Die Millon'sche Reaktion des Harns und ihre Beeinflussung durch Zufuhr von Tyrosin

Zusammenfassung Es werden einige Versuche an Kaninchen und Menschen über die Millon'sche Reaktion des Harns mitgeteilt. Ihre Intensität steigt an, wenn Tyrosin zugeführt wird, und zwar erheblich mehr nach dl-Tyrosin als nach l-Tyrosin. Ein Teil der Millon-Substanzen ist in Äther löslich, der ebenfalls nach der razemisierten stärker zunimmt als der nach der natürlichen Aminosäure.     

UV photoelectron spectra of 5- and 6-azauracil

The He(I) photoelectron spectra of 5-azauracil (1,3,5-triazine-2,4(1H,3H)-dione) and 6-azauracil (1,2,4-triazine-3, 5(2H,4H)-dione) are presented. The spectra are assigned by using INDO/S calculations and comparison arguments with uracil. The first ionization energy in the title compounds is higher than in the usual nucleic acid bases.     

Screening for the beta-39 mutation in thalassemia by capillary electrophoresis in free solution in strongly acidic, isoelectric buffers

A novel method is reported for screening for point mutations in genomic DNA: free-zone capillary electrophoresis in very acidic buffers. This method exploits the charge difference among the four different bases (C, T, A, G) in a pH window between 2.5 and 3.5, where the four titration curves fan out. The method is applied to the detection of the beta-39 missense mutation in the beta-globin gene in thalassemias. A 60-mer fragment straddling the mutation site has been amplified. In an isoelectric buffer (iminodiacetic acid) of pH 3.3, partial resolution between the wild type and mutated strands is obtained. In a pH 3.0 phosphate buffer, baseline resolution is achieved between the two strands in a heterozygous individual. Due to the short size of the amplified fragment, this method can only be applied to routine screening for known mutations because resolution was lost in a fragment 100 bases long.     

Enantioseparations of polyhalogenated 4,4’-bipyridines on polysaccharide-based chiral stationary phases and molecular dynamics simulations of selector–selectand interactions

2’-(4-Pyridyl)- and 2’-(4-hydroxyphenyl)-TCIBPs (TCIBP = 3,3’,5,5’-tetrachloro-2-iodo-4,4’-bipyridyl) are chiral compounds that showed interesting inhibition activity against transthyretin fibrillation in vitro. We became interested in their enantioseparation since we noticed that the M-stereoisomer is more effective than the P-enantiomer. Based thereon, we recently reported the enantioseparation of 2’-substituted TCIBP derivatives with amylose-based chiral columns. Following this study, herein we describe the comparative enantioseparation of both 2’-(4-pyridyl)- and 2’-(4-hydroxyphenyl)-TCIBPs on four cellulose phenylcarbamate-based chiral columns aiming to explore the effect of the polymer backbone, as well as the nature and position of substituents on the side groups on the enantioseparability of these compounds. In the frame of this project, the impact of subtle variations of analyte and polysaccharide structures, and mobile phase (MP) polarity on retention and selectivity was evaluated. The effect of temperature on retention and selectivity was also considered, and overall thermodynamic parameters associated with the analyte adsorption onto the CSP surface were derived from van ’t Hoff plots. Interesting cases of enantiomer elution order (EEO) reversal were observed. In particular, the EEO was shown to be dependent on polysaccharide backbone, the elution sequence of the two analytes being P-M and M-P on cellulose and amylose tris(3,5-dimethylphenylcarbamate), respectively. In this regard, a theoretical investigation based on molecular dynamics (MD) simulations was performed by using amylose and cellulose tris(3,5-dimethylphenylcarbamate) nonamers as virtual models of the polysaccharide-based selectors. This exploration at the molecular level shed light on the origin of the enantiodiscrimination processes.     

