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1.
J Sci Food Agric ; 100(3): 1099-1105, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31667840

RESUMO

BACKGROUND: γ-Aminobutyric acid (GABA) is a non-protein amino acid with several functions in the human body. Although freeze-thawing could effectively accumulate GABA in soybean sprouts, the mechanism has not been revealed. The mechanism by which freeze-thawing enhances GABA accumulation in germinated soybean was revealed by evaluating GABA content, the activity of related synthesis enzymes, and the microstructure of the tissues and cells of sprouts. The germinated soybeans were treated at different temperatures (from -196 °C to 25 °C) for 12 h and then thawed at 25 °C for 6 h. RESULTS: The results showed that GABA content in frozen soybean sprouts did not change significantly before thawing. After thawing, the GABA content of sprouts increased by 83.9% and 82.9% when treated by liquid nitrogen flash freeze at - 80 °C for 12 h compared with the control (4 °C treatment for 12 h). The results indicated that GABA formation mainly occurred during thawing. However, glutamate decarboxylase (GAD), diamine oxidase (DAO), and aminoaldehyde dehydrogenase (AMADH) activity decreased during thawing. Based on the malonaldehyde (MDA) content and microstructure of sprouts, it was suggested that freezing at lower temperatures (< -20 °C) maintained the integrity of the cell structure, while the tissues and cell membranes were broken during thawing. CONCLUSION: These results could provide evidence for the hypothesis that GABA formation resulted from full contact between enzymes and substrates during thawing, rather than the contribution of higher enzyme activity. © 2019 Society of Chemical Industry.


Assuntos
Produção Agrícola/métodos , Sementes/química , Soja/crescimento & desenvolvimento , Ácido gama-Aminobutírico/metabolismo , Amina Oxidase (contendo Cobre)/análise , Amina Oxidase (contendo Cobre)/metabolismo , Temperatura Baixa , Congelamento , Germinação , Glutamato Descarboxilase/análise , Glutamato Descarboxilase/metabolismo , Malondialdeído/análise , Malondialdeído/metabolismo , Proteínas de Plantas/análise , Proteínas de Plantas/metabolismo , Sementes/crescimento & desenvolvimento , Sementes/metabolismo , Soja/química , Soja/metabolismo , Ácido gama-Aminobutírico/análise
2.
Toxicol Lett ; 319: 58-65, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31730884

RESUMO

This study proposes the application of the comet assay for the evaluation of DNA damage from frozen human whole blood samples that could be readily used in human biomonitoring and epidemiological studies. It was done on simply frozen whole blood samples collected from male volunteers (N = 60) aliquoted in small volumes and stored at -80 °C without the addition of cryopreservatives for a period of 5 years. To test the applicability of the alkaline comet assay for the evaluation of DNA damage in frozen whole blood, samples were quickly thawed at 37 °C and immediately embedded in an agarose matrix followed by an alkaline comet assay procedure. We concluded that the whole blood freezing and prolonged storage do not severely affect comet assay values, although background values were higher compared to our historical control data from the fresh whole blood. Even the influence of the variables tested, such as age, body mass index, smoking habit and alcohol consumption were in agreement with our previous data using fresh blood. The obtained results suggest that the comet assay could be applied to frozen blood samples, if properly stored, even for decades, which would certainly facilitate large-scale human biomonitoring and long-term epidemiological studies.


Assuntos
Preservação de Sangue/efeitos adversos , Sangue , Ensaio Cometa/métodos , Dano ao DNA , Adolescente , Adulto , Fatores Etários , Idoso , Índice de Massa Corporal , Criopreservação , Congelamento , Humanos , Estilo de Vida , Masculino , Pessoa de Meia-Idade , Monitorização Fisiológica , Adulto Jovem
3.
Food Chem ; 303: 125401, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31466031

