Investigation of Serine‐Proteinase‐Catalyzed Peptide Splicing in Analogues of Sunflower Trypsin Inhibitor 1 (SFTI‐1)

Serine‐proteinase‐catalyzed peptide splicing was demonstrated in analogues of the trypsin inhibitor SFTI‐1: both single peptides and two‐peptide chains (C‐ and N‐terminal peptide chains linked by a disulfide bridge). In the second series, peptide splicing with catalytic amount of proteinase was observed only when formation of acyl–enzyme intermediate was preceded by hydrolysis of the substrate Lys–Ser peptide bond. Here we demonstrate that with an equimolar amount of the proteinase, splicing occurs in all the two‐peptide‐chain analogues. This conclusion was supported by high resolution crystal structures of selected analogues in complex with trypsin. We showed that the process followed a direct transpeptidation mechanism. Thus, the acyl–enzyme intermediate was formed and was immediately used for a new peptide bond formation; products associated with the hydrolysis of the acyl–enzyme were not observed. The peptide splicing was sequence‐ not structure‐specific.     

Drying of Herbal Product in Closed System

A new product from a low temperature drying method that reduces the loss of highly volatile essential oils is presented. The proposed drying method consists of evaporation/sublimation of water and aromatic substances in a dryer with a closed drying agent cycle. In parallel, the evaporated compounds are continuously condensed in a heat exchanger. As a result of the drying process, high-quality dried plants and Fluidolat as liquid phase containing water and volatile organic compounds are obtained. The aim of presented investigations was to optimize the developed technology for the herb lavender.     

Melt fracture and rheology of linear low density polyethylene ‐ calcium carbonate composites

Rheological behavior and melt fracture of linear low‐density polyethylene (LLDPE) calcium carbonate (CaCO₃) composites were investigated. Two types of commercial inorganic fillers were used, unmodified and modified with stearic acid. Rheological capillary studies were conducted to assess the influence of inorganic filler incorporation as well as chemical treatment on the rheological properties and instability sequence of polyethylene‐based composites. Strong suppression of melt flow instabilities was observed for both types of composites. Mooney analysis was applied to examine the influence of mineral filler addition and stearic acid modification on the wall slip. Moreover, chemical treatment of calcium carbonate allows to obtain better dispersion of the inorganic filler in a polymeric matrix. POLYM. ENG. SCI., 57:998–1004, 2017. © 2016 Society of Plastics Engineers     

Application of new oligomeric plasticizers based on waste poly(ethylene terephthalate) for poly(vinyl chloride) compositions

In this study, chemical recycling products of waste poly(ethylene terephthalate) with oligoesters were used as new plasticizers for poly(vinyl chloride) (PVC). The preparation conditions of the dry blend mixtures of the suspension PVC containing synthesised plasticizers were similar to the conditions of the preparing mixtures with commercial plasticizers. The plasticization efficiency of PVC plasticizers was then examined by analysis of the mechanical, physical and chemical properties, as well as the thermal resistance and migration of plasticizer molecules from polymer matrix. Test results proved that compositions with synthesised oligomeric plasticizers possessed similar or better properties than those containing commercial oligomeric plasticizers and much better properties than those having monomeric plasticizers. Thermal stabilities of the proposed plasticizers were higher than those of the commercial plasticizers either monomeric (bis(2-ethylhexyl)phthalate) or oligomeric, despite the fact that the synthesised oligoesters did not contain any antioxidant. The best properties, especially low volatility, very good mechanical properties, low migration were resulted of the transesterification of the waste PET with oligoesters based on adipic acid, triethylene glycol and 2-ethylhexanol which were selected as plasticizers synthesised on the technical scale. The tested plasticized PVC compositions possessed very good tear resistance, tensile strength, decrease of weight loss after 168 h at 80 °C and low migration. Processing properties of PVC compositions containing these synthesised plasticizers confirmed their effectiveness in these compositions for extrusion process.     

The effect of structural features on mechanical properties of loose optical fiber poly(butylene terephthalate) tubes

Results of a study on the modifying mechanical properties of loose optical‐fiber poly(butylene terephthalate) (PBT) tubes, produced during the standard industrial extrusion process, show that heat treatment make the structure of their material to change. The study comprised measurements of mechanical strengths properties of the tubes (tensile strength, compression strength, kinking) and determination of tube material structure [by differential thermal analysis (DTA), wide angle X‐ray scattering analysis (WAXD), and scanning electron microscopy (SEM)]. Results of the study allowed observation that the annealing at 70°C for 34 h of the tubes caused the crystalline α phase to increase in the tube material from ～28.5% to ～31.5% and the structure of the existing crystallites to become more perfect. This made the values of certain mechanical properties of the tubes to increase even by as much as 30%. The tubes following such thermal treatment could be used in cables exposed to heavy‐duty operation in arduous environments, where a larger margin from the standpoint of mechanical properties is required. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2130–2134, 2002     

Studies on obtaining of aluminium ammonium calcium phosphates

Aluminium ammonium calcium phosphates were prepared with the use of AlCl₃, CaCO₃, H₃PO₄. The influence of the process parameters (pH 5 ± 3, the molar ratios of Ca²⁺:Al⁺³:PO₄^?3 in the substrates, respectively 0.31:0.62:1; 0.5:0.5:1; 0.72:0.36:1, temperature 40 ± 20 °C) on the phase composition and the product properties was determined. The process parameters that enable to obtain the material with expected physicochemical properties were determined based on the statistical evaluation of the experiments (fractional factorial design at three levels 3^(k?p)27). The phase composition of the obtained samples was studied with the use of XRD analysis. The specific surface area was calculated with the use of S_BET method and the particle size was determined by the laser scanning microscopy. The materials with the molar ratio of Al³⁺/NH₄⁺ and Al³⁺/Ca²⁺ in the range of 0.70–27.93 and 0.47–24.48, respectively, with an absorption oil number of 95–157 g/100 g paraffin oil, the S_BET within 25–118 m²/g, the pore volume within 0.14–0.74 cm³/g and the particle size in the range of 168–285 nm were obtained.     

