X-ray Diffraction and the Discovery of the Structure of DNA. A Tutorial and Historical Account of James Watson and Francis Crick's Use of X-ray Diffraction in Their Discovery of the Double Helix Structure of DNA

Abstract

A step-by-step method of teaching the X-ray diffraction analysis of DNA using the approach employed by James Watson, Francis Crick, Maurice Wilkins, Rosalind Franklin, and Raymond Gosling at an upper undergraduate and graduate level is described. This method includes a historical account of the 1953 articles by James Watson and Francis Crick, Maurice Wilkins et al., and Rosalind Franklin et al. Throughout the X-ray diffraction analysis, excerpts of their articles are included to describe the obstacles encountered by these researchers, the contributions each person made to the determination of the structure of DNA, and the degree to which X-ray diffraction aided their determination of the DNA structure. The article is organized with the assigned problem as the main part of the text and the intermediate steps leading to the solutions given in the Supplemental Material. Helpful hints and information are also given in the Supplemental Material. Writing the article in this way allows the project to be quickly implemented into upper-level undergraduate and graduate physics, chemistry, and materials science and engineering course curricula.

Modelos de explicação científica, inferência da melhor explicação e a história da dupla-hélice do DNA

“…Ainda sobre a virtude de adequação empírica, vale ressaltar que foram as fotografias de raio-X do DNA produzidas pelas técnicas de cristalografia de Rosalind Franklin (1920-1958 que guiaram a construção do modelo molecular da dupla de Cavendish (Crouse, 2007). Isso, por si só, é um exemplo de como a observação de fatos empíricos, aliada ao arcabouço técnico e teórico do conhecimento de fundo da comunidade científica, oferece insights que direcionam o processo de formulação de novas hipóteses (e não se faz importuno lembrar que esse é um fato não contemplado ou explorado pelas teorias filosóficas de explicação tradicionais).…”

Simulación de perfiles de difracción de rayos X de muestras problema para aplicaciones académicas

“…Otras aplicaciones de la difracción de rayos X han estado orientadas al estudio cristalográfico de diversas sustancias, y cómo diversos factores pueden afectar su estructura cristalina. Entre una de sus mayores contribuciones se encuentra la determinación de la estructura tridimensional del ADN (Crouse, 2007;Mayer, 2017).…”

Single-Molecule Localization to Demonstrate the Optical Diffraction of Materials with 2D or Helical Structures

“…In this demonstration, we introduce undergraduate and graduate students to this important concept using optical diffraction. X-ray diffraction crystallography is one of the best scientific tools to analyze the structures of biological molecules including DNA, RNA, proteins, and associated complexes, − as well as of chemicals, including inorganic supramolecules and most organic molecules. − Compared to spectroscopic tools, it offers a much more direct method to investigate the structure of molecules. Although vibrational and rotational spectroscopy has also been used to identify the structure of molecules, those methods do not provide direct data about the structure of molecules but only provide information on specific parts of molecules, such as chemical functional groups.…”