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In situ quantum cascade laser (QCL) absorption spectroscopy is used to investigate the effect of admixed water in a pulsed CO2 glow discharge on the vibrational excitation of CO2 and CO and the conversion of CO2. Time-resolved transmittance spectra of the non-equilibrium CO2 plasma are measured with a 100 μs time resolution. A custom fitting routine is used to extract the time evolution of the gas temperature, rotational temperature and vibrational temperatures of CO2 and CO, while the CO2 conversion is determined from measured CO2 and CO number densities. Rotational Raman scattering is additionally performed in the centre of the reactor to verify measured rotational and vibrational temperatures from line-of-sight absorption spectroscopy. The plasma is operated at 6.7 mbar, with up to 10% water admixed, and is pulsed with a 5–10 ms on-off cycle, with a current of 50 mA supplied during the plasma on-time. Vibrational temperatures and CO2 conversion are not significantly affected by water admixtures below 0.5%. However, the asymmetric stretch temperature of CO2 (T 3) shows considerable quenching upon admixing 10% water vapour, with the maximum elevation above the rotational temperature (T rot) decreasing from 580 ± 86 K to 230 ± 63 K. For the vibrational temperature of CO (T CO), a similar trend is measured. However, the slopes of T 3 and T CO within the first few hundred μs after the start of the plasma remain unchanged, even when admixing 10% water vapour, suggesting equal excitation of the vibrational modes through e–V and V–V interactions. The conversion decreases by almost a factor of 4 when admixing 10% water. We argue that vibrational quenching of CO2 by water can explain part of the decrease. Changes in electron density and temperature and reactions between CO and OH can also play a role.

We report first measurements of time-resolved absolute CO number densities and rotational temperatures in a non-thermal CO 2 plasma environment using TALIF with a nanosecond pulsed laser. Two-photon excitation spectra from the B 1Σ+(v′ = 0) ← X 1 Σ+ (v″ = 0) Q-branch are recorded and fitted to extract rotational temperatures. Absolute number densities are determined from the frequency-integrated excitation spectrum. The plasma under investigation is a pulsed glow discharge operated at a frequency of 60 Hz with an plasma-on time of 5 ms per plasma cycle, 50 mA plasma current and a pressure of 6.67 mbar. CO number densities range from (2.6 ± 0.6) × 10 22 m -3 to (1.2 ± 0.3) × 10 22 m -3, while rotational temperatures range from 370 ± 40 K to 700 ± 70 K at the beginning and end of the plasma-on phase, respectively. Our results show fair agreement with literature data.

This work uses in situ narrowband quantum cascade laser (QCL) absorption spectroscopy to study the effect of N2 on the time evolution of gas temperature, rotational temperature and the vibrational temperatures of CO2 and CO in a pulsed glow discharge. Three colinear QCLs are used to scan three regions of about 1 cm-1 between 2179.20 and 2253.51 cm-1, including (v 1,v2-l 2,v 3)\to (v 1,v 2-l2,v3+1) C O 2 transitions up to the asymmetric stretch level v 3 = 6, as well as (v CO) → (v CO + 1) CO transitions up to v CO = 1. A fitting routine is used to extract temperatures from the measured absorption spectra. The time resolved measurements are performed in CO2, admixed with up to 90% N2, with the plasma operated with a 5-10 ms on-off cycle, a discharge current of 50 mA and a pressure of around 6.7 mbar. The time evolution of the gas temperature has been measured and agrees well with the time evolution of the rotational temperature. The asymmetric stretch vibrational temperature T 3 of CO2 reaches a maximum of 1060 K at 0.7 ms for pure CO2, while T 3 goes up to 2250 K for a N2 content of 90% and stays constant until the plasma is switched off. Both T 3 and the vibrational temperature of CO T CO show a clear non-equilibrium with respect to the rotational temperature T rot. Both do not equilibrate with the rotational temperature T rot between consecutive plasma cycles for a N2 content above 70%, although T 3 and T CO always equilibrate with each other in the afterglow. The symmetric stretch and bending mode temperature T 12 is elevated more with respect to the rotational temperature for increasing N2 content, while the maximum of the rotational temperature decreases for increasing N2 admixtures, which might be attributed to the energy stored in the vibrational modes of N2, CO2 and CO. Additionally, an indication of an increase in the total pressure during the plasma on-time due to heating and a subsequent decrease in the afterglow due to cooling was found for a pure CO2 plasma.

The implementation of in situ rotational Raman spectroscopy is realized for a pulsed glow discharge in CO2 in the mbar range and is used to study the rotational temperature and molecular number densities of CO2, CO, and O2. The polarizability anisotropy of these molecules is required for extracting number densities from the recorded spectra and is determined for incident photons of 532 nm. The spatiotemporally-resolved measurements are performed in the same reactor and at equal discharge conditions (5-10 ms on-off cycle, 50 mA plasma current, 6.7 mbar pressure) as in recently published work employing in situ Fourier transform infrared (FTIR) spectroscopy. The rotational temperature ranges from 394 to 809 K from start to end of the discharge pulse and is constant over the length of the reactor. The discharge is demonstrated to be spatially uniform in gas composition, with a CO2 conversion factor of 0.15 ± 0.02. Rotational temperatures and molecular composition agree well with the FTIR results, while the spatial uniformity confirms the assumption made for the FTIR analysis of a homogeneous medium over the line-of-sight of absorption. Furthermore, the rotational Raman spectra of CO2 are related to vibrational temperatures through the vibrationally averaged nuclear spin degeneracy, which is expressed in the intensity ratio between even and odd numbered Raman peaks. The elevation of the odd averaged degeneracy above thermal conditions agrees well with the elevation of vibrational temperatures of CO2, acquired in the FTIR study.

