Engineering Silk Protein to Modulate Polymorphic Transitions for Green Lithography Resists.

Silk protein is being increasingly introduced as a prospective material for biomedical devices. However, a limited locus to intervene in nature-oriented silk protein makes it challenging to implement on-demand functions to silk. Here, we report how polymorphic transitions are related with molecular structures of artificially synthesized silk protein and design principles to construct a green-lithographic and high-performative protein resist. The repetition number and ratio of two major building blocks in synthesized silk protein are essential to determine the size and content of ß-sheet crystallites, and radicals resulting from tyrosine cleavages by the 193 nm laser irradiation induce the ß-sheet to α-helix transition. Synthesized silk is designed to exclusively comprise homogeneous building blocks and exhibit high crystallization and tyrosine-richness, thus constituting an excellent basis for developing a high-performance deep-UV photoresist. Additionally, our findings can be conjugated to design an electron-beam resist governed by the different irradiation-protein interaction mechanisms. All synthesis and lithography processes are fully water-based, promising green lithography. Using the engineered silk, a nanopatterned planar color filter showing the reduced angle dependence can be obtained. Our study provides insights into the industrial scale production of silk protein with on-demand functions.

A safe and sustainable bacterial cellulose nanofiber separator for lithium rechargeable batteries.

Bacterial cellulose nanofiber (BCNF) with high thermal stability produced by an ecofriendly process has emerged as a promising solution to realize safe and sustainable materials in the large-scale battery. However, an understanding of the actual thermal behavior of the BCNF in the full-cell battery has been lacking, and the yield is still limited for commercialization. Here, we report the entire process of BCNF production and battery manufacture. We systematically constructed a strain with the highest yield (31.5%) by increasing metabolic flux and improved safety by introducing a Lewis base to overcome thermochemical degradation in the battery. This report will open ways of exploiting the BCNF as a "single-layer" separator, a good alternative to the existing chemical-derived one, and thus can greatly contribute to solving the environmental and safety issues.

Improvement of succinate production by release of end-product inhibition in Corynebacterium glutamicum.

Succinate is a renewable-based platform chemical that may be used to produce a wide range of chemicals including 1,4-butanediol, tetrahydrofurane, and γ-butyrolactone. However, industrial fermentation of organic acids is often subject to end-product inhibition, which significantly retards cell growth and limits metabolic activities and final productivity. In this study, we report the development of metabolically engineered Corynebacterium glutamicum for high production of succinate by release of end-product inhibition coupled with an increase of key metabolic flux. It was found that the rates of glucose consumption and succinate production were significantly reduced by extracellular succinate in an engineered strain, S003. To understand the mechanism underlying the inhibition by succinate, comparative transcriptome analysis was performed. Among the downregulated genes, overexpression of the NCgl0275 gene was found to suppress the inhibition of glucose consumption and succinate production, resulting in a 37.7% increase in succinate production up to 55.4g/L in fed-batch fermentation. Further improvement was achieved by increasing the metabolic flux from PEP to OAA. The final engineered strain was able to produce 152.2g/L succinate, the highest production reported to date, with a yield of 1.1g/g glucose under anaerobic condition. These results suggest that the release of end-product inhibition coupled with an increase in key metabolic flux is a promising strategy for enhancing production of succinate.

GST2 is required for nitrogen starvation-induced filamentous growth in Candida albicans.

Candida albicans, the major human fungal pathogen, undergoes morphological transition from the budding yeast form to filamentous growth in response to nitrogen starvation. In this study, we identified a new function of GST2, whose expression was required for filamentous growth of C. albicans under nitrogen-limiting conditions. The ΔGst2p showed Gst activity and required response to oxidative stress. The Δgst2 mutant displayed predominantly yeast phase growth in low ammonium media. Such morphological defect of Δgst2 mutants was not rescued by overexpression of Mep2p, Cph1p, or Efg1p, but was rescued by either overexpression of a hyperactive RAS1(G13V) allele or through exogenous addition of cyclic AMP. In addition, the Δgst2 mutants had lower levels of RAS1 transcripts than wild-type cells under conditions of nitrogen starvation. These results were consistent with the Ras1-cAMP pathway as a possible downstream target of Gst2p. These findings suggest that Gst2p is a significant component of nitrogen starvation-induced filamentation in C. albicans.

Simultaneous integration of multiple genes into the Kluyveromyces marxianus chromosome.

