HPLC estimation of iothalamate to measure glomerular filtration rate in humans

Glomerular filtration rate (GFR) is usually determined by estimation of iothalamate (IOT) clearance. We have developed and validated an accurate and robust method for the analysis of IOT in human plasma and urine. The mobile phase consisted of methanol and 50 mM sodium phosphate (10:90; v/v). Flow rate was 1.2 mL/min on a C18 reverse phase column, Synergi-hydro (250 × 4.6 mm) 4 µm 80 Å, with an ultraviolet detector set to 254 nm. Acetonitrile was used for the deproteination and extraction of IOT from human plasma and urine. Precision and accuracy were within 15% for IOT in both plasma and urine. The recoveries of IOT in urine and plasma ranged between 93.14% and 114.74 and 96.04–118.38%, respectively. The linear range for urine and plasma assays were 25–1500 and 1–150 µg/mL respectively. The lower limits of detection were 0.5 µg/mL for both urine and plasma, with no interference from plasma and urine matices. This method has been fully validated according to FDA guidelines and the new HPLC assay has been applied to a new formulation of IOT (Conray? 43), to calculate GFR in healthy volunteers. The new method is simple, less expensive and it would be instrumental in future clinical and pharmacokinetic studies of iothalamate in kidney patients.     

Stability criteria for stochastic Takagi‐Sugeno fuzzy Cohen‐Grossberg BAM neural networks with mixed time‐varying delays

This article is concerned with the asymptotic stability analysis of Takagi–Sugeno stochastic fuzzy Cohen–Grossberg neural networks with discrete and distributed time‐varying delays. Based on the Lyapunov functional and linear matrix inequality (LMI) technique, sufficient conditions are derived to ensure the global convergence of the equilibrium point. The proposed conditions can be checked easily by LMI Control Toolbox in Matlab. It has been shown that the results are less restrictive than previously known criteria. They are obtained under mild conditions, assuming neither differentiability nor strict monotonicity for activation function. Numerical examples are given to demonstrate the effectiveness of our results. © 2014 Wiley Periodicals, Inc. Complexity 21: 143–154, 2016     

New fixed point theorems for $${\alpha}$$-$${H\Theta}$$HΘ-contractions in ordered metric spaces

Recently, Jleli and Samet [J. Inequal. Appl. (2014), 2014:38] introduced and studied a new contraction to prove a generalization of the Banach contraction principle. In this paper, we introduce the concept of \({\alpha}\)-\({H\Theta}\)-contraction with respect to a general family of functions H and we establish Jleli–Samet-type fixed point results in metric and ordered metric spaces. As an application of our results we deduce Suzuki-type fixed point results for \({H\Theta}\)-contractions. We also derive certain fixed and periodic point results for orbitally continuous generalized \({\Theta}\)-contractions. Moreover, we present an illustrative example to highlight the obtained improvements.     

Doubly Strapped Zwitterionic NIR-I and NIR-II Heptamethine Cyanine Dyes for Bioconjugation and Fluorescence Imaging

Heptamethine cyanine dyes enable deep tissue fluorescence imaging in the near infrared (NIR) window. Small molecule conjugates of the benchmark dye ZW800-1 have been tested in humans. However, long-term imaging protocols using ZW800-1 conjugates are limited by their instability, primarily because the chemically labile C4′-O-aryl linker is susceptible to cleavage by biological nucleophiles. Here, we report a modular synthetic method that produces novel doubly strapped zwitterionic heptamethine cyanine dyes, including a structural analogue of ZW800-1 , with greatly enhanced dye stability. NIR-I and NIR-II versions of these doubly strapped dyes can be conjugated to proteins, including monoclonal antibodies, without causing undesired fluorophore degradation or dye stacking on the protein surface. The fluorescent antibody conjugates show excellent tumor-targeting specificity in a xenograft mouse tumor model. The enhanced stability provided by doubly strapped molecular design will enable new classes of in vivo NIR fluorescence imaging experiments with possible translation to humans.     

Biochemical properties of Cu/Zn-superoxide dismutase from fungal strain Aspergillus niger 26

The fungal strain Aspergillus niger produces two superoxide dismutases, Cu/Zn-SOD and Mn-SOD. The primary structure of the Cu/Zn-SOD has been determined by Edman degradation of peptide fragments derived from proteolytic digests. A single chain of the protein, consisting of 153 amino acid residues, reveals a very high degree of structural homology with the amino acid sequences of other Aspergillus Cu/Zn-SODs. The molecular mass of ANSOD, measured by MALDI-MS and ESI-MS, and calculated by its amino acid sequence, was determined to be 15821 Da. Only one Trp residue, at position 32, and one disulfide bridge were identified. However, neither a Tyr residue nor a carbohydrate chain occupying an N-linkage site (-Asn-Ile-Thr-) were found. Studies on the temperature and pH dependence of fluorescence, and on the temperature dependence of CD spectroscopic properties, confirmed that the enzyme is very stable, which can be explained by the stabilising effect of the disulfide bridge. The enzyme retains about 53% of its activity after incubation for a period of 30 min at 60 degrees C, and 15% at 85 degrees C.     

