| The Effects of Solvent Environment on the Optical Rotatory Dispersion Parameters of Polypeptides Biophysical Journal, Volume 5, Issue 4, 1 July 1965, Pages 573-589 Joseph Y. Cassim and Edwin W. Taylor Abstract The Moffitt parameter of poly-L-glutamic acid in the presumed helical state varied with solvent composition, ranging in magnitude from less than 600° in aqueous solution to 800° in methanol. was also dependent on temperature throughout the excessable temperature range. The value in aqueous solution is at least 100° smaller than the values for a number of polypeptides in organic solvents, when compared at the same refractive index. Therefore the optical rotatory dispersion data do not provide evidence that the molecule is completely helical in aqueous solution. Since other types of evidence for helical content are not sufficient to establish that PLGA is a complete helix, the helical content of proteins and polypeptides determined by rotatory dispersion measurements should be regarded as uncertain by about 20 per cent. Abstract | PDF (938 kb) |
| The Structure of Tobacco Mosaic Virus and Its Components Biophysical Journal, Volume 1, Issue 1, 1 September 1960, Pages 55-62 Norman S. Simmons and Elkan R. Blout Abstract An investigation has been made of the optical rotatory dispersion in the region 226 to 366 mμ of tobacco mosaic virus (TMV), the protein subunits isolated therefrom, the rods synthesized from the protein subunits, and the ribonucleic acid (RNA) isolated from TMV. Both TMV and the protein rods show anomalous rotatory dispersion. The RNA shows a Cotton effect with an inflection point around 260 mμ, which is shifted to 272 mμ in concentrated urea solution. A suggested interpretation of the RNA rotatory dispersion is given. The rotatory dispersion of the protein subunits shows an incipient Cotton effect with an inflection point around 293 mμ and the beginnings of a large negative Cotton effect with a trough at 232 mμ. The dispersion data from the protein subunits can be interpreted to indicate that they contain between 25 and 35 per cent α-helix. On the basis of recent sequence investigations and the relationship between amino acid composition and polypeptide structure, the helical portion of the protein subunits can be located in the central section of the protein chain. Abstract | PDF (427 kb) |
| ATP Hydrolysis in the βTP and βDP Catalytic Sites of F1-ATPase Biophysical Journal, Volume 87, Issue 5, 1 November 2004, Pages 2954-2967 Markus Dittrich, Shigehiko Hayashi and Klaus Schulten Abstract The enzyme F-adenosine triphosphatase (ATPase) is a molecular motor that converts the chemical energy stored in the molecule adenosine triphosphate (ATP) into mechanical rotation of its -subunit. During steady-state catalysis, the three catalytic sites of F operate in a cooperative fashion such that at every instant each site is in a different conformation corresponding to a different stage along the catalytic cycle. Notwithstanding a large amount of biochemical and, recently, structural data, we still lack an understanding of how ATP hydrolysis in F is coupled to mechanical motion and how the catalytic sites achieve cooperativity during rotatory catalysis. In this publication, we report combined quantum mechanical/molecular mechanical simulations of ATP hydrolysis in the and catalytic sites of F-ATPase. Our simulations reveal a dramatic change in the reaction energetics from strongly endothermic in to approximately equienergetic in . The simulations identify the responsible protein residues, the arginine finger R373 being the most important one. Similar to our earlier study of , we find a multicenter proton relay mechanism to be the energetically most favorable hydrolysis pathway. The results elucidate how cooperativity between catalytic sites might be achieved by this remarkable molecular motor. Abstract | Full Text | PDF (320 kb) |
Copyright © 1964 The Biophysical Society. All rights reserved.
Biophysical Journal, Volume 4, Issue 1, 43-54, 1 January 1964
doi:10.1016/S0006-3495(64)86925-3
Physical Chemistry of Macromolecules
Walter Kauzmann
The general nature of the problem of molecular structure in protein chemistry is discussed. As in all of organic chemistry, this problem has two aspects: the determination of the structural formula (a province of classical organic chemistry) and the determination of the molecular conformation. Recent progress in both of these areas has been great. Information on the amino acid sequences in proteins is rapidly accumulating (essentially a problem which concerns the structural formulae of proteins). Detailed knowledge of the conformations of proteins in general, and recently of myoglobin and hemoglobin in particular, has come from various kinds of x-ray crystallographic studies. Other physical tools (especially optical rotatory power and ultraviolet spectroscopy) give less detailed but still highly useful information about molecular conformation. The current state of our knowledge of the nature of the forces responsible for the molecular conformations of proteins is briefly reviewed.