RESUMO

Salt addition and thermal pretreatment were used to improve the freeze-thaw stability of Pickering emulsion gels (PEGs) stabilized by compound proteins. Thermal pretreatment with the presence of salt could promote the formation of gel-like structure and alter the interactions between the emulsion droplets of PEGs, sequentially increase the resistance of the PEGs to water separation, creaming, and oiling-off during freeze-thaw cycles (freeze at -20 °C for 22 h and thawing at 37 °C for 2 h), especially at higher salt levels (200 and 500 mM). Microstructures indicated that the presence of high salt concentration and heat pretreatment could help to maintain the gel-like structures of PEGs during freeze-thaw cycles. Overall, our results showed that novel viscoelastic food materials with good freeze-thaw stability can be produced by controlling the electrostatic interactions between the emulsion droplets and the gelation of emulsion gels. These materials may be useful for application in frozen food products.


Assuntos
Fixadores/química , Géis/química , Emulsões/química , Congelamento , Temperatura Alta , Óleos/química , Concentração Osmolar , Cloreto de Sódio/análise , Água/química
4.
Food Chem ; 308: 125570, 2020 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-31648089

RESUMO

The effect of pre-treatment (dipping and vacuum impregnation in lemon juice solution), freezing and frozen storage (FS) on single and total polyphenols (free and conjugated) content and antioxidant activity (AOA) of organic and conventional apples, was investigated. Fresh organic and conventional fruits showed different profiles of free and conjugated polyphenols while their total phenolic content and AOA were similar. Organic and conventional apple tissues showed different physiological responses to physical stresses described by changes in phenolic profiles. Vacuum impregnation in lemon juice affected the polyphenols extractability of both the organic and conventional apples and favored their enrichment with bioactive compounds (AOA = +11.5%). FS decreased the single and conjugated polyphenols content of the pre-treated apple samples and the effect was different between organic and conventional fruits. After FS, not pre-treated organic apples showed a lower AOA reduction than the conventional ones (-13% vs -25%), while no differences were found on pre-treated samples.


Assuntos
Antioxidantes/análise , Malus/química , Polifenóis/análise , Citrus/química , Alimentos Orgânicos/análise , Congelamento , Frutas/química , Sucos de Frutas e Vegetais , Vácuo
5.
Food Chem ; 308: 125571, 2020 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-31655480

RESUMO

Grape seed maturation involves the gradual oxidation of tannins, decreasing excessive bitterness and astringency in wine. In cool climates, this process is limited by the short growing season, affecting wine quality. A "freeze-thaw" treatment on seeds of red vinifera cultivars at veraison and harvest was used to evaluate the effect of oxidation and extractability on seed phenolic fractions. Freezing increased the extraction of total phenolics and o-diphenols quantified from fractionation (fraction 1, vacuolar tannins; fraction 2, hydrogen bonded tannins; fraction 3, covalently bonded tannins), especially at harvest. Despite this, colorimetry, microscopy, oxidation reactivity index (ORI), and correlations between the color index and fractions indicated that freezing disrupted vacuole integrity, enhancing oxidation in the seed coat. In conclusion, vacuolar tannins (which are the main seed phenolics extracted during fermentation) were highly correlated with seed color change, potentially providing information for winemaking in cool climate regions.


Assuntos
Extratos Vegetais/química , Taninos/isolamento & purificação , Vitis/química , Vinho/análise , Clima , Fermentação , Congelamento , Oxirredução , Fenóis/química , Sementes/química
6.
Food Chem ; 306: 125563, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31606626

RESUMO

The storage stability of two kinds of interesterified blend-based fast-frozen special fats (PS:SO-IBSF, PS:RO-IBSF) with varied triacylglycerols (TAGs) compositions under different temperatures for 4 weeks was investigated. Rancimat and peroxide values experiments indicated that both IBSFs display good oxidation stability throughout a 4-week storage. As for the physical properties of both IBSFs, the solid fat content and hardness decreased with the increase of storage temperature, and IBSFs still exhibited a viscoelastic solid-like behavior. X-ray diffraction results showed that crystal transformation from ß'- to ß-form was more serious when stored at 25 °C. The more content of ECN 50-type TAGs in PS:RO-IBSF is helpful to reduce its crystal transformation from ß'-to ß-form compared to PS:SO-IBSF. On the other hand, storage at 4 °C was beneficial for both IBSFs to keep their crystal network integrity, and the PS:RO-IBSF maintained better quality under the same storage conditions.


