Role of Iron Phthalocyanine Coordination in Catecholamines Detection

Catecholamines are an important class of neurotransmitters responsible for regularizing, controlling, and treating neural diseases. Based on control and diseases treatment, the development of methodology and dives to sensing is a promissory technology area. This work evaluated the role of iron phthalocyanine coordination (FePc) with the specific groups from catecholamine molecules (L-dopa, dopamine, epinephrine, and the amino acid tyrosine) and the effect of this coordination on electrochemical behavior. The in situ coordination analysis was performed through isotherms π-A of FePc Langmuir films in the absence and presence of catecholamines. The π-A isotherm indicates a strong interaction between FePc monolayer and L-Dopa and DA, which present a catechol group and a side chain with a protonated amino group (-NH3+). These strong interactions with catechol and amine groups were confirmed by characterization at the molecular level using the surface-enhanced Raman spectroscopy (SERS) from a Langmuir–Schaefer monolayer deposited onto Ag surfaces. The electrochemical measurements present a similar tendency, with lower oxidation potential observed to DA>L-Dopa>Ep. The results corroborate that the coordination of the analyte on the electron mediator surface plays an essential role in an electrochemical sensing application. The FePc LS film was applied as a sensor in tablet drug samples, showing a uniformity of content of 96% for detecting active compounds present in the L-Dopa drug samples.

Opioid Receptors and Protonation-Coupled Binding of Opioid Drugs

Opioid receptors are G-protein-coupled receptors (GPCRs) part of cell signaling paths of direct interest to treat pain. Pain may associate with inflamed tissue characterized by acidic pH. The potentially low pH at tissue targeted by opioid drugs in pain management could impact drug binding to the opioid receptor, because opioid drugs typically have a protonated amino group that contributes to receptor binding, and the functioning of GPCRs may involve protonation change. In this review, we discuss the relationship between structure, function, and dynamics of opioid receptors from the perspective of the usefulness of computational studies to evaluate protonation-coupled opioid-receptor interactions.

Crystal structure of 3,6,6-trimethyl-4-oxo-1-(pyridin-2-yl)-4,5,6,7-tetrahydro-1H-indazol-7-aminium chloride and its monohydrate

The title compounds, C15H19N4O+·Cl−and C15H19N4O+·Cl−·H2O, obtained in attempts to synthesize metal complexes using tetrahydroindazole as a ligand, were characterized by NMR, IR and X-ray diffraction techniques. The partially saturated ring in the tetrahydroindazole core adopts a sofa conformation. An intramolecular N—H...N hydrogen bond formed by the protonated amino group and the N atom of the pyridyl substituent is found in the first structure. In the hydrochloride, the organic moieties are linked by two N—H...Cl−hydrogen bonds, forming aC(4) graph-set. In the hydrate crystal, a Cl−anion and a water molecule assemble the moieties into infinite bands showing hydrogen-bond patterns with graph setsC(6),R64(12) andR42(8). Organic moieties form π–π stacked supramolecular structures running along thebaxis in both structures.

An efficient and sensitive fluorescent pH sensor based on amino functional metal–organic frameworks in aqueous environment

In this work, an amino group functionalized MOF (Al-MIL-101-NH2), which shows strong blue luminescence, is used as pH sensor. Due to the protonated amino group, the fluorescence intensity of Al-MIL-101-NH2almost increases with increasing pH and gives a good linear relationship (R2= 0.99688) with the pH value.

Thermodynamic dissociation constants of risedronate using spectrophotometric and potentiometric pH-titration

Risedronate inhibits bone resorption in diseases like osteoporosis, Paget’s disease, tumor bone diseases or the malfunction of phosphocalcium metabolism. The acid-base properties of risedronate in an aqueous solution have been studied in a pH range from 2 to 12 and can be described in terms of four dissociation steps: pK a,2, pK a,4, pK a,5 (related to the dissociation of POH groups) and pK a,3 related to the dissociation of protonated amino group NH3+. The mixed dissociation constants were determined at different ionic strengths I = 0.02 to 0.20 mol dm−3 KCl and of 25°C and 37°C using pH-spectrophotometric and pH-potentiometric titration methods. Determination of group parameters L 0, H T might lead to false estimates of common parameters p K a;therefore, the computational strategy employed is important. A comparison between the two programs ESAB and HYPERQUAD demonstrated that the ESAB program provides a better fit of potentiometric titration curve. The thermodynamic dissociation constants pK aT were estimated by a nonlinear regression of (pK a, I) data and a Debye-Hückel equation at 25°C and 37°C, pK a,2T = 2.37(1) and 2.44(1), pK a,3T = 6.29(3) and 6.26(1), pK a,4T = 7.48(1) and 7.46(2) and pK a,5T = 9.31(7) and 8.70(3) at 25°C and 37°C using pH-spectroscopic data and pK a,2T = 2.48(3) and 2.43(1), pK a,3T= 6.12(2) and 6.10(2), pK a,4T = 7.25(2) and 7.23(1) and pK a,5T = 12.04(5) and 11.81(2) at 25°C and 37°C. The ascertained estimates of three dissociation constants pK a,3, pK a,4, pK a,5 are in agreement with the predicted values obtained using PALLAS

