Thermodynamic characterization of the mixture (1-butanol + iso-octane): Densities,viscosities, and isobaric heat capacities at high pressures

The densities at high pressures of 1-butanol and iso-octane were measured in the range (0.1 to 140) MPa at seven different temperatures, from (273.15 to 333.15) K, and their mixtures were measured in the range (0.1 to 50) MPa at four different temperatures, from (273.15 to 333.15) K. The measurements were performed in a high-pressure vibrating tube densimeter. The pressure–volume–temperature behavior of these compounds and their mixtures was evaluated accurately over a wide range of temperatures and pressures. The data were successfully correlated with the empirical Tamman–Tait equation. The experimental data and the correlations were used to study the behavior and the influence of temperature and pressure on the isothermal compressibility and the isobaric thermal expansivity.Also, the isobaric heat capacities were measured over the range (0.1 to 25) MPa at two different temperatures (293.15 and 313.15) K for the pure compounds and their mixtures. The measurements were performed in a high-pressure automated flow calorimeter. The excess molar heat capacities were assessed for the mixture and a positive deviation from the ideality was obtained.     

Informed Molecular Design of Conjugated Oligoelectrolytes To Increase Cell Affinity and Antimicrobial Activity

Membrane‐intercalating conjugated oligoelectrolytes (COEs) are emerging as potential alternatives to conventional, yet increasingly ineffective, antibiotics. Three readily accessible COEs, belonging to an unreported series containing a stilbene core, namely D4 , D6 , and D8 , were designed and synthesized so that the hydrophobicity increases with increasing side‐chain length. Decreased aqueous solubility correlates with increased uptake by E. coli. The minimum inhibitory concentration (MIC) of D8 is 4 μg mL^?1 against both E. coli and E. faecalis, with an effective uptake of 72 %. In contrast, the MIC value of the shortest COE, D4 , is 128 μg mL^?1 owing to the low cellular uptake of 3 %. These findings demonstrate the application of rational design to generate efficacious antimicrobial COEs that have potential as low‐cost antimicrobial agents.     

Syntheses and structures of highly hindered N-functionalised alkyl and amido group 12 complexes MR2 (M=Zn, Cd, and Hg), [MRCl]2 (M=Zn and Hg)

The reaction of MCl₂ (M=Zn, Cd and Hg) with Li(2-(C(SiMe₃)₂)(6-Me-C₅H₃N)), [Li(MeR)], affords mononuclear metal(II) alkyls. These, in the solid state, show intramolecular M-N interactions in their four-membered chelate rings, which progressively weaken down the series, the C-M-C angles becoming more open (〈M-N〉= 2.30(2), 2.52(2), 2.913(4) Å, C-M-C=160.7(2), 168.5(2), 180(-)°). Alkylmercury chloride complexes have been prepared by the reaction of HgCl₂ with [Li(MeR)], Li(2-(C(SiMe₃)₂)(C₅H₄N)), [Li(HR)], or Li(2-(NSiMe₃)(6-Me-C₅H₃N)), [Li(mpsa)], or from the redistribution reaction of the dialkyl (or amido) mercury complex with HgCl₂. The alkylmercury chloride complexes are dimeric or polymeric in nature with near-linear 2-coordination; (Hg-Cl=2.329(5), 2.318(4), 2.272(8) Å, Cl-Hg-C(N)=175.0(4), 174.7(4), 175.6(5)°). Cd(2-(CH(SiMe₃))(6-Me-C₅H₃N))₂(tmen), prepared from the reaction of Li(2-(CH(SiMe₃))(6-Me-C₅H₃N)) and CdCl₂ in the presence of tmen, has also been structurally authenticated as the rac isomer with the ipso protons directed towards the tmen.     

