Far‐Red Emitting Fluorescent Dyes for Optical Nanoscopy: Fluorinated Silicon–Rhodamines (SiRF Dyes) and Phosphorylated Oxazines

Far‐red emitting fluorescent dyes for optical microscopy, stimulated emission depletion (STED), and ground‐state depletion (GSDIM) super‐resolution microscopy are presented. Fluorinated silicon–rhodamines (SiRF dyes) and phosphorylated oxazines have absorption and emission maxima at about λ≈660 and 680 nm, respectively, possess high photostability, and large fluorescence quantum yields in water. A high‐yielding synthetic path to introduce three aromatic fluorine atoms and unconventional conjugation/solubilization spacers into the scaffold of a silicon–rhodamine is described. The bathochromic shift in SiRF dyes is achieved without additional fused rings or double bonds. As a result, the molecular size and molecular mass stay quite small (<600 Da). The use of the λ=800 nm STED beam instead of the commonly used one at λ=750–775 nm provides excellent imaging performance and suppresses re‐excitation of SiRF and the oxazine dyes. The photophysical properties and immunofluorescence imaging performance of these new far‐red emitting dyes (photobleaching, optical resolution, and switch‐off behavior) are discussed in detail and compared with those of some well‐established fluorophores with similar spectral properties.     

Synthesis and antigenic analysis of the BclA glycoprotein oligosaccharide from the Bacillus anthracis exosporium

The glycoprotein BclA is an important constituent of the exosporium of Bacillus anthracis spores. This glycoprotein is substituted with an oligosaccharide composed of a beta-L-rhamnoside substituted with the previously unknown terminal saccharide, 2-O-methyl-4-(3-hydroxy-3-methylbutanamido)-4,6-dideoxy-D-glucopyranose, also referred to as anthrose. Anthrose has not been found in spores of B. cereus and B. thuringiensis, making it a potential species-specific marker for B. anthracis. In order to study the antigenicity of anthrose, efficient syntheses of an anthrose-containing trisaccharide and a series of structurally related analogues were developed. The analogues lacked either the methyl ether at C-2 or contained modified C-4 amino functionalities of anthrose. The synthetic compounds were equipped with an aminopropyl spacer to facilitate conjugation to the carrier proteins mariculture Keyhole Limpet Hemocyanin (mcKLH) and bovine serum albumin (BSA). Serum antibodies of rabbits immunized with live or irradiated spores of B. anthracis Sterne 34F(2) were able to recognize the synthetic trisaccharide-mcKLH conjugate. The specificity of the interaction was confirmed by competitive inhibition with the free- and BSA-conjugated trisaccharides. Inhibition using the trisaccharide analogues demonstrated that the isovaleric acid moiety of anthrose is an important structural motif for antibody recognition. These data demonstrate that 1) anthrose is a specific antigenic determinant of the B. anthracis Sterne spore; 2) this antigen is presented to the immune system of rabbits receiving the anthrax live-spore vaccine; 3) synthetic analogues of the oligosaccharide retain the antigenic structure; and 4) the antigenic region is localized to specific terminal groups of the oligosaccharide. Collectively these data provide an important proof-of-concept step in the synthesis and development of spore-specific reagents for detection and targeting of non-protein structures in B. anthracis.     

Solubility of AlPO4 in cryolite melts

The solubility of aluminium orthophosphate in cryolite melts was determined. Part of the binary phase diagram of the system Na₃AlF₆-AlPO₄ was investigated. The eutectic point was determined to be at 43.7 mass% (or 57.2 mol%) AlPO₄ and (696 ± 1) °C. It is suggested that in pure molten cryolite melts the orthophosphate ion dissociates partly into a metaphosphate ion and an oxide ion.     

Hydrogen network fluctuations of associating liquids: dielectric relaxation of ethylene glycol oligomers and their mixtures with water

Complex dielectric spectra of ethylene glycol and of various derivatives as well as of mixtures of water with an ethylene glycol oligomer and with a poly(ethylene glycol) dimethyl ether oligomer have been measured. The spectra can be well represented by a Cole-Cole [Cole and Cole, J. Chem. Phys. 9, 341 (1941)] spectral function. The extrapolated low frequency (static) permittivity of this function has been evaluated to yield the effective dipole orientation correlation factor of the liquids. The relaxation time of the ethylene glycols displays a characteristic dependence upon the ratio of concentrations of hydrogen bond donating and accepting groups, indicating two opposing effects. With increasing availability of hydrogen bonding sites effects of association and also of dynamical destabilization increase. Both effects exist also in the mixture of water with the oligomers. They are discussed in terms of a wait-and-switch model of dipole reorientation in associating liquids. Another feature in the dependence of the dielectric relaxation time of poly(ethylene glycol)/water mixtures upon mixture composition has been tentatively assigned to precritical demixing behavior of the binary liquids in some temperature range.     

