SynopsisTheoretical treatment of resonance interaction of amide-I vibration has been done in a dipole-dipole approximation on the basis of perturbation theory. A single infinite antiparallel-chain pleated sheet as well as different kinds of its finite fragments have been considered. A good agreement has been obtained between calculated spectral parameters of amide I of the infinite sheet and observed ones in infrared and Raman spectra of synthetic polypeptides and fibrous proteins. A theoretical dependence of the resonance frequency shift of the main component and frequency splitting of two components active in the infrared spectra on the number of polypeptide chains in the finite sheet has been found.

SynopsisAmide-I and I1 vibrations of a-helix have been treated on the basis of the perturbation theory in a dipole-dipole approximation. The infinite helix and its finite fragments have been considered as models. The calculated infrared spectra for the infinite helix are in good agreement with the spectra of synthetic polypeptides. In the case of finite fragments of the a-helix, the characteristic contours of the amide-I and I1 bands appear when the number of peptide groups is about 10 and 6, respectively.

SynopsisResonance vibrational interactions of amide I for the parallel-chain pleated-sheet structure have been treated on the basis of the perturbation theory in a dipole-dipole approximation. The infinite sheet and finite fragments of different types have been considered. The possibility of experimental observation by infrared spectra of parallel-chain pleatedsheet fragments in globular proteins is discussed.

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The amino acid sequence and crystal structure of the ribosomal protein S6 from the small ribosomal subunit of Thermus thermophilus have been determined. S6 is a small protein with 101 amino acid residues. The 3D structure, which was determined to 2.0 A resolution, consists of a four‐stranded anti‐parallel beta‐sheet with two alpha‐helices packed on one side. Similar folding patterns have been observed for other ribosomal proteins and may suggest an original RNA‐interacting motif. Related topologies are also found in several other nucleic acid‐interacting proteins and based on the assumption that the structure of the ribosome was established early in the molecular evolution, the possibility that an ancestral RNA‐interacting motif in ribosomal proteins is the evolutionary origin for the nucleic acid‐interacting domain in large classes of ribonucleic acid binding proteins should be considered.