A study of the interactions of porcine pancreatic lipase (PPL) with chitosan is the most interesting and important in order to regulate the enzymatic properties of the future nanomaterials based on ...these biopolymers. A decrease in catalytic activity of pure PPL towards triacetin during prolonged operation and storage is shown: activity decreases by 24.1% within 1 hour and by 54.0% - in the case of the lipase storage in solution for 1 month. The optimum temperature of 40°C was determined for samples of pure PPL, whereas a small shift from 40° to about 45°C - for PPL:Chit complex (50:1). The catalytic activity of free PPL at 40°C was the highest (as compared to lower and higher temperatures) and stable for 20 min. However, the dynamics showed a pronounced decrease to almost 2 times within further 30-60 minutes. In contrast, at 40°C the catalytic activity of PPL in complex with chitosan (50:1) stabilized at almost the same level (although it was lower than the activity of free PPL in the first 30 minutes of measurement). The PPL:Chit complex can be considered as promising catalytic nanomaterials (based on chitosan and lipase) for further applications.
Quantum dots (QDs) are widely used as biomarkers that has both fundamental and applied importance. Since cell membranes are mainly composed of lipids such as phosphatidylcholine (PC) and its ...derivatives, it is important to investigate the interaction of QDs with PC in monolayers to understand the penetration mechanism. This work is devoted to the study of the interaction of QDs with PC by determining their surface-active properties at various interfaces by dynamic surface tension. The isotherms of the surface tension of 5 μg/L QDs solution or 0.17 mM (0.86 mM) PC solutions, as well as the solutions of the mixtures of QDs and PC: 0.17 mM (0.86 mM) PC and 5 μg/L QDs or 0.17 mM (0.86 mM) PC and 15 μg/L QDs were obtained. The mixed QDs/PC monolayers (at low content of QDs equal to 1:100) were characterized by the formation of a stable domain structures. An adsorption of PC at QDs allows to vary the degree of surface modification by changing the amount of the lipid. Such nanoparticles have dimensions not very different from the sizes of the initial QDs, due to the small size of lipids and are well suited for incorporation into biomembrane models.
Immobilization of enzymes (IoE) from animal origin on natural carriers increases the system stability; facilitates the separation and accelerates the recovery of the enzyme; makes reuse possible; ...provides a significant reduction in operating costs. There are numerous IoE methods and systems, including immobilization of various lipases on major carbohydrate biopolymers (chitin, chitosan, cellulose, etc.), discussed in this review. The key points of the most encouraging methods “for increasing the activity and stability” of such biopolymer systems are the “chitosan particle activation” by “ultra-sonication” and multiplicative “addition of glutaraldehyde” to these abovementioned systems. The design of such complex biopolymer preparations (in their various forms) is an important area of modern agrosciences, biomedicine, veterinary, zootechnology and bionanotechnology.
The effect of added Mo, WC, and ZrO2 nanopowders on the graphitization of diamond grains in metal–matrix composites was studied by Raman spectroscopy. In the presence of Mo and ZrO2 nanoadditives, ...the graphitization process was found to get intensified. But the addition of WC nanopowder was found to suppress the graphitization by 25–30%. This can be expected to improve the adhesion of binder to diamond grains and hence the service life of related cutting tools.
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•Nano alloying of Fe-based binders affects the graphitization of diamond grains.•ZrO2 and Mo nanoparticles promote the graphitization of diamond grains.•WC nanoparticles suppress the graphitization process.
One of the ways to use a focused ion beam in lithographic processes to create nanostructures is through the exposure of special sensitive materials, i.e., resists. As a result of exposure, the ...solubility of such a material increases (“positive” resist) or, conversely, decreases (“negative” resist). Subsequent selective irradiation and development of the resist make it possible to create a predetermined pattern on the substrate. This work is aimed at developing the theoretical foundations for this ion lithography method. A practically important case of stopping heavy ions in an organic resist, the average atomic mass of which is much less than the mass of the incident ion, is considered. Expressions for the “energy” and transport lengths of ions are obtained. The calculations are carried out assuming a power-law interaction potential. The “energy” length characterizes the depth of penetration of ions into the material, and the transport length is related to beam expansion due to scattering. Therefore, these lengths are the main characteristics of the zone in which the ion-beam energy is absorbed.