Polyurethane/Polylactide-Based Electrospun Nonwovens as Carriers for Human Adipose-Derived Stromal Stem Cells and Chondrogenic Progenitor Cells

Articular cartilage dysfunctions are major cause of pain and disability and lead to serious health complications. Cell-based therapies are proposed as treatment methods for cartilage regeneration. In this study, we proposed polyurethane/poly(L-lactide-co-D, L-lactide)-based electrospun nonwovens as carriers for the delivery of human adipose-derived stromal stem cells. We found that 6:4 and 8:2 polyurethane/poly(L-lactide-co-D, L-lactide) initially enhance proliferative rate of human adipose-derived stromal stem cells, shorten their population doubling time, promote creation of functional chondrogenic nodules during chondrogenic differentiation, improve the collagen-2-to-collagen-1 protein ratio, and upregulate the expression of collagen-2 and aggrecan genes.     

The influence of electron beam irradiation,plastic deformation,and re‐irradiation on crystallinity degree,mechanical and sclerometric properties of GUR 1050 used for arthroplasty

The article describes the influence of an electron beam irradiation (I), plastic deformation (D), and re‐irradiation (R) on the properties of ultrahigh molecular weight polyethylene (GUR 1050). It was found that the modification through irradiation entailed a gradual increase in the degree of crystallinity (after irradiation–I). After plastic deformation and re‐irradiation (IDR) the degree of crystallinity decreases which had a direct influence on the mechanical properties. The polymer irradiation only (technique I) resulted in an increase in the maximum stress as compared with the material in the initial state. The application of deformation and re‐irradiation (technique IDR) allowed increasing the deformation resistance by more than 40%. Moreover, the irradiation with an electron beam resulted in the increase in hardness (H) and Young's modulus (E) proportionally to the applied irradiation dose and in the reduction of total indentation work (W_tot) and its components. After deformation and re‐irradiation the polyethylene hardness went down. The application of technique (I) caused an improvement to the material abrasion resistance (reduction of parameter PD–working scratch depth) with the increasing irradiation dose. The introduction of deformation and re‐irradiation did not have a material impact on parameter (PD) increasing at the same time elastic properties of UHMWPE (increase in parameter NPS–elastic recovery). Modification IDR has changed the wear mechanism (β) toward ploughing and has increased the abrasion‐resistance index (W_β) and also significantly reduced the coefficient of friction (μ) of GUR 1050. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43683.     

Kinetics of nucleation and growth of L-sorbose crystals in a continuous MSMPR crystallizer with draft tube: Size-independent growth model approach

The experimental data concerning kinetics of a continuous mass crystallization in L-sorbose - water system are presented and discussed. Influences of L-sorbose concentration in a feeding solution and mean residence time of suspension in a working volume of laboratory DT MSMPR crystallizer on the resulting crystal size distributions, thus on the nucleation and growth kinetics, were determined. The kinetic parameter values were evaluated on the basis of size-independent growth (SIG) kinetic model (McCabe’s ΔL law). It was observed that within the investigated range of crystallizer productivity (220–2,200 kg of L-sorbose crystals m⁻³ h⁻¹), a crystal product of mean size Lm from 0.22 to 0.28 mm and CV from 68.8 to 44.0% was withdrawn. The values of linear growth rate show increasing trend (from 6.6·10⁻⁸ to 7.6·10⁻⁸ m s⁻¹) with the productivity enlargement (assuming constant residence time τ=900 s). Occurrence of secondary nucleation phenomena within the circulated suspension, resulting from the crystals attrition and breakage was observed. The parameter values in a design equation, matching linear growth rate and suspension density with nucleation rate were determined.     

导流筒浆态连续结晶器内鸟粪石的反应结晶动力学——器内流体力学的影响

A laboratory-scale reaction-crystallization process of struvite synthesis from diluted water solution of Mg2+, and ions was studied. The research covered the tests of two original constructions of continuous jet-pump Draft Tube Magma (DTM)-type crystallizers with internal circulation of suspension (upward/downward). Interactions between constructional, hydrodynamic and kinetic factors were established and discussed. Nucleation and linear growth rates of struvite crystals were calculated on the basis of population density distribution. Kinetic model of idealized Mixed Suspension Mixed Product Removal (MSMPR) crystallizer considering the size-dependent growth mechanism was applied (Rojkowski hyperbolic equation). For comparison purposes the kinetic data corre-sponded to a simpler, continuous draft tube-type crystallizer equipped with propeller agitator were analyzed. It was concluded that crystal product of larger size was withdrawn from the jet-pump DTM crystallizer of the descending flow of suspension in a mixing chamber.