Synthesis of Peptide Cysteine Dimedone Using Fmoc-Cys(Dmd)-OH: Glutathione Cysteine Dimedone as a Probe in Investigating the Sulfenic Acid Mediated Oxidation of Glutathione

Dimedone is the most widely used chemical probe for detection of cysteine sulfenic acid in peptides and proteins. The reaction of dimedone with cysteine sulfenic acid results in the formation of unique cysteine dimedone motif containing thioether bridge. Based on the structure of cysteine dimedone residue in polypeptide, a new building block of Fmoc-Cys(Dmd)-OH was developed for solid phase synthesis of peptide cysteine dimedone. Mass spectrometric sequencing of synthetic peptides have confirmed successful incorporation of cysteine dimedone in peptide chain using HBTU/HOBt as a coupling agent. The new method permits synthesis of peptides containing both cysteine thiol and cysteine dimedone in the same sequence which was difficult to achieve by conventional methods. The synthetic peptide of glutathione cysteine dimedone was used as a standard in probing the air-mediated oxidation of thiol to disulfide form of glutathione. The co-elution of standard peptide and reaction mixture of oxidation of glutathione in presence of dimedone using RP-HPLC have confirmed the formation of glutathione cysteine sulfenic as an intermediate in the air-mediated oxidation of glutathione. The synthetic peptides of cysteine dimedone may find application in the field of redox proteomics and generation of antibodies against modified cysteine residue.     

Synthesis and studies on photochromic properties of vanadium doped TiO2 nanoparticles

Pure and (0.5–3 at%) vanadium doped TiO₂ nanoparticles have been synthesized by wet chemical method. The as synthesized materials have been characterized by using XRD, atomic force microscope (AFM), Raman, EPR and UV–vis spectroscopy techniques. From XRD studies, both pure as well as vanadium doped TiO₂ have been found to show pure anatase phase. The value of lattice constant c is smaller in doped TiO₂ as compared to undoped and has been found to decrease with increase in vanadium concentration. AFM studies show formation of spherical particles with particle size ～23 nm in all the samples. Photochromic behavior of these materials has been studied by making their films in alkyd resin. Vanadium doped TiO₂ films show reversible change in color from beige-yellow to brownish violet on exposure to UV light. The mechanism of coloration and bleaching process has been discussed.     

Effect of doping concentration and annealing temperature on luminescence properties of Y2O3:Eu3+ nanophosphor prepared by colloidal precipitation method

Eu³⁺ doped Y₂O₃ nanophosphors have been synthesized using the simple colloidal precipitation method. Doping of Eu³⁺ ions in host yttria lattice has been achieved through slow re-crystallization process under wet-chemical conditions followed by annealing at high temperatures (300–1400 °C). The nanophosphors were characterized by using powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), atomic force microscopy (AFM) and spectrofluorometer techniques. XRD analysis reveals formation of pure cubic phase of Y₂O₃ in samples annealed at 700 °C or above. Further, the XRD data was successfully used to retrieve the crystallite size and size distribution from powder samples using the FW((1/5)/(4/5))M method. Crystallite size (11–50 nm) extracted from XRD has been found to be consistent with AFM measurements. The PL emission spectra of nanophosphors show bright red emission at 612 nm due to hypersensitive electric dipole (ED) ⁵D₀–⁷F₂ transition of Eu³⁺ ions in Y₂O₃ lattice. Further, photoluminescence studies indicate that optimum value of the Eu³⁺ to get best luminescence properties is 12 at%. Surface conjugations of these nanophosphors with water soluble dextran biomolecules have also been performed. Surface conjugated rare earth nanophosphors have great potential for bio-applications.     

Thermally-Induced Phase Transitions in the Uniaxially-Oriented δ Form of Syndiotactic Polystyrene

The empty δ (δ_e) form of uniaxially-oriented syndiotactic polystyrene (sPS) samples were obtained by extracting the solvent molecules from the δ form of sPS and solvent complex in acetone and methanol. Temperature dependence of the X-ray fiber diagrams starting from the uniaxially-oriented δ_e and δ form has been measured successfully at various temperatures for the first time. The transition behavior was traced clearly by separating the equatorial and layer line reflections. The δ_e form transformed to the γ form via an intermediate form. The intermediate form is speculated to take disordered structure due to the empty cavities present in the δ_e form. Calorimetric studies showed an endotherm followed by an exotherm during this phase transition, which is consistant with such a speculation. On the other hand the δ form transformed to the γ form directly without passing through the intermediate form or δ_e form. During the δ to γ phase transition the solvent molecules evaporate through the columnar structure in a broad range of temperature, allowing the transition to occur smoothly.     

