C8 C10 Research Articles

Rational evolution of a medium chain-specific cytochrome P-450 BM-3 variant

The single mutant F87A of cytochrome P-450 BM-3 from Bacillus megaterium was engineered by rational evolution to achieve improved hydroxylation activity for medium chain length substrates (C8–C10). Rational evolution combines rational design and directed evolution to overcome the drawbacks of these methods when applied individually. Based on the X-ray structure of the enzyme, eight mutation sites (P25, V26, R47, Y51, S72, A74, L188, and M354) were identified by modeling. Sublibraries created by site-specific randomization mutagenesis of each single site were screened using a spectroscopic assay based on ω-p-nitrophenoxycarboxylic acids (pNCA). The mutants showing activity for shorter chain length substrates were combined, and these combi-libraries were screened again for mutants with even better catalytic properties. Using this approach, a P-450 BM-3 variant with five mutations (V26T, R47F, A74G, L188K, and F87A) that efficiently hydrolyzes 8-pNCA was obtained. The catalytic efficiency of this mutant towards ω-p-nitrophenoxydecanoic acid (10-pNCA) and ω-p-nitrophenoxydodecanoic acid (12-pNCA) is comparable to that of the wild-type P-450 BM-3.

Synthesis and anti-varicella-zoster virus activity of some novel bicyclic nucleoside inhibitors: effect of enhanced aqueous solubility.

We have recently reported the discovery of an entirely new category of potent antivaricella-zoster virus agents based on novel deoxynucleoside analogues bearing unusual fluorescent bicyclic furo base moieties. Initial studies revealed an absolute requirement of a long alkyl side-chain, with an optimal length of C8-C10, for antiviral activity. However, the impact of this requirement on the physical properties of these compounds is high: inherent lipophilicity and extremely poor aqueous solubility, which may limit the use of these nucleosides as drugs. In order to address this issue, we have now prepared a new series of analogues, bearing ether and glycol type side-chains, designed to improve the aqueous solubility of the compounds. Synthesis of target nucleosides involved Pd-catalysed coupling of terminal alkynes with 5-iodo-2'-deoxyuridine. The 5-alkynyl nucleosides thus obtained were then treated with copper (I) iodide to produce the desired bicyclic analogues. As anticipated, the new compounds exhibited a dramatic increase in aqueous solubility, although antiviral activity was significantly reduced. A possible correlation between antiviral activity and overall compound lipophilicity is discussed.

Electronic absorption spectra of linear C6, C8 and cyclic C10, C12 in neon matrices

The electronic absorption spectra of the even-numbered carbon molecules C6–C14 have been measured in neon matrices. Bare carbon anions were produced in a cesium sputter source, mass selected, codeposited with neon at 6 K, and neutralized. The spectra show, apart from the known (1) Σu−3←X 3Σg− transition of linear C6, C8, and C10 in the visible, absorption bands in the UV region. The spectral data when considered in conjunction with ab initio calculations show that the linear forms of C6 and C8 have the next strong (2) Σu−3←X 3Σg− transition with band maximum near 238 and 277 nm, respectively, whereas the band systems of C10, C12, and C14 at 316, 332, and 347 nm are due to the monocyclic species.

Removal of Heavy Metals and Lanthanides from Industrial Phosphoric Acid Process Liquors

To diminish the discharge of heavy metals and lanthanides by the phosphoric acid industry, these impurities have to be removed from the mother liquor before their incorporation in the gypsum crystals. This can best be achieved by means of solvent extraction or ion exchange during the recrystallization of hemihydrate to dihydrate gypsum. Various commercial carriers and two ion-exchange resins were screened for their efficiency and selectivity. Light and heavy lanthanide ions are extracted from the recrystallization acid by didodecylnaphthalenesulfonic acid (Nacure 1052) and di-(2-ethylhexyl)phosphoric acid (D2EHPA), and the heavy-metal ions by bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301) and by bis(2,4,4-trimethylpentyl)monothiophosphinic acid (Cyanex 302). Mercury is also extracted by the anion carriers tri(C8–C10)amine (Alamine 336) and tri(C8–C10) monomethyl ammonium chloride (Aliquat 336). Both Dowex C-500 and Amberlite IR-120 extract lanthanide and heavy-metal ions. Unfortunately, D2EHPA, Nacure 1052, and the two ion-exchange resins also show affinity for ions present in much higher concentrations, like calcium or iron ions.

