Interactive propagation of photosensitive chemical waves on two circular routes

The propagation of chemical waves in the photosensitive Belousov-Zhabotinsky (BZ) reaction was investigated using an excitable field composed of two rings in slight contact, which were drawn using computer software and then projected on a film soaked with BZ solution using a liquid-crystal projector. When the initial phase difference between the two chemical waves in the individual rings was smaller than a critical value, this initial value was maintained after collision of the chemical waves. However, when the initial phase difference was larger than this critical value, the phase difference converged to the same value after the second collision. The critical value increased with an increase in the thickness of the rings. These experimental results on the geometry of the excitable field are discussed in relation to the nature of chemical wave propagation. These results suggest that the photosensitive BZ reaction may be useful for creating spatiotemporal patterns that depend on the geometric arrangement of excitable fields.     

Chirotopical properties of cisoid enones from circular dichroism (CD) and anisotropic circular dichroism (ACD) spectroscopy

Substituted cisoid 4-en-6-one steroids with isotropically distributed and partially oriented molecules were analyzed by circular dichroism (CD) and anisotropic circular dichroism (ACD) spectroscopy, respectively. CD and ACD data supplement their respective phenomenological information. For a series of C3-substituted enones 1 to 7, the difference of CD (Delta epsilon) and ACD (Delta epsilon(A)) values, that is, Delta epsilon -Delta epsilon(A), vary in the n-* transition region in the same direction, independently of the nature and position (3 alpha or 3 beta) of the substituent. For 7-bromo-substituted enones 5 and 6 the sign of the n-pi* CD band is opposite to that predicted by the enone helicity rule. The ACD data indicate that this behavior is a consequence of the effect of vibronic coupling caused by the 7-bromo substituent. In contrast to the results obtained for the series of C7-unsubstituted compounds 1 to 4, the intensity of the CD bands for 5 and 6 is determined by the vibrational progressions of a different symmetry. Therefore, the helicity rule must fail in both cases because the rule can only be applied to those vibrational transitions for which the rule was developed. The sign of the coordinates Delta epsilon(*)(II), estimated from the ACD data, yields additional stereochemical information that cannot be obtained from the CD data alone. The CD and ACD spectra in the region of the pi-pi* transition vary for enones 1 to 4 in a different fashion and indicate dependence upon spatial orientation (3 alpha or 3 beta) of substituents. This dependence may lead to the possibility of extracting additional stereochemical information from the ACD spectra. Furthermore, the experimental findings indicate that the second CD band located at about 220 nm belongs to a forbidden transition and not to an allowed pi-pi* transition.     

A program for evaluation of gamma-spectra (ANA)

A program (ANA) for evaluation of -spectra is reported. The program is based on a nonlinear least-squares procedure which uses a composite algorithm called KATOK. The program includes spectrum visualization, energy and FWHM calibration, automatic peak search with data preparation, possibility for manual data preparation and utilities.     

Advantages of Thermococcus kodakaraenis (KOD) DNA Polymerase for PCR-mass spectrometry based analyses

The advantages of the thermostable DNA polymerase from Thermococcus kodakaraensis (KOD) are demonstrated for PCR amplification with subsequent detection by mass spectrometry. Commonly used DNA polymerases for PCR amplification include those from Thermus aquaticus (Taq) and Pyrococcus furiosus (Pfu). A 116 base-pair PCR product derived from a vWA locus was amplified by Taq, Pfu, or KOD DNA polymerase and compared by agarose gel electrophoresis and electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS). KOD DNA polymerase demonstrated a 2- to 3-fold increase in PCR product formation compared to Pfu or Taq, respectively, and generated blunt-ended PCR product which allows facile interpretation of the mass spectrum. Additionally, we demonstrate the advantage of using high magnetic fields to obtain unit resolution of the same 116 base pair (approximately 72 kDa) PCR product at high m/z.     

Fluorescence detected circular dichroism (FDCD) for supramolecular host–guest complexes

Fluorescence-detected circular dichroism (FDCD) spectroscopy is applied for the first time to supramolecular host–guest and host–protein systems and compared to the more known electronic circular dichroism (ECD). We find that FDCD can be an excellent choice for common supramolecular applications, e.g. for the detection and chirality sensing of chiral organic analytes, as well as for reaction monitoring. Our comprehensive investigations demonstrate that FDCD can be conducted in favorable circumstances at much lower concentrations than ECD measurements, even in chromophoric and auto-emissive biofluids such as blood serum, overcoming the sensitivity limitation of absorbance-based chiroptical spectroscopy. Besides, the combined use of FDCD and ECD can provide additional valuable information about the system, e.g. the chemical identity of an analyte or hidden aggregation phenomena. We believe that simultaneous FDCD- and ECD-based chiroptical characterization of emissive supramolecular systems will be of general benefit for characterizing fluorescent, chiral supramolecular systems due to the higher information content obtained by their combined use.

