Strategies for positioning fluorescent probes and crosslinkers on formyl peptide ligands

Chemoattractant receptors represent a major subset of the G-protein coupled receptor (GPCR) family. One of the best characterized, the N-formyl peptide receptor (FPR), participates in host defense responses of neutrophils. The features of the ligand which regulate its interaction with the FPR are well-known. By manipulating these features we have developed new ligands to probe structural and mechanistic aspects of the peptide-receptor interaction. Three ligand groups have been developed: 1) ligands containing a Lys residue located in positions 2 through 7 that can be conjugated to FITC (N-formyl-Met1-Lys2-Phe3-Phe4, N-formyl-Met1-Leu2-Lys3-Phe4, N-formyl-Met1-Leu2-Phe3-Lys4, N-formyl-Met1-Leu2-Phe3-Phe4-Lys5, N-formyl-nLeu1-Leu2-Phe3-nLeu4-Tyr5-Lys6 and N-formyl-Met1-Leu2-Phe3-Phe4-Gly5-Gly6-Lys7; 2) fluorescent pentapeptide ligands (N-formyl-Met-X-Phe-Phe-Lys(FITC) where X = Leu, Ala, Val or Gly); and 3) small crosslinking ligands where the photoaffinity crosslinker 4-azidosalicylic acid (ASA) was conjugated to Lys in positions 3 and 4 and p-benzoyl-phenylalanine (Bpa) was located in position 2 in N-formyl-Met1-Bpa2-Phe3-Tyr4. The peptides were characterized according to activity and affinity in human neutrophils and cell lines transfected with FPR. All of the peptides were agonists, with parallel affinity and activity. In the first group, the peptide activity decreases as Lys is placed closer to the N-formyl group and the activity is improved by 1-3 orders of magnitude by conjugation with FITC. In the second group, the dissociation rate of the peptide from the receptor increases as position 2 is replaced by aliphatic amino acids with smaller alkyl groups. In the third group, crosslinking ligands remain biologically active, display nM affinity and covalently label the FPR.     

Growth and characterization of some I–III–VI2 compound semiconductors

Single crystals of CulnS₂, CulnSe₂, CulnTe₂, CuGaS₂, AgGaS₂ CulnSSe, AgGaSSe have been grown by chemical vapour transport technique on the basis of a new general thermodynamical model which enables the minimum source temperature T _s, and the minimum deposition temperature, T _d, to be determined. X-ray analysis, X-ray photoelectron spectroscopic analysis, surface analysis, and microhardness studies have been carried out on the single crystals grown.     

Synthesis and characterization of heterocyclic core-based polybenzoxazine matrices

In the present work, four types of heterocyclic core-based polybenzoxazine matrices (HC-PBZ) developed based on pyridine, thiophene, and thiazole and their molecular structure, thermal, flame-retardant and luminescent properties were studied and discussed. The heterocyclic core-based benzoxazine monomers (HC-BZ) were synthesized using two types of phenols (phenol, and 4-hydroxyphenylacetonitrile), and two types of heterocyclic diamines [2,6-Bis-(4-aminophenyl)-4-thiophen-2-yl-pyridine (BATP) and 4-(2-methylthiazol-5-yl)-2,6-bis-(4-aminophenyl)-pyridine (BAMTP)] with formaldehyde through Mannich reaction. The structure of the four HC-BZ monomers was confirmed by various spectral analysis such as Fourier-transform infrared spectroscopy (FTIR), and Nuclear magnetic resonance spectroscopy (¹HNMR and ¹³CNMR). All the four HC-BZ monomers have the maximum range of curing temperature (T _p) between 252 and 267 °C. Data resulted from the thermal studies indicate that the HC-PBZ exhibits better T _g, thermal stability and flame-retardant properties. Among the four HC-PBZ systems the thiazole based system possesses the higher value of T _g of 268 °C and thermal stability when compared to those of other matrices. It was also observed that the HC-BZ monomers and HC-PBZ polymers exhibit a photoluminescent (PL) emission range between 441–445 and 414–417 nm, respectively. Overall, it seems that the thiazole and thiophene based HC-PBZ can be considered as competitive materials for luminescent applications with high thermal and flame-retardant properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47134.     