FTIR and EXAFS investigations of microstructures of gold solvent extraction: hydrogen bonding between modifier and Au(CN)2-

The microstructures of loaded organic phases of three quaternary amine solvent extraction systems for gold, which were N263–xylene, N263–tributyl phosphate (TBP)–dodecane and N263–2-ethylhexanol (isooctanol)–dodecane (N263-trialkylmethylammonium chloride; alkyl=C8–C10), were studied by Fourier transform infrared (FTIR) spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy. According to the EXAFS results, it was found that the gold coordination environment was the same before and after extraction. However, the C3N stretching vibrations of Au(CN)2- in the three systems differed greatly. The second derivative spectra of C3N stretching bands of Au(CN)2- were also found to be different. In order to explain the differences in the IR characteristics of C3N in the three extraction systems, three microstructure models are proposed. For the N263–xylene system, the model is a simple ion pair. For the other two systems with a modifier (TBP and isooctanol), the models are two supramolecular structures based on hydrogen bonding between the modifier and Au(CN)2-. Some related work such as on the hydration of acetonitrile and the fine structure of C3N in solid KAu(CN)2 was also performed in order to offer additional supporting evidence for the reliability of the proposed models.

The influence of a preserved colon on the absorption of medium chain fat in patients with small bowel resection

Background—Medium chain C8–C10 triglycerides (MCTs) improve fat absorption in short bowel patients. Effects on overall energy absorption remain unknown.Aims—To determine whether MCTs and medium chain fatty acids (MCFAs) are absorbed...

98/02128 Results of laboratory and industrial tests of pitch coke in the manufacture of carbon structural materials

Guayule (Parthenium argentatum) is a woody desert shrub cultivated in the southwestern United States as a source of natural rubber, organic resins, and high energy biofuel feedstock from crop residues. We used guayule bagasse, the residual biomass after latex extraction as feedstock in a pyrolysis process that employs a reactive gas environment to formulate a special intermediate bio-oil product that allows use of conventional hydrotreating with conventional noble metal catalysts and a simple distillation process to synthesize hydrocarbon (drop-in) fuels. The said guayule-bagasse tail gas reactive pyrolysis (TGRP) process comprises pyrolyzing the guayule bagasse in a fluidized-bed reactor in the presence of a reactive and flammable tail gas (comprising CO ∼ 30%, CH4 ∼ 16%, CO2 ∼ 40%, H2 ∼ 10%, C2H4 ∼ traces) generated in the pyrolysis process and without the use of catalyst to produce bio-oil with C/O molar ratio of 14/1 in organic yields of 34–40 wt% having an energy content of 31–37.5 MJ/kg. When we further processed the said bio-oil by centrifugation, we obtained 85 wt% yield and further 50–65 wt% yields following a continuous hydrotreatment over common noble metals (Pt, Ru or Pd) on a carbon support. Distillation of this mixture yielded >95 wt% hydrocarbon liquid fuel mixture comprising 30.4% gasoline (C5–C7), 37% jet (C8–C12) and 24% diesel (C13–C22). Analysis of a composite mixture of the hydrotreated product from the bagasse showed the majority of the sample (66%) was C12 and below, which falls within the gasoline (naphtha) range with the greatest fraction of naphtha falling within the C8–C10 range. Beyond C12, the molecular weights increased through the diesel range (34%), with C37 being the highest observable molecular weight. The product met several ASTM standards for drop-in fuels, but the sulfur content (primarily due to latex extraction additives) was relatively high at around 300 ppm, indicating that hydrodesulfurization may be required to be infrastructure ready.

Acidolysis of several vegetable oils by mycelium‐bound lipase of Aspergillus flavus link

AbstractThe ability of mycelium‐bound lipase of a locally isolated Aspergillus flavus to modify the triglyceride structure of vegetables oils was studied. The catalysis involved the acidolysis of vegetable oils, such as palm olein, coconut oil, cotton‐seed oil, rapeseed oil, corn oil and soybean oil, with selected fatty acids (FA). The reactions were followed against time, and the percentages of FA incorporated were determined by gas chromatography. Percentage of FA incorporated after 20‐h reaction was in the range of 13 to 18%. Reaction between cottonseed oil with lauric acid gave the highest percentage of incorporation (18%), followed by soybean oil with lauric acid (16%) and coconut oil with oleic acid (16%). The results indicated that the hydrolytic affinity of A. flavus lipase demonstrates an acyl group specificity toward short‐chain FA (C8–C10). Changes in triglyceride profiles of each oil were also monitored by reverse‐phase high‐pressure liquid chromatography. In all products, there were increases in the concentrations of several existing triglycerides and formation of new triglycerides. The melting points of all acidolyzed vegetable oils were determined by differential scanning calorimetry, and significant changes in melting profiles were noted.

