Ratio Of Mono Research Articles

The Influence of Devulcanization and Revulcanization on Sulfur Cross-Link Type/Rank: Recycling of Ground Tire Rubber.

Devulcanized rubber could be a valuable material feedstock to help in the manufacture of sustainable rubber products. However, the differences in the chemistry and structure of devulcanized rubber have limited industrial uptake. This work demonstrates how devulcanization affects the concentration and ratios of mono-, di-, and polysulfidic cross-links. These residual cross-links make devulcanized rubber chemically dissimilar from virgin rubber, affecting (re)vulcanization. The hypothesis that the sulfur rank of revulcanized material can be modified by the sulfur/accelerator ratio was evaluated by two different cure packages. Despite substantial differences in the accelerator/sulfur ratio, both recycled rubber compounds favored the formation of polysulfidic cross-links.

ON/OFF Spiroconjugation through Peripheral Functionalization: Impact on the Reactivity and Chiroptical Properties of Spirobifluorenes.

Spirobifluorenes are an important class of spiro compounds frequently used in the field of organic electronics. However, harnessing spiroconjugation to obtain high-performance in such structural motifs remains unexplored. We herein propose that peripheral functionalization may serve as a useful tool to control spiroconjugation in an ON/OFF manner on both chemical reactivity and photophysical properties. In particular, the ratio of mono- and di-functionalized spirobifluorenes found experimentally during their synthesis were found to be 3/2, 7/2, and 12/2 for phenyl, nitro-phenyl and amino-phenyl analogues, respectively. These remarkable reactivity differences correlate with the spiroconjugation character evaluated theoretically at the CAM-B3LYP/6-31G(d,p) level of theory. Additionally, comparison of experimental and predicted optical and chiroptical responses shows that spiroconjugated molecular orbitals have a significant or negligible involvement on the main electronic transitions depending on the peripheral functionality of the spirobifluorene.

The relationship between urinary phthalate metabolites and polycystic ovary syndrome in women undergoing in vitro fertilization: Nested case-control study

Certain endocrine disruptor chemicals are involved in the pathogenesis of polycystic ovary syndrome (PCOS), a hormonal disease related to infertility in women. Phthalates are the most common plasticizers found in several consumer products. Experimental and epidemiologic evidence suggests that some phthalates disrupt endocrine functions in reproductive mechanisms and development. We previously measured the levels of eight phthalate metabolites in the urine of 599 Saudi women who underwent in vitro fertilization (IVF) treatment and were enrolled in a prospective study (2015–2017). The current nested case-control study aimed to determine the association between urinary levels of phthalate metabolites and PCOS. Overall, 441 women from the IVF study were identified as eligible for this study. Women in the case group included those diagnosed with PCOS (N = 82). The control group comprised those unable to conceive due to male azoospermia or who underwent preimplantation genetic diagnosis (N = 359). Most urinary phthalate metabolite levels were several-fold higher than those reported in national surveys from other countries. The ratio of luteinizing hormone to follicle-stimulating hormone, an index of PCOS, was significantly higher in the case than in the control group, with no indication of its association with phthalate metabolites. The logistic regression model was applied after adjusting for confounders to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for each metabolite modeled as a natural logarithm (ln). For each ln-unit increase in the sum of the four di (2-ethylhexyl) phthalate (∑4DEHP) metabolites as well as two individual metabolites, mono-(2-ethyl-5-oxohexyl) phthalate and mono-(2-ethyl-5-carboxypentyl) phthalate, the odds of PCOS increased by 40.5% [OR = 1.405 (95% CI: 1.025, 1.925)], 41.1% [OR = 1.055 (95% CI: 1.055, 1.885)], and 38.6% [OR = 1.386 (95% CI: 1.033, 1.86)], respectively. In contrast, the % odds of PCOS decreased marginally significantly by 44% [OR = 0.560 (95% CI: 0.313, 1.002)] with an ln-unit increase of %MEHP4, the ratio of mono-(2-ethylhexyl) phthalate to ∑4DEHP. These findings suggest that DEHP may contribute to PCOS, and further investigation is required to understand the underlying mechanisms.

