The role of the histidine residue in the coordination abilities of peptides with a multi-histidine sequence towards copper(II) ions

Cu²⁺ complexes with peptides containing three histidine residues have very specific metal binding abilities and can mimic the structures of various multi-histidine metal binding sites in proteins. The main goal of the work concerns the investigations of coordination abilities of the group of N-terminally protected Ac-His-Arg-His-Gly-His-Gly, Ac-His-Gly-His-Arg-His-Gly, Ac-Gly-His-His-Arg-His-Gly and Ac-His-His-Gly-His-Arg-Gly, and their unprotected analogs His-Arg-His-Gly-His-Gly, His-Gly-His-Arg-His-Gly, Gly-His-His-Arg-His-Gly and His-His-Gly-His-Arg-Gly towards Cu²⁺ ions. Detailed spectroscopic (UV/Vis, CD and EPR) and potentiometric studies have been made. The stoichiometry and binding mode for each ligand–Cu²⁺ system were determined.     

Kinetics of the hydrogen abstraction R−OH + H → R•−OH + H2 reaction class: An application of the reaction class transition state theory

This paper presents an application of the reaction class transition state theory (RC‐TST) to predict thermal rate constants for hydrogen abstraction reactions of the type R‐OH + H → R^?‐OH + H₂. We have derived all parameters for the RC‐TST method with linear energy relationships (LERs) and the barrier height grouping (BHG) approach for this reaction class from rate constants of 37 representative reactions divided in two types of hydrogen abstraction, namely from α carbon sites and non‐α carbon sites two training sets. Error analyses indicate that the RC‐TST/LER, where only reaction energy is needed, and RC‐TST/ BHG, where no other information is needed, can predict rate constants for any reaction in this reaction class with satisfactory accuracy for combustion modeling. Specifically for this reaction class, the RC‐TST/LER and RC‐TST/BHG methods have, respectively, less than 40% and 90% systematic errors in the predicted rate constants, when compared to the explicit full TST/Eckart method. The branching ratio analysis shows that in the low‐temperature regime α abstractions are dominant, whereas, for T > 1500 K, abstractions at other sites become more important. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 43: 78–98, 2011     

Peptidomics and proteomics based on CE‐MS as a robust tool in clinical application: The past,the present,and the future

Capillary electrophoresis combined with mass spectrometry (CE‐MS) has been used for several years for the investigation of proteins and peptides as biomarkers for diagnosis and prognosis of diseases. In addition, the technology has recently been introduced to support the stratification of patients in clinical trials and in large clinical studies. In this review, we aim at presenting the development of CE‐MS over the last 20 years, by focusing on the clinical potential of proteome and peptidome analysis and highlighting some of the key technical issues and advancements that have been made in this context towards implementation. Based on the reviewed literature, it has become evident that CE‐MS is now an accepted tool in clinical application in several disease areas. Apart from a critical overview on the current state‐of‐the‐art in CE‐MS, we also indicate the expected developments for potential future use.     

Preparation and characterization of collagen/chitosan poly (ethylene glycol)/nanohydroxyapatite composite scaffolds

Porous three‐dimensional collagen/chitosan scaffolds combined with poly (ethylene glycol) (PEG) and hydroxyapatite were obtained through a freeze‐drying method. Physical cross‐linking was examined by dehydrothermal treatment. The prepared materials were characterized by different analyses, eg, scanning electron microscopy (SEM), measurements of porosity and swelling, mechanical properties, and resistance to enzymatic degradation. The porosity of scaffolds and their swelling ratio decreased with the addition of hydroxyapatite. Moreover, after exposure to collagenase, the collagen/chitosan matrices containing PEG showed much faster degradation rate than matrices with the addition of hydroxyapatite. The results indicated that the addition of hydroxyapatite led to improvement of stiffness. The highest degree of porosity and swelling were demonstrated by collagen/chitosan/PEG matrices without hydroxyapatite.     

In vitro anti-denaturation and anti-hyaluronidase activities of extracts and galactolipids from leaves of Impatiens parviflora DC

The in vitro anti-denaturation and anti-hyaluronidase activities of Impatiens parviflora extracts and isolated galactolipids (MGDG-1, DGDG-1) were investigated. This is the first report on these compounds in I. parviflora. All extracts showed anti-hyaluronidase activity, but only methanolic extract from fresh leaves exhibited significant activity against heat-induced denaturation of BSA in a dose-dependent manner. At 500 μg/mL, the extract and the reference drug showed 79.05% and 99.81% inhibition of protein denaturation, respectively. These results indicate that fresh leaves of I. parviflora may be beneficial in inflammatory conditions, especially those associated with protein denaturation, such as rheumatoid arthritis. The study revealed that only MGDG-1 showed weak activity in anti-denaturation assay but both galactolipids were potent inhibitors of hyaluronidase. MGDG-1 completely inhibited the enzyme activity at the concentration of 127.9 μg/mL. These results indicate the potential of galactolipids in the treatment of diseases associated with the loss of hyaluronic acid.     

