mice. These results suggest that long-term threonine supplementation inhibited fat mass and improved lipid metabolism, making it a potential agent to prevent the development of diet-induced obesity.

Branched-chain amino acids (BCAA) showed multiple functions in glycolipid metabolism and protein synthesis. However, the impacts on the metabolic health of low or high dietary BCAA remain controversial due to the various experimental conditions. Gradient levels of BCAA were supplemented in lean mice for four weeks: 0BCAA (without BCAA), 1/2BCAA (half BCAA), 1BCAA (regular BCAA), and 2BCAA (double BCAA). The results showed that the diet without BCAA caused energy metabolic disorders, immune defects, weight loss, hyperinsulinemia, and hyperleptinemia. 1/2BCAA and 2BCAA diets reduced body fat percentage, but 1/2 BCAA also decreased muscle mass. 1/2BCAA and 2BCAA groups improved lipid and glucose metabolism by affecting metabolic genes. Meanwhile, significant differences between low and high dietary BCAA were observed. The results of this study provide evidence and reference for the controversy about dietary BCAA levels, which indicates that the main difference between low and high BCAA dietary levels may present in the longer term.

Emerging evidence shows that amino acids can modulate lipid metabolism. Aromatic amino acids (AAAs) serve as important precursors of several neurotransmitters and metabolic regulators that play a vital role in regulating nutrient metabolism. But whether AAAs have a lipid-lowering function remains unknown. Here mice were fed amino acid-defined diets containing AAAs at 1.82% and 3.64% for 3 weeks. We demonstrated that double AAA intake significantly decreased the serum and hepatic triglycerides and serum low-density lipoprotein cholesterol, but increased the high-density lipoprotein cholesterol as well as insulin tolerance. Combined metabolomic and transcriptomic analysis showed that the hepatic acidic pathway of bile acid synthesis was responsible for the improvement in lipid metabolism by AAA treatment. This study suggests that AAAs have the potential to ameliorate steatosis and provides a new alternative to improve lipid metabolism.

The impact of titanium dioxide nanoparticles (nano-TiO2) on the aquatic environment is an important issue due to their increasing application. Although nano-TiO2 was reported to show an effect on heavy metal toxicity to aquatic organisms, the underlying mechanism is not well understood. In this study, two bacterial species (Bacillus thuringiensis (B. thuringiensis) and Bacillus megaterium (B. megaterium)) from sediment were selected to study the effects of nano-TiO2 on copper toxicity. Nano-TiO2 was found to inhibit the growth of B. thuringiensis and enhance the oxidative stress damage caused by copper, whereas these effects were not observed for B. megaterium. Transmission electron microscopy and flow cytometry showed that B. thuringiensis has stronger association ability to nano-TiO2 than B. megaterium. The existence of the S-layer on the surface of B. thuringiensis might be the possible reason, leading to the difference in copper toxicity. This indicates that the characteristics of bacterial surfaces might be important to the toxicity responses of nanoparticles.

Branched chain amino acids (BCAAs), especially leucine (Leu), have been reported to decrease fat deposition. However, extensive studies have not been conducted to determine whether Leu and isoleucine (Ile) have the same effects in mice fed a high fat diet (HFD). Already obese mice induced by HFD were assigned to the following groups: HFD, HFD + Leu, HFD + Ile, and HFD + Leu + Ile. Chow diet was set as a negative control throughout the study. The results showed that adding Leu, Ile and their combination in drinking water significantly decreased relative white adipose tissue (WAT) weight and serum triglycerides, low-density lipoprotein, free fatty acid, and insulin compared with the HFD control. Insulin sensitivity and hepatic steatosis impaired by HFD were alleviated after Leu or Ile supplementation. Furthermore, lipid metabolism-related genes were modified, and the genes involved in the browning of WAT and beige selective markers were upregulated by dietary supplementation with Leu, Ile and their combination. Intestinal microbiota analysis showed that the ratio of Firmicutes-to-Bacteroidetes was decreased after Leu or Ile treatment. This study indicated that dietary supplementation with Leu or Ile reduced body weight and WAT weight by regulating lipid metabolism-related genes and browning of WAT, providing a new tool in the management of obesity and metabolic disorders.