ANOPARTICLES ОF PLATINUM(II) OXO-HYDROCOMPLEXES: COMPOSITION, STRUCTURE, FORMATION MECHANISM

Formation, composition, and structure of nanoparticles of oxo-hydroxocomplexes (Pt(II)О-NPs) are studied with a number of physicochemical methods such as NMR, EXAFS, ТЕМ, SAXS, and UV spectroscopy. The obtained 195Pt, 133Cs, 17O NMR, and UV spectroscopy data are used as the basis to propose a mechanism of Pt(II)O-NP formation from K2PtCl4 aqueous solutions whose temperature and acidity effects on the reaction rate are also studied. The dimensional characteristics of obtained nanoparticles are studied by ТЕМ and SAXS. According to EXAFS data, the structure of freshly prepared Pt(II)О-NP samples is composed of PtCl2 fragments bridged by oxygen atoms. The Pt–O, Pt–Cl, and Pt…Pt distances are 2.01 A, 2.31 A, and 3.30 A, respectively. In the course of NP aging, chloride ligands leave the composition of nanoparticles which are gradually acquiring a structure similar to that of PtO. It is established that the K2PtCl4:NaOH ratio equal to 1:1 is sufficient for mononuclear Pt(II) complexes to transform into the oligomeric state. A possibility to control the ratio of mono- and polynuclear Pt(II) compounds in solution is discovered.

Effects of increased irradiance on biomass, photobiology, nutritional quality, and pigment composition of Arctic sea ice algae

Ice algae are key contributors to primary production and carbon fixation in the Arctic, and light availability is assumed to limit their growth and productivity. We investigated photo-physiological responses in sea ice algae to increased irradiance during a spring bloom in West Greenland. During a 14 d field experiment, light transmittance through sea ice was manipulated to provide 3 under-ice irradiance regimes: low (0.04), medium (0.08), and high (0.16) transmittances. Chlorophyll a decreased with elevated light availability relative to the control. Maximum dark-adapted photosynthetic efficiency (ΦPSII_max) showed an initially healthy and productive ice algae community (ΦPSII_max > 0.6), with ΦPSII_max decreasing markedly under high-light treatments. This was accompanied by a decrease in the light utilization coefficient (α) and photosynthetic capacity (maximum relative electron transfer rate), and a decrease in the ratio of mono- to polyunsaturated fatty acids. This was partly explained by a corresponding increase of photoprotective pigments (diadinoxanthin and diatoxanthin), and a development of mycosporine-like amino acids as identified from a distinctive spectral absorption peak at 360 nm. After 14 d, in situ fluorescence imaging revealed significant differences in ΦPSII_max between treatments of dark-adapted cells (i.e. those sampled before sunrise and after sunset), during diel cycles, with clear chronic photoinhibition in high and medium treatments. Data demonstrate the high sensitivity of spring-blooming Arctic sea ice algae to elevated irradiance caused by loss of snow cover. The predicted loss of snow cover on landfast ice will negatively impact ice algae, their potential primary production, and nutritional quality for higher trophic levels.

Influence of Group Hydrocarbon Composition of Diesel Fuels on Depressant Additive Efficiency

The physicochemical properties of nine summer base diesel fuels were compared. The influence of the group hydrocarbon composition on the low-temperature properties was examined using two fuels with similar physicochemical properties as examples. The physicochemical characteristics of the fuel were shown not to be definitive, rather, its detailed group chemical composition reflecting the molecular-mass distribution of n-alkanes and ratio of mono-, bi-, and polycyclic aromatic hydrocarbons that affect the injectivity of the fuel additives was important. A study of the cold filter plugging point and pour point of these fuels in the presence of two depressant additives based on ethylene-vinyl acetate copolymers showed that additive 1 exhibited more universal properties in fuels differing in group chemical composition while additive 2 reduced effectively the cold filter plugging point in fuels with lower contents of high-melting n-alkanes and exhibited pour point depression comparable to that of additive 1 in fuels with high contents of this hydrocarbon group.

