Ligand exchange chiral separations by cyclodextrin derivatives in capillary electrophoresis

A beta-cyclodextrin substituted by an imidazole-bound histamine (CDmh) was successfully used to separate underivatised tryptophan racemate in capillary electrophoresis in the presence of copper(II) ion by the ligand exchange mechanism. To the best of our knowledge, this is the first example of a cyclodextrin derivative behaving as the first coordination sphere ligand in the complex added to the background electrolyte (BGE).     

Ordered Mesoporous Silica Incorporating Platinum Nanoparticles as Electrode Material for Paracetamol Detection

High ordered mesoporous materials (SBA-15) modified with Al and/or B and Pt nanoparticles (Pt NPs) were used for preparing modified graphite paste electrodes (Pt/M−SBA-15-GPE, where M=Al−, B− or Al−B−) and applied for paracetamol (PA) detection. The electrodes were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Square wave voltammetry (SWV) technique was used to obtain the analytical parameters for PA detection. The acquired values of electrochemical and analytical parameters recommend the mesoporous compound containing Pt NPs to be used as composite electrode material for PA detection in real samples.     

A novel diamine adduct of zinc bis(2-thenoyl-trifluoroacetonate) as a promising precursor for MOCVD of zinc oxide films

A novel diamine (N,N,N',N'-tetramethyletilendiamine) adduct of zinc bis(2-thenoyl-trifluoroacetonate) has been synthesized in a single-step reaction. Single-crystal X-ray diffraction studies of Zn(tta)(2).tmeda provide evidence of a mononuclear structure with a six-coordinated zinc ion. The thermal behavior of this adduct points to mass-transport properties suitable for its application to MOCVD processes. This novel compound has been successfully applied as a precursor for the deposition of ZnO films on (100) Si and quartz substrates. The good quality of the deposited films indicates that the adduct is a very attractive precursor for MOCVD applications.     

Synthesis of New Carnosine Derivatives of β‐Cyclodextrin and Their Hydroxyl Radical Scavenger Ability

Several in vitro and in vivo studies have suggested that carnosine can act as a scavenger of reactive oxygen species and intracellular proton buffer. On the other hand, carnosinase is a specific peptidase able to destroy the biological active dipeptide. To overcome this constraint, β‐cyclodextrin (β‐CD) was functionalized with carnosine to give the following new compounds: 6^A‐[(3‐{[(1S)‐1‐carboxy‐2‐(1H‐imidazol‐4‐yl)ethyl]amino}‐3‐oxopropyl)amino]‐6^A‐deoxy‐β‐cyclodextrin ( 1 ), 6^A‐[(β‐alanyl‐L ‐histidyl)amino]‐β‐cyclodextrin ( 2 ), and (2^AS,3^AR)‐3^A‐[(3‐{[(1S)‐1‐carboxy‐2‐(1H‐imidazol‐4‐yl)ethyl]amino}‐3‐oxopropyl)amino]‐3^A‐deoxy‐β‐cyclodextrin ( 3 ). Pulse‐radiolysis investigation showed that the β‐CD derivatives 1 – 3 are excellent scavengers of OH^. radicals. Their activity is not only due to the formation of the stable imidazole‐centered radical, but also to the scavenger ability of the glucose moieties of the macrocycle (Scheme). This effect is independent of the disposition of the imidazole ring. In fact, the quenching constant values are similar for the three compounds.     

Carnoquinolines Target Copper Dyshomeostasis,Aberrant Protein–Protein Interactions,and Oxidative Stress

Metal dysregulation, oxidative stress, protein modification, and aggregation are factors strictly interrelated and associated with neurodegenerative pathologies. As such, all of these aspects represent valid targets to counteract neurodegeneration and, therefore, the development of metal-binding compounds with other properties to combat multifactorial disorders is definitely on the rise. Herein, the synthesis and in-depth analysis of the first hybrids of carnosine and 8-hydroxyquinoline, carnoquinolines (CarHQs), which combine the properties of the dipeptide with those of 8-hydroxyquinoline, are reported. CarHQs and their copper complexes were characterized through several techniques, such as ESI-MS and NMR, UV/Vis, and circular dichroism spectroscopy. CarHQs can modulate self- and copper-induced amyloid-β aggregation. These hybrids combine the antioxidant activity of their parent compounds. Therefore, they can simultaneously scavenge free radicals and reactive carbonyl species, thanks to the phenolic group and imidazole ring. These results indicate that CarHQs are promising multifunctional candidates for neurodegenerative disorders and they are worthy of further studies.     