Assuntos
Gorduras/química , Cristalização , Esterificação , Congelamento , Oxirredução , Estresse Oxidativo , Temperatura Ambiente , Difração de Raios X
7.
Food Chem ; 306: 125641, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31606628

RESUMO

Temperature fluctuation is a common problem in the frozen storage of shrimp products. This study investigated the influence of carrageenan oligosaccharide (CO) and xylooligosaccharide (XO) on the growth and recrystallization of ice crystals in frozen peeled shrimp exposed to temperature fluctuations. Shrimp soaked with water and 3.0% (w/v) Na4P2O7 solution were designated as the negative and positive controls, respectively. Our data revealed that both CO- and XO-soaked shrimp had significant improvements in thawing and cooking loss, myofibrillar protein content, Ca2+-ATPase activity, and textural variables when exposed to temperature fluctuations compared to control samples. Microstructural imaging indicated that soaking the shrimp in CO and XO slowed the progression of damage caused to tissue myofibrils by large ice crystals, as well as inhibited the growth and recrystallization of ice crystals in muscle tissues. SDS-PAGE analysis confirmed that treatment with the oligosaccharides exhibited marked effects on the stability of muscle proteins and inhibited the degradation of muscle proteins affected by the temperature fluctuations. Based on these data, we hypothesize that the incorporated CO and XO may bind to muscle proteins and capture water molecules in the myofibrillar network through hydrogen bonding, thereby suppressing the myofibrillar denaturation and tissue structure destruction induced by the growth and recrystallization of ice crystals.


Assuntos
Carragenina/química , Glucuronatos/química , Oligossacarídeos/química , Penaeidae/química , Animais , Congelamento , Ligações de Hidrogênio , Gelo/análise , Temperatura Ambiente , Água/química
8.
Sud Med Ekspert ; 62(6): 53-57, 2019.
Artigo em Russo | MEDLINE | ID: mdl-31825334

RESUMO

The authors propose a new express method of low-temperature sample preparation based on the use of extractive freezing-out combined with a sample centrifugation as a stage of a preliminary preparation of a biological object (cadaveric liver, kidneys). The method made it possible to minimize sufficiently the so-called chemical noise of endogenous coextractive substances and to improve sufficiently the conditions of the GC-MS method.


Assuntos
Técnicas Biossensoriais , Manejo de Espécimes , Congelamento , Cromatografia Gasosa-Espectrometria de Massas , Humanos
9.
Ying Yong Sheng Tai Xue Bao ; 30(12): 4195-4201, 2019 Dec.
Artigo em Chinês | MEDLINE | ID: mdl-31840465

RESUMO

The stability of 3-5 mm aggregates of black soil collected from Heilongjiang Province were analyzed by Le Bissonnais method under different freeze-thaw cycle treatments (0, 1, 3, 5 and 9). The aggregate porosity were measured by wax-coated method. The results showed that the contents of different size aggregates fluctuated with the freeze-thaw cycles, and the variation coefficient of aggregate content turned stable gradually. There were significant differences of the content of above 0.25 mm aggregate among the treatments of fast wetting, slow wetting, and wet stirring. Aggregate porosity increased with increasing freeze-thaw cycles, ranging from 32.4% to 41.4%. Low variation of aggregate contents occurred in different breakdown patterns with increasing freeze-thaw cycles. There was negative correlation between porosity and mean weight diameter, suggesting the aggregate porosity was important in the aggregate stability under freeze-thaw condition.


