Rich and Crick solved the structure of collagen, the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole-body protein content. Collagen consists of amino acids bound together to form a triple helix of elongated fibril known as a collagen helix. 
See also:
Rich, Alexander - Crick, Francis H.C. The Structure of Collagen. 1957. Offprint from "Recent Advances in Gelatin and Glue Research" (Pergamon Press: London, 1957), the Proceedings of a Conference sponsored by the British Gelatine and Glue Research Association and held at the University of Cambridge, 1-5 July 1957, pp. 20-24.

Alexander Rich discovered polysomes, clusters of ribosomes which read one strand of mRNA simultaneously. Order of authorship in the original publication: Warner, Knopf, Rich.

Digital facsimile from PubMedCentral at this link.

Order of authorship in the original publication: Rosenberg, Seeman,...Rich. This paper was the first confirmation of the double-helix structure at atomic resolution.
See also:
Roberta Ogilvie Day, Nadrian C. Seeman,... Alexander Rich, "A crystalline fragment of the double helix: The structure of the dinucleoside phosphate guanylyl-3'5'-cytidine," Proc. Nat. Acad. Sci. (U.S.A.) 70, 849-853. Digital facsimile from PubMedCentral at this link.

(Thanks to Juan Weiss for this reference and its interpretation.)