Sweet potato vine, the byproduct of sweet potato, has a high nutritional value. Silage is an effective solution for nutrient preservation. This article explored the effects of sweet potato vine silage (SPVS) supplementation on meat quality, antioxidant capacity and immune function in finishing pigs. One hundred and eighty finishing pigs (Berkshire × Licha Black) with a body weight of 74.54 ± 3.32 kg were randomly divided into three groups. The three groups were separately fed basal diet (Ctrl), Ctrl supplemented with 2.5% SPVS (LSPVS) or 5% SPVS (HSPVS) on a dry matter basis. Results showed that the eye muscle area in the LSPVS group was significantly increased. The carcass weight in the HSPVS was significantly reduced compared with Ctrl. For the meat quality, only cooking loss in both HSPVS and LSPVS was reduced while other indexes had no significant differences. For the antioxidant capacity, the hepatic level of glutathione (GSH) peroxidase (GSH-PX) was significantly upregulated in LSPVS but downregulated in HSPVS. In the serum, HSPVS decreased GSH level and increased GSH-PX level. HSPVS significantly reduced hepatic interleukin-1β (IL-1β) levels and LSPVS significantly reduced IL-12 levels and increased IL-8 and IL-6 levels. Moreover, HSPVS and LSPVS promoted the secretion of immunoglobulin M (IgM) and IgG in the serum. Our data showed that low-dose SPVS supplementation improved carcass traits and high-dose SPVS supplementation increased immune function in finishing pigs, which provides a new alternative to improve animal health.

While the biological uptake of nanomaterials (NMs) has been widely investigated, few studies have correlated the adsorption of natural organic matter (NOM) to uptake patterns. NOM is ubiquitous in the aquatic environment, inevitably leading to adsorption. In the present study, mixtures of bovine serum albumin (BSA) and humic acid (HA) were adopted to simulate NOM, and the effects of organic matter adsorption on uptake and intracellular trafficking of AgNPs with varied alkyl chain lengths in Tetrahymena thermophila were investigated. Notably, adsorption of BSA was shown to enhance the uptake rate of hexyl AgNPs in T. thermophila via the caveolae-mediated pathway while HA exerted no effect. Moreover, coating with BSA induced transfer of NPs into a more acidic intracellular environment, which was dependent on the association constant between BSA and NPs. A lower association constant resulted in rapid dissociation of BSA from the nanosurface, which terminated further acidification of NPs. Our collective results suggest that the composition of adsorbed organic matter strongly affects the bioavailability of NPs. Additionally, these effects are highly dependent on the physicochemical properties and interactions of NPs with organic matter.

Branched chain amino acids (BCAA), especially leucine (Leu), have been reported to decrease fat deposition. However, opposite effects of BCAA on lipid metabolism have been observed. To determine the role of BCAA in lipid metabolism, an amino acid-defined diet was formulated and C57BL/6J mice were assigned into the following groups: amino acid-defined control diet and control diet supplemented with Leu, isoleucine, or valine. Nitrogen was balanced by proportionally mixed amino acids except BCAA. Results showed that dietary Leu supplementation significantly increased the levels of serum triglycerides, total cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol and urea nitrogen. Metabolomics showed that biosynthesis of unsaturated fatty acids was altered by Leu supplementation. Leu treatment up-regulated the expression of genes related to fat synthesis and down-regulated the expression of genes related to fatty acid synthesis. Furthermore, the genes and proteins of selective markers involved in browning of white adipose tissue (WAT) were up-regulated by dietary supplementation with Leu. This study indicated that dietary supplementation with Leu, but not isoleucine or valine, significantly affected lipid metabolism by regulating lipid metabolism-related genes and serum fatty acid concentration, providing a new tool in the management of obesity and metabolic disorders.

