Spectroscopic (NMR, UV, FT-IR and FT-Raman) analysis and theoretical investigation of nicotinamide N-oxide with density functional theory

The spectroscopic properties of the nicotinamide N-oxide (abbreviated as NANO, C(6)H(6)N(2)O(2)) were examined by FT-IR, FT-Raman, NMR and UV techniques. FT-IR and FT-Raman spectra in solid state were observed in the region 4000-400 cm(-1) and 3500-50 cm(-1), respectively. The (1)H and (13)C NMR spectra were recorded in DMSO. The UV absorption spectrum of the compound that dissolved in water was recorded in the range of 200-800 nm. The structural and spectroscopic data of the molecule in the ground state were calculated by using Density Functional Theory (DFT) employing B3LYP methods with the 6-311++G(d,p) basis set. The geometry of the molecule was fully optimized, vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. The optimized structure of compound was interpreted and compared with the reported experimental values. The observed vibrational wavenumbers, absorption wavelengths and chemical shifts were compared with calculated values. As a result, the optimized geometry and calculated spectroscopic data show a good agreement with the experimental results.     

Essential oil composition of three species of Scutellaria from Turkey

The chemical compositions of the essential oils obtained by hydrodistillation from the aerial parts of Scutellaria diffusa, Scutellaria heterophylla and Scutellaria salviifolia were separately identified simultaneously by gas chromatography and gas chromatography-mass spectrometry. The main components were determined as hexadecanoic acid (30%) and caryophyllene oxide (9%) in the oil of S. diffusa. Germacrene D (21%), hexadecanoic acid (16%) and β-caryophyllene (13%) were found as major components in the oil of S. heterophylla. The main components of the oil of S. salviifolia were germacrene D (40%), bicyclogermacrene (14%) and β-caryophyllene (11%). Overall, individually 63, 68 and 43 constituents were identified in the aerial parts of S. diffusa, S. heterophylla and S. salviifolia essential oils representing 92.1%, 89.9% and 90% of the total, respectively.     

Effect of the Amount of Polysorbate 80 and Oregano Essential Oil on the Emulsion Stability and Characterization Properties of Sodium Alginate Microcapsules

Essential oils have a high volatility that leads to evaporation and loss of their pharmacological effect when exposed to the environment. The objectives of the present work were to prepare microcapsules with oregano essential oil by extrusion using sodium alginate as a shell material and non-ionic surfactant polysorbate 80 as an emulsifier to stabilize the emulsion. The present study was aimed to evaluate the physical parameters of microcapsules and to compare the influence of the amount of emulsifier and the essential oil-to-emulsifier ratio on the capsules’ physical parameters and encapsulation efficiency; to our knowledge, the existing research had not yet revealed whether unstable emulsion affects the encapsulation efficiency of oregano essential oil. This study showed that increasing the emulsifier amount in the formulation significantly influenced encapsulation efficiency and particle size. Moreover, increasing the emulsion stability positively influenced the encapsulation efficiency. The emulsion creaming index depended on the emulsifier amount in the formulation: the highest creaming index (%) was obtained with the highest amount of polysorbate 80. However, the essential oil-to-polysorbate 80 ratio and essential oil amount did not affect the hardness of the microcapsules (p > 0.05). In conclusion, the obtained results could be promising information for production of microcapsules. Despite the fact that microencapsulation of essential oils is a promising and extremely attractive application area for the pharmaceutical industry, further basic research needs to be carried out.     

Vibrational Spectra of Cluster Anions. 2. Vibrational Spectra of Compounds with the Cluster Anions [E4]4−: M4E4 (M = K,Rb, Cs; E = Ge,Sn) and β‐Na4Sn4

Vibrational spectra of the compounds M₄E₄ (M = K, Rb, Cs; E = Ge, Sn) and of β‐Na₄Sn₄ with the cluster anions [E₄]^4? were analysed based on the point group of isolated tetrahedranide units. The lower individual symmetry of the anions in the real structure being more patterned and complex primarily affects the spectra of the tetrahedro‐tetragermanides. ν₃(F₂) clearly splits both in Raman and IR and in the case of K₄Sn₄ only in IR. Rb₄Sn₄ and Cs₄Sn₄ exhibit very simple spectra with three bands in Raman and one band in IR. The breathing mode ν₁(A₁) for the quasi isolated [E₄]^4? cluster appears only in the Raman spectrum and is hardly influenced by the structural environment and by the nature of the alkali metal cations: ν₁(A₁) = 274 cm^?1 ([Ge₄]^4?) and 183‐187 cm^?1 ([Sn₄]^4?), respectively. The calculated valence force constants f_d(E–E) are: [Ge₄]^4? : f_d = 0.89 Ncm^?1 ( K ), 0.87 Ncm^?1 ( Rb ), 0.86 Ncm^?1 ( Cs ) and [Sn₄]^4? : 0.67 Ncm^?1 ( Na ), 0.66 Ncm^?1 ( K ), 0.67 Ncm^?1 ( Rb ), 0.68 Ncm^?1 ( Cs ). Both, the frequencies and the force constants fit well into the range previously reported.     