Main chain thermotropic liquid crystalline polyurethanes containing biphenyl mesogens based on novel AB‐type self‐polycondensation route: FT‐IR and XRD studies

The detailed mesophasic characterization of main chain liquid crystalline polyurethanes containing biphenyl mesogen, which were synthesized by the novel AB‐type self‐polycondensation approach, was carried out by using Differential Scanning Calorimetry (DSC), Polarized Optical Microscopy (POM), variable temperature X‐ray Diffraction (XRD), and Fourier Transform Infrared (FT‐IR) spectroscopic studies. The type of mesophase present in these polymers was identified to be the smectic A phase by POM and XRD studies. The smectic layer thickness was found to increase as the length of the spacer increased. The effect of temperature on the hydrogen bonding was analyzed by FT‐IR studies. The curve‐fitting analysis of the NH stretching and C?O stretching modes of vibrations indicated a gradual decrease in hydrogen bonding during the transition from the crystalline state to the mesophase. The mesophase to isotropic liquid transition was then accompanied by the complete disappearance of the hydrogen bonding. The biphenyl bands also showed changes during phase transitions due to the coupling of biphenyl vibration modes with the urethane linkage attached to it. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1903–1912, 2005     

Aegirine-augite syenite from gundlapalle,guntur district,andhra pradesh

Aegirine-augite syenite occurs as small hillocks or dome-shaped mounds around Gundlapalle, Satehnapalli Taluk, Guntur District. It is composed of abundant microclineperthite, subordinate oligoclase, aegirine-augite, occasional ferro-actinolite, katophorite, barkevikite and accessories like calcite, chlorite, apatite, zircon, sphene, fluorite, pyrites and iron ore. Aegirine-augite syenite is an alkaline rock, similar to fenite in its mineral assemblage and it has undergone alkali metasomatism to give rise to the soda amphiboles. Evidences are given in support of the above conclusion.     

Peptide Cysteine Thiols Act as Photostabilizer of Avobenzone through Stabilizing the Transition State of Keto-Enol Tautomerization

Photostabilizers have been used to impart stability to an FDA-approved chemical UV-A filter avobenzone against the UV-A radiations and sunlight. The thiol group of glutathione plays a critical role in imparting the photostabilization activity of glutathione on avobenzone. The current report aims to evaluate the photostabilization activity of multiple thiols containing cysteine peptides on avobenzone. Cysteine-tripeptide and cysteine-pentapeptide were chemically synthesized and characterized using mass spectrometry. Synthetic peptides were assessed for their photostabilization activity on the enolic-form of the avobenzone under natural sunlight using UV spectroscopy in both protic and aprotic solvents. Unlike glutathione, which has pronounced activity in protic solvents, cysteine-pentapeptide exhibits similar photoprotection activity in both protic and aprotic solvents. Computational calculations using DFT suggest that peptide cysteine thiols may assist in the reversal of the photoketonization process of avobenzone thereby exhibiting the photoprotection activity to the enolic-form of avobenzone. Peptide cysteine thiols lower the activation energy barrier of keto-to-enol tautomerization of avobenzone by 30 kcal mol⁻¹ by assisting the proton shuttle through a six-membered transition state. The current report emphasizes the applications of peptide thiols in cosmetics and may help in the development of peptides as aesthetic medicines.     

Conformational Analysis of a 20‐Membered Cyclic Peptide Disulfide from Conus virgo with a WPW Segment: Evidence for an Aromatic–Proline Sandwich

A novel peptide containing a single disulfide bond, CIWPWC (Vi804), has been isolated and characterised from the venom of the marine cone snail, Conus virgo. A precursor polypeptide sequence derived from complementary DNA, corresponding to the M‐superfamily conotoxins, has been identified. The identity of the synthetic and natural peptide sequence has been established. A detailed analysis of the conformation in solution is reported for Vi804 and a synthetic analogue, CI^DWPWC (^DW3‐Vi804), in order to establish the structure of the novel WPW motif, which occurs in the context of a 20‐membered macrocyclic disulfide. Vi804 exists exclusively in the cis W3?P4 conformer in water and methanol, whereas ^DW3‐Vi804 occurs exclusively as the trans conformer. NMR spectra revealed a W3?P4 type VI β turn in Vi804 and a type II′ β turn in the analogue peptide, ^DW3‐Vi804. The extremely high‐field chemical shifts of the proline ring protons, together with specific nuclear Overhauser effects, are used to establish a conformation in which the proline ring is sandwiched between the flanking Trp residues, which emphasises a stabilising role for the aromatic–proline interactions, mediated predominantly by dispersion forces.     

Mechanical performance of Buckminster fullerene-reinforced composite with interface defects using finite element method through homogenization techniques

Several times, preferred properties are not accomplished when the fiber-reinforced composites are tested after they are prepared and the similar observations are also observed in the case of nanoparticle-reinforced composites. While the composites are manufactured under controlled conditions with stringent quality measures, it is complex to circumvent fiber-matrix interfacial debonding. The amount of debonding decides the final mechanical properties of composite material. In this study, an effort is made to quantify the debonding effect of nanoparticles on mechanical properties of nanoparticle-filled composites using finite element models with homogenization approach. Buckminster fullerene and conventional fiber T300 are selected as reinforcement medium. The predictions revealed that the longitudinal Young’s modulus is not affected by debonding.