Thermal decomposition of chemotherapeutic preparations and expectorants

The thermal decomposition of 31 drugs containing sulphonamides, antituberculous agents, dyes, an oxidant, carboxylic acid derivatives and formaldehyde, expectorants and codeine phosphate has been studied by differential thermal analysis (DTA) and thermogravimetry (TG). The DTA, TG and differential TG curves have been used for identification of the drugs and their qualitative and quantitative analysis. The results for 18 of the drugs were in good agreement with those calculated from the formulation.     

Synthesis and mesomorphic properties of four ring,rod-like fluorene derivatives – the influence of the lateral substitution on mesomorphic properties of 2,7-bis(4-alkylphenyl)-fluorenes

ABSTRACT

This work presents new rod-like compounds being fluorene derivatives linked with other parts of the core at 2 and 7 positions – its synthesis and properties. The fluorene moiety is located in the central position of the four rings molecular core. The chain system in most cases was symmetrical and limited to pentyl or hexyl chains. To study the influence of the lateral substituents on mesomorphic properties two types of substituents have been incorporated, centrally located various short alkyl groups at fluorene’s 9,9 positions and outer core fluorosubstitutions located at side phenyl rings. All synthesised compounds exhibit liquid crystalline properties, where for laterally non-substituted and fluorosubstituted derivatives the dominant phases are smectics, while the nematics phases (nematic and chiral nematic – observed mostly on cooling cycle) occurs for compounds having alkyl substituents at 9,9 positions of fluorene. The synthetic methodology and mesomorphic properties of title compounds will be presented in detail as well as photophysical properties such as UV-visible absorption spectra and fluorescence spectra.     

Trimethylsilyl fluorosulfonyldifluoroacetate (TFDA): a new, highly efficient difluorocarbene reagent

TFDA is readily prepared from the reaction of fluorosulfonyldifluoroacetic acid with trimethylsilyl chloride, and it is a very effective and efficient source of difluorocarbene for use in addition reactions to alkenes of a broad scope of reactivities. Acid-sensitive substrates may require an additional purification step involving treatment of the distilled TFDA with sufficient Et₃N to remove the acid impurity. Other trialkylsilyl fluorosulfonyldifluoroacetates can also be prepared, and they have been found to have reactivities similar to TFDA. The triethyl derivative, TEFDA is more convenient to prepare in a pure state and has similar reactivity to TFDA. Thus, it may prove to be a superior reagent.     

Vibrational studies of the solid imidazole and pyridine adducts of metal(II) saccharinates. III. Zn(II) and Hg(II) imidazole saccharinates

Adducts of bis(o-sulfobenzimidato)zinc(II) and mercury(II) with imidazole are synthesized for the first time and their mid-infrared vibrational spectra at ambient conditions and at 77 K are coupled with the earlier spectra-structural inferences to predict aspects of the respective solid-state structures. The spectrum of the H2O-matrix isolated OD fundamentals in the hydrated zinc compound is also investigated. The structure of the latter adduct contrasts the octahedral isostructural tetrad of mixed imidazole-saccharinates [M(H2O)2(C3H4N2)4](C7H4NO3S)2 [M = Mn(II), Fe(II), Co(II) and Ni(II)] in that it bears only a single crystallographic type of hydrogen bonded C2v water molecules and at least two structurally different o-sulfobenzimidate ligands, some of them likely utilized in a bridging fashion. The rotation and the partial ionic character of a pair of N-monodentate o-sulfobenzimidato ligands placed about 212-214 pm from the metal accommodates another pair of imidazole molecules in the tetrahedral arrangement around the metal in the neutral unhydrous mercury complex.     

Effects of Addition of Ion-Pair Reagent to the Mobile Phase on Electroosmotic Flow Velocity in Pressurized Planar Electrochromatography

JPC – Journal of Planar Chromatography – Modern TLC - In the paper, the influence of the addition of different ion-pair reagents — sodium-1-heptane sulfonate (HS),...     

Impact of Mercury(II) on proteinase K catalytic center: investigations via classical and Born-Oppenheimer molecular dynamics

Mercury(II) has a strong affinity for the thiol groups in proteins often resulting in the disruption of their biological functions. In this study we present classical and first-principles, DFT-based molecular dynamics (MD) simulations of a complex of Hg(II) and proteinase K, a well-known serine protease with a very broad and diverse enzymatic activity. It contains a catalytic triad formed by Asp39, His69, and Ser224, which is responsible for its biological activity. It was found previously by X-ray diffraction experiments that the presence of Hg(II) inhibits the enzymatic action of proteinase K by affecting the stereochemistry of the triad. Our simulations predict that (i) the overall structure as well as the protein backbone dynamics are only slightly affected by the mercury cation, (ii) depending on the occupied mercury site, the hydrogen bonds of the catalytic triad are either severely disrupted (both bonds for mercury at site 1, and the His69–Ser224 contact for mercury at site 2) or slightly strengthened (the Asp39–His69 bond when mercury is at site 2), (iii) the network of hydrogen bonds of the catalytic triad is not static but undergoes constant fluctuations, which are significantly modified by the presence of the Hg(II) cation, influencing in turn the triad’s ability to carry out the enzymatic function—these facts explain the experimental findings on the inhibition of proteinase K by Hg(II).     

Reversed-Phase Pressurized Planar Electrochromatography and Planar Chromatography of Acetylsalicylic Acid,Caffeine, and Acetaminophen

JPC – Journal of Planar Chromatography – Modern TLC - We have investigated the use of pressurized planar electrochromatography (PPEC) and planar chromatography (TLC) for reversed-phase...     

Radical Stability Directs Electron Capture and Transfer Dissociation of β‐Amino Acids in Peptides

We report on the characteristics of the radical‐ion‐driven dissociation of a diverse array of β‐amino acids incorporated into α‐peptides, as probed by tandem electron‐capture and electron‐transfer dissociation (ECD/ETD) mass spectrometry. The reported results demonstrate a stronger ECD/ETD dependence on the nature of the amino acid side chain for β‐amino acids than for their α‐form counterparts. In particular, only aromatic (e.g., β‐Phe), and to a substantially lower extent, carbonyl‐containing (e.g., β‐Glu and β‐Gln) amino acid side chains, lead to N? C_β bond cleavage in the corresponding β‐amino acids. We conclude that radical stabilization must be provided by the side chain to enable the radical‐driven fragmentation from the nearby backbone carbonyl carbon to proceed. In contrast with the cleavage of backbones derived from α‐amino acids, ECD of peptides composed mainly of β‐amino acids reveals a shift in cleavage priority from the N? C_β to the C_α? C bond. The incorporation of CH₂ groups into the peptide backbone may thus drastically influence the backbone charge solvation preference. The characteristics of radical‐driven β‐amino acid dissociation described herein are of particular importance to methods development, applications in peptide sequencing, and peptide and protein modification (e.g., deamidation and isomerization) analysis in life science research.