To enable efficient degradation of perfluorooctanoic acid (PFOA), we prepared and investigated a nanosheet photocatalyst (Pt/La

Background Sweet potato vine is the stem and leaf of sweet potato and is nutritious as feedstuff. Silage is an effective solution to retain nutritional value and is beneficial for the preservation. This article explored the effects of Sweet potato vine silage (SPVS) supplementation on meat quality, antioxidant capacity and immune function in finishing pigs. 180 finishing pigs (Berkshire×Licha Black) with body weight of 74.54 ± 3.32 kg were randomly divided into three groups with six pigs per pen and six replicate per treatment: control diet (CON), CON supplemented with 2.5% SPVS (LSPVS) and 5.0% SPVS (HSPVS). Results It showed that eye muscle area in the LSPVS group was significantly increased and carcass weight in the HSPVS was significantly reduced. Cooking loss in both HSPVS and LSPVS were significantly reduced. Hepatic level of glutathione peroxidase (GSH-PX) was significantly upregulated in LSPVS but downregulated in HSPVS. In serum, HSPVS decreased glutathione (GSH) level and increased GSH-PX level. HSPVS significantly reduced hepatic IL-1 level and LSPVS significantly reduced IL-12 level and increased IL-8 level. Moreover, HSPV promoted the secretion of IgM and IgG in serum. Conclusions SPVS supplementation improved animal performance, meat quality, antioxidant capacity and immune performance in finishing pigs, which provide a new alternative to improve animal health and substitute traditional feedstuff.

Scanning electrochemical microscopy (SECM) is used to measure the local electrochemical behavior of liquid/solid, liquid/gas and liquid/liquid interfaces. Atomic force microscopy (AFM) is a versatile tool to characterize micro- and nanostructure in terms of topography and mechanical properties. However, conventional SECM or AFM provides limited laterally resolved information on electrical or electrochemical properties at nanoscale. For instance, the activity of a nanomaterial surface at crystal facet levels is difficult to resolve by conventional electrochemistry methods. This paper reports the application of a combination of AFM and SECM, namely, AFM-SECM, to probe nanoscale surface electrochemical activity while acquiring high-resolution topographical data. Such measurements are critical to understanding the relationship between nanostructure and reaction activity, which is relevant to a wide range of applications in material science, life science and chemical processes. The versatility of the combined AFM-SECM is demonstrated by mapping topographical and electrochemical properties of faceted nanoparticles (NPs) and nanobubbles (NBs), respectively. Compared to previously reported SECM imaging of nanostructures, this AFM-SECM enables quantitative assessment of local surface activity or reactivity with higher resolution of surface mapping.

Branched-chain amino acids (BCAAs), particularly leucine, were reported to decrease obesity and relevant metabolic syndrome. However, whether valine has a similar effect has rarely been investigated. In the present study, mice were assigned into four treatments (n = 10): chow diet supplemented with water (CW) or valine (CV) and high-fat diet supplemented with water (HW) or valine (HV). Valine (3%, w/v) was supplied in the drinking water. The results showed that valine treatment markedly increased serum triglyceride and insulin levels of chow diet-fed mice. The body weight, serum triglyceride level, white adipose tissue weight, and glucose and insulin intolerance were significantly elevated by valine supplementation in high-fat diet-fed mice. Metabolomics and transcriptomics showed that several genes related to fat oxidation were downregulated, and arachidonic acid and linoleic acid metabolism were altered in the HV group compared to the HW group. In conclusion, valine supplementation did not suppress lipid deposition and metabolic disorders in mice, which provides a new understanding for BCAAs in the modulation of lipid metabolism.

