X-ray crystallography elastic X-ray scattering include powder diffraction, Small-Angle X-ray Scattering (SAXS) and several types of X-ray fiber diffraction, which was used by Rosalind Franklin in determining the double-helix structure of DNA. In general, single-crystal X-ray diffraction offers more structural information than these other techniques; however, it requires a sufficiently large and regular crystal, which is not always available. These scattering methods generally use "monochromatic" X-rays, which are restricted to a single wavelength with minor deviations. A broad spectrum of X-rays (that is, a blend of X-rays with different wavelengths) can also be used to carry out X-ray diffraction, a technique known
Triple-stranded DNA Triple-stranded DNA Triple-stranded DNA (also known as H-DNA or Triplex-DNA) is a DNA structure in which three oligonucleotides wind around each other and form a triple helix. In triple stranded-DNA, one strand binds to a B-form DNA (Watson–Crick base-pairing) through Hoogsteen base pair or reversed Hoogsteen hydrogen bonds. A thymine (T) nucleobase can bind to a Watson–Crick base-pairing of T-A by a Hoogsteen hydrogen bond. The thymine attaches to the adosine (A) of the origin double stranded DNA to create a T-A*T base-triplet. In acidic conditions, a protonated cytosine, represented as C+, can form a base-triplet with a C-G pair