Electron Capture vs Transfer Dissociation for Site Determination of Tryptic Peptide Tyrosine Sulfation: Direct Detection of Fibrinogen Sulfation Sites and Identification of Novel Isobaric Interferences.

Tyrosine sulfation, an understudied but crucial post-translational modification, cannot be directly detected in conventional nanoflow liquid chromatography-tandem mass spectrometry (nanoLC-MS/MS) due to the extreme sulfate lability. Here, we report the detection of sulfate-retaining fragments from LC-electron capture dissociation (ECD) and nanoLC-electron transfer higher energy collision dissociation (EThcD). Sulfopeptide candidates were identified by Proteome Discoverer and MSFragger analysis of nanoLC-HCD MS/MS data and added to inclusion lists for LC-ECD or nanoLC-EThcD MS/MS. When this approach failed, targeted LC-ECD with fixed m/z isolation windows was performed. For the plasma protein fibrinogen, the known pyroglutamylated sulfopeptide QFPTDYDEGQDDRPK from the beta chain N-terminus was identified despite a complete lack of sulfate-containing fragment ions. The peptide QVGVEHHVEIEYD from the gamma-B chain C-terminus was also identified as sulfated or phosphorylated. This sulfopeptide is not annotated in Uniprot but was previously reported. MSFragger further identified a cysteine-containing peptide from the middle of the gamma chain as sulfated and deamidated. NanoLC-EThcD and LC-ECD MS/MS confirmed the two former sulfopeptides via sulfate-retaining fragment ions, whereas an unexpected fragmentation pattern was observed for the third sulfopeptide candidate. Manual interpretation of the LC-ECD spectrum revealed two additional isobaric identifications: a trisulfide-linked cysteinyl-glycine or a carbamidomethyl-dithiothreiotol covalent adduct. Synthesis of such adducts confirmed the latter identity.

Fabrication of heart tubes from iPSC derived cardiomyocytes and human fibrinogen by rotating mold technology.

Due to its structural and functional complexity the heart imposes immense physical, physiological and electromechanical challenges on the engineering of a biological replacement. Therefore, to come closer to clinical translation, the development of a simpler biological assist device is requested. Here, we demonstrate the fabrication of tubular cardiac constructs with substantial dimensions of 6 cm in length and 11 mm in diameter by combining human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) and human foreskin fibroblast (hFFs) in human fibrin employing a rotating mold technology. By centrifugal forces employed in the process a cell-dense layer was generated enabling a timely functional coupling of iPSC-CMs demonstrated by a transgenic calcium sensor, rhythmic tissue contractions, and responsiveness to electrical pacing. Adjusting the degree of remodeling as a function of hFF-content and inhibition of fibrinolysis resulted in stable tissue integrity for up to 5 weeks. The rotating mold device developed in frame of this work enabled the production of tubes with clinically relevant dimensions of up to 10 cm in length and 22 mm in diameter which-in combination with advanced bioreactor technology for controlled production of functional iPSC-derivatives-paves the way towards the clinical translation of a biological cardiac assist device.

Molecular Basis for Surface-Initiated Non-Thrombin-Generated Clot Formation Following Viral Infection.

In this paper, we propose a model that connects two standard inflammatory responses to viral infection, namely, elevation of fibrinogen and the lipid drop shower, to the initiation of non-thrombin-generated clot formation. In order to understand the molecular basis for the formation of non-thrombin-generated clots following viral infection, human epithelial and Madin-Darby Canine Kidney (MDCK, epithelial) cells were infected with H1N1, OC43, and adenovirus, and conditioned media was collected, which was later used to treat human umbilical vein endothelial cells and human lung microvascular endothelial cells. After direct infection or after exposure to conditioned media from infected cells, tissue surfaces of both epithelial and endothelial cells, exposed to 8 mg/mL fibrinogen, were observed to initiate fibrillogenesis in the absence of thrombin. No fibers were observed after direct viral exposure of the endothelium or when the epithelium cells were exposed to SARS-CoV-2 isolated spike proteins. Heating the conditioned media to 60 °C had no effect on fibrillogenesis, indicating that the effect was not enzymatic but rather associated with relatively thermally stable inflammatory factors released soon after viral infection. Spontaneous fibrillogenesis had previously been reported and interpreted as being due to the release of the alpha C domains due to strong interactions of the interior of the fibrinogen molecule in contact with hydrophobic material surfaces rather than cleavage of the fibrinopeptides. Contact angle goniometry and immunohistochemistry were used to demonstrate that the lipids produced within the epithelium and released in the conditioned media, probably after the death of infected epithelial cells, formed a hydrophobic residue responsible for fibrillogenesis. Hence, the standard inflammatory response constitutes the ideal conditions for surface-initiated clot formation.