Weaning transition usually impairs intestinal architecture and functions and results in gut-associated disorders in pigs. Understanding the changes in intestinal transcriptome and gut microbiota during weaning transition is important for elucidating the underlying mechanism of weaning stress. In the present study, we performed RNA-seq to determine the changes in intestinal transcriptome and 16S rRNA sequencing to measure the gut microbiota changes in the weaning transition. Transcriptome results indicated that weaning transition altered intestinal gene expression involved in nutrient transport and metabolism. Regarding fatty metabolism, fatty acid-binding protein 1 (FABP1), acyl-CoA dehydrogenase (ACADSB), and carnitine palmitoyltransferase 2 (CPT2) expression in the intestine was decreased by weaning. Genes related to bile acid metabolism were increased by weaning, including FABP6, farnesoid X receptor (FXR or NR1H4) and organic solute transporter-α (SLC51A). In addition, genes associated with oxidative stress were altered by weaning transition, including decreased catalase (CAT) and lactate dehydrogenase (LDHA) and increased glutathione peroxidase 2 (GPX2) and superoxide dismutase 3 (SOD3). Results of microbiota composition showed that the Firmicutes abundance and Firmicutes/Bacteroidetes ratio were increased and that the Proteobacteria abundance in the fecal microbiota was decreased by the weaning process; during the weaning transition, the Bacteroides and Fusobacterium abundances decreased markedly, and these bacteria nearly disappeared, while the Prevotella abundance showed a marked increase. Moreover, the levels of the microbial metabolites butyrate and acetate increased with changes in gut microbiota composition. In addition, predictive metagenome by PICRUSt analysis showed that the pathways related to D-glutamine and D-glutamate metabolism, citrate cycle (TCA cycle), peroxisome proliferators-activated receptor (PPAR) signaling, alpha-linolenic acid metabolism were decreased and the pathway related to retinol metabolism was increased in the gut microbiota of piglets during weaning transition. Our results showed that early weaning alters intestinal gene expression involved in nutrient metabolism, which may be due to the changes in microbiota composition.

Some amino acids (AAs) have been proven to suppress fat mass and improve insulin sensitivity. However, the impact of important essential AAs, threonine, lysine, and methionine, on obesity has not been clarified. In the present study, after an 8 week period of obesity induction, mice were grouped to receive either a high-fat diet (HFD) or HFD supplemented with lysine, threonine, or methionine (3% in drinking water) for another 10 weeks. The results showed that dietary supplementation with threonine significantly decreased body weight, epididymal and perirenal fat pad weights, serum concentrations of glucose, triacylglycerols, total cholesterol, and LDL-cholesterol compared to the HFD group. HOMA-IR and serum leptin and adiponectin were improved by threonine supplementation. In epididymal adipose tissue, threonine treatment significantly down-regulated the expression levels of lipogenesis and up-regulated expressions of lipolysis compared to the HFD group. Threonine addition stimulated the expression of UCP-1 and related genes in brown adipose tissue. However, lysine or methionine supplementation showed little effect on body weight, WAT weight, serum lipid profiles, and lipid-metabolism-related gene expressions of HFD-fed mice. These findings suggest that threonine inhibited fat mass and improved lipid metabolism of already obese mice, providing a potential agent in treating obesity.

Currently, the majority of antibiotics in clinical use have broad activity spectra, killing pathogenic and beneficial microorganisms indiscriminately. The disruption of the ecological balance of normal flora often results in secondary infections or other antibiotic-associated complications. Therefore, targeted antimicrobial therapies capable of specifically eliminating pathogenic bacteria while retaining the protective benefits of a normal microflora would be advantageous. In this study, we successfully constructed a series of Enterococcus faecalis-targeted antimicrobial peptides from wide-spectrum antimicrobial peptide precursors. These peptides are designed based on fusion of the species-specific peptide pheromone cCF10 and modification of the active region of the antimicrobial peptide. The results showed that cCF10-C4 possessed specific antimicrobial activity against E. faecalis and was not active against other types of bacteria tested. The specificity of this hybrid peptide was shown by the absence of antimicrobial effects in the pheromone-substituted derivative. Further studies indicated that cCF10-C4 and its parent peptide C4 exert their activities by damaging cytoplasmic membrane integrity. The present study reveals the application potential of these molecules as “probiotic” antimicrobials for the control of specific bacterial infections, and it also helps to elucidate the design and construction of species-specific antimicrobials with precise targeting specificity.

