= G. Kartha
{c}
<G. Kartha> worked with <G. N. Ramachandran> on the structure of <collagen>. Their 1955 paper developed a model in which three <polypeptide> chains wind around one another, contributing to the explanation of the <collagen triple helix>. The proposed arrangement had to accommodate the <amino acid> composition, <hydrogen bonding> and the pattern of experimental <X-ray diffraction>.<Structure of collagen by G. N. Ramachandran and G. Kartha>[Nature 176, 593–595, 1955; original paper reprinted in National Medical Journal of India, Classics in Indian Medicine]{ref}
The history illustrates how a structural model is tested. A geometrically plausible arrangement can still require revision if its predicted repeat disagrees with measured <X-ray diffraction>. The value of the model lies in connecting molecular packing with several independent observations, while leaving its detailed geometry open to correction. A proposed <protein structure> and a later experimentally refined atomic structure represent different stages of that process.<Structure of collagen by G. N. Ramachandran and G. Kartha>[Opening discussion of the revised 1955 model and disagreement of the earlier proposal with diffraction data]{ref}
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