The strongest protein binder is surprisingly labile.

Bacterial adhesins are cell-surface proteins that anchor to the cell wall of the host. The first stage of infection involves the specific attachment to fibrinogen (Fg), a protein found in human blood. This attachment allows bacteria to colonize tissues causing diseases such as endocarditis. The study of this family of proteins is hence essential to develop new strategies to fight bacterial infections. In the case of the Gram-positive bacterium Staphylococcus aureus, there exists a class of adhesins known as microbial surface components recognizing adhesive matrix molecules (MSCRAMMs). Here, we focus on one of them, the clumping factor A (ClfA), which has been found to bind Fg through the dock-lock-latch mechanism. Interestingly, it has recently been discovered that MSCRAMM proteins employ a catch-bond to withstand forces exceeding 2 nN, making this type of interaction as mechanically strong as a covalent bond. However, it is not known whether this strength is an evolved feature characteristic of the bacterial protein or is typical only of the interaction with its partner. Here, we combine single-molecule force spectroscopy, biophysical binding assays, and molecular simulations to study the intrinsic mechanical strength of ClfA. We find that despite the extremely high forces required to break its interactions with Fg, ClfA is not by itself particularly strong. Integrating the results from both theory and experiments we dissect contributions to the mechanical stability of this protein.

Controlled release of vancomycin from PEGylated fibrinogen polyethylene glycol diacrylate hydrogel.

Surgical site infection (SSI) is a common issue post-surgery which often prolongs hospitalization and can lead to serious complications such as sternal wound infection following cardiac surgery via median sternotomy. Controlled release of suitable antibiotics could allow maximizing drug efficacy and safety, and therefore achieving a desired therapeutic response. In this study, we have developed a vancomycin laden PEGylated fibrinogen-polyethylene glycol diacrylate (PF-PEGDA) hydrogel system that can release vancomycin at a controlled and predictable rate to be applied in SSI prevention. Two configurations were developed to study effect of the hydrogel on drug release, namely, vancomycin laden hydrogel and vancomycin solution on top of blank hydrogel. The relationship between the rigidity of the hydrogel and drug diffusion was found to comply with a universal power law, i.e., softer hydrogels result in a greater diffusion coefficient hence faster release rate. Besides, vancomycin laden hydrogels exhibited burst release, whereas the vancomycin solution on top of blank hydrogels exhibited lag release. A mathematical model was developed to simulate vancomycin permeation through the hydrogels. The permeation of vancomycin can be predicted accurately by using the mathematical model, which provided a useful tool to customize drug loading, hydrogel thickness and stiffness for personalized medication to manage SSI. To evaluate the potential of hydrogels for bone healing applications in cardiovascular medicine, we performed a proof-of-concept median sternotomy in rabbits and applied the hydrogels. The hydrogel formulations accelerated the onset of osteo-genetic processes in rabbits, demonstrating its potential to be used in human.

PEG-functionalized aliphatic polycarbonate brushes with self-polishing dynamic antifouling properties.