Electrochemical membrane filtration has proven to be successful for microbial removal and separation from water. In addition, membrane fouling could be mitigated by electrochemical reactions and electrostatic repulsion on a reactive membrane surface. This study assessed the filtration performances and fouling characteristics of electrochemically reactive ceramic membranes (a Magneli phase suboxide of TiO

Charge generation and separation are two key processes for semiconductor photocatalysis. Here, we use Pt as a single atom catalyst to systematically examine the facet-dependent electronic band structure and light absorption of the layered perovskite-type wide-gap semiconductor, lanthanum titanium oxide (La2Ti2O7, LTO) by means of density functional theory simulations. It is found that single Pt atom doping of different LTO surfaces (here, (100), (101) and (001)) can not only create states in the bandgap that would promote the formation of recombination centers, but also shift the optical absorption edge to the visible region. Interestingly, the Pt doping forms a heterojunction, with the valence band maximum consisting of Pt states and the conduction band minimum consisting of LTO states, respectively. To study the facet dependent surface activity, acetic acid (CH3COOH) was used as a model molecule to investigate the adsorption and charge transfer on the (101), (100) and (001) Pt-LTO surface facets. The results show that the (101) facet could enable stronger adsorption of CH3COOH by promoting more electron transfer during the interfacial interaction. Our theoretical findings aim to promote the design and optimization of the single atom catalysts (SACs) for photocatalytic applications and other broad catalysis systems.

Milk is an important food for mammalian neonates, but its insufficient production is a nutritional problem for humans and other animals. Recent studies indicate that dietary supplementation with l-arginine (Arg) increases milk production in mammals, including sows, rabbits, and cows. However, the underlying molecular mechanisms remain largely unknown. The present study was conducted with porcine mammary epithelial cells (PMECs) to test the hypothesis that Arg enhances milk protein synthesis via activation of the mechanistic target of rapamycin (mTOR) cell signaling. PMECs were cultured for 4 days in Arg-free basal medium supplemented with 10, 50, 200, or 500 μmol/L Arg. Rates of protein synthesis and degradation in cells were determined with the use of l-[ring-2,4-3H]phenylalanine. Cell medium was analyzed for β-casein and α-lactalbumin, whereas cells were used for quantifying total and phosphorylated levels of mTOR, ribosomal protein S6 kinase (p70S6K), 4E-binding protein 1 (4EBP1), ubiquitin, and proteasome. Addition of 50–500 μmol/L Arg to culture medium increased (P

Conventional membrane distillation (MD) undergoes interfacial temperature polarization and thus may suffer from a reduced thermal efficiency when using the hot saline water as the primary thermal driver. To address this issue, this study employed a conductive Fe3O4/polyaniline (PANI) coated polytetrafluoroethylene (Fe3O4/PANI@PTFE) membrane to achieve local interfacial heating under electromagnetic induction and promote the thermal efficiency of direct-contact MD (DCMD). Induction-responsive Fe3O4 nanoparticles were dispersed in a conductive PANI polymer matrix that binds to the hydrophobic porous PTFE membrane by spray coating. Dispersing Fe3O4 nanoparticles in a conductive PANI polymer matrix doubled the heating efficiency (2.0 °C s−1) than directly dispersing Fe3O4 nanoparticles onto PTFE without PANI (1.1 °C s−1). This enhanced heating efficiency is ascribed to the formation of multiple conductive pathways or eddy current channels via the conductive polymer networks. A parametric study of the DCMD performance revealed that the permeate flux increased from 0.7 to 3.4 L m−2 h−1 with the increase of the coolant flow velocity (1.4–22.9 cm min−1) and induction power (0.9–3.6 kW). However, increasing the feed (3.5 wt% NaCl solution) flow velocity (1.4–8.6 cm min−1) significantly reduced the permeate flux from 5.0 to 1.6 L m−2 h−1 due to the insufficient time of water/membrane contact for mass transfer. Moreover, thermal and mass transport processes at the induction-heated membrane interface were analyzed by finite element analysis (FEA), which matched well the experimental results and determined the thermal efficiency up to 88% as opposed to the reported levels (20–58%) for the conventional DCMD. Our study laid additional foundation for induction-heating DCMD by devising new composite membrane materials and new interfacial thermal and mass transfer mechanisms.