The synthesis and aggregation behaviour of simple dialkylamine-imidazole and dialkylamine-pyrazole surfactants is described. In the presence of one equivalent of HCl the imidazole surfactants form stable vesicular dispersions. Addition of copper(II) dichloride to these dispersions leads to formation of metallo-vesicles in which four imidazole groups are coordinated to one copper(II) ion. These metallo-vesicles are unstable and are slowly converted into stacked bilayers, which precipitate. The pyrazole surfactants on the other hand do not form vesicles but give, with one molar equivalent of HCl, water-insoluble stacked bilayers. The pyrazole moieties in these stacked bilayers do not coordinate copper(II) ions. This behaviour is most probably due to the formation of an intramolecular hydrogen bond in the mono-protonated pyrazole surfactant molecule. The imidazole surfactants cannot form such a hydrogen bond.

When measured in "French scenes" (dramatic units demarcated by the entrances and exits of speaking characters), the surviving corpus of Greek tragedy shows that, as ancient dramatists gained a better understanding of their craft, there is a general trend toward shorter, faster scenes. But contrary to expectation, the average length of scenes in Sophocles' and Euripides' surviving plays gradually increases over time, dropping only during the last decade of their careers. The reason for this appears to be the tragedians' reaction to the rising popularity of Old Comedy, a theatrical form which naturally turns over scenes quickly.

The synthesis and properties of gemini surfactants of the type (R(1)(CO)-Lys(H)-NH)2(CH2)n are reported. For a spacer length of n = 6, the hydrophobic acyl tail was varied in length (R(1) = C8, C10, C12, C14, C16, and C18) and, for R(1) = C18, the degree of unsaturation. For R(1)(CO) = oleoyl (C18:1 Z) the spacer length (n = 2-8) and the stereochemistry of the lysine building block were varied; a 'half-gemini' derivative with a single oleoyl tail and head group was also prepared. The potential of the gemini surfactants to transfer polynucleotides across a cell membrane was investigated by transfection of HeLa cells with beta-galactosidase, both in the presence and absence of the helper lipid DOPE. Oleoyl was found to be by far the best hydrophobic tail for this biological activity, whereas the effect of the lysine stereochemistry was less pronounced. The effect of an optimum spacer length (n = 6) was observed only in the absence of helper lipid. The most active surfactant, i.e. the one with oleoyl chains and n = 6, formed liposomes with sizes in the range of 60-350 nm, and its lipoplex underwent a transition from a lamellar to a hexagonal morphology upon lowering the pH from 7 to 3.

We report the design, synthesis, and characterization of a novel type of cationic lipopeptide, gemini-like amphiphilic peptides or 'geminoids'. As an example, the SPKR peptide, inspired by biological nucleic acid binding motifs, was appended with unsaturated (oleoyl/oleyl) alkyl tails. The compound shows remarkable DNA and siRNA delivery, without lysogenic helper lipid, in a variety of cells, with a moderate cytotoxic effect. It aggregates to nanoparticles that combine with DNA to lipoplexes, which undergo a change from lamellar to the more lysogenic hexagonal packing upon lowering the pH. The versatility of the chemical approach allowed us to study peptides related to SPKR, and to establish that the Pro and at least one of the cationic (Lys, Arg) residues are essential for the biological activity. (C) 2010 Elsevier B.V. All rights reserved.

In this paper, a straightforward and generic protocol is presented to label the C-terminus of a peptide with any desired moiety that is functionalized with a primary amine. Amine-functional molecules included are polymers (useful for hybrid polymers), long alkyl chains (used in peptide amphiphiles and stabilization of peptides), propargyl amine and azido propyl-amine (desirable for 'click' chemistry), dansyl amine (fluorescent labeling of peptides) and crown ethers (peptide switches/hybrids). In the first part of the procedure, the primary amine is attached to an aldehyde-functional resin via reductive amination. To the secondary amine that is produced, an amino acid sequence is coupled via a standard solid-phase peptide synthesis protocol. Since one procedure can be applied for any given amine-functional moiety, a robust method for C-terminal peptide labeling is obtained. Copyright  2006 European Peptide Society and John Wiley & Sons, Ltd.

Correction for ‘Structure–delivery relationships of lysine-based gemini surfactants and their lipoplexes’ by Mark Damen et al., Soft Matter, 2014, 10, 5702–5714.

There is a well known but little discussed rule of Greek drama that only three actors played all the speaking characters in a tragedy.1 The rule had an unquestionably strong impact on the structure of Greek tragedy, as can be seen, for example, in Jocasta's early exit (Oedipus The King, 1072), which allows the actor to change mask and costume and return as the herdsman (1110).2 While scholars have researched the origin and nature of this rule in some depth, relatively little attention has been given to the ways in which Greek playwrights dealt with the rule.3