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Lucía Abarca-Cabrera,Paula Fraga-García,Sonja Berensmeier 한국생체재료학회 2021 생체재료학회지 Vol.25 No.2
The major interest in nanoparticles as an application platform for biotechnology arises from their high surface-tovolume ratio. Iron oxide nanoparticles (IONPs) are particularly appealing due to their superparamagnetic behavior, which enables bioseparation using external magnetic fields. In order to design advanced biomaterials, improve binding capacities and develop innovative processing solutions, a thorough understanding of the factors governing organic-inorganic binding in solution is critical but has not yet been achieved, given the wide variety of chemical and physical influences. This paper offers a critical review of experimental studies of the interactions between low cost IONPs (bare iron oxides, silica-coated or easily-functionalized surfaces) and the main groups of biomolecules: proteins, lipids, nucleic acids and carbohydrates. Special attention is devoted to the driving forces and interdependencies responsible of interactions at the solid-liquid interface, to the unique structural characteristics of each biomolecular class, and to environmental conditions influencing adsorption. Furthermore, studies focusing on mixtures, which are still rare, but absolutely necessary to understand the biocorona, are also included. This review concludes with a discussion of future work needed to fill the gaps in knowledge of bio-nano interactions, seeking to improve nanoparticles’ targeting capabilities in complex systems, and to open the door for multipurpose recognition and bioseparation processes.
( Jorge Frias ),( Duarte Toubarro ),( Alexandra Fraga ),( Claudia Botelho ),( Jose Teixeira ),( Jorge Pedrosa ),( Nelson Simoes ) 한국미생물생명공학회(구 한국산업미생물학회) 2021 Journal of microbiology and biotechnology Vol.31 No.2
Fibrinolytic enzymes with a direct mechanism of action and safer properties are currently requested for thrombolytic therapy. This paper reports on a new enzyme capable of degrading blood clots directly without impairing blood coagulation. This enzyme is also non-cytotoxic and constitutes an alternative to other thrombolytic enzymes known to cause undesired side effects. Twenty-four Bacillus isolates were screened for production of fibrinolytic enzymes using a fibrin agar plate. Based on produced activity, isolate S127e was selected and identified as B. subtilis using the 16S rDNA gene sequence. This strain is of biotechnological interest for producing high fibrinolytic yield and consequently has potential in the industrial field. The purified fibrinolytic enzyme has a molecular mass of 27.3 kDa, a predicted pI of 6.6, and a maximal affinity for Ala-Ala-Pro-Phe. This enzyme was almost completely inhibited by chymostatin with optimal activity at 48℃ and pH 7. Specific subtilisin features were found in the gene sequence, indicating that this enzyme belongs to the BPN group of the S8 subtilisin family and was assigned as AprE127. This subtilisin increased thromboplastin time by 3.7% (37.6 to 39 s) and prothrombin time by 3.2% (12.6 to 13 s), both within normal ranges. In a whole blood euglobulin assay, this enzyme did not impair coagulation but reduced lysis time significantly. Moreover, in an in vitro assay, AprE127 completely dissolved a thrombus of about 1 cc within 50 min and, in vivo, reduced a thrombus prompted in a rat tail by 11.4% in 24 h compared to non-treated animals.
Determination of diarrhetic shellfish toxins in various dinoflagellate species
Lee, Jong-Soo,Igarashi, Teruo,Fraga, Santiago,Dahl, Einal,Hovgaard, Peter,Yasumoto, Takeshi 國立統營水産專門大學 附設 水産科學硏究所 1989 수산과학연구소보고 Vol.1 No.-
Sixteen species of unialgal samples of dinoflagellate, either wild or cultured, were tested for production of diarrhetic shellfish toxins such as okadaic acid (OA), dinophysistoxin-1 (DTX1), and pectenotoxins(PTXs). Determination of micro-quantities of the toxins was facilitated by fluorometry and UV HPLC. Seven Dinophysis species were confirmed to produce either OA or DTX1, or both. Toxin content and composition varied regionally and seasonally. Intraspecies variation was also observed among cultured strains of prorocentrum lima. PTX2 was the only toxin detected among PTX family, and D. fortii was the only species to contain this toxin.