Total synthesis of FK-506. Part 2: Completion of the synthesis

The C15C16 bond of FK-506 was formed via sulfone anion coupling followed by chelation controlled reduction of the C15 ketone. Efficient methylation of the C15-OH was accomplished by a combination of Me 3OBF 4-4Å molecular sieves in the presence of Proton Sponge®. A procedure was developed to avoid epimerization at the C2 position of the pipecolinate section during alkaline hydrolysis. A reductive fragmentation of the C21–C24 [6,6]-spiroketal iodide using active Zn/Ag-graphite delivered the α′-allyl aldol section. The C9–C10 [5,6]-spiroketal acetonide was de-blocked via a novel β-elimination, using a combination of LiHMDS-Mg(HMDS) 2 in HMPA-DME (1:1), to afford an enediol acetal, which was oxidized with dimethyl dioxirane to generate the C8–C10 α, β-diketoamide acetal function. Final desilylations completed the total synthesis of FK-506.

Effects of Fifth-Instar Volatiles on Sexual Maturation of Adult Desert Locust Schistocerca gregaria

The effect of the presence of gregarious fifth-instar nymphs on the sexual maturation of newly molted gregarious immature adult males and females of the desert locust S. gregaria was investigated by monitoring color changes (yellowing of body), sexual activity, aggregation–maturation pheromone titers (as measured by phenylacetonitrile levels in males), oocyte length, and oviposition time. Maturation was significantly delayed in adults that were reared together with fifth-instar nymphs (visual, tactile, and chemical signals present) with respect to all parameters measured. Male and female nymphs were equally effective in inducing this delay. Nymphs kept in an upper compartment of two-chamber cages (no visual or tactile contact possible) were similarly effective, but their feces were ineffective, suggesting the mediation of a volatile signal from the nymphs themselves. This was confirmed by examining the effect of volatiles trapped from nymphs and testing synthetic blends of previously identified nymphal aggregation pheromone components (C6, C8–C10 aliphatic aldehydes and acids, guaiacol, and phenol) on the sexual maturation of adults. These and previous studies suggest a dual role for nymphal volatiles as nymphal aggregants and adult maturation retardants, similar to the adult volatiles that are known as adult aggregants and maturation accelerants. The results are discussed in terms of the role of the two pheromone systems in synchronizing maturation of the gregarious adults.

Decane reforming reaction over Pt, Ir, Pt-Ir and Pt-Ni bimetallic catalysts supported on Y-zeolite

Pt, Ir, Pt-Ir and Pt-Ni bimetallic catalysts supported on NaY- and HY-zeolite were examined as a catalyst for producing gasoline from n-decane via simultaneous reforming and cracking. The catalysts were prepared by calcining and reducing metal-ion-exchanged Y-zeolite with O2 and H2 at 300°C., respectively. Thus prepared catalysts were characterized by hydrogen chemisorption and temperature programmed desorption of ammonia. Pt-Ni/NaY and Pt-Ir/NaY bimetallic catalysts offered the improved activity maintenance compared to Pt/NaY monometallic catalyst. The catalysts supported on HY-zeolite showed higher selectivity toward C5–C7 and skeletal isomers of C5–C7- and C8–C10 than those of the catalysts supported on NaY-zeolite, which is a desired characteristic for increasing octane value of gasoline these days. However, deactivation with reaction time was much more pronounced on HY-zeolite-supported catalyst. When the catalyst was prcsulfided with H,S, the stability with time on stream was enhanced and the selectivity was quite different from that of the catalyst before presulfiding. The acidity of Y-zeolite and presulfiding of catalyst greatly influenced the activny, selectivity and stability of Pt, Ir, Pt-Ir and Pt-Ni bimetallic catalysts supported on Y-zeolite in n-decane reforming reaction.