NEAR-UV INDUCTION OF SISTER CHROMATID EXCHANGES UNDER AEROBIC AND ANAEROBIC CONDITIONS

Abstract— The induction of sister chromatid exchanges (SCE) and cell sensitivity in mouse myeloma cells (66.2 subclone of MPC11) by irradiation with monochromatic near-UV (365 nm) light were studied under aerobic and anaerobic conditions. Sister chromatid exchanges were studied using the fluorescence-plus-Giemsa technique, and sensitivity was determined by the ability of irradiated and nonirradiated control cells to form colonies in soft agar. Cells were found to be 16 times more sensitive to near-UV light under aerobic exposure, producing an F₃₇ value of 7 × 10⁴ J/m² compared to the F₃₇ value of 11.5 × 10⁵ J/m² under anaerobic conditions. The induction of SCE was also 12 times more efficient for aerobic irradiation than for anaerobic irradiation. The data suggest that the SCE-inducing potential of DNA lesions differs when near-UV irradiation is performed in the presence or absence of air. In addition, the DNA lesions responsible for lethality and also those lesions leading to SCE induction may differ under the two irradiation conditions.     

Synthesis, Conformational Analysis, and Biological Evaluation of Heteroaromatic Taxanes

The asymmetric syntheses of heteroaromatic 3-[(tert-butyldimethylsilyl)oxy]-2-azetidinones 12-16 via chiral ester enolate-imine cyclocondensation chemistry are described. The azetidinones contain heteroaromatic moieties which, in certain cases, contribute to a decrease in enantioselectivity due to possible alternate coordinations in the transition states. The (3R,4S)-3-[(tert-butyldimethylsilyl)oxy]-4-heteroaryl-2-azetidinones were subsequently converted to the heteroaromatic taxanes 31-36 and 43-45. Conformational analyses of the 3'-(2-pyridyl) analogue 31 and 3'-(2-furyl) analogue 43 indicate they have solution conformational preferences virtually identical to paclitaxel and docetaxel. Heteroaromatic N-acyl paclitaxel analogues 47-51 were prepared from N-debenzoylpaclitaxel via Schotten-Baumann acylation. The majority of the 14 analogues displayed good to excellent activity in a microtubule assembly assay in comparison to paclitaxel. The analogues were also tested for cytotoxicity against B16 melanoma cells. 3'-Dephenyl-3'-(2-pyridyl)paclitaxel (31), 3'-dephenyl-3'-(2-furyl)paclitaxel (34), N-BOC-3'-dephenyl-3'-(2-furyl)paclitaxel (43), 3'-dephenyl-3'-(2-furyl)-N-(hexanoyl)paclitaxel (44), and N-debenzoyl-N-(3-furoyl)paclitaxel (51) were found to be more cytotoxic than paclitaxel against this cell line. 3'-Dephenyl-3'-(4-pyridyl)paclitaxel (33) and N-debenzoyl-N-(2-furoyl)paclitaxel (50) displayed cytotoxicity against B16 melanoma cells similar to paclitaxel.     

Contrasting chemistry of cis- and trans-platinum(II) diamine anticancer compounds: hydrolysis studies of picoline complexes

cis-[PtCl2(NH3)(2-picoline)] (AMD473) is currently on clinical trials as an anticancer drug. The trans isomer, AMD443 (1), is also cytotoxic in a variety of cancer cell lines. The X-ray crystal structure of the trans isomer (1) shows that the pyridine ring is tilted by 69 degrees with respect to the platinum square-plane in contrast to the cis isomer in which it is almost perpendicular (103 degrees ). In the 3-picoline (2) and 4-picoline (3) trans isomers, the ring is tilted by 58 degrees /60 degrees (2 molecules/unit cell) and by 56 degrees , respectively. Hydrolysis may be an important step in the intracellular activation and anticancer mechanism of action of these complexes. The first hydrolysis step is relatively fast even at 277 K, with rate constants (determined by 1H,15N NMR) of k1 = 2.6 x 10(-5) s(-1), 12.7 x 10(-5) s(-1), and 5.2 x 10(-5) s(-1) (I = 0.1 M) for formation of the monoaqua complexes of 1-3, respectively. Although the hydrolysis of 3 is slower than 2, it is hydrolyzed to a greater extent. No formation of the diaqua complex was observed for any of the three complexes at 277 K, and it accounts for <3% of the platinum species at 310 K. In general the extent of hydrolysis of the trans complexes is much less than for their cis analogues. The pK(a) values for the monoaqua adducts of 1-3 were determined to be 5.55, 5.35, and 5.39, respectively, suggesting that they would exist largely as the monohydroxo complex at physiological pH. The pKa values for the diaqua adducts were determined to be 4.03 and 7.01 for 1, 3.97 and 6.78 for 2, and 3.94 and 6.88 for 3, the first pK(a) being >1 unit lower than for related cis complexes.     

