New strategy to improve acrylic/casein compatibilization in waterborne hybrid nanoparticles

The grafting of casein to acrylic polymers is needed to fully exploit the possibilities of hybrid nanoparticles containing such materials. The explored alternative up to now, based on the primary radical formation onto the protein chains through the redox initiation between the casein amino groups and a hydroperoxide, produces a limited degree of compatibilization to guarantee the synergic effect between both components. A novel strategy that overcomes these limitations is presented. The strategy is based on the use of a crosslinkable casein, which in addition to the characteristic grafting capacity by redox initiation with hydroperoxides, contains acrylic groups able to radically polymerize. The degree of grafting of both acrylic and casein is significantly increased by functionalizing casein with varied amounts of pendant propagating points per protein. Moreover, it is observed that the improved degree of compatibility obtained when using the crosslinkable casein considerably enhanced the properties of the acrylic/casein films, such as their mechanical behavior and resistance to both water and organic solvent. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42421.     

Removal of proteins from natural rubber with urea and its application to continuous processes

The removal of proteins from natural rubber through a batch process was studied by the incubation of the rubber latex with urea in the presence of sodium dodecyl sulfate. Under suitable conditions, the total nitrogen content of deproteinized natural rubber (DPNR) decreased from 0.38 to 0.02 wt % after incubation for 10 min; this was similar to that of the rubber deproteinized with a proteolytic enzyme for 12 h. For applications, continuous incubation and centrifugation were individually investigated by the use of a semicircular channel and a continuous centrifuge, respectively, to scale up DPNR preparation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Behavioral responses to chemical cues by bacteria

Bacterial chemotaxis presents a model sensory system in which cells modulate the direction of rotation of their flagella in response to gradients of certain chemicals. The chemotactic machinery ofEscherichia coli is currently being systematically reduced to its individual components through the accomplishments of behavioral, physical, genetic, molecular genetic, and biochemical analyses. Thirteen of the so called MCP-related class of chemotaxis gene products are known. Transmembrane methyl-accepting chemotaxis proteins (MCPs) are important for the chemical sensing, signal generation, and sensory adaptation processes. Soluble chemotaxis proteins relay information from these MCPs to structural components of the flagella referred to as switch proteins. Emphasis here is on the separate roles each of these groups of chemotaxis proteins perform, as well as their protein-protein relationships.     

Thermal behavior of fat droplets as related to adsorbed milk proteins in complex food emulsions. A DSC study

The thermal behavior of hydrogenated palm kernel oil-in-water emulsions, which differed in their milk-protein composition, was studied in parallel with other characteristic parameters such as the aggregation/coalescence of fat droplets, and the proportion of adsorbed proteins at the oil/water interface. DSC was applied to monitor the crystallization and melting behavior of nonemulsified and emulsified fat samples. Comparison between nonemulsified and emulsified fat samples showed that in emulsified samples the initial temperature of fat crystallization and the temperature of the completion of melting were invariably lower and slightly higher, respectively. Furthermore, in complex food emulsions the supercooling temperature needed to initiate fat crystallization and the variation in its growth rate in the cooling experiment were dependent on the amount and nature of the adsorbed proteins. Our results indicate that the total replacement of milk proteins by whey proteins affected the fat crystallization behavior of emulsified fat droplets, in parallel with changes in their protein surface coverage and in their physical stability against fat droplet agglomeration.     

Representation of the Protein Universe using Classifications,Maps, and Networks

A meaningful and coherent global picture of the protein universe is needed to better understand protein evolution and the underlying biophysics. We survey the studies that tackled this fundamental challenge, providing a glimpse of the protein space. A global picture represents all known local relationships among proteins, and needs to do so in a comprehensive and accurate manner. Three types of global representations can be used: classifications, maps, and networks. In these, the local relationships are derived, based on the similarity of the proteins′ sequences, structures, or functions (or a combination of these). Alternatively, the local relationships can be co-occurrences of elements in the protein universe. The representations can be based on different objects: full polypeptide chains, fragments, such as structural domains, or even smaller motifs. Different protein qualities were revealed in each study; many point out the uniqueness of domains of the alpha/beta SCOP (structural classification of proteins) class.     

