Flow-induced conformational changes in gelatin structure and colloidal stabilization

Flow can change the rate at which solutes adsorb on surfaces by changing mass transfer to the surface, but moreover, flow can induce changes in the conformation of macromolecules in solution by providing sufficient stresses to perturb the segmental distribution function. However, there are few studies where the effect of flow on macromolecules has been shown to alter the structure of macromolecules adsorbed on surfaces. We have studied how the local energy dissipation alters the adsorption of gelatin onto polystyrene nanoparticles ( r = 85 nm). The change in the nature of the adsorbed layer is manifest in the change in the ability of the nanoparticles to resist aggregation. Circular dichroism spectroscopy was used to assess conformational changes in gelatin, and dynamic light scattering was used to assess the colloid stability. Experiments were conducted in a vortex jet mixer where energy density and mixing times have been quantified; mixing of the gelatin and unstable nanoparticles occurs on the order of milliseconds. The adsorption of the gelatin provides steric stabilization to the nanoparticles. We found that the stability of the gelatin-adsorbed nanoparticles increased with increasing mixing velocities: when the mixing velocities were changed from 0.9 to 550 m/s, the radius of the nanoclusters (aggregates) formed 12 h after the mixing decreased from 2620 to 600 nm. Increasing temperature also gave rise to similar trends in the stability behavior with increasing temperature, leading to increasing colloid stability. Linear flow birefringence studies also suggested that the velocity fields in the mixer are sufficiently strong to produce conformational changes in the gelatin. These results suggest that the energy dissipation produced by mixing can activate conformational changes in gelatin to alter its adsorption on the surfaces of nanoparticles. Understanding how such conformational changes in gelatin can be driven by local fluid mechanics and how these changes are related to the adsorption behavior of gelatin is very important both industrially and scientifically.     

Quantitation of donepezil and its active metabolite 6-O-desmethyl donepezil in human plasma by a selective and sensitive liquid chromatography-tandem mass spectrometric method

A sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for the simultaneous determination of donepezil (D) and its pharmacologically active metabolite, 6-O-desmethyl donepezil (6-ODD) in human plasma is developed using galantamine as internal standard (IS). The analytes and IS were extracted from 500 microL aliquots of human plasma via solid-phase extraction (SPE) on Waters Oasis HLB cartridges. Chromatographic separation was achieved in a run time of 6.0 min on a Waters Novapak C18 (150 mm x 3.9 mm, 4 microm) column under isocratic conditions. Detection of analytes and IS was done by tandem mass spectrometry, operating in positive ion and multiple reaction monitoring (MRM) acquisition mode. The protonated precursor to product ion transitions monitored for D, 6-ODD and IS were at m/z 380.1-->91.2, 366.3-->91.3 and 288.2-->213.2, respectively. The method was fully validated for its selectivity, interference check, sensitivity, linearity, precision and accuracy, recovery, matrix effect, ion suppression/enhancement, cross-specificity, stability and dilution integrity. A linear dynamic range of 0.10-50.0 ng mL(-1) for D and 0.02-10.0 ng mL(-1) for 6-ODD was evaluated with mean correlation coefficient (r) of 0.9975 and 0.9985, respectively. The intra-batch and inter-batch precision (%CV, coefficient of variation) across five quality control levels was less than 7.5% for both the analytes. The method was successfully applied to a bioequivalence study of 10mg donepezil tablet formulation in 24 healthy Indian male subjects under fasting condition.     

Synthesis,Characterization and Photocatalytic Activity of Ag+‐ and Sn2+‐Doped KTi0.5Te1.5O6

In this study, the photocatalytic dye degradation efficiency of KTi_0.5Te_1.5O₆ synthesized through solid‐state method was enhanced by cation (Ag⁺/Sn⁺²) doping at potassium site via ion exchange method. As prepared materials were characterized by XRD, SEM‐EDS, IR, TGA and UV–Vis Diffuse reflectance spectroscopic (DRS) techniques. All the compounds were crystallized in cubic lattice with space group. The bandgap energies of parent, Ag⁺‐ and Sn⁺²‐doped KTi_0.5Te_1.5O₆ materials obtained from DRS profiles were found to be 2.96, 2.55 and 2.40 eV, respectively. Photocatalytic efficiency of parent, Ag⁺‐ and Sn⁺²‐doped materials was evaluated against the degradation of methylene blue (MB) and methyl violet (MV) dyes under visible light irradiation. The Sn⁺²‐doped KTi_0.5Te_1.5O₆ showed higher activity toward the degradation of both MB and MV dyes and its higher activity is ascribed to the lower bandgap energy compared to the parent and Ag⁺‐doped KTi_0.5Te_1.5O₆. The mechanistic degradation pathway of methylene blue (MB) was studied in the presence of Sn²⁺‐doped KTi_0.5Te_1.5O₆. Quenching experiments were performed to know the participation of holes, super oxide and hydroxyl radicals in the dye degradation process. The stability and reusability of the catalysts were studied.     