Assuntos
Solo , Congelamento
10.
Sci Total Environ ; 694: 133732, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31756836

RESUMO

Currently, little is known about soil improvement by biochar in seasonally frozen soil areas. It is not clear whether the effects of biochar application on soil physical properties differ based on application period. Therefore, the purpose of this study was to explore the effects of biochar on soil structure and water retention in cold regions during different application periods. Three biochar applications during different periods were set up through field trials (A: in the early stage of freezing, B: in the middle period of thawing and C: addition of half of the biochar in the early stage of freezing and other half in the middle period of thawing), including four biochar application rates (3, 6, 9 and 12 kg·m-2), and no biochar was applied as a control (CK). The results showed that the selection of the biochar application period had a significant effect on the soil structure, but there was no significant difference in the stability of the soil structure. Biochar significantly increased the total porosity (TP) and the content of aggregates with diameters >0.25 mm in the soil, and all 9 kg·m-2 biochar treatments showed the best structural stability index. The improvement of the soil structure led to the enhancement of the water storage capacities. The plant available water content (PAWC) increased from 0.0638 to 0.0927-0.1767 cm3·cm-3, and this result was significantly related to the increases in soil TP and large aggregates (LAs: >2 mm). The optimum field capacity (FC = 0.372 cm3·cm-3) was obtained when the applied amount was 9 kg·m-2. This was beneficial for the stable storage of soil moisture. However, compared with the CK, none of the treatments in area B increased the liquid water content in the field soil. In summary, we suggest that treatment C9 is the most suitable method for application in seasonally frozen soil areas.


Assuntos
Carvão Vegetal/química , Congelamento , Solo/química , Água/análise
11.
AAPS PharmSciTech ; 20(8): 328, 2019 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31673810

RESUMO

This work presents a new user-friendly lyophilization simulation and process optimization tool, freely available under the name LyoPRONTO. This tool comprises freezing and primary drying calculators, a design-space generator, and a primary drying optimizer. The freezing calculator performs 0D lumped capacitance modeling to predict the product temperature variation with time which shows reasonably good agreement with experimental measurements. The primary drying calculator performs 1D heat and mass transfer analysis in a vial and predicts the drying time with an average deviation of 3% from experiments. The calculator is also extended to generate a design space over a range of chamber pressures and shelf temperatures to predict the most optimal setpoints for operation. This optimal setpoint varies with time due to the continuously varying product resistance and is taken into account by the optimizer which provides varying chamber pressure and shelf temperature profiles as a function of time to minimize the primary drying time and thereby, the operational cost. The optimization results in 62% faster primary drying for 5% mannitol and 50% faster primary drying for 5% sucrose solutions when compared with typical cycle conditions. This optimization paves the way for the design of the next generation of lyophilizers which when coupled with accurate sensor networks and control systems can result in self-driving freeze dryers.


Assuntos
Química Farmacêutica/métodos , Manitol/síntese química , Sacarose/síntese química , Dessecação/métodos , Liofilização/métodos , Congelamento , Temperatura Alta , Temperatura Ambiente
12.
Environ Sci Technol ; 53(23): 13802-13811, 2019 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-31697066

RESUMO

Freezing is essential in the light-mediated transformation of organic pollutants. However, the effects of the freezing process on the reduction of Ag+ by natural organic matter (NOM) remains unclear, causing significant uncertainties in the natural formation of silver nanoparticles (AgNPs). This study investigated the sunlight-induced reduction of Ag+ by NOM under natural or controlled freezing processes. Natural (outdoor) freezing experiments demonstrated intense aggregation and precipitation of AgNPs in three aqueous media, including a NOM solution and two river water samples, under natural sunlight irradiation. Indoor experiments under simulated sunlight irradiation and controlled freezing processes showed that freezing at -20 °C and repeated freeze-thaw cycles (-20 to 4 °C) drastically accelerated the formation and growth of AgNPs compared to maintenance at 4 °C. Finally, under the natural freezing process, commercial AgNPs were found to influence the redox reduction of Ag+ probably through a reduction in dissolution rates and homoaggregation with AgNPs newly formed in the river water samples. Additionally, the enhancement effect of freezing on AgNP formation was confirmed in the presence of Ag+ and AgNPs both at environmentally relevant concentration levels, especially upon light irradiation. This work emphasizes the importance of freezing processes on the natural formation of AgNPs.