Modification of wheat gluten with citric acid to produce superabsorbent materials

Wheat gluten was reacted with citric acid to produce natural superabsorbent materials able to absorb up to 78 times its weight in water. The properties of the modified gluten samples were characterized using Fourier Transform Infra‐red (FTIR) spectroscopy, thermogravimetric analysis, and water uptake. The reaction between gluten and citric acid was examined for gluten : citric acid ratios of 0.38 : 1 to 0.75 : 1 at temperatures from 100 to 130°C. More citric acid reacted for samples containing higher citric acid concentrations and at higher temperatures. FTIR analyses indicated the presence of carboxylate groups on the modified gluten samples, which resulted in modified samples having higher water uptake values than neat gluten. The sample with a gluten:citric acid ratio of 0.5 : 1 and reaction temperature of 120°C had the largest water uptake value. Also, all modified gluten samples had lower thermal stability than neat gluten. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Recent molecular advances on downstream plant responses to abiotic stress

Abiotic stresses such as extremes of temperature and pH, high salinity and drought, comprise some of the major factors causing extensive losses to crop production worldwide. Understanding how plants respond and adapt at cellular and molecular levels to continuous environmental changes is a pre-requisite for the generation of resistant or tolerant plants to abiotic stresses. In this review we aimed to present the recent advances on mechanisms of downstream plant responses to abiotic stresses and the use of stress-related genes in the development of genetically engineered crops.     

Renal Handling of Albumin—From Early Findings to Current Concepts

Albumin is the main protein of blood plasma, lymph, cerebrospinal and interstitial fluid. The protein participates in a variety of important biological functions, such as maintenance of proper colloidal osmotic pressure, transport of important metabolites and antioxidant action. Synthesis of albumin takes place mainly in the liver, and its catabolism occurs mostly in vascular endothelium of muscle, skin and liver, as well as in the kidney tubular epithelium. Long-lasting investigation in this area has delineated the principal route of its catabolism involving glomerular filtration, tubular endocytic uptake via the multiligand scavenger receptor tandem—megalin and cubilin-amnionless complex, as well as lysosomal degradation to amino acids. However, the research of the last few decades indicates that also additional mechanisms may operate in this process to some extent. Direct uptake of albumin in glomerular podocytes via receptor for crystallizable region of immunoglobulins (neonatal FC receptor) was demonstrated. Additionally, luminal recycling of short peptides into the bloodstream and/or back into tubular lumen or transcytosis of whole molecules was suggested. The article discusses the molecular aspects of these processes and presents the major findings and controversies arising in the light of the research concerning the last decade. Their better characterization is essential for further research into pathophysiology of proteinuric renal failure and development of effective therapeutic strategies.     

Utilization of dairy beta stream to produce phospholipids products by salt precipitation and solvent fractionation

Dairy phospholipids (PLs) have unique functional and nutraceutical properties over PLs obtained from other sources that typically lack phosphatidylserine (PS) and sphingomyelin (SM). In this study, an underutilized dairy by-product, beta stream, was used for the production of enriched dairy PLs products and membrane proteins by solvent extractions. After calcium salt precipitation of the membrane components, various green (i.e., safer or bioderived) solvent systems were evaluated for their capabilities for PLs extraction from the PLs-protein-salt precipitate in comparison to the standard Folch extraction (chloroform: methanol, 2:1, v/v). Among the five solvent systems (Folch alternatives) evaluated, the combination of hexane and isopropanol (H:IP, 3:2, v/v) was identified as the best for total lipid and PLs extraction, resulting in a recovery of 74.4% and 65.7% (w/w), respectively. EDTA chelating of the calcium ions was applied to produce a salt-free membrane protein product. A treatment with 0.2% EDTA was able to significantly reduce the calcium content to 0.20 mg/g protein compared to 58.81 mg/g in the initial calcium-precipitated MFGM. EDTA chelating of cations also facilitated the extraction of lipids during H:IP (3:2) treatment, which increased the total recovery of total lipid and PLs to 90.7% and 82.5% (w/w), respectively. Overall, this study demonstrates a great potential for the utilization of beta stream and other low-solids content aqueous dairy by-products for PLs recovery and further fractionation. Value-added dairy products (PLs and membrane proteins) can be obtained using green solvents identified in this study, and the process is industrially scalable.     

Rapid Estimation of Membrane Protein Orientation in Liposomes

The topological organization of proteins embedded in biological membranes is crucial for the tight interplay between these enzymes and their accessibility to substrates in order to fulfil enzymatic activity. The orientation of a membrane protein reconstituted in artificial membranes depends on many parameters and is hardly predictable. Here, we present a convenient approach to assess this important property independent of the enzymatic activity of the reconstituted protein. Based on cysteine-specific chemical modification of a target membrane protein with a cyanine fluorophore and a corresponding membrane-impermeable fluorescence quencher, the novel strategy allows rapid evaluation of the distribution of the two orientations after reconstitution. The assay has been tested for the respiratory complexes bo₃ oxidase and ATP synthase of Escherichia coli and the results agree well with other orientation determination approaches. Given the simple procedure, the proposed method is a powerful tool for optimization of reconstitution conditions or quantitative orientation information prior to functional measurements.     