Synthesis of carba analogs of 6-O-(benzyl)-d-allal- and -d-galactal-derived allyl epoxides and evaluation of the regio- and stereoselective behavior in nucleophilic addition reactions

The new racemic diastereoisomeric epoxides 6α and 6β, the carba analogs of the corresponding d-galactal- and d-allal-derived allyl epoxides have been synthesized and their regio- and stereoselective behavior examined in addition reactions with model O-, C-, N-, and S-nucleophiles. The results have indicated that epoxide 6β has a pronounced tendency toward anti-1,2-addition, whereas epoxide 6α shows interesting levels of syn- and/or anti-1,4-addition processes. A chiral recognition process found with epoxide 6β, turned out to be consistently reduced in epoxide 6α. All the results have been rationalized on the basis of conformational, steric, and stereoelectronic effects.     

Application of matrix-assisted laser desorption/ionization mass spectrometry to the detection of melanins formed from Dopa and dopamine.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry was used to study melanogenesis starting from Dopa and dopamine, the latter considered one of the precursors of neuromelanins. These substrates were left to react with the peroxidase - H(2)O(2) system, which is postulated to play an important role in melanin biosynthesis. Samples were prepared by ultrafiltering the substrate - enzyme solution after 30, 60, 120, 240 and 360 min of reaction and aliquots were immediately lyophilized. The reaction of dopamine with peroxidase - H(2)O(2) favoured the formation of dopamine oligomers up to octamers. In contrast, the action of either peroxidase or H(2)O(2) alone, studied for comparison, did not lead to melanin production and only dimeric and trimeric species were observed. Also for Dopa, analogous results were obtained in the presence of either peroxidase or H(2)O(2) alone, without melanin formation. Conversely, Dopa with the peroxidase - H(2)O(2) system led to the formation of a black precipitate after 120 min of reaction, and oligomers of 5,6-dihydroxyindole (DHI), an intermediate of melanogenesis, were detected, together with products of further oxidation. Faster kinetics were observed when Dopa was treated with tyrosinase, the enzyme catalysing the oligomerization of tyrosine to melanins, leading to the formation mainly of DHI oligomers.     

Formation of 2-substituted benzofuran fragment ions from 6-alkyl- and 6-aryldibenzo(d,f)(1,3)dioxepine derivatives under electron ionization-a useful precursor ion for isomeric differentiation

Tandem mass spectrometry has been applied to differentiate three sets of o-, m- and p-methyl, -methoxy and -nitro-substituted-6-phenyl-dibenzo(d,f)(1,3)dioxepines. Collision-induced dissociation (CID) experiments have been carried out on 2-phenylbenzo[b]furan fragment ions, which originate from the decomposition of the molecular ions after their EI-induced isomerization to spirocyclic structures. With the exception of m- and p-methylphenylbenzo[b]furan isomers, which display identical CID mass spectra, the three isomeric methoxy- and nitrophenylbenzo[b]furan fragment ions display very characteristic CID behavior which allows unequivocal differentiation of the 6-phenyl-dibenzo(d,f)(1,3)dioxepine isomers. 6-(o-nitrophenyl)-dibenzo(d,f)(1,3)dioxepine isomer, does not form a 2-(o-nitrophenyl)benzo[b]furan ion and, therefore, it can be differentiated from the m- and p- isomers based on the mere EI mass spectra. Furthermore, it shows a characteristic ion most likely due to an ortho effect between the nitro group and the dioxepine ring. Multiple stage mass spectrometric techniques (MSn), labeled derivatives and reference compounds were used in order to gain additional information on the structures of product ion from the CID fragmentation.