Structural studies of a novel bioactive benzophenone derivative: (4-Chloro-2-hydroxy-phenyl)-phenyl-methanone

The title compound (4-Chloro-2-hydroxy-phenyl)-phenyl-methanone was synthesized and the product obtained was characterized by spectroscopic techniques, and finally the structure was confirmed by X-ray diffraction studies. The compound crystallizes in the orthorhombic crystal system with the space group Pbca with unit cell parameters, a = 14.0359(5) Å, b = 6.8084(3) Å, c = 23.1097(8) Å, and Z = 4. The structure exhibits an intramolecular hydrogen bond which closes an S(6) ring. No directional interactions beyond the van der Waals packing contacts were identified in the crystal structure.     

Possible singlet oxygen generation from the photolysis of indigo dyes in methanol, DMSO, water, and ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate

We suggest that singlet molecular oxygen [¹O₂ (¹Δ_g)] is formed upon irradiation of indigo 1 [in air or O₂-saturated DMSO and DMSO (0.5% H₂SO₄)] and indigo carmine 2 [in air or O₂-saturated CH₃OH, D₂O, and 1-butyl-3-methylimidazolium tetrafluoroborate (BmIm-BF₄)]. The quantum yield for production of ¹O₂ is estimated to be 0.6 for 1 and 0.3-0.5 for 2. The rates of reaction of ¹O₂ with 1 and 2 were determined by monitoring the emission of ¹O₂ at 1270 nm over time. Low molar absorptivities (at 532 nm) and rapid physical quenching caused by 1 and 2 limit their utility as ¹O₂ photosensitizers in solution. Compounds 1 and 2 degrade slowly during the photolysis due to a self-sensitized (type I or II) photooxidation reaction. Oxidative cleavage of 1 by singlet oxygen and superoxide, and 2 by superoxide has been noted before (Kuramoto, N.; Kitao, T. J. Soc. Dyers Color. 1979, 95, 257-261; Kettle, A. J.; Clark, B. M.; Winterbourn, C. C. J. Biol. Chem. 2004, 279, 18521-18525).     

Structural Conformation of a Novel 1-Benzhydrylpiperazine Derivative: 1-Benzhydryl-4-(toluene-4-sulfonyl)-piperazine

Abstract  The title compound 1-benzhydryl-4-(toluene-4-sulfonyl)-piperazine was synthesized and the structure was investigated by X-ray crystallography. The title compound, C₂₄H₂₆N₂O₂S crystallizes in the monoclinic crystal class in the space group P2₁/c with cell parameters a = 13.5800(10) ?, b = 8.9630(7) ?, c = 18.9040(10) ?, β = 106.851(3)°, Z = 4 and V = 2202.1(3) ?³. The structure has been solved by direct methods and refined to R ₁ = 0.0468 for 3174 observed reflections I > 2σ(I). The structure reveals that the piperazine ring is in a chair conformation. The geometry around the S atom is a distorted tetrahedron. Graphical Abstract  The title compound 1-benzhydryl-4-(toluene-4-sulfonyl)-piperazine was synthesized and the structure was investigated by X-ray crystallography. The title compound, C₂₄H₂₆N₂O₂S crystallizes in the monoclinic crystal class in the space group P2₁/c with cell parameters a = 13.5800(10) ?, b = 8.9630(7) ?, c = 18.9040(10) ?, β = 106.851(3)°, Z = 4 and V = 2202.1(3) ?³. The structure has been solved by direct methods and refined to R ₁ = 0.0468 for 3174 observed reflections I > 2σ(I). The structure reveals that the piperazine ring is in a chair conformation. The geometry around the S atom is a distorted tetrahedron.

Radii of starlikeness associated with the lemniscate of Bernoulli and the left-half plane

A normalized analytic function f defined on the open unit disk in the complex plane is in the class SL if zf′(z)/f(z) lies in the region bounded by the right-half of the lemniscate of Bernoulli given by ∣w² − 1∣ < 1. In the present investigation, the SL-radii for certain well-known classes of functions are obtained. Radius problems associated with the left-half plane are also investigated for these classes.     

Synthesis,Characterization, and Biological Evaluation of 10H‐Phenothiazines,Their Sulfones and Ribofuranosides

10H‐phenothiazines are synthesized via Smiles rearrangement. These prepared phenothiazines act as a base to prepare ribofuranosides by treating them with b‐D ‐ribofuranosyl‐1‐acetate‐2,3,5‐tribenzoate. 10H‐phenothiazines on refluxing with hydrogen peroxide in glacial acetic acid gave 10H‐phenothiazine‐5,5‐dioxides. The synthesized compounds were evaluated for their antioxidative properties through in vitro studies, and they are also screened for their antimicrobial activity. The structure of the synthesized compounds has been established by elemental analysis and spectroscopic data.