Cross metathesis with strained exocyclic enones: synthesis of 3-alkylideneoxetan-2-ones from 3-methyleneoxetan-2-ones

[reaction: see text] 3-Alkylideneoxetan-2-ones have been prepared in good to excellent yields with high Z-selectivity by olefin cross metathesis with 3-methyleneoxetan-2-ones in the presence of second generation metathesis catalysts 1 or 2.     

Raman spectra of osmotic solutes of halophiles

Organic osmotic solutes (compatible solutes) are accumulated within the cytoplasm of many microorganisms living in hypersaline environments to provide osmotic balance and to protect the cells against extreme osmotic pressure. Some hyperthermophilic prokaryotes also contain high intracellular concentrations of such compounds. A great diversity of organic osmotic solutes, including small sugars, sugar alcohols, amino acids, and amino acid derivatives, is found in nature. Thanks to the high concentrations in which these compounds are often present, Raman spectroscopy may be a useful technique for rapid analysis of such solute(s) both in individual organisms and in natural microbial communities in high‐salt environments, including the possible use of portable miniaturised Raman spectrometers outdoors. Here, we present a database of Raman spectra of some of the most commonly encountered compatible solutes, as well as some less common ones such as ectoine, hydroxyectoine, glycine betaine, glucosylglycerol, mannosylglycerate (potassium salt), and di‐myo‐inositol phosphate, complementing existing information on the Raman spectra of other such solutes such as glycerol, sucrose, and trehalose. Spectra were collected using excitation at 785 nm, and assignment of the major bands was proposed. The data presented complement our knowledge of the spectroscopic characteristics of biomolecules and enable the rapid assessment of the mode of osmotic adaptation used by halophilic microorganisms in culture; this information may be used to obtain information on the distribution of the different solutes in extreme environments on earth and has the added potential for astrobiological applications to estimate the presence of such solutes in stressed environments elsewhere in the universe. Copyright © 2011 John Wiley & Sons, Ltd.     

Application of approximations for joint cumulative k-distributions for mixtures to FSK radiation heat transfer in multi-component high temperature non-LTE plasmas

Approximations for joint cumulative k-distribution for mixtures are efficient for full spectrum k-distribution (FSK) computations. These approximations provide reduction of the database that is necessary to perform FSK computation when compared to the direct approach, which uses cumulative k-distributions computed from the spectrum of the mixture, and also less computational expensive when compared to techniques in which RTE's are required to be solved for each component of the mixture. The aim of the present paper is to extend the approximations for joint cumulative k-distributions for non-LTE media. For doing that, a FSK to non-LTE media formulation well-suited to be applied along with approximations for joint cumulative k-distributions is presented. The application of the proposed methodology is demonstrated by solving the radiation heat transfer in non-LTE high temperature plasmas composed of N, O, N₂, NO, N₂⁺ and mixtures of these species. The two more efficient approximations, that is, the superposition and multiplication are employed and analyzed.     

'q-Titration' of long-chain and short-chain lipids differentiates between structured and mobile residues of membrane proteins studied in bicelles by solution NMR spectroscopy