Fluorescence-detected circular dichroism (FDCD) spectroscopy is applied for the first time to supramolecular host–guest and host–protein systems and compared to the more known electronic circular dichroism (ECD).     

Effects of vacuum on tetrakis-isocyanide complexes of silver(I) and copper(I): Implications for sims analyses

Vacuum-promoted ligand loss has been detected for the complexes [Ag(CNMe)(4)]PF(6) (Me = methyl), [Ag(CN-t-Bu)(4)]ClO(4) (t-Bu = tert-butyl) and [Ag(CNCy)(4)]ClO(4) (Cy = cyclohexyl). The analogous Cu(I) isocyanide complexes are stable under the same conditions. These conclusions are based on infrared spectroscopy, secondary-ion mass-spectrometry (SIMS) and weight-loss measurements.     

An efficient quantitative technique for the simultaneous analyses of radon daughters (210)Pb, (210)Bi and (210)Po

An improved and time efficient technique has been developed for quantitative determination of the long-lived (222)Rn daughters ((210)Pb, (210)Po and (210)Bi) in atmospheric and oceanic samples. The sample is first spiked with yield tracers for polonium (208 or 209), bismuth (207), and lead (stable lead carrier). These nuclides may then be scavenged through iron hydroxide precipitation and redissolved in a dilute (pH approximately 2) nitric acid plating medium with citrate and hydroxylamine hydrochloride at 90 degrees centrigrade with constant stirring. First a silver planchet is suspended in the solution which plates polonium to high efficiency. Second, a nickel planchet is suspended in the same solution which is maintained hermetic (e.g. bubbling with helium) and bismuth is plated next with high efficiency. Third, lead is purified from the same solution using anion exchange techniques and isolated for beta counting as the sulfate. Polonium is analyzed by isotope dilution alpha spectrometry. Bismuth and lead are analyzed by anti-coincident beta counting in a low level shield. In the case of bismuth, the 207 tracer is added in quantities at least comparable to the background of the beta system such that counting before and after the decay of (210)Bi gives the bismuth yield. The unique characteristics of this technique are its speed and efficiency; all three radon daughters can be isolated for counting within 4 hr of pre-treating the sample. The remaining solution can be treated subsequently for other analyses as appropriate.     

Statistical evaluation of non‐profile analyses for the in vitro bioequivalence

For locally acting drug products such as nasal aerosols and nasal sprays, the 2003 US Food and Drug Administration (FDA) draft guidance suggests that bioequivalence between generic and brand‐name products be established through in vitro tests. In addition, for non‐profile analyses based on spray content uniformity, droplet size distribution, spray pattern, priming, and re‐priming, the draft US FDA guidance recommends that the population bioequivalence (PBE) between generic and innovator's products be demonstrated. However, the linearized criterion recommended in the draft FDA guidance does not take into consideration the variations due to batches, samples, and life stages. Hence, under a two‐stage nested random effects model, we apply the methods of modified large‐sample (MLS) and generalized pivotal quantities (GPQs) to construct the upper 95% confidence limit for in vitro PBE criterion with consideration of variance components as the statistical testing procedures for establishing the in vitro BE. A simulation study was conducted to compare empirical size and empirical power among the three methods. A numerical example illustrates the proposed methods. Copyright © 2010 John Wiley & Sons, Ltd.     

Accurate electrophoretic analyses of concentrated suspensions (electrophoresis of concentrates)

In conventional moving-boundary electrophoresis, boundary anomalies and erroneous analyses were shown to result in work with concentrated suspensions. An apparatus and a technique are described which, using auxiliary probes and an electrolyte tailored to the test suspension, allowed accurate data to be obtained even with highly concentrated suspensions. Thus, the usefulness of moving-boundary electrophoresis has been expanded, as now concentrated as well as dilute suspensions can be investigated.     

An evaluation of the utility of in vacuo methylation for mass-spectrometry-based analyses of peptides

In vacuo trimethylation of the N-terminus of a lyophilized peptide with methyl iodide was previously reported to enhance the peptide's signal in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and to suppress alkali adduct formation in electrospray ionization mass spectrometry (ESI-MS). Both the signal enhancement and alkali adduct suppression observed for methylated peptides are believed to be due to the permanent positive charge on the N-terminus of the peptide resulting from the formation of a quaternary ammonium moiety. The present work evaluates the general utility of the in vacuo methylation procedure for the MS analysis of peptides, and specifically addresses the issue of whether the methylation of nucleophilic sites other than the N-terminal amine affects the MALDI signal of modified peptides. This work establishes that, although certain side-chain modifications are inevitable using present reaction conditions, the derivatization leads to significant MALDI-MS signal improvement. The experimental results demonstrate that the N-terminal trimethylammonium derivatives of peptides exhibit MALDI signals comparable to or exceeding those of arginine-containing standards such as angiotensin I. The advantages and limitations of the in vacuo methylation procedure are discussed.     

