Biomolecular structure chemical probing, hydroxyl radical probing, nucleotide analog interference mapping (NAIM), and in-line probing. Protein and nucleic acid structures can be determined using either nuclear magnetic resonance spectroscopy (NMR) or X-ray crystallography or single-particle cryo electron microscopy (cryoEM). The first published reports for DNA (by Rosalind Franklin and Raymond Gosling in 1953) of A-DNA X-ray diffraction patterns—and also B-DNA—used analyses based on Patterson function transforms that provided only a limited amount of structural information for oriented fibers of DNA isolated from calf thymus. An alternate analysis was then proposed by Wilkins et al. in 1953 for B-DNA X-ray diffraction and scattering
James Watson and the bases pointing outwards. Her identification of the space group for DNA crystals revealed to Crick that the two DNA strands were antiparallel. The X-ray diffraction images collected by Gosling and Franklin provided the best evidence for the helical nature of DNA. Franklin's experimental work thus proved crucial in Watson and Crick's discovery. Watson and Crick had three sources for Franklin's unpublished data: Prior to publication of the double helix structure, Watson and Crick had little interaction with Franklin. Crick and Watson felt that they had benefited from collaborating with Wilkins. They offered him a co-authorship on the article