Results of a European inter-laboratory comparison study on the determination of EU priority polycyclic aromatic hydrocarbons (PAHs) in edible vegetable oils

A collaborative study on the analysis for 15 + 1 EU priority PAHs in edible oils was organised to investigate the state-of-the-art of respective analytical methods. Three spiked vegetable oils, one contaminated native sunflower oil, and one standard solution were investigated in this study. The results of 52 laboratories using either high-performance liquid chromatography with fluorescence detection or gas chromatography with mass-selective detectors were evaluated by application of robust statistics. About 95% of the laboratories were able to quantify benzo[a]pyrene together with five other PAHs included in the commonly known list of 16 US-EPA PAHs. About 80% of the participants also quantified seven additional PAHs in most samples, two of which were benzo[b]fluoranthene and benzo[k]fluoranthene, which were also known from the EPA list. Only about 50% of the participants quantified cyclopenta[cd]pyrene, benzo[j]fluoranthene, and benzo[c]fluorene. The robust relative standard deviations of the submitted results without discrimination between the methods applied ranged between 100% for 5-methylchrysene in spiked olive oil and 11% for the same analyte in spiked sunflower oil. The results clearly showed that for these analytes the methods of analysis are not yet well established in European laboratories, and more collaborative trials are needed to promote further development and to improve the performances of the respective methods.     

Vanadium complexes with thiosemicarbazones: Synthesis,characterization, crystal structures and anti-Mycobacterium tuberculosis activity

The development of more efficient anti-tuberculosis drugs is of interest. Three oxovanadium(IV) and three cis-dioxovanadium(V) complexes with thiosemicarbazone derivatives bearing moieties with different lipophilicity have been prepared and had their inhibitory activity against Mycobacteriumtuberculosis H₃₇Rv ATCC 27294 evaluated. The analytical methods used by the complexes’ characterization included IR, EPR, ¹H, ¹³C and ⁵¹V NMR spectroscopies, elemental analysis, cyclic voltammetry, magnetic susceptibility measurement and single crystal X-ray diffractometry. [VO(acac)(aptsc)], [VO(acac)(apmtsc)] and [VO(acac)(apptsc)] (acac = acetylacetonate; Haptsc = 2-acetylpyridinethiosemicarbazone; Hapmtsc = 2-acetylpyridine-N(4)-methyl-thiosemicarbazone and Happtsc = 2-acetylpyridine-N(4)-phenyl-thiosemicarbazone) are paramagnetic and their EPR spectra are consistent with the monoanionic N,N,S-tridentate coordination of the thiosemicarbazone ligands, resulting in octahedral structures of rhombic symmetry and with the oxidation state +IV for the vanadium atom. As result of oxidation of the vanadium(IV) complexes above, the diamagnetic cis-dioxovanadium(V) complexes [VO₂(aptsc)], [VO₂(apmtsc)] and [VO₂(apptsc)] are formed. Their ¹H, ¹³C and ⁵¹V NMR spectra were acquired and support a distorted square pyramidal geometry for them, in accord with the solid state X-ray structures determined for [VO₂(aptsc)] and [VO₂(apmtsc)]. In general, the vanadium compounds show comparable or larger anti-M. tuberculosis activities than the free thiosemicarbazone ligands, with MIC values within 62.5–1.56 (μg/mL).     

(Cycloheptatrienyl)hydridotungsten Complexes

Carbonyl(cycloheptatrienyl)iodo(phosphorus donor)tungstens ([WI(C₇H₇)(CO)L]; L = P(OMe)₃, 1a ; L = P[O(i-Pr)]₃, 1b ; L = PPh₃, 1c ) were prepared from dicarbonyl(cycloheptatrienyl)iodotungsten ([WI(C₇H₇)(CO)₂)] via a carbonyl-substitution process. Similarly, bromocarbonyl(phosphorus donor)(1,2,4,6-tetramethylcycloheptatrienyl)tungstens ([WBr(Me₄C₇H₃)(CO)L]; L = P(OMe)₃, 6a ; L = P[O(i-Pr)]₃, 6b ; L = PPh₃, 6c ) were obtained from the reaction of bromodicarbonyl(1,2,4,6)-tetramethylcycloheptatrienyl)tungsten ([WBr(Me₄C₇H₃)(CO)₂]; 4 ) with L. The reduction of 1a - c , 4 , and 6a , b with sodiumdihydridobis(2-methoxyethoxy)aluminium in toluene led to stable hydrido complexes [WH(R₄C₇H₃)(CO)L] (R = H, L = P(OMe)₃, 2a ; R = H, L = P[O(i-Pr)]₃, 2b ; R = H, L = PPh₃, 2c ; R = Me, L = P(OMe)₃, 7a ; R = Me, L = P[O(i-Pr)]₃, 7b ; R = Me, L = CO, 7d ). Complexes 2a and 7b were characterized by X-ray structure analyses.     

Synthese,IR-Spektrum und Kristallstruktur von PPh4[OsCl4(NO)(NSCl)]

Synthesis, I.R. Spectrum, and Crystal Structure of PPh₄[OsCl₄(NO)(NSCl)] Molten trithiazyl chloride reacts with OsCl₃(NO) to yield a product mixture consisting mainly of S₄N₃[OsCl₄(NO)(NSCl)] and S₄N₃Cl. Extraction of this mixture with a solution of tetraphenylphosphonium chloride in dichloromethane affords green (PPh₄)₂[OsCl₅(NO)] · 2 CH₂Cl₂ and the red title compound. PPh₄[OsCl₄(NO)(NSCl)] was characterized by its IR spectrum and an X-ray crystal structure analysis (3001 independent observed reflexions, R = 0.048). Crystal data: monoclinic, space group P2₁/c, Z = 4, a = 1716, b = 1054, c = 1588 pm, β = 96.25°. The compound consists of PPh₄⊕ cations and [OsCl₄(NO)(NSCl)]? anions in which the nitrosyl and the chlorothionitrene ligands have a cis arrangement. Due to positional disorder the NO and NSCl groups are superimposed statistically in the structure model.