Investigation of the Separation of Higher Fatty Acid Methyl Esters by Reversed-Phase HPTLC

JPC – Journal of Planar Chromatography – Modern TLC - Separations of eight methyl esters of higher fatty acids on RP-18 stationary phase with methanol—water and...     

Sum-fuzzy implementation of a choice function using artificial learning procedure with fixed fraction

In one if his paper Luo transformed the problem of sum-fuzzy rationality into artificial learning procedure and gave an algorithm which used the learning rule of perception. This paper extends the Luo method for finding a sum-fuzzy implementation of a choice function and offers an algorithm based on the artificial learning procedure with fixed fraction. We also present a concrete example which uses this algorithm.     

Structure and properties of the ion pair charge-transfer complex of octacyanotungstate(IV) with the 2,2′-bipyridinium dication

The X-ray crystal structure of (bpyH2)2[W(CN)8]·4H2 O (bpyH2=2,2-bipyridinium) is described. The [W(CN)8]4– anion has an approximately square antiprismatic (D4d) conformation, seemingly imposed by strong anion–water–cation hydrogen-bonding interactions. Bond distances in the anion are: WC 2.150(5), 2.163(5); CN 1.128(6), 1.145(6)Å and the angles WCN are 177.6(5), 178.3(5)°. The dihydrate and the anhydrous salt are both intensely black solids, exhibiting ion-pair charge-transfer interaction between cation and anion. E.s.r. spectra indicate that 30% of the tungsten is present as WV in the solid state, but that in solution only the WIV complex is present. The electron withdrawing effect of the cation is discussed and compared with that in a series of salts with different bipyridinium cations.     

A capillary electrophoresis and off-line capillary electrophoresis/electrospray ionization-quadrupole time of flight-tandem mass spectrometry approach for ganglioside analysis

A systematic study for the optimization and implementation of high-performance capillary electrophoresis (HPCE) in conjunction with negative ion electrospray ionization-quadrupole time of flight-tandem mass spectrometry (ESI-QTOF-MS/MS) for the analysis of complex glycolipids is described. The performance of the capillary electrophoresis (CE) and off-line CE/ESI-QTOF-MS approach has been explored for screening a complex ganglioside mixture from bovine brain. All instrumental and solution parameters demonstrated to require special adjustment and to have the most substantial effect on the CE separation, abundance of product ions produced in a low-energy collision-induced dissociation (CID) process and their detection by MS/MS, when attempting to identify and sequence single ganglioside molecular species from CE eluted fractions. Upon optimization of the experimental parameters, an efficient methodology emerged providing the general basic requirements for combined CE/ESI-MS analysis of this type of complex glycoconjugate.     

Simultaneous in-situ monitoring of parallel polymerization reactions using light scattering; a new tool for high-throughput screening

A recently introduced technique, simultaneous multiple sample light scattering (SMSLS), was used to monitor parallel polymerization reactions in situ. SMSLS is designed for real-time, high-throughput screening and provides a time-dependent light scattering signature for each reaction, which contains both qualitative and semiquantitative information. Qualitatively, the signature immediately indicates whether the reaction occurs or not, whether there is an initial lag period, and how long the reaction takes until it stops. The signature also provides estimates of the reaction rate and weight average molecular mass M(w), and its shape can help identify mechanistic aspects, for example, controlled versus free radical polymerization, presence of impurities, etc. The method is inherently adapted to small sample volumes and requires no special sample preparation or postpolymerization characterization. The demonstration here involved the free radical polymerization of acrylamide under varying conditions and should be readily applicable to a wide variety of other reactions. Results were cross-checked with multi-detector gel permeation chromatography.     

Pyranopyrazoles. II. Synthesis and reactions of 1H,6H-pyrano[2,3-c]pyrazol-6-ones

Various 1H,6H-pyrano[2,3-c]pyrazol-6-ones (III-XXIII) were obtained from β-keto esters and 1H-pyrazol-5-ones or hydrazines. Nitrations, chlorinations and brominations of these pyranopyrazoles were also carried out giving the corresponding derivatives (XXIV-LXIV). The pyrone ring is the more reactive one in these reactions and the preferred position of attack is the 5-position. The substitution products are formed by the addition-elimination route.     

Characterization of a putative sensory [FeFe]-hydrogenase provides new insight into the role of the active site architecture

[FeFe]-hydrogenases are known for their high rates of hydrogen turnover, and are intensively studied in the context of biotechnological applications. Evolution has generated a plethora of different subclasses with widely different characteristics. The M2e subclass is phylogenetically distinct from previously characterized members of this enzyme family and its biological role is unknown. It features significant differences in domain- and active site architecture, and is most closely related to the putative sensory [FeFe]-hydrogenases. Here we report the first comprehensive biochemical and spectroscopical characterization of an M2e enzyme, derived from Thermoanaerobacter mathranii. As compared to other [FeFe]-hydrogenases characterized to-date, this enzyme displays an increased H₂ affinity, higher activation enthalpies for H⁺/H₂ interconversion, and unusual reactivity towards known hydrogenase inhibitors. These properties are related to differences in active site architecture between the M2e [FeFe]-hydrogenase and “prototypical” [FeFe]-hydrogenases. Thus, this study provides new insight into the role of this subclass in hydrogen metabolism and the influence of the active site pocket on the chemistry of the H-cluster.

Characterization of a group D putative sensory [FeFe]-hydrogenase reveals how the active site can be tuned to decrease CO inhibition and increase stability of a reduced H-cluster while retaining the ability to catalyze H⁺/H₂ interconversion.     

Structural characterization of chondroitin/dermatan sulfate oligosaccharides from bovine aorta by capillary electrophoresis and electrospray ionization quadrupole time-of-flight tandem mass spectrometry

An analytical approach based on high-performance capillary electrophoresis (CE) in conjunction with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS) has been developed for providing the basis to obtain new insights into the domain structure of the glycosaminoglycan (GAG) moiety of proteoglycans. The feasibility and performance of the off-line CE/ESI-QTOF-MS approach in GAG oligosaccharide analysis were assessed by screening a chondroitin/dermatan sulfate (DS) oligosaccharide mixture obtained from bovine aorta by enzymatic depolymerization by chondroitin B lyase. The CS/DS mixture was analyzed by CE using 50 mM ammonium acetate, pH 12.0, dissolved in aqueous methanol (2:3; v/v), as a CE carrier. Structural identification of the GAG components was achieved using off-line CE/nanoESI-QTOF-MS and-MS/MS experiments. ESI-QTOF instrumental parameters were found to play an important role in the MS screening of the CE-separated GAG species. By optimizing the ESI conditions, oligosaccharides differing in chain length and degree of sulfation could be detected. The building block composition, the size of the carbohydrate chain, as well as structural features of the repeating HexA-GalNAc, HexA-GalNAc(S) units, have been determined using MS/MS by applying collision-induced dissociation at low energies. Cleavage of GAG chains by chondroitin B lyase occurs with formation of structural markers useful for identification of IdoA-containing domains.