943 resultados para gelatin-SDS-PAGE


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Instructions for Authors. Back cover with map.

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Hydrogels are promising materials for bioengineering applications, and are good model materials for the study of hydrated biological tissues. As these materials often have a structural function, the measurement of their mechanical properties is of fundamental importance. In the present study gelatin gels reinforced with ceramic microspheres are produced and their poroviscoelastic response in spherical indentation is studied. The constitutive responses of unreinforced gels are determined using inverse finite element modeling in combination with analytical estimates of material parameters. The behavior of composite gels is assessed by both analytical and numerical homogenization. The results of the identification of the constitutive parameters of unreinforced gels show that it is possible to obtain representative poroviscoelastic parameters by spherical indentation without the need for additional mechanical tests. The agreement between experimental results on composite gelatin and the predictions from homogenization modeling show that the adopted modeling tools are capable of providing estimates of the poroviscoelastic response of particle-reinforced hydrogels.

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A biomimetic reactor has been developed to synthesize hydroxyapatite- gelatin (HAP-GEL) nanocomposites that mimic ultra-structures of natural bone. We hypothesize that in the reactor, gelatin concentration controls morphology and packing structures of HAP crystals. To test the hypothesis, three types of mechanical tests were conducted, including nanoindentation, compression, and fracture tests. Nanoindentation tests in conjunction with computer modeling were used to assess effects on gelatin-induced microstructures of HAP. The results showed that increasing gelatin content increased both the plane strain modulus and the fracture toughness. The gelatin appeared to shorten the HAP crystal distance, which consolidated the internal structure of the composite and made the material more rigid. The fracture toughness KIC increased partially due to the effect of fiber bridging between gelatin molecules. The highest fracture toughness (1.12 MPa·1/2) was equivalent to that of pure hydroxyapatite. The compressive strength of the HAP-GEL (107.7±26.8 MPa) was, however, less sensitive to microstructural changes and was within the range of natural cortical bone (human 170 MPa, pig: 100 MPa). The compression strength was dominated by void inclusions while the nanoindentation response reflected ultra-structural arrangement of the crystals. The gelatin concentration is likely to modify crystal arrangement as demonstrated in TEM experiments but not void distribution at macroscopic levels. © 2006 Materials Research Society.

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经sephadex G-75凝胶过滤、QAE-Sephadex A-50和CM-Sephadex C-25离子交换步骤,从湖南产尖吻蝮(Deinagkistrodon acutus)蛇毒中纯化出两个出血毒素,被命名为HaHT-1和HaHT-2。用聚丙烯酰胺凝胶电泳(PAGE)和SDS-聚丙烯酰胺凝胶电泳鉴定呈单一的蛋白染色带。两个出血毒素的分子量相同,均为 23.5kDa。等电聚焦电泳测定它们的等电点分别为5.6和5.2。HaHT-1和HaHT-2均具有较强的出血活性(MHD分别为0.5和0.8μg),都有酪蛋白水解活力,无精氨酸酯酶、胆碱酯酶和磷脂酶A_2活力。用CD谱测定HaHT-l和HaHT-2的溶液构象,HaHT-1的α-螺旋、β-折叠和无规卷曲分别为36.9%、35.5%和27.6%,而HaHT-2的α-螺旋、β-折叠和无规卷曲分别为23.4%、31.3%和45.3%。pH的变化对它们构象有影响,在pH2-11范围内,酸性比碱性大。随着酸性或碱性的增加其α-螺旋含量减少,无规卷曲增加,β-折叠结构变化不大。

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The composite nature of mineralized natural materials is achieved through both the microstructural inclusion of an organic component and an overall microstructure that is controlled by templating onto organic macromolecules. A modification of an existing laboratory technique is developed for the codeposition of a CaCO3-gelatin composite with a controllable organic content. First, calibration curves are developed to determine the organic content of a CaCO3-gelatin composite from infrared spectra. Second, a CaCO3-gelatin composite is deposited on either glass coverslips or demineralized eggshell membranes using an automated alternating soaking process. Electron microscopy images and use of the infrared spectra calibration curves show that by altering the amount of gelatin in the ionic growth solutions, the final organic component of the mineral can be regulated over the range of 1-10%, similar to that of natural eggshell. © 2012 Materials Research Societ.

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A severe shortage of good quality donor cornea is now an international crisis in public health. Alternatives for donor tissue need to be urgently developed to meet the increasing demand for corneal transplantation. Hydrogels have been widely used as scaffolds for corneal tissue regeneration due to their large water content, similar to that of native tissue. However, these hydrogel scaffolds lack the fibrous structure that functions as a load-bearing component in the native tissue, resulting in poor mechanical performance. This work shows that mechanical properties of compliant hydrogels can be substantially enhanced with electrospun nanofiber reinforcement. Electrospun gelatin nanofibers were infiltrated with alginate hydrogels, yielding transparent fiber-reinforced hydrogels. Without prior crosslinking, electrospun gelatin nanofibers improved the tensile elastic modulus of the hydrogels from 78±19 kPa to 450±100 kPa. Stiffer hydrogels, with elastic modulus of 820±210 kPa, were obtained by crosslinking the gelatin fibers with carbodiimide hydrochloride in ethanol before the infiltration process, but at the expense of transparency. The developed fiber-reinforced hydrogels show great promise as mechanically robust scaffolds for corneal tissue engineering applications.