Critical Configurations for a System of Semidegenerate Fermions
Carlos R. Arg¨uelles,Remo Ruffini,Bernardo M. O. Fraga 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.6
We study an isothermal system of semidegenerate self-gravitating fermions in general relativity. Such systems present mass density solutions with a central degenerate core, a plateau and a tail, thislast following a power law behavior r−2. The different solutions are governed by the free parametersof the model: the degeneracy and the temperature parameters at the center and the particle mass m. We then analyze in detail the free parameter space for a fixed m in the keV region, by studying theone-parameter sequences of equilibrium configurations up to the critical point, which is representedby the maximum in a central density (0) vs. core mass (Mc) diagram. We show that for fullydegenerate cores, the known expression for the critical core mass Mcrc / m3pl/m2 is obtained, whilefor low degenerate cores, the critical core mass increases, showing temperature effects in a nonlinearway. The main result of this work is that when applying this theory to model the distribution ofdark matter in galaxies from the very center to the outer halos, we do not find any critical corehaloconfiguration of self-gravitating fermions that would be able to explain the super-massive darkobject in their centers and the outer halo simultaneously.
Fibers of Ultra-High Molecular Weight Polyethylene Obtained by Gel Spinning with Polyalphaolefin Oil
Naiara Pirahi da Silva Chagas,Geíza Lopes da Silva Fraga,Maria de Fátima Vieira Marques 한국고분자학회 2020 Macromolecular Research Vol.28 No.12
The rapid growth of polymer technology has provided viable and more straightforward methods for the development of ultra-high molecular weight polyethylene (UHMWPE) fibers. The gel spinning process yields fibers with improved properties and less impact on the environment. The material used as a solvent for the swelling of the polymer reveals an excellent potential for the processing of new fibers. In the present work, the influence of a new spinning solvent based on polyalphaolefin (PAO100) in the UHMWPE was evaluated. All fibers were obtained by extrusion in concentrations of 0.04 to 60% m/m of PAO100 oil, with screw rotation speed increasing from 20 to 60 rpm, leaving the extruder nozzle of 1.82 mm. Besides, n-hexane was used in the process of extracting oil from UHMWPE fibers. The fibers did not undergo to the drawing process. The results show that the fibers containing 20-40% m/m of PAO100 presented higher linear density, indicating the orientation of the crystals in a compact morphology and the higher relaxation after leaving the nozzle, increasing die-swell. After extraction of PAO100 with n-hexane, huge voids were observed in SEM images, which indicates the alignment of subfibers inside the fiber. The average size of the crystallite related to the polyethylene orthorhombic crystal increased significantly, showing that the number of entanglements decreased. The results indicate that PAO100 oil acts as a lubricant, increasing the mobility of the chains, leading to higher crystallization. The present study presents exciting findings on the effects of PAO100 oil on the morphology, crystalline structures, and thermal properties of UHMWPE fibers, pointing out the oil concentration necessary for the formation of fibers with higher crystallinity and thermal resistance.
On the Distribution of Dark Matter in Galaxies: Quantum Treatments
Carlos R. Arg¨uelles,Remo Ruffini,Ivan Siutsou,Bernardo Fraga 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.6
The problem of modeling the distribution of dark matter in galaxies in terms of equilibriumconfigurations of collisionless self-gravitating quantum particles is considered. We first summarizethe pioneering model of a Newtonian self-gravitating Fermi gas in thermodynamic equilibriumdeveloped by Ruffini and Stella (1983), which is shown to be a generalization of the King modelfor fermions. We further review the extension of the former model developed by Gao, Merafinaand Ruffini (1990), done for any degree of fermion degeneracy at the center (0), within generalrelativity. Finally, we present here for the first time the solutions of the density profiles and rotationcurves corresponding to the model of Gao et al. Those solutions have a definite mass Mh and acircular velocity vh at the halo radius rh of the configurations, which are typical of spiral galaxies. This treatment allows us to determine a novel core-halo morphology for the dark-matter profiles,as well as a novel bound on the particle mass associated with those profiles.
Redaelli, M.,Kepler, S. O.,Costa, J. E. S.,Winget, D. E.,Handler, G.,Castanheira, B. G.,Kanaan, A.,Fraga, L.,Henrique, P.,Giovannini, O.,Provencal, J. L.,Shipman, H. L.,Dalessio, J.,Thompson, S. E.,Mu Blackwell Publishing Ltd 2011 Monthly notices of the Royal Astronomical Society Vol.415 No.2
<P><B>ABSTRACT</B></P><P>PG 1351+489 is one of the 20 DBVs – pulsating helium‐atmosphere white dwarf stars – known and has the simplest power spectrum for this class of star, making it a good candidate to study cooling rates. We report accurate period determinations for the main peak at 489.334 48 s and two other normal modes using data from the Whole Earth Telescope (WET) observations of 1995 and 2009. In 2009, we detected a new pulsation mode and the main pulsation mode exhibited substantial change in its amplitude compared to all previous observations. We were able to estimate the star's rotation period, of 8.9 h, and discuss a possible determination of the rate of period change of (2.0 ± 0.9) × 10<SUP>−13</SUP> s s <SUP>−1</SUP>, the first such estimate for a DBV.</P>