Deglycosylation of ovalbumin prohibits formation of a heat-stable conformer

Novel Ti4+-Chelated Polyoxometalate/Polydopamine Composite Microspheres for Highly Selective Isolation and Enrichment of Phosphoproteins

Selective isolation and enrichment of phosphoproteins play critical roles for identification of biomarkers in biological applications. Herein, a kind of polyoxometalate (P₅W₃₀)/polydopamine (PDA) composite microspheres is readily synthesized via an in situ polymerization way, followed by immobilization of Ti⁴⁺ on the surface of the microspheres to obtain P₅W₃₀/PDA-Ti⁴⁺. Due to metal affinity and π stacking interaction, this novel material exhibits high selectivity to β-casein (β-ca), and the theoretical maximum adsorption capacity is as high as 1250 mg g^-1, fitting well with the Langmuir model. The captured β-ca can be collected by using Britton-Robinson (B-R) buffer at pH 7.0, and a recovery of 81.5% is acquired. The enrichment factor is over 150 at a mass ratio of BSA/β-ca = 100:1, indicating that phosphoproteins can be purified by P₅W₃₀/PDA-Ti⁴⁺. Moreover, the application of P₅W₃₀/PDA-Ti⁴⁺ as sorbent in real biological samples has been investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, and the consequences show that this kind of material is able to selectively isolate phosphoproteins from complex samples such as drinking milk and chicken egg white.

Immobilization of a Ce(IV)-substituted polyoxometalate on ethylenediamine-functionalized graphene oxide for selective extraction of phosphoproteins

A sorbent for selective extraction of phosphoproteins was obtained by immobilization of a Ce(IV)-substituted polyoxometalate on ethylenediamine-functionalized graphene oxide (CeEGO). The resulting composites exhibit an adsorption capacity of 981 mg g^-1 for β-casein due to the synergistic effect of metal-affinity interaction between Ce(IV) and phosphate groups and π-stacking interaction between the polyoxometalate framework and the phosphate groups. The results of LC-MS and SDS-PAGE analysis show that the CeEGO composites can be applied to the extraction of phosphoproteins from protein mixture, and as little as 50 μg mL^-1 of the phosphoprotein β-casein can be detected by SDS-PAGE. It was also applied to the extraction of β-casein from spiked biological samples such as drinking milk, whole blood and swine heart tissue extract. Graphical abstract An efficient sorbent is obtained by immobilization of a Ce(IV)-substituted polyoxometalate on ethylenediamine-functionalized graphene oxide (CeEGO). The resulting composites exhibit highly selective capture capacity towards phosphoproteins due to the synergistic effect of metal-affinity interaction between Ce(IV) and phosphate groups and π-stacking interaction between the polyoxometalate framework and the phosphate groups.

Heterologous expression of the antimyotoxic protein DM64 in Pichia pastoris

Snakebite envenomation is a neglected condition that constitutes a public health problem in tropical and subtropical countries, including Brazil. Interestingly, some animals are resistant to snake envenomation due to the presence of inhibitory glycoproteins in their serum that target toxic venom components. DM64 is an acidic glycoprotein isolated from Didelphis aurita (opossum) serum that has been characterized as an inhibitor of the myotoxicity induced by bothropic toxins bearing phospholipase A₂ (PLA₂) structures. This antitoxic protein can serve as an excellent starting template for the design of novel therapeutics against snakebite envenomation, particularly venom-induced local tissue damage. Therefore, the aim of this work was to produce a recombinant DM64 (rDM64) in the methylotrophic yeast Pichia pastoris and to compare its biological properties with those of native DM64. Yeast fermentation in the presence of Pefabloc, a serine protease inhibitor, stimulated cell growth (~1.5-fold), increased the rDM64 production yield approximately 10-fold and significantly reduced the susceptibility of rDM64 to proteolytic degradation. P. pastoris fermentation products were identified by mass spectrometry and Western blotting. The heterologous protein was efficiently purified from the culture medium by affinity chromatography (with immobilized PLA₂ myotoxin) and/or an ion exchange column. Although both native and recombinant DM64 exhibit different glycosylation patterns, they show very similar electrophoretic mobilities after PNGase F treatment. rDM64 formed a noncovalent complex with myotoxin II (Lys49-PLA₂) from Bothrops asper and displayed biological activity that was similar to that of native DM64, inhibiting the cytotoxicity of myotoxin II by 92% at a 1:1 molar ratio.