To enable efficient degradation of perfluorooctanoic acid (PFOA), we prepared and investigated a nanosheet photocatalyst (Pt/La2Ti2O7). Doping platinum nanoparticles on La2Ti2O7 varied the band structure and improved the photocatalytic activity due to the enhanced charge separation. Methanol as the electron donor and sacrificial reagent significantly promoted the photocatalytically reductive degradation of PFOA that reduced by 40% within 180 min under UV254 irradiation (1 mW∙cm 2). The density functional theory calculations were used to analyze the effects of Pt doping and band structures on interfacial electron transfer and degradation pathways. As opposed to photocatalytic oxidation, this UV/Pt/La2Ti2O7/CH3OH photocatalysis could abstract electrons from methanol and convert to free reactive radicals and photo-generated electrons to reductively defluorinate PFOA and potentially other polyhalogenated or perhalogenated organic compounds.

The intrinsic physicochemical properties of dissolved organic matter (DOM) may affect the mobility and toxicity of arsenic in aquatic environments. In the present study, the humic acid (HA) was ultra-filtered into five fractions according to molecular weight, and their physicochemical properties were characterized. Complexation of HA fractions with arsenite and arsenate was first determined by differential pulse polarography (DPP). The influences of HA fractions on arsenic toxicity were then examined using Daphnia magna as a model organism. As(V) had a higher affinity with HA than As(III), and their complexation was dependent on the total acidity and fluorescence characteristics of DOM. We demonstrated that the acidity and fluorescence also better explained the As toxicity to daphnids than UV absorbance and hydraulic diameter. Arsenic speciation determined by DPP significantly affected the toxicity of arsenite and arsenate. The results extended the free-ion activity model application to the case of arsenic. The present study clearly indicated that DOM with different molecular weights has distinct physicochemical properties, and could influence the speciation and toxicity of As to different extent.

The impact of titanium dioxide nanoparticles (nano-TiO

The C-terminal sequences of porcine thrombin encode a series of peptides with the characteristics of net positive charge and hydrophobicity, suggesting antimicrobial potential. In this study, we synthesized truncated C-terminal peptides to explore their antimicrobial potency and structure-activity relationship. The results showed that some peptides exerted antimicrobial activity against Gram-positive and Gram-negative bacteria, with selectivity for microbial membranes. The antimicrobial potency of the peptides increased with the extension of chain length. Considering toxicity to red blood cells, the 21-mer peptide T-6 displayed the highest therapeutic index of 43.4, suggesting its higher cell selectivity. Typical α-helical conformations were observed upon binding to a bacteria-mimicking environment. The derivatives tended to interact preferentially with negatively charged vesicles compared to zwitterionic vesicles. Flow cytometry and electron microscopy revealed that the peptides targeted bacterial cell membranes and disrupted cytoplasmic membrane integrity, thereby causing the release of cellular contents leading to cell death. Peptide-membrane interaction experiments provided evidence that the peptides killed bacteria via a membrane-mediating mechanism. In summary, the C-terminal sequence of porcine thrombin has antimicrobial functions.

