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  • 蛋白质

    Comparison of normal and sickle red blood cells in blood vessels.

    A serious shift?
    ::严重的转变?

    Hemoglobin is a complex which has a quaternary structure and contains iron. There are four subunits in the hemoglobin molecule – two alpha subunits and two beta subunits. Each subunit contains one iron , whose oxidation state changes from +2 to +3 and back again, depending upon around the iron. When the oxygen binds to the iron, the three-dimensional shape of the molecule changes. Upon release of the oxygen to the cells, the shape changes again.
    ::血红蛋白是一个复合体,具有四面结构,含有铁。血红蛋白分子中存在四个子单位 — — 两个α子单位和两个β子单位。每个子单位都含有一个铁,其氧化状态依铁周围的变化而从+2到+3,再从一个铁的氧化状态变化一次。当氧与铁结合时,分子的三维形状会发生变化。当氧向细胞释放氧气时,形状会再次变化。

    With hemoglobin of normal structure, this shift in conformation does not present any problems. However, individuals with hemoglobin S do experience serious complications. This hemoglobin has one in the two beta chains that is different from the amino acid at that point in the primary structure of normal hemoglobin. The result of this one structural change is aggregation of the individual protein molecules when oxygen is released. Adjacent hemoglobin molecules come in contact with one another and clump up, causing the red cells to deform and break.
    ::随着正常结构的血红蛋白,这种异质变化不会产生任何问题,但是,血红蛋白S的人确实会经历严重的并发症,这种血红蛋白在正常血红蛋白初级结构的这两个乙型链条中有一个与氨基酸不同,在正常血红蛋白初级结构的这一点,这种血红蛋白在结构上发生变化的结果是在释放氧气时将个别蛋白分子聚合在一起。相邻的血红蛋白分子相互接触并聚集在一起,导致红细胞变形和破裂。

    This abnormality, known as sickle cell, is genetic in nature. A person may inherit the gene from one parent and have sickle cell trait (only some of the hemoglobin is hemoglobin S), which is usually not life-threatening. Inheriting the gene from both parents will result in sickle cell disease, a very serious condition.
    ::这种非正常现象,即镰状细胞,具有遗传性质。 一个人可以继承父母一方的基因,并具有镰状细胞特征(只有部分血红蛋白是血红蛋白 S ) , 通常不会危及生命。 父母双方的基因继承将导致镰状细胞疾病,这是非常严重的疾病。

    Proteins
    ::蛋白质

    A polypeptide is a sequence of amino acids between ten and one hundred in length. A protein is a peptide that is greater than one hundred amino acids in length. Proteins are very prevalent in living organisms. Hair, skin, nails, muscles, and the hemoglobin in red blood cells are some of the important parts of your body that are made of different proteins. The wide array of chemical and physiological properties of proteins is a function of their amino acid sequences. Since proteins generally consist of one hundred or more amino acids, the number of amino acid sequences that are possible is virtually limitless. 
    ::聚虫化物是100至100长度的氨基酸序列。蛋白质是一种超过100氨基酸长度的酸。蛋白质在活生物体中非常普遍。头发、皮肤、指甲、肌肉和红细胞中的血红蛋白都是你身体中由不同蛋白组成的一些重要部分。蛋白质的化学和生理特性是其氨基酸序列的函数。由于蛋白质通常由100或100多个氨基酸组成,因此可能发生的氨基酸序列数量几乎是无限的。

    The three-dimensional structure of a protein is very critical to its function. This structure can be broken down into four levels. The primary structure is the amino acid sequence of the protein. The amino acid sequence of a given protein is unique and defines the function of that protein. The secondary structure is a highly regular sub-structure of the protein. The two most common types of protein secondary structure are the alpha helix and the beta sheet. An alpha helix consists of amino acids that adopt a spiral shape. A beta sheet is alternating rows of amino acids that line up in a side-by-side fashion. In both cases, the secondary structures are stabilized by extensive between the side chains. The interaction of the various side chains in the amino acid, specifically the hydrogen bonding, leads to the adoption of a particular secondary structure.
    ::蛋白质的三维结构对于它的功能非常关键。 此结构可以细分为四个层次。 主要结构是蛋白质的氨基酸序列。 给定蛋白的氨基酸序列是独特的, 并定义了蛋白质的功能。 第二结构是蛋白质的非常常规的子结构。 两种最常见的蛋白二级结构类型是阿尔法螺旋和贝塔薄。 甲型螺旋由氨基酸组成, 采用螺旋形状。 乙型环形是双向排列的氨基酸行。 在这两种情况下, 双向结构通过侧链进行广泛的稳定。 氨基酸的不同侧链的相互作用, 特别是氢联结, 导致采用特定的辅助结构 。

    Depiction of alpha helix and beta sheet structures in proteins.