Topological investigations on the association of alkanols: excess volume of pyridine–alkanol (C1–C10) mixtures

The excess volume (VE) has been determined dilatometrically for 10 binary pyridine–alkanol mixtures over the whole composition range at 298.15 K. The VE values were negative for pyridine–alkanol (C1–C6) mixtures, sigmoid for pyridine–heptanol mixtures (with negative VE values at lower mole fractions of pyridine) and positive for pyridine–alkanol (C8–C10) mixtures over the complete mole fraction range. VE values increased in a positive direction with increase in chain length of the alkanol (C1–C10). Experimental VE data have been analysed in terms of graph theory which utilises the concept of the third-degree molecular connectivity index. The results obtained from graph theory have been used to predict the association of pyridine and alkanols in the pure and mixed states.The VE data have also been analysed using the Prigogine–Flory–Patterson theory. An analysis of each of the three contributions viz. interactional, free volume and P* to VE shows that the interactional contribution and the free volume effects are negative for all systems, whereas the P* contribution is negative for methanol and ethanol and positive for remainder of the alkanols.

Halomethylated polysulfone: Reactive intermediates to neutral and ionic film‐forming polymers

AbstractHalomethylation of polysulfone (PS) with C8H17OCH2X (X = Cl, Br) in the presence of SnX4 (X = Cl, Br) led to PS–CH2X (X = Cl or Br or both) (Scheme 1). Under controlled conditions, PS–CH2X could be isolated and retains the good film forming properties of PS itself. Interhalogen exchange reactions occur in the presence of SnX4 (X = Cl, Br) under anhydrous conditions (Scheme 1), or a quaternary ammonium phase transfer catalyst R*R3N+X−, under aqueous conditions (Scheme 2). The exchange reactions with R*R3N+X−, are favored when R = C8C10, and with R = C4 only if n‐octanol is added; otherwise gelation occurs. Exchange in CHCl3 is attributed to dehydrohalogenation (and generation of dichlorocarbene) of the solvent in the presence of tetrabutyl ammonium hydroxide. Further chemical modifications of PS–CH2X by reaction with strong nucleophiles, led to hydroxymethyl polysulfone, acetoxymethyl polysulfone, and t‐butyl‐oxymethyl polysulfone (Scheme 3). Hydroxymethyl polysulfone sometimes gels under basic hydrolytic conditions and is best obtained by methanolysis of PS–CH2‐OAc. Both PSCH2OAc and PSCH2O‐t‐Bu are very stable, and provide a way to generate PSCH2Br on need by cleavage with HBr in acetic acid.Direct oxidations with DMSO or tetrabutyl ammonium dichromate (Scheme 4) or indirect oxidations (Scheme 5) produce polysulfone with pendent CHO, CO2R and PO3R groups. Finally, polysulfones with linker arms including, carboxy alkyl, hexaglycol or sulfonamido crowns are described (Scheme 6). The reaction products were characterized by 1H‐ and 13C‐NMR. Double irradiation experiments, proved unequivocally, that the first substitution occurred on the B ring of the bisphenol A moiety (see Table I); the second substitution occurs on the A ring in position a. Thermogravimetric analysis generally shows for all modified polysulfones an extra transition at a lower temperature. The area of this band agrees generally with the values expected from calculated substitution degrees.

Intercalation of Salts of Fatty Acids into Kaolinite

AbstractIntercalation of sodium and potassium salts of lauric, myristic, palmitic, elaidic, oleic, 12-hydroxystearic, and a blend of C8–C10 acids in kaolinite has been followed by X-ray powder diffraction, nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy, and thermal studies. The 7-Å ‘c’ axis spacing in kaolinite expands to 11 Å as a result of intercalation; this expansion is independent of the alkyl chain length of the fatty acid. The orientation of the organic molecules in the kaolinite interlayer is nearly flat, and 1H NMR indicates an enhanced ordering in the potassium laurate intercalate. The reversal or equalization of the relative intensities of hydroxyl bands at 3696 and 3619 cm-1 of kaolinite are related to the phenomenon of intercalation. The decomposition temperature of these salts decreases when they are intercalated in kaolinite.