Hydrophilic antifouling polymers provide excellent antifouling effects under usual short-term use conditions, but the long-term accumulation of contaminants causes them to lose their antifouling properties. To overcome this drawback, surface-initiated ring-opening graft polymerization (SI-ROP) was performed on the surface of the material by applying the cyclic carbide monomer 4'-(fluorosulfonyl)benzyl-5-methyl-2-oxo-1,3-dioxane-5-carboxylate (FMC), which contains a sulfonylfluoride group on the side chain, followed by a "sulfur(IV)-fluorine exchange" (SuFEx) post click modification reaction to link the hydrophilic polyethylene glycol (PEG) to the polyFMC (PFMC) brush, and a novel antifouling strategy for self-polishing dynamic antifouling surfaces was developed. The experimental results showed that the antifouling surface could effectively prevent the adsorption of proteins such as bovine serum albumin (BSA, ∼96.4%), fibrinogen (Fg, ∼87.8%) and lysozyme (Lyz ∼69.4%) as well as the adhesion of microorganisms such as the bacteria Staphylococcus aureus (S. aureus) (∼87.5%) and HeLa cells (∼67.2%). Moreover, the enzymatically self-polished surface still has excellent antifouling properties. Therefore, this modification method has potential applications in the field of biosensors and novel antifouling materials.

Rapid Separation and Display of Active Fibrinogenolytic Agents in Sipunculus nudus through Fibrinogen-Polyacrylamide Gel Electrophoresis.

Fibrinogenolytic agents that can dissolve fibrinogen directly have been widely used in anti-coagulation treatment. Generally, identifying new fibrinogenolytic agents requires the separation of each component first and then checking their fibrinogenolytic activities. Currently, polyacrylamide gel electrophoresis (PAGE) and chromatography are mostly used in the separating stage. Meanwhile, the fibrinogen plate assay and reaction products based PAGE are usually adopted to display their fibrinogenolytic activities. However, because of the spatiotemporal separation of those two stages, it is impossible to separate and display the active fibrinogenolytic agents with the same gel. To simplify the separating and displaying processes of fibrinogenolytic agent identification, we constructed a new fibrinogen-PAGE method to rapidly separate and display the fibrinogenolytic agents of peanut worms (Sipunculus nudus) in this study. This method includes fibrinogen-PAGE preparation, electrophoresis, renaturation, incubation, staining, and decolorization. The fibrinogenolytic activity and molecular weight of the protein can be detected simultaneously. According to this method, we successfully detected more than one active fibrinogenolytic agent of peanut wormhomogenate within 6 h. Moreover, this fibrinogen-PAGE method is time and cost-friendly. Furthermore, this method could be used to study the fibrinogenolytic agents of the other organisms.

Apigenin Provides Structural Protection to Human Fibrinogen against Nitrosative Stress: Biochemical and Molecular Insights.

BACKGROUND: Peroxynitrite (ONOO-) is an oxidant linked with several human pathologies. Apigenin, a natural flavonoid known for its health benefits, remains unexplored in relation to ONOO- effects. This study investigated the potential of apigenin to structurally protect fibrinogen, an essential blood clotting factor, from ONOO--induced damage. METHODS: Multi-approach analyses were carried out where fibrinogen was exposed to ONOO- generation while testing the efficacy of apigenin. The role of apigenin against ONOO--induced modifications in fibrinogen was investigated using UV spectroscopy, tryptophan or tyrosine fluorescence, protein hydrophobicity, carbonylation, and electrophoretic analyses. RESULTS: The findings demonstrate that apigenin significantly inhibits ONOO--induced oxidative damage in fibrinogen. ONOO- caused reduced UV absorption, which was reversed by apigenin treatment. Moreover, ONOO- diminished tryptophan and tyrosine fluorescence, which was effectively restored by apigenin treatment. Apigenin also reduced the hydrophobicity of ONOO--damaged fibrinogen. Moreover, apigenin exhibited protective effects against ONOO--induced protein carbonylation. SDS-PAGE analyses revealed that ONOO-treatment eliminated bands corresponding to fibrinogen polypeptide chains Aα and γ, while apigenin preserved these changes. CONCLUSIONS: This study highlights, for the first time, the role of apigenin in structural protection of human fibrinogen against peroxynitrite-induced nitrosative damage. Our data indicate that apigenin offers structural protection to all three polypeptide chains (Aα, Bß, and γ) of human fibrinogen. Specifically, apigenin prevents the dislocation or breakdown of the amino acids tryptophan, tyrosine, lysine, arginine, proline, and threonine and also prevents the exposure of hydrophobic sites in fibrinogen induced by ONOO-.