Особливості вегетативної нервової регуляції кальцію, фосфору, магнію в організмі корів за застосування кормової добавки “Гермацинк”

Особливості вегетативної нервової регуляції кальцію, фосфору, магнію в організмі корів за застосування кормової добавки “Гермацинк”

Impact of oil type and pH value on oil-in-water emulsions stabilized by egg yolk granules

The aim of this study was to investigate the effect of oil type, i.e. sunflower, rapeseed, peanut and corn oil on the emulsification effect. Knowledge about the impact of the different oils on the emulsification process in a head-to-head comparison is lacking. The hypothesis was that various oils as such or with their special compositions of by-products will have an impact on the properties of the resulting emulsion. As a novel aspect, a single fraction of egg yolk (EY), i.e. the egg yolk granules, were used as emulsifier. Because of their different sources and production processes, the oils differ in composition of fatty acids, degree of saturation and contain various surface-active components like cell membrane fragments, phospholipids and vitamins which influence the emulsification process and therefore the emulsions. In addition, the pH value of the aqueous phase was varied in a broad range. The dynamic interfacial tension between oil and water as well as the adsorption behavior of granules at the interface was analyzed by drop shape analysis. Oil-in-water emulsions with high ratio of dispersed phase (80%) were produced using a colloid mill. The resulting particle size distribution was determined by laser diffraction. There were significant differences in interfacial tension and adsorption of surface-active components at the interface among the oils due to their composition, fatty acid chain length and ratio of mono-, di-, and triglycerides, resulting in different droplet sizes ascribable to the oils. A correlation could be found for the initial decrease of the analytically measured interfacial tension at the oil-water interface and the resulting emulsion droplet size. Furthermore, it could be shown that the droplet size of the emulsions decreased with increasing pH-value of the continuous phase.

Abstract 401: Polyploidy Increases in Murine Cardiomyocytes Following Myocardial Infarction

Introduction: De novo cardiomyogenesis versus polyploidy in myocardial homeostasis, aging, and response to injury is a controversial research area of intense investigation. Our lab recently created the Fluorescent Ubiquitin Cell Cycle Indicator transgenic (FUCCI-Tg) mouse model to study cardiomyocyte (CM) cell cycle progression. Therefore, the FUCCI-Tg model was used to track CM cell cycle correlated to ploidy state in response to myocardial infarction (MI). Hypothesis: Adult FUCCI-Tg cardiomyocytes progress into S/G2/M phase of cell cycle by 10 days after infarction resulting in binucleation rather than de novo cardiomyogenesis. Methods and Results: CMs isolated from FUCCI-Tg were analyzed 3 and 10 days following MI using confocal microscopy and flow cytometry. At 3 days post-MI, the ratio of mono- to binucleated CMs remained unchanged from non-injury CMs. At day 10 post-MI, frequency of mononuclear CMs significantly decreased compared to normal or 3-day post-MI CMs. Coincident with nucleation state, myocytes were only found to enter S/G2/M phase at day 10 post-MI. These results were verified by visualization of FUCCI in isolated CMs using Amnis ImageStream flow cytometry. Ploidy state and CM size was assessed in the infarction / border (left ventricle (LV)) and remote zone (right ventricle (RV)) at day 10 post-MI and compared to the normal and sham LV and RV. Binucleation significantly increased in the LV after MI compared to normal LV, whereas RV CM binucleation and size significantly increased in both sham and MI at 10 days after MI compared to normal RV. Conclusion: Adult murine CMs enter cell cycle in response to MI but primarily undergo endomitosis / endoreplication rather than complete cell cycle reflecting increases in nucleation and/or myocyte size rather than de novo cardiomyogenesis. Future studies will assess CM ploidy in mouse strains purported to possess enhanced cardiomyogenesis following MI injury and the biological significance of ploidy for mediating myocardial repair.