Assuntos
Nanopartículas Metálicas , Prata , Congelamento , Oxirredução , Luz Solar
13.
Yonsei Med J ; 60(11): 1067-1073, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31637889

RESUMO

PURPOSE: Bone flap resorption (BFR) after cranioplasty with an autologous bone flap (ABF) is well known. However, the prevalences and degrees of BFR remain unclear. This study aimed to evaluate changes in ABFs following cranioplasty and to investigate factors related with BFR. MATERIALS AND METHODS: We retrospectively reviewed 97 patients who underwent cranioplasty with frozen ABF between January 2007 and December 2016. Brain CT images of these patients were reconstructed to form three-dimensional (3D) images, and 3D images of ABF were separated using medical image editing software. ABF volumes on images were measured using 3D image editing software and were compared between images in the immediate postoperative period and at postoperative 12 months. Risk factors related with BFR were also analyzed. RESULTS: The volumes of bone flaps calculated from CT images immediately after cranioplasty ranged from 55.3 cm³ to 175 cm³. Remnant bone flap volumes at postoperative 12 months ranged from 14.2% to 102.5% of the original volume. Seventy-five patients (77.3%) had a BFR rate exceeding 10% at 12 months after cranioplasty, and 26 patients (26.8%) presented severe BFR over 40%. Ten patients (10.3%) underwent repeated cranioplasty due to severe BFR. The use of a 5-mm burr for central tack-up sutures was significantly associated with BFR (p<0.001). CONCLUSION: Most ABFs after cranioplasty are absorbed. Thus, when using frozen ABF, patients should be adequately informed. To prevent BFR, making holes must be kept to a minimum during ABF grafting.


Assuntos
Transplante Ósseo , Craniotomia , Congelamento , Imagem Tridimensional , Retalhos Cirúrgicos , Adolescente , Adulto , Reabsorção Óssea/diagnóstico por imagem , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pacientes , Estudos Retrospectivos , Crânio/diagnóstico por imagem , Crânio/cirurgia , Software , Cirurgiões , Transplante Autólogo , Adulto Jovem
14.
AAPS PharmSciTech ; 20(8): 322, 2019 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-31650263

RESUMO

The objectives of this work were to prepare a 5 wt% lidocaine-diclofenac ionic liquid drug-loaded gelatin/poly(vinyl alcohol) transdermal patch using a freeze/thaw method and to evaluate its physicochemical properties, in vitro release of lidocaine and diclofenac, and stability test. The lidocaine-diclofenac ionic liquid drug was produced by the ion pair reaction between the hydrochloride salts of lidocaine and the sodium salts of diclofenac. The thermal properties of the final drug product were significantly changed from the primary drugs. The ionic liquid drug could be dissolved in water and mixed in a polymer solution. The resulting transdermal patch was then exposed to 10 cycles of freezing and thawing preparation at - 20°C for 8 h and at 25°C for 4 h, respectively. As a result, it was found that the lidocaine-diclofenac ionic liquid drug-loaded transdermal patch showed good physicochemical properties and could feasibly be used in pharmaceutical applications. The lidocaine-diclofenac ionic liquid drug was not affected by the properties of the transdermal patch due to the lack of chemical interaction between polymer base and drug. The high drug release values of both lidocaine and diclofenac were controlled by the gelatin/poly(vinyl alcohol) transdermal patch. The patch showed good stability over the study period of 3 months when kept at 4°C or under ambient temperature.


Assuntos
Diclofenaco/farmacocinética , Gelatina/farmacocinética , Líquidos Iônicos/farmacocinética , Lidocaína/farmacocinética , Álcool de Polivinil/farmacocinética , Adesivo Transdérmico , Administração Cutânea , Anestésicos Locais/química , Anestésicos Locais/farmacocinética , Anti-Inflamatórios não Esteroides/química , Anti-Inflamatórios não Esteroides/farmacocinética , Preparações de Ação Retardada/química , Preparações de Ação Retardada/farmacocinética , Diclofenaco/química , Combinação de Medicamentos , Liberação Controlada de Fármacos , Congelamento , Gelatina/química , Líquidos Iônicos/química , Lidocaína/química , Álcool de Polivinil/química
15.
J Dairy Sci ; 102(12): 10779-10789, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31606218