Tissue-Penetrating Ultrasound-Triggered Hydrogel for Promoting Microvascular Network Reconstruction.

The microvascular network plays an important role in providing nutrients to the injured tissue and exchanging various metabolites. However, how to achieve efficient penetration of the injured tissue is an important bottleneck restricting the reconstruction of microvascular network. Herein, the hydrogel precursor solution can efficiently penetrate the damaged tissue area, and ultrasound triggers the release of thrombin from liposomes in the solution to hydrolyze fibrinogen, forming a fibrin solid hydrogel network in situ with calcium ions and transglutaminase as catalysts, effectively solving the penetration impedance bottleneck of damaged tissues and ultimately significantly promoting the formation of microvascular networks within tissues. First, the fibrinogen complex solution is effectively permeated into the injured tissue. Second, ultrasound triggered the release of calcium ions and thrombin, activates transglutaminase, and hydrolyzes fibrinogen. Third, fibrin monomers are catalyzed to form fibrin hydrogels in situ in the damaged tissue area. In vitro studies have shown that the fibrinogen complex solution effectively penetrated the artificial bone tissue within 15 s after ultrasonic triggering, and formed a hydrogel after continuous triggering for 30 s. Overall, this innovative strategy effectively solved the problem of penetration resistance of ultrasound-triggered hydrogels in the injured tissues, and finally activates in situ microvascular networks regeneration.

Influence of Proteins and Building Direction on the Corrosion and Tribocorrosion of CoCrMo Fabricated by Laser Powder Bed Fusion.

Cobalt-chromium-molybdenum (CoCrMo) alloys are common wear-exposed biomedical alloys and are manufactured in multiple ways, increasingly using additive manufacturing processes such as laser powder bed fusion (LPBF). Here, we investigate the effect of proteins and the manufacturing process (wrought vs LPBF) and building orientation (LPBF-XY and XZ) on the corrosion, metal release, tribocorrosion, and surface oxide composition by means of electrochemical, mechanical, microscopic, diffractive, and spectroscopic methods. The study was conducted at pH 7.3 in 5 g/L NaCl and 5 mM 2-(N-morpholino) ethanesulfonic acid (MES) buffer, which was found to be necessary to avoid metal phosphate and metal-protein aggregate precipitation. The effect of 10 g/L bovine serum albumin (BSA) and 2.5 g/L fibrinogen (Fbn) was studied. BSA and Fbn strongly enhanced the release of Co, Cr, and Mo and slightly enhanced the corrosion (still in the passive domain) for all CoCrMo alloys and most for LPBF-XZ, followed by LPBF-XY and the wrought CoCrMo. BSA and Fbn, most pronounced when combined, significantly decreased the coefficient of friction due to lubrication, the wear track width and severity of the wear mechanism, and the tribocorrosion for all alloys, with no clear effect of the manufacturing type. The wear track area was significantly more oxidized than the area outside of the wear track. In the reference solution without proteins, a strong Mo oxidation in the wear track surface oxide was indicative of a pH decrease and cell separation of the anodic and cathodic areas. This effect was absent in the presence of the proteins.

Controlling nanoparticle-induced endothelial leakiness with the protein corona.

Understanding nanoparticle-cell interaction is essential for advancing research in nanomedicine and nanotoxicology. Apart from the transcytotic pathway mediated by cellular recognition and energetics, nanoparticles (including nanomedicines) may harness the paracellular route for their transport by inducing endothelial leakiness at cadherin junctions. This phenomenon, termed as NanoEL, is correlated with the physicochemical properties of the nanoparticles in close association with cellular signalling, membrane mechanics, as well as cytoskeletal remodelling. However, nanoparticles in biological systems are transformed by the ubiquitous protein corona and yet the potential effect of the protein corona on NanoEL remains unclear. Using confocal fluorescence microscopy, biolayer interferometry, transwell, toxicity, and molecular inhibition assays, complemented by molecular docking, here we reveal the minimal to significant effects of the anionic human serum albumin and fibrinogen, the charge neutral immunoglobulin G as well as the cationic lysozyme on negating gold nanoparticle-induced endothelial leakiness in vitro and in vivo. This study suggests that nanoparticle-cadherin interaction and hence the extent of NanoEL may be partially controlled by pre-exposing the nanoparticles to plasma proteins of specific charge and topology to facilitate their biomedical applications.