Inter-cycle variation in whole-body vibration exposures of operators driving track-type loader machines

Whole-body vibration (WBV) measurements are an important aspect of performing risk assessments for those exposed to vibration. A large array of variables affect the outcome of a vibration measurement and its extrapolation to a daily dose measure: e.g. variability in driving style, road surface roughness, loading. The variability in vibration emission is an inherent property for most vibrating environments and there is a risk that a vibration measurement might not be representative of the long-term exposures. It is important to acknowledge the variation inherent to WBV exposure to help understand how this variation will affect health risk assessments. A field investigation was conducted in order to characterise the variation of WBV magnitudes between work cycles of track-type loaders. Six different track-type loaders were measured at four different work sites. The vibrations were measured at the operators seat in three translational axes (x-, y-, and z-axis) in accordance with ISO 2631-1 (1997). The findings indicate the worst axis of vibration for the track-type loaders was predominantly the fore-and-aft (x-axis), for most operations. The most severe emission values were measured for machine C at site 2 (1.12 ms⁻² rms) and machine D at site 2 (1.03 ms⁻² rms). These machines would exceed the action value of the Physical Agents (Vibration) Directive within 2 h of exposure. All of the machines measured would exceed the exposure action value of the Directive within an 8 h working period. The lateral (y-axis) produced the greatest amount of variability between work cycles (coefficient of variation up to 20%). It is concluded that the inherent variability between work cycles and tasks reinforces the requirement to perform a full task analysis prior to measuring WBV exposures to ensure that all tasks are measured and that adequate cycles are measured to obtain a reliable indication of the vibration emission.     

Pyridinium salt liquid crystals Effect of mesogen extension and alkyl chain length

The thermotropism of 1-n-alkyl-(4-methyl and 4-tolyl)pyridinium bromides were compared for alkyl chain lengths ranging from n = 12 to 22 carbons. A smectic A mesophase is present in both series for the longer chain compounds, n ≥ 16, with the clearing temperature being similar for both series but increasing rapidly with chain length. The series with the elongated mesogen also possesses an ordered mesophase identified as smectic G. The transition between this mesophase and the S_A or isotropic phase in the 4-tolyl series, and the transition to and from the crystalline phase in both series, are affected relatively little by the alkyl chain length. It seems that the S_A mesophase is governed primarily by the amphiphilic character of the substances, whereas elongation of the ionic head group is responsible for the appearance of a more ordered mesophase at intermediate temperatures.     

Streamlined process for the chemical synthesis of RNA using 2'-O-thionocarbamate-protected nucleoside phosphoramidites in the solid phase

An improved method for the chemical synthesis of RNA was developed utilizing a streamlined method for the preparation of phosphoramidite monomers and a single-step deprotection of the resulting oligoribonucleotide product using 1,2-diamines under anhydrous conditions. The process is compatible with most standard heterobase protection and employs a 2'-O-(1,1-dioxo-1λ(6)-thiomorpholine-4-carbothioate) as a unique 2'-hydroxyl protective group. Using this approach, it was demonstrated that the chemical synthesis of RNA can be as simple and robust as the chemical synthesis of DNA.