While Kluyveromyces marxianus is a promising yeast strain for biotechnological applications, genetic engineering of this strain is still challenging, especially when multiple genes are to be transformed. Sequential gene integration, which takes advantage of repetitive insertion/excision of the URA3 gene as a marker, has been the best option until now, because the URA3-deletion mutant is the only precondition for this method. However, we found that the introduced gene is co-excised during the URA3 excision step for next gene introduction, resulting in a very low cumulative probability (<1.57×10⁻6 % for 4 genes) of integrating all genes of interest. To overcome this extremely low probability, and to reduce labor and time, all 4 genes were simultaneously transformed. Surprisingly, the infamously high 'non-homologous end joining' activity of K. marxianus enabled simultaneous integration of all 4 genes in a single step, with a probability of 7.9%. Various K. marxianus strains could also be similarly transformed. Our finding not only reduces the labor and time required for such procedures, but also removes a number of preconditions, such as pre-made vectors, selection markers and knockout mutants, which are needed to introduce many genes into K. marxianus.

Inhibition of yeast-to-hypha transition in Candida albicans by phorbasin H isolated from Phorbas sp.

Phorbasin H is a diterpene acid of a bisabolane-related skeletal class isolated from the marine sponge Phorbas sp. In this study, we examined whether phorbasin H acted as a yeast-to-hypha transition inhibitor of Candida albicans. Growth experiments suggest that this compound does not inhibit yeast cell growth but inhibits filamentous growth in C. albicans. Northern blot analysis of signaling pathway components indicated that phorbasin H inhibited the expression of mRNAs related to cAMP-Efg1 pathway. The exogenous addition of db-cAMP to C. albicans cells had no influence on the frequency of hyphal formation. The expression of hypha-specific HWP1 and ALS3 mRNAs, both of which are positively regulated by the important regulator of cell wall dynamics Efg1, was significantly inhibited by the addition of phorbasin H. This compound also reduced the ability of C. albicans cells to adhere in a dose-dependent manner. Our findings suggest that phorbasin H impacts the activity of the cAMP-Efg1 pathway, thus leading to an alteration of C. albicans morphology.

Acylated kaempferol glycosides from Laurus nobilis leaves and their inhibitory effects on Na+/K+-adenosine triphosphatase.

Na(+)/K(+)-adenosine triphosphatase (ATPase) inhibitors have considerable therapeutic potential against some heart diseases like congestive heart failure and cardiac arrhythmias. Through bioassay-guided separation of the leaf extract of Laurus nobilis, six acylated kaempferol glycosides (compounds 1-6) were isolated. Their structures were determined on the basis of spectroscopic analysis and comparison with reported data. All the isolates were subjected to in vitro bioassays to evaluate their inhibitory activities against Na(+)/K(+)-ATPase from porcine cerebral cortex and bacterial growth. These studies led to the identification of compounds 1-6 as potent Na(+)/K(+)-ATPase inhibitors, with IC(50) values in the range of 4.0 ± 0.1-10.4 ± 0.6 µM. These compounds also exhibited a broad spectrum of antibacterial activity. In particular, compounds 4 and 6 showed potent inhibitory activities against several bacterial strains, except Escherichia coli, with minimum inhibitory concentration (MIC) values in the range of 0.65-2.08 µg/mL. Thus, L. nobilis-derived acylated kaempferol glycosides may have a potential to be leads for the development of Na(+)/K(+) ATPase inhibitors (1-6) and antibacterial agents (4, 6).

Actin depolymerizing effect of trisoxazole-containing macrolides.

Oxazole-containing macrolides (1-5) isolated from the marine sponge Chondrosia corticata were evaluated for their actin depolymerizing activities by monitoring fluorescent intensity of pyrene F-actin. These studies led to the identification of (19Z)-halichondramide (5) as a new actin depolymerizing agent. The actin depolymerizing activity by (19Z)-halichondramide (5) was four times more potent than that of halichondramide (1). Compounds 1 and 5 also have potent antifungal activity. The preliminary structure-activity relationship of these compounds is described to elucidate the essential structural requirements.

Sargachromanols as inhibitors of Na+/K+ ATPase and isocitrate lyase.

Sargachromanols A-P (1-16), 16 meroterpenoids of the chromene class isolated from the brown alga Sargassum siliquastrum, were evaluated for their inhibitory activities toward Na(+)/K(+) ATPase from porcine cerebral cortex and isocitrate lyase (ICL) from Candida albicans. These studies led to the identification of compounds 4, 6, 8, and 12 as potent Na(+)/K(+) ATPase inhibitors. Compounds 12, 13, and 16 exhibited moderate ICL inhibitory activity. Compound 12 also showed weak antibacterial activity. The preliminary structure-activity relationship of these compounds is described to elucidate the essential structural requirements.

In vitro sortase A inhibitory and antimicrobial activity of flavonoids isolated from the roots of Sophora flavescens.