'q-Titration' refers to the systematic comparison of signal intensities in solution NMR spectra of uniformly (15)N labeled membrane proteins solubilized in micelles and isotropic bicelles as a function of the molar ratios (q) of the long-chain lipids (typically DMPC) to short-chain lipids (typically DHPC). In general, as q increases, the protein resonances broaden and correspondingly have reduced intensities due to the overall slowing of protein reorientation. Since the protein backbone signals do not broaden uniformly, the differences in line widths (and intensities) enable the narrower (more intense) signals associated with mobile residues to be differentiated from the broader (less intense) signals associated with "structured" residues. For membrane proteins with between one and seven trans-membrane helices in isotropic bicelles, we have been able to find a value of q between 0.1 and 1.0 where only signals from mobile residues are observed in the spectra. The signals from the structured residues are broadened so much that they cannot be observed under standard solution NMR conditions. This q value corresponds to the ratio of DMPC:DHPC where the signals from the structured residues are "titrated out" of the spectrum. This q value is unique for each protein. In magnetically aligned bilayers (q>2.5) no signals are observed in solution NMR spectra of membrane proteins because the polypeptides are "immobilized" by their interactions with the phospholipid bilayers on the relevant NMR timescale (～10(5)Hz). No signals are observed from proteins in liposomes (only long-chain lipids) either. We show that it is feasible to obtain complementary solution NMR and solid-state NMR spectra of the same membrane protein, where signals from the mobile residues are present in the solution NMR spectra, and signals from the structured residues are present in the solid-state NMR spectra. With assigned backbone amide resonances, these data are sufficient to describe major features of the secondary structure and basic topology of the protein. Even in the absence of assignments, this information can be used to help establish optimal experimental conditions.     

Evolution of crystallinity in photodegraded polyethylene films studied by ft-raman spectroscopy

FT-Raman spectroscopic studies of photodegraded polyethylene films have enabled the evolution of the crystallinity process to be measured. Commercial polyethylene films of M_w=90 000 were exposed in a weathering UV-chamber under known conditions of exposure time and radiant energy. The spectral profiles were modelled using Fourier methods. The relative amounts of the orthorrombic crystalline phase, α_c, the amorphous phase, α_a and the interphase, α_b, were calculated using Raman bands at 1416 cm⁻¹ characteristic of the crystalline phase and the bands at 1080, 1305 cm⁻¹, characteristic of the amorphous phase. The interphase content can be calculated from the relationship αb= 1-(α_c+α_a). It was found that the weathering process affects only the relative intensities of the bands attributed to crystalline and amorphous fractions; the crystalline content increases at the expenses of the amorphous fraction. These results are discussed in terms of the changes in the intermolecular forces caused by radiation exposure.     

Controlled flux behaviour of membrane processes

Controlling ultrafiltration (UF) and microfiltration (MF) membrane fluxes at or around a region where fouling is minimal can provide an interesting and economic operating regime. Selectivity may be enhanced and cleaning may be easier. For a given flux it is sometimes possible to filter a product suspension at the same trans-membrane pressure (TMP) as for pure water (PWP), but this can require a lot of energy input to maintain cross-flow or high shear in other ways if high fluxes are required. The critical flux is the flux above which one starts to observe fouling. By operating at lower cross-flow velocities and just above the critical flux, and thus, with lower TMPs, periodic cleaning can be effected by temporarily stopping permeation. A change in feed rate demands a change in flux which is obtained by temporarily increasing energy inputs. Controlled flux improves macromolecular fractionation. As flux increases the rejection of high molecular weight materials decreases whilst that of lower molecular weight materials decreases. This paper discusses the causes of fouling and the use controlled flux operation to mitigate its effects.     

Lichen colonization of an active volcanic environment: a Raman spectroscopic study of extremophile biomolecular protective strategies

The Raman spectra of some sixteen lichen specimens from eight genera growing on basaltic lava and wood substrates on new lava fields on the Kilauea volcano, Kona, Hawaii, have been analysed in therms of the pigments and biomolecules produced in this extreme environment. Chlorophyll and a carotenoid, probably lutein or astaxanthin, are ubiquitous, but otherwise, a range of protective pigments have been identified, including atranorin, usnic acid, gyrophoric acid, parietin and pulvinic acid dilactone. In addition, some species were observed to produce calcium oxalate monohydrate and dihydrate. Clearly, several strategies for survival were being adopted by the lichens to combat radiation insolation, desiccation and high temperatures; in one case, of the same lichen species colonizing wood and lava in the same location, a different survival strategy could be detected related to their substrate, but further long‐term ecological experiments would be indicated to derive more detailed information on this aspect. Copyright © 2009 John Wiley & Sons, Ltd.