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A severe shortage of good quality donor cornea is now an international crisis in public health. Alternatives for donor tissue need to be urgently developed to meet the increasing demand for corneal transplantation. Hydrogels have been widely used as scaffolds for corneal tissue regeneration due to their large water content, similar to that of native tissue. However, these hydrogel scaffolds lack the fibrous structure that functions as a load-bearing component in the native tissue, resulting in poor mechanical performance. This work shows that mechanical properties of compliant hydrogels can be substantially enhanced with electrospun nanofiber reinforcement. Electrospun gelatin nanofibers were infiltrated with alginate hydrogels, yielding transparent fiber-reinforced hydrogels. Without prior crosslinking, electrospun gelatin nanofibers improved the tensile elastic modulus of the hydrogels from 78±19. kPa to 450±100. kPa. Stiffer hydrogels, with elastic modulus of 820±210. kPa, were obtained by crosslinking the gelatin fibers with carbodiimide hydrochloride in ethanol before the infiltration process, but at the expense of transparency. The developed fiber-reinforced hydrogels show great promise as mechanically robust scaffolds for corneal tissue engineering applications. © 2013 Elsevier Ltd.

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A severe shortage of donor cornea is now an international crisis in public health. Substitutes for donor tissue need to be developed to meet the increasing demand for corneal transplantation. Current attempts in designing scaffolds for corneal tissue regeneration involve utilization of expensive materials. Yet, these corneal scaffolds still lack the highly-organized fibrous structure that functions as a load-bearing component in the native tissue. This work shows that transparent nanofiber-reinforced hydrogels could be developed from cheap, non-immunogenic and readily available natural polymers to mimic the cornea's microstructure. Electrospinning was employed to produce gelatin nanofibers, which were then infiltrated with alginate hydrogels. Introducing electrospun nanofibers into hydrogels improved their mechanical properties by nearly one order of magnitude, yielding mechanically robust composites. Such nanofiber-reinforced hydrogels could serve as alternatives to donor tissue for corneal transplantation.

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通过Sephadex G-75凝胶过滤,QAE-Sephadex A-50和CM_Sephadex C-25离子交换的步骤,我们从湖南产尖吻蝮(Dienagkistrodon acutus)蛇毒中纯化出两个出血毒素,分别称之为DaHT-1和DaHT-2。在聚丙烯酰胺凝胶电泳(PAGE)和SDS-聚丙烯酰胺凝胶电泳中均呈单一蛋白带,显示两个出血毒素皆为电泳纯。DaHT-1和DaHT-2的分子量相同,都为23,500道尔顿,具有相似的氨基酸组成,其中酸性氨基酸(Asx和GLx)分别占23%和24%。经等电聚焦(IEF)测得它们的等电点分别为5.6和5.2。两个出血毒素具有较强的出血活性(MHD分别为0.5和0.8μg),都具蛋白水解酶活力,无精氨酸水解酶和PLA~2活性,但蛋白水解酶活性与出血活性并非正相关。DaHT-1,DaHT-2的最适温度分别为35 ℃,40 ℃;最适pH为6-9。对热不稳定,温度变高于60 ℃,活性完全丧失。在中性和碱性条件下稳定,在酸性条件下不稳定,pH<3,出血活性丧失。EDTA完全抑制,半胱氨酸部分抑制它们的出血活性,表明两个出血毒素都是依赖金属离子的蛋白酶,且二硫键对其活性是必需的。金属离子的分析表明每摩尔毒蛋白大约含0.5摩尔的Zn,1摩尔的Ca,较多的Na,K。Mg,不含Co。两者是糖蛋白,含糖总量分别为11%和7%。用远紫外CD谱探讨DaHT-1和DaHT-2的溶液构象所得DaHT-1的α-螺旋,β-折叠和无规卷曲分别为36.9%,27.6%和31.4%;DaHT-2的α-螺旋,β-折迭和无规卷曲分别为23.4%,37.3%和45.3%。随着pH的增大或减少,DaHT-1和DaHT-2的峰位蓝移,在酸性条件下的变化比在碱性条件下大,计算表明:α-螺旋减少,无规卷曲增多,β-折迭基本未变。温度的影响和pH相似,50 ℃时峰位蓝移,α-螺旋减少,无规卷曲增多。EDTA对其影响很大,0.02M EDTA便导致两个出血毒素呈极度的无序状态。