Myricetin suppresses lipoteichoic acid‐induced interleukin‐1β and cyclooxygenase‐2 expression in human gingival fibroblasts

Periodontitis is an inflammatory disease affecting the connective tissue and supporting bone surrounding the teeth. In periodontitis, human gingival fibroblasts (HGFs) synthesize IL‐1β, causing a progressive inflammatory response. Flavones demonstrate a variety of biological activity: among others, they possess anti‐inflammatory properties. Myricetin is a flavone with a strong anti‐inflammatory activity. The objective of this study was to evaluate the effect of the flavonoid myricetin on HGFs under inflammatory conditions induced by lipoteichoic acid (LTA). the effect of myricetin on HGFs was assessed by measuring cell viability, signaling pathways and IL‐1β expression and synthesis. It was found that, over time, myricetin did not affect cell viability. However, it inhibited activation of p38 and extracellular‐signal‐regulated kinase‐1/2 in LTA‐treated HGFs and also blocked IκB degradation and cyclooxygenase‐2 and prostaglandin E2 synthesis and expression. These findings suggest that myricetin has therapeutic effects in the form of controlling LTA‐induced inflammatory responses.     

Uptake and incorporation of choline and ethanolamine into lipoteichoic acid and teichoic acid by the choline-independent mutant JY2190 of Streptococcus pneumoniae

Lipoteichoic acid- and teichoic acid-containing muropeptides were isolated from choline- or ethanolamine-grown cells of the choline-independent mutant JY2190 of Streptococcus pneumoniae. Choline was taken up and incorporated into lipoteichoic acid and teichoic acid with 81% efficiency, compared with the parent strain Rx1. With similar efficiency, ethanolamine was incorporated. Accordingly, the mutant is a valuable tool for identifying the individual genes encoding the enzymes of choline utilisation, because any of these genes can be deleted without affecting viability and growth rate.     

Inhibition of bacterial wall lysins by lipoteichoic acids and related compounds

Lipoteichoic acid (LTA) from several Gram-positive microorganisms, Forssman antigen (Fag) from $\text{Diplococcus pneumoniae}$ R36A, and an acidic lipopolysaccharide (ALP) from $\text{Micrococcus luteus}$ were examined for effects on four wall lysis systems. The LTAs inhibited the N-acetylmuramidases of $\text{Streptococcus faecalis}$ and $\text{Lactobacillus acidophilus}$, and the amidase of $\text{Bacillus subtilis}$ 168. Deacylated LTA failed to inhibit. LTAs failed to inhibit the amidase of pneumococcus. Fag inhibited the pneumococcal amidase, but had no effect on the other three systems.     

Antimicrobial activity and stability of protonectin with D‐amino acid substitutions

The misuse and overuse of antibiotics result in the emergence of resistant bacteria and fungi, which make an urgent need of the new antimicrobial agents. Nowadays, antimicrobial peptides have attracted great attention of researchers. However, the low physiological stability in biological system limits the application of naturally occurring antimicrobial peptides as novel therapeutics. In the present study, we synthesized derivatives of protonectin by substituting all the amino acid residues or the cationic lysine residue with the corresponding D ‐amino acids. Both the D ‐enantiomer of protonectin (D ‐prt) and D ‐Lys‐protonectin (D ‐Lys‐prt) exhibited strong antimicrobial activity against bacteria and fungi. Moreover, D ‐prt showed strong stability against trypsin, chymotrypsin and the human serum, while D ‐Lys‐prt only showed strong stability against trypsin. Circular dichroism analysis revealed that D ‐Lys‐prt still kept typical α‐helical structure in the membrane mimicking environment, while D ‐prt showed left hand α‐helical structure. In addition, propidium iodide uptake assay and bacteria and fungi killing experiments indicated that all D ‐amino acid substitution or partially D ‐amino acid substitution analogs could disrupt the integrity of membrane and lead the cell death. In summary, these findings suggested that D ‐prt and D ‐Lys‐prt might be promising candidate antibiotic agents for therapeutic application against resistant bacteria and fungi infection. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.     