The increase in infections caused by multidrug-resistant microorganisms is currently one of the most serious medical issues. In fact, antimicrobial resistance is viewed by the World Health ...Organization as one of the most serious threats to health worldwide. The problem is exacerbated by the lack of new antibiotics with respective benefits for the treatment of multidrug-resistant bacteria. While new compounds are being developed a number of "old" antibiotics used in clinical practice for several decades may acquire new indications for use.
The feature of the promising tool of lithographic nanostructuring based on selective exposure of polymer resist by ion beam is very compact (of about tens of nanometers) beam interaction volume. ...Herewith the main part of beam energy is deposited in the resist and is spent to its modification. It causes the set of advantages specific for this method: sub-10 nanometer resolution achievable, very high energy efficiency and almost complete absence of proximity effect. But also due to this feature absorbed doze essentially inhomogeneous in resist and the dissolution rate is strongly dependent on depth. So the common procedure of resist contrast determination cannot be applied anymore. In the present work a new method for resist contrast determination considering the relation between dissolution rate and deposited energy density is suggested and realized. By using it for PMMA resist irradiated by 30 keV Ga
+
ion beam the value of contrast was determined to be 3.1 and ions energy length was estimated to be 42 nm.
—Both synthetic and natural polymers are promising carriers for the immobilization of enzymes, including lipases from different sources. This research trend is of fundamental and applied importance, ...since immobilized lipases are widely used in various biotechnological processes. In the present work, we study how synthetic and natural polymers (polystyrene, polylysine, and chitosan) influence the catalytic properties of lipases from the hog’s pancreatic gland (LPP), yeast fungus
Сandida cylindracea
(LCC), and wheat germs (LWG) in the hydrolysis of triacetin (used as a substrate in all the experiments). A polystyrene-based latex (even without surface modification) is found to have a strong effect on the activity of lipases of different origins. In the presence of large particles with a size of about 1 μm (irrespective of their concentration in the range of 1–10%), the activity of all three lipases (LPP, LCC, and LWG) significantly increases compared to the nonimmobilized enzyme. A polystyrene latex with a carboxylated surface shows another effect on the catalytic properties of these lipases. The activity of LPP is found to depend on the concentration of chitosan (at ratios ranging from 100 : 1 to 1 : 1), as well as on the parameters of the medium (pH and temperature). The measurement of the catalytic activity of lipase with polylysine showed that, at ratios of 10 : 1 and 5 : 1 (LPP was in excess), the activity of enzyme increased by 17 and 9% relative to the free form, respectively. This is due to the interaction between the positively charged polylysine and the enzyme having an extra negative charge. The results obtained seem promising for biotechnological applications.
The use of the achievements attained in colloid chemistry and other fields of chemical sciences allows us to develop new nanoscale systems for chemosensorics. Mixed monolayers consisting of a new ...chemosensory amphiphilic dithia-18-crown-6, which contains a dye of 4-alkylpyridine series with polyvinyl stearate at the water–air interface, are obtained and studied. The influence of various concentrations of silver ions on these mixed monolayers is studied. A promising method for the detection of silver ions in water using the given nanoscale systems based on chemosensory amphiphilic dithia-18-crown-6 is proposed.
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The use of a special device that limits the field of view of a detector, i.e., a confocal collimator, is one of the approaches to obtaining information about the spatial distribution of the ...detected material in the methods for radionuclide diagnostics (in medicine) and X-ray fluorescence analysis (in material science). This device is a monolithic construction with a large number of straight channels whose axes are directed towards a single point that is the focus of the confocal collimator. The possibility of fabricating confocal collimators using 3D printing technology is demonstrated. The advantages of 3D printing are simplicity, reliability, and wide availability. It is shown that the use of a confocal collimator in radionuclide diagnostics instead of a single-channel collimator is advantageous, since it substantially increases the sensitivity (by 2−7 times) with the simultaneous improvement of the resolution (approximately by 9 times). The applicability of the confocal collimator for determining the depth of occurrence of a radiation source, i.e., for measuring the three-dimensional distribution of the emitting (fluorescent) substance, is also demonstrated.
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