Two structurally similar fucosylated chondroitin sulfates from the holothurian species Stichopus chloronotus and Stichopus horrens

Two fucosylated chondroitin sulfates SC and SH were isolated from the holothurian species Stichopus chloronotus and Stichopus horrens, respectively. The molar ratio of monosaccharides and sulfate (GalNAc:GlcA:Fuc:SO3Na) was suggested as ∼1:1:1:4 for both polysaccharides. Really this theoretical ratio was slightly distorted by the presence of some fucan sulfate in both preparations (about 2% in SH and 10% in SC), which could not be separated probably due to coincidence with the main components in charge density and molecular weight. The 1D and 2D NMR spectroscopic methods were applied for the detailed structural characterization of SC and SH, which were found to have similar structures. The main chain of SC and SH was shown to be composed of the repeating disaccharide units →4)-β-d-GlcA-(1 → 3)-β-d-GalNAc-(1→ sulfated at O-4 or both at O-4 and O-6 of the N-acetyl-galactosaminyl residues. The ratio of mono- and disulfated GalNAc residues was determined as 1:9 for SC and SH. Only one type of branches linked to O-3 of glucuronyl residues, namely fucosyl 2,4-disulfate residues, were found in both polysaccharides. Therefore polysaccharides SC and SH are two new examples of highly regular fucosylated chondroitin sulfates.

English

АBSTRACT: General composition of seeds isolated from four Bulgarian grape varieties and their changes during growing was studied. The total content of the main compounds in the seeds was: glyceride oil: 11.6-16.5%; proteins:6.3-8.9%, carbohydrates:65.5-70.9%, ash:2.1-2.8%. The water soluble saccharides were found to be 3.66.3%. The ratio of mono-, di- and trisaccharides was 13.5-19.4%, 70.2-73.8% and 7.1-16.3% respectively. In monosaccharide fraction the main components were fructose (16.2-33.9%), glucose (38.2-44.4%) and galactose (17.6-39.2%). Xylose, rhamnose and arabinose were detected too. In the disaccharide fraction predominated iso-maltose (82.1-91.5%), followed by saccharose and maltose.The changes of the content and composition of soluble carbohydrates in grape seeds during growing were also examined.The content of saccharides decreased relatively from 6.9% in the first to 5.1% in the third stage. The percentage of trisaccharidesrised from 7.1% to 16.3% at the expense of the decrease of the quantity of monosaccharides from19.4% to 13.5% and of the disaccharides from 73.5% to 70.2%. The content of fructose increased from 23.7% to 33.9% at the expense the galactose level which dropped from 32.7% to 17.6%. The increase of the content isomaltosefrom 55.9% to82.1% at the expense of all other disaccharides was detectedin the disaccharide fraction.

Direct N-Alkylation of Aromatic Amines Using a Microflow Reactor: Enhancement of Selectivity and Reactivity

A simple and highly atom-economical method for the direct N-alkylation of aromatic amines by using a microflow reactor was developed to overcome the problem of over-alkylation. In the developed method, high-yield conversion (up to 100%) was achieved in a relatively short reaction time. The ratio of mono- to di-benzylated products (3.57:1) was higher than that achieved with batch reactions conducted in a 1 L scale flask (0.87:1). The structural features of the microflow reactor meant that short-chain alkyl halides could be converted into products with high reactivity and selectivity under superheating conditions, although their boiling point was much lower than the reaction temperature. This method was successfully applied to the synthesis of a range of secondary amines including an intermediate of indobufen synthesis.

Influence of the hydrocarbon composition of diesel fuels on their performance characteristics

The influence of different groups of diesel hydrocarbons on the physicochemical properties and performance characteristics of diesel fuels has been considered. The parameters to be evaluated have been cetane number, cetane index, diesel index, pour point, and cold filter plugging point. It has been shown that the hydrocarbon group composition, which reflects only the amount of arenes and paraffinic-naphthenic hydrocarbons, gives insufficient information for prediction of the performance properties of fuels. A more detailed study of the hydrocarbon composition of each group of compounds—the ratio of mono-, bi-, polycyclic arenes, the concentration and the ratio of high- and low-melting-point n-alkanes and isoalkanes—has made it possible to reveal the influence of each group on individual fuel characteristics.

Rhamnolipid biosurfactants-past, present, and future scenario of global market.

