The role of TLC in the screening of inherited metabolic diseases

Summary Thin-layer chromatography (TLC) is a rapid, reliable and inexpensive screening technique for diagnosis of inherited metabolic diseases (IMD). Our screening program encompasses five main situations where the use of TLC is considered to be vindicated: (i) analysis of amino acids; (ii) screening for sugar defects; (iii) detection of pathological oligosaccharidurias; (iv) screening for organic acid disorders; and (v) detection of abnormalities in tryptophan metabolism. Examples are presented of chromatograms obtained from pathological samples. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

Transition metal complexes with thiosemicarbazide-based ligands

Solvate complexes of UO ₂ ²⁺ andN(1), N(4)-bis(salicylidene)-S-methylisothiosemicarbazone, (H₂Me-L¹), of general formula [UO₂(Me-L¹)S] (S= H₂O, MeOH, EtOH, Py, DMF and DMSO) were synthesized. The methanolic UO ₂ ²⁺ ” adducts of N(1)-benzoylisopropylidene-N(4)-salicylidene-S-alkylisothiosemicarbazone, (H₂R-L²,R=Me, Prⁿ) of general formula [UO₂(R-L²)· MeOH], were also prepared. Thermal decomposition of the complexes was investigated in air and argon. The complexes decompose to α-U₃O₈ in air, while in argon the decomposition is not completed up to 1000 K. The temperature and the mechanism of decomposition of the complexes are a function of the solvent belonging to the inner coordination sphere.     

Isoperichoric focusing field-flow fractionation and thin layer isoperichoric focusing based on coupling of gradient generated by primary field with secondary field action: general principles and performances

The primary field forces can generate spatially oriented gradient of the effective property of a continuum or pseudo-continuum fluid (carrier liquid). When this gradient is coupled with the action of a secondary field of identical or different nature the isoperichoric focused zones of the dispersed species can appear. Consequently, they can be separated according to differences responding to the property gradient of the carrier liquid. This concept can be applied under static (non-flow) conditions in thin layer focusing as well as under dynamic conditions with the elution due to the carrier liquid flow in focusing field-flow fractionation. The gradient established by the action of the primary field and the concentration distribution of the isoperichoric focused zone formed by the coupled effect of the gradient and of the primary or secondary field are described theoretically. The rigorous relationship describing the shape of the focused zone is compared with the approximate solutions. The performances of the proposed principle were evaluated by model calculations. Potential experimental configurations considering the implementation of the static and dynamic conditions are discussed. The generalized isoperichoric focusing theory can be applied to describe the particular processes operating in analytical and preparative focusing separations of the particles of various, but especially of biological origin.     

Thermoluminescence analysis for testing the irradiation of spices

Thermoluminescence signals of irradiated and unirradiated spices and herbs are due to inorganic matter grains adhering to the surfaces. This study reports the mineral composition of this dust being, mainly quartz, calcite and philosilicates; it shows the differences between samples exposed and non-exposed to -radiation on the basis of TL signals after long storage periods (1–16 months). A saturation process in the TL signal is found when the samples absorb doses higher than 5 kGy. Finally, the TL glow curve intensities do not suffer significant changes with the dose rate of the -source used in the radiation process.     

Capillary electrophoresis as an alternative to HPLC for determination of honey flavonoids

Summary The general objective is to provide an alternative methodology based on capillary electrophoresis (CE) to characterize flavonoids from honey and hence determine its botanical origin. The specific objective is to compare the separation of flavonoids by CE with those achieved by HPLC to assess CE as an alternative technique for the determination of honey flavonoids. Fourteen different flavonoids isolated from honey were analysed by MECC and compared to the HPLC separations. It was difficult to find specific experimental conditions to separate all the flavonoids from honey in a single MEKC run. Three chromatographic conditions are optimized and, depending on the flavonoid markers sought in honey, the appropriate detection method should be chosen. Compared to the HPLC results, it is clear that CE could be an alternative technique in honey flavonoids analysis and particularly in the study of its geographical and floral origin.     

Synthesis of new guanidine derivatives from 2′,3′,4′,9′-tetrahydrospiro[piperidine-4,1′-[1H]pyrido[3,4-b]indole]

The reaction of the isothiourea derivative 2 with methylaminc or pyrrolidine resulted in guanidines 3a-3b . Using hydrazine under the same conditions the tetrazole derivative 4 was obtained. On reacting 2 with piperidine, morpholine, methylhydrazine, phenylhydrazine, hydroxylamine or sodium hydroxide, cycliza-tion took place leading to the novel 4-cyanimino-1,2,3,4,6,7,12,12b-octahydro-3,12b-ethanopyrim-ido[1′,6′:1,2]pyrido[3,4-b]indole ( 5 ). Some structural aspects of 5 and other model compounds were analysed mainly by ¹³C nmr spectroscopy.     