Optimization of nonionic surfactants for hard‐surface cleaning

AbstractThe hard‐surface cleaning performance of various nonionic homologs was evaluated as a function of carbon chain length, ethylene oxide (EO) content, blending and concentration. Results show carbon chain length to be very important to hard‐surface cleaning. Performance significantly increases as carbon‐chain length decreases, probably as a result of an increase in solvency properties as carbon chain length is decreased. EO content is also important, particularly if nonionics with longer carbon chain lengths are used. Surfactant concentration (dilution) has little effect on the optimum ethylene oxide content but significantly affects the optimum carbon chain length of the hydrophobe. With 5% homolog solutions, the optimally performing nonionic contains a C6 hydrophobe, but with 0.2% solutions, the optimal carbon chain length is shifted to the C8–C10 range. This is thought to result from a trade‐off between the surfactant and solvent properties of the nonionic. Overall results show the optimal nonionic for hard‐surface cleaning to consist of a blend of C6, C8 and C10 alcohols ethoxylated to a 50% EO level. Commonly used surfactant systems, e.g., alkylphenol ethoxylates and alkylphenol ethoxylate (APE)‐butyl cellosolve (BC) blends, were also examined. Results show that alkylphenol ethoxylates give relatively poor performance compared with lower molecular weight linear nonionics because of the large size of their hydrophobe. Under concentrated use, a synergism does exist between APE and BC, but under dilute conditions, the addition of BC is ineffective. BC does not help the performance of low molecular weight nonionics. Surfactant‐soil diffusion studies indicate that surfactant penetration of the soil may be the primary mechanism involved in the hard‐surface cleaning of solid soils.

The effect of pressure on the micelle formation of octyltrimethylammonium octyl sulfate and its homologous surfactants

The critical micelle concentrations (CMC) of three double long-chain salts, octyltrimethylammonium ortyl sulfate (C8–C8), decyl sulfate (C8–C10) and dodecyl sulfate (C8–C12), were determined at 298.15 K as a function of the pressure up to 200 MPa. With respect to C8–C8, the CMCs at 293.15 and 303.15 K were also determined as a function of the pressure. The CMCs for a homologous series of double long-chain salts decreased logarithmically with an increase in the alkyl chain length. The standard free energy change for the micelle formation of the double long-chain salt was—3.4 kJ mol −2 per CH 2 group. The presence of a maximum In the CMC-pressure curve was presented. Below the CMC the double long-chain salt behaved as a strong 1:1 electrolyte, while above the CMC the micelle was almost unchanged even at high pressure up to 200 MPa. The partial molar volume change on micellization (Δ V m) calculated from the pressure dependence of the CMC was 7.6, 8.5 and 11.3 cm 1 mol −1 for C8–C8, C8–C10 and C8–C12, respectively. Δ V ̄ m decreased monotonously with an increase in the pressure and changed its sign from plus to minus at about 75 MPa. The partial molar entropy change on micellization of (Δ S m)C8–C8, which was determined from the temperature dependence of the CMC, increased initially with an increase in the pressure up to 75 MPa and then decreased with the pressure. The dependence of Δ V m and Δ S m upon the pressure were interpreted by the differences in the partial molar compressibilities and expansibilities of the double long-chain salts respectively, between the singly dispersed state and the micellar state.

ChemInform Abstract: SIMPLE METHODS FOR OXIDATION OF O‐ALLYLPHENOLS TO CHROM‐3‐ENES

AbstractDie Allylphenole (I) werden durch Kaliumdichromat, das in Benzol mit Adogen 464, einem Methyl‐ trialkylammoniumchlorid, gelöst wird, zu den Chromenen (II) cyclisiert.

Simple methods for oxidation of o-allylphenols to chrom-3-enes

The reaction of o-allylphenols (1) with potassium dichromate dissolved in benzene using Adogen 464, a commerical mixture of methyl-trialkyl-(C8–C10)-ammonium chloride, or with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) in ether affords the corresponding chrom-3-enes (3) in good yields.

THE EFFECT OF SATURATED FATTY ACIDS ON OXYGEN UPTAKE BY PENICILLIUM CHRYSOGENUM

Summary:The respiration of washed mycelium of Penicillium chrysogenum suspended in phosphate buffer solutions in the presence of the sodium salts of n‐fatty acids containing even numbers of carbon atoms was examined, using mycelium which had been grown in a lactose‐corn steep liquor‐salts medium in submerged culture. At pH 6.4 and at a concentration of 1.0% (w/v), acids of short (C2–C4) and long (C16–C18) chain length were readily oxidized, but acids of intermediate chain length (C8–C10) were toxic and completely inhibited even the endogenous respiration. The two latter acids were however oxidized at lower concentrations at pH 6.4. The toxicity of sodium caprate (C10) also depended on the pH of the system. At pH 7.0 and above, 0.02% caprate was readily oxidized; but below pH 6.0 that concentration became increasingly toxic and at pH 4.5 all respiration was inhibited. However, even at pH 4.5 very low concentrations of sodium caprate were oxidized. At pH 6.3, 0.025% sodium caprate completely inhibited the oxidation of glucose, peptone and sodium acetate but the oxidation of oleic acid was only partially suppressed. A concentration of 0.05% was required to inhibit completely the oxidation of oleic acid.