Milk is an important food for mammalian neonates, but its insufficient production is a nutritional problem for humans and other animals. Recent studies indicate that dietary supplementation with L-arginine (Arg) increases milk production in mammals, including sows, rabbits, and cows. However, the underlying molecular mechanisms remain largely unknown. The present study was conducted with porcine mammary epithelial cells (PMECs) to test the hypothesis that Arg enhances milk protein synthesis via activation of the mechanistic target of rapamycin (mTOR) cell signaling. PMECs were cultured for 4 days in Arg-free basal medium supplemented with 10, 50, 200, or 500 μmol/L Arg. Rates of protein synthesis and degradation in cells were determined with the use of L-[ring-2,4

Our previous study reported Val/Arg-rich peptides, and the relationship was linear between hydrophobicity and antimicrobial potency within a certain range. Here, we further develop a new series of analogs to investigate the effect of net charge and Pro residue on activity. Replacement of Gly with Ala or Pro led to the decrease in antimicrobial activity. The substitution of Gly with Ala retained its hemolytic activity, while the substitution with Pro significantly decreased the toxicity, suggesting positive effect of Pro on hemolytic activity. The increase in net charge from +4 to +6 significantly improved antimicrobial activity and decreased the hemolysis. However, antibacterial and hemolytic activities were not affected by increasing the net charge from +6 to +8, indicating a moderate net positive charge. The peptides produced larger blue shifts in PE/PG than in PC/cholesterol, suggesting a stronger affinity with negatively charged membrane over zwitterionic membrane. Lowering the net charge or insert of Pro led to the lack of α-helical structure in SDS micelles, which may be correlated with weakened antimicrobial potency. This study indicated that Val/Arg-rich peptides should have moderate net charge and Pro may play a role in reducing the toxicity against red blood cells.

Antimicrobial peptides (AMPs), which are produced by multicellular organisms as a defense mechanism against competing pathogenic microbes, appear to be excellent candidates for the development of novel antimicrobial agents. Amphipathicity is traditionally believed to be crucial to the de novo design or systematic optimization of AMPs. In this study, we designed a series of short α-helical AMPs with imperfect amphipathicity to augment the arsenal of strategies and to gain further insights into their antimicrobial and hemolytic activity. These imperfectly amphipathic α-helical AMPs were designed by replacing the paired charged amino acid residues on the polar face of an amphipathic peptide with tryptophan residues on the basis of α-helical protein folding principles. PRW4, an imperfectly amphipathic α-helical AMP with hydrogen bonds formed by paired tryptophan residues, was observed to be more selective towards bacterial cells than toward human red blood cells. PRW4 was also effective against Gram-negative and Gram-positive bacteria, and fluorescence spectroscopy, flow cytometry, scanning electron microscopy and transmission electron microscopy indicated that PRW4 killed microbial cells by permeabilizing the cell membrane and damaging their membrane integrity. Therefore, disruptive amphipathicity has excellent potential for the rational design and optimization of AMPs with promising antimicrobial activities.

In this study, the influence of isoleucine and arginine on the biological activity and peptide-membrane interactions of linear avian β-defensin-4 (RL38) analogs was investigated. Results of biological activities showed that the antimicrobial activities of AvBD-4 analogs were closely related to hydrophobicity and amphipathicity. The peptide GLI19 with high hydrophobicity value and amphipathicity displayed broad spectrum antimicrobial activity against both gram-negative and gram-positive, whereas GLR19 with increasing multiple charges only exhibited activity against gram-negative. The interaction between peptides and the liposome membrane demonstrated that the peptides preferentially bound to negatively charged phospholipids over zwitterionic phospholipids, which supported the antimicrobial activity data. The outer membranes assay further demonstrated that GLI19 had a greater capacity than the other tested peptides to penetrate the cell membrane at a low concentration. Collectively, the peptides derived from the bactericidal domain of linear β- defensins by truncation and hydrophobic amino acid substitution may be effective high-potential antibacterial agents.