G. N. Ramachandran

Ramachandran’s early training in physics and crystallography set the stage for an unusual career at the boundary of physics, chemistry, and biology. After studies in India and a stint in Cambridge, he returned to the University of Madras, where he gathered a small group of students and colleagues and began building instruments and problems from the ground up. The lab tackled fiber diffraction, where partially ordered biological polymers like collagen yield patterns that must be interpreted with both caution and imagination. His 1954–55 work on collagen proposed a triple helix with appropriate axial rise and twist, respecting known peptide geometry and hydrogen‑bonding possibilities. The model was not guesswork: it balanced stereochemistry with diffraction constraints and explained observed meridional intensities. Subsequent refinements and independent work by others converged on triple‑helical architectures, securing a paradigm that connected structure to the remarkable mechanical properties of collagen in connective tissue. The Ramachandran plot, introduced later in the 1960s, distilled steric hindrance into a two‑dimensional map. By treating the peptide unit as planar and accounting for van der Waals radii, one can enumerate regions of φ (phi) and ψ (psi) torsion angles that avoid atomic clashes. The result is a simple diagram with deep consequences: most residues in solved protein structures fall into allowed regions corresponding to α‑helices, β‑sheets, and loops; outliers often indicate errors or unusual environments. This tool became a standard quality check for protein crystallography and NMR, and later for computational models. Ramachandran’s group also contributed to Fourier methods in crystallography, optical transforms for teaching diffraction, and studies of other fibrous proteins and polysaccharides. What stands out is resourcefulness. With limited funds, they assembled apparatus, ground lenses, and pursued precise measurement. The intellectual culture he nurtured emphasized clear reasoning and careful writing; his papers are models of how to communicate across disciplines without sacrificing rigor. Recognition arrived in waves—election to academies, awards, visiting appointments—but perhaps the deeper achievement was sociological: demonstrating that Indian universities could incubate fundamental structural biology. Students trained in his lab went on to build programs elsewhere, spreading a methodology and a sensibility: make models that respect chemistry; use mathematics as a scalpel; teach with diagrams that condense insight. Late in his career, Ramachandran moved to the Indian Institute of Science, broadening the institutional base for biophysics. He continued to write and to advocate for quantitative biology long before it became fashionable. For today’s students, the Ramachandran plot is part of the furniture of bioinformatics; few tools are so simple and so indispensable. Behind the diagram is a story about attention to constraints: that truth in molecules is as much about what is forbidden as what is allowed.