A series of flavonoids (1-14) was isolated from the roots of Sophora flavescens. We evaluated their ability to inhibit both microbial growth and sortase A, an enzyme that plays a key role in cell wall protein anchoring and virulence in Staphylococcus aureus. Most prenylated flavonoids (7-13) displayed potent inhibitory activity against gram-positive and gram-negative bacteria except E. coli, with minimum inhibitory concentrations values ranging from 4.40 to 27.7 µM, and weak or no activity against fungal strains tested. Kurarinol (6) was a potent inhibitor of sortase A, with an IC(50) value of 107.7 ± 6.6 µM. A preliminary structure-activity relationship, including essential structural requirements, is described.

Candida albicans PHO81 is required for the inhibition of hyphal development by farnesoic acid.

Farnesoic acid is a signaling molecule that inhibits the transition from budding yeast to filament formation in Candida albicans, but the molecular mechanism regulated by this substance is unknown. In this study, we analyzed the function of CaPHO81, which is induced by farnesoic acid. The pho81Δ mutant cells existed exclusively as filaments under favorable yeast growth conditions. Furthermore, the inhibition of hyphal growth and repression of CPH1, EFG1, HWP1, and GAP1 mRNA expression in response to farnesoic acid were defective in pho81Δ mutant cells. These data suggest a role for CaPHO81 in the inhibition of hyphal development by farnesoic acid.

Production of chromopyrrolic acid by coexpression of inkOD in a heterologous host Streptomyces albus.

Two ink genes, inkO and inkD, responsible for the earliest steps of K252a biosynthetic pathway, from Nonomurea longicantena JCM 11136 were heterologously coexpressed in Streptomycesalbus J1074. The resultant strain accumulated compound that was purified by HPLC and studied by NMR. Coexpression of inkOD yielded chromopyrrolic acid, the key intermediate in an indolocarbazole biosynthesis.

5-Hydroxyindole-type alkaloids, as Candida albicans isocitrate lyase inhibitors, from the tropical sponge Hyrtios sp.

Chemical investigations of the tropical marine sponge Hyrtios sp. have resulted in the isolation of a new alkaloid, 1-carboxy-6-hydroxy-3,4-dihydro-beta-carboline (1) together with the known metabolites, 6-hydroxy-3,4-dihydro-1-oxo-beta-carboline (2), 5-hydroxy-1H-indole-3-carboxylic acid methyl ester (3), serotonin (4), hyrtiosin A (5), 5-hydroxyindole-3-carbaldehyde (6), and hyrtiosin B (7). Their structures were elucidated on the basis of mass spectrometry and detailed 2D NMR spectroscopic data. Hyrtiosin B (7) displayed a potent inhibitory activity against isocitrate lyase (ICL) of Candida albicans with an IC(50) value of 89.0 microM.

Synthesis and antimicrobial activities of halogenated bis(hydroxyphenyl)methanes.

A series of halophenols was prepared by the reaction of bis(hydroxyphenyl)methanes with effective halogenating agents such as bromine and sulfuryl chloride. One of these compounds, a biologically active halophenol--2,2',3,3'-tetrabromo-4,4',5,5'-tetrahydroxydiphenylmethane (1)--frequently isolated from red algae, was synthesized for the first time. Other halophenols included several novel compounds, together with known derivatives that were synthesized from the phenolic intermediates, bis(3,4-dihydroxyphenyl)methane (5) and bis(2-hydroxyphenyl)methane (14). All of the synthesized compounds were tested for antimicrobial activity against Gram-positive, Gram-negative bacteria and fungi. The preliminary structure-activity relationship was investigated in order to determine the essential structural requirements for their antimicrobial activity. Of all these halophenols, 2,2',3,3',6-pentabromo-4,4',5,5'-tetrahydroxydiphenylmethane (8) was found to be the most active against Candidaalbicans, Aspergillusfumigatus, Trichophytonrubrum, and Trichophytonmentagrophytes while 3,3',5,5'-tetrachloro-2,2'-dihydroxydiphenylmethane (18) exerted a powerful antibacterial effect against Staphylococcusaureus, Bacillussubtilis, Micrococcusluteus, Proteusvulgaris, and Salmonellatyphimurium.

Sorangiadenosine, a new sesquiterpene adenoside from the myxobacterium Sorangium cellulosum.

Sorangiadenosine (1), a novel nucleoside possessing a bicyclic, eudesmane-type sesquiterpene as an auxiliary component, was isolated from the culture broth of the gliding bacterium Sorangium cellulosum KM1003, collected from Korean soil. The chemical structure of this compound was determined by combined spectroscopic and chemical analyses. The new compound exhibited moderate antibacterial activity against a wide range of bacterial strains.

Antimicrobial activities of the bromophenols from the red alga Odonthalia corymbifera and some synthetic derivatives.