Covalent immobilization of acetylcholinesterase on a novel polyacrylic acid‐based nanofiber membrane

In this study, polyacrylic acid‐based nanofiber (NF) membrane was prepared via electrospinning method. Acetylcholinesterase (AChE) from Electrophorus electricus was covalently immobilized onto polyacrylic acid‐based NF membrane by demonstrating efficient enzyme immobilization, and immobilization capacity of polymer membranes was found to be 0.4 mg/g. The novel NF membrane was synthesized via thermally activated surface reconstruction, and activation with carbonyldiimidazole upon electrospinning. The morphology of the polyacrylic acid‐based membrane was investigated by scanning electron microscopy, Fourier Transform Infrared Spectroscopy, and thermogravimetric analysis. The effect of temperature and pH on enzyme activity was investigated and maxima activities for free and immobilized enzyme were observed at 30 and 35°C, and pH 7.4 and 8.0, respectively. The effect of 1 mM Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Mg²⁺, Ca²⁺ ions on the stability of the immobilized AChE was also investigated. According to the Michaelis–Menten plot, AChE possessed a lower affinity to acetylthiocholine iodide after immobilization, and the Michaelis–Menten constant of immobilized and free AChE were found to be 0.5008 and 0.4733 mM, respectively. The immobilized AChE demonstrated satisfactory reusability, and even after 10 consecutive activity assay runs, AChE maintained ca. 87% of its initial activity. Free enzyme lost its activity completely within 60 days, while the immobilized enzyme retained approximately 70% of the initial activity under the same storage time. The favorable reusability of immobilized AChE enables the support to be employable to develop the AChE‐based biosensors.     

Surface immobilization and entrapping of enzymes on glutaraldehyde crosslinked gelatin particles

A mild and reproducible method has been developed for the surface-immobilization of enzymes on glutaraldehyde crosslinked gelatin beads. In this method glutaraldehyde is used in a dual capacity, as crosslinking agent and as the enzyme coupling agent. Glucoamylase (exo-α-1,4-d-glucosidase, EC 3.2.1.3), β-d-fructofuranosidase (invertase, EC 3.2.1.26) and β-d-glucoside (cellobiase, β-d-glucoside glucohydrolase, EC 3.2.1.21) have been successfully immobilized by this method, on the surface of the crosslinked gelatin particles. The method can be combined with the existing technology for the production of gelatin-entrapped enzymes. Thus, dual immobilized enzyme conjugates of glucoamylase and invertase have been prepared using this method, by entrapment of one enzyme in, and surface-binding of the other to, the gelatin matrix. The coupling of glucoamylase onto cross-linked gelatin particles by precipitation with poly(hexamethylenebiguanide hydrochloride) was also tested.     

Development of a thiol‐ene based screening platform for enzyme immobilization demonstrated using horseradish peroxidase

Efficient immobilization of enzymes on support surfaces requires an exact match between the surface chemistry and the specific enzyme. A successful match would normally be identified through time consuming screening of conventional resins in multiple experiments testing individual immobilization strategies. In this study we present a versatile strategy that largely expands the number of possible surface functionalities for enzyme immobilization in a single, generic platform. The combination of many individual surface chemistries and thus immobilization methods in one modular system permits faster and more efficient screening, which we believe will result in a higher chance of discovery of optimal surface/enzyme interactions. The proposed system consists of a thiol‐functional microplate prepared through fast photochemical curing of an off‐stoichiometric thiol‐ene (OSTE) mixture. Surface functionalization by thiol‐ene chemistry (TEC) resulted in the formation of a functional monolayer in each well, whereas, polymer surface grafts were introduced through surface chain transfer free radical polymerization (SCT‐FRP). Enzyme immobilization on the modified surfaces was evaluated by using a rhodamine labeled horseradish peroxidase (Rho‐HRP) as a model enzyme, and the amount of immobilized enzyme was qualitatively assessed by fluorescence intensity (FI) measurements. Subsequently, Rho‐HRP activity was measured directly on the surface. The broad range of utilized surface chemistries permits direct correlation of enzymatic activity to the surface functionality and improves the determination of promising enzyme‐surface candidates. The results underline the high potential of this system as a screening platform for synergistic immobilization of enzymes onto thiol‐ene polymer surfaces. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1267–1277, 2017     

Directed self‐immobilization of alkaline phosphatase on micro‐patterned substrates via genetically fused metal‐binding peptide