Efficiency of decomposition procedures for the determination of some elements in soils by atomic spectroscopic methods

Nine decomposition procedures for soil samples, such as via acid mixtures and fusion in open systems and microwave and autoclave dissolution (in closed systems under elevated temperature and pressure) were assessed using certified soil reference materials. The determination of various elements in solutions was performed by FAAS and ICP-OES and the results were compared with certified values and with direct current arc OES analysis. Received: 3 March 1997 / Revised: 30 May 1997 / Accepted: 3 June 1997     

Ab initio study of the binding of Trichostatin A (TSA) in the active site of histone deacetylase like protein (HDLP)

Histone deacetylase (HDAC) inhibitors have recently attracted considerable interest because of their therapeutic potential for the treatment of cell proliferative diseases. An X-ray structure of a very potent inhibitor, Trichostatin A (TSA), bound to HDLP (an HDAC analogue isolated from Aquifex aeolicus), is available. From this structure, an active site model (322 atoms), relevant for the binding of TSA and structural analogues, has been derived, and TSA has been minimized in this active site at HF 3-21G* level. The resulting conformation is in excellent accordance with the X-ray structure, and indicates a deprotonation of the hydroxamic acid in TSA by His 131. Also, a water molecule was minimized in the active site. In addition to a similar deprotonation, in accordance with a possible catalytic mechanism of HDAC as proposed by Finnin et al. (M. S. Finnin, J. R. Donigian, A. Cohen, V. M. Richon, R. A. Rifkind and P. A. Marks, Nature, 1999, 401, 188-193), a displacement of the resulting OH- ion in the active site was observed. Based on these results, the difference in energy of binding between TSA and water was calculated. The resulting value is realistic in respect to experimental binding affinities. Furthermore, the mechanism of action of the His 131-Asp 166 charge relay system was investigated. Although the Asp residue in this motif is known to substantially increase the basicity of the His residue, no proton transfer from His 131 to Asp 166 was observed on binding of TSA or water. However, in the empty protonated active site, this proton transfer does occur.     

Coalescence in three-phase fluid systems

Summary The gravity coalescence of drops at flat fluid/liquid interfaces was studied in three-phase systems. Rest-time distributions were in qualitative agreement with the earlier theory of Charles and Mason for two-phase systems. The probability of coalescence increased inversely with the square of intervening film thickness. Partial coalescence was similar to that previously observed in two-phase systems. The viscosity of the drop affected the mechanism of coalescence more than the viscosities of the other phases.

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Zusammenfassung Es wurde die Koaleszenz von Tropfen an ebenen Flüssigkeits-Flüssigkeitsgrenzfl?chen in Dreiphasensystemen untersucht. Die beobachtete Verteilung der Verweilzeiten ist in qualitativer übereinstimmung mit der Theorie von Charles und Mason für Zweiphasensysteme. Die Wahrscheinlichkeit dafür, da? Koaleszenz auftritt, nimmt umgekehrt proportional mit dem Quadrat der Filmdicke zwischen Tropfen und Phasengrenze zu. Die partielle Koaleszenz war ?hnlich, wie sie früher in Zweiphasensystemen beobachtet worden war. Die Viskosit?t des Tropfens beeinflu?t den Mechanismus der Koaleszenz mehr als die Viskosit?t der anderen Phasen.

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High yield synthesis and reactivity of a phosphinidene bridged dimolybdenum complex

Protonation of [Mo2Cp2(mu-H)(mu-PHR*)(CO)4] (Cp = eta5-C5H5, R* = 2,4,6-C6H2tBu3) with HBF4.OEt2 gives the hydridophosphinidene complex [Mo2Cp2(mu-H)(mu-PR*)(CO)4]BF4, which is easily deprotonated with H2O to give the known phosphinidene complex [Mo2Cp2(mu-PR*)(CO)4] in 95% yield. Reaction of the latter with I2 gives the unsaturated phosphinidene complex [Mo2Cp2I2(mu-PR*)(CO)2], which exhibits an intermetallic distance of 2.960(2) A. Irradiation of solutions of [Mo2Cp2(mu-PR*)(CO)4] with UV light gives a mixture of the triply bonded [Mo2Cp2(mu-PR*)(mu-CO)2] and the hydridophosphido derivative [Mo2Cp2(mu-H){mu-P(CH2CMe2)C6H2tBu2}(CO)4] as major species. The latter complex results from an intramolecular C-H bond cleavage from a tBu group and has been characterized by spectroscopy and an X-ray study. Irradiation in the presence of HCC(p-tol) results in the insertion of the alkyne into the Mo-P bond to give [Mo2Cp2{mu-eta1:eta2,kappa-C(p-tol)CHPR*}(CO)4] structurally characterized through an X-ray study.