Isolation and Functional Characterization of Erythrofibrase: An Alfa-Fibrinogenase Enzyme from Trimeresurus erythrurus Venom of North-East India.

Green pit viper bites induce mild toxicity with painful local swelling, blistering, cellulitis, necrosis, ecchymosis and consumptive coagulopathy. Several bite cases of green pit vipers have been reported in several south-east Asian countries including the north-eastern region of India. The present study describes isolation and characterization of a haemostatically active protein from Trimeresurus erythrurus venom responsible for coagulopathy. Using a two-step chromatographic method, a snake venom serine protease erythrofibrase was purified to homogeneity. SDS-PAGE of erythrofibrase showed a single band of ~30 kDa in both reducing and non-reducing conditions. The primary structure of erythrofibrase was determined by ESI LC-MS/MS, and the partial sequence obtained showed 77% sequence similarity with other snake venom thrombin-like enzymes (SVTLEs). The partial sequence obtained had the typical 12 conserved cysteine residues, as well as the active site residues (His57, Asp102 and Ser195). Functionally, erythrofibrase showed direct fibrinogenolytic activity by degrading the Aα chain of bovine fibrinogen at a slow rate, which might be responsible for causing hypofibrinogenemia and incoagulable blood for several days in envenomated patients. Moreover, the inability of Indian polyvalent antivenom (manufactured by Premium Serum Pvt. Ltd., Maharashtra, India) to neutralize the thrombin-like and plasmin-like activity of erythrofibrase can be correlated with the clinical inefficacy of antivenom therapy. This is the first study reporting an α-fibrinogenase enzyme erythrofibrase from T. erythrurus venom, which is crucial for the pathophysiological manifestations observed in envenomated victims.

Global O-glycoproteome enrichment and analysis enabled by a combinatorial enzymatic workflow.

A comprehensive analysis of site-specific protein O-glycosylation is hindered by the absence of a consensus O-glycosylation motif, the diversity of O-glycan structures, and the lack of a universal enzyme that cleaves attached O-glycans. Here, we report the development of a robust O-glycoproteomic workflow for analyzing complex biological samples by combining four different strategies: removal of N-glycans, complementary digestion using O-glycoprotease (IMPa) with/without another protease, glycopeptide enrichment, and mass spectrometry with fragmentation of glycopeptides using stepped collision energy. Using this workflow, we cataloged 474 O-glycopeptides on 189 O-glycosites derived from 79 O-glycoproteins from human plasma. These data revealed O-glycosylation of several abundant proteins that have not been previously reported. Because many of the proteins that contained unannotated O-glycosylation sites have been extensively studied, we wished to confirm glycosylation at these sites in a targeted fashion. Thus, we analyzed selected purified proteins (kininogen-1, fetuin-A, fibrinogen, apolipoprotein E, and plasminogen) in independent experiments and validated the previously unknown O-glycosites.

Selective binding of cationic fibrinogen-mimicking chitosan nanoparticles to activated platelets and efficient drug release for antithrombotic therapy.