Preparation and Basic Characterizations of Alginate-Chitosan Hydrogel

The aim of this study is to prepare and characterize an alginate-chitosan hydrogel for wound dressing application. The influence of alginate concentrations (1%, 2%, 3% and 4% (w/v)) was investigated. This polyelectrolyte hydrogel is observed to be transparent and flexible. The SEM morphological structure of hydrogel is composed of a dense outer skin layer and a porous cross-section layer. The FTIR and DSC measurements indicated the protonated amino group of chitosan has reacted with the carbonyl group of alginate. Some other properties for the wound dressing application are also reported in other paper. Taken together these results point out that alginate-chitosan polyelectrolyte hydrogel can be considered for wound dressing applications.

Homoselenocysteine — An oxygen or selenium acid in the gas phase?

The potential energy surface of l-homoselenocysteine (HSEC) has been explored through the use of B3LYP/6-311+G(d,p) calculations. In this survey, seventy-seven different conformers have been located. These local minima can be classified in four groups, A–D. Structures A, B, and D are stabilized by intramolecular hydrogen bonds (IMHBs) with the amino group acting as the hydrogen bond (HB) donor and the carbonyl group (structures A and D) or the hydroxyl group (structure B) as HB acceptors. The structures in set C present an IMHB with the amino group acting as the HB acceptor and the hydroxyl group as the HB donor. The stability order decreases in the following order: A > B > C > D. From their relative stabilities it can be concluded that only three of these conformers, namely A1, A4, and A5, would exist in the gas phase at room temperature. The most stable deprotonated form corresponds to a Se-deprotated species stabilized by a strong IMHB between the hydroxyl group and the Se atom. However, a direct deprotonation of the most stable neutrals lead to O-deprotonated species, which eventually isomerize to yield the global minimum. Hence, we can conclude that, quite unexpectedly, HSEC behaves as a Se acid in the gas phase, its intrinsic acidity being 1374 kJ mol–1 at the B3LYP/6-311++G(3df,2p) level of theory. The most stable protonated forms are systematically the N-protonated ones, the global minimum being a structure stabilized through an IMHB involving the protonated amino group as the HB donor and the SeH group as the HB acceptor. The calculated gas-phase proton affinity (PA) at the B3LYP/6-311++G(3df,2p) level of theory is 930 kJ mol–1.

Synthesis and Characterization of Novel Ruthenium(III) Complexes with Histamine

Novel ruthenium(III) complexes with histamine[RuCl4(dmso-S)(histamineH)]⋅O(1a) and[RuCl4(dmso-S)(histamineH)](1b) have been prepared and characterized by X-ray structure analysis. Their crystal structures are similar and show a protonated amino group on the side chain of the ligand which is not very common for a simple heterocyclic derivative such as histamine. Biological assays to test the cytotoxicity of the compound1bcombined with electroporation were performed to determine its potential for future medical applications in cancer treatment.

Complexation of glycylglycine by the methylmercury cation: a vibrational spectroscopy and X-ray diffraction study

Two different crystalline complexes have been obtained from aqueous mixtures of glycylglycine (GlyGly) and methylmercury(II), and they were studied by vibrational spectroscopy and X-ray diffraction. In the first compound, a hydrogen atom of the protonated amino group of GlyGly is substituted by the CH3Hg+ cation, giving (CH3Hg)GlyGly: orthorhombic, Pna21, a = 7.920(6) Å, b = 13.473(5) Å, c = 8.059(3) Å, and Z = 4. Further complexation on the carboxylate group yielded the complex [(CH3Hg)2GlyGly]ClO4: monoclinic, P21/c, a = 6.407(4) Å, b = 24.439(6) Å, c = 8.461(2) Å, β = 93.82(4)°, and Z = 4. The sites of complexation and the conformations of these solid complexes are well reflected in their vibrational spectra. Raman spectra indicate that complexation in aqueous solutions is limited to substitution on the —NH3+ group of GlyGly.