Instant controlled pressure drop extraction of lavandin essential oils: Fundamentals and experimental studies

Détente Instantanée contrôlée (DIC), French for Instant Controlled Pressure Drop, was performed on laboratory apparatus as well as on a pilot plant for proving its feasibility, and identifying the optimized processing conditions and recognizing the energy consumption and the quantity of water used for such an operation. GC–MS and SPME analysis of the extracts and residue material were carried out to assess the extracts and solid residues. The lavandin essential oils obtained by using the new DIC extraction process was studied, modeled and quantitatively and qualitatively compared to the conventional hydrodistillation method. The most important differences between the two essential oils were reflected in the yields, with 4.25 as against 2.3 g EO/100 g of raw matter, and in the extraction time, with 480 s as against some hours for respectively the DIC and the hydrodistillation operations. These differences have been previewed through the fundamental analysis. They can normally explain the great decreasing of energy consumption to be 662 kWh/t of raw material. The amount of water to be added was about 42 kg water/t of raw material.     

Structural effects of various modifiers on M−Fe/MgO catalysts (M=Al,Co, K)

Effects of typical modifiers (Al: textural, Co: alloying and K: electronic) have been studied on Fe/MgO catalysts. Addition of Al modified the structure of iron oxide phase; the Co additive was incorporated mainly in bimetallic Fe?Co particles, while the potassium promoter has not exerted observable structural change. The results of Mössbauer studies are correlated with data of catalytic measurements in CO+H₂ reaction.     

A Ruthenium(II)–Copper(II) Dyad for the Photocatalytic Oxygenation of Organic Substrates Mediated by Dioxygen Activation

Dioxygen activation by copper complexes is a valuable method to achieve oxidation reactions for sustainable chemistry. The development of a catalytic system requires regeneration of the Cu^I active redox state from Cu^II. This is usually achieved using extra reducers that can compete with the Cu^II(O₂) oxidizing species, causing a loss of efficiency. An alternative would consist of using a photosensitizer to control the reduction process. Association of a Ru^II photosensitizing subunit with a Cu^II pre‐catalytic moiety assembled within a unique entity is shown to fulfill these requirements. In presence of a sacrificial electron donor and light, electron transfer occurs from the Ru^II center to Cu^II. In presence of dioxygen, this dyad proved to be efficient for sulfide, phosphine, and alkene catalytic oxygenation. Mechanistic investigations gave evidence about a predominant ³O₂ activation pathway by the Cu^I moiety.     

Enzymatic Method for the Synthesis of Long DNA Sequences with Multiple Repeat Units

A polymerase chain reaction (PCR) derived method for preparing long DNA, consisting of multiple repeat units of one to ten base pairs, is described. Two seeding oligodeoxynucleotides, so‐called oligoseeds, which encode the repeat unit and produce a duplex with 5′‐overhangs, are extended using a thermostable archaeal DNA polymerase. Multiple rounds of heat–cool extension cycles, akin to PCR, rapidly elongate the oligoseed. Twenty cycles produced long DNA with uniformly repeating sequences to over 20 kilobases (kb) in length. The polynucleotides prepared include [A]_n/[T]_n, [AG]_n/[TC]_n, [A₂G]_n/[T₂C]_n, [A₃G]_n/[T₃C]_n, [A₄G]_n/[T₄C]_n, [A₉G]_n/[T₉C]_n, [GATC]_n/[CTAG]_n, and [ACTGATCAGC]_n/[TGACTAGTCG]_n, indicating that the method is extremely flexible with regard to the repeat length and base sequence of the initial oligoseeds. DNA of this length (20 kb≈7 μm) with strictly defined base reiterations should find use in nanomaterial applications.     

Oxidation of Zn(Cys)4 zinc finger peptides by O2 and H2O2: products, mechanism and kinetics

The reactivity of a series of Zn(Cys)(4) zinc finger model peptides towards H(2)O(2) and O(2) has been investigated. The oxidation products were identified by HPLC and ESI-MS analysis. At pH<7.5, the zinc complexes and the free peptides are oxidised to bis-disulfide-containing peptides. Above pH 7.5, the oxidation of the zinc complexes by H(2)O(2) also yields sulfinate- and sulfonate-containing overoxidised peptides. At pH 7.0, monitoring of the reactions between the zinc complexes and H(2)O(2) by HPLC revealed the sequential formation of two disulfides. Several techniques for the determination of the rate constant for the first oxidation step corresponding to the attack of H(2)O(2) by the Zn(Cys)(4) site have been compared. This rate constant can be reliably determined by monitoring the oxidation by HPLC, fluorescence, circular dichroism or absorption spectroscopy in the presence of excess ethyleneglycol bis(2-aminoethyl ether)tetraacetic acid. In contrast, monitoring of the release of zinc with 4-(2-pyridylazo)resorcinol or of the thiol content with 5,5'-dithiobis(2-nitrobenzoate) did not yield reliable values of this rate constant for the case in which the formation of the second disulfide is slower than the formation of the first. The kinetic measurements clearly evidence a protective effect of zinc on the oxidation of the cysteines by both H(2)O(2) and O(2), which points to the fact that zinc binding diminishes the nucleophilicity of the thiolates. In addition, the reaction between the zinc finger and H(2)O(2) is too slow to consider zinc fingers as potential sensors for H(2)O(2) in cells.     

NMR study of the complexation of boric acid with catechol (1,2-dihydroxybenzene)

The boric acid–catechol system in aqueous solutions has been studied by means of ¹¹B, ¹H and ¹³C NMR over wide ranges of concentration and pH. ¹¹B spectra show a striking difference between the complexation possibilities of dilute and more concentrated solutions of boric acid. Both the 1:1 and 1:2 complexes can be simultaneously observed by ¹³C NMR.     

Development of an integrated optic oxygen sensor using a novel, generic platform

This paper describes the development of a generic platform for enhanced, integrated optic sensors based on fluorescence detection. The platform employs a novel optical configuration in order to achieve enhanced performance and has inherent multianalyte detection capability. The sensor element comprises a multimode ridge waveguide that has been patterned with an analyte-sensitive fluorescent spot, which is excited directly using a LED. The platform was applied to the detection of gaseous oxygen as a proof of principle. The sol-gel-derived sensor spots were doped with an oxygen-sensitive fluorescent dichlororuthenium dye complex and intensity-based calibration data were generated from the oxygen-dependent waveguide output. The sensor achieved a LOD of 0.62% and a resolution of less than 0.96% gaseous oxygen, which compares favourably with a similar, recently reported system. This device highlights the combination of inexpensive rapid prototyping techniques and a dedicated sensor enhancement strategy that together facilitate the production of an effective prototype sensor platform.     

RCM of tripeptide dienes containing a chiral vinylcyclopropane moiety: impact of different Ru-based catalysts on the stereochemical integrity of the macrocyclic products

[structures: see text] Tripeptide dienes containing an (1R,2S)-vinyl aminocyclopropylcarboxylate residue were cyclized to beta-strand scaffolds under ring-closing metathesis (RCM). Conformational factors, ligand effects, and reaction conditions were evaluated. A protocol was developed for the efficient synthesis of 15-membered ring peptides in high diastereomeric purity. These peptides are key synthetic precursors to antiviral agents that target the hepatitis C virus and represent the first class of clinically validated pharmaceutical agents that are synthesized in large scale using RCM.