Thrombosis is the main cause of catastrophic events including ischemic stroke, myocardial infarction and pulmonary embolism. Acetylsalicylic acid (ASA) therapy offers a desirable approach to antithrombosis through a reduction of platelet reactivity. However, major bleeding complications, severe off-target side effects, and resistance or nonresponse to ASA greatly attenuate its clinical outcomes. Herein, we report a cationic fibrinogen-mimicking nanoparticle, denoted as ASA-RGD-CS@TPP, to achieve activated-platelet-targeted delivery and efficient release of ASA for safer and more effective antithrombotic therapy. This biomimetic antithrombotic system was prepared by one-pot ionic gelation between cationic arginine-glycine-aspartic acid (RGD)-grafted chitosan (RGD-CS) and anionic tripolyphosphate (TPP). The platform exhibited selective binding to activated platelets, leading to efficient release of ASA and subsequent attenuation of platelet functions, including the remarkable inhibition of platelet aggregation through a potent blockage of cyclooxygenase-1 (COX-1). After intravenous administration, ASA-RGD-CS@TPP displayed significantly prolonged circulation time and successful prevention of thrombosis in a mouse model. ASA-RGD-CS@TPP was demonstrated to significantly enhance antithrombotic therapy while showing minimal coagulation and hemorrhagic risks and excellent biocompatibility in vivo as compared to free ASA. This platform provides a simple, safe, effective and targeted strategy for the development of antithrombotic nanomedicines.

A role of methionines in the functioning of oxidatively modified fibrinogen.

Posttranslational modifications in fibrinogen resulting from induced oxidation or oxidative stress in the organism can have deleterious influence on optimal functioning of fibrinogen, causing a disturbance in assembly and properties of fibrin. The protective mechanism supporting the ability of fibrinogen to function in ROS-generating environment remains completely unexplored. The effects of very low and moderately low HOCl/-OCl concentrations on fibrinogen oxidative modifications, the fibrin network structure as well as the kinetics of both fibrinogen-to-fibrin conversion and fibrin hydrolysis have been explored in the current study. As opposed to 25 Μm, HOCl/-OCl, 10 µM HOCl/-OCl did not affect the functional activity of fibrinogen. It is shown for the first time that a number of Met residues, AαMet476, AαMet517, AαMet584, BßMet367, γMet264, and γMet94, identified in 10 µM HOCl/-OCl fibrinogen by the HPLC-MS/MS method, operate as ROS scavengers, performing an important antioxidant function. In turn, this indicates that the fibrinogen structure is adapted to the detrimental action of ROS. The results obtained in our study provide evidence for a protective mechanism responsible for maintaining the structure and functioning of fibrinogen molecules in the bloodstream under conditions of mild and moderate oxidative stress.

Physicochemical Targeting of Lipid Nanoparticles to the Lungs Induces Clotting: Mechanisms and Solutions.

Lipid nanoparticles (LNPs) have become the dominant drug delivery technology in industry, holding the promise to deliver RNA to up or down-regulate any protein of interest. LNPs have mostly been targeted to specific cell types or organs by physicochemical targeting in which LNP's lipid compositions are adjusted to find mixtures with the desired tropism. Here lung-tropic LNPs are examined, whose organ tropism derives from containing either a cationic or ionizable lipid conferring a positive zeta potential. Surprisingly, these LNPs are found to induce massive thrombosis. Such thrombosis is shown in the lungs and other organs, and it is shown that it is greatly exacerbated by pre-existing inflammation. This clotting is induced by a variety of formulations with cationic lipids, including LNPs and non-LNP nanoparticles, and even by lung-tropic ionizable lipids that do not have a permanent cationic charge. The mechanism depends on the LNPs binding to and then changing the conformation of fibrinogen, which then activates platelets and thrombin. Based on these mechanisms, multiple solutions are engineered that enable positively charged LNPs to target the lungs while ameliorating thrombosis. The findings illustrate how physicochemical targeting approaches must be investigated early for risks and re-engineered with a careful understanding of biological mechanisms.

Preparation and Hemocompatibility of Novel Antioxidant-Modified Polyethersulfone Membranes as Red Blood Cell Thrombosis Inhibitors.