A series of bromophenols was obtained by isolation from red alga Odonthalia corymbifera and by reactions of bis(hydroxyphenyl)methanes with bromine. New bromophenols including 3,3',5,5'-tetrabromo-2,2',4,4'-tetrahydroxydiphenylmethane (10), a regioisomer of the potent antimicrobial natural product, together with known derivatives were synthesized in high yield. All of the isolated and synthesized compounds were tested for antimicrobial activity against gram-negative, gram-positive bacteria and fungi. The preliminary structure-activity relationship, to elucidate the essential structure requirements for antimicrobial activity, has been described. Among the isolated natural products 2,2',3,3'-tetrabromo-4,4',5,5'-tetrahydroxydiphenylmethane (4) was found to be the most active derivative against Candida albicans, Aspergillus fumigatus, Trichophyton rubrum, and Trichophyton mentagrophytes. The synthetic bromophenols 3,3'-dibromo-6,6'-dihydroxydiphenylmethane (13) and 3,3',5,5'-tetrabromo-6,6'-dihydroxydiphenylmethane (14) showed potent antibacterial effect against Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus, Proteus vulgaris, and Salmonella typhimurium.

Aaptamines as sortase A inhibitors from the tropical sponge Aaptos aaptos.

Four aaptamines (1-4), 1H-benzo[de][1,6]-naphthyridine alkaloids, were isolated from the marine sponge Aaptos aaptos and their inhibitory activities against sortase A (SrtA), an enzyme that plays a key role in cell wall protein anchoring and virulence in Staphylococcus aureus, were evaluated. Isoaaptamine (2) was a potent inhibitor of SrtA, with an IC(50) value of 3.7+/-0.2 microg/mL. The suppression of fibronectin-binding activity by isoaaptamine (2) highlights its potential for the treatment of S. aureus infections via inhibition of SrtA activity. Our studies have identified a series of SrtA inhibitors, providing the basis for further development of potent inhibitors.

Inhibition of the pathogenicity of Magnaporthe grisea by bromophenols, isocitrate lyase inhibitors, from the red alga Odonthalia corymbifera.

Magnaporthe grisea is a fungal pathogen of rice that forms appressoria that penetrate the outer cuticle of the rice plant. Data from recent studies indicate that M. grisea isocitrate lyase (ICL), a key enzyme in the glyoxylate cycle, is highly expressed during appressorium-mediated plant infection. Bromophenols isolated from the red alga Odonthalia corymbifera exhibited potent ICL inhibitory activity and blocked appressoria formation by M. grisea in a concentration-dependent manner. In addition, these compounds protected the rice plants from infection by M. grisea. Rice plants infected with wild-type M. grisea Guy 11 exhibited significantly lower disease severity with bromophenol treatment than without, and the treatment effect was comparable to the behavior of the Deltaicl knockout mutant I-10. The protective effect of bromophenols and their strong inhibition of appressorium formation on rice plants suggest that ICL inhibitors may be promising candidates for crop protection, particularly to protect rice plants against M. grisea.

Inhibition of the bacterial surface protein anchoring transpeptidase sortase by isoquinoline alkaloids.

The inhibitory activity of Coptis chinensis rhizome-derived material was evaluated against sortase, a bacterial surface protein anchoring transpeptidase, from Staphylococcus aureus ATCC 6538p and compared to that of four commercially available isoquinoline alkaloids. The biologically active constituent of C. chinensis extract was characterized as the isoquinoline alkaloid, berberine chloride, by spectral analysis. The isolate was a potent inhibitor of sortase, with an IC50 value of 8.7 microg/ml and had antibacterial activity against Gram-positive bacteria with a minimum inhibitory concentration (MIC) in the range of 50-400 microg/ml. Among the four isoquinoline alkaloids tested, berberine chloride had strong inhibitory activity. These results indicate that berberine is a possible candidate for the development of a bacterial sortase inhibitor.

Inhibition of sortase, a bacterial surface protein anchoring transpeptidase, by beta-sitosterol-3-O-glucopyranoside from Fritillaria verticillata.

A glucosylsterol, beta-sitosterol-3-O-glucopyranoside, has been isolated as an active principle with sortase inhibitory effect from the bulbs of Fritillaria verticillata by bioassay-guided chromatographic fractionation. The isolate was a potent inhibitor of sortase, with an IC(50) value of 18.3 microg/ml and had antibacterial activity against Bacillus subtilis, Staphylococcus aureus, and Micrococcus leuteus with MIC values of 50, 200, and 400 microg/ml, respectively, indicating that this compound is a possible candidate for the development of a bacterial sortase inhibitor. In addition, sitosterol was found to be inactive upon sortase and bacterial cell growth. These results suggest that the inhibitory potency of beta-sitosterol-3-O-glucopyranoside is sensitively dependent upon the glucopyranoside side chain moiety.