Snakebite envenomation causes medical emergencies that, depending on the species responsible for the bite, involve different organs and tissues. Envenomation by snakebite is a worldwide problem, and Brazil presents a high incidence of Bothrops bites. Bothrops venoms cause pathological alterations with prominent local effects, such as edema, blistering, hemorrhage, dermonecrosis and myonecrosis, usually followed by poor tissue regeneration and permanent sequelae. Bleeding, coagulopathy, cardiovascular shock and renal failure are typical systemic effects of these venoms. The clinical treatment for snakebite envenoming is intravenous administration of the specific antivenom. However, serotherapy does not efficiently protect against local tissue damage. Additional challenges faced by classical antivenom therapy include the wide antigenic variation of venoms across species and even within the same snake species and the frequent occurrence of adverse reactions that are associated with the administration of immunobiologicals. The development of new effective toxin inhibitors based on the structure of natural antiophidic proteins is an attractive therapeutic alternative. DM64 is a myotoxin inhibitor that was isolated from opossum serum, and its expression as a recombinant protein is paramount to the characterization of its structure-function relationship, an essential step toward the development of alternative strategies to better manage bothropic snakebite envenomations.

Keratinocyte-Releasable Factors Stimulate the Expression of Granulocyte Colony-Stimulating Factor in Human Dermal Fibroblasts

Interaction between keratinocytes and fibroblasts plays a critical role in maintaining skin integrity under both normal and pathological conditions. We have previously demonstrated that keratinocyte-releasable factors influence the expression of key extracellular matrix components, such as collagen and matrix metalloproteinases in dermal fibroblasts. In this study, we utilized DNA microarray analysis to examine the effects of keratinocyte-releasable factors on the expression of several cytokines in human dermal fibroblasts. The results revealed significantly higher granulocyte colony-stimulating factor (G-CSF) expression in fibroblasts co-cultured with keratinocytes relative to mono-cultured cells, which was verified by RT-PCR and western blot. G-CSF is an important hematopoietic factor also thought to play a beneficial role in wound healing through stimulating keratinocyte proliferation. To partially characterize the keratinocyte-releasable factors responsible for stimulating G-CSF production, keratinocyte-conditioned medium (KCM) was subjected to thermal treatment and ammonium sulfate precipitation before treating fibroblasts. The results showed that keratinocyte-releasable G-CSF-stimulating factors remain stable at 56°C and upon 50% ammonium sulfate precipitation. Knowing that keratinocytes release IL-1, which stimulates G-CSF expression in various immune cells, several experiments were conducted to ask whether this might also be the case for fibroblasts. The results showed that the addition of recombinant IL-1 markedly increased G-CSF expression in fibroblasts; however, IL-1 receptor antagonist only partially abrogated KCM-stimulated G-CSF expression, indicating the role of additional keratinocyte-releasable factors. These findings underline the importance of cross-talk between keratinocytes and fibroblasts, suggesting that communication between these cells in vivo modulates the production of cytokines required for cutaneous wound healing and maintenance. J. Cell. Biochem. 118: 308-317, 2017. © 2016 Wiley Periodicals, Inc.

Green and catalyst-free preparation of triazinyl polyimide for the efficient adsorption of glycoproteins

Triazinyl polyimide is prepared via a solvent-free and catalyst-free imidization reaction by using melamine and pyromellitic dianhydride as precursors and it exhibits excellent selectivity towards glycoprotein.

Preparation of a cobalt mono-substituted silicotungstic acid doped with aniline for the selective adsorption of ovalbumin

A cobalt mono-substituted silicotungstic acid doped with aniline (SiW₁₁Co–PANI composite, where PANI denotes polyaniline) possesses a porous framework structure and exhibits favorable selectivity towards ovalbumin adsorption.

Determinants of allergenicity

The question "What makes an allergen an allergen?" has puzzled generations of researchers, and we still do not have a conclusive answer. Despite increasing knowledge about the molecular and functional characteristics of allergens that have been identified, we still do not fully understand why some proteins are clinically relevant allergens and most are not. Different approaches have been taken to identify the structural and functional features of allergens, aiming at developing methods to predict allergenicity and thus to identify allergens. However, none of these methods has allowed a reliable discrimination between allergenic and nonallergenic compounds on its own. This review sums up diverse determinants that contribute to the phenomenon of allergenicity and outlines that in addition to the structure and function of the allergen, factors derived from allergen carriers, the environment, and the susceptible individual are of importance.