Current biotechnological applications such as biosensors, protein arrays, and microchips require oriented immobilization of enzymes. The characteristics of recognition, self‐assembly and ease of genetic manipulation make inorganic binding peptides an ideal molecular tool for site‐specific enzyme immobilization. Herein, we demonstrate the utilization of gold binding peptide (GBP1) as a molecular linker genetically fused to alkaline phosphatase (AP) and immobilized on gold substrate. Multiple tandem repeats (n = 5, 6, 7, 9) of gold binding peptide were fused to N‐terminus of AP (nGBP1‐AP) and the enzymes were expressed in E. coli cells. The binding and enzymatic activities of the bi‐functional fusion constructs were analyzed using quartz crystal microbalance spectroscopy and biochemical assays. Among the multiple‐repeat constructs, 5GBP1‐AP displayed the best bi‐functional activity and, therefore, was chosen for self‐immobilization studies. Adsorption and assembly properties of the fusion enzyme, 5GBP1‐AP, were studied via surface plasmon resonance spectroscopy and atomic force microscopy. We demonstrated self‐immobilization of the bi‐functional enzyme on micro‐patterned substrates where genetically linked 5GBP1‐AP displayed higher enzymatic activity per area compared to that of AP. Our results demonstrate the promising use of inorganic binding peptides as site‐specific molecular linkers for oriented enzyme immobilization with retained activity. Directed assembly of proteins on solids using genetically fused specific inorganic‐binding peptides has a potential utility in a wide range of biosensing and bioconversion processes. Biotechnol. Bioeng. 2009;103: 696–705. © 2009 Wiley Periodicals, Inc.     

Interactions between chensinin‐1, a natural antimicrobial peptide derived from Rana chensinensis,and lipopolysaccharide

Lipopolysaccharide (LPS) plays a critical role in the pathogenesis of sepsis caused by gram‐negative bacterial infections. Therefore, LPS‐neutralizing molecules would have important clinical applications. Chensinin‐1, a novel antimicrobial peptide with atypical structural features, was found in the skin secretions of the Chinese brown frog Rana chensinensis. To understand the role of LPS in the bacterial susceptibility to chensinin‐1 and to investigate its anti‐endotoxin effects, the interactions of chensinin‐1 with LPS were investigated in this study using circular dichroism, in situ IR, isothermal titration calorimetry, and zeta potential. This study is the first to use in situ IR spectroscopy to evaluate the secondary structural changes of this peptide. The capacity of chensinin‐1 to block the LPS‐dependent cytokine secretion of macrophages was also investigated. Our results show that chensinin‐1 can form α‐helical structures in LPS suspensions. LPS can affect the antimicrobial activity of chensinin‐1, and chensinin‐1 was able to mitigate the effects of LPS. These data may facilitate the development of antimicrobial peptides with potent antimicrobial and anti‐endotoxin activities. © 2015 Wiley Periodicals, Inc. Biopolymers 103: 719–726, 2015.     

NMR structure of rALF‐Pm3, an anti‐lipopolysaccharide factor from shrimp: Model of the possible lipid A‐binding site

The anti‐lipopolysaccharide factor ALF‐Pm3 is a 98‐residue protein identified in hemocytes from the black tiger shrimp Penaeus monodon. It was expressed in Pichia pastoris from the constitutive glyceraldehyde‐3‐phosphate dehydrogenase promoter as a folded and ¹⁵N uniformly labeled rALF‐Pm3 protein. Its 3D structure was established by NMR and consists of three α‐helices packed against a four‐stranded β‐sheet. The C³⁴? C⁵⁵ disulfide bond was shown to be essential for the structure stability. By using surface plasmon resonance, we demonstrated that rALF‐Pm3 binds to LPS, lipid A and to OM®‐174, a soluble analogue of lipid A. Biophysical studies of rALF‐Pm3/LPS and rALF‐Pm3/OM®‐174 complexes indicated rather high molecular sized aggregates, which prevented us to experimentally determine by NMR the binding mode of these lipids to rALF‐Pm3. However, on the basis of striking structural similarities to the FhuA/LPS complex, we designed an original model of the possible lipid A‐binding site of ALF‐Pm3. Such a binding site, located on the ALF‐Pm3 β‐sheet and involving seven charged residues, is well conserved in ALF‐L from Limulus polyphemus and in ALF‐T from Tachypleus tridentatus. In addition, our model is in agreement with experiments showing that β‐hairpin synthetic peptides corresponding to ALF‐L β‐sheet bind to LPS. Delineating lipid A‐binding site of ALFs will help go further in the de novo design of new antibacterial or LPS‐neutralizing drugs. © 2008 Wiley Periodicals, Inc. Biopolymers 91: 207–220, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Anti‐biofilm and sporicidal activity of peptides based on wheat puroindoline and barley hordoindoline proteins

