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Bonding analysis in β-diketiminate boron and related systems has been performed. For the optimized geometries (MP2/aug-cc-pVTZ), the post-SCF electron density function has been produced and its topological parameters have been analyzed according to Atoms in Molecules Quantum Theory approach. The B–N bond has characteristics similar to those found for TM–ligand bonding. The symmetric character of the B–N interaction found for the β-diketiminate boron results from the fully π-electron delocalized character of the β-diketiminate moiety. If the π-electron system in NCCCN sequence of bonds is localized, the asymmetric B–N bonding is enforced. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Marcin PalusiakEmail:
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3.
In the present study, the potential of lead and cadmium removal by the extracellular polymeric substances (EPS) produced from Parachlorella kessleri and Chlorella vulgaris were investigated. Carbohydrates were the dominant components of EPS from both analyzed species. The contents of reducing sugars, uronic acids, and amino acids were higher in EPS synthesized by C. vulgaris than in EPS from P. kessleri. The analysis of the monosaccharide composition showed the presence of rhamnose, mannose and galactose in the EPS obtained from both species. The ICP-OES (inductively coupled plasma optical emission spectrometry) analyses demonstrated that C. vulgaris EPS showed higher sorption capacity in comparison to P. kessleri EPS. The sorption capacity of C. vulgaris EPS increased with the increase in the amount of metal ions. P. kessleri EPS had a maximum sorption capacity in the presence of 100 mg/L of metal ions. The FTIR analysis demonstrated that the carboxyl, hydroxyl, and carbonyl groups of EPS play a key role in the interactions with metal ions. The present study showed C. vulgaris EPS can be used as a biosorbent in bioremediation processes due to its biochemical composition, the presence of significant amounts of negatively charged uronic acids, and higher sorption capacity.  相似文献   
4.
The reactions of R2P–P(SiMe3)2 (R = Ph, iPr and iPr2N) with BuLi in THF or DME solution lead to ion-contacted lithium derivatives R2P–P(SiMe3)Li · 3THF (R = iPr, iPr2N) with tetrahedrally surrounded Li atoms and to the solvent-separated ionic [Li · 3DME]+[Ph2P–PSiMe3] with an octahedrally surrounded Li atom as confirmed by X-ray crystal structure analysis. The reaction of BuLi with Ph2P–P(SiMe3)2 is accompanied with a significant side-reaction leading to Ph2P–PPh2 and to LiP(SiMe3)2.  相似文献   
5.
A capillary electrophoretic method with UV detection for separation and quantitation of perfluorocarboxylic acids (PFCAs) from C6-PFCA to C12-PFCA has been developed. The optimization of measurement conditions included the choice of the most appropriate type and concentration of buffer in the background electrolyte (BGE), as well as the type and the content of an organic modifier. The optimal separation of investigated PFCAs was achieved with 50 mM phosphate buffer and 40% isopropanol in the BGE using direct UV detection. The optimum wavelength for direct UV detection was optimized at 190 nm. For indirect detection, several chromophores were studied. Five mM 3,5-Dinitrobenzoic acid (3,5-DNBA) in 20 mM phosphate buffer BGE and indirect UV detection at 280 nm gave the optimal detection and separation performance for the investigated PFCAs. The possibility of on-line preconcentration of solutes by stacking has been examined for indirect detection. The detection limits (LODs) determined for direct UV detection ranged from 2 microg/mL for C6-PFCA to 33 microg/mL for C12-PFCA. The LODs obtained for indirect UV detection were comparable to those obtained for direct UV detection.  相似文献   
6.
