DNA 奈米技術
DNA nanotechnology

context: zh_tw: 奈米技術常被限定為在小於 100 奈米的尺度下對材料和物體的研究。DNA 奈米技術是自下而上分子自組裝的一個例子，即分子成分自發地組成穩定結構；這些結構的特殊形態是由設計者所挑選的成分的物化特性所引發的。在 DNA 奈米技術中，構建成分是核酸鏈，如脫氧核糖核酸。脫氧核糖核酸很適合奈米級的構造，因為一條脫氧核糖核酸雙螺旋直徑為 2nm，螺旋重複長度為 3.5nm。核酸比其他材料更適合構造結構的主要特性是兩條核酸鏈間簡單的鹼基配對法則，透過鹼基連線可以形成一個具體明確的結構。這使核酸結構的組合容易透過核酸設計得到控制。這種特性在其他被用於奈米技術的材料中並不存在（包括蛋白質和奈米顆粒）。核酸分子的結構由含不同鹼基的核苷酸的排列順序決定。在脫氧核糖核酸中，四個鹼基為腺嘌呤、胞嘧啶、鳥嘌呤和胸腺嘧啶。如果核酸的兩條鏈是互補的，它們將相互連線形成雙螺旋結構（A-T，C-G）。因為正確的鹼基配對是積極有利的，在大多數情況下，核酸鏈相互連線時，都要使正確配對的鹼基數目最大化。鏈中鹼基的排列決定了連線的方式和整體結構，這簡單可控。在 DNA 奈米技術中，研究者設計合理的鹼基序列，從而使得整條鏈按照研究者希望的那樣組合起來。
en: Nanotechnology is often defined as the study of materials and devices with features on a scale below 100 nanometers.  DNA nanotechnology, specifically, is an example of bottom-up molecular self-assembly, in which molecular components spontaneously organize into stable structures; the particular form of these structures is induced by the physical and chemical properties of the components selected by the designers.  In DNA nanotechnology, the component materials are strands of nucleic acids such as DNA; these strands are often synthetic and are almost always used outside the context of a living cell. DNA is well-suited to nanoscale construction because the binding between two nucleic acid strands depends on simple base pairing rules which are well understood, and form the specific nanoscale structure of the nucleic acid double helix. These qualities make the assembly of nucleic acid structures easy to control through nucleic acid design.  This property is absent in other materials used in nanotechnology, including proteins, for which protein design is very difficult, and nanoparticles, which lack the capability for specific assembly on their own.The structure of a nucleic acid molecule consists of a sequence of nucleotides distinguished by which nucleobase they contain. In DNA, the four bases present are adenine (A), cytosine (C), guanine (G), and thymine (T).  Nucleic acids have the property that two molecules will only bind to each other to form a double helix if the two sequences are complementary, meaning that they form matching sequences of base pairs, with A only binding to T, and C only to G.  Because the formation of correctly matched base pairs is energetically favorable, nucleic acid strands are expected in most cases to bind to each other in the conformation that maximizes the number of correctly paired bases.  The sequences of bases in a system of strands thus determine the pattern of binding and the overall structure in an easily controllable way.  In DNA nanotechnology, the base sequences of strands are rationally designed by researchers so that the base pairing interactions cause the strands to assemble in the desired conformation.  While DNA is the dominant material used, structures incorporating other nucleic acids such as RNA and peptide nucleic acid (PNA) have also been constructed.
qas: question: zh_tw: 什麼酸結合在一起形成 DNA
en: What type of acids bind together to form DNA
answers: zh_tw: text: 核酸
en: text: nucleic

context: zh_tw: DNA 鏈是用分子建模和熱力學建模軟體計算設計的。核酸用標準的寡核苷酸合成法合成，通常用寡核苷酸合成器自動進行合成，自定義序列的鏈是市售的。如果需要的話，鏈可以透過變性凝膠電泳純化，精確的濃度可用紫外線吸收光譜來定量測定。完全形成的目標結構可用非變性凝膠電泳檢驗，將會得到關於核酸合成物形態大小的資訊。電泳遷移率變動分析可以評估一個結構是否包含所有的所需鏈。熒游標記和熒光共振能量轉移（FRET）有時用一表示合成物結構的特性。核酸結構可以直接用原子力顯微鏡看到，這很適合延伸的二維結構，但對三維結構沒有多大用處，因為顯微鏡尖端會與脆弱的核酸結構相互作用；因此透射電子顯微鏡和低溫電子顯微鏡常用以觀察三維結構。延伸的三維晶格用 X 光晶體學分析。
en: The sequences of the DNA strands making up a target structure are designed computationally, using molecular modeling and thermodynamic modeling software. The nucleic acids themselves are then synthesized using standard oligonucleotide synthesis methods, usually automated in an oligonucleotide synthesizer, and strands of custom sequences are commercially available.  Strands can be purified by denaturing gel electrophoresis if needed, and precise concentrations determined via any of several nucleic acid quantitation methods using ultraviolet absorbance spectroscopy.The fully formed target structures can be verified using native gel electrophoresis, which gives size and shape information for the nucleic acid complexes.  An electrophoretic mobility shift assay can assess whether a structure incorporates all desired strands.  Fluorescent labeling and Förster resonance energy transfer (FRET) are sometimes used to characterize the structure of the complexes.Nucleic acid structures can be directly imaged by atomic force microscopy, which is well suited to extended two-dimensional structures, but less useful for discrete three-dimensional structures because of the microscope tip's interaction with the fragile nucleic acid structure; transmission electron microscopy and cryo-electron microscopy are often used in this case.  Extended three-dimensional lattices are analyzed by X-ray crystallography.
qas: question: zh_tw: 電泳遷移率變動分析可以對什麼進行評估？
en: What does the mobility shift assess?
answers: zh_tw: text: 一個結構是否包含所有的所需鏈
en: text: whether a structure incorporates all desired strands