    Secondary structure: alpha helix and beta sheet.
    ::二级结构:阿尔法螺旋和贝塔表。

    The tertiary structure is the overall three-dimensional structure of the protein. A typical protein consists of several sections of a specific secondary structure (alpha helix or beta sheet) along with other areas in which a more random structure occurs. These areas combine to produce the tertiary structure.
    ::第三层结构是蛋白质的整体三维结构,典型的蛋白质由特定的第二层结构(alpha helix 或 beta place)的若干部分以及结构更随机的其他领域组成,这些区域合在一起形成第三层结构。

    Some protein molecules consist of multiple protein subunits. The quaternary structure of a protein refers to the specific interaction and orientation of the subunits of that protein Hemoglobin is a very large protein found in red blood cells and whose function is to bind and carry oxygen throughout the bloodstream. Hemoglobin consists of four subunits – two α subunits (yellow) and two β subunits (gray) – which then come together in a specific and defined way through interactions of the side chains (see Figure ). Hemoglobin also contains four iron atoms, located in the middle of each of the four subunits. The iron atoms are part of a structure called a porphyrin, shown in red in the figure.
    ::一些蛋白分子由多个蛋白分元素组成。蛋白质的四角结构是指该蛋白血红蛋白分元素的具体互动和定向。血红蛋白是红细胞中发现的一个非常大的蛋白质,其功能是在整个血液中粘合和携带氧气。血红蛋白由四个分单位组成 — — 两个α分单位(黄)和两个β分单位(灰色) — — 它们随后通过侧链的相互作用以具体和明确的方式聚集在一起(见图 ) 。 Hemoglobin还包含四个铁原子,分别位于四个子单位的中间。铁原子是图中称为porphyrin(porphyrin)的结构的一部分,以红色显示于图中。

    3D structure of hemoglobin showing subunits and iron atoms in a complex arrangement.

    Hemoglobin
    ::血红素

    Some proteins consist of only one subunit and thus do not have a quaternary structure.  Figure diagrams the interaction of the four levels of protein structure.
    ::有些蛋白质只有一个子单位,因此没有四面结构,图示了四个层次蛋白结构的相互作用。

    Diagram illustrating the four levels of protein structure: primary, secondary, tertiary, and quaternary.

    The four levels of protein structure.
    ::四个层次的蛋白质结构。

     

     

    Science Friday : The Medical Wonders of Worm Spit
    ::科学星期五:虫虫病的医学奇迹

    How useful is worm spit? It turns out that worm spit, also known as silk, is a very useful material in medicine. In this video by Science Friday , Dr. David Kaplan describes how silk is used in a variety of medical applications.
    ::蠕虫唾液有多么有用? 事实证明,蠕虫唾液(又称丝绸)是医学上非常有用的材料。 在科学周五的这段影片中,大卫·卡普兰博士讲述了丝绸在各种医疗应用中是如何使用的。

     

    Review
    ::回顾

    1. A protein has the following sequence: ser-his-thr-tyr. What component of protein structure is this?
      ::蛋白质有以下序列: ser-his- thr- tyr。 这是蛋白质结构的哪些成分?
    2. What do we call the overall three-dimensional shape of a protein?
      ::我们怎么称呼一个蛋白质的三维整体形状?
    3. A protein has one subunit. Would it have a quaternary structure?
      ::蛋白质有一个子单位。 它有四面形结构吗 ?

    Explore More
    ::探索更多

    Use the resource below to answer the questions that follow.
    ::利用以下资源回答以下问题。

     

    1. What is part of what determines how a protein folds?
      ::什么是决定蛋白质如何折叠的部分?
    2. What holds secondary structure together?
      ::二级结构是什么组合在一起的?
    3. What holds the tertiary structure together?
      ::是什么将第三级结构结合在一起?