RESUMO

Whole milk powder (WMP) is a universal raw material component that can overcome the problem of seasonality of raw milk. It can be used to provide high-nutritional products to remote areas experiencing a raw milk shortage. Its long shelf life depends on the conditions of storage and transportation, which are recommended to be carried out in a range from 0 to 10°C. At higher temperatures, the quality of WMP deteriorates because of a substantial increase in the degradation of fat and protein fractions. A range of low negative temperatures for storage have not been systematically investigated. Previous studies have shown that freezing WMP results in protein denaturation, crystallization of lactose, and extraction of free fat, all of which reduce the quality characteristics of the product, including deterioration of solubility, quick rancidification, and microbiological changes. However, these previous studies did not simulate the possible situations of transportation and storage of milk powder at low negative temperatures that occur in practice. Given the volume of transportation, distances and climatic characteristics of transportation routes play an important role in WMP preservation. In this study, we simulated storage and transport of WMP at -20°C. The samples were periodically thawed to 10 and 20°C and examined for physicochemical, functional-technological, thermodynamic, microbiological, and organoleptic parameters. Based on our results, storage of WMP at -20°C for 40 d did not have a significant effect on its qualitative characteristics. We observed some compaction of product structure and clustering or clumping, which was reversible by slight mechanical impact. Artificial contamination of the packaging surface with yeast and molds, followed by thawing of the samples, indicated the absence of the contaminants, which was explained by possible redistribution of moisture in the system.


Assuntos
Laticínios , Armazenamento de Alimentos , Leite , Animais , Bovinos , Congelamento , Leite/química , Pós , Temperatura Ambiente
16.
J Environ Qual ; 48(4): 889-898, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31589665

RESUMO

Reducing agricultural runoff is important year round, particularly on landscapes that receive wintertime applications of manure. No-tillage systems are typically associated with reduced runoff loads during the growing season, but surface roughness from fall tillage may aid infiltration on frozen soils by providing surface depressional storage. The timing of winter manure applications may also affect runoff, depending on snow and soil frost conditions. Therefore, the objective of this study was to evaluate runoff and nutrient loads during the freezing season from combinations of tillage and manure application timings. Six management treatments were tested in south-central Wisconsin during the winters of 2015-2016 and 2016-2017 with a complete factorial design: two tillage treatments (fall chisel plow vs. no-tillage) and three manure application timings (early December, late January, and unmanured). Nutrient loads from winter manure application were lower on chisel-plowed versus untilled soils during both monitoring years. Loads were also lower from manure applied to soils with less frost development. Wintertime manure applications pose a risk of surface nutrient losses, but fall tillage and timing applications to thawed soils can help reduce loads.


Assuntos
Esterco , Nutrientes , Agricultura , Congelamento , Fósforo , Estações do Ano , Solo , Wisconsin
17.
J Chem Phys ; 151(12): 124706, 2019 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-31575160

RESUMO

Most theories of the binding of molecules to surfaces or for the association between molecules treat the binding species as structureless entities and neglect their rigidity and the changes in their stiffness induced by the binding process. The binding species are also taken to be "ideal," meaning that the existence of van der Waals interactions and changes in these interactions upon molecular binding are also neglected. An understanding of the thermodynamics of these multifunctional molecular binding processes has recently come into focus in the context of the molecular binding of complex molecules, such as dendrimers and DNA grafted nanoparticles, to surfaces where the degree of binding cooperativity and selectivity, as well as the location of the binding transition, are found to be sensitive to the number of binding units constrained to a larger scale polymeric scaffold. We address the fundamental problem of molecular binding by extending classical Langmuir theory to describe the particular example of the reversible binding of semiflexible polymer chains to a solid substrate under melt conditions. The polymer chains are assumed to have a variable number N of binding units (segments) and to exhibit variable bending energies and van der Waals interactions in the bulk and on the surface, in addition to strong directional interactions with the surface. The resulting generalized Langmuir theory is applied to the examination of the influence of the chain connectivity of ideal polymers on the surface coverage Θ, transition binding temperature T1/2 at which Θ = 1/2, and on the derivative |dΘ/dT|T=T1/2 and the constant volume specific heat of binding, Cv bind, measures of the cooperativity and "sharpness" of the binding transition, respectively. Paper II is devoted to the impact of the van der Waals attractive interactions and chain stiffness on the reversible binding of nonideal polymer chains to a solid surface, including the enthalpy-entropy compensation phenomenon observed experimentally in many molecular and particle binding processes.


