•The highly purified fractions of algal laminaran, fucoidan and alginate were isolated.•Seaweed polysaccharides catalyzed the formation of silver nanoparticles.•Alginate possessed the highest ...reduction potential among studied polysaccharides.•The cytotoxicity of nanoparticles varied depending on the properties of polysaccharides.•Silver nanoparticles had antibacterial activity against plant and animal pathogens.
In this report, polysaccharides – alginate, fucoidan, laminaran – were isolated from marine algae Saccharina cichorioides and Fucus evanescens and their activity as a reducing and stabilizing agents in the biogenic synthesis of silver nanoparticles was evaluated. The cytotoxic and antibacterial properties of obtained nanoparticles were also assessed. It was found that all tested polysaccharides could be used as a reducing agent; however, their catalytic activities varied significantly in the following range alginate < fucoidan < laminaran. Nanoparticles demonstrated cytotoxicity against rat C6 glioma cells. It was considerably higher for alginate- and laminaran-obtained nanosilver samples compared to fucoidan. Additionally, silver nanoparticles possessed considerable antibacterial properties more pronounced in fucoidan-obtained samples. Our data demonstrate that different algal polysaccharides can be used for the synthesis of silver nanoparticles with varying bioactivities.
Peptide-membrane interactions play a key role in the mechanisms of activity of antimicrobial peptides. Here, methods of fluorescence spectroscopy, zeta potential, and molecular dynamics modeling were ...used to study the interaction of new antimicrobial peptide megin with model bacterial membrane. The Gibbs free energy of −6 kcal/mol characterizes the interaction of the peptides with liposomes containing DOPE and POPG lipids. Fluorescence data, acrylamide quenching, and MD simulations show that megin peptides are mainly located at the lipid/water interface and are aligned parallel to the bilayer surface in a carpet like manner. Measurements of zeta potential demonstrate the decrease of the negative potential of liposomes in the presence of peptides. The influence of megin on the membrane properties is also confirmed by molecular dynamics simulations. Insertion of peptides into the membrane disturbs lipid ordering, decreases the order parameters of lipids, and facilitates penetration of water molecules through the membrane. According to our results, we proposed that the megin antimicrobial activity can be explained by the carpet model of peptide activity.
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•Negative potential of liposomes decreases in the presence of peptides.•Interaction of peptides with membrane facilitates penetration of water molecules through the membrane.•Megin peptides are mainly located at the lipid/water interface.
Multicolour labelling with fluorescent proteins is frequently used to differentially highlight specific structures in living systems. Labelling with fusion proteins is particularly demanding and is ...still problematic with the currently available palette of fluorescent proteins that emit in the red range due to unsuitable subcellular localization, protein-induced toxicity and low levels of labelling efficiency. Here we report a new monomeric red fluorescent protein, called FusionRed, which demonstrates both high efficiency in fusions and low toxicity in living cells and tissues.
•k-Carrageenan retains its overall secondary structure upon complexation with lysozyme.•Unordered k-carrageenan perturbs lysozyme loops and stabilizes β-structure.•Helical k-carrageenan does not ...remarkably affect lysozyme structure.
The interactions between κ-carrageenan and hen egg-white lysozyme have been studied. In dilute solutions, the insoluble complexes with constant κ-carrageenan/lysozyme ratio of 0.3, or 12 disaccharide units per mole of protein are formed. FTIR-spectroscopy revealed that κ-carrageenan retains its unordered conformation and induces the rise of β-structure in lysozyme. In the complexes formed in concentrated mixtures, κ-carrageenan adopts helical conformation and lysozyme retains its native-like structure. These complexes contain 21 disaccharide units per mole of protein. Molecular modeling showed that flexible coil and rigid double helix of κ-carrageenan have different binding patterns to lysozyme surface. The latter has a strong preference to positively charged spots in lysozyme α-domain while the former also interacts to protein β-domain and stabilizes short-living β-structures. The obtained results confirm the preference of unordered κ-carrageenan to β-structure rich protein regions, which can be further used in the development of carrageenan-based protection of amyloid-like aggregation of proteins.