Thermodynamic compatibility of actives encapsulated into PEG‐PLA nanoparticles: In Silico predictions and experimental verification

Achieving optimal solubility of active substances in polymeric carriers is of fundamental importance for a number of industrial applications, including targeted drug delivery within the growing field of nanomedicine. However, its experimental optimization using a trial‐and‐error approach is cumbersome and time‐consuming. Here, an approach based on molecular dynamics (MD) simulations and the Flory–Huggins theory is proposed for rapid prediction of thermodynamic compatibility between active species and copolymers comprising hydrophilic and hydrophobic segments. In contrast to similar methods, our approach offers high computational efficiency by employing MD simulations that avoid explicit consideration of the actual copolymer chains. The accuracy of the method is demonstrated for compatibility predictions between pyrene and nile red as model dyes as well as indomethacin as model drug and copolymers containing blocks of poly(ethylene glycol) and poly(lactic acid) in different ratios. The results of the simulations are directly verified by comparison with the observed encapsulation efficiency of nanoparticles prepared by nanoprecipitation. © 2016 Wiley Periodicals, Inc.     

N-triazinylammonium tetrafluoroborates. A new generation of efficient coupling reagents useful for peptide synthesis

A new generation of triazine-based coupling reagents (TBCRs), designed according to the concept of "superactive esters", was obtained by treatment of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium (DMTMM) chloride with lithium or silver tetrafluoroborate. The structure of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium tetrafluoroborate was confirmed by X-ray diffraction. Activation of carboxylic acids by using this reagent proceeds via triazine "superactive ester". The coupling reagent was successfully used for the synthesis of Z-, Boc-, and Fmoc-protected dipeptides derived from natural and unnatural sterically hindered amino acids and for fragment condensation, in 80-100% yield and with high enantiomeric purity. The manual SPPS of the ACP(65-74) peptide fragment (H-Val-Gln-Ala-Ala-Ile-Asp-Tyr-Ile-Asn-Gly-OH) proceeded significantly faster than with TBTU or HATU, as well as the automated SPPS of the same fragment gave a purer product than by using TBTU or PyBOP. The reagent was also demonstrated to be efficient in on-resin head-to-tail cyclization of constrained cyclopeptides, in SPPS synthesis of Aib peptides, and in the synthesis of esters from appropriate acids, alcohols, and phenols. The high efficiency and versatility of this new generation of TBCRs confirm, for the first time, the usefulness of the concept of "superactive esters" in rational design of the structure of coupling reagents.     

Bioactive Properties of a Novel Antibacterial Dye Obtained from Laccase-Mediated Oxidation of 8-Anilino-1-naphthalenesulfonic Acid

Fungal laccase obtained from a Cerrena unicolor strain was used as an effective biocatalyst for the transformation of 8-anilino-1-naphthalenesulfonic acid into a green-coloured antibacterial compound, which can be considered as both an antimicrobial agent and a textile dye, simultaneously. The process of biosynthesis was performed in buffered solutions containing methanol as a co-solvent, allowing better solubilisation of substrate. The transformation process was optimised in terms of the buffer pH value, laccase activity, and concentrations of the substrate and co-solvent. The crude product obtained exhibited low cytotoxicity, antibacterial properties against Staphylococcus aureus and Staphylococcus epidermidis, and antioxidant properties. Moreover, the synthesised green-coloured compound proved non-allergenic and demonstrated a high efficiency of dyeing wool fibres.     

Nanosorbents as Materials for Extraction Processes of Environmental Contaminants and Others

The aim of this work focuses on the application of nanomaterials (NMs) in different sorptive extraction techniques for the analysis of organic contaminants from environmental samples of distinct matrix compositions. Without any doubt, the integration of specific NMs such as carbonaceous nanomaterials, magnetic nanoparticles (MNPs), metal–organic frameworks (MOFs), silica nanoparticles, and ion-imprinted NPs with solid-phase extraction techniques counting d-SPE, solid-phase microextraction (SPME), and stir bar sorptive extraction (SBSE) impact on the improvements in analytical performance. The application of NMs as sorbents in the extraction of organic pollutants in environmental samples allows for providing better sensitivity, repeatability, reproducibility, and reusability.     

New Simple and Robust Method for Determination of Polarity of Deep Eutectic Solvents (DESs) by Means of Contact Angle Measurement

The paper presents a new method for evaluating the polarity and hydrophobicity of deep eutectic solvents (DESs) based on the measurement of the DES contact angle on glass. DESs consisting of benzoic acid derivatives and quaternary ammonium chlorides–tetrabutylammonium chloride (TBAC) and benzyldimethylhexadecylammonium chloride (16-BAC)—in selected molar ratios were chosen for the study. To investigate the DESs polarity, an optical goniometer and an ET(30) solvatochromic scale based on Reichardt’s dye were used. The research demonstrated the high accuracy and precision of the developed procedure. The simplicity of the examination and the availability of basic equipment allow for the implementation of the developed method in routine investigations of DESs.