Phylogenetic distribution and structural analyses of cyanobacterial glutaredoxins (Grxs)

Glutaredoxins (Grxs), the oxidoreductase proteins, are involved in several cellular processes, including maintenance of cellular redox potential and iron-sulfur homeostasis. The analysis of 503 amino acid sequences from 167 cyanobacterial species led to the identification of four classes of cyanobacterial Grxs, i.e., class I, II, V, and VI Grxs. Class III and IV Grxs were absent in cyanobacteria. Class I and II Grxs are single module oxidoreductase while class V and VI Grxs are multimodular proteins having additional modules at their C-terminal and N-terminal end, respectively. Furthermore, class VI Grxs were exclusively present in marine cyanobacteria. We also report the identification of class VI Grxs with two novel active site motif compositions. Detailed phylogenetic analysis of all four classes of Grxs revealed the presence of several subgroups within each class of Grx having variable dithiol and/or monothiol catalytic active site motif and putative glutathione binding sites. However, class II Grxs possess CGFS-type highly conserved monothiol catalytic active site motif. Sequence analysis confirmed the highly diverse nature of Grx proteins in terms of their amino acid composition; though, sequence diversity does not affect the overall 3D structure of cyanobacterial Grxs. The active site residues and putative GSH binding residues are uncharged amino acids which are present on the surface of the protein. Additionally, the presence of hydrophilic residues at the surface of Grxs confirms their solubility. Protein-ligand interaction analysis identified novel glutathione binding sites on Grxs. Regulation of Grxs encoding genes expression by light quality and quantity as well as salinity suggests their role in determining the fitness of organisms under abiotic factors.     

Thermal analyses (TGA and DSC) of some spironolactone solvates

Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) studies have been performed on a commercial preparation of spironolactone and on five solvates (acetonitrile, ethyl acetate, ethanol, methanol, and benzene) prepared from it by recrystallization at room temperature. The results of these studies are discussed and compared with those recently reported in the literature for similar preparations. The variable behaviour of these solvates in their release (and partial retention) of solvent before the onset of melting, meant that their stoichiometry had to be measured by elemental microanalyses. Solvent loss from solvate decomposition was followed by thermogravimetric analysis (TGA). Solvate decomposition and spironolactone melting temperatures and enthalpies were determined by differential scanning calorimetry (DSC). The parent substance and two of the solvates (methanol and ethanol) exhibited small exotherms in addition to the expected endotherms.     

Biodegradation analyses of trichloroethylene (TCE) by bacteria and its use for biosensing of TCE

Trichloroethylene (TCE) is a toxic, recalcitrant groundwater pollutant. TCE-degrading microorganisms were isolated from various environments. The aerobic bacteria isolated from toluene- and tryptophan-containing media were Pseudomonas sp. strain ASA86 and Burkholderia sp. strain TAM17, respectively; these are necessary for inducing TCE biodegradation in a selective medium. The half-degradation time of TCE to a concentration of 1 mg/L was 18 h for strain ASA86 and 7 days for strain TAM17. While identifying toluene/TCE degradation genes, we found that in strain ASA86, the gene was the same as the todC1 gene product encoding toluene dioxygenase identified in Pseudomonas putida F1, and that in strain TAM17, the gene was similar to the tecA1 gene product encoding chlorobenzene dioxygenase identified in Burkholderia sp. PS12. A novel TCE biosensor was developed using strain ASA86 as the inducer of toluene under aerobic conditions. The TCE biosensor exhibited a linear relationship below 3 ppm TCE. Detection limit of the biosensor was 0.05 ppm TCE. The response time of the biosensor was less than 10 min. The biosensor response displayed a constant level during a 2 day period. The TCE biosensor displayed sufficient sensitivity for monitoring TCE in environmental systems.     

Optical rotatory dispersion and circular dichroism studies of copoly(propyl-L-aspartate-benzyl-L-aspartate)

Copoly(propyl-L -aspartate-benzyl-L -aspartate)s with various compositions were synthesized by propylation of a parent poly(β-benzyl-L -Aspartate). The variation of helix sense of copolyaspartate obtained against a degree of propylation and temperature was examined by optical rotatory dispersion and circular dichroism method. Copolyaspartate of propylation less than about 70% is in a left-handed α helix conformation and its Moffitt parameter b₀ and molecular ellipticity [θ]₂₂₂ decreased gradually with increasing propylation. On the other hand, a different temperature dependence of b₀ and [θ]₂₂₂ was observed for copolyaspartate of propylation more than about 80%, i.e., the reversible transition of the helix sense from right- to left-handed α helix took place by temperature increasing. These features were basically similar to the variation in helix sense of copoly(ethyl-L -aspartate-benzyl-L -aspartate), although a slight difference was seen for copoly(propyl-L -aspartate-benzyl-L -aspartate). The thermodynamic treatment indicating larger entropy of right-handed α helix suggests much mobile side chain of the right-handed α helix than the left handed one.