Facial Recognition System for Suspect Identification Using a Surveillance Camera

Nowadays, finding and Tracking a person in the world of technology is becoming a necessary task for various security purposes. Since the advent of technology, the development in the field of Facial Recognition plays an important role and has been exponentially increasing in today’s world. In this, a model is proposed for facial recognition to identify and alert the system when a person in search has been found at a specific location under the surveillance of a CCTV camera. The CCTV cameras are connected to a centralized server to which the live streaming feed is uploaded by cameras at each location. The server contains a database of all persons to be found. Based on the video feed from each camera, if a particular person in search is found in a certain feed, then the location of that person will be tracked and also a signal is passed to the system responsible. This model is based on image processing concepts to match live images with the existing trained images of the person in search. Since this model recognizes a person based on the first and foremost primary unique feature of a human, that is, only the person’s face image is required and will be found to be stored in the database. Hence the task of finding a person reduces to the task of detecting human faces in the video feed and matching with the existing images from the database.     

Development of non-precious oxygen reduction reaction catalyst for polymer electrolyte membrane fuel cells based on substituted cobalt porphyrins

Active and stable cobalt-based non-precious metal catalysts for the oxygen reduction reaction (ORR) in PEM fuel cells were developed through high-temperature pyrolysis of metal-porphyrins supported on carbon. The roles of substituted porphyrins, carbon support, and catalyst loading on ORR activity were studied using rotating disc electrode (RDE) measurements. It was observed that the carbon support plays a major role in improving the catalytic activity. The results showed that among the supported catalysts, the homemade mesocarbon-supported cobalt-porphyrin catalyst with 20 wt% loading displayed higher ORR activity; the cell performance showed maximum current density of 1.1 A cm⁻² at 0.13 V in H₂/O₂ fuel cells.     

High temperature operation of PEMFC: A novel approach using MEA with silica in catalyst layer

Composite membranes with inorganic substances can retain water and allow the operation of polymer electrolyte membrane fuel cells (PEMFCs) at high temperature under low humidity. In this work, the single cell was operated at high temperature using silica–Nafion composite membrane in addition with silica in catalyst layer. The cell was operated at various temperatures under different relative humidity conditions. We observed that the single cell performance decreased steeply as the cell temperature increased. The role of silica in the catalyst layer at high temperature operation was studied by varying the silica content in the catalyst layers. There was a gradual decrease in cell performance when the silica content increased in catalyst layer. The single cell performance of membrane electrode assemblies (MEAs) with composite membrane and electrode was higher than that of MEA with commercial Nafion 112 membrane for high temperature operation.     

Two-dimensional mullite nanostructure: Synthesis and reinforcement effect on polypropylene/maleic anhydride graft ethylene vinyl acetate matrix

In the present work, we studied the reinforcement effect of mullite nanosheets (MNs) on the properties of polypropylene (PP)/maleic anhydride graft ethylene-vinyl acetate (EVA-g-MA) blend matrix. MNs have been prepared in the presence of polyvinylpyrrolidone (PVP) as the macromolecular surfactant through the sol–gel process followed by a thermal annealing method. The sheet-like morphology of mullite was confirmed by transmission electron microscopy analysis. The surface of the MNs was modified using 3-aminopropyltriethoxysilane. One weight percent of amine-functionalized MNs (AMNs) improved the impact strength of PP/EVA-g-MA blend matrix, which is about 52%. Melt rheology analysis resulted that the nanocomposite exhibited a viscous behavior up to 2.5 wt % of AMNs and above the content ensued a viscoelastic solid-like behavior. X-ray diffraction analysis showed a complete dispersion of AMNs in the PP/EVA-g-MA blend matrix. TEM analysis confirmed that the MNs sheets are residing mostly in EVA-g-MA phase and the interface of PP/EVA-g-MA blend. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48233.