Proteins of Unknown Function in the Protein Data Bank (PDB): An Inventory of True Uncharacterized Proteins and Computational Tools for Their Analysis

Proteins of uncharacterized functions form a large part of many of the currently available biological databases and this situation exists even in the Protein Data Bank (PDB). Our analysis of recent PDB data revealed that only 42.53% of PDB entries (1084 coordinate files) that were categorized under “unknown function” are true examples of proteins of unknown function at this point in time. The remainder 1465 entries also annotated as such appear to be able to have their annotations re-assessed, based on the availability of direct functional characterization experiments for the protein itself, or for homologous sequences or structures thus enabling computational function inference.     

Effect of electrostatic functional monomers on lysozyme recognition by molecularly imprinted hydrogel

Electrostatic functional monomers (EFMs) play an important role in noncovalent molecular imprinting due to their formed complexes with the complementary segment(s) of the template molecule. In this work using UV difference spectroscopy, interaction saturations of methacrylic‐acid and 2‐dimethyl‐amino‐ethyl‐methacrylate in complex formation with lysozyme (Lyz) surface was found to occur at molar ratios to Lyz of 400 and 100, respectively. Based on these results and the estimated free to total EFMs ratios, four sets of imprinted/nonimprinted hydrogel samples were synthesized alongside the two sets based on lysozyme surface charges and equal EFMs. Comparisons showed that the highest absorption capacity of 59 mg/g and imprinting effect of 1.58 correspond to samples with EFM/Lyz ratios at saturation and minimum free to total EFM/Lyz ratios, respectively. Minimization of free monomers is hence important in recognition of proteins by avoiding the nonspecific binding. This can have generic application for specific separation of other macromolecules. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41366.     

Application of silk sericin to polyester fabric

Sericin powder was prepared from a boiled solution of silk cocoons through salting-out with ammonium sulfate. The obtained sericin powder was characterized with Fourier transform infrared (FTIR), X-ray, ultraviolet (UV) absorption, and nitrogen content measurements. The aqueous sericin solution was applied onto the polyester fabric (pretreated with NaOH) along with glutaraldehyde as a crosslinking agent with a pad–dry–cure method. The processing conditions of the crosslinking agent were optimized. The presence of sericin was confirmed by the estimation of the nitrogen content and amino groups on the treated fabric. The dyeability of the treated fabric with acid and reactive dyes was studied. The performance properties, such as the moisture content, UV absorption, antistatic, crease recovery, and bending length, of the treated fabric were tested. The FTIR, X-ray, UV absorption, and nitrogen content results confirmed the purity of the sericin powder obtained with the salting-out method. The amino acid content, nitrogen content, and Kubelka Monk function (K/S) values of the sericin-treated fabric increased with an increase in the concentration of sericin in the padding liquor. The K/S value of the dyed samples was found to be linearly correlated with the number of amino groups present on the samples. There was a noticeable improvement in the moisture content and antistatic and UV absorption properties of the sericin-treated fabrics. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

DNA Demethylation in Response to Heat Stress in Arabidopsis thaliana

Environmental stress is one of the most important factors affecting plant growth and development. Recent studies have shown that epigenetic mechanisms, such as DNA methylation, play a key role in adapting plants to stress conditions. Here, we analyzed the dynamics of changes in the level of DNA methylation in Arabidopsis thaliana (L.) Heynh. (Brassicaceae) under the influence of heat stress. For this purpose, whole-genome sequencing of sodium bisulfite-treated DNA was performed. The analysis was performed at seven time points, taking into account the control conditions, heat stress, and recovery to control conditions after the stress treatment was discontinued. In our study we observed decrease in the level of DNA methylation under the influence of heat stress, especially after returning to control conditions. Analysis of the gene ontology enrichment and regulatory pathways showed that genes characterized by differential DNA methylation are mainly associated with stress response, including heat stress. These are the genes encoding heat shock proteins and genes associated with translation regulation. A decrease in the level of DNA methylation in such specific sites suggests that under the influence of heat stress we observe active demethylation phenomenon rather than passive demethylation, which is not locus specific.     

A Copper Story: From Protein Folding and Metal Transport to Cancer

Enzymes need to fold into unique three-dimensional structures in order to function. Copper ions are cofactors in many essential enzymes. Such enzymes need to couple polypeptide folding with metal incorporation, as the metal sites are often integrated within the folded structure. Since free copper ions are toxic, most organisms have highly specialized copper transport systems. The human cytoplasmic copper chaperone Atox1 delivers copper to P_1B-type ATPases in the Golgi, for incorporation into copper-dependent enzymes following the secretory path. Copper plays key roles in cancer development, as copper-dependent enzymes are needed for tumor growth and metastasis. In addition, platinum-based drugs are exported out of cells by the copper transport machinery. Recent findings also imply that some copper transport proteins regulate cell growth and development. In this brief journey of my later career, I will discuss the roles of copper in protein folding, mechanisms of copper ion transport, and cisplatin hitchhiking. The identification of new partners for Atox1 underscore the importance of further research in this area for combating cancer.