Preparation and characterization of an anionic dye-polycation molecular films by electrostatic layer-by-layer adsorption process

This communication reports the formation and characterization of self-assembled films of a low molecular weight anionic dye amaranth and polycation poly(allylamine hydrochloride) (PAH) by electrostatic alternating layer-by-layer (LBL) adsorption. It was observed that there was almost no material loss occurred during adsorption process. The UV-vis absorption and fluorescence spectra of amaranth solution reveal that with the increase in amaranth concentration in solution, the aggregated species starts to dominate over the monomeric species. New aggregated band at 600 nm was observed in amaranth-PAH mixture solution absorption spectrum. A new broad low intense band at the longer wavelength region, in the amaranth-PAH mixture solution fluorescence spectrum was observed due to the closer association of amaranth molecule while tagged into the polymer backbone of PAH and consequent formation of aggregates. The broad band system in the 650-750 nm region in the fluorescence spectra of different layered LBL films changes in intensity distribution among various bands within itself, with changing layer number and at 10 bilayer LBL films the longer wavelength band at 710 nm becomes prominent. Existence of dimeric or higher order n-meric species in the LBL films was confirmed by excitation spectroscopic studies. Almost 45 min was required to complete the interaction between amaranth and PAH molecules in the one-bilayer LBL film.     

The chemoselective and efficient deprotection of silyl ethers using trimethylsilyl bromide

An efficient and chemoselective cleavage of silyl ethers (primary, secondary and aromatic) by using catalytic quantities of trimethylsilyl bromide (TMSBr) in methanol is reported. A wide range of alkyl silyl ethers such as TBS, TIPS, and TBDPS can be chemoselectively cleaved in high yield in the presence of aryl silyl ethers. The deprotection of silyl esters was also achieved employing catalytic quantities of TMSBr.     

Interaction of metallic nanoparticles with a biologically active molecule, dopamine

We present the results of first-principles molecular orbital calculations describing the interaction of metallic nanoparticles, represented by Mn(13), Ag(13), and Al(13) atomic clusters, with a biologically active molecule, dopamine. The interaction strength, determined in terms of the nanoparticle-molecule complex binding energy, is found to be higher for Mn than either Ag or Al and can be explained in terms of the degree of the hybridization of the (metal) atomic orbitals with the molecular orbitals in the complex. Furthermore, smaller interaction strength of these metallic nanoparticles with water compared to that with dopamine predicts the preference of forming a complex of dopamine with the metallic nanoparticles in the aqueous solution. The calculated results may therefore suggest that the presence of these metallic nanoparticles could induce different levels of dopamine depletion in solution.     

Self-assembly of brush-like poly[poly(ethylene glycol) methyl ether methacrylate] synthesized via aqueous atom transfer radical polymerization

Self-assembly of brush-like well-defined poly[poly(ethylene glycol) methyl ether methacrylate] homopolymers, abbreviated as P(PEGMA-475) and P(PEGMA-1100) is investigated in aqueous solution by employing dynamic/static light scattering (DLS/SLS) and transmission electron microscopy (TEM), whereas 475 and 1100 is molar mass of the respective PEGMA macromonomer. The mentioned brush-like homopolymers are synthesized by aqueous ATRP at room temperature. The critical association concentration (CAC) of the synthesized polymers in water depends on the length of the PEG side chains but not on the overall molar mass of the polymer. Thus, approximately the same CAC of approximately 0.35 mg/mL is estimated for various P(PEGMA-1100) samples, and approximately 0.7 mg/mL is estimated for P(PEGMA-475) series. All the investigated P(PEGMA-1100) samples form multimolecular micelles in aqueous solution, where the hydrodynamic size (Rh) and the aggregation number (Nagg) of micelles decreases as the molecular weight of P(PEGMA-1100) increases. This can be attributed to the increased steric hindrances between the PEG side chains in corona of micelles formed by higher molar mass P(PEGMA-1100). The tendency of micelle formation by samples of P(PEGMA-475) series is significantly lower than that of P(PEGMA-1100) series, as demonstrated by their significantly higher CAC and micelles of lower Nagg. The Rh of micelles does not depend strongly on polymer concentration, which suggests that these micelles are formed via the closed association model. Micelles formed by P(PEGMA-1100) series slightly shrink with increase in temperature from 25 to 60 degrees C, while those of P(PEGMA-475) series are found to be insensitive to the same temperature variation. Finally, TEM is carried out to visualize the formed micelles after transferring the aqueous solution to carbon film.