The broad‐spectrum activity of antimicrobial peptides (AMPs) and low probability of development of host resistance make them excellent candidates as novel bio‐control agents. A number of AMPs are found to be cationic, and a small proportion of these are tryptophan‐rich. The puroindolines (PIN) are small, basic proteins found in wheat grains with proposed roles in biotic defence of seeds and seedlings. Synthetic peptides based on their unique tryptophan‐rich domain (TRD) display antimicrobial properties. Bacterial endospores and biofilms are highly resistant cells, with significant implications in both medical and food industries. In this study, the cationic PIN TRD‐based peptides PuroA (FPVTWRWWKWWKG‐NH₂) and Pina‐M (FSVTWRWWKWWKG‐NH₂) and the related barley hordoindoline (HIN) based Hina (FPVTWRWWTWWKG‐NH₂) were tested for effects on planktonic cells and biofilms of the common human pathogens including Pseudomonas aeruginosa, Listeria monocytogenes and the non‐pathogenic Listeria innocua. All peptides showed significant bactericidal activity. Further, PuroA and Pina‐M at 2 × MIC prevented initial biomass attachment by 85–90% and inhibited >90% of 6‐h preformed biofilms of all three organisms. However Hina, with a substitution of Lys‐9 with uncharged Thr, particularly inhibited Listeria biofilms. The PIN based peptides were also tested against vegetative cells and endospores of Bacillus subtilis. The results provided evidence that these tryptophan‐rich peptides could kill B. subtilis even in sporulated state, reducing the number of viable spores by 4 log units. The treated spores appeared withered under scanning electron microscopy. The results establish the potential of these tryptophan‐rich peptides in controlling persistent pathogens of relevance to food industries and human health. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.     

Demonstration of the presence of alditols and galacturonic acid in Vibrio parahaemolyticus O10 lipopolysaccharide

Abstract Identification of 4 unidentified neutral substances (X₁, X₂, X₃ and X₄) in lipopolysaccharides of Vibrio parahaemolyticus (Miyano et al. (1980) FEMS Microbiol. Lett. 8, 23–28, and 14, 145–148) was attempted. X₁ (1,4-anhydroribitol) was found to be formed from ribitol-5-phosphate during hydrolysis. X₂ was identified to be 2- O -methylribitol. X₃ and X₄ were found to be formed during hydrolysis of galacturonic acid and D-glycero-L-mannoheptose (or L-glycero-D-mannoheptose), respectively. The chemical structures of X₃ and X₄ remain to be determined.     

Short cationic antimicrobial peptides bind to human alpha‐1 acid glycoprotein with no implications for the in vitro bioactivity

Several drugs interact with the major plasma proteins serum albumin and alpha‐1 acid glycoprotein. Such binding may be either beneficial or disadvantageous from a pharmacokinetic perspective. In the present paper, we investigate the thermodynamics involved in the binding of a series of promising cationic antimicrobial peptides to the alpha‐1 acid glycoprotein using isothermal titration calorimetry. The drug‐like peptides are able to effectively destroy multiresistant bacterial strains, and members of this peptide class are currently in clinical phase II trials. Similar peptides, in a previous study, have been shown to bind to serum albumin resulting in a 10‐fold reduction in the peptides ability to kill bacteria in vitro. Here, it is shown that the peptides also are ligands for alpha‐1 glycoprotein with moderate binding affinities. The binding mode is investigated in detail using molecular docking, which maps the interaction to sub‐pockets I, II and III of the binding site. Despite this interaction, protein binding is shown to have little or no effect on the ability of the peptides to kill bacteria in vitro, either at normal physiological or acute phase concentrations. The results show that although the peptides interact with the binding pocket of alpha‐1 acid glycoprotein, the low stoichiometric binding ratio ensures that the interaction is not an obstacle for further development of these promising peptides as antimicrobial therapies. Copyright © 2013 John Wiley & Sons, Ltd.     