The contact between the dialysis membrane and blood can induce oxidative stress and thrombosis, causing oxidative organ damage and impaired toxin clearance. To date, the selection of anticoagulants has focused on mechanisms inhibiting white, but not red (erythrocytes) thrombus formation. In the present study, polyethersulfone (PES) membranes are modified with the antioxidant drug tiopronin; the physicochemical properties and dialysis performance of the Tio-PES membranes are evaluated. The effects on erythrocyte thrombosis are evaluated in terms of erythrocyte morphology, prothrombotic properties (adhesion, aggregation, viscosity, sedimentation, and hemolysis), and fibrinogen (FIB)-erythrocyte interactions. The regular anticoagulant and antiplatelet properties are also assessed. Superoxide dismutase, malondialdehyde, plasma protein, and complement C3a are further determined. Finally, the biosafety of the Tio-PES membranes is evaluated both in vitro and in vivo. The Tio-PES membranes exhibit excellent physicochemical properties and improved dialysis performance. It is found that the Tio-PES membranes stabilize erythrocyte morphology, reduce erythrocyte prothrombotic properties, decrease FIB adsorption, and prevent red thrombus formation. In addition, the Tio-PES membranes exhibit excellent antioxidant properties and show biosafety in primary toxicity studies. Thus, Tio-PES membranes hold promise as novel, safe, and effective dialysis materials for potential clinical application.

Degradation protection and enhanced biocompatibility of Mg alloys pretreated with plasma proteins.

After implantation of the Mg alloy in the human body, the adsorption of plasma protein on surface will cause a series of cell reactions and affect the degradation of Mg alloys. Herein, in vitro biological reactions of the ZK60 and AZ31 Mg alloys are analyzed in plasma protein environment. Combined with mass spectrometry analysis of the type of adsorbed proteins, it is shown that proteins such as fibrinogen, vitronectin, fibronectin, and prothrombin are prone to get adsorbed on the surface of the alloys than other proteins, leading to the promotion of MG63 cell adhesion and proliferation. The effect of selected proteins (fibrinogen, fibronectin, and prothrombin) on degradation of ZK60 and AZ31 Mg alloys is investigated using immersion tests. The degradation of AZ31 Mg alloy is significantly restrained with the presence of proteins. This is due to the protein adsorption effect on the sample surface. The molecular dynamics simulation results indicate that both fibrinogen and fibronectin tend to adsorb onto the AZ31 rather than ZK60, forming a stable protein layer on the AZ31 Mg alloy retarding the degradation of the samples. As to ZK60 alloy, the addition of protein inhibits the degradation in the short term, however, the degradation increases after a long time of immersion. This phenomenon is particularly pronounced in fibronectin solution.

A novel mutation in the FGG gene causes hypofibrinogenemia in a Chinese family.

Congenital fibrinogen disorders are a group of coagulation deficiencies caused by fibrinogen defects and are divided into four types, including afibrinogenemia, hypofibrinogenemia, dysfibrinogenemia, and hypodysfibrinogenemia. In this study, we collected a family with hypofibrinogenemia, and genetics analysis identify a novel pathogenic variants (c.668G > C, p.Arg223Thr) in the FGG gene. And electron microscope observation revealed significant changes in the ultrastructure of fibrin of the proband. Our research expands the phenotypic and genetic spectrum associated with the FGG gene, which would facilitate in genetic counselling and prenatal genetic diagnosis.

Mesoscopic Model for Reversible Adsorption Stage of Albumin and Fibrinogen on TiO2 Surface.

The competitive behavior of proteins in the reversible adsorption stage plays a crucial role in determining the composition of the protein layer and the subsequent biological responses to the biomaterial. However, such competitive adsorption is a mesoscopic process at physiological protein concentration, and neither a macroscopic experiment nor microscopic MD (molecular dynamics) simulation is suitable to clarify it. Here, we proposed a mesoscopic DPD (dissipative particle dynamics) model to illustrate the competitive process of albumin and fibrinogen on TiO2 surface with its parameters deduced from our previous MD simulation, and proved the model well retained the diffusion and adsorption properties of proteins in the competitive adsorption on the plane surface. We then applied the model to the competitive adsorption on the surfaces with different nanostructures and observed that when the nanostructure size is much larger than that of protein, the increase in surface area is the main influencing factor; when the nanostructure size is close to that of protein, the coordination between the nanostructure and the size and shape of protein significantly affects the competitive adsorption process. The model has revealed many mechanical phenomena observed in previous experimental studies and has the potential to contribute to the development of high-performance biomaterials.