Blood flows through vessels as a segregated suspension. Erythrocytes distribute closer to the vessel axis, whereas platelets accumulate near vessel walls. Directed platelet migration to the vessel ...walls promotes their hemostatic function. The mechanisms underlying this migration remain poorly understood, although various hypotheses have been proposed to explain this phenomenon (e.g., the available volume model and the drift-flux model). To study this issue, we constructed a mathematical model that predicts the platelet distribution profile across the flow in the presence of erythrocytes. This model considers platelet and erythrocyte dimensions and assumes an even platelet distribution between erythrocytes. The model predictions agree with available experimental data for near-wall layer margination using platelets and platelet-modeling particles and the lateral migration rate for these particles. Our analysis shows that the strong expulsion of the platelets from the core to the periphery of the blood vessel may mainly arise from the finite size of the platelets, which impedes their positioning in between the densely packed erythrocytes in the core. This result provides what we believe is a new insight into the rheological control of platelet hemostasis by erythrocytes.
In female Wistar rats, mammary gland hyperplasia (MGH) was modeled according to a modified protocol involving estrogen-progesterone induction and taking into account the duration of the estrous cycle ...of this animal species. MGH was induced over four 7-day cycles; each cycle included subcutaneous administration of 17β-estradiol (0.5 mg/kg) for 4 days, injection of progesterone (5 mg/kg) on day 5, then 2 days without injections. In females with MGH, a significant increase in the height and diameter of the nipples of the mammary glands was recorded, two types of changes were observed in the gland tissue: tubuloalveolar and lobuloalveolar hyperplasia. The study confirmed the development of MGH in rats by a modified method.
In this paper, the effect of ultrasonic impact on the macrostructure and strength of dissimilar titanium and aluminum alloy joints produced by friction stir welding has been investigated. The weld ...width, tool plunge depth, and interface complexity were chosen as criteria for macrostructure evaluation. It was found experimentally that the ultrasonic impact can both intensify stirring of materials and worsen them. In the selected range of modes, ultrasonic impact led to a decrease in the joint strengths. It was found that the interface complexity was inversely proportional to the heat input during welding in the joints that were made without ultrasonic impact. It was also found that the strength of joints correlates with the interface complexity.
SiBCN films are synthesized by plasma-enhanced chemical vapor deposition at a reduced pressure and 500-600 °C. Organoelement silicon and boron compounds are selected as precursors, namely, ...hexamethyldisilazane HN(SiMe
3
)
2
and triethylaminoborane Et
3
N·BH
3
that were not used previously in the synthesis of SiBCN films. Vapor flows of initial compounds and additional gas (ammonia) were separately supplied to the reactor without premixing. The chemical bonding structure, elemental composition, surface morphology, and film deposition rate are studied by FTIR, XPS, wave dispersive X-ray spectroscopy, SEM, and Raman spectroscopy techniques. The surface morphology analysis of the samples shows that the films are smooth, homogeneous, and uniform without features. Variation of precursor concentrations in the initial mixture allows changes in the film composition in a wide range. The boron concentration in four-component coatings reaches 45 at.%. The study of chemical bonding structures of the films reveals the occurrence of Si–C, Si–N, B–N, C–H bonds along with the hybrid BC
n
N
3–
n
bond.
Complexes of phosphorylated betaine, butyl (
N
-benzyl-
N
,
N
-dibutylammonio)methyl phosphonate, were studied by IR spectrometry, which, according to X-ray diffraction analysis, crystallizes as a ...zwitterionic compound in the
P
21/
c
space group with one water molecule. Complex formation with mineral acids, as well as with nitrates of rare earth metals, proceeds with the participation of the phosphoryl fragment of the betaine molecule; in metal complexes, the nitro group acts as a counterion.
The interface formation process was investigated in bimetallic joints of commercially pure titanium alloy and 5056 aluminum alloy produced by friction stir welding, including with ultrasonic ...assistance. Lap welding was performed with the titanium sheet on top of the aluminum one. Macrostructural geometric characteristics were analyzed such as weld width, plunge depth, the total cross-sectional area of defects, and the complexity of the interface between dissimilar layers. It was shown that the application of ultrasound during welding promotes better stirring of titanium and aluminum in the joint and makes their interface more complex, due to which the weld strength usually increases. This effect at low axial load can outweigh the antifriction effect. Experiments showed that ultrasonic-assisted friction stir welding provides the joint strength up to 87% of the aluminum alloy strength.
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