Tissue structure and macromolecular diffusion in umbilical cord immobilization of endogenous hyaluronic acid

Diffusion of endogenous hyaluronic acid and ¹²⁵I-labelled albumin, monitored by desorption from umbilical cord (Wharton's jelly) slices, was studied in relation to tissue structure. Diffusion of hyaluronic acid was Fickian and some two orders of magnitude slower than that in free solution. After treatment of tissue with trypsin which removes proteoglycan(s) and degrades glycoprotein microfibrils, hyaluronic acid mobility through the collagen fibril network that remains is increased by an order of magnitude. These findings indicate that the mobility of hyaluronic acid in tissue is reduced both by the collagen network and by the presence of proteoglycan(s) and/or microfibrils. Estimates of the reduction in mobility due to physical entanglements with the fibrillar networks show that these play a major role The mobility of hyaluronic acid found for intact tissue is sufficient for it to permeate the extracellular space within its metabolic turnover. time. Labelled albumin diffusion is intact tissue, on the other hand, is reduced by only some 30% relative to free solution. This is consistent with the approximate 10% reduction found for the polysaccharide-free tissue (given by the excluded volume fraction) and the approximate 20% reduction expected for the polysaccharides in the interstitial fluid. Similar effects appear to be involved in the mobility of endogenous diffusible proteins in tissue.     

Fine‐tuning sortase‐mediated immobilization of protein layers on surfaces using sequential deprotection and coupling

Increasing interest in protein immobilization on surfaces has heightened the need for techniques enabling layer‐by‐layer protein attachment. Here, we report a technique for controlling enzyme‐mediated immobilization of layers of protein on the surface using a genetically encoded protecting group. An enterokinase‐cleavable peptide sequence was inserted at the N‐terminus of bifunctional fluorescent proteins containing Sortase A substrate recognition tags at both ends to control Sortase A‐mediated protein immobilization on the surface layer‐by‐layer. Efficient, sequential immobilization of a second layer of protein using Sortase A required removal of the N‐terminal protecting group, suggesting the method enables multilayer synthesis using cyclic deprotection and coupling steps. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:824–831, 2017     

Suitability of buttermilk for fermentation with Lactobacillus helveticus and production of a functional peptide‐enriched powder by spray‐drying

Aim: To ferment buttermilk, a low‐cost by‐product of the manufacture of butter, with a proteolytic strain of Lactobacillus helveticus, to enhance its value by the production of a functional peptide‐enriched powder. Methods and Results: Buttermilk was fermented with Lact. helveticus 209, a strain chosen for its high proteolytic activity. To enhance the release of peptidic fractions, during fermentation pH was kept at 6 by using NaOH, Ca(CO)₃ or Ca(OH)₂. Cell‐free supernatant was recovered by centrifugation, supplemented or not with maltodextrin and spray‐dried. The profile of peptidic fractions released was studied by RP‐HPLC. The lactose, Na and Ca content was also determined. The powder obtained was administered to BALB/c mice for 5 or 7 consecutive days, resulting in the proliferation of IgA‐producing cells in the small intestine mucosa of the animals. Conclusions: Buttermilk is a suitable substrate for the fermentation with Lact. helveticus 209 and the release of peptide fractions able to be spray‐dried and to modulate the gut mucosa in vivo. Significance and Impact of the Study: A powder enriched with peptides released from buttermilk proteins, with potential applications as a functional food additive, was obtained by spray‐drying. A novel use of buttermilk as substrate for lactic fermentation is reported.     

Enhanced protein stability through minimally invasive,direct, covalent,and site‐specific immobilization

Bioconjugating protein to nonbiological surfaces is an essential component of many promising biotechnologies impacting diverse applications such as medical diagnostics, biocatalysis, biohazard detection, and proteomics. However, to enable the widespread economical use of immobilized‐protein technologies, long‐term stability, and reusability is essential. To enhance protein stability in harsh conditions, herein we report a minimally invasive and covalent bioconjugation that enables precise control of the immobilization location at potentially any surface‐accessible location where the incorporated unnatural amino acid does not impact protein structure and function. Specifically, the PRECISE system is introduced where a uniquely reactive unnatural amino acid was incorporated site‐specifically at a prespecified location in GFP using cell‐free protein synthesis. The GFP was then directly and covalently attached to superparamagnetic beads by the unnatural amino acid in a single click reaction. The immobilized GFP was probed for retained activity and stability under harsh conditions including freeze‐thaw cycling and incubation in urea at elevated temperatures. The immobilized GFP was more stable compared to unattached protein in all cases and for all durations observed. The enhanced stability of the immobilized protein is a promising step towards long‐term protein stability for biocatalysis and other immobilized‐protein applications. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2013