Light‐Induced Click Reactions

Spatial and temporal control over chemical and biological processes, both in terms of “tuning” products and providing site‐specific control, is one of the most exciting and rapidly developing areas of modern science. For synthetic chemists, the challenge is to discover and develop selective and efficient reactions capable of generating useful molecules in a variety of matrices. In recent studies, light has been recognized as a valuable method for determining where, when, and to what extent a process is started or stopped. Accordingly, this Minireview will present the fundamental aspects of light‐induced click reactions, highlight the applications of these reactions to diverse fields of study, and discuss the potential for this methodology to be applied to the study of biomolecular systems.     

Structural rearrangement of Neisseria meningitidis transferrin binding protein A (TbpA) prior to human transferrin protein (hTf) binding

Gram-negative bacterium Neisseria meningitidis, responsible for human infectious disease meningitis, acquires the iron (Fe³⁺) ion needed for its survival from human transferrin protein (hTf). For this transport, transferrin binding proteins TbpA and TbpB are facilitated by the bacterium. The transfer cannot occur without TbpA, while the absence of TbpB only slows down the transfer. Thus, understanding the TbpA-hTf binding at the atomic level is crucial for the fight against bacterial meningitis infections. In this study, atomistic level of mechanism for TbpA-hTf binding is elucidated through 100 ns long all-atom classical MD simulations on free (uncomplexed) TbpA. TbpA protein underwent conformational change from ‘open’ state to ‘closed’ state, where two loop domains, loops 5 and 8, were very close to each other. This state clearly cannot accommodate hTf in the cleft between these two loops. Moreover, the helix finger domain, which might play a critical role in Fe³⁺ ion uptake, also shifted downwards leading to unfavorable Tbp-hTf binding. Results of this study indicated that TbpA must switch between ‘closed’ state to ‘open’ state, where loops 5 and 8 are far from each other creating a cleft for hTf binding. The atomistic level of understanding to conformational switch is crucial for TbpA-hTf complex inhibition strategies. Drug candidates can be designed to prevent this conformational switch, keeping TbpA locked in ‘closed’ state.     

Influence of Dispersing Agents on the Solubility of Perovskites in Water

In this study, solubility behavior of lead magnesium niobate (PMN) powders in water was investigated in the presence of pure polyacrylic acid and polyacrylic acid/polyethylene oxide comb polymers. Experiments were performed by measuring the solubility of PMN in terms of the concentration of Pb⁺² and Mg⁺² ions in supernatant as a function of pH and dispersing agent dosage. The concentrations of the metal ions in supernatant were found to be affected by the dispersant concentration, stirring time and the suspension pH. Results revealed that both dispersing agents enhance the cation dissolution from PMN surface at pH 9 due to weak (reversible) adsorption and complexation of Pb⁺² and Mg⁺² by carboxylate groups. On the other hand, under acidic conditions cation dissolution from PMN is inhibited and this was attributed to the strong adsorption of dispersing agents onto the powder surface and formation of a dense polymer layer.     

trans‐Bis­[O‐2,4‐di‐tert‐butyl­phenyl (4‐methoxy­phenyl)­di­thio­phosphonato‐κ2S,S′]­nickel(II)

In the the title compound, [Ni(C₂₁H₂₈O₂PS₂)₂], the Ni atom resides on an inversion centre and is coordinated in a square‐planar array by four S atoms, with Ni—S and P—S bond lengths of 2.2336 (12)/2.2351 (13) and 1.9910 (16)/2.0010 (17) Å, respectively. The two O‐2,4‐di‐tert‐butyl­phenyl and two 4‐methoxy­phenyl moieties adopt trans configurations about the central Ni atom.     

Enhanced Maturation of 3D Bioprinted Skeletal Muscle Tissue Constructs Encapsulating Soluble Factor-Releasing Microparticles

Several microfabrication technologies have been used to engineer native-like skeletal muscle tissues. However, the successful development of muscle remains a significant challenge in the tissue engineering field. Muscle tissue engineering aims to combine muscle precursor cells aligned within a highly organized 3D structure and biological factors crucial to support cell differentiation and maturation into functional myotubes and myofibers. In this study, the use of 3D bioprinting is proposed for the fabrication of muscle tissues using gelatin methacryloyl (GelMA) incorporating sustained insulin-like growth factor-1 (IGF-1)-releasing microparticles and myoblast cells. This study hypothesizes that functional and mature myotubes will be obtained more efficiently using a bioink that can release IGF-1 sustainably for in vitro muscle engineering. Synthesized microfluidic-assisted polymeric microparticles demonstrate successful adsorption of IGF-1 and sustained release of IGF-1 at physiological pH for at least 21 days. Incorporating the IGF-1-releasing microparticles in the GelMA bioink assisted in promoting the alignment of myoblasts and differentiation into myotubes. Furthermore, the myotubes show spontaneous contraction in the muscle constructs bioprinted with IGF-1-releasing bioink. The proposed bioprinting strategy aims to improve the development of new therapies applied to the regeneration and maturation of muscle tissues.