Assuntos
Modelos Químicos , Polímeros/química , Adsorção , Congelamento , Termodinâmica
18.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 36(5): 803-809, 2019 Oct 25.
Artigo em Chinês | MEDLINE | ID: mdl-31631629

RESUMO

Cell freeze-drying can be divided into the freezing and drying processes. Mechanical damage caused by ice crystals and damage from solute during freezing shall not be ignored and lyoprotectants are commonly used to reduce those damages on cells. In order to study the mechanism of lyoprotectants to protect cells and determine an optimal lyoprotectant formula, the thermophysical properties and percentage of unfrozen water of different lyoprotectants in freezing were investigated with differential scanning calorimeter (DSC). The survival rate indicated by trypan blue exclusion test and cell-attachment rate after 24 h using different lyoprotectants to freeze hepatoma Hep-G 2 cells were measured after cell cryopreservation. The results show that 40% (W/V) PVP + 10% (V/V) glycerol + 15% (V/V) fetal bovine serum + 20% (W/V) trehalose formula of lyoprotectant demonstrate the best effect in protecting cells during freezing, for cell-attachment rate after 24 h is 44.56% ± 2.73%. In conclusion, the formula of lyoprotectant mentioned above can effectively protect cells.


Assuntos
Criopreservação , Crioprotetores/química , Congelamento , Trealose/química , Varredura Diferencial de Calorimetria , Liofilização , Células Hep G2 , Humanos
19.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 36(5): 827-833, 2019 Oct 25.
Artigo em Chinês | MEDLINE | ID: mdl-31631632

RESUMO

In the present study, the performance of the liquid nitrogen frozen and thinned bovine pericardium was studied and compared with the porcine pericardium. The microstructure and mechanical properties of the bovine pericardium were observed and tested by hematoxylin-eosin (HE) staining and tensile test respectively. In all conditions, porcine pericardium was selected as a control group. The results showed that there was little difference in the performance of bovine pericardium after being frozen by liquid nitrogen. The secant modulus and ultimate strength of the thinned bovine pericardium were similar to those of porcine pericardium, however, the elastic modulus was a little higher than porcine pericardium. The study suggested that the performance of the thinned bovine pericardium was similar to those of porcine pericardium. It was easy for the thinned bovine pericardium to obtain a relatively ideal thickness and expected performance, therefore, the thinned bovine pericardium can be used as the materials of transcatheter aortic valve leaflets.


Assuntos
Bioprótese , Congelamento , Próteses Valvulares Cardíacas , Pericárdio/fisiologia , Animais , Valva Aórtica , Bovinos , Módulo de Elasticidade , Nitrogênio , Suínos
20.
Dokl Biochem Biophys ; 487(1): 269-271, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31559595

RESUMO

The freezing tolerance of Arabidopsis thaliana (L.) Heynh. was studied in relation to functioning of the ethylene signaling pathway. Constitutive freezing tolerance was compared in wild-type plants (ecotype Col-0) and ethylene-insensitive mutants etr1-1 and ein2-1. For the first time it was established that the ethylene-insensitive mutants had a 25-30% lower net photosynthesis rate, a decreased content of soluble sugars, and, as a result, a lower freezing tolerance. Our work provides evidence that the perception and transduction of ethylene signal are necessary for constitutive tolerance of Arabidopsis to low temperature.


Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Arabidopsis/fisiologia , Etilenos/metabolismo , Congelamento , Mutação , Receptores de Superfície Celular/genética , Arabidopsis/citologia , Arabidopsis/metabolismo , Transdução de Sinais/genética , Fatores de Tempo
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