RHAMNOLIPIDS—BRIEF OUTLINE Biosurfactants, widely known as surfaceactive agents of biological origin, have carved a niche for themselves in the market due to their unique environmentfriendly properties. They have come a long way since first biosurfactant “surfactin” was purified and characterized by Arima et al. (1968). Biosurfactants have been researched thoroughly and satisfactorily since then by many research groups across the world yet there are aspects that elude our understanding. There are five major categories of biosurfactants viz. glycolipids, phospholipids and fatty acids, lipopeptides and lipoproteins, polymeric biosurfactants and particulate biosurfactants that have found applications in agricultural, pharmaceutical, food, cosmetics, and detergent industries. Data reveals there are more than 250 patents obtained on these wonder biodegradable molecules so far (Shete et al., 2006; Rahman and Gakpe, 2008). It has also been observed that microbial biosurfactants are advantageous over plantbased surfactants because of the scale-up capacity, rapid production, and multifunctional properties. Several plant-based biosurfactants for example saponins, lecithins, and soy proteins have excellent emulsification properties but are expensive to produce at industrial scale and have other debatable issues such as solubility and hydrophobicity (Xu et al., 2011). Among the various categories of biosurfactants the glycolipid biosurfactants “rhamnolipids” stand apart. Rhamnolipid, primarily a crystalline acid, is composed of β-hydroxy fatty acid connected by the carboxyl end to a rhamnose sugar molecule. Rhamnolipids are predominantly produced by Pseudomonas aeruginosa and classified as: mono and di-rhamnolipids. Other Pseudomonas species that have been reported to produce rhamnolipids are P. chlororaphis, P. plantarii, P. putida, and P. fluorescens. Some bacteria are known to produce only mono-rhamnolipids while some produce both. The ratio of mono and di-rhamnolipid can also be controlled in the production method. There are enzymes available that can convert monorhamnolipids into di-rhamnolipids. In 1984, the first patent for the production of rhamnolipids was filed by Kaeppeli and Guerra-Santos (US 4628030) and obtained in 1986 for their work on Pseudomonas aeruginosa DSM 2659 (Kaeppeli and Guerra-Santos, 1986). Subsequently, Wagner et al. filed a patent (US 4814272) in 1985 for the biotechnical production of rhamnolipids from Pseudomonas sp. DSM 2874 and obtained the same in 1989 (Wagner et al., 1989). In the past close to three decades, there has been a great body of research work carried on rhamnolipids revealing many of their astonishing applications and making them reach the pinnacle of popularity among all the categories of biosurfactants in the global market. The reason behind the current global interest in rhamnolipid production owes to their broad range of applications in various industries along with many spectacular “eco-friendly” properties. The current critique articulates to present opinion on rhamnolipid research and is an attempt to retrospect what brings rhamnolipids in the forefront. This article is a bird’s-eye view on a timeline of rhamnolipids story so far and also a critical analysis on why despite so many patents and research work rhamnolipids still do not rule the global biosurfactant market.

The effect of age, sex, and lifestyle factors on micronucleus frequency in peripheral blood lymphocytes of the Bosnian population

This study confirmed that the frequency of human lymphocyte biomarkers measured with the cytokinesis-block micronucleus cytome (CBMNcyt) assay, is associated with age, sex, and lifestyle factors. Cytogenetic analysis was carried out on samples from 100 healthy individuals living in Bosnia and Herzegovina. Cells were cytologically scored for viability status, defined by the proportion of necrotic and apoptotic cells; mitotic status, corresponding to the proportion and ratios of mono-, bi- and multinucleated cells; the nuclear division index and chromosomal damage, determined by the presence of micronuclei, nucleoplasmic bridges or nuclear buds of bi-nucleated cells.Ageing is positively associated with the frequency of cytogenetic biomarkers. The micronucleus frequency in females was significantly higher than the micronucleus frequency in males. The micronucleus frequency is positively associated with family history of cancer.Furthermore, it is positively correlated with smoking: the frequency is higher in male subjects with a smoking habit than in female smokers. However, alcohol is observed to decrease the frequency of apoptotic cells in human lymphocytes. The frequency of micronuclei was positively correlated with exposure to medication. Lastly, the frequency of nuclear buds and apoptotic and necrotic cells negatively correlated with exposure to radiation.

