Cryoprotective activities of FK20, a human genome-derived intrinsically disordered peptide against cryosensitive enzymes without a stereospecific molecular interaction

Background Intrinsically disordered proteins (IDPs) have been shown to exhibit cryoprotective activity toward other cellular enzymes without any obvious conserved sequence motifs. This study investigated relationships between the physical properties of several human genome-derived IDPs and their cryoprotective activities. Methods Cryoprotective activity of three human-genome derived IDPs and their truncated peptides toward lactate dehydrogenase (LDH) and glutathione S-transferase (GST) was examined. After the shortest cryoprotective peptide was defined (named FK20), cryoprotective activity of all-D-enantiomeric isoform of FK20 (FK20-D) as well as a racemic mixture of FK20 and FK20-D was examined. In order to examine the lack of increase of thermal stability of the target enzyme, the CD spectra of GST and LDH in the presence of a racemic mixture of FK20 and FK20-D at varying temperatures were measured and used to estimate Tm. Results Cryoprotective activity of IDPs longer than 20 amino acids was nearly independent of the amino acid length. The shortest IDP-derived 20 amino acid length peptide with sufficient cryoprotective activity was developed from a series of TNFRSF11B fragments (named FK20). FK20, FK20-D, and an equimolar mixture of FK20 and FK20-D also showed similar cryoprotective activity toward LDH and GST. Tm of GST in the presence and absence of an equimolar mixture of FK20 and FK20-D are similar, suggesting that IDPs’ cryoprotection mechanism seems partly from a molecular shielding effect rather than a direct interaction with the target enzymes.

Grand Canonical Monte Carlo Simulations to Determine the Optimal Interlayer Distance of a Graphene Slit-Shaped Pore for Adsorption of Methane, Hydrogen and their Equimolar Mixture

The adsorption—for separation, storage and transportation—of methane, hydrogen and their mixture is important for a sustainable energy consumption in present-day society. Graphene derivatives have proven to be very promising for such an application, yet for a good design a better understanding of the optimal pore size is needed. In this work, grand canonical Monte Carlo simulations, employing Improved Lennard–Jones potentials, are performed to determine the ideal interlayer distance for a slit-shaped graphene pore in a large pressure range. A detailed study of the adsorption behavior of methane, hydrogen and their equimolar mixture in different sizes of graphene pores is obtained through calculation of absolute and excess adsorption isotherms, isosteric heats and the selectivity. Moreover, a molecular picture is provided through z-density profiles at low and high pressure. It is found that an interlayer distance of about twice the van der Waals distance of the adsorbate is recommended to enhance the adsorbing ability. Furthermore, the graphene structures with slit-shaped pores were found to be very capable of adsorbing methane and separating methane from hydrogen in a mixture at reasonable working conditions (300 K and well below 15 atm).

Self-Assembly of an Equimolar Mixture of Liquid Crystals and Magnetic Nanoparticles

We studied the equilibrium self-assembly of an equimolar mixture of uniaxial liquid crystals (LCs) and magnetic nanoparticles (MNPs) using molecular dynamics simulations. The LCs are modeled by ellipsoids interacting via Gay–Berne potential, and MNPs are represented by dipolar soft spheres (DSS). We found that the LCs show isotropic, nematic, and smectic phases when the mixture is compressed at a fixed temperature. The DSS form chain-like structures, which remain randomly oriented at low densities where the LCs are in the isotropic phase. At intermediate and high densities, the DSS chains align along the nematic and smectic directors of LCs. We found that the DSS inside a chain follow a ferromagnetic ordering. However, the mixture does not show a significant macroscopic magnetization. The extent of nematic order in the DSS remains very similar to the LCs in intermediate densities. At high densities, the DSS have a lower extent of nematic order than the LCs. The structure of the LC–DSS mixture was further analyzed via projected pair correlation functions for distances parallel and perpendicular to directors in the nematic and smectic phases.

Synergetic anticancer activity of gold porphyrin appended to phenyl tin malonate organometallic complexes

The covalent attachment of these two anticancer chemotherapeutics makes it more efficient and selective than the equimolar mixture.

Can oppositely charged polyelectrolyte stars form a gel? A simulational study

A Langevin MD study of an equimolar mixture of monodispersed oppositely charged di- block four-armed polyelectrolyte stars is presented. We determine the minimal charged block length which results in gels and we study the ionic bond kinetics.

Influence of the summer feeding by carbohydrates on catalase activity in honey bees

The nutritional composition of rations determines the strength of honey bee families. Feeding with various carbohydrate solutions is widely used in beekeeping. The form of carbohydrate intake in insects can adversely affect their health, leading to redox imbalances. Catalase activity (CAT) is a marker of oxidative stress. It was investigated the catalase activity in foraging bees Apis mellifera during their summer feeding with carbohydrates in the field after grass flowering. The research was perfomed on a private apiary in Chernivtsi region with the local bees (hybrids of Carpathian, Ukrainian steppe and Caucasian breeds). 32 bee colonies, eight experimental groups, were fed various carbohydrates for four days. These are 30 % and 60 % sugar solution, a mixture of honey and 60 % sugar solution (2: 3), without feeding, 30 % glucose and fructose solutions, a mixture of 15 % glucose and fructose solutions (1: 1), a mixture of 30 % fructose solutions glucose (1: 1). Then all bees were fed with 30 % sugar solution. CAT activity was determined in the head, thorax and abdomen of bees by Aebi method with modifications. The highest CAT activity was detected when using 30 % sugar solution for insect feeding. While doubling the sugar concentration and adding honey to the sugar syrup reduced the activity of this enzyme in all bee tagmas. Feeding the colonies with 30 % solutions of glucose or fructose also decreased CAT activity. The cessation of additional feeding decreased the CAT activity in abdomen tissues. It should be noted that the 60 % concentration of sugar, which results equimolar amount of monosaccharides by hydrolysis, differently affects the CAT activity in the tissues of the head and thorax. Decrease of CAT activity is observed on a diet with disaccharide, and this activity does not change on a diet with an equimolar mixture of monosaccharides. At the same time, two fold reducing the sugars concentration (30 % sugar compared to 15 % glucose + 15 % fructose) has the opposite effect – a decrease of enzyme activity in head tissues on an equimolar mixture of monosaccharides and no changes in thorax tissues. Conclusions. It was shown that feeding bee colonies in the period of cessation of the main honey plants flowering with 30 % sugar solution increased the CAT activity in foraging bees. Feeding with 30 % solutions of monosaccharides (glucose, fructose) and 60 % solution of sugar led to decrease of enzyme activity in all studied tagmata (head, thorax, abdomen) of bees. The tagmaspecific responce to various types of a carbohydrate diet in bees was found: in the abdominal tissues of all experimental groups there was a decrease of catalase activity compared to feeding with 30 % sugar solution (preparatory stage), while in the tissues of the thorax and head CAT activity depended on the type of carbohydrate diet. It was demonstrated that the form of carbohydrate intake (disaccharide or equimolar mixture of monosaccharides) affects the CAT activity in the tissues of the head and thorax of insects.