We report the studies on the mechanism of oxidation of 3′,4′-dihydroxy-l-phenylalanine (l-DOPA) to neurotoxic dopachrome catalyzed by enzyme horseradish peroxidase (EC 1.11.1.7) using the kinetic (KIE), and solvent (SIE), isotope effect methods. For kinetic studies two specifically deuterated isotopomers: [2′,5′,6′-2H3]-l -DOPA was synthesized by the acid catalyzed isotopic exchange between native l-DOPA and heavy water, and [5′-2H]-l-DOPA was synthesized in two step reaction. The first step involved acid catalyzed isotopic exchange between l-tyrosine and deuterated water and resulting product [3′,5′-2H2]-l-tyrosine was hydroxylated by enzyme tyrosinase (EC 1.14.18.1). The values of deuterium KIEs and SIE’s in the enzymatic oxidation of l-DOPA and its isotopomers are determined using non-competitive spectrophotometric method. The measured values were: KIE on V max (1.1 and 2.2) and KIE on V max/K M (1.7 and 3.2) for [2′,5′,6′-2H3]-l-DOPA and [5′-2H]-l-DOPA, respectively, while the corresponding values of SIE were: SIE on V max (2.1, 2.4, and 2.1) and SIE on V max/K M (1.3. 1.6, and 1.1) for l-DOPA, [2′,5′,6′-2H3]-l-DOPA, and [5′-2H]-l-DOPA, respectively. The size of KIE and SIE, typical for secondary isotope effects indicate that both the solvent and presence of deuterium at the 2′-, 5′, and 6′-positions of l-DOPA has the little impact on the enzymatic oxidation of this compound.  相似文献   
7.
The Hirshfeld surface analysis, theoretical calculation, and IR and Raman spectra of p-acetotoluidide and p-thioacetotoluidide were reported. Hirshfeld surfaces and fingerprint plot have been used for visualizing, exploring, and quantifying intermolecular interactions in the crystal lattice of the title compounds. The packing of the molecules in the crystal structure of p-acetotoluidide and p-thioacetotoluidide forms the chains of N–H···O and N–H···S hydrogen bonds, respectively. The close contacts are also dominated by H···H and H···C/C···H interactions. The analysis of Hirshfeld surface has been well correlated with the spectroscopic studies. Theoretical calculations of the title compounds’ isolated molecule have been carried out using DFT at the B3LYP level.  相似文献   
8.
JPC – Journal of Planar Chromatography – Modern TLC - Coffee, due to its common consumption, is one of the main sources of polyphenols in human diet. Coffee species and coffee-related...  相似文献   
9.
Multimeric presentation, a rather effective way of enhancing peptide immunogenicity, is best exemplified by MAP (multiple antigenic peptide) dendrimers consisting of a branched Lys core on which several copies of the peptide epitope are displayed. While accessible by solid-phase synthesis, MAPs can also be conveniently made in solution, e.g., by linking the epitope (N-acetylated and with a C-terminal Cys) through a thioether bond onto the α and ε (haloacetyl-activated) positions of the Lys core. We now report the reverse version of this approach, whereby a chloroacetyl-derivatised epitope is tethered to a thiol-functionalised form of a Lys dendron core. This convergent approach can be carried out either in solution or in the solid phase and is advantageous because (i) in situ tris(2-carboxyethyl)phosphine (TCEP)-mediated reduction of disulfide bonds maintains the thiol platform reactive throughout the ligation process; (ii) the low amounts of TCEP used pose minimal risk to chloroacetyl groups in the peptide, resulting in (iii) significantly reduced byproduct formation, hence cleaner products. For the solid phase version of the method, an optimised procedure has been devised to convert the Lys core into a tetrathiol dendron.  相似文献   
10.
Liquid chromatography electrospray ionization tandem mass spectrometric (LC-ESI-MS/MS) qualitative and quantitative analysis of different extracts from the aerial parts and roots of Alchemilla acutiloba led to the identification of phenolic acids and flavonoids. To the best of our knowledge, isorhamnetin 3-glucoside, kaempferol 3-rutinoside, narcissoside, naringenin 7-glucoside, 3-O-methylquercetin, naringenin, eriodictyol, rhamnetin, and isorhamnetin were described for the first time in Alchemilla genus. In addition, the antioxidant, anti-inflammatory and cytotoxic activity of all extracts were evaluated. The results clearly showed that among analyzed extracts, the butanol extract of the aerial parts exhibited the highest biological activity comparable with the positive controls used.  相似文献   
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