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相关概念视频

Protein Diffusion in the Membrane01:24

Protein Diffusion in the Membrane

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Proteins show rotational as well as lateral diffusion across the membrane. The lateral diffusion of proteins was confirmed through the cell fusion experiment where mouse and human cells were fused, resulting in hybrid cells. When the human and mouse cells fused, the specific membrane proteins on human and mouse cells were marked with the red and green-fluorescent markers, respectively. Initially, the red and green fluorescence was located on the respective hemisphere of the cell. As time...
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Site-Targeted Drug Delivery Systems: Polymeric Carriers01:24

Site-Targeted Drug Delivery Systems: Polymeric Carriers

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Polymeric carriers enhance targeted drug delivery by increasing efficacy while minimizing off-target effects. These carriers comprise a biodegradable polymeric backbone integrated with functional elements that enable targeting, improve physicochemical properties, and regulate drug release.Targeting MechanismsThe targeting ability of polymeric carriers is mediated by a homing device, which is a molecular recognition component designed to selectively bind to specific tissues or cells. Monoclonal...
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Polymers02:34

Polymers

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The word polymer is derived from the Greek words “poly” which means “many” and “mer” which means “parts”. Polymers are long chains of molecules composed of repeating units of smaller molecules, known as monomers. They either occur naturally, such as DNA and proteins, or can be constructed synthetically, like plastics. They have varied structural characteristics, such as linear chains, branched chains, or complex networks, that contribute to the...
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Polymers: Molecular Weight Distribution01:10

Polymers: Molecular Weight Distribution

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For any given polymer, the weight average molecular weight (Mw) is higher than, if not equal to, the number average molecular weight (Mn). The only situation in which the weight average molecular weight and the number average molecular weight are equal is when a polymer consists only of chains with equal molecular weight. However, this never happens in a synthetic polymer, since it is difficult to control the polymerization process up to a molecular level with accuracy to a hundred percent.
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Polymer Classification: Crystallinity01:21

Polymer Classification: Crystallinity

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Unlike ionic or small covalent molecules, polymers do not form crystalline solids due to the diffusion limitations of their long-chain structures. However, polymers contain microscopic crystalline domains separated by amorphous domains.
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
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Factors Affecting Dissolution: Polymorphism, Amorphism and Pseudopolymorphism01:21

Factors Affecting Dissolution: Polymorphism, Amorphism and Pseudopolymorphism

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Polymorphism refers to the existence of a drug substance in multiple crystalline forms, known as polymorphs. Recently, this term has been expanded to include solvates (forms containing a solvent), amorphous forms (non-crystalline forms), and desolvated solvates (forms from which the solvent has been removed).
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Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
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在多电解质复合物和多层中,网站与聚合物的扩散

Hadi M Fares1, Joseph B Schlenoff1

  • 1Department of Chemistry and Biochemistry, The Florida State University , Tallahassee, Florida 32306-4390, United States.

Journal of the American Chemical Society
|October 6, 2017
PubMed
概括

多电解质复合物的形成依赖于快速的位点扩散,而不是缓慢的聚合物扩散. 这一发现解释了多层生长,并透露了通过交叉链传输的动态组装.

科学领域:

  • 聚合物科学
  • 材料科学
  • 物理化学

背景情况:

  • 多电解质复合物 (PEC) 和多层的自发形成传统上归因于充电聚合物的相互扩散.
  • 人们对PEC形成和生长的动力学知之甚少,特别是驱动多层组装的机制.

研究的目的:

  • 研究聚合物分子与PEC薄膜内的充电位点的不同质量传输机制.
  • 阐明点扩散在PEC多层的动力学和生长模式中的作用.
  • 根据扩散特征确定促进完整多层生长的条件.

主要方法:

  • 使用敏感的同位素标记技术,单独追踪聚合物分子和PEC薄膜内的外部位点的扩散.
  • 在聚二甲 (PDADMA) 和聚二硫酸盐 (PSS) 复合物中检查了位点和聚合物的扩散系数.
  • 与环境盐度 (离子强度) 相关的位点扩散系数.

主要成果:

  • 由于局部重新排列,PEC内部的位点扩散速度至少比聚合物扩散快两倍.
  • 部位扩散高度依赖盐度,PDADMA部位的扩散速度快于PSS部位,解释了不对称的多层生长.
  • 位点扩散控制了线性和指数式模式的多层生长,使PDADMA通过PSS层透等现象成为可能.
  • 通过将扩散长度与薄膜厚度相匹配来确定完全指数增长的条件,独立于分子重量,这表明离子配对密度是关键.

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Assembly and Characterization of Polyelectrolyte Complex Micelles

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结论:

  • 多电解质复合组合和多层生长主要是由快速的位点扩散驱动的,而不是缓慢的聚合物扩散.
  • 位点扩散为PEC形成,动力学和生长动态提供了新的机制理解.
  • PEC是通过交叉连接或缺陷运输组装的动态散装材料,为自组装过程提供了更广泛的视角.