X-ray spectroscopic characterization of Cu2+-phenanthroline complexes intercalated in α-zirconium phosphate

X-ray photoelectron spectroscopy provides evidence that when [Cu(phen)₂]²⁺(phen = 1,10-phenanthroline) is diffused between the layers of -zirconium phosphate, the complex species does not remain intact after intercalation, but some Cu-N bonds are broken, replaced with Cu-O bonds and the released nitrogen atoms can now interact with the PO₃-OH groups of the host. XPS also provides evidence for coordination of the Cu²⁺ ions when they are diffused by ion exchange in the phenanthroline--zirconium phosphate intercalation compound. Although Cu²⁺ and phen are in a 1 : 1 molar ratio in the interlayer region of the host, so that a 1 : 1 coordination could be expected between the two species, the characteristic peaks of the uncoordinated phenanthroline, even though at a low intensity, are still present. The differences between the two Cu(II)-intercalation compounds are discussed.     

Volatiles,color characteristics and other physico–chemical parameters of commercial Moroccan honeys

Seven commercial Moroccan honeys were considered for chemical characterisation. Volatile fraction, total polyphenols content, antioxidant and antiradical activities were evaluated by employing different analytical methodologies. Several physical parameters such as refractive index, pH, water content, solids content and colour were measured. Volatile fraction revealed an abundant presence of cis- and trans-linalool oxide in the seven studied samples. The presence of high levels of compounds related to the Maillard reaction, like furfural and hydroxymethylfurfural, could be the result of thermal treatments used to liquefy commercial honeys or of long storage times. The CIE L^*a^*b^*C_ab^*h_ab° chromatic coordinates confirmed the advanced stage of the Maillard reaction, showing L^* values lower than the common values found for honey of similar typologies.     

Optimization of the HPLC enantioseparation of 3,3′‐dibromo‐5,5′‐disubstituted‐4,4′‐bipyridines using immobilized polysaccharide‐based chiral stationary phases

The HPLC enantioseparation of nine atropisomeric 3,3′,5,5′‐tetrasubstituted‐4,4′‐bipyridines was performed in normal and polar organic (PO) phase modes using two immobilized polysaccharide‐based chiral columns, namely, Chiralpak IA and Chiralpak IC. The separation of all racemic analytes, the effect of the chiral selector, and mobile phase (MP) composition on enantioseparation and the enantiomer elution order (EEO) were studied. The beneficial effect of nonstandard solvents, such as tetrahydrofuran (THF), dichloromethane (DCM), and methyl t‐butyl ether on enantioseparation was investigated. All selected 4,4′‐bipyridines were successfully enantioseparated on Chiralpak IA under normal or PO MPs with separation factors from 1.14 to 1.70 and resolutions from 1.3 to 6.5. Two bipyridines were enantioseparated at the multimilligram level on Chiralpak IA. Differently, Chiralpak IC was less versatile toward the considered class of compounds and only five bipyridines out of nine could be efficiently separated. In particular, on these columns, the ternary mixture n‐heptane/THF/DCM (90:5:5) as MP had a positive effect on enantioseparation. An interesting phenomenon of reversal of the EEO depending on the composition of the MP for the 3,3′‐dibromo‐5,5′‐bis‐(E)‐phenylethenyl‐4,4′‐bipyridine along with an exceptional enantioseparation for the 3,3′‐dibromo‐5,5′‐bis‐ferrocenylethynyl‐4,4′‐bipyridine (α = 8.33, R_s = 30.6) were observed on Chiralpak IC.     

Advancements of thermal analysis and calorimetry in Central-Eastern Europe and Mediterranean region

Journal of Thermal Analysis and Calorimetry -     

Rhodium catalyzed hydroformylation of 2-phenylsulfonylbicyclo[2.2.1] alkenes: effect of the phenylsulfonyl group

The preliminary results of the hydroformylation of 2-phenylsulfonyl substituted norbornene and norbornadiene derivatives catalyzed by the unmodified Rh(CO)₂acac system are presented. The reaction, occurring under standard oxo conditions, gives polyfunctionalized exo norbornene- and exo norbornanecarboxaldehydes. The effect of the phenylsulfonyl group has been evaluated: it has been found that the steric properties of the sulfonyl substituent, more than the electronic ones, influence the regioselectivity of the process.