The apparent solubility of aluminum (III) in Hanford high-level waste

The solubility of aluminum in Hanford nuclear waste impacts on the processability of the waste by a number of proposed treatment options. For many years, Hanford staff has anecdotally noted that aluminum appears to be considerably more soluble in Hanford waste than the simpler electrolyte solutions used as analogues. There has been minimal scientific study to confirm these anecdotal observations, however. The present study determines the apparent solubility product for gibbsite in 50 tank samples. The ratio of hydroxide to aluminum in the liquid phase for the samples is calculated and plotted as a function of total sodium molarity. Total sodium molarity is used as a surrogate for ionic strength, because the relative ratios of mono-, di- and trivalent anions are not available for all of the samples. These results were compared to the simple NaOH-NaAl(OH)4-H2O system, and the NaOH-NaAl(OH)4-NaCl-H2O system data retrieved from the literature. The results show that gibbsite is apparently more soluble in the samples than in the simple systems whenever the sodium molarity is greater than 2M. This apparent enhanced solubility cannot be explained solely by differences in ionic strength. The change in solubility with ionic strength in simple systems is small compared to the difference between aluminum solubility in Hanford waste and the simple systems. The reason for the apparent enhanced solubility is unknown, but could include kinetic or thermodynamic factors that are not present in the simple electrolyte systems. Any kinetic explanation would have to explain why the samples are always supersaturated whenever the sodium molarity is above 2M. Real waste characterization data should not be used to validate thermodynamic solubility models until it can be confirmed that the apparent enhanced gibbsite solubility is a thermodynamic effect and not a kinetic effect.

A special role of phosphate in the stability of lactate dehydrogenase against destruction by a polyelectrolyte

X-ray analysis shows the presence of specific anion-binding sites in proteins for sulfate, citrate and phosphate ions, but the functional role of these anions is not always clear. Thus, it is unknown which of the two types, mono- or divalent phosphate, plays an important role in the stability of proteins to stress effects on cells. In the present work, the influence of phosphate, sulfate, and chloride salt on the stability of lactate dehydrogenase (LDH) to its destruction by poly(styrenesulphonate) (PSS) was investigated by the methods of steady-state kinetics and the own protein fluorescence. The analysis was based on the differences between the influence of phosphate and sulfate ions on the process at two pH values, 6.2 and 7.0, at which the ratio of mono- and divalent phosphate changed, whereas sulfate remained in the divalent form. It was shown that the difference between the influence of phosphate and sulfate ions increased with increasing pH, which indicates that divalent phosphate ions much more effectively stabilized LDH compared to sulfate and monovalent phosphate. The differences in the effect of sulfate and chloride salts on the protein corresponded to differences in ionic strength of their solutions. The study of the own fluorescence of LDH in the complex with PSS showed that the rate of fluorescence quenching and the amplitude of the fast stage significantly decreased with increasing concentration of divalent phosphate in solution, as compared to the same effect in the presence of sulfate anions. The conclusion was made that, from two anion-binding sites in the LDH molecule, the intersubunit center is most important in stabilizing the protein to the destruction by polyelectrolyte, and from two phosphate anions, hydrophosphate HPO4(-2) plays the stabilizing role.

Influence of Surface Temperature on the Mechanism of Atomic Layer Deposition of Aluminum Oxide Using an Oxygen Plasma and Ozone

We have examined the role of substrate temperature on the surface reaction mechanisms during the atomic layer deposition (ALD) of Al(2)O(3) from trimethyl aluminum (TMA) in combination with an O(2) plasma and O(3) over a substrate temperature range of 70-200 °C. The ligand-exchange reactions were investigated using in situ attenuated total reflection Fourier transform infrared spectroscopy. Consistent with our previous work on ALD of Al(2)O(3) from an O(2) plasma and O(3) [Rai, V. R.; Vandalon, V.; Agarwal, S. Langmuir 2010, 26, 13732], both -OH groups and carbonates were the chemisorption sites for TMA over the entire temperature range explored. The concentration of surface -CH(3) groups after the TMA cycle was, however, strongly dependent on the surface temperature and the type of oxidizer, which in turn influenced the corresponding growth per cycle. The combustion of surface -CH(3) ligands was not complete at 70 °C during O(3) exposure, indicating that an O(2) plasma is a relatively stronger oxidizing agent. Further, in O(3)-assisted ALD, the ratio of mono- and bidentate carbonates on the surface after O(3) exposure was dependent on the substrate temperature.

The Influence of Ceric Oxide on Phase Composition and Activity of Iron Oxide Catalysts

The process of dehydrogenation of methyl butenes to isoprene is conducted in the presence of iron oxide catalysts whose composition may include oxides of alkaline metals, alkaline earth metals, and transition metals. Catalysts of latest generation can also contain oxides of rare earth elements, particularly cerium oxide. However there is no any common opinion concerning its effect on catalytic properties of iron oxide catalysts. It is well known that ceric oxide has a positive effect on the quantity and stability of active centers and can play a critical role in a redox cycle of the dehydrogenation process. By means of differential thermal analysis, dispersion analysis and X-ray phase analysis, it was found in present study that introducing of ceric oxide promotes the decrease in hematite crystallite sizes. At the same time, it prevents potassium polyferrites formation, with the equilibrium of topochemical reaction between ferric oxide and po tassium carbonates moving predominantly to the formation of intermediate products–monoferrite systems, having greater catalytic activity. The increase in potassium monoferrite content results in dispersion of particles in the Fe2O3-K2CO3-СеО2 system that is accompanied by modification of texture characteristics. For this catalyst composition, the optimum concentration of ceric oxide (8.7 wt.%), leading to the formation of a certain ratio of mono- and polyferrite phases, was found. If more than 8.7 wt.% of СеО2 is introduced, the modification of texture characteristics of catalyst samples takes place, that negatively affects their selectivity.

Metabolic relationship between polyhydroxyalkanoic acid and rhamnolipid synthesis in Pseudomonas aeruginosa: Comparative 13C NMR analysis of the products in wild-type and mutants

Polyhydroxyalkanoic acids (PHAs) and rhamnolipids considered as biotechnologically important compounds are simultaneously produced by Pseudomonas aeruginosa. Both are synthesized from common precursors, ( R)-3-hydroxyfatty acids. To find the probable metabolic relationship between their syntheses, we investigated the PHA and rhamnolipids production in four pha ( phaC1, phaC2, phaZ, and phaG), four rhl ( rhlA, rhlB, rhlR, and rhlI) and rpoS mutant strains of P. aeruginosa PA14 and PAO1 grown in minimal medium containing 70 mM fructose or 30 mM decanoic acid. Higher PHA accumulation was found in the rhamnolipid-negative mutants than in the wild-type strains, suggesting that 3-hydroxyfatty acid precursors become more available for PHA synthesis when rhamnolipids synthesis is absent. However, compared to the wild-type strains, rhamnolipids production was not enhanced in the four pha mutants of P. aeruginosa PA14 and PAO1 which indicates that rhamnolipids production in P. aeruginosa could be tightly regulated at the transcriptional level by a quorum-sensing response. The metabolic pathways for PHA and rhamnolipid synthesis from medium-chain-length fatty acids were also investigated using octanoic- 1- 13 C acid. 13C NMR analysis revealed that the monomer-unit ( R)-3-hydroxyoctanoate- 1- 13 C being converted from the octanoic acid substrate was effectively incorporated into PHA. In the rhamnolipid synthesis, the ( R)-3-hydroxyoctanoate- 1- 13 C is suggested to be firstly converted to ( R)-3-hydroxydecanoate- 1, 3- 13 C via fatty acid de novo biosynthesis pathway and then further processed into ( R)-3-(( R)-3-hydroxyalkanoyloxy)alkanoic acids (HAAs) via RhlA. The ratio of mono- to dirhamnolipids in the product depended on the type of carbon sources. The rhlB mutant could be exploited as an efficient producer of the important biosurfactant HAAs (e.g., ∼